石油实验地质

2012, 34(6)

Abstract(1388) PDF-CN(993)

Abstract:

Petroleum distribution characteristics and subtle reservoir exploration in South America

Li Pilong, Zhang Dajing, Zong Guohong

2012, 34(6): 559-563. doi: 10.11781/sysydz201206559

Abstract(2213) PDF-CN(1095)

Abstract:
Forearc,compressed backarc,foreland,cratonic and passive margin basins have developed in South American ever since Paleozoic.The discovered subtle traps are mainly lithologic(tectonic-lithologic)and unconformity(basement-unconformity,lithologic-unconformity and structural-lithologic unconformity)ones.For the foreland basins,unconformity and lithologic reservoirs are the main reservoir types.For the passive margin basins,lithologic subtle reservoirs are contributive.In the latest decade of exploration,the subtle reservoirs(turbidite,pre-salt carbonate/reef and overlap reservoirs)in the passive margin basins have turned to be the main discoveries.Resource of the subtle reservoirs in South America is assessed to be over 89 billion Barrels Oil Equivalent,mainly as liquid,showing a good exploration prospect.

Stratigraphic classification and correlation of Triassic in Caohu Sag of Shaya Uplift, Tarim Basin

Cai Xiyao, Wei Ling, Tian Wenquan, Yang Yufang, Zhao Lina, Cheng Junfeng

2012, 34(6): 564-570. doi: 10.11781/sysydz201206564

Abstract(2129) PDF-CN(1106)

Abstract:
Triassic was found well-developed and thick in the Caohu Sag of the Tarim Basin;however,stratigraphic classification was not precise,restricting petroleum exploration.According to the study of plentiful of Triassic sporopollen fossils in mudstones from several wells,4 sporopollen fossil assemblages were established,including Lundbladispora-Limatulasporites-Taeniaesporites,Punctatisporites-Aratrisporites-Calamospora,Apiculatisporis-Rugulatisporites-Colpectopollis,and Dictyophyllidites-Aratrisporites-Alisporites.Triassic was divided into three series,three formations and five members.From bottom to top,there are the Ketuer Formation(it was revised as the upper and lower segments)in the lower series,the Akekule Formation(the upper and lower segments)in the middle series and the Halahatang Formation in the upper series.Lithologic and logging characteristics are obvious in each member.The "pure mudstone segment" at the top of the lower member of the Ketuer Formation and the "big mud" at the top of the Halahatang Formation were regarded as the key beds in this area.There is lacuna between the lower series and the middle series.Triassic was divided into three second-order sequences and five third-order sequences.Based on biostratigraphy,combined with rock stratigraphy,sequence stratigraphy and logging strata,Triassic in the area was classified and correlated more precisely,providing data for the analyses of sedimentary facies,tectonic movement and petroleum accumulation.

Stratigraphic meaning and application case of interpretation mode of subtle trap

Li Qun, Gao Jianjun, He Jinhai, Zeng Yong, Liu Jiao

2012, 34(6): 571-574. doi: 10.11781/sysydz201206571

Abstract(2154) PDF-CN(1085)

Abstract:
In view of the difficulties of subtle trap exploration in the middle Junggar Basin,based on the theories of sequence stratigraphy and slope break belt,it was proposed for the first time in this paper the name and definition of "isochronous-trap seismic geologic interpretation mode".The mode was discussed and practiced in single subtle trap formed by single lobes body according to the isochronous nature of sequence contrast and the effectiveness of morphology trap.In solving the problem of serial layers between well Z6 and well Z7,the time and space combination features of subtle trap among lobes bodies were summarized as jigsaw puzzles.A new interpretation method based on the idea of "connection along axial direction and isolation between layers" was put forward.

Reservoir coupling and accumulation pattern of depression in Yaoyingtai area of Changling Sag, Songliao Basin

Gong Xue, Shen Wuxian

2012, 34(6): 575-581. doi: 10.11781/sysydz201206575

Abstract(2351) PDF-CN(1107)

Abstract:
Based on the comprehensive analyses of tectonic settings,sedimentary sequence evolution backgrounds and geologic conditions for petroleum accumulation,Yaoyingtai area in the Changling Sag was qualified for the generation of tectonic-lithologic composite reservoirs.Regional hydrocarbon accumulation conditions were well coupled and composite traps were formed earlier than or at the same time as large scale hydrocarbon source maturation.Oil and gas generated and migrated into the nearest traps.Faults and sand bodies worked as migration channels and matched well with composite traps.By analyzing the collocation relationship between a series of north-south oriented normal faults and various types of sand traps,tectonic-lithologic reservoirs were mainly divided into six formation patterns.According to favorable reservoir area assessments,the area to the east of the western ramp in Yaoyingtai area was predicted as favorable reservoir zone.Yaoyingtai area,which was controlled by tectonic evolution pattern and sedimentary facies superposition,has a good prospect for billions of tons of large and medium-sized tectonic-lithologic composite reservoirs.

