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2016 Vol. 38, No. 2

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2016, 38(2): .
Abstract(474) PDF-CN(1213)
Abstract:
Uplift event in the middle Hercynian period and its influence on the sedimentary-tectonic pattern of the western Tarim Basin
Guo Shuyuan, Zhan Wei, Huang Taizhu, Cai Xiyao
2016, 38(2): 147-155. doi: 10.11781/sysydz201602147
Abstract(1355) PDF-CN(944)
Abstract:
An uplift event in the middle Hercynian period in the western Tarim Basin was called "Bachu Movement" by early researchers, and mainly occurred between the Xiaohaizi Formation and the standard limestone sequence. Some researchers denied its existence, some researchers believed that it occurred between the Xiaohaizi Formation and the limestone sequence, some other researchers believed that it occurred between the upper mudstone sequence and the sandstone-mudstone sequence, and most researchers did not mention it. According to well-strata contrast and seismic interpretation and tracking, the authors have concluded that a tectonic uplift event occurred between the upper sandstone sequence and the sandstone-mudstone sequence in the Kalashayi Formation, which led to the erosion of the upper mudstone sequence, the standard limestone sequence and the middle mudstone sequence in the Kalashayi Formation and even the Bachu Formation. Afterwards, seawater encroached from the southwestern Tarim Basin towards north and east, and the sandstone-mudstone sequence and limestone sequence in the Mazhatage Formation and the Xiaohaizi Formation were deposited. The Bachu Movement occurred between the middle and late stages of the Datang period of the Early Carboniferous, and made the southwestern Tarim Basin reverse from a north dipping slope to a south dipping one. Hydrocarbons expelled from the Cambrian and Ordovician mature source rocks migrated to the north instead of south. The structural belts formed in the late Hercynian period on the Mengaiti Slope and the Bachu Uplift are favorable areas for hydrocarbon accumulation. The Hetianhe, Niaoshan, Bashituo, Yasongdi gas fields and the Haimiluosi gas-bearing structure have been discovered.
Strike-slip faults and their controls on hydrocarbon reservoirs in the Yuecan block of the Northern Tarim Uplift, Tarim Basin
Tian Peng, Ma Qingyou, Lü Haitao
2016, 38(2): 156-161. doi: 10.11781/sysydz201602156
Abstract(1231) PDF-CN(1031)
Abstract:
We studied the production performance of about 30 wells in the Yuecan block of the Northern Tarim Uplift in the Tarim Basin, and considered the controls of the X-shaped strike-slip faults in the study area on the Ordovician fractured and vuggy system reservoirs, combined with core sample observations and testing. The strike-slip faults were active during multiple stages, and formed a large number of high-angle tectonic fractures, which developed a large fractured and vuggy system during the following thermal evolution. Oil and gas migrated upwards along the main strike-slip faults, then redistributed along secondary faults, and finally determined the hydrocarbon properties and charging extentin the study area. Reservoirs with a high charging degree and excellent crude oil properties were found in the main strike-slip faults, and the wells showed a good production performance. On the contrary, the secondary strike-slip faults had a low charge and poor crude oil properties, and the wells showed poorer production performance. In addition, the direction of strike-slip faults, the relative position of fault walls, and the distance to faults also played important roles in controlling hydrocarbon enrichment.Results showed that hydrocarbon was most enriched in the upper wall of the NE-oriented strike-slip faults.
Reservoir characteristics and favorable zone prediction of tight sandstone gas of the Ahe Formation in Yinan area, Kuqa Depression
Kang Hailiang, Lin Changsong, Li Honghui, Wang Kaizhong
2016, 38(2): 162-169. doi: 10.11781/sysydz201602162
Abstract(986) PDF-CN(973)
Abstract:
The Lower Jurassic Ahe Formation in Yinan area of the Kuqa Depression has favorable geologic conditions for the formation of tight sandstone gas reservoirs. Core, logging, drilling data, thin section observation, cast thin section identification, scanning electron microscope and the X-ray diffraction analysis of clay minerals showed that the tight sandstone reservoirs in the study area mainly originated from braided distributary channels and underwater distributary channels.Lithic sandstones are dominant with low compositional maturity and medium textural maturity. Fractures were well developed. The porosity is 4%-12%, averages 7.53%. The permeability is (0.1-100)×10-3 μm2, average 12.33×10-3 μm2. The samples with a permeability less than 1×10-3 μm2 account for 75%, consistent with typical tight sandstone reservoirs. Reservoir formation is related to sedimentation, diagenesis and tectonism. Favorable facies belts and characteristic curves were applied to reconstruct sandstone thickness and fracture distribution, and to predict favorable exploration targets combined with tectonic background. The study showed that the area to the south of wells Yinan2, Yinan5 and Tuzi2 is a potential play for tight sandstone gas exploration, especially the area to the south and southwest of well Yinan2.
