Monday, January 12, 2015

Mapping the Bakken

Mason Inman created an interactive map to capture drilling activity in the Bakken:
US oil production has been booming the past few years, due in large part to North Dakota’s Bakken formation, a rock layer tapped through fracking. Each well travels down about two miles, then turns horizontally and snakes through the rock formation for another two miles. There were 8,406 of these Bakken wells, as of North Dakota’s latest count. If you lined them all up—including their vertical and horizontal parts—they’d loop all the way around the Earth.
As a journalist digging into the long-term potential for shale oil—how much oil it might supply, and at what economic and environmental costs—I wanted to create a map showing the extent of this drilling boom to help me look for trends...
There are some maps out there already, including an online interactive map from North Dakota’s Department of Mineral Resources (ND DMR), and other groups have created their own maps of fracked wells across the nation, like the non-profit FracTracker. To get an impression of the extent of the boom, there are the mind-bending graphics in this New York Times piece, showing a tangle of lines obscuring the sky. But I haven’t seen any interactive maps out there that let ordinary citizens easily explore the extent of this boom.
To make my map (see a larger version here), I took the same data the New York Times used and plotted it out using the open-source program TileMill, creating an interactive map that allows you to, um, drill into the data. It appears the New York Times used a large shapefile available from the ND DMR, for nearly all horizontal wells, showing their curvy paths in detail. To get this file, I went to their ArcIMS Server, and clicked on the button in the upper-right, which opened up a list of shape files. The one I used was “”. I unzipped it, created a new project in Tilemill and added the shapefile as a layer.
On top of this layer, I’ve added the locations of each wellhead, with the most recently drilled ones highlighted in red. This wellhead data is available only through ND DMR’s basic subscription at $50 a year. If you’re into this kind of data, it’s definitely worth the price, since it gives you access to all sorts of details—monthly production rates for each well and well files that give extensive details, including which rock layer the well is tapping.
With the wells drilled during 2014 highlighted in red, it’s clear that drilling has contracted to focus mainly on a core area in the center, rather than pushing out into new areas.
Also, North Dakota allows drillers to put new wells on “confidential” status, typically for about six months. I’ve marked those in orange. The details on these wells—where exactly each horizontal well threaded its way through the rock, when the wells started producing oil, and how much they yielded—is kept private until confidential status expires. Since the horizontal well paths are kept private, they don’t show up on this map, so you’ll see lone orange dots with no horizontal wells—not because they’re not there, but because the data isn’t available yet. Since most wells get put on confidential status initially, the locations of these wells gives you an idea of where companies have been drilling most recently.
From afar, it’s just a forest of lines. But if you zoom in, you’ll see that some areas have wells tightly packed in, whereas other areas have a solo wells. From what I’ve read—such as in assessments like those from geologist David Hughes in his recent report “Drilling Deeper”—the densely drilled areas are those where wells yield the most oil. These are the “sweet spots,” as the industry calls them.
To help distinguish the drilling hotspots from the less attractive areas, I’ve made all the wellhead location markers partially transparent. This is because companies often drill several wells on a single “pad,” an area of they clear where they set up the drilling rig and park all the trucks that bring in the millions of gallons of water that they pump into the wells at enormous pressures to fracture the rock, and the thousands of tons of sand that the water forces into those fractures. (The sand stays behind, holding the cracks open so that the oil and gas will continue to flow out.)
His previous article in Nature here.  He also has a website here. Looks like they've really worked over the sweet spots.  More on the sweet spots in the Bakken, and whether they are played out, including this chart, at OilPrice:

The chart shows the rapid decline in LTO extraction by vintage.
What is the month over month legacy decline in total LTO extraction?
The month over month total decline for LTO extraction wobbles around due to seasonal effects, differences in productivity of the wells started in any month, variations to when in the calendar month the wells were started and number of days of the month.
Measurements from actual data showed that the smoothed month over month legacy decline varied between5 – 6%.
From figure 03 it may be observed that the legacy decline rate slows with time.
How many net producing wells need to be added to sustain the LTO extraction level from October 2014?
In October 2014 total LTO extraction from the Middle Bakken and Three Forks formations in North Dakota was 1.12 Mb/d.
The “average” well, so far in 2014, had a first month flow of 486 b/d.
This works out to a need of net monthly additions of 115 – 135 producing wells to sustain the October 2014 extraction level.
If drilling activity in the Bakken falls off due to low oil prices, you may see an unrecoverable decline in overall production as the most recently drilled wells decline and enough new ones aren't drilled to replace them. When prices eventually do increase, there might not be enough new places to drill wells to get back to the previous peak.

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