(Adds natgas and basin details in paragraphs 4 and 7)
By Scott DiSavino
Sept 25 (Reuters) - U.S. energy firms cut oil rigs for a fourth week in a row this week, data showed on Friday, a sign the continued weak prices were causing energy firms to reduce drilling plans.
Drillers removed four oil rigs in the week ended Sept. 25, bringing the total rig count down to 640, the lowest since July, after cutting a total of 31 rigs over the three prior weeks, oil services company Baker Hughes Inc said in its closely followed report.
That compared with 1,592 oil rigs in the same week a year ago and an all-time high of 1,609 in October 2014.
Combined with the reduction in natural gas rigs, total U.S. rigs were at a 12-year low. Natural gas rigs were down one this week to 197, up just one from its lowest level since at least 1987, according to the Baker Hughes data.
The reductions over the past few weeks have cut into the 47 oil rigs that energy firms added in July and August after some drillers followed through on plans to add rigs announced in May and June when U.S. crude futures averaged $60 a barrel.
U.S. oil futures this week however were averaging $45 a barrel for a third week in a row, near the lowest levels for the year on continued lackluster global demand and lingering oversupply concerns.
In the country's major shale basins, drillers this week cut three oil rigs in both the Permian in West Texas and eastern New Mexico and the Eagle Ford in South Texas and one in the Bakken in North Dakota and Montana. The Niobrara in Colorado and Wyoming remained unchanged.
On Friday, U.S. crude prices were up about 1 percent, following gains in Wall Street stocks on stronger revised U.S. economic data.
Despite the short-term price gain on Friday, U.S. oil production has declined over the past several weeks due to the weak crude market.
U.S. oil output last week held around 9.1 million barrels per day (bpd) for a third week in a row, according to government data. That was down from average production of 9.6 million bpd from late May to mid-July, which was the highest output since the early 1970s.
"The current rig count is pointing to U.S. production declining sequentially between the second quarter and the fourth quarter of 2015 by 255 thousand barrels a day," analysts at Goldman Sachs said in a note. (Reporting by Scott DiSavino; Editing by Marguerita Choy)