Characteristics of deep gas transportation in Changling Fault Depression, Songliao Basin

Zhang Yanxia, Li Haihua, Wang Baohua, Lu Jianlin

2012, 34(6): 582-586. doi: 10.11781/sysydz201206582

Abstract(2030) PDF-CN(1080)

Abstract:
There are four deep transportation types in the Changling Fault Depression: fault,sandstone,fracture and unconformity surface.Faults are the main pathways for gas vertical migration.Sandstones which interbed with source rocks are the main pathways for gas lateral migration.Fractures in volcanic rocks provide favorable pathways for gas migration,which is the controlling factor for the effectiveness of volcanic reservoirs.The effectiveness of deep transportation system in the Changling Fault Depression is affected by the matching of hydrocarbon kitchen location and hydrocarbon generation and expulsion stages as well as the matching of gas migration pathway and transportation system.The transportation system which exists during hydrocarbon generation and expulsion stages and is connected along favorable migration pathways is critical for gas accumulation.Closely related to the time and space distributions of transportation system,natural gas is widespread laterally and is found in multiple layers vertically.Fault transportation close to source rocks is the most common transportation way for volcanic reservoirs in the Changling Fault Depression,which controlls the regular migration pattern of deep gas.Gas migrates along faults and accumulates nearby.

Characteristics and petroleum geologic significances of clay rims in sandstones of Mingshui Formation, well Songke 1, Songliao Basin

Fu Meiyan, Zhang Shaonan, Ding Xiaoqi, Liao Qiming, Xiong Di, Zhu Zhiliang

2012, 34(6): 585-593. doi: 10.11781/sysydz201206585

Abstract(2225) PDF-CN(1168)

Abstract:
Clay rim is one of the influencing factors of sandstone properties.The characteristics of clay rims in sandstones from the Mingshui Formation in well Songke 1 in the Songliao Basin have been studied by means of casting thin section observation,XRD,SEM and EDS.The clay rims in sandstones from the Mingshui Formation are composed of montmorillonites with potassium and iron,and the contents of potassium and iron increase as burial depth increases.The clay rims are original ones,and can be further divided into inherited and infiltrated clay rims.They mainly distribute in fine-grained and silt-grained sandstones in shore sand platform,and are poorly developed in fine-grained and medium-grained sandstones in subaqueous distributary channels in delta fronts.The generation of clay rims is mainly controlled by source,climate,granularity and hydrodynamic condition.The genetic type,mineral composition and crystal feature of clay rims all influence the preservation of porosity.As a result,the studies of the composition and distribution of clay rims have an important significance for clastic rock reservoir evaluation.

Recovery of compact history of Yanchang reservoir in Upper Triassic, Ordos Basin

Guo Zhengquan, Qi Yalin, Chu Meijuan, Cheng Dangxing

2012, 34(6): 594-598. doi: 10.11781/sysydz201206594

Abstract(2349) PDF-CN(1293)

Abstract:
Microscopy and scanning electron microscopy identifications of cast thin sections of sandstones from the Yanchang Formation of the Ordos Basin have been made in view of the characteristics of low and ultra-low porosity and permeability.Diagenesis effects such as compaction,cementation,dissolution and hydrocarbon emplacement have been proved in the sandstone reservoir of the Yanchang Formation and the diagenesis sequence has been made clear.The difference of diagenesis sequence between delta sandstone and gravity flow sandstone has been studied.Chlorite membrane is well-developed in delta sandstone and the compaction effect is weak.In gravity flow sandstone,chlorite membrane does not exist and the compaction effect is severe.Through the quantitative calculation of diagenesis,the evolution history of porosity has been restored.Early compaction and late cementation lead the decrease of porosity.After the early compaction,reservoir is not tight.And after the late cementation,porosity has decreased to below 12% while permeability is about 1×10^-3μm²,both referring to extra-low and ultra-low permeability reservoir.These perceptions have an important guiding significance in predicting relatively high permeability reservoirs and discovering oil fields.

