Environmental Instrumentation for the Offshore Oil Industry
Authors: Jewett P.E. 
Published: December 2007

This paper was prepared for the Second European Meeting of the Society of Petroleum Engineers of AIME, to be held in London, England, April 2–3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

With exploration and production work being carried out in new and challenging areas, the of industry is coming to play a major role in the study of the offshore environment. play a major role in the study of the offshore environment. Cost and efficiency of operations, and in some cases, to basic operation feasibility, are related to severity of conditions.

Detailed information on the environmental conditions likely to be met in an area is, in many cases, just not available. The normal period for thorough data collection is 10 years or more. This presents quite unrealistic time scales for operational planning and a certain number of short-cuts are, therefore, essential.

Environmental studies of the nature discussed in this paper are rapidly developing into a definite experimental science. It is made up of a balance between data available and applied theory. Preliminary studies of an area give a basis for "tailor made" measurement programmes, from which a maximum of information can be obtained.

Introduction

Each offshore area is unique. On a large scale, geographically, the differences are readily apparent. But even when areas are adjacent to each other, subtle differences in conditions can have significant effects. In northern areas, for instance, a relatively short rig move might bring it out of a warm current into a cold one, with results seen in increased amounts of superstructure icing. As another example, a change in exposure over an area can mean a shift in predominant wave periods. This could mean that a drillship might be suitable for working one end of an offshore holding, but a semisubmersible needed for the other end.

The North Sea has served as an ideal "test tank" for understanding the environment and in developing basic theories. From its southern end to north of the Shetlands there are seen to be gradual increases in water depths, exposure, wind speeds, wave heights and wave periods. One cannot under-estimate the value of information obtained here, both for use in the North Sea, and for theoretical application to conditions in other areas.

There is much to be learned about the North Sea still, but the implements for obtaining knowledge there are becoming well established. Measurement programmes are underway from fixed platforms in the south and from a growing number of mobile rigs in the north. One of the most ambitious programmes is being carried out by the North Sea Oceanographic Study Group (N.S.O.S.G.) with a fully instrumented weather ship maintained in the northern North Sea. Such programmes would not be underway without the fullest amount of individual and cooperative support of the oil companies involved. Information no longer has to be taken at face value. A grid network of ships, platforms, rigs and coastal stations gives the basis for continual comparisons, while more attention paid to the installation and maintenance of measuring paid to the installation and maintenance of measuring equipment offshore is resulting in more reliable and continuous data being collected.

MEASURING INSTRUMENTS

It is perhaps starting the wrong way around to begin by discussing the instruments themselves. All aspects of studying the environment are a part of a large circle. Preliminary studies and planning dictate the type of Preliminary studies and planning dictate the type of measurements required and the measurement format. The rig or platform, and the degree of cooperation that might be expected of its crew, dictate the type of instruments required.