石油实验地质

2015, 37(3): .

Abstract(563) PDF-CN(815)

Abstract:

Prospects and challenges of continental shale oil development in China

Sheng Xiang, Chen Xiang, Zhang Xinwen, Jia Yanyu, Luo Xi

2015, 37(3): 267-271. doi: 10.11781/sysydz201503267

Abstract(1250) PDF-CN(944)

Abstract:
With the development of shale gas exploration in China, shale oil has attracted more and more attention. This investigation of shale oil exploration at home and abroad has reviewed the shale oil definition and characteristics, forming conditions, resource scale, key technology, problems and challenges with the shale oil exploration practice in the Biyang Sag. The results show that continental faulted basins in China have favorable shale oil conditions and rich resources. Technologies such as comprehensive geological evaluation, horizontal well drilling and completion, and multi-stage segmental fracturing have already been applied in China and important progress has been made in the Biyang Sag and the Jiyang Depression by using these technologies. There are three main problems in shale oil exploration and development. The first one concerns flow mechanism and reservoir evaluation. The second one is the independent research and development of some key engineering technologies such as a rotary steering system and micro-seismic fracture monitoring. The third one is the realization of economical exploration. All the problems above are the main research subjects in the future.

Comprehensive evaluation of fracture-cave units in karst carbonates in Tahe Oilfield, Tarim Basin

Jin Qiang, Tian Fei, Zhang Hongfang

2015, 37(3): 272-279. doi: 10.11781/sysydz201503272

Abstract(1073) PDF-CN(998)

Abstract:
Karstified carbonate is a complicated reservoir rock. Some fracture-cave units are connected and occur as oil reservoirs. Based on the studies of karst zones in the weathered crust of Ordovician carbonates, the genetic construction of fracture-caves and the filling materials in fracture-caves, a four-step method to identify and evaluate the fracture-cave units in karstified Ordovician carbonates in the Tahe Oilfield was proposed. Firstly, the genetic construction and boundaries of fracture-cave units were defined. Secondly, the genetic types and distribution of fillings in the caves were identified. Thirdly, the porosity and permeability of the fillings in the caves and the carbonates of cave walls were predicted. Finally, the connectivity between wells in the fracture-cave units were dynamically estimated. The four-step identification of fracture-cave units is a comprehensive evaluation. In addition, oil production potential is predicted for the fracture-cave units. This method was applied to several fracture-cave units in the Tahe Oilfield, which resulted in the re-recognition of reservoir rocks with karst fracture-caves and their contents.

Characteristics of Late Hercynian paleokarsts in Akekule Uplift, Tarim Basin

Liu Cunge, Xu Mingjun, Yun Lu, Liu Yongli, Wang Shengli, Luo Mingxia

2015, 37(3): 280-285. doi: 10.11781/sysydz201503280

Abstract(1003) PDF-CN(991)

Abstract:
Based on 3D seismic and drilling data, combined with modern karstology, this paper discussed the characteristics of Late Hercynian paleokarsts in the Yuqi and Lunan areas of the Akekule Uplift, the Tarim Basin. Study results showed that the Yuqi area was a peneplain, developing karst landforms such as grikes and depressions, which were controlled by faults. The surface water system featured multiple periods. The formation of peneplain in the Yuqi area was closely related to tectonic position, stratum attitude, paleoclimate and the base level of erosion. The Lunan area rose higher than the Yuqi area in the Late Hercynian. Some peak clusters remained since peneplanation was not complete. Large peak cluster and depression karst landforms formed in the Early Hercynian, and groundwater systems were well developed, which was different from the situation in the Late Hercynian. Fracture and cave reservoirs related to the Late Hercynian paleokarsts were mainly distributed along fault zones in the Yuqi area. They were widespread in the Lunnan area, and were controlled by the base level of erosion, fault and peneplanation degree.

