英文摘要

Influenceofcarbonatenear-surfacestructuresonseismicwaveenergy.ZhongMinshou1,XieQuanmin2,ChangJian3,LiuShaoguang4,LongYuan1andLiuYing1.OGP,2018,53(3):437-442.

In order to study the change of seismic wave energy and frequency in layered near-surface,we carry out physical simulation tests.Based on this simulation,certain frequency components have tuned amplification effects when the near-surface consists of rock inter-beds,and if seismic frequency components have tuned amplification strong seismic energy will be recorded in good near-surface conditions.In order to study the influence of bare limestone on seismic energy,we conduct some field tests.The following observations are obtained: A.The main explosive stress energy concentrates in several thousand MHz which attenuates rapidly,while low-frequency energy is recorded; B.Low-frequency mixed with stress wave forms seismic wavelet.Seismic wavelet energy is rather weak due to limestone thickness and density,so recorded seismic wave energy is weak in carbonate areas; C.In limestone near-surface areas,reflection quality is very poor with the distortion of amplitude,frequency and phase,which makes more difficult in carbonate exploration.Our research results might be a reference for hydrocarbon exploration and development in carbonate areas.

Keywords: seismic exploration,carbonate,blasting seismic wave,energy attenuation

1.Army Engineering University of PLA,Nanjing,Jiangsu 210007,China

2.Ornance N.C.O.Academy of Army Engineering University of PLA,Wuhan,Hubei 430075,China

3.Nanjing Geophysical Department,Research Institute of Petroleum Exploration and Development,SINOPEC,Nanjing,Jiangsu 210014,China

4.Ningde Public Security Bureau,Ningde,Fujian 352100,China

DeghostingwithGaussbeammigration.WuJuan1,BaiMin1andZhangHua2.OGP,2018,53(3):443-448.

In marine seismic data,the ghost contaminates primary waves,reduces data resolution,and sometimes even produces false events.Ghost removal during migration for better geological interpretation is one of the challenges in marine seismic exploration at present.In this paper we propose a deghosting approach with Gauss beam migration.Firstly,the Gaussian beam migration algorithm of common shot gathers is put forward.Then compensation terms for source and receiver ghosts are added to the migration formula.At the same time,an appropriate algorithm is given to ensure the stability in order to compensate ghost effects.Finally,numerical experiments demonstrate the feasibility and effectiveness of the proposed approach.After deghosting,the primary wave migration is achieved and data resolution is improved,which is favorable for subsequent interpretation and inversion.

Keywords: deghosting,Gaussian beam,seismic migration,source,receiver,stability

1.School of Resources and Environment,North China University of Water Resources and Electric Power,Zhengzhou,Henan 450046,China

2.School of Geephysics and Mearsurement-control Technology,East China University of Technology,Nanchang,Jiangxi 330013,China

Automaticfirstbreakpickingbasedonlocalsimilarityattribute.LiuBaihong1,LiJianhua2,ZhengSi-lian1,SongZhixiang1,ZhangJingdong2andSunWeizhao3.OGP,2018,53(3):449-453.

We propose in this paper a new approach for automatic first break picking.First,local similarity attributes such as local cross-correlation are calculated on traces of shot records.At the same time,a central point of first-break search is calculated based on near-surface velocity and offset for every trace of shot gathers.And a first-break search scope is determined for every trace of the shot gather.Then local cross-correlation trace is used as the input of the modified energy ratio method to detect first-breaks.The location of the maximum energy ratio in the search range can be considered as first break of the trace.Model and real data tests show that the proposed approach is robust under noisy conditions and easy to use.

Keywords: first breaks,automatic picking,local similarity attribute,energy ratio

1.Geophysical Research Institute,SINOPEC,Nanjing,Jiangsu 211103,China

2.Geological Research Center,GRI,BGP Inc.,CNPC,Zhuozhou,Hebei 072751,China

3.Overseas Biseness Department,GRI,BGP Inc.,CNPC,Zhuozhou,Hebei 072751,China

Amatchingpursuittime-frequencyanalysismethodbasedonOpenMPparallelcomputing.DengShiguang1,2,WangShuyan3,ZhaoWenjin2,LiuZhiwei2andHeRun4.OGP,2018,53(3):454-461.