Stratigraphic correlation and source rock distribution of the Middle-Upper Ordovician in the Shaya Uplift and Kalpin outcrop, Tarim Basin
Liu Cunge, Li Guorong, Luo Mingxia, Shao Xiaoming, Luo Peng, Liu Yongli, Gao Lijun
2016, 38(2): 170-177. doi: 10.11781/sysydz201602170
Abstract(1183) PDF-CN(953)
Abstract:
The Ordovician strata in the Kalpin outcrops are the westward extension of a large carbonate platform in the Tarim Basin, and they have experienced the same sedimentary evolution process as the basin. Based on biostratigraphy and carbon isotope stratigraphic correlation, the Middle Darriwilian Isotope Carbon Excursion (MDICE) of the Middle Ordovician Yijianfang Formation and the Guttenberg Isotope Carbon Excursion (GICE) of the Upper Ordovician Lianglitag Formation of the Shaya Uplift correspond to the positive excursions in the lower part of the Salgan Formation and the lower-middle parts of the Qilang Formation in the Kalpin outcrops, respectively. It was inferred that an unconformity of the second episode tectonic movement of the Middle Caledonian existed in the upper part of the Qilang Formation, and the Qilang and Yingan formations above the unconformity corresponded to the Sangtamu Formation of the Upper Ordovician in the Shaya Uplift. The eastern side of the Lower-Middle Ordovician platform in northern Tarim showed a steep slope due to the rise of global sea level in the Early-Middle Ordovician, and the platform thickness gradually thinned to the northwest. The northwestern Shaya Uplift and the Awat-northern Kalpin region belong to the slope to basin sedimentary system. The Salgan marine source rocks mainly comprise the condensed section of the middle-upper Darriwilian, and are distributed in the Awat and the northwestern Shaya uplift as indicated by the electrical characteristics of outcrops and drill cuttings. The depression between the small carbonate platforms of Kalpin, central Tarim and Shaya Uplift are favorable development regions of source rocks corresponding to GICE during the deposition of the Lianglitag Formation. The Yingan source rocks are most widely distributed in the Awat and Shaya uplift.
Geological characteristics of the Jurassic shale gas play in the frontal area of the southern Altun Tagh
Li Weiqi, Kang Zhihong, Zhou Lei, Tong Xuefei, Huangfu Jingjing
2016, 38(2): 178-182. doi: 10.11781/sysydz201602178
Abstract(1645) PDF-CN(981)
Abstract:
The Jurassic shales were deposited in the frontal area of the southern margin of the Altun Tagh, but shale gas exploration or assessment has not be carried out. Some samples have been analyzed and tested using field geological surveys and core observation and description to determine the distribution and organic geochemical characteristics of shale layers in the Jurassic. Also the occurrence and distribution of effective shales in the frontal area of the Altun Tagh were identified. The Dameigou Formation, which forms the majority of the Jurassic shale layers, developed in a semi-deep lacustrine environment and shale was distributed in the NE-SW direction along the frontal area. Total organic carbon (TOC) ranges from 1.00% to 5.19% for high organic matter abundance, the organic matter maturity (Ro) varies from 1.11% to 2.87%, and the organic matter is dominated by type-Ⅱ1 kerogen to type-Ⅱ2 kerogen. The shale layers of the Dameigou Formation in the frontal area are thick, the abundance of organic matter is high, the type and the thermal evolution stage are favorable to produce gas, and comparison with North American deposits suggests that the geological conditions to accumulate shale gas are good. There are four favorable exploration targets for shale gas, including Yueyashan, Heishishan-Sanjiaojia, Chaishuigou-Qingshuihe, and Mangya areas.
