Effect of Fractures on Forming Dibei Tight Sandstone Gas Reservoir of Ahe Formation in Yangxia Sag of Tarim Basin
Ahe formation of Jurassic is a large braided river delta deposit in Yangxia sag in Tarim basin. The thick sand bodies of braided river channel occur in shape of longitudinal overlapping and lateral cross connecting,and the low-porosity and low-permeability reservoir is extensively distributed in this area. The field survey,core observation,microscopic identification and imaging logging show that the fractures in the Ahe sandstone are well-developed. Dibei gas reservoir in this sag has the characteristics of a typical fractured tight sandstone gas reservoir. The fracture development has very important controlling effect on such a gas accumulation,including reducing initial charging pressure,forming advantageous charging,shaping network charging channels,improving the efficiency of gas charging,enhancing tight sandstone permeability,increasing gas saturation and pore space as well as enlarging the size of the reserves.