低渗透井注入/压降资料试井解释方法

Well Test Interpretation Method by Injection/Fall off Test Data for Low Permeability Well

低渗透井产液量很低,压力测试和DST测试资料往往不能进行试井分析。为正确评价地层参数,提出注入/压降测试,向低渗地层注入高压水,结合停注后井底压力降落数据进行试井分析。由于注水压力过高,往往出现压破地层现象。根据压裂与渗流理论,建立井筒、裂缝流动方程及地层渗流方程,通过点源积分得到井底压力表达式,并对裂缝闭合后形成的椭圆流进行分析,给出考虑注入时间影响的椭圆流等效时间修正关系式。给出一个注入/压降试井资料解释实例,并与G函数压降分析法解释结果进行比较,结果较为接近。本研究结果也适用于气体注入,但需定义拟压力后再进行试井分析。

As production in low permeability well is very low,pressure test and DST test data could not be used for well test analysis. To correctly evaluate formation parameters,an injection /fall off test was proposed by Xinjiang Oil Corp,which injects high pressure water into low permeability reservoirs and applies pressure drop data after injection for well test analysis. As injection pressure is extremely high,formation breakdowns are always confronted. Based on fracturing and percolation theories,fluid flow equations in both well-bore and fracture,and formation percolation equation are established. Bottom hole pressure is obtained by integration of point source. Also the elliptic flow after fracture closure is discussed and an equivalent elliptic flow time modification equation which considers injection time is obtained. Finally,a field application is presented for an injection /falloff test case,and results are compared with that obtained by using G-function pressure drop analysis method and the results are close. The researching results are also applied to gas injection,but only pseudo pressure need to be defined before well testing analysis.