Research On The Tight Gas Reservoir Characteristics And Dist Ribution Regularities Of Member 3 Of Xujiahe Formation In T He Northeastern Sichuan Basin

Reservoir characters and distribution are the key technology for low-permeability sandstone gas exploration and development.The average value of porosity and permeability are 2.33% and 0.082md of the member 3 of Xujiahe Formation. Well capacity affected by the degree of fracture development.This article using sedimentary geology, sequence stratigraphy, mineralogy and reservoir architecture analyse to research the sedimentary facies and reservoir characters of the member 3 of Xujiahe Formation in the north-east of Sichuan basin. Though well logging analyse to evaluate fracture development degree, and then made a deep study of reservoir control factors and distribution.① The member 3 of Xujiahe gas reservoir belongs to a braided river delta sedimentary system. Based on the combination of core facies, logging facies and seismic fac ies, the analysis of single-well and well-tie facies, and the division of sand groups, the vertica 1 sedimentary evolution and lateral distribution of sedimentary microfacies for each sand grou p were discussed to identify the favorable micro facies belts. Finally, distributary channel and river mouth bar micro facies were confirmed.② The member 3 of Xujiahe gas reservoir is very tightand its belong tolower porosity and permeability reservoir. The main reservoir rock types are calcarenaceous sandstone and glutenite. The main reservoir space of calcarenaceous sandstone is composed of intergranular dissolved pore, dissolved pore and intracrystalline pore,and clay mineral intercrystal pore. The main reservoir space of glutenite is micro fracture. The calcarenaceous sandstone average value of porosity and permeability are 2.6% and 0.0155md, and 1.95% and 0.0621md of glutenite.③ Fracture is the key factor for reservoir effectiveness and gas productivity.The main fracture is tectonic fracture, then the layers fracture. In different areas fracture distribution characteristics is different. The first sand bodies of YL10-YB205 well, third sand bodies of YL12-YB6 well and YL7 well have better thickness and gas-bearing.④ The main controlling factors of reservoir are lithology,high quality reservoir thickness and fracture development degree. The main type of reservoir are middle-coarse calcarenaceous sandstone and glutenite. Reservoir types changes a lot in vertical, when size becomes coarser,pore structure becomes worse. The favorable reservoir developed in favorable reservoir types and fracture development areas.⑤ The tight reservoir could devide into two types by lithology,thickness, physical properties, reservoir space and fracture. The main reservoir type is III. High quality reservoir is II, a few I. The thickness and gas-bearing of Reservoir in the west area is better than the east and middle area. There are four potential areas are first sand bodies of YL10-YB205 well, third sand bodies of YL12-YB6 well and YL7 well.