Hydrocarbon accumulation dating by fluid inclusion characteristics in Chang7 tight sandstone reservoirs of Yanchang Formation in Ordos Basin

Shi Baohong, Zhang Yan, Zhang Lei, Yang Yajuan, Li Hui

2012, 34(6): 599-603. doi: 10.11781/sysydz201206599

Abstract(2577) PDF-CN(1609)

Abstract:
There are various fluid inclusions in the Chang 7 reservoir of the Yanchang Formation in the Ordos Basin.According to the diagenetic stages and homogenization temperatures of host minerals for fluid inclusions,two different phases of hydrocarbon inclusions have been identified.The hydrocarbon inclusions of the first phase locate in the interiors and fissures of quartz overgrowth area and the homogenization temperature of brine inclusions is from 120℃ to 140℃.The hydrocarbon inclusions of the second phase locate in the late fissures which cut across quartz and(or)feldspars and the homogenization temperature of brine inclusions is mainly from 90℃ to 110℃.Combined with the thermal and burial histories of the Chang 7 Formation,the tight reservoirs has experienced two stages of fluid filling.The main accumulation took place during the late period of Early Cretaceous.

Distribution and evolution of sedimentary system in different types of basin edge：A case study of peripheral regions of Bodong Buried Hill, Dongying Sag

Yang Yongqiang, Qiu Longwei, Li Cong, Yin binxiang, Wang Yaming

2012, 34(6): 604-610. doi: 10.11781/sysydz201206604

Abstract(2459) PDF-CN(1363)

Abstract:
Based on core,logging,borehole and oil testing data,it was discussed in this paper the distribution of depositional systems and oil reservoir types in the upper subsection of the 4th member of the Shahejie Formation in the peripheral regions of the Bodong Buried Hill,the Dongying Sag.Due to strong source supply,delta sediments were widespread during the LST period in the eastern stable basin edge(the Guangrao Uplift).In the western active basin edge(the Bodong Buried Hill),sandy beach bar sediments generated as the result of source shortcoming.Meanwhile,the sedimentary boundary of beach bar moved southwards with the lifting of the Shicun Fault.During the TST and HST periods,carbonate beach bar sediments were common,and the scale of carbonate beach bar in active basin edge decreased;however,it had good physical properties because of weathering and leaching effects.The active basin edge has complex accumulation characteristics.Early stratigraphic reservoirs,late structural-lithologic reservoirs and carbonate lithologic reservoirs are the main exploration target.In the stable basin edge,only one trap type is found,indicating early stratigraphic reservoirs.

Characteristics and prediction of overpressure in continental strata, YB area, northeastern Sichuan Basin

Sun Qi, Li Tianyi, Zhou Yan, Yang Jun, Tao Ze, Yang Gansheng, Fan Dehua

2012, 34(6): 611-616. doi: 10.11781/sysydz201206611

Abstract(2424) PDF-CN(1937)

Abstract:
In YB area of the northeastern Sichuan Basin,several sets of pressure systems exist.From the upper Triassic to Jurassic,especially in continental strata,overpressure and strong overpressure are common.Based on DST(drill stem test)and logging data,the present pressure features in YB area and the logging responses of mudstone overpressure sections in 3 typical wells are analyzed.The pressure coefficient of continental strata from the Upper Triassic to Jurassic in YB area ranges from 1.3 to 2.2,indicating overpressure or strong overpressure.The top burial depth of overpressure zones locates at 3 600-4 000 m.The logging responses of mudstone overpressure sections show that the resistance of mudstones changes obviously while DT and mudstone density do not change very much.It might be related to the obvious difference between ancient and present burial depth and the high saturation of gas.The formation pressures converted from mudstone DT by means of Eaton formula are close to field testing results.A pressure prediction model to revise mudstone acoustic logging based on tested pressure has been made and might achieve good prediction results.

