Facing the water-injection difficulty and low oil recovery in ultra-low permeability reservoirs, single-well water injection-production (SWWIP), which transforms water injection between different wells to between horizontal-well fracture stages, was recently proposed as an innovative water-injection approach for EOR. However, SWWIP under some well patterns could cause even worse production performance in development applications. Therefore, this work conducts an adaptability study of SWWIP under common well patterns and aims to find suitable patterns for carrying out SWWIP. We summarized three kinds of SWWIP modes based on the reported work. An industry-standard reservoir simulator (CMG-IMEX) is used to simulate the production of three modes under five kinds of well patterns, including five-spot, rhombus five-spot, seven-spot, staggered seven-spot and nine-spot patterns. Under the same well pattern, we first compared oil recovery of different SWWIP modes and conventional injection-production mode to find the best/worst modes. Then, based on the best mode, we compared oil recovery of different well patterns to find the optimal pattern. The results show that the average oil recoveries of mode 1,2,3 and the conventional injection-production mode under five kinds of well patterns are 13.9%, 9.7%, 17.9%, and 12.9%, respectively. Mode 3 is optimal to improve oil recovery. It is demonstrated that the oil recoveries of mode 1 under staggered seven-spot and nine-spot patterns and mode 2 under rhombus five-point, seven-spot, staggered seven-spot and nine-spot patterns are generally lower than conventional injection-production mode. Therefore, mode 1 under staggered seven-spot and nine-spot patterns and mode 2 under rhombus five-point, seven-spot, staggered seven-spot and nine-spot patterns are not suitable for development operation. The results also show that the mode 3 under seven-spot pattern can obtain the highest oil recovery with the same water injection.
Keywords EOR, single-well water injection-production (SWWIP), well pattern, ultra-low permeability reservoirs