Genetic types and exploration potential of pre-Mesozoic dolomite reservoirs in Yakela fault arch and its surrounding areas, Tarim Basin

Fei Jianwei, Yang Hongcai, Zhou Fangfang, Li Ye, Gu Rong

2015, 37(3): 286-292. doi: 10.11781/sysydz201503286

Abstract(814) PDF-CN(836)

Abstract:
The analyses of drilling cores, thin sections and physical properties show that there are at least three types of pre-Mesozoic dolomite reservoirs in the Yakela fault arch and its surrounding areas, including weathering crust, exposed shoal and buried karst. The weathering crust reservoirs are mainly controlled by ancient buried hills, and serve as the most important reservoir type in the study area. The exposed shoal reservoirs are controlled by sedimentary microfacies, and the environments like platform shoal, atmospheric fresh-water leaching and organic acid corrosion play important roles during reservoir formation. The buried karst reservoirs are controlled by the fluid during the burial period and the diagenetic environment. The dolomite reservoirs in the study area are formed under various geological processes during different stages. Ancient tectonic location, favorable facies, constructive diagenetic effects (dolomitization, dissolution) as well as faults and fissures are the key elements for dolomite reservoir formation. The covering formations, especially the Shushanhe Formation, are decisive for hydrocarbon accumulation in dolomite reservoirs.

Feldspar dissolution and its effect on reservoir in Kepingtage Formation, Shuntuoguole Low Uplift, central Tarim Basin

Zhao Shanshan, Zhang Shaonan, Wan Youli

2015, 37(3): 293-299. doi: 10.11781/sysydz201503293

Abstract(825) PDF-CN(541)

Abstract:
Thin section data showed that primary intergranular poreswere dominant in the tight sandstone reservoirs in the Silurian Kepingtage Formation in the Shuntuoguole Low Uplift of the Tarim Basin, while secondary pores formed by feldspar dissolution took the second place. The feldspar dissolution characteristics, mechanism and its effect on reservoir physical property were analyzed using thin sections, scanning electron microscopy (SEM), energy spectrum and X-ray diffraction (XRD). The proportion of secondary porosity formed by potassium feldspar dissolution was much larger than that from plagioclase, and albite was almost not dissolved. From the early Devonian to the late Jurassic, potassium feldspar dissolution resulted in the formation of secondary porosity, and the secondary pores only developed in the area not covered by asphalt. Dissolution products were mainly illite and the mixture of illite/smectite, although they could hinder secondary quartz overgrowth to some extent, greatly reduce connectivity among the pore throats of the sand body reservoir, and greatly influence the reservoir permeability.

Main controlling factors of carbonate reservoirs of Xiaohaizi Formation in Xianbazha area, Tarim Basin

Ma Zhongyuan, Yang Suju, Xu Qinqi, Zhang Li, Zhang Junzi, Huang Wei

2015, 37(3): 300-306. doi: 10.11781/sysydz201503300

Abstract(1072) PDF-CN(1038)

Abstract:
The basic characteristics and controlling factors of the Carboniferous reservoirs of the Xiaohaizi Formation in the Xianbazha area of the Tarim Basin have been studied based on core and thin section analysis, scanning electron microscopy, well logging and reservoir geochemical data. The Xiaohaizi reservoirs are mainly composed of limestones, dolomitic limestones, calcareous dolomites and dolomites. The reservoir porosity includes intergranular, intragranular and intercrystalline dissolved pores and fractures. The reservoirs are mainly of fracture-pore type and fracture type. The carbonate reservoirs in the Xiaohaizi Formation are controlled by many factors. Sedimentary facies is the foundation for reservoir formation. Favorable reservoirs are found in the platform shoal in the study area. Exposure erosion (proved by seepage powder sands, iron oxides and a large number of pores) and burial erosion (proved by fluorites, needle-like pores, carbon and oxygen isotopic anomalies) play important roles in reservoir development. Dolomitization promotes reservoir development to a certain extent. The tectonic fracture effect contributes to the development of fractured reservoirs, and offers a good channel for the occurrence of seepage erosion, which expands the scope of denudation.

