Eliminating the Silver Bullet from SAGD Casing Cementing

Abstract

Abstract A “Silver Bullet” is defined as a solution that relies on using one portion of a number of complex processes to quickly and easily achieve a desired result. In the case of Steam Assisted Gravity Drainage (SAGD) casing cementing, the objective is to achieve complete annular zonal isolation from the intermediate casing shoe to surface. Cement is often cited as providing a “Silver Bullet” solution for a number of well construction deficiencies. An integrated design approach is a philosophy that incorporates critical design criteria, operational best practices and fit for purpose equipment to achieve a desired result. An integrated design approach is only effective if full participation occurs from both the operator and service providers. Design and operations personnel should be fully utilized in this philosophy. This approach has been employed with respect to the well construction and casing cementing operations at Foster Creek/Christina Lake (FCCL) SAGD projects. The operator and cementing service provider employed an integrated design approach to SAGD cementing operations and the results are presented in this paper. SAGD wells present sub-surface well construction engineers with a difficult environment in which to achieve a competent annular seal when cementing intermediate casing strings. SAGD well designs typically consist of large diameter drill holes and casing, set horizontally at relatively shallow true vertical depths (TVDs), through formations of variable competency. SAGD production operations then, via steam injection, subject the wells to extreme temperature cycles up to 275°C. These operating environments require design consideration of all aspects of the drilling and casing cementing operations to achieve and maintain annular isolation. Relying on one piece of a puzzle to make up for a number of missing parts rarely provides a consistent, reliable outcome. An integrated design approach that leverages all the various aspects of wellbore construction is essential to achieving high quality well performance throughout the life of project. Drilling a hole with a uniform diameter (minimizing washouts) and trajectory, drilling fluid conditioning and solids removal, coupled with proper casing centralization and movement during cementing operations is essential to ensure an adequate cement sheath is obtained around casing. Flushes and spacers are utilized in cementing operations to seal off porous formations, reduce cement fallback and provide a reactive film on the borehole and casing to improve the quality of the cement bond. The placement of cementing fluids into wells at higher annular velocities has a 30+ year history in Western Canada of improving drilling fluid/solids removal from casing annuli and enhancing cement to formation/pipe bond, reducing well problems associated with incomplete zonal isolation and casing support. A recent introduction into SAGD cementing operations of a formulated spacer fluid and “fit for purpose“ mixing and pumping equipment has resulted in quantifiable improvements in intermediate casing bond quality. A cementing system has been designed to provide these results, while reducing the required location personnel and equipment footprint. The background, case history and the definitive bond log comparison will be presented to illustrate these improvements.