Method for calculating methane-carbon dioxide-propane mixed gas diffusion coefficient by considering volume expansion of thickened oil

Abstract

The invention relates to a method for calculating a methane, carbon dioxide and propane mixed gas diffusion coefficient by considering volume expansion of thickened oil. The method is based on a Fick law and a mass conservation principle and considers the volume expansion of the thickened oil and change of a gas compression factor in a diffusion process. In combination with a binary interaction coefficient calculation formula provided by the invention, the density of the thickened oil system is calculated, a new mixed gas diffusion coefficient calculation method is established by utilizing an implicit difference method, and the method can accurately calculate parameters such as the gas diffusion coefficient, the system density and the gas phase concentration in the diffusion experiment process. The problem that research on the diffusion coefficient of the mixed gas in the thickened oil is insufficient for a long time is solved, and the defect that expansion of the thickened oil volume and change of a gas compression factor are not considered at the same time in an existing model is overcome. The requirement of a production field worker for simply and conveniently mastering key parameters for researching diffusion of methane, carbon dioxide and propane mixed gas injected into thickened oil is met. The method has great significance in researching the technology for increasing the recovery ratio through thick oil gas injection, the oil-gas mass transfer theory, oil field ground engineering construction and the like, and therefore the method can be widely applied to the field of thick oil gas injection efficient development.

Description

technical field [0001] The invention relates to a method for calculating the diffusion coefficient of methane-carbon dioxide-propane mixed gas considering the volume expansion of heavy oil, and belongs to the technical field of heavy oil reservoir development. Background technique [0002] Under the new energy strategy situation, the enhanced oil recovery technology for heavy oil reservoirs needs to be developed urgently. At present, thermal oil recovery is commonly used for heavy oil recovery. However, for complex oil and gas reservoirs such as thin layers, low permeability, and edge-bottom water, the thermal recovery technology for heavy oil has problems such as large heat loss, low efficiency, and damage to the reservoir. The cost is higher and not environmentally friendly. However, heavy oil gas injection technology can effectively avoid the above problems. Heavy oil gas injection technology can promote the expansion of heavy oil, replenish formation energy, reduce the...

AI Technical Summary

Problems solved by technology

However, the gas diffusion calculation methods established at present often do not consider the volume expansion of heavy oil and the change of gas compressibility factor at the same time.

[0006] ②At present, most of the heavy oil gas injection diffusion experiments use only a single gas, and the research on the diffusion behavior of methane-carbon dioxide-propane mixed gas in heavy oil has not yet been involved.

[0007] ③The heavy oil-methane-carbon dioxide-propane system is an unconventional fluid with excess volume, so the existing formula for calculating the density of the mixture is not applicable to this system, and it is difficult to accurately describe the expansion effect during the gas diffusion process

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