Diagenetic characteristics of ultra-shallow reservoirs and influences on hydrocarbon accumulations: case study of Chunfeng Oilfield, Junggar Basin

Song Fan, Yang Shaochun, Su Nina, Zhang Ruixiang, Xiang Kui

2015, 37(3): 307-313. doi: 10.11781/sysydz201503307

Abstract(1643) PDF-CN(479)

Abstract:
Located in the northeast of the Chepaizi Uplift of the Junggar Basin, the Chunfeng Oilfield is regarded as a typical ultra-shallow reservoir since the main producing strata are about 500 m deep. Core and thin section observations show that the reservoir can be divided into three structural layers: basal conglomerates, gritstones and gravel sandstones in the middle, and fine sandstones on the top. Carbonate cementation is the most typical diagenetic effect, which took place mainly early during deposition, so that clastic grains are usually floating or have point contacting. Accordingly, compaction and dissolution are weak. The oil storage ability of the top and the bottom layers is poor due to strong cementation and poor sorting respectively. The oil and water distribution of the middle reservoir is complex that oil/water inversion phenomenon is a serious concern. The studies of hydrocarbon accumulation show that the unconformities at the bottom of the Shawan Formation, the Hongche Fault Zone and the thick sandstones widespread in the study area provide good pathways for hydrocarbon migration. Influenced by paleo tectonics and hydrocarbon filling, large-scale calcium carbonate deposition took place in the north, northwest and west of the Chunfeng area during the early stage, which blocked later oil migration and resulted in the oil/water inversion phenomenon. The special diage-nesis and reservoir distribution made it clear that there is not only stratigraphic or lithologic reservoirs developed in the shallow region, but also a certain size of diagenetic traps developed under the influence of carbonate cementation. This special trap, different from the conventional dissolution diagenetic traps, provides for useful exploration potential in the northwestern margin of the Junggar Basin.

Diagenesis of Middle and Upper Cambrian Loushanguan Group reservoirs in Nanchuan area, Sichuan Basin

Jiang Xiaoqiong, Guan Honglin, Liu Guangxiang, Li Jianming, Luo Kaiping, Yan Jiaxin, Ye Kai, Han Yu

2015, 37(3): 314-319. doi: 10.11781/sysydz201503314

Abstract(1158) PDF-CN(614)

Abstract:
The Middle and Upper Cambrian Loushanguan Group reservoirs in the Nanchuan area of the Sichuan Basin mainly consist of platform margin shoal sediments. The main lithology is dolomite. The main diagenesis effects include dolomitization, solution, structural disruption, consolidated fill, compaction and pressure solution, among which, the first three of these work as the key effects for reservoir formation. According to dolomite types, order degree and C, O isotope analyses, the dolomites in the study area developed from three diagenesis effects, including penecontemporaneous dolomitization, mixing water dolomitization and burial dolomitization, among which the penecontemporaneous dolomitization is dominant. The Loushanguan reservoirs have experienced three periods of dissolution, including the corrosion action of atmospheric fresh water, the deep burial solution and the hypergene dissolution, among which the hypergene dissolution is the main controlling factor. Dolomitization and hypergene dissolution contribute to high-quality reservoir formation in the Middle and Upper Cambrian Loushanguan Group. Cementation and filling effects destroy a large number of primary and secondary pores, which is unfavorable for reservoir formation.

Sedimentary microfacies characteristics and their control on reservoirs in Daanzhai Member, Lower Jurassic, Sichuan Basin

Feng Rongchang, Wu Yinye, Tao Shizhen, Zhang Tianshu, Yue Ting, Yang Jiajing, Liu Min

2015, 37(3): 320-327. doi: 10.11781/sysydz201503320

Abstract(1687) PDF-CN(991)

Abstract:
The Daanzhai Member of the Lower Jurassic in the Sichuan Basin is an important exploration target with complicated petrogeologic features. The Daanzhai Member includes eight lithofacies: thick blocks of recrystallized limestone, sparry shell limestone blocks, micritic shell limestone blocks or thin sections, argillaceous shell limestone thin sections, interbedded mudstones and shale shell limestones, shell mudstone thin sections, black mudstones, and red to green mudstones. A depositional model was established, consisting of five sedimentary microfacies: mud from littoral to shallow lake, back beach shell, shell beach core, beach front shell, and mud from shallow to intermediate depth lake. The controls of sedimentary microfacies on reservoir properties were determined according to the relationship between porosity/permeability and depositional environment. The beach front shell facies was favorable for tight oil accumulation.

