Abstract

This study aims to analyze and compare the influence of the diameter selection on the optimal gathering system position. Taking into account different well positions scenarios. Utilizing both manifold and trunk line layouts, this study will rank the results considering the oil production and costs of the subsea arrangement. The optimal position will be calculated through the usage of multiphase flow simulations and a genetic algorithm. The results will show that the relation between the flowline and trunk line diameter is critical for maximizing efficiency, and that the manifold's optimal position is greatly affected by certain changes in flowline diameter.

Introduction

Being able to plan the most efficient subsea layout in deep water environment is one of the most important parts in designing an offshore production system. Aside from a refined study about wellhead and platform positions, the key to maximize revenue is to determine the best way to arrange the subsea equipments such as manifolds and trunk lines, being aware of its installation costs, amount of associated flowline's extent and production capability.

Adequately manipulating the quantity and type of subsea equipments will bring down the overall subsea layout cost as it reduces the number of individual risers and flowlines of each well. By gathering as many wells as possible into one single flowline to the production unit, it is possible not only reduce the cost associated with installed flowline length, but also reduce the total weight load on the platform, as fewer risers will be connected to it. Considering the space on the riser balcony is a limited parameter in the production unit, the reduction of the number of risers attached will also allow for more wells to be connected directly to the production unit.

Both manifold and trunk lines are assets which offer a multitude of ways to interconnect wells in petroleum fields. These gathering systems are an arrangement of piping and/or valves designed to combine, distribute, control and often monitor fluid flow (Bai & Bai, 2010). As shown in (Fig. 1), manifolds converge the production from multiple wells at a unique point, and from there the oil flows along a single flowline to the host production unit (Leffler et al., 2011). Trunk lines, as seen on (Fig. 2), are typically major-long distance line united by headers, gather production into a single flowline from multiple wells at different points of its length until eventually flowing upwards to the host unit. (Sukumar, 2018). These connection points are commonly called headers.

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