Developing HP/HT Landing String Technologies
Authors: Dick A.J. , Cassells R. 
Published: October 2008

The Expro Group has been actively involved in the HP/HT market for the past decade, by supporting Drill Stem Test (DST) operations with landing string tooling. Part of the current technological gap in HP/HT subsea developments is the availability of reliable landing string tooling.

An HP/HT landing string design with the features to meet this technology gap is scheduled for product launch in 2004. This paper will capture the innovative aspect of this technology solution which will provide operators with the capability to meet the challenges of HP/HT environments.

Introduction

High Pressure / High Temperature (HP/HT) subsea developments are becoming more visible in the industry. While Amerada Hess's Conger field is the only current HP/HT subsea development, projects such as Statoil's Kristin field and BP's Thunder Horse and Rhum projects are on the horizon. Many operators are watching the results closely before committing to future development activity.

With a growing number of fields rated up to 15,000 Psig (1034 bar) and with temperatures elevating up to 350°F (177°C), there is an escalation of requirements for HP/HT rated subsea equipment. This requirement has been acknowledged by Expro and, using their in-house New Expro Technology (nEXt) process, a solution has been delivered in a methodical way.

This paper describes the development of an HP/HT version of the award winning Enhanced Landing String Assembly (ELSA) through a description of a landing string requirements and it's configuration to cover the materials selection, development and qualification of this new system.

Introduction to Landing Strings

Live conditions introduce a range of issues with well control whereby Governing bodies and industry legislation dictates the requirements that operators must abide by. During drilling phases the Blow Out Preventor (BOP), drilling fluids, casing and drill string provide the operator with the necessary barriers and tooling to perform operations safely and efficiently. During testing and development stages, hydrocarbons are normally allowed to flow to surface to clean-up the well, to test reserves and for production operations. Flow to surface will also provide well data for interpretation. Performing these operations places additional demands on equipment which is not apparent during normal drilling operations. With safety being paramount, additional tooling is required to enable operators to conduct the operation safely and efficiently. Subsea safety systems enable primary and contingency well operations to be performed without detriment to personnel, equipment or the environment. The Expro solution satisfies the requirements of both exploration and production applications.

Operations can be performed from both a fixed or mobile installation, Expro's subsea safety systems offer the ability to adapt to the specifics of the type of installation being used. Performing operations in live wells from a floating vessel presents a number of challenges, particularly with respect to rig motion and well control. As a consequence subsea safety systems are more normally associated with Mobile Drilling Units (MODU's) (Figure 1).