Mars, Gulf of Mexico, USA

Mars is located in the Gulf of Mexico about 130 miles south-east of New Orleans.

The discovery well was drilled on Mississippi Canyon block 763 using the drillship, Discoverer Seven Seas. Data from four other wells and six sidetrack wells was utilised, together with 3D seismic work, in order to make the necessary decisions about development.

DEVELOPMENT

The initial development was designed to recover about 500 million barrels of oil equivalent. The development for the initial project phase is approximately $1.0 billion. About 55% of the project costs were spent on the fabrication and installation of the hull, deck, facilities and pipelines. The other 45% of the project costs are to be spent on drilling and completion of the wells. Ten of the tension leg platform (TLP) development wells were predrilled using Sonat’s semisubmersible George Richardson. The remaining wells will be drilled with H&P 201 (a contract rig) installed on the TLP.

TENSION LEG PLATFORM

The TLP is 3,250ft high, from the seafloor to the crown block of the drilling rig and its steel weight is approximately 36,500t. The TLP was designed to withstand hurricane force waves of 71ft and winds of 140mph, simultaneously.

The hull is comprised of four circular steel columns, which are 66.5ft in diameter and 162ft high, and four pontoons, 27ft wide and 24ft high, which connect the bottoms of the four columns. It weighs approximately 15,650t. The fabrication of the hull was completed by Belleli SpA of Taranto, in Italy.

The deck is composed of five modules: the wellbay, living quarters, processing, power and drilling. It has an open-truss framing design, which is 245ftx245ftx45ft-high and it weighs approximately 7,200t. The fabrication of the modules was completed by McDermott.

TENDONS/PILES

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

DRILLING AND PRODUCTION TOPSIDES

There are 24 well slots and additionally, a subsea well is tied back to the TLP, which includes complete separation, dehydration and treatment facilities. The accommodation module houses 106 people, along with a control room and an emergency-response centre.

INTEGRATION AND INSTALLATION

The integration contract was awarded to Aker Gulf Marine of Ingleside, Texas. This included module setting and interconnecting steel, piping, electrical and instrumentation. The integration was completed during the second quarter of 1996. The contract for the installation of the TLP was awarded to Heeremac in May 1996.

PRODUCTION

The current daily production from Mars (the largest Gulf of Mexico discovery in more than 25 years) is averaging about 21,000 barrels of oil and 25 million ft³ of natural gas.

Oil is transported 116 miles to the shore in the $135 million Mars Pipeline system, which initially is capable of handling 250,000 barrels of oil per day, with expansion plans of up to 500,000 barrels per day. The Mars Pipeline system consists of an 18in line, extending from the TLP, about 40 miles to West Delta block 143, where it connects with a 24in line that comes ashore 55 miles away in Fourchon, South Louisiana. From there, the line parallels the Louisiana Offshore Oil Port (LOOP) pipeline about 29 miles to LOOP’s Clovelly storage facilities, where the oil will go into a dedicated 3 million barrel salt dome cavern, which can feed any of five major interconnecting pipelines serving the national refining market.