Geosteering is a process used to optimize the positioning of a horizontal wellbore to maximize the reservoir exposure. Each wellbore design can vary greatly in terms of risk and complexity, which can have an impact on the final well performance. This paper proposes a novel methodology to identify an optimal well path, which minimizes the drilling risk and maximizes the productivity of the well based on its placement in the reservoir.

The methodology presented uses a new comprehensive approach to calculate productivity index (PI) for a 3D wellbore. A new drilling risk index (RI) is proposed, which includes torque, drag, and trajectory risk factors. The torque and drag risk factors are normalized with respect to a base case trajectory, which can be selected based on field experience. In the present case, the authors selected a straight horizontal well as the base case. The trajectory risk factor is associated with the well profile energy, which is also normalized with a base case scenario. The final RI is the summation of the three individual risk indices.

Applications of the methodology proposed are evaluated on a synthetic case in which a sensitivity analysis was performed on different possible well trajectories, and each trajectory was evaluated by comparing the proposed drilling risk and well productivity. The optimal trajectory is identified by differentiating the well productivity with RI among the low-risk trajectories to find the profile with maximum productivity. The well productivity is translated to revenue to highlight the commercial implications of the drilling project. The results demonstrate the trajectories with maximum reservoir exposure have a high risk associated, which can be translated into problems when running the completions. Neither the trajectory with the lowest risk nor the best performance is the optimum well trajectory. The authors also found that the dogleg distribution along the trajectory could have a significant impact on the RI and well productivity. The outcomes demonstrate usefulness of the approach in providing the engineer with a well path choice backed with good engineering approach on a real-time basis.

This paper introduces a novel methodology to quantify the production and risk associated with different well trajectories while geosteering. To account for productivity estimation in complex undulated trajectories, a new comprehensive model is proposed. This is the first time both drilling and production parameters are considered in identifying an optimal well trajectory. The approach helps in placing the well in the sweet spot efficiently, which ultimately translates to revenue.

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