HOUSTON -- With offshore drilling accelerating worldwide, owners and operators of the rigs searching for ocean oil only see sunny days ahead.

Though business all but collapsed in the wake of the 2010 Gulf of Mexico oil spill, offshore rig owners are now telling their investors that the environment has turned around. Demand for all types of equipment is up, but especially for ultra-deepwater and harsh-environment-capable drilling rigs, as the world's largest oil and gas companies explore new frontier areas for hydrocarbons.

As a result, day rates are climbing back to historic highs and will likely hit a new peak average this year. Rates for the most advanced rigs are gradually creeping up to the $500,000 range and up to $650,000 in at least one case. There's speculation that prices will continue to rise as demand gradually outstrips supply, perhaps by the end of this year.

The industry is enjoying a further lift on the back of a depressed global shipping market. Not a lot of new cargo vessels are being built, so underused shipyards are eager for energy industry business, providing rig operators with attractive pricing and contractual terms on both ends that are helping companies to improve their profit margins.

The new environment is overall increasing the clout and bargaining position of companies that control advanced offshore equipment. And so far, their customers seem more than willing to play by the new rules as international crude oil prices continue to hover around $100 per barrel and more countries are entering the offshore and deepwater drilling frenzy.

"The ultra-deepwater market, as everyone is seeing, is very robust," said Greg Cauthen, executive vice president at Transocean Ltd. "Our customers are very nervous about access to rig capacity."

Transocean officials acknowledge that their company has been struggling as of late.

The company owned the ill-fated Deepwater Horizon rig that exploded and caused the 2010 Gulf spill, and it is still dealing with the aftermath. At a conference in Austin hosted by UBS, Cauthen warned investors that his firm still expects the government to issue more indictments against companies and individuals involved in the spill, and that a fiscal settlement won't be finalized until November.

But looking forward, Cauthen said, his firm is optimistic. While a relatively small proportion of Transocean's equipment is currently under firm contract, he said the company is busy tying up a larger percentage to new work, with several oil and gas companies talking to Transocean about getting access to rigs.

The delay is mainly due to Transocean firming up the contractual terms, a situation that benefits the company. Because demand is robust, Transocean and other firms can now demand stronger day rate pricing, better legal protections in the event of an accident and better terms for compensation during unanticipated downtimes than the industry has been willing to accept before.

"Even though 2012 shows a lot of availability, a lot of that has now been locked in, and we're just in the final stages of executing contracts," Cauthen said. This year promises "a lot of opportunity to benefit the improving market conditions that we find ourselves in," he added.

Owner of the world's largest offshore fleet, Transocean reported that it has about $1.9 billion worth of drilling contracts signed and $2.3 billion in letters of intent -- deals the company has not yet announced.

As drilling activity increases, the company believes that nearly all its available equipment will be busy in the coming years, even its older jack-up rig fleet. By 2015, Transocean estimates 96 percent of its standard jack-up rigs and 90 percent of its midwater floating rigs will be committed to contracts. Cauthen said the company is in talks with clients about possibly building new rigs, especially ice-class rigs and vessels capable of drilling in Arctic conditions.

Noble upgrading its fleet

Executives at Noble Corp., a smaller competitor to Transocean, express even more optimism about their near-term prospects.

In contrast to Transocean, which is focused on reducing debt and recovering from the Macondo well blowout, Noble is spending big in an effort to unload aging equipment and replace the fleet with a newer, more advanced one, sporting rigs and drillships that many in the oil and gas industry are now demanding.

At a recent meeting in Houston for financial analysts, Noble's senior vice president for finance reported that his company expects to spend around $1.9 billion building new rigs this year, and a further $2.3 billion in 2013 and $2 billion in 2014 on the same mission. Capital spending on new builds is expected to drop off to $700 million in 2015.

Despite the high price tag, officials at Noble say that the market demand justifies the investment and that now is the time to make that investment. Like Transocean, Seadrill Ltd., Maersk Drilling and others, Noble reports benefiting from strong day rates and bargaining position with oil and gas majors, as well as good pricing and payment terms from shipyards that are losing business elsewhere.

Since 2007, Noble says, it has added eight new rigs to its fleet -- one jack-up, three deepwater drillships and four semisubmersible rigs. Five more drillships and six new jack-up rigs are being built and are scheduled for delivery in 2013 to 2014. Noble CEO David Williams says the company is confident it will find customers for the newer equipment, barring any unforeseen events like a collapse in oil prices or another major offshore spill that halts activity.

Noble's upcoming rigs "will provide excellent opportunities in today's very robust environment, and we further expect that several of these units could be committed to contracts within 2012," Williams said. "We believe that further expansion is likely. The opportunity to construct purpose build units with attractive shipyard pricing with good, favorable payment terms in an industry environment with solid fundamentals like we see today is hard to ignore."

Successfully drilling programs off Brazil, eastern and western Africa, the North Sea, Southeast Asia, and elsewhere are encouraging larger and smaller independent oil and gas firms to try exploring ever-more-remote locations. Arctic Russia, Alaska and Canada are among the new regions gaining strong interest, and Noble says it's considering adding more semisubmersible rigs that can handle ice and rough seas to its fleet because, like its competitors, the company is getting requests from major oil and gas companies for harsh-environment rigs.

Earnings aren't keeping pace

Earnings for rig owners so far haven't been as robust as the optimistic business forecasts seem to suggest.

Last month, Noble reported first-quarter 2012 earnings of $120 million, down from $127 million in the previous quarter. But that's well above the $54 million the company said it pulled in during the first quarter of 2011, when business conditions in offshore energy were still depressed.

Larger rig operator Seadrill this month reported a first-quarter 2012 profit of $456 million, up slightly from $436 million in the previous quarter. But like the other firms, Seadrill told investors and analysts to expect even stronger financial performance in the near future so long as the current conditions persist, namely an offshore drilling industry with "demand outpacing supply" and "very few rigs available until 2013."

Companies say the best opportunities remain in the ultra-deepwater business, where demand for drillships and advanced floating rigs is strongest. Transocean's Cauthen said he sees "demand easily exceeding supply for the ultra-deepwater market."

The Gulf of Mexico, offshore Africa and especially Brazil will likely attract the bulk of new ultra-deepwater-capable ships. Analysts at the Noble meeting joked that Brazilian energy firm Petrobras seemed to want an infinite supply of rigs at its disposal, just one anecdotal sign of the anxiety building over equipment availability among the offshore oil and gas industry.