Reservoir Characteristics And Favorable Area Prediction Of Xujiahe Formation Of Xujiahe Formation In Fog - Zhongshan - Baimiao Temple Area

The Xujiahe Formation of Wuzhongshan-Baimamiao Region is a typical tight sandstone gas reservoir characterized with low porosity and permeability. It is one of the key researching areas for Sichuan Basin’s hydrocarbon exploration. Studies from this paper show that the3rd Member of Xujiahe Formation (simply as Xu3) has positive oil and gas shows, indicating good exploration prospect. Therefore, it is crucial to have detailed researches on reservoir characterization of the Xujiahe Formation.The paper integrated previous researching results and applied mineral petrology, sedimentology, petroleum geology, geochemistry, reservoir evaluation and other relative methodologies to analyze Xu3’s reservoir petrology, sand body type, sand body distribution, basic reservoir characteristics, pore characteristics, reservoir diagenesis and main controlling factors for reservoir developmentThe paper indicated that the main depositional environment of Xu3is braided river delta plain-delta front. The reservoir lithology is mainly fine-medium, medium lithic sandstone and feldspathic sandstone. The main pore type is intragranular dissolved pores from lithics and feldspar. The high energy sand bodies belt is favourable for development of good quality reservoir at this region. The middle and lower part of distributary channels and upper mouth bar are the inherent conditions for generating good quality reservoir. Strong compaction and carbonates cementation has caused reservoir densification. The secondary dissolution from feldspar and lithic has improved the reservoir quality in a certain degree. The fracture development is poor and has little impact on reservoir physical properties. The quality of reservoir is mainly controlled by sandstone sedimentary composition, micro-sedimentary facies and diagenesis.The paper set up reservoir evaluation criteria by integrating sedimentary composition, sedimentary facies and diagenetic factors. Based on the criteria, the paper classifies the favourable exploration zone into level Ⅰ, Ⅱ and Ⅲ. The Xu31sub-zone from Pingluo4well-Pingluo5well-Pingluo3well zone belongs to level Ⅰ. The Xu32sub-zones from Pingluo3well-Pingluo5well zone and Qiongxi3well-Qiongxi4well-Qiongxi12well zone are also recognized as level Ⅰ.