Coincidental Pressures Led to Normal Human Heuristic and Error

NPT Test Gauges TOO SIMILIAR to Riser Margin For Crew To Ignore

Pressure of Reservoir Pushing “UP” is

~1,400 psi

Pressure of Riser Mud Pushing “DOWN” is

~1,400 psi

Water Depth 4,992'

Water Density 8.6 ppg

RKB 75'

Gauge Height Off Mud Line 25'

Riser Mud Weight 14.0 ppg

Riser Margin 1,439 psi

Blowout Reservoir Pressure Density Equivalent 13.1 ppg

Blowout Reservoir Pressure (BRP) 12,073 psi

BRP Depth (can argue reservoir yet not 1,400 psi gauge result) 17,791'

Drillstring Depth 8,367'

Pressure of hydrostatic down to bottom of drillstring 3,759 psi

Pressure of hydrostatic from drillstring to reservoir Depth 6,861 psi

Pressure of reservoir at choke line pressure gauge 1,453 psi

"BLIPS" in NPT shows bottom plug acting as Back Pressure Valve of 50 psi 50 psi

Calculated Pressure 1,403 psi

NPT Pressure that the Macondo Crew Saw on Pressure Gauge 1,400 psi

Difference -3 psi

Coincidental Pressure Led to Normal Human Heuristic and Error

•Bizarre Coincidence?

OR•Mitigatable Confusion?

Coincidental Pressure Led to Normal Human Heuristic and Error

• A quick check of the numbers available to the engineer that designed the NPT would have shown how close these numbers were to one another and known that this would confuse the crew into thinking the “closing pressure” on the Annular “Bag” preventer needed to be increased because the mud above the “Bag” created a “Differential” very close to 1,400 psi

Coincidental Pressure Led to Normal Human Heuristic and Error

• Heuristic /hjʉˈrɪstɨk/; Greek: "Εὑρίσκω", "find" or "discover") refers to where the exhaustive search is impractical, heuristic methods are used to speed up the process of finding a satisfactory solution via mental shortcuts to ease the cognitive load of making a decision.

Coincidental Pressure Led to Normal Human Heuristic and Error

• James Reason and other experts say the way to establish “Fault” is to use the “Substitution Test”. Basicly ask if any other worker in the same situation ‘might’ have come to the same conclusion. The answer is an emphatic, Yes!

• Everyone on the rig came to exactly the same conclusion. The heuristic. The pressure was very close to the expected riser margin and thus the bladder effect WAS the heuristic.