* Combines subsea businesses, pose risk to some rivals * Schlumberger shares rise 2.2 pct, Cameron up 3.6 pct Nov 15 (Reuters) - Schlumberger Ltd, the world's largest oilfield services company, and oilfield equipment maker Cameron International Corp said they would combine their subsea businesses as they look to tap into rising demand for drilling in deeper waters. Oil companies, bolstered by high oil prices, have raised exploration spending, venturing into areas like the Arctic or heading to very deep sea levels in regions like West Africa, requiring new techniques to access oil. About 200 such fields are expected to come online in the next four years and by 2020 more than 11,000 subsea wells will be operating worldwide, Schlumberger Chief Executive Paal Kibsgaard said at a recent energy conference. Cameron, which will manage the joint venture and hold a 60 percent stake, will receive $600 million from Schlumberger. The structure is similar to Schlumberger's MI-Swaco drilling fluid JV with Smith International, which held 60 percent of MI-Swaco before it was bought by Schlumberger for $11 billion in 2010. Shares of Cameron rose 3.6 percent to $52.63, and Schlumberger rose 2 percent to $69.16 - both outperforming a 1.3 percent rise in the Philadelphia oil service index. "The JV's mission is to unlock greater reservoir potential from customers' subsea developments," Cameron CEO Jack Moore said on a conference call on Thursday. Subsea production equipment is based on the sea floor and is built to withstand strong ocean currents and harsh temperatures. Schlumberger will contribute its Framo, Surveillance, Flow Assurance and Power and Controls businesses to the venture, and own the remaining 40 percent stake. "The partnership brings together Schlumberger's expertise in subsea processing and platform integration with Cameron's vast capabilities in subsea tree manufacturing," Barclays analyst James West said, referring to the equipment that manages the flow in and out of underwater wells. Doug Sheridan of EnergyPoint Research in Houston said the financial implications seemed less significant to the two companies than to competitors such as Dril-Quip and FMC Technologies Inc, which both make subsea products. "We also believe the move, to some extent, represents evidence of Schlumberger and Cameron taking steps to provide greater focus in the respective core businesses," Sheridan said. Credit Suisse advised Cameron while Goldman, Sachs & Co advised Schlumberger on the venture.