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2017 Vol. 39, No. 1

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2017, 39(1): .
Abstract(247) PDF-CN(333)
Abstract:
Research significance, advances and trends on the role of bedding fracture in tight oil accumulation
Luo Qun, Wei Haoyuan, Liu Dongdong, Zhang Chen, Zu Deyu, Zhang Yunzhao, Wang Jian
2017, 39(1): 1-7. doi: 10.11781/sysydz201701001
Abstract(879) PDF-CN(555)
Abstract:
At present, the research on fractures in petroleum accumulation are limited to tectonic fractures, and mainly deal with conventional petroleum accumulation (including low permeability petroleum accumulation). For tight reservoirs, the studies are also limited to tectonic fractures. Previous investigations revealed that bedding fracture was the most important type because of its common growth and obvious contribution to tight oil accumulation. The time-space matching relationship between bedding fracture opening or closing and petroleum charge is the key of tight oil accumulation. However, research on the effect and role of fractures in tight oil accumulations were very limited, especially on the relationship between bedding fractures and tight oil accumulations as well as the contribution of bedding fractures to tight oil accumulations. This makes bedding fracture opening and closing mechanism and petroleum charge effect an important science question. So, the main geological reasons and the opening and closing mechanism of bedding fractures, the coupling relationship between bedding fracture opening and closing and petroleum charge, and the lower limit of bedding fractures for petroleum charge in tight reservoirs are research trends on tight oil accumulations in the future.
Origin of pre-existing basement faults and their controls on new fault formation in Gaoyou Sag, Subei Basin
Shu Ningkai, Wu Lin, Wang Xinwen, Guo Jianping
2017, 39(1): 8-14. doi: 10.11781/sysydz201701008
Abstract(998) PDF-CN(575)
Abstract:
The Zhenwu and Wubu faults are two major pre-existing basement faults in the Gaoyou Sag, Subei Basin. They were formed during the Indosinian period when the Lower Yangtze plate collided with the North China plate, and strike NEE in the west and NNE in the east. The regional stress field and 3D seismic data showed that the controls of the two faults on the development of the southern terrace can be divided into four periods as follows. (1) Tectonic compression. The north of the Lower Yangtze plate collided with the southeast of the North China plate, developing a series of thrust slip, thrust-motion and complicated dislocation. (2) Tectonic reverse. The Zhenwu fault reversed from a normal fault to a reverse fault. (3) Orthogonal rifting. The Zhenwu fault diffe-rentiated into the Zhen① and Wu① faults which controlled the formation of Zhenwu and Wubu terraces. (4) Oblique rifting. The Zhenwu and Wubu terraces were controlled by NS oriented extensional environment instead of the Zhenwu fault. Tectonic deformations were different in the Zhenwu and Wubu terraces. According to the activity of pre-existing basement faults in new faults, they were classified into four types from strong to weak in turn: inherited, variable, adjusted, and induced. Pre-existing basement faults were the foundation of the southern terrace formation and evolution, and strongly influenced the development of new faults.
Active source rocks of Chang 7 member and hydrocarbon generation and expulsion characteristics in Longdong area, Ordos Basin
Guo Kai
2017, 39(1): 15-23. doi: 10.11781/sysydz201701015
Abstract(1016) PDF-CN(329)
Abstract:
The distribution, hydrocarbon generation and expulsion history and intensity of active source rocks in the Chang 7 member of the Yanchang Formation in the Longdong area of the Ordos Basin were studied based on geoche-mical data, TOC calculation by well logging, hydrocarbon generation potential and expulsion history simulation. Dark mudstone (including oil shale) thickness with an organic carbon content (w(TOC)) more than 1.0% in the Chang 7 member mainly ranges from 20-90 m, and the average w(TOC) is mainly between 2%-9%. Active source rocks of the Chang 7 member have a w(TOC) value over 1.0% and Ro value over 0.7%, and are widely distributed in the Longdong area. They became mature and generated hydrocarbon at the end of Jurassic, expelled hydrocarbon during the early stage of the Early Cretaceous (140-130 Ma,Ro≈0.7%), and reached peak at the end of the Early Cretaceous (100 Ma, Ro≈1.0%). At this time, the oil generation ratio reached 400 mg/g TOC, and the oil expulsion ratio could be 308 mg/g TOC. But oil generation was forced to stop as a result of regional tectonic uplift since the Late Cretaceous. The oil expulsion intensity is mainly (10-250)×104 t/km2, showing the characteristics of strong oil expulsion. Oil reservoirs of the Yanchang Formation dominated with tight oil of the Chang 6-Chang 8 members mainly developed in the area with an oil expulsion intensity over 20×104 t/km2, which indicated that oil accumulation in tight sandstones has characteristics of being near the oil source with a short migration distance.
