深层煤岩气二氧化碳泡沫压裂压后评价方法

Post-fracturing Evaluation Method of the Deep Coal Bed Methane Reservoir Stimulated with CO_(2)/Foam Fracturing Technology

为了评价CO_(2)泡沫压裂对深层煤岩气的适用性及分析深层煤的压裂地质特征,文章以鄂尔多斯盆地深层煤岩气水平井X1井的CO_(2)泡沫压裂作业为例,通过采用压裂停泵压降速率分析、G函数压降曲线分析及压裂注入沿程管路摩阻分析等压力诊断方法,评价了X1井的压裂地质特征、裂缝扩展特征及压裂液类型对压后效果的影响。研究结果表明:鄂尔多斯盆地的深部煤岩具有较好的渗透性;CO_(2)压泡沫压裂工艺能够满足鄂尔多斯盆地深层煤岩气水平井的压裂作业需要,增能助排优势突出,压后增产效果明显;与胍胶压裂液相比,CO_(2)泡沫压裂液改造后的停泵压降速率更快、渗透性更好;通过提高单簇进液强度、提高压裂的裂缝内压力能够改善地层的渗透性。此外,与砂岩相比,煤岩CO_(2)泡沫压后的CO_(2)喷势小、气体浓度低,见到了CO_(2)在地层中被吸附的预期。本研究可为深层煤岩气的压裂工艺优选及压裂参数优化提供经验及建议。

In order to evaluate the applicability of CO_(2)foam fracturing to deep coal bed methane and analyze the fracturing geological characteristics of deep coal,this paper takes the CO_(2)foam fracturing operation of Well X1 in the deep coal bed methane horizontal well in the Ordos Basin as an example,and evaluates the influence of the fracturing geological characteristics,fracture propagation characteristics and fracturing fluid type on the post-fracturing effect of Well X1 by using pressure diagnosis methods such as pump-stopping pressure drop rate analysis,G-function pressure drop curve analysis and friction analysis of the pipeline along the fracturing injection.The results show that:the deep coal bed methane reservoir in the Ordos Basin has good permeability.The CO_(2)foam fracturing process can meet the fracturing needs of deep coal bed methane horizontal wells in in the Ordos Basin,and the advantages of energy enhancement and drainage are prominent,and the effect of post-fracturing stimulation is obvious.Compared with guar gum fracturing fluid,the pump-stopping pressure drop rate is faster and permeability better after the application of CO_(2)foam fracturing fluid.The permeability of the formation can be improved by increasing the single-cluster injection intensity and increasing the pressure in the fracture.In addition,compared with the operation in sandstone reservoir,the CO_(2)flow rate and concentration of CO_(2)are lower after CO_(2)foam fracturing in deep coal bed methane,which confirms the expectation that CO_(2)is adsorbed in formation.This study can provide experience and suggestions for the optimization of fracturing process and fracturing parameters in deep coal and rock gas.