The smoothed-pseudo Wigner-Ville distribution (SPWVD) based on matching pursuit has a high time-frequency resolution,but the calculation is extremely large in the matching pursuit algorithm and SPWVD calculation of all the wavelets.To improve the efficiency of this method,we propose a parallel computing method for the matching pursuit time-frequency analysis based on OpenMP.The searching process in the matching pursuit algorithm and the SPWVD calculation of all the wavelets are achieved in parallel.Field seismic data processing shows that the efficiency of the proposed parallel algorithm is significantly improved,and its computation precision is the same as the serial algorithm.Parallel calculation performance shows that the speedup grows linearly as the number of processors increases,and larger computation amount can fully exploit the advantage of multi-core processors.

Keywords: parallel computing,matching pursuit,time-frequency analysis,OpenMP,smoothed-pseudo Wigner-Ville distribution (SPWVD)

1.China Earthquake Networks Center,Beijing 100045,China

2.Chinese Academy of Geological Sciences,Beijing 100037,China

3.The Marine Information Technology Research Institute Co.Ltd.,CETC,Beijing 100041,China

4.Northwest Branch,Research Institute of Petroleum Exploration & Development,PetroChina,Lanzhou,Gansu 730020,China

3DtraveltimeraytracingbasedonChebyshevpolynomials.MiaoHe1,SunJianguo1,WangRui1,YanHongqun1,YinChang1andWeiPuli1.OGP,2018,53(3):462-468.

In this paper,we use the fast marching method (FMM) algorithm to calculate the traveling time field.According to the definition of the function approximation and orthogonal polynomial,we use Chebyshev orthogonal polynomials to approximate the traveltime field so that the error minimizes in the least-square sense.Then the differential function in the Chebyshev interpolation function is directly used to calculate the gradient of the traveling field.And finally the ray path is obtained.Numerical experiments show that the proposed method improves greatly the accuracy and efficiency of ray path calculation.

Keywords: ray tracing,traveltime gradient,Chebyshev polynomial,approximation function,preliminary wave,seismic tomography

1.College for Geoexploration Science and Technology,Jilin University,Changchun,Jilin 130026,China

Least-squaresreversetimemigrationbasedontheangularfilteringimagingcondition.LiuMengli1,2,HuangJianping1,2,LiChuang1,2,CuiChao1,2andRenYingjun1,2.OGP,2018,53(3):469-477.

On the basis of predecessors’ researches,we first analyze the cause of the low frequency noise in the reverse time migration (RTM).Then we deduce the angular filtering imaging condition using the reflection angle information obtained from wavefield data,combine it with the least-square reverse time migration (LSRTM),and develop least-squares reverse time migration based on the angular filtering imaging condition (ALSRTM).The feasibility and amplitude of ALSRTM is analyzed with the energy conservation of wave equation.Numerical test on the international standard SEG-EAGE 2-D salt dome model validates our ALSRTM and proves that the ALSRTM can not only significantly suppress migration artifacts,but also has a better amplitude-preserved capacity compared with those results obtained with the conventional LSRTM.Besides,ALSRTM has a stronger adaptability than the conventional LSRTM in the presence of migration velocity errors.

Keywords: least-squares migration,angular filtering imaging condition,acoustic homogeneous wave equation,sparse acquisition,low-frequency noise

1.School of Geosciences,China University of Petroleum (East China),Qingdao,Shandong 266580,China

2.Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266071,China

Hybriddomainparallelalgorithmfor3DKirchhoffprestackdepthmigrationintheheterogeneousenvironment.WangYida1,ZhaoChanghai2,LiChao1,ZhangJianlei2,YanHaihua1andZhangWeiyi2.OGP,2018,53(3):478-486.

The 3D Kirchhoff prestack depth migration (KPSDM) is the most important depth-domain imaging method in the seismic data processing.Currently seismic data size of a single survey exceeds 100TB,and will increase to more than 1PB in the near future.Considering the continuous increasing survey sizes and the introduction of programmable graphic process unit (GPU),the conventional parallel strategy is no longer appropriate for the large-scale heterogeneous processing clusters.In this paper,we propose a practical hybrid domain parallel KPSDM algorithm based on two-level decomposition including imaging space and seismic data.The algorithm eliminates the dependency among tasks.In a heterogeneous environment,we implement the computing part on GPU and design a “dynamic and asynchronous” task allocation policy to achieve load balancing on heterogeneous computing system.Because KPSDM,as part of its execution,usually requires repeated access to huge seismic data and a large amount of travel time tables,the scalability is always limited by the shared storage maximum throughput.To solve the scalability problem,we build a distributed cache system using the local storage for a KPSDM job spans.It can provide a very high aggregate data bandwidth to supply seismic data and travel time table to a running task timely.The KPSDM implementation can obtain close to linear speedup when it processes real seismic data on a 256-node cluster.

