低渗气藏溢流关井孔隙压力计算方法探讨

在钻井作业中发生溢流时，一般是通过关井求得地层孔隙压力，从而确定合理的压井钻井液密度，这种传统的方法对高渗透储层是可靠的，然而对于低渗透储层要获得准确的结果需要等待较长的时间，这样会影响压井作业时间。针对低渗透气藏压力恢复特征，应用渗流理论推导了一套适合于低渗气藏在溢流关井求取地层孔隙压力的计算模型，并提出了两种数据处理方法，即回归处理方法和作图法，既可满足计算机分析的需要，又可满足现场技术人员快速分析的需要。为了准确预测地层孔隙压力，建议应用录井仪记录关井数据。

PROBE ON FORMATION PORE PRESSURE CALCULATION UPON WELL SHUT-IN AFTER WELL KICKS OUT OF LOW-PERMEABILITY GAS RESERVOIRS

When well kicks during drilling, it is a common practice to shut in the well, calculate the formation pore pressure , and determine the proper kill fluid density. It works well when the reservoir has high permeability. For low-permeability reservoirs, it will take a long time before the accurate calculation result is obtained, which is not good for well killing. In this paper, based on the pressure buildup in low-permeability gas reservoirs and the filtration theories, a set of calculation models for low-permeability reservoirs to obtain the formation pore pressure at the well shut-in after well kicks are derived, and two data-processing methods are introduced, including regression method and graphical construction. Those models can meet needs of both computer analysis and quick manual analysis at the well site. To accurately predict the formation pore pressure, it is recommended to record the shut-in data using logging tools.