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Deep Gas Wells
 

The development of deep gas resources is one way to ensure that the nationís 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 Councilís 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 Committeeís (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 PGCís 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 nationís 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:

  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  
Average Drilling Cost per well
(1995-1999), M$
4,449 3,497 2,643 5,173 2,806 12,649 3,251  
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)
33.76 18.06 6.36 11.63 8.69 14.88 6.01  
PGC Potential Resource
(12-31-02), BCF
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.