Table of Content

17 October 2013, Volume 27 Issue 5

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Tectonic and Sedimentary Characteristics

Formation of JX Transfer Zone in the Liaodongwan Depression，Offshore Bohai Bay Basin

Yun Yi-xin，ZHOU Xin-huai，XU Chang-gui，WEI Gang，WU Kui，ZHANG Xin-ying，YANG Ke-ji

2013, 27(5):  999-1004. 

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Based on seismic data and displacement-distance scaling，this paper analyzes the formation of the JX transfer zone in the middle part of the Liaodongwan depression.  The oil-bearing JX structure is a large-scale strike-slip duplex structure where two segmented faults of the Liaozhong-No. 1 strike-slip fault overstep and interact each other.The rhombic faulted block between the two segmented and overstepped faults transferred their displacements，and the conservation of fault displacements formed the JX transfer zone which belongs to the type of oblique anticline.The JX transfer zone experienced four evolution stages，including the isolated faults，transfer zones initiation，complication and rupture.The integrated study on transfer zones has important significance to oil and gas exploration in the offshore part of the Bohai Bay basin.

Sedimentary Response to the Strike-slip Activities of Tan-lu Fault in Central And Southern Parts of East Liaodong Bay Area in Bo Hai Sea

JIANG Zi-wen，WANG Si-min，XU Chang-gui，WU Guo-qiang，NIU Xin-jie，PAN Long

2013, 27(5):  1005-1012. 

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Tan-lu fault is a famous strike-slip fault in East Asian and many significant achievements have been made after years of study.  This article discusses the response of the fault activity based on study of the influence to the sedimentary system，deposition center and sequence stratigraphic in central and south part of the east Liao-dong Bay area，Bohai Sea. It is revealed that the Tan-lu fault activity has controlled and modified the distribution and migration of the sedimentary system and deposition center:(1)the strike-slip movement faulted the previously formed sedimentary system and depositional center;(2)the fault activity leads to the horizontal migration of sedimentary system and depositional center formed in the same period;(3)the fault activity makes the progradation characteristic of the delta unobvious.  Fault activity has influenced the sequence configuration and internal composition of the sedimentary facies distribution model by changing the accommodation space.

Characteristics of Kalashayi Fault Zone Activities in Bachu Uplift，Tarim Basin

LU Ming，TANG Liana-jie

2013, 27(5):  1013-1022. 

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Based on the interpretation of seismic data，the residual thickness of sediment strata，contact relationship between overlying and underlying strata，interfaces in the hanging wall and footwall blocks，and development characteristics and variational rules of unconformitv in Kalashayi fault in Bachu uplift of Tarim Basin were researched，moreover the characteristics of activities of Kalashayi fault in different stages were investigated.  The results show that the east section and the west section of Kalashayi fault have different activities. In the east section，the fault is inactive from Late Cambrian to Ordovician，and thrusting nappe fault occurs from the late stage of Early Silurian to Early Permian；in Middle Permian the fault is inactive and thrusts again in Late Permian.  The subsidiary faults located in the south of main fault are inactive from Late Cambrian to Earlv-Middle Silurian，then strongly thrust since Early Devonian and continue to thrust until Early Permian；after a quiet period within Middle Permian，the faults are weakly active in Late Permian. In the west section，the fault is inactive since Late Cambrian；in  Ordovician，the fault is active to be an extensional fault；from Silurian to Middle Permian，there occurs a quiet stage；in Late Permian，the fault has undergone a positive inversion movement.  The subsidiary faults in the west section are inactive from Late Cambrian to Middle Permian and are strongly active to be thrusting nappe faults since Late Permian.

Extensional Tectonic Feature and Its Control on Hydrocarbon Accumulation of Saihantala Sag in Erlian Basin

QU Xiao-yang，YANG Ming-hui，LUO Xiao-hua，DING Chao，ZHOU Duo，GONG Ting

2013, 27(5):  1023-1032. 

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Based on the seismic profile interpretation，the tectonic feature of Saihantala Sag in Erlian Basin and its control on reservoir-forming were researched. It was concluded that there were different levels of faults which constituted the fault system in Saihantala Sag. The faults can be classified into four classes:the first-class faults controlled the tectonic pattern;the second-class faults controlled the secondary structural belt;the third-class faults controlled the local structure;the fourth-class faults complicated the local structure. The fault active stages can be divided into five stages as follows，the fault-depression period in Jurassic，the initial fault-depression period in Aershan Formation，the strong fault-depression period in Tengger Formation，the fault-depressed diversionary period in Tengger Formation and the ending of fault-depression period in Saihantala Formation. The Saihantala Sag exhibited a east-west belted and south-north partitioned pattern，and developed five first-order tectonic units，four secondary structural belts and various types of local structures. The fault activity controlled the source-reservoir-cap assemblage and its  development，and the fault provided oil and  gas  accumulation space. The long-term active faults were major transporting hydrocarbon fault types in Saihantala Sag. Controlled by structural belts，the oil of Saihantala Sag has accumulated mainly in the central fault zone and the eastern depression zone.

Geological and Hydrocarbon Accumulation Characteristics in Piedmont Zone

LIU Chuan-peng，LUO Liang，QI Jia-fu，YU Hong-zhou

2013, 27(5):  1033-1041. 

