The Research on the Injection Interval's Reasonable Water Injection Rate for Multi-Layer Sandstone Oilfield at Ultra-High Water Cut Stage

Abstract

KEYWORD: Water injection well; Water injection rate of intervals; Water injection efficiency; Grey correlation; Multiple regression ABSTRACT: The oilfield of Daqing placanticline is a typical multi-layer sandstone oilfield, which water flooding production occupies over 50% of the total yield of Daqing oilfield, and it has made great contribution to oilfield stable production. For the average water cut is more than 94% at present, a finer potential tapping for water flooding is needed. In recent years, there is an increasing in interval subdivision of water injection wells, and the average number of intervals is 5 or more in each well. The determination of the injection interval's water injection rate has becoming a problem in that the difference of reservoir nature between intervals is great and the connectivity degree be- tween injection wells and oil wells around is various. The water cut has not risen, meanwhile, the production has not reduced for 5 years in the fine potential tapping demonstration area of the water flooding oilfields in the placanticline, which has been the model of fine water flooding development effect. The reasonable water injection wells are optimized with the demonstration area as the object of analysis and the effect evaluation of oil and water wells as foundation. The rationality of water in- jection rate of intervals was evaluated based on the water injection efficiency, so as to optimize the reasonable injection interval. The correlation between water injection rate of each interval and the af- fecting factors was studied using grey correlation and cluster analysis. Then a functional relationship between the water injection rate and the main affecting factors was built using multiple regression. So that a method for the quantitative of water injection rate in intervals is provided. It is convenient to choose the parameters and the method has strong practicality. It has important significance for the extension of water injection optimization technology in the demonstration area.