Offtake levels, under natural flow, from Thistle and Deveron wells A46(45) and A51(03) are both constrained by relatively poor pressure support. It was decided to install jet pumps in the existing completions to test the reservoir performance under artificial lift. If enhanced offtake levels could be supported permanent gas lift completions would be installed at a later date. In addition to this interim increases in the production rates would be achieved prior to workover.
A wireline retrievable jet pump, complete with a integral sub-surface safety valve (SSSV), has been designed for installation in the (open) sliding side door (SSD) of the existing completions. Power fluid, supplied from the water injection system, is routed via the casing-tubing annulus and returns are produced up the tubing string. Downhole isolation of both the tubing and the annulus is achieved by means of the annulus pressure operated SSSV which is located immediately below the jet pump.
The design procedure for the selection of the optimum nozzle/throat combination is described. Operating procedures have been developed to ensure successful operation of the device and details are given of both the downhole and surface hardware.
Results of actual field performance are presented and comparisons made with predicted values. Finally details are given of design modifications which were implemented in response to problems which developed during field trials.