[Code of Federal Regulations]
[Title 30, Volume 2, Parts 200 to 699]
[Revised as of July 1, 1998]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR250.702]

[Page 314-316]

                       TITLE 30--MINERAL RESOURCES

 CHAPTER II--MINERALS MANAGEMENT SERVICE, DEPARTMENT OF THE INTERIOR

PART 250--OIL AND GAS SULPHUR OPERATIONS IN THE OUTER CONTINENTAL SHELF--Table of Contents

                     Subpart G--Abandonment of Wells

Sec. 250.702  Permanent abandonment.

    (a) Isolation of zones in open hole. In uncased portions of wells,
cement plugs shall be set to extend from a minimum of 100 feet below the
bottom to 100 feet above the top of any oil, gas, or freshwater zones to
isolate fluids in the strata in which they are found and to prevent them
from escaping into other strata or to the seafloor. The placement of
additional cement plugs to prevent the migration of formation fluids in
the wellbore may be required by the District Supervisor.
    (b) Isolation of open hole. Where there is an open hole below the
casing, a cement plug shall be placed in the deepest casing by the
displacement method and shall extend a minimum of 100 feet above and 100
feet below the casing shoe. In lieu of setting a cement plug

[[Page 315]]

across the casing shoe, the following methods are acceptable:
    (1) A cement retainer and a cement plug shall be set. The cement
retainer shall have effective back-pressure control and shall be set not
less than 50 feet and not more than 100 feet above the casing shoe. The
cement plug shall extend at least 100 feet below the casing shoe and at
least 50 feet above the retainer.
    (2) If lost circulation conditions have been experienced or are
anticipated, a permanent-type bridge plug may be placed within the first
150 feet above the casing shoe with a minimum of 50 feet of cement on
top of the bridge plug. This bridge plug shall be tested in accordance
with paragraph (g) of this section.
    (c) Plugging or isolating perforated intervals. A cement plug shall
be set by the displacement method opposite all perforations which have
not been squeezed with cement. The cement plug shall extend a minimum of
100 feet above the perforated interval and either 100 feet below the
perforated interval or down to a casing plug, whichever is the lesser.
In lieu of setting a cement plug by the displacement method, the
following methods are acceptable, provided the perforations are isolated
from the hole below:
    (1) A cement retainer and a cement plug shall be set. The cement
retainer shall have effective back-pressure control and shall be set not
less than 50 feet and not more than 100 feet above the top of the
perforated interval. The cement plug shall extend at least 100 feet
below the bottom of the perforated interval with 50 feet placed above
the retainer.
    (2) A permanent-type bridge plug shall be set within the first 150
feet above the top of the perforated interval with at least 50 feet of
cement on top of the bridge plug.
    (3) A cement plug which is at least 200 feet long shall be set by
the displacement method with the bottom of the plug within the first 100
feet above the top of the perforated interval.
    (d) Plugging of casing stubs. If casing is cut and recovered leaving
a stub, the stub shall be plugged in accordance with one of the
following methods:
    (1) A stub terminating inside a casing string shall be plugged with
a cement plug extending at least 100 feet above and 100 feet below the
stub. In lieu of setting a cement plug across the stub, the following
methods are acceptable:
    (i) A cement retainer or a permanent-type bridge plug shall be set
not less than 50 feet above the stub and capped with at least 50 feet of
cement, or
    (ii) A cement plug which is at least 200 feet long shall be set with
the bottom of the plug within 100 feet above the stub.
    (2) If the stub is below the next larger string, plugging shall be
accomplished as required to isolate zones or to isolate an open hole as
described in paragraphs (a) and (b) of this section.
    (e) Plugging of annular space. Any annular space communicating with
any open hole and extending to the mud line shall be plugged with at
least 200 feet of cement.
    (f) Surface plug. A cement plug which is at least 150 feet in length
shall be set with the top of the plug within the first 150 feet below
the mud line. The plug shall be placed in the smallest string of casing
which extends to the mud line.
    (g) Testing of plugs. The setting and location of the first plug
below the surface plug shall be verified by one of the following
methods:
    (1) The lessee shall place a minimum pipe weight of 15,000 pounds on
the cement plug, cement retainer, or bridge plug. The cement placed
above the bridge plug or retainer is not required to be tested.
    (2) The lessee shall test the plug with a minimum pump pressure of
1,000 pounds per square inch with a result of no more than a 10-percent
pressure drop during a 15-minute period.
    (h) Fluid left in hole. Each of the respective intervals of the hole
between the various plugs shall be filled with fluid of sufficient
density to exert a hydrostatic pressure exceeding the greatest formation
pressure in the intervals between the plugs at time of abandonment.
    (i) Clearance of location. All wellheads, casings, pilings, and
other obstructions shall be removed to a depth of at least 15 feet below
the mud

[[Page 316]]

line or to a depth approved by the District Supervisor. The lessee shall
verify that the location has been cleared of all obstructions in
accordance with Sec. 250.704 of this part. The requirement for removing
subsea wellheads or other obstructions and for verifying location
clearance may be reduced or eliminated when, in the opinion of the
District Supervisor, the wellheads or other obstructions would not
constitute a hazard to other users of the seafloor or other legitimate
uses of the area.
    (j) Requirements for permafrost areas. The following requirements
shall be implemented for permafrost areas:
    (1) Fluid left in the hole adjacent to permafrost zones shall have a
freezing point below the temperature of the permafrost and shall be
treated to inhibit corrosion.
    (2) The cement used for cement plugs placed across permafrost zones
shall be designed to set before freezing and to have a low heat of
hydration.
[53 FR 10690, Apr. 1, 1988. Redesignated and amended at 63 FR 29479,
29485, May 29, 1998]