Abstract
The mobility profiles of gases used in enhanced oil recovery (EOR) have been thoroughly investigated through the coupling operations of data mining of oilfield data and experimental data analyses. Mobility as an EOR objective function has not been previously applied to characterize potential reservoirs for EOR selection and application, even though it is a robust combinatorial function that benefits from two petrophysical variables, permeability and viscosity. The data mining approach identified mobility as a reliable objective function for reservoir characterisation. The data distribution and clustering results indicate that Gas EOR reservoirs have relatively higher mean mobility than Thermal, Microbial and Chemical EOR reservoirs. The experimental approach investigated EOR gases, CO2, CH4, N2, and Air. A modified Darcy Equation of State for gas flow through porous media was applied to evaluate which gas would competitively attain the oil displacement optimisation criterion for mobility ratio, M ≤ 1. Coupling the data mining with the experimental data results reveals that gas reservoirs can be further categorized by mobility. CH4 (18.16 mD/cp) was observed to have the highest mobility followed by Air (14.60 mD/cp), N2 (13.61 mD/cp), and CO2 (12.96 mD/cp). The gas mobility order significantly corresponds with the mobility distribution of reservoirs that implemented gas EOR processes. It was concluded that CO2 offers relatively lower mobility, therefore, it is the most competitive EOR gas to approach the mobility ratio criterion of unity or less.
Highlights
IntroductionUnderstanding the behaviour of the respective enhanced oil recovery (EOR) gases would enable engineers to effectively compare their EOR suitability and oil recovery prospect in a reservoir of interest
It was observed through data mining that intrinsic mobility Mi was a more robust reservoir factor for characterising enhanced oil recovery (EOR) reservoirs and evaluating EOR applicability and potential
It was discovered from the clusters that reservoirs with relatively high intrinsic mobility (>1650 mD/cp) implemented CH4 (18.16 mD/cp) gas EOR
Summary
Understanding the behaviour of the respective EOR gases would enable engineers to effectively compare their EOR suitability and oil recovery prospect in a reservoir of interest. This study aimed to evaluate and identify the competitiveness of EOR gases in displacing trapped oil. Several authors have statistically applied different petrophysical parameters and properties to characterise EOR reservoirs and evaluate their effect on the application and performances of EOR technologies. Such authors include [20]-[25] Their studies were conducted on a single or two gases basis (usually CH4 or CO2), thereby missing the opportunity for comparing and contrasting the broad spectrum of EOR gases with respect to gas properties, such as viscosity and molecular weight, and reservoir parameters, such as pore size and heterogeneity and mobility. This study aims to tackle the knowledge gap and provide statistical and experimental solutions in EOR gas selection, application and potential
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