Title 20 . Miscellaneous Boards and Commissions

Chapter 25 . Mental Health Trust Authority

Section 30. Casing and cementing

20 AAC 25.030. Casing and cementing

(a) A complete proposed well casing and cementing program must be submitted with an application for a Permit to Drill (Form 10-401). Unless modified or altered by pool rules established under 20 AAC 25.520, a well casing and cementing program must be designed to

(1) provide suitable and safe operating conditions for the total measured depth proposed;

(2) confine fluids to the wellbore;

(3) prevent migration of fluids from one stratum to another;

(4) ensure control of well pressures encountered;

(5) protect against thaw subsidence and freezeback effects within permafrost;

(6) prevent contamination of freshwater;

(7) protect significant hydrocarbon zones; and

(8) provide well control until the next casing is set, considering all factors relevant to well control including formation fracture gradients, formation pressures, casing setting depths, and proposed total depth.

(b) General well casing and cementing provisions are as follows:

(1) casing design and setting depth must be based on engineering and geologic factors relevant to the immediate vicinity, including the presence or absence of hydrocarbons, potential drilling hazards, and permafrost;

(2) for all casing strings on which blowout prevention equipment (BOPE) will be installed, cement may not be drilled out until sufficient compressive strength has been reached to obtain a valid formation integrity test;

(3) within permafrost intervals, fluids that have a freezing point above the minimum permafrost temperature may not be left in casing-by-casing annuli or inside the casing upon completion, suspension, or shutdown of well operations, without commission approval of an alternate method that the commission determines will prevent damage to the casing;

(4) if casing is subjected to prolonged drilling operations, the commission will, as necessary to verify casing integrity, require the casing to be pressure-tested, calipered, or otherwise evaluated by a method approved by the commission;

(5) if zonal coverage is required under (a) of this section, and the commission believes zonal isolation might not have been established, the commission will require a cement quality log or other method to demonstrate isolation of the zone.

(c) Specific well casing provisions are as follows:

(1) structural casing must be set by driving, jetting, or drilling to a minimum depth of 70 feet in offshore wells to support unconsolidated shallow strata, to provide hole stability for initial drilling operations, and to provide a competent anchor for a diverter system;

(2) for onshore wells, conductor casing must be set by driving, jetting, or drilling to a depth sufficient to provide anchorage for a diverter system, and for offshore wells, conductor casing must be set no less than 300 feet and no more than 1,000 feet below the mudline datum; however, the commission will

(A) approve a different casing setting depth if necessary to permit the casing shoe to be set in a competent formation or below formations that should be isolated; or

(B) authorize an operator to drill without setting conductor casing based upon information from wells drilled in the immediate vicinity and other available data, if the commission determines that the absence of conductor casing will not jeopardize well control;

(3) surface casing must be set below the base of all strata known or reasonably expected to serve as a source of drinking water for human consumption and at a depth sufficient to provide a competent anchor for BOPE;

(4) one or more intermediate casing strings must be set if required for protection of oil or gas or for protection against abnormally geo-pressured strata and lost circulation zones, or if otherwise required by well conditions;

(5) production casing must be set and cemented through, into, or just above the production interval;

(6) slotted liners, pre-perforated liners, and screens installed below a production packer are considered production equipment and not casing.

(d) Specific well casing cementing provisions are as follows:

(1) if structural casing is set by drilling or jetting, the structural casing must be cemented with sufficient cement to fill the annular space from the shoe to the surface;

(2) if conductor casing is set by drilling or jetting, the conductor casing must be cemented by filling the annular space with cement from the shoe to the surface; if BOPE is to be installed on the conductor casing, the adequacy of the cement to contain potential wellbore pressures and fluids must be demonstrated by a formation integrity test;

(3) conductor casing cement may be washed out to a depth not exceeding the depth of the structural casing shoe, if installed;

(4) surface casing must be cemented by filling the annular space with cement from the shoe to the surface; however, if cement does not circulate to the surface, if an excessive quantity of cement circulates to the surface, or if the formation integrity test shows an inadequate cement job,

(A) the operator shall notify the commission before drilling ahead; and

(B) the commission will require

(i) a cement quality log or other approved method to evaluate the adequacy of the cement to contain potential wellbore pressures and fluids; and

(ii) remedial action as necessary to meet the requirements of (a) of this section before drilling ahead;

(5) intermediate and production casing must be cemented with sufficient cement to fill the annular space from the casing shoe to a minimum of 500 feet above all significant hydrocarbon zones and abnormally geo-pressured strata or, if zonal coverage is not required under (a) of this section, from the casing shoe to a minimum of 500 feet above the casing shoe; if indications of improper cementing exist, such as lost returns, or if the formation integrity test shows an inadequate cement job, remedial action must be taken;

(6) if the intermediate or production string is a liner, a minimum of 100 feet overlap between the outer and inner strings is required; the interval of overlap must be made pressure competent and must be pressure-tested in accordance with (e) of this section;

(7) for intermediate or production casing in a service well used for injection, a cement quality log or other evaluation log approved by the commission must be run to demonstrate isolation of the injected fluids to the approved interval.

(e) A casing pressure test must be performed if BOPE is to be installed on a casing. The casing must be tested to hold a surface pressure equal to 50 percent of the required working pressure of the BOPE as specified in the Permit to Drill under 20 AAC 25.035(e) (3) or 20 AAC 25.036(c) (3). The results of this test and any subsequent tests of the casing must be recorded as required by 20 AAC 25.070(1) .

(f) Except for through-tubing drilling, a formation integrity test must be performed if BOPE is installed on a casing. The test must be performed to a predetermined equivalent mud weight, leak-off, or fracture pressure as specified in the application for the Permit to Drill. The test must be conducted after drilling out of the casing shoe into at least 20 feet but not more than 50 feet of new formation. The test results must demonstrate that the integrity of the casing shoe is sufficient to contain anticipated wellbore pressures identified in the application for the Permit to Drill. The test procedure followed and the data from the test and any subsequent tests of the formation must be recorded as required by 20 AAC 25.070(1) .

(g) Upon request of the operator, the commission will, in its discretion, approve variances from the requirements of (b) - (f) of this section to allow for special or unusual conditions if the design requirements of (a) of this section are satisfied.

History: Eff. 4/13/80, Register 74; am 4/2/86, Register 97; am 11/7/99, Register 152

Authority: AS 31.05.030