Subsea Satellite Wells Development And Practical Operational Experience In The North Sea
Authors: Wilson Roy 
Published: October 2008

In the Northern sector of the North Sea, subsea satellite wells are providing a significant contribution to the producing ability of the Beryl ‘A’ platform. This paper traces the development of a specific type of subsea satellite completion system. The installations described are located in 400 ft. of water. Development of equipment and procedures during experimental and further phases highlighted evolution stages and illustrated design and procedural errors which have been overcome by modification of ideas and techniques. The experiences and knowledge accumulated during these learning processes, therefore, are the main ingredients of this paper and are intended to provide foundations considered to be the most suitable for this particular application. Also reviewed are reliability of electro-hydraulic control systems, maintenance, mechanical integrity, monitoring ability and ease of installation.

The paper examines the application of principles in the North Sea as they exist and elaborates upon the potential of these systems to extend the scope of satellite subsea wells to a complex capable of satisfying production development of an entire field.

The performance of the wells now producing in the Beryl field establishes the subsea completion concept as an extremely viable proposition with a definite growth potential.

INTRODUCTION

Recent years have seen an ever-increasing involvement in subsea well installations. Mobil North Sea have been heavily involved in relatively sophisticated satellite completions which have provided valuable experience in a field which is still in its infancy.

The first subsea wellhead was ordered in 1974 to be installed on the Beryl field discovery well 9/13-1. SEAL (Subsea Equipment Associated Limited) were commissioned to provide a modified intermediate system (SIS) which was the first commercial application of equipment under development since 1970. The SEAL system was considered a viable proposition both as a test bed for the subsea wellhead techniques and as a means of achieving accelerated production to the Beryl ‘A’ platform under construction and scheduled for installation June 1975. The location of the subsea wellhead relative to the platform was unknown during early stages of delineation drilling and, in the event, placed approximately 3000 ft. distant, easily within reach of platform wells. Future satellite wells were to be located in excess of 22,000 ft. from the platform and well outside reach of directionally drilled wells. This first subsea wellhead was a deep water prototype system and proved to be considerably more difficult to install than was first anticipated. Operational difficulties and unforeseeable minor component malfunctions caused problems from the onset, but the learning process was in motion.

Types of operations, normally day-to-day routine onboard a platform, were at times almost insurmountable problems when conducted subsea, consequently experience was gathered on procedures and design.

Many difficulties were encountered during activities which were finally solved or simply resolved. The experimental nature of the first project meant that the installation did attempt to try out new concepts and also satisfy the purely functional requirement.