Ultradeep shelf well logs four apparent pays

Alan Petzet
Chief Editor-Exploration

HOUSTON, Oct. 24 -- The ultradeep Gulf of Mexico shelf well known as Blackbeard has logged four "potential hydrocarbon-bearing zones below 30,067 ft," said operator McMoRan Exploration Co., New Orleans.

Having reached 32,997 ft earlier this month, McMoRan and partners had to decide this week whether to halt drilling and attempt to test the zones encountered thus far or continue drilling to basement, expected below the permit depth of 35,000 ft, in an effort to penetrate at least another 2,000 ft of sediments.

It is too soon to tell whether the four zones, in the Miocene Rob-L formation, contain crude oil or gas-condensate, James R. Moffett, co-chairman of McMoRan said on an Oct. 20 webcast. On Oct. 23, McMoRan said, "The well will be temporarily abandoned while the necessary long lead time completion equipment is procured for this anticipated high pressure test."

Bottomhole pressure exceeds 25,000 psi, and the four zones exhibit the high resistivity seen in Rob-L elsewhere.

Moffett said, "No one ever tried to flow a well at these depths." The well is presently cased to 27,000 ft.

About 18 months after previous operators gave up on the well after drilling to just below 30,000 ft, McMoRan's group took over. It deepened the well routinely except for a 3½-week period of lost returns and ran conventional logs to the new total depth, Moffett said.

Wide area impact
The well is on the crest of a massive structure covering more than 10,000 acres, and test results have implications out to a 50-mile radius of the well, Moffett said.

"Seismic data on the prospect indicates the potential for significantly thicker sands on the flanks of the structure as confirmed in recent major deepwater discoveries," McMoRan said. "Based on information obtained to date in the South Timbalier Block 168 well, McMoRan believes additional drilling on the flanks could result in significant reserve potential."

A drillsite 2½ miles southeast of the Blackbeard well, for example, might encounter a depositional wedge in which the same formations are two to three times as thick as at the crest, Moffett said. The great thickness and large areal extent makes for large recoverables.

Moffett said this conclusion is based on McMoRan's interpretation of data made public by the partners in the K2 deepwater field 90 miles south-southeast on Green Canyon Block 562, where sands were transported from the onshore Mississippi River Delta.

Operators naturally drill the top of structures in deep water because they lack well control and historically found the greatest chance for hydrocarbons is at the crest, Moffett noted.

McMoRan's confidence in Blackbeard is further bolstered because it is exploring for the same formations as at its large Flatrock discovery in 10 ft of water on South Marsh Island Block 212 about 100 miles north-northwest of Blackbeard. The Rob-L formation encountered at 28,000-35,000 ft at Blackbeard is producing gas at 14,000-16,500 ft at Flatrock.

Flatrock discovery
Flatrock field, with five successful wells, is producing gas from Rob-L and the underlying Miocene Operc formation.

The Flatrock-6 delineation well, expected to spud in the current quarter, targets deeper Rob-L sands than those producing, Operc sands, and possibly the even deeper Miocene Upper Gyro sand section of the Flatrock/Hurricane Deep structure. It is projected to 19,700 ft and will probe the south half of Flatrock.

Successful wells can be placed on production quickly through Tiger Shoal field facilities.

McMoRan said Thursday that the Flatrock-4 well tested 109 MMcfd of gas and 2,500 b/d of condensate on a 50/65-in. choke with 8,170 psi flowing tubing pressure. The same sand is producing 100 MMcfd in the Flatrock-2 well, which went online in July.

The first three Flatrock wells are producing a combined 170 MMcfed of gas and condensate, and wireline logs indicated 100 net ft of pay in the Rob-L section of the Flatrock-5 development well. That well is drilling towards 18,400 ft to deeper Rob-L and Operc sands.

McMoran is also preparing to drill the Ammazzo prospect in South Marsh Island 251. It is 16 miles and 11 miles south-southeast of Flatrock and JB Mountain fields, respectively, and lies along the structural axis of a ridge trending from Flatrock. Objectives are the same three Miocene formations.

Deep shelf economics
Moffett pointed out that the deep shelf play is not so price sensitive as onshore shale plays, for instance, because the reserves are large, the gas is found in conventional, soft rock that requires no horizontal drilling or frac treatments, and production infrastructure is everywhere.

The South Timbalier Block 168 No. 1 well, formerly Blackbeard West, is the deepest ever drilled below the mud line in the gulf. It is in 70 ft of water 115 miles southwest of New Orleans (see map, OGJ, June 7, 2004, p. 40).

McMoRan operates the well with 32.3% working interest. Plains Exploration & Production Co. and Energy XXI USA Inc., both of Houston, have 35% and 20%, respectively.

McMoRan is one of the largest acreage holders on the gulf shelf with rights to 1.5 million gross acres including 450,000 gross acres associated with the ultradeep trend.

Contact Alan Petzet at alanp@ogjonline.com.

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