Abstract
This paper describes the successful resin squeeze operation to seal off a micro-annulus between the 7" and 9-5/8" casings on a sour gas well located in Sichuan Basin, China. Integrated plug and abandonment were also essential to eliminate the risk of potential H2S exposure presented to the residents around this area.
Resin, as a new alternative sealing technology, was technically evaluated, laboratory tested, and then chosen for squeezing into a micro-annulus to stop gas migration for its solids-free and low-viscosity properties compared to a conventional cement. The squeeze job was designed by taking the casing yield strength as the pressure limit (Confirmed by caliper log the casing was in good condition) and determining the resin pumping volume based on estimated resin squeeze volume and the remaining resin plug length. A "Braden-head" squeeze method was selected considering the low injection rate observed during the water injection test. Both stage-up and stage down squeezing techniques (hesitation squeeze of increasing and decreasing wellhead pressure stage by stage) were performed to maximize the injected volume of the resin sealant. A total of 800 L of 9.16 lb/gal resin was placed into a 4 ft milled interval, and 50 L were successfully squeezed into the 7" × 9-5/8" casing annulus. An operational learning was that resin injection is greatly improved during the stage-down process while keeping the casing annulus open. Evidence that the micro-annulus leak path had been sealed was an observation of 0 psi on the 7" × 9-5/8" casing annulus after resin fully set.
The method of locating the optimal spot to squeeze resin involved noise logging to analyze for a potential gas source in the annulus. The post job results confirmed that resin acts effectively as an annular barrier in the repair of gas leaks in the small volume situations where micro-annulus exists in the cement sheath. For large voids such as inside 7" casing, a combination of cement plug plus mechanical barrier is recommended to be placed directly above resin plugs to complete permanent plug and abandonment of the wellbore.
Investigating on the Prediction Model of Sulfur Deposition in High Sour Gas-Well