The Oil Drum

This is a post by Piccolo, a petroleum engineer working in the petroleum industry.

The Bakken formation in North Dakota and Montana has generated a lot of buzz in the past year. Reserve numbers in the billions of barrels, even tens or hundreds of billions show up in press reports and blogs. Now the USGS has weighed in with a comprehensive assessment of the resource. So just how much will this oil accumulation help the world's largest importer of oil? Is it time to relax or is this just another small blip in the long-term decline of domestic production? We'll examine these questions and others below the fold, using data from the IHS database.

Figure 1 - Location of the Bakken Formation in the Williston Basin, adapted from esask.uregina.ca/entry/williston_basin.html

There are a couple of points that are worth bringing forward from the comments over the past couple of days or so, and with your indulgence I would like to do this.

The first related to some discussion on the relative production of Saudi Arabia, among others, and the fact that, with Haradh, they had just added 300,000 bd to their capability. The point that has been made here before, is that the Saudi wells are currently seeing about 8% depletion from existing structures, on average. We have referenced the relevant Aramco quotes on this before, but it has just popped up again.

"Saudi Aramco's mature crude oil fields are expected to decline at a gross average rate of 8%/year without additional maintenance and drilling," a Saudi Aramco spokesman said Tuesday.
But Saudi Aramco has taken a number of measures to offset a decline in output from the country's aging oil fields, the spokesman added. "A variety of remedial activities are always being taken in oil fields influencing their effective decline rates," the spokesman said. "The drilling of additional development wells in the producing fields is Saudi Aramco's standard practice to offset normal declines of older wells."

 The Aramco intent is to carry out a sufficiently aggressive drilling program so that

"This maintain potential drilling in mature fields combined with a multitude of remedial actions and the development of new fields, with long plateau lives, lowers the composite decline rate of producing fields to around 2%," the spokesman said.

Now those of you who have removed your socks, will quickly calculate that this is still around 180,000 bd, or about half of the slated production from Haradh, but wait! This depletion rate INCLUDES the development of new fields. Oh!

And, another gentle cough and a quick visit to Baker Hughes tells us that they have 37 rigs drilling for oil and 17 drilling for gas. If the oil rigs are 90% successful and can drill 6 wells each a year, and each producing well averages 3,100 bd, then the new production they will generate this year is 37 x 6 x 3,100 x 0.9 = 619,380 bd, regardless of how big their reserves are.