HOUSTON, May 17 (Xinhua) -- The number of active drilling rigs in the United States increased to 604 this week, up by one from the previous week but down by 116 from last year, according to the weekly data released by Houston-based oilfield services company Baker Hughes on Friday.
These active drilling rigs included 497 oil rigs operating in U.S. oil fields, up by one from the previous week; 103 gas rigs, unchanged; and four miscellaneous rigs, the same as last week.
The rigs included 584 land drilling rigs, zero inland water drilling rigs, and 20 offshore drilling rigs.
Of them, 41 were directional drilling rigs, 545 were horizontal drilling rigs and 18 were vertical drilling rigs.
So far, the Permian Basin in western Texas and eastern New Mexico has been the largest source of shale oil production growth in the United States, having become an engine of supply growth outside the Organization of the Petroleum Exporting Countries in the past years.
