NEW YORK ( TheDeal) -- Oil and gas has long been a primary object of scorn from environmental activists angered by Exxon Mobil ( XOM - Get Report)'s Valdez oil spill in Prince William Sound in 1989 and more recently with BP ( BP)'s Deepwater Horizon explosion in the Gulf of Mexico in 2010.

However, activists of a different sort -- that is, activist investors -- have increasingly tried over the past year to force change at several oil and gas companies. Targets have included Occidental Petroleum ( OXY - Get Report) Nabors Industries ( NBR - Get Report), Chesapeake Energy ( CHK - Get Report), Transocean ( RIG - Get Report), Hess ( HES - Get Report), CVR ( CVI - Get Report) and SandRidge Energy ( SD - Get Report).

The latest is Houston's Oil States International ( OIS - Get Report). The activist has been Barry Rosenstein's Jana Partners LLC, which holds a 9% stake in Oil States, and is urging the company to spin off its lodging business into a separate company or a real estate investment trust, better known as a REIT.

Speculation has heightened that Swiss-based Weatherford International Ltd. may be next after missing earnings targets for the past three quarters. Another potential target is Oklahoma City-based Devon Energy ( DVN - Get Report), which is attempting to raise cash by putting its gas gathering and processing assets into a master limited partnership.

What's the reason for all this attention from activist investors?

Simmons & Co. International analyst Bill Herbert wrote in a recent report that "full-throttled aggression" by shareholder activists is due to the largely uninspired results for energy companies, and the "ongoing intransigence" of the industry to more sensibly allocate capital and improve corporate governance.

"What is interesting, however, is the degree to which activists have been emboldened and are now pursuing agendas with previously unassailable management teams," the report said, noting the Oil States case. "Prior exemplary track records are not deterrents if the perception is that managements are being unresponsive to seemingly legitimate shareholder agendas."

New Orleans-based Global Hunter Securities LLC said activists are urging not only asset changes for capital needs or better focus to wholescale management changes. The call for replacing top executives extents from the general cause of increasing shareholder value to anger with overpaid managers, entrenched boards and old-fashioned mismanagement.

"We believe other underperformers, APA Apache ( APA - Get Report) a chief example, are pre-emptively looking to shed some noncore assets and even buy back shares to stave off potential activism," the firm said.

Some activists have been successful in the energy sector, others have not. Paul Singer's Elliott Management Corp. was able to get Hess CEO John Hess, son of the company's founder, to give up the chairmanship, but New York-based Hess was able to keep its new board nominees after agreeing to add three from Elliott.

And TPG-Axon Capital Management LP won in its fight with Oklahoma City's SandRidge, gaining board seats (although not control of the company), management changes (including the potential departure of founder and CEO Tom Ward by June 30), a formal review of related party transactions by an independent firm and a strategic review process that could lead to a sale of assets or of the entire company. "If all goes according to the activists' plans, we should see a leaner, meaner SD SandRidge emerge, with a renewed focus on capital discipline, risk management and project economics," Global Hunter wrote in a note May 8.

Carl Icahn has had mixed results. While he was able to take control of Sugar Land, Texas-based refiner CVR Energy, which issued a special $6.50 per share dividend to shareholders on May 28, and got CEO Aubrey McClendon of Oklahoma City's Chesapeake booted, he only achieved a partial victory with Transocean, convincing the board to vote out chairman Michael Talbert and install one of his own nominees but failing to boost the annual dividend to $4 per share from the Swiss-based offshore driller's proposed $2.24.

Even a whisper of potential activism can send an energy stock soaring, whether a big change is coming or not, given a tough energy stock market plagued by directionless crude oil prices, mixed industry fundamentals and general commodity skittishness, Houston's Tudor, Pickering, Holt & Co. Securities Inc. said. The firm cites Key Energy Services Inc., which said May 24 it was expanding its board of directors to include Mark Rosenberg, principal of MHR Fund Management LLC and Key's largest shareholder. The Houston oil service provider's stock added 10% over two days on the news. "Activists have had much success moving energy stocks over the past year," the firm wrote.

However, a professional involved in several of these situations said activists' focus on boosting near-term share prices doesn't make for the best long-term profitability. "This is a fad, and in two years, I suspect, there won't be much activity," the professional said.

Allen Brooks, an analyst at Houston energy services investment banking boutique PPHB, agreed, describing the emergence of activist shareholders targeting exploration and production companies for mismanaging their businesses as the normal counterbalance of capital markets and may slow with the doubling of natural gas prices this spring. But for managements of truly troubled companies, he said: "We would remind them of what one of our stock market-savvy bosses used to remind us: 'Wishing and hoping isn't a strategy.' "

Written by Claire Poole in New York