scispace - formally typeset
Search or ask a question

Showing papers on "Submarine pipeline published in 2002"


Journal ArticleDOI
TL;DR: In this article, the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and on sediment movement on the inner shelf was examined, and three different approaches were used in the analysis of grain-size distribution pattern.

89 citations


Journal ArticleDOI
Martin Hovland1, Steinar Vasshus1, Arne Indreeide1, Leslie Austdal1, Øivind Nilsen1 
TL;DR: In this paper, the authors used a combined side scan sonar and sub-bottom profiler system to detect deep-water coral reefs in a few specific areas, such as the Tjeldbergodden - Skogn pipeline project.
Abstract: The survey and mapping group (SMG) of Statoil is responsible for all seafloor mapping for pipelines and field development in Statoil. During numerous reconnaissance and pipeline route surveys over large portions of our contintental shelf, in the North, Norwegian and Barents Seas, we have only detected deep-water coral reefs in a few specific areas. The first reef we found was in 1982, using a combined side scan sonar and sub-bottom profiler system off Fugloy, northern-Norway. Thereafter, numerous reefs were mapped with similar systems off mid-Norway, during the period 1985–1990 for the reconnaissance and final route mapping of the Haltenpipe project. During 1997, we also mapped some previously known reefs in the Trondheimsfjord area while surveying a route for the Tjeldbergodden - Skogn pipeline project. Between 1997 and 2000, we have mapped more reefs along pipeline routes on the outer mid-Norway continental shelf. These reefs are of a smaller size (less than 5 m high) than those mentioned above (5–31 m high). Although side scan sonar and sub-bottom profilers provide a less ambiguous detection of reefs, we have found that modern multi-beam echosounder data can provide adequate remotely sensed data for deep-water coral reef mapping. The interpretation of the reefs is based on visual documentation by ROV (remotely operated vehicle) or by sampling with gravity corers and grabs (ground-truthing). Based on a limited amount of such ground-truthing, it has been possible to extrapolate and use the specific morphological characteristics of the reefs to map their density and distribution. For the Haltenpipe project, we mapped an offshore route corridor of about 200 km length at a width of 3 km with multi-beam echosounder. On the basis of ground-truthing 14 of the suspected coral reefs, we have found the total number of reefs to be 57 within the 600 km2 mapped area. All these reefs are higher than 5 m (the highest is 31 m) and of diameters at their base of more than 50 m. Although they occur in local clusters with up to 10 reefs per km2, the mean density of reefs along the entire (200 km long) transect is only 0.09 suspected reefs per km2. However, there is a large regional density variation, with the highest regional density being 1.2 reefs per km2 in an area of subcropping Palaeocene sedimentary rocks. A brief discussion of why the corals have constructed their reefs in the deep, cool, and generally `hostile' waters of the Norwegian continental shelf and fjords concludes with them probably subsisting on a reliable and steady nutrient source, independent of season and variations in the Atlantic Drift (`Gulf stream'). This positive environmental component is called `hydraulically active substrata'. It is thus speculated that micro-organisms, bacteria etc., utilizing the hydraulically activated chemical porewater gradients, cause a local enrichment on which the cnidarian organisms ultimately depend.

39 citations


Journal ArticleDOI
TL;DR: In this article, a series of experiments have been conducted in a U-shaped oscillatory flow tunnel, which provides a more realistic simulation than the previous actuator loading methods, based on the experimental data of pipe displacement with two different constraint conditions (freely laid pipelines and anti-rolling pipelines).

37 citations


Journal ArticleDOI
TL;DR: In this paper, the wave induced pressure on a pipeline buried in a sandy bed at different burial depth ratios is analyzed. But the results show that wave induced pressures are significantly controlled by the wave period analyzed in terms of the scattering parameter (ka).