Middle Cambrian oolitic carbonate rocks in the central ancient upwelling area, the Ordos Basin
Xu Bo, Wang Baoqing, Sun Liuyi, Wang Hongwei, Liu Baoxian, Jing Xianghui, Liu Liping
2017, 39(1): 24-31. doi: 10.11781/sysydz201701024
Abstract(1920) PDF-CN(388)
Abstract:
Middle Cambrian oolitic carbonate rocks were deposited in small shoals of the ramp in a central ancient upwelling area in the Ordos Basin. The oolitic carbonate rocks mainly consist of calcites and dolomites. The δ18O and δ13C values range from -11.3‰ to -4.9‰ and from -1.7‰ to 0.3‰, averaging -6.5‰ and -0.8‰ V-PDB, respectively. Since they were deposited in oolitic shoals under meteoric leaching and experienced deep burial diagenesis, the δ18O values of the oolitic carbonate rocks are obviously low. During diagenesis, the influence of organic materials was slight, leading to normal δ13C values for the oolitic carbonate rocks. The δ18O values of dolomites are higher than those of limestones. The results of analyses by laser-microsampling indicate that the δ18O and δ13C values of ooids are lower than those of the cements because the ooids formed in turbulent environments, and were leached by meteoric water after their formation. The cements precipitated in pore water with marine characteristics and high salinity, and were slightly influenced by meteoric water after their formation. The oolotic carbonate rocks are characterized with low Na and Sr, very high Fe, and medium Mn contents because of deep burial diagenesis. Most dolomites with low order degrees and high MgCO3 contents generally formed through replacement in brine during the burial stage. Deep burial diagenesis and good development of cements resulted in the development of extremely low porosity in the oolitic carbonate rocks.
Sequence stratigraphic framework and sedimentary model of Niubao Formation in Lunpola Basin, central Tibet
Wei Wei, Lu Yongchao, Liu Zhongrong, Pan Lei, Lin Weibing, Jian Hui
2017, 39(1): 32-40. doi: 10.11781/sysydz201701032
Abstract(1105) PDF-CN(287)
Abstract:
Based on an integrated investigation of well logging, seismic data, cores and outcrops, the Niubao Formation in the Lunpola Basin was subdivided into one first order sequence, three second order sequences, corresponding to the first, second and third members of Niubao Formation, and seven third order sequences from base to top, namely SQ1, SQ2, SQ3, SQ4, SQ5, SQ6, and SQ7. Two sequence stratigraphic patterns including faulted slope zone and flexure slope break zone were identified within the sequence stratigraphic framework. There are several exploration targets, including fan deltas on the gentle slope of HST and large-scale low stand fans in the slope break zone of LST in the flexure slope break zone, and high stand braided river deltas and large-scale low stand fans in the slope break zone in the faulted slope zone. A sedimentary model was established through the analyses of spatial and temporal distribution of the sequences. Three main sand bodies developed in the Niubao Formation, namely the northern, southwestern and eastern sand bodies, and their distribution was controlled by the slope break zone.
Hydrocarbon accumulation mode of Shuntuo 1 well block in the Shuntuoguole lower uplift, Tarim Basin
Zhu Xiuxiang, Chen Xuyun, Cao Zicheng
2017, 39(1): 41-49. doi: 10.11781/sysydz201701041
Abstract(965) PDF-CN(356)
Abstract:
Oil and gas were acquired from the Ordovician carbonate and the Silurian clastic rocks of Shuntuo 1 well block in the Tarim Basin. The two reservoirs were in communication via a fault, but their temperature, pressure coefficient and oil and gas properties are different. By analyzing their geochemical characteristics (GC of saturated hydrocarbons, GC-MS of saturated and aromatic hydrocarbons and isotopes) we determined that the two reservoirs are different oil and gas systems, which have the same oil source, experienced multiple stages of filling, and are correlated with each other. Combined with the research of fault activity timing and intensity, oil and gas vertical distribution, migration direction and charging period, we confirmed that the main forming stage of Silurian reservoir was in the late Hercynian, and the condensate gas reservoir in the Ordovician was formed during the Himalayan period. Fault activity intensity during the main accumulation period determined hydrocarbon accumulation strata and oil and gas properties in the area. We established a hydrocarbon accumulation mode of "hydrocarbon supply of vertical and lateral sources, vertical migration by faults, controlling layer by fault activity intensity, and optimal aggregation in lower traps".
