双渗三重介质油藏试井分析

Well test analysis of a dual-permeability triple-medium reservoir

针对基岩、裂缝、溶洞三重介质油藏,在考虑裂缝和溶洞与井筒连通的情况下,给出三重介质试井物理模型的描述,提出双渗三重介质的概念,建立考虑井筒储集效应和表皮效应的双滲三重介质油藏有效井径数学模型。通过拉普拉斯变换和数值反演方法对数学模型进行求解,绘制了双渗三重介质油藏试井典型曲线,分析了窜流系数、储容比、渗透率比对曲线特征的影响。曲线分析表明,完整的双渗三重介质油藏试井曲线在半对数曲线上出现2个台阶,在双对数曲线上出现2个凹陷。曲线上台阶或凹陷的位置和形态与基岩、裂缝和溶洞三者之间的窜流系数和储容比有关。窜流系数主要影响下凹段出现时间的早晚,弹性储容比影响下凹段的深度和宽度。对比分析了双渗三重介质和普通三重介质在试井曲线特征上的区别。

This paper introduces a physical model of reservoir test for triple-medium reservoir of matrix,fractures and cavern with consideration of the connectivity between fractures,cavern and borehole.A mathematical model of apparent wellbore radius is established with consideration of wellbore storage effect and skin effect,and solved by Laplace transform and numerical inversion.The type curves of dual-permeability triple-medium reservoir testing are drawn.The influence of crossflow factor,storativity ratio and permeability ratio on curve characteristics is discussed.The well test curves of dual-porosity triple-medium reservoir show two steps in semi-log plot and two concaves in log-log plot.The locations and shapes of the steps and concaves are related to the storativity ratio and crossflow factor among matrix,fracture and caverns.Crossflow factor mainly affects the time when the concave section appears;and elastic storativity ratio affects the depth and width of the concave section.The difference of well test curves between dual-permeability triple-medium reservoir and general triple-medium reservoir is compared and analyzed.