Three Forms of Minimum Flow Pore Throat Radius of Reservoir and Its Determination Method

Abstract

The minimum flow pore throat radius of the reservoir is an important indicator to characterize the seepage capacity of the reservoir pore throat. At present, the type of minimum flow pore radius is single, and there are few quantitative methods to determine it. To this end, through the analysis of the seepage capacity at different scale pores and the experimental method of mercury intrusion, the minimum flow pore throat radius and the determination method of the reservoir under the three seepage states of theoretical seepage, production seepage and filling seepage were studied and an example is applied. The analysis shows that the theoretical minimum flow pore throat radius corresponds to the lower limit of the capillary pore radius, and its size is related to the reservoir pore structure, which can be directly determined according to the mercury intrusion curve. The production minimum flow pore throat radius is the lower limit of the flowing pore radius of the reservoir. Its size is related to the reservoir pore structure and the production pressure difference. It can be determined by combining the mercury intrusion curve and the production pressure difference. The filling minimum flow pore throat radius is the lower limit of the filling pore radius. Its size is related to both the pore structure and the filling dynamics. It can be determined by combining the mercury intrusion curve and the original oil saturation. The above method was used to determine the minimum flow pore throat radius of Chang 63 reservoir in X Oilfield, Ordos Basin: the theoretical minimum flow pore throat radius is 0.015 μm, the production minimum flow pore throat radius is 0.017 μm, and the filling minimum flow pore throat radius is 0.085 μm. This study deepened the understanding of the minimum flow pore throat radius of the reservoir, and clarified the determination method of the minimum flow pore throat radius under different seepage states, which has reference significance for the calibration of the lower limit of the reservoir physical properties and the study of the reservoir utilization status.