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Compositional modelling of imbibition oil recovery processes in naturally-fractured reservoirs
Abstract
The excessive channeling of injected water in waterflooding a low-permeability, naturally-fractured reservoir causes poor sweep efficiency. Imbibition carbonated waterflood may improve the waterflood oil recovery by enhancing the rate of water imbibition into and expelling the oil from the tight matrix. This study is a part of a multi-disciplinary study$sp{1-5}$ to investigate the potential of imbibition carbonated waterfloods in naturally-fractured reservoirs. This dissertation presents two mathematical models: a semi-analytical dual-porosity model (IMOD) and a three-dimensional, three-phase, compositional, dual-porosity reservoir simulator (COMABS) to describe the imbibition carbonated waterfloods. IMOD uses the iterative procedure to solve the nonlinear integro-differential equation describing imbibition waterflood. The major achievement of IMOD is providing non-linear solutions, oil and water saturation distributions in the fracture and matrix systems, for a range of oil to water viscosity ratios. The computed imbibition oil recoveries match the laboratory imbibition carbonated waterflood performances$sp3$ very well. For a more rigorous treatment of the complex imbibition oil recovery mechanisms, COMABS is developed. COMABS allows partitioning of CO$sb2$ from the injected water phase into the oil phase based upon the CO$sb2$ solubility in each phase. The partitioning of CO$sb2$ decreases oil viscosity and increases oil density, prompting the update of the transmissibilities in the simulator as a function of CO$sb2$ concentration. Two grid systems are used in a cross-sectional, dual-porosity modelling of the laboratory tests.$sp3$ Three and fifteen dual-porosity gridblock systems are used in simulation of laboratory imbibition carbonated waterflood performances. It is assumed that the interaction between carbonated water and chalk core alters the wettability causing the reduction in residual oil saturation. Capillary pressure curves and relative permeability curves are constructed according to the estimated residual oil saturations provided by IMOD. The simulator is capable of matching the laboratory imbibition oil recoveries. The oil recovery enhancement by the carbonation of injected water is analyzed by examining the computed oil saturation, oil viscosity, oil density and CO$sb2$ concentration distributions in fracture and matrix systems. A hypothetical two-dimensional field imbibition carbonated waterflood is used to demonstrate the use of COMABS for field-scale applications.
Description
Vita.Collections
Citation
Shenawi, Shamsuddin H. (1994). Compositional modelling of imbibition oil recovery processes in naturally-fractured reservoirs. Texas A&M University. Texas A&M University. Libraries. Available electronically from https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1552123.
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