Keywords: Kirchhoff prestack depth migration (KPSDM),parallel algorithm,hybrid domain,graphic process unit (GPU),heterogeneous cluster,distributed cache

1.School of Computer Science and Engineering,Beihang University,Beijing 100191,China

2.Research & Development Center,BGP Inc.CNPC,Zhuozhou,Hebei 072751,China

Seismicreflectiondatawaveformimagingbasedonreflectionwaveequation.ChenShengchang1.OGP,2018,53(3):487-501.

Under the high frequency approximation on wave phenomena and spatial variations of physical parameters of subsurface medium,scattering waves degrade into reflection waves,and the corresponding scattering wave equation degrades into reflection wave equation based on impedance relative perturbation.Reflection wave equations based on the reflectivity is derived through the definition of reflectivity as the directional derivative of the impedance relative perturbation with respect to the propagation direction of incident wave.Using these reflection wave equations and the linear inverse theory,we establish a waveform imaging method based on reflection wave equations for seismic primary reflection data.According to the reflection wave equation based on the impedance relative perturbation and the reflection wave equation based on the reflectivity,we first apply adjoint operators of reflection wave propagator to establish an approximate inversion of impedance relative perturbation and a reflectivity waveform migration,then reapply the least squares inverse operator of refection wave propagator to establish a least squares inversion of impedance relative perturbation and a reflectivity least squares waveform migration.Aiming at the huge amount of calculation and the instability of the least squares inverse operator of reflection wave propagator,we use an iterative solution to the least squares inversion of impedance relative perturbation and the reflectivity least squares waveform migration.The waveform imaging method proposed in this paper can faithfully use the waveform information of seismic data in the sense of wave equation,and it is a real wave equation migration imaging.

Keywords: seismic reflection data,reflection wave equation,impedance relative perturbation,inversion,reflectivity,waveform migration

1.School of Earth Sciences,Zhejiang University,Hangzhou,Zhejiang 310027,China

Focalmechanismofshear-tensilemicroseismicandamplitudedistributioncharacteristics.TangJie1,2,WangHao1,2,WenLei1,2andZhangWenzheng1,2.OGP,2018,53(3):502-510.

Microseismic events induced by hydraulic fracturing contain many non-double couple types,shear tensile rupture may occur in rocks.Shear-tensile type microseismic show many differences in source and amplitude characteristics compared with shear type earthquake.We study in this paper the shear-tensile mechanism,and analyze shear-tensile source microseismic radiation pattern and energy propagation characteristics.The main understandings are included: A.Shear-tensile sources generate shear and tensile motions and the source tensor can be described with strike,dip,rake,and tensile angle;B.Moment tensors of shear-tensile source can be decomposed to double-couple (DC) and non-double-couple (Non-DC) components.Non-double-couple components comprise the compensated linear vector dipole (CLVD) and the isotropic (ISO) component;C.Radiation energy of shear-tensile source will change with the tensile angle,the amplitude distribution at surface receivers is relative to focal mechanism,model parameters,and sensor positions.Based on study of the focal mechanism and amplitude distribution characteristics of shear-tensile microseismic,we can get a better understanding of the source characteristics and signal distribution.

Keywords: microseismic,source tensor,moment tensor,radiation pattern,shear-tensile source,tensile angle

1.School of Geosciences,China University of Petroleum (East China),Qingdao,Shandong 266580,China

2.Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266071,China

BrittlenessandfracabilitypredictionfortightoilreservoirinJimsarSag,JunggarBasin.RenYan1,CaoHong1,YaoFengchang1,LuMinghui1,YangZhifang1andYanXinfei1.OGP,2018,53(3):511-519.

