Research Progress and Trend of Bedding-parallel Fractures in Unconventional Sedimentary Reservoirs
[Significance]The widespread development of bedding-parallel fractures(BPFs)in sedimentary reser-voirs is the key to improve the overall rock permeability and promote fluid flow,and it is increasingly important for unconventional hydrocarbon exploration and development.[Progress]Scholars at home and abroad have examined the characteristics of BPFs and their relationship with hydrocarbon migration and accumulation,identification and prediction,formation mechanism,and major controlling factors.The following conclusions have been made:(1)BPFs are characterized by high linear density and high horizontal permeability.The existence of BPFs is one of the basic conditions affecting the large-scale accumulation of hydrocarbons in unconventional sedimentary reservoirs.(2)Seismic inversion,image logging and conventional logging identification,fracture related major controlling fac-tors prediction,geological parameter modeling,and numerical simulation prediction are commonly used to identify and predict fractures;however,there are still limitations in regards to low accuracy,high cost,and immature methods.With the application of scanning electron microscopy,automatic mineral quantitative analysis,nanometer and micron computed tomography(CT)scanning,and digital core technology,the study of BPFs has gradually entered the level of microscopization,visualization,and quantification.(3)The formation of BPFs is the result of complex factors such as sedimentary diagenesis,structure,overpressure and crystallization stress.(4)Sedimentary rock type,bedding type,mineral composition,and total organic carbon(TOC)content are the main internal factors affecting the development of BPFs.The development degree of fault and fold,the distance from fault core and fold axis,the depth of stratum burial,and the intensity of uplift and denudation are the main external factors affecting the development of BPFs.[Conclusions and Prospects]However,there are still lack of comprehensive,systematic and quantitative research on the comprehensive mechanism of BPFs formed by different types of sedimentary rocks and bedding,the establishment of fine identification and quantitative prediction models for different types of BPFs,and the determination of the specific relationship between BPFs and hydrocarbon migration or accumulation.These prob-lems limit the exploration and development of fractured reservoirs to a certain extent,and are also important research directions of BPFs in the future.
bedding-parallel fracturesidentification and predictionformation mechanismmajor controlling factorsmigration and accumulation
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