Holistic Approach to Mitigating Well Integrity Risk in Deepwater Surface Casing Strings in All Phases of Execution

Abstract

Abstract As well construction progressed into increasingly deeper water depths targeting deeper reservoirs, surface casing strings became exposed to additonal risks during various phases of execution and well design requirements. Beginning with handling and installation, they are subjected to handling and environmental loads from various metocean conditions. Once set in place, they see increased exposure to higher well and structural loads while being subjected to deeper hole sections before additional casing strings are set in place. Deepwater casing strings are installed prior to the drilling riser being installed, which creates additional exposure to loads and risks not seen by other casing strings as well as loads induced by the well. To ensure the casing string is fit for duty, a "cradle to grave" approach is utilized to identify and classify the risks created by loads induced on the casing string. Each risk is analyzed and mitigated with a technological solution or best practice to ensure the design parameters of the well are achieved. Introducing advanced mechanized tubular running technologies resulted in up to 20% reduction in exposure of the surface casing string to dangerous seastates and ocean currents and a 41% reduction in red zone entries. Exposure of the surface casing string to environmental loads was further reduced by 7% with the use of an innovative hands-free anti-rotation key, which requires no installation on the rig floor during tubular handling operations and lowers red zone entries beyond current mechanized handling solutions. Once set in place, surface casing strings are subjected to a higher classification of well service as structural and well loads increase in severity. To address this, a new weld-on connector qualified to connection assessment level I+ for gas tight service with elevated temperature per API RP 5C5 / ISO 13679 was installed, allowing deeper wells in deeper waters to be achieved. It is sometimes necessary to temporarily protect the well with deeper hole sections exposed to the surface casing string. Additional challenges to effectively seal the well are present when the string contains internal weld seams and inside diameter restrictions such as the high-pressure wellhead housing and supplemental casing adapters. To overcome these challenges, a unique retrievable packer system was developed and validated to API 11D1 and ISO 14310, allowing well protection from the surface casing string and below.