Subsea completions in recent years have been approached as development engineering for future deep water applications. The Plain Jane concept addresses the immediate need for simple, and economical completion systems, using field proven techniques for water depths of 300 - 800 feet.
The salient features of the concept are:
Conversion of the exploration wellhead to a safe production facility, locking the casing program down and providing a tubing hanger interface.
A simple, rugged tubing hanger and tool. The tubing hanger running tool has full bore access to production bores and dual usage as high pressure tieback to xmas tree.
Structural support for ancillary equipment.
Running the xmas tree on the rig's drilling riser.
Retrievable controls for workover.
While design criteria were taken from the North Sea operating area, application of the system can be worldwide. The overriding consideration in this concept is simplicity. This is achieved by using equipment and running procedures which are similar to drilling operations. Use of existing rig equipment is maximised and special equipment and training is minimized.
The wellhead conversion, the tubing hanger, and installation tools have been factory tested. The running of a production string, and subsequent tieback to the tree via a single tool has been computer analyzed as safe, and highly adaptable.
The use of a drilling riser and blow-out preventer like control pod in this application is yet to be proven. However, with considerable experience of handling blow-out-preventer stacks, it is envisaged that the installation/workover program shall be the most acceptable system yet for completion operations. The inclusion of the receiver plate, (again like a B.O.P), at the top of the tree also means vastly simplified control circuits with maximum control flexibility.
The paper shall include field data, design analysis, and factory test program results obtained during the course of the development.
Subsea completions for the recovery of liquid and gaseous hydrocarbons have, to date, been mostly confined to individual satellite wells. Such satellite wells have varied in complexity from simple land type installations transferred subsea to highly sophisticated, remote operated, diverless completions including both the "wet" and "dry" type systems.
Recent development work and discussion has been biased towards total subsea field development work. The underlying trend has been towards more adventurous projects requiring new technology, significant sums of money and engineering expertise in feasibility studies alone. This latter factor is, perhaps, the most significant and limiting. This is not to suggest this effort is in any way unnecessary, but to emphasise that these long term projects can detract from what is possible at moderate cost by rationalisation of existing technology and techniques.
Many simple completions, adequate in design and economic in areas of stable weather conditions, would not necessarily be so in other areas, as the industry learned when drilling equipment was first introduced to the northern areas of the North Sea.
