Leakage from pipes is a major issue in both the oil and gas sectors, not only in environmental and economic terms, because of wasting important natural resources, but importantly from a safety perspective. Optical fibre technology offers the possibility of continuous acoustic monitoring of pipelines and remote detection of leaks. In this paper we present results from gas leak measurements made on a specially designed, buried pipeline test rig, for which leak energy radiated directly from the leak (orifice noise) dominates over energy radiated from the pipe wall. Measurements of the orifice noise are made using an optical fibre distributed acoustic sensing system as well as conventional geophones. Both the geophones and the optical fibres are shown to be able to detect the orifice noise, particularly when the fibres were located close to the pipeline. Fibre measurements are found to be limited by both high background noise and by gauge length, which limited the upper frequency limit for accurately determining the phase of the ground response. The measurements indicate that the orifice noise sets up Rayleigh waves in the ground, largely contained in frequencies below 100Hz, the magnitude of which are found to be compatible with predictions from idealised jet theory.The effect of fibre ducting and armouring is also evaluated.

No abstract

T h e G e o r g e W a s h i n g t o n U n i v e r s i t y L o g i s t i c s Research P r o j e c tTo establish a perspective, a discussion is made of the over-all planning process involved in the determination of military requirements for the merchant shipping needed to support a prescribed military plan.Three of the principal p a r t s of the planning process, namely: the determination of "pure" pipeline requirements, ship repair loads, and repair replacement ships, under convoy and nonconvoy conditions, a r e examined. After this, the newly developed models, assumptions, and methodologies for these a r e dissected and illustrated by means of figures.Typical characteristics and behavior of both the nonconvoy and convoytype pipelines and the effect of the repair policies upon them a r e presented. planning process and which require further research, a r e outlined.Additional logistics problems, which were generated in the The logistic problems to be described are concerned with the determination of the military requirements for the merchant shipping necessary to support a prescribed military plan. By using this information, plus comparable data on the merchant shipping requirements of the civilian economy under the same plan, a capability study will be made to see whether available merchant ship resources a r e adequate to meet the requirements.In order to establish a perspective, the general problem area of the over-all planning process i s outlined in Figure 1. (Parts of the process a r e already in being, others are being worked on, and others are yet untouched. At this point the term "notional ship" is used to mean a standard reference ship in terms of which actual ships can be expressed. This equivalence will be discussed in more detail subsequently. ) been developed for three principal parts of this flow sheet, namely: the determination of "pure" pipeline requirements, ship repair loads, and repair replacement ships.ments from each service. The lift-requirement data covers cargo (M/T), 1 POL (bulk)(Bbls), personnel (number), delivery schedule, origin (source), and destination.Measurement ton is the space available for cargo measured in units of 40 cubic feet to the long ton (2240 pounds).We shall now examine in detail the models, assumptions, and methodologies that have 545