Approach Optimizes Presalt Geohazard Assessment and Well-Trajectory Planning

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 36174, “Presalt Geohazard Assessment and Well-Trajectory Multiobjective Optimization,” by Ana Carolina Abreu, Pontifical Catholic University of Rio de Janeiro, and Marco Antonio Cardoso, and Daniel Ullman de Brito, Petrobras, et al. The paper has not been peer-reviewed. Copyright 2025 Offshore Technology Conference. _ The complete paper aims to optimize well trajectories in offshore reservoir development by applying a Pareto-based multiobjective approach. The methodology seeks to minimize key factors influencing well performance and cost, including the number of drilling phases, well length, geomechanical problems, and geohazards. Extending geohazard assessment beyond the main reservoir into the overburden section ensures safer and more-efficient well planning, crucial for maximizing recovery and net present value (NPV). Introduction A major source of uncertainty in presalt drilling stems from the interaction between complex geological features and geomechanical instabilities within the overburden. The high capital expenditures and extended planning timelines involved in offshore developments make optimization a critical component of field success. The industry increasingly has adopted multiobjective optimization techniques, especially evolutionary algorithms. Most existing approaches treat well placement and trajectory design as disconnected problems, failing to integrate subsurface risk assessment, overburden complexity, infrastructure constraints, and trajectory geometry into a unified framework. This issue is particularly critical in congested or high-risk environments such as Brazil’s presalt fields, where an apparently optimal well placement may become infeasible because of geohazards or proximity to existing subsea infrastructure. A clear need exists for an integrated approach that addresses placement and trajectory decisions simultaneously, guided by geological, operational, and risk-informed constraints. To address this challenge, this study proposes a unified, Pareto-based multiobjective optimization framework that integrates well trajectory and placement planning in offshore fields. The approach combines use of NSGA-II (nondominated sorting genetic algorithm) with geohazard maps derived from interpreted 3D seismic volumes, infrastructure constraints, and geomechanical models. Geohazard-Assessment and Well-Trajectory Multiobjective Optimization Geohazards-Based Evaluation. The first step of the proposed approach is an integrated methodology for optimizing drainage networks in offshore oil fields by explicitly incorporating geomechanical risk conditions (geohazards) at the early stages of planning. The objective is to ensure that the proposed well locations not only maximize economic indicators such as NPV, but also meet technical criteria for drillability and operational safety, thereby reducing rework caused by postoptimization rejections. Methodological innovation in this stage lies in the incorporation of a penalization function by geohazards-based evaluation into well-placement-optimization algorithms, which automatically generate multiple well-drainage plans and assess their technical and economic performance. The key indicator considered at this step is not only the NPV, but also penalization of well placements that present increased geohazards or geomechanical risk.