Showing papers on "Submarine pipeline published in 1993"

Design of a Submarine Oil Pipeline

Abstract: Submarine oil pipelines carry hot crude oil obtained from offshore oil wells to an onshore location. As the flow proceeds, the crude oil progressively cools down, drastically changing its kinematic viscosity. This cooling increases the surface resistance to flow considerably. Analysis of such a pipeline is complicated because it involves a large number of variables representing fluid, flow, thermal properties, and geometry. Furthermore, as the liquid cools down the flow may change from turbulent to laminar. This paper reports a unified friction factor equation valid in laminar as well as in turbulent flow that deals with this complex flow situation. This equation can aid development of a methodology for analysis and design of offshore pipelines.

Fluid transfer system for an offshore moored floating unit

Abstract: To compensate considerable movements between a floating unit and a seabed structure which are interconnected by a fluid line, the invention proposes to embody this fluid line in an upper catenary and a lower portion. The upper catenary is on the one hand supported by the floating structure and on the other hand by a subsurface buoy. The lower portion is on the one hand supported by the subsurface buoy and on the other hand connected to the seabed structure. This lower portion is provided with buoyancy beads. In this way it is possible that the floating structure may be displaced a considerable distance relative to the seabed structure. In addition, the system can withstand considerable environmental loading. This means that the connection between the seabed structure and floating unit can be maintained even under unfavorable conditions.

Sequence architecture, facies development and carbonate-cemented horizons in the Troll Field reservoir, offshore Norway

Abstract: Abstract The Sognefjord Formation in the Troll Field area was deposited during a general rise in sea-level during the Late Callovian to Early Volgian. A detailed study including palynology, sedimentology, response modelling and petrography of carbonate cement has been performed on 15 wells primarily from the western part of the field. All wells have been extensively cored through the reservoir enabling detailed palynological and sedimentological study of the depositional sequences in the wells. The Sognefjord Formation is interpreted, in this study, as a shoreline-attached tidally-influenced shelf complex. The study is based on the general consistency found between the eustatic sea-level curve published by Haq et al. in 1987 and the biostratigraphical zonation for the Troll Field described here. The response to sea-level fluctuations in a shallow marine environment is discussed and a response model is established. A theoretical assessment of the criteria for recognizing important events is presented. The maximum flooding surfaces (mfs) and sequence boundaries (sb) are easiest to recognize. Theoretically there is a higher probability of forming carbonate cements in connection with maximum flooding surfaces. The stratigraphically important dinocysts on Troll are classified according to their relation to sea-level fluctuations. Most of the palynozone boundaries are related to maximum flooding surfaces, except for a few which coincide with sequence boundaries. A stratigraphical subdivision of the Troll Field reservoir is presented based on a comprehensive palynological study. Lithofacies analysis in conjunction with palynofacies interpretation have been applied to delineate the depositional environment. As an aid to the interpretation a theoretical model was established. The predicted succession and variability of sequences and facies types outlined by the theoretical model could be recognized in all wells. Petrographical analysis shows that early diagenetic, near-surface cementation has occurred in connection with maximum flooding surfaces and sequence boundaries on Troll. With the help of the stratigraphical framework the presence or absence of sequence boundaries, transgressive systems tracts, maximum flooding surfaces, and highstand systems tracts in each cycle has been defined in each well. This has given the detailed geometry of the reservoir sands of the field, and also allowed correlation of carbonate cemented horizons which are associated with bounding surfaces of the systems tracts. Knowledge of the distribution and extent of these cemented horizons has considerable significance for oil production strategy, particularly the siting of horizontal wells.

Wave-induced pore pressure acting on a buried submarine pipeline

Abstract: The response of a sandy seabed to surface water waves, with a special emphasis to wave-induced excess pore water pressure oscillations is studied here in relation to the vertical stability of submarine buried pipelines. The main object of the peper is to present a study of the distribution patern of the pore water pressure acting around the pipeline, and to calculate the seepage force, the up-lift force particularly, affecting the pipelne stability, under the assumption of compressible both the pore fluid and soil skeleton, for the case of an arbitrary seabed depth as well as for the infinite thickness of the subsoil.

Multiple unit floating offshore wind farm (MUFOW)

Abstract: This paper introduces the concept of the Multiple Unit Floating Offshore Wind Farm (MUFOW) in which an offshore array of wind turbines is mounted upon a single floating structure, rather than the more usual system where each turbine has its own supporting platform. The advantages and disadvantages of the proposed arrangement are discussed in relation to a number of parameters including costs, stability, maintenance and impact damage, and the effect of system size is examined. A design methodology is outlined and a possible arrangement described. (Author)

Installation of a Polyethylene Outfall Pipeline

Abstract: Construction of the Latrobe Valley Outfall Sewer involved installation of an 1350 metre length, 800mm diameter high Density Polyethylene offshore pipeline, stabilised by star shaped concrete anchor weights, by surface tow and submergence. The offshore pipeline was assembled on a light rail line, on a launch way, in a 1000 metre string and towed from a temporary works jetty and submerged into position. Connection to the onshore works was made with the installation of a 350 metre length inshore pipestring in a trench prepared by a sand dredge mounted on the temporary works jetty. Use of HDPE for outfall pipelines has major time and cost savings when compared to steel pipelines and the construction techniques used have application to many coastal pipeline projects.

