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Marathon applies to expand gas field pad on Kenai Peninsula Company continuing in-fill drilling program at Kenai gas field, in production since 1961 Kristen Nelson Petroleum News Editor-in-Chief
Marathon Oil Co. continues to look for gas at its Kenai gas field, an onshore Cook Inlet basin field which has been in production for more than 40 years.
In late July the company applied to expand Pad 41-18 at the field by 5.9 acres so that up to five additional wells can be drilled from the pad and pad operations can be reconfigured. The company said the project would be phased, with part of the work to be completed before Oct. 31 and the remainder during the 2006 summer construction season.
Marathon expanded the Kenai gas field 41-7 pad in 2003 to add four wells, and told regulators at that time that while the field has been producing gas since 1961, and is a mature field, “Marathon is still identifying promising pay intervals within the structure that have not been produced previously.”
Marathon said in a July 26 application for the Pad 41-18 expansion that within the last few years it “has engaged in a rigorous evaluation of reserve recovery and drilling locations. Recent drilling success on other pads has provided supporting data that developable gas reserves exist in this southern portion of the structure.” 2003, the last year for which the Alaska Division of Oil and Gas shows production figures, Kenai produced 28.6 billion cubic feet of natural gas from the Sterling, Beluga and Tyonek formations. The state estimates that the field has reserves of 181.6 bcf and that production from will continue through 2014. This pad’s first well drilled in 1971 The first well at the 41-18 pad, the KU 41-18 well, was completed in October 1971. “No construction records are available for this site and it is assumed that the pad was constructed in advance of drilling in either 1970 or 1971,” the company said.
When the wells were originally drilled “it appears that little consideration was given to the need for future well work or the potential that additional wells would be drilled from this location,” the company said.
There are five wells on Pad 41-18 now. The pad is in section 18, township 4 north, range 11 west, Seward Meridian. Marathon said two of the wells are producing gas, one is suspended and two are permitted as Class II disposal wells for exempt exploration and production wastes. Wastes are stored at the pad before being processed for downhole injection into the disposal wells.
Space is needed at the pad for additional production wells, Marathon told regulators, and to permit relocation of exploration and production storage and processing equipment away from existing wells, which prevent a workover rig from reaching the wells.
Earlier this year, the company said, “it became necessary to conduct a workover operation on one of the Class II wells and this in turn necessitated temporary relocation of facilities to enable the rig to access the pad and the well.” Marathon said further evaluation confirmed that surface equipment would have to be relocated to reach the remaining four wells. First of new wells would be drilled this year This year’s pad expansion would allow the drilling of two new wells; three additional could be drilled after the 2006 work. The relocation of waste handling and processing facilities will allow access to the existing wells with a workover rig. Once the waste handling and processing facilities are consolidated Marathon said it can then undertake production facility upgrades.
Marathon said the pad expansion is necessary “to develop gas reserves within the southern portion of the structure. … An updated reservoir analysis has identified five additional well locations that are necessary to effectively drain reserves within this portion of the structure.” There is no room on the existing pad to drill the wells.
Marathon said there is a pad to the north, Pad 41-7, but it isn’t possible to reach the additional reserves by drilling south from that pad because of “the shallow depth of the reservoirs and horizontal distance.” Pad 41-7 is approximately a mile to the north, and Marathon said with the shallow reservoir intervals the rock isn’t well compacted, resulting “in ‘soft rocks’ that do not retain competency after drilling and this condition is highly problematic in extended reach wells at shallow depths.” The current well pattern is also an issue: there would be interference problems with existing wells if new wells were drilled from Pad 41-7.
The new gas wells will be at the north and east portion of the phase I expansion to be completed this fall; one of the new wells would be drilled late this fall and the second in the first or second quarter of 2006. Phase II, expansion of the pad to the east and south, will accommodate production facilities and be used to reconfigure facilities used to store and process exempt wastes, and create sufficient space for the drilling of three additional wells. New control building will also be built In addition to pad expansion, Marathon said the work will also include construction of a new control building and an electric utility upgrade, which will be accomplished using existing overhead electric poles. A new water well will be drilled at the pad for drilling and production operations. Marathon said an existing water well is dedicated to the grind and injection process for the exempt waste.
A one-mile segment of new high-pressure gas pipeline from Pad 41-18 to Pad 41-7 may also be necessary, depending on the success of the new wells. “High-pressure gas and low-pressure gas production within the field must be conveyed in separate pipelines and the introduction of high-pressure gas into the existing system would be at the expense of downstream low-pressure gas wells,” the company said. Whether or not a new segment of high-pressure gas pipeline is needed will be confirmed after the first well is drilled. The earliest a pipeline segment could be constructed would be in the first quarter of 2006 during the winter construction season. Marathon said a new line to carry wastewater production between Pad 41-7 and Pad 41-18 may also be needed, to handle production water for disposal. Produced water is currently shipped in a small-diameter line that would be upgraded at the same time a gas line was built.
Pipeline permitting would be done after the need for the pipelines has been confirmed.
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