Llano Subsea Development

In May 2002, Shell Exploration & Production Company acquired Enterprise Oil, making Shell the leaseholder for GB 385 and 386. Enterprise Oil had acquired the field from Enserch Exploration (EEX) in 1997. Enserch Exploration (EEX) originally acquired GB 385 in OCS Lease Sale 115 in 1988. EEX then acquired GB 386 in OCS Lease Sale 161 in 1996.
 
Working interests in Llano are Shell, operator, (27.5%), Amerada Hess (50%), and ExxonMobil (22.5%).
 
After two sidetracks, the discovery well was drilled to measured depth of approximately 27,800 feet in 1998 using the Transocean Voyager & Omega. The target reserves are in turbidite sands at depths of approximately 24,000 feet subsea in the Pliocene layer and 26,000 feet subsea in the Miocene layer of the Gulf of Mexico. Located in two zones, the net thickness averages 150 feet in the Pliocene and 95 feet in the Miocene.
 
The reserves are both oil and gas. API gravity is 28° and sulfur is about 1%.

Development Plans

Shell developed Llano utilizing a subsea system tied back 11.5 miles to its Auger tension leg platform on Garden Banks Block 426 in 2,860 feet of water.
 
The expandable subsea system initially consisted of two wells tied back to Auger via an 8 x 12-inch pipe-in-pipe looped flowline. Llano is SEPCo’s second project to utilize 15,000-psi subsea equipment.
 
Major contractors participating in this development are:  

• FMC  
• SIMRAD  
• Sea Cat
• Tenaris
• V&M
   

Production
Llano production began April 29, 2004 through one well. The second well came on stream May 25.