ABSTRACT

Drilling packages to be used on Tension Leg Platforms (TLP's) must be designed to fulfill a number of additional requirements compared to "conventional" packages. Being a combination of a floating vessel and a fixed bottom-founded structure a TLP has motion characteristics that makes drilling and workover operations rather challenging. To reduce drilling times per well and the operational downtime to a minimum, it is essential that a TLP drilling package is optimized to the operations that are to take place. This paper highlights some of the aspects to be considered in design of such packages, with focus on the experience gained from the design of the Snorre and Heidrun TLP's drilling packages, which will be installed in 320 and 350 meters of water in 1992 and 1995 respecively.

1.0 INTRODUCTION

A substantial cost of any field development is the cost involved in drilling of the development wells to provide the required number of production and injection wells. And as the water gets deeper and deeper this cost tends to constitute a larger and larger share of the total field development cost. This is especially true for a TLP, mainly due to the requirement to establish connection with the subsea wellhead for each well and the special efforts that have to be taken due to TLP motions. Drilling of deepwater wells from a TLP involves a number of time consuming and costly operations, as well as a large and complex drilling package on the platform, which occupies a large portion of the topside deck area and load capacity. Of the two TLP's that sofarhave been installed worldwide, namely Conoco's Hutton and Jolliet TLP's, only the Hutton TLP is capable of doing full drilling operations from the platform.

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