随钻地层压力测试中的增压效应分析

Research Institute of Drilling and Production Engineering Technology, Chuanqing Drilling Engineering Company, CNPC, Guanghan 618300, China School of Petroleum Engineering, Southwest Petroleum University, Chengdu 610500, China School of Electronic Engineering, University of Electronic Science and Technology, Chengdu 610000, China

当钻开地层后，钻井液渗入地层，使得近井壁的地层压力升高（即增压效应），这时随钻测试获得的地层压力偏离真实值，严重影响钻井优化决策和后期储层评价。基于径向渗流理论和非线性泥饼增长理论，建立井壁增压模型，分析增压效应与井筒环境及地层特征的关系，并开展了随钻地层压力测试地面模拟实验和井下实验。研究表明，地层渗透率、泥饼渗透率、泥饼压实系数对增压效应的影响较大，而泥饼厚度、地层孔隙度对增压效应的影响较小。建立的增压模型可以有效预测地层钻开后短期内近井壁压力分布的增压特征，为开展随钻地层压力测试获得高精度的地层压力值提供技术支持。

After formation is drilled, the drilling fluid filtrates into the formation and forms an additional pressure near the wellbore, called the supercharging. At this time, the formation pressure obtained by test while drilling deviates from the true values, which seriously affects the drilling optimization decision and late reservoir evaluation. Using radial-flow theory and nonlinear mud cake growth theory, this paper establishes supercharging model and analyzes the relationship between the supercharging and wellbore environment and formation characteristics. The groud simulation and underground experiments of formation pressure test while drilling are conducted. Study shows that formation permeability, mud cake permeability and mud cake compaction coefficient affect supercharging greatly; the thickness of mud cake and the porosity affect supercharging weakly. The supercharged model can effectively predict the supercharging characteristics, which can provide for strong technical support for obtaining the high accuracy of formation pressure value.

10.6056/dkyqt201406031