This paper is intended to present a system and its components which have been developed and used to perform totally diverless flowline and control line umbilical connections. This system is part of a totally diverless subsea satellite well installed in water depths of approx 135 metres (440 ft.).
The topic of diverless completion operations in the offshore oil industry is a popular one. By combining the obvious dangers and operational complications of diver assistance, with increasing water depth at completion sites, it is clear why the development of this type of hardware is considered necessary.
Over the years many different types of flowline connection have been developed. These range from the simplest of flange type connections to terminations using hydraulic collet connectors on the flowline outlet of the subsea xmas tree. In practically all cases a great deal of diver assistance and intervention is 'designed in'.
Consider the two methods mentioned:-
In the case of the flanges the diver is normally required to tie-in the flowline, align the connection, tighten and preload the flange fastenings. The diver is also required to disconnect, replace sealing elements and reconnect this tie-in as part of an x.t. workover or retrievalprogramme.
A collet connector type of once connected allows for arrangement xmas tree retrieval and sealing element replacement without diver assistance, but only after the flowline has in some way been fixed to the guide frame in a manner which allows collet connector location usually installed with the x.t. assembly. The use of such hydraulic equipment of course implies a reliability risk due to long term soak of elastomers in their operating medium, usually glycol based control fluids.
The system discussed in this paper utilises a completely mechanical connection, it does not require diver assistance for any part of flowline pull in, initial connection, or during any workover procedure. It does not contain elastomer sealing elements or rely on permanently installed hydraulic equipment.
It does however benefit from a certain amount of visual aid in the form of camera's and lighting and/or a suitable remotely operated vehicle (R.O.V.).
It is probably important to note at this point that although this particular system may not be the first of its kind, its aim is to be the latest generation in the development of this area of subsea completions and it is probably the only system to fulfill such stringent design parameters.
The basic principles which have been applied to the design of the equipment, proof testing and procedures are the result of many previous generations of flowline and umbilical tie-ins.