The Study On Effect Of Gravity Waterflooding For Thick Massive Heavy Oil Reservoir

G 2-4-6 block belongs to thick massive heavy layer oil reservoir. Having been placing on production from 1977, it went though steam stimulation and water flooding. In the process of water flooding, the horizontal and vertical producing effect of water flooding in reservoir is poor becausing of the restriction factors such as high oil/water viscosity ratio, great reservoir heterogeneity, sand and bottom water production.Considerable oil remaining are hold up in the top of oil reservoir and between oil wells. It is difficult to extract the remaining oil by traditional upright well. So it is necessary to change the development mode to deep development and multivariate development.Based on this situation, the block has taken the application of horizontal well development method in the middle and supreme part of the reservoir to increase the production degree. This paper research on the the development modes of horizontal wells injection and straight wells production. To make a scientific and objective evaluation for whether this mode can improve the ultimate recovery rate and the effect factor of enhanced oil recovery. To provide reference technique examples for the deep development and multivariate development of normal heavy oil reservoir in Liaohe oil field.This paper carried out research on similarity criteria of gravity water flooding first of all and indoor physical simulation experiments based on the criteria. The experiments provides the effect of heavy oil viscosity and gravity on the development of the horizontal wells crest water flooding, the application of water/oil front and saturation degree monitoring methods to monitor the saturation field of the moving fluid on the base of the horizontal wells crest water flooding in the thick massive heavy reservoir.Some conclusions are made through analysis and studies as follows:The gravity water flooding similarity criteria are fundamentally same to the similarity criteria based on the horizontal well physical analog, expect the oil/water phase coefficient of comressibillity add to the gravity. Without the consideration of coefficient of comressibillity, the criterias are completely the same.The alternative regulation of water content and the degree of reserve recovery under different viscosity of crude oil shows that as the increasing of viscosity, the water cut raising, the degree of reserve recovery declining and the viscosity greater, the ascending rate of water cut fast, the declining scope of the degree of reserve recovery bigger. The viscosity of crude oil 200cp is a critical value of the development in this heavy block. The results of the laboratory experiment show that it is not ideal for oil field development when the ratio of gravity and the driving force is too great or too small. Under this experimental condition, the optimal is about 3Mpa.The diagrams of comprehensive oil recovery and water content show that the ultimate recovery rate of water flooding is only 38.61% and the water content increases rapidly. The results are mainly because that the horizontal well flooding increases sweep efficiency, but it could not improve the oil displacement efficiency, even if there are still a large number of residual oil in the areas where the injected water swept.