Table of Content

24 August 2008, Volume 29 Issue 4

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The Yanshanian movement and its control over hydrocarbon accumulation in western China

He Zhiliang, Gao Shanlin

2008, 29(4):  419-427.  doi:10.11743/ogg20080401

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The mid-Yanshan tectonic movement had rebuilt the tectonic framework in western China.At the end of Late Jurassic,the Yarlung-Tsangbo oceanic lithosphere of the Neo-Tethys subducted northward,Bangong CoNu Jiang ocean was closed,Lasha and Qiangtang blocks collided,and the Okhotsk sea in the north was also closed.The regional tectonic compression reactivated the ancient suture and large old faults and accelerated the uplifting of the Orogenic belt in western China.It also led to the formation of angular unconformities of various scopes and types between the Jurassic and Cretaceous in the western basins,the formation of new structures at the margins of the basin and along the faults,and further reconstruction of the existing structures.Accompanying with the movement,the basins in western China entered a new evolution stage since the Cretaceous (the timing might be a little bit different in different regions).The significances of Yanshan movement to hydrocarbon accumulation and reservoir readjustment include:(1)it exerted dual influences to the underlying source rocks through speeding up thermal evolution in the relatively continuous and rapid subsidence zones at piedmont and postponing the peak of hydrocarbon generation and expulsion in zones experienced multi-stage uplifting and slow subsidence,thus providing conditions for the highly effective hydrocarbon accumulation during the Himalayan period;(2)deformation,uplifting,weathering,erosion,and leaching greatly improved the poroperm characteristics of the reservoirs underlying the unconformities,and extensive glutenite reservoirs of high quality were deposited in the lower part of the Cretaceous above the unconformities;(3)the various types of traps in combination with the paleohighs and faulted zones laid down foundation for the formation of different types of hydrocarbon accumulations in various strata.

Characteristics of development of deep fault depressions and hydrocarbon accumulation in the Songliao Basin

Chen Bo, Huang Famu, Xia Yongtao, Luo Mingxia, Liu Jiyong

2008, 29(4):  428-432.  doi:10.11743/ogg20080402

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More than 70 fault depressions of various scales occur in the Songliao Basin and they have significantly different levels of development and hydrocarbon enrichment.Study of the characteristics of the fault depression and the associated volcanics shows that the subduction of the Pacific plate to the Northeast-Asia plate in different directions and speeds during the Late Jurassic and Early Cretaceous resulted in the development of fault depressions of various scales in different stages.In the Late Jurassic,the positive subduction of the Pacific plate to the Northeast-Asia plate caused the rising of the upper Mantle and the thinning of the earth crust,and resulted in the characteristics of fault depression distribution similar to "triple junction".Influenced by the hysteretic effect of tectonic stress transmission,fault depressions near the triple junction are characterized by early development, strong extension,large scale and thick deposits.In contrast,fault depressions far from the triple junction are characterized by late development,weak extension,small scale and thin deposits.In the Early Cretaceous,the regional tectonic stress field converted from extension to transtension,with its influences limited to the eastern fault depression and the fault depressions on both sides of the central uplift.The continuous development of the fault depression in this region and the stagnant of the development of fault depressions in other regions further enhanced the unbalance of development of fault depressions.The continuously developed fault depressions are characterized by large scale,thick fault depression sequences,multiple sets of source rocks,high level of hydrocarbon enrichment,and large potential of exploration.The fault depressions developed in late stage have relatively smaller exploration potential.The fault depressions developed in early stage are characterized by small scale, thin sequence and the least exploration potential.

Hydrocarbon pooling conditions and exploration potential in the Fulin sub-sag of the Zhanhua Sag,the Jiyang Depression

Le Dafa, Hou Shuaijun

2008, 29(4):  433-436,443.  doi:10.11743/ogg20080403

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Fulin sub-sag is a secondary structural unit in Zhanhua sag of Jiyang depression,Bohai Bay Basin. Geochemical analysis and oil-source correlation show that the sag not only contains mid-and low-mature oils from the central and eastern parts of the sub-sag,but also mature oil from the third member of the Paleogene Shahejie Formation in Gunan sag,in which the mid-mature oil is predominant.The conditions and characteristics of hydrocarbon migration determine the formation and distribution of oil and gas reservoirs.The complex pathway network consisting of unconformities and faults in Fulin sub-sag and its periphery as well as the spatial configuration of reservoir sandbodies in various strata controlled the migration and distribution of oil and gas.

