Integrated Reservoir Simulation and Drilling-Complexity Assessment for Well-Trajectory Selection in the Upper Safa Reservoir, Western Desert, Egypt

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Abstract
Well-trajectory optimization is frequently framed as maximizing reservoir contact, although additional contact does not necessarily enlarge the dynamically connected drainage volume. Here, vertical, J-shaped and horizontal trajectories were evaluated at three locations in the Upper Safa reservoir (Middle Jurassic Khatatba Formation), Western Desert, Egypt, using a controlled Petrel–ECLIPSE workflow that combines simulated cumulative reservoir response with relative drilling complexity under a consistent reservoir model realization. For every location, the reservoir realization, target interval, and operating constraints were held constant, and only the well path and completed grid cells were varied. The resulting nine cases were compared using modeled contact length, early productivity index, cumulative oil and gas recovery, and an authorization for expenditure (AFE)-based relative drilling cost index, used as a decision support indicator rather than a full economic evaluation. Within these single realization cases, the trajectory ranking was location-specific: vertical at SE-1X (1.92 MMSTB oil, 8.6 BSCF gas), J-shaped at SW-1X (1.78 MMSTB, 8.2 BSCF) and horizontal at SE-5 (1.55 MMSTB, 8.7 BSCF). The SE-1X and SW-1X selections were supported by implemented well geometries and production test observations, whereas the SE-5 horizontal case remains a simulation-based outcome because it was not field-implemented. The horizontal cases returned the highest early productivity index at every location but the highest cumulative recovery only at SE-5, indicating that geometric exposure alone was not sufficient to predict cumulative recovery. Directional surveys and discrete production tests for the two implemented wells were consistent with the selected simulation cases (oil-rate MAPE 7.0–7.9%; gas-rate MAPE 2.3–4.9%). Overall, cumulative response, interpreted together with reservoir quality and connectivity diagnostics, provided a more informative basis for trajectory optimization than geometric contact length alone.

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