High Performance Tailored Mechanically Enhanced Cement Slurry Helped in Delivering Dependable Barriers Across HPHT Reservoir: Case Study from UAE Offshore
Abstract The concept of zonal isolation has evolved recently addressing new industry challenges to provide dependable barriers throughout the life of the well. This helps ensure long term well integrity for safer and more efficient hydrocarbon production, especially for the fields predicted to have a long lifetime. This leads to tailoring of cement slurry designs for superior mechanical parameters to avoid deteriorating them under post cementing operational loads. Following cementing best practices is a key parameter to achieve a successful cementing job, however adequate mechanical properties will help a cement slurry to withstand all the cyclic loads that the well will experience during its lifetime. Determining these properties and tailoring cement slurry designs to meet these properties will help ensure that the cement slurry will still survive these loads, all the way from placement until it has experienced all the post cementing operational loads including but not limited to multiple pressure testing, unloading the well, perforations, various thermal loads during well production, hydraulic fracturing etc. The tailored cement slurry was able to provide an adequate solution of such challenges faced by an operator in Offshore UAE under a high pressure – high temperature (HPHT) environment. Stress modelling was performed for the life of the well considering post cementing operations. This helped in determining optimum mechanical properties required for the cement slurries considered. Specialized testing was performed in both lab and yard to achieve such properties for field execution. Based on various stress and hydraulic modelling, slurries ranging from 13 to 17.5 ppg were designed and pumped successfully in the wellbore. Post cementing bond logs showed adequate placement of a tailored dependable barrier across a complete wellbore including an HPHT reservoir section. This approach can be used for wells with similar challenges around the world for long term zonal isolation.