34 citations


01 Jan 2002
TL;DR: In this article, an assessment of the offshore distribution of gray whales and an estimate of the proportion of whales that migrate beyond the visual range of shore-based observers was provided. But the distribution within 3 n.miles of the shore differed by year but the shifts in the distribution were minor.
Abstract: Aerial surveys provide an assessment of the offshore distribution of gray whales and an estimate of the proportion of whales th at migrate beyond the visual range of shore-based observers. Six surveys were conducted concurrent with shore-based surveys during 1979, 1 980, 1988, 1993, 1994 and 1996. Annual differences were tested for in the distribution of whales within an area 3 n.miles north and south of Granite Canyon, and it was found that the distributions within 3 n.miles of the shore differed by year but the shifts in the di stribution were minor ( 2.25 n.miles) distribution of gray whale pods did not differ s ignificantly between survey years. An average of 4.76% (SE = 0.85%) of the whale pods were observed beyond 2.25 n.miles and only 1.28% (SE = 0.07%) beyond 3 n.miles.

24 citations


Journal Article
TL;DR: A number of prominent structures were detected in the area such as slumping, sliding, pockmarks, faults and dome-like structures as mentioned in this paper, which can lead to the failure of offshore installations.
Abstract: The Black Sea is one of the largest inland seas in the world. Off the shelf, the water depth quickly plunges to an average depth of 2 km. The Black Sea sediments are rich in calcite and organic carbon, the latter showing a high degree of preservation due to anoxia in the waters below 100-150 m. Slope failures and sediment instability related to immense gas and gas hydrate accumulations are serious problems that can lead to the failure of offshore installations. Marine geophysical surveys have been carried out in the Eastern Black Sea basin using state-of the-art technology to produce sonar and high-resolution maps. A number of prominent structures were detected in the area such as slumping, sliding, pockmarks, faults and dome-like structures. In the Turkish near shore and the abyssal plain, shallow gas accumulations have been detected and are continuous about 25-65 m beneath the seafloor. The gas-bearing strata appear as bright spots and cloudy spots, sometimes pockmarks and acoustic blanking. The sediments on the Turkish shelf contain certain concentrations of gas which can seep to the seabed surface and generate pockmarks. Gas-hydrate layers in the sediments often appears as dark and strong reflection pockets on sub-bottom profiler records.

24 citations


Patent
13 Jun 2002
TL;DR: In this paper, a method for j-laying a pipeline from an offshore vessel to the floor of the ocean comprising a multiplicity of winches for supporting the upper end of the pipeline at its natural hanging angle is described.
Abstract: A method for j-laying a pipeline from an offshore vessel to the floor of the ocean comprising a multiplicity of winches for supporting the upper end of the pipeline at its natural hanging angle, a mast in a fixed angle to the vessel, holding new pipe section in the mast for welding to the upper end of the pipeline, and flexing the lower end of the new pipe section into alignment with the upper end of the pipeline to allow welding to the pipeline and flexing the remainder of the new pipe section to remain within the mast

14 citations


Proceedings ArticleDOI
01 Jan 2002
TL;DR: In this paper, a transfer process was proposed to reduce both the hydrostatic head in the riser and the pressure in the pipeline, thereby lessening or eliminating severe slugging in pipeline/riser systems.
Abstract: Exploitation of offshore petroleum reservoirs has recently moved to ever-increasing water depths. Production from fields in water deeper than 1800 m is now a reality. The use of long deepwater risers that conduct production from multiple wellheads on the sea-floor to the surface predisposes the system to severe slugging in the riser for a wide range of flow rates and seabed topography. When one considers the length of the deepwater risers, the problem is expected to be more severe than in production systems installed in shallower waters. Severe slugging could occur at high pressure, with the magnitude of the pressure fluctuations so large as to cause a shorter natural flow period with subsequent consequences, such as premature field abandonment, loss of recoverable reserves, and earlier-than-planned deployment of boosting devices. In this study, a novel idea to lessen or eliminate severe slugging in pipeline/riser systems has been thoroughly investigated. This idea was first proposed by Barbuto 1 and later developed independently by Sarica and Tengesdal. 2 The principle of the technique is to transfer pipeline gas to the riser at a point above the riser base. The transfer process will reduce both the hydrostatic head in the riser and the pressure in the pipeline, consequently lessening or eliminating severe slugging by maintaining steady-state two-phase flow in the riser. An experimental study has been conducted with a 7.62-cm-inside-diameter (ID) riser (14.63 m high) and pipeline (19.81 m long) system. A broad range of data was collected from the facility in both the severe slugging and stable regions. It was found that the severe slugging models currently available do not predict the region accurately for larger-diameter pipes. Data acquired with the external gas bypass have proved the proposed elimination technique.