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The piedmont zone includes fold-thrust belt and foreland basin adjacent to the orogen. According to the formation mechanism classification of foreland basin，piedmont zones can be divided into three types，i. e. retro-arc foreland piedmont zone，peripheral foreland piedmont zone and rejuvenated foreland piedmont zone. Based on the superimposed basin classification，piedmontzones can be divided into positive inversion piedmont zone and successor foreland piedmont zone. Rejuvenated foreland piedmont zone and successor foreland piedmont zone are only found in the middle and western China. Some principles of hydrocarbon accumulation in piedmont zone have been summarized. Pre-foreland shale is source rock，foreland sandstone and pre-foreland carbonate rock are good reservoirs，and mudstone，gypsum salt and salt rock are cap rocks. Fault is the main channel of hydrocarbon migration. Structural trap is the main type in the fold-thrust belt，while structural-stratigraphic trap is dominated in the foreland basin.

“Four-in-One”Response Characteristic in Sequence Boundary Surfaces of Silurian to Devonian inTarim Basin and Its Significance to Petroleum Geology

TIAN Jing-chun，SHAO Xiao-yan，ZHANG Xiang，LIN Xiao-bing

2013, 27(5):  1042-1050. 

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Based on detailed observation of outcrops of basin rim and the typical drilling cores in basin，analylogs and interpretation of seismic cross-section，the“four-in-one" response characteristic of critical sequence boundary  surfaces  during the  sedimentary  evolution   of Silurian  to  Devonian in  Tarim Basin  are detailedly researched ( including S/O sequence boundary surface，corresponding to T⁰₇ in seismic corss-section；sequence boundary surface between Upper Silurian and Lowe-Middle Silurian,corresponds to T¹₆ in seismic cross-section;sequence boundary surface between Upper Devonian and Middle Devonian,corresponds to T⁰₆ in seismic cross-section;sequence boundary surface between Carboniferous and Devonian,corresponds to T⁷₅ in seismic cross-section),in other words,characteristics of sequence boundary surfaces in outcrops ,cores,well logs and seimic cross-section.The results show that the sequence boundary surfaces display unconformity in outcrops and cores，saltation in well logs and uplap，downlap or truncation in seismic cross-section.Afterwards,the petroleum geological significance of sequence boundary surface formation is detailedly elaborated as follows：（1）the sequence boundary reflects the conversion of the basin nature in critical period;(2)the sequence boundary is an important channel for oil and gas migration;(3)the sequence boundary surfaces are beneficial to the formation of trap.The acquisition of the thesis research will provide an important foundational geological data further oil and gas exploration of Silurian to Devonain in Tarim Basin.

Sedimentary Facies of Lower Permian in Southeast of Ordos Basin

WANG Wei，JI Han-cheng，MEN Xiang-yong，AI Jia-yi

2013, 27(5):  1051-1057. 

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In recent years，enormous resource potential of unconventional gas has been found in the Lower Permian in southeast of Ordos Basin. Aimed at finding out the sedimentary environment,  based on the detailed core，logging and indoor analysis，with the theory of sedimentology，the research on sedimentary facies in the Lower Permian in southeast of Ordos Basin were carried out. The results revealed that barrier, lagoon，tidal flat and neritic shelf facies developed in the Taiyuan Formation and that delta and lake fades developed in the Shanxi Formation.  This paper concluded that the environment changed from transitional facies to terrestrial facies from Taiyuan Formation to Shanxi Formation.

Sedimentary System and Provenance Orientation of the Red-Bed Sedimentary Period in Dongying Sag

JIA Hai-ho，JI Han-cheng，WU Zhi-ping，LI Wei，ZHANG Hong-guo，WANG Zheng-kai

2013, 27(5):  1058-1069. 

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Based on the detailed analysis of geological data，seismic data and geochemical data，through the method of the dividing of structure evolution stages and recovery of palaeogeomorphic，combined with provenance sedimentary system，the paper studied the temporal and spatial evolution features of sedimentary system and provenance orientation in the red-bed sedimentary period in the western area of Dongying Sag. The period in the western area of Dongying Sag was divided into the 1st of Kongdian Formation and the lower part of the 4th member of Shahejie Formation. Before deposition of the 1st member of Kongdian Formation，the Luxi uplift，Guangrao bump，Chenjiazhuang bump，Binxian bump and Wudi bump were formed. The main faults are Chennan Fault，Binnan Fault，Yangxin Fault，Shicun Fault and Gaoqing-Pingnan Fault and so on. The whole basin presents the palaeogeomorphic of bumps around，east low，and w est high and flat terrain in the west. The provenance of the western area of Dongying Sag in the early stage of Kongdian-Shasi is mainly from the northwest and the south orientations. There are two further provenance systems of Wudi to Binxian bump，Luxi uplift，and one provenance system of Pingnan Fault.  There are sedimentary systems such as alluvial fan-braided river-lake system，alluvial fan-alluvial plain-lake system，lake-beach bar and subaqueous fan-lake system. The changes of palaeogeomorphic，provenance and ancient climate influence the temporal and spatial evolution of the sedimentary system with the characteristics of inheritance and difference.

Hydrocarbon Accumulation Condition

Evaluation on Jurassic Hydrocarbon Source Rock Developed in Southern Margin of Junggar Basin

LONG Hua-shan，WANG Xu-long，XIANG Cai-fu，LEI De-wen，GUO Ji-gang，ABU

2013, 27(5):  1070-1080. 

