SUBSTANTIATION OF AN ANALYTICAL MODEL OF RESERVOIR PORE CHANNELS HYDRAULIC TORTUOSITY IN WESTERN SIBERIA BASED ON CAPILLARY RESEARCH DATA

Abstract

Relevance. Hydraulic tortuosity has a significant impact on the filtration parameters of the reservoir. The study and creation of an analytical model of hydraulic tortuosity are important for improving the reliability and accuracy of oil and gas reservoirs' absolute and phase permeability determining. Purpose: improvement of absolute and phase permeability mathematical model based on the capillarimetric studies data for using in development computer stimulation. Facilities: productive strata of individual fields of the Jurassic and Lower Cretaceous age in Western Siberia. Methods: statistical processing of capillarimetric data, analysis, and substantiation of the hydraulic tortuosity mathematical model of reservoir pore channels. Results. In accordance with the electrohydrodynamic analogy, when substantiating the analytical model of hydraulic tortuosity, it is proposed to use electrical tortuosity, which is quite well obtained by geophysicists for the following models of the void space geometry of oil and gas reservoir rocks: 1) a set of different cross sections capillaries, 2) simple dumbbell model, in which the tortuosity is determined by the narrowing and expansion of the pore channels sections, 3) complex dumbbell model, in which not only the cross section, but also the actual length of the pore channels changes. Based on the mathematical models analysis for media with different geometries, it was found that the electrical tortuosity is expressed as an inverse power function of the open porosity coefficient. The authors note that if the electrical tortuosity is determined by the open porosity coefficient, then the hydraulic tortuosity is determined by the part of the porosity along which the fluid moves: for the water of a saturated reservoir, this is the effective porosity, and for the reservoir, it is the dynamic porosity. In the conditions of Western Siberia for any field on a collection of core samples, capillary characteristics are obtained in the laboratory, as well as the porosity and permeability of the reservoir. Further, by complex statistical processing of capillarimetry data and porosity characteristics of the formation, the parameters of the analytical model of tortuosity are determined. The paper shows that the use of the proposed hydraulic tortuosity of pore channels analytical model significantly increases the reliability and accuracy of absolute permeability determining according to capillary measurements.

Keywords

• hydraulic tortuosity
• capillarimetric studies
• absolute permeability
• pore channels
• dumbbell model