Evolution characteristics of methane stable carbon isotope in thermal simulation experiment:Discussion of δ¹³C₁-R_o relationship under experimental and natural conditions

Xue Luo, Xu Sihuang, Yuan Caiping, Liu Xiaoxia, Li Songfeng

2012, 34(6): 617-622. doi: 10.11781/sysydz201206617

Abstract(2369) PDF-CN(1262)

Abstract:
By means of thermal simulation experiment,5 mudstone samples from Palaeogene of the Zhu Ⅰ Depre-ssion have been tested.The studies of methane stable carbon isotope have shown that when R_o is below 1.2%-1.3%,methane stable carbon isotope decreases as R_o increases.When R_o is over 1.2%-1.3%,methane stable carbon isotope increases as R_o increases.The changing principle may be explained by the differences of activation energy between ¹³C methane(heavy methane)and ¹²C methane(light methane).Under experimental and natural conditions,the relationship between methane stable carbon isotope and R_o are different,which might be the results of "effects after hydrocarbon generation".Due to the effects,massive gas migration leads to the weaken-ing of carbon isotope fractionation.The studies may guide gas field exploration.Heavy methane carbon isotope indicates high-mature gas source rocks,large-scale migration and good prospects for gas exploration.

Geochemical features and environmental significances of deposits in Ordovician karstic fractures and caves, Lunnan area, Tarim Basin

Dan Yong, Liang Bin, Cao Jianwen, Zhang Qingyu

2012, 34(6): 624-628. doi: 10.11781/sysydz201206624

Abstract(2235) PDF-CN(1283)

Abstract:
In the Ordovician karstic fractures and caves in Lunnan area of the Tarim Basin,three types of depo-sits have been identified including water mechanical fillings,chemical deposits and gravity collapse debris.The comparisons of chemical and trace element compositions between deposits and bedrocks have indicated that when different deposits were formed,fluid properties and hydrological environment were different,and the migration,enrichment and fractionation of elements were also different.As a result,the chemical and trace element compositions can be used to judge the fluid properties and hydrological environment when the Ordovician karstic fractures and caves were filled.Three kinds of filling environment have been found including oxidizing active freshwater environment in seepage-active undercurrent zone,freshwater environment in stagnant undercurrent zone as well as pressure-released and hot water environment in shallow-buried zone.The study is helpful for karstic re-servoir prediction and evaluation.

Evaluation of hydrocarbon generating conditions of Palaeogene source rocks from Xidalinzi Sag in Sanjiang Basin

Li Zhongyuan, Ma Liyuan, Tao Ye, Sun Yipu

2012, 34(6): 630-634. doi: 10.11781/sysydz201206630

Abstract(2284) PDF-CN(1201)

Abstract:
The Palaeogene source rocks from the Xidalinzi Sag of the Qianjin Depression of the Sanjiang Basin were evaluated systematically and were compared with those from the Yishu Graben.In the Xidalinzi Sag,mudstones developed well in Palaeogene,especially in the Baoquanling Formation.From the 2nd member of the Baoquanling Formation to the Dalianhe Formation,the organic abundance of mudstones increased and the organic type gradually improved;however,the maturity of organic matters was lower,generally during the immature and low mature stages.The mudstones in the Dalianhe Formation and the lower part of the 1st member of the Baoquanling Formation served as the effective source rocks for the Xidalinzi Sag which has good exploration prospect.

Experiment geology research of carbonate dolomitization

Fan Min, Xu Liangfa, Liu Weixin, Yu Lingjie, Zhang Wentao, Li Zhimin, Tenger, Li Songyang

2012, 34(6): 635-640. doi: 10.11781/sysydz201206635

Abstract(2399) PDF-CN(1030)

Abstract:
According to the dynamic mechanisms of dissolution and preciptation of carbonate rocks,two modelling approaches for dolomitization were proposed: 1)repeated heating and cooling;2)convectional circulation.The modelling products were characterized using several different instruments.The results suggested that dolomites could be obtained by both of the two methods.Through thermodynamic analysis and experimental study,the influences of Mg/Ca concentration ratio,sulfate ion and temperature on dolomitization process were discussed.The study suggested that it was hard to obtain dolomite in the lab because of the difficulty in the growth of dolomite germ.Once the germ appeard,the growing speed of dolomite would be faster than that of calcite.This paper explained why no young age dolomite exists in the natural environment and supplied new thoughts on dolomitization research and carbonate reservoir prediction.

