A New Offshore Platform and Drilling Concept Effects Reduced Costs
Authors: Sybert Jack H. 
Published: December 2007

The best way to cut costs and keep a protective eye on everyone is to go family plan. This family consists of six dually completed wells, accommodated in two 48-in. piles of an offshore platform. A 12-well platform is being constructed-and that earns you a group rate.

Introduction

Offshore platforms represent some of the world's most expensive real estate. Designers are continually trying to reduce this cost, but face higher costs with increasing water depths, higher material and labor costs, and regulatory action. A new concept for a platform and drilling operation has been developed, platform and drilling operation has been developed, and significant savings may be realized from its use. The cost reduction is achieved by drilling through the legs of the platform. In itself, this concept is not new because it has been used in platforms in Cook Inlet and off the West Coast of the U. S. In those platforms, columns approximately 16 ft in diameter platforms, columns approximately 16 ft in diameter contained wells drilled on spacings as close as 5 ft on centers. The wells were drilled through individual guides driven or drilled to the desired depth below the mud line. The new concept presented here is the close spacing of the wells and an absence of individual guides for each well.

Typical Multiwell Platforms

Multiwell platforms usually have six or more pilings for support. The deck section is normally trussed and provides two levels of producing and drilling operations. The wells are located in the inside bay and are drilled through 24-in.-diameter conductor pipes that are driven into the bottom and supported pipes that are driven into the bottom and supported by the platform.

Main Pass 133-A Platform

The Main Pass 133-A platform is located 48 miles east northeast of Venice, La., in the Gulf of Mexico. The water depth is 180 ft. It is a four-pile platform (Fig. 1) that has seven dually-completed wells. The jacket was placed over one well that was an on-bottom, suspended well drilled from a mobile drilling barge. The remaining six wells were drilled from the platform. The deck section was built with a grid of 12-ft-high plate girders that are framed intercoastally. plate girders that are framed intercoastally. Nominal dimensions are 117 X 75 ft. The area around each well cluster is covered with floor plate, but the remainder is left without permanent decking during the drilling phase. Temporary walkways provide the needed accesses. The advantage of this provide the needed accesses. The advantage of this arrangement is that production facilities can be fabricated into units that provide decking and can be placed on the structure after drilling operations are placed on the structure after drilling operations are completed. One level of equipment may be placed at the bottom of the plate girders and another at the top. The jacket was designed to receive four 48-in. diameter pilings; two are vertical and two are battened on a 7:1 slope. Three wells were drilled through each of the vertical pilings. The piles provided the guide and support for the well pipe, provided the guide and support for the well pipe, eliminating the need for a cluster of individual well guides.

JPT

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