A Study Of Intra-layer Longitudinal Force And Residual Oil Distribution In Sandstone Reservoir

At ultra-high water cut stage,large recoverable reserves of the sandstone reservoir are still realizable even though the production rate keeps low.However,some problems that restrict the development effect exist.Therefore,in order to economically and effectively develop the oil field at ultra-high water cut stage,we should clearly understand the intra-layer contradiction and study the residual oil distribution.Aimed at these problems at ultra-high water cut stage,this paper focused on the crossflow and characterized the forces that lead to longitudinal flow and studied the distribution of residual oil.Based on substantial literature investigation and mathematical derivation,we investigated the forces that lead to crossflow and obtained the equations of the forces through characterization.Using practical data from oilfield,we established reservoir numerical simulation model by a commercial software ECLIPSE.After that,the simulation results were put back into the equations so that we could calculate and compare the forces quantificationally.According to that,we analyzed the dominant forces in different rhythmic layers with different wettability and we obtained curves of the influence degree of intra-layer longitudinal forces.Furthermore,two indexes,which are overwater multiple and nonuniformity coefficient respectively,were defined and combined with the analysis of the forces to investigate longitudinal water flooding degree in different rhythmic layers with different wettability.In the process of studying residual oil distribution,we defined another index which is concentration degree of movable residual oil and it turned out that residual oil in four kinds of reservoirs concentrated to varying degree at ultra-high water cut stage.Finally,the orthogonal experiment was designed to screen the main influencing factors of remaining oil enrichment and the prediction models with single and multiple factors were established for the prediction of residual oil reserves.With proper values,the prediction models can be used to preliminarily forecast the residual oil content in rich areas of reservoirs at ultra-high water cut stage,which provides a theoretical basis for the longitudinal tapping of potential.