低速非达西双渗油藏DST段塞流试井研究

DST slug well test for low velocity non-Darcy flow in dual-permeability reservoirs

根据低速非达西渗流理论,导出了双渗(达西渗流和低速非达西渗流)两层油藏DST测试(中途测试)非自喷井的有效井径数学模型,采用拉氏变换和格林函数方法,得到拉氏空间的解析解,并绘制了新的样板曲线。参数敏感性分析表明,低渗非达西流的启动压力梯度、层间储容比、地层系数比的变化对样板曲线变化的影响比较大,样板曲线的晚期段会出现曲线上翘,这是与达西渗流情况最明显的差别。用该试井模型进行实例分析,可解释出双渗油藏的启动压力梯度、各层渗透率及表皮系数等重要参数。

The mathematical model of effective well radius for non gusher wells in DST slug well test of two layered reservoirs has been educed. Using Laplace transformation and Green Function method, the analytical solution of the model in Laplace space is obtained and new type curves is plotted for well test. The parameter sensitivity indicates that the change of the threshold pressure gradient, the storativity ration between layers and formation capacity ration will greatly influence the type curves. This is the main distinctive difference between Darcy flow and low velocity non-Darcy flow. Some important parameters such as the threshold pressure gradient, permeability and skin of separate layer can be obtained by using this model of DST slug well test analysis.