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The hydrocarbon resources from Jurassic source rocks account for more than 30% and the natural gas resources account for 28% of the total amount in the Junggar Basin according to the third resource evaluation in 2000. According to the evaluation result，about 30.7% of the oil and 45.7% of the natural gas of the Jurassic resource are from the southern margin of the Junggar Basin(SMJB).Thus，it is critical to keep on studying the characteristics and the hydrocarbon generating potentials of the Jurassic source rocks. Data compiled during the hydrocarbon exploration in the last ten years are helpful for a better characterization of the source rocks in the SMJB. Three sets of source rocks were recognized. The Badaowan Formation of the Lower Jurassic was high quality source rocks. Source rocks from the Sangonghe Formation in the Lower Jurassic and the Xishanvao Fomation in the Middle Jurassic are characterized by medium quality. The above three sets of source rocks are characterized by humic organic types which fall within type II₂ and type III source rocks. All the source rocks are mature-overmature source rocks. The source rocks were buried to the peak of oil generation at the end of Cretaceous. Neocene is the period when the source rocks were buried to the peak of gas generation.  The perfeet match between the key period of hydrocarbon generation and the initiation and formation of the trap facilitate large-scale hydrocarbon migration and accumulation. The research is significant in guiding the hydrocarbon exploration in SMJB.

Study on Expulsion Efficiency of Hydrocarbon for the Jurassic Source Rock in the Southern Margin of Junggar Basin

GUO Ji-gang，LI Jian-hua，PANG Xiong-qi，XIANG Cai-fu，JIANG Fu-jie，WANG Peng-wei

2013, 27(5):  1081-1088. 

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The below oil-reservoir combination in the southern margin of Junggar basin is playing an importantrole in the hydrocarbon exploration，thus it is necessary to focus our attention on the research on hydrocarbonpotential and expulsion efficiency of hydrocarbon of chief source. In this paper, based on the theory of hydrocarbon-expulsion threshold，models of hydrocarbon generation and expulsion of the Jurassic source rocks were established and their quantity of hydrocarbon generation and expulsion，expulsion efficiency of hydrocarbon were calculated by using the hydrocarbon-generation potential method.  The results showed that the vitrinite reflectance corresponding to hydrocarbon-expulsion threshold of both mudstone and coal seam is0.7%.The total hydrocarbon generation quantity and the total hydrocarbon expulsion quantity of the Jurassic  source rocks are 3 ,973. 84 x 108t and 1 ,402. 71 x 108t respectively. Of all the hydrocarbon expulsion quantity，69. 85 percentages of them were expulsed by the source rocks in Badaowan Formation.  The average hydrocarbon expulsion efficiencv of Jurassic source rocks is 35. 30% in the southern margin of Junggar basin.  The hydrocarbon expulsion efficiency of source rock with different series of strata and different lithology is obviously different. The hydrocarbon expulsion efficiency of mudstone is much higher than that of coal seam. In general，source rocks in the Jurassic have generated and expulsed large amounts of hydrocarbons，and the expulsion efficiency of hydrocarbon is quite high，indicating a promising resource prospect of the below oil-reservoir combination in the southern margin of Junggar basin.

Distribution of Kaolinite and Its Influencing Factors in the Reservoir of Shahejie Formation in Dongying Depression

GUO Jia，ZENG Jian-hui，SONG Guo-qi3，ZHANG Yong-wang，WANG Xue-jun，MEND Wei

2013, 27(5):  1089-1098. 

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Kaolinite widely distributed in the sandstone reservoir of the Shahejie Formation in Dongying depression，which is an important factor affecting the reservoir physical properties. But the research on its distribution characteristics and controlling factors is less comparatively. This paper goes on to research the distribution characteristics and controlling factors of kaolinite by analyzing the data from casting lamella，X-ray diffraction，cathode luminescence image，electron scan microscope. Research results show that kaolinite mainly developed in the range of depth 1，200一3，600 m. The average relatively content of kaolinite are much higher in Es₂ and Es ₃ .As to the kaolinite content in Es₁ to Es₃，the central uplift belt is higher than northern steep slope and southern ramp zone of Dongying depression. Distribution of kaolinite in the sandstone reservoirs of Shahejie Fororation is obviously affected by thermal evolution of organic matter. Different temperatures(buried depth)affect the content of kaolinite in different horizons of Shahejie Formation and its distribution in plane and profile by controlling the formation and transformation of clav minerals .The overpressure has an important influence or the distribution of kaolinite. Due to overpressure，the overpressured top boundary is generally characterized by well-developed kaolinite. Tectonic activity of central uplift belt of Dongying is strong，which is advantageous to the acidic fluid from deep to shallow filling. And hydrodynamic force is strong，leading to kaolinite content in Es₁ to Es₃ of the central uplift belt is higher. The pathway system composed of fault and unconformitv surface transport a large number of acidic fluid into the shallow reservoirs，which lead to considerable development of kaolinite. Lithology and sedimentary microfacies change the fluid chemistry and hydrodynamic conditions，thus has an important influence on kaolinite distribution.

Tight Reservoir Beds and Control Factors of Lower Jurassic System in Well YNS，Eastern Kuqa Depression

GAO Xiao-yue，LIU Luo-fu，JIANG Zhen-xue，SHANG Xiao-qing，SU Tian-xi，DAI Qi-wen1

2013, 27(5):  1099-1019. 

