A Shot in the Dark: Sustained Casing Pressure Eliminated in 10 Wells Leveraging Advanced Logging, Sealant, and Monitoring Technologies

Abstract The following paper details the best practices and lessons learned from a ten well case study where an operator and technology company deployed a new process for identifying defects in cemented annuli, sealing the leakage pathways with a biogenic sealant, and confirming success through real-time gas flow meter devices on surface and post-treatment bond logs. Each well deployed the same pre-treatment logging and full raw and segmented waveform analysis to identify intervals in need of remediation to stop gas flow. Each well was prepared for treatment with the same perforation strategy to maintain consistency in understanding leakage pathway intersection capabilities in the cemented annulus. Real-time permeability modification to the cement sheath was measured while squeezing sealant fluids downhole with each treatment squeezed under a packer for each well. Impact to the sustained casing pressure were also monitored simultaneously on surface by measuring real-time gas flow rate up the cemented annulus. Each of the ten wells treated experienced a 100% reduction in annular gas flow, passing bubble tests to satisfy Colorado Energy and Carbon Management (ECMC) rules for permanent plug and abandonment. Pre-treatment log analysis aided in selecting intervals and maintaining treatment consistency with each cemented annular treatment at an initial injection rate of 2 gallons per minute (gpm) or less. Several wells required additional shallower treatments due to little or no impact to the annular gas flow by the deeper perforated interval and subsequent treatment. Hydrochloric acid (HCL) was required on approximately half of the wells and was delivered as the first stage of treatment prior to injecting sealant to either 1) evaluate the impact to gas flow rate on surface or 2) achieve an initial feed rate of at least 0.25 gpm into the cemented annulus. The successful sealing achieved was confirmed by a continuous reduction in injection rates during treatment, the presence of new solids visible in the post-treatment cement bond logs, and a real-time reduction in annular gas flow rates at surface. Wells with sustained casing pressure are often among the most difficult and expensive to remediate due to difficulty in confirming successful intersection of leakage pathways within the cement and their subsequent sealing. By taking a more granular approach to pre-treatment log analysis, utilization of a sub-micron biogenic sealant, and gas flow meters at surface to measure real-time impact to gas, solving difficult sustained casing pressure problems is no longer a shot in the dark.