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**********************

- MMS said on Thursday personnel remain evacuated from 43 production platforms or 6 percent of 717 manned platforms in the Gulf, down from 62 July 23, and from four drilling rigs or 3.25 percent of 123 currently operating in the Gulf, down from eight July 23.

- Anadarko said Wednesday it was sending back to work all 180 employees that had been evacuated from Nansen, Boomvang and Gunnison platforms in the western Gulf of Mexico.

- Apache Corp said it was pulling 140 people from Gulf of Mexico platforms.

- Shell said Thursday it was returning to work 200 personnel evacuated from offshore facilities.

- BP Plc, Exxon Mobil and Chevron also removed workers from platforms, but Chevron said Thursday it was remobilizing workers for full operations.

*********************REFINERIES*******************************

- Valero Energy Corp said it expected to restore full operations by the end of the week after run cuts of 10-20 percent at its Houston refinery, capacity 130,000 bpd, and its Port Arthur refinery, 295,000 bpd, because of shipping delays.

- Citgo Petroleum Corp, Flint Hills Resources LP and Valero refineries in Corpus Christi, Texas, said they were monitoring but still operating.

**********************PORTS************************************

- Port of Corpus Christi remained shut Thursday. Serves 784,000 bpd of refinery capacity and handled 74.9 million short tons of petroleum in 2007.

- Ports of Houston and Texas City reopened at midday Thursday July 24 after being shut because of Dolly.

- Louisiana Offshore Oil Port near Port Fourchon, Louisiana, unaffected. Only U.S. offshore oil import terminal and the largest single U.S. port of entry for foreign oil.

(Reporting by Bruce Nichols)