An operator launched a "water shutoff" polymer development project for a monobore gas well completion in the Gulf of Thailand. The shutoff concept involved a conservative tubing pad application in which a water shutoff polymer technique was used to help prevent wellbore restriction by sealing off the target reservoir permeability zone. Job planning and careful laboratory testing were conducted to simulate bottomhole conditions. In 2009, the treatment was used to perform shutoff of the top water producing zone using bullheading. The design consisted of the shutoff treatment followed by a loss circulation material (LCM) to help ensure wellbore fluid placement in the designed positions and that the pressure response could be monitored from the surface. The shutoff operation was performed according to plan, and coiled tubing (CT) was used for cleanup after placing the shutoff treatment. As a result of well testing after the shutoff treatment, water production dramatically decreased by 50%, demonstrating the effectiveness of the technique in terms of safety, economics, and operation. A long-term monitoring program was established to evaluate the polymer's seal-off performance for development of future field strategies.Since 2009, water production monitoring has proven that the shutoff polymer is one of the best solutions for long-term water shutoff in terms of safety, economics, and operation. This technique does not require mechanical sealing off of the perforations, making it more feasible for future well interventions.

Coiled Tubing (CT) catenary technology supports the possibility of executing offshore interventions on platforms with space and weight limitations. Having the majority of the CT equipment remain on a separate support vessel vastly increases the platform working area and minimizes offshore heavy lifting. The system allows the operation of well control and pumping equipment from the vessel for a single control source and an overall faster, safer, lower-cost operation. Limited offshore platform space and crane capacity are a significant concern for intervention operations in the Gulf of Thailand. A conventional CT unit is simply unable to fit on a small offshore facility. The catenary system was introduced to eliminate these limitations by keeping the main CT equipment on the vessel while providing the connection and interface between the vessel and platform equipment, allowing a safe and efficient operation. It also has the flexibility to enable the vessel to adjust its location during bad weather if required, without affecting the overall safety of the operation. The same system can also be used on regular platforms without space and weight limitations during the same campaign. The catenary system saved two days per well, resulting in savings due to less equipment utilization, reduced personnel, and accommodation requirements, and reduced consumables used. Less heavy lifts also saved time, associated costs, and increased safety during the preparation phase. The CT operator can also load the maximum length of CT pipe onto the vessel without concerns about having to join multiple strings or using split reel spooler equipment. All well control equipment was function tested and operated as standard with real-time monitoring and capturing of well conditions, operation parameters, and CT fatigue the same as expected from a conventional CT setup. The paper will elaborate on the catenary principles, concepts, and engineering background for these types of operations. The CT catenary was proven to bring significant efficiency improvements, safety enhancements, and faster operations, leading to cost-saving when carrying out CT interventions in the Gulf of Thailand. The techniques and details will be elaborated on in the paper.

The permanent tubing patch is a primary method widely used to isolate water production zones, especially in slim-hole wells. As the name implies, the permanent tubing patch is non-retrievable equipment and presents a significant challenge when removal is needed. None of the global records of permanent tubing patches installed in slim-hole wells demonstrate successful removal. This paper will discuss the methods used to achieve the first-ever Coiled Tubing (CT) milling of a permanent tubing patch in a slim-hole well. CT was selected to convey the BHA for milling the tubing patch sealing section. An eccentric pilot milling bit (2.780 in OD) was carefully designed as it needed to pass an ID restriction (2.813 in) in the Downhole Safety Valve (DHSV) while still being able to peel off the tubing patch sealing ID (2.250 in) until reaching the full drift of tubing ID (2.992 in) and ensure that the tubing wall would not be damaged during the milling operation. Once the tubing patch sealing section was removed, a braided-line (WL) operation was run to pull free and retrieve the tubing patch body to surface. The well was then restored to enable further intervention and production. CT performed the milling operation flawlessly, and a carefully designed surface equipment stack-up design provided downhole tool deployment accessibility and convenience for both CT and WL intervention. Nitrified fluid was used with CT to mitigate loss problems in several depleted zones above the milling depth. As a result, the tubing patch seal was successfully milled without jeopardizing the tubing integrity. Once the tubing patch seal element was successfully removed and the patch body became free, the WL was deployed through the CT stack to fish the tubing patch body. This is the first-ever operation to remove and retrieve a permanent tubing patch to the surface in this way without damaging the primary completion. Its success results from a well-thought-out pilot mill bit design and careful execution. This case study can now be shared across the industry to improve intervention efficiency and minimize the chance of early plug and abandonment due to permanent tubing patch removal issues.