Key moments for hydrocarbon accumulation in Shaximiao Formation on the eastern slope of West Sichuan Depression, Sichuan Basin
Lin Xiaoyun, Wei Minsheng, Feng Yong, Li Lu, Han Yan
2017, 39(1): 50-57. doi: 10.11781/sysydz201701050
Abstract(1049) PDF-CN(339)
Abstract:
The West Sichuan Depression in the Sichuan Basin is a foreland basin formed under the compressional thrusting of the Longmen Mountain. 3D seismic was obtained on five exploration blocks on the eastern slope of the central depression, including Hexingchang-Gaomiaozi, Fenggu, Yongtai, Zhongjiang-Huilong and Zhixinchang-Shiquanchang, covering three tectonic belts. The hydrocarbon evolution history of source rocks was studied, and 22 fluid inclusion samples from 6 wells were analyzed using fluorescence, homogenization temperature and salinity measurements. Source rocks in the fifth member of the Upper Triassic Xujiahe Formation entered the hydrocarbon generation threshold at 151-145 Ma, and reached a peak at 130 Ma. Three stages of fluid activities related to hydrocarbon accumulation took place in sandstone reservoirs in the Jurassic Shaximiao Formation at 141-128 Ma (J3-K1), 105-88 Ma (K1-K2) and 83-68 Ma (K2), respectively. The peak of hydrocarbon generation of source rocks at 130-68 Ma (K1-K2) is the key moment for hydrocarbon accumulation.
Sequence characteristics of the fourth member of Xujiahe Formation in the middle area of Western Sichuan Depression, Sichuan Basin
Chen Xianliang, Ji Youliang, Yang Keming
2017, 39(1): 58-64. doi: 10.11781/sysydz201701058
Abstract(837) PDF-CN(256)
Abstract:
The sequence characteristics of the fourth member of Xujiahe Formation in the middle area of Western Sichuan Depression have been studied by using outcrop, core, logging and seismic data. The fourth member of Xujiahe Formation is a three-order sequence and was divided into lowstand system tract, transgressive system tract and highstand system tract. An isochronous sequence stratigraphic framework was established, and its internal sedimentary characteristics were clarified, mainly developing an alluvial fan-alluvial plain-delta-lacustrine depositional system. The sequence was divided into three types based on depositional settings: symmetrical type, asymmetrical type A1 and A2. Type A1 developed in the piedmont region before the Longmen Mountain, the type A2 mainly developed in Zhongjiang-Luodai area, and the symmetrical type mainly developed in the piedmont region before the Longmen Mountain and the depression between Zhongjiang and Luodai. LST and HST of the asymmetric type and symmetric type A2 sequence were advantageous for the development of high-quality reservoirs.
Fault characteristics and their controls on hydrocarbon accumulations in Neogene, Kendong area, Bohai Bay Basin
Wu Yunyun, Ma Lichi, Yang Guili, Liu Xiaolin, Wang Zhiying, Zhao Yuehan, Xie Chuanjin
2017, 39(1): 65-70. doi: 10.11781/sysydz201701065
Abstract(1171) PDF-CN(247)
Abstract:
We studied the geometric and kinematic characteristicsof faults in the Kendong area of the Bohai Bay Basin, and analyzed their controls on hydrocarbon accumulations, based on basic geology, well drilling, testing, logging and 3D seismic data. The study area mainly developed on NNE, NEE and NWW oriented fracture systems. Affected by the early activity of Tanlu Fault, faulting in the western and southern parts of the study area was stronger than that of the eastern and northern parts in the Paleogene, but the reverse in the Neogene.Different types of fractures had different controlling functions on hydrocarbon accumulation elements. Tensile fractures mainly formed simple fault block traps, transtensional(torsion) fractures formed complex fault block and fault-lithological traps, and compresso-shear fractures formed anticlinal structural traps. Reservoirs controlled by faults generally followed a principle that sand bodies developed near extensional faults and away from torsion faults. Sealing of extensional faults, transtensional (torsion) faults, compresso-shear faults enhanced in order, and hydrocarbon usually accumulated near the oil source faults with better sealing conditions.
