Abstract
In this paper, we present a mathematical model to predict the evolution of rock permeability depending on effective pressure during oil production. The model is based on the use of the results of well testing data from wells operating in the oil fields of the Perm–Solikamsk region in the north of the Volgo Ural oil and gas province. Dependences of the change in flow characteristics in the reservoir on the effective pressure were established. We performed a comparative assessment using permeability and effective pressure data that were normalized to dimensionless forms of k/ko and P/Po. The factors and their influence on the nature of the change in permeability from the reservoir pressure were determined. Depending on the type of rock, its composition, initial permeability, and bedding conditions, we determined the limits of variation of the constants in empirical equations describing the change in the permeability of rocks from the effective pressure. The mathematical model we developed enables the prediction of the change in permeability of rocks during oil production from reservoirs on the basis of reservoir properties such as initial permeability, initial reservoir pressure, average bedding depth, net-to-gross ratio, and initial effective rock pressure.
Highlights
Permeability is an important property of various media [1,2]
One of the main reasons for the change in flow properties of a productive formation, and in particular, permeability, is a change in reservoir pressure, which entails a change in effective rock pressure [4]
The effective pressure is created by the difference between the confining pressure and the pressure of the fluid pumped through the plug
Summary
Permeability is an important property of various media [1,2]. Great attention is given to permeability as a property of a medium by the oil and gas industry since it characterizes how efficiently hydrocarbons are extracted. As a result of such experimental studies, many authors have revealed the nonlinear nature (decrease) of rock permeability depending on the effective pressure. Despite the fact that today laboratory studies on core samples are the main source of data on the nature of change in rock permeability related to effective pressure, the determined experimental dependence only characterizes a certain interval (interlayer) in the payzone and the area in which a well (the origin of core material) is located. The model aimed to generate pressure build-up curves on the basis of the results of the core study that could be adjusted for the existing field data from well tests This approach does not take into account the heterogeneity of the reservoir parameters and can introduce inaccuracies in the result when predicting permeability.
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