Explorers need to sharpen up their shots in the dark
Upstream, Friday May 2
A lack of quality prospects in the US Gulf of Mexico is compounding the softness in floating rig demand being signalled by operators, write Blake Wright and Anthony Guegel.
While many believe the deep-water US Gulf still holds vast untapped riches, they also think that much of the 'low-hanging fruit' -- easily defined via 3D seismic technology early on -- has been exploited.
That only leaves the more difficult, hard-to-image fields buried in the deep for operators to discover.
One subscriber to that school of thought is Shell International vice president of global technical services Richard Sears.
According to Sears, reservoir visualisation and the application of sub-surface technology will have to keep improving if the early success in deep-water is to continue.
He adds that many of the early discoveries were easy to see as amplitude anomalies or 'bright spots' on seismic charts.
"Future success will depend on being able to see the potential new accumulations in non-amplitude supported areas," he says. "We have to get smarter to find them, especially if they are harder to see."
One example is the tremendous difficulty of seeing below salt.
Dense sheets of tabular salt -- a legitimate hazard to both visualisation and drilling efforts alike -- cover much of the Gulf of Mexico's shallows as well as its deep-water areas.
"It's still shooting in the dark," Sears adds. Another example was the rush to exploit Miocene-aged turtle structures after BP's billion-barrel-plus success with its Thunder Horse discovery in the Mississippi Canyon area.
ExxonMobil drilled turtle structures at Hawkes and Timberwolf, ConocoPhillips at Kate, Spa and Voss, and Unocal at Bohr -- all with no commercial success.
As well as with the changes in technology required to find new deep-water fields, economic considerations have also raised the bar on the commerciality threshold.
The bottom line is that what was once considered a lucrative find may not be anymore.
BP's head of exploration Peter Carragher says the deep-water discovery rate has declined since 2001 and agrees that geophysical understanding of these structures must improve if that trend is to be reversed, requiring stepped-up efforts in pre-drill preparation. The supermajor's own 'elephant-hunting' mentality has left it with some lofty economic requirements for deep-water finds.
For BP, a new discovery in the deep-water Gulf would have to net in the neighbourhood of 200 million barrels of oil equivalent if it is to be considered a viable satellite development -- a subsea tie-back to another host facility or an existing export pipeline.
If the discovery is remote, as much of the deep-water Gulf remains, then the threshold jumps up to at least 500 million boe or more.
The high reserve numbers are necessary, says the supermajor, to justify the steep cost of acquiring leases and drilling wells with expensive rigs.
"We're looking for multi-billion-barrel provinces," Carragher says.
Nevertheless, he maintains the Gulf of Mexico will continue to provide both the fiscal and technical benchmarks by which all other deep-water provinces will be measured. |
