Mr. Erik Milito - The House Committee on Natural Resources ...

ENVIRONMENTAL PROTECTION FOR ONSHORE OIL AND GAS PRODUCTION OPERATIONS AND LEASES 17
Other nuisances, such as light emittance from a lighted flare, odors, and dust, should be controlled as considered
appropriate for the location.
6.4 Plugging and Abandonment
6.4.1 General
Permanent abandonment is done when the wellbore has no further utility and is permanently sealed against fluid
migration. Temporary abandonment operations may be performed when a wellbore has future utility, such as for
EOR projects, and must be maintained in a condition where routine workover operations can restore a wellbore to
service. <strong>The</strong> same environmental concerns exist in both cases. Refer to API E3.
6.4.2 Subsurface
6.4.2.1 General
Several environmental concerns related to well abandonment should be addressed. <strong>The</strong> primary environmental
concerns are protection of freshwater aquifers and USDW, as well as isolation of downhole formations containing
hydrocarbons or used for injection. Additional issues, which should be evaluated, are the protection of surface soils
and surface waters, future land use, and permanent documentation of abandoned wellbore locations and conditions.
6.4.2.2 Plugging Purpose
<strong>The</strong> purpose of plugging wells is to prevent interzonal migration of fluids; the contamination of freshwater aquifers,
surface soils, and surface waters, and to conserve hydrocarbon resources either in the production interval or
potential production intervals. Generally, contamination by an improperly plugged and abandoned well can occur in
two ways:
a) the abandoned well can act as a conduit for fluid flow between penetrated strata, into USDW, or to the surface;
b) contaminated water can enter the abandoned wellbore at the surface and migrate into USDW.
Such contamination is prevented when a well is properly plugged. Not only do the plugging operations prevent an
abandoned well from becoming a conduit for contamination to occur, but well construction and completion methods
also contribute to the prevention of contamination.
Well plugging operations are focused primarily on protecting USDW, isolating downhole formations productive of
hydrocarbons or used for injection, and protecting surface soils and surface waters. A surface plug prevents surface
water runoff from seeping into the wellbore and migrating into USDW cement plugs isolating hydrocarbon and
injection/disposal intervals and a plug at the base of the lowermost USDW accomplish this primary purpose. Surface
water entry into an abandoned well is a concern because the water may contain contaminants from agricultural,
industrial, or municipal activities. API E3 recommends that operators set a cement plug at the base of the lowermost
freshwater aquifer or USDW during plugging and abandonment operations applicable to the well.
NOTE
<strong>The</strong> cement plugs also work to protect surface soils and water from wellbore fluids by confining those fluids in the well.