Oil and Gas at Your Door? (2005 Edition) - Earthworks

Oil and Gas Development and Impacts
TIGHT SANDS AND GAS SHALES
The methods used to extract the gas from sands and shales are similar to those used for
coalbed methane, i.e., drilling of a well, followed by a period of dewatering, and then gas production.
As with coalbed methane, developers of tight sands and gas shales are fairly certain
that they will encounter gas when drilling.
The main issue for companies seeking to extract gas from tight sands and gas shales is that
more than 90 % of wells require some form of stimulation to achieve commercial production
rates. This tends to make most operations uneconomic. Should highly efficient technologies for
extracting gas from tight sands ever be developed, the potential for tight sands development is
enormous, as most geologic basins contain some tight-sands gas. 185
Many drilling, completion and stimulation technologies for tight sands and gas shales were
developed during the 1980s and 1990s, when industry received a tax credit on nonconventional
natural gas production. 186 Numerous stimulation experiments were conducted in an
attempt to increase the flow of gas by creating fractures in the tight-sand formations. Massive
hydraulic fracturing projects and stimulation using nuclear explosions were undertaken, with
some success. The tax incentives were critical in the development of both gas shales and tight
sands. When the tax credit expired, there was a decline in the drilling of tight sands and gas
shale wells.
Five basins currently dominate tight sands activity in the US: South Texas, East Texas, San
Juan (Colorado/New Mexico), Permian (Texas and New Mexico) and the Green River basin of
Wyoming. In 1999, annual tight sands gas production was 2,900 billion cubic feet (Bcf), up
from 1,500 Bcf in the mid 1970’s. 187
Today more than 28,000 gas shale wells produce nearly 380 Bcf of gas yearly from five U.S.
basins: Appalachian (New York, Kentucky, West Virginia, Ohio), Michigan, Illinois, Fort Worth
(Texas) and San Juan (Colorado and New Mexico) 188 More than 17,000 productive gas shales
wells were drilled between 1978 and 1999, with a peak of 1,799 gas shale wells in 1992, the
last year wells could quality for tax credits. 189
The major issues related to tight sands and gas shales are similar to CBM: impacts associated
with drilling; produced water; and methods used to stimulate gas flow (e.g., hydraulic fracing).
These issues are discussed elsewhere in this document.
TAR SANDS AND OIL SHALES
Nonconventional oil deposits include heavy oils, tar sands and oil shales. As mentioned previously,
petroleum is a broad term for hydrocarbons that includes gases, highly fluid “light” oils,
viscous “heavy” oils, tars and bitumens. Today, light oils comprise approximately 95 % of petroleum
production. 190 As will be discussed below, when compared to conventional deposits and
methods, the amount of work required to produce an equivalent amount of crude oil from tar
sands or oil shales makes it cost prohibitive under most circumstances. 191
Tar sands (also known as oil sands) are grains of sand that are intermixed with bitumen (heavy,
black, viscous, asphalt-like oil). Often, the bitumen is much too viscous to be recovered by conventional
methods.
There are two primary methods of extracting heavy oils and bitumen from tar sands:
1. The deposits are mined, the oil removed, and the sands returned to the pit or disposed of in
another manner. Approximately two tons of tar sands must be dug up, moved and processed
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