UPDATE, 11/29/12, 5:45, p.m. EST: Information about the lawyers advising on ConocoPhillips’s sale of Kashagan oil field assets to India’s ONGC has been added to the ninth and tenth paragraphs of this story.

Allen & Overy, Borden Ladner GervaisCMS Cameron McKenna, and DLA Piper are the latest firms to reap the benefits from the energy M&A boom.

London-based oil giant BP, which has kept its outside lawyers busy with a series of asset sales over the past two years, announced plans to raise nearly $1.1 billion from the sale of its stakes in several North Sea oil and gas fields to the Abu Dhabi National Energy Company, which is also known as Taqa. BP also unveiled plans to sell its liquefied petroleum gas distribution business in Poland to King of Prussia, Pennsylvania-based UGI Corporation, which is being advised on the deal by a team of lawyers from DLA.

Stephen Millar, an energy partner with CMS Cameron McKenna in Aberdeen, Scotland, is advising BP on the sale of North Sea assets to Taqa. CMS has been a longtime legal adviser to BP, having worked with several other firms on the company’s $7 billion sale in 2010 of assets in Canada, Egypt, and the United States, according to our previous reports.

CMS has also handled two notable deals for BP so far this year: The firm teamed up with Norwegian shop Schodt in September to advise BP on the $240 million sale of its 18.36 percent stake in the Draugen field to Royal Dutch Shell and it partnered with Field Fisher Waterhouse in March for BP’s $400 million sale of U.K. gas assets to Perenco.

Chris Sawyer, managing counsel at BP in Aberdeen, took the lead in-house on the North Sea sale to Taqa. Rupert Bondy serves as group general counsel for BP, which this month agreed to pay $4.5 billion in fines and other payments as a result of a massive 2010 oil spill in the Gulf of Mexico. (The Environmental Protection Agency has temporarily banned BP from entering into contracts with the U.S. government, according to sibling publication The National Law Journal.)

Allen & Overy handled some legal aspects of the North Sea acquisition for Taqa, which was formed in 2005 and is controlled by the government of Abu Dhabi. Several media representatives for the Magic Circle firm did not respond to a request for information on the identities of the lead lawyers working on the matter.

Taqa’s CEO Carl Sheldon is a former A&O partner who previously served as general counsel of the company. Former Morrison & Foerster partner Steven Phillips has served as Taqa’s general counsel since December 2010.

A&O also took the lead this week advising India’s Oil and Natural Gas Corporation (ONGC) on its $5 billion purchase of the 8.4 percent stake in Kazakhstan’s Kashagan oil field held by ConocoPhillips. The Indian government owns about 74 percent of ONGC, which is the country’s largest oil exploration and production company. ONGC’s deal with ConocoPhillips is the sixth-largest acquisition involving an Indian company, according to reports by the nation’s business press.

The A&O team on the Kashagan deal was led by Edwin Tham, managing partner of the Magic Circle firm’s Moscow office and global head of its Russia/CIS practice, and Moscow-based senior corporate associate Gareth Irving. A&O was across the table from ONGC in September when it represented Hess Corporation on the sale of minority stakes in oil fields in the Caspian Sea to the Dehradun-based company’s offshore investment arm, according to our previous reports. (British firm Simmons & Simmons took the lead for ONGC on that deal.)

According to ConocoPhillips general counsel Janet Langford Kelly, an in-house legal team led by senior counsel Harry Sullivan, Jr., managing counsel S. John Granmayeh, and legal counsel Ilia Popov handled the company’s negotiations on the Kashagan deal with ONGC. Reuters reported last month that Houston-based ConocoPhillips had numerous suitors for its holdings in the coveted Kashagan, which is one of the largest potential oil discoveries of the past 30 years.

ConocoPhillips also stayed in-house earlier this year for the $1.29 billion sale of its Vietnamese assets to British and French oil company Perenco. The Am Law Daily reported last year that Wachtell, Lipton, Rosen & Katz, which represented predecessor company Phillips Petroleum on its $15.6 billion merger with Conoco in 2002, is once again advising ConocoPhillips on its plan to split itself into two publicly traded companies. (Wachtell also handled ConocoPhillips’s $3.4 billion sale of its stake in Lukoil back to the Russian oil company in 2010.)

Kelly, the company’s general counsel, is a former corporate associate at Wachtell who went on to become a partner at Sidley Austin and Zelle Hoffmann Voelbel & Mason. In July, Harvard Law School professor Jody Freeman was named to the board of ConocoPhillips.

Finally, Canada’s second-largest integrated oil company, Imperial Oil Limited, announced Wednesday that it would acquire a 50 percent stake in Calgary-based Celtic Exploration, which Exxon Mobil is in the process of purchasing.

The Am Law Daily reported last month on the roles snagged by Canadian firms Blake, Cassels & Graydon and Borden Ladner Gervais for Exxon Mobil’s $3.2 billion acquisition of Celtic. The deal is currently awaiting shareholder and regulatory approval, and now Imperial, about 70 percent of which is owned by Exxon Mobil, is seeking to pick up its 50 percent stake in Celtic after the previous transaction closes, according to The Canadian Press.

Celtic’s corporate secretary is Borden Ladner energy partner William Guinan in Calgary. Guinan, who also serves as an independent director for Celtic, did not respond to a request for comment on the names of the lawyers handling the latest transaction involving Celtic.

Brian Livingston, general counsel and corporate secretary for Imperial Oil, also did not respond to a request for comment about its potential external legal advisers. Reuters reports that Imperial Oil’s bid for half of Celtic might speed Canadian approvals of the target company’s proposed sale to Exxon Mobil, although regulators up north already have their hands full with several large oil and gas mergers.

One of those deal under review—a $15.1 billion acquisition of Canadian oil producer Nexen by The China National Offshore Oil Corporation (CNOOC)—represents the largest-ever purchase of a foreign company by a Chinese buyer. U.S. regulators are also currently evaluating the landmark transaction, according to The Deal.