Tight oil and gas reservoirs are characterized by significant heterogeneity,poor physical properties,low single-well production,and great difficulties in the development.In order to identify high brittle formations and establish accurately a fracability prediction model,we summarize and compare the applicability of the existing brittleness index for the brittleness evaluation of tight oil reservoirs,and put forward a modified mineralogical brittleness index with favorable applicability in Jimsar Sag,Junggar Basin.On this basis,we analyze the relationships between fracability and brittleness,fracability and fracture toughness,and fracability and compressive strength.Finally we propose a new fracability index.Based on our study,the following understandings are obtained: a.The contents of dolomite,feldspar,and pyrite are the main factors which affect rock brittleness of tight oil reservoirs in Jimsar Sag; b.Formations with high brittleness index do not necessarily have good fracturing candidate due to the complex condition of tight oil reservoir,only brittleness alone cannot characterize accurately the fracability; c.Based on the new fracability index,formations with higher brittleness,lower fracture toughness and compressive strength are considered as good fracturing la-yers.This new method is applied in the fracability prediction for the Well J174 in Jimsar Sag,which optimizes fractured sections to guide hydraulic fracturing operations.

Keywords: Jimsar Sag,tight oil reservoir,rock brittleness,fracture toughness,compressive strength,fracability index

1.Research Institute of Petroleum Exploration & Development,PetroChina,Beijing 100083,China

Verticalresolutionofbroadband,wide-azimuthandhigh-densityseismicdata.RanJianbin1,ZhangMingyu2,LiHaiying1,ChenJia1,ZhuZhe1andXingHongge1.OGP,2018,53(3):520-527,537.

We discuss in this paper the vertical resolution of broadband,wide-azimuth and high-density (BWH) seismic data acquired in 2015 in Pubei Oilfield,Tuha Basin.With synthetic seismogram,filtering in an octave,and inversion,it is found that different-band reflections present different resolutions of strata interface in different scales.Lower-frequency seismic data resolution can identify large-scale interfaces,and high-frequency seismic data resolution can identify both large-scale and small-scale interfaces.When seismic data lasts low-frequency information,fewer interfaces could be identified.Low frequency of seismic data determines seismic inversion accuracy,and high frequency of seismic data decides seismic inversion resolution.Reservoir prediction based on BWH seismic data is significantly improved by broadband seismic inversion,and effectively guided lithologic reservoirs exploration in Tuha Basin.

Keywords: Tuha Basin,filtering in an octave,vertical resolution,inversion

1.GRI,BGP Inc.,CNPC,Zhuozhou,Hebei 072750,China

2.Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China

Seismiccharacteristicsandhydrocarbonsignificanceofsaucer-shapedintrusionsinQiongdongnanBasin.WuXiaochuan1,2,ZhangGongcheng3andPuRenhai1,2.OGP,2018,53(3):528-537.

There are two types of saucer-shaped intrusions: sandstone intrusion and magmatic intrusion.Both of them have similar seismic response characteristics.Abnormal reflection bodies in Qiongdongnan Basin show obviously saucer-shaped high amplitude;the lower disordered columnar reflection from the crystalline basement of the basin is regarded as the vent of magma upwelling;and the upper strata was forced to become fold and form overlap unconformity.The forced fold width is larger than the saucer-shaped intrusion,and the earliest time of intrusion indicated by the overlap unconformity is 10.5Ma.Based on VSP data from periphery wells and reflection strength of intrusions,wave impedance could be calculated,and its value 1.1×107kg·m-2·s-1much bigger than drilling statistics of the maximum value of sand wave impedance 5.3×106kg·m-2·s1-.In addition,the adjacent layers of intrusions do not display over-pressure or material conditions which would lead sand liquefaction.Therefore,the saucer-shaped intrusions are igneous sills.According to the damaged degree of the low penetrative chilled selvage at the sill margin,the sill traps can be divided into covered trap,cap rock trap,lenticular trap,and secondary trap in country rocks,which are potentials in the oil and gas exploration.

Keywords: saucer-shaped intrusion,wave impedance,chilled borders,trap,Qiongdongnan Basin

1.State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi’an,Shaanxi 710069,China

2.Department of Geology,Northwest University,Xi’an,Shaanxi 710069,China

3.CNOOC Research Institute,Beijing 100027,China

Small-scalecavedetectionbasedonfrequency-segmentedimaging.ZhuBohua1,YangJiangfeng1,LüQiuling1,WangZhen2,MaYongqiang1andZhangWei1.OGP,2018,53(3):538-544.

