Development and Performance Evaluation of Novel Solid-Free Epoxy Resin System for Remediation of Sustained Casing Pressure

• Published in: Energies (Basel) 2023-03, Vol.16 (6), p.2771
• Main Authors: Dou, Ninghui, Wang, Zhiyuan, Leng, Guangyao, Liu, Haoya, Hu, Zhiqiang, Jiang, Ke
• Format: Article
• Language: English
• Subjects: Analysis; break elongation; Cement; Compressive strength; Curing; curing agent; Curing agents; Elongation; Epoxy resins; Gas wells; Life span; Low temperature; Maintenance and repair; Mechanical properties; Microcracks; Performance evaluation; Permeability; Phenols; Polymers; Pressure; Sealing; Sealing compounds; Sheaths; Slurries; solid-free resin; Tightness; Viscosity; viscosity reducer; Well drilling
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en16062771

Sustained casing pressure (SCP) is a common problem during an entire life span of oil and gas wells. When conventional methods are deployed to resolve the issue, the methods seem to have some setbacks by being unable to seal microcracks in the wellbores. A new solid-free resin sealant was developed by increasing the amount of active hydrogen in the curing agent. This low-temperature cure results in low viscosity, excellent mechanical properties, and chemical stability. The experimental results show that the resin sealant can be used at temperatures ranging from 20 to 50 °C, and the curing time can be controlled within 0.25 to 20 h by increasing the curing agent content. The viscosity of the resin is reduced from 35.7 Pa·s to less than 0.065 Pa·s with the addition of the viscosity reducer, which can greatly promote resin penetration into the microcracks of the cement sheath. After 24 h of curing, the compressive strength can reach 55 Mpa, which is significantly higher than conventional cement. With an increase in the viscosity reducer content from 0% to 25%, the elongation of the sealant demonstrates a remarkable rise, ranging from 1.9% to 18%. The cement with 20% resin caused a significant decrease in permeability by 46.3% as compared to conventional cement. Additionally, the sealing pressure attained an impressive value of 14.7 Mpa. The solid-free resin sealant is miscible with cement slurry, which improves cement tightness, reduces permeability, and improves wellbore annulus sealing ability.