Study On Tight Sandstone Gas Reservoir Characteristics Of Shuixigou Group In Kekeya Structural Belt Of Tuha Basin

On basis of regional geological data and relevant literature information, this paper is guided by fundamental theories and techniques of sedimentology, reservoir geology, petroleum geology, and supported by core, mud logging, logging data etc. By utilizing the lab analysis and assay data of microscopic thin section, grading analysis, SEM and mercury injection experiment, this paper researched the petrologic characteristics, pore structure characteristics, physical characteristics, diagenesis characteristics of study area reservoir. Combing with depositional microfacies and reservoir essential features, the paper ultimately conducted reservoir classification and favorable zone prediction.The reservoir research shows that the Shuixigou Group is a tight sandstone reservoir. The rock types are mainly lithic sandstone and feldspar lithic sandstone. The reservoir space is mainly secondary pore, with general existed intragranular dissolved pores. The diagenesis and sedimentary facies are the dominant factors to affect the reservoir physical property. The pore structures can be divided into four types: middle pore and middle throat, middle pore and thin throat, micro pore and thin throat, micro pore and micro throat. The diagenesis types of target stratum include compaction(pressolution), replacement, cementation, dissolution, and the reservoir is situated in the late diagenetic stages.Combing with some evaluation methods of tight sandstone gas reservoir, which are supported by conventional logging technology, graphic technology and gas-logging comprehensive analysis technology, this paper established comprehensive assessment criterion of tight sandstone gas reservoir, and confirmed the lower limit of reservoir physical property. The lower limit is the porosity greater than 3% and the permeability granter than 0.05×10-3μm2. On this basis, this paper conducted classification of reservoir. The Badaowan Formation mainly develops II type reservoir, while the Xishanyao Formation and Sangonghe Formation develop both the II and III type reservoir, giving priority to the III type reservoir.