Characteristics And Developmental Patterns Of Microbolite Reservoir Of Shawbrak Formation In The Tarim Basin

Microbolite is one of the most important fields of oil and gas exploration.In recent years,related research in this field has become more and more popular in the world.The Shawbrak Formation of Lower Cambrian in the Tarim Basin mainly develops microbolite-relevant reservoirs and has good exploration prospects.However,there are still problems such as the unclear types,characteristics and depositional patterns of Microbolites,the main controlling factors and distribution characteristics of reservoirs.This paper will focus on three main aspects: microbial rock types,characteristics and development patterns,main controlling factors of microbial reservoirs,and predicting the Distribution characteristics of high-quality reservoirs,in order to understand the distribution of carbonate oil and gas resources in the study area.It has a point in guiding exploration and finding out the reservoir distribution of Shawbrak Formation.This paper takes Shawbrak outcrop area as the main research object,through the observation and comprehensive description of cores,field outcrops and rock thin sections,the microbiological types and characteristics of Shawbrak Formation are clarified.There are five types of microbiological rocks in the Shawbrak Formation in the study area,namely thrombolite,stromatolite,spongiostromata,oncolite and laminate.Based on the developmental characteristics and growth environments of these five types of microbolite,we found that the sedimentary pattern of the Shawbrak Formation microbolite is a gentle platform environment.The ancient uplift controls the overall distribution of Microbolites and hillocks,and develops internal gentle slope-middle gentle slope-outside gentle slope outward.The diagenetic environment is determined by core slices and geochemical characteristics combined with its geological background,and then the main controlling factors of reservoir development are analyzed.It is found that the microbial dolomite reservoir is mainly controlled by the microbial type and the high frequency sequence interface.The microbial mat dolomite reservoir is mainly controlled by the microbial type and the buried dissolution.Through the drilling profiles,outcrop profiles,sedimentary facies and sequence interface effects on the reservoir to comprehensively predict the distribution of high-quality reservoirs.It was found that the outcrop area of the Shawbrak Formation was mainly dominated by microbolite,and mainly developed microbial dolomitic reservoirs,gradually transited to the algal sand beach as the dominant phase,the beach body gets thicker,and also the reservoir thickness.In general,the characteristics of “east thicker west thinner” appear horizontally,and the characteristics of “better in the middle and superior,worse in the inferior” are presented in the vertical direction.