14 citations


Proceedings ArticleDOI
08 May 2002
TL;DR: In this paper, the authors provide a brief historical overview of how the techniques used to monitor pipe settlement have evolved over the life of the Trans-Alaska Pipeline System (TAPS) and provide a discussion of the pipe geometry is currently monitored using the BJ Pipeline Inspection Services (BJ) smart pig.
Abstract: An important aspect of the ongoing operation of the buried sections of the Trans-Alaska Pipeline System (TAPS) is the curvature imposed on the pipeline by differential settlement of the surrounding soil as a result of thawing of ice-rich subsurface soils. High pipe curvature is a source of concern since it can potentially lead to wrinkling of the pipe wall and/or tensile fracture of the pipe at girth welds. Alyeska Pipeline Service Company has monitored pipeline settlement using different techniques since start up of the line in 1977. This paper provides a brief historical overview of how the techniques used to monitor pipe settlement have evolved over the life of TAPS. The paper also provides a discussion of the how the pipe geometry is currently monitored using the BJ Pipeline Inspection Services (BJ) Geopig® smart pig. The discussion includes a brief description of the Geopig measurements which are numerically processed to obtain the three-dimensional pipeline displacement and curvature (bending strain) profiles. Several illustrations of this technology are presented. The paper concludes with a summary of how Alyeska's state-of-the art pipeline geometry monitoring program is used to help make decisions related to maintaining the structural integrity of TAPS.

9 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a quantitative method to assess two failure patterns by combining boundary element and finite element methods, which is a nonlinear fluid-structure interaction problem, and an iteration procedure is used to solve it.

8 citations


01 Jan 2002
TL;DR: In this paper, the authors used a hyperbolic model to estimate the equilibrium scour depth below the submarine pipeline, which was found to be 45% of the pipe diameter for consistency index of 0.17.
Abstract: Experimental investigations on scour due to waves under the submarine pipeline resting on the clay soil bed for different consistency index of the soil were carried out. Based on the scour measurements for few hours of wave action, the ultimate scour depth is estimated using hyperbolic model. The equilibrium scour depth below the pipeline is estimated as 45% of the pipe diameter for consistency index of 0.17 and is 35% of the pipe diameter for consistency index of 0.23. Investigations on wave pressures around the submarine pipeline (exposed, half buried and fully buried) are also carried out. It is found that the pressure is reduced by about 40%, if the pipeline is just buried in clay soil. It is also found that the consistency index of the soil significantly affects the wave-induced pressure.

Patent
10 Jan 2002
TL;DR: A method of stabilising a submarine pipeline (10) on a seabed (12) includes delivering a settable cementitious material (16) from a marine vessel (18) through a conduit (28) to a former (30) located over the pipeline.
Abstract: A method of stabilising a submarine pipeline (10) on a seabed (12) includes delivering a settable cementitious material (16) from a marine vessel (18) through a conduit (28) to a former (30) located over the pipeline (10) The former (30) includes a reciprocating plate (44) for compacting the material (16) and extruding it from a nozzle (38) at the rear of the former (30) The action of the plate (44) in compressing the material (16) creates a reaction force to propel the former (30) in the direction D along the pipeline (10) The cover (14) is of a low profile generally convex transverse section

Journal ArticleDOI
TL;DR: In this paper, a single pipe and dual pipe in various trench sections are simulated and compared with experimental results obtained from particle image velocimetry measurement, and the stability of various trench conditions is addressed in terms of mean amplitudes of oscillating lift and drag and reduction factors for each case.
Abstract: Offshore pipelines are to be stabilized against external loading caused mainly by wave and currents. When pipelines are placed in a trench, the forces acting on them are reduced considerably. To investigate the stability in various trench sections, the flow over the pipeline is numerically simulated and compared with experimental results obtained from particle image velocimetry measurement. This paper consists of two parts: single pipe and dual pipe in various trench sections. Each part compares numerical results with experimental results, which include mean flow pattern, drag-force coefficient, and lift-force coefficient. For a single pipe, Smagainsky's eddy viscosity model combined with a truncated deductive model is applied to represent the stress field in a quadrilateral structured grid system. In the numerical simulation for dual pipes, the Navier-Stokes equation and elliptic mesh generation method are used. The stability of various trench conditions is addressed in terms of mean amplitudes of oscillating lift and drag and reduction factors for each case. The results can be effectively applied to pipeline design.

