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Cement is critical to well integrity. It provides hydraulic isolation, preventing fluid flow between producing zones, ground water aquifers, and the surface. In steam stimulated wells, such as for Steam Assisted Gravity Drainage (SAGD) or Cyclic Steam Stimulation (CSS), the heat-up period places severe mechanical loading on the cement sheath. Heat is transferred from high temperature steam, through completion strings and annular fluids, to the casing, cement and formation. Thermal expansion of the casing combined with axial constraint make radial expansion of the casing the most severe in the energy industry. Furthermore, with constrained expansion of the cement, the range of deformations that must be accommodated by the cement sheath while maintaining isolation is challenging. These deformations can cause shear or tensile failure of the cement and result in leakage paths through the cement (e.g. cracks or global changes in cement permeability), or leave a micro-annulus when recovery has been completed and thermal operations halt. This paper describes the impact of key thermal and mechanical properties on the structural performance of cement blends in thermally stimulated wells. The work is based on laboratory testing of thermal cement blends and the use of Finite Element Analysis (FEA) to examine cement performance under operating conditions. The findings provide insight into important cement behaviours that impact longterm integrity of cement and highlight the significance of conducting tests under field representative conditions. Results indicate the importance of compressive strengths, flexibility, and shrinkage/expansion characteristics to ensure the cement sheath remains structurally intact during initial heat-up.

Although thermal heavy oil recovery methods are extensively used, no unified and standardized basis exists for selecting materials and configuring intermediate (production) casing/connection systems for these extreme-service applications. Thermal intermediate casing systems must accommodate a wide variety of mechanical and environmental loads sustained during well construction, thermal service at temperatures exceeding 200°C, and well abandonment. Numerous operator- and field-specific designs have been used with good success and only a few isolated challenges, but industry's use of its operating experience to calibrate tubular design bases for future wells has been limited. This paper identifies the benefits and components of a unified casing system design basis for thermal wells, aimed to be technically comprehensive, inclusive of the available elements of industry's collective knowledge and experience, and adaptable to technological advancements. The technical element of the unified basis broadly relates to the engineering foundation used to make three primary design selections: material, pipe body, and connections. For each design selection, the paper provides an overview of the associated technological challenges and the current state of the industry in addressing those challenges, including the commonly-adopted design approaches. Key performance considerations include integrity during well construction, connection thermal service structural integrity, pipe thermal service integrity and deformation tolerance, connection sealability, and casing system environmental cracking resistance. Where applicable, the paper identifies interdependencies that exist between design selections (for instance, the impact of pipe material selection on the thermally-induced axial load that must be borne by the tubular and connection), and discusses mechanisms for accounting for those added complexities in the design. Ultimately, the intent of this paper is to provide a framework for referencing existing technical knowledge and for considering further development and field benchmarking work that will reduce the technological uncertainty and increase simplicity in thermal casing system designs. Industry will benefit from a unified engineering approach that offers operators sufficient flexibility to accommodate application requirements and prior experience.

Summary Slotted liner is a sand–control technology used for completion of thermal wells. During installation, liners are subjected to tensile and compressive loads generated by string weight, wellbore drag, and bending when run through curved wellbores. Additionally, torque might be applied to “break” friction, when needed, to reduce axial drag and extend reach. These conditions lead to combined loading of liners with simultaneous axial, bending, and torsional loads. Combined loading that exceeds the elastic capacity of the liner during installation can alter the structural capacity of the liner and reduce its ability to withstand subsequent operational loads. In particular, permanent deformation of liner struts during installation could create weak zones that trigger localization of deformations and liner failure under thermal–service loading conditions. Further, the presence of residual torque (from installation) can trigger and exacerbate the tendency of the liner struts to buckle. Previously published works described slotted–liner installation limits and thermal operating limits separately. This paper examines the impact that rotation (during installation) can have on the subsequent thermal–service capacity and sand–control performance of a slotted liner. Specifically, the relationships between both plastic twist and residual torque from installation loads and the critical strain capacity and slot–width changes of a slotted liner under constrained thermal expansion were studied. Results demonstrated that a slotted liner can tolerate some plastic twist (during installation) without a significant impact on slot width or thermal–service performance. However, large amounts of plastic twist or residual torque from installation can bias the liner to fail in torsional buckling during thermal service. Slotted–liner tolerance, to both the plastic twist applied during installation and the residual torque remaining after installation, varies with liner configuration. Small amounts of plastic twist (0.5°/m) imposed on a high–density 60–slots–per–column (spc) liner resulted in a reduction in thermal–service capacity. In contrast, a low–density 35–spc liner with substantial imposed plastic twist (4°/m) demonstrated negligible changes in performance. Residual torque has a greater potential to impact liner performance, and its effect is less sensitive to the slotting density. Both the high–density 60–spc liner and the low–density 35–spc liner showed significant incremental slot–width changes during thermal service resulting from 5 kN·m of residual torque. The findings of this work provided the basis for a proposed method to select appropriate engineering limits for the torque that can be applied safely to a slotted liner during running and for recommendations to reduce the potential for residual torque following installation.

A family of new polymeric nonlinear optical materials with high second order non-linearities, good thermo-oxidative and reorientational stability, and low waveguide losses have been prepared from a series of chromophores containing hydrazone moieties. These new polymerizable chromophores can be readily prepared by the acid-catalyzed condensation of substituted arylhydrazines with functionalized ketones or aldehydes to give molecules that have μ3 values up to 2440 × 10−48 esu (1579 nm) in solution. Thermoplastic polycarbonates and poly(hydroxy ethers) containing hydrazone chromophores have been prepared with Tg's ranging from 135 °C to 285 °C. Epoxy systems crosslinked with amino-functional arylhydrazones, have high d33 values and high glass transition temperatures, albeit with lower relative thermo-oxidative stability. Simple Mach-Zehnder modulators and registered multi-level structures based on these polymers have been reported previously. One device, prepared from a hydrazone-containing poly(hydroxy ether), has an r33 value of 10 pm/V (1320 nm), and retains most of that activity to 140 °C.