Morpeth Subsea Production System
Authors: Lochte Glen E. , Dean Timothy L. , Gray David , Kochenower Chris , Loper Cobie , Tarlton Oran 
Published: October 2008

The Morpeth field is developed using three satellite subsea production wells and one water injection well clustered together in a line with 50 ft well spacing. The cluster of wells produces to a SeaStar mini-TLP located approximately 1500 feet to the North. The satellite wells produce through individual flowlines linked near the trees by pigging loops, reflecting a concern with wax deposition and hydrate prevention and remediation. The subsea wells are controlled through two umbilicals from the SeaStar.

Introduction

Unlike a subsea satellite tieback to an existing surface facility, the Morpeth subsea production system is designed as an integral part of the initial field development influencing both the surface facility and the field layout. The design of the surface facility and hull reflect integrally designed provisions for flowline and umbilical installation. Dedicated space is provided for a coiled tubing unit to be used for removing flowline blockage.

The field layout is designed to accommodate rig anchoring around all flowline, pipeline, and umbilical paths, for initial design and future tie-ins (Fig. 1). The schedules for installation activities and drilling and completion activities are integrated to optimize the time to first oil.

A great deal of emphasis is placed on operability of the system and flow assurance. The system operating procedures were generated early, reviewed and revised periodically during the system design. An operations person was employed as part of the project team early in the project. The operations crews were mobilized as part of the site team during the shore integration of the facilities and all the subsea production procedures were reviewed and critiqued in detail.

The selection of the subsea engineering group within the main field installation contractor extends a philosophy of minimizing the number of interfaces and contracts that the intentionally small BBEI team is required to manage. The installation contractor is responsible for the design of the subsea production system, purchase of the equipment and installation of most of the equipment, with an advisory role in equipment installed from the BBEI-contracted drilling rig.

The Morpeth subsea production system comprises three subsea production trees, one subsea water injection tree, two direct hydraulic control umbilicals with individual wires for instrumentation, three insulated flexible production risers and one water injection riser. The wells are controlled at the surface facility using a PLC driven combination hydraulic power unit and well control panel.

The "fast-track" nature of the project requires decisions on configuration to be made early. Long lead-time components have to be ordered based on non-optimized conservative criteria. Everywhere possible, field proven equipment and installation methods are utilized. No changes in concept and minimal changes or restarts of design effort were required during the project execution.

Design Requirements

Several key design requirements and philosophies are reflected in the design of the Morpeth subsea production system.

Subsea wells.

Utilizing subsea wells allows the SeaStar to be a smaller, more simple design. Flexibility in the project schedule is required so drilling does not have to be completed prior to facility installation. The project economics are aided by shorter time to first oil and by simultaneous drilling and production.