致密油储层支撑裂缝导流能力预测模型

Prediction Model of Fracture Conductivity in Tight Oil Reservoirs

压裂改造是提高致密油储层初始产量和最终采收率的有效手段,其中裂缝导流能力保持是压裂设计的目标之一。现有支撑裂缝导流能力预测模型由于考虑影响因素不全,理论计算值与实际值存在较大偏差,文章基于Kozeny公式,以弹性力学理论为基础,考虑支撑剂强度、粒径、铺砂浓度、闭合压力、支撑剂嵌入、破碎、支撑剂与裂缝壁面变形综合影响,推导出支撑裂缝导流能力预测数学模型,通过室内实验可以知道,不同类型支撑剂、不同闭合压力下的支撑剂裂缝导流能力相差较大,当闭合压力和铺砂浓度一定时,陶粒和树脂砂的裂缝导流能力远大于石英砂。在铺砂浓度相同条件下,支撑剂的粒径对裂缝导流能力的影响也很大,在闭合压力未达到支撑剂的最大抗压强度时,支撑剂的粒径越大,其裂缝导流能力就越高。利用文章新推出的模型预测实验支撑剂的裂缝导流能力,计算结果表明,预测值与实验值吻合度较高,说明新模型具有良好的实用性。从实验和计算结果可以看出,支撑剂嵌入、破碎、支撑剂与裂缝壁面变形对支撑裂缝导流能力影响较大。仅考虑单一影响并不能完全反映真实情况。文章研究成果为致密油储层在考虑支撑剂嵌入、破碎和变形等情况下的支撑剂强度、粒径、铺砂浓度等优选提供了参考。

Fracturing is an effective means to improve the initial production and ultimate recovery of tight oil reservoir,and the fracture conductivity is one of the goals of fracturing design.Due to the incomplete consideration of influencing factors in the existing prediction model of proppant fracture conductivity,the theoretical calculation value has a large deviation from the actual value.Based on the Kozeny formula and the theory of elasticity,the proppant fracture conductivity is deduced considering the comprehensive influence of proppant strength,particle size,sand concentration,closing pressure,proppant embedding,crushing,proppant and fracture wall deformation.According to the laboratory experiments,the fracture conductivity of different proppant types and different closure pressures is quite different.When the closure pressure and sand concentration are fixed,the fracture conductivity of ceramsite and resin sand is much greater than that of quartz sand.Under the condition of the same sand concentration,the particle size of proppant has a great influence on the fracture conductivity.When the closing pressure does not reach the maximum compressive strength of proppant,the larger the particle size of proppant is,the higher the fracture conductivity.The new model is used to predict the fracture conductivity of the experimental proppant.The calculation results show that the predicted values are in good agreement with the experimental values,indicating that the new model has good practicability.The experimental and calculation results show that proppant embedding,breaking,proppant and fracture wall deformation have great influence on propped fracture conductivity.Considering only a single impact can not fully reflect the real situation.The research results of this paper provide a reference for the optimization of proppant strength,particle size and sand concentration in tight oil reservoir considering proppant embedding,crushing and deformation.