SAGD start-up has considerations for both well integrity and warm-up efficiency. Interest in using insulated tubing to address issues related to both considerations is evolving. The scope of this work is to demonstrate how start-up performance is affected by the use of tubing insulation, both in terms of well integrity and reservoir warming efficiency. Both of these considerations are sensitive to operational and reservoir factors that are specific to the implementation. The basis for using insulated tubing for start-up insulation should therefore take those factors into consideration. This paper demonstrates the use of wellbore thermo-hydraulics modelling to determine the sensitivity of primary metrics of well integrity and SAGD start-up efficiency to the configuration of tubing, insulation, reservoir injectivity, and various thermal characteristics of casing, cement and formations. The wellbore thermo-hydraulics model includes heat transfer across tubing and casing, between fluid conduits and into the formation. Furthermore, it incorporates a convective heat transfer model to take into account fluid injection association with partial or full "bull-heading" into the reservoir. Boundary conditions allow injection rates to be ramped up consistent with field operations, and and the model calculates the pressure ramp-up associated with the transient mass flow rate applied to the well. The results include a comprehensive description of the transient temperature in the casing, corresponding to the applied mass injection transient. This information can be used for well integrity interpretations, and start-up rates can be evaluated to manage the risk associated with start-up. Furthermore, the injection temperature and steam quality distribution in the tubing strings and tubing/liner annulus can be determined over the start-up period and during the circulation phase as a basis for determining circulation duration required to reach conditions for SAGD start-up. Temperature distributions in the reservoir can also be determined at prescribed distances from the wellbore.

Industry experience indicates the vast majority of well failures in SAGD wells occur in the liner, and most of these appear to be related to a loss of subcool control. This paper presents an example of how two factors, well trajectory and reservoir performance, can combine to produce problems with subcool control that are difficult to discern under normal operation and likely to lead to a steam breakthrough event. Simulation of steam trap conformance is an important tool for optimizing SAGD efficiency, but it can also be instrumental for diagnosing, avoiding, and resolving subcool control issues. To be effective, the simulator must account for the parameters that govern conformance, which include reservoir performance, well geometry, reservoir properties, completion details, and operational controls. This example employs a rigorous simulation basis that captures the contributions of both injection well hydraulics and production well hydraulics to steam trap conformance, or the lack thereof. The example demonstrates how enhanced monitoring systems and procedures can be used to diagnose subcool control problems before a failure results. Furthermore, various mitigation strategies are explored to alleviate the subcool control problem and facilitate more efficient SAGD operation. The mitigation strategies include changes to the initial well design, such as customized injector or producer liners. The simulation basis enables the mitigation strategies to be assessed based on the uniformity and stability of the liquid level above the production well. The simulation results reveal different levels of effectiveness between the various mitigation options. This paper provides new insight into how factors like well trajectory and reservoir performance can compromise subcool control and explores creative solutions for improving SAGD performance.

Horizontal liners in extended-reach drilling (ERD) wells can experience severe loading during running. Sometimes, downhole loads approach the limits of the tubular system and must be actively managed to ensure long-term well integrity. This paper describes a Canadian thermal operator's approach to managing installation and service performance of slotted liner and wire-wrapped screen systems in a steam-assisted gravity drainage (SAGD) application with unwrapped reach ratios approaching 13:1, and the associated evolution of liner running practices. The Operator's approach combines well-characterized liner body installation loading limits and a rigsite digital solution that leverages available measurements and a real-time torque-and-drag and tubular integrity monitoring system to inform the drilling team during running. Surface loads and rates measured by the rig are used as input to top-down torque-and-drag analysis to estimate downhole load distributions. Those downhole load estimates are then compared to the local loading limits of the liner at all depths. These local loading states (and their associated uncertainties) are integrated into a safe surface loading envelope that is displayed to the drilling team and updated in real time to support running decisions. The evolution of the Operator's running practices has provided a strong basis for confidence in protecting a critical tubular system, and over 250 liner runs have been monitored to date using the digital system. Prior to implementing the system, a conservative approach to managing downhole loads during liner running was used. The integration of a strong engineering basis for the tubular structure with top-down torque-and-drag analysis and uncertainty characterization has provided a running optimization basis and measurable indicators of tubular health that can serve as an enduring quality record and be referenced for the remainder of the well life. Forecasting of running loads and liner limits to total depth has also enabled early recognition of running challenges and opportunities for optimization. Interestingly, the edge-deployed digital system has also led to operational efficiencies during the running process. Running stages involving higher risk to tubular integrity are recognized early and treated with due care, as are opportunities for increasing the efficiency of certain parts of the running process. As the Operator considers longer-reach wells, the system also provides insights into likely running challenges and provides strong history-match datasets that provide a field-calibrated basis for predicting running and tubular integrity limits. The Operator leveraged a novel digital methodology for monitoring liner system integrity during well construction. The ongoing use of this system has allowed optimization of planning, real-time, and post-run practices, and provides a well-conditioned historical dataset for future well planning. The methodology has enabled the Operator to unify work done by drilling engineers, consultants, and the rig crew for optimal liner system integrity and running efficiency.

Liner designs for extended-reach horizontal wells should include a unified approach to mechanical integrity that considers all stages of the well life, beginning with the well design and tubular selection process and extending to well construction, operation, and decommissioning. Digital oilfield technologies present considerable opportunities for optimizing liner installation and integrity, particularly through simulation, measurement, analysis, and prediction of running loads during well construction. This paper presents a multi-timescale workflow for optimizing liner installation and integrity in extended-reach horizontal wells. Given accurate models and planned well trajectories, liner installations can be simulated, problem depths identified, and mitigation plans put in place weeks to months before running liner. Since actual field running conditions rarely match design assumptions and predictions, it is beneficial to monitor and respond to installation loads in real time during the liner run. Furthermore, in a multi-well development, plans can be refined in the days between liner runs based on recent experience. Finally, on the order of months to years, well designs can be optimized based on field experience to meet both installation and operational needs. Design-time simulation, live monitoring and predictions, inter-well tuning, and long-term design optimization make a powerful combination. Damage to downhole components or excessive drag on the running string can be predicted and prevented. Capital costs and construction costs can be reduced substantially without incurring additional risk or compromising well performance. Integration of well construction loading can enable tailored operating strategies that account for well-specific construction issues. The workflow presented in this paper is novel in its breadth, spanning timescales from seconds out to years, and in its incorporation of new technologies for measuring and analyzing well construction data. Many elements of the workflow can be implemented independently to provide incremental gains and continuous improvement.

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.