Fuel Fix: George Mitchell: The duty to fracture responsibly
Natural gas is a wondrous fuel. It emits less carbon dioxide, less mercury, less nitrogen oxide, less sulfur oxide than any other hydrocarbon energy source. Natural gas is the perfect bridge fuel on the way to a less carbon-dependent economy. There is no question that accidents have occurred and mistakes have been made during the rush to develop this vast new resource, but this remarkable resource can be developed by industry following region-specific best practices and regulators carefully monitoring industry activities.
Far below the city of Fort Worth is a geological formation of sedimentary rocks that was shaped 354 to 323 million years ago – give or take an eon.
Take a much smaller jump back in time, to the 1970s, when an independent Texas company, Mitchell Energy & Development Corp., drilled into this ancient formation without much success. Company rigs had pulled up some curious rock samples of organic-rich shales (sedimentary rocks with large amounts of clay) indicating that natural gas in abundance, millions of years old, was trapped in these sediments. But because of the extremely low permeability of the shales, even the best engineers and geologists in the industry had no way to produce it in commercial quantities.
Innovation loves a challenge, however. After seven long years of effort, the Mitchell company devised a method that combined horizontal drilling and hydraulic fracturing of the shale formation, that released the gas in commercial quantities. It was a stunning victory not just for Mitchell, but for the nation’s small, independent energy companies, achieved with an approach mostly ignored or abandoned by the international oil and gas giants.
In the petroleum industry, hydraulic fracturing goes back at least to the 1940s, but the adaptation of fracturing in horizontal wells was critical to the success of Mitchell Energy & Development Corp.’s efforts. If you drill a vertical well through a relatively impermeable rock formation, even if you hydraulically fracture the rock to increase its permeability, the pay-zone is still limited to the formation thickness. If you drill horizontally through the gas-bearing formation, as the dogged Mitchell company engineers were finally able to do, and create multiple hydraulic fractures along its length, you dramatically increase the producing zone of the well. MORE