一种三重介质溶洞与溶孔尺寸界线的确定方法

A Method to Determine the Size Limit Between Dissolution Pores and Vugs in Triple Medium

缝洞型碳酸盐岩油藏中单相及多相流动常采用双重介质或三重介质的数学模型进行模拟,这类油藏的储集空间包括溶洞、裂缝和基质3种类型.裂缝系统是流体流动的主要通道,溶洞和基质中的溶孔和微裂缝是流体主要的储集空间.一个值得研究的问题就是如何从渗流力学的角度定义溶洞和溶孔.本文的目的是建议一种溶洞与溶孔尺寸界线的确定方法.这一方法首先设定三重介质的缝洞概念模型;对三重介质单相水平径向流动问题进行研究,采用Laplace变换和数值反演求解,通过压力导数曲线分析三重介质的流动特征;最后根据压力导数曲线上溶洞到裂缝的拟稳态串流期临近消失的临界状态,确定溶孔与溶洞的尺寸界线.

Dual-continuum or triple-continuum models are commonly used as mathematical models for simulating single-phase or muhiphase flow in naturally fractured-vuggy carbonate reservoirs. Three porosity types, rugs, fractures and matrix, are usually present in such reservoirs. The fracture system is primarily responsible for the occurrence of global flow. The dissolution rugs, the dissolution pores and microfractures in matrix provide storage space for fluid. One of the interesting problems is how to define vug and pore in the discipline of flow mechanics. The goal of this study was to propose a method to determine the size limit between dissolution pores and dissolution vugs. First, using a vuggy-fracture-matrix conceptual model for triple medium, a typical single-phase radial flowed into a well with constant production rate was analyzed. The analytical solution was obtained by use of Laplace transform and numerical Laplace invers method. The characteristics of the pressure derivative curve for triple medium were investigated. Finally,the size limit between dissolution pores and vugs could be obtained from the critical state which the vugs-fracture pseudo-steady period approaches disappearing