Mineral composition andmicroscopic reservoir features of Longmaxi shales in southeastern Sichuan Basin

Liu Youxiang, Yu Lingjie, Zhang Qingzhen, Bao Fang, Lu Longfei

2015, 37(3): 328-333. doi: 10.11781/sysydz201503328

Abstract(1470) PDF-CN(1269)

Abstract:
Mineral compositions and microscopic reservoir features of the Longmaxi shales in the southeastern Sichuan Basin were comprehensively studied using the analyses of petrological characteristics, mineral compositions, microscopic pore structures and rock mechanics.The results show that quartz and clay minerals are abundant in the Longmaxi shales with average contents of 36.07% and 41.55% respectively, while carbonate minerals are poor with an average content of 9.92%.Quartz is especially rich at the bottom of the Longmaxi shales. As burial depth decreases, the content of quartz is less while clay mineral content increases. Abundant bioclasts indicate that siliceous matter is mainly biogenetic. Many inorganic and organic pores are found in the Longmaxi shales. Granular margin micro-fractures develop well in inorganic pores,while intergranular and intragranular pores are less common. There is a positive correlation between quartz content and pore volume, which indicates that biogenic silica pores play an important role in the development of porosity.Biogenic silica contributes to a high content of brittle minerals, which is favorable for fracturing treatment.

Reservoir main controlling factors of Chang8 sandstones in Jiyuan and Huangling areas, Ordos Basin

Qi Yalin, Zhao Yande, Wang Ke, Huang Jinxiu, Lü Jianwen, Zhang Xuefeng

2015, 37(3): 334-340. doi: 10.11781/sysydz201503334

Abstract(1174) PDF-CN(1854)

Abstract:
There are obvious differences of reservoir physical properties of Chang8 sandstones between the Jiyuan area in the northwest and the Huangling area in the southeast of the Ordos Basin. The factors influencing intergranular and dissolution pores were discussed based on granularity, thin section and SEM analyses. In this way, the controlling factors for reservoir physical properties and the mechanism for reservoir compaction were determined. The deposition system controlled the petrologic composition of the sandstones, the content of minerals with different physical and chemical stabilities, the content of feldspar, which caused secondary porosity, and the content of minerals with different mechanical properties (rigid, semi-plastic or plastic). Depositional environment controlled the granularity and sorting of clastic compositions in reservoir. The content of detrital mud components controlled the content of authigenic clay minerals. The difference in deposition system and environment between the two areas led to the difference of intergranular and dissolution pores, and explain the obvious differences of reservoir property.

Basic characteristics and key factors of gas accumulation in Yanchuannan coalbed gas field

Guo Wei

2015, 37(3): 341-346. doi: 10.11781/sysydz201503341

Abstract(1258) PDF-CN(1439)

Abstract:
The basic characteristics of the Yanchuannan coalbed gas field were analyzed in a case study of the No.2 coalbed in the Shanxi Formation. The gas field is featured by simple structure, stable thickness, low porosity, low permeability, low pressure gradient, high hydrocarbon potential, high gas content, and high thermal maturity. The relationships between faults and gas content, formation water, formation pressure gradient, the relationships between local structure and cleat development, coalbed gas content, and the characteristics of methane carbon isotopes were studied. Conclusions were drawn as follows. (1) Faults significantly controlled the enrichment of coalbed gas. Coalbed gas content decreased in fracture belts. (2) The central fault belt controlled the pressure gradient of coalbed and the distribution of formation water. (3) The coalbed gas was mixed self-sourced gas and thermogenic gas. Positive structure with certain amplitude is helpful for the enrichment of coalbed gas.

