Definition(s)
Fluid Migration Potential
The API inactive well program evaluates the potential for wellbore fluids to migrate through an inactive wellbore. Four fluid migration potential categories are defined in Table 3-1 as minimum, low, moderate, and significant. The appropriate fluid migration potential category for an inactive well is determined by the presence, or absence, of pressured formations and by the number of levels of protection.
Concerns in evaluating the fluid migration potential are pressured formations existing as the completion interval or pressured formations existing behind uncemented casing in the same uncemented annulus as a fresh water aquifer that is not completely covered by surface casing. Pressured formations behind cemented casing are isolated and have minimum potential for fluid migration.
TABLE 3-1
CATEGORIES OF FLUID MIGRATION POTENTIAL INTO FRESH WATER AQUIFERS
Fluid Migration Potential Category
Minimum
There are no pressured formations, or the only pressured formations are isolated from the fresh water aquifers by cemented production casing, liner, or intermediate casing.
Low
The well has two or more levels of protection, there is no sustained pressure on the surface casing annulus, and The completion interval is a pressured formation, and all other pressured formations are isolated from the fresh water aquifers by cementing production casing, liner, or intermediate casing, or The completion interval may or may not be a pressured formation, but there are two or more levels of protection between the shallowest uncemented pressured formation and the lowermost fresh water aquifers.
Moderate
The well has one level of protection, there is no sustained pressure on the surface casing annulus, and The completion interval is a pressured formation, and all other pressured formations are isolated from the fresh water aquifers by cemented production casing, liner, or intermediate casing, or The completion interval may or may not be a pressured formation, but there is one level of protection between the shallowest uncemented pressured formation and the lowermost fresh water aquifer.
Significant
The well has zero levels of protection, and the completion interval is a pressured formation, or There is sustained pressure on the surface casing annulus, or The Christmas-tree or stuffing-box assembly design and mechanical integrity is not sufficient to provide long-term containment of the wellbore fluids, or A pressured formation and a fresh water aquifer exist in the same uncemented annulus.
Source: API BULLETIN E3, Environmental Guidance Document: Well Abandonment and Inactive Well Practices for U.S. Exploration and Production Operations, First Edition, January 1993 (Reaffirmed June 2000). Global Standards