Abstract
In serious vertical heterogeneity reservoir, the injected-water along the high-permeability layer break fastly into the production well, while in low-permeability layer there are many death oil region that the injected-water does not spread. For injected-water did not affect crude oil within a low permeability layer, displacement efficiency significantly reduced [1][2]. Further spread of the injected water to the low permeability regions, improvement of vertical sweep of injected-water, creating equilibrium displacement front can raise oil recovery, prolong water-free production period and reduce volumes of injected-water. In view of this, theoretical study on water flooding characteristic in heterogeneous plane models of sandstone in this article has been done. The main conclusions are as follows: (1) establishes a vertical exchange of oil-water relationship, exchange capacity is related mainly to capillary force, gravity, start-up pressure and flow cross-sectional area. (2) water-bearing saturation gradients makes injected-water flow from high water to low water areas. For water-wet reservoir, the injected-water flows from the higher layer to low-permeability layers, and for oil-wet reservoirs, precisely the opposite. (3) as the density of the injected water was increased, the efficiency of water flooding didn't change obviously in anti-prosodic models of sandstone and ultimate recovery rates was little difference between the two. And with increasing the density of injected water, vertical flowing cross-sectional area and oil displacement efficiency increased all.