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The Well YNS is located in the Yidikelike structural belt in the eastern Kuda Depression. The Yangxia Formation develops sandstone and conglomerate of braided river delta，while the Ahe Formation develops thick lacustrine mudstone with the interlaver of sandstone and coal seam.  Based on the thin section observation and physical property test of the sample，it is revealed that in the rock types of the Lower Jurassic reservoir, the litharenite is predominant with relatively more detritus of igneous rock. The ferruginous and argillaceous cements are dominated in the Yangxia Formation，while the siliceous and calcareous cements are the major cements in the Ahe Formation.  The porosity of the Lower Jurassic reservoir is smaller than 12%，mostly between 2%  and 8%，the permeability is largely between0.1 x 10^-3μm² and 5.0x 10^-3μm²，and the average pore throat radius varies from0.2 -3μm to 0.6 -3μm.Generally，the reservoir physical properties of the Ahe Formation are better than those of the Yangxia Formation. The porosity and permeability of Yangxia Formation and Ahe Formation both display characteristics of two sections varying to worse along the increasing depth，due to the compaction and original materials. There are superior intragranular pores and micropores in the Low er Jurassic reservoir owing to the dissolution of the soluble constituent such as feldspar and detritus.  Relatively，the reservoir of Ahe Formation develops more vuggy porosities because of its coarse grains and more feldspar and detritus.  The fractures by the tectonic stress play an important role to improve the reservoir physical properties.

Geochemical Characteristics and Origin of Shahejie Formation Water in Huimin Sag

LIU Yuan-qing，ZENG Jian-hui，ZHOU Le，ZHAI Sheng-jia

2013, 27(5):  1110-1119. 

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Based on the analysis of Shahejie Formation water in Huimin Sag，the geochemical characteristics and origin of formation water were analyzed. The results show that these waters are of CaCl₂ type with main chemical composition of anion Cl^- and cation (Na⁺+K⁺).Vertically，the chemical composition of these waters alternately increased and decreased. The water chemistry parameters reflect the Member 2 and Member 4，the middle and lower Member 3 of Shahejie Formation have good sealing. The formation water was saturated by CaCO₃，but not vet saturated by CaSO₄. The degree of ions' enrichment and deletion can be presented by using of the composition contrasting with the seawater and lacustrine saline-water evaporation trajectory. Thereby，the origin of formation water was analyzed based on ions' enrichment and deletion，and the result indicates the appearance of concentration of Cl^- and Na⁺，enriohment of cazenrichment of Ca²⁺，deletion of Mg²⁺ and SO₄^2- are owing to the combine effects of evaporation，dolomitization，desulfitation and hydrocarbon generation. Moreover，the lower-salinity areas in which each formation above the Member 4 of Shahejie Formation has lower-salinity water all occur in Linnan sag，and the clay mineral dehydration in Linnan sag can be used to interpret this phenomenonin the plane.

Comparison of Chang 7 Member of Yanchang Formation in Ordos Basin with Bakken Formation in Williston Basin and Its Significance

ZHANG Ni-ni，LIU Luo-fu，SU Tian-xi，WU Kang-jun，ZHAO Yuan-yuan

2013, 27(5):  1120-1130. 

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Since the tight oil of Bakken Formation in north America developed successfully in industry，the tight oil has become a hot spot in the exploration and development of unconventional oil and gas resources，and the Chang 7 Member of Yanchang Formation in Ordos Basin has already got a great breakthrough to some extent in this hot area. Based on geological background，lithofacies features，oil-generating conditions and reservoir characteristics，this paper compared the mechanism of petroleum accumulation and the rule of enrichment of the tight oil in Bakken Formation with that in the Chang 7 Member of Yanchang Formation.  The results show that the two formations are quite similar in geological background，disposition of source and reservoir rock，characteristics of source rock and reservoir. The only difference is that the average thickness of the shale in Yanchang Formation is thicker than that in the Bakken Formation.  The comparison results indicate that the Yanchang Formation in Ordos Basin has a good exploration prospect.

Effects of Fission-track Angle to Crystallographic C Axis in Apatite on Thermal History

JIAO Ya-xian，QIU Nan-sheng，QUE Yong-quanz

2013, 27(5):  1131-1136. 

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Thermal histories modeled from apatite fission-track( FT) data are dependent upon the annealing behavior of apatite fission-tracks. It has been confirmed that the rate of fission-track annealing correlates with apatite structure and the annealing rate is faster for fission-tracks with higher angle to crystallographic C axis，so different rates of fission-track annealing will eventually lead to different length distributions. In this study, the apatite fission-track length C axis projection model was used to eliminate the effects of different angles to crystallographic C axis，and then the difference of thermal histories modeled from apatite fission-tracks with the same length and different angle to crystallographic C axis was discussed. This paper has showed that the largest difference of the maximum palaeo-geotemperatures among the modeling history amount，cooling uplift rate and initial uplift time is 430 m is 15℃，and the largest difference in the erosion and 1. 5 ℃/Ma，respectively.  And the result reveals that the largest difference of initial uplift time in each tectonic movement can reach up to 2 Ma. In the actual thermal history simulation，we should pay more attention to the influence of this parameter.  Ideally，the angles of each apatite fission-track to crystallographic C axis should be measured to improve the thermal history precision.

Hydrocarbon Accumulation Mechanism

The Controlling of Fault on the Tight Sandstone Gas Migration and Accumulation in West Sichuan Depression

CHEN Dong-xia，WANG Lei，PANG Xiong-qi，GUO Ying-chun，LUO Xiao，XIE Ming-xian

2013, 27(5):  1137-1146. 

