Mr. Larry Greenstein
P.O. Box 196247
Anchorage, AK 99519-6247
|Re:||Disposal Injection Order 23Ivan River Unit Well 14-31 (175-008)
Request to Change Mechanical Integrity (MIT) Interval
Dear Mr. Greenstein:
By letter dated March 31, 2004, Unocal requested an Administrative Approval under Rule 6 of Disposal Injection Order No. 23 to change the interval between Mechanical Integrity demonstrations (MIT) for the Ivan River Unit Well 14-31 (175-008) from annual to once every 4 years. Unocals basis for the request is that the well is used intermittently and a 4-year test interval is specified for other intermittent service disposal wells. Unless superceded by a conservation order, 20 AAC 25.252 (d) requires that the mechanical integrity (MI) of a disposal well be demonstrated at least once every 4 years as specified in 20 AAC 25.412 (c).
DIO No. 23 was issued March 9, 2001. In Rule 4, the MIT interval specified was 1 year and in addition to the standard inner annulus pressure test a temperature log was required. Findings in the order file indicate the annual MIT frequency was specified because of close proximity to 2 production wells on the pad. Finding 14 of DIO No. 23 indicated IRU well 13-31 is 114 north and IRU well 44-36 is 342 north of the disposal well at the top of the injection interval.
Unocal has disposed of Class II wastes in accordance with DIO No. 23 from September 9 November 27, 2001 and July 19 August 11, 2002. A successful pressure MIT was performed in advance of each injection and a temperature log was obtained August 14, 2002. Approximately 39,000 barrels of waste were injected at about 1.5 bpm and 2000 psi. The rate and pressure correspond to the fracture initiation pressure determined by the injectivity test performed in June 2001. The temperature log showed cooling reversals at about 3050 md and in the perforated interval at 3190 md. The temperature plot appears to validate Finding 22 of the injection order that the planned disposal will not reach or penetrate the confining interval at 2945 md. Aquifer Exemption Order No. 6 exempts aquifers between the measured depths of 2500 3450.
After mid 1999, MIT intervals were specified at 2 years in 5 of the 7 orders issued on disposal wells. The basis for the decreased test interval is to increase scrutiny of wells that inject solids from waste grinding operations. Ivan River 14-31 is approved for the disposal of liquid and ground solid waste. Intermittent operation has not been a consideration with regard to the MIT interval. A temperature log has not been required in the other orders, however none of the other disposal wells have wells in such close proximity to the disposal well. Disposal of liquefied solids slurry is accomplished via fracturing the receiving formation (Finding 21). A temperature log after slurry is pumped is a valid method to confirm the slurries are confined to the receiving formation. Surveillance of offset well annular pressure is the best method to identify slurry breakthrough to a nearby well.
The diagnostic information provided by Unocal indicates that the wastes disposed have been contained as designed and in accordance with the requirements of DIO No. 23. Increasing the time interval between MIT demonstrations should not result in an increased risk of contaminating fresh water provided future disposal operations are conducted as required by the DIO. Unocal has not requested modification of any other rule in the Order.
Now therefore, as provided by Rule 6 of DIO No. 23, it is Ordered that:
1. When disposal operations are resumed, Unocal shall perform an MIT and thereafter at intervals of not more than once every 2 years.
2. A temperature log will not be routinely required, except when operating parameters or offset well annular pressures indicate liquefied slurry may be leaving the confined receiving interval; or; if requested by the Commission.
DONE at Anchorage, Alaska and dated June 1, 2004.
John K. Norman, Chair
Daniel T. Seamount, Jr.
BY ORDER OF THE COMMISSION