Study On The Evaluation Of Water Flooding Development For Low Permeability Oilfield In Wangyao

This paper take full account of the influence of low permeability reservoirs, such as well pattern type, degree of heterogeneity, artificial fracture, by the methods containing theoretical calculation analysis, core experiment, glass model experiment and numerical simulation, establishing computational method of volumetric sweep efficiency. The original evaluation system of water flooding development effect brings in the volumetric sweep efficiency of low permeability oil reservoirs and forms a set of evaluation method in line with the water flooding development characteristics of low permeability oilfield, which is applied to the developed adjustment of Ansai Wangyao oil field. It obtains the following results:(1) The low permeability core parallel model experiments indicate that the stronger the longitudinal heterogeneity, the smaller the longitudinal water flood sweep efficiency, and when the permeability ratio is larger than 9, the injected water hardly sweeps low permeability layer.(2)The water flooding experiments of visual tabular sand filling model further defines that the sweep efficiency of low permeability reservoir must consider the influencing factors, including well pattern type, degree of heterogeneity, artificial fracture.(3) The results of numerical simulation indicate that the larger the fracture penetrating ratio, the stronger the degree of heterogeneity, the smaller the plane sweep efficiency of water flooding. During middle or high water cut period, the plane sweep efficiency of square inverted nine-spot well pattern is a little larger than rectangle five-spot well pattern’.(4) On the basis of the above three methods, it establishes the computational model of waterflooding volumetric sweep efficiency of low permeability oil reservoir: Ev=EAEz Whereby,(5)The original evaluation system brings in the water flooding volumetric sweep efficiency reflecting the characteristics of low permeability reservoir development, which enriches the evaluation system of low permeability oilfield water flooding development effect, and establishing the evaluation system for the water flooding development of low permeability oilfield by the fuzzy theory.(6) This paper applies the evaluation system for the water flooding development of low permeability oilfield and the fuzzy synthetic evaluation to experimental zone in Wangyao. Before the well pattern adjustment, the comprehensive Evaluating value is in "class Ⅲ", but after the well pattern adjustment, it rises to "class Ⅱ". The results of comprehensive evaluation manifest that the new evaluating method of water flooding development is significance for well pattern adjustment time and the judgment of effect after the well pattern adjustment.