Study On Reservoir Development And Forming Mechanism Of Fractured Shale Reservoirs In Bonan Sub-Sagin

Based on the data of geology, geochemistry and geophysics, this paper analyzes characteristics of fractured shale reservoirs and the development characteristics of the fractured reservoir in Bonan Sub-Sagin, analyzes the control facts of fractured shale reservoir development in-depth; By core calibration logging, the litho-electric identification standards of fracture development have been established, on the basis of these studies, this paper summarizes the hydrocarbon accumulation regularity of fractured shale reservoirs and predicts the fractured shale reservoir development areas in lower Sha3 of Bonan Sub-Sagin.The source rocks are good in lower Sha3 of Bonan Sub-sag, and fractured shale reservoirs are controlled by the development degree of fractured shale reservoir. Based on petrology character of reservoir, muddy reservoir could be classified into four lithologic association patterns: lime-mudstone and marlite association, metamorphic mudstone and igneous roc association, oil shale and oil mudstone interbed association, sandy belt mudstone and mudstone association.On the Base of controlling factors of fracture, the fractures are divided into structural fracture, diagenetic fracture, abnormal pressure fracture and metamorphic contraction fracture by corresponding, and the structural fracture is the most in the research area. Adopting the fault-stratum ratio to predict the structural fractures, the paper compares the parameter value of 12% as the lower limit of structural fractures; using the method of equivalent depth to calculate formation pressure, the paper compares the pressure coefficient of 1.3 as the lower joints of the development of abnormal pressure fractures; The formation below 1500m in Bonan Sub-Sagin is divided into early diagenetic A, B phase and late diagenetic A, B, C phase, and a lot of diagenetic fractures form in late diagenetic A phase; The metamorphic contraction fractures are controled by the faults that regard as the upwelling channels of magma .On the basis of these studies, the hydrocarbon accumulation regularity of fractured shale reservoirs is summarized as follows: The source -reservoir-cap of fractured shale reservoirs rolle into one, reservoir is fracture growth area within source rocks, the cap is the dense mudstone around source rocks. The development level of fractured shale reservoir following Hydrocarbon-generating threshold controls the hydrocarbon enrichment degree. The distribution of reservoirs consistes with abnormal-high pressure area and the single well productivity is positively related to formation pressure. Lime mudstone and marlite association with rich Calcium, siliceous in Luojia gentle slope is most conducived to the formation of fracture and those faults which were active in Dongying period and unactive in accumulation stage are beneficial to the hydrocarbon accumulation.By core calibration logging,analyzing the characteristics of the mudstone fracture in conventional logging data, using cross-plot and principal factor analysis to reconstruct the log curve, fracture identification modes of different lithologic associations are established. Integrating controlling factors of fracture, fracture reservoir has three levels:â… class reservoir,â…¡class reservoir,â…¢class reservoir and this paper predicts fractured shale development areas as follows:â… class reservoir developed in Luojia gentle slope from Luo 42 north to Xinyishen 9 and Luo 151 area;â…¡class reservoir developed in west wing of Luojia nasal shape tectonic belt and the area from Xinyishen 9 to Boshen 4 fault;â…¢class reservoir scattered in other areas.