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The controlling of fault on the tight sandstone gas migration and accumulation of the continental strata in West Sichuan depression is very apparent.  On basis of the research of the fault distribution characters，fault property，geometric characteristics，formation period，combined with the analysis of the connection of faults and sandstone，statistic of the developing wells state，the controlling factors of faulting on gas migration and accumulation are studied in detail.  The research shows that five models can be identified by the controlling of fault on the tight sandstone gas.  The first model shows that the fault growth prompted the natural gas accumulation in the tight sandstone in the deep strata of the Upper Triassic Xujiahe Formation reservoir.  The second model indicates the fault development destroyed the natural gas reservoir in the deep strata of the Upper Triassic Xujiahe Formation.  The third model means that the faults transported the deep natural gas migrating and accumulating in the shallow Jurassic tight sandstone.  The fourth model indicate the fault destroyed badly the natural gas reservoir in Jurassic tight sandstone.  The last model shows the lack of fault growth is not good for the natural gas accumula tion in the shallow Jurassic reservoir.The distance between the well and fault is also an important factou effecting the well production capcity.Different scale faults may create different gas accumulation.Scale I fault (spreads higher than 100 km)and Scale II fault (spreads higher than 10 km and lowe than 100 km)show the same regularity of medium distance between well and fault is most favorable for the gas accumulation,too far or too close is not good for gas reservoir.Scale III fault has the apparent positive controls that on the well production capacity increase with the increase of distance of well and fault.

Petroleum Accumulation Characteristics and the Main Controlling Factors of the Second Member of Shawan Formation in Chepaizi Uplift，Junggar Basin

MA Li-chi

2013, 27(5):  1147-1152. 

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Through the analysis on reservoir formation factors，such as source condition，sedimentary reservoir characteristics，migration path and space-time coupling，and by means of the correlation and comparison on multiple geological parameters from reservoir and failed reservoir,  the reservoir accumulation mechanism and main factors are clarified herein for the second member of Shawan Formation in Chepaizi uplift. It is revealed that，the hydrocarbon in the study area is mainly from the Jurassic and Permian source rocks in Changji sag. The underwater distributary channel sandstone and beach bar sand holy are the most favorable storage rocks of reservoir. The stable distribution，good physical properties，and great thickness of sand stone in the first number of Shawan Formation and fractures acted as the conduit system of net-carpet model. Thanks to the favorable time -space coupling，the study area is characterized by gentle slope with remote source，lateral migration along thick sandbodv，and low to moderate charging.  The lithology，porosity and permeability of reservoir control the oil and gas-filling.  Three factors，the fault clip in shallow formation，distance between trap and thick sandstone in the first number of Shawan Formation，and total thickness of interlayer mudstone，control the oil and gas transporting efficiency and trap oil probability.

Formation of Unconformity Surface at Cretaceous Bottom and Its Significance for Hydrocarbon Migration in Chepaizi and Its Surrounding Areas of Junggar Basin

WU Kang-jun, LIU Luo-fu，ZENG Li-yuan , BAI Zhen-hua

2013, 27(5):  1153-1160. 

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The unconformity surface at Cretaceous bottom，which widely develops in Chepaizi area of Junggar Basin，is one of the most important pathways for migration of the Permian and Jurassic oils to the Cretaceous and Neogene reservoirs.  The micro一structures and geometric configurations of the unconformity are important for the exploration of petroleum.  By analyzing data of cores，logging curves and cuttings logging，three-layer structure of unconformities is identified.  Then，further study on the rocks on the unconformity surface，and weathered clay bed and semi-weathered crust of the unconformity surface at Cretaceous bottom is carried out，in which the formation of the unconformity surface and the effects of each layer on hydrocarbon migration are investigated. The formation of the unconformity surface at Cretaceous bottom in the study area is divided into four stages: uplift-weathering period，denudation-transportation period，subsidence-deposition period and diagenetic compaction period.  The study shows that the rocks above and below weathered clay bed can be effective hydrocarbon migrating pathways，and the weathered clay bed could be local caprock in the area where faults are rare.  Oil and gas migrated along the Cretaceous bottom unconformity from south-east to the uplift of Chepaizi.

An New Method Applied to Analyzing the Unsuccessful Drills:Take the Cambrian in the Platform of the Tarim Basin as an Example

CHEN Jun-qin，JIANG Zhen-xue，PANG Xiong-qi，PANG Hong，JIANG Fu-jie

2013, 27(5):  1161-1172. 

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The proved carbonate hydrocarbon reservoirs in burial hills of Cambrian have shown the huge exploration potential;however because the basin has done through multiple structural events,the reservoirs formed previously in Cambrian were affected by later structural events and they were a山usted，transformed，destroyed and reformed.  The complexity of the superimposed basin leads to a loss to present theories.  At present，the success ratio of exploration about 25% in Cambrian is low. This paper discusses the failure reasons of these 15 holes from the geological process of hydrocarbon enrichment by the methods of “functional elements matching，structural process superimposing and facies-potential-sources coupling at late stage"，and tries to bring to light the hydrocarbon accumulation mechanism to improve the efficiency of exploration.  The results turns out that，80 percent of abortive holes locating out of the promising accumulation districts failed because they did not match functional factors; 7 percent of them locating out of promising exploration areas failed because the previous reservoirs were destroyed in the later structural events;13 percent of them failed because they did not meet the facies-potential-source couple in late stage.  The methods successfully explained the reasons of failure holes in Cambrian in the Tarim basin and proven the feasibility and validity of the new theory and prediciton methods, showing a great practical significance to the future petroleum exploration.

