Release Date: July 17, 2006

WASHINGTON, DC — The Department of Energy today announced the selection of two cost-shared research and development projects targeting America's major source of natural gas: low-permeability or "tight" gas formations.

Tight gas is the largest of three so-called unconventional gas resources?the other two being coalbed methane (natural gas) and gas shales.

Production of unconventional gas in the United States represents about 40 percent of the Nation's total gas output in 2004, but could grow to 50 percent by 2030 if advanced technologies are developed and implemented.

The constraints on producing tight gas are due to the impermeable nature of the reservoir rocks, small reservoir compartments, abnormal (high or low) pressures, difficulty in predicting natural fractures that aid gas flow rates, and need to predict and avoid reservoirs that produce large volumes of water.

To create fractures in the reservoir that will improve the rate of gas flow to the wells, operating companies inject specially engineered, water-based fluids at high rates and pressures to hydraulically fracture the reservoir rock, creating pathways through which the tightly trapped gas can flow to the wellbore.

Potential techniques to enhance the fracturing process and methods to better locate naturally fractured "sweet spots" in tight formations may increase domestic natural gas production, which helps energy security and lowers gas prices to consumers.

These two aspects of tight gas recovery technology are the focus of the two projects chosen under the DOE funding opportunity. Both projects, which are described below, are managed by the DOE Office of Fossil Energy's National Energy Technology Laboratory.

• The University of Texas at Austin will design and implement energized frac jobs in tight gas sands. As many tight gas sand basins mature, an increasing number of wells are drilled into the depleted sections of the reservoirs to recover additional gas; consequently, reservoir pressures decline and operators encounter reductions in well productivity due to water blockage and insufficient cleanup of frac fluid residues. In addition, many tight gas sand reservoirs all too readily absorb water, which interferes with frac fluid injection efficiency. A frac job in which the frac fluids are "energized" with carbon dioxide or nitrogen can avoid these problems, but no existing 3-D computer model of standard hydraulic fracturing can adequately simulate energized fracs. The main goal of this project is to add thermal and compositional capabilities to 3-D hydraulic fracture models, which will allow operators to design and optimize energized frac jobs systematically. The new model will be tested by designing and implementing energized frac jobs in collaboration with Houston-based Anadarko Petroleum Corp. in Carthage field in East Texas and/or Ozona field in West Texas. DOE will provide about $694,000 of the project's nearly $1.5 million cost.
  
• The Massachusetts Institute of Technology will develop a novel analytical technique to better locate and characterize naturally fractured sweet spots and induced fractures in tight gas formations. Operators commonly use acoustic energy data gathered by 3-D seismic surveys on the surface to characterize the subsurface. Grouped as "waves," these acoustic signals sometimes scatter underground. Deploying seismic data-gathering devices down the borehole instead of on the surface yields an even clearer picture of the subsurface by eliminating much of the surface noise; one such borehole seismic technique is dubbed vertical seismic profiling (VSP). When multiple 3-D seismic surveys are conducted over time, a technique known as 4-D, operators can glean important clues about the behavior and characteristics of fluids in the subsurface formation. The objective of this project is to develop a new method of scattered-wave analysis of 4?D VSP in order to locate and characterize natural and induced fractures and optimize well placement. After developing the required processing and interpretation methods, university researchers will work with Denver-based EnCana Oil & Gas Inc. to demonstrate these methods in Jonah field in Wyoming. DOE will provide over half of the project's nearly $1 million total cost.