新型分流量解析方程的建立与应用

在确定新型广义水驱特征曲线的基础上,利用反向推理,先将水驱特征曲线反演为含水变化规律,再结合Welge方程,可导出水驱油分流量解析方程。新的分流量方程属超越方程,在特定条件下,可简化为经典油水两相渗流实验结果;若与莱文莱特函数结合,可得到表征两相渗流特征的油水相渗比值关系式。选用4个不同类型油藏的水驱油实验数据进行拟合,新方程拟合程度高,拟合效果好;同时,其对应的含水变化规律,不仅可以描述凸形采出程度与含水率关系,而且也可描述“S”形、凹形等采出程度与含水率的关系。以巴喀油田西山窑组油藏为例,给出了利用生产数据来确定油藏实际水驱油分流量解析方程。

Establishment and Application of a New Analytical Fractional Flow Equation

On the basis of determining the new generalized water flooding characteristic curves, by using reverse reasoning methods, the water flooding characteristic curves can be inverted into the laws of water cut variation, and then combined with the Welge equation, the analytical fractional flow equation when water drives oil can be derived. The new fractional flow equation is a transcendental equation, and under certain conditions, it can be simplified to the results of typical oil-water two-phase seepage experiment. If the new analytical fractional equation is combined with the Levinlet function, the relation of oil-water permeability ratio that characterizes the two-phase seepage characteristics can be obtained. The water-flooding experimental data from 4 different types of reservoirs were used to perform fitting, the results showed that the fitting degree of the new equation was high, and the fitting effects were satisfactory. Furthermore, the laws of water cut variation corresponding to the new equation can not only describe the relationship between convex-shaped recovery degree and water cut, but also can describe the correlation between S-shaped, concave-shaped recovery degree and water cut. Taking the reservoirs in Xishanyao formation of Baka oilfield as an example, the analytical fractional flow equation of actual water displacing oil was given by using production data.