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Deep Gas Wells
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The development of deep gas resources is one way
to ensure that the nation’s growing demand for
natural gas can be met. Throughout the 1990's,
annual consumption of natural gas grew from 19.3
trillion cubic feet (TCF) to nearly 22 TCF. The
National Petroleum Council’s September 2003
report projects demand for natural gas is likely
to increase to 26 TCF in 2020 and could increase
beyond 31 TCF by 2025. Two major forces are
driving this increased demand - wider use of
natural gas for electricity generation and
growing concerns about the adverse environmental
consequences of burning coal and fuel oil.
Natural gas from deep reservoirs will play an
important role in ensuring a dependable supply
of clean energy.
A "deep" gas well is defined as any well that
produces from a depth below 15,000 feet.
According to the Potential Gas Committee’s (PGC)
2003 Report, there are about 2575 active well
completions below that depth in the Lower 48
states, producing from 183 separate reservoirs.
These deep gas reservoirs are primarily found in
the onshore and offshore basins of the Louisiana
and Texas Gulf Coast, in the Anadarko and
Permian basins of the mid-continent, and in a
number of Rocky Mountain basins.
Deep gas wells are about three times as deep as
the average onshore gas well, and roughly twelve
times as expensive. According to the API Joint
Association Survey on Drilling Costs for 1996,
the cost to drill and equip an average 6000 ft
onshore gas well in 1996 was about $465,000. In
comparison, the cost to drill and equip an
onshore deep gas well in the Louisiana and Texas
Gulf Coast, where the average deep gas well is
nearly 17,400 ft deep, was about $5.2 million.
However, the time, money, and effort expended
in deep drilling are not without significant
rewards. In Wyoming's Wind River Basin for
example, five wells drilled through nearly five
miles of strata encountered one of the most
prolific gas fields in the US. The PGC reported
that the average recoverable reserve for an
individual deep gas well can vary from 6 to
nearly 34 billion cubic feet (BCF), depending on
the basin. While only 0.5 percent of the gas
well completions in the Lower 48 states qualify
as deep completions, together they have produced
55 TCF (6 percent) of the natural gas produced
through 2002.
In addition, a significant volume of deep gas
remains to be discovered. The PGC’s estimate of
technically recoverable gas remaining to be
discovered at depths between 15,000 and 30,000
ft is 133 TCF, or about 29 percent of the
nation’s potential gas resource. More than half
this potential lies beneath the onshore and
offshore areas of the Gulf of Mexico.
The U.S. Department of Energy (DOE) is
sponsoring the Deep Trek Program to help develop
the high-tech drilling technology the industry
needs to develop these deep reserves. The goal
is to make the production of a greater portion
of the deep gas resource economically feasible.
Statistical Summary of Primary US Deep Gas
Basins:
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| |
Rockies |
Permian |
Anadarko |
LA & TX Gulf Coast |
LA-MS-AL Salt Basins |
LA-TX Shelf Slope OCS |
All Others |
Total |
| Total Deep Gas completions with production |
263 |
865 |
1,221 |
2,108 |
271 |
1,148 |
68 |
5,944 |
| Total active Deep Gas completions |
113 |
345 |
755 |
465 |
85 |
760 |
52 |
2,575 |
| Fields |
46 |
128 |
104 |
278 |
78 |
252 |
45 |
931 |
| Reservoirs |
38 |
25 |
43 |
33 |
15 |
14 |
15 |
183 |
| Average Total Depth per well, ft |
17,319 |
19,213 |
17,584 |
17,365 |
16,818 |
17,313 |
16,275 |
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Average Drilling Cost per well
(1995-1999), M$
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4,449 |
3,497 |
2,643 |
5,173 |
2,806 |
12,649 |
3,251 |
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| Total Cum Production (BCF) |
2,825 |
13,350 |
6,464 |
19,986 |
1,660 |
10,215 |
262 |
54,762 |
| Current Production Rate (MMCFD) |
430.8 |
318.9 |
367.8 |
1,155.2 |
99.3 |
1,478.8 |
51.2 |
3,902 |
Average Recoverable Reserves
per well (BCF)
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33.76 |
18.06 |
6.36 |
11.63 |
8.69 |
14.88 |
6.01 |
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PGC Potential Resource
(12-31-02), BCF
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18,811 |
12,119 |
16,200 |
41,095 |
8, 924 |
25,000 |
10,836 |
132,985 |
Source: Appendix III of Potential Supply of Natural Gas 2002, published January 2003 by PGC. Includes only wells with TVD greater than 15,000 ft.
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