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Khan, Saeed U.; R J Brown and Associates (Far East) Pte Ltd, Singapore
The advances in offshore pipeline technology, in recent years, have been achieved by using innovative engineering to reduce construction risks and total capital costs. New design concepts and installation techniques namely: pipeline installation using the bottom tow method, pipe connections using the deflect-to-connect method and pipe trenching using marine plows have successfully been used in the North Sea, Canadian Arctic, South China Sea and Australian waters and which have resulted in significant cost savings in the material and installation costs.
With the spiraling hikes in the price of oil in the early seventies, the search and development of offshore oil/gas fields even in more non-traditional and remote areas with adverse environmental conditions, where equity capital and return ratios for such developments were previously considered significantly unattractive, was accelerated. The previously considered significantly unattractive, was accelerated. The requirements of high financial outlays for such offshore projects clearly dictated the necessity of cost savings in the materials and installation costs in order to make such developments economically viable. This obviously prompted concerted efforts towards the development of new design concepts, construction techniques and a so more sophisticated engineering analyses to reduce the construction risks and capital costs and also to alleviate maintenance and repair problems of such oil/gas transportation systems. The more severe requirements of pipelines long term stability in harsh environment and remote areas where maintenance and repair problems might result in higher costs than the actual installation cost put more emphasis on front-end engineering to obtain optimum solutions and cost-effective pipe installation and burial techniques. New design concepts and construction techniques have already proven their practicality and cost effectiveness especially in those areas where previously it was thought to be either too difficult or too expensive to develop.
This paper discusses the development and successful use of three such design concepts and installation and techniques for pipelines. These are:
- pipeline installations using the bottom tow method; - remote connections by the deflect-to-connect methods; - pipe trenching using the marine plows.
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BoardOur paper is concerned with the mine planning aspect of rockburst control. We did not intend to discuss destressing or increased fill modulus as means of controlling rockburst. I would like to explain a few matters not covered in the commentary, which did indeed cover most things. The previous mining method at the Star mine was a horizontal cut and fill method in which a flat backed pillar was created. The horizontal fill progressed up in a line toward the previously mined area above it, leaving the flat backed sill pillar. When this pillar is reduced below about 60 to 70 feet severe rockburst problems occur. The primary consideration in this paper, to make it immediately applicable in industry, was mainly the economics of the problem. We wished to devise a new mine design that would fit in directly with the present mining system, and hence must be a horizontal system, without affecting production, since the ore in the Star mine is marginal and any reduction in production could close the mine down. Economic considerations were dominant. The energy release rate design method involves nothing new. It is well documented in the literature, being first proposed by Cook at the 8th Symposium on Rock Mechanics. It is now used as a general design procedure in South Africa and accepted by mining companies throughout Africa. Hence we are doing nothing new in applying that design procedure to a mine here in the United States. What is new is a system we have arrived at of mining the center stopes approximately 50 ft. ahead of the two abutment stopes to get the lowest rate of energy release. This system could be fitted into existing practice at the Star mine with no change in machinery, and has now been operating for approximately 8 months and at the 7500 ft. level is now nearing completion. As our paper indicates the two center stopes are about 25-30 ft. from holing through the 7300 ft. level. At present we are trying to correlate the data that we are getting. We have installed a microseismic network which is now providing ample data. Previous records are not suitable to readily correlate with present data. However, the general feeling of personnel at the mine is that the severity of rockbursting has decreased significantly. More detailed conclusions will be possible in about a year. At present the 7500 ft. level is being finished and the same system is being implemented at the 7700 ft. level. With the microseismic system in operation it should be possible to obtain some correlation between the two levels. To put our paper in context I would like to first remark that at present there is only one commercial size oil shale mine in operation in America. This severely influences the design method since there is not a large data base from which to correlate pillar size and strength information as has been possible in the past in coal and some copper mines around the world.
INNOVATIONS IN PETROLEUM EXPLORATION IN THE HIGH ARCTIC Abstract The depletion of oil and gas reserves in Western Canada has made the rapid development of Canada's frontier areas one of prime importance. For seven years Panarctic has been operating successfully in one of these areas, the Arctic Islands, reaching above the mainland towards the North Pole. By exploring almost all the year round, even in total darkness and in tem- peratures to -60"F, the company is well on its way to discovering gas and oil in marketable quantities. In doing this Panarctic has overcome the harsh en- vironment by pioneering innovative techniques in- cluding the ability to drill from the ocean ice using a conventional land rig. Résumé En raison de l'épuisement des réserves de pétrole et de gaz de l'ouest canadien, la rapide mise en valeur des zones frontalières du Canada est devenue de première importance. La société Panarctic opère depuis sept ans avec succès, dans une de ces régions: les îles arctiques, qui s'étendent du continent au pôle Nord. En explorant durant presque toute l'année, même par obscurité totale et par des températures atteignant -51"C, la société est sur la bonne voie pour découvrir du pétrole et du gaz en quantités commercialisables. En agissant ainsi, Panarctic a dû surmonter les diffi- cultés d'un milieu hostile grâce à des innovations techniques comme la possibilité de forer à travers la banquise au moyen d'une installation de forage classique terrestre. 1.
Seven years ago far sighted oilmen foresaw the decline in reserves of oil and gas in the western Canada sedimentary basin and began serious explora- tion in three new frontier areas (Fig. i). Major multinational oil companies pioneered the exploration work in the first two areas-the Mackenzie Delta and the Beaufort Basin off Canada's northern main- land and the Continental Shelf off the east coast. Work in the third frontier area, the Sverdrup Basin in the Canadian Arctic Islands was spearheaded by Panarctic Oils Ltd, a consortium of 30 oil and mining companies and the Canadian Government. Success in the form of both gas and oil discoveries has been registered in all three areas. In its years of operation Panarctic has accumulated over 80 million gross permit acres and, to the end of 1974, two hundred and fifty million dollars had been spent on these lands with 70 wildcats and 10 delinea- tion wells being drilled. Six prolific shallow gas fields, - by CHARLES R. HETHERINGTON and H. J. STRAIN, Panarctic Oils Ltd, 703-6th Avenue S. W., Calgary, Canada one oil field and several encouraging shows of oil and gas have been discovered (Fig. 2). Proven gas reserves in the Arctic Islands are estimated at 12 trillion cubic feet, about half the threshold reserve required to permit economic marketing. Estimates, by various authorities, of undiscovered reserves in the Arctic Islands vary between 90 and 200 trillion cubi