Effect of Effective Pressure on the Permeability of Rocks Based on Well Testing Results

Evgenii Vasilevich Kozhevnikov,Mikhail Sergeevich Turbakov,Vladimir Valerevich Poplygin,Evgenii Pavlovich Riabokon

doi:10.3390/en14082306

Evgenii Vasilevich Kozhevnikov, Mikhail Sergeevich Turbakov + Show 2 more

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https://doi.org/10.3390/en14082306

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Journal: Energies	Publication Date: Apr 19, 2021
Citations: 12	License type: CC BY 4.0

Affiliation: Perm National Research Polytechnic University

Abstract

During the development of oil and gas fields, the permeability of the reservoirs decreases due to a decrease in reservoir pressure and an increase in effective pressure, as a result of which significant reserves of oil and gas remain in the reservoir. To predict the rate of decrease in oil production rates during field development and to respond quickly, it is necessary to know the law of permeability decrease with an increase in effective pressure. Existing methods for describing the change in the permeability of rocks were analyzed in the paper. Numerical analysis of the results of core studies from previously published papers and the results of field well testing on the examples of the north Perm region oil fields showed that in both cases, regardless of the type of rock and the type of reservoir, the change in permeability can be described by the same equations (exponential and power-law). Obtained equations can be used to predict changes in the permeability of terrigenous reservoirs of the north Perm region oil fields. At the same time, according to the results of well testing, an intensive decrease in permeability is observed with an increase in effective pressure. Analysis of the nature of permeability changes using the Two-Part Hooke’s Model showed that significant irreversible deformations are currently taking place in the formations of the oil fields under consideration. Predicting the change in permeability from effective pressure can allow to optimize the development of oil deposits.

Highlights

Permeability is the ability of a medium to pass a liquid or gas through itself in the presence of a pressure drop
Analysis of the existing methods for determining the change in the rock’s permeability depending on the effective pressure showed that at the early times researchers attempted to describe the changes in permeability by rock’s elastic and structure properties while significant assumptions were made, which eventually led to the use of some empirical coefficients in the equations
Depending on the type of void space—pore or fractured—the change in permeability from the effective pressure can occur in different ways and can be described by different equations

Summary

Introduction

Permeability is the ability of a medium to pass a liquid or gas through itself in the presence of a pressure drop. If the permeability of manufactured materials is mainly due to their characteristics and can be set during manufacture [1], in the case of natural materials, such as rocks, their properties are determined by their composition, and by the condition of their occurrence [2]. Permeable can be both clastic sedimentary deposits and hard rocks in which there are cracks. Numerous studies have established that for all types of rocks, their permeability and porosity decrease as their depth increases [2,5,6,7,8]

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