This report describes the work performed during the second year of the project, "Investigating of Efficiency Improvements during CO 2 Injection in Hydraulically and Naturally Fractured Reservoirs." The objective of this project is to perform unique laboratory experiments with artificial fractured cores (AFCs) and X-ray CT to examine the physical mechanisms of bypassing in HFR and NFR that eventually result in less efficient CO 2 flooding in heterogeneous or fracture-dominated reservoirs. To achieve this objective, in this period we concentrated our effort on modeling the fluid flow in fracture surface, examining the fluid transfer mechanisms and describing the fracture aperture distribution under different overburden pressure using X-ray CT scanner.Modeling Fluid Flow through a Single Fracture using Experimental, Stochastic, and Simulation Approaches In this report, sensitivity of fracture modeling, error involved in the experiments and saturation match of fracture imbibition experiments using X-ray CT Scanner are established. A fracture is usually assumed as a set of smooth parallel plates separated by a constant width. However, the flow characteristics of an actual fracture surface are quite different, affected by tortuosity and the impact of surface roughness. Though several researchers have discussed the effect of friction on flow reduction, their efforts lack corroboration from experimental data and have not converged to form a unified methodology for studying flow on a rough fracture surface. The goal of this research is to examine the effect of surface roughness for flow through fractures and to effectively incorporate them into simulations with the aid of geostatistics. In this study, we have shown an integrated methodology, involving experiments, stochastics and numerical simulations that incorporate the fracture roughness and the friction factor, to describe flow on a rough fracture surface. Laboratory experiments were performed to support the study in quantifying the flow contributions from the matrix and the fracture under varying confining pressures. The results were used to modify the cubic law through reservoir simulations. Observations suggest that the fracture apertures need to be distributed to accurately model the experimental results. The methodology successfully modeled fractured core experiments, which were earlier not possible through parallel plate approach. A gravity drainage experiment using an Xray CT scan of a fractured core has also validated the methodology.
Simulation of Naturally Fractured Reservoirs using Empirical Derived Transfer FunctionThis research utilizes the imbibition experiments and X-Ray Tomography results for modeling fluid flow in naturally fractured reservoirs. Conventional dual porosity simulation requires large number of runs to quantify transfer function parameters for history matching purposes. In this study empirical transfer functions (ETF) are derived from imbibition experiments and this allows reduction in the uncertainty in modeling of transfer of f...