清水压裂自支撑裂缝面闭合残留宽度数值模拟

Numerical simulation on residual width of fractures in wells with clear water fracturing without proppant

清水压裂技术在低渗透油气藏中获得了成功应用。清水压裂技术不需加沙,使压裂形成的裂缝只能依靠其表面的凹凸不平形成自支撑,从而达到导流的目的。因此,裂缝表面的凹凸不平程度将影响清水压裂的效果。以粗糙度表征岩石表面凹凸不平的程度,结合岩石裂缝表面的分形特性,利用二元分形差值函数,构造了不同粗糙度的岩石裂缝表面,利用有限元软件,模拟了不同粗糙度条件下岩石裂缝面闭合残留宽度值。模拟结果表明,裂缝闭合残留宽度与岩石裂缝面的粗糙度有关,粗糙度越大,残留宽度越大。研究结果为确定是否采用清水自支撑压裂技术和实施清水压裂后产能预测提供必要的参考数据。

The clear water fracturing technology has been successfully applied in the low-permeability reservoirs.The surface roughness of cracks made by using the hydraulic fracturing technology under the condition of no proppant and non-added sand can result in the self-supporting channel to achieve conductivity of fluid.The surface roughness of cracks has great effect on the hydraulic fracturing process.The surface asperities were used to characterize the roughness degree of rock surface.The fractured rock surfaces with different asperities were constructed using the binary fractal interpolation function and combining the fractal characteristics of rock crack.The residual width of the fractured rock surfaces with different asperities was simulated using the finite element analysis.The simulation shows that the residual width of the fractured rock surfaces is relative to the surface asperities of rock cracks.The surface asperities of rock cracks increase,and the residual width of rock surfaces will also rise.The results can provide the necessary referent data for adapting the clear water fracturing technology or not,and forecasting production capacity of fractured wells.