Mississippian Barnett Shale,Fort Worth basin,north-central texas: Gas-shale play with multi-trillion cubic foot potential
Scott L. Montgomery; Daniel M. Jarvie; Kent A. Bowker; et al.
Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment
Daniel M. Jarvie; Ronald J. Hill; Tim E. Ruble; et al.
Shale gas potential of the Lower Jurassic Gordondale Member,northeastern British Columbia,Canada
Ross,DJK; Bustin,RM
Characterizing the shale gas resource potential of Devonian-Mississippian strata in the Western Canada sedimentary basin: Application of an integrated formation evaluation
Ross DJK,Bustin RM
中国页岩气勘探开发进展与发展前景*
董大忠1,邹才能1,杨桦1,王玉满1,李新景1,陈更生2,王世谦2,吕宗刚2,黄勇斌2
(1. 中国石油勘探开发研究院,北京100083;2. 中国石油西南油气田公司,四川成都650001)
中国页岩气形成机理、地质特征及资源潜力*
邹才能1,2,董大忠1,2,王社教1,2,李建忠1,2,李新景1,2,王玉满1,2,李登华1,2,程克明1,2
(1. 中国石油勘探开发研究院;2. 提高石油采收率国家重点实验室)
页岩气成藏机理和分布
张金川,金之钧,袁明生
页岩气
·编者按·
“页岩气(shale gas)”是最重要的非常规天然气资源,资源潜力超过致密气和煤层气之和,美国“页岩气革命”对全球能源格局已产生深刻影响.科罗拉多矿业学院Curtis教授系统阐述了页岩气的概念,页岩气是连续生成的生物化学成因、热成因或两者混合的天然气聚集,具有普遍含气、大面积分布、多种岩性封闭、短距离运移等特点,以游离形式存在于天然裂缝和孔隙中,以吸附状态存在于干酪根和粘土颗粒表面,以溶解状态存在于干酪根和沥青质中.近年来,“页岩气”概念被广泛引入国内,普遍认为,页岩气是赋存于富有机质泥页岩层段中,以吸附态和游离态为主要赋存方式、大面积连续分布的非常规天然气,为典型“自生自储、原地滞留”聚集模式,成分以甲烷为主.
相比常规天然气,页岩气开发较为困难,但具有开发寿命长和生产周期长的优点.大部分产气页岩分布范围广、厚度大、普遍含气,这使得页岩气井能够长期产气,但是页岩气储集层渗透率低,开采难度较大.页岩气为完全的、独立的、自生自储的含油气系统,富有机质黑色页岩本身就是源岩、储层和封盖层,为源储一体、原位持续聚集、早成藏的典型源岩气藏,它既不同于常规天然气,也有别于致密砂岩气、煤层气等非常规天然气,具有五个重要的地质与开发特征:(1)页岩气可形成于有机质演化的各个阶段,包括生物气、干酪根热降解气和原油热裂解气.研究表明,页岩产气能力与热成熟度、TOC等密切相关,一般生物成因页岩气产量低,热成因页岩气产量高.(2)页岩气储层致密,以纳米级孔隙为主,具有极低的孔隙度和超低渗透率.(3)页岩气在成藏、开采机理上与其它类型天然气有明显的不同.页岩气气体主要以吸附、游离2种状态赋存.吸附气含量一般为20%~85%,并随深度不同有较大的变化,这一赋存形式类似于煤层吸附气,但其吸附气量小于煤层吸附气(85%以上).游离气含量一般为80%~20%,和常规天然气相似,储层物性愈好,游离气含量愈高.(4)页岩气大面积连续分布,资源规模大,源储一体,含气范围与有效气源岩相当,没有明显的圈闭界线,分布不受构造的控制.(5)单井产量低,生产周期长,采收率变化较大.随着水平井、多级水力体积压裂等钻完井、储层增产改造等技术的进步,页岩气采收率正在逐步提高.
页岩气发现较早,1821年美国在东部泥盆系钻探第一口页岩气井,1914年美国发现第一个页岩气大气田—Big Sandy气田,1981年页岩气之父乔治·米歇尔对Barnett页岩实施大规模压裂,实现了页岩气开采真正意义上的大突破.页岩气由南部地区的Barnett页岩,到Haynesville页岩,再到东部地区的Marcellus页岩,持续获得重大发展,至2014年,北美地区在约50个富有机质页岩区带中证实存在页岩气资源,在其中9个区带实现了页岩气的规模开发,2014年美国页岩气产量为3637×108m3,占美国天然气总产量的50%,依靠页岩气,美国实现了天然气自给.全球正在进行一场“页岩气革命”,北美以外地区已有20多个国家正在进行页岩气资源的前期评价和勘探开发先导试验,中国、阿根廷、英国、印度、新西兰等国已发现了页岩气,全球页岩气资源量约为456×1012m3,勘探开发前景广阔.中国页岩气资源丰富,发育海相、海陆过渡相—湖沼煤系和湖相3类富含有机质页岩,均具备页岩气形成条件.近年来,页岩气已得到国家和企业的高度重视,已在地质基础研究、资源评价和核心区优选、水平井压裂等技术创新、工业化试验区建设等攻关取得重大进展.2004—2007年,引入页岩气概念;2008年,钻探第一口页岩气地质井长芯1井;2009年,首次在中国页岩气储集层中发现丰富的纳米级孔隙;2010年,成立国家能源页岩气研发(实验)中心;2010年,四川盆地威201井在志留系龙马溪组获日产大于1×104m3页岩气;2011年,国家第一个页岩气重大专项《页岩气勘探开发关键技术》立项;2012年四川盆地焦石坝构造焦页1HF在志留系龙马溪组获日产气20.3×104m3工业气流,发现了中国首个大型页岩气田—涪陵气田,并已启动一期50×108m3产能建设,中国页岩气勘探取得战略突破.目前,中国已在重庆焦石坝、巫溪,四川长宁-威远、富顺-永川,云南昭通、陕西延安等地区开展页岩气工业开采或先导试验.截至2014年底,中国累计投资200亿元,完钻页岩气井400口,压裂获气160口井,2013年页岩气产量2×108m3,2014年产量13×108m3,中国页岩气开发利用已顺利实现工业起步.
中国页岩气开发利用面临保存较差、埋藏较深、地表复杂、水源短缺、环境保护等一系列问题,大规模经济有效开发难度较大.中国页岩气规模化发展,需要突破理论关、技术关、成本关、环境关“四道关”,需注意优先解决四川盆地龙马溪组构造型“甜点”和连续型“甜点区”页岩气递减规律、四川盆地筇竹寺组优质资源落实、3500 m以深页岩气效益开发技术与装备研发、海陆过渡相/陆相页岩气资源潜力评价等关键问题.初步估算,中国页岩气技术可采资源量大约为(10~25)×1012m3.预计未来5~10年,将是中国页岩气技术攻关与先导试验的关键期,需要制定“加快‘核心区’评选、加大‘试验区’建设、加强‘生产区’规划”等战略发展路线图,力争2020年前后实现页岩气工业化全面突破和规模发展.
本专题得到了邹才能教授(中国石油勘探开发研究院)、郝梓国教授(中国地质学会)的大力支持.
·热点数据排行·
截至2015年4月20日,中国知网(CNKI)和Web of Science(WOS)的数据报告显示,以页岩气(shale gas)为词条可以检索到的期刊文献分别为1726与1020条,本专题将相关数据按照:研究机构发文数、作者发文数、期刊发文数、被引用频次进行排行,结果如下.
研究机构发文数量排名(CNKI)
研究机构发文数量排名(WOS)
作者发文数量排名(CNKI)
作者发文数量排名(WOS)
期刊发文数量排名(CNKI)
期刊发文数量排名(WOS)
根据中国知网(CNKI)数据报告,以页岩气(shale gas)为词条可以检索到的高被引论文排行结果如下.
国内数据库高被引论文排行
(数据来源:中国知网,检索时间:2015-4-20)
根据Web of Science统计数据,以页岩气(shale gas)为词条可以检索到的高被引论文排行结果如下.
国外数据库高被引论文排行
·经典文献推荐·
基于Web of Science检索结果,利用Histcite软件选取LCS(Local Citation Score,本地引用次数)TOP 30文献作为节点进行分析,得到本领域推荐的经典文献如下.
来源出版物:AAPG Bulletin,2002,86(11): 1921-1938
Mississippian Barnett Shale,Fort Worth basin,north-central texas: Gas-shale play with multi-trillion cubic foot potential
Scott L. Montgomery; Daniel M. Jarvie; Kent A. Bowker; et al.
Abstract: The Mississippian Barnett Shale serves as source,seal,and reservoir to a world-class unconventional natural-gas accumulation in the Fort Worth basin of north-central Texas. The formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce. At present,production is mainly confined to a limited portion of the northern basin where the Barnett Shale is relatively thick(>300 ft; >92 m),organic rich(present-day total organic carbon >3.0%),thermally mature(vitrinite reflectance >1.1%),and enclosed by dense limestone units able to contain induced fractures. The most actively drilled area is Newark East field,currently the largest gas field in Texas. Newark East is 400 mi2(1036 km2)in extent,with more than 2340 producing wells and about 2.7 tcf of bookedgas reserves. Cumulative gas production from Barnett Shale wells through 2003 was about 0.8 tcf. Wells in Newark East field typically produce from depths of 7500 ft(2285 m)at rates ranging from 0.5 to more than 4 mmcf/day. Estimated ultimate re coveries per well range from 0.75 to as high as 7.0 bcf. Efforts to extend the current Barnett play beyond the field limits have encountered several challenges,including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth. Patterns of oil and gas occurrence in the Barnett,in conjunction with maturation and burial-history data,indicate a complex,multiphased thermal evolution,with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas in portions of the basin where paleotemperatures were especially elevated. These and other data imply a large-potential Barnett resource for the basin as a whole(possibly >200 tcf gas in place). Recent assessment by the U.S. Geological Survey suggests a mean volume of 26.2 tcf of undiscovered,technically recoverable gas in the central Fort Worth basin. Recovery of a significant portion of this undiscovered resource will require continued improvements in geoscientific characterization and approaches to stimulation of the Barnett reservoirs.
Keywords: interdisciplinary approach; Pennsylvanian; marattialean pecopterids; functional groups; FTIR
来源出版物:AAPG Bulletin,2005,89(2): 155-175
Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment
Daniel M. Jarvie; Ronald J. Hill; Tim E. Ruble; et al.
Abstract: Shale-gas resource plays can be distinguished by gas type and system characteristics. The Newark East gas field,located in the Fort Worth Basin,Texas,is defined by thermogenic gas production from low-porosity and low-permeability Barnett Shale. The Barnett Shale gas system,a self-contained source-reservoir system,has generated large amounts of gas in the key productive areas because of various characteristics and processes,including(1)excellent original organic richness and generation potential;(2)primary and secondary cracking of kerogen and retained oil,respectively;(3)retention of oil for cracking to gas by adsorption;(4)porosity resulting from organic matter decomposition; and(5)brittle mineralogical composition. The calculated total gas in place(GIP)based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf/section(5.78×109M-3/1.73×104m3). We estimate that the Barnett Shale has a total generation potential of about 609 bbl of oil equivalent/ac-ft or the equivalent of 3657 mcf/ac-ft(84.0 m3/m3). Assuming a thickness of 350 ft(107 m)and only sufficient hydrogen for partial cracking of retained oil to gas,a total generation potential of 820 bcf/section is estimated. Of this potential,approximately 60% was expelled,and the balance was retained for secondary cracking of oil to gas,if sufficient thermal maturity was reached. Gas storage capacity of the Barnett Shale at typical reservoir pressure,volume,and temperature conditions and 6% porosity shows a maximum storage capacity of 540 mcf/ac-ft or 159 scf/ton.
Keywords: Sichuan Basin; middle paleo-uplift; pyrobitumen; natural gas potential; upper Proterozoic strata
来源出版物:AAPG Bulletin,2007,91(4): 475-499
Shale gas potential of the Lower Jurassic Gordondale Member,northeastern British Columbia,Canada
Ross,DJK; Bustin,RM
Abstract: The Lower Jurassic Gordondale Member is an organic-rich mudrock and is widely considered to have potential as a shale gas reservoir. Influences of Gordondale mudrock composition on total gas capacities(sorbed and free gas)have been determined to assess the shale gas resource potential of strata in the Peace River district,northeastern British Columbia. Sorbed gas capacities of moisture-equilibrated samples increase over a range of 0.5 to 12 weight percent total organic carbon content(TOC). Methane adsorption capacities range from 0.05 cc/g to over 2 cc/g in organic-rich zones(at 6 MPa and 30 degrees C). Sorption capacities of mudrocks under dry conditions are greater than moisture equilibrated conditions due to water occupation of potential sorption sites. However,there is no consistent decrease of sorption capacity with increasing moisture as the relationship is masked by both the amount of organic matter and thermal maturation level. Clays also affect total gas capacities in as much as clay-rich mudrocks have high porosity which may be available for free gas. Gordondale samples enriched with carbonate(calcite and dolomite)typically have lower total porosities than carbonate-poor rocks and hence have lower potential free gas contents. On a regional reservoir scale,a large proportion of the Gordondale total gas capacity is free gas storage(intergranular porosity),ranging from 0.1-22 Bcf/section(0.003-0.66 m3/section). Total gas-in-place capacity ranges from 1-31.4 Bcf/section(0.03-0.94 m3/section). The greatest potential for gas production is in the south of the study area(93-P)due to higher thermal maturity,TOC enrichment,higher reservoir pressure,greater unit thickness and improved fracture-potential.
Keywords: shaly sand; pore-scale model; conductivity; clays
来源出版物:Bulletin of Canadian Petroleum Geology,2007,55(1): 51-75
Characterizing the shale gas resource potential of Devonian-Mississippian strata in the Western Canada sedimentary basin: Application of an integrated formation evaluation
Ross DJK,Bustin RM
Abstract: Devonian-Mississippian strata in the northwestern region of the Western Canada sedimentary basin(WCSB)were investigated for shale gas potential. In the subsurface,thermally mature strata of the Besa River,Horn River,Muskwa,and Fort Simpson formations attain thicknesses of more than 1 km(0.6 mi),encompassing an area of approximately 125000 km2(48300 mi2)and represent an enormous potential gas resource. Total gas capacity estimates range between 60 and 600 bcf/section. Of particular exploration interest are shales and mudrocks of the Horn River Formation(including the laterally equivalent lower Besa River mudrocks),Muskwa Formation,and upper Besa River Formation,which yield total organic carbon(TOC)contents of up to 5.7 wt.%. Fort Simpson shales seldom have TOC contents above 1 wt.%. Horn River and Muskwa formations have excellent shale gas potential in a region between longitudes 122°W and 123°W and latitudes 59°N and 60°N(National Topographic System [NTS] 94O08 to 94O15). In this area,which covers an areal extent of 6250 km2(2404 mi2),average TOC contents are higher(>3 wt.% as determined by wire-line-log calibrations),and have a stratal thickness of more than 200 m(656 ft). Gas capacities are estimated to be between 100 and 240 bcf/section and possibly greater than 400 tcf gas in place. A substantial percentage of the gas capacity is free gas caused by high reservoir temperatures and pressures. Muskwa shales have adsorbed gas capacities ranging between 0.3 and 0.5 cm3/g(9.6-16 scf/t)at reservoir temperatures of 60-80°C(140-176°F),whereas Besa River mudrocks and shales have low adsorbed gas capacities of less than 0.01 cm3/g(0.32 scf/t; Liard Basin region)because reservoir temperatures exceed 130°C(266°F). Potential free gas capacities range from 1.2 to 9.5 cm3/g(38.4 to 304 scf/t)when total pore volumes(0.4%-6.9%)are saturated with gas. The mineralogy has a major influence on total gas capacity. Carbonate-rich samples,indicative of adjacent carbonate platform and embayment successions,commonly have lower organic carbon content and porosity and corresponding lower gas capacity(<1% TOC and <1% porosity). Seaward of the carbonate Slave Point edge,Muskwa and lower Besa River mudrocks can be both silica and TOC rich(up to 92% quartz and 5 wt.% TOC)and most favorable for shale gas reservoir exploration because of possible fracture enhancement of the brittle organic- and siliceous-rich facies. However,an inverse relation between silica and porosity in some regions implies that zones with the best propensity for fracture completion may not provide optimal gas capacity,and a balance between favorable reservoir characteristics needs to be sought.
