ExxonMobil sets oil well tie-back, depth record in Gulf of Mexico

ExxonMobil Corp. has started production at its $330-million subsea Mica development on Mississippi Canyon Blocks 167 and 211 in the Gulf of Mexico. Mica is in 4,350 ft of water and tied back 29 miles to BP PLC's Pompano platform in 1,290 ft of water.

By the OGJ Online Staff

HOUSTON, Aug. 17 -- ExxonMobil Corp. has begun production at its $330-million subsea Mica development on Mississippi Canyon Blocks 167 and 211 in the Gulf of Mexico.

Mica is in 4,350 ft of water and tied back 29 miles to BP PLC's Pompano platform in 1,290 ft of water.

ExxonMobil is operator with a 50% interest and BP has the rest. ExxonMobil does not hold any interest in the Pompano platform.

According to ExxonMobil, the 29-mile tie-back length is a record for an oil development at that water depth. It said production started about 3 months ahead of schedule in June 2001.

The field is producing more than 13,000 b/d of oil and 140 MMcfd of gas from two wells. The subsea system will accommodate two future wells. One of the completed wells produces primarily oil while the other is primarily a gas well. The combined liquids produced have about a 40° gravity and only a trace of sulfur.

ExxonMobil said production will peak later this year at 15,000 b/d of oil and 150 MMcfd of gas. It expects ultimate recovery to reach 100 million boe.

The $330-million project cost includes two future wells and recompletion work, the timing of which depends on the production decline in the first two wells.

Mike Flynn, vice-president of ExxonMobil Development Co., said the 1990 Mica discovery has been recognized as the first field found entirely beneath salt in the deepwater gulf. He said the 3,500 ft salt sill above the producing horizons complicated the seismic interpretation and was a challenge to drill through.

For placing the development wells, ExxonMobil used computer visualization to target the three stacked sands with designer type wells that reach a 15,000-ft depth. The producing sands are at various depths over several thousand ft.

ExxonMobil drilled the two development wells in 2000 and installed the subsea system and flowlines in early 2001. One of the 29-mile flowlines is an 8-in. uninsulated line that handles the production from the well that primarily produces gas. The other flowline, an 8-in. by 12-in. insulated line, is for the well primarily producing oil. The insulation helps maintain the temperature in the flowline to help inhibit wax formation.

The manifold's design allows the wells to flow into either flowline and connects the flowlines to form a loop through which the lines can be pigged. The manifold and wells are in Block 211, while the wells target producing sands in both blocks.

The wells are clustered about 150 ft around the manifold.

A combined electric-hydraulic umbilical controls the manifold and well heads.

Other long tie-back records in the Gulf of Mexico are:

For gas projects, Shell Exploration & Production Co.'s Mensa is tied back 68-miles and is in 5,300 ft of water.

For gas-condensate projects, Mariner Energy Inc.'s Pluto also has a 29-mile tie back but is in only 2,700-ft of water.

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