Controlling factors of pore types in shale reservoirs:A case study from the Longmaxi Formation in Jiaoshiba area, eastern Sichuan Basin
Geng Yikai, Jin Zhenkui, Zhao Jianhua, Wen Xin, Wang Yang
2017, 39(1): 71-78. doi: 10.11781/sysydz201701071
Abstract(1187) PDF-CN(476)
Abstract:
Ar-ion beam scanning electron microscope (SEM) imaging and the quantitative analysis of pore types were performed on 7 shale samples from the Longmaxi Formation in the eastern Sichuan Basin to define the vertical distribution characteristics of pore types in various lithofacies of shale. Five regions were selected in each sample to accommodate the heterogeneity of the shales, and each region (100 μm×100 μm) was analyzed using 100 SEM photographs which were magnified 14 000×. A 2000 point-count method was employed to count the plane porosity of various pores on each SEM photograph, and then the average percentage of various pores in each sample was obtained. The results showed that interparticle (interP) pores, intraparticle (intraP) pores and organic matter (OM) pores could be observed in the study area, and the contents of various pore types were different in various lithofacies. The lithofacies of Longmaxi Formation changed from argillaceous shale, silty shale to siliceous shale from top to bottom. The main pore type changed from intraP pores to OM pores with the increase of TOC content and the decrease of clay content. The content of brittle minerals controlled the quantity of interP pores, clay content controlled the development degree of intraP pores, while TOC and authigenic quartz contents determined the quantity of OM pores. Siliceous shale in the lower segment of Longmaxi Formation is the most favorable reservoir for shale gas.
Controlling factors for petroleum accumulation and exploration potential of the eastern branch of East African Rift System
Zhang Yan, Tian Zuoji, Wen Zhixin, Wang Zhaoming, Song Chengpeng, Wu Yiping
2017, 39(1): 79-85. doi: 10.11781/sysydz201701079
Abstract(906) PDF-CN(362)
Abstract:
The eastern branch of the East African Rift System belongs to an intracontinental rift basin group formed during the Cenozoic. The South Lokichar Basin is located in the north of Kenya. Since 2012, 8 oil fields have been discovered here, with 2C resource being 766 million bbl. Through integrated study of seismic, well and other geological data, we investigated the petroleum geological features and developed reservoir-forming rules. The basin has small-scale, mono-faulted structural characteristics, faulting to the west and overlapping to the east. In the western steep-slope zone, there are mainly structural-lithologic combination traps, and in the eastern gentle slope zone is structural traps. Depositional fill is characterized by a river-(fan) delta-lacustrine sedimentary system, presenting a cycle of initial rifting stage-expanding stage-waning stage. There are two sets of plays, one is Oligocene-Lower Miocene combination and the other one is Middle-Lower Miocene combination. Based on the analysis of discovered fields in the South Lokichar Basin, it was determined that mature source rocks, significant reservoirs and reasonable positioning of accumulation elements were the main controlling factors in the eastern branch rifts. The exploration potential of the eastern branch rift system was analyzed through comprehensive interpretation of gravity, seismic and depositional thickness data. The most favorable targets deserving attention are the Kerio Valley Basin to the south of South Lokichar Basin, the northwest onshore of the Turkana Basin and the Kerio Basin.
Origin and significance of monomethylalkanes from Yanchang Formation source rocks in Ordos Basin
Qian Yu, Wang Zuodong, Tuo Jincai, Zhang Ting, He Yonghong
2017, 39(1): 86-93. doi: 10.11781/sysydz201701086
Abstract(808) PDF-CN(255)
Abstract:
Monomethylalkanes are common branched alkanes in the saturated hydrocarbon fraction of lacustrine source rocks. However, there is no agreement about their original source. The abundance of monomethylalkanes, from the Triassic Yanchang Formation source rocks in the Ordos Basin is relatively high. Determination of TOC, Rock-Eval, compound specific carbon isotopic composition, and GC-MS analysis of saturated hydrocarbons show that the organic matter of source rocks from Chang7-Chang10 have a mixed source, and that the type of organic matter is Ⅱ-Ⅲ. The steroid hydrocarbon distributions of source rocks showed nearly equal abundances of C27 and C29 steranes, suggesting mixed organic matter. The monomethylalkanes have 12 to 32 carbons, having a similar distribution to the n-alkanes, and the 2-MMAs and 3-MMAs are predominant. The δ13C values of Pr and Ph are 1‰ to 2‰ heavier than corresponding n-alkanes. 2-MMAs and 3-MMAs with the same carbon number have almost the same δ13C value, indicating they have the same source. The δ13C values of monomethylalkanes range from -29.3‰ to -32.8‰, which are higher than n-alkanes. Moreover, combining with the sedimentary environment information of the Ordos Basin, it appears that the monomethylalkanes might come from phytoplankton and heterotrophic bacteria, and they can be used as a biomarker to judge the predecessor of sediment and petroleum.
