RIASSUNTO
Abstract
Improved coiled tubing (CT) technology, development of specially-designed hydraulically-actuated service tools, and increased emphasis on cost efficiency have made coiled tubing a viable option for many fishing jobs. Before the emergence of coiled tubing fishing technology, traditional service procedures included use of wireline to retrieve fish from oil and gas wells. If wireline was unsuccessful, a rig or hydraulic workover (snubbing) unit had to work over the well and remove the fish.
This paper addresses the successful use of CT in fishing operations. The capability of CT to circulate fluids at the fish and generate high downhole forces enables the retrieval of fish in situations that would not be possible or cost effective by other service options. CT fishing can be performed under pressure on live, highly-deviated or horizontal wells; the job can be completed and the well returned to production within 1 to 3 days for only a fraction of the cost of a workover.
The paper will describe the tools, their capabilities, and service techniques currently in use for CT fishing operations as well as new equipment being developed. Data from several case histories will be used to provide considerations, surface rig-up, and job limitations.
Introduction
An oilfield definition of fishing might be: ""an attempt to engage and retrieve unwanted, unserviceable, or often damaged equipment from a wellbore. "" The term ""fishing"" is generally used when downhole equipment cannot be retrieved from the well using the tools or method designed to operate or retrieve that piece of equipment. Generally, fish fall into two categories - some are simply nuisances, causing decreased production or increased operating difficulties and costs, but some must be removed for safety or mechanical reasons if the well is to continue production.
In production operations, fish might include:
Stuck, damaged, or inaccessible subsurface flow controls, plugs or subsurface safety equipment that cannot be pulled by wireline.
Lengths of wireline or logging (E-line) cable.
Service tool strings.
Other foreign objects.
Before 1980, the quality of the CT, particularly the weld joints, was relatively low, and tubing failures resulted in fishing jobs to remove the dropped pipe.
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