Methods for Studying Optimal Fracturing Timing Selection About Large Well Spacing Polymer Flooding in Heterogeneous Reservoirs

Abstract

In this paper, the pattern of 175-m long well-spacing which inject polymer flooding in the second-type reservoir belong to the Sazhong development zone of Changyuan Oilfield is taken as the research object. Entering the middle period of polymer injection, plane contradictions are increasingly intensified. The imbalance of injection and production in local area needs to be adjusted accordingly.Starting with the analysis of reason that cause high pressure in certain direction which polymer breakthrough of the well group. Changes of statistical data before and after the measures are adopted, and comparing the measures data with less effective and the better. Summarize the law, and finding correlation parameters. Making discriminant chart, the displacement pressure differential is introduced as a judging indicator of reasonable timing.As the reason of the polymer features (viscous effect, elastic effect and retention effect), polymer flooding in the heterogeneous reservoirs cause the production parameters are correspondingly lagging gradually. And the shortcomings of large well spacing pattern control degree have aggravated this disadvantage. Consequently, the solution to the imbalance of injection and production in the plane lies in getting the optimal timing of fracturing measures and adjusting the flow direction. Earlier than the time, not only wasting costs, but also reducing the displacement pressure in advance before the oil wall is formed is not conducive to expanding the swept volume. Later than the time, in the direction of well group flooding, the displacement fluid is mostly concentrated in the high-permeability layer due to longitudinal heterogeneity. As a result, based on certain molecular weight concentration conditions, the low-permeability layer is difficult to use, and the contradiction between the layers is intensified.This paper is devoted to finding the source of the problem, and has been able to form a set of methods for studying fracturing timing and well selection standards suitable for polymer flooding with large well spacing in the second-type reservoir. And further consider the characteristics of each stage of injection polymerization, make the applicability throughout the entire injection development process is more meaningful.KeywordsOptimal Fracturing TimeInjection-production imbalanceDisplacement pressure differential