Investigation of the efficiency of gas and water injection into an oil reservoir
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stigation of the Efficiency of Gas and Water Injection into an Oil Reservoir A. A. Afanasyeva,* and E. A. Vedeneevaa,** a Moscow
State University, Institute of Mechanics, Moscow, 119991 Russia *e-mail: [email protected] **e-mail: [email protected]
Received March 4, 2020; revised April 9, 2020; accepted April 9, 2020
Abstract—Oil displacement by a miscible fluid in a porous medium, which is related to injection of hydrocarbonic gas into an oil reservoir, is investigated. A compositional model is used to describe flow of multicomponent mixtures through the porous medium. The thermophysical properties of the mixtures are given by the equation of state of the van der Waals type. The reservoir simulation software for compositional modeling of flow through a porous medium is developed within the framework of this model. The efficiencies of oil displacement from the porous medium by methane or water are compared using the above software. It is shown that in the initial stages of injection oil displacement by water is more efficient under a fixed volume flow rate of the injected fluid. However, in the last stages gas injection becomes more efficient for displacement of light hydrocarbon components. Keywords: porous medium, flow through a porous medium, miscible displacement, gas injection, compositional simulation DOI: 10.1134/S0015462820050018
The prediction of petroleum reservoir performance and hydrocarbon recovery represents a complex scientific and technical problem in which it is necessary to take into account both the inhomogeneity of permeable geological reservoirs and the multicomponent composition of fluids and gases which saturate these reservoirs [1–4]. These factors call for the use and improvement of the methods of solving the coupled hydrodynamic and thermodynamic problems which presuppose iterative calculation of vapor-liquid equilibria and thermophysical parameters of multiphase mixtures by employing a multicoefficient equation of state [3]. In this case the model of flow through a porous medium becomes significantly nonlinear. In the generic case the corresponding equations have no exact analytical solutions promoting the development of the numerical simulation methods [5]. Creation of such calculation methods requires application of additional efforts directed to their verification which can be carried out by means of comparison with the solutions of self-similar problems. Taking the multicomponent oil composition into account is of particular importance in oil displacement by gas mixtures, for example, in using the technology of gas injection into reservoirs with the aim to enhance oil recovery [2, 4, 6]. Gas injection (for example, methane or carbon dioxide injection) results in gas dissolution in oil and reduction in the oil viscosity. Similar technology is widely used in many foreign oil deposits [2, 7]. The technology of water flooding of oil reservoirs based on oil displacement by water is more traditional including the domestic oil industry. If the hydrocarbon mixture remains in the s
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