Geochemical characteristics of rare earth elements and their geological significance in the fourth member of the Middle Triassic Leikoupo Formation in western Sichuan Basin
Liang Shiyou, Chen Yingbin, Zhao Guowei, Wang Yanqing, Hu Ye
2017, 39(1): 94-98. doi: 10.11781/sysydz201701094
Abstract(866) PDF-CN(248)
Abstract:
The composition and characteristic parameters of rare earth elements in sediments provided sedimentary environment as well as fluid and source information, which can be used to judge the sedimentary environment of source rocks and reservoirs and the sources of oil and gas. The tests of rare earth elements in carbonate rocks from the fourth member of the Middle Triassic Leikoupo Formation in the western Sichuan Basin indicated that the total REE content was low. The LREE and HREE differentiation were obvious. Obvious negative δCe and positive δEu anomalies were observed. The low total REE content and negative δCe anomaly reflected a relatively open and weakly oxidizing low-energy environment when the fourth member of the Middle Triassic Leikoupo Formation was deposited. This environment was favorable for the breeding and growth of hydrocarbon generation organisms, hence providing a material basis for the formation of hydrocarbon source rocks in the Middle Triassic Leikoupo Formation. The positive δEu anomaly suggested a strongly reducing environment for fluid activity during the late period, which was favorable for organic matter preservation. Enriched LREE, poor HREE, positive δEu anomaly and a REE distribution pattern similar to hydrothermal fluid indicated that the fourth member of Leikoupo Formation experienced late hydrothermal alteration. Hydrothermal migration channels also provided good permeability for deep oil and gas migration.
Genesis and evolution of reservoir bitumen in Xiaocaoba paleo-oil reservoir, Qianbei Depression
Zhang Runhe, Si Chunsong, Huang Ling, Bao Jianping, Ma Liqiao, Wang Pengwan, Lu Huili, Jiang Xingchao
2017, 39(1): 99-105. doi: 10.11781/sysydz201701099
Abstract(1524) PDF-CN(338)
Abstract:
The solid bitumen in the Xiaocaoba paleo-oil reservoir of Devonian in the Qianbei Depression fills solution caves, intracrystalline pores and fractures of dolomites containing biodetritus. The solid bitumen, with an equivalent Ro of 4.08%-4.14%, hardly dissolves in organic solvent. The n-alkanes have a high n-C21-/n-C22+ value at the range of 1.5-9.0. Most bitumen samples have a higher abundance of cheilanthanes relative to hopanes, and also a relatively higher abundance of C21-pregnane and C22-pregnane relative to C27-29-sterane. The bitumen and bitumen inclusions do not fluoresce, and the bitumen has no absorption peaks of aliphatic series-containing groups or oxygen-containing groups in the infrared spectrum. The physical, optical and geochemical characteristics of bitumen indicate that it formed in the process of thermal cracking under high temperature. The sterane and terpane parameters and the δ13C of the bitumen are obviously different from those of sources rocks in the Cambrian Qiongzhusi Formation and Silurian Longmaxi Formation. But the δ13C of the bitumen are very close to that of the Upper Paleozoic sources rocks, indicating that the bitumen derived from these source rocks. Ancient oil reservoirs are interpreted to have been trapped in the Middle-Late Triassic period. The bitumen formed in the Early Cretaceous period while oil reservoirs were deeply buried and then uplifted to ground level in the Yan-shanian and Himalayan periods.
