Abstract:

The fourth member of Xiangxi Group in southern Sichuan is tight packed and low permeable sandstone reservoir.Its porosity is less than 3.95%,its permeability is lower than 0.25×10^-3 μm².Microfractures are the main passages for gas migration.Formation water minerality is high.Further research proves that formation micronites and drilling fluid precipitates resulted from mud percolate and formation water may plug passages and decrease productivity.The tests of velosity sensitivity and alkali sensitivity suggest that the critical velosity of formation water is better to be 1.0 ml/min;the critical pH value of operating fluid is better to be 10.The long term static analysis of reservoir rock and mud percolate shows that none of new substance appeares.