Oct 19 (Reuters) - U.S. oilfield firm Halliburton Co (HAL.N) on Tuesday posted its third consecutive quarterly profit and said customer spending in the United States could jump 20% next year, as stronger oil prices and drilling activity boost demand for services and equipment. Oil prices have rallied to multi-year highs with global crude futures climbing 4.5% in the quarter ended Sept. 30, helped by OPEC+"s decision to maintain its planned output increase rather than raising it on global supply concerns. Brent oil futures are trading around $84.4 a barrel, up about 63% so far this year, while benchmark U.S. crude is at roughly $82.5 a barrel, up 70% over the same period. "I see a multiyear upcycle unfolding. Structural global commodity tightness drives increased demand for our services, both internationally and in North America," Halliburton Chief Executive Officer Jeff Miller said. Miller said the company is reallocating some equipment to drive better returns, and that it has seen some net pricing gains for its services. Next year"s jump in customer spending will be the result of both better pricing and inflation, he said. "We expect customers to drill more new wells to offset steep decline rates," Miller told investors during a conference call on Tuesday. Companies have begun the tender process for equipment early amid a tight market, he added. Houston-based Halliburton posted adjusted net income attributable to the company of $248 million, or 28 cents per share, in the three months ended Sept. 30, up from the $100 million or 11 cents per share reported a year earlier. Its third-quarter profit was in line with analysts" estimates, while revenue of $3.86 billion was slightly under consensus expectations of $3.912 billion, according to Refinitiv IBES. The company had previously guided down its third-quarter expectations due to Hurricane Ida, which caused unexpected downtime in the U.S. Gulf of Mexico. Halliburton"s shares were up 1.2% midday at $26.32, after falling more than 2% in morning activity. They are up 39% year-to-date, trailing gains seen in oil prices. Halliburton, a leading provider of hydraulic fracturing services to the U.S. market, is the first major oilfield services firm to report its third-quarter earnings. Rivals Baker Hughes (BKR.N) and Schlumberger will report later this week. Oilfield firms should be supported by the jump in activity, as the number of active U.S. hydraulic fracturing fleets climbed to 263 in early October, up from around 100 a year ago, according to data from Primary Vision. Wall Street analysts said Halliburton"s results were neutral to slightly negative, as some financial metrics came in under estimates. They lauded Halliburton"s report of $469 million in free cash flow, which topped expectations. Reporting by Arunima Kumar in Bengaluru and Liz Hampton in Denver; Editing by Shinjini Ganguli, Emelia Sithole-Matarise, Bernadette Baum and Andrea Ricci Our Standards: The Thomson Reuters Trust Principles