来源出版物:AAPG Bulletin,2008,92(1): 87-125
·推荐综述·
中国页岩气勘探开发进展与发展前景*
董大忠1,邹才能1,杨桦1,王玉满1,李新景1,陈更生2,王世谦2,吕宗刚2,黄勇斌2
(1. 中国石油勘探开发研究院,北京100083;2. 中国石油西南油气田公司,四川成都650001)
页岩气是典型的非常规天然气,产自极低孔渗、以富有机质页岩为主的储集岩系中.页岩气的形成与富集为自生自储、以游离气和吸附气为主、原位饱和富集于以页岩为主的储集岩系的微—纳米级孔隙—裂缝与矿物颗粒表面[1-2].页岩气常被称为“人造气藏”,开采必须通过大型人工储层造缝(网)才能形成工业生产能力,初期产量一般较高、早期递减较快,后期低产稳产且生产时间长(一般30-50年).页岩气是国外最早认识的天然气,自1821年在美国阿帕拉契亚盆地成功钻探第1口页岩气井以来,页岩气的发展已近200年历史.但20世纪90年代前,当时只重视了致密(岩石)气与煤层气,页岩气在天然气大家族中的地位微不足道[3],21世纪以来,随着页岩气地质与开发理论的创新和勘探开发关键技术的进步,尤其是水平井钻完井与分段压裂技术的进步及规模推广应用,页岩气迈进了大发展阶段.2005年以来,中国借鉴北美经验,开始了中国页岩气地质条件评价与勘探开发先导性试验[1,3-4].迄今,不仅在地质认识上取得进展,在勘探开发实践上也取得突破,成为全球除北美以外地区率先发现页岩气的国家.笔者在全球页岩气发展现状与中国页岩气勘探开发实践现状把握基础上,初步探讨了中国页岩气形成与富集条件,对中国页岩气勘探开发前景做了预测,以期对推动中国页岩气的发展有所帮助.
1全球页岩气资源发展概况
在全球,北美地区的页岩气资源勘探开发最为成功,2000年北美地区的页岩气年产量突破了100×108m3,至2010年该地区的页岩气年产量达到1500×108m3[3-7],10年间增长了10倍以上.美国能源信息署预测统计(图1)[5-7],2010年北美地区在约50个富有机质页岩区带中证实存在页岩气资源,在其中9个主要页岩区带进行页岩气生产,页岩气年产量1500×108m3,占北美天然气总产量的20%左右.
北美页岩气的快速发展,改变了北美天然气供应格局,影响到了全球能源供给格局的变化,页岩气在全球迅速成为重要的天然气勘探开发新目前.目前,全球掀起了轰轰烈烈的绿色“页岩气革命”(图2),各国政府和油气/能源公司几乎都将页岩气提到了重要日程[8],北美以外地区已有20余个国家在进行页岩气资源的前期评价和勘探开发先导试验,中国、英国、印度、新西兰等国已纷纷宣称在本国发现了页岩气.
中国为全球除北美以外地区率先发现页岩气的国家.至2010年,中国已在富有机质页岩地质特征、页岩气形成与富集地质条件、页岩气远景区带优选等基础地质理论与认识上取得重要了进展;在四川盆地南部古生界、四川盆地北部中生代、鄂尔多斯盆地三叠系等多个地区和多个时代的海相、陆相富有机质页岩中取得重要页岩气突破和发现.
2中国页岩气勘探开发进展
2.1中国页岩气勘探历程
与北美的页岩气勘探开发成就相比,中国的页岩气勘探开发起步较晚,而与全球其他地区相比,中国的页岩气勘探开发则处于领先地位,为全球除北美以外地区率先进入页岩气勘探评价突破和工业化开发先导性试验的国家[1-4].实际上,从历史发展分析,中国的油气勘探开发对页岩气并不陌生,过去的常规油气勘探开发中页岩气的发现已屡见不鲜.自20世纪60年代以来,不断在松辽、渤海湾、四川、鄂尔多斯、柴达木等几乎所有陆上含油气盆地中都发现了页岩气或泥页岩裂缝性油气藏,典型代表有1966年在四川盆地威远构造上钻探的威5井,在古生界寒武系筇竹寺组海相页岩中获得了日产气2.46×104m3.1994—1998年间中国还专门针对泥、页岩裂缝性油气藏做过大量工作,此后许多学者也在不同含油气盆地探索过页岩气形成与富集的可能性[2].2000—2005年中国广大石油地质学者再次关注北美在富有机质页岩中勘探开发天然气的新成就,从2005年起把视角投向中国本土,寻求中国页岩气形成与富集的地质条件,调查页岩气资源潜力,探索中国页岩气的发展前景.归纳起来,中国页岩气勘探开发历史暂可划分为泥页岩裂缝性油气藏勘探开发、页岩气地质条件研究与关键开发技术储备、勘探评价突破与开发先导性试验等过程,其里程碑事件总结于表1.
2.2中国页岩气勘探开发进展
中国的页岩气资源的勘探开发热潮始于2005年.在前期对北美页岩气资源发展进程的跟踪、研究基础上,于2005年起,中国主要石油企业、石油与地质类高等院校、国土资源部与国家能源局等相关政府机构[4],从老资料复查、露头地质调查等基础着手,开展了中国页岩气形成与富集地质条件研究和页岩气资源潜力评价,在页岩气远景区带进行了地质浅井、地质评价参数井等的钻探,取得了早期页岩气地质评价与页岩气资源潜力预测等关键参数,优选了一批有利页岩气区带,钻探了页岩气评价井和页岩气开发先导性试验井,建立了四川威远—长宁、云南昭通等多个国家级页岩气工业化开发先导性示范区(图3).
2006年中国石油与美国新田石油公司进行了国内首次页岩气研讨,依据四川盆地南部威远、阳高寺等地区的常规天然气勘探开发过程中,钻遇寒武系筇竹寺组和志留系龙马溪组时出现的丰富含气显示现象,提出中国具备海相页岩气形成与富集的基本地质条件[9-10].2007年即与新田石油合作,开展了威远地区寒武系筇竹寺组页岩气资源潜力评价与开发可行性的联合研究,该研究项目为中国与国外的第一个页岩气联合研究项目.与此同时,对整个蜀南地区古生代海相页岩地层开展了露头地质调查与老资料(井)复查.为探索页岩气地质与资源前景评价方法,2008年中国石油勘探开发研究院在四川盆地南部长宁构造志留系龙马溪组露头区钻探了中国第一口页岩气地质评价浅井即长芯1井,井深154.3 m,取心151.6 m[1].通过2007—2008年的前期地质研究与选区评价,初步认识到上扬子地区古生界发育多套海相富有机质页岩,厚度大,有机碳含量高,具有较好的页岩气形成条件.2009年中国石油率先在四川盆地威远—长宁、云南昭通等地区进行页岩气钻探评价,与壳牌(shell)公司在四川盆地富顺—永川地区进行中国第一个页岩气国际合作勘探开发项目.同时,国土资源部在全国油气资源战略选区调查与评价专项中设立了“中国重点地区页岩气资源潜力评价和有利区带优选”项目,中国石化在贵州大方—凯里方深1井区开展了寒武系牛蹄塘组页岩气老井复
查.2010年以来,中国页岩气勘探开发陆续取得单井突破,进入到了开发先导性试验区建设阶段.初步统计,迄今中国已在四川、鄂尔多斯、渤海湾、沁水、泌阳等盆地,重庆黔江、云南昭通、贵州大方湖北建南、湖南涟源、贵州铜仁等地区,钻探页岩气井(直井与水平井,直井为主)50余口,水力压裂试气井近20口,获工业页岩气(油)流井10口,多口井初期产量超过了1×104m3/d(图4),实现了中国海相(古生界)页岩气的突破,海陆过渡相煤系(二叠系)页岩气与陆相(中生界)页岩气/油的发现.
3中国页岩气勘探开发前景
3.1中国页岩气形成条件
与北美相比,中国页岩气形成与富集条件具明显特殊性,中国沉积盆地发育3类富有机质页岩[1-3,11-14],包括海相富有机质页岩、海陆过渡相与湖沼相煤系富有机质页岩和湖相富有机质页岩.不同时代、不同地区发育不同类型富有机质页岩组合,页岩成气潜力差异明显.
3.1.1海相富有机质页岩
中国海相富有机质页岩分布广泛,主要发育在中国南方地区、华北地区及西部塔里木盆地的上震旦统、下寒武统、上奥陶统—下志留统等(表2).海相富有机质泥页岩分布面积大、横向变化稳定,厚度一般在100~500 m.海相富有机质页岩有机质丰富,平均含量1.0%~5.12%,其中高TOC含量(TOC含量大于2%)的富含有机质页岩段发育,厚度一般为20~180 m.海相富有机质页岩有机质类型以腐泥型—混合型为主,属倾成油型母质,热演化程度处在裂解成气阶段(1.0%<Ro<5.2%)[11],页岩气以原油热裂解气为主.海相高演化页岩基质孔隙、有机质微—纳米级孔隙发育,构成了页岩气良好的储集空间.海相页岩脆性矿物丰富,黏土矿物单一.海相页岩成气藏条件优越,勘探开发前景好.
中国南方地区是海相页岩气较有利地区,尤以上扬子地区为好,如四川盆地筇竹寺组富有机质页岩分布面积18.5×104km2,厚200~600 m,有效页岩厚度110~163 m,TOC含量0.82%~4.68%,平均2.3%,页岩含气量0.13~5.02 m3/t,石英、长石和碳酸盐岩等脆性矿物为49%~58%;五峰组—龙马溪组富有机质页岩分布面积13.7×104km2,厚300~500 m,有效页岩厚度40~125 m,TOC含量0.5%~7.12%,平均2.1%,页岩含气量0.2~6.5 m3/t,石英、长石和碳酸盐岩等脆性矿物含量为33.0%~51.2%.2010年钻探的W201、N201两口页岩气评价井(直井),经大型水力压裂,在筇竹寺组页岩和五峰组—龙马溪组页岩中均获得了初始页岩气产量过1.0×104m3/d的高产页岩气流,实现了中国页岩气首次突破.
3.1.2海陆过渡相—煤系富有机质页岩
海陆过渡相—煤系富有机质页岩可划分为海陆过渡相、湖沼相煤系富有机质泥页岩[1-2,11-14].海陆过渡相富有机质泥页岩主要分布在中国东部的石炭系—二叠系[15]、南方的二叠系;湖沼相煤系富有机质泥页岩包括四川盆地及周缘的上三叠统—下侏罗统、中国西部地区的侏罗系,具有分布面积大、有机质类型复杂、热演化程度适中等特点[1-2](表3).
研究发现,中国海陆过渡相—煤系富有机质泥页岩除上扬子及滇黔桂地区单层厚度较大外,其余多数地区的海陆过渡相—煤系富有机质泥页岩单层厚度都不大,不利于页岩气单层独立开发.但海陆过渡相—煤系富有机质泥页岩总有机碳含量较高、演化程度一般在过成熟早期以下,有利于成气且泥页岩层多与煤、致密砂岩互层,易形成页岩气、煤层气和致密砂岩气等多种类型天然气藏叠置.
3.1.3陆相富有机质泥页岩
中国中生代、新生代盆地多为陆相沉积,深湖和半深湖相形成的富有机质黑色泥页岩是盆地的主力烃源岩[1-2,11-14].研究发现,现阶段多数泥页岩正进入大量生油期,仅在埋深较大的凹陷中的部分烃源岩才演化至生气阶段,因此,湖相页岩气勘探开发领域,将会是页岩油和页岩气并存的局面,纵向上具有“上油下气”的展布特点,横向上埋深大的凹陷区及近凹陷斜坡区是页岩气的主要富集区.渤海湾盆地沙河街组、松辽盆地青山口组、鄂尔多斯盆地延长组、四川盆地侏罗系等都具备湖相页岩气形成基本地质条件(表4).
3.2中国页岩气资源发展前景
有关中国页岩气资源发展前景,国内不少机构/学者对此做出了较为乐观的预测(表5).预测显示中国页岩气资源丰富,其中地质资源量为(30~166)×1012m3,技术可采资源量为(7~45)×1012m3.无论是从地质资源量还是技术可采资源量上看,中国页岩气资源都具备良好发展基础.甚至已有机构/学者根据资源预测结果及目前进展,认为中国未来5年将实现页岩气规模化生产,页岩气产量达到65×108m3,至2020年前后,突破页岩气勘探开发关键技术,页岩气产量有望达到(600~1000)×108m3[4].页岩气储层比任何致密油气储层都还要致密,实现有效开发难度非常大.中国的页岩气勘探开发虽已在先导性试验井中取得突破,但仍为起步阶段.中国页岩气地质条件与开发条件都与北美不同(表6).首先,从地质条件上看,中国的富有机质页岩,尤其是古生界海相富有机质页岩大多经历了复杂的构造改造,在盆地周缘页岩地层抬升出露、断裂切割严重,保存条件是海相页岩气勘探开发面临的严峻挑战;中国富有机质页岩热成熟度复杂,海相页岩形成时间早,演化程度高,陆相页岩形成时间晚,演化程度低,两个端元的热演化程度都将直接导致中国富有机质页岩含气量变化大、含气量偏低.其次,从开发条件上看,中国富有机质页岩在盆地内主体埋深较大,超过了3500 m或更大,在南方海相页岩发育区,地表多以山地和丘陵等复杂地表区为主,且不是常规油气生产的主产区,地面设施与管网缺乏.由此可见,中国页岩气资源丰富,具有良好发展前景,但是,中国页岩气地质与开发条件复杂,决定了中国页岩气勘探开发不会一蹴而就,需要一定时间准备与探索.未来5~10年需要坚持深化地质认识与技术攻关,突出基础地质研究、核心区评价和先导试验区建设.海相富有机质页岩气重在深化基础地质研究,落实经济可采资源,优选开发核心区,强化关键技术攻关,推进先导试验区建设,形成一定规模页岩气产量.海陆过渡相—煤系与湖相富有机质页岩以地质条件评价为重点,以技术可采资源潜力落实为核心,钻探一批先导试验井,优选有利页岩气区带和层系,实现中国页岩气持续稳定发展.
4结论
(1)中国页岩气勘探开发起步较晚,但在全球为北美以外地区率先进入页岩气勘探突破和工业化开发先导性试验的国家.中国页岩气地质条件研究与关键开发技术储备已有较好基础,在古生界海相、石炭-二叠系海陆过渡相—煤系与中生界-新生界陆相(湖相)页岩气/油上陆续取得单井突破与发现,正进入开发先导性试验区建设阶段.
(2)中国发育海相、海陆过渡相—陆相煤系与陆相湖相3类富有机质页岩,页岩气资源潜力大.古生界海相页岩分布面积广,厚度大,有机碳含量丰富,成熟度高,页岩气形成与富集条件优越,是中国页岩气开发的重点领域.
(3)中国页岩气资源发展前景良好,目前勘探开发程度低,与北美典型页岩气产区地质与开发条件有明显差异,未来发展,需要借鉴北美的成功经验,针对中国的特点,加强基础地质条件和关键开发技术攻关,努力寻求环境友好、低成本的开发模式.
