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conducted a Geotap survey to determine the sand pore pressure. The sand pore
pressure was determined to be 14.15 ppg. BP also converted this pore pressure
to an estimated fracture gradient of 15.0 ppg. The open‐hole section drilled
utilized a surface mud weight range of 14.1–14.5 ppg, which allowed for a safe
drilling margin to be maintained between pore pressure and fracture gradient.
Throughout this interval, however, BP encountered multiple problems
associated with both lost returns and regressing pore pressures (1.9 ppg
difference) between 17,001 and 18,066 feet. BP lost approximately 4,000 barrels
(“bbls”) of mud in the production open‐hole interval. BP utilized loss circulation
material in this interval to attempt to control these losses.

Open Hole Interval below 9 7/8-in Liner @ 17,168 - FIT 15.98 PP 13.9
Date Depth MW Losses PP Remarks Hydrocarbon Zones
2-Apr 17,007 - 17,321 14.3 17,168 FIT 16.22 PPG 17,684 - 17,693 M-57C 14.1 PPG
3-Apr 17,321 - 17,835 14.5 233 bbls 17,723 - GeoTap 14.15 ppg (PP) 17,786 - 17,791 M-56A 13.1 PPG
3-Apr 17,835 - 17,909 14.3
4-Apr 17,909 - 18,195 14.3 12.58 @ 18,089 Schematic - 12.6 ppg at 18,066 18,061 - 18,223 M-56E 12.6 PPG
4-Apr 18,215 - 18,250 14.4 639 bbls Lost full returns
5-Apr 18,260 14.0 1263 - Total
6-Apr 14.0 1586 - Total
7-Apr 14.0
8-Apr 14.0
9-Apr 18,360 14.0 called TD

Figure 2 ‐ Drilling margin data from IADC reports and BP Daily Reports

BP continued drilling until it concluded it had run out of drilling margin
between mud weight and formation pore pressure. Robert Bodek, BP Geological
Operations Coordinator, emailed Michael Bierne, another BP employee, on April
13, 2010, and explained the reasons why BP concluded that it had run out of
drilling margin at 18,360 feet. He said that the team decided to stop drilling
because it had become “a well integrity and safety issue.” The email also states:
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We had one major problem however: the sand that we took the initial
GeoTap pressure in was measured at 14.15 ppg. The absolute minimum
surface mud weight we could use to cover the pore‐pressure in this sand
was 14.0 ppg. This would give us approximately a 14.2 ppg ESD over the
aforementioned sand. If we were to drill ahead with a 14.0 surface mud
weight/14.2 ESD, our equivalent circulating density (ECD) would be
approximately 14.4‐14.5 ppg. We had already experienced static losses
with a 14.5 ppg ESD! It appeared as if we had minimal, if any, drilling
margin . . . Drilling ahead any further would unnecessarily jeopardize the
wellbore. Having a 14.15 ppg exposed sand, and taking losses in a 12.6

66 BP‐HZN‐MBI00126338.

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