首先,针对石油储层水力压裂岩体损伤机制,考虑岩体受载后基质孔隙和微裂缝体积均发生变化,采用基质孔隙和微裂缝体积变化分别定义岩体损伤和裂缝演化的张量型损伤变量,建立水力压裂岩体损伤模型;然后,假设水力压裂过程微裂缝动态演化满足Logistic分岔标准模型,建立基于损伤理论的微裂缝动态演化损伤模型,根据水力压裂能量守恒原理,确定岩体损伤演化过程体积应变和介质孔隙度、损伤变量的内在联系;最后,建立水力压裂岩体基质孔隙和微裂缝渗透张量演化模型。将新方法和传统方法通过模块程序导入有限元软件对吉林油田29-3,4生产井进行产能模拟,计算结果对比表明,基于损伤理论的新模型与实际情况吻合更好。
Firstly,according to the mechanism of rock damage of hydraulic fracturing for oil reservoir,considering the changes of matrix porosity and micro-cracks volumes after loading on rock,the tensor damage variable of rock damage is defined by using the changes of matrix porosity and microfracture volumes,and the rock damage deterioration model of hydraulic fracturing is obtained based on damage theory.Secondly,assuming the dynamic evolution of microfracture of the process of hydraulic fracturing satisfies with the Logistic fork standard model,the microfracture dynamic evolution model is established based on the damage theory and according to energy conservation principle of hydraulic fracturing,the internal relation among the volumetric strain,medium porosity and damage variable of the process of rock damage evolution is determined.Finally,the model of matrix porosity and the evolution of permeability tensor of Microfracture for hydraulic fracturing rock is established.Taking the well named 29-3,4 in Jilin oil field for example,the traditional method and the new one are implemented as modules into finite element software to simulate productivity to verify the advantage of new model.The comparison result shows that the new model is more suitable for practical situation.