It appears that a trend that has been taking shape among integrated oil companies will continue when ConocoPhillips (NYSE: COP), the third-largest U.S.-based member of Big Oil, figuratively oversees the divorce of its exploration and production business from its refining and marketing operation.

According to a conference call conducted by Conoco's CEO Jim Mulva on Thursday, the company's powers-that-be have concluded that the separation "was the best way to create value for our shareholders." With crude prices having moved steadily upward during the past couple of years, exploration and production (upstream) earnings have generally been robust, while refining and marketing (downstream) margins have been squeezed, creating in imbalance in the sectors' respective contributions to the integrated companies' earnings.

Marathon Oil (NYSE: MRO) was the most recent company to formally separate its upstream and downstream operations. Recently, the company exchanged one share of a new company composed of its refining and sales operations for every two shares held in Marathon Oil. The newly formed company, called Marathon Petroleum (NYSE: MPC), operates from a Findlay, Ohio, headquarters, while Marathon Oil remains in Houston.

Among the two U.S. majors that are larger than Conoco, Chevron (NYSE: CVX) has been steadily trimming its downstream assets during the past couple of years, without fully separating the two operations. At the same time, ExxonMobil (NYSE: XOM), the big enchilada of Big Oil, appears comfortable with its status as a fully integrated company.

For ConocoPhillips, the jettisoning of its downstream operations could be something of a coup de grace for a now two-year-old program to increase the value of the company's shares. During an active buying program in the past decade, the company accumulated considerable debt.

As a result, in 2009 it initiated an effort to reshape its balance sheet by selling at least $10 billion of non-core assets, along with its stake in Russia's big oil company, OAO Lukoil. The program was extended earlier this year.

Mulva intends to retire once the spinoff of the downstream operation is completed -- probably during the first half of 2012. The new refining company would have a throughput capacity of about 2.4 million barrels a day, placing it slightly ahead of Valero Energy (NYSE: VLO) regarding size supremacy in the group.

Among all the members of Big Oil, then, ConocoPhillips clearly leads the pack in recasting itself. As such, my inclination is to advise Fools with a yen for energy investments to keep a close eye on the company, but to permit the restructuring process to advance farther before grabbing your wallets with buy orders on your minds. There's not a better way to initiate such an effort than by adding Conoco to your version of My Watchlist.