Thermal Sealants Improve Cementing in SAGD Areas

Abstract

IntroductionThe long-term integrity of a cement sheath throughout a well's life is the ultimate factor for determining whether the sealant will withstand the planned operations, production and injection that are planned for the well. In the case of heavy oil operations, the primary design considerations for a long-lasting sealant are the temperature and pressure regimes. The stresses caused by the extreme changes are exerted on casing, cement and the rock. It is important that all involved parameters are known and taken into consideration to formulate the final design of sealants. Also, at an earlier stage of the process, when the cement is pumped in the wellbore, proper best practices can help to ensure cement sheath integrity after the cement is set and hardened. Placing the cement slurry at the designed parameters is crucial to the success of the zonal isolation. The effectiveness of the slurry placement can significantly influence the cement sheath integrity and the future of the well. The hydration process, as well as the long-term compressive strength, tensile strength and permanent bonding capability of the cement system, are directly related to the density control and flow regime as the cement slurry is being pumped downhole (1,2) .A complementary component of a successful cement job is the use of cementing best practices (3) . Regardless of the fitness of the sealant, the wellbore may still exhibit steam breakthrough or annulus pressure buildup (APB) in SAGD or CSS operations caused by improper slurry placement. Of course, future damage to the cement sheath from post-cementing operations or from new, unanticipated conditions could also have the same effects.To examine each of the elements involved in heavy oil cementing separately, we begin by studying the design of the sealant systems. Cement Slurry Design and PlacementThe design stage and laboratory testing of the candidate systems of the cement slurry to be used in a thermal operation are the beginning stages of the process. This initial phase requires the drilling engineer and cementing specialist's highest level of coordination. A successful thermal cementing operation execution requires a clear understanding of the mechanical/physical aspects of the wellbore and selected sealant(s). Field development plans and delivery expectations from the cemented wellbores are the determining factors of the future life of the field. The objectives and operational details must be clearly understood by the cementing engineer, with the cooperation of the drilling engineer. Mechanical aspects of the design should cover two main areas: 1) the minimum mechanical property requirements of the set/cured cement needed to comply with regulatory directives and future planned operations; and 2) the hydraulic optimization of the slurry placement necessary to reduce or eliminate the chances of lost circulation and best-fit flow regime to effectively place the slurry. AbstractWith the high demand for oil and gas, operators are becoming increasingly interested in unconventional ...

Evaluation of Specialized Cement System for Long-Term Steam Injection Well Integrity

“…5: a conventional system comprising cement and silica described by Stiles, 2006, and a foam cement system described by Witt, 2009. It may be concluded that to pass through the first steaming cycle, a cement system should have an optimum combination of compressive strength-to-Young's modulus ratio (CS/YM) and tensile strength-to-Young's modulus ratio (TS/YM). 5: a conventional system comprising cement and silica described by Stiles, 2006, and a foam cement system described by Witt, 2009. It may be concluded that to pass through the first steaming cycle, a cement system should have an optimum combination of compressive strength-to-Young's modulus ratio (CS/YM) and tensile strength-to-Young's modulus ratio (TS/YM).…”