煤岩二次压裂裂缝扩展影响因素试验研究

Experimental study on influencing factors of propagation mechanism of hydraulic refracture in coalbed

煤岩二次压裂能一定程度提高油气井产能。为研究煤岩二次压裂的裂缝扩展规律,采用真三轴模拟试验系统进行了煤岩二次压裂试验,考虑了地应力、天然割理、施工排量等因素对柿庄南煤岩二次水力裂缝的影响。试验表明:煤岩二次压裂裂缝扩展受到地应力差、天然裂隙和割理的综合影响;当水平主应力差较小时,天然裂隙对裂缝扩展起主导作用,二次压裂中难以形成新的裂缝;当水平应力差较大时,最大水平主应力对裂缝扩展起主导作用,并且裂缝会发生转向;在煤层气生产中适当提高排量能有效提高储层改造体积,增加水力裂缝的复杂性。

Coalbed refracturing can improve the productivity to a certain extent.Through several groups ture tri-axial tests,influences of ground stress,natural cleats or fractures,construction displacement on hydraulic refracture propagation in coal samples deprived from the south of Shizhuang were studied.The results show that geostress difference,natural fracture or cleat have a comprehensive influence on fracture propagation.When the horizontal principal stress difference is small,it's difficult to form new fractures in refracturing because of natural fractures.When the horizontal stress difference is large,the maximum horizontal principal stress plays a dominant role in the crack growth,and the reorientation of hydraulic fractures occurs at the same time.In the production of coal-bed methane,the appropriate increase of displacement can effectively improve the volume of reservoir reconstruction and increase the complexity of hydraulic fractures.