Study of Severe Slugging in Real Offshore Pipeline Riser-Pipe System

1987 ◽  
Author(s):  
M.A. Farghaly
Keyword(s):  
Pipe System ◽  
Riser Pipe ◽  
Offshore Pipeline

Severe Slugging in Offshore Pipeline Riser-Pipe Systems

1985 ◽  
Vol 25 (01) ◽  
pp. 27-38 ◽  
Author(s):  
Zelimir Schmidt ◽  
Dale R. Doty ◽  
Kunal Dutta-Roy
Keyword(s):  
Slug Flow ◽  
Offshore Platforms ◽  
Liquid Slug ◽  
Two Phase ◽  
Pipe System ◽  
Flow Capacity ◽  
Riser Pipe ◽  
Offshore Pipeline ◽  
Carry Over ◽  
The Cost

Abstract Severe slug flow (i.e., terrain-dominated slug flow) was studied in a simulated offshore pipeline riser-pipe system. Severe slug flow is characterized by extremely long liquid slugs generated at the base of the vertical riser. This phenomenon occurs at low gas and liquid flow rates and for negative pipeline inclinations. Slugging in some offshore platforms has required the use of operating procedures that drastically curtail production. Losses in flow capacity up to 50% have been reported. production. Losses in flow capacity up to 50% have been reported. A hydrodynamic model has been developed for severe slug flow. The model's predictions agree with experimental data. The model can be used to design predictions agree with experimental data. The model can be used to design new pipeline riser-pipe systems or to adjust the operation of existing systems to prevent the occurrence of severe slug flow. Also, a flow-regime map is presented for predicting the severe slug flow regime, where the boundaries are determined analytically. Finally, additional methods are proposed to prevent the flooding of separation facilities by riser-pipe proposed to prevent the flooding of separation facilities by riser-pipe generated slugs. This study is an extension of Ref. 1, in which severe slug flow was introduced and was only partially modeled. Introduction Two-phase flow in pipelines frequently involves the formation of liquid slugs. Processing of these slugs with separators can be extremely difficult if the size of the slugs becomes abnormally long. When a long liquid slug reaches a separator, it is possible for the liquid level in the separator to rise faster than the separator can purge the liquid, resulting in possible liquid carry-over into the gas stream. A technique often used for possible liquid carry-over into the gas stream. A technique often used for protecting separators from liquid slugs is to install an additional vessel protecting separators from liquid slugs is to install an additional vessel ahead of the separator, which usually is called a "slug catcher." The combined cost of the two smaller vessels is usually lower than the cost of a single large separator, which must be designed to process liquid slugs. However, the size of the slug catcher and/or separator must increase with increasing expected liquid slug sizes. The cost of installation of large separators and slug catchers, especially in the hostile environments found in Alaska, in swamps, or on offshore platforms, may be prohibitive. Therefore, it is desirable to have a technique that can predict and control both the occurrence and magnitude of liquid slugs so that separation facilities can be designed properly and their size decreased. Recently, studies have been performed that have increased dramatically the accuracy of both slug size and frequency predictions. Earlier studies, performed under laboratory conditions, indicated that slug lengths would performed under laboratory conditions, indicated that slug lengths would be no more than 100 ft [30.48 m]. However, recent studies performed on full-scale pipelines have indicated that slug lengths of more than 2,000 ft [609.6 m] are possible. In addition, it has been discovered that slug flow can be generated by several different mechanisms, each producing liquid slugs with different physical properties. Schmidt et al., in studying slug flow in a simulated offshore pipeline riser-pipe system, found two distinct slug flow patterns: normal (e.g., hydrodynamic) and severe (e.g., terrain-dominated) slug flow. Severe slug flow is characterized by the generation of liquid slugs at the base of the riser pipe, with the remainder of the pipeline in stratified flow. Normal slug flow is characterized by many liquid slugs being generated along the length of the pipeline and occurs at higher gas and liquid flow rates. The liquid slugs generated during severe slug flow were found to range in length from one to several riser-pipe heights, which, at the time this study was performed, generally exceeded the slug lengths associated with normal slug flow. Therefore, riser-pipe-generated slug flow was designated "severe" slug flow, in comparison to "normal" pipeline-generated slug flow. Severe slug flow was found to depend on the geometry of the pipeline riser-pipe system. The pipeline must be in stratified flow, as well as inclined negatively for the liquid slug to be generated at the base of the riser. Also, because of the mechanism by which severe slugs are generated, it was found that the degree of slug aeration for severe slugs was much lower than that associated with normal slug flow. Also, the study showed that the phenomena of severe and normal slug flow are mutually exclusive because normal pipeline slugs and bubbles will flow through the riser pipe nearly unchanged, excluding the possibility of a riser-generated slug. Finally, a hydrodynamic model was developed for severe slug flow. The model was formulated on basic physical principles and was limited to a description of how the liquid slug is generated at the base of the riser pipe. No attempt was made to model the full behavior of the severe slug pipe. No attempt was made to model the full behavior of the severe slug flow cycle. Bendiksen et al. developed a dynamic one-dimensional two-phase flow model for the Norwegian state oil company, Statoil. They gave the mass and momentum conservation equations for each phase, and solved them numerically by using finite difference techniques. SPEJ P. 27

