An integrated model to optimize artificial islands developments in shallow water fields

Artificial Islands are often an effective strategy to develop shallow-water fields. However, their layout and design are affected by numerous drilling and surface facility constraints, such as water depth, number of wells, proximity to shore, and well spacing. When these constraints cannot be honored, conventional offshore wellhead platforms must be installed instead. This paper reviews previous artificial island projects to identify their key constraints, and then proposes a numerical model that accounts for these constraints when determining whether artificial islands or offshore platforms would generate the highest Net Present Value (NPV) configuration. The model uses a combination of discrete and continuous mathematical algorithms to find the optimum development plan in shallow-water fields. Specifically, the model analyses the water depth, drilling and surface facilities of the field to suggest the optimum facility type to drill the wells using a k-means algorithm and Mixed-Integer Linear Programming (MILP). Then, a local optimization routine is used to connect islands to well targets. The model accounts for limitations on well spacing and the well paths to ensure that wells conform to the available drilling-rig capabilities and well-pad design requirements. The overall field configuration is optimized using a stochastic-perturbation method that adjusts the field network to maximize the NPV of the development. The model explores the numerous possible scenarios that exist when planning shallow-water offshore field developments, especially when a high number of wells is required. The coupling of continuous and discrete optimization techniques provides a quick and effective method to analyze these possible scenarios and select an optimal strategy. Results from the model indicate that offshore wellhead platforms are not always favored over artificial islands in offshore field developments, particularly when extended reach wells are present. This is illustrated with a case study that demonstrates each stage in the integrated model starting from the analysis of the reservoir simulation model, through to well planning, and design of the facility network. The study highlights how such integrated analysis can aid in the selection of the highest development NPV plan in shallow-water fields by not only minimizing the cost associated with the development but also reducing the time required to generate the optimum plan.