REGINA, ESTEVAN – One of the ongoing themes of the Aquistore project – examining the injection of carbon dioxide into deep saline aquifers — has been the establishment of baseline parameters long before CO2 from the Boundary Dam Unit 3 Integrated Carbon Capture and Storage Project was ever injected.

One of those numerous baselines was running a “crosswell seismic tomography” survey between the injection and observation wells. That basically mean putting an energy source in one well, then putting a seismic array down the second, and doing a vertical seismic survey. The initial crosswell survey was done nine years ago before injection began. Now, starting on Oct. 25, the Petroleum Technology Research Centre (PTRC), which administers Aquistore for SaskPower, started doing a follow up crosswell seismic tomography survey.

Reached by phone and email from Regina on Oct. 25, Aquistore project manager Zeinab Movahedzadeh said, “Today PTRC is running a gauge ring test on both injection and observation wells to prepare for the crosswell seismic tomography that will happen in November/December of 2021.

“The gauge ring is a simple test used to confirm if certain tools can pass through restrictions in the well. The objective of this test is to find what is the TD (total depth) of the well and whether tools can reach to the injection intervals,” she said, adding they will also see “what is the minimum diameter at the bottom of the wells to ensure contractors for the crosswell survey can get down to the required depth with their source and receiver tools.”

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Movahedzadeh continued, “The Aquistore injection well did not receive any CO2 from June to September of 2021. The nature of injection at Aquistore is variable. The well has a history of solid accumulations/salt precipitations at the injection intervals in the well. This test will help understand whether there are new restrictions at the bottom of the well.”

The original plan was to do this work a few days later, but PTRC needed to move the gauge test up before the plant started producing CO2 again. Movahedzadeh noted she experienced  a short supply of wellsite supervisors when trying to conduct the test.

“It was a crazy few days. We had a lot of problems finding wellsite supervisors. Everybody’s busy with other jobs, but we were able to pull it together and it looks like things are happening at the site, which is exciting.”

Aquistore project manager Zeinab Movahedzadeh. Photo by Brian Zinchuk

“We had to move the test to the 25th because the capture plant is temporarily offline, and SaskPower is planning some tests at the capture plant. After the plant comes back online, they don’t want any interruptions. For our test, we want no CO2 injected into the wells, so it’s best to do it at a time that is not disruptive for SaskPower. This was a good opportunity to have the test moved to the 25th. But that meant it was only four or five days for me to find a wellsite supervisor, which was a little bit difficult. I think it’s obvious the oilpatch is busy again in Estevan area, given the difficulty finding a supervisor.”

The test involves a wireline and a crane. Movahedzadeh explained, “Crosswell seismic tomography is a survey technique that measures the seismic signal that is transmitted from a source that is located in one well to a receiver in a close-by well. The objective for the crosswell seismic tomography at Aquistore is to document the CO2 saturation between the injection and observation wells.

“To date, snapshots of the of the CO2 distribution are provided by PND logs showing the detailed CO2 saturation at the observation well, and 3D time-lapse seismic, which primarily show the areal extent of the CO2 plume. Crosswell tomography could provide the CO2 distribution/saturation between the wells, which will calibrate the flow simulations after 6-1/2 years of injection, calibrate the extensive 3D time-lapse seismic results, and improve estimates of capacity parameters. This would result in high added-value to existing information for the project.”

She added, “This is not the first crosswell survey at the Aquistore site. There was a pre injection baseline crosswell survey that was conducted at site in 2012. The value of a new survey comes from the availability of the baseline data versus the new CO2 totals in the formation of over 380,000 tonnes. Furthermore, the value of a time-lapse survey would warrant application of state-of-the-art imaging techniques (e.g., full waveform inversion (FWI)) that to date have not been applied. There will be two parts to the survey. Part A and Part B. Both geophone tool and distributed acoustic sensing (DAS fiber optic cables) will be used as receivers. This survey is planned to be complete in five days about a month from now.”

Part A involves running the source in the injection well, and the receiver in the observation well. Part B is just the opposite.

The PTRC set up a live feed video camera of the 24-hour operation, which can be seen here.

 

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