FACTBOX: Dolly's impact on Gulf of Mexico oil sector

(Reuters) - Companies begin returning workers to U.S. Gulf of Mexico oil and gas platforms and restoring oil and gas output shut due to Tropical Storm Dolly. Shut-in gas was down to 5.5 percent of Gulf output, down from 7.9 percent July 23, and shut-in oil was down to 1.4 percent of Gulf output, down from 4.5 July 23.

Dolly became a hurricane Tuesday afternoon and came ashore north of Port Isabel, Texas, about midday Wednesday. It dumped flooding rain over south Texas before weakening into a tropical depression Thursday.

The Gulf provides 25 percent of U.S. oil output and 15 percent of U.S. natural gas production.

Following are energy industry developments so far in response to the threat from Dolly.

******************OFFSHORE PRODUCTION IMPACT******************

- Mexican state oil company Pemex said it evacuated 66 workers from a maintenance facility in the Gulf but Dolly had no impact on production. Workers may return Thursday.

- Exxon Mobil Corp shut 12,000 barrels per day of liquids and 100 million cubic feet per day of natural gas.

- Anadarko Petroleum Corp. restarts all Gulf of Mexico production shut during Dolly. Peak shutdown was 30,000 barrels per day of oil and natural gas liquids.

- Apache Corp returns 11 mmcfd gas to production. Shut-in capacity reduced to 104 mmcfd from 115 mmcfd as Dolly passed and said they planned to resume full production soon.

- Chevron said it was restoring output in the Gulf after storm threat forced "minimal" shut-in production.

- Shell, one of the largest U.S. Gulf of Mexico producers, said there was no effect on its offshore oil and gas flow but an undisclosed amount was shut onshore.

- El Paso shut down "a handful" of onshore oilfield drilling and maintenance operations with no production impact. The company said Thursday it was preparing for restart.

- U.S. Minerals Management Service said Thursday (July 24) 420 million cubic feet per day (mmcfd) of natural gas shut, 5.5 percent of Gulf total, down from 606 mmcfd July 23, and 18,047 bpd of offshore oil shut, 1.4 percent of Gulf total, down from 58,122 bpd July 23.

*****************OFFSHORE PIPELINE IMPACT********************

- Williams Cos Inc said its Transco pipeline system was carrying 250 mmcfd less natural gas at the peak but that wells were restarting Thursday and volumes were rising again.

********************OFFSHORE EVACUATIONS**********************