Innovative Application of Ultra-Lightweight Epoxy Resin-Cement Slurry Mixture Achieved Zonal Isolation Objectives and Secured Well Integrity: Case History From Offshore Gulf of Suez

Abstract

While drilling an offshore well in the Gulf of Suez (GoS), Egypt, an operator experienced severe losses of approximately 14,500 bbl of costly oil-based mud (OBM) during the drilling of a 12 1/4-in. hole section through depleted zones. It became obvious that zonal isolation objectives would not be achieved unless equivalent circulating density (ECD) was significantly reduced during cementing to help minimize and control downhole losses. Therefore, a special design of ultralightweight cement slurry combined with epoxy resin was prepared. The goal was to help reduce downhole losses during cementing while enhancing mechanical properties and achieving higher compressive strength of the set cement sheath as per well integrity requirements. This would help prevent formation stress and be helpful during future well construction operations. Epoxy resins are primarily used as secondary barriers to the primary cement sheath, curing tight casing leaks, squeezes, and during well abandonment. Generally literature on resin discusses its resilient mechanical properties, highlighting that the Poisson's ratio of epoxy resin can be closer to that of rubber, while cement is closer to that of glass. It was observed that mixing resin with cement enhances other mechanical properties of cement in addition to enhancing compressive strength. A 9-lbm/gal resin-cement slurry mixture was designed for the discussed treatment, combining 90% cement and 10% epoxy resin. The combined mixture provided all of the necessary properties of the desired cement slurry. The cement treatment was performed as designed and met all zonal isolation objectives. This cement-resin mixture can become a new solution within the industry, replacing conventional cement in many crucial primary cementing applications, particularly replacing ultralightweight high-compressive-strength slurries. This paper highlights the necessary laboratory testing, field execution procedures, and treatment evaluation methods so that this technology can be a key resource for such operations in the future.