大尺度溶洞压力响应特征

Pressure response characteristics of large size cave

刘洪¹ 王新海² 杨锋¹ 陈岩¹

长江大学油气资源与勘探技术教育部重点实验室，湖北 荆州 434023 中国石油大学石油工程教育部重点实验室，北京 102249

MOE Key Laboratory of Exploration Technologies for Oil and Gas Resources, Yangtze University, Jingzhou 434023, China MOE Key Laboratory for Petroleum Engineering, China University of Petroleum, Beijing 102249, China

缝洞型油藏数值模拟中的重点和难点是溶洞系统处理，现有解释模型不能有效解释、评价含大尺度裂缝洞穴的碳酸盐岩储层。将溶洞视为一个内部处处压力相等的整体，利用溶洞质量守恒原理建立了含大尺度溶洞缝洞型油藏数学模型，使用直接边界元方法计算了溶洞压力响应，求解计算得到了溶洞的大小及离井距离、窜流系数、储能比对溶洞压力响应曲线的影响，为缝洞型油藏数值模拟溶洞处理提供了参考依据。定产量开采时，溶洞压力导数先上升到一个峰值，然后下降到0。双孔介质油藏中裂缝窜流会使得上升段出现一个台阶，窜流系数影响着台阶出现时间和台阶的高低，储能比影响着台阶持续时间。溶洞半径相同情况下，离井距离越小，溶洞压力导数峰值越大。溶洞离井距离相同情况下，溶洞半径越大，压力导数峰值越小。

Cave system disposing is the focus and difficulty in the numerical simulation of fractured-vuggy reservoir. The existing model can not interpret the carbonate reservoir with large size cave. To provide a reference for cave system disposing, cave system is regarded as a whole whose internal pressure is equal everywhere. The mathematical model of fractured-vuggy reservoir is established based on cave system mass conservation. The cave system pressure responses are calculated by direct boundary element method and the influence of the size and distance from well, inter-porosity flow coefficient, storage properties ratio on cave pressure response curves are calculated for solution. Cave pressure derivative increases to a peak value, then decreases to zero when well producing. For dual porosity medium reservoir, fracture cross flow increases a ledge and cross flow factor affects the appearing time and height of ledge and storage factor affects the duration time of ledge. The smaller cave distance from well with same radius is, the  larger peak value of cave pressure derivative is. The bigger cave radius with same distance from well is, the smaller peak value of cave pressure derivative is.

10.6056/dkyqt201201023