01 Jan 2002
TL;DR: In this article, a free spanning submarine pipeline is constructed in a seismically active region and a model experiment is performed on an underwater shaking tahle to simulate the response of submarine pipelines under dynamic input.
Abstract: Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is con-structed in a seismically active region. The model experiment is performed on an underwater shaking tahle to simulate the response of submarine pipelines under dynamic input. In consideration of the effects of the terrestrial and submarine pipeline , water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response, 120 groups of experiments are conducted. Affecting factors are analyzed and conclusions are drawn for reference. For the con-trol of dynamic response, the span of a submarine pipeline is by far more important than the other factors. Meanwhile, the rosponse difference between a submarine pipeline under sine excitation and that under random excitation exists in ex-periments.

Proceedings ArticleDOI
01 Jan 2002
TL;DR: The first subsea Arctic oil production pipeline was installed by BP Exploration (Alaska) Inc. in 2000 for the Northstar Development Project as mentioned in this paper, which runs approximately 10 km from Seal Island, through a lagoon area, to a shore crossing and then overland for approximately 18 km.
Abstract: BP Exploration (Alaska) Inc. completed the installation of the first subsea Arctic oil production pipeline in April 2000 for the Northstar Development Project. The drilling and production facilities are located at Seal Island, approximately 10 km offshore of the Alaskan Beaufort Sea coast. Twin 273.1 mm (10-inch) oil and gas pipeline systems run approximately 10 km from Seal Island, through a lagoon area, to a shore crossing, and then overland for approximately 18 km. The unique aspects of this design included the pipeline environmental loadings, geotechnical considerations, and the use of limit state design procedures for extreme loading conditions. Environmental loadings and geotechnical conditions (in-situ and backfill) along the pipeline route were a major factor in the design of the offshore portion of the pipelines. Data collection of environmental conditions (e.g. ice gouging and strudel scour) and proper evaluation of the same were required to provide appropriate design data. Comprehensive field and laboratory programs were undertaken to generate the necessary geotechnical data for design. The evaluation of and design for unique Arctic environmental loading conditions including ice gouging, offshore permafrost, upheaval buckling, and strudel scour are described. Trenching and backfilling aspects of the pipeline design are also discussed. The paper closes with a general overview of the pipeline operations since the start of oil production in November 2001.Copyright © 2002 by ASME

Journal ArticleDOI
TL;DR: In this paper, a comparison of near-surface channels with channel reservoirs at Bonga, offshore Nigeria (OML118, 1000 m water depth), demonstrates some important lessons in using shallow analogs for reservoir prediction.
Abstract: Comparison of near-surface channels with channel reservoirs at Bonga, offshore Nigeria (OML118, 1000 m water depth), demonstrates some important lessons in using shallow analogs for reservoir prediction. Studies of shallow hazards and pipeline routing, integrating 3D and high-resolution 2D seismic with well logs, illustrate seafloor and nearsurface features including a large mud-draped canyon, mud volcanoes, and numerous pockmarks, which indicate fluid expulsion. Both the shallow overburden (Plio-Pleistocene) and the main reservoir intervals (Miocene) are characterized by deepwater channel geometries visible in seismic profiles, on map views, and within 3D volume views. Most near-surface channel features inhabit broad, relatively straight scours 1-3 km wide and 30-300 m deep, filled by composite packages of smaller, often sinuous channels 100500 m wide and 5-50 m deep. Although many of these near-surface channels display a chaotic to low-continuity, high-amplitude seismic facies character often associated with sandy fill, well logs through the near-surface section indicate these are mainly filled with mud. Channel geometries at reservoir level show different characteristics. The smaller-scale map-view geometries are consistent in size with the near-surface channels but the larger host scours are not as prevalent or obvious, and some thin, sheet-like sands are also present. A transition from lower slope to upper slope at the end of the Miocene probably accounts for this variation. A fundamental understanding of geologic setting and rock/fluid variation is critical before extrapolating seismic facies information from shallow analogues to deeper reservoirs.

