Providing coverage of Alaska and northern Canada's oil and gas industry
June 2022

Vol. 27, No. 26 Week of June 26, 2022

Ensuring gas supplies

CINGSA takes actions to ensure continuing reliable Southcentral gas storage

Alan Bailey

for Petroleum News

During a Regulatory Commission of Alaska public meeting on June 8 officials of Cook Inlet Natural Gas Storage Alaska described actions that they have taken in the past year to ensure the continuing reliability of the natural gas storage services that they provide for electric and gas utilities in Southcentral Alaska. The CINGSA facility, on the Kenai Peninsula, stores gas in what used to be a subsurface sand reservoir of the Cannery Loop gas field, south of the city of Kenai.

In operation since 2012

The facility first went into operation in April 2012, in anticipation of the deliverability of gas from Cook Inlet gas fields falling below the levels required to meet peak winter gas demand in the region. Essentially, as the gas fields declined, there remained enough total gas to meet local utilities’ annual needs, but the maximum deliverability, or rate of gas supply, was dropping below the levels required during peak winter demand. So, CINGSA provides a vital service in which utilities can store excess produced gas when gas demand is low, especially during the summer, and then retrieve the gas during high winter demand to ensure sufficient gas can be delivered.

Natural gas is currently the primary fuel used for heating buildings and generating electricity in Southcentral Alaska. Any shortfall in gas deliverability, especially during the winter, would cause major problems for businesses and residents.

The storage facility has five wells that are used for both injecting and retrieving gas. The facility can potentially store up to 11 billion cubic feet for future withdrawal, with additional gas also being stored to maintain the pressure in the underground reservoir. The original design concept assumed that all five wells would have similar performance characteristics. However, in practice each well has performed differently, a factor that impacts some of the well monitoring and management activities.

Dealing with reservoir sand

One issue is the possible blocking of well bores by sand that can be sucked into a well from the reservoir. CINGSA conducts tests for sand entering into the wells at different fluid withdrawal pressures, Matt Federle, CINGSA director of storage operations, explained to the commission. The idea is to keep the withdrawal pressures at levels below those at which sand will become a problem and, thus, ensure that the wells continue to perform effectively.

CINGSA President John Sims commented that this testing is particularly important for well 1, which is by far the strongest performing well in the facility. Following past experience of another well sanding in, the company cannot take any risk of having the same problem happen with well 1, he said.

Federle commented that well 1 is a critical well in that it contributes just over 40% of total field activity.

Water issues in well 5

Another issue is the potential for water to flow into a well bore from the reservoir and reduce the flow of gas. When gas is injected into a well during the summer, the gas tends to push water away from the well in the reservoir rock. However, during gas withdrawals during the winter water tends to move back towards the well and can enter the well, thus diminishing gas production. This phenomenon has proven particularly problematic for well 5, Federle said. As a consequence, the gas withdrawal performance of this well had progressively declined since the well went into operation in 2012. To try to rectify the problem, last year CINGSA installed small diameter tubing into the well, to increase the flow velocity up the well. So far the results of doing this have been very promising, with gas flow rates increasing to levels near those of the first year of operation, Federle said.

Federle particularly thanked consulting company PRA for its work in designing this “velocity string” arrangement.

Compressor upgrade

A further issue for CINGSA revolves around the compressor power needed to pump stored gas into the storage facility reservoir - achieving the maximum storage capacity of 11 billion cubic feet would have overloaded the compression system. Consequently CINGSA has been limiting the storage capacity to around 10.3 billion cubic feet, Federle said. However, in November and December CINGSA upgraded the compressor horsepower.

“It puts us into a much more reliable position to deliver an uninterrupted service,” Federle said.

Continuing reliable service

And CINGSA has been continuing its record of reliably supporting the needs of its customers. Sustained abnormally cold weather last November resulted in high rates of gas withdrawal for several weeks. However, CINGSA maintained a substantial inventory of stored gas and was able to continue an uninterrupted firm service of gas withdrawals for its customers throughout the winter - major gas injections for the summer injection period have already begun, Federle said.

“It was a good season,” he said.

Asked about any plans for expanding the CINGSA facility or, perhaps, constructing an additional storage facility, Sims commented that his company is evaluating this possibility, especially given recent discussions around the reliability of future gas supplies.

“The one thing that seems to be unanimously clear and obvious is that storage is going to be critical to meeting all of the utilities’ needs in the future,” Sims said. “I think that you can anticipate something very shortly on additional wells. I think you can also anticipate additional storage options being evaluated and, when we have clear line of sight for additional storage, we will absolutely be bringing them in front of the commission, more than likely in a public setting.”

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