Innovative Epoxy Resin Formulation for Downhole Casing Repair Applications

Abstract

Downhole casing repair is a major workover operation worldwide, especially in wells which were drilled and put on production decades ago. The presence of corrosive formations is considered a common downhole source that slowly corrodes steel strings over time. Several remedial options are available on the commercial shelf including cement slurry, resin chemicals, and mechanical casing patch technologies. Yet, these suffer from several disadvantages including limited isolation and integrity, cost, internal diameter restriction, etc. These drawbacks could lead to casing leaks reoccurring across the same depth shortly after applying the commercial treatments. In other scenarios, they result in internal diameter reduction and inability to pass tools, such as plugs, packers, whipstocks, etc. The proposed epoxy resin formulation retains improved mechanical and chemical properties over the commercial products to repair challenging downhole casing leaks, especially those with low injectivity. This formulation is composed of a combination of two different resins and one curing agent. Compared to other commercial epoxy and polyester products, this formulation showed lower rheology of less 50% at room temperature, deeper crack penetration, improved compressive strength and elasticity, and enhanced corrosion resistance. The product was deployed in the field to cure downhole 7 in. casing leaks with 73 pcf CaCl2 brine in place. The subject leak showed low injectivity of 0.4 bpm at 1,000 psi, requiring solid-free solutions. The innovative formulation was introduced as a result, and 20 bbl were spotted as a balanced plug and squeezed in hesitation to achieve the required pressure integrity of 600 psi after resin plug cleanout. Manganese Tetroxide was used as the weighing agent to mix up 80 pcf epoxy resin as per design. The low-rheology allowed for maximum injected volume at the required lock-up pressure of 1,000 psi. Meanwhile, the elastic nature enabled more resistance during the following re-entry operations and relatively higher rates of penetration during resin plug cleanout. This paper will discuss the nature of the resin formulation and experimental work to compare this innovative product to the commercial products. The pilot testing, job simulation, and field deployment will be highlighted to emphasize the added value and potential of this product.