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Jiao W.-W.,Chongqing Institute of Geology and Mineral Resources | Jiao W.-W.,Chongqing Shale gas Research Center | Zhang J.,Petrochina | Cheng L.-J.,Chongqing Institute of Geology and Mineral Resources | And 3 more authors.
Advanced Materials Research | Year: 2012

Carbonate reservoir is one of the main controlling factors of hydrocarbon accumulation. But the exploration proved that high-quality reservoir and commercial hydrocarbon flow had no absolute corresponding relationship, high-quality reservoir just was the necessary condition of hydrocarbon accumulation. It was found that local construction highs had an important control function to hydrocarbon accumulation. So it has a realistic guiding significance to exploration that enhancing the detailed study on carbonate fracture-cave unit. This paper selected Well Block ZG7 with complex oil-water relationship as a case, and comparative analyzed the structural position, structural characteristics, reservoir characteristics and fluid producing status before and after acid fracturing. It indicated that structural position of fracture-cave unit had a crucial control function to the fluid property in it, whose high accumulated hydrocarbon and the low was water commonly. The structure of facture-cave unit had a close relationship with the fluid producing status, which differed from the variation of fracture-cave unit structure. Carbonate reservoir and local construction were the important controlling factors of hydrocarbon accumulation, under the background of high-quality reservoir, local structures and structural highs were the favorable accumulation areas. © (2012) Trans Tech Publications.

Jiao W.,Chongqing Institute of Geology and Mineral Resources | Jiao W.,Chongqing Shale Gas Research Center | Yang H.,Petrochina | Cheng L.,Chongqing Institute of Geology and Mineral Resources | And 3 more authors.
Energy Exploration and Exploitation | Year: 2013

The Northern Slope of the Tazhong area is one of the important areas to increase reserve and production in carbonate reservoirs in the Tarim Basin, west China. But in the complex superimposed basin, multiple-stage charging from multiple-sources, and mixed sources in different proportions have resulted in the complexity of oil-water relationship. Major controlling factors and play models are not clear, which has brought great difficulties to exploration. Therefore, it is necessary to study hydrocarbon generation, migration, accumulation and distribution, and recognize the dynamic process of hydrocarbon accumulation. Our research on geology, petrology and geochemistry of trace elements indicated that controlled by the key elements of cap rock, karsted weathering crust reservoir bed and strike-slip faults, accumulation of hydrocarbons in the lower Ordovician on the Northern Slope of the Tazhong area is characterized by vertical zonation and horizontal section-wise distribution. Transport framework of fault-unconformity-karsted fracture and void was established by our research on the static characteristics of faults, unconformity and karstification. Hydrocarbon migration parameters of V/Ni ratio and physical properties of oil indicated that strike-slip faults developed in the lower Ordovician were important migration pathways in the vertical direction. Hydrocarbons migrated up to the unconformity and then were charged towards both sides of the fault, like letter T. Through the analysis of matching between play elements and reservoir formation, the play model "Letter T charging through strike-slip faults, and multiple-stage reservoiring with earlier oil and later gas" was established. According to the model, the deeper formations under the Yingshan formation could be a new worthy exploration target.

Long P.-Y.,Chongqing Institute of Geology and Mineral Resources | Long P.-Y.,Chongqing Shale Gas Research Center | Zhang J.-C.,China University of Geosciences | Nie H.-K.,Sinopec | And 3 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012

The sample collected from the Yuye-1 well, located in the Pengshui County of Chongqing, helps to understand the pores forming features and favorable conditions for shale gas reservoir of Long-ma-xi formation of lower Silurian system black shale in the high-steep, Southeast Chongqing area. The types of mud shale pore type, identification features, basic parameters and geologic factor of shale gas were studied. The results show that pores are so well developed in the sample collected from the Yuye-1 well, and there are two kinds of main existing pores forms, namely crack and bedrock pores. Cracks include structural fractures (extensional crack, shearing crack and extensional-shearing crack), diagenetic crack (lamellation crack, bedding glide crack, emposieu and diagenetic shrink micro-cracks) and abnormal pressure crack of organic evolution. Basement pores include organic micro-pore, mineral substance pores (residual intergranular pores and intergranular dissolution pores), pores between organic and mineral. There are nine kinds of main existing crack combinations of configuration on Cross-section and section, and these configurations of crack combination match the cracks in the bedrock so as to form an effective network. Geologic factors controlling the formation of pores are complex, mineral composition and maceral are the base to control the formation of pores, tectonism is a key factor in the formation of pores, and sedimentary diagenesis is a control action in the formation of non-structured crack.

