STATE OF ALASKA
OIL AND GAS CONSERVATION COMMISSION
3001 Porcupine Drive
Anchorage, Alaska 99501-3192
Re: THE APPLICATION OF
Disposal Injection Order No. 15
MARATHON OIL COMPANY
North Trading Bay Unit S-5 well
("Marathon") for an order allowing the
North Trading Bay Unit S-5 well
underground disposal of Class II fluids in )
the North Trading Bay Unit S-5 well.
August 31, 1998
IT APPEARING THAT:
By letter dated June 9, 1998, Marathon requested authorization from the
Alaska Oil and Gas Conservation Commission to dispose of Class II oil field
waste fluids by underground injection into the North Trading Bay Unit S-5
well, located on the Spark Platform.
The Commission published notice of an opportunity for public hearing in
the Anchorage Daily News on June 12, 1998.
The Commission did not receive protest or a request for a public hearing.
Marathon is the operator of the North Trading Bay Unit ("NTBU"). There
are no other operators within a one-quarter mile radius of the proposed
disposal injection project. The State of Alaska is the surface owner.
Marathon and Unocal are the only working interest owners within the NTBU.
The U.S. Environmental Protection Agency has exempted portions of aquifers
beneath the Cook Inlet described by a one-quarter mile area beyond and
lying directly below the Trading Bay Field. C.F.R. § 147.102(b)(2)(iv).
The NTBU is within the geographical area known as the Trading Bay Field.
Fluids proposed for disposal will consist of Class II oil field waste fluids
associated with the production of natural gas from the NTBU, and primarily
will be produced water and associated natural gas condensate from the NTBU
S-2rd well. The NTBU S-2rd well is currently producing less than 200 barrels
of water per day.
The NTBU S-5 well was originally drilled as a Hemlock and "G" oil producer
in 1969. The well was converted to a waterflood injector in 1974. Over
13 million barrels of water were injected into the well between December
1974 and March 1981.
Marathon suspended NTBU Hemlock and "G" zone oil production in 1992. At
the time of shut in, the cumulative oil recovery exceeded 40% of the original
oil in place. Combined with the high water cut of wells, Marathon concluded
that the Hemlock and "G" zones had been fully swept and no longer had economic
The Hemlock and "G" zones in the NTBU are common to and correlate with
the 10,070¢ – 10,635¢
measured depth ("MD") interval in the Texaco-Superior TS No. 1 well as
defined by Conservation Order 69.
The proposed waste disposal will occur in the depleted Hemlock and "G"
zones through existing perforations located between 10,826¢
-11,397¢ MD in the NTBU S-5 well.
The depleted Hemlock and "G" zones are separated from the overlying gas
productive sands of the "basal F" and "upper G" formations by an aggregate
thickness of over 200¢ of shale and coal
The NTBU S-2rd well was recompleted in 1996 to develop gas reserves from
the "basal F" and "upper G" formations.
Produced water from the NTBU S-2rd well is currently being disposed of
down the annulus of the NTBU S-4 well under the authority of Disposal Injection
Order #13, however, produced water rates continue to increase and injection
pressures are approaching the pressure limitations of the S-4 well.
The requested maximum injection rate for the NTBU S-5 well is 1000 barrels
of fluid per day. The anticipated maximum and average surface injection
pressures are 3000 psi and 1000 psi, respectively.
Model studies indicate that fracture growth out of the proposed disposal
zone will not occur under the estimated injection pressures and rates.
The NTBU S-5 well was constructed with 13 3/8¢
¢ , 61 lb./ft, K-55 surface casing set
at 2,245¢ MD and cemented to surface, and
9 5/8¢ ¢
, 47 lb./ft BTC, N-80 and P-110 production casing set at 11, 527¢
MD and cemented to 7998¢ MD (calculated).
The well is equipped with tubing and packer.
The NTBU S-5 well passed a mechanical integrity test of the casing-tubing
annulus on June 12, 1998.
NOW, THEREFORE, IT IS ORDERED THAT:
The requirements of 20 AAC 25.252 for authorization to dispose of Class
II fluids in the NTBU S-5 well have been met.
Waste fluids authorized for disposal under this order will consist exclusively
of Class II wastes generated from the production of natural gas from the
Movement of waste fluids will be confined within appropriate receiving
intervals by confining lithology, cement isolation of the perforated intervals,
and operating parameters.
Monitoring of disposal rates and pressures will help ensure fluids are
contained within the disposal interval. Abnormalities in operating conditions
may be an indication that fluid is escaping beyond the authorized disposal
Disposal injection into the NTBU S-5 well will not occur into, through,
or above a non-exempt freshwater aquifer, and will not result in an increased
risk of movement of fluids into a freshwater source.
The mechanical integrity of this well has been demonstrated in accordance
with 20 AAC 25.412.
Disposal injection operations in the NTBU S-5 well will not cause waste
nor jeopardize correlative rights, and will result in greater ultimate
recovery from the NTBU.
Rule 1 Authorized Injection Strata for Disposal
Class II oil field fluids may be injected into the NTBU S-5 well in
conformance with 20 AAC 25 for the purpose of disposal into strata that
is common to and correlates with the 10,070¢
– 10,635¢ MD interval in the Texaco-Superior
TS No. 1 well.
Rule 2 Demonstration of Tubing/Casing Annulus Mechanical Integrity
The tubing/casing annulus must be tested for mechanical integrity in
accordance with 20 AAC 25.412 prior to initiating injection and at least
once every four years. A test surface pressure of 1500 psi or 0.25 psi/ft.
multiplied by the vertical depth of the packer, whichever is greater, but
not to exceed a hoop stress greater than 70% of the minimum yield strength
of the casing is to be used. The test pressure must show stabilizing pressure
and a decline of less than 10% in a thirty-minute period. The Commission
must be notified at least twenty-four (24) hours in advance to enable a
representative to witness pressure tests.
Rule 3 Well Integrity Failure
Whenever disposal rates and/or operating pressure observations or pressure
tests indicate pressure communication or leakage of any casing, tubing
or packer, the operator must notify the Commission on the first working
day following the observation, obtain Commission approval of a plan for
corrective action and obtain Commission approval to continue injection.
Rule 4 Operational Criteria
Maximum disposal rates shall not exceed 1000 bbls/day. Maximum surface
disposal pressure shall not exceed 3000 psi.
Operating parameters including disposal rate, disposal pressure, annulus
pressure and fluid volume must be monitored and reported according to the
requirements of 20 AAC 25.432. An annual report evaluating the performance
of the disposal operation must be submitted on or about July 1 of each
Upon request, the Commission may administratively revise and reissue
this order upon proper showing that any changes are based on sound engineering
practices and will not allow waste fluids to escape from the disposal zone.
DONE at Anchorage, Alaska and dated August 31, 1998.
Return to Disposal Injection Order
David W. Johnston, Chairman
Robert N. Christenson, Commissioner
Camillé Oechsli, Commissioner