Usually, the preferred way to restore production in wells with accessibility heavily compromised is by rig workover activity. However, a preliminary approach in rigless mode followed by rig activity can be even more effective in the presence of several critical issues. Here we illustrate the methodology and technical solutions adopted to perform a challenging rigless fishing job to make the subsequent rig workover operation quicker, cheaper, and safer. A workflow was developed for a course of actions to perform a complex fishing intervention while fully respecting the well control requirements. Considering the well status—1½-in. coiled tubing (CT) stuck in 4½-in. tubing at 7582 ft due to scale buildup, parted in two segments side by side, top of fish at 1345 ft and with no injectivity in the well—it was decided to adopt a fit-for-purpose rigless strategy by combining conventional fishing tools (flow release overshot, continuous cutting overshot) with a CT anchor, which guided the electrical line (EL) cutting tools inside the pipe while keeping it in tension. To accomplish the target, a robust design, with multiple contingency plans was properly defined and successfully implemented. In addition to the main constraint of having a CT pipe parted and stuck in the tubing, the scale deposit prohibited killing the well by bullheading. Consequently, the overall fishing operations were planned and managed as if the well was alive. The alternate use of CT fishing tools, CT anchor, and EL cutting operations allowed recovering approximately 6958 ft over a total length of 7398 ft, leaving just 440 ft of CT pipe stuck in hole inside the scale deposit (with the new top of fish at 7142 ft). As a result, a complex well situation, which could have led to a long and expensive rig operation, was successfully approached in rigless mode, leaving the well ready for a simpler workover activity. The use of Continuous Cutting Overshot (CCO), through a standard "cut & drop" approach, was limited by the CT lubricator height. An innovative fishing approach was then deployed: a proper CT anchor BHA, to latch and hang the CT pipe in the tubing wall, was run. The beveled shape of the CT anchor allowed EL tools to enter inside the CT pipe and cut the same above the free point, so recovering longer sections of pipe.
Re-entry of subsea wells can always hide unforeseen difficulties. Contingency mobilization of coiled tubing (CT) usually gives a wide spread of solutions to overcome most of the possible events. However, when operating on a winterized semisubmersible rig in the remote fields of the Barents Sea, rig-up of CT spread can be costly and complicated. Furthermore, lighter and easily deployable wireline powered mechanical tools have proven to be effective in tackling most of the possible challenges. Possible tubing obstruction issues can be resolved via clean-out/suction, pumping, or milling methods. In this instance, all three were used with different tools to clear the obstruction from the tubing and to clean with precision inside an internal fishing profile of a well head barrier plug to allow for well access. The first challenge encountered when re-entering the tubing in Well-1 was the presence of a 151m long hydrate plug. It was easily removed by an e-line tool capable of applying 10 bar of dynamic underbalance, while maintaining a continuous flow circulation. Such an application is a novel development in the use of existing tools. After removing the hydrate plug, it was discovered that the tubing was plugged by 246m of wax deposits, which were preventing communication with the reservoir. To overcome this problem, a jetting tool was utilized to continuously pump fresh wax solvent inside the landing string. Pumping continuously fresh wax dissolvent provided a unique and effective means to mechanically and chemically remove a significant obstruction. Once the communication with the reservoir was re-established, an additional obstruction of almost 129m (resistant to the wax dissolvent) was encountered. To overcome this challenge an e-line milling tool was utilized, and the resulting debris was bullheaded down into the reservoir. Similarly, when re-entering Well-2 a challenge was encountered to pull a barrier plug due to debris deposits inside the internal fishing profile. Both e-line milling and suction tools were sequentially used to resolve the problem and prepare the plug for retrieval. The tools used were already available on the market for different applications. In this case the tools were used in an alternative way, using their features to solve issues beyond conventional expectations. The result fosters confidence to plan future re-entry without the need for mobilizing a CT spread.
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