油井水力压裂摩阻计算和井口压力预测

FRICTION LOSS CALCULATION AND SURFACE PRESSURE PREDICTION IN OIL WELL HYDRAULIC FRACTURING

对水力压裂过程中射孔孔眼摩阻和管柱沿程摩阻计算方法进行分析。列出射孔孔眼摩阻计算公式并讨论其中的各个影响因素,给出压裂液密度和孔眼流量系数的计算公式,提出新的孔眼直径计算公式。基于大庆油田的施工数据,建议一种修正的降阻比计算公式,能够得到更为准确的管柱沿程摩阻历程曲线。通过有限元软件ABAQUS对大庆油田肇15-平56井2150.0～2160.0m井段分段压裂过程进行数值模拟,模拟得到的井底压力、井口压力曲线与现场施工曲线吻合良好,验证计算模型和管柱沿程摩阻计算公式的正确性。对大庆油田南214-平324井限流压裂过程进行数值模拟,模拟得到的压裂作业曲线和现场施工曲线吻合良好,验证射孔孔眼摩阻计算公式的正确性。

The methods of calculating the pipe string friction and the perforation friction are analyzed. Perforation friction and pipe string friction are analyzed and further the surface pressure is predicted in the process of hydraulic fracturing. The formula of perforation friction is presented and the correlative factors are discussed. The formulae of fracturing fluid density and perforation discharge coefficient are obtained, and the formula of perforation diameter is modified. The formula of drag ratio is modified based on the measured data in Daqing Oilfield, and further more the treatment history of pipe string friction could be obtained by use of drag ratio method. The staged fracturing processes of well interval 2 150.0 - 2 160.0 m of well Zhao 15 - Ping 56 in Daqing Oilfield are simulated by finite element software ABAQUS. The evolution of bottom hole pressure and surface pressure obtained from simulation are in good coincidence with corresponding field measurement data, which verifies the correctness of the simulation model and the proposed formula of pipe string friction. The limited entry fracturing process of well Nan 214 -Ping 324 in Daqing Oilfield is simulated. The stimulation history fits well with field measurement fracturing curves, which validates the correctness of the formula of perforation friction.