校正致密岩心中末端效应及相渗计算误差的计算方法

The Calculating Method for Correcting End Effect and Relative Permeability Calculation Error in Tight Core

室内相渗曲线测试常采用非稳态方法。传统测量方法未考虑末端效应及相渗曲线的计算误差。基于末端效应机理研究,建立了考虑致密砂岩末端效应的数学模型;并分析了末端效应和JBN计算方法对致密砂岩岩心非稳态法相渗测试结果的误差。研究表明:增大驱替压差或提高岩心长度可有效降低末端效应导致的测试误差;但降低幅度存在极限值。同时,仅改变实验条件无法完全消除JBN计算方法导致的测试误差。因此,得到考虑末端效应的致密砂岩岩心非稳态法测定相渗曲线的校正图版,能够保证相渗曲线测试结果的准确性、提高油田生产动态预测的可信度。

The indoor relative permeability curve test often adopts unsteady state method. The traditional measurement method does not consider the end effect and the calculation error of the relative permeability curve. Based on the study of the end effect mechanism, a mathematical model considering the end effect of tight sandstone is established. The error of the end effect and the JBN calculation method for the relative permeability curve test of the tight sandstone core in the unsteady state is analyzed. The research shows that increasing the displacement pressure difference or increasing the core length can effectively reduce the test error caused by the end effect, but there is a limit value for the reduction. At the same time, only changing the experimental conditions can not completely eliminate the test error caused by the JBN calculation method. Therefore, there is a calibration plate for determining the phase permeability curve of a tight sandstone core with unsteady state considering the end effect. It can ensure the accuracy of the relative permeability curve test results and improve the credibility of the oilfield production dynamic prediction.