Abstract
Optimizing the trajectory of directional wellbores is essential to minimize drilling costs and the impacts of potential drilling problems. It poses multi-objective optimization challenges. Well-design optimization models initially focus on wellbore-length minimization, but ideally also need to consider minimizing the surface torque during drilling and address, among other constraints, collision avoidance with offset wells. A novel trajectory-optimization model is described that computes the separation factor along the wellbore. It employs a genetic optimization algorithm with an objective function that maximizes the minimum separation factor along the entire length of a wellbore. Plausible well trajectories are identified within a feasible solution space defined by user-identified constraints. The simplicity and effectiveness of the proposed model are demonstrated using a case study involving real well data from the Reshadat oil field offshore southern Iran. In the case considered, a proposed well trajectory is identified as unsafe in terms of its minimum separation factor with an offset well and is re-planned with the proposed model to achieve a safer trajectory.
Highlights
The gas and oil drilling industry in recent years has become focused on optimizing its performance from various perspectives, in particular safety, cost, time and more generally achieving the objectives stated in approved drilling plans
Minimizing wellbore length for complex directional well trajectories taking into account a range of constraints including, inclinations, build rates, azimuths, dog-leg severity (DLS) and frictional torque on the drill string has been the focus of several studies (Atashnezhad et al 2014; Mansouri et al 2015; Wood 2016a), some using a range of evolutionary optimizers and metaheuristic algorithms (Wood 2016b; Khosravanian et al 2018)
We further develop an existing wellbore trajectory-optimization model employing a multi-objective genetic algorithm (Mansouri et al 2015) to consider an anti-collision objective
Summary
The gas and oil drilling industry in recent years has become focused on optimizing its performance from various perspectives, in particular safety, cost, time and more generally achieving the objectives stated in approved drilling plans. An issue more regularly impacting the industry is the increase in directional drilling of cluster wells, i.e., multiple wellbores drilled from a single surface site, both on land with pad drilling for the development of unconventional oil and gas resources (Buchanan et al 2013) and offshore from field platforms. In such cases, a major concern is potential collisions between new and existing wellbores. This well is one of 30 wells drilled from the surface site (platform) making the wells in the near surface section quite closely spaced and with a high risk of collision for new well from that surface location
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