Optimization of Waterflood Pattern Geometry and Well Spacing in a Tight/Shale Oil Reservoir

Tight and shale oil reservoirs have become increasingly important in meeting global energy demand due to the decline of conventional hydrocarbon resources. However, their development remains challenging because of ultra-low permeability, rapid production decline, low recovery factors, and complex fluid-flow behavior. This study investigates the optimization of waterflood pattern geometry and well spacing in a tight/shale oil reservoir using numerical reservoir simulation (Rubis Kappa).

A sensitivity analysis was conducted to evaluate the effect of well spacing, injection rate, and bottomhole injection pressure on recovery factor and reservoir pressure behavior. Four spacing configurations of 250 m, 350 m, 450 m, and 550 m were analyzed under injection rates of 4000, 6000, and 8000 bbl/day and injection pressures of 200, 300, and 500 psi. The simulation model was developed using representative tight reservoir properties, including a permeability of 0.02 mD and porosity of 0.08. Five well patterns (1x1, 1x3, 1x4, 1x7, and 1x9) were evaluated.

The results demonstrated that reservoir performance strongly depends on achieving balanced displacement conditions. Larger spacing generally improved sweep efficiency and reduced well interference, while excessively high injection rates accelerated water channeling and early breakthrough. Moderate injection rates produced more stable displacement fronts and improved oil–water contact, leading to higher recovery performance. Higher injection pressures also contributed to maintaining reservoir energy and stabilizing production behavior.

Among the analyzed scenarios, the combination of 550 m well spacing, a 1×4 well pattern, 500 psi injection pressure, and 4000 bbl/day injection rate produced the most favorable overall performance. The study also highlights polymer flooding as a promising enhancement technique for improving mobility control and reducing fracture-driven channeling in tight reservoirs.

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