Abstract
Viscoelastic polymer solution shows shear thinning behavior at low shear rates and shear thickening behavior at high shear rates in reservoirs. However, models that ignored shear thickening behavior were commonly employed to interpret transient pressure data derived from tested wells in viscoelastic polymer flooding systems; although, viscoelastic polymer solutions show shear thickening behavior in the near-wellbore region due to high shear rate. To better characterize the oilfield with pressure transient analysis in viscoelastic polymer flooding systems, we developed a numerical model that takes into account both shear thinning behavior and shear thickening behavior. A finite volume method was employed to discretize partially differential flow equations in a hybrid grid system including PEBI mesh and Cartesian grid, and the Newton-Raphson method was used to solve the fully implicit nonlinear system. To illustrate the significance of our model, we compared our model with a model that ignores the shear thickening behavior by graphing their solutions on log-log plots. In the flow regime of near-wellbore damage, the pressure derivative computed by our model is distinctly larger than that computed by the model ignoring shear thickening behavior. Furthermore, the effect of shear thickening behavior on pressure derivative differs from that of near-wellbore damage. We then investigated the influence of shear thickening behavior on pressure derivative with different polymer injection rates, injection rates, and permeabilities. The results can provide a benchmark to better estimate near-wellbore damage in viscoelastic polymer flooding systems. Besides, we demonstrated the applicability and accuracy of our model by interpreting transient pressure data from a field case in an oilfield with viscoelastic polymer flooding treatments.
Highlights
Crude oil plays an important role in contributing to the world’s energy consumption
The duration of the flow regime of the nearwellbore damage keeps constant when considering the effect of the shear thickening behavior
Viscoelastic polymer solutions show shear thickening behavior in the near-wellbore region due to high shear rate, the effect of shear thickening behavior on the pressure transient response was commonly ignored in well test interpretation
Summary
Polymer flooding is widely employed in oilfields as a mature and economic process by increasing sweep efficiency in oil development [1,2,3,4,5]. In the design and adjustment of the polymer flooding process, basic information of an oilfield is the key to success. To expand pressure transient analysis to polymer flooding, we must overcome several challenges. The most important one is that polymer solution shows either or both shear thinning and shear thickening in porous media. Shear thinning behavior is that the viscosity of the viscous polymer solution decreases with the shear rate [21,22,23,24]. Due to the above non-Newtonian nature of the polymer, the well test model used for the water flooding system is no longer suitable for the polymer flooding system
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