中国页岩气形成机理、地质特征及资源潜力*
邹才能1,2,董大忠1,2,王社教1,2,李建忠1,2,李新景1,2,王玉满1,2,李登华1,2,程克明1,2
(1. 中国石油勘探开发研究院;2. 提高石油采收率国家重点实验室)
1页岩气勘探开发现状
油气工业的生命周期大致有300年(1880—2180年)历史,发展主要历经构造油气藏、岩性地层油气藏、非常规油气藏(场)勘探开发3个阶段和三大领域.油气藏分布方式分别有单体型、集群型、连续型3种类型.从构造油气藏向岩性地层油气藏转变是第一次理论技术创新,以寻找油气圈闭为核心;从岩性地层圈闭油气藏向非常规连续型油气藏转变是第二次理论技术创新或革命,以寻找有利油气储集体为核心,致密化“减孔成藏”机理新论点突破了常规储集层物性下限与传统圈闭找油的理念[1].随着勘探开发技术不断进步,占有80%左右资源的非常规油气(一般将空气渗透率大于1×10-3μm2或地层渗透率大于0.1×10-3μm2储集层内的油气称为常规油气,把空气渗透率小于1×10-3μm2或地层渗透率小于0.1×10-3μm2的油气称为非常规油气)如页岩气、煤层气、致密气、致密油、页岩油等已引起广泛关注(见图1),并得到有效开发,在油气储、产量中所占比例也逐年提高.传统观点仅认识到页岩可生油、生气,没认识到页岩亦可储油、储气,更未认识到还能聚集工业性页岩油、页岩气.近年来,典型页岩气的发展尤为迅速,地质认识不断进步,优选核心区方法、实验分析技术、测井评价技术、资源评价技术、页岩储集层水平井钻完井、同步多级并重复压裂等先进技术获得应用,形成“人造气”是页岩气快速发展的关键因素.页岩气突破的意义在于:突破资源禁区,增加资源类型与资源量;挑战储集层极限,实现油气理论技术升级换代,水平井多级压裂等核心技术应用于其他致密油气等非常规和常规油气储集层中更加经济有效,可大幅度提高油气采收率;带动非常规油气技术发展,推动致密油气、页岩油等更快成为常规领域.
全球页岩气勘探开发自1821年在美国东部泥盆系页岩中钻成第1口页岩气井、1914年发现第1个页岩气田——Big Sandy气田[2]以来,历经1821—1978年偶然发现、1978—2003年认识创新与技术突破、2003—2006年水平井与水力压裂等技术推广应用、2007—2010年全球化发展(页岩气中国年、欧州年)等4个阶段.1981年被誉为“页岩气之父”的乔治·米歇尔对Barnet t页岩C. W. Slay No. 1井实施大规模压裂并获成功以来,实现了真正意义的页岩气突破.至2009年底,北美发现页岩气盆地30个,开发井50000余口,井深2500~4500 m;2009年年产量950×108m3[3],占北美天然气总产量的12%(其中美国产量889×108m3).中国页岩气走过了裂缝油气藏勘探与偶然发现(2005年以前)、基础研究与技术准备(2005—2009年)和工业化突破(2010年)等3个阶段.1966年四川威5井在寒武系筇竹寺组页岩中获日产气2.46×104m3,为中国最早的页岩产气井[4];2008年中国石油勘探开发研究院在四川长宁地区钻探的长芯1井[5]为中国第1口页岩气地质井;2009年中国石油在四川威远-长宁、富顺-永川等地区启动了首批页岩气工业化试验区建设;2010年中国石油勘探开发研究院在四川长宁地区建立了第1条中国页岩气数字化标准剖面;2010年中国石油钻探的四川盆地威201井在寒武系、志留系页岩中获工业气流,实现中国页岩气首次工业化突破.
北美地区经过多年的研究和开发实践,在页岩气形成机理、富集条件等方面已形成重要认识和技术[6-15].本文重点分析中国页岩气基本特征、形成机理与富集条件、面临的难题等,对中国页岩气资源潜力进行预测,以期为中国页岩气的研究和勘探开发提供依据.
2中国富有机质页岩分布特征
源岩油气是一种新资源类型,包括页岩油、页岩气、煤层气等,自生自储,主要产自源岩内储集层中.
页岩(shale)是由粒径小于0.0039 mm的细粒碎屑、黏土、有机质等组成,具页状或薄片状层理、易碎裂的一类沉积岩,亦即美国所称的粒径小于0.0039 mm的细粒沉积岩.
页岩气(shale gas)是指从富有机质黑色页岩中开采的天然气,或自生自储、在页岩纳米级孔隙中连续聚集的天然气.
中国3类富有机质页岩泛指海相、海陆交互相以及陆相页岩和泥岩,重点指含油气盆地中的优质泥质烃源岩,图2为依据中国页岩发育的层系和分布特点编制的3类页岩分布图.中国南方扬子地区海相页岩多为硅质页岩(如扬子地区牛蹄塘组底部页岩)、黑色页岩、钙质页岩和砂质页岩,风化后呈薄片状,页理发育.海陆过渡相页岩多为砂质页岩和炭质页岩.陆相页岩页理发育,渤海湾盆地、柴达木盆地新生界陆相页岩钙质含量高,为钙质页岩,鄂尔多斯盆地中生界陆相页岩石英含量较高.
2.1富含页岩气的核心区特征
目前进行页岩气经济开发的核心区有5个富集高产条件(见表1),通常是指TOC值大于2%、处在生气窗内、脆性矿物含量大于40%的有效页岩.有效页岩厚度大于30~50 m(有效页岩连续发育时大于30 m,断续发育或TOC值小于2%时,累计厚度大于50 m)时亦足以满足商业开发要求.北美产气页岩有效厚度最小为6 m(Fayet teville),最大为304 m(Marcellus),核心区有效页岩厚度均大于30 m.
基于北美页岩气勘探开发实践、统计分析及关键实验等结果,认为有利页岩气及核心区具有4方面主要地质特征和3方面主要开发特点,详见表1.
2.2中国页岩形成的区域地质背景
古生代,在中国南方、华北及塔里木地区形成了广泛的海相和海陆过渡相沉积,发育多套海相富有机质页岩和海陆过渡相煤系炭质页岩[6].在后期改造过程中,部分古生界海相页岩经历了挤压变形或隆升,如南方的扬子地区,多为后期隆升改造.四川盆地、华北地区、塔里木盆地构造相对稳定,地层保存条件较好.
中、新生代以来,形成了中国独特的陆相湖盆沉积[6].陆相沉积盆地一般面积不大,但在盆地稳定沉降阶段常形成分布广泛的陆相生油岩,生烃潜力很大[6],如松辽盆地下白垩统青山口组、鄂尔多斯盆地上三叠统延长组陆相页岩,均是盆地主要烃源岩.
2.3页岩的沉积特征
盆地不同演化阶段直接控制富有机质页岩的发育与分布[16].根据沉积环境,可将富有机质页岩划分为海相页岩、海陆交互相煤系炭质页岩、陆相页岩3种基本类型(见表2).
中国南方、华北地台及塔里木地台发育的古生界海相黑色页岩多形成于水深200 m左右、生物化石丰富、强还原环境的深水陆棚相,如四川盆地发育的寒武系筇竹寺组、志留系龙马溪组黑色页岩为受大陆边缘坳陷控制的深水陆棚相沉积[17](见图3),富有机质黑色页岩面积13.5×104~18.0×104km2,厚200~400 m,有机质丰富,含海洋浮游生物笔石化石及自生黄铁矿等,有机碳含量1.85% ~4.36%,最高达11.0%~22.3%.在这两套黑色页岩中均发现了大量页岩气.
海陆过渡相形成的煤系页岩,如鄂尔多斯盆地石炭系本溪组及下二叠统山西组-太原组、准噶尔盆地石炭-二叠系、塔里木盆地石炭-二叠系、华北地区石炭-二叠系、中国南方地区的二叠系龙潭组等,也是大型油气田的主要烃源岩,如鄂尔多斯盆地上古生界炭质页岩是苏里格等大气区的主要气源岩.三叠系-侏罗系和第三系发育多套与煤层相伴生的炭质页岩,同样亦是优质气源岩,吐哈盆地发现的油气田多数来源于侏罗系煤系页岩.
中国发育陆相含油气盆地页岩:渤海湾盆地古近纪、松辽盆地白垩纪、鄂尔多斯盆地三叠纪、四川盆地侏罗纪、塔里木盆地三叠纪)侏罗纪、准噶尔盆地侏罗纪均为大型湖盆沉积,在湖盆的扩张期,形成了分布广泛且厚度大的湖相页岩,有机质十分丰富,含介形虫、孢粉、细菌、高等植物等化石,厚度200~2500 m,有机碳含量2%~3%,最高达到7%~14%.在中新生代发现了众多规模不等的油气聚集带[18],大庆油田、胜利油田、辽河油田、鄂尔多斯中生界油气聚集区等,其油气就源于该套湖相泥岩.
2.4页岩的分布特征
中国海相页岩十分发育,分布广、厚度大[19].主要发育在古生界的陡山沱组(Z2)、筇竹寺竹组(-C1)、大乘寺组(O1)、五峰-龙马溪组(O3-S1)、罗富组(D2)、德坞组-大塘组(C1)、龙潭组(P2)(见表3).发育最好的页岩分布在下寒武统、上奥陶统顶部-下志留统底部,以扬子克拉通地区最为典型.
下寒武统海相页岩在中上扬子区发育好,有机质类型为腐泥型-混合型.从沉积环境看,川东-鄂西、川南及湘黔3个深水陆棚区下寒武统海相页岩最发育[20],平均厚度100 m,TOC值平均高达8%左右.四川盆地下寒武统海相页岩全盆地发育,以硅质页岩、炭质页岩、粉沙质页岩和黑色页岩为主,厚度平均为139 m,TOC值平均1.0%~5.5%,盆地南部页岩埋藏浅于4000 m.
上奥陶统-下志留统海相页岩在川东南、川东北、鄂西渝东、中下扬子等区广泛发育[5],以黑色页岩、炭质页岩、黑色笔石页岩、钙质页岩为主,平均厚120 m,TOC值平均4%左右,干酪根为腐泥型.四川盆地上奥陶统-下志留统海相页岩在川南-川东地区发育较好.据笔者综合运用伽马能谱、元素捕获、探地雷达及陆地激光三维全信息扫描等手段建立的长宁双河上奥陶统五峰组-下志留统龙马溪组海相页岩地层数字化标准剖面(见图4)统计,川南上奥陶统五峰组-下志留统龙马溪组黑色页岩厚度大于308 m,有机质类型为腐泥型,TOC值平均2.94%,最高达8.75%.
海陆交互相及陆相煤系炭质页岩在华北、华南地区和塔里木盆地广泛分布(见表4).北部主要发育在天山-兴蒙海槽.鄂尔多斯盆地海陆交互相山西组-太原组-本溪组页岩厚40~120 m,单层厚度不大,多数与煤层、致密砂岩甚至薄层灰岩交互出现.准噶尔盆地石炭系滴水泉组炭质页岩最厚达249 m,二叠系芦草沟组黑色页岩累计厚度超过200 m.中国南方地区的二叠系龙潭组(P2)炭质页岩厚20~200 m,最厚达670 m,分布面积约30×104~50×104km2.其中,滇黔桂地区上二叠统龙潭组页岩厚度为20~60 m,四川盆地上二叠统页岩厚10~125 m,川中和川西南一带厚80~110 m,四川盆地西北缘、北缘及东北缘较薄,多小于20 m.中新生代陆相煤系炭质页岩主要发育在坳陷和断陷湖盆中,如鄂尔多斯盆地和准噶尔盆地侏罗系、四川盆地上三叠统(厚150~1000m)、吐哈盆地侏罗系(厚50~400 m,最厚达1200 m)等.
总体上,中国海陆交互相和中新生代陆相炭质页岩除上扬子及滇黔桂地区单层厚度较大外,多数地区单层厚度都不大,常与煤和致密砂岩甚至灰岩互层,单层平均厚度一般小于15 m,单独开发这套薄层煤系页岩气将面临很大的挑战,进行页岩气、致密气、煤层气等多目的层联合开发是有效开发的新途径.
主要分布于陆相含油气盆地的湖相页岩沉积范围最广(见表5),广泛发育湖相页岩油、致密砂岩油与致密页岩油.松辽、鄂尔多斯、四川等中新生代坳陷盆地[21]及渤海湾新生代断陷盆地都沉积了厚层湖相富有机质页岩、砂岩与泥岩[22].如松辽盆地嫩江组和青山口组两套页岩十分发育,嫩江组在全盆地稳定分布,中央坳陷区厚度超过250 m,青山口组一段在中央坳陷区几乎全部为黑色页岩,厚度为60~80 m,干酪根类型为ⅳ—型,Ro值为0.9%~1.8%.鄂尔多斯盆地延长组长7段主要为深湖相沉积,富有机质页岩平均厚度20~40 m,分布面积超过4×104km2,有机碳含量平均高达14%,干酪根类型为ⅳ—型,Ro值为0.6%~1.2%.最近,在该套湖相页岩地层内发现了大量致密油,油层为厚10~20 m、孔隙度10.2%、渗透率0.21×10-3μm2的致密粉砂岩,有工业油气流井近200口,平均产量8.6 t/d.该特征与北美在Williston盆地Bakken页岩层中发现的致密油极为相似[23].Bakken地层位于上泥盆统顶部,由下向上分9段,最下面第1段页岩厚度12~15 m,TOC值高达14%~18%,Ro值为1.1%~1.3%,为富有机质页岩层.上覆第2段致密粉砂岩油层孔隙度10%~13%,渗透率0.01×10-3~1×10-3μm2,厚5~15 m,面积约75563 km2,1999年USGS专家估算页岩中致密油地质资源量为578×108t,一般预测为241×108~518×108t.致密油是继页岩气突破后又一重大发现,成为新亮点.
3中国页岩气地球化学特征
页岩气是富有机质烃源岩层系中以甲烷为主的天然气.作为一种重要的“有机矿物颗粒”,有机质不仅为常规油气藏提供丰富的物质基础,其自身也可以储集并产出油气.大量研究表明,对于热成因页岩气区带的初步筛选,通常要求页岩达到某些地球化学指标,如:有机质丰度(TOC)大于2%,成熟度(Ro)大于1.1%,满足这些约束条件的地区,可有效降低页岩气勘探开发风险.
3.1页岩的基本地球化学特征
中国海相、海陆交互相以及陆相页岩广泛分布[24-27],不同沉积环境形成的有机质类型不同,倾油、倾气性也有差别,很多盆地或区块达到富集页岩气所需基本地球化学标准(见表6).四川盆地下古生界寒武系筇竹寺组和志留系龙马溪组两套海相黑色页岩属ⅳ—1型干酪根,显示良好的倾油性,当Ro值高于1.2%时,在高过成熟的页岩地层中,先生油,后裂解成气,形成海相页岩“连续”生气与聚气.中国北方古生界石炭-二叠系、中生界侏罗系含煤层系炭质页岩作为重要的气源岩,已形成了大规模天然气聚集,有机质主要是型,属腐殖型干酪根,在整个成熟演化阶段,以成气为主:Ro值为1.0%时,天然气转化率已达到40%以上;Ro值为2.5%时,天然气转化率达到95%;Ro值为0.8%~2.5%是煤系有机质主生气期[28].富氢组分含量相对较高区块,更有利于形成页岩气富集区.可见,中国的3类主要页岩具备形成页岩气资源的条件.
中国页岩气潜力区的部分地球化学特征不同于北美页岩气主产区.如:包括四川盆地在内的扬子地台大部分地区古生界烃源岩是区域主力烃源,虽属ⅳ型干酪根,但成熟度普遍为高或过成熟,连续生油、生气、聚气,残余生烃潜力低;中国大中型煤型气田,如鄂尔多斯、塔里木、华北地区上古生界石炭-二叠系炭质页岩,其有机质丰度一般都比较高,Ro值为1.1%~2.5%,有机质类型则多为型;鄂尔多斯盆地中生界三叠系长7黑色页岩为优质烃源岩,呈较高自然伽马、高电阻率、较低密度、高声波时差,有机质类型为ⅳ型,具有很高的生烃潜力,但Ro值为0.90%~1.16%,尚属生油高峰阶段.
