通道压裂过程中主裂缝支撑剂铺置影响因素实验研究

Experimental study on influence factors of proppant placement in main fracture of channel fracturing process

由于聚合物易滞留于支撑剂颗粒间的间隙,导致均匀铺砂的常规水力压裂技术对低渗透、超低渗透和页岩气气藏的改造存在局限性。通道水力压裂技术通过非均匀铺砂形成高导流通道,可有效提高油气产量。评价通道压裂技术的效果主要取决于所形成砂堤的通道率大小。利用相似准则,建立可视化通道压裂模拟实验方法,系统研究了压裂液黏度、支撑剂浓度、纤维加量、布孔方式、脉冲时间和施工排量等多因素对通道压裂支撑剂铺置形态和通道率的影响。利用偏最小二乘回归和变量投影重要性分析方法研究了各因素对通道率的影响程度。在实验条件下,研究表明,现场施工排量为4～6m3/min、压裂液黏度为150～250 m Pa·s时,支撑剂浓度越低、纤维加量越大、脉冲时间越短、射孔簇数越多,通道率越高。通过偏最小二乘回归、变量投影重要性分析和皮氏积矩相关系数等方法分析表明,各通道率影响程度依次为:压裂液黏度>射孔方式>脉冲时间>支撑剂浓度>纤维浓度>排量。

The polymer is easily trapped in the gap between the proppant particles,so the conventional hydraulic fracturing technol-ogy of the uniform sand production has limitation for the transformation of the low permeability,ultra-low permeability and shale gas reservoirs.The channel hydraulic fracturing technology can effectively increase the oil and gas production by forming a high diversion channel by non-uniform sand deposition.The effects of channel fracturing technique are mainly determined by the channel size of the formed sand embankment.By the similarity criterion,we established the experimental method of visual simulation system of channel fracturing to systematically analyzed the influence of the fracturing fluid viscosity,proppant concentration,fiber addition,pore arrangement,pulse time and construction displacement on the proppant placement pattern and channel ratio.Then we used the methods of the partial least squares regression and the importance of variable projection to analyze the influence degree of various factors on the channel rate.Under the experimental conditions,it is indicated that when the injecting volume is 4~6 m^3/min and the viscosity of fracturing fluid is 150~250 mPa·s,the concentration of proppant is lower,the concentration of fiber is higher,the pulse time is shorter,the perforation methods is more,and the higher viscosity is better.By means of partial least squares regression,importance analysis of variable projection,and Pearson product-moment correlation coefficient,the influence degree of each channel rate is in a descending order as:viscosity of fracturing fluid>perforation methods>pulse time>concentration of fracturing proppant>concentration of fiber>injecting volume.