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Since the Forties Field FB Platform, my company has been involved in the design and installation of the following jackets in the British sector of the North Sea; Forties FD; Brent A; Claymore; Heather and Ninian. The Forties Field was underlain by normally consolidated clays, sands and at depth by overconsolidated clay. The other four fields are further north and are underlain by very hard clays and dense sands. No major pile installation problems were encountered at these northern sites. It was reassuring to find that the design methods used for planning pile installations work just as well for preconsolidated sands and clays as they do for normally consolidated soils.Professor T. J. Poskitt, Queen Mary College, London My comments are on the use of the wave equation in driveability analyses and on the problem of plugging.71. By any standards the piles used offshore are extremely large. Load testing is clearly out of the question and it is therefore natural for engineers to seek ways in which they can relate the soil resistance at the time of driving (SRD) to the static capacity. This is proving to be an extremely difficult job because the SRD is essentially a dynamic phenomenon which has to be studied by the wave equation. In addition pore pressure changes and thixotropy in the remoulded soil will produce time dependent changes which are difficult to predict analytically. These are areas of piling behaviour which are not fully understood and research is necessary in order to gain a better understanding of the mechanisms involved.72. The Authors give a comprehensive description of the use of the wave equation in drivability studies. In principle the wave equation is a powerful tool which will enable the designer to take into account the many different factors known to affect piles. However, in my experience considerable skill is needed if it is to give meaningful answers. Parameters such as quake,, damping factors etc., are as important as shear strength. This is not always sufficiently well appreciated by engineers and must have led to many disillusioned users of the wave equation. It is my opinion that where the wave equation is being used intensively as the Authors suggest in 0 7(e)-(g), the determination of the constants for use in the wave equation should have the same priority as is attached to other soil tests.

This investigation essentially highlights development of novel high-performance fire-resistant polymeric nanocomposite with respect to its orientation towards future generation aviation. Therefore, an attempt has been made to increase thermal stability and fire resistivity of phenolic/cotton fabric reinforced polymer composite, which is desirable for aircraft interiors. There is considerable increase in adhesion characteristics of phenolic fabric reinforced polymer composite due to atmospheric pressure plasma treatment. The phenolic fabric reinforced polymer is subsequently coated with nanosized calcium silicate reinforced polybenzimidazole composite in order to increase thermal stability and fire resistance property. Thermogravimetric analysis reveals that polybenzimidazole-coated fabric reinforced polymer shows significantly better thermal stability than the uncoated phenolic fabric reinforced polymer. There is a significant increase in the limiting oxygen index characteristics of polybenzimidazole-coated fabric reinforced polymer when compared to the uncoated phenolic composite resulting in considerable improvement in fire resistivity of the polymers.

An innovative platform for marginal oil and gas field developments is described. Its principal features are that it can be installed by a jack-up drilling rig as part of the drilling program, it does not require foundation piles and has superior boat impact resistance when compared with other designs. This paper describes the design of the structure, with particular emphasis on jack-up installation aspects, boat impact resistance and foundation design. A number of practical applications are described. Introduction A large number of innovative platform structure designs have been developed in recent years that are cheaper to construct and install than conventional three or four legged steel jackets. Ref. 1 gives a good summary of the range of platform designs currently available. The platform designs usually comprise a superstructure supported on a single vertical caisson (monotower) with bracing near its base that attaches to piles driven into the sea floor. Such structures are simpler than conventional jackets, making them cheap to construct. They are also lighter, so they can sometimes be installed by a jack-up drilling rig rather than by a specially chartered crane vessel, making them cheap to install. The guyed caisson platform design introduced here is believed to have advantages over these established designs in that it is still cheaper and easier to construct and install. In addition, it has superior resistance to boat impact forces, which will usually govern the design of small platforms in moderate water depths. Further, some of the conductors and risers can be on the outside of the central caisson, without the requirement for a boat impact frame. This allows the conductors to be spaced well apart, which leads to a good layout of the wellheads and production equipment in the superstructure and aids drilling operations. For multiple conductors it also has the effect of reducing the wave loads and the self-weight of the structure. Platform General Description Figure 1 shows an example of the structure design for a central North Sea site in 60m water depth with a 5,000kN topsides operational weight, 9 well slots and an export riser. The platform is unmanned and requires only limited access during normal operation. The platform comprises a superstructure supported above the wave crest level on a guyed caisson founded on a shallow spud-can on the sea floor. Six of the conductors are supported on the outside surface of the caisson through guides; the export riser and other conductors are inside the caisson. The caisson is 2500mm-diameter fabricated from high strength steel plate with maximum thickness 50mm. Three pairs of wire rope guy lines are attached to the caisson. One end of each line is attached to the caisson near the top, above the water surface with the other end attached to an anchorage at the sea floor. Anchorages may be vertical load plate anchors, suction anchors, piles or anchor blocks, depending on the soil conditions and the loads to be resisted.