Geochemical Characteristics and Genetic Analysis of Shallow-buried Natural Gas in South Songliao Basin

SUN Hao, ZHANG Min, Li Su-mei

2013, 27(5):  1173-1179. 

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There is lack of genetic research on shallow-buried natural gas in South Songliao Basin.  By analyzing the component，carbon isotope and light hydrocarbon of the natural gas samples collected in Quantou Formation，Fulongquan，it shows that in the study area there are two types of shallow gas:oil-gas and bio-degradation gas. The characteristics of the first type natural gas include:the methane carbon isotope value is about -35‰, carbon isotope of methane and its homologs are presented as normal carbon distribution; methylcyclohexane index is about 20%，and cyclohexane index is a little higher than 10%; the R₀ value which was calculated by methane carbon isotope，the heptane value and the isoheptane value are all in high to over mature range，which confirms that it is belong to high mature oil-gas.  The second type natural gas is characterized by rich light methane carbon isotope and rich heavy butane carbon isotope;cycloalkanes is displayed as the main peak in gas chromatogram of light hydrocarbon; cycloalkanes and branched alkanes are highly abundant in light hydrocarbon; all of the light hydrocarbon parameters (methylcyclohexane index， heptane value，K1，etc.)are fluctuated in a wide range，which confirms that it is belong to bio-degradation gas.  This research has great significance on natural gas exploration，resource evaluation and revealing the mechanism of oil and gas accumulation.

Genesis and Generation Condition of Natural Gas in Gas Hydrate in the Northern South China Sea

ZHANG Yin, GUO Yi-qun, MO wu-ling, HU Yu-bo

2013, 27(5):  1180-1185. 

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The composition of the natural gas in hydrates in the drilling holes of the sediments in the Shenhu sea area is mainly methane, which is the typical dry gas. According to the values of methane δ^13C and δD, the gas hydrates of Shenghu sea area are biogenic gas, originating from carbon dioxide reduction. The northern South China Sea entered the biogenic gas generation stage under the Sulfate Methane Interface( SMI). The temperate salinity condition is favourable for methanogens survivance and biogenic methane generation. The burial depth from 200 to 1 ,500 m is suitable for the biogenic methane generation. The main marine sediments of Middle-Late Miocene，Pliocene and Quaternary are mainly mudstone，partially interbed with sand and shale，which contain abundant，good-typed and immature organic matter. The condition of biogenic gas generation is superior，which can provide sufficient source for the generation of gas hydrate in shallow part of the northern South China Sea.

Genesis Type and Source Analysis in Lower Cretaceous of Changling Depression in Songliao Basin

SUN Ming-liang，LIU Guang-di

2013, 27(5):  1186-1192. 

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The component and generation of natural gases are complicated in Lower Cretaceous of Changling depression in Songliao Basin. It is significance to confirm the generation and source rock of natural gases，which is importance to oil exploration in this area. On the basis of the component analysis and carbon isotope characteristics，the genesis types of natural gases in Lower Cretaceous were identified.  The natural gas was coal-type gas in Haerjin structure， and oil-type gas in Dalaoyefu structure and upper part of Fulongquan structure，and mixing-type gas in Shuangtuosi structure and lower part of Fulongquan structure. The dioxide carbon gas in No.2 and No. 6 Changling structure is inorganic genetic gas of mantle source. The abnormal sequence of stable carbon isotopes in hydrocarbon accumulation was properly caused by gas diffusion.  Combined with the genesis type of natural gases and geology conditions，the main source rocks were confirmed to be Yingcheng Formation and Shahezi Formation.

Applying Molecular Compositions of Inclusion Data to Restore Hydrocarbon Charge History in the Tazhong Area

JIANG Zhen-xue,LI Fend, LI Zhuo

2013, 27(5):  1193-1201. 

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In order to restore the hydrocarbon charge history in the Tazhong area，an improved molecular composition of inclusion(MCI ) method is applied using oils from oil-hearing inclusions(FI-oils)and crude oils. The results show that the FI-oils and the crude oils in the Tazhong oil field originated from different source rock intervals and the crude oils are more mature than the FI-oils.  The FI-oils adsorbed and inclusion oils of the reservoir rocks generally have high concentrations of gammacerane and C₂₈ steranes，similar to the Cambrian-Lower Ordovician source rocks. In contrast，the crude oils generally have low concentrations of gammacerane and C₂₈ Steranes，similar to the Middle-Upper Ordovician source rocks.  The coexistence of 25-norhopane and the intact n-alkanes in all crude oils，and the higher concentration of 25-norhopanes in crude oils than in FI-oils，suggest that later non-biodegraded oil continue to charge and mix in the productive intervals during and/or after early biodegradation. Three episodes of oil charge from two source rock intervals can be restored in the Tazhong area.  The first and the second episodes of oil charge，origin of the Cambrian-Lower Ordovician source rocks，were determined in Late Silurian and Late Permian，followed by the third episode of oil charge derived from the Middle-Upper Ordovician source rocks in the Late Permian.

Study of Inhomogeneous Fluid Inclusion in the Hinterland of Junggar Basin

ZHOU Yong-shui，QIU Nan-sheng, SONG Xin-Ying

2013, 27(5):  1202-1210. 

