The shallow biogenic gas play in the Niobrara Chalk in the eastern Denver-Julesburg Basin is attracting strong interest. One of the newest entrants is Denver-based Teton Petroleum Co. The firm recently acquired approximately 180,000 acres in the rapidly expanding DJ play, which is centered in eastern Colorado and extends into southwestern Nebraska and northwestern Kansas. Teton was well known for its long involvement in Russia, but the company sold its Russian assets in 2004 after it encountered some contractual problems in Western Siberia. "From August through December 2004, we were looking for new projects," says Karl Arleth, president and chief executive officer. The company wished to redeploy its capital into drilling deals and close-in exploration, and it was looking for plays in which it could create and grow value. Teton liked several attributes of the DJ Basin play, which is an extension of existing shallow production in the Upper Cretaceous Niobrara. On the eastern flank of the basin, the Niobrara is a continuous-type biogenic gas deposit. It is a low-permeability chalk that covers an extensive area, with commercial fields developed on "sweet spots" that are usually associated with structural features. More than 30 fields have produced more than 300 billion cubic feet (Bcf) of gas from the Niobrara in this area. "The Niobrara play is fairly well controlled, as it was drilled to some extent during the late 1970s," says Arleth. "Many of those early wells tested gas volumes that were noncommercial at the time, but today are very commercial." Drilling depths vary from around 3,000 feet to less than 1,000 feet, so drilling and completion costs are reasonable. Much of the acreage is fee and is not held by production, so large lease positions can be assembled. The eastern DJ also offers several prospective horizons in addition to the Niobrara, most notably the Cretaceous Sharon Springs and Permian Chase. The largest Niobrara field is Waverly, in Yuma County, Colorado, which has already produced 170 Bcf. Other significant Yuma County finds are Republican, Beecher Island and Bonny fields, which have estimated ultimate recoveries of 87 billion cubic feet equivalent (Bcfe), 130 Bcfe and 79 Bcfe, respectively. Kansas has Cherry Creek, with an estimated ultimate recovery of 15 Bcfe, and Goodland, with 13 Bcfe. "Not much exploration has been done in Nebraska, but we think that part of the play could have potential for some bigger fields because of differences in the stratigraphy and geology there." Teton expects to spend $900,000 on exploration in its new play this year. It joins an active group of operators working the Niobrara, including several joint ventures with sizeable positions. Houston-based Houston Exploration Co. and Denver-based Tipperary Oil & Gas Corp. are partners in the 170,000-acre Republican and 159,000-acre Frenchman joint ventures in eastern Colorado. Through April, the partners had drilled 39 wells on the Republican project, of which 32 were completed. Tipperary also owns a 100% interest in 3,000 acres in the Frenchman area, on which it has completed 11 out of 14 drilled wells. Bakersfield, California-based Berry Petroleum Co. moved into the eastern DJ early this year with a $105-million purchase of producing assets in Yuma County. Berry bought a 52% interest in 130,000 gross acres, including more than 650 producing wells, net production of 8.8 million cubic feet per day and 87 Bcf of proved reserves. This year, it plans to drill 60 wells and recomplete another 25 in Yuma County. In addition, Berry formed a joint venture covering 368,000 gross acres in the three states in the play with Bill Barrett Corp. of Denver. The partners have drilled their first joint-venture well in Sherman County, Kansas, and plan to drill a horizontal well. Naturally, some bumps in the road have been encountered. Another prominent player is Western Gas Resources, which has a 340,000-net-acre position in Colorado and Nebraska and has drilled 12 wells. Results have been a mixed bag, according to the company. It found that 3-D seismic worked very well in identifying drilling locations, but its wells encountered higher volumes of water than anticipated. Denver-based Western has six wells onstream and is completing another three. Near-term, the company plans to produce its wells and evaluate results before initiating additional drilling.