煤层气井水力压裂伴注氮气提高采收率的研究

最大限度地提高CH4气体初始解吸压力是提高其采收率的重要途径之一。针对我国"低压"煤储层的临储压力比小、初始解吸压力低、活性水压裂效果不甚理想的现状,系统分析了水力压裂伴注N2增能压裂提高采收率的机理,结合施工现场情况,设计了水力压裂伴注N2增能压裂煤储层工艺参数。屯留井田水力压裂伴注N2增能压裂与常规活性水压裂的临界解吸压力对比表明:水力压裂伴注N2能提高煤层气井排采初期的临界解吸压力,在其他条件相同的情况下,一定程度上能提高煤层气井的采收率。

Study on Improving Coal-bed Gas Recovery Rate by Hydraulic Fracturing and Nitrogen Injection of Borehole

The maximum increase of the initial desorption pressure of CH4 is one of the important ways for improving its recovery rate.To counter the present states of the lower pressure of the "low-pressure" coal reservoirs,the low initial desorption pressure and the worse hydraulic fracturing effect in our coal mines,systematic analysis was made on the mechanism of improving coal-bed gas recovery rate by hydraulic fracturing with nitrogen injection for energy accumulation,and the technological parameters of the hydraulic fracturing and nitrogen injection for energy accumulation were designed by the combination with the actual site conditions.The contrast of the hydraulic fracturing with nitrogen injection for energy accumulation with the critical desorption pressure of conventional hydraulic fracturing showed that the hydraulic fracturing and nitrogen injection for energy accumulation can improve the critical desorption pressure of the coal-bed gas boreholes at the early extraction stage and the gas extraction rate of the coal-bed gas boreholes to a certain extent under other same conditions.