Petroleum accumulation systems and oil enrichment patterns of Yanchang Formation in Zhenjing area, southern Ordos Basin

Xiao Chengyu, Yin Wei, Zhang Ying, Xu Shilin, Yang Yu, Liu Zhenfeng

2015, 37(3): 347-353. doi: 10.11781/sysydz201503347

Abstract(1051) PDF-CN(1801)

Abstract:
Detailed analysis of the distribution of source rocks, the source-reservoir assemblages, the characteristics and the accumulation mechanisms of oil pools, etc. allow the Yanchang Formation in the Zhenjing area to be divided into near-source-contact type and near-source-leap type petroleum accumulation systems. The near-source-contact type petroleum accumulation system is characterized by lithologic traps, short migration distance, with the pressure difference between source and reservoir serving as major migration force and subtle transportation system in which hydrocarbon enrichment is mainly controlled by high-quality source rocks, favorable sand bodies as well as fractures. The oil enrichment pattern can be described as "source rock-sedimentary microfacies-fracture combined control". The near-source-leap type petroleum system is characterized by structural-lithologic traps, relatively longer migration distance, with the pressure difference between source and reservoir or buoyancy force serving as the major migration driving forces and the faults connecting source rocks serving as the main pathway, in which hydrocarbon enrichment is mainly controlled by the faults connecting source rocks, high quality sand bodies and fractures. The oil enrichment pattern can be summarized as "faults connecting source rock-sedimentary microfacies-fracture combined control".

Reservoir characteristics of mud shales from Upper Permian Linxi Formation in Suolun-Linxi area, Inner Mongolia

Zhu Zhanping, Zhang Mingyang, Sun Lei, Liu Yang, Cui Tong, Dai Dengliang

2015, 37(3): 354-360. doi: 10.11781/sysydz201503354

Abstract(1124) PDF-CN(1279)

Abstract:
In the Suolun-Linxi regions of the Inner Mongolia, extensive mud shales with a good hydrocarbon potential occur in the Upper Permian Linxi Formation. The thickness of the mud shales reaches a peak in the northwest of the Guandi-Bayanhua-Suolun areas. The total thickness is up to 911 m, and the maximum thickness of a single layer is 63 m.Field scanning electron microscopy and X-ray diffraction show that the mud shales are rich in brittle minerals, with an average content of 62.9% and a maximum content of 70.8%. The average content of clay minerals is 37.1%, and the maximum content is 41.5%. Micro pores and micro cracks are common. The pores are mainly intergranular and intragranular ones, with an average diameter of 1-3 μm and the maximum diameter of 8 μm. The average and maximum porosities of the mud shales are 1.288% and 4.42%, respectively. The average and maximum permeabilities of the matrix are 0.026 2×10^-3μm² and 0.275 8×10^-3μm², respectively. Compared to the shale gas basins already found in China and abroad, the mud shales of the Linxi Formation are favorable for shale gas accumulation, and possess the petrological characteristics of development. In conclusion, the northwest of the Chagannaoer-Baiyinnuoer area has a good exploration potential.

Hydrocarbon distribution and major controlling factors of Bengal Basin, Bangladesh

Liu Tieshu, Xi Zhugang, Luo Zongqiang

2015, 37(3): 361-366. doi: 10.11781/sysydz201503361

Abstract(1479) PDF-CN(1441)

Abstract:
The Bengal Basin is a typical remnant ocean basin in the southeastern India subcontinent. Based on the studies of basin evolution, petroleum geology conditions and hydrocarbon distribution characteristics, the gas accumulation regularity and its main controlling factors were analyzed in order to provide references for remnant basins. The Bengal Basin underwent syn-rifting, post-rifting and foredeep episodes, and developed good source-reservoir-cap rock assemblages during the remnant ocean basin development stage. The Oligocene Jenam and Miocene Bhuban shales are the most important source rocks. The Miocene Bhuban and Boka Bil sandstones are the principle reservoir objectives, which were deposited in a tide-dominated delta to shelf environment. The seal is the widely developed Miocene-Pliocene oceanic shales. Traps are mostly anticlines. The Bengal Basin is dominated by gas, and most gas fields distribute in the Surma depression, the Tangail uplift, the Hatia depression and the eastern fold belt on the plane. Gas accumulates in the Miocene Bhuban and Boka Bil formations. Gas distribution is closely related to the formation of remnant ocean basin. The gas-bearing sequence is impacted by basin evolution and gas plane distribution is impacted by the basin framework. Gas exploration should focus on the Surma depression, the Hatia depression and the eastern fold belt in the eastern part of the basin in the near future, and the main objectives are sandstone reservoirs of the Surma Group in the pressure transition zone.