Identification and division of high-frequency cycles based on Milakovitch theory：A case study on Miocene Sanya and Meishan Formations in Qiongdongnan Basin

Mao Kainan, Xie Xinong, Xu Wei, Kang Bo

2012, 34(6): 641-647. doi: 10.11781/sysydz201206641

Abstract(2405) PDF-CN(981)

Abstract:
Natural gamma data from the wells LS-33A,YC-35B and ST-36A in different structures of the Qiongdongnan Basin have been used for spectral analysis and continuous wavelet transform.In different wells,the Miocene Sanya and Meishan Formations are mainly dominated by the 404 ka and 95 ka eccentricity cycles.A high-resolution astronomical timescale of each formation is established based on the analysis of cycle filter and Milankovitch cycle curve which controls strata development.Finally,the sequence stratigraphy of high-frequency cycles in the Sanya and Meishan Formations is divided and correlated by using short eccentricity cycle curve as the reference curve for the fifth-order sequence units.The investigation provides a new effective approach to build the correlating framework of high-resolution sequence in the offshore basins.

High-precision analysis technology of seismic sequence strata and its application：A case study of Binhai region in Qikou Sag, Bohai Bay Basin

Zhang Zhaohui, Su Mingjun, Liu Huaqing, Li Shuangwen, Hong Zhong, Yuan Shuqin

2012, 34(6): 648-652. doi: 10.11781/sysydz201206648

Abstract(2162) PDF-CN(924)

Abstract:
Common technology of seismic interpretation on sequence strata has much limitation.For example,the space distribution and imbricate pattern of sedimentary units within system tract can not be interpreted.Also,strictly speaking,it is hard to establish isochronous stratigraphic sequence framework.The strata slices which are of isochronous meaning are difficult to achieve.In order to resolve these problems,this paper adopts a new seismic interpretation technology of sequence strata to identificate the boundary of sequence and system tract,and to calibrate and demonstrate the variation of deposition cycle displayed in Wheeler domain,and to clarify the distribution law of sand,and finally to identify lithologic trap.This paper confirms the maximum flooding surface,first flooding surface and sequence boundary by the technology in Binhai region of the Qikou Sag,and progresses constrained seismic inversion,and finds many lithologic traps in LST.The practical application of this technology has been proved feasible and efficient.

Primary study of recovery rate of undeveloped gas reservoir in Changxing Formation, Yuanba Gas Field

Qian Qin, Yan Wei, Wang Xueling

2012, 34(6): 653-655. doi: 10.11781/sysydz201206653

Abstract(2214) PDF-CN(740)

Abstract:
The Changxing reservoir in the Yuanba Gas Field is a deep-buried carbonate gas pool with high sulfur content,low porosity and low permeability.At present,the Changxing reservoir is undeveloped.Various methods such as empirical equation,analogy and material balance have been applied to determine the recovery rate of different calculation units.Technologically recoverable reserves have been calculated,providing an important basis for preparing development program scientifically and reasonably.

Determination of gas deviation factor for abnormal overpressure gas reservoir

Li Dingjun

2012, 34(6): 656-658. doi: 10.11781/sysydz201206656

Abstract(1969) PDF-CN(1274)

Abstract:
Gas deviation factors in formation conditions are the critical data to calculate gas reserves.As to abnormal overpressure gas reservoirs,several methods such as experimental determination,chart and analytic model can be used to determine gas deviation factors.A case study has been carried out in abnormal overpressure gas reservoir in the lower section of the fourth member of the Xujiahe Formation,the Xinchang Gas Field.It has been concluded that in abnormal overpressure reservoirs,gas deviation factors can be determined by means of experimental determination(PVT),chart under high pressure and LXF analytic model.

Application of mathematic statistics in tracing oil migration trend：A case study of Ordovician crude oil in Tahe Oil Field

Xu Jin, Xi Binbin, Rao Dan, Zhang Meizhen

2012, 34(6): 660-663. doi: 10.11781/sysydz201206660

Abstract(1998) PDF-CN(811)

Abstract:
A new method,based on the theory of mathematic statistics,is constructed to analyze the crude oil migration trends.A good deal of indices tracing crude oil migration trend are characterized as a parameter: migration index(I_m).Contour maps by Im can figure the direction of oil migration.A reliability parameter(K)which is used to judge the credibility of the results is also defined in this method.Concentration data(66)of polar compounds,maturity parameters(13)and isomer ratios(15)of polar compounds of Ordovician crude oil samples(22)from the Tahe Oil Field were analyzed respectively.The results show that crude oil migration directions are from east to west and from south to north.Compared with the K values of the three groups of parameters,the Im of polar compound concentration can indicate the direction most accurately.

2012 Vol. 34, No. 6

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