Vastar, Elf report deepwater gulf finds

Operators have made two significant hydrocarbon finds in the deepwater Gulf of Mexico.

Vastar Resources Inc., Houston, and Elf Aquitaine's U.S. unit Elf Exploration Inc. last week disclosed the separate strikes, both in the gulf's Mississippi Canyon area.

Partners involved in both discoveries call their respective finds "significant."

Vastar discovery

Vastar made an oil discovery on the deepwater Mirage prospect on Mississippi Canyon Block 941. The well was drilled to a measured depth of 16,600 ft in 3,927 ft of water about 80 miles south-southeast of Venice, La.

The well cut about 300 ft of net oil pay in five intervals and is the deepest well yet to be drilled in the Mars basin, said Vastar. Some zones are laminated or thinly bedded, but none of these zones was tested. The accumulation found was oil with associated gas with gas-oil ratios of 1,000:1. The pay was in Miocene sands, known to be productive elsewhere in the Mars basin, and the oil gravity is in the mid-20°s, which is typical of Mars basin crudes, said Vastar. Operator Vastar holds a 75% working interest in the block, and Unocal Corp. unit Spirit Energy 76 holds the remaining 25%. The well is 12 miles south of Vastar's King discovery on Mississippi Canyon Block 764. Vastar made its first operated deepwater discovery on its King prospect last year (OGJ, Mar. 2, 1998, p. 62).

Mirage's drilling program also included a sidetrack well drilled to a measured depth of 22,435 ft. At the deepest point, this measured depth translates into 21,744 ft TVD. The deepest previous well in the Mars basin reached 19,828 ft TVD. Initial drilling in the area indicates the presence of over 100 million boe, said Vastar, although further drilling would be needed to confirm the volume. The cost of the well, including the sidetrack portion, totaled $65 million. About $10 million of this sum was due to weather delays.

Next on Vastar's drilling schedule is the drilling of its Sting prospect on Viosca Knoll Block 1001. Following will be its Horn Mountain prospect on Mississippi Canyon Block 127. Vastar was the apparent successful bidder, either alone or with partners, on 18 blocks at the most recent central gulf lease sale.

If the blocks are awarded to Vastar, it will hold interests in 146 deepwater gulf blocks.

Elf discovery

Elf encountered a hydrocarbon-bearing section with a gross thickness exceeding 200 ft on the Aconcagua prospect in the Gulf of Mexico in 7,073 ft of water. The discovery was made on Mississippi Canyon Block 305 off Louisiana's coast.

None of the partners in the well would comment on whether the find was oil or gas, but the well logged multiple pay sands and cut additional sands with productive potential. Trans- ocean 7-Seas drillship drilled the well to a depth of 14,000 ft. An appraisal well will be drilled in the third or fourth quarter of this year. Elf Exploration Inc. is operator of the Mississippi Canyon block and holds 50% interest. Mariner Energy and Pioneer Natural Resources USA Inc. each holds 25% interest.