Geochemical characteristics of source rocks and natural gas in Zitong Sag, Sichuan Basin

Dong Jun, Wang Peng, Yuan Dongshan, Ren Qingsong, Wang Shunyu, Li Bin

2015, 37(3): 367-373. doi: 10.11781/sysydz201503367

Abstract(1244) PDF-CN(2496)

Abstract:
The characteristics and genetic types of natural gas in the Zitong Sag of the Sichuan Basin have been studied according to the development and geochemical features of source rocks. The hydrocarbon source rocks in the study area mainly located in the first, third and fifth members of the Xujiahe Formation, among which the third member is the thickest. The TOC content of the source rocks is generally greater than 1.0%. Organic matter is of humic type, usually mature or highly mature. A large amount of hydrocarbon has been generated, and the generation intensity is greater than 3×10⁹ m³/km². Favorable source rock conditions enhance the accumulation of natural gas in the study area. Both dry gas and wet gas have been found. In the Jiulongshan, Jianmen, Weicheng and Bailongchang areas, dry gas is dominant. In the Zhongba and Laoguanmiao areas, wet gas is common. In the Wenxingchang, Zhebachang, Fenggu and Mianyang areas, both dry gas and wet gas exist. The natural gas in the study area is mainly thermogenic coal gas originating from the Xujiahe Formation. Oil type gas exists only in the Jiulongshan area, and is sourced from the underlying marine source rocks.

Geochemical characteristics and development model of transitional source rocks during the continental margin rifting stage, Bonaparte Basin, Australia

Hou Yuguang, He Sheng, Yang Xianghua, Duan Wei, Zhu Guanghui, Xu Xiaoming, Dong Tian

2015, 37(3): 374-382. doi: 10.11781/sysydz201503374

Abstract(1071) PDF-CN(1391)

Abstract:
The comprehensive analyses of tectonic settings, depositional fillings and organic geochemical characteristics indicated that the source rocks in the Bonaparte Basin were deposited during the main stage of continental margin rifting, and the well-developed river delta sedimentary system was beneficial for terrigenous organic matter input. The episodic rifting of the basin and the differential subsidence of contemporaneous faults provided both plentiful accommodation space and an underfilled depositional environment. Moreover, the pattern of "uplift alternating with sag" was favorable for the development of a semi-restricted depositional environment. The transitional source rocks were deposited in an oxic depositional environment with a large amount of terrigenous input. They mainly consist of carboniferous mudstones and coal-bearing series. Abundant terrigenous plant debris and some marine planktonic debris were observed. The terrigenous materials played a very important role in organic matter accumulation. With shifting sediment sources, the organic matter enrichment was decreasing and the kerogen was increasingly dominated by sapropelic organic matter. The n-alkane distribution was characterized by a back-end biased and bimodal pattern. The (n-C₂₁+n-C₂₂)/(n-C₂₈+n-C₂₉) and αααC₂₇R/αααC₂₉R ratios were increasing, while the Pr/Ph ratio was decreasing. All these variations also indicated that the source organic matter was changing from terrigenous to marine, and the depositional environment was changing from oxic to dysoxic conditions.

Design and key factors of a hall for workshop of meta-synthetic engineering (HWME) for petroleum geology

Sun Xudong, Wu Chonglong, Chen Lisheng

2015, 37(3): 383-389. doi: 10.11781/sysydz201503383

Abstract(1050) PDF-CN(1144)

Abstract:
The synthetic study of petroleum exploration geology is indispensable to decreasing risks in exploratory decision making and project deployment. This research which draws lessons from the theory of the hall for workshop of meta-synthetic engineering (HWME) proposed by Hsue-shen Tsien, has resolved a series of key technologies such as the real-time retrieval of multi-source and heterogeneous geology data, the knowledge management of research subjects, the data fusion of research results, and the interactive analyses of multi-touch on a big screen. An efficient work mode for cooperatively studying comprehensive geologic problems by many multi-subject experts has been set up. Furthermore, some hardware and software systems corresponding to HWME for petroleum exploration geology have been constructed and applied to some typical applications. These applications show that the research results proposed by this paper are effective, efficient and promising.

