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
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
- 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
- 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