Showing papers on "Submarine pipeline published in 1992"

Effect of Spoilers on Scour at Submarine Pipelines

Abstract: This paper investigates the effect of a spoiler on local scour around submarine pipelines. Experiments conducted in a unidirectional flow show that the spoiler is capable of increasing both the scour depth beneath (tunnel erosion) and downstream of (lee erosion) the pipeline. The increase is related to the location of the spoiler compared with the direction of the incoming flow. The spoiler attached on top of the pipeline is effective in increasing the blockage to the incoming flow, which deflects a large proportion of the flow downward beneath the pipe, resulting in an increased scour depth. The increase in lee erosion, due to the protrusion of the spoiler above the pipeline, is important in the stimulation of the self-burial potential of the submarine pipeline. Spoilers attached to the lower half of the pipeline effected the formation of a wake zone beneath the pipe, which acts to deflect the flow downward, causing the formation of a deeper tunnel scour hole.

Asymmetric effects of prop imperfections on the upheaval buckling of pipelines

Abstract: Submarine pipelines often carry products which are much hotter than the surrounding seawater. The potential thermal expansion is restrained by friction between the pipeline and the seabed, causing the development of large compressive axial forces in the line, which can lead to buckling of the pipeline. This paper takes a fresh look at the vertical buckling of a pipeline encountering a point irregularity on an otherwise perfectly flat seabed, the so-called ‘prop case’. Some approximations and assumptions in earlier work in this area are reexamined and their effects are calculated. Most importantly, the assumption that buckling is symmetric about the prop is tested. Asymmetric results are found, at a lower critical temperature than the symmetric mode, a fact which may have significant implications for design.

Submarine flow slide in Puget Sound

Abstract: In December 1985, construction began on the offshore portion of the Renton Effluent Transfer System. Under the auspices of the Municipality of Metropolitan Seattle (Metro), treated effluent is pumped to Duwamish Head where the flow is separated into two 1.63-m-diameter steel pipes that extend about 3,050 m offshore into Puget Sound. A 155-m long diffuser section at the end of each pipe rests in about 185 m of water. A submarine slide occurred in Puget Sound during the dredging operation for the construction of the offshore portion of the pipeline. The slide occurred during low tide and involved 400,000 m³ of medium-dense sands to a thickness of up to 12 m. The failure and an evaluation of the contributing causes are described in this paper. The failure is attributed to a collapse mechanism in the soil causing liquefaction as a result of low tidal conditions combined with details of the dredging operations.

Early Tertiary submarine fan deposits in the Porcupine Basin, offshore Ireland

Abstract: Abstract The Porcupine Basin, offshore western Ireland, contains up to 10 km of Mesozoic and Cenozoic sediments. Seismic sequence analysis of the Palaeocene-Eocene strata on the southwestern and southeastern margins of the basin reveals a mounded and draped geometry. Four seismic sequences are defined and are coeval with a series of deltaic deposits in the northern and central parts of the basin. In the southwestern area these are interpreted as stacked submarine fan deposits. In the southeastern area the lower two sequences are interpreted as shelf-slope deposits which are overlain by two submarine fan complexes. Funnelling of the sediment was controlled by erosive channelling through interfan topographic lows. The seismic response indicates that the fans are dominated by lower fan sheet sand deposits with minor amounts of upper fan channellized sandstones. They probably developed in response to an interplay of eustatic sea level changes, tectonic uplift on the basin margins, and thermal subsidence towards the basin centre.