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Previous studies indicate that the homogenization temperature of many fluid inclusions from the Lower Jurassic J1s and J1b sandstone samples in the hinterland of Junggar Basin are much higher than the maximum temperature that the formation experienced.  In this paper，it is confirmed that three-phases inclusions trapped from oil-water heterogeneous environment are predominant in the abnormal inclusions.  Gas，liquid oil and liquid water can be observed in these inclusions by microscope.  Oil releases yellow fluorescence while gas and water do not under the UV-light.  These inclusions，rich in J₁s and J₁b of many wells，are mainly discovered in the healed cracks，corroded hollows and secondary outgrowth cementation of rock particles. And they usually associated with gaseous hydrocarbon inclusions，salt water inclusions with gaseous hydrocarbon，salt water inclusions and liquid inclusions.  Their homogeneous temperatures range from 130 to 200℃without obvious law.  The abnormal fluid inclusions were trapped in the moved oil-water transitional zone during the secondary migration and adjustment of oil and gas in Eocene-Miocene.  The trapped time of these inclusions were revealed to be about 38-17 Ma based on the homogenization temperatures of salt water inclusions and the burial and thermal histories of the samples.  In addition，the trapped time become older with increase of depth and represent the time the paleo-oil-water contact reached same depth.

Quantitative Study on Pressure Evolution During Gas Charging to Reservoirs

LIU Yi-Feng，YAO Qian-Ying，XIE Zeng-Ye，QIU Nan-Sheng

2013, 27(5):  1211-1218. 

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Overpressure plays an important role in oil and gas exploration. Pressure transfer with gas charging is a dominant overpressure mechanism in reservoirs.  Because of the tremendous difference in gas solubility and compressibility between formation water and oil, there are different pressure evolutions in the aquifer and the oil layer. In this paper pressure changes caused by methane filling in reservoirs with different kinds of initial pore were simulated.  And the quantitative relationship between volume of charged methane and overpressure was established. Then the influencing factors of pressure evolution during gas chargingwere analyzed.The results indicate the following aspects:gas charging could cause increase of pressure in reservoirs; pressue evolution paths are different with different initial pore fluids; strong overpressure is easier to form in aquifer than in oil-bearing formation; in the same sealing condition, it is easier to form ovepressure in shallow strata than in deep strata as well as in high tempeature basin than in low temperature basin.

Characteristics of Methane Isothermal Adsorption for Paleozoic Shale in Subei Area

LIU Xiao-ping, DONG Qian, DONE Qing-yuan, PAN Ji-Ping, DING Wei-xing

2013, 27(5):  1219-1224. 

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The shale has content is one of the most important indicators to evaluate shale reservoirs，and of great significance to forecast reserves. As adsorbed has content plays an important proportron in shale has content the evaluation of adsorptive capacity in shale reservoirs is very necessary.Through methane isothermaladsorption experiments of Paleozoic shale samples from three different sets of strata in Subei Area，the shale isothermal adsorption curves are obtained to analyze the main affecting factors of adsorption gas contents in shale reservoirs.  The results show that the saturated adsorption(VL)are 1.18-4. 85 m³/t with an average of 2. 89 m³/t，and the Langmuir pressure constant(PL)are2.01一4. 24 MPa with an average of 2. 67 MPa.The adsorption capacity varies among these three different sets of shale strata.  Mufushan，Dalong and Longtanformations have much more adsorption gas contents than Wufeng-Gaojiabian and Gufeng formations. The main affecting factors of adsorption gas contents are concluded as follows:(1)TOC directly affects the maximumadsorption gas content，the higher the organic carbon，the greater the maximum adsorption gas content;(2)with similar values of the organic matter content，organic maturity and the same pressure，the shale with high clay contents adsorbs more gas;in the shale with low organic carbon，illite plays a vital role in the adsorption， and the adsorbed gas contents is relatively high in those shales with high contents of illite;(3)the recruired minimum pressure(critical pressure)making shale saturated with adsorbed gas will decrease with the increase of TOC.The experiments  also  show  that the organic maturity has no obvious relation with the  saturated adsorbed gas contents.

Hydrocarbon Distribution

Hydrocarbon Distribution Patterns and Controlling Factors in North West Shelf，Australia

BAI Guo-ping，DENG Chao，TAO Chong-zhi，WANG Da-peng，LIU .Jun-lan

2013, 27(5):  1225-1232. 

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Australia's North West ich in oil and gas resources，particularly gas，and is one of the key bases for supplying LNG in the world.The shelf not only has the highest petroleum exploration potential in Australia, but it is also one of the important regions targeted by Chinese oil companies for expanding international petroleum exploration and production. Based on data collected from various sources,this paper discusses the oil and  gas  distribution  patterns， documents the factors controlling such disrtibutions and optimizes the favorable exploration areas.Regionally,the discovered oil and gas reserves are largely confined to the North Carnarvon Basin.Stratigraphically,they are mostly reservoired in clastic reservoirs in the Upper Triassic,Jurassic or Lower Cretaceous，which are sealed by the extensive Lower Cretaceous mudstones and shales.  The distribution is characterized by patterns of oil in the inner fairway and gas in the outer fairway，gas in the lower reservoirs and oil in the upper reservoirs，and dominance of gas over oil.  Oil fields mainly occur in sub-basins，which were developed during Jurassic rifting and contain effective oil source rocks.  The humic kerogen type and high maturity of source rocks determine that the petroleum resources are dominated by gas in the North West Shelf. The Jurassic rift controlled the areal distribution of oil.  On basis of integrated studies of petroleum geology and discovery process of oil and gas fields，this study selected 7 favorable exploration areas:Exmouth Plateau，Exmouth Sub-basin，Barcoo Sub-basin，Caswell Subbasin，Sahul Platform，Calder Graben and Vulcan Sub-basin.