Aimed at the difficulties of small-scale fracture-cavern reservoir detection in Tarim Basin,we propose in this paper a new small-scale cave detection method.First with the concept of seismic resolution,we demonstrate the importance of high frequency seismic data for improving the detection accuracy of small-scale fracture-carven reservoirs through forward modeling with different dominant frequency.Then we analyze the small-scale bead-like reflection to determine the bandwidth of small-scale caves and obtain frequency segmenting parameters.After that,we carry out the frequency segmenting and prestack time migration for CMP gathers and get high frequency data volume.Finally we conduct small-scale cave detection based on the high frequency data volume.Based on seismic data processing results,small-scale caves can be effectively detected on high frequency data volume,but they cannot be detected on conventional data,and it is also very helpful to characterize cave boundaries.Our prediction is highly consistent with drilling results,which greatly avoids risks in the exploration and development.

Keywords: carbonate,seismic resolution,forward modeling,bead-like reflection,prestack frequency- segmented,small-scale cave detection

1.Geophysical Research Institute,SINOPEC,Nanjing,Jiangsu 211103,China

2.Exploration and Development Research Institute,Northwest Oilfield Branch Co.,SINOPEC,Urumqi,Xinjiang 830011,China

AVOinfluencefactorsanalysisinheavyoilsaturatedreservoirs.XieXiang1,WuKui1,ZhangJinhui1,GaoJinghua1andFanJianhua1.OGP,2018,53(3):545-551.

Due to a special temperature-pressure environment and forming mechanism,the heavy oil density is very close to the water density,which makes seismic response characteristics of heavy oil reservoirs very similar to that of water-bearing strata.Hence heavy oil reservoirs are very difficult to be identified with AVO.For this purpose,we propose a new petrophysical property analysis method for heavy oil reservoirs based on AVO sensitive factors.Firstly,after rock physics analysis based on Zoeppritz-equation and Biot-Gassmann theory,the relationships between reflection coefficient and petrophysical property (porosity),and reflection coefficients and oil-gas possibility (oil saturation) are established with rock elastic parameters.The influences of oil saturation and porosity on AVO characteristics of heavy oil reservoirs are then successively analyzed by the integration of fluid substitution,porosity substitution,and AVO forward modeling.Results indicate that the porosity is the major sensitive factor of AVO characteristics while the influence of oil saturation is negligible.Finally,this method is applied to the Jinzhou-A Oilfield,the lateral variation of porosity within targets is analyzed,and the result is consistent with drilling data,which confirms the effectiveness of the proposed method.

Keywords: AVO,heavy oil reservoir,reservoir petrophysical property,fluid substitution,porosity substitution,forward modeling

1.Bohai Oilfield Research Institute,Tianjin Branch,CNOOC,Tianjin 300459,China

Faultdetectionbasedonmagicmatrix.LiJun1,ZhangJunhua1,GongMingping1,YangYong2,DuYushan2andWuGang2.OGP,2018,53(3):552-557.

Edge detection methods are efficient and important for fault detection in seismic exploration.However most edge detection algorithms do not consider seismic dip and orientation information,and they cannot well detect some geological bodies such as faults and fractures.Therefore we propose in this paper a fault detection method based on magic matrix.The specific steps are as follows: ①Select a magic cube,subtract the center value of all the elements of the matrix to obtain a new matrix,assign non-zero elements in the new matrix to 0 apart from the maximum and minimum absolute value of the elements,and obtain fault detection operator template; ②Follow the clockwise direction to rotate the fault detection operator template at 45° intervals to obtain the detection operator in other directions; ③Select a data sub-cube centered on a point of seismic data,The convolution operation is respectively to the data sub-cube and each direction of the cube operator to obtain data sub-cubes of different directions; ④The maximum absolute value of the obtained each direction convolution data is used as the each direction edge detection result.The maximum value of the fault detection results in different directions is selected as the edge detection result of the calculated point,and the corresponding direction is the tendency of this point.Model test and real data application show that the proposed method can effectively detect faults and give the corresponding dip information.

Keywords: magic matrix,fault detection,detection operator template,anti-noise performance,inclination

1.School of Geosciences,China University of Petroleum (East China),Qingdao,Shandong 266580,China

2.Exploration & Production Research Institute,Shengli Oilfield Branch Co.,SINOPEC,Dongying,Shandong 257015,China

DensityandvelocityanalysisandseismicreflectionmodelconstructionofmarineMesozoic-PaleozoicintheNorthJiangsu-to-SouthYellowSeaBasin.LeiBaohua1,2,3,ChenJianwen1,2,3,WuZhiqiang1,2,3,ZhangYinguo1,2,3,LiangJie1,2,3andLiGang1.OGP,2018,53(3):558-567.

