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Proposed Rules Regulating Sustained Casing Pressures in Development Wells Within the West Fork Field.

Conservation Order No. 525.000

West Fork Field: All Pools

July 20, 2004


1. On its own motion, the Alaska Oil and Gas Conservation Commission ("Commission" or “AOGCC") proposed to adopt rules regulating sustained annulus pressures in West Fork Field development wells.

2. Notice of opportunity for a public hearing on the proposal was published in the Anchorage Daily News on October 30, 2003.

3. No request for a hearing was received.

4. The Commission received written comments on the proposal from West Fork Field operator, Marathon Oil Company (“MOC”).


1. In considering proposed rules regulating sustained casing pressures in West Fork Field development wells, the Commission reviewed: the Halliburton Cementing Tables; Commission files for West Fork Field wells; information on well pressures provided by the operator; written comments by MOC in response to the October 30, 2003 notice of opportunity for public hearing; and the records of annular pressure rules for other fields in the state.

2. Unless otherwise specifically authorized by the Commission, AOGCC regulations require all producing wells capable of unassisted flow to be completed with suitable tubing and packer that effectively isolate the tubing-casing annulus from fluids being produced.

3. No current regulation or Commission order for the West Fork Field establishes annular pressure management requirements for producing wells. However, the Commission established such requirements for producing wells in other Alaska fields.

4. Annulus pressure is common in development wells. Pressures may be purposely imposed, thermally induced or the result of leaks in tubing, casing, packer or other well components.

5. Excessive annular pressure can develop in wells as a result of thermal effects. Well startup can involve significant annular pressure increases due to fluid expansion as a well heats above ambient temperature. Changing produced fluid characteristics and production mechanisms can also create thermal conditions that affect annular pressures.

6. Pertinent characteristics of well construction in the West Fork Field are similar to those in other Alaska fields.

7. The West Fork Field is a mature gas field in which reservoir pressures have declined substantially since production commenced. Well pressures in the West Fork Field are now low relative to other Alaska fields, ranging up to a maximum surface pressure of approximately 600 psi.

8. Low pressure in the inner annulus of West Fork Field development wells means that there is little risk of overpressuring the outer annulus.

9. West Fork Field wells produce primarily natural gas. Annular pressure increases due to thermally induced fluid expansion are thus expected to be substantially less than thermally induced annular pressure increases in wells of oil-producing fields, due to the compressibility of gas and its generally lower temperature.

10. Well tubulars in West Fork Field development wells are of sufficient burst pressure rating to contain the full range of reasonably anticipated well pressures.

11. The wellheads of many West Fork Field development wells were installed in below-ground cellars, making access to the outer annulus difficult and somewhat hazardous.


1. It is not essential to adopt rules regulating sustained casing pressures for West Fork Field development wells at this time.

NOW, THEREFORE, IT IS ORDERED that this proceeding is concluded without amending the West Fork Field pool rules.

By Order of the Commission at Anchorage, Alaska, this 20th day July 2004.

John K. Norman, Chair
Alaska Oil and Gas Conservation Commission

Daniel T. Seamount, Jr., Commissioner
Alaska Oil and Gas Conservation Commission

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