压裂施工过程中的井底压力计算

Calculation of bottomhole pressure during fracturing

李达 贾建鹏 滕飞启 朱更更 吴明松

中国石油长庆油田公司苏里格气田研究中心，陕西 西安 710018 低渗透油气田勘探开发国家工程实验室，陕西 西安 710018

影响井底压力计算的主要因素是压裂过程中压裂液的流动阻力，包括井筒摩阻和近井摩阻，其中近井摩阻包括射孔孔眼摩阻和近井弯曲摩阻。文中基于工程流体力学、岩石力学等相关理论，利用物质平衡原理，建立井筒摩阻、射孔孔眼摩阻和近井弯曲摩阻的数学模型，并对模型参数及物理意义进行分析和求解。计算结果表明：井筒摩阻可利用理论公式直接计算求取；若孔眼数、孔眼大小和相位等适当，射孔孔眼摩阻对井底压力的影响可忽略不计；近井弯曲摩阻主要通过降排量法和现场方法获得，但降排量法成本较高，采用现场方法可快速获得近井弯曲摩阻。该计算方法对于准确获取井底压力与施工时间的动态关系具有重要意义。

It is significant to obtain bottomhole pressure exactly in gas well development. Main influential factors of bottomhole pressure calculation are flow resistance of fracture fluid during fracturing, including wellbore friction and near wellbore friction. Near wellbore friction contains perforation friction and bending friction. In this paper, wellbore friction, near wellbore friction and bending friction model are developed on the basis of material balance principle and the theories of engineering fluid mechanics and rock mechanics. Model parameter and physical significance are analyzed. Calculated results show that the wellbore friction can be calculated using theorical formula; and that the perforation friction can be ignored if the number, diameter and phase of perforation hole are scientific and reasonable; bending friction can be obtained by discharge reduction testing method and field method, but discharge reduction testing method need high cost pirce and field method is a useful and convenient method in bending fiiction calculation. The method has an improtant sense in getting the dynamic relation between bottomhole pressure and operation time during fracturing.

10.6056/dkyqt201303028