Advancing Well Integrity: Petronas’ First Application of Time-Activated Sealant Technology
Authors: Jalil M Izwan B A , Nair Puvethra , Shahril Sy , Shan Youngbin , Jin Xiaohu , Chandar Chandar 
Published: November 2024

Background and Scope

Within aging brownfields, maintaining the integrity of wellheads and control lines presents a prevalent challenge. This issue becomes particularly acute in wells with high production rates, especially those containing elevated levels of CO2 and sand, requiring urgent rectification measures. Whether stemming from leaks in the neck seal, tubing hanger MTM, elastomers, or control lines, the leak rates can vary significantly, ranging from as large as 1000 ml/min at 3000 psi to as small as 50 ml/min at 500 psi.

Traditionally, plastic packing and pressure-activated sealants have been employed to address these integrity concerns. However, these solutions have frequently encountered recurrent failures within six months of application. For instance, in the case of Well A, which experienced a control line leak and was treated with pressure-activated sealant, the solution proved ineffective, resulting in a failure within three months. Subsequent diagnostics revealed a leak rate of 2000 ml/min at 150 psi, indicating the inadequacy of the applied solution. Given the urgency and magnitude of the leak issue, the proposed solution involves the application of a time-activated sealant to address the leak rate of 2000 ml/min.

Process and Selection Method

The time-activated sealant is a specialized polymer sealant engineered to effectively seal various types of leaks, including flange leaks, neck seal leaks, and void pack-off leaks in tubing and casing hanger elastomeric seals. Its primary function is to prevent continuous communication and pressure transmission from the annulus. Notably, it does not form bonds with metal surfaces, facilitating easy dismantlement during future wellhead operations.

This sealant boasts exceptional properties, including extreme high compressive strengths exceeding four times that of advanced cement slurries. Additionally, it exhibits ultra-high shear bond strengths exceeding 1,650 psi and generates an exothermic reaction upon curing. Importantly, it is not soluble in water or oil. Its curing process occurs at low temperatures and utilizes a total liquid system, enabling it to penetrate small channels and micro-annuli effectively.

Moreover, the sealant offers controlled pump times and set times, utilizing a crosslink design tailored to specific well specifications and downhole conditions. This comprehensive set of attributes makes it a highly versatile and reliable solution for sealing applications in oil and gas wells.

Result

Performed squeeze and wait on crosslinking (WOC) process by injecting fresh water into the control line at maximum pumping pressure and ensuring a pump rate of 2000 ml/min. Mixed the sealant and commenced pumping it into the control line, purging all excess sealant until pressure peaked. Followed by pumping 200 ml of fresh water, followed by 400 ml of sealant until pressure reached maximum pumping pressure, then waited for 48 hours. Conducted a pressure test up to 80% of the Christmas tree rating and observed no pressure drop, confirming the restoration of integrity. For void area leak Application, eight times injection into void were performed. Major void area leak at 2000ml/min is successfully shut off with no injectivity at 2700 psi and pressure drop reduced from 3 to 1.6 psi/min. However, with negative pressure test on PCP while bleeding off the void area indicates that the void area leak is not cured.

Conclusion

The time-activated sealant (TAS) utilized for Control Line (CL) Abandonment is deemed successful. However, in void area application, it has significantly reduced the leak rate but did not fully isolate pressure from PCP to Void Area.