|
Chevron looking to expand Cook Inlet natural gas storage The company is asking for permission to store natural gas in ‘nearly depleted’ sand at Ivan River unit on west side of Cook Inlet; would provide more deliverability at high demand Eric Lidji Petroleum News
Chevron is looking to store more natural gas in Cook Inlet.
Through its affiliate Union Oil Company of California, Chevron is asking the Alaska Oil and Gas Conservation Commission to begin injection at the Ivan River unit this summer.
The unit sits on the west side of Cook Inlet, near the mouth of the Susitna River.
Excluding the Kenai liquefied natural 8gas plant that sometimes supplies Southcentral, Chevron owns more storage capacity than any other company in Cook Inlet, more than 60 million cubic feet per day at full capacity. The proposed injections could add as much as 20 million cubic feet per day, increasing deliverability during periods of high demand.
Chevron also operates storage facilities at the Pretty Creek field due west of Ivan River and at the Swanson River field on the Kenai Peninsula. Marathon Oil operates storage at the Kenai gas field. Aurora Gas wants to start third-party storage at the Nicolai Creek field.
Additional storage is needed in Cook Inlet because of the extreme seasonal swings in subarctic Alaska and because deliverability is falling in the aging Cook Inlet basin.
Chevron’s proposal calls for injecting excess natural gas, mostly methane, into a “nearly depleted” gas-bearing sand at Ivan River using the existing IRU 44-36 well. The initial plans calls for converting IRU 44-36 into a production and injection well, but the company said it might decide to work over or re-drill IRU 44-36, or drill additional wells.
A nearly depleted Beluga sand Chevron wants to use the Beluga 71-3 sand for storage.
The Beluga formation is wedged between the Lower Sterling and the Tyonek formations, and all three formations have produced natural gas at Ivan River. Several wells drilled in the unit have encountered the top of the Beluga 71-3 sand at depths around 5,300 feet.
While other wells have passed through the sand, only IRU 44-36 ever produced from it.
Chevron believes the Beluga 71-3 sand at the northern end of the unit around IRU 44-36 is isolated from the southern end of the unit, because the sand encountered at the IRU 41-01 well to the south “appears to transition to overbank siltstone and silty mudstone.”
Chevron said the Beluga 71-3 sand is isolated from above and beyond by layers of siltstone and by coal seams ranging in thickness from four to six feet that “act as a seal.”
There are three wells within a quarter mile radius of IRU 44-36, but Chevron said they don’t pose a problem for potential storage in the Beluga 71-3 sand. IRU 14-31 and IRU 13-31 are active Class II disposal wells cemented above the proposed gas storage zone. IRU 11-06 is a producing well, but is also cemented above the proposed storage zone.
Chevron said it would test IRU 44-36 for mechanical integrity on a regular basis. The company also said that well tests in February 1993 and December 2009 show the injection pressure proposed for gas storage would not cause the reservoir to fracture.
Drawn out production history Ivan River was discovered in September 1966, but the lack of infrastructure on the west side of Cook Inlet limited activity at the unit. Only three wells were drilled through 1975.
Union Oil brought the field into production in 1990 after building a pipeline into the existing Enstar Natural Gas grid, and drilled development wells in 1992 and 1993.
Production peaked at the field in 1994 at nearly 16 billion cubic feet. The unit produced 80.3 bcf through the end of 2009, the most recent figures available from the state.
Union Oil drilled IRU 44-36 in March 1993, perforating the Sterling 58-4, Sterling 59-6 and Beluga 71-3 sands. Initially, the well co-mingled production from all three of those gas-bearing zones, but production peaked in September 1993 at 10.731 million cubic feet per day.
Water breakthrough jeopardized production in January 1995 and attempts to plug the breakthrough chemically failed. By September 1995, the well no longer produced.
A rig workover in September 2001 re-perforated the initial three sands and opened three deeper sands, but water, sand and coal kept the lower sands from producing.
In January 2002, production from Beluga 71-3 peaked at 6.6 million cubic feet per day. It continued to produce until March 2004, when water and pressure problems afflicted the well. Union Oil isolated the interval, hoping to produce from shallower Sterling sands, but those intervals brought sand and water into the well bore and IRU 44-36 hasn’t produced since.
Chevron estimates 3.9 bcf of original gas in place in the Beluga 71-3 sand.
| 