FACTBOX: Oil market fear of Gustav fed by 2005 memories

(Reuters) - Forecasters say Tropical Storm Gustav could become the first major storm threat to the U.S. Gulf of Mexico oil fields since Katrina and Rita in 2005.

The U.S. government and the International Energy Agency said they are prepared to release emergency crude oil stockpiles if the storm causes a significant supply disruption, helping crude futures in New York drop Thursday for the first time this week.

The Gulf is the source of 25 percent of domestically produced U.S. oil and 15 percent of the natural gas. In addition, more than one-third of the nation's refining capacity is located on the U.S. Gulf Coast.

The 2005 one-two punch had a devastating impact and -- coupled with less severe Hurricane Ivan in 2004 -- forced upgrades to drilling rigs, production platforms and pipelines. Gustav could be the first big test of those changes.

----IMPACT OF KATRINA AND RITA IN 2005----

- Katrina struck the New Orleans and Mississippi Gulf Coast in late August of 2005. Rita came ashore near the Texas-Louisiana line in late September.

- Some 3,050 of the Gulf's 4,000 platforms and 22,000 of the 33,000 miles of pipelines were in the direct path of either Katrina or Rita, the U.S. Minerals Management Service said.

- The storms forced near total shutdown of Gulf oil and gas production at that time, 1.5 million barrels per day of oil and 10 billion cubic feet per day of gas.

- Twenty-nine percent of U.S. refining capacity was shut down at the peak of storm disruptions, the American Petroleum Institute said.

- Winds and waves destroyed 124 platforms and damaged about 50 others, damaged or wrecked 535 pipeline segments and sank or set adrift 28 drilling rigs, MMS said.

- Nine months later, 22 percent of federal offshore oil production and 13 percent of gas production remained shut, MMS said.

- Both Katrina and Rita became Category 5 storms as they crossed the Gulf, reaching to the top of the commonly used hurricane intensity scale.

---MMS/INDUSTRY CHANGES TO STRENGTHEN FACILILITIES---

- Strengthened existing platforms and raised design standards for new ones.

- Boosted worst-case wave-height estimates from 70.5 feet to as much as 91.9 feet in the central U.S. Gulf for designing offshore facilities.

- Increased mooring requirements for floating drilling rigs and raised minimum heights for jackup drilling rigs above the water.