Mars Tension Leg Platform

The discovery well was drilled on Mississippi Canyon Block 763 in 1989 using the drillship, Discoverer Seven Seas. The geologic age of the Mars formations above 14,000 feet are Pliocene and the deeper reservoirs are Miocene. The average API gravity of the crude is about 30° and sulfur is about 2.1%. Data from four other wells, six sidetrack wells and 3D seismic work were utilized in making a decision on development.

Development Plans
Shell announced in October 1993 its plans to develop Mars utilizing a tension leg platform (TLP) to be installed on Block 807.
 
The TLP was installed in May 1996 in a water depth of 2,940 feet, which surpassed the depth record in the Gulf of Mexico for a permanent drilling and production platform - Shell's Auger TLP - which was installed in 2,860 feet of water in the latter part of 1993. 

About 55% of the project costs were spent for fabrication and installation of the hull, deck, facilities, and pipelines. The other 45% of the project costs was for drilling and completion of the wells.
 
Ten of the TLP development wells were predrilled beginning in the fourth quarter of 1993 using Sonat's semisubmersible, George Richardson. The remaining wells were drilled with H&P 201 (contract rig) installed on the TLP.

Production
The oil is transported 116 miles via an 18/24-inch diameter pipeline to the Clovelly, LA area, and the gas is transported 55 miles via a 14-inch pipeline to West Delta 143. Both pipelines were installed as part of the Mars development.

• The Mars TLP was designed and engineered by Shell Oil Company. 
• The TLP is 3,250 feet high, from seafloor to the crown block of the drilling rig. 
• The steel weight of the TLP is approximately 36,500 tons.
• The TLP is designed to simultaneously withstand hurricane force waves of 71 feet and winds of 140 mph.

Hull 

• The hull is comprised of four circular steel columns, 66.5 feet in diameter and 162 feet high, and four pontoons 27 feet wide and 24 feet high, which connect the bottoms of the four columns. 
• The hull weighs approximately 15,650 tons. 
• The fabrication of the hull was completed by Belleli S.p.A. of Taranto, Italy, in August 1995 and it arrived in Corpus Christi, TX, on August 31, 1995. 
   

Deck 

• The deck is composed of five modules: wellbay, quarters, process, power and drilling. 
• The deck is an open truss framing design, 245 feet x 245 feet x 45 feet high and weighs approximately 7,200 tons. 
• The fabrication of the modules was completed by McDermott Inc. in Morgan City, LA, with the first module loaded out on September 13, 1995, and the last module arriving in Corpus Christi on November 13, 1995. 

Tendons/Piles 

• There are 12 tendons, three per corner, each with a diameter of 28 inches and a wall thickness of 1.2 inches. 
• Each tendon is approximately 2,852 feet long and the total weight for the 12 tendons is 6,150 tons. 
• The tendons are connected directly to piles in the seafloor. 
• There are 12 piles about 84 inches in diameter and 375 feet long, weighing 260 tons each. 
• Aker Gulf Marine fabricated the piles and tendons at its Ingleside, TX, yard. 

Drilling and Production Topsides 

• There are 24 well slots. Additionally, a subsea well is tied back to the TLP. 
• There are complete separation, dehydration and treatment facilities. 
  The Accommodation module houses 106 people, along with a control room and emergency response center. 
   

Integration and Installation

• The contract for integration was awarded to Aker Gulf Marine of Ingleside, TX, including the module setting and interconnect steel, piping, electrical and instrumentation. 
• The integration was completed during the second quarter of 1996. 
  The contract for installation of the TLP was awarded to Heeremac. 
  Installation occurred in May 1996.

The Mars TLP, heavily damaged during Hurricane Katrina in 2005, returned to production ahead of schedule in May 2006 and was producing slightly above its pre-Katrina rates in July 2006. 

Among the first-ever accomplishments were, most notably, the lift of the 1,000 ton damaged rig substructure, the repairs to both of the Mars product export pipelines in 2,000 feet of water and the mooring of the Safe Scandinavia in 3,000 foot water depth.

The Mars recovery project encompassed more than one million man-hours without a recordable injury.

In 2007, the Mars TLP Recovery Team was the recipient of the prestigious Offshore Energy Achievement Project of the Year Award. This Award honors outstanding achievement in the upstream, offshore oil and gas industry. Winners are selected by a 21-member judging panel of senior leaders from major oil and gas producers and service providers.