中国陆相地层中广泛发育页岩油.页岩油是生油岩内纳米-微米级孔隙与裂缝聚集的石油,如在松辽盆地古龙凹陷已发现下白垩统青山口组和嫩江组页岩油聚集,页岩富有机质,总厚300~620 m,一般异常高压,干酪根为ⅳ—型,Ro值为0.9%~1.2%.最早在大安构造大4井青山口组泥岩段获日产油2.66 t,另有50余口井见油气显示,4口井产少量油气-古501井、英15井、英3井、大111井),5口井获工业油气流(英12井、英18井、英16井、古1井、大4井).盆地南部新北油田泥岩裂缝性油藏几口井已开采10余年,累计产油超过3×104t.鄂尔多斯、渤海湾等盆地生油层系中也发育页岩油.页岩油是页岩气之后又一“源岩油”领域,值得重视.
3.2关键地球化学参数与页岩储集能力的相关性
自生自储的页岩气储集层,其有机地球化学关键参数,如有机质丰度和成熟度等,与页岩储集层含气性、储集空间的发育密不可分.北美地区页岩含气量往往与有机质丰度(TOC)呈正相关性,ⅳ、型干酪根往往具有较高的吸附能力[29].中国四川盆地高)过成熟海相页岩实验测试数据也证明,有机质丰度高者,含气量相对丰富,更有条件成为优质页岩储集层.
随着成熟度增加,干酪根、原油热裂解大量生烃,除了生成大量油气、为常规油气藏提供丰富的物质来源之外,有机质本身可产生5~200 nm左右纳米级孔隙[30].笔者在对中国四川盆地寒武系和志留系高-过成熟海相页岩储集层的研究中首次发现,这两套地层下部不仅有机质丰度高、含气量高,而且呈分散状、纹层状分布的“有机质颗粒”内部形成大量微米-纳米级孔隙(见图5),这些孔隙大者3~4 μm,小至几个纳米,一般都大于100~200 nm,为丰富的页岩气资源提供了充足的储集空间,有力地说明中国南方致密的海相页岩具备优质储集条件,在有机质丰度比较高的层段和区域,勘探开发前景良好.澳大利亚Beetaloo盆地在全球最老地层(约14×108a)——元古界发现了页岩气,有机碳含量4%,Ro值高达3.49%,预测页岩气资源量5600×108m3.
4页岩气形成机理及储集层特征
4.1页岩气形成机理
页岩气形成机制是原位“滞留成藏”,连续型分布.甲烷在页岩微孔(孔径小于2 nm)中顺序填充,在介孔(孔径为2~50 nm)中多层吸附至毛细管凝聚,在大孔(孔径大于50 nm)中甲烷以压缩或溶解态赋存.成藏中经过吸附、解吸、扩散等作用.有机质生气或油裂解成气,天然气先在有机质孔内表面饱和吸附;之后解吸扩散至基质孔中,以吸附、游离相原位饱和聚集;过饱和气初次运移至上覆无机质页岩孔中;气再饱和后,二次运移形成气藏(见图6)[31,32].
4.2岩石矿物组成
脆性矿物含量是影响页岩基质孔隙和微裂缝发育程度、含气性及压裂改造方式等的重要因素.页岩中黏土矿物含量越低,石英、长石、方解石等脆性矿物含量越高,岩石脆性越强,在人工压裂外力作用下越易形成天然裂缝和诱导裂缝,形成多树-网状结构缝,有利于页岩气开采.而高黏土矿物含量的页岩塑性强,吸收能量,以形成平面裂缝为主,不利于页岩体积改造.美国产气页岩中石英含量为28%~52%、碳酸盐含量4%~16%,总脆性矿物含量为46%~60%.笔者对中国3种不同类型页岩的矿物组成进行测试后发现,无论是海相页岩、海陆过渡相炭质页岩,还是陆相页岩,其脆性矿物含量总体比较高,均达到40%以上,如:上扬子区古生界海相页岩石英含量24.3%~52.0%、长石含量4.3%~32.3%、方解石含量8.5%~16.9%,总脆性矿物含量40%~80%(见表7、图7);四川盆地上三叠统须家河组黏土矿物含量一般为15%~78%,平均为50%左右,石英、长石等脆性矿物含量一般为22%~85%,平均为50%左右.鄂尔多斯盆地上古生界含煤层系炭质页岩石英含量32%~54%,平均48%,总脆性矿物含量40%~58%;鄂尔多斯盆地中生界陆相页岩石英含量27% 47%,平均40%,总脆性矿物含量58%~70%.
岩石矿物组成对页岩气后期开发至关重要,具备商业性开发条件的页岩,一般其脆性矿物含量要高于40%,黏土矿物含量小于30%.
4.3孔渗特征与微裂缝
4.3.1孔渗特征
岩石孔隙是储存油气的重要空间和确定游离气含量的关键参数.据统计,有平均50%左右的页岩气存储在页岩基质孔隙中.页岩储集层为特低孔渗储集层,以发育多类型微米甚至纳米级孔隙为特征,包括颗粒间微孔、黏土片间微孔、颗粒溶孔、溶蚀杂基内孔、粒内溶蚀孔及有机质孔等.孔隙大小一般小于2 μm,有机质孔喉一般100~200 nm,比表面积大,结构复杂,丰富的内表面积可以通过吸附方式储存大量气体[33].一般页岩的基质孔隙度为0.5%~6.0%,众数多为2%~4%.四川盆地华蓥山红岩煤矿龙马溪组和威远地区筇竹寺组页岩实测结果:龙马溪组页岩孔隙度为2. 43%~15.72%,平均4.83%;筇竹寺组页岩孔隙度为0.34%~8.10%,平均3.02%.鄂尔多斯盆地中生界陆相页岩实测孔隙度0.4%~1.5%,渗透率0.012×10-3~0.653×10-3μm2.
中国海相富有机质页岩微米-纳米孔十分发育(见图5),既有粒间孔,也有粒内孔和有机质孔,尤其有机质成熟后形成的纳米级孔喉甚为发育,这些纳米级孔喉是页岩气赋存的主要空间.
4.3.2微裂缝
裂缝包括地下原始裂缝和后期人造裂缝,可为页岩气提供充足的储集空间、运移通道,更能有效提高页岩气产量[2].在不发育裂隙情况下,页岩渗透能力非常低.石英含量的高低是影响裂缝发育的重要因素,富含石英的黑色泥页岩段脆性好,裂缝的发育程度比富含方解石的泥页岩更强[34].Nelson认为,除石英外,长石和白云石也是泥页岩中脆性组分[35].一般页岩中具有高含量的黏土矿物,但暗色富有机质页岩中的黏土矿物含量通常则较低.页岩气勘探必须寻找能够压裂成缝的页岩,即页岩的黏土矿物含量足够低(<50%)、脆性矿物含量丰富,使其易于成功压裂.中国海相页岩、海陆交互相炭质页岩和陆相页岩均具有较好的脆性特征,无论是野外地质剖面还是井下岩心观察,发现其均发育较多的裂缝系统.如:上扬子地区寒武系筇竹寺组、志留系龙马溪组黑色页岩性脆、质硬,节理和裂缝发育,在三维空间成网络状分布,岩石薄片显示,微裂缝细如发丝,部分被方解石、沥青等次生矿物充填;鄂尔多斯盆地上古生界山西组岩心切片可看到呈网状分布的微裂缝;鄂尔多斯盆地中生界长7段黑色页岩页理十分发育,风化后呈薄片状.
4.4含气性
页岩气区根据含气性可划分为核心区、外围区.页岩含气量是衡量页岩气核心区是否具经济开采价值和进行资源潜力评估评价的重要指标,页岩含气量包括游离气、吸附气及溶解气等.哈里伯顿公司认为商业开发远景区的页岩含气量最低为2.8 m3/t,目前北美已商业开发的页岩气,其含气量最低约为1.1 m3/t,最高达9.91 m3/t.实测发现四川盆地下寒武统寒武系筇竹寺组黑色页岩含气量为1.17~6.02 m3/t,平均2.82 m3/t,龙马溪组黑色页岩含气量为1.73~3.28 m3/t,与北美产气页岩的含气量(见表7)相比,均达到了商业性页岩气开发下限,具备商业性开发价值.由于中国页岩气尚未进入开发阶段,钻探页岩气井少,因此无法获取更多的页岩含气量数据.但根据老井复查结果,在已往的钻井中,钻遇的黑色页岩段发现了大量的气测显示,有井涌和井喷现象发生,证明页岩段含气性很好.如:四川盆地威远地区钻穿筇竹寺组的107口井中,32口井52个井段出现不同级别气测显示,威5井在钻至2795~2798 m筇竹寺组页岩层段时发生井喷,中途测试获日产2.46×104m3的天然;钻穿川南地区下志留统龙马溪组页岩层段的15口井中32个层段见良好气测显示,阳63井3505~3518 m龙马溪组页岩段测试后获日产天然气3500 m3.
5资源潜力及特殊性
有不少学者或机构对中国页岩气资源潜力做过预测,总体评价偏乐观[36-38].
页岩气与常规气存在明显差异,不仅包括地质条件的不确定性,也有开发中的经济风险性,尤其是采收率的确定需要依赖井控数据.因此,客观、准确预测页岩气资源潜力具挑战性.
中国页岩气勘探开发尚处于起步阶段,可用于页岩气资源潜力预测的资料非常有限.尽管中国不同地区在富有机质页岩发育规模、页岩质量等方面具广泛的相似性,但中国地质条件复杂,尤其是构造演化、沉积环境、热演化过程等,使不同地区页岩气形成、富集存在许多差异.中国古生界海相富有机质页岩分布范围广、连续厚度大、有机质丰度高,但演化程度高、构造变动多;中新生界陆相富有机质页岩横向变化大,以厚层泥岩或砂泥互层为主,有机质丰度中等,热成熟度低.因此,基于地质类比对中国页岩气资源潜力进行预测.中国古生界海相富有机质页岩有利领域展布面积63×104~90×104km2,中新生界陆相富有机质泥页岩有利领域展布面积23×104~33×104km2,有效页岩厚度20~300 m,有机碳含量0.50%~25.71%,Ro值为0.8%~4.5%,预测页岩气资源量30×1012~100×1012m8,这些预测数据都是初步结果,而中国页岩气的技术与经济可采资源量正在研究之中.
目前,中国已在四川盆地南部等地区启动了多个页岩气工业化生产试验区建设,已取得突破;正在开展的中下扬子、鄂尔多斯、塔里木等地区的前期评价,将优选出页岩气有利接替地区.开发页岩气对缓解中国天然气资源紧缺现状、改变能源结构、保障国家能源安全具有战略意义,同时对石油地质理论创新与勘探开发技术革新也有重大科学价值.
中国页岩气与北美页岩气对比,有3个特殊性:海相页岩热演化程度较高(Ro值为2.5%~5.0%)、构造活动较强,需寻找保存条件有利的地区,避开露头和断裂破坏区;陆相页岩热演化程度较低、分布非均质性较强,有效开发需针对性技术;地面多山地、丘陵等复杂地表,埋藏较深(5000~7000 m),还面临水资源与环保等问题,需采用适用技术降低成本.因此,中国页岩气勘探开发应特别注意复杂地表、埋藏深度、后期保存等特殊地质条件,如塔里木盆地海相页岩埋藏深度大,南方部分地区页岩出露后面临保存、开发中地表多山地等难题,因此,要加强有利核心区优选与经济评价.
6结论
中国陆上广泛发育海相、海陆过渡相、陆相三大套富有机质黑色泥页岩,均具备形成页岩气的基本地质条件.它们有共性,也有特殊性,勘探开发实践与研究中一定要注意区别对待.盆地内古生界页岩以海相沉积为主,区域稳定分布,厚度大,有机质丰富,演化程度高,已见大量气显示,是页岩气勘探开发的现实领域.
中国石炭-二叠系、三叠-侏罗系煤系中发育高炭泥页岩、煤层,与砂岩伴生,连续分布有页岩气与致密气.中新生界陆相泥页岩、泥岩与砂岩、灰岩互层,成熟度低,连续分布的页岩油与致密油是战略新领域.
源岩油气是新领域,包括页岩油、页岩气、煤层气等形成机制是原位“滞留成藏”.页岩气与上下连续型分布的致密砂岩气、煤层气等同步开发,可提高产量和效益.
四川盆地内发育海相、海陆过渡相、陆相多套页岩气层系,是中国页岩气勘探开发最现实的地区.四川盆地古生界页岩地层发育丰富的微米-纳米级孔隙,页岩含气饱和度较高,盆地中南部的威远-长宁等地区是页岩气有利分布区,也是勘探开发突破的重要核心区之一.对中国其他盆地要加强核心区优选与经济评价.
·高被引论文摘要·
被引频次:628
页岩气成藏机理和分布
张金川,金之钧,袁明生
对页岩气成藏机理进行了全面分析,获得了四个方面的认识.①页岩气成藏机理兼具煤层吸附气和常规圈闭气藏特征,体现出了复杂的多机理递变特点.②在页岩气的成藏过程中,天然气的赋存方式和成藏类型逐渐改变,含气丰度和富集程度逐渐增加.③完整的页岩气成藏与演化可分为3个主要的作用过程,自身构成了从吸附聚集、膨胀造隙富集到活塞式推进或置换式运移的机理序列.④相应的成藏条件和成藏机理变化对页岩气的成藏与分布产生了控制和影响作用,岩性特征变化和裂缝发育状况对页岩气藏中天然气的赋存特征和分布规律具有控制作用.研究了我国的情况,认为我国的许多盆地存在工业性页岩气藏发育的基本地质条件,其中,吐哈盆地吐鲁番坳陷的水西沟群是页岩气发育的重要区域之一.
页岩气;赋存状态;成藏机理;序列递变
来源出版物:天然气工业,2004,24(7): 15-18联系邮箱:张金川,zhangjc@cugb.edu.cn
被引频次:352
中国页岩气形成机理、地质特征及资源潜力
邹才能,董大忠,王社教,等
摘要:以四川盆地为重点,介绍中国海相、海陆过渡相、陆相三大类型页岩形成的沉积环境、地球化学与储集层特征、含气量与远景资源量.中国海相页岩是一套高有机质丰度(TOC为1.0%~5.5%)、高—过成熟(Ro值为2.0%~5.0%)、富含页岩气(含气量1.17~6.02 m3/t)、以陆棚相为主的沉积,主要分布在华南扬子地区古生界、华北地台古生界和塔里木盆地寒武系—奥陶系;海陆过渡相煤系炭质页岩有机质丰度高(TOC为2.6%~5.4%)、成熟度适中(Ro值为1.1%~2.5%);中新生界陆相页岩有机质丰度高(TOC为0.5%~22.0%)、低熟—成熟(Ro值为0.6%~1.5%).在对四川盆地下古生界页岩储集层研究中首次发现,寒武系和志留系海相页岩发育大量与北美地区相似的微米—纳米级孔隙.综合评价认为四川盆地发育的多套页岩气层系是勘探开发的现实领域,四川盆地中南部威远—长宁等地区的寒武系和志留系是页岩气勘探开发的核心区与层系,其特点是:热演化程度较高(Ro值为2.0%~4.0%)、孔隙度较高(3.0%~4.8%),含气量较高(2.82~3.28 m3/t)、脆性矿物含量较高(40%~80%)、埋深适中(1500~4500 m),有利于开采.
关键词:非常规油气;页岩气;纳米级孔喉;页岩油;致密油;源岩油气
来源出版物:石油勘探与开发,2010,37(6): 641-653
被引频次:327
中国页岩气资源勘探潜力
张金川,徐波,聂海宽,等
摘要:页岩气是以吸附和游离状态同时存在于泥页岩地层中的天然气,它分别在天然气的成因机理、赋存相态、成藏聚集机理、分布变化特点及其与其他类型气藏关系之间存在广泛的变化性.由于页岩气成藏边界条件可有适度地放宽且变化较大,各成藏地质要素之间具有明显的互补性.基于地质、测井、地震等方法和手段,可对页岩气进行快速识别.研究表明,中国存在页岩气大量发育的区域地质条件,初步计算中国页岩气资源量约为(15~30)×1012m3.平面上以中国南方和西北地区最为有利(也包括鄂尔多斯盆地及其周缘),剖面上以古生界资源量为最大,中生界位居其次.
