Starter Wellhead: Achieving Mechanical Barrier Isolation in Large Casings Annuli While Countering Wellhead Thermal Growth

Abstract

This paper describes the method and apparatus of the Low-Pressure Starter Wellhead System used for 36" and 30" conductor casings to provide the required wellhead sealing integrity for surface formations that have the potential to release formation fluids to environment during the well life cycle without restricting the casing thermal growth. The current industry approach is to rely on cement as the only barrier for casings annuli larger than 24" to seal off shallow hydrocarbon formations without any consideration for thermal growth resulting from well production. Cement, the current barrier for surface casings (greater than 24" size), is prone to failure due to cracks resulted from the wellhead thermal growth as well as cement placement challenges. Therefore, this necessitates mechanical means of preventing hydrocarbon or water release to atmosphere via proper and sustainable solutions. This will provide the required support to prevent any negative impact on the environment, risks to personnel and to assets. Risks will be higher if the well is close to residential/ populated area and/or located in offshore environment. The Low-Pressure Starter Wellhead System is new design concept in oil and gas industry (Patent Number: US11396785B2) as currently there are no available technologies to provide mechanical sealing for big surface casings while encountering thermal growth. It will provide a complete solution to isolate surface zones, provide seal and load integrity and cater for the casing thermal growth during the well production lifecycle. The new design, also, will facilitate the drilling operations while maintaining the well control capability at all times. The benefits of the new device are significant. Achieving mechanical isolation for big casing sizes greatly enhances well integrity, especially for wells with shallow hydrocarbon or water formations. Accommodating for wellhead thermal expansion due to high well temperature provides a redundancy and eliminates the associated challenges with cement failures and formation fluid release to the atmosphere. This results in substantial cost avoidance, safety improvement and better environmental protection. Sealing potential problematic surface formations is paramount for any well integrity considering the current industry gap with these large conductor sizes. This system presents a unique design in the oil and gas industry to establish a mechanical barrier for larger casings while accommodating for wellhead thermal growth.