Mechanics and evolution of Mesozoic and Cenozoic basins in the East Qinling-Dabie Orogenic Belt
Zhang Miao, Yun JinBiao
2016, 38(2): 183-188. doi: 10.11781/sysydz201602183
Abstract(1230) PDF-CN(1132)
Abstract:
In the East Qinling-Dabie Orogenic Belt, the Mesozoic and Cenozoic basins controlled by the Mesozoic and Cenozoic stretching and strike-slip faults formed a complete stretching and detachment system together with metamorphic core complexes in Dabie area. These basins have experienced two evolution stages including orogenic extrusion and regional extension in response to the NWW and NE oriented basement faults, the changes of basin subsidence direction, and the time-space relationship of foreland basins to the north of the orogenic belt, which is in accordance with the evolution history of the East Qinling-Dabie Orogenic Belt. The geophysical characteristics of deep formations in the orogenic belt and the generation of granite complex during the late stage of orogenic movement showed that the basins in the orogenic belt were controlled by regional extension and deep adjustment. The basins were formed due to the subduction and relaxation of the East Qinling-Dabie Orogenic Belt and regional extension.
Sandy mass transport deposit model and its natural gas accumulation in the Yinggehai Basin
Zhang Yingzhao, Wang Lifeng, Li Xushen, Zhong Zehong, Zhan Yeping, Xu Tao
2016, 38(2): 189-196. doi: 10.11781/sysydz201602189
Abstract(1173) PDF-CN(1455)
Abstract:
The sandy mass transport deposit of the first member of the Huangliu Formation in the Upper Miocene was newly recognized using 3D seismic data and drilling data collected from the XF13 area of the Yinggehai Basin. The depositional model and natural gas accumulation mechanism have been investigated. Cores recorded sedimentary characteristics of sandy mass transport deposit very well, developing massive stratifications and parallel stratifications, abrupt contact surfaces, mudstone avulsions, and deformation layers. The sandy mass transport deposit had distinct seismic reflection features compared with those of surrounding rocks. They consisted of multiple periods of sedimentation, and each period experienced early erosion, filling, migration and a late abandonment stage. They developed a double-layer sedimentary architecture, which consisted of massive thick compound lobe sandbody and sheety sandbody, respectively. Each period of sandy mass transport deposit developed sandy debris flow massive thick sandstones with slide-slump movement near provenance, and muddy turbidity current deposits laterally far from the source. A new model with a transgressive-highstand systems tract and outer continent environment was proposed. A case study was made in the XF13 gas field. Through the integrated analyses of sandy mass transport deposit, structural-lithological trap formation, fault/fissure migration pathway and natural gas pooling process, natural gas accumulation mechanism were considered. The central and deep sections of the basin have favorable geologic conditions for gas enrichment and preservation.
Shale reservoir characteristics of the Lower Cambrian Qiongzhusi Formation in the southern Sichuan Basin
Wang Tong, Xiong Liang, Xu Meng, Dong Xiaoxia, Zhou Ruiqi, Fu Xiaoning
2016, 38(2): 197-203. doi: 10.11781/sysydz201602197
Abstract(1183) PDF-CN(1563)
Abstract:
Experimental source-reservoir data from three wells in the Mianyang-Changning intracratonic sag in the southern Sichuan Basin showed that the Qiongzhusi Formation in the study area features high TOC, thick black shale, high maturity, and high brittleness. Although the southern Sichuan Basin has experienced multiple episodes of tectonic movement, the B1 well block still has favorable preservation conditions. Micro-reservoir space includes organic pores, inorganic pores (intercrystal pores in clay minerals, intergranular pores and intragranular dissolution pores in brittle minerals, and intergranular pores in pyrites), and micro-cracks (micro-structural seams, diagenetic shrinkage joints and dissolution seams), and can be further subdivided into 9 types. Most of the pores have narrow necks, and some are slit type holes. Fractures are tablet or wedge shaped. Mesopores were abundant, and there also exist micropores and macropores. High quality shales have high entrance and BET specific surface area, which is favorable for the preservation of free and adsorbed gas. TOC, maturity, diagenesis and pore fluid pressure determined the difference of pore type and distribution.
