Development of Differentiated Injection-Production Patterns and Precision Waterflood Management for Carbonate Stacked Reservoirs: A Case Study from the Mishrif Formation

Abstract

This study addresses key challenges in carbonate stacked reservoirs, including severe interlayer conflict, rapid water cut rise, and low recovery efficiency resulting from commingled injection-production. It proposes differentiated injection-production patterns and precision waterflood management technologies, with the Mishrif Formation in Iraq’s B Oilfield as a case study. Based on strong reservoir heterogeneity, characterized by a thick MB21 layer (74.8 m) with high permeability contrast and a thin MC11 layer (17.9 m) with two stable interlayers, differentiated strategies were designed. For the thick MB21 layer, a “bottom-injection top-production” pattern was applied, injecting water into low-permeability sub-layers VII-VIII and producing oil from high-permeability sub-layers I-II. This approach reduced the waterflood front variation coefficient to 0.59, effectively delaying water channeling in high-permeability zones. For the thin, interlayered MC11 layer, full-zone perforation and same-layer injection-production were implemented. Precision waterflood management involved the use of intelligent zonal injection for separate control of MB21 and MC11 layers, which significantly increased fluid intake in mid-to low-permeability zones. Areal management through well-group dynamic analysis helped optimize flow fields, injection-production parameters, and well patterns, achieving balanced pressure distribution. Field application demonstrates that the proposed approach effectively resolves interlayer conflict by aligning with inherent reservoir characteristics. The integrated technical framework of “pattern construction, intelligent control, dynamic optimization” offers a transferable solution for the efficient development of highly heterogeneous carbonate stacked reservoirs.