Vitrinite reflectance modeling under overpressure retardation and hydrogen suppression:A case study of source rocks from the third member of Dongying Formation, West Bozhong Sub-depression,Bohai Bay Basin
Hu Anwen, Li Huiyong, Jiang Tao, Xu Peng, Shi Panpan
2017, 39(1): 106-111. doi: 10.11781/sysydz201701106
Abstract(797) PDF-CN(295)
Abstract:
The Easy%Romodel,in which only temperature and time were considered,was calibrated to take into consideration the suppression of vitrinite reflectance by hydrogen-rich organic matter and overpressure.A new model was developed by introducing a hydrogen-rich correction coefficient and overpressure inhibiting coefficient.Using the data collected from both the double-suppressed wells and the normal wells in the West Bozhong Sub-depression of Bohai Bay Basin,China, some relative parameters were determined and the model was tested.The results show that the computed vitrinite reflectance values in double-suppressed formation agree with the mea-sured data,but are significantly different from those predicted by the Easy%Romodel.And the vitrinite reflectance values were reduced by 0.2%~0.4% in double-suppressed formations. Organic matter maturation was retarded by overpressure.It led to the increase of depths of the hydrocarbon generation threshold and the delay of time of hydrocarbon generation,which was advantageous for late hydrocarbon accumulation.
Quantitative characterization of microscopic pore throat structure in tight sandstone oil reservoirs:A case study of Chang7 reservoir in Xin'anbian oil field, Ordos Basin
Zhang Hao, Chen Gang, Zhu Yushuang, Dang Yongchao, Chen Juan, Wang Hengli, Si Yang, Bai Chao, Li Xue
2017, 39(1): 112-119. doi: 10.11781/sysydz201701112
Abstract(935) PDF-CN(358)
Abstract:
The Chang7tight sandstone oil reservoir in the Xin'anbian oil field in the Ordos Basin has good potential for hydrocarbon exploration. However, the studies of microscopic pore throat structure were limited, which restricted tight oil exploration and long-term development. Size, shape and spatial distribution of pore throats in tight oil reservoirs were studied in this paper by using scanning electron microscope (SEM), casting thin section, high-pressure mercury injection and Nano-CT technologies. Pores in the Chang7tight oil reservoir in the Xin'anbian oil field were divided into three categories, namely intergranular pores, dissolution pores and microfractures. A large number of nanoscale pore throats developed in this area, which contributed to reservoir capacity and permeability. Pore throat distributions on capillary pressure curves of different samples showed that when threshold pressure is less than 1MPa, there are many micron-sized pores with a good connectivity and pore throats are large tubular and striped with throat diameters being in the range of 100-380nm. When the threshold pressure ranges from 1to 3MPa, there are many nanoscale pores with a good connectivity locally, intragranular dissolution pores are developed and pore throats are tube bundle and spherical shape with throat diameter being in the range of 75-250nm. When the threshold pressure is greater than 3MPa, small isolated spherical nanopores occur, leading to a poor vertical connectivity, only local micro-fracture development provides storage space, and throat diameter is concentrated in the range of 15-75nm.
Catalytic hydropyrolysis for highly mature Carboniferous source rocks in the northern Xinjiang
Li Yanli, Lin Huixi
2017, 39(1): 120-125. doi: 10.11781/sysydz201701120
Abstract(976) PDF-CN(213)
Abstract:
The Carboniferous source rocks in the northern Xinjiang have the characteristics of high thermal evolution, which leads to the low level of biomarkers from conventional extraction. Catalytic hydropyrolysis was carried out in order to study the sedimentary background and organic matter biological sources. The results show that the n-alkanes and steranes from hydrogenolysis are representative of parent materials. The n-alkanes have a bimodal pattern with the main carbon peaks at n-C18 and n-C22-24 in shallow mudstones, indicating a contribution of pelagic aquatic zooplankton, and have a single-peak pattern with the main carbon peak at n-C18-n-C24 in deep mudstones, indicating a contribution of aquatic bacteria and algae. The contents of C29 and C27 steranes are comparable, which indicates a mixed source. In the pyrolysis products, the content of C29 steranes is much higher, which clearly indicates a single parent material. Moreover, hydropyrolysis products contain more βα-moretanes and ββ-homohopanes. The Carboniferous source rocks were mainly developed in a reducing environment. High-quality marine source rocks of Carboniferous are mainly distributed in the lower segment with aquatic organisms such as bacteria and algae as a single source of organic matter. The experiments also confirmed that the hydrogen hydrolysis reaction could recover more information of biolo-gical markers, which is a useful supplement to conventional extraction methods.
