Well construction in deepwater environments poses many challenges from a cementing perspective. Limited options for controlling cement density and rheological profile can present significant risks to wellbore stability, especially in narrow fracture gradient wells. In addition, poor compatibility between traditional aqueous-based cement and synthetic-based drilling fluids (SBFs) commonly used in deepwater drilling can lead to issues with cement-to-casing and cement-to-formation bond integrity. To address these issues, a new epoxy-resin based cement alternative has been developed with highly tunable specific gravity and drilling fluid-like rheology.
The combination of a highly tunable specific gravity and maintenance of drilling fluid-like rheology yields minimal equivalent circulating density (ECD) increases upon placement of the resin in the wellbore and enhanced management of narrow fracture-gradients. Furthermore, the new resin formulations have been shown to provide excellent compatibility with SBFs used in deepwater applications. The resin shows applicability over the broad temperature range of 90 to 225°F, with resin densities of 7.0 to 18.0 lb/gal. In addition, elevated shear bond strengths with minimal shrinkage upon cure were observed for the resins.
The paper presents detailed studies of the new resin systems at 90°F, 160°F, and 225°F with 9.0 to 14.0 lb/gal densities. It also discusses set time/pump time issues and the control of resin rheological properties and density by means of a judicious choice of added particle types and particle sizes. The resin systems tolerated a high volume percentage of SBF contamination, and excellent compressive strengths were observed with and without SBF contamination. Combined, the data indicates that the new resin potentially provides substantial advantages over traditional cement and mitigates many of the challenges associated with the application of cement in deepwater well construction.