Occurrence of organic matter in different mudstone lithofacies and its influence on specific surface area:A case study of the Paleogene in the Zhanhua Sag, Bohai Bay Basin
Liu Weixin, Zhu Xiaojun, Ma Anlin, Cai Jingong, Lu Longfei
2016, 38(2): 204-210. doi: 10.11781/sysydz201602204
Abstract(1498) PDF-CN(1021)
Abstract:
Some core and cast thin section samples of shales were collected from different depths of the lower section of the third member of the Paleogene Shahejie Formation in well L in the Zhanhua Sag. X-ray diffraction (XRD), pyrolysis and specific surface area (SSA) measurements were applied to examinethe characteristics of organic matter (OM) occurrence and analyze the effect of OM on the SSA of different mudstone lithofacies. Results showed that the shales can be categorized into lithofacies A (lack of organic laminae) and lithofacies B (rich in organic laminae). The former has a low TOC content with high SSA, and the latter has a high TOC content with low SSA. The relationship between TOC and mineral SSA is convergent in the lithofacies A and divergent in the lithofacies B, which indicates that OM in the lithofacies A is mainly adsorbed on mineral surfaces while OM in lithofacies B is chiefly accumulated as organic laminae. The variation of OM occurrence clearly affected shale SSA. The SSA of lithofacies A is lower than that of lithofacies B, and the contribution of minerals to SSA is similar in both lithofacies, which indicates that the variation of SSA in different lithofacies (A and B) is correlated with the abundance of organic laminae.
Mineral composition and brittleness characteristics of the inter-salt shale oil reservoirs in the Qianjiang Formation, Qianjiang Sag
Wang Furong, He Sheng, Zheng Youheng, Hou Yuguang, Wu Shiqiang
2016, 38(2): 211-218. doi: 10.11781/sysydz201602211
Abstract(1607) PDF-CN(1185)
Abstract:
Core samples of shales from the second (Eq2), third (Eq3) and fourth (Eq4) members of the Qianjiang Formation in the Qianjiang Sag were analyzed using X-ray diffraction (XRD) analyses to determin their mineral composition, brittleness and geochemical characteristics. The results showed that the shales from different formations have different mineral compositions and geochemical characteristics. The shales in Eq2 have sapropelic organic matter. The TOC content averages 1.38%. The Ro value ranges from 0.26%-0.5%, indicating an immature to low-maturity thermal evolution stage. Evaporite rocks are in high content. The shales in Eq3 have sapropelic and humic-sapropelic organic matter. The TOC content averages 2.53%. The Ro value ranges 0.5%-0.88%, indicating a low to medium-maturity thermal evolution stage. Quartz and clay minerals are in high content. The shales in Eq4 have sapropelic and humic-sapropelic organic matter. The TOC content averages 0.69%. The Ro value ranges 0.55%-1.3%, indicating a medium-maturity to mature thermal evolution stage. Carbonate minerals are in high content. The inter-salt shales in the Qianjiang Formation are characterized by "low clay content, low quartz content, high carbonate content, and low brittle mineral content" compared to those in the USA and other regions in China. The shales in Eq3 have higher brittle mineral content (average 56%) and higher brittleness index (average 75.3%), which show excellent exploration potential.
Initial porosity reduction phase of ultra-deep tight sandstone reservoirs:A case study of the Rub' Al Khali Basin in the Middle East
Jiang Hui, Fan Shengli, Zhao Yingquan, Zhang Shaonan, Zhou Jin, Liu Zhiqiang
2016, 38(2): 219-223. doi: 10.11781/sysydz201602219
Abstract(890) PDF-CN(892)
Abstract:
The Ordovician S Formation in the Rub' Al Khali Basin in the Middle East is a typical ultra-deep tight sandstone reservoir. Siliceous cementation dominated by the secondary overgrowth of quartz is the main cause for reservoir porosity reduction in the study area. The period of the pyrobitumen charge is taken as the beginning of reservoir tightening, while the secondary overgrowth of quartz, which sharply reduced porosity, is taken as the end of reservoir tightening. We combined mineral cathodoluminescence, fluid inclusion temperature, authigenic illite isotopic dating with tectonic subsidence, burial and thermal evolution history analyses, and concluded that the Ordovician reservoirs were cemented from the Late Triassic to Early Jurassic with a tightening rate of 30.6 m/Ma. The reservoir continued thermal evolution after tightening. Oil partially cracked to gas, some of which condensed in traps, and some of which escaped upwards or migrated through micro-pores to become diffused mixtures of oil and gas.
