Subsalt pressure prediction in the Miocene Mad Dog field, Gulf of Mexico

Merrell, Michael P.; Flemings, Peter B.; Bowers, Glenn L.

doi:10.1306/06251312156

Cited by 9 publications

(3 citation statements)

References 24 publications

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“…It is well recognized that in many basins, regionally connected high-permeability aquifers at a nearly constant overpressure are encased in low-permeability overpressured mudstone such as is illustrated here in the M56 21–24 . A key question is, what controls the aquifer overpressure in these systems?…”

Section: Basin Hydrodynamicsmentioning

confidence: 88%

“…ref. 21 ), and use the mudstone pressure and overburden to calculate effective stress ( u = σ v − ). Next, we determine the mudstone porosity at each location from the velocity log after 42 :where v ma is matrix velocity, v is the velocity log measurement, and x is an empirically derived acoustic formation factor exponent.…”

Section: Methodsmentioning

confidence: 99%

“…Next, we determine the mudstone porosity at each location from the velocity log after 42 :where v ma is matrix velocity, v is the velocity log measurement, and x is an empirically derived acoustic formation factor exponent. We assume x = 2.19 and v ma = 14,909 ft/s (4,545 m/s) following precedent for Gulf of Mexico Neogene sediments 21,35,42 . The shallow locations with cooler in-situ temperatures have a higher porosity for a given effective stress than the deeper and warmer locations (Fig.…”

Section: Methodsmentioning

confidence: 99%

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Overpressure at the Macondo Well and its impact on the Deepwater Horizon blowout

Pinkston

Flemings

2019

Sci Rep

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At the Macondo well, the overpressure (fluid pressure greater than hydrostatic) in the main reservoir is nearly identical to that within a stratigraphically equivalent sandstone at the Galapagos development 21 miles (34 km) to the south; we interpret that the reservoirs share a permeable, laterally extensive, and hydraulically connected aquifer. At Macondo, pore pressure approximately parallels the overburden stress to a depth of 17,640 ft (5,377 m) subsea and thereafter decreases abruptly by 1,200 psi (8.3 MPa) over 370 ft (113 m) as the main sandstone reservoir is approached. In contrast, at Galapagos, pore pressure increases with the overburden stress for the entire well depth. The pore pressure regression at Macondo was responsible for a reduction in the least principal stress. This, in combination with the extreme pore pressures within overlying strata, drastically narrowed the range of safe operational borehole pressures. These geologic phenomena produced challenging conditions for drilling, prevented successful temporary abandonment of the well, and contributed to the well’s failure.

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Section: Basin Hydrodynamicsmentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%