Journal ArticleDOI
TL;DR: In this paper, the authors describe all the geotechnical engineering works associated with the hydraulic skirt extraction/jacking of the gravity platform from the seabed, which were executed prior to the refloat and tow of the platform to deep water inshore moorings.
Abstract: The Maureen Oil Field, located in the UK sector of the North Sea, was developed in the early 1980s, with the installation of the world's largest steel gravity platform, together with the installation of an export pipeline to an offshore concrete articulated loading column. Production in the field ceased in October 1999, and the facilities at the Maureen location were removed in the summer of 2001 as part of the decommissioning process. The largest element for removal and decommissioning was the steel gravity platform of about 1100 MN (110 000 t). This paper describes all the geotechnical engineering works, associated with the hydraulic skirt extraction/jacking of the gravity platform from the seabed, which were executed prior to the refloat and tow of the platform to deep water inshore moorings, together with a summary of results from the actual skirt extraction/jacking process, which was executed in June 2001.

Patent
16 Oct 2002
TL;DR: In this article, the authors proposed a pipeline compensator for offshore water injection, comprising a pipeline and a compensator which is composed of a catch hoop joint, a compensation rod, a sealing assembly, a groove, a sealed chamber, an outer pipe, an expansion pipe and a pressure ring.
Abstract: The utility model discloses a pipeline compensator for offshore water injection, comprising a pipeline and a compensator which is composed of a catch hoop joint, a compensation rod, a sealing assembly, a groove, a sealed chamber, a sealing ring, an outer pipe, an expansion pipe and a pressure ring. The catch hoop joint of the utility model is connected with the water injection pipeline, which enables a spherical pair of the compensator to swing in any direction in the plane perpendicular to the axis of the compensator and enables a sliding pair to move horizontally along the axis of the compensator. The utility model has the advantages that the offshore water injection pipeline can be kept from damage due to the relative swing of an oil production platform and a trestle by combining the spherical pair with the sliding pair; the utility model is mainly used for water injection pipelines of the offshore oil production platform, and the utility model can also be used for other pipeline flows requiring compensation.

Patent
15 Oct 2002
TL;DR: In this article, an auxiliary member is employed which restricts radial movement of the pipeline below the clamp, and the auxiliary member comprises an elongate element, such as a pipe, whose upper end is fixed to the vessel and whose lower end carries a member connecting it to the pipeline.
Abstract: During recovery of an offshore pipeline, to a floating vessel for repair, for example, the pipeline is secured to a hang-off clamp. Due to the motion of the vessel, oscillating bending moments can be caused in the pipeline below the clamp. To reduce these bending moments an auxiliary member is employed which restricts “radial” movement of the pipeline below the clamp. The auxiliary member comprises an elongate element, such as a pipe, whose upper end is fixed to the vessel and whose lower end carries a member connecting it to the pipeline. Axial movement of the pipeline with respect to the connecting member is permitted. The auxiliary member is designed to have predetermined amount of flexibility, this being provided in particular by flexibility of the pipe, and it thus restricts the amount of radial movement of the pipeline which is permitted below the clamp.