Piping Design Handbook

Abstract: Part 1 Fluid flow: fluid flow crude oils gas flow pressure drop measurement natural gas slurry systems, nomograph slurry systems and pipelines two-phase design two-phase pressure drop computation water hammer. Part 2 Fluidics. Part 3 Piping design: piping design economic diameter equivalent length estimation fittings, number and types fittings, pressure drop flashing steam condensate gravity flow liquid carbon dioxide maximum pressure for steel piping offshore considerations photogrammetry and computer-aided polytropic compression sizing economics steam lines, optimum diameter temperature (high) considerations temperature (low) considerations tracing costs vacuum considerations piping and instrumentation diagrams thermoplastic hose around control valves. Part 4 Pipeline design: dynamic programming manifolds non-Newtonian flow slurry systems slurry systems, energy reduction two-phase flow, pressure drop and holdup equations waxy crude oils permafrost considerations flow basics loops or expansion joints materials - selection costs, installation. Part 5 Buried pipelines: corrosion control design heat loss. Part 6 Pipeline support design. Part 7 Pipeline shortcut methods: collapsing pressure collapsing pressure, nomograph discharge from horizontal pipes discharge from vertical pipes economic pipe sizes expansion of pipe fow rates friction losses, contraction or expansion friction losses, fittings friction losses, incompressible and compressible flow friction losses, nonstandard ducts friction losses, straight gas flow looped lines parallel lines parallel lines, computer method pressure drop relative capacities of pipes sizing for steam traps steel pipe properties two-phase flow weight of piping. Part 7 Pipeline operation and maintenance: friction reduction cleaning coatings wear repairing, in-service service problems freezing, prevention of by bleeding leak detection leak detection using SCADA information. Part 8 Pipeline failure: pipeline failure outside-force damage subsidence strains rupture replacement projects, risk analysis. Part 9 Pipeline economics and costs: pipeline economics and costs construction, worldwide.

Geologic report for the Gulf of Alaska planning area. Final report

Abstract: The report is a summary of the regional geology, geologic history, petroleum potential, and environmental characteristics of the Gulf of Alaska Planning Area The geologic interpretations are based on offshore seismic reflection lines, subsurface data obtained from onshore and offshore wells, dredge samples, shallow core holes, and geologic investigations of outcrops onshore The primary emphasis, however, is on 13 wells drilled offshore between 1975 and 1983 Despite the lack of exploration success thus far, industry interest in the Gulf of Alaska area as a potential petroleum province remains high

Physical model analysis of iceberg scour in dry and submerged sand

Abstract: Ice scour is still a phenomena of great concern in the development of offshore oil and gas fields located in a cold ocean environment. Ice scour could also create problems for power cables or pipelines which pass through inland waters such as the Great Lakes. Cables, pipelines, and wellheads are in danger offshore. Direct impact between ice and a subsea installation will most likely cause damage. A seabed installation, such as buried pipeline, might be subjected to additional loading or intolerable displacements through close proximity of an ice keel. The question still remains as to how deep is safe. -- In an attempt to further understand the ice scour process, a series of four physical model tests was carried out at Memorial University's scour tank facility. The first two tests were conducted in a clean, dry silica sand while the remaining two were conducted in the same sand in a submerged state. The objectives of this experimental program were to measure forces and pressures on the model, to measure the response of the soil in the testbed, and, most importantly, to measure displacements in the testbed below the scour. -- The measured results compare well with computed values. The results have also been compared with previous works and models. The analysed experimental results show that there is seabed response and displacement up to 3 1/2 scour cut depths below the unscoured testbed surface. Finally, it was observed that the scouring process was similar for tests in both the dry and submerged state; measured forces and loads less for the submerged tests.

Assessment of coastal processes for teh design and the construction of the zeepipe landfall in zeebrugge

Abstract: Early 1991, Statoil started with the installation of a 40 inch diameter gas pipeline between the Sleipner and later Troll field in the Norvegian sector of the North Sea and the harbour of Zeebrugge on the Belgian coast. The connection between the offshore and the onshore pipeline was performed in August 1991, in the landfall area of Zeebrugge. The design and the construction of the landfall in the nearshore area required an extensive survey and engineering program taking the environmental parameters and the coastal processes into account.

Insulation/coating system developed for pipeline

Abstract: This paper reports that three years of effort by BP Engineering, working closely with the Miller Gas System Project, resulted in the development, testing and manufacture of a unique insulation and coating system used in construction of the St. Fergus-to-Boddam Pipeline. The 147-mile, 30-in. offshore pipeline has a design pressure of 175 bara and operates in the dense phase with a gas cricodenbar of 100 bara. Due to safety considerations, a design pressure of 35 bara was chosen for the onshore section, which is below the gas cricodenbar. The hydrocarbon dewpoint at this pressure is approximately 20 C. Gas pressures are reduced at the St. Fergus terminal and the gas is heated to give a pipeline inlet temperature between 40 C and 80 C, depending on flow conditions. The pipeline is insulated to avoid excessive heat loss and liquid dropout. The decision to insulate the pipeline was made with the knowledge that experience with insulated, buried pipelines has not been good. Considerable time and effort would be required if problems were to be avoided.