关键词:中国;页岩气;地质特征;有利区;分布;资源量;潜力
来源出版物:天然气工业,2008,28(6): 136-140联系邮箱:张金川,zhangjc@cugb.edu.cn
被引频次:313
北美裂缝性页岩气勘探开发的启示
李新景,胡素云,程克明
摘要:北美实践证明,非常规油气资源——页岩气是现实的接替能源了,勘探风险在于能否从低渗透的页岩储集层中获取经济可采储量,勘探目标是有机质和硅质含量高、裂缝发育的脆性优质烃源岩.页岩气生产机制复杂,涉及吸附气与游离气、天然裂缝与诱导裂缝系统之间的相互关系.在地质、地化、测井和地震综合评价基础上,通过水力压裂等增产措施提高储集层渗透能力是页岩气开采的关键.中国广泛分布海相和湖相细粒碎屑岩,有效烃源岩多富含炭质、灰质或硅质,已陆续发现裂缝性油气藏,有条件寻找丰富的页岩气资源,特别是液态烃在高成熟或过成熟阶段裂解产生的甲烷气滞留在烃源岩内形成的连续分布式非常规页岩气资源.
关键词:页岩气;吸附气;裂缝;压裂;烃源岩储集层
来源出版物:石油勘探与开发,2007,34(4): 392-400
被引频次:283
页岩气成藏控制因素及中国南方页岩气发育有利区预测
聂海宽,唐玄,边瑞康
摘要:在系统研究美国页岩气成藏理论和成藏条件的基础上,分析了页岩气成藏的主要控制因素,分为内部因素和外部因素:前者指页岩本身的因素,包括有机质类型和含量、成熟度、裂缝、孔隙度和渗透率、矿物组成、厚度、湿度等;后者主要包括深度、温度和压力等.其中,有机质类型和含量、成熟度、裂缝及孔隙度和渗透率是控制页岩气成藏的主要因素.结合主要影响参数,建立了预测页岩含气的种类、比例和页岩气藏发育有利区的参数模型.运用此模型类比研究发现,中国南方古生界海相页岩层中,寒武系和志留系是页岩气发育的最有利层系.寒武系页岩气藏发育最有利区位于四川盆地和米仓山—大巴山前陆以及渝东、黔北、湘西—江南隆起北缘一线;志留系页岩气藏发育最有利区位于上扬子的四川盆地和米仓山—大巴山前陆和渝东—鄂西一带、中扬子鄂北以及下扬子苏南等地.并对各有利区的泥页岩指标进行分析,以期为中国页岩气早期评价提供参考.
关键词:页岩气;主控因素;中国南方;寒武系;志留系;页岩气有利区
来源出版物:石油学报,2009,30(4): 484-491联系邮箱:聂海宽,niehaikuan@126.com
被引频次:250
四川盆地页岩气成藏地质条件
张金川,聂海宽,徐波,等
摘要:与传统上的“泥页岩裂缝气”并不完全相同,页岩气是主体上以吸附相和游离相同时赋存于泥岩及页岩地层中的天然气.四川盆地经历了克拉通和前陆盆地演化过程中复杂的构造变动,形成了与美国典型页岩气盆地相似的构造演化特点和地质条件,其中的古生界页岩不仅是盆地内常规气藏的烃源岩,而且还是页岩气成藏及勘探的主要对象,目前已发现了页岩气存在的大量证据.根据演化及勘探地质特点,四川盆地非常规天然气具有两分格局,东南部以页岩气为主而西北部以根缘气为主,古生界主体发育页岩气而中生界主体发育根缘气.川东和川南地区(包括川西南)古生界生气页岩发育厚度大、有机质含量高、埋藏深度小,下寒武统和下志留统具有良好的页岩气成藏及勘探地质条件;川中地区同时发育中、古生界烃源岩,上三叠统、下志留统和下寒武统可作为页岩气勘探的有利层位;川西中生界泥/页岩常与致密砂岩形成频繁互层并产生具有砂岩底部含气特点的根缘气,整体上存在着页岩气发育和勘探的远景条件,局部埋藏相对较浅的高碳泥/页岩是页岩气勘探的基本对象.
关键词:四川盆地;页岩气;成藏条件;勘探前景
来源出版物:天然气工业,2008,28(2): 151-156联系邮箱:张金川,zhangjc@cugb.edu.cn
被引频次:192
我国页岩气富集类型及资源特点
张金川,姜生玲,唐玄,等
摘要:根据页岩气聚集的机理条件和中、美页岩气地质条件的相似性对比结果认为:中国页岩气富集地质条件优越,具有与美国大致相同的页岩气资源前景及开发潜力.中国含气页岩具有高有机质丰度、高有机质热演化程度及高后期改造程度等“三高”特点,页岩气具有海陆相共存、沉积分区控制以及分布多样复杂等特点.以间接型和直接型页岩气划分方法为基础并结合中国区域地质特点,将中国的页岩气富集模式划分为南方型、北方型及西北型等3种,分别具有以下特点:①以扬子地台为核心的南方型页岩气聚集条件有利并以改造较为严重的海相古生界海相页岩聚气为主,具有单层厚度大、发育层位多、分布面积广、热演化程度高、后期改造强等特点;②以华北地台为主体的北方型页岩气具有古—中—新生界页岩发育齐全、沉积迁移特征明显、薄互层变化频率高、沉积相带分隔明显等特点;③以塔里木地台为基础的西北型页岩气储层以中—古生界为主,沉积类型多、有机碳丰度高、有机质热演化程度相对较低.结论认为:中国页岩气可采资源量约为26×1012m3,大致与美国的28×1012m3相当.
关键词:中国;页岩气;资源评价;分区特点;富集模式;开发潜力;华北地台;扬子地台;塔里木地台
来源出版物:天然气工业,2009,29(12): 109-114
被引频次:189
常规与非常规油气聚集类型、特征、机理及展望——以中国致密油和致密气为例
邹才能,朱如凯,吴松涛,等
摘要:油气勘探开发领域从常规油气向非常规油气跨越,是石油工业发展的必然趋势,二者在油气类型、地质特征及聚集机理等方面明显不同.常规油气研究的灵魂是成藏,目标是回答圈闭是否有油气;非常规油气研究的灵魂是储层,目标是回答储集有多少油气.非常规油气主要表现在连续分布、无自然工业产量.目前,常规油气面临非常规的问题,非常规需要发展成新的“常规”.伴随技术的进步,非常规可向常规转化.常规油气聚集包括构造油气藏、岩性-地层油气藏,油气以孤立的单体式或较大范围的集群式展布,圈闭界限明显,储集体发育毫米级—微米级孔喉系统,浮力成藏.非常规油气聚集包括致密砂岩油和气、致密碳酸盐岩油和气、页岩油和气等,一般源储共生,大面积连续或准连续分布于盆地斜坡或中心,圈闭界限不明显,页岩系统储集体广泛发育纳米级孔喉,浮力作用受限,油气以原位滞留或短距离运移为主.以中国重点盆地致密油和致密气为例,系统分析了其地质特征与勘探潜力.非常规油气储集空间主体为纳米级孔喉系统,局部发育微米—毫米级孔隙,其中页岩气储层孔径为5~200 nm,致密灰岩油储层孔径为40~500 nm,致密砂岩油储层孔径为50~900 nm,致密砂岩气储层孔径为40~700 nm.针对全球石油工业和纳米等技术的快速发展,提出了“纳米油气”的概念,指出“纳米油气”是未来石油工业的发展方向,需要发展纳米油气透视观测镜、纳米油气驱替剂、纳米油气开采机器人等换代技术,油气智能化时代将随之到来.
关键词:常规油气;非常规油气;页岩系统油气;纳米油气;致密油;致密气;页岩气;页岩油;连续型油气聚集
来源出版物:石油学报,2012,33(2): 173-187联系邮箱:邹才能,zcn@petrochina.com.cn
被引频次:187
页岩气储层的基本特征及其评价
蒋裕强,董大忠,漆麟,等
摘要:页岩气独特的赋存状态,“连续成藏”的聚集模式,区别于常规天然气储层的特征以及评价内容等决定了页岩气储层研究的特殊性.目前,国内针对页岩气储层特征及评价的工作开展得相对较少,需要建立相应的评价标准.在大量调研国外文献的基础上,综合利用四川盆地最新的浅井钻探和野外露头取样资料,从常规储层研究思路入手,详细分析了页岩气储层的基本特征(有机质特征、矿物组成、物性特征、储渗空间特征),进而总结了页岩气储层评价的主要内容;同时,借鉴美国页岩气勘探成功经验,从实际资料出发,筛选出有机质丰度、热成熟度、含气性等8大关键地质因素,进而提出了一套较为适用的储层评价标准.据该标准评价后认为,四川盆地下古生界筇竹寺组和龙马溪组2套海相黑色页岩具有良好的勘探开发前景.
关键词:页岩气;储集层;溶蚀孔隙;有机孔隙;裂缝;评价内容;评价标准;关键地质因素
来源出版物:天然气工业,2010,30(10): 7-12联系邮箱:蒋裕强,xnsjij93055@126.com
被引频次:168
页岩气资源评价方法及其在四川盆地的应用
董大忠,程克明,王世谦,等
摘要:近10年来,在高天然气价格、水平井钻井技术和压裂技术进步的推动下,页岩气成为美国最重要的天然气开发目标,形成了适合于不同勘探开发阶段的页岩气资源潜力评价方法,对页岩气资源的认识不断得到深化.在详细研究美国页岩气资源评价方法基础上,探索了我国现阶段页岩气资源评价方法,并针对四川盆地西南部地区及威远气田区下古生界下寒武统筇竹寺组的页岩气资源做了初步预测.结果认为四川盆地页岩气资源丰富,不少于盆地常规天然气资源量,是未来值得重视的重要天然气勘探开发新领域.
关键词:页岩气;资源;评价方法;四川盆地;应用;
来源出版物:天然气工业,2009,29(5): 33-39联系邮箱:董大忠,ddz@petrochina.com.cn
被引频次:194
Methane and the greenhouse-gas footprint of natural gas from shale formations
Howarth,Robert W; Santoro,Renee; Ingraffea,Anthony
Abstract: We evaluate the greenhouse gas footprint of natural gas obtained by high-volume hydraulic fracturing from shale formations,focusing on methane emissions. Natural gas is composed largely of methane,and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the life-time of a well. These methane emissions are at least 30% more than andperhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured-as methane escapes from flow-back return fluids-and during drill out following the fracturing. Methane is a powerful greenhouse gas,with a global warming potential that is far greater than that of carbon dioxide,particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales,dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon,but particularly so over 20 years. Compared to coal,the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.
Keywords: Methane; Greenhouse gases; Global warming; Natural gas; Shale gas; Unconventional gas; Fugitive emissions; Lifecycle analysis; LCA; Bridge fuel; Transitional fuel; Global warming potential; GWP
来源出版物:Climatic Change,2011,106(4): 679-690联系邮箱:Howarth,Robert W; rwh2@cornell.edu
被引频次:158
Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment
Jarvie,Daniel M; Hill,Ronald J; Ruble,Tim E; Pollastro,Richard M
Abstract: Shale-gas resource plays can be distinguished by gas type and system characteristics. The Newark East gas field,located in the Fort Worth Basin,Texas,is defined by thermogenic gas production from low-porosity and low-permeability Barnett Shale. The Barnett Shale gas system,a self-contained source-reservoir system,has generated large amounts of gas in the key productive areas because of various characteristics and processes,including(1)excellent original organic richness and generation potential;(2)primary and secondary cracking of kerogen and retained oil,respectively;(3)retention of oil for cracking to gas by adsorption;(4)porosity resulting from organic matter decomposition; and(5)brittle mineralogical composition. The calculated total gas in place(GIP)based on estimated ultimate recovery that is based on production profiles and operator estimates is about 204 bcf/section(5.78×109M-3/1.73×104m3). We estimate that the Barnett Shale has a total generation potential of about 609 bbl of oil equivalent/ac-ft or the equivalent of 3657 mcf/ac-ft(84.0 m3/m3). Assuming a thickness of 350 ft(107 m)and only sufficient hydrogen for partial cracking of retained oil to gas,a total generation potential of 820 bcf/section is estimated. Of this potential,approximately 60% was expelled,and the balance was retained for secondary cracking of oil to gas,if sufficient thermal maturity was reached. Gas storage capacity of the Barnett Shale at typical reservoir pressure,volume,and temperature conditions and 6% porosity shows a maximum storage capacity of 540 mcf/ac-ft or 159 scf/ton.
Keywords: primary migration; organic-matter; source rocks; carbon; basin; hydrocarbons; adsorption; diffusion; kerogen; play
来源出版物:AAPG Bulletin,2007,91(4): 475-499联系邮箱:Jarvie,DM; danjarvie@humble-inc.com
被引频次:157
Fractured shale-gas systems
Curtis,JB
Abstract: The first commercial United States natural gas production(1821)came from an organic-rich Devonian shale in the Appalachian basin. Understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s. Shale-gas systems essentially are continuous-type biogenic(predominant),thermogenic,or combined biogenic-thermogenic gas accumulations characterized by widespread gas saturation,subtle trapping mechanisms,seals of variable lithology,and relatively short hydrocarbon migration distances. Shale gas may be stored as free gas in natural fractures and intergranular porosity,as gas sorbed onto kerogen and clay-particle surfaces,or as gas dissolved in kerogen and bitumen. Five United States shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters: thermal maturity(expressed as vitrinite reflectance),sorbed-gas fraction,reservoir thickness,total organic carbon content,and volume of gas in place. The degree of natural fracture development in an otherwise low-matrix-permeability shale reservoir is a controlling factor in gas producibility. To date,unstimulated commercial production has been achievable in only a small proportion of shale wells,those that intercept natural fracture networks. In most other cases,a successful shale-gas well requires hydraulic stimulation. Together,the Devonian Antrim Shale of the Michigan basin and Devonian Ohio Shale of the Appalachian basin accounted for about 84% of the total 380 bcf of shale gas produced in 1999. However annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed: the Devonian New Albany Shalein the Illinois basin,the Mississippian Barnett Shale in the Fort Worth basin,and the Cretaceous Lewis Shale in the San Juan basin. In the basins for which estimates have been made,shale-gas resources are substantial,with in-place volumes of 497-783 tcf. The estimated technically recoverable resource(exclusive of the Lewis Shale)ranges from 31 to 76 tcf. In both cases,the Ohio Shale accounts for the largest share.
Keywords: subsequent thermal history; appalachian basin; organic-matter; rome trough; accumulation; methane
来源出版物:AAPG Bulletin,2002,86(11): 475-499
被引频次:123
Mississippian Barnett Shale,Fort Worth basin,north-central texas: Gas-shale play with multi-trillion cubic foot potential
Montgomery,SL; Jarvie,DM; Bowker,KA; et al.
