Waterflooding strategies for Cretaceous carbonate reservoirs with high permeability zones in the Middle East

Abstract

Based on the waterflooding development in carbonate reservoirs in the Middle East, this study analyzes the geological characteristics and waterflooding behaviors/patterns of different types of high permeability zones (HPZs), and proposes rational waterflooding strategies and modes. Four types of HPZs, i.e. sedimentation-dominated, sedimentation-diagenesis coupling, biogenic and composite, are identified in the carbonate reservoirs in the Middle East. Based on their distribution patterns, flow mechanisms, and waterflooding behaviors/patterns, five waterflooding modes are established: (1) the mode with stepwise-infilled areal vertical well pattern, for composite HFZs in patchy distribution; (2) the mode with regular row vertical well pattern for Type I channel “network” HFZs (with dominant water flow pathways at the base), and the mode with irregular differentiated vertical well pattern for Type II channel “network” HFZs (where multi-stage superimposition leads to “layered flooding”), for sedimentation-diagenesis coupling HFZs; (3) the mode with row horizontal wells through bottom injection and top production, for biogenic HFZs characterized by thin, contiguous distribution and rapid advancing of injected water along a 工-shaped path; and (4) the mode with progressive waterflooding through edge water injection via vertical well and oil production via horizontal well, for sedimentation-dominated HFZs characterized by thick, contiguous distribution and flood first in upper anti-rhythmic reservoirs. Development practices demonstrate that the proposed waterlooding modes are efficient in the highly heterogeneous carbonate reservoirs in the Middle East, with balanced employment of reserves in the adjacent reservoirs and enhanced oil recovery.