Abstract
A non-rig Coiled Tubing Unit (CTU)-deployed tubing patch technique was developed at Prudhoe Bay, Alaska, which provides an inexpensive remediation for wells with production tubing by "A" annulus communication. Extended-length patches (which consist of two retrievable hydraulically set packers spanned by jointed pipe) are a vast improvement over older technology that limited patch length to 35’. Patches of up to 5000’ of 3.5" OD jointed pipe can now be deployed, significantly increasing the viability of repairing a larger percentage of the wells shut in due to loss of tubing integrity.
Extended-length patches are deployed with a crane, a service CTU, and a wellwork platform. The wellwork platform provides adequate clearance for the existing wellhead and workover BOP stack, and protects against arctic conditions of -40 degrees F ambient and -80 degrees F wind chill. The advantages of this system over conventional rig workovers are that there is no need to pull tubing and it has faster mobility and ease of scheduling. Typically, extended- length patches are only 10-20% of the costs to replace tubing with a rig workover.
This paper outlines the results of this work and provides a systematic approach for design and deployment of an extended-length jointed patch. The technique has its greatest application where rig mobilization costs are high, such as offshore, remote, or arctic locations.
