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

42 API STANDARD 65-2
5) the replacement fluid inside the casing is much cooler than the displacement fluid;
6) casing pressure tests or other imposed pressure applications are performed:
a) after the cement starts to gain SGS during WOC,
b) after the cement sets at a test pressure above the cement’s tensile strength,
c) repeatedly during the life of the well that exceed the cement’s fatigue limits;
7) mechanical seals are activated before the cement has gained enough structural integrity to resist pipe
expansion from the loss of hydrostatic head pressure in the annulus.
6000
Annulus Pressure Minus Casing Pressure During
Cement Curing, psi.
4000
2000
0
-2000
-4000
-6000
600 1200 1800 2400 3000 3600
Bond Failure Pressure, psi.
Reproduced with permission.
Copyright, SPE. Bearden, W.G., Spurlock, J.W., Howard, G.C. 1964. Control and Prevention of Inter-Zonal Flow. J. Pet Tech 17 (5): 579-584; SPE-
903-PA
Figure A.1—Effect of Curing Pressure on Bond Failure
Some of the preventive measures mentioned by Bearden [6] included the use of float equipment, displacing with
lighter density fluids, and, in some cases, attaching annular seal rings (type of mechanical barrier) to the casing. <strong>The</strong>
latter method was proven successful in 25 out of 27 well applications. More preventive measures such as new types
of annular mechanical barriers have been developed since then and are described in Section 4.
Garcia and Clark [18] disclosed the results of a seven year (1968 to 1975) lab and field study of annular gas flows in
numerous wells to better define the issues, challenges, and recommend preventive practices. <strong>The</strong> significance of this
study is the identification of annular flows in the 1960’s by various investigators and postulating of the hypothesis or
theory that of the loss of hydrostatic head pressure on top of and within the annular column of unset cement slurry
was the root cause. A new cause for this loss of hydrostatic pressure was discovered and reported to be premature