Quantitative calculation of tight sandstone reservoir porosity evolution based on different diagenesis:A case study of Chang 63 reservoir in Huaqing area, Ordos Basin
Zhang Xi, Sun Wei, Yang Xiaojing, Li Hao
2017, 39(1): 126-133. doi: 10.11781/sysydz201701126
Abstract(1201) PDF-CN(326)
Abstract:
The Chang 63 tight sandstone reservoirs in Huaqing area of the Ordos Basin was deposited in delta front and stable,semi-deep lake environments. A simulation equation corresponding to porosity was established according to the characteristics of diagenetic evolution or the comprehensive geological effect of a clastic reservoir. Mineral components and porosity types were described by using casting thin section and SEM analyses. Granularity images were applied to get the structural characteristics and sorting features of clastic particles. Sedimentary microfacies, well logging, normal physical characteristics and depth analyses were applied to determine the depositional environment, burial depth and physical characteristics. Simultaneously,we tested paleotemperature, vitrinite reflectance, the highest pyrolysis temperature and clay minerals to study diagenesis, porosity evolution and relatively high permeability formation. Burial history analysis of the study area provided a theoretical reference for oil-and-gas exploration and development of tight sandstone reservoirs. According to the analysis of four typical samples, we consi-dered that the properties were mainly controlled by compaction, and differentiated diagenetic evolution was the root cause that led to different physical characteristics and porosity structures.
FTIR analyses of source rock kerogen from different hydrous pyrolysis experiments
Yu Xiaolu, Ma Zhongliang, Zheng Lunju, Zhao Zhongxi
2017, 39(1): 134-140. doi: 10.11781/sysydz201701134
Abstract(911) PDF-CN(280)
Abstract:
The generation of hydrocarbons occurred through a complex physical and chemical reaction process in finite pore space under lithostatic pressure and fluid pressure (PVT-L jointly controlled condition). Most of the hydrous pyrolysis experiments have been carried out with low-pressure and relatively large reaction space due to experimental device limitations. PVT-L jointly controlled experiments and conventional autoclave hydrous pyrolysis experiments have been carried out with immature shale from the Biyang Sag, Nanxiang Basin, and kerogens from the experiments were characterized by FTIR, which expressed four trends: (1) Accompanying aliphatic group cracking, oxygen-containing group shedding and aromatic group condensation, the evolution of kerogen experienced three periods including slow oil generation, fast oil generation and finishing oil generation. (2)FTIR parameters show more extensive aliphatic group cracking for conventional autoclave hydrous pyrolysis experiments, while there is still relatively strong hydrocarbon generation in the PVT-L jointly controlled experiment. (3)The lower aromatization of saturated hydrocarbons in PVT-L jointly controlled experiment may be relevant to higher fluid pressure in a finite space. (4)The slight increase of oxygen level implies the role of water in the hydrocarbon generation process. Different evolutionary characters of kerogen reflected the differences of reaction mechanism, which implied that it is important to choose an appropriate experimental mode in practical research.
Microbial anomaly distribution in Chen22 block, Chenjiazhuang oil field, Bohai Bay Basin
Yang Fan, Shen Zhongming, Tang Yuping, Xu Kewei, Gu Lei
2017, 39(1): 141-146. doi: 10.11781/sysydz201701141
Abstract(997) PDF-CN(178)
Abstract:
We collected 469 soil samples above Chen22 block in Chenjiazhuang oil field in the Bohai Bay Basin in order to study the microbial anomaly distribution above oil reservoirs. Methane-oxidizing bacteria and hydrocarbon oxidizing bacteria in the soil samples were cultured, and the number of bacteria detected was counted by using the MPN method. There was a good alignment between the upper abnormalities of the two indicative microorganisms and the position of wells on the connecting-well profile which had an obvious background area on the north and south ends. It showed that the two kinds of microorganism were effective indicators for the hydrocarbon microseepage of reservoirs. Combined with geological and drilling information, the response between the abnormal distribution of microorganisms and the underlying reservoir was researched by an accurate survey on the area. The distribution of underground reservoirs could be predicted by detecting microbiological anomalies, which also had a certain guiding significance to well drilling.
Zhang Wentao
2017, 39(1): 142-142.
Abstract(388) PDF-CN(391)
Abstract:

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