Mariner Energy, Inc. shares dropped more than 4% Thursday following news that one of its production platforms exploded in the Gulf of Mexico. Mariner shares lost 96 cents, more than 4%, at $22.39 in afternoon trading.

Mariner Energy, owner and operator of the Vermilion 380 offshore production platform that exploded and caught fire about 9:30 am Central Daylight time on Thursday in the Gulf of Mexico, reports a “slight sheen” on the water measuring about one nautical mile by about 100 feet.

An offshore oil rig has exploded in the Gulf of Mexico, about 80 miles south of Louisiana’s Vermilion Bay. This is west of the site of the April 20 Deepwater Horizon blast that caused the massive oil spill.

INPEX Corp., through its wholly-owned subsidiary INPEX Alpha Ltd., has commenced crude oil production from the BHP Billiton operated Ravensworth field in the production license area WA-43-L offshore Western Australia.

Houston-based Pride International Inc. has dedicated the second of its four new deepwater drillships under construction by Samsung Heavy Industries in South Korea, the Deep Ocean Clarion.

After the deal met with resistance, US-based Kosmos Energy sent a letter to the government of Ghana cancelling the Share Purchase Agreement with ExxonMobil that would have resulted in the oil major acquiring nearly US$4 billion in Ghana assets.

In its 2Q10 earnings statement, Plains Exploration & Production Co. noted, that after studying its Gulf of Mexico (GOM) operations over the past few months, it plans to “reduce its GOM exposure and related capital spending.”

A plan to build and deploy a rapid response system that will be available to capture and contain oil in the event of a potential future underwater well blowout in the deepwater Gulf of Mexico was announced Wednesday, July 21, by Chevron, ConocoPhillips, ExxonMobil, and Shell.

In the deepwater Gulf of Mexico, the Droshky development has started production for Marathon Oil Corp. Production, which is expected to reach 50,000 net barrels of oil equivalent per day at its peak (45,000 b/d of liquid hydrocarbons and 30 million cubic feet per day of natural gas), has started on time and–with final a development cost of less than $900 million–under its projected $1.3 billion budget.