North Brae is the first North Sea gas condensate field to be developed using gas cycling for pressure maintenance and improved recovery. Deviated wells have been drilled to depths of up to 18,900’ MDRKB. Typical shut-in tubing head pressures (SITHP’s) are in the region of 4, 000 psi for producers and 5,000 psi for gas injectors. Moderate concentrations of C0 2 and H2S at these pressures give partial pressures which cause a corrosive environment.

Coiled tubing (C.T.) well intervention in these conditions initially proved to be difficult. Failures of pressure control equipment and. the C. T. itself were encountered. Despite this, upgrading of equipment and improved procedures have allowed implementation of a highly successful C. T. programme at North Brae.

This paper provides information on the operational difficulties encountered, and resulting improvements made to overcome them. It outlines some of the equipment and technique upgrades necessary to ensure efficient and safe C.T. intervention in these difficult conditions.

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