Interwell connectivity inversion method of steam flooding: Based on an analytical model and genetic algorithm

Abstract

The steam channeling between wells of steam flooding in heavy oil reservoirs is an important factor impacting the development effect. Interwell connectivity is a key indicator for analyzing and predicting steam channeling. At present, only the correlation between injection and production is used to analyze the interwell connectivity, and the variation characteristics of liquid production and bottom hole temperature are not comprehensively considered to achieve the quantitative prediction of interwell connectivity in steam flooding. In this paper, based on the mass-conservation equation and energy-conservation equation, the analytical-calculation model of liquid production and bottom hole temperature of steam flooding in one injection well and one production well model is established. The ‘interwell connectivity coefficients’ are used as the splitting parameter of injected steam to each production well, and the analytical-calculation model of multiwell injection-production is extended. Taking the minimum mean square deviation of the error between the liquid production and bottom hole temperature as the objective function, the genetic algorithm is used to fit the liquid production and bottom hole temperature, and the ‘interwell connectivity coefficients’ of steam flooding are inverted. The innovation of this method lies in the establishment of analytical models of multiwell injection-production fluid production and bottom hole temperature and the establishment of a variable weight function in the objective function, which improves the accuracy of interwell connectivity inversion of steam flooding. Utilizing reservoir numerical simulation technology, the accuracy of the method is verified by synthetic models of homogeneous and high-permeability channels. The method is applied to the steam flooding reservoir of the Ng5 unit in Zhongerbei, Shengli Oilfield, China. The interwell connectivity of the two steam flooding well groups is inverted, and the results are consistent with the tracer analysis results. The findings of this study can help for better understanding of the geological conditions of the steam flooding reservoirs, and provide guidance for the selection of the next development plan.