Seismic imaging of marine Mesozoic-Paleozoic is difficult in the North Jiangsu-to-South Yellow Sea Basin,which brings many difficulties to the petroleum exploration.A reflection model can be built based on the principle that rock density and velocity differences cause different seismic reflection waves,and seismic markers can be recognized and formation properties can be predicted.Therefore we investigate target density and velocity data in the study area,analyze velocity and density variation with depth,lithology,stratigraphic,and diagenesis.Then we build velocity,density,and reflection models of the target,and compare them with seismic data.Based on this research,there is large difference in velocity and density between carbonate rocks and clastic rocks in the upper marine strata of the target,and there is little difference between them in the lower strata.In the built reflection model,there are 3 markers of strong reflection in the Paleozoic,corresponding to 3 interfaces: they are the interface between Qixia formation and Gufeng formation in the lower Permian,the interface between Gaolishan formation and Hezhou formation of the Lower Carboniferous,and the interface between Tangtou formation and Wufeng formation of the upper Ordovician.These model interfaces can compare with the first quality of latest seismic data in the South Yellow Sea Basin.

Keywords: velocity and density,reflection model,marine strata,North Jiangsu Basin,South Yellow Sea Basin

1.Qingdao Institute of Marine Geology,China geology Survey,Qingdao,Shandong 266071,China

2.Laboratory for Marine Mineral Resource,Qing-dao National Laboratory for Marine Science and Technology,Qingdao,Shandong 266071,China

3.Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology,Ministry of Land and Resources,Qingdao,Shandong 266071,China

Jointinversionofelastic-electricaldataforgashydratereservoirsbasedonBayesiantheory.PanHaojie1,ZhangYan1,LiHongbing1,LiuTanyan2,DengJian3andZhaoYi3.OGP,2018,53(3):568-577,586.

A single set of sonic velocity or resistivity data are usually used to estimate hydrate reservoir parameters based on simple linear or logarithmic linear rock physics.However,elastic data and electrical data have different sensitivity of reservoir parameters;the estimation based on different data may generate different values of reservoir parameters.In order to solve this problem,we propose a new method of elastic-electrical joint inversion based on a nonlinear simplified three-phrase equation and a modified Archie equation under the frame of Bayesian theory,with which we can simultaneously predict gas hydrate saturation,porosity,clay content,and their corresponding uncertainty.The feasibility of the joint inversion method is verified by both synthetic data tests and real well logging data tests.The results indicate that the joint inversion of elastic-electrical data can not only produce reliable reservoir parameter estimations,but also reduce effectively the uncertainty caused by different sensitivity and noise.

Keywords: Bayesian theory,elastic-electrical data,gas hydrate,rock physics model,reservoir parameters

1.Research Institute of Petroleum Exploration and Development,CNPC,Beijing 100083,China

2.State Key Laboratory of Marine Geology (Tongji University),Shanghai 200092,China

3.Exploration and Development Research Institute,Huabei Oilfield Company,PetroChina,Renqiu,Hebei 062552,China

Responsecharacteristicsofanewcoplanarcoilsysteminthinbeds.ZhangMiaoyu1,2,GuoBaolong1,WuJie2andWuYinchuan1,2.OGP,2018,53(3):578-586.

Thin beds cannot be distinguished since the conventional tri-component coplanar coil system causes various responses in them.Therefore we propose a new coplanar coil system based on two-transmitters and one-receiver sub-array configuration.First a modelling is achieved with the analytic method.With tangential continuity in a bed boun-dary and the Bessel function,the horizontal component of magnetic field intensity is obtained.Then we calculate the response of 8 sub-arrays of two coplanar coil systems in bedded formations,and analyze logging response influence caused by coil spacing,bed thickness,and thin-bed conductivity.The following understandings are obtained: a.The boundary position is clearly shown by the new coplanar coil system when the thin bed thickness is greater than the distance between the primary transmitting and receiving coils,and the measurement accuracy is improved by 53.1% compared with the conventional coplanar coil system; b.Fluctuations occur at the bed boundary due to the influence of the coplanar coil system and surrounding rocks when the thin bed thickness is less than the distance between the primary transmitting and receiving coils,but these fluctuations are less than that of the conventional coplanar coil system.Based on the analysis of the eddy-current distribution of the transmitter coil,we have found the mechanism that the skin-effect and negative-response are reduced by the new coplanar coil system.Our research results have an important significance for the tri-component array meter design and logging response evaluation.