Wu G.,Chongqing Institute of Geology and Mineral Resources | Wu G.,Chongqing Shale Gas Research Center | Sang S.,China University of Mining and Technology | Cheng J.,Chongqing Institute of Geology and Mineral Resources | And 5 more authors.
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2013

Against the background of progresses made in the ground exploitation of pressure-relieved methane in the Huainan mining area, we tested poricidal fracture systems of tectonic coals from this mining area by SEM and mercury injection, and discussed poroperm characteristics of tectonic coal beds based on well-testing data of penetrability and permeability of borehole coal seams. A comparative analysis of differences in permeability variations measured in practical exploitation of pressure-relieved methane was performed and it revealed influencing factors of permeability variations of tectonic coals under conditions of pressure-relieved exploitation and control effects of the coal texture difference on coal bed reworking, by doing so, a classification method of tectonic coal beds was introduced. The result indicates that with increasing structural deformation, the scale of exogenously poricidal fractures in coals increases, and correspondingly other parameters including pore volume, median aperture and porosity increase as well. The seepage pore content of coal beds is positively correlated with structural deformation, while seepage properties of real tectonic coal beds are controlled by pressure, coal texture, underground water, etc. Characteristics of tectonic coal beds make development techniques of in-situ CBM infeasible, while some problems encountered in CBM development, such as low permeability, difficulty in pressure transmission and poor effects of fracturing of coal beds, can be solved with techniques of pressure-relieved methane exploitation, The effect of "increasing permeability and fluidity by pressure relief" caused by reworking of coal beds in pressure-relieved methane exploitation is controlled mainly by coal textures, i.e. the stronger the coal deformation, the better the reworking effect. Based on the consistency of the seepage pore content of different coal textures in coal beds with the reworking effect, a mylonitic coal is considered to be a high-quality coal bed for pressure-relieved methane exploitation, a granulated coal comes next, fractured/scaly coals are ecumenic, while a coal with original texture is a poor coal bed for pressure-relieved methane exploitation.

Zhu Y.,Chongqing Institute of Geology and Mineral Resources | Zhu Y.,Chongqing Shale gas Research Center
Applied Mechanics and Materials | Year: 2013

To analyse the potential evaluation of shale gas resources and to know the resources of shale gas in Chongqing northeast, it is very important to research on the methods of shale gas resources potential evaluation in the application of Chongqing northeast. Based on the research of shale gas resources potential evaluation by comparing with the American, and combined with the characteristics of shale gas in Chongqing northeast and the thickness, density, buried depth, TOC, Ro, organic types, conditions of cap rock and reservoir, using abundance analogy method, volume method and Delphi method in this area to forecast preliminarily the shale gas resources in Chongqing northeast. The results show that there are rich in shale gas resources of Chongqing northeast and have broad prospect for exploration. © (2013) Trans Tech Publications, Switzerland.

Li D.,Chongqing Institute of Geology and Mineral Resources | Li D.,Chongqing Shale Gas Research Center | Jiao W.,Chongqing Institute of Geology and Mineral Resources | Jiao W.,Chongqing Shale Gas Research Center | And 6 more authors.
Energy Exploration and Exploitation | Year: 2015

Natural fractures in shale are important for the preservation and exploitation of shale gas. The classification of fracture types and characterization of system parameters would help to better evaluate reservoir properties. An evaluation of the relationship between natural fractures and hydraulic fractures may help to predict the effects of fracturing on reservoir properties and assist fracturing design. This study focuses on fractures in Lower Cambrian marine shale in southeast Chongqing, China. The fracture system is characterized in detail through observations and descriptions of several outcrops, cores, and thin sections. Hydraulic fracturing experiments were conducted using a large-size triaxial simulator, enabling us to discuss the effects of natural fractures on the creation of hydraulic fractures in a reservoir. The shale contains three primary fracture types: structural fractures, digenetic fractures, and abnormal pressure fractures. High-angle shear fractures (75°-90° from bedding) are the dominant type of seepage fractures observed in the study area. Three sets of tectonic fractures were formed during three tectonic movements. East-west fractures formed mainly in the Yanshanian. Hydraulic fracturing experiments indicated that the Lower Cambrian shale had a good level of reconstruction. The interference between natural fractures and hydraulic fractures has resulted in the segmentation. This study maybe have some reference for fracturing parameter design.

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