Characteristics and origin of high porosity and low permeability carbonate reservoirs in the Sa'di Formation, Halfaya Oil Field, Iraq
Wang Yuxiang, Zhou Wen, Guo Rui, Fu Meiyan, Shen Zhongmin, Zhao Liming, Chen Wenling
2016, 38(2): 224-230. doi: 10.11781/sysydz201602224
Abstract(1438) PDF-CN(1152)
Abstract:
The high-porosity and low-permeability reservoir in the Sa'di Formation of the Halfaya oil field in Iraq makes this a special oil and gas reservoir in the Middle East. Reservoir characteristics and the origin of high porosity and low permeability were studied by core observation, cast thin sections, physical property testing and mercury injection experiments. Rocks in the reservoir include grained limestones (oolitic limestones and limestones), packstones, wackestones and micritic limestones. The Sa'di Formation is characterized by ramp facies, and develops inner ramp and outer ramp subfacies. The lower part of the formation has better physical properties than the upper part. Pores are mainly intrafossil and intragranular. Mercury injection experiments showed a high driving pressure, small throat radius and poor flowability. The reservoir is mainly controlled by sedimentary facies, and the reservoirs of different facies showed different properties. Diagenetic transformation has constructive effects on the formation of secondary pores, resulting in poor cementation. High porosity and low permeability of the reservoir can be explained by the following factors:(1) Intrafossil pores developed, yet were poorly connected. (2) Sedimentary environment was featured by poor hydrodynamic conditions, and was poorly reformed. (3) The reservoir was controlled by sedimentary process, and the digenesis impact was very weak. (4) Pore types varied, but had low contribution to permeability.
Kinetic analysis of hydrocarbon generation components in shales from the Bonan sub-Sag and its significance for hydrocarbon exploration
Jiang Qigui, Shen Baojian, Yang Yunfeng, Li Zhiming, Ma Yuanyuan, Qian Menhui
2016, 38(2): 231-239. doi: 10.11781/sysydz201602231
Abstract(1305) PDF-CN(1331)
Abstract:
The Paleogene shales in the East China contain Type I organic matter comprised mainly of planktonic algae. A kinetic analysis of the hydrocarbon generation of this source rock was made using a pyrolysis-gas chromatograph. The hydrocarbon generation potential, composition and oil saturation of shales in the Bonan sub-Sag were studied in the context of the thermal history of the Shahejie Formation. The hydrocarbon conversion rates of light and heavy hydrocarbons in source rocks in the middle section of the third member of Shahejie Formation (Es3) are 31.1% and 43.8%, respectively, indicating the oil generation period. The oil saturation index might reach 273.24 mg/g, showing some shale oil potential. However, the oil is too heavy for exploitation. The lower section of Es3 (and the upper section of Es4) has a high oil saturation up to 571.17 mg/g and a high elastic force with coexisting oil and gas, and hence is an excellent target for shale oil exploitation. The middle and lower sections of Es4 arrived at the peak of methane generation. Any residual oil would have been cracked. Shale gas should be the main exploration focus unless an overpressure system developed.
Benzohopane maturity index in source rock thermal simulation
Song Xiaoying, Zhang Caiming, Zheng Lunju, Zhang Qu, Cheng Qiuquan
2016, 38(2): 240-243. doi: 10.11781/sysydz201602240
Abstract(1358) PDF-CN(1383)
Abstract:
Gas chromatography-mass spectrometry (GC-MS) analysis of the thermal simulation products of the Eocene oil shales from the Huadian Basin in Jilin province show that a series of benzohopanoids disappeared at a simulation temperature≥340℃. The benzohopane index (BHI) correlates well to the equivalent vitrinite reflectance, which can be used to judge maturity for low-maturity source rocks, and to distinguish mature and immature source rocks.
