Study on CO₂ Flooding Effect of Heterogeneous Reservoir Under Different Well Pattern

Abstract

Both Well pattern and reservoir heterogeneity are important factors affecting the effectiveness of CO₂ flooding development, and blind well placement in inhomogeneous reservoirs can seriously limit the efficient development of CO₂ flooding. In this paper, the effects of square and triangular well pattern with different degrees of inhomogeneity on the flowline field and residual oil distribution field are investigated using numerical simulations, and their effects on the drive effectiveness are evaluated comprehensively by sweep efficiency, miscibility degree, production gas oil ratio and recovery degree. The results show that the heterogeneity of the reservoir changes the intensity of the streamline in the process of CO₂ flooding, the presence of the main river channel causes the injected CO₂ in the low-permeability zone to preferentially accumulate and break through to the high-permeability zone, and the oil displacement efficiency in the sweep region of the main river channel decreases compared to that of the homogeneous reservoir. The use of different well patterns for CO₂ drive will result in different sweep characteristics and residual oil distribution. Compared with the diamond-shaped inverted nine-spot well pattern, the straight-line row well pattern is more likely to spread to the center of the area and the surrounding crude oil, and still maintains a high sweep efficiency in heterogeneous reservoirs. Compared with the homogeneous reservoir, the recovery rate of the high-grade poor reservoir increases by 3.1%, while the recovery rate of the diamond-shaped inverted nine-spot well pattern decreases by 11.95%. The recovery rate of the staggered well pattern in the high-grade poor reservoir is 31.58% lower than that of the homogeneous reservoir, and the sweep efficiency was reduced by 26.49% compared to homogeneous reservoirs when the CO₂ injection reached 2.0 HCPV. The research results have certain guiding significance for the deployment of CO₂ flooding well pattern in heterogeneous reservoirs.

Copyright 2023, IFEDC Organizing Committee.

This paper was prepared for presentation at the 2023 International Field Exploration and Development Conference in Wuhan, China, 20–22 September 2023.

This paper was selected for presentation by the IFEDC Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the IFEDC Technical Team and are subject to correction by the author(s). The material does not necessarily reflect any position of the IFEDC Technical Committee its members. Papers presented at the Conference are subject to publication review by Professional Team of IFEDC Technical Committee. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of IFEDC Organizing Committee is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of IFEDC. Contact email: paper@ifedc.org.