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Abstract
Surfactant-alternating-gas (SAG) is a favored method of foam injection, which has been proved as an efficient way for enhancing oil recovery. However, foam flow is extremely complicated, and there are still unsolved problems for foam application. One is liquid injectivity. Our previous studies suggest that the injectivity in a SAG process is determined by propagation of several banks near the injection well that are not represented by current foam models. Uniform bank properties were assumed. However, in a companion paper, our experimental results show that the dimensionless propagation velocity and the total mobility of banks during the liquid-injection period depends on superficial velocity. Shearing-thinning behavior is observed. In radial flow, the superficial velocity varies with distance from the well. In this study, we scale-up the experimental results using a radial bank-propagation model. The comparison of liquid injectivity estimated from conventional foam simulators (Peaceman equation) and the bank-propagation model show that the conventional foam models cannot represent the effect of the superficial-velocity-dependent fluid properties during liquid injection in a SAG process. The shear-thinning behavior can lead to much better liquid injectivity than expected, which should be accounted for in a field application of a SAG foam process.
Highlights
Gas injection is one of the most common methods for enhancing oil recovery
We point out the potential errors in estimation of liquid injectivity given by the conventional foam simulator, and the importance of considering the shear-thinning behavior in estimating liquid injectivity in a SAG process
Liquid injectivity is strongly affected by the liquid injection rate due to the shear-thinning behavior during the liquid-injection period
Summary
Gas injection is one of the most common methods for enhancing oil recovery. It can often recover all the oil where it sweeps. VFI vs λtb λtFI λtGD pressure difference across the gas-dissolution bank during liquid injection for linear-flow and radial-flow models, Pa total pressure difference for linear-flow and radial-flow models, Pa pore volumes, dimensionless (based on the total pore volume of a core or a formation) reference volumetric injection rate, m3/s total volumetric flow rate, m3/s radial position, m outer radius for Peaceman equation, m wellbore radius, m surfactant-alternating-gas cross-section area, m2 water saturation, dimensionless total superficial velocity, m/s dimensionless propagation velocity of the gas-dissolution bank at various radial positions, dimensionless dimensionless propagation velocity of the forced-imbibition bank at various radial positions, dimensionless superficial velocity at various positions, m/s total mobility of a bank, m2/Pa s total mobility of the forced-imbibition bank, m2/Pa s total mobility of the gas-dissolution bank, m2/Pa s conventional foam models do not represent the effect of gas injection on the subsequent liquid injectivity They can greatly underestimate the liquid injectivity in a SAG process. Our recent experimental results [21] present that the forced-imbibition bank and gas-dissolution bank during liquid injection following gas show strong shear-thinning behavior The properties of these two banks depend on the liquid superficial velocity. We point out the potential errors in estimation of liquid injectivity given by the conventional foam simulator, and the importance of considering the shear-thinning behavior in estimating liquid injectivity in a SAG process
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