Abstract: The Mississippian Barnett Shale serves as source,seal,and reservoir to a world-class unconventional natural-gas accumulation in the Fort Worth basin of north-central Texas. The formation is a lithologically complex interval of low permeability that requires artificial stimulation to produce. At present,production is mainly confined to a limited portion of the northern basin where the Barnett Shale is relatively thick(>300 ft; >92 m),organic rich(present-day total organic carbon>3.0%),thermally mature(vitrinite reflectance>1.1%),and enclosed by dense limestone units able to contain induced fractures. The most actively drilled area is Newark East field,currently the largest gas field in Texas. Newark East is 400 mi2(1036 km2)in extent,with more than 2340 producing wells and about 2.7 tcf of booked gas reserves. Cumulative gas production from Barnett Shale wells through 2003 was about 0.8 tcf. Wells in Newark East field typically produce from depths of 7500 ft(2285 m)at rates ranging from 0.5 to more than 4 mmcf/day. Estimated ultimate re coveries per well range from 0.75 to as high as 7.0 bcf. Efforts to extend the current Barnett play beyond the field limits have encountered several challenges,including westward and northward increases in oil saturation and the absence of lithologic barriers to induced fracture growth. Patterns of oil and gas occurrence in the Barnett,in conjunction with maturation and burial-history data,indicate a complex,multiphased thermal evolution,with episodic expulsion of hydrocarbons and secondary cracking of primary oils to gas in portions of the basin where paleotemperatures were especially elevated. These and other data imply a large-potential Barnett resource for the basin as a whole(possibly >200 tcf gas in place). Recent assessment by the U.S. Geological Survey suggests a mean volume of 26.2 tcf of undiscovered,technically recoverable gas in the central Fort Worth basin. Recovery of a significant portion of this undiscovered resource will require continued improvements in geoscientific characterization and approaches to stimulation of the Barnett reservoirs.
来源出版物:AAPG Bulletin,2005,89(2): 155-175联系邮箱:Montgomery,SL; scott.montgomery@prodigy.net
被引频次:110
The importance of shale composition and pore structure upon gas storage potential of shale gas reservoirs
Ross,Daniel J.K; Bustin,R. Marc
Abstract: The effect of shale composition and fabric upon pore structure and CH4sorption is investigated for potential shale gas reservoirs in the Western Canadian Sedimentary Basin(WCSB). Devonian-Mississippian(D-M)and Jurassic shales have complex,heterogeneous pore volume distributions as identified by low pressure CO2and N2sorption,and high pressure Hg porosimetry. Thermally mature D-M shales(1.6%-2.5% VRo)have Dubinin-Radushkevich(D-R)CO2micropore volumes ranging between 0.3 and 1.2 cc/100 g and N2BET surface areas of 5-31 m2/g. Jurassic shales,which are invariably of lower thermal maturity ranging from 0.9 to 1.3% VRo,than D-M shales have smaller D-R CO2micropore volumes and N2BET surface areas,typically in the range of 0.23-0.63 cc/100 g(CO2)and 1-9 m2/g(N2). High pressure CH4isotherms on dried and moisture equilibrated shales show a general increase of gas sorption with total organic carbon(TOC)content. Methane sorption in D-M shales increases with increasing TOC and micropore volume,indicating that microporosity associated with the organic fraction is a primary control upon CH4sorption. Sorption capacities for Jurassic shales,however,can be in part unrelated to micropore volume. The large sorbed gas capacities of organic-rich Jurassic shales,independent of surface area,imply a portion of CH4is stored by solution in matrix bituminite. Solute CH4is not an important contributor to gas storage in D-M shales. Structural transformation of D-M organic matter has occurred during thermal diagenesis creating and/or opening up microporosity onto which gas can sorb. As such,D-M shales sorb more CH4per weight percent(wt %)TOC than Jurassic shales. Inorganic material influences modal pore size,total porosity and sorption characteristics of shales. Clay minerals are capable of sorbing gas to their internal structure,the amount of which is dependent on clay-type. Illite and montmorillonite have CO2micropore volumes of 0.78 and 0.79 cc/100 g,N2BET surface areas of 25 and 30 m2/g,and sorb 2.9 and 2.1 cc/g of CH4,respectively(dry basis)-a reflection of microporosity between irregular surfaces of clay platelets,and possibly related to the size of the clay crystals themselves. Mercury porosimetry analyses show that total porosities are larger in clay-rich shales compared to silica-rich shales due to open porosity associated with the aluminosilicate fraction. Clay-rich sediments(low Si/Al ratios)have unimodal pore size distributions <10 nm and average total porosities of 5.6%. Siliceous/quartz-rich shales(high Si/Al)exhibit no micro- or mesopores using Hg analyses and total porosities average 1%,analogous to chert.
Keywords: Pore structure; Microporosity; Sorption; Shale gas reservoirs
来源出版物:Marine and Petroleum Geology,2009,26(6): 916-927
联系邮箱:Ross,Daniel J.K; daniel.ross@shell.com
被引频次:70
Mississippian Barnett Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Fort Worth Basin,Texas
Loucks,Robert G; Ruppel,Stephen C
Abstract: The Mississippian Barnett Formation of the Fort Worth Basin is a classic shale-gas system in which the rock is the source,reservoir,and seal. Barnett strata were deposited in a deeper water foreland basin that had poor circulation with the open ocean. For most of the basin's history,bottom waters were euxinic,preserving organic matter and,thus,creating a rich source rock,along with abundant framboidal pyrite. The Barnett interval comprises a variety of facies but is dominated by fine-grained(clay-to silt-size)particles. Three general lithofacies are recognized on the basis of mineralogy,fabric,biota,and texture:(1)laminated siliceous mudstone;(2)laminated argillaceous lime mudstone(marl); and(3)skeletal,argillaceous lime packstone. Each facies contains abundant pyrite and phosphate(apatite),which are especially common at hardgrounds. Carbonate concretions,a product of early diagenesis,are also common. The entire Barnett biota is composed of debris transported to the basin from the shelf or upper oxygenated slope by hemipelagic mud plumes,dilute turbidites,and debris flows. Biogenic sediment was also sourced from the shallower,better oxygenated water column. Barnett deposition is estimated to have occurred over a 25-m.y. period,and despite the variations in sublithofacies,sedimentation style remained remarkably similar throughout this span of time.
来源出版物:AAPG Bulletin,2007,91(4): 579-601联系邮箱:Loucks,Robert G; bob.loucks@beg.utexas.edu
被引频次:68
Water Management Challenges Associated with the Production of Shale Gas by Hydraulic Fracturing
Gregory,Kelvin B; Vidic,Radisav D; Dzombak,David A
Abstract: Development of unconventional,onshore natural gas resources in deep shales is rapidly expanding to meet global energy needs. Water management has emerged as a critical issue in the development of these inland gas reservoirs,where hydraulic fracturing is used to liberate the gas. Following hydraulic fracturing,large volumes of water containing very high concentrations of total dissolved solids(TDS)return to the surface. The TDS concentration in this wastewater,also known as “flowback”,can reach 5 times that of sea water. Wastewaters that contain high TDS levels are challenging and costly to treat. Economical production of shale gas resources will require creative management of flowback to ensure protection of groundwater and surface water resources. Currently,deep-well injection is the primary means of management. However,in many areas where shale gas production will be abundant,deep-well injection sites are not available. With global concerns over the quality and quantity of fresh water,novel water management strategies and treatment technologies that will enable environmentally sustainable and economically feasible natural gas extraction will be critical for the development of this vast energy source.
Keywords: shale gas; hydraulic fracturing; produced water; flowback
来源出版物:Elements,2011,7(3): 181-186联系邮箱:Gregory,Kelvin B; kelvin@cmu.edu
被引频次:58
Impact of Shale Gas Development on Regional Water Quality
Vidic,R.D; Brantley,S.L; Vandenbossche,J.M; et al.
Abstract: Unconventional natural gas resources offer an opportunity to access a relatively clean fossil fuel that could potentially lead to energy independence for some countries. Horizontal drilling and hydraulic fracturing make the extraction of tightly bound natural gas from shale formations economically feasible. These technologies are not free from environmental risks,however,especially those related to regional water quality,such as gas migration,contaminant transport through induced and natural fractures,wastewater discharge,and accidental spills. We review the current understanding of environmental issues associated with unconventional gas extraction. Improved understanding of the fate and transport of contaminants of concern and increased long-term monitoring and data dissemination will help manage these water-quality risks today and in the future.
Keywords: potential contaminant pathways; hydraulically fractured shale; marcellus shale; methane contamination; appalachian basin;pennsylvania; aquifers; wells; extraction; challenges
来源出版物:Science,2013,340(6134)文献号:1235009联系邮箱:Vidic,R.D; vidic@pitt.edu
被引频次:58
Nanoscale gas flow in shale gas Sediments
Javadpour,F; Fisher,D; Unsworth,M
Abstract: Production of gas out of low permeability shale packages is very recent in the Western Canadian Sedimentary Basin(WCSB). The process of gas release and production from shale gas sediments is not well understood. Because of adsorptive capacity of certain shaleconstituents,including organic carbon content: coalbed methane models are sometimes being applied to model and simulate tight shale gas production behaviour. Alternatively,conventional Darcy flow models are sometimes applied to tight shale gas. However,neither of these approaches takes into account the differences in transport mechanisms in shale due to additional nanopore networks. Hence,the application of existing models for shale results in erroneous evaluation and predictions. Our analysis shows that a combination of a nanopore network connected to a micrometre pore network controls the gas flow in shale. Mathematical modelling of gas flow in nanopores is difficult since the standard assumption of no-slip boundary conditions in the Navier-Stokes equation breaks down at the nanometre scale,while the computational times of applicable molecular-dynamics(MD)codes become exorbitant. We found that the gas flow in nanopores of the shale can be modelled with a diffusive transport regime with a constant diffusion coefficient and negligible viscous effects. The obtained diffusion coefficient is consistent with the Knudsen diffusivity which supports the slip: boundary condition at the nanopore surfaces. This model can be used for shale gas evaluation and production optimization.
来源出版物:Journal of Canadian Petroleum Technology,2007,46(10): 55-61
被引频次:58
Life-Cycle Greenhouse Gas Emissions of Shale Gas,Natural Gas,Coal,and Petroleum
Burnham,Andrew; Han,Jeongwoo; Clark,Corrie E; et al.
Abstract: The technologies and practices that have enabled the recent boom in shale gas production have also brought attention to the environmental impacts of its use. It has been g debated whether the fugitive methane emissions during natural gas production and transmission outweigh the lower carbon dioxide emissions during combustion when compared to coal and petroleum. Using the current state of knowledge of methane emissions from shale gas,conventional natural gas,coal,and petroleum,we estimated up-to-date life-cycle greenhouse gas emissions. In addition,we developed distribution functions for key parameters in each pathway to examine uncertainty and identify data gaps such as methane emissions from shale gas well completions and conventional natural gas liquid unloadings that need to be further addressed. Our base case results show that shale gas life-cycle emissions are 6% lower than conventional natural gas,23% lower than gasoline,and 33% lower than coal. However,the range in values for shale and conventional gas overlap,so there is a statistical uncertainty whether shale gas emissions are indeed lower than conventional gas. Moreover,this life-cycle analysis,among other work in this area,provides insight on critical stages that the natural gas industry and government agencies can work together on to reduce the greenhouse gas footprint of natural gas.
来源出版物:Environmental Science & Technology,2012,46(2): 619-627联系邮箱:Burnham,Andrew; aburnham@anl.gov
·推荐论文摘要·
页岩油形成机制、地质特征及发展对策
邹才能,杨智,崔景伟,等
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关键词:页岩油;页岩气;页岩系统油气;纳米级孔喉;非常规油气;常规—非常规“有序聚集”体系
来源出版物:石油勘探与开发,2013,40(1): 14-26联系邮箱:邹才能,zcn@petrochina.com.cn
川南下寒武统筇竹寺组页岩气形成条件及资源潜力
黄金亮,邹才能,李建忠,等
摘要:利用四川盆地南部地区最新钻探的井下资料、周边露头地质调查资料及大量样品的分析测试结果,从富有机质页岩区域展布、地球化学特征、岩石储集特征、含气性等方面研究川南地区下寒武统筇竹寺组页岩气形成条件与资源前景.研究区筇竹寺组有机质含量高(TOC值为0.55%~25.70%,平均值大于2%),页岩有效厚度大(黑色页岩厚60~300 m),脆性矿物含量较高(大于40%),页岩中发育丰富的纳米一微米级孔隙和微裂缝,含气量高(页岩含气量0.27~6.02 m3/t,平均1.90 m3/t),有利于页岩气的形成与富集.钻井过程中筇竹寺组气显示频繁并获得了工业性突破,是目前中国最有利的页岩气勘探开发层系之一,综合对比研究认为威远、叙永一筠连地区是研究区内筇竹寺组页岩气勘探开发最有利的地区.
关键词:四川盆地南部;下寒武统;筇竹寺组;页岩气;形成条件;资源前景
来源出版物:石油勘探与开发,2012,39(1): 69-75联系邮箱:黄金亮,huangjl1983@petrochina.com.cn
煤层气/页岩气开发地质条件及其对比分析
孟召平,刘翠丽,纪懿明
摘要:从煤层气、页岩气基本概念入手,系统分析了煤层气/页岩气开发地质条件,主要包括成藏地质条件、赋存环境条件和开发工程力学条件3个方面,进一步对煤层气/页岩气开发地质条件进行了对比分析,揭示了煤层气/页岩气开发地质条件的共性和差异性.煤层气/页岩气赋存于煤层/页岩中的一种自生自储式非常规天然气,其富集成藏主要取决于“生、储、保”基本地质条件是否存在、质量好坏以及相互之间的配合关系.在一定埋藏深度范围内煤层气/页岩气都发生过解吸-扩散-运移,并普遍存在“垂向分带”现象,有机质演化程度越高解吸带深度越小,风化带越深解吸带深度越大,解吸带内煤层气/页岩气富集在一定程度上服从于常规天然气的构造控气规律;原生带内煤层气/页岩气富集却可能更多地受控于煤储层/页岩层的吸附特性.不同赋存环境条件下所形成的煤/页岩储层差异性大,使煤/页岩储层中吸附气和游离气相互转化,导致煤层气/页岩气成藏类型、规模和质量等方面的差异性.影响煤层气开发的主要地质因素有:煤层厚度及其稳定性、含气量大小或煤层气资源丰度、构造及裂隙发育与渗透性和煤层气保存条件等方面;影响页岩气开发的主要地质因素包括页岩厚度、有机质含量、热成熟度、含气量、天然裂缝发育程度和脆性矿物含量等.
关键词:煤层气;页岩气;开发地质;对比分析
来源出版物:煤炭学报,2013,38(5): 728-736联系邮箱:孟召平,mzp@ cumtb.edu.cn
中国南方海相页岩气高效开发的科学问题
王红岩,刘玉章,董大忠,等
摘要:中国页岩气资源丰富,已在多个地区获初步发现,其中中国南方古生界寒武系、奥陶系和志留系中发育多套海相富有机质页岩,技术可采资源量占全国的3/4,将是重点开发地区.与北美相比,中国南方海相页岩气储集层具有构造改造强、地应力复杂、埋藏较深、地表条件特殊等特点,照搬国外现有理论与技术难以有效开发.页岩气储集层纳米级孔隙对页岩气产能的影响尚不明确,页岩气产能预测方法尚未建立,钻井过程中水平段垮塌严重、钻井周期长,增产改造效果不理想、单井产量较低,需要针对纳米级孔隙成因及多尺度储集空间定量表征、复杂介质多场耦合非线性流动机理、页岩失稳与缝网形成的力学机制3个科学问题进行研究.
关键词:海相页岩气;高效开发;科学问题;中国南方;纳米级孔隙
来源出版物:石油勘探与开发,2013,40(5): 574-579
非常规油气地质学重要理论问题
贾承造,郑民,张永峰
摘要:2012年常规能源燃料的消费量和生产量达到创纪录的历史最高水平,石油和天然气在能源消费结构中仍然占据主导地位,非常规油气产量的大幅上升使油气供需基本达到平衡.但目前对非常规油气还有很多重要的基础理论问题没有解决,对非常规油气的分布富集规律、勘探开发特点还没有把握.本文以此为出发点,回顾了近期全球油气勘探形势,提出了非常规油气地质学的4项重要理论问题:①“含油气系统”理论的深化再认识,提出了含油气盆地“全含油气系统”的“全过程成藏”模式,从烃类生-排-运-聚全过程定量化研究的4个关键问题出发,分析了非常规油气成藏机理;②细粒沉积体系与致密相带沉积学,通过解析细粒沉积与非常规油气生成关系的角度提出了3个研究结合点;③页岩与致密储层中微-纳米孔隙系统和流体相态,提出了微-纳米孔隙系统在非常规油气研究方面应重点关注的5个方面,并解析了微-纳米孔隙发育特点及微-纳米孔隙中流体相态的特征;④非常规油气富集规律与资源评价,从非常规油气聚集特征出发,优选建立了非常规油气资源评价方法体系.
