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Hilcorp wants to increase CIGGS flow Tells RCA additional gas compression needed on east side of Cook Inlet to move more gas across inlet as west-side production drops Alan Bailey Petroleum News
Hilcorp Alaska is proposing to install additional gas compression in the natural gas pipeline system on the east side of Cook Inlet to increase the maximum flow rate of gas east to west through the Cook Inlet Gas Gathering System, or CIGGS, the dual pipeline that runs under the inlet, Ed Jaroch, Hilcorp manager of regulated pipelines, told the Regulatory Commission of Alaska on Sept. 10.
The idea is to add two new compressors to the existing single compressor at the pipeline junction at the east end of CIGGS, to increase the east to west capacity on the line from 62 million cubic feet per day, as at present, to some 118 million cubic feet per day, Jaroch said. The upgrade would also result in a level of redundancy in the compression equipment, thus enabling continuity of gas supplies should a compressor fail, Jaroch explained.
Hilcorp anticipates the compressor upgrade to cost some $16 million. The upgrade is necessary to ensure an adequate flow of gas through the gas transmission pipeline system on the west side of the inlet up toward the Matanuska and Susitna valleys, the company says. The project is currently in a preliminary design phase, with an anticipated startup of the additional compression in the fall of 2015.
Changing usage Built during the early years of the Cook Inlet gas industry, at a time when the huge gas fields of the region produced a surplus of gas, CIGGS was originally designed to deliver excess gas from fields on the west side of the inlet to liquefied natural gas and fertilizer plants at Nikiski on the west coast of the Kenai Peninsula. Chugach Electric Association’s major gas-fired power station was built at Beluga on the west side of the inlet, to use gas from the nearby Beluga gas field. And in the 1980s gas utility Enstar Natural Gas Co. built a transmission line on the west side of the inlet, for shipping gas supplies north from Beluga into the Matanuska and Susitna valleys.
But over the years, as production from the Cook Inlet gas fields declined, the Nikiski fertilizer plant closed. The liquefied natural gas plant was eventually mothballed, although it has since re-opened, albeit with a relatively low throughput. And production declines from the fields on the west side of the inlet have become especially notable in comparison to production on the east side.
Single compressor In 2011, amid growing concerns about the continuity of gas supplies for the Beluga power station, Marathon Oil Co., the then owner of CIGGS, installed a single compressor at the junction between the Kenai Nikiski pipeline and CIGGS, on the Kenai Peninsula. By activating the new compressor, the gas pressure at the pipeline junction could be increased, thus pushing gas into CIGGS, westward under the inlet.
The completion of the Cook Inlet Natural Gas Storage Alaska facility near Kenai provided further reason for having the ability to flow gas east to west through CIGGS - the bidirectional flow capability of the pipeline system would provide needed flexibility in directing gas from CIGGS to support high utility gas demand during cold winter weather.
Need for increase As gas production from the west side gas fields continues to decline, while gas demand in the Matanuska and Susitna valleys continues to increase, there is a need to increase the CIGGS east-to-west capacity, to ensure an adequate flow of gas through the pipeline system on the west side of the inlet, Jaroch told the commission.
In the winter of 2013-14, during efforts to maintain adequate gas supplies, there were a couple of days when east to west flow in CIGGS reached its 62 million-cubic-feet-per-day limit, Jaroch said. And in future winters, if there were to be some unanticipated disruption to gas supplies on the west side of the inlet, there may be insufficient gas available through CIGGS to meet demand unless the east to west capacity increases, he said.
Since bidirectional flow started on CIGGS, the east to west flow through the system has gradually increased and Hilcorp anticipates the east-to-west throughput continuing to rise, Jaroch said.
Two more compressors After evaluating different options for increased compression at the eastern end of CIGGS, Hilcorp decided to add two compressors of the same type as the single compressor that Marathon had previously installed, Jaroch said, commenting that this arrangement would simplify maintenance arrangements for the equipment.
In routine operations, with gas flowing east to west through CIGGS, Hilcorp would have just one of the compressors working. But should throughput needs exceed the capacity of a single machine, a second compressor would kick in, almost doubling the pipeline throughput limit. The third compressor would be for emergency use, if two compressors are needed but one of the compressors is offline.
The next step in the compression project is to do the detailed engineering and design work, with a view to finding out by the end of October whether the companies that ship gas through the pipeline network will support the project. In terms of impacts on the pipeline tariffs, $1 million of expenditure would generally correlate with a tariff impact of about 0.3 cents per thousand cubic feet of gas shipped, Jaroch said.
Timeline Critical to the project timeline is a need to order the compressors in November of this year. And Hilcorp anticipates RCA approval for the compression upgrade in April 2015, so that the new compression can be in service for the winter of 2015-16.
Jaroch said that Hilcorp is also considering, but has not yet made a decision on, another $10.8 million project that would involve installing another compressor in the pipeline system at East Foreland on the Kenai Peninsula. That would further increase the east to west capacity on CIGGS to 165 million cubic feet per day. By enabling more gas to be shipped up the west side of Cook Inlet, that project would mitigate the risk of a problem with one of the two Enstar gas lines under Turnagain Arm that supply gas to Anchorage, Jaroch said.
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