Dissertation
01 Jan 2002
TL;DR: In this paper, a model was developed to estimate iceberg grounding rates on the seabed and verified using data from the Grand Banks, where iceberg parameters are fairly well established, and the model was verified using scour rates estimated at the Hibernia and White Rose sites.
Abstract: An iceberg risk analysis was performed for a network of 3 pipelines proposed by Petro-Canada (1983) to allow the transport of natural gas on the Makkovik Bank to a landfall at Cape Harrison on the Labrador Coast. The risk analysis originally performed indicated that scouring icebergs would make direct contact with these three pipelines an average of thirteen times per year (total for all three) if the pipelines were trenched to provide a cover depth of 2.5 m. The required burial depth to reduce failure rates to one every second year for the pipeline network was estimated to be approximately 5 m, which was not considered technically feasible. -- Since the original Petro-Canada (1983) analysis, a significant amount of work has been done on iceberg scour and the associated risk to subsea facilities. Given increasing interest in the development of offshore natural gas reserves, it was considered worthwhile to perform a review of the original work and, if warranted, perform another risk analysis. Certain elements of the original risk analysis were identified as being extremely conservative: the mean scour depth, the iceberg draft distribution, and the method used to determine the proportion of icebergs scouring over the pipelines. -- In order to perform a risk analysis for the pipeline network, a model was developed to estimate iceberg grounding rates on the seabed. The model was tested using data from the Grand Banks, where iceberg parameters are fairly-well established. The model was verified using scour rates estimated at the Hibernia and White Rose sites from seabed surveys and was found to provide reasonable estimates of iceberg scour rates. -- Data for the Makkovik Bank was reviewed for use in the grounding model, to allow calculation of pipeline scour crossing rates and to determine the scour depth distribution. The failure rates depend on the criterion used to define pipeline failure. If direct contact between a scouring iceberg keel and a trenched pipeline was defined as failure (which was the criterion used for the Petro-Canada (1983) analysis) then the mean time between failures for the three pipelines with 2.5 m cover varied from 18 to 23 years, with a resulting mean time between failures of 7.5 years for the entire network. While the direct-contact criterion was commonly used at the time of the original analysis, modern analyses require a clearance between a scouring iceberg keel and the top of the pipeline. If a conservative criterion of 1 scour depth clearance between the scouring pipeline keel and the crown of the pipeline (i.e. 2 m cover for 1 m scour) is used to define pipeline failure, the mean time between failures for the three pipelines (2.5 m cover) varies from 3.4 to 5.3 years, with a mean time between failure events for the pipeline network of 1.4 years. A detailed analysis of pipeline response would yield more favourable results. -- Additional work is recommended to allow better definition of scour parameters and iceberg frequency. A high-quality seabed survey would likely indicate a shallower mean scour depth than was used in the analysis (0.75 m), potentially in the range currently used for pipeline risk analyses for the Grand Banks (< 0.5 m).


Proceedings ArticleDOI
01 Jan 2002
TL;DR: In this article, the authors applied structural reliability analysis to a high-pressure natural gas pipeline having both onshore and offshore sections, in order to determine the extent to which the asset life could be increased beyond the design life without any significant reduction in reliability and hence safety levels.
Abstract: Pipeline designers and operators recognize that the commercial viability of operating high-pressure gas pipelines decreases with time. This is because the structural integrity levels of the pipeline decrease, due to the action of deterioration processes such as corrosion and fatigue, until the level of mitigation required to ensure adequate safety levels becomes uneconomical. For this reason pipelines are assigned a nominal design life of typically 40 years. This paper describes the application of structural reliability analysis to a high-pressure natural gas pipeline having both onshore and offshore sections, in order to determine the extent to which the asset life could be increased beyond the design life without any significant reduction in reliability and hence safety levels. The approach adopted was to identify the credible failure modes that could affect each of the onshore and offshore sections and determine the probability of failure due to each failure mode taking account of the uncertainties in the parameters that affect each mode. Based on a detailed consideration of the results of the study it was concluded that the life of the asset considered here could be extended to 60 years without any significant reduction in safety levels. Moreover, it was concluded that if certain mitigating measures were to be implemented in the future then it would be possible to increase the asset life to significantly more than 60 years.Copyright © 2002 by ASME

李昕, 刘亚坤, 周晶, 马恒春, 朱彤 
01 Jan 2002
TL;DR: In this article, a free spanning submarine pipeline is constructed in a seismically active region and a model experiment is performed on an underwater shaking table to simulate the response of submarine pipelines under dynamic input, considering the effects of the terrestrial and submarine pipeline, water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response.
Abstract: Seismic load has a significant effect on the response of a free spanning submarine pipeline when the pipeline is constructed in a seismically active region. The model experiment is performed on an underwater shaking table to simulate the response of submarine pipelines under dynamic input. In consideration of the effects of the terrestrial and submarine pipeline, water depth, support condition, distance from seabed, empty and full pipeline, and span on dynamic response, 120 groups of experiments are conducted. Affecting factors are analyzed and conclnsions are drawn for reference. For the control of dynamic response, the span of a submarine pipeline is by far more important than the other factors. Meanwhile, the rosponse difference between a submarine pipeline under sine excitation and that under random excitation exists in experiments.

