Underbalanced Perforating of Long Reach Horizontal Wells Using Coiled Tubing: Three North Sea Case Histories

摘要

It is acknowledged that in many reservoirs, perforating in under-balanced conditions can bring significant and obviousproduction benefits. Under-balanced perforating in vertical or“near” vertical wells may be performed with wire-line, whilstperforating in highly deviated or horizontal wells through thecompletion tubing normally requires intervention with either awire-line tractor, hydraulic work-over unit unit, or CoiledTubing. Consideration of all parameters surrounding thechoice of what method should be used to transport the gunsinto long reach horizontal wells will quite often direct the operatorto choose Coiled Tubing as the optimumconveyance tool.Achieving true under-balanced perforation of a long reservoirsection(s) utilising coiled tubing in an offshore environmentpresents a collection of technical, logistical andfinancial challenges.Three North Sea case histories of such operations areillustrated. These examples demonstrate how gun lengths ofover 2,800 ft and 24,500 lb in weight can be deployed to ameasured depth of 17,800 ft through a challenging wellprofile. Particular attention is paid to equipment challengesand selection, the use of friction reducers and techniquesemployed to maximise the operating window, hence achievingthe operator’s desired results and realise the benefitsassociated with under-balanced perforating.