More than 1,700 wells were reported completed in the first quarter of 2011 in unconventional plays in the U.S. Ann Priestman, editor of Hart Energy's UGcenter.com website, compiled the statistics from IHS Inc. data.

Priestman sorted completions by play, by operator and by county. In total, 1,755 wells in 13 plays were reported by more than 130 operators.

Surprisingly, the Barnett shale of North Texas led all unconventional plays with 357 completions. Although rig counts have dropped dramatically since the Barnett's heyday, the large number of completions attests to the backlog of drilled wells that exists in the play.

The second rank was held by the Piceance/Uinta. The two western basins, located in eastern Utah and western Colorado, have been seeing active drilling, especially in Duchesne and Uintah counties, Utah, and Garfield County, Colorado. The Utah counties had 150 total completions, nearly evenly split between the two, and the Colorado county had 54. Several liquids-rich targets, including the Mancos and Mesaverde, are the focus of fresh interest, along with established oil plays in the Wasatch and Green River formations.

The third most popular play, based on numbers of completions, was the Niobrara. In addition to the hefty activity of Anadarko Petroleum noted below, other operators with large programs included Noble Energy, with 30 completions, and PDC Energy, with 20.

The Fayetteville, Bakken, Haynesville and Eagle Ford plays fell in a tight range, between 152 and 136 completions. "In these plays, activity was spread fairly evenly across several counties in each area," says Priestman. White County, Arkansas, was busiest for the Fayetteville, and Williams and Mountrail counties were tops for the Bakken. DeSoto took the lead for Haynesville completions, and Dimmit for Eagle Ford.

"One county that surprised me with its level of activity was Wyoming's Sublette, in the Green River Basin," she says. Home to both Pinedale and Jonah fields, Sublette posted 81 total completions, split 49 for Pinedale and 32 for Jonah. Indeed, after Colorado's Weld and Texas' Tarrant, Sublette was the third most active county in the nation.

"It also surprised me that the Utica and New Albany plays did not have any reported completions during the first quarter," she says. In the case of the Utica, it's an emerging play with few documented producers, and for the New Albany it's an early, vertical shale play that has waned.

Priestman had a few caveats: completions information tends to lag, so quarterly counts will change as more information becomes available. Reporting requirements vary among states, so plays such as Appalachia's Marcellus can initially be undercounted. She also searched by producing formations, fields or basins, depending on the targeted play.

From the operator perspective, Anadarko Petroleum and its Kerr McGee subsidiary led the list, reporting 231 completions. Some 60% of those were in the Niobrara, with most located in the traditional producing area of Wattenberg Field in Weld County, Colorado. Of the remainder, most were in Uintah County, Utah, and Dimmit County, Texas. In the former area, Anadarko drills Wasatch and Mesaverde wells in Natural Buttes Field and in the latter, Eagle Ford shale wells.

The operators following Anadarko were Chesapeake Energy and ExxonMobil, with 165 and 147 completions, respectively. Chesapeake posted 74 completions in the Barnett shale, primarily in Johnson and Tarrant counties, and 40 in the Haynesville. Its work there was mainly on the Louisiana side, but it completed wells in seven counties spread across the entire play. ExxonMobil, working in large measure under its XTO Energy subsidiary, completed 38 wells in both the Cotton Valley and Barnett plays, and 40 wells in the Fayetteville.

Rounding out the Top Five operators were EOG Resources and Southwestern Energy. EOG led all operators in Barnett completions, bringing in 82 wells in North Texas alone, mainly in the combo play in Montague and Cooke counties. Southwestern, the discoverer of the Fayetteville shale, continued its long-standing dominance with 99 completions in that play.