Hindcast Storm Waves for Compilation of Wave Statistics

This paper was prepared for the Second Annual 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 OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal 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 discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The offshore industry needs storm wave information, particularly wave statistics, for structure designs. Measured wave data are too short in time span and too sparse in areal distribution for compilation of such statistics. A large data base, timewise and areawise, can be created by hindcasting waves occurring in historical storms using meteorological data records as input. A systematic wave hindcast study requires data for historical storms, development of wind method, calculation of waves from winds, allowing for water depth effects, and compilation of wave statistics from hindcast data. An example of using a systematic hindcast approach for hurricane waves along the Louisiana Gulf coast is described. By dividing the overall hindcast work into separate phases and by devoting concentrated research effort in each phase, substantially improved methods were developed for hindcasting hurricane winds and waves. Although the specific methods developed for Gulf of Mexico hurricanes cannot directly be used elsewhere, a similar program for developing a detailed wave hindcast method is generally feasible. For the North Sea area, particular attention should be given to the distribution of high winds associated with storm frontal s and to the modification of waves by bottom friction, shoaling and refraction effects. Introduction Structures of various types are key elements in offshore petroleum development. These structures are from time to time subjected to storm forces caused by winds, waves and other phenomena. In the Gulf of Mexico some offshore phenomena. In the Gulf of Mexico some offshore structures or platforms have failed under hurricane conditions. Fortunately, practices followed by the offshore industry have avoided any consequent loss of life or pollution catastrophe. Nevertheless, failure of offshore structures can represent a substantial economic loss. There is, therefore, a need for such structures to have a relatively high degree of reliability to withstand storm forces, but at the same time a need to avoid wasteful overdesign. To achieve the optimum structure design one must, first of all, have reliable information on expected high values for wind, waves and other natural phenomena in the ocean. For conventional offshore phenomena in the ocean. For conventional offshore platforms, information about waves is of platforms, information about waves is of particular importance. particular importance. The occurrence of storms at sea and the resulting waves is a random phenomenon. One cannot predict the occurrence of a severe storm in a particular ocean area such as the North Sea, one month hence, nor can one predict how high waves would be should a storm occur.