Excessive solids production and liner issues are familiar complications in maturing SAGD operations, potentially causing well integrity concerns. There are several factors that can occur, in isolation or in combination, to cause excessive solids production and/or liner failures in SAGD wells. Reservoir characteristics, well construction and known downhole conditions contribute to production results and potential liner degradation over time. The production strategy typically considers fluid mechanics, metallurgy, and thermal cycling to limit steam breakthrough, channeling, and/or low sub-cool events. Even with the best construction and production practices, the gradual accumulation of solids in a production well can limit optimal productivity. SAGD Operators may choose a downhole intervention to mitigate the potential of a future failure or require an intervention to prepare for liner remediation.
The paper begins by outlining common cleanout methods used in SAGD wells. Then, it discusses a SAGD downhole intervention in three stages: (1) a jetting venturi cleanout, (2) a gauge mill run, and (3) installation of a remedial liner system. The jetting venturi cleanout is comprised of concentric coiled tubing coupled with an engineered jet pump. It is designed to artificially lift wellbore materials, cleaning the SAGD wellbore while recording the volume of solids returned from a specific location. The gauge mill run confirms an acceptable diameter for smooth liner installation. These first two stages ensure seamless installation of the remedial liner system to mitigate detrimental mechanisms that limit production or impact well integrity.
Two case studies, in two heavy oil formations from two Operators, support the effectiveness of the SAGD liner intervention. The case summaries and results demonstrate the success of the SAGD liner intervention, corroborate its consistent and repeatable use and show its compatibility with remedial techniques in SAGD operations. The paper establishes the importance of effectively cleaning and clearing a SAGD wellbore in preparation for liner remediation and to provide insight into future well integrity operations.