Single-Trip TAML Level-4 Multilateral Junction Reduces Well Costs in Norwegian Sea Subsea Well - Case History
Authors: Denney Dennis 
Published: February 2015

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 123935, ’New Single-Trip, TAML Level-4, Multilateral-Junction Technology Reduces Well Costs in Norwegian Sea Subsea Well - A Case History,’ by Olle Balstad, Statoil, and Mark Glaser, SPE, and Tage Heng, Weatherford, prepared for the 2009 SPE Offshore Europe Oil & Gas Conference & Exhibition, Aberdeen, 8-11 September.

Installation of a single-trip Technology Advancement for Multilaterals (TAML) Level-4 multilateral (ML) junction was completed in a subsea gas-injection well. The well was drilled to support oil production from the Tilje and Ile formations in the Smørbukk Sør field in the Norwegian Sea, approximately 193 km offshore in 300-m water depth. After injecting for 10 years, the well will be converted to a gas producer from the same formations.   

Introduction

The åsgard license is a subsea development incorporating three fields, Smørbukk, Smørbukk Sør, and Midgard. This area of the Norwegian Sea experiences very unpredictable and extreme weather conditions. Winds can change from dead calm to full gale in a period of less than 1 hour, and the accompanying sea conditions present major challenges to both equipment and personnel. Prospect development is well advanced, with only a few slots remaining in the subsea templates for new-well development.

New wells are more cost effective if an ML approach is used that maximizes the number of drainage points in the reservoirs. The Smørbukk Sør field has four templates—three for production wells and one for injection, with only one available slot (R-3). Studies of injection patterns and requirements concluded that additional injection was required into both the Ile and Tilje formations to optimize production patterns. Another complication was that both zones would require sand control. An ML well was planned with the objectives of providing the needed gas injection and subsequent conversion to a gas producer after 10 years. To achieve these goals, a TAML Level-4 ML completion was planned. Injection into the well would be controlled by the use of a newly developed downhole-instrumentation and -control system, and as a result, it was deemed that no subsequent access to the main bore would be required after completion. The decision was made to construct the ML junction with a single-trip hollow-whipstock system that can withstand high temperatures (static downhole temperature anticipated to be 140°C) and can reduce the number of trips into the well in the hostile operating environment prevailing in the area. A single-trip hollow-whipstock design was chosen for installation in the Smørbukk Sør R-3 well.

Drilling and Completion

The drilling and completion of Well R-3 were performed from a semisubmersible rig. The well was drilled and cased without incident.

Main-Bore Completion. A detailed procedure was written to communicate all stages of the completion process clearly including risk analysis, contingencies, comprehensive pretesting of assemblies, and other details to provide a smooth transition between phases, a seamless operation, and clear quality, health, safety, and environmental guidelines. Following a thorough cleanout of the main bore to TD and the running of the requisite logs, the main bore was completed with a 5½-in.-sand-screen section. Because of the required total length of the section, the decision was made to run the sand screen in two sections because the need to reach the correct depth with the top liner hanger was critical.