缝洞型油藏钻遇溶洞油井的压力曲线特征

在缝洞型油藏实际钻井过程中经常出现钻杆放空、泥浆大量漏失等现象。这类油藏使用常规三重介 质试井方法解释时困难较大，建立溶洞型储层试井解释模型并对这类油藏进行测试资料试井解释具有实 际意义。在双重介质模型基础上，将溶洞简化为一个等势体，内部压力处处相等，溶洞外流体流动满足达 西定律；基于溶洞质量守恒方程，建立了缝洞型油藏试井解释数学模型；采用Laplace 变换和Stehfest 数 值反演算法得到了井底压力解析解；分析了溶洞储能比、溶洞大小、基质窜流系数、裂缝储能比等参数对 井底压力及压力导数双对数曲线的影响。利用建立的钻遇溶洞模型双对数曲线图版对塔中地区某井进行 了解释，并见到了良好效果。该研究结果可以为缝洞型油藏试井解释提供理论指导。

Pressure curve characteristics for wells drilled in cave of fracture-cavity carbonate reservoirs

Drilling stem emptying,massive mud leakage and acidification transformation appeared during the drilling process of fracture-cavity reservoirs,which increased difficulties for reservoir well test interpretation if using triple porosity well test method.It has great actual significance to establish well test interpretation model for wells drilled in cave and carry out well test interpretation of this reservoir.Based on the double porosity model,taking inner cave as an equipotential body whose internal pressure was equal everywhere,making outer fluid flow observe Darcy law,and according to cave mass conservation equation,a new well test interpretation model for wells drilled in cave was presented.Laplace transform and Stehfest reverse method were used to solve the model.The influences of cave storage ratio,size of cave,matrix interporosity flow coefficient and fracture storage ratio on the bottom pressure were analyzed.And the double log curve for wells drilled in cave of fracture-cavity carbonate reservoirs was used to interpret the measured pressure of some well in TZ area.Good results have been obtained,and this research can provide theory guidance for fracture-cavity reservoirs well test interpretation.