Features of carrier beds and distribution of oil and gas in the Gaoyou Sag,the Subei Basin

Qiu Xuming

2008, 29(4):  437-443,436.  doi:10.11743/ogg20080404

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Analysis of the distribution of three sets of source rocks and their contact relationship with surrounding rocks in Gaoyou sag reveals that the lower part of the first member of the Dainan Formation,the upper parts of the first member of the Funing Formation and the first member of the Taizhou Formation,are the main hydrocarbon carrier beds.The complicated fault systems in combination with sandstone carrier beds form a three dimensional hydrocarbon carrier network,which can be classified into many types according to different carrier modes. The types of these carrier systems decide the distribution of hydrocarbons in the sag.

An analysis on the process of hydrocarbon accumulation in the central depression belt of the Junggar Basin

Yin Wei, Zheng Herong, Xu Shilin, Ma Lijuan, Jia Qingsu, Wu Xinhe

2008, 29(4):  444-452.  doi:10.11743/ogg20080405

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The formation and evolution of the Che-Mo palaeo-high controlled hydrocarbon accumulation and evolution in the central depression.The relatively large volume of hydrocarbon charging during the Middle and Late Jurassic formed the early "Che-Mo fossil hydrocarbon accumulation belt",part of which was wrecked by the uplifting and denudation in the Late Jurassic.Another large-scale hydrocarbon charging happened and formed the middle "Che-Mo fossil hydrocarbon accumulation belt" during the late Early Jurassic-Paleogene,which was also the main reservoiring stage for the primary oil and gas reservoirs in the Jurassic and Cretaceous in the central depression.The "Che-Mo fossil hydrocarbon accumulation belt" was finally destructed since the Neogene,resulting in the present distribution of oil and gas.Generally speaking,the early uplifting during the late Middle JurassicPaleogene controlled the oil and gas accumulation of the Mesozoic in the central depression,while the late structural adjustment since the Neogene determined the present distribution of oil and gas.The Che-Mo paleo-high and its flanks,especially areas in its south flank where the Middle and Upper Jurassic were denuded,are rich in oil and gas resources because of the favorable preserving conditions and slight influence from later tectonic movement,thus are important areas for future exploration.

Direction for future oil & gas exploration in SINOPEC's exploration area in the Junggar Basin

Song Chuanchun, Peng Yongmin, Qiao Yulei,Shi Haoguo, Wang Shuhua,Zhuang Wenshan

2008, 29(4):  453-459.  doi:10.11743/ogg20080406

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SINOPEC' s exploration area in the Junggar Basin is characterized by small acreage,deep burial of reservoirs and scattering of blocks,causing difficulties in exploration.Exploration results show that it is challenging to correlate the main oil layers discovered in the study area with that in the adjacent oilfields of CNPC Xinjiang Oilfield Company.The major oil layers mostly occur at a higher horizon than the designed targets.It is believed that there possibly exist four horizontal and four vertical plays in the Jungar Basin.These plays are thought to have different characteristics and their distributions can be related to the orientations of deep faults and the locations of traps.Their levels of hydrocarbon enrichment might be related to the location of hydrocarbon kitchens and the stratigraphic positions of the source rocks,especially the carrier system formed by the unconformities and the source rock-rooted faults.The analyses of petroleum geological characteristics,reservoiring conditions,and main types of oil reservoir,reveal that the exploration in the study area shall take stratigraphic-lithologic reservoirs in the western margin as the primary targets,and that in Huaizhong block as the second targets,while the stratigraphic-structural reservoirs in the northern margin and Qingelidi Mountain block as the future exploration targets.

Diagenetic evolution and its effects on hydrocarbon migration:a case from the Fuyang reservoir in the Qijia-Gulong Sag,the West Songliao Basin

Cai Lixue, Jin Xiaohui, Xiao Wenling

2008, 29(4):  460-465.  doi:10.11743/ogg20080407

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Based on the analysis of various data such as casting sandstone thin section,scanning electron microscope (SFM) and X-ray diffraction (XRD),this paper summarizes the petrological and mineralogical charaeteristics,diagenesis and its evolution of the Fuyang reservoir in the Songliao Basin,and studies the relationships between the diagenetic evolution and the physical and oil-bearing properties of sandstone carrier beds.Comprehensive study shows that the Fuyang reservoir is characterized by deep burial depth and strong diagenesis,and the diagenetic evolution controlled the physical and oil-bearing properties of the sandstone carrier beds and directly influenced the patterns of hydrocarbon migration.