关键词:能源消费结构;非常规油气;勘探形势;理论难题;含油气系统;致密相带;微-纳米孔隙系统
来源出版物:石油学报,2014,35(1): 1-10联系邮箱:郑民,zhenmin@petrochina.com.cn
滇黔北地区筇竹寺组高演化页岩气储层微观孔隙特征及其控制因素
梁兴,张廷山,杨洋,等
摘要:页岩气钻探资料表明,滇黔北地区下寒武统筇竹寺组页岩储层富气状况明显不如下志留统龙马溪组页岩,由此严重影响其勘探部署决策,查明其原因是当务之急.为此,以页岩气钻井岩心为基础,采用环境扫描电镜、原子力显微镜、比表面积测量、低温液氮吸附等试验手段,分析了筇竹寺组页岩储层的微观孔隙类型、结构特征等.结果表明:①筇竹寺组页岩储层呈现出极为发育的以纳米级为主的微观孔隙结构特征,发育黏土矿物层间孔、有机质孔、晶间孔、矿物铸模孔、次生溶蚀孔等多类型的基质孔隙,具有比表面积小和面孔率大的特点;TOC②、干酪根类型、黏土矿物和Ro是控制筇竹寺组微观孔隙结构的主要因素,以Ro的影响最为明显,且在页岩达到过成熟状态后,其比表面积和孔体积随着Ro的增大而急剧减小.结论认为:已处于过成熟中后期的该区筇竹寺组页岩层,长期的地质作用过程和过高热演化程度严重制约了其微观孔隙发育,呈现微孔隙骤减和比表面积、孔体积明显较小的情形,不利于页岩气的吸附储集,由此导致该区筇竹寺组页岩气富集程度不如龙马溪组的结果.
关键词:滇黔北地区;页岩气;储集空间类型;微观孔隙结构;主控因素;富气程度;早寒武世;比表面积
来源出版物:天然气工业,2014,34(2): 18-26联系邮箱:梁兴,liangx85@petrochina.com.cn
常规-非常规油气“有序聚集”理论认识及实践意义
邹才能,杨智,张国生,等
摘要:在分析全球常规-非常规油气发展态势、梳理中国近10年油气地质理论与技术创新成果基础上,系统阐述了常规-非常规油气“有序聚集”内涵,指出常规油气供烃方向有非常规油气共生、非常规油气外围空间可能有常规油气伴生,强调常规油气与非常规油气协同发展,找油思想从“源外找油”深入到“进源找油”.非常规油气甜点着眼于烃源性、岩性、物性、脆性、含油气性与应力各向异性“六特性”匹配评价,以页岩气为例,中国有利页岩气TOC大于2%,纹层状硅质钙质或钙质硅质页岩,孔隙度3%~8%,脆性矿物含量50%~80%,含气量2.3~4.1 m3/t,压力系数1.0~2.3,天然裂缝发育;北美有利页岩气TOC大于4%,硅质页岩、钙质页岩或泥灰岩,孔隙度4%~9%,脆性矿物含量40%~70%,含气量2.8~9.9 m3/t,压力系数1.30~1.85,天然裂缝发育.重点论述了“甜点区”评价、平台式“工厂化”生产模式等方法与技术:提出非常规油气富集“甜点区”8项评价标准,其中3项关键指标是TOC大于2%(其中页岩油S1大于2 mg/g)、孔隙度较高(致密油气大于10%,页岩油气大于3%)和微裂缝发育;阐述了多井平台式“工厂化”生产内涵及其实施需要具备“批量布井、标准设计、流水作业、重复利用”4要素;通过地下含油气地层各方向水平井体积压裂,形成大型人工缝网系统“人造油气藏”.
关键词:非常规油气;有序聚集;协同发展;“甜点区”评价;平台式“工厂化”生产;“人造油气藏”;致密油;页岩油;页岩气;致密气;“进源找油”
来源出版物:石油勘探与开发,2014,41(1): 14-26
论四川盆地页岩气资源勘探开发前景
董大忠,高世葵,黄金亮,等
摘要:四川盆地是目前中国页岩气勘探开发的重点地区,也是最成功的地区.四川盆地页岩气资源勘探开发前景,将在较大程度上反映和影响中国页岩气未来的发展前景.通过全面总结近年来该盆地页岩气勘探开发的新进展,得出了以下认识:①四川盆地经历了海相、陆相两大沉积演化,发育了海相、海陆过渡相、陆相三类富有机质页岩,形成了震旦系陡山沱组、寒武系筇竹寺组、奥陶系五峰组—志留系龙马溪组、二叠系龙潭组、三叠系须家河组、侏罗系自流井组6套有利的页岩气富集层系;②深水陆棚相、集中段厚度大、热演化程度适中、正向构造背景下裂缝发育、储层超压是五峰组—龙马溪组页岩气富集的“五大”关键要素;③该盆地页岩气勘探开发仍面临资源富集“甜点区”及资源潜力不清、深度超过3500 m的深层页岩气勘探开发技术不成熟等两大挑战.结论认为:四川盆地已在侏罗系、三叠系和寒武系初步实现了页岩气发现,在奥陶系—志留系实现了工业化突破和初步规模生产,未来发展前景较好;该盆地页岩气资源可以实现经济有效勘探开发,预期可实现年产量300×108~600×108m3;对该盆地页岩气资源勘探开发将为中国页岩气资源规模发展提供重要的理论与技术支撑.
关键词:四川盆地;页岩气;勘探开发;新进展;富集条件;发展前景;面临挑战;年产量
来源出版物:天然气工业,2014,34(12): 1-15联系邮箱:董大忠,ddz@petrochina.com.cn
页岩气储层孔隙发育特征及主控因素分析: 以上扬子地区龙马溪组为例
黄磊,申维
摘要:运用扫描电镜、氩离子抛光场发射电子扫描显微成像与核磁共振测试技术,对渝东南地区Y1井龙马溪组页岩的微米级孔隙、纳米级孔隙和微裂缝发育特征3个层面分别进行定量表征.结合总有机碳含量、有机质显微组分及成熟度、黏土矿物及全岩X射线衍射分析等测试数据,对孔隙发育特征主控因素进行分析.对页岩微米级孔隙发育有促进作用的因素有石英含量和伊利石含量,具有抑制作用的因素有碳酸盐含量和埋藏深度;对有机质纳米级孔隙发育有促进作用的因素有有机质成熟度和伊蒙混层含量,具有抑制作用的因素为方解石含量;对微裂缝发育有促进作用的因素有石英含量、有机质成熟度和总有机碳含量,具有抑制作用的因素是碳酸盐含量.
关键词:页岩气;储层;孔隙;龙马溪组;主控因素
来源出版物:地学前缘,2015,22(1): 374-385联系邮箱:黄磊,huangleicomvn@163.com
涪陵页岩气勘探开发重大突破与启示
王志刚
摘要:中国海相页岩气分布领域广,资源丰富,但与北美相比,具有页岩时代老、热演化程度高的特点;同时由于经历多期次的构造改造,具有保存条件和埋深差异大的特殊性.针对这些特点和特殊性,提出了生烃条件、储集条件和保存条件为核心的页岩气“三元富集”理论.以此为指导,中国石化集团公司的页岩气勘探向四川盆地及其近缘聚焦,确定川东南地区下志留统是首选的页岩气勘探突破领域.建立了海相页岩气区带和目标评价方法,优选涪陵焦石坝构造为页岩气突破目标,2012年部署钻探焦页1井,一举发现了中国首个大型页岩气田——焦石坝龙马溪组海相页岩气田.同时,借鉴、集成和研发关键技术,形成了中、浅层海相页岩气钻井技术和大井段分段压裂的海相页岩储层改造技术.在勘探开发一体化的工作思路指导下,通过精细高效的组织管理实现焦石坝大型页岩气田的快速高效开发.
关键词:三元富集;勘探开发一体化;海相地层;页岩气;志留系;焦石坝气田
来源出版物:石油与天然气地质,2015,36(1): 1-6
压裂水平井产能预测方法研究综述
刘洪平,赵彦超,孟俊,等
摘要:水平井压裂技术已经在薄层、低渗透油气藏以及页岩气的开发中得到了广泛的应用,其产能预测方法是进行油气层评价、合理高效开发的基础.在对产能影响因素分析的基础上,系统总结了致密砂岩油气藏和页岩气藏压裂水平井的产能评价方法;认为除了对储层基质以及裂缝内流动机理进行表征外,裂缝的分布规律以及储层应力敏感性对产能的影响不容忽视;同时应重视大量钻井资料与物理模拟和数值模拟的结合,以提高产能预测的精度.
关键词:压裂水平井;致密砂岩;页岩气;产能预测
来源出版物:地质科技情报,2015,34(1): 131-139联系邮箱:刘洪平,liuhongping12@126.com
Petrophysical Considerations in Evaluating and Producing Shale Gas Resources
C.H. Sondergeld; K.E. Newsham; J.T. Comisky; et al.
Abstract: We present a practical assessment of petrophysical properties of shales and their measurement in the lab and via logs. Gasbearing shale present unique measurement challenges due to their ultra-low permeability and complicated pore volume connectivity. Thecombination of low intrinsic permeability and gas sorption effects renders these reservoirs “unconventional”. Advances in horizontal drilling and hydraulic stimulation have transformed gas-shale resources into economic reserves. Given their economic significance,there is a strong drive to understand gas shale petrophysical property measurements,both in the laboratory and in the subsurface. We note that various core analysis protocols are used in different laboratories leading to physical property measurements that are inconsistent,even when measured on identical sample sets. In addition,log analysis of kerogen-rich shale is ‘unconventional’ compared to classical techniques used in tight gas sands. As shale gas evaluation is becoming widely practiced among service companies and operators,we will focus on three reservoir assessment categories: storage capacity(gas-in-place),flow capacity(gas deliverability)and mechanical properties impacting hydraulic stimulation. Within each of these categories we have identified influential petrophysical properties such as rock composition,total organic carbon(TOC)content,porosity,saturation,permeability and mechanical properties. Specifically,we demonstrate the importance of estimating accurate mineral and kerogen content as these properties directly impact rock quality,hydraulic fracturing protocols,and gas-in-place estimations. In reviewing these practices,we also will show the need and possible direction of new technologies that will be required for making evaluations more accurate and quantitative in the future.
来源出版物:SPE 2010,131768: 1-34
Thirty Years of Gas Shale Fracturing: What Have We Learned?
George E. King
Abstract: Although high gas flow rates from shales are a relatively recent phenomenon,the knowledge bases of shale-specific well completions,fracturing and shale well operations have actually been growing for more than three decades and shale gas production reaches back almost one hundred ninety years. During the last decade of gas shale development,projected recovery of shale gas-in-place has increased from about 2% to estimates of about 50%; mainly through the development and adaptation of technologies to fit shale gas developments. Adapting technologies,including multi-stage fracturing of horizontal wells,slickwater fluids with minimum viscosity and simultaneous fracturing,have evolved to increase formation-face contact of the fracture system into the range of 9.2 million m2(100 million ft2)in a very localized area of the reservoir by opening natural fractures. These technologies have made possible development of enormous gas reserves that were completely unavailable only a few years ago. Current and next generation technologies promise even more energy availability with advances in hybrid fracs,fracture complexity,fracture flow stability and methods of re-using water used in fracturing. This work surveyed over 350 shale completion,fracturing and operations publications,linking geosciences and engineering information together to relay learnings that will identify both intriguing information on selective opening and stabilizing of micro-fracture systems within the shales and new fields of endeavor needed to achieve the next level of shale development advancement.
来源出版物:SPE 2010,133456: 1-50
Pore structure characterization of North American shale gas reservoirs using USANS/SANS,gas adsorption,and mercury intrusion
Clarkson,CR; Solano,N; Bustin,RM; et al.
Abstract: Small-angle and ultra-small-angle neutron scattering(SANS and USANS),low-pressure adsorption(N2and CO2),and high-pressure mercury intrusion measurements were performed on a suite of North American shale reservoir samples providing the first ever comparison of all these techniques for characterizing the complex pore structure of shales. The techniques were used to gain insight into the nature of the pore structure including pore geometry,pore size distribution and accessible versus inaccessible porosity. Reservoir samples for analysis were taken from currently-active shale gas plays including the Barnett,Marcellus,Haynesville,Eagle Ford,Woodford,Muskwa,and Duvernay shales. Low-pressure adsorption revealed strong differences in BET surface area and pore volumes for the sample suite,consistent with variability in composition of the samples. The combination of CO2and N2adsorption data allowed pore size distributions to be created for micro-meso-macroporosity up to a limit of similar to 1000 angstrom. Pore size distributions are either uni- or multi-modal. The adsorption-derived pore size distributions for some samples are inconsistent with mercury intrusion data,likely owing to a combination of grain compression during high-pressure intrusion,and the fact that mercury intrusion yields information about pore throat rather than pore body distributions. SANS/USANS scattering data indicate a fractal geometry(power-law scattering)for a wide range of pore sizes and provide evidence that nanometer-scale spatial ordering occurs in lower mesopore-micropore range for some samples,which may be associated with inter-layer spacing in clay minerals. SANS/USANS pore radius distributions were converted to pore volume distributions for direct comparison with adsorption data. For the overlap region between the two methods,the agreement is quite good. Accessible porosity in the pore size(radius)range 5 nm-10 μm was determined for a Barnett shale sample using the contrast matching method with pressurized deuterated methane fluid. The results demonstrate that accessible porosity is pore-size dependent.
Keywords: Shale gas; Pore structure; Small-angle neutron scattering; Gas adsorption; Mercury intrusion
来源出版物:Fuel,2013,103: 606-616联系邮箱:Clarkson,CR; clarksoc@ucalgary.ca
Generation,transport,and disposal of wastewater associated with Marcellus Shale gas development
Lutz,Brian D; Lewis,Aurana N; Doyle,Martin W
Abstract: Hydraulic fracturing has made vast quantities of natural gas from shale available,reshaping the energy landscape of the UnitedStates. Extracting shale gas,however,generates large,unavoidable volumes of wastewater,which to date lacks accurate quantification. For the Marcellus shale,by far the largest shale gas resource in the United States,we quantify gas and wastewater production using data from 2189 wells located throughout Pennsylvania. Contrary to current perceptions,Marcellus wells produce significantly less wastewater per unit gas recovered(approximately 35%)compared to conventional natural gas wells. Further,well operators classified only 32.3% of wastewater from Marcellus wells as flow back from hydraulic fracturing; most wastewater was classified as brine,generated over multiple years. Despite producing less wastewater per unit gas,developing the Marcellus shale has increased the total wastewater generated in the region by approximately 570% since 2004,overwhelming current wastewater disposal infrastructure capacity. Citation: Lutz,B. D.,A. N. Lewis,and M. W. Doyle(2013),Generation,transport,and disposal of wastewater associated with Marcellus Shale gas development,Water Resour.
Keywords: natural-gas; pennsylvania; challenges; methane; brine
来源出版物:Water Resources Research,2013,49(2): 647-656联系邮箱:Lutz,Brian D; blutz6@kent.edu
Desalination and Reuse of High-Salinity Shale Gas Produced Water: Drivers,Technologies,and Future Directions
Shaffer,Devin L; Chavez,Laura H. Arias; Ben-Sasson,Moshe; et al.