The Status of Arctic Offshore Pipeline Standards and Technology

2020 ◽  
Author(s):  
Mike Paulin ◽  
Jonathan Caines ◽  
Amy Davis ◽  
Duane DeGeer ◽  
Todd Cowin
Keyword(s):  
Best Practice ◽  
Gap Analysis ◽  
The Arctic ◽  
Design Standards ◽  
Offshore Pipelines ◽  
Comprehensive Review ◽  
Pipe System ◽  
Offshore Pipeline ◽  
The Status ◽  
Pipeline Design

Abstract Offshore pipelines in an Arctic or ice-covered environment face unique challenges different from traditional subsea pipeline design. In 2018, Intecsea as lead consultancy delivered a report to the US Bureau of Safety and Environmental Enforcement (BSEE) Alaska Region which provided a comprehensive review and gap analysis of the Status of Arctic Pipeline Standards and Technology. The objective of this study was to provide BSEE with a comprehensive review and gap analysis of current offshore Arctic pipeline design standards, codes and regulations pertaining to design and development of offshore pipelines in the Arctic, and to report on the state-of-the-art and emerging technologies for offshore pipelines in Arctic applications. Project development information from nine existing offshore Arctic pipelines in the U.S., Canada, and Russia was summarized, as well as guidelines and industry best-practice for monitoring and leak detection. This paper provides an overview of the results of this study; what offshore Arctic-specific pipeline design and construction challenges may entail, how they have been overcome in past projects, perceived gaps in regulations, and technology advancements that may help with future developments. This paper also summarizes the results of a comprehensive review and gap analysis of Arctic pipeline standards, assessment of the suitability of a single-walled versus pipe-in-pipe system for Arctic applications and presents information on some of the advancements in pipeline design, installation, operations and repair solutions that may be applicable to an Arctic environment.

Experimental Study of Two-Phase Normal Slug Flow in a Pipeline-Riser Pipe System

1981 ◽  
Vol 103 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Zˇ. Schmidt ◽  
J. P. Brill ◽  
H. D. Beggs
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Production Facility ◽  
Two Phase ◽  
Flow Rates ◽  
Pipe System ◽  
Void Fractions ◽  
Riser Pipe ◽  
Measured Flow ◽  
Phase Normal

Slug flow was studied with air-kerosene flow in a 2-in. pipeline-riser pipe system consisting of a 100-ft pipeline and a 50-ft vertical riser. Pipeline inclinations of ± 5 deg, −2 deg, and horizontal were used. Pressures, flow rates, flow patterns and void fractions were measured. Flow pattern maps were developed and normal slug flow was modeled, permitting prediction of variables necessary to consider when designing a production facility operating under normal slug flow.

