World's First TAML Level 5 Multi-lateral Well with Individual Remote Inflow Control of Three Branches on Troll Oil Field

Abstract

The Troll oil field has been drilled and completed with more than 100 geo-steered extended-reach multi-lateral (MLT) subsea wells having two, three or four branches each to maximize reservoir contact. The Troll team has drilled multilateral wells from semi-submersibles for more than 10 years. The wells are equipped with complex intelligent top completion (ITC) systems to optimize production.The oil column of the Troll oil field was initially between 11 and 26m thick, with an overlaying gas cap. The wells are 2-5,000-m-long horizontal multi-lateral branches; many completed with stand-alone sand screens and autonomous inflow control valves (AICD) for the lower completions, with up to 80-90% screen coverage per branch lateral.Production life of MLT wells on Troll is limited by gas break-through and/or high water cut. To increase production life and reservoir meters per well there is a need for flexibility through flow control from the surface.Until recently, the ITC system only allowed for individual control of two-branches by two dedicated inflow control valves (ICVs). For three or more branched wells, the upper-most branch would be individually controlled while flow for the other branches controlled together. If break-through occurs in one of the lower laterals, they would have to be choked/or shut-in together, resulting in lost production and reduced recovery from the other laterals. As a result, there was a need for greater flexibility and inflow control for wells with more than two branches.The operator requested contributions from a supplier for a system based on the existing multi-lateral system, the FlexRite® intelligent completion interface (ICI), which would allow for flow control of all branches. A development project began in 2010, and a new multi-lateral system, multibranch inflow control (MIC), was created in 2011. This system has an increased internal diameter (ID) for installation of the completion string with ICVs and swellable packers through the junction for enhanced well control.In October 2012, the Troll team installed the first multibranch MIC system on the Troll well N-24. This system is believed to be the first TAML Level-5, three-branched well with individual branch control worldwide. With this new and innovative junction and completion system, the operator now has the ability to optimize the oil production from new extended-reach multi-lateral wells.In the future, this innovative multi-lateral solution will enable the operator to increase oil recovery from Troll and other fields, which will help the operator to continue to push the functionality and economic viability of multi-lateral technology worldwide, especially in thin reservoirs.

Multilateral Gravel-Pack Solutions for Single Wellbore Branches

“…The wells are 2-5000m long horizontal multi-lateral branches; many completed with stand-alone sand screens and autonomous inflow control valves (AICD) for the lower completions, with up to 80-90% screen coverage per branch lateral (Prebeau-Menezes et al 2013). The Troll team has drilled multi-lateral wells from semi-submersibles for more than 10 years.…”

“…Therefore, to maximize oil production and to reduce gas break-through for as long as possible there is a need for flexibility and control for flows in Troll MLT wells (Prebeau-Menezes et al 2013). However, during production, even with the geo-steered optimized placement, gas break-through eventually occurs, and reduces the oil production.…”

“…These valves, combined with swellable packers, provide zonal isolation and delay gas break-through within the oil-producing branches (Prebeau-Menezes et al 2013). Stand-alone screens are used to limit sand production.…”