St. Paul, AB Urban Well Abandonment Case Study
In 2014, the client was a licensee of a previously abandoned well within the town of St. Paul, Alberta. The client was contacted by the AER to test the well for soil methane levels as related to Directive 079: Surface Development in Proximity to Abandoned Wells.
The well was originally drilled as a gas well on the outskirts of St Paul, Alberta in 1946. The well was completed in two intervals and never produced. In 1955 the well was abandoned by a previous operator. In the early 1970’s the population of St. Paul, AB grew, and a residential area developed over the area of the abandoned well.
The development of the area from farmland to a residential neighborhood created several challenges for the project, not the least of which was locating the well. After looking at historical records and making some estimates as to the location of the well, the thought was that a house might have been constructed on top of the well when the area was developed in the 1970’s. After examining the home, it was determined, much to the relief of all involved, that the well was not located beneath any homes.
The next step in finding the well involved an extensive review of historical aerial photographs of the town from the time the well was drilled initially to the 1970’s when
The area around well center was excavated with a
An application was submitted to the Alberta Energy Regulator (AER) for approval to re-enter the well to complete tests and determine the correct course of action to abandon the well successfully.
The AER approved the application to proceed with the abandonment operations, and the well was reentered. A wellhead was installed below the ground surface to secure the well any natural gas from migrating to the surface. An underground vault was installed around the wellbore to allow for future access and to secure and conceal the well and ensure the safety of the public.
If We Can Abandon This Well, We Can Abandon Your Well!
With the well secure, tests were performed to determine the gas source. A small amount of gas was found to be migrating up the production casing as well as through the annulus between the casing and surface casing causing a surface casing vent flow. Gas samples were taken from each point and sent to the lab for analysis to help determine the formation source.
The location of the well provided some unique challenges compared to an average abandonment since the well is on a residential street. Safety of the residents and workers was our number one concern when working in a highly populated area with very little space. Codeco prepared and implemented a Risk Management Plan that consisted of a Risk Assessment Matrix, Congested Lease Risk Assessment, Proposed Site Layout, Fire and Explosion Prevention Plan, Traffic Control Plan and addressing many other safety concerns. A Site Specific Emergency Response Plan (ERP) was prepared to ensure residents safety in case of an actual emergency.
Behind the scenes, the Codeco engineering team reviewed the well details and prepared a program that included procedures to drill out the existing cement plugs within the well, and re-abandon the well following the regulations contained in Alberta Energy and Resources, Directive 20 Well Abandonment Guide to stop the leaking gas from entering the well.
Once the client and the AER approved the plan, a town hall meeting was conducted by Codeco and the client to inform the residents about the nature of the project, the operations that were to take place and answer any questions or concerns they may have prior beginning the abandonment operation.
With all government approvals in place, residents notified and informed operations to re-abandon the well commenced. A service rig was mobilized and rigged up on the street, a drilling assembly was installed on the work string and existing cement inside the casing from the original abandonment was drilled out. Cased hole logs were run to identify casing and cement integrity. The casing integrity log indicated that the condition of the casing was in despair including many areas of potential and existing holes throughout the production casing. The cement bond indicated that there was very little cement originally circulated between the casing and the open hole, which was common at the time the well was drilled in the 1940’s. Cement quality was poor and the cement top was low and below the base of ground water. A noise/temperature log was also run to help identify the source of the gas that had been migrating up the hole previously.
Once the gas sources were identified, a total of 5 cement squeezes were performed at different intervals to stop the gas from entering the wellbore and prevent the gas from migrating on the outside of the casing.
The final results were successful! Since the re-abandonment in August 2017, there is no sign of leaking gas or increased methane levels through the surface casing vent, production casing or the outside of the surface casing. In discussions with the AER after the job, we agreed to monitor the well until the summer of 2018 to confirm there are no changes before cutting and capping the well, filling the hole around well center and re-seeding to grass.
Assuming tests continue to be negative for any sign of gas by next summer, the final work will be completed, and there will be no evidence that a well existed on the street in St. Paul, AB.
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