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Cement Integrity Multiclient Project

Cement is critical to well integrity, being responsible for hydraulic isolation between producing zones and the surface, as well as between formations traversed by the wellbore. Cement also provides structural support to casing strings and reduces the potential for casing movement or burst. Successful cement selection and placement is important to well economics and responsible development of energy resources. A successful cement program will provide effective isolation throughout the life of the well.

SAGD and other thermal recovery processes introduce a number of unique challenges for cement integrity compared to conventional or offshore oil recovery projects:

• High thermal loading on casing and cement due to high wellbore temperatures (i.e., typically 200°C or greater). This results in greater thermal expansion of the casing, increased possibility for cement degradation/strength retrogression, and formation movements.

• High number of temperature and pressure cycles. Although SAGD is designed to be a “continuous” oil recovery process, facility outages, steam management, pump failures, or other well issues result in shutdowns that cause temperature and pressure cycling.

• Comparatively shallow reservoir depths. This provides less length to accumulate flow restriction through the cement sheath or to build confining stress that is beneficial to improving the elastic range (or deformation tolerance) of cement.

The early warm-up period for a SAGD well is expected to provide the most severe loading on the cement sheath. Heat transfer and temperature distributions are very dynamic during this period. Severe radial temperature gradients cause large differences in thermal strain between the casing and cement. This can cause shear or tensile failure of the cement sheath that could cause permanent changes in the sheath’s global permeability or cracks (i.e., leakage paths) to form.

The Cement Integrity Multiclient Project is focused on evaluating the impact of this early warm-up on long-term cement integrity. Through the first and second stages of the project, a combination of physical testing and finite element analysis has been used to evaluate the response of cement in SAGD environments and develop a design basis for selection of cement systems in SAGD wells. The design basis will:

• Support operator decisions on the selection of cement blends
• Identify directions for future cement development
• Identify cement quality assurance activities

For more information on this project and upcoming participation opportunities, contact Mark Chartier, at +1 (780) 784–3199 or mchartier@noetic.ca