DOE Digest

Rocky Mountain Natural Gas, Resource Potential and Prerequisites to Expanded Production

A recently released Department of Energy (DOE) report, intended to stimulate discussion on meeting the Nation's energy challenges, describes well the three prerequisites to advancing natural gas production in the Rocky Mountain region: (1) addressing land-use and environmental concerns, (2) access to markets, and (3) technology advances. All three factors are key to future growth, however this article focuses only on the technology realm. Readers are encouraged to peruse the full report (www.fe.doe.gov/programs/
oilgas/publications/naturalgas
rockymtn_final.pdf).

Estimates for technically recoverable natural gas range from 226 to 383 Tcf. Estimates include conventional, tight gas and coalbed methane resources. Volume estimates have historically increased with improved geologic knowledge and technology advances and that trend is forecast to continue. Proved natural gas reserves in the Rocky Mountain states now represent 27% of U.S. reserves, providing 18% of supply.

One of the keys to tight gas development is identifying fracture-prone areas that will have higher deliverability. Advances are being made, but some wells with good fracture networks have encountered high water production early in their life. Thus, exploration technologies are needed to predict both "the presence" of fracture network and "likely saturations."

Continued advances in logging technologies to identify "pay zones" within a broad interval are needed, as well as are advances in hydraulic fracturing technology itself. Horizontal and underbalanced drilling technologies, which are used extensively in Canada and other areas, also could be more widely used.

In 2001, coalbed methane represented over half of Rocky Mountain gas production and 8 percent of U.S. natural gas supply. Industry has learned that drilling/operational practices need to be tailored to different CBM basins. This knowledge base is developing and refinements will continue. Environmental concerns will remain important in further CBM development.

In cost-shared projects, MASI LLC and Terralog Technologies will investigate "smart drilling" options in two projects managed by DOE's National Energy Technology Laboratory. Total project funding is $1.885 million, with industry providing about 42% of that as cost share.

MASI LLC, Houston, will conduct a two-phase project to determine how micro-bubbles called aphrons help seal permeable and fractured wellbore rock during drilling, minimizing reservoir damage. An aphron is a uniquely structured micro-bubble of air or gas created by combining surfactants and polymers in drilling fluid. Aphrons fill fractures and pores in rocks and other media, creating seals that stop or slow the entry of fluid.

Terralog Technologies, Arcadia, Calif., will research the basic physical mechanisms involved in combined percussion and rotary drilling. There is clear evidence that the combination of percussion and rotary drilling provides significant improvement in penetration rates in hard-rock environments. This has led to advances in "percussion" or "hammer" drills using both mud and air systems. However, the fundamental rock mechanics have not been fully defined and adequately modeled. In addition, there are no practical simulation tools available. As a result, cost and reliability concerns have limited broader application. By addressing these needs, the project will help industry recover vast untapped gas resources contained in deep, hard-rock environments more economically and efficiently.

See DOE Techline for full information (www.fossil.energy.
gov/news/techlines/
03/tl_smartdrilling_
2projects.html).

The use of CO2 for EOR development has evolved from early laboratory research on miscible fluids in the 1950s, through the pilots and pursuit of CO2 sources in the 1970s, to full-scale floods in the

1980s, to lower cost floods today. The focus of early DOE research was on phase behavior, mobility control and candidate fields. By the 1970s and 1980s the focus had shifted to field demonstration and model development. Finally in the late 1980s and early 1990s funding was provided for investigating optimal flood design, mobility control, and expanding beyond the Permian basin.

Today, there are 68 commercial CO2 floods producing approximately 230,000 barrels/day, nearly 4% of the domestic oil production. The majority are still in the Permian basin. Research by the DOE indicates the potential oil recovery could be increased 8- to 10-fold if CO2 could be made available at all potential target reservoirs for $0.50/mcf or less. Increasingly, new projects are utilizing CO2-rich anthropogenic sources. The most notable are the Weyburn project in Saskatchewan with CO2 pipelined from the Great Plains synfuel plant in North Dakota and the recently announced Anadarko Salt Creek project in Wyoming.

Research is focused on understanding the processes and identifying depleted oil, deep coal or saline formations in which CO2 can be sequestered. The first targets will be the marginal oil fields where most is known, but the focus will shift from maximizing oil recovery to maximizing the CO2 remaining in the reservoir at the end of the project. Geological formations in the U.S. have the capacity of sequestering over 100 years of total anthropogenic CO2 generated. Other current research is focused on the capture and separation of CO2, terrestrial and ocean sequestration, and advanced modeling.

Article courtesy of Dwight Rychel, Northrup Grumman, contractor supporting DOE's National Energy Technology Laboratory in Tulsa, Okla.