Keywords: tri-component,array induction,coplanar coil system,inter-beds

1.Institute of Intelligent Control and Image Engineering,Xidian University,Xi’an,Shaanxi 710071,China

2.School of Electronic Engineering,Xi’an Shiyou University,Xi’an,Shaanxi 710065,China

Marinemoving-wire-sourceCSEM3Dresponsesi-mulationwiththecoupledpotentialfinitevolumemethod.ZhouJianmei1,LiXiu1andQiZhipeng1.OGP,2018,53(3):587-596.

We propose a marine controlled-source (moving-wire-source) electromagnetic (CSEM) 3D response simulation with a coupled potential finite volume method.First Maxwell’s equations are transformed into coupled scalar-vector potential Helmholtz equations with the electric field scalar-vector potential decomposition.A discrete linear equation with symmetry coefficient matrix is obtained with Lorentz gauge.Then the direct discrete method is used for the source.The linear equation of marine CSEM is solved with BICGSTAB iteration after ILUT pre-conditioning.In order to speed up the moving-source iteration calculation and forward modeling,we develop a solution initial value reset technique,namely the response before source moving is used as a solution initial value for the discrete equation after source moving.Based on numerical model tests,the discrete error around the source is significantly reduced when the length of source is four times of the source-mesh length;and the forward modeling with initial value reset is faster than conventional forward modeling.All this proves the effectivity of the proposed approach.

Keywords: marine controlled-source electromagne-tic (MCSEM),moving-wire source,finite volume method,Lorentz gauge

1.College of Geology Engineering and Geomatics,Chang’an University,Xi’an,Shaanxi 710054,China

Highresistivityreservoiridentificationbasedonsynthetic-sourcesmarinecontrolled-sourceelectromagneticdata.LiPan1andLiYuguo1,2.OGP,2018,53(3):597-605.

In shallow water areas,the marine controlled-source electromagnetic (CSEM) method faces challenges because the air wave from the air-sea interface interacts with signals from the seabed and dominates the electromagnetic responses,which makes it difficult to acquire signals and improve the ability to identify resistance reservoirs.The synthetic-source processing based on radar field synthetic aperture can be used to highlight high resistivity anomaly of thin beds and identify high resistivity reservoirs.In this paper,we discuss the source-interference method of marine CSEM field.We first calculate normalized amplitude,effective anomaly,and detectivity for 1D model,and compare their identification of high resistivity reservoirs.Then we calculate the normalized amplitude,effective anomaly,detectivity for 2D marine model,and the detectivity of synthetic sources for 3D model.Finally,we apply the proposed method to real data.The examples show that the detectivity can improve high-resistivity reservoir identification on synthetic-source marine CSEM data.

Keywords: marine controlled-source electromagne-tic (MCSEM),normalized amplitude,detectivity,synthetic aperture

1.School of Geosciences,Ocean University of China,Qingdao,Shandong 266100,China

2.Key Laboratory of Submarine Geosciences and Prospecting Technology,Ministry of Education,Ocean University of China,Qingdao,Shandong 266100,China

Animprovedstablealgorithmofthereduction-to-the-poleatlowlatitudes.ZhangQi1,2,ZhangYingtang1,LiZhining1andFanHongbo1.OGP,2018,53(3):606-616.

As the routine reduction-to-the pole (RTP) operator at low latitudes is usually unstable in the frequency domain,we propose an improved stable RTP algorithm at low latitudes.First the high frequency noise in amplification zones is suppressed with the local-suppression and global-suppression RTP approaches based on routine RTP operator (RO) modifications.Then the introduced parameters are optimized by calculating the correlation coefficient between the RTP results and the norma-lized source strength.RTP results with the optimal parameters are obtained,and the accuracy of these RTP results is accordingly improved.Finally,to resolve the problem of high-frequency amplification effect in the optimal RTP operators,the Tikhonov regularization method is utilized to stabilize the operators.Experimental results on theoretical model indicate that the proposed algorithm eliminates the high-frequency noise in the original data and improves the signal-to-noise ratio of the RTP results,and the accuracy and stability of the low latitude RTP are greatly improved.

