Gas flow at the CO2 Lab site
Top image: Gas pockets in the wells at the UNIS CO2 Lab site create challenges for the scientists. Photo: Alvar Brathen/UNIS.
Recently there has been substantial gas flow from two of the wells drilled at the CO2 Lab well park in Adventdalen. This creates challenges for the operation on the well site and the scientists are looking at several solutions.
14 September 2012
Text: Eva Therese Jenssen
The sedimentary bedrocks of Svalbard contain several layers with organic material, which might produce gas that seeps through the bedrock and get pocketed in other bedrock layers. Seepage of natural gas from the ground is common at drilling sites, for example at coal prospecting drill sites.
The UNIS CO2 lab has so far drilled seven deeper wells out in Adventdalen over the past couple of summers. The wells’ depths vary between 190 m and 970 m.
The lab now faces a new challenge: In two of the wells there is recorded increased pressure due to substantial gas flow. One of the affected wells, drilled this summer, is 703 m deep. The gas flow is quite substantial, giving a pressure of nearly 25 bars in the top of the well.
Water injection tests
– Over the next few days we will perform water injection tests in this particular well, explained UNIS Professor Alvar Braathen, one of the principal investigators in the UNIS CO2 Lab project.
The water injection tests will give the scientists more detailed information about the reservoir.
The main goal is to further establish how fast and how much CO2 can be pumped into the rocks at 670-700 m depth. The on-going tests build on promising results from 2010 and 2011.
– As our project focuses on CO2 storage, not gas, we hope that the water injections will remove the gas from the well but, to be on the safe side, we are also prepared for increased gas flow, he said.
The scientists cannot draw any final conclusions before the water injection tests are completed in a few days.
– Our headache is that we need access to instruments inside the wells, and we cannot open them before we remove the gas pressure. We burned gas from the well last week, and with a controlled gas flow it actually took hours before the gas pressure was reduced down to atmospheric pressure, said Braathen.
In addition to the CO2 research, the scientists need to find out how much gas there is in the well and in the reservoir as a whole. A spin-off could be a model for gas migration into and within the reservoir.
These wells are closed and opened several times to remove or insert new instrumentation. Thus, if there is increased pressure in the wells, it has to be dealt with before the well is opened.
– We are in the process of implementing safety measures in order to handle this gas flow, said Fred Skancke Hansen, director of HSE at UNIS. The concrete measures will include routines for monitoring the pressure on the well-head as well as measures to prevent unwanted access to the wells.
Measures might include airing out the gas or burning it off. Another solution could be a shut-down of the well, Hansen said.
Currently the gas flow pressure evens out at 25 bar, but the well can handle a pressure of up to 300 bar, according to Braathen.
Heavy machinery is used at the drill site in Adventdalen, and in the area there are traces on the tundra of the on-going operations.
– We realize this does not look very good, but we have the full intention of cleaning up after the drill project is completed. The CO2 Lab is a project with focus on the environment and thus we do not want any negative impact on the local environment, said Skancke Hansen.
The clean-up does not only involve removing the heavy equipment and protecting the well heads, but also restoring the tundra as far as possible back to a normal condition.
UNIS is also currently cleaning up the area around the old aurora station where old scientific equipment are disassembled and removed.