Experimental Study of Severe Slugging in a Two-Phase-Flow Pipeline - Riser Pipe System

1980 ◽  
Vol 20 (05) ◽  
pp. 407-414 ◽  
Author(s):  
Z. Schmidt ◽  
J.P. Brill ◽  
H.D. Beggs
Keyword(s):  
Flow Pattern ◽  
Flow Rate ◽  
Liquid Flow ◽  
Test Section ◽  
Slug Flow ◽  
Pressure Fluctuations ◽  
Phase Flow ◽  
Two Phase ◽  
Pipe System ◽  
Riser Pipe

Abstract Slug flow was studied in a simulated, offshore, pipeline-riser pipe system. Two distinct slug flow patterns were identified: severe slugging and normal slug flow. Severe slugging, characterized by generation of slugs ranging in length from one to several riser pipe heights, occurs at low gas and liquid flow rates and for negative pipeline inclinations. A mathematical model was developed for severe slugging. Results agree well with experimental data. Choking was found to be an effective method of eliminating severe slugging. Introduction Gas and liquid frequently are transported simultaneously in pipes, such as in gas and oil fields, in refineries and process plants, and in steam injection and geothermal production systems. When two-phase flow occurs in a pipeline, the phases separate in the pipe into various flow patterns.When the flow pattern at the exit of a pipe consists of alternating slugs of gas and liquid, special operating procedures frequently are required.Slugging in some of these facilities has required the use of operating procedures which drastically curtail production. Yocum reported that flow capacity reductions up to 50% have been necessary to minimize slugging on offshore platforms. The reported losses occur when platform backpressure is increased until a flow regime is reached in which slugging and pressure fluctuations are reduced to levels which can be handled by gathering facilities.Cady used an existing vertical flow pattern map to determine the conditions under which slugging would occur in a riser. Schmidt et al. described a comprehensive review of slugging problems of this nature and proposed automatic choking as a means of alleviating slugging in risers.This study describes the generating of long liquid slugs in a pipeline-riser pipe system and develops a mathematical method to predict slug characteristics. In addition, it has been found that severe slug flow can be eliminated or minimized by careful choking which results in little or no change in either flow rate or pipeline pressure and in elimination of pressure fluctuations. Description of Equipment An experimental facility was designed and constructed to permit study of flow in a pipeline-riser pipe system. The fluids flowed through a 100-ft-long, 2-in.-diameter pipeline and then up a 50-ft-long, 2-in.-diameter vertical riser. All pipe was made of Lexan and was transparent. Both sections are supported by aluminum I-beams that can be pivoted at their free ends through angles of +/- 5 degrees, to the horizontal and vertical. This study was conducted at pipeline angles of −5, −2, 0, and +5 degrees, with the riser pipe vertical.The fluids used in the study, air and kerosene, were mixed at the entrance of the test section, At the end of the test section, the air/kerosene mixture was separated in a horizontal separator. The air was vented, and the kerosene was returned to a storage tank.Kerosene was pumped from the tank into the system by means of a single-stage Gould centrifugal pump. The liquid flow rate was metered with a Camco 4-in, orifice meter and a Brooks rotameter.The air was obtained from a Joy two-stage compressor with a maximum output capacity of 0.6 MMscf/D at 120 psig. A Camco 2-in. orifice meter and a 0.75-in. Daniel orifice meter were used to measure the air flow rates.On each test section there were two pressure taps separated by a 25-ft span. SPEJ P. 407＾

Simulation of Two Phase Flow Dynamics in Flexible Riser Exit Geometries for Oil and Gas Applications

2018 ◽  
Vol 39 ◽  
pp. 1-13
Author(s):  
Ikpe E. Aniekan ◽  
Owunna Ikechukwu ◽  
Satope Paul
Keyword(s):  
Oil And Gas ◽  
Two Phase Flow ◽  
Flow Analysis ◽  
Computational Cost ◽  
Maximum Velocity ◽  
Oil Well ◽  
Phase Flow ◽  
Two Phase ◽  
The Third ◽  
Riser Pipe

Four different riser pipe exit configurations were modelled and the flow across them analysed using STAR CCM+ CFD codes. The analysis was limited to exit configurations because of the length to diameter ratio of riser pipes and the limitations of CFD codes available. Two phase flow analysis of the flow through each of the exit configurations was attempted. The various parameters required for detailed study of the flow were computed. The maximum velocity within the pipe in a two