The Solution And Application Of The Low-permeability Reservoir Percolation Models

The development efficiency of low permeability reservoir is at a low level due to the existence of start-up pressure gradient. Therefore, how to improve water flood sweep efficiency has been the main concerned topic of petroleum workers, and it has been proved that infilling well pattern, shorting producer-injector spacing can greatly enhance oil recovery.This paper is about the technical policies of well spacing in low permeability reservoir with an emphasis on rational spacing between wells, pattern of spacing and the optimization between well spacing and well pattern. Based on the experiment of obtaining start-up pressure gradient parameters, all the expressions of low permeability reservoir motion equation are studied in order to find the most accurate and convenient expression. As a result, nonlinear flow continuity model was selected. According to this, stable and unstable transfusion functions are established and solved. Combined with stable stepwise replacement method and integration method, the rules of pressure distribution and spread were detailed derived. Then using the critical velocity method and the displacement pressure gradient method, the process to obtain technical limit well spacing was presented. Besides, combinations of well pattern and well spacing was analysised and strengths or weaknesses of each combination was also analysised.There are several main conclusions in this paper as follows. Nonlinear flow continuity model can express the concave download curve of the non-Darcy flow curve, and it can express the low-permeability reservoir non-Darcy flow motion equation more accurately. The individual-well producting rate drops with time. It drops faster at the beginning and then drops more slowly. The propagation radius goes slower when using nonlinear flow continuity model than Darcy model, and it goes faster than using non-darcy model. The range of technical limit radius of low permeability reservoir is between 45~150m, so the technical limit well spacing is between 90~300m. When fractured, the cross row well pattern is better than rectangular pattern, and the rectangular pattern is better than the diamond shaped pattern.