Research on three pore-throat system identification methods based on mercury injection efficiency curve

Conventional mercury injection and constant velocity mercury injection combined curve configuration analysis are used to identify the three types of pore-throat systems of large, medium, and small reservoirs, and it is necessary to carry out conventional mercury injection and constant velocity mercury injection experiments of parallel rock samples, which is difficult to be widely used on a large scale because of the high cost of the experiments and the long period. Therefore, drawing on the idea of the Swanson curve for identifying small and large pore-throat systems, this paper proposes a new method for identifying large, medium, and small reservoir pore-throat systems based on the mercury injection efficiency curve. Firstly, mercury injection curve data is used, and a new mercury injection efficiency curve was constructed to represent the change of seepage capacity in the whole process of mercury injection with mercury injection saturation as the independent variable and mercury injection efficiency (interval mercury saturation/interval mercury injection pressure) as the dependent variable. Then, the systems of the three types of pore throat systems, large, medium, and small, are determined quantitatively based on the morphology variation regularity of the curve and its two seepage mutation points. An example analysis proves the effectiveness and reliability of the proposed method, which provides a new technical means for the quantitative identification of large, medium, small, and three types of pore throat systems in reservoirs.