Analysis on the sequence stratigraphic framework and its forming mechanism of the first member of Yaojia Formation in the North Songliao Basin

Hou Yanping, Ren Jianye, Ren Yanguang, Zhuang Xinguo, Wang Yafeng

2008, 29(4):  466-470.  doi:10.11743/ogg20080408

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A sequence stratigraphic framework is established for the first member of Yaojia Formation in northern Songliao Basin by using seismic,log,core and paleontologic data.Three fourth-order retrograding sequences are recognized in the first member of Yaojia Formation.They are in unconformable contact with the underlying Qingshankou Formation,indicating that the Songliao Basin experienced transient uplifting during the early deposition of the first member of Yaojia Formation before subsiding and receiving deposits once again and getting larger in lake basin area.The first member of the Yaojia Formtion was deposited in ca.88-87Ma when restructuring occurred in the Pacific plate.An analysis of the sequence stratigraphic framework and its forming mechanism demonstrates that compression initiated in the basin during the deposition of the first member of Yaojia Formation and its sequence stratigraphic framework was a result of this plate restructuring event.

Groundwater hydrodynamics and hydrocarbon accumulation in the Jurassic of the Turpan Depression

Lou Zhanghua, Jin Aimin, Li Huaming, Zhang Huiting

2008, 29(4):  471-478,501.  doi:10.11743/ogg20080409

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The evolution of groundwater hydrodynamic field and origin of groundwater in sedimentary basins control the distribution patterns of chemical field of ground water.At the margin of a basin,groundwater desalinates due to the downward infiltration of atmospheric water,while in the central depression,groundwater desalinates due to discharge from mudstone under compaction.In contrast,groundwater concentrates in bypassing discharge area.During centrifugal and endoeentric flow processes,groundwater concentrates and gets salinized,forming a relative high salinity zone in the bypassing discharge area.Centrifugal flow from mudstone compaction serves as the main driving force of hydrocarbon migration in sedimentary basins and provides a favorable environment for large scale hydrocarbon accumulation during the bypassing and discharging of ground water.Moreover,it also can contribute some hydrocarbons to the lithologic,stratigraphic,fault traps located on the pathway of hydrocarbon migration.The advancement of endocentric flow may destroy the earlier hydrocarbon pools and also possibly lead to the formation of hydrodynamic traps at specific geologic conditions.

Analysis on groundwater hydrodynamic systems of the Mesozoic in the central Ordos Basin

Wang Xiaomei, Wang Zhenliang

2008, 29(4):  479-484,501.  doi:10.11743/ogg20080410

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Groundwater serves as the carrier for hydrocarbon migration.The modes of groundwater occurrence have an effect on hydrocarbon migration,accumulation,and distribution in a basin.Therefore,a correct division of groundwater hydrodynamic systems can be a useful guidance for hydrocarbon exploration and development. The analyses of the present groundwater pressure field,geochemical field and stable isotope features of the Mesozoic (T₃y-K) in central Ordos Basin revealed three kinds of groundwater hydrodynamic systems of various characteristics.They are the relative open zone in the shallower part,the transitional zone in the middle part,and the relative confining zone in the deeper part.The relative confining zone in the deeper part has the most favorable conditions for hydrocarbon preservation and can be the target for future exploration.

Petroleum geologic characteristics and play prediction in the Sirte Basin,Libya

Tian Naxin, Chen Wenxue, Huo Hong, Tian Jianbo, Wu Jie

2008, 29(4):  485-490.  doi:10.11743/ogg20080411

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Sirte Basin,an intracratonic rifted basin in North Africa,is the most important petroliferous basin in Libya.It has experienced three stages of evolution:the Early Paleozoic eratonic margin depression,the Early Cretaceous-Late Eocene rift and the post-Oligocene depression.Three sets of source rocks were developed :the Lower Cretaceous shale,the Upper Cretaceous shale and the Paleogene shale,of which the Upper Cretaceous Sirte Formation shale is the main source rock.Reservoirs occur at various horizons from the basement to the Oligocene. The Pre-Cretaceous reservoirs are dominated by clastic rocks,while the Upper Cretaceous reservoirs and their overlying reservoirs mainly consist of carbonate rocks.Cap rocks are mainly the Upper Cretaceous and Lower Eocene shale,marl and evaporite.A series of horsts and grabens in parallel with the faults were developed under the control of the NW-NE-trending normal faults.Laterally,three hydrocarbon accumulation zones in correspondence with three roughly parallel horst uplifts were recognized:the western,central and eastern zones.Vertically, two oil-bearing sequences were recognized:the pre-horst and horst fillings.According to the above analysis,three types of favorable plays occur in the Sirte Basin:type Ⅰ in the horst zone,type Ⅱ in the graben zone and type Ⅲ in the northern offshore area.

Fluid inclusion types and their geological significance in petroliferous basins

Liu Dehan, Xiao Xianming, Tian Hui, Lu Jialan, Min Yushun

2008, 29(4):  491-501,478,484.  doi:10.11743/ogg20080412

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This paper presents a systematic nomenclature and taxonomy for fluid inclusions.Three groups of inclusions,namely the hydrocarbon inclusions,hydrocarbon-containing inclusions,and aqueous/non-hydrocarbon inclusions ,have been recognized based on microscopic fluorescence and transmitted light properties of inclusions.The hydrocarbon inclusions can be further divided into nine types based on their composition and phase characteristics :liquid hydrocarbon-liquid-gaseous hydrocarbon inclusions,gaseous hydrocarbon inclusions,bitumen-containing inclusions,hydrocarbon-bearing aqueous inclusions,hydrocarbon-bearing gaseous inclusions,liquid phase aqueous inclusions,two-phase aqueous inclusions,non-hydrocarbon gaseous inclusions,and childmineral-bearing aqueous inclusions.The liquid hydrocarbon-liquid-gaseous hydrocarbon inclusions can also be divided into four subclasses:heavy-oil inclusions,medium-oil inclusions,light-oil inclusions,and condensed oil inclusions.In addition,the paper also focuses on the distribution patterns of hydrocarbon inclusion in reservoirs, source rocks,and carrier beds,and the geological application of these fluid inclusions to the generation,migration,accumulation,and evolution of hydrocarbon.

Application of tectonic-thermal evolution history to hydrocarbon accumulation timing in sedimentary basins

Ren Zhanli, Liu Li, Cui Junping, Xiao Hui, Gao Shengli

2008, 29(4):  502-506.  doi:10.11743/ogg20080413

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The hydrocarbon generation,migration,accumulation,and reservoiring,are controlled by basin tectonic-thermal history.The sedimentary basins in China are mostly superimposed basins with complicated thermal history.Basins with different tectonic-thermal evolution history and different thermodynamic settings vary dramatically in source rock maturity,depth of oil-generation threshold,key hydrocarbon generation time,and period and times of hydrocarbon accumulation.Multiphase hydrocarbon accumulation is one of the characteristics of the superimposed basins in China.It was controlled by the multiphase hydrocarbon generation of the source rocks and ultimately by the tectonic-thermal evolution history of the basin.The methods for the timing of hydrocarbon accumulation are plenty but all have upsides and downsides with their different approaches and principles.A detailed description of tectonic-thermal history is regarded as an effective way to deal with the contradictory caused by these methods.

Application of fluid inclusion to the study of hydrocarbon charge history of the south slope in the Huimin Sag

Liu Chaoying, Yan Xiangbin, Xu Xuhui, Zhou Qingfan, Qin Weijun

2008, 29(4):  507-510,542.  doi:10.11743/ogg20080414

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The analytical methods of homogenization-temperature and chromatogram-mass spectrum of inclusions are applied to the study of the hydrocarbon charge history of the south slope in Huimin sag.It is suggested that the difference in hydrocarbon charge history is one of the key factors for the differences in hydrocarbon abundance.According to the analysis,the hydrocarbons in Qianguantun were charged in the Mid-Minghuazhen period,while that in the upper and lower reservoirs of Qu-10 well in Quti oilfield were charged in two stages based on the mass spectrum analysis of hydrocarbon inclusions.The conditions of application of these inclusion-testing methods are also discussed in detail.

Application of the 3-D fluorescence fingerprint technology to the analysis of oil sources in the western slope of the Dongpu Depression

Zou Wei

2008, 29(4):  511-516.  doi:10.11743/ogg20080415

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A correlative study was carried out on the crude,oil sands,and source rocks in Huqing oilfield by adopting the 3D fluorescence analysis method and integrating the analysis result of aromatic fractions of crude oil.The result shows that crudes in Huqing oilfield can be divided into 5 types and the source rocks can be classified into 3 types according to their spectrum characteristics.The dominant fluorescence wavelengths of the crude oil samples from all the reservoirs are lower than that of the type C source rocks,but higher than that of the type A and type B source rocks.It is therefore suggested that crudes widely distributed in various fault blocks of Huqing oilfield are the mixture of low-mature and mature oil generated during the early hydrocarbon generating cycle.

Weakness and difficulty of petroleum geology study and resource assessment:hydrocarbon dissipation

Liu Chiyang, Ma Yanping, Wu Bolin, Liu Chao

2008, 29(4):  517-526.  doi:10.11743/ogg20080416

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Hydrocarbon migration may have three results:(1)accumulation,(2)diffusion in rocks and fluids,or (3) loss due to interactions with fluids and surrounding rocks or surface exposure.The latter is defined here as dissipation.The dissipation is most active during hydrocarbon migration and is closely linked to hydrocarbon accumulation,thus study of the phenomenon become an indispensible part of petroleum geology research,and petroleum exploration and resource assessment.Hydrocarbon dissipations can be divided into four types according to the differences of quantity and quality of hydrocarbons before and after dissipation:quantity decrease,phase transformation,composition alteration,and quality conversion,reflectting the differences in environment,conditions and characteristics of dissipation.The quality conversion often occurs at surface or near surface,where hydrocarbons will interact with surrounding rocks,pore fluids or air.The epigenetic products and minerals resulted from these interactions generally have no apparent features of hydrocarbons,but the amount of dissipated hydrocarbons is huge,thus much attention should be given to this phenomenon.These products in combination with direct evidences of hydrocarbon dissipation ( such as seepage,bitumen and heavy oil) can not only serve as an important means to address the puzzle of hydrocarbon dissipation and its scale,but also provide effective clues and significant indicators for tracing hydrocarbon pathways,searching for oil and gas pools,and evaluating the scale of dissipations.This paper analyzes and discusses the types,basic characteristics,geochemical properties,environments of formation and distributions of various epigenetic products related with gas dissipation in the Upper Paleozoic in northeastern Ordos Basin.

Numerical simulation analysis of secondary hydrocarbon migration

Zhou Bo, Jin Zhijun, Wang Yi

2008, 29(4):  527-532.  doi:10.11743/ogg20080417

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The analysis of the physical experiment and numerical simulation results shows various oil migration modes.There are three modes of oil migration under actual geological conditions:stable mode,fingering mode, and spring mode.Different migration modes have different patterns of migration,thus using single numerical simulation method to simulate all the modes is not very scientific.Therefore,different migration modes shall be described with different numerical simulation methods.Invasion percolation method is suitable for the description of the fingering mode and the spring mode,while the Darcy equation is applicable for the stable mode.The fluid potential method can be applied to all the three modes,but its results are qualitative.In order to determine the real oil migration process ,the mathematical simulation shall be based on detailed geological data,oil and gas shows and geochemical data.

An experimental study of oil saturation in different secondary migration modes

Hou Ping, Luo Xiaorong, Fan Changjiang, Zhou Bo

2008, 29(4):  533-536.  doi:10.11743/ogg20080418

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There are three modes of secondary oil migration,including stable displacement mode,fingering mode, and spring mode.In order to observe the changing patterns of oil saturation,residual oil saturation,and the ratio of residual oil volume to pathway space under these three migration modes,glass cylinder systems with mediums of different materials and different grain sizes packed with wet-packing method were used to carry out experiments with buoyancy as the only driving force or pumping pressure and buoyancy as the combined driving force. The results show that the oil saturation of the migration pathway and the ratio of residual oil volume to inner space of cylinder vary greatly under different migration modes,while the residual oil saturation remains almost the same.

Reservoir modeling of Che-2 well-block in the Junggar Basin

Liu Jingliang

2008, 29(4):  537-542,510.  doi:10.11743/ogg20080419

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The Qigu Formation reservoir of Che-2 well block in the Junggar Basin is mainly of braided river deposits.Lithology,lithofacies and reservoir structure models were established for the Qigu Formation.The interpolation between wells and stochastic simulation were conducted for each facies according to the quantitative distribution of reservoir parameters in different sedimentary facies.The quality and speed of reservoir characterization were improved,realizing accurate description of reservoir features in respects of structure,sedimentation,physical property and oil-bearing property.The study results lay a solid foundation for the future numerical simulation in this area.