关键词: 低渗透储集层, 启动压力梯度, 不稳定渗流, 测量

Abstract: Many experiments justify that there is a threshold pressure gradient (TPG) in low permeability reservoirs.The TPG of a core is usually measured by steady flow method,but the condition is very difficult to be attained,and the period to reach steady states is long.A new transient measurement of TPG is devised to measure the transient pressure of core.The detail procedures are as follow.At initial time the core is saturated by oil or water,and put the core into a sample holder with two pressure transducers at ends;Then make the core in a high pressure condition and shut-in the ends of holder;After the pressure of core is steady,open one end of holder to one certain pressure,in the same time, measure the pressurd of sealed end,until attain to another balance state.In the analysis side,the percolation equation is built with effects of TPG and moving boundary.Used numerical method,the solutions are gotten,and the transient pressure curves are drawn.The TPG is solved by comparison testing pressure curve with theory curves in single-log coordinate system.Finally,two samples applications show that the method is simple,fast and easy to control.

Key words: low permeability reservoir, threshold pressure gradient, transient flow, measurement