强化中途测试,提高对低渗气层的勘探评价能力

IMPROVING DST TECHNOLOGY FOR THE EVALUATION OF TIGHT GAS SANDS DURING EXPLORATORY DRILLING

低渗气层具有两大特点,即细小孔隙的高曲折流道和随压力而变的介质特性(K,φ,(?)g,μ_g 等)。这些特性决定了中途测试工艺设计和分析方法的复杂性。本文从理论和实际现点出发,提出适合于低渗气层的特殊程序,有效地进行中连测试,提高其在勘探阶段的评价功能。这些程序包括:小压差、慢排液,尽量恢复测试层的原始状态;引入线性变换函数,消除与压力相关的某些参数对评价结果的影响。

Low permeability gas reservoir has very different characteristics from conv- entional ones.There are two special features:the highly tortuous flow path in the small pores in the reservoir formation and the dependency of flow parameters (K,μ,φ,c_g etc) of the porous medium on pressure.These will bring a com- plication for designing and analyzing of DST.If traditional methods are used, it would not give effective results.This paper suggests a special program for DST in low permeability gas reservoir both in theory and practice.Certainly, it would improve the formation evaluation at the exploration stage.It includes restoring original formation properties with small pressure difference and slow flow,and introducing linear transformation function,to eliminate some parame- ters with strong dependency on pressure.