Abstract

When conducting deepwater interventions, control system reliability is critical for safety valve operation. Consequently, the emerging operational demand for Subsea Safety Systems to operate at critical stages whilst on high cost deepwater wells / field developments has necessitated the introduction of increasingly sophisticated control systems whilst retaining simplicity and redundancy for optimal well control. This paper explains the operation of subsea safety systems in deepwater and its field application using smart control solutions, enabling the highest standards in reliability to be attained.

This paper captures the status of a large bore deepwater control system, field trialled in 2003 to provide fast and efficient operation of a landing string during the testing, completion and clean-up of a subsea well. The paper will also provide an update on the client focused enhancements demanded of this technology and how these have been incorporated.

Introduction

Expro Group's subsea safety systems deliver critical well control functions in challenging oilfield production conditions. This technology is based on over 20 years of deepwater well testing experience that has sought to deliver cost-effective, engineered solutions, which meet industry standards and client demands.

These landing string and controls systems have been specifically developed to minimise risk in subsea completion and intervention operations and achieve secure well status in the event of an emergency. Compatible with all horizontal subsea christmas trees (HXT), these systems are qualified for use in water depths of up to 10,000 feet and their success is backed up by a track record of over 500 operations around the world.

To cater for evolving market needs, Expro has developed its range of large bore subsea intervention tools, or landing strings, for well operations with horizontal subsea christmas tree architecture. These tools provide well control functions and disconnection capabilities during well installation, work-over, intervention and well test operations. The landing string is a critical component in the protection and safety of personnel, the well and the rig. The landing string also provides the capability for safe, low-cost well re-entry for future well intervention and workover.

Technology History

Starting with the hydraulically piloted downhole accumulator system or Deep Water Vent Pack (DWVP), a solution that has been in operation for over 10 years, the controls technology has progressed through the addition of an electro-hydraulic interface enabling the field proven system know as Express, to function in water depths of up to 10,000 feet. The original 3" bore version was introduced into the Gulf of Mexico (GOM) during a Drill Stem Test (DST) in 2002 for a major client, with earlier successful applications being run in West Africa. The latest 7" bore variant was first deployed in 2003 and this paper will cover the successes of the initial field operations.

Introduction to Landing Strings

Expro's landing string technology utilises a patented high integrity ball valve system that enables the landing strings to provide reliable 'cut and seal' ability in a single device.

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