Bottom Founded Experience

Type of Vessel: Jack-Up Unit,
Le Tourneau - Independent Leg

Type of Project: Conversion to Production Unit

Client: Century Offshore Management Corporation

Description of Project:

This jack-up unit was converted for use as a production platform in 75 feet of water, offshore Louisiana on West Cameron Block 368. ACMA's analysis was based on API RP2A, AISC, ABS and MMS requirements. The fatigue was reviewed in accordance with API RP2A and ABS requirements. ACMA analyzed the structure for resistance to overturning, maximum stresses and long-term fatigue. The scope of the project included six major areas:

• Determine weight and centers of gravity of the unit in its current mode

• Calculate on-site preload requirements and overturning resistance capacity

• Analyze strength of the hull to ascertain the contribution of the main deck to the strength of the hull

• Analyze strength of the legs

• Perform fatigue analysis of the hull and legs

• Review afloat stability

The finite element program ALGOR was used to analyze the structure. Rig checks were made to verify the condition of the unit with particular emphasis on the legs and jack towers.

Reinforcements of the legs in way of the lower guides at the jacked-up elevation were recommended and their installation was overseen in the yard. A report was submitted to ABS and MMS for their respective review and approval.

Preload procedures were written to simulate the maximum expected load on the spud cans. The weight of the rig was reduced substantially from its previous use requiring a large amount of permanent ballast onboard to prevent overturning in severe storms. This impacted the amount and location of the preload ballast that could be added. A method was developed whereby the legs could be preloaded as required. The afloat stability analysis was submitted to the USCG for review.

A one-time load line certificate was obtained to enable tow out to the site. The rig has been on location since October 1989.