Geochemical characteristics and genetic analysis of Ordovician medium-light oils from well YQX1 in the northwest of Tahe Oil Field
Luo Mingxia, Xia Yongtao, Shao Xiaoming, Liu Yongli
2016, 38(2): 244-250. doi: 10.11781/sysydz201602244
Abstract(1196) PDF-CN(1323)
Abstract:
Medium-light oils were tested in well YQX1 in the Ordovician super heavy oil area in the northwest of Tahe Oil Field. We studied their geochemical characteristics including physical character, group composition, GC-MS of saturated and aromatic hydrocarbons, and made a comparison with the Ordovician super heavy oils in the Yuqi area and the condensate oils in the Yakela area, in order to confirm their genetic types. The medium-light oils from well YQX1 have a high saturate hydrocarbon content, medium aromatic hydrocarbon content, and low non-hydrocarbon and asphaltene contents. The n-alkane series is complete with a single mode. An obvious "UCM" hump appears in chromatogram. The distributions of steranes and terpanes has a good correlation with the super heavy oils of Yuqi area and the condensate oils of Yakela area, which indicates that they have the same source. Maturity parameters such as Ts/(Ts+Tm) and 4-/1-MDBT show that oils from well YQX1 have a high maturity, which is similar to the condensate oils in Yakela and higher than the super heavy oils of the Yuqi area. Combined with terminal accumulation background and tectonic evolution in the northwest of Tahe Oil Field, it is inferred that the oils from well YQX1 mainly came from the north. The high-maturity light oil and gas migrated along the Luntai fault during the Himalayan period, transformed the early heavy oil reservoirs along unconformity from north to south, and finally formed the medium-light oil currently present in the reservoir.
Petrologic and geochemical characteristics and the origin of dolomites in the Qixia Formation in Nanjiang county of the Sichuan Basin
Li Xiaoning, Huang Sijing, Huang Shuguang, Huang Keke, Yuan Tao, Luo Wen
2016, 38(2): 251-258. doi: 10.11781/sysydz201602251
Abstract(1029) PDF-CN(1374)
Abstract:
Limestones are locally dolomitized in the 2nd member of the Middle Permian Qixia Formation of Qiaoting section, located in Nanjiang county of the Sichuan Basin. Matrix dolomites primarily consist of non-planar xenotopic dolomite crystals, and vugs and fractures are filled with saddle dolomites and crystalline calcites. Dissolution occurs mainly in dolomites. Characteristics and origin of matrix dolomites and saddle dolomites have been determined based on petrographic examinations, integration of carbon and oxygen stable isotopes, trace element content, fluid inclusion data, cathodoluminescence images, burial and thermal maturation history and abnormal thermal events associated with the Emeishan basalt eruption. The research showed that the fluid inclusion homogenization temperatures of matrix dolomites, saddle dolomites and crystalline calcites range 100~110℃, 130~230℃ and 130~230℃, respectively. The δ18O values of the samples which mainly consist of matrix dolomites, saddle dolomites and crystalline calcites range -4.27‰~-6.28‰, -4.87‰~-5.80‰ and -5.16‰~-6.50‰, respectively. Saddle dolomites and crystalline calcites have the characteristics of more negative δ18O values than matrix dolomites. The δ13C values of the samples which mainly consist of matrix dolomites, saddle dolomites and crystalline calcites range 3.97‰~5.22‰, 4.88‰~5.35‰ and 2.73‰~4.29‰, respectively, indicating that the carbon source is generally from the coeval seawater. The δ18O values of dolomitizing fluids for matrix dolomite and saddle dolomite range +3‰~+6‰ (SMOW) and +7‰~+14‰ (SMOW), respectively. This is consistent with the formation of matrix and saddle dolomites in fluids with elevated salinity and temperature. Matrix dolomites, saddle dolomites and crystalline calcites were influenced by thermal events caused by Emeishan basalt eruption activity. The kinetic barrier of dolomite precipitation was overcome by high salinity and temperature, and it allowed the transformation of limestones into replacive matrix dolomites and precipitate saddle dolomites in vugs and fractures. Due to lasting high temperature and Mg2+ loss, calcites with high temperature precipitated, which showed that hydrothermal fluids altered the carbonate rocks.
Geochemical characteristics and geological significance of natural gas in Jinshan area of the Lishu Fault Depression
Lu Qinghua, Gu Yi, Song Zhenxiang, Zhou Zhuoming, Li Kuang
2016, 38(2): 259-265. doi: 10.11781/sysydz201602259
Abstract(1004) PDF-CN(1382)
Abstract:
Jinshan area is located in the southeast slope belt of the Lishu Fault Depression, which is an important gas exploration target. The geochemical characteristics of natural gas in Jinshan area indicate that there are two genetic types. (1) In well Jin2, non-hydrocarbon gas reservoirs with a high inorganic CO2 content were found. The hydrocarbon gas is featured by a high dryness coefficient. Inorganic gas was mixed with oil associated organic gas. (2) Hydrocarbon gas reservoirs were discovered in the other wells. The gas is coal-type wet gas with a high CH4 content, and is mature or over-mature.
