Strategic Infill Drilling Optimization and Sweep Efficiency Enhancement in Mature Carbonate Reservoirs: Quantifying Untapped Recovery Potential Through Integrated Analytics

Abstract Mature waterflooded carbonate reservoirs in complex depositional environments face significant recovery optimization challenges, particularly in fields characterized by laterally extensive high-permeability zones, viscosity contrasts and mobility variations across reservoir and extensive well inventories. This study addresses critical challenges in a representative mature carbonate field through systematic assessment of sweep efficiency limitations and quantification of remaining movable oil reserves. The primary objectives are: (1) to diagnose injector-producer performance interactions and their impact on reservoir sweep patterns; (2) to quantify distribution and accessibility of remaining movable oil at field, block, and zone scales; and (3) to identify high-impact infill drilling locations and optimize injection/production strategies to maximize incremental recovery. The work bridges the gap between static geological understanding and dynamic flow behavior, enabling data-driven development decision-making in mature fields approaching economic limits. The methodology integrates three complementary advanced analytical techniques: (1) dynamic reservoir simulation coupled with streamline analysis to visualize and quantify flow patterns, drainage efficiency, and areal sweep characteristics; (2) rigorous producer-injector interaction assessment through correlation analysis of well production/injection rates, pressure profiles, and performance trends across multi-well patterns; and (3) systematic well trajectory and completion evaluation to identify geometrically-optimized infill drilling locations. The approach employs customized cross-plot analysis to reveal correlations between well placement, reservoir architecture, and hydrocarbon accessibility. Unlike conventional approach, this methodology quantifies remaining movable oil by integrating dynamic flow simulation with spatial distribution analysis, accounting for pressure depletion, fluid contact evolution, and aquifer support. The integrated analytics platform enables targeted identification of development drilling opportunities specifically designed to drain previously inaccessible reserves while optimizing recovery from existing well patterns. Comprehensive analysis across representative field sectors yielded quantitative insights into injector performance classification: high-performance injectors achieved approximately 35% flood efficiency, compared to 21% and 20% for moderate and low-performance categories. Spatial distribution analysis identified substantial remaining movable oil (54%, 27%, and 19% across the three principal development blocks), with primary accumulation in lower reservoir sections beneath high-permeability zones. Critically, the study revealed that conventional vertical wells failed to access approximately 40-50% of movable oil in heterogeneous intervals. Streamline analysis identified four strategically-positioned infill drilling locations projected to recover an additional 8-12 million barrels of oil equivalent (MBOE) through improved reservoir contact and sweep. Optimization recommendations, including targeted injection rate adjustments and selective production rate modifications in high-watercut areas, offer potential reserve recovery gains of 6%-10% of original oil in place (OOIP) without substantial capital expenditure. This work presents a transformative advance in mature field development through deployment of integrated dynamic analytics and strategic infill drilling identification. The innovative approach combines streamline-based sweep visualization with quantitative infill targeting methodology; a combination rarely applied in mature carbonate systems. The study demonstrates that advanced analytics can identify substantial incremental recovery opportunities previously unrecognized through conventional assessment. Key innovations include: (1) a proprietary injector efficiency classification framework enabling objective performance tier assignment; (2) a spatial distribution methodology quantifying accessible versus inaccessible reserves at sub-block resolution; and (3) a well-placement optimization protocol delivering high-confidence infill drilling recommendations with projected IRR and recovery impact calculations. The framework provides operators with immediately implementable strategies for maximizing value from maturing assets through disciplined analytics-driven development. Findings are particularly applicable to similar mature carbonate systems in resource-constrained environments where maximizing recovery per well and optimizing existing infrastructure represent critical value drivers. The study delivers the technical foundation and decision-support framework enabling operators to unlock 5-10% additional recovery from mature portfolios.