The Feasibility Study Of Equivalent Water Flooding In High Water-cut Reservoir

Because of the complex geological conditions and frequent adjustment measures,most oilfields enter high water-cut late-development stages.The reservation control degree is low,recovery degree is low,distribution of remaining oil is extensive and other issues.Well encryption can improve the effect of the development of oilfields in some degrees.In the long run,how to further control the development costs in the development strategy level,exploring the use of a smaller number of development wells,more reasonable well pattern deployment to achieve "stable liquid,controlling water,adjustable structure" are the key problems which restrict the development of the old oilfields.Paper presents the concept of equivalent water flooding,that is the study of changes in sweep efficiency which does not change the production of pressure gradient.The paper study the theory in three ways,which are Fluid mechanics,laboratory test and simulation technology.The calculation models are based on the similar theory,using indoor physical simulation and computer numerical simulation method to study the relationship of different well forms,different well spacing under different stratigraphic characteristics and the sweep efficiency,and obtained the following findings:(1)The thesis presents the equivalent water-flooding theory,under the condition of stable pressure gradient,analyzing the sweep efficiency.Heterogeneous reservoir five-point method well sweep efficiency calculation model has been obtained according to the flow tube theory,analyzing the influence of different factors on the sweep efficiency,emphasizes the relationship between well spacing and sweep efficiency,indicating that without changing the driving pressure gradient,increasing well spacing,sweep efficiency remained unchanged.Therefore,the equivalent water drive theory is feasible.(2)For vertical wells-horizontal wells jointly developed ways,using the actual data of Shengtuo oilfield,analyzing the effect of the horizontal length,well spacing and row on the sweep efficiency,the calculation method of horizontal well sweep coefficient has been obtained.It is proved that the equivalent water drive theory is feasible.(3)Combining the indoor physical simulation and numerical reservoir simulation technology,study the effect of the different well spacing,different displacement pressure gradient on the heterogeneity plane sweep efficiency.The reservoir of high water-cut equivalent water flooding development is feasible.By analyzing and summarizing the above findings it can be considered equivalent water flooding theory is feasible.But due to the reservoir heterogeneity,this theory used reasonably in well spacing should be based on the geological characteristics of the reservoir,in order to achieve economic efficiency.