A Simulator for Predicting Thermal Recovery Behavior Based on Streamline Method

摘要

The general tendency in simulation technique of thermalrnrecovery processes has been to use the fully implicit finiterndifference method to solve the mass and heat transport. Thernmethod has been proven favorable to handle rapidly changingrnproperties and complex physical mechanisms encountered inrnthe processes. However, this method is limited in the grid sizerndue to restrictions in computational power. In addition, thernmethod could also erroneously predict recovery performance ifrncare is not taken in the choice of numerical scheme. Forrnexample, when the mobility ratio of the displacement isrnunfavorable, calculations often result in exaggerated globalrnsweep and may adversely affect reservoir performancernprediction. Local grid refinement is a natural process to handlernthis situation but requires a great amount of memory and highrncomputational cost. This becomes inefficient when multiplernsimulations are required to assess a wide range of reservoirrndevelopment scenarios.rnAn alternative approach to solve the problem is to use thernstreamline method. Because fluid transport occurs alongrnstreamlines rather than between discrete grid blocks on whichrnthe reservoir pressure field is solved, the problems associatedrnwith the fully implicit finite difference method are minimizedrnand the simulations can run much faster. This is supported byrnthe results presented in this paper. We applied the developedrnthermal streamline simulator to a hot water-flooding process.rnTest simulations were performed in the two-dimensional (2D)rnareal quarter five spot pattern. The heavy oil reservoir isrnassumed to have undergone cold water injection. Water at therninitial conditions is about 45 times more mobile than oil,rnwhich leads to unfavorable displacement. The results ofrnsimulations are compared with those from the fully implicitrnmethod using the 5-point and 9-point finite difference schemes. Although simplified, the simulation demonstrates thernmain features of our simulator.