Journal ArticleDOI
TL;DR: The East Spar gas condensate field is located in production licence WA-13-L in the offshore Carnarvon Basin this article, where two subsea wells linked to processing facilities on Varanus Island via a multi-phase pipeline.
Abstract: The East Spar gas condensate field is located in production licence WA-13-L in the offshore Carnarvon Basin. Production commenced in 1996 with two subsea wells linked to processing facilities on Varanus Island via a multi-phase pipeline. The pressure performance of the field has been significantly different to pre-development expectations. This prompted a re-examination of the seismic and well data to investigate the potential for alternative reservoir models. Integrated stratigraphic and seismic interpretation reveals that the Barrow Group reservoir sands were deposited within an incised valley of limited lateral extent. Sea level fall instigated erosion of avalley that on transgression was filled with successive fluvial, estuarine and marine sediments. Good quality sands are expected to be limited to this valley, the upper part of which can be mapped on seismic. Poor sand development in East Spar-2ST is consistent with its location at the edge of the incised valley. Before development, the primary production mechanism was expected to be a strong bottom water drive comparable with other Barrow Group fields in the Carnarvon Basin. The revised depositional model, however, and the observed decline in reservoir pressure, indicate that connection to this regional aquifer is limited. This implies that water influx will probably be later, and ultimate recovery higher, than previously anticipated.

Journal ArticleDOI
01 Jan 2002
TL;DR: Kioka et al. as mentioned in this paper examined the main factors for scour-processes, and obtained many results needed for a future work (numerical simulation of scour events) as described later.
Abstract: In addition to our previous experiments on ice-scour event including the medium-scale model test (Kioka et al., 2000, 2001a,b), we have performed many series of model tests under various conditions. We examined the main factors for scour-processes, and obtained many results needed for a future work (numerical simulation of scour events) as described later. In all cases, the scour depth or the scour curve depended on the attack angle. As the attack angle decreased, the model keel moved upward due to the slip between the seabed and the model keel. While we showed that the bulldozing force related to the excess pore water pressure, and it was proportional to the square of velocity of the keel and to the inverse of the coefficient of permeability from a simple model, we also proved this relationship by the experimental results. In order to conduct a small-scale model test, these results showed that the grain size of sand of seabed and the velocity of the keel should be controlled. We then examined its scale-effect. INTRODUCTION Ice-Scour Event is a phenomenon that occurs when ice comes into contact with seabed. Ice-scour has been reported to cause damage to communication cables and water intake pipelines. Since oil and natural gas exploration projects in offshore areas of (sub)arctic seas are becoming popular, more care must be taken over the design and installation of oil/gas pipelines in such areas in order to avoid accidents due to ice-scour. It will be very important to acknowledge the mechanisms (ice motions, sub-seabed conditions on scour events). In addition to our previous tests including the medium-scale model test (Kioka et al., 2000, 2001a,b), we have performed many series of model tests under various conditions. We examined the main factors for Scour-process, and obtained many results needed for a future work (numerical simulation of ice-scour event) as described later. We also examined the control methods of test conditions due to an excess pore water pressure that influences the scour-processes, including its scale-effect. 1 Port and harbor eng. division, Civil Engineering Research Institute of Hokkaido, Hiragishi 1-3-1-34, Toyohira-ku, Sapporo, 062-8602, Japan 2 MAEDA Corporation, Fujimi 2-10-26, Chiyoda-ku, Tokyo, 102-8151, Japan 3 Division of Environmental Resources Eng. Hokkaido University, N-13 W-8, Sapporo 060-8628, Japan


Journal Article
TL;DR: In this article, the damage causes of submarine pipeline are analyzed and several repairing methods for damaged pipeline are introduced in detail, the advantages and disadvantages of each method are analyzed, and the choosing of right repairing method based on damage conditions and the features of the damaged pipeline is recommended.
Abstract: The damage causes of submarine pipeline are analyzed and several repairing methods for damaged pipeline are introduced in detail.The advantages and disadvantages of each method are analyzed and the choosing of right repairing method based on damage conditions and the features of the damaged pipeline are recommended.

Journal Article
TL;DR: Tubb explores planned and new construction projects both offshore and onshore around the world in this paper, and explores the potential of these projects both onshore and offshore, both on and off-shore.
Abstract: Managing editor Rita Tubb explores planned and new construction projects both offshore and onshore around the world.