HOUSTON, Dec. 22 (Xinhua) -- The number of active drilling rigs in the United States decreased to 620 this week, down by three from the previous week and by 159 from last year, according to the weekly data released by Houston-based oilfield services company Baker Hughes on Friday.
These active drilling rigs included 498 oil rigs operating in U.S. oil fields, down by three from the previous week; 120 gas rigs, up by one; and two miscellaneous rigs, down by one.
The rigs included 601 land drilling rigs and 19 offshore drilling rigs.
Of them, 46 were directional drilling rigs, 563 were horizontal drilling rigs and 11 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.
