The industry posted yet more new horizontal oil and gas-liquids plays.

As 2011 has come to a close, here’s a list of some of the top U.S. oil and gas E&P-industry stories of the past year. Add yours by e-mailing ndarbonne@hartenergy.com.

(+) Mississippi Lime. This horizontal oil play in northern Oklahoma and southern Kansas exploded onto the E&P scene in the spring of 2011 with SandRidge Energy Inc. reporting it had amassed nearly 1 million acres over the Chester, Manning, Meramec and Osage mix of limestone, weathered chert or chat, and dolomite. Chesapeake Energy Corp. later reported it had amassed, well, yet more. By year-end Spanish energy giant Repsol YPF bought into SandRidge’s play in a $1-billion joint venture: $250 million in cash upfront and $750 million in drilling carries.

(+) Utica Shale. Chesapeake Energy Corp. and partner EV Energy Partners LP/EnerVest Management Ltd. reported results in September of an initial four horizontal wells into Ohio’s Utica shale, proving gas-liquids production in that state. Four weeks later, Chesapeake had a letter of intent with a still-to-be-identified company for a $3.4-billion joint venture within its Utica leasehold. Chesapeake and EV are working now to prove the oil window of the play. Ohio Gov. Kasich and team are, well, elated.

(-) The New York Times “Hit Piece.” Both industry and non-industry members were apoplectic this summer about an NYT article that claimed scientifically accepted principles in determining future potential of shale-gas production to be a hoax. This was based mostly on old e-mails among a few critics; there was no industry comment. NYT public editor Arthur Brisbane took issue as well with how the article was handled, concluding a couple of weeks later, “My view is that such a pointed article needed more convincing substantiation, more space for a reasoned explanation of the other side and more clarity about its focus.”

(-, +) The Keystone XL Postponement. President Obama shocked Republicans and Democrats alike in November when announcing he would postpone a decision on permitting the Keystone XL Canada-to-the-Gulf-Coast oil-pipeline project until after the 2012 presidential election. The Senate answered 89-10 shortly before Christmas with an amendment to Obama’s payroll-tax-reduction-extension bill that requires he make a decision within 60 days. After some foot-dragging and tongue-wagging, the House concurred with the amended bill before cutting out for the holidays. The amendment’s authors—Senators Lugar (Indiana), Hoeven (North Dakota) and Vitter (Louisiana)—say Obama can only reject the project if he deems trade with Canada to not be in U.S. interest. We’ll see if there are any rabbits left in the White House hat.

(+) Three Forks 2 Horizontal Discovery. Continental Resources Inc., which founded the horizontal Bakken oil play in 2004 and the horizontal Upper Three Forks (Bench 1) play in 2008, made the horizontal Three Forks Bench 2 discovery in the spring of 2011 with its Charlotte 2-22H. The well tested 1,140 BOE per day, mostly oil, from a 9,700-foot lateral after 30 frac stages on a 26/64-inch choke. The company is determining now whether Three Forks 2 produces independent of Three Forks 1; if so, the potential for oil production from the Bakken petroleum system will grow yet again.

(+) Louisiana Eagle Ford Oil Discovery. Going with almost no notice amongst media or industry analysts, privately held Indigo Minerals LLC reported the horizontal Louisiana Eagle Ford discovery in early December. The Bentley Lumber 34H #1 well in central Louisiana flowed 543 barrels oil equivalent (80% light, sweet oil) during a 24-hour test period. The balance of the BOEs was 1,520-Btu, 11-gallon-per-Mcf gas liquids. It’s planning more of these wells in 2012 and is seeking a joint-venture partner.

(+, -) The WTI/Brent Spread. As onshore U.S. oil production became congested at Cushing, Oklahoma, the price differential between WTI (or Nymex) and Brent (or seaborne oil) soared to as much as $25 in Brent’s favor. The spread has narrowed now to about $8. With oil above $90 for most of 2011, onshore U.S. producers weren’t too disadvantaged; their play economics still worked fine. But the spread wreaked havoc on refiners and fuel retailers—those on contract to buy seaborne crude versus those using cheaper WTI-priced oil. In the Northeast U.S., Brent-fed refineries were closed or have been pegged for closure.

(+) Tuscaloosa Marine Shale. Devon Energy Corp. revealed in May that it was putting its super-independent E&P might behind the bit in this oil-filled, sloughing shale in eastern Louisiana and southwestern Mississippi from which many E&Ps have tried to produce commercially during the past 50 years and failed. The horizontal attempts cost $12 million apiece or more, but the prize upon figuring out how to keep the hole open is large: This shale may contain some 7 billion barrels of oil.

(+) Brown Dense. Southwestern Energy Corp., the founder of the horizontal Fayetteville shale-gas play in north-central Arkansas, revealed in late July that it had put together more than 400,000 acres over the Lower Smackover or Brown Dense formation that is believed to be the source of decades of Upper Smackover oil production. It hasn’t revealed results from two wells in the rock but confirms this: It’s oil.

(+, -) Exporting U.S. Natural Gas. While Washington won’t commit to using abundant new U.S. natural gas supply at home, the Department of Energy permitted Cheniere Energy Partners LP in May to export gas from Cheniere’s Sabine Pass, Louisiana, LNG (liquefied natural gas) receiving terminal to any country with which the U.S. does not prohibit trade. The actual construction of the liquefaction facilities is in the FERC-clearance process now. Washington’s green light to exporting U.S. gas is a win for free markets and monetization of assets to their greatest potential, while also a sad statement on its interest in using this high-Btu, clean and abundant resource at home.

–Nissa Darbonne, Editor-at-Large, Oil and Gas Investor, OilandGasInvestor.com, Oil and Gas Investor This Week, A&D Watch, A-Dcenter.com, UGcenter.com. Contact Nissa at ndarbonne@hartenergy.com.