Introduction

While the concept of offshore tanker loading has been around for many years, it was not until the early 1970's that the idea of employing a Single Point Mooring (SPM) terminal as an integral part of on offshore production facility achieved wide industry acceptance. In this production facility achieved wide industry acceptance. In this application, the SPM provides both a permanent (or semi-permanent) mooring for the tanker and a means for transporting oil from the seafloor to the tanker. The SPM thus eliminates the requirement for a pipeline from the offshore field to the shore which often significantly reduces the overall project cost and may allow development of marginal fields which have project cost and may allow development of marginal fields which have insufficient recoverable reserves to justify a pipeline system.

A second economic consideration in the election to use offshore loading is that it makes it possible to ship crude and receive income as soon as oil is available for a relatively small investment and in a relatively short time frame. Thus, production from initial wells con be generating cash flow while the drilling program continues with delineation of the reservoir. Even if the economics can support the cost of a pipeline, on offshore loading system ensures income during the sometimes lengthy design and construction period and is often retained subsequent to pipeline completion as a backup system in the event of pipeline outage.

Selection of on offshore loading scenario obviously will often require in depth analysis of many economic considerations. However, the fact that viable concepts for offshore loading are available is of prime importance and offers a much greater flexibility to the operator in his planning than previously existed. previously existed.

THE SPM CONCEPT

There are several distinct types of SPM's, all of which share two common features:

  1. They all provide a single point which may rotate 360 degrees in the horizontal plane, to which the tanker moors its bow (or stern) viahawsers or structural steel frame.

  2. They all employ fluid transfer systems which ore capable of 360degrees rotation in the horizontal plane.

The tanker moored only by connection to its bow or stern is free to "weathervane" about the single point mooring and, thus, stay oriented head-on into the prevailing environment.

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