During the pumping and displacement of the heavyweight spacer used to displace the mud, a breach in pressureintegrity resulted in the undetected loss of drilling mud into the probably uncemented well-bore.
If pressure bleeds off there is clearly a problem with the pressureintegrity of the shoe, However, industry practice dictates that a positive test, that is no pressure drop, is not diagnostic, simply because the reservoir pressure is sufficient to retain the pressure being applied.
"This has really helped us understand how long under submerged pressure the recorder is able to maintain its integrity, so you don't have corrosion or sea water entering into it, " he told CNN.