Experimental Investigation Of Two-phase Seepage Characteristics And Deliverability Of Carbonate Gas Reservoir

Carbonate gas reservoirs have extensive development potential,and its efficient development could greatly alleviate the shortage of global energy supply.In this study,the impact of pore structure and test conditions on gas-water two-phase relative permeability are investigated by experimental simulation on whole core samples such as CT-Scanning,and relative permeability measurement under different test conditions.Besides,in order to provide scientific instruction and guidance for carbonate gas reservoir development,reservoir physical lower-bound is determined by conducting productivity simulation experiment on pore-type core plugs under high temperature high pressure(HTHP).The conclusions are as follows:(1)For fractured core samples,the fracture is mainly in closed or semi-closed state,and the fluid flow conforms to Darcy’s law under HTHP.The degree of vug development and its connection control the petrophysical properties of pore-and vug-type core samples,threshold pressure gradient occurs in pore-type core samples under single gas-phase flow;(2)Slippage effect could significantly affect the gas relative permeability under ambient condition.Overestimation of gas relative permeability could up to 41.72%-52.34% for four different samples under an assumed core heterogeneity(m=1.2);(3)Relative permeability curve switches to a higher gas saturation when the wettability change from strong water-wet to less water-wet,which is caused by the change of test condition from ambient condition to HTHP.Moreover,relative permeability curves show two contrary curve profiles of gas relative permeability,corresponding to the distinctive micro-pore structure acquired from CT-Scanning;(4)Based on the industrial oil & gas production standard of a single well: 0.5 million cubic meters per day,the plates of physical lower-bound under four different drawdown pressure and reservoir thickness are obtained.The key factors affecting gas well productivity are reservoir physical properties and pressure differential,followed by reservoir thickness.