Pipeline isolation using remotely-activated spheres

Abstract: This paper, winner of the Pipeline Industries Guild's JW Jones Memorial Arward, desccribes recent work by Shell UK Expro and Acurite Ltd in the development of a remotely-operated sphere for offshore pipeline isolation.

Welding the Maui A-B pipeline

Abstract: Submarine pipelines have been installed all over the world, in diameters ranging from 76 mm (3 in.) up to 1270 mm (50 in.) or more and in water depths up to 500 m (1600 ft) using the S-lay method. In the 1950s, the J-lay concept was developed. With the J-lay technique, the pipe is suspended near vertically from the lay barge, thus reducing the horizontal force required to prevent pipe buckling. The J-lay technique has obvious advantages for deep-water applications where it is possible to eliminate the use of anchors by using dynamic positioning. The main drawback of the J-lay technique is that the near vertical pipe is difficult to handle and multiple workstations cannot be used. Only one length of pipe can be welded onto the pipeline at a time and subsequent inspection and coating must be done before the next weld can be made, resulting in low production rates compared to that achieved by S-lay barges. In 1989, Heerema, A Dutch company, which operates a fleet of semi-submersible crane vessels (SSCV) used for the installation of offshore oil and gas production platforms, decided to diversify into marine pipe laying. Realizing direct competition with established pipe lay contractors usingmore » S-lay barges could not be commercially competitive, an innovative J-lay system was designed which took advantage of the unique capabilities of the SSCV. Although the J-lay concept was some 30 years old, no functional system had been constructed as there was no immediate market for it, especially one which could justify inferior productivity when compared to S-lay barges. Heerema's solution to this limitation was to maximize the length of each piece of pipe added to the pipeline. By fabricating the pipe on shore into lengths up to 72 m (240 ft) and using the massive crane capacity (4000 tons) of the SSCV to lift each pipe string into position for welding, they could compensate for a lower productivity rate.« less

Fault-associated seabed mounds in the Porcupine basin - offshore Ireland

Abstract: Some 31 separate mounds have been identified from seismic reflection records located in a relatively narrow east-west swath across the Porcupine Basin off western Ireland in water depths ranging from 650m to 1000m. The isolated reef-like features are found on a generally smooth and unlithified seabed. Their size is impressive, often being over 1km across and over 100m high.

Instabilities, waves and slugs in pipeline

Abstract: This paper is concerned with multi-phase fluid flow models that can be represented by systems of one-dimensional hyperbolic equations, with particular application to pipeline two-phase flows. It is shown how the governing equations can be rewritten in a form which enables analogies to be drawn with the flow of liquid down open, inclined channels. For such flows, smooth periodic solutions do not satisfy the basic equations but a train of piecewise smooth waves joined together by shocks can be constructed. These waves evolve non-linearly to their asymptotic form following a physical instability occurring in the flow. For pipeline two-phase flows, the top of the pipe puts a constraint on the maximum amplitude of the waves but also encourages the growth of the instability. When the wave bridges the pipe a liquid slug is formed, which is often an unwelcome problem in production facilities, especially offshore. These ideas can be extended to other systems of multi-phase flows. For example, a third phase can be added to pipeline flows and the governing equations can be rearranged into a form enabling similar solutions to be obtained. Dispersed two-phase flows and granular flows can also be represented by analogous sets of equations with similar solutions for appropriate values of the physical parameters. These types of solutions, viz piecewise smooth waves joined together by shocks are typical for systems of hyperbolic equations with source terms indicating that instabilities and growth of waves in a wide variety of multi-phase systems are closely related phenomena. understanding pipeline multi-phase flows is of increasing importance to the oil and gas industry, especially with the development of small offshore reservoirs. Depending on the respective flowrates, many flow regimes are possible. If both the oil and gas flowrates are small the gas flows smoothly over the stratified oil layer underneath. As the flowrates increase an instability may occur on the interface between the oil and gas leading to the formation of large amplitude waves which may

North West Shelf gets extensive pipeline, plant management system

Abstract: A trunkline management system (TMS) utilizing dynamic pipeline and plant process simulation is scheduled to start up near the end of first quarter 1994 at Woodside Offshore Petroleum Pty Ltd's North West Shelf gas project at Karratha, Western Australia The TMS is a real-time, dynamic two-phase model of the pipeline system and relevant portions of the onshore facilities Its budget was approximately $4 million (Australian) This first part of a two-part series on the system describes the operating conditions that prompted its installation; the concluding article will describe the models it incorporates

Instabilities, Waves and Slugs in Pipeline Two-Phase Flows

Abstract: This paper is concerned with multi-phase fluid flow models that can be represented by systems of one-dimensional hyperbolic equations, with particular application to pipeline two-phase flows. It is shown how the governing equations can be rewritten in a form which enables analogies to be drawn with the flow of liquid down open, inclined channels. For such flows, smooth periodic solutions do not satisfy the basic equations but a train of piecewise smooth waves joined together by shocks can be constructed. These waves evolve non-linearly to their asymptotic form following a physical instability occurring in the flow. For pipeline two-phase flows, the top of the pipe puts a constraint on the maximum amplitude of the waves but also encourages the growth of the instability. When the wave bridges the pipe a liquid slug is formed, which is often an unwelcome problem in production facilities, especially offshore.

Pipeline isolation using remotely-activated spheres

Abstract: This paper, winner of the Pipeline Industries Guild's JW Jones Memorial Arward, desccribes recent work by Shell UK Expro and Acurite Ltd in the development of a remotely-operated sphere for offshore pipeline isolation.