TOGI Production Control System Challenges and Experiences
Authors: Nilsen P.A. 
Published: October 2008

TOGI Production Control System is a multiplexed electrohydraulic system comprising features like acoustic sand and gas leak detectors.

The system detailed design was presented at the annual OTC in Houston, May 1989.

The TOGI scenario included challenges like:large offset from existing infrastructure (48 km)relatively deep waters (305 m)extensive monitoring requirements (sand detection and gas leak detection) Extensive development of new equipment and qualification of existing equipment was required.

Even though we have experienced some difficulties in the manufacturing test and installation phase, the equipment was installed on schedule, within budget, and performing according to the requirements.

The success of TOGI has set new standards for development of control systems for subsea production systems.

INTRODUCTION

TOGI Production Control System (PCS) must be regarded as an unique and relative complex control system. This as a result of:the inherent risk and cost involved when retrieving the large manifold module led to the decision to keep this module free of active components/equipment i.e. distributed functions.a challenging scenario with deep waters and large offset from existing infrastructure.redundancy requirements to reduce the probability for a needed intervention.specific monitoring requirements, such as sand detection, gas leak detection and requirements for very accurate well head production pressure monitoring (no downhole monitoring installed on TOGI). A simplified sketch indicating the main parts of the PCS is presented in fig. 01 as a reference for the discussions in the paper.

The experiences so far are that the challenges have been solved and that the problems encountered were not larger than expected. There are however areas that could be improved to reduce the problems and consequently cost even further.

The novelty and complexity of the system were the main contributing factors when the test strategy for the PCS was defined.

The test program was defined to ensure that all subsystems and interfaces were tested prior to installation.

In addition a commissioning program were defined to ensure correct installation prior to start up.

This paper is one in a series of six which are presented at the OTC 1991.

CHALLENGES AND EXPERIENCES

There where numerous challenges when designing the TOGI Production Control System (PCS).

Power and signal transmission

Transfer of power and signal over 48 km had no track record in the business, and hence the system had to be customised for TOGI.

The system was designed with signals superimposed on power lines. Such design requires filter systems which are very important both for signal transfer (impedance matching) and power transfer (power factor).

Superimposing signals on power lines is a well proven technology, although it was not to our knowledge utilised on any subsea applications before TOGI. Because of this none of the potential contractors had systems that could meet our specifications.

In order to reduce the inherent problems like crosstalk, attenuation and low signal/noise ratio, very strict requirements were given to the manufacturer of the electrical cable.

As part of the development work a 50 km test core was manufactured.