Pore throat structure and flow characteristics of sandstone reservoirs

Hu Yong, Guo Changmin, Xu Xuan, Jiao Chunyan, Yan Yongqiang

2015, 37(3): 390-393. doi: 10.11781/sysydz201503390

Abstract(1055) PDF-CN(1228)

Abstract:
Mercury injection testing, gas-water relative permeability testing and physical simulation experiments of gas reservoir depletion were carried out with cores from the Xujiahe Formation in the Sichuan Basin (permeability: 0.002-70.28 mD). The differences between tight sand gas reservoirs and high permeability gas reservoirs of the pore structure characteristics, force characteristics and gas-water relative permeability characteristics were analyzed. The approach was as follows: (1) The pore structure characteristics of sandstones with different permeability were described by three parameters: pore throat ratio, average throat radius and median throat radius, and the pore structure characteristic differences between tight sand gas reservoirs and high permeability gas reservoirs were comparatively analyzed. (2) The force situations of gas and water flowing in the sandstones with different permeability were quantitatively evaluated by threshold pressure and frictional drag, and the impacts of pore structure on the capacities of tight sand gas reservoirs and high permeability gas reservoirs were analyzed. (3) The relation diagram of gas relative permeability and water saturation were derived, and the impact of water saturation on the gas relative permeability of cores with different permeability was analyzed. The research results will provide a reference for gas reservoir microcosmic modeling and the study of gas and water percolation mechanism.

Technique and application of fracture detection in fracture-cavity reservoirs in Yingshan Formation, Yubei area, southwestern Tarim

Yuan Xiaoyu, Li Yingtao, Zhang Shaonan, Ye Ning

2015, 37(3): 394-401. doi: 10.11781/sysydz201503394

Abstract(1034) PDF-CN(1388)

Abstract:
The geological characteristics of the reservoirs in the Ordovician Yingshan Formation in the Yubei area of the southwestern Tarim Basin showed that fractures controlled the development of karst reservoirs. Seismic fracture detection technology was significant for carbonate reservoir prediction. The combination of four kinds of crack detection technology was adopted in this paper. (1) Dip azimuth attribute was used to recognize large-scale fractures and faults. (2) Curvature technique was adopted to identify cracks resulted from the structural bending deformation of formations. (3) Fine coherence technology was used to accurately identify stratigraphic discontinuity and small-scale rivers. (4) Spectrum decomposition technique was effectively introduced into the tracking technology to predict tectonic shear and expansion cracks resulting from structural deformation extrusion. The results showed that, in addition to the area near the fault zone, micro-cracks were also widely developed in the zone which was away from the fault zone. This is consistent with the long term tectonic compression background and the fracture development features revealed by wells and cores, and shows that the technological combination method was effective to detect the fracture development zone.

Optimization of shale gas desorption method in field

Yu Lingjie, Fan Ming, Jiang Qigui, Tang Qi, Zhang Wentao, Su Xiangwei

2015, 37(3): 402-406. doi: 10.11781/sysydz201503402

Abstract(1004) PDF-CN(1010)

Abstract:
This paper optimized conventional shale gas desorption method by applying 110 ℃ as second stage desorption temperature with self-designed smart desorption apparatus. The proposed rapid method largely increased efficiency by reducing desorption time from more than 40 h to 8 h approximately and avoiding residual gas test. Water steam blocking problem was avoided by using "T" type bronze condensation tube and quartz sand filling. Six group of shale samples were selected to compare rapid and conventional desorption method. The result showed that the data difference was smaller than 0.15 m³/t mainly from heterogeneity. In addition, the result of shale gas content exhibited the same trend as well logging. The study shows that the rapid method could obtain reliable results with high efficiency and could meet the demand of intensive tests to improve accuracy of resources estimate.

Yu Lingjie, Fan Ming

2015, 37(3): 407-407.

Abstract(605) PDF-CN(1246)

Abstract:

2015 Vol. 37, No. 3

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