State-of-the-Art Summary

the Barnett. Moving westward, this lower frac barrier disappears. Moving southward, both its upper and lower frac barriers disappear. Horizontal wells where frac barriers are absent are said to stand the best chance of staying in zone. And they are being oriented according to prevailing stress orientations that run southwest to northeast.

Over time, will re-fracing the Upper Barnett create similar reorientations as experienced in the Lower Barnett? For either, would a second re-frac after an extended production period create yet another frac orientation that would give production an economic boost? Stay tuned. "When I went to school at Oklahoma State University and took geology," noted conference presenter Kent Bowker with Star of Texas Energy Services, "we did not discuss this rock as a reservoir rock. We have to re-educate ourselves and try to understand how we can take what we learn from the Barnett and apply it to other basins."

Woodford Shale: Decades of Potential

If it took 15 to 20 years to realize significant value from the Barnett Shale, our goal with the Woodford Shale is to half the Barnett's learning curve—even if the Woodford doesn't become as significant a resource as the Barnett has. The prime area for this Upper Devonian/Lower Mississippian shale's gas potential lies just a couple hundred miles north of the Barnett Shale, but it is considered to be where the Barnett Shale was 15 to 20 years ago and gas wells have not yet proliferated. Current Woodford Shale production stands at 24 Woodford-only gas leases and 48 Woodford-only oil leases (oil and associated gas). Cumulative production may be minimal, but the resource potential is large.

Many questions remain about how to turn Woodford Shale gas-resource potential into production. As in the Barnett, will thermal maturity combined with stimulation technology be the keys to economic production? Or will it be natural fracturing? Or will it be something else entirely? Coalbed-methane researchers have developed a six-element producibility model. Will that model or a modification thereof help operators unlock the secret to shale gas reservoirs such as the Woodford?

Midcontinent
Coalbed Methane

CBM activity is robust in the Cherokee Basin in southeast Kansas and northeast Oklahoma, as well as in the Arkoma Basin in Oklahoma and Arkansas. In the Arkoma Basin, the Oklahoma Geological Survey reports that 605 vertical CBM wells produced 44 Bcf of gas from 1989 to mid-2003 and 182 horizontal CBM wells in the Arkoma produced over 27 Bcf of gas from 1998 to mid-2003. Eight hundred and forty-four CBM wells in the northeast Oklahoma shelf produced over 45 Bcf of gas between 1994 and 2003.

Cherokee Basin production, which with a few exceptions comes from vertical wells, is now about 11 Bcf per year in northeast Oklahoma and 10 Bcf per year in southeast Kansas. In the Oklahoma side of the Arkoma Basin, production from horizontal-well completions has now exceeded that from vertical wells-around 12 Bcf per year versus 8 Bcf per year from vertical wells. CBM activity in Arkansas is embryonic, limited almost exclusively to horizontal wells in the Lower Hartshorne coal.

When it comes to Midcontinent CBM, what we know depends on where we are. In Kansas, there is a strong focus on CBM resource definition, including looking further north into the Forest City Basin. The Kansas Geological Survey has developed isopach maps for different coals and is developing depositional interpretations that will turn them into treasure maps. Understanding gas content is still critical in Kansas. Limited sampling indicates that it can be quite variable. Contrary to logic, some of the shallower coals can have higher gas content!

"The Western Interior Coal Region is vast, located in six states and 87,000 square miles," commented Simon Testa, who summarized some of his results gathered by TICORA Geosciences, Inc. (www.ticora.com) for a three-year study on frontier basin resource and production potential sponsored by the Gas Technology Institute. "Our sample density was low. But you'll be amazed at some of the regression that we've found across the general region." An interpretative framework is developing to explain observed gas content trends for the study, which is schedule to be completed in August.

And then there's Arkansas. Because of its nascence, resource definition is paramount to its Arkoma Basin activity. According to Bill Prior with the Arkansas Geological

CBM Data
Sources Sidebar

Oklahoma

Save some time by checking out the Oklahoma Geological Survey's coal and coalbed methane Web page at ogs.ou.edu/fossilfuels/coal.htm. Aside from general information about Oklahoma's coal resources, such as maps and stratigraphy, you can get links to coal rank and production data, details about activity in the Arkoma Basin and northeast Oklahoma shelf, and even a CBM completion histogram. The links section will get you to all major Oklahoma CBM data from national, government and academic sources. And don't forget the coal database, where you can search for CBM completions by county, bed, operator and other useful categories.
 

Kansas

Interested in the Western Interior Coal Region? A visit to the Kansas Geological Survey's Coalbed Methane Project page at www.kgs.ukans.edu/
CBM/index.html  is a must. Links to Kansas and regional sites, plus nationwide and USGS endeavors alone make the site worth a look. But its real beauty is Kansas-specific reports, presentations and other information available for download. From stratigraphy reports to isopach maps to chemical analysis-there is a lot of good material. Some great PowerPoint presentations are there for the taking, too. Check back this fall to see the final results of the GTI study on which Simon Testa presented at the Oklahoma show!
 

Arkansas

With Arkansas unconventional gas production still short in the tooth, CBM public data resources are more limited than in other states. But it is a highly developed region conventionally, and the Arkansas Geological Commission offers a nice, comprehensive resource for Arkansas geology at www.state.ar.
us/agc/agc.htm, which includes extensive research on stratigraphy, mineral resource estimates and maps, as well as links to a number of useful other resources. Also, the site offers an impressive list of maps and publications available for purchase.