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Pore pressure and stress at the Macondo well, Mississippi Canyon, Gulf of Mexico
| Content Provider | Semantic Scholar |
|---|---|
| Author | Pinkston, F. William M. |
| Copyright Year | 2018 |
| Abstract | At the Macondo well (MC 252-1), the overpressure (fluid pressure greater than hydrostatic) in the main reservoir is nearly identical to that within a stratigraphically equivalent sandstone at the Galapagos Field 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 Field, pore pressure increases with the overburden stress for the entire well depth. We infer that lateral flow through the permeable sandstone controls the reservoir pressure. The pore pressure regression at Macondo was responsible for a reduction in fracture pressure. This, in combination with the extreme pore pressures above, drastically narrowed the range of safe operational borehole pressures. These geologic factors led to drilling, casing, and cementing decisions that contributed to the Deepwater Horizon blowout. SIGNIFICANCE STATEMENT The Deepwater Horizon blowout of the Macondo well created one of the worst environmental disasters in the history of the United States, highlighting the complexity of deepwater hydrocarbon exploration. A well-studied chain of engineering failures ultimately culminated in the blowout, but here, we focus on the natural pore pressure and stress conditions encountered in the well. By synthesizing a 3-D seismic survey, petrophysical logs, and drilling data, we establish that regional hydraulic connectivity of 5 the main reservoir caused a dramatic and unexpected drop (regression) in the pore pressure and stress profile at the bottom of the well. These geologic phenomena produced challenging conditions for drilling, prevented successful temporary abandonment of the well, and contributed to well failure. |
| File Format | PDF HTM / HTML |
| DOI | 10.15781/T2JQ0TC04 |
| Alternate Webpage(s) | http://www-udc.ig.utexas.edu/geofluids/Theses/Pinkston_Thesis_2017.pdf |
| Alternate Webpage(s) | https://doi.org/10.15781/T2JQ0TC04 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
