煤层气压裂井裂缝参数优化及效果评价

Fracturing parameters' optimization and evaluation of CBM fractured wells

因煤层复杂渗流机理及低孔低渗特征,煤层气均需采取压裂改造措施进行开采。为了正确认识压裂参数对煤层气井产能、采出程度及井网部署的影响规律,从储层应力形变及煤层气解吸、扩散、渗流流固耦合分析出发,建立压裂井气水两相非线性渗流模型,研究裂缝参数、储层非均质性对井距及井网类型优化的影响,并且采用注入压降试井解释对压裂工艺参数进行评价。研究结果表明:煤层流体以非线性渗流为主,物性呈现先下降后上升的特征,存在启动压力梯度的影响;井距优化应考虑裂缝方向、裂缝穿透比、裂缝导流能力等因素的影响;矩形与菱形井网选择要参考储层各向异性系数的临界值;避免注入压降测试中井筒液面的变化及测试段的选择对试井解释结果的影响,提高压裂效果解释评价准确性。研究对煤层气压裂井裂缝、井网参数优化及提高压裂效果评价准确性具有较好的指导意义。

Due to complex seepage mechanism and weak reservoir property, CBM reservoir requires exploitation by hydraulic fracturing.In order to study fracturing parameters＇ influencing laws on productivity,recovery efficiency and well network, this paper establishes one non-linear gas-water seepage model for fractured wells.Stress deformation, fluid-solid interaction, CBM desorption, and diffusion researches are carried out.Injection pressure-drop well test method is taken to evaluate fracturing effects.The result proves that reservoir porosity declines initially and rises later, permeability is non-linearly affected by threshold pressure gradient;well space optimization depends on fracture orientation, fracture penetration ratio, and fracture conductivities; rectangle and rhombus well pattern selection refers to critical ratio of reservoir anisotropy values.Due to dynamic changes of wellbore liquid level injection pressure-drop well test interpretation should be improved further.This study is of great significance to improve fracturing evaluation and parameters＇ optimization.