Thermosetting Resin: Plugging Abandoned Oil Wells

Researchers are assessing a novel resin for plugging unused oil wells as an alternative to cement.

Oil wells go through the plug and abandonment (P&A) process when no longer in use. This prevents hazardous fluids from entering groundwater, soil, the marine environment, or the atmosphere. The P&A process can be costly and time-consuming, contributing up to 25% of the total offshore exploration well drilling cost. Typically, workers plug P&A wells using cement, but it has drawbacks. The harsh conditions inside wells can lead to cement failure, resulting in possible environmental contamination. The cement slurry particles prevent penetration into small voids and cracks when repairing leakage paths. Researchers developed a safe, sustainable, thermally stable liquid resin for oil well P&A in search of a solution.

Testing at Lab-Scale

To create the resin, researchers mixed functionalized poly(vinylidene fluoride) (PVDF) with pentaerythritol tetraacrylate (PETA) with a 1.1:3 ratio. The mixture also contained potassium persulfate indicator and HDK H2000. Researchers cross-lined the resin in both a cuboid mold and a steel tube. The tube mimicked well geometry to simulate the well plug at laboratory scale.

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The resin plugs containing 0.5 and 1 wt.% initiators withstood atmospheric water pressure for up to 30 days. The 10 wt.% initiator sample could not withstand atmospheric water pressure due to its less uniform structure. The solid polymer exhibited thermal stability beyond 90 °C, the temperature in the chosen downhole conditions.

Filling the Holes in Current Technologies

Results of the study showed that samples with 0.5 wt.% potassium persulfate performed the best. The material demonstrated improved morphology, enhanced thermal stability, and reduced environmental impact. Well P&A occurs in the field, rather than beforehand in the lab. Thus, in this study, it was crucial that workers would be able to mix the material on an offshore platform. Researchers concluded that this would be possible due to the resin’s setting time. The reaction time at room temperature was 20 hours, but only 5 minutes at 90 °C. After 24 hours, a homogenous, stiff material had formed.

This study showed a proof-of-concept of the material as an alternative to cement. Future research will demand the investigation of larger-scale feasibility, as well as cost-effectiveness. Nevertheless, this material showed good performance, with thermal stability  up to 190 °C and good adherence to the steel casing. The solid resin also had a higher compressive strength than API class-G cement, commonly used for P&A. Important to note, the researchers designed the material on the concept of Safe-and-Sustainable-by-Design. The acute toxicity of the resin required no labeling, and the substances were not bioaccumulative. In this early design phase, results showed a better solution compared to current P&A technologies in terms of environmental impact. Long-term effects will need to be a subject of larger scale, future.