Geochemical characteristics of source rocks and oil-source correlation in the Kashi Sag, Tarim Basin
Meng Miaomiao, Kang Zhihong, Xu Yaohui, Yu Chao, Liu Qi
2016, 38(2): 266-272. doi: 10.11781/sysydz201602266
Abstract(1639) PDF-CN(1295)
Abstract:
The Kashi Sag in Tarim Basin shows good hydrocarbon exploration prospects with superior accumulation conditions. However, the only discovery is the Akmomu gas field. One important reason is that there is no clear understanding of hydrocarbon source rocks. Through systematic sampling and geochemical analysis of 9 profiles in the Kashi Sag, we concluded that the Lower Carboniferous and Lower-Middle Jurassic are the main hydrocarbon source rocks in the Kashi Sag. The Lower Carboniferous marine mudstones and marlstones are medium-good hydrocarbon source rocks with type Ⅱ organic matter that are widely distributed with large thickness. They are highly mature and mainly produce dry gas. Lacustrine mudstones of organic matter type Ⅱ in the Middle Jurassic Yangye Formation and swamp facies mudstones of organic matter type Ⅲ in the Lower Jurassic Kangsu Formation are lower quality potential sources. They are mature and mainly produce oil and light oil. Oil-source correlation indicated that the source rocks of Heiziwei oil seepage, Kelatuo oil sand and well Ake1 natural gas is Carboniferous, which is the main source rock sequence in the sag. The Lower-Middle Jurassic source rocks have restricted hydrocarbon generation potential and are distributed locally and were less important for hydrocarbon accumulation.
Methodology of reservoir prediction in areas with complicated lithology in saline lake basins:A case study of the Qianjiang Sag, Jianghan Basin
Luo Jin, Li Minghua, Guo Libin, Zhong Qingliang, Kong Jinping, Zha Guangyu
2016, 38(2): 273-277. doi: 10.11781/sysydz201602273
Abstract(1193) PDF-CN(1131)
Abstract:
Sandstone reservoirs were predicted so as to propose a new method for the studies of reservoirs with complicated lithology in saline lake basins. The study area was the semi-saline period in the oil group no.0 in the fourth member of the Paleogene Qianjiang Formation (E2q40) in areas W, G, and H in the Qianjiang Sag of Jianghan Basin. The method was called "four-definition", which defines sedimentary facies through integrating geologic data with seismic data, defines markers through petrophysical modeling, defines geological boundaries through comprehensive multi-attribute geological analysis, and defines stratigraphic thicknesses through definitive inversion. Applications in the Qianjiang Sag succeeded in finding several high-yielding oil pools of beach bar facies, showing that the method can improve the prediction accuracy in reservoirs with complicated lithology.
Application of hand-held X-ray fluorescence spectrometry in the core analysis of Paleogene lacustrine shales in the Jiyang Depression
Ma Xiaoxiao, Li Maowen, Pang Xiongqi, Huang Zhenkai, Jiang Qigui, Li Zhiming, Cao Tingting, Li Zheng
2016, 38(2): 278-286. doi: 10.11781/sysydz201602278
Abstract(1440) PDF-CN(1766)
Abstract:
Lacustrine sedimentary facies vary rapidly in rift basins in China, exhibiting significant heterogeneity in shale fabric and chemical composition. In order to characterize the heterogeneity effectively, the analysis of closely spaced geological samples is required to obtain such data as element geochemistry. We employed the technique of X-ray fluorescence spectral analysis (XRF) to study core samples systematically collected from the mudstone/shale section of the third and fourth members of the Eocene Shahejie Formation in the Jiyang Depression, and optimized the experiment conditions of core testing conducted using a hand-held X-ray fluorescence spectrometer. Subsequently, this method was tested with selected shale and sandstone samples to determine the XRF response of diverse lithologies. Through the closely spaced XRF testing on cores, we determined the element composition and petrologic characteristics of cores. Preliminary applications showed the effectiveness of the technique for determining shale lithology and lithofacies, and thus provided a diagnostic tool for shale heterogeneity characterization.
2016, 38(2): 287-287.
Abstract(320) PDF-CN(91)
Abstract:

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