The Highlander Field - One Year's Operating Experience
Authors: Dover Steve , Cooling M. Turlough 
Published: December 2007

In 1985 the Highlander field was brought on stream from one of the first generation of advanced remote-controlled subsea production facilities in the North Sea only 15 months after the U. K. Dept. of Energy approved development. The successful development of the Highlander field was made possible by a combination of innovative ideas and the advancement of existing technology. This paper describes the problems and successes during 1 year of operating experience.

Introduction

The Highlander field is located in Block 14/20, 8 miles [12.9 km] northwest of the Tartan platform in 420 ft [128 m] of water (Fig. 1). Because "stand-alone"-type developments were seen as uneconomical, the decision was made to develop the field with a remote-controlled subsea production and water-injection facility would be controlled by and produced to the Tartan platform.

The development was completed in two phases, a procedure that substantially reduced the time from project approval to first oil being produced. Phase 1 consisted of running well completions in predrilled, offtemplate wells and connecting these wells to the Tartan platform through two 8-in. [200-mm] service lines. During Phase 2, the template and slug catchers were installed; the wells were reconnected to the template; and the template, test and bulk production pipelines, slug catchers, and risers were commissioned. These two phases are described more fully by Smith and Batcheler. This paper deals with the operating experience of Phase 2.

The development originally consisted of four wells-Wells HS12, HS13, HS14, and HS15-previously drilled and suspended between 1980 and 1983. In 1985, these wells were completed and tied into a subsea template that has 12 additional slots for future wells. Since then, three wells (Wells H1, H2, and H3) have been drilled successfully through the template. All wells and services are interconnected by manifolds on the template.

Production to the Tartan platform is through 12-in. [300-mm] bulk and 8-in. [200-mm] test multiphase pipelines. The pipelines are connected into two subsea slug catchers at the base of the Tartan platform.

These slug catchers are designed to eliminate slugging before oil is pumped up to the platform through two 7-in. [180-mm] casing strings. Gas is separated out of the crude at the slug catchers and routed to the platform through the 18 5/8x7-in. [470X180-mm] riser annuli.

The template is also connected to the Tartan platform by 8-in. [200-mm] waterinjection, 8-in. [200-mm] gas-lift, and 4-in. [100-mm] utility flowlines. Umbilicals provide hydraulic and electrical power and chemical injection to the template.

Maintenance is by diver intervention during well servicing, and workovers require a diving support vessel or semisubmersible drilling rig. A new subsea wireline technique, successfully tested on Well HS14 in Nov. 1987, allows routine well work to be carried out from either a diving support vessel or a semisubmersible drilling rig simultaneously with the drilling of new wells. This will substantially reduce well-servicing costs.