Keywords: reduction-to-the pole (RTP),low latitude,frequency domain,correlation coefficient,re-gularization

1.Department of Vehicle and Electrical Enginee-ring,Shijiazhuang Campus,Army Engineering University,Shijiazhuang,Hebei 050003,China

2.Unit 94019 PLA,Hetian,Xinjiang 848000,China

Comparisonof3Dcontrolled-sourceelectromagneticforwardmodelingbasedonthenodalfiniteelementandtheedge-basedfiniteelement.TangWenwu1,LiuJianxin2,YeYixin1andZhangHua1.OGP,2018,53(3):617-624.

In the early stage,the nodal element was mainly used for the forward modeling of the 3D controlled-source electromagnetic (EM) responses,but its spurious mode affected calculation efficiency and solution accuracy.The edge-based finite element method is increasingly adopted in the 3D EM modeling since it can avoid spurious solutions.To study details of the efficiency and accuracy between these two methods,comparison experiments are carried out.First the construction of the boundary-value problem is discussed.Then the forward modeling based on these two methods are achieved on both a horizontal-layered model and a single low-resistivity body model.Our comparison experiments show that under the same modeling condition,the result accuracy with the edge-based finite element is better than that with the nodal element while the edge element is slower than the nodal element as the first one spends about twice of calculation time of the latter one.

Keywords: nodal element,edge element,controlled-source electromagnetic (EM),3D forward modeling

1.School of Geophysics and Measurement-Control Technology,East China University of Technology,Nanchang,Jiangxi 330013,China

2.School of Geosciences and Info-physics,Central South University,Changsha,Hunan 410083,China

Someprogressinreservoirfracturestochasticmodelingresearch.DongShaoqun1,2,ZengLianbo1,2,XuChaoshui3,CaoHan4,WangShengjiao1,2andLüWenya1,2.OGP,2018,53(3):625-641.

Reservoir fracture modelings are important ways to research the reservoir fracture system distribution.These modelings can be divided into two kinds: deterministic modelings and stochastic modelings.In the most used stochastic modelings,five modelings can be found,namely space-subdivision fracture modeling,discrete-fracture network modeling,fracture modeling based on variogram,fracture modeling based on multiple-point geostatistics,and fracture modeling based on fractal iteration.This paper introduces the principle,characteristics and applicability of these five fracture modelings in detail.The first one is suitable for simple fracture systems.The second,third and fourth ones are suitable for most fracture systems.The fifth one is suitable for simple fracture systems with obvious fractal characteristics,such as hydraulic induced fracture.In addition,the advantages and shortcomings of these methods are systematically analyzed and the development trend of fracture stochastic modeling methods is summarized.

Keywords: fracture,stochastic modeling,space subdivision,discrete fracture network,variogram,multiple-point geostatistics,fractal

1.College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China

2.State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum (Beijing),Beijing 102249,China

3.School of Civil,Environmental,and Mining Engineering,University of Adelaide,Adelaide 5005 SA,Australia

4.Institute of Remote Sensing and Digital Earth,Chinese Academy of Sciences,Beijing 100094,China

Currentsituationsandrecentprogressindifferentazimuthsseismicexploration.GongMingping1,ZhangJunhua1,WangYanguang2,LiuLibin2,LiHongmei2andWuXiyuan1.OGP,2018,53(3):642-658.

This paper summarizes recent progress in different azimuth seismic exploration from three aspects including acquisition,processing,and interpretation: A.Using coil gathers and snail gathers combined with multi-source simultaneous shooting can reduce the exploration cost and efficiency improve wide-azimuth acquisition; B.The offset vector tile (OVT) can solve azimuth anisotropy problems,preserve offset and azimuth information,and improve seismic imaging accuracy in the process; C.Azimuthal anisotropy within seismic wave propagation in fractured strata can be used to improve fracture prediction,but there are very fewer application examples of surface seismic.So the future research should pay more attention to the aspect in order to improve fracture prediction accuracy; D.Azimuth-relative attribute (for instance AVAZ) fusion with coherence consistency can effectively predict fractures and stratigraphic lithology.

Keywords: coil gather,snail gather,different azimuths,seismic attribute,offset vector tile (OVT)

1.School of Geosciences,China University of Petroleum (East China),Qingdao,Shandong 266580,China

2.Geophysical Research Institute,Shengli Oilfield Branch Co.,SINOPEC,Dongying,Shandong 257022,China