Abstract: In the rapidly developing shale gas industry,managing produced water is a major challenge for maintaining the profitability of shale gas extraction while protecting public health and the environment. We review the current state of practice for produced water management across the United States and discuss the interrelated regulatory,infrastructure,and economic drivers for produced water reuse. Within this framework,we examine the Marcellus shale play,a region in the eastern United States where produced water is currently reused without desalination. In the Marcellus region,and in other shale plays worldwide with similar constraints,contraction of current reuse opportunities within the shale gas industry and growing restrictions on produced water disposal will provide strong incentives for produced water desalination for reuse outside the industry. The most challenging scenarios for the selection of desalination for reuse over other management strategies will be those involving high-salinity produced water,which must be desalinated with thermal separation processes. We explore desalination technologies for treatment of high-salinity shale gas produced water,and we critically review mechanical vapor compression(MVC),membrane distillation(MD),and forward osmosis(FO)as the technologies best suited for desalination of high-salinity produced water for reuse outside the shale gas industry. The advantages and challenges of applying MVC,MD,and FO technologies to produced water desalination are discussed,and directions for future research and development are identified. We find that desalination for reuse of produced water is technically feasible and can be economically relevant. However,because produced water management is primarily an economic decision,expanding desalination for reuse is dependent on process and material improvements to reduce capital and operating costs.
Keywords: contact membrane distillation; mechanical vapor compression; ammonia-carbon dioxide; osmosis desalination; seawater desalination; natural-gas; waste-water; energy-requirements; process performance; fouling behavior
来源出版物:Environmental Science & Technology,2013,47(17): 9569-9583
联系邮箱:Elimelech,Menachem; menachem.elimelech@yale.edu
A Critical Review of the Risks to Water Resources from Unconventional Shale Gas Development and Hydraulic Fracturing in the United States
Vengosh,Avner; Jackson,Robert B; Warner,Nathaniel; et al.
Abstract: The rapid rise of shale gas development through horizontal drilling and high volume hydraulic fracturing has expanded the extraction of hydrocarbon resources in the U.S. The rise of shale gas development has triggered an intense public debate regarding the potential environmental and human health effects from hydraulic fracturing. This paper provides a critical review of the potential risks that shale gas operations pose to water resources,with an emphasis on case studies mostly from the U.S. Four potential risks for water resources are identified:(1)the contamination of shallow aquifers with fugitive hydrocarbon gases(i.e.,stray gas contamination),which can also potentially lead to the salinization of shallow groundwater through leaking natural gas wells and subsurface flow;(2)the contamination of surface water and shallow groundwater from spills,leaks,and/or the disposal of inadequately treated shale gas wastewater;(3)the accumulation of toxic and radioactive elements in soil or stream sediments near disposal or spill sites; and(4)the over extraction of water resources for high-volume hydraulic fracturing that could induce water shortages or conflicts with other water users,particularly in water-scarce areas. Analysis of published data(through January 2014)reveals evidence for stray gas contamination,surface water impacts in areas of intensive shale gas development,and the accumulation of radium isotopes in some disposal and spill sites. The direct contamination of shallow groundwater from hydraulic fracturing fluids and deep formation waters by hydraulic fracturing itself,however,remains controversial.
Keywords: potential contaminant pathways; disinfection by-products; southern high-plains; natural-gas; marcellus shale; drinking-water;waste-water; sedimentary basin; barnett shale; methane contamination
来源出版物:Environmental Science & Technology,2014,48(15): 8334-8348联系邮箱:Vengosh,A; vengosh@duke.edu
Life Cycle Greenhouse Gas Emissions and Freshwater Consumption of Marcellus Shale Gas
Laurenzi,Ian J; Jersey,Gilbert R
Abstract: We present results of a life cycle assessment(LCA)of Marcellus shale gas used for power generation. The analysis employs the most extensive data set of any LCA of shale gas to date,encompassing data from actual gas production and power generation operations. Results indicate that a typical Marcellus gas life cycle yields 466 kg CO2eq/MWh(80% confidence interval: 450-567 kg CO2eq/MWh)of greenhouse gas(GHG)emissions and 224 gal/MWh(80% CI: 185-305 gal/MWh)of freshwater consumption. Operations associated with hydraulic fracturing constitute only 1.2% of the life cycle GHG emissions,and 6.2% of the life cycle freshwater consumption. These results are influenced most strongly by the estimated ultimate recovery(EUR)of the well and the power plant efficiency: increase in either quantity will reduce both life cycle freshwater consumption and GHG emissions relative to power generated at the plant. We conclude by comparing the life cycle impacts of Marcellus gas and U.S. coal: The carbon footprint of Marcellus gas is 53%(80% CI: 44-61%)lower than coal,and its freshwater consumption is about 50% of coal. We conclude that substantial GHG reductions and freshwater savings may result from the replacement of coal-fired power generation with gas-fired power generation.
Keywords: natural-gas; footprint; coal
来源出版物:Environmental Science & Technology,2013,47(9): 4896-4903
联系邮箱:Laurenzi,Ian J; ian.j.laurenzi@exxonmobil.com
Natural gas from shale formation-The evolution,evidences and challenges of shale gas revolution in United States
Wang,Qiang; Chen,Xi; Jha,Awadhesh N; et al.
Abstract: Extraction of natural gas from shale rock in the United States(US)is one of the landmark events in the 21st century. The combination of horizontal drilling and hydraulic fracturing can extract huge quantities of natural gas from impermeable shale formations,which were previously thought to be either impossible or uneconomic to produce. This review offers a comprehensive insight into US shale gas opportunities,appraising the evolution,evidence and the challenges of shale gas production in the US. The history of US shale gas in this article is divided into three periods and based on the change of oil price(i.e.,the period before the 1970s oil crisis,the period from 1970s to 2000,and the period since 2000),the US has moved from being one of the world's biggest importers of gas to being self-sufficient in less than a decade,with the shale gas production increasing 12-fold(from 2000 to 2010). The US domestic natural gas price hit a 10-year low in 2012. The US domestic natural gas price in the first half of 2012 was about $2 per million British Thermal Unit(BTU),compared with Brent crude,the world benchmark price for oil,now about $80-100/barrel,or $14-17 per million BTU. Partly due to an increase in gas-fired power generation in response to low gas prices,US carbon emissions from fossil-fuel combustion fell by 430 million ton CO2-more than any other country-between 2006 and 2011. Shale gas also stimulated economic growth,creating 600000 new jobs in the US by 2010. However,the US shale gas revolution would be curbed,if the environmental risks posed by hydraulic fracturing are not managed effectively. The hydraulic fracturing is water intensive,and can cause pollution in the marine environment,with implications for long-term environmental sustainability in several ways. Also,large amounts of methane,a powerful greenhouse gas,can be emitted during the shale gas exploration and production. Hydraulic fracturing also may induce earthquakes. These environmental risks need to be managed by good practices which is not being applied by all the producers in all the locations. Enforcing stronger regulations are necessary to minimize risk to the environment and on human health. Robust regulatory oversight can however increase the cost of extraction,but stringent regulations can foster an historic opportunity to provide cheaper and cleaner gas to meet the consumer demand,as well as to usher in the future growth of the industry.
Keywords: Natural gas from shale formation; Energy revolution; Environmental challenge; Best practices; US shale gas
来源出版物:Renewable & Sustainable Energy Reviews,2014,30: 1-28联系邮箱:Wang,Qiang; qiangwang7@gmail.com
Water resource impacts during unconventional shale gas development: The Pennsylvania experience
Brantley,Susan L; Yoxtheimer,Dave ; Arjmand,Sina; et al.
Abstract: Improvements in horizontal drilling and hydrofracturing have revolutionized the energy landscape by allowing the development of so-called “unconventional” gas resources. The Marcellus play in the northeastern U.S.A. documents how fast this technology developed: the number of unconventional Marcellus wells in Pennsylvania(PA)increased from 8 in 2005 to similar to 7234 today. Publicly available databases in PA show only rare evidence of contamination of surface and groundwaters. This could document that incidents that impact PA waters have been relatively rare and that contaminants were quickly diluted. However,firm conclusions are hampered by i)the lack of information about location and timing of incidents; ii)the tendency to not release water quality data related to specific incidents due to liability or confidentiality agreements; iii)the sparseness of sample and sensor data for the analytes of interest; iv)the presence of pre-existing water impairments that make it difficult to determine potential impacts from shale-gas activity; and v)the fact that sensors can malfunction or drift. Although the monitoring data available to assess contamination events in PA are limited,the state manages an online database of violations. Overall,one fifth of gas wells drilled were given at least one non-administrative notice of violation(NOV)from thePA regulator. Through March 2013,3.4% of gas wells were issued NOVs for well construction issues and 0.24% of gas wells received NOVs related to methane migration into groundwater. Between 2008 and 2012,161 of the similar to 1000 complaints received by the state described contamination that implicated oil or gas activity: natural gas was reported for 56% and brine salt components for 14% of the properties. Six percent of the properties were impacted by sediments,turbidity,and/or drill cuttings. Most of the sites of groundwater contamination with methane and/or salt components were in previously glaciated northern PA where fracture flow sometimes allows long distance fluid transport. No cases of subsurface transport of fracking or flow back fluids into water supplies were documented. If Marcellus-related flowback/production waters did enter surface or groundwaters,the most likely contaminants to be detected would be Na,Ca,and Cl,but those elements are already common in natural waters. The most Marcellus-specific "fingerprint" elements are Sr,Ba,and Br. For example,variable Br concentrations measured in southwestern PA streams were attributed to permitted release of wastewaters from unconventional shale gas wells into PA streams through municipal or industrial wastewater treatment plants before 2011. Discharge has now been discontinued except for brines from a few plants still permitted to discharge conventional oil/gas brines after treatment. Overall,drinking water supply problems determined by the regulator to implicate oil/gas activities peaked in frequency in 2010 while spill rates increased through 2012. Although many minor violations and temporary problems have been reported,the picture that emerges from PA is that the fast shale-gas start may have led to relatively few environmental incidents of significant impact compared to wells drilled; however,the impacts remain difficult to assess due to the lack of transparent and accessible data.
Keywords: Unconventional shale gas; Environmental impact; Hydraulic fracturing; Hydrofracturing; Water quality; Marcellus Shale
来源出版物:International Journal of Coal Geology,2014,126(S1): 140-156
Molecular simulation of shale gas adsorption and diffusion in inorganic nanopores
Sharma,Aman; Namsani,Sadanandam; Singh,Jayant K
Abstract: We studied the structural and dynamical properties of methane and ethane in montmorillonite(MMT)slit pore of sizes 10,20 and 30 angstrom using grand canonical Monte Carlo and classical molecular dynamics(MD)simulations. The isotherm,at 298.15 K,is generated for pressures up to 60 bar. The molecules preferentially adsorb at the surface as indicated by the density profile. In case of methane,we observe only a single layer,at the pore wall,whose density increases with increasing pressure. However,ethane also displays a second layer,though of low density in case of pore widths 20 and 30 angstrom. In-plane self-diffusion coefficient,DII,of methane and ethane is of the order of 10-6m2/s. At low pressure,DIIincreases significantly with the pore size. However,DIIdecreases rapidly with increasing pressure. Furthermore,the effect of pore size on DIIdiminishes at high pressure. Ideal adsorbed solution theory is used to understand the adsorption behaviour of the binary mixture of methane(80%)and ethane(20%)at 298.15 K. Furthermore,we calculate the selectivity of the gases at various pressures of the mixture,and found high selectivity for ethane in MMT pores. However,selectivity of ethane decreases with increase in pressure or pore size.
Keywords: methane; shale gas; GCMC; ethane; montmorillonite
来源出版物:Molecular Simulationk,2015,41(5-6): 414-422联系邮箱:Singh,Jayant K; jayantks@iitk.ac.in
Study on gas flow through nano pores of shale gas reservoirs
Guo,Chaohua; Xu,Jianchun; Wu,Keliu; et al.
Abstract: Unlike conventional gas reservoirs,gas flow in shale reservoirs is a complex and multiscale flow process which has special flow mechanisms. Shale gas reservoirs contain a large fraction of nano pores,which leads to an apparent permeability that is dependent on pore pressure,fluid type,and pore structure. Study of gas flow in nano pores is essential for accurate numerical simulation of shale gas reservoirs. However,no comprehensive study has been conducted pertaining to the gas flow in nano pores. In this paper,experiments for nitrogen flow through nano membranes(with pore throat size: 20 nm,55 nm,and 100 nm)have been done and analyzed. Obvious discrepancy between apparent permeability and intrinsic permeability has been observed; and the relationship between this discrepancy and pore throat diameter(PTD)has been analyzed. Then,based on the advection-diffusion model,a new mathematical model has been constructed to characterize gas flow in nano pores. A new apparent permeability expression has been derived based on advection and Knudsen diffusion. A comprehensive coefficient for characterizing the flow process was proposed. Simulation results were verified against the experimental data for gas flow through nano membranes and published data. By changing the comprehensive coefficient,we found the best candidate for the case of argon with a membrane PTD of 235 nm. We verified the model using experimental data with different gases(oxygen,argon)and different PTDs(235 nm,220 nm). The comparison shows that the new model matches the experimental data very closely. Additionally,we compared our results with experimental data,the Knudsen/Hagen-Poiseuille analytical solution,and existing models available in the literature. Results show that the model proposed in this study yielded a more reliable solution. Shale gas simulations,in which gas flowing in nano pores plays a critical role,can be made more accurate and reliable based on the results of this work.
Keywords: Shale gas; Nano pores; Apparent permeability; Advection-diffusion model; Knudsen diffusion
来源出版物:Fuel,2015,143: 107-117联系邮箱:wei,mingzhen; weim@mst.edu
编辑:卫夏雯
The first commercial United States natural gas production(1821)came from an organic-rich Devonian shale in the Appalachian basin. Understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s. Shale-gas systems essentially are continuous-type biogenic(predominant),thermogenic,or combined biogenic-thermogenic gas accumulations characterized by widespread gas saturation,subtle trapping mechanisms,seals of variable lithology,and relatively short hydrocarbon migration distances. Shale gas may be stored as free gas in natural fractures and intergranular porosity,as gas sorbed onto kerogen and clay-particle surfaces,or as gas dissolved in kerogen and bitumen. Five United States shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters: thermal maturity(expressed as vitrinite reflectance),sorbed-gas fraction,reservoir thickness,total organic carbon content,and volume of gas in place. The degree of natural fracture development in an otherwise low-matrix-permeability shale reservoir is a controlling factor in gas producibility. To date,unstimulated commercial production has been achievable in only a small proportion of shale wells,those that intercept natural fracture networks. In most other cases,a successful shale-gas well requires hydraulic stimulation. Together,the Devonian Antrim Shale of the Michigan basin and Devonian Ohio Shale of the Appalachian basin accounted for about 84% of the total 380 bcf of shale gas produced in 1999. However annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed: the Devonian New Albany Shalein the Illinois basin,the Mississippian Barnett Shale in the Fort Worth basin,and the Cretaceous Lewis Shale in the San Juan basin. In the basins for which estimates have been made,shale-gas resources are substantial,with in-place volumes of 497-783 tcf. The estimated technically recoverable resource(exclusive of the Lewis Shale)ranges from 31 to 76 tcf. In both cases,the Ohio Shale accounts for the largest share.
fractured sandstone; liquid permeability; gas permeability; laboratory study
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文章题目第一作者来源出版物1Fractured shale-gas systemsCurtis JBAAPG Bulletin,2002,86(11): 1921-1938 2 Mississippian Barnett Shale,Fort Worth basin,north-central texas: Gas-shale play with multi-trillion cubic foot potential Montgomery SL AAPG Bulletin,2005,89(2): 155-175 3 Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment Jarvie DMAAPG Bulletin,2007,91(4): 475-499 4 Shale gas potential of the Lower Jurassic Gordondale Member,Bulletin of Canadian Petroleum Geology,northeastern British Columbia,Canada Ross DJK 2007,55(1): 51-75 5 Characterizing the shale gas resource potential of Devonian-Mississippian strata in the Western Canada sedimentary basin: Application of an integrated formation evaluation Ross DJKAAPG Bulletin,2008,92(1): 87-125
Fractured shale-gas systems
JB Curtis
*摘编自《石油学报》2012年33卷 增刊1:107~114页
*摘编自《石油勘探与开发》2010年37卷6期:641~653页