二阶导数法识别压力导数曲线“上翘”的类型

The Identification of the Type of "Upwarping" in the Pressure Derivative Curve by Using Second Pressure Derivative Method

启动压力梯度和断层的存在都会使压力导数曲线发生"上翘",对压力导数曲线"上翘"类型的识别,是正确选择试井解释模型的关键。分别给出了考虑启动压力梯度影响和断层影响的二阶导数计算理论基础,绘制了压力曲线、压力导数曲线以及二阶导数曲线,并对其特征进行了分析。提出了一种对启动压力梯度影响在压力导数曲线上引起的"上翘"和断层影响在压力导数曲线上引起的"上翘"进行识别的方法——二阶导数法。分析结果表明:二阶导数法简单易用,可以对两种不同情况引起的"上翘"进行有效的识别。

The pressure derivative curve will upwarp because of the existence of the threshold pressure gradient and the fault. The identification of the type of ＂upwarping＂ in the pressure derivative curve is crucial to the selection Of the well testing model. The theoretical basis of computing the second pressure derivative curve considering effects of the threshold pressure gradient and the fault was provided respectively. The pressure curve, the pressure derivative curve and the second derivative curve are drawn and their characteristics are analyzed. Then, the meth- od-the second derivative method, which can identify the two types of ＂upwarping＂ due to the threshold pressure gradient and the fault, is provided. The analytical results show that this method is simple and practical, and can identify the two different types of ＂upwarping＂ effectively.