基于数值法的三维缝洞溶蚀演化主控因素研究

碳酸盐岩储层油气储量丰富，经过长期的地质构造运动形成了复杂的缝洞结构，给油气开采工作带来了一定的难度，针对这一工程问题本文采用自主研发的岩溶演化模拟软件KarstEvolSys为数值模拟工具，研究裂缝密度和降雨补给量对碳酸盐岩岩体溶蚀演化的影响，通过控制嵌入基质体中的裂缝数量和水流补给到系统中的流速来完成模拟。研究发现:当降雨补给量不变时，基质体内嵌入的裂缝条数越多，每一裂缝捕获水流量越少，从而导致裂缝系统开度增加速率减慢，岩体的溶蚀速率变缓；当对同一岩溶系统分别补给不同的降雨量时，由于水流对系统中Ca2+浓度的稀释作用，促进了水岩化学反应，加速了含CO₂的水流对裂缝壁的溶蚀，导致岩体溶蚀速率随着降雨补给量的增加而增加。

Numerical investigation on the main controlling factors of the dissolution evolution of three-dimensional fracture-cavity reservoirs

Carbonate reservoir is rich in oil and gas reserves； however， the complex fracture and cave structure of the carbonate reservoir， forming through a long-term geological structural movement， lead to some difficulties in oil and gas exploitation. For this engineering problem， we use an in-house numerical model-KarstEvolSys to study the effects of fracture density and the magnitude of rainfall on the dissolution of carbonate rocks. Numerical simulations have been performed by controlling the number of fractures embedded in the matrix and the velocity supply to the fracture system. Our results show that the more fractures embedded in the matrix， the less water flow captured by each fracture， which leads to a relatively slow increase of the fracture aperture when the fracture density increases. When the magnitude of rainfall remains constant， the dissolution rate of rock mass becomes slow accordingly. If the same karst system is supplied by different amounts of rainfall， the water would dilute Ca2+ concentration in the system，speeding up the water-rock reaction. Therefore， the increasing rainfall would lead to a higher dissolution rate of the rock mass.