Comparison among Petroleum Distribution Patterns of Three Richest Foreland Basins in Petroleum Resources in the World

ZHANG Ming-hui，BAI Guo-ping，PAN Long，TAO Chong-zhi，NIU Xin-jie

2013, 27(5):  1233-1243. 

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The Persian Gulf Basin，Eastern Venezuela Basin and Western Canada Basin are the richest petrolife rows foreland basins in the world.  Analyses of the up-to-date oil and gas geological data indicate that there are significant differences in oil and gas distribution features and hydrocarbon resource mixes among the three foreland basins.  Within the foreland basins，oil and gas are widely distributed throughout both the thrust-fold beltand foredeep一slope，but the discovered reserves are mainly concentrated in the foredeep-slope. Stratigraphical1v，passive margin tectono-strata host over 91.0% of the discovered reserves in the Persian Gulf Basin while foreland sequences are the major reservoir intervals in the Eastern Venezuela Basin and the Western Canada Basin.  The petroleum resources of the Persian Gulf Basin are dominated by conventional oil and gas while the Eastern Venezuela Basin and the Western Canada Basin are endowed with unconventional heavy oil and natural bitumen. The spatial configuration relationship between regional seals and petroleum migration pathways controls the different mixes of hydrocarbon resources in the foreland basins.

Comparison of Ordos and Foreign Similar Basins and Prediction  for Mesozoic Oil Reserves in Ordos Basin

WANG Yin,LIU Luo-fu，ZHANG Zhi-huan，LI Wei，WANG Yan-ru

2013, 27(5):  1244-1250. 

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West Siberia，Paris and Illinois basins were chosen to do comparison with Ordos Basin. The Ordos Basin is a cratonic basin that was developed above aulacogen base，so it has good tectonic basis for accumulating abundant oil and gas resources.  Besides continental sedimentation，limited distribution of source rocks and complex trap types，all the other geologic conditions of Mesozoic Ordos Basin are similar to those of the three foreign basins. The results of basins comparison and calculation show that the Mesozoic Ordos Basin can possess proved oil reserves as 17. 21 x 10⁸ t(based on West Siberia Basin)，22. 67 x 10⁸ t(based on Paris Basin) and 24. 40x10⁸t(based on Illinois Basin)，indicating that the Mesozoic Ordos Basin has great oil resource potential and exploration prospect.

Relationship between Reservoir Development and Hydrocarbon Distribution of Huomatu Tectonic Zone in Southern Junggar Fold-Thrust Belt

BAI Zhen-hua，JANG Zhen-xue，SONG Yan，ZHAO Meng-jun，FANG Shi-hu，ZHANG Jian

2013, 27(5):  1251-1257. 

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Ziniquanzi Formation of Paleocene is the main oil-bearing formation in Huomatu tectonic zone with various oil and gas phase and complex oil-gas-water relationship.  Oil and gas exploration and evaluation results show that the complexity of reservoir development is another important factor except for the complex tectonic deformation and style，which controlled the oil and gas accumulation and distribution of Huomatu tectonic zone in Southern Junggar fold-thrust belt.  This paper based on the study on the reservoir development and evolution of Ziniquanzi Formation，combination with its oil-water distribution rule，the relationship between the reservoir development and oil-gas distribution would be discussed from two respects that were the reservoir geometry shapes and internal properties. It is suggested that the reservoir architecture type of Zinicruanzi Formation was labyrinth with violent fades lateral change，whose single sand body thickness was small and the lateral continuities were medium or worse.  Reservoir sand bodies pinchout and properties deterioration often become oil-gas-water lateral barrier. In addition，large sets of mudstone interlayer would play a role in the segmentation of oil gas water relations，and the upper and lower different oil-water systems were formed，which resulted in the complexity of vertical oil and gas distribution.  Furthermore，the characteristics of reservoir porosity and permeability，and differences of hydrocarbon filling intensity in three anticlines of Huomatu tectonic zone were analyzed and comparedcomprehensively.  The coupling relationship between reservoir characteristics and hydrocarbon filling strength would he considered as an important factor which influenced reservoir phase and abundance.

Hydrocarbon Distribution Features and Main Controlling Factors in the Nanpu Sag

JIANG Fu-jie，DONE Yue-xia，PANG Xiong-qi，WANG Ying-xun，GUO Ji-gang

2013, 27(5):  1258-1264. 

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hydrocarbon accumulation，oil and gas distribution in the Nanpu sag are mainly controlled by the following factors.  Firstly，source rocks have controlled the distribution areas of hydrocarbon reservoirs.  The study located in the place which is within 15 kilometers from shows more than 80% of hydrocarbon reservoirs have expulsion center.Secondly the favorable sedimentary fades have controlled the sand distribution and reservoir propertiesthe lays of hydrocarbon reservoirs and their scales.  Finally，faults are the most important factor controlling hydrocarbon reservoirs' distribution. On the one hand faults have controlled thetrap types and their spatial distribution，further,  the  size  and  location  of  hydrocarbon  reservoirs. On the ether hand,as channels for hydrocarbon's vertical migration，faults control their vertical migration distance.To sum up,the hydrocarbon distribution of the Nanpu sag is under the controlling effects of the combination of source rocks,sedimentary facies and faults.The deltas near the source rocks , channel sands and the fault zones interconnecting vertically are favorable exploration areas.