Abstract
Cementing gas wells in Khuff reservoir where sustained annular pressure has been reported in many wells, presents a big challenge offshore in Umm Sheif field in Abu Dhabi. The main challenges are preventing gas migration and achieving long-term zonal isolation using a competent cement sealant system able to withstand downhole stresses and high temperatures during production cycles.
An extensive study was carried out on two previously cemented wells, and an in-depth analysis was performed on the cement systems pumped in this field. The knowledge gained paved the way for designing, planning, and executing successful cementation on a recent well.
A mathematical model simulating downhole stresses in terms of pressure and temperature was used in designing the cement sealant system. Unlike conventional cement systems, properties such as high Poisson's ratio and low Young's modulus value compared to that of the rock were optimized in the new system to achieve mechanical resistance and durability.
This paper describes a case history whereby this cement sealant system was used to cement and secure the critical phases of this well. Cement evaluation logs across all the liners showed complete cement coverage and zonal isolation, especially across the Khuff gas reservoir.
