Troika Subsea Production Control System
Authors: Hesketh-Prichard R.M. , Brown N. , Twyford L.R. , Given M.J. 
Published: October 2008

The ability to display real time data at BP's Houston offices is an important feature of the Troika production control system. The data, which includes downhole pressure, temperature, flow, and water cut, is key to making production and operations decisions regarding well control. In addition, the data enables the reservoir engineers to calibrate the reservoir model and to manage the reservoir. Subsea choke settings and valve configurations can be optimized on a real time basis. The time invested by Shell's Bullwinkle operators early in the design ensured that the operator interface was well advanced at the commencement of system integration testing. This almost eliminated time consuming design changes and minimized the time required for operator training. Integrating and streamlining the document approval and interface management systems greatly reduced the volume of paperwork, duplication of information, and consequent ambiguities.

Introduction

The Troika subsea development is located 150 miles offshore Louisiana in the Green Canyon area of the Gulf of Mexico. The development consists of an eight-slot subsea manifold tied back to Shell's Bullwinkle platform 14 miles to the northwest. The water depths at Bullwinkle and the manifold are 1,350 ft. and 2,700 ft. respectively. Troika is owned equally by BP, Shell, and Marathon with BP serving as the designated operator. Five wells are planned initially. These are clustered around the manifold within a radius of 250 ft.; however, the system is designed to allow for the possible addition of a fourslot template about two miles away. The Troika subsea facilities are controlled by a multiplex electrohydraulic system. The subsea components of the control system are connected to the surface components on Bullwinkle by separate electric and hydraulic umbilicals.

Design Requirements

A field development study performed by Intec Engineering compared the merits of several alternative schemes. A further study performed by the integrated project team (IPT) narrowed down the alternatives and defined the scheme thatformed the basis for the requirements specification.

Contractor Selection

The control system contractor was selected by the competitive bid process. The request for quotation (RFQ) was issued to two potential contractors in mid January, 1996. Bids were due 30 days later. ABB Seatec was the successful bidder and a purchase order for the preliminary engineering was awarded soon thereafter. The purchase order also covered the ordering of critical components and long lead materials. The main purchase order was awarded at the end of April, 1996 covering the supply of fixed price items. The purchase order incorporated incentives based on delivery performance and other factors. A work and services contract was placed in April, 1997 to cover engineering and technical services in support of system integration testing, installation, commissioning, training, and equipment rental.

Preliminary Engineering

The preliminary engineering established the foundation for the detail engineering and subsequent phases of the project. It lasted for approximately ten weeks and necessitated close interaction between the control system contractor, the integrated project team (IPT), and the contractors responsible for other aspects of the project.