Theory And Application Of Streamline Simulation For Areal Well Patterns

Due to its incomparable advantages of fast computational speed, stablecomputational algorithm and easily visualized simulation results, streamline simulationhas been widely used in oil recovery, such as water flooding, gas flooding as well asthermal flooding. However, nowadays, the streamline simulation for polymer floodingconsidering viscosity variations and adsorption effects has not been well investigated yet.In this paper, we first established the streamline simulation models for both waterflooding and polymer flooding. Then combined with the method of characteristics (MOC),the displacement characteristics of the two flooding methods are analyzed in detail. Inaddition, horizontal well streamline models are also presented and then the performanceof water flooding and polymer flooding in different well patterns are investigated，whichcan be used as a guide for production prediction and flooding type deciding.Streamline updating method is proposed by recalculating pressure filed. The methodcan be accomplished by the following procedures: firstly, the basic equations should bebuilt from material balance equation; secondly, by discretizing pressure equation withfinite difference method, pressure and velocity can be obtained. Then streamlines can betracked using Pollock’s method and the time of flight (TOF) grids is subsequentlydetermined. Meanwhile, parameters are also mapped from the underlying grids to theTOF grids. Thirdly, the one-dimensional (1D) transport equations are solved with TVDscheme and then parameters on the streamlines are mapped back to the underlying grids.Finally, pressure for further streamline tracking can be recalculated. It is recommendedthat the HIHP (horizontal injectors-horizontal producers) should be used for injectivityimprovement in polymer flooding.The streamline simulation model of water flooding is well reproduced, and thesimulation results are validated through the software Eclipse. Furthermore, the influenceof number of streamlines, streamline updating,1D solver and merge factor of TOF gridson streamline simulation is investigated. It is indicated that the assumption of fixedstreamlines is just reasonable for an unfavorable displacement process; however, for a favorable displacement the streamlines should be periodically updated for more accuratesimulation results.By taking into account viscosity variations and adsorption phenomenon, streamlinesimulation model of polymer flooding is proposed. The method of characteristics isemployed to analyze the characteristics of one-dimensional polymer flooding. It issuggested that the streamlines should be updated in polymer flooding. The influence ofpolymer concentration, adsorption effect and slug size on polymer flooding in a Five-Spotwell pattern is investigated and optimal parameters are suggested.The proposed streamline simulation method of water flooding and polymer floodingare extended to study the performance of VIHP (vertical injectors-horizontal producers)well pattern. Compared with the VIVP (vertical injectors-vertical producers) well pattern,the injectivity capacity can be remarkably improved in water flooding; but in contrast,this improvement is not obvious in the further polymer flooding after the water flooding.Finally, a field example is performed to apply the streamline simulation methodsdeveloped in this paper. The eastern district of Beiyi fault block in Daqing oil field is inthe second stage polymer flooding after the first stage polymer flooding. Suggestions forwell pattern adjustments are recommended based on calculating and evaluating of themajor parameters of polymer flooding.