April 15, 1977 - Maritime Reporter and Engineering News

Mobile, Bottom Supported Drilling And Production Platform

Marathon LeTourneau Offshore Company And Combustion Engineering, Inc. Form A Co-Venture To Produce A Self-Elevating Drilling And Production Platform Offering Lower Costs At the time when energy-producing companies are increasingly concerned with the time lags encountered in bringing newly discovered offshore production on line, Marathon LeTourneau Offshore Company and Combustion Engineering, Inc. are proposing a solution which will be featured in Marathon's 1977 Offshore Technology Conference booth.

The two companies are forming a co-venture to produce a self-elevating drilling and production platform which will offer lower capital risks, higher salvage values, and lower abandonment costs than conventional offshore production methods.

In simplified terms, here is how the selfelevating production platform works: A Marathon self-elevating jackup platform is built with the same basic design used successfully for more than 20 years by offshore drillers around the world. Skidmounted drilling equipment of the customer's choice is fitted onto the platform, along with production equipment supplied by the C-E Natco Division of Combustion Engineering's Process Equipment Group. Natco's equipment, which has been proven to offshore producers over many years of successful use, is specially modularized to ensure optimum performance under these conditions.

Next, a free-standing well-protector jacket platform is attached or "piggybacked" to the mobile platform at the dock. Then the platform and the piggyback jacket are towed to the desired offshore location. The self-elevating drilling and production platform can be used in up to 250 feet of hostile waters and up to 350 feet in calmer areas.

Ideally, prior to the arrival of the selfelevating drilling and production platform, another offshore rig has drilled a successful exploratory well — one that appears to indicate that commercial quantities of hydrocarbons exist in the reservoir. As soon as such a well is encountered, the well is completed with a mud-line suspension, and then an undersea template is added. This means that it is not necessary to plug and abandon the discovery well(s). A template which contains a provision for drilling additional wells is lowered to the ocean floor, using the first well conductor as a guide.

The self-elevating drilling and production platform arrives at the location, and proceeds to lower its legs into the ocean floor.

The process is continued until the platform is elevated above the ocean's surface.

Next, machinery on the platform lowers the free-standing well-protector jacket to the sea floor. Piling necessary for the jacket's stability is driven into the ocean floor, using the on-deck cranes. Then, skid-mounted drilling and completion equipment is moved in place, above the jacket.

After the well-protector jacket is secured, the casing strings of the initial discovery well or wells are tied back to the surface, and the wellhead installed so that production can begin. Gas produced in connection with the oil is either flared or, if possible, piped to shore.

The oil produced by the platform can be transported to shore in several different ways, after having passed through the processing facilities in the hull: (1) metered and pumped into a pipeline, if available, or (2) metered and pumped to adjacent or nearby producing platforms, there to be tankered or pipelined to shore site facilities, or (3) metered and pumped into one of a number of types of short-term storage and subsequently loaded to transport tankers through a single-point mooring system.

After all the development wells have been completed through a seabed template wellprotector jacket system, a conventional piled jacket production platform should be ready for permanent installation, if the reservoir economics justify this step. A deck is then installed on the well jacket, and a bridge connection is made from it to the production platform.

Advantages of the self-elevating drilling and production platform system: When a producer is dealing with undefined reservoirs where the lack of production history makes the economic justification of a production platform uncertain, the self-elevating drilling and production platform system offers an economical alternative. The rapid construction of a new (or the modification of an existing) jackup platform should greatly reduce the time lapse between oil discovery and production, while at the same time gaining reservoir history. The new platform also permits the possible use of some exploratory wells as producing wells, thus saving the drilling investment involved. The platform needs no other construction equipment to install it on location, thus minimizing mobilization costs. In addition, it affords maximum salvage value since the jackup platform may be used as a drilling rig and, after completing that duty, as a production platform.

When producing any reservoir whose economics dictate a "pay as you go" plan, the self-elevating drilling and production platform system's faster positive cash flow feature allows the initial reservoir development to be carried out with less capital investments than for permanent facilities.

And finally, and of possible major interest to U.S. energy companies whose exploration budgets have been reduced by certain governmental activities (such as the elimination of the oil depletion allowance)—if a permanent production platform is justified, the cash flow generated by the self-elevating drilling and production platform approach allows an orderly permanent installation without incurring large capital requirements.

Combustion Engineering has a group of divisions and subsidiaries which serve the oil and gas producing industry, including C-E Natco, C-E Crest, C-E Invalco, Gray Tool, and the newly formed C-E Resource Development Services Division which offers project management for large offshore oil and gas production projects.

Marathon LeTourneau Offshore Company is a subsidiary of Marathon Manufacturing Company of Houston, Texas. The parent firm is a multi-product company serving industries in marine construction and transportation, heavy equipment and steel products, as well as a group of diversified companies producing chemicals, batteries, consumer goods, and providing paving and utility construction services.

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