A Novel and Robust Mixing Rule Model Coupled with Neural Network for Rapid Determination of Minimum Miscibility Pressure

Abstract

Miscible gas injection is one of the most effective enhanced oil recovery techniques. Minimum miscibility pressure is one of the most important parameters in the gas injecting process in oil reservoirs. Accurate determination of this parameter is critical for an adequate design of injection equipment and project investment prospects. In this study, 128 samples of experimental data are used based on a slim tube test. Effective parameters on minimum miscibility pressure are investigated to define independent variables. The mixing rules method is coupled with an artificial neural network to present a new model for simulating the slim tube apparatus. A comparison between the results of the proposed model and the other conventional methods indicated that it is more accurate and rapid in predicting minimum miscibility pressure. The new model yields the lowest average absolute relative error equal to 2.21%, and the lowest standard deviation of error equal to 3.03%. The proposed model is applicable for various injected gases, such as light hydrocarbons gases, pure and impure CO₂, nitrogen, and flue gases.

Keywords:

• enhanced oil recovery
• minimum miscibility pressure
• miscible gas injection process
• mixing rule
• recovery factor
• slim tube

ACKNOWLEDGMENT

The authors gratefully acknowledge the R&D Directorate of National Iranian Oil Company for supporting this research by providing the required data.

NOMENCLATURE

Tci	=	critical temperature of component i
Tcm	=	pseudo-critical temperature defined by Eq. (1)
Tcmix_Oil	=	pseudo-critical temperature oil reservoir
Tcmix_Gas	=	pseudo-critical temperature injected gas
TR	=	reservoir temperature
Pci	=	critical pressure of component i
Pcm	=	pseudo-critical pressure defined by Eq. (2)
yi	=	mole fraction of component i
wi	=	Weight fraction of component i
Vci	=	critical volume of component i
Vcm	=	pseudo-critical volume
Zci	=	critical compressibility factor of component i
Zcm	=	pseudo-critical compressibility factor
	=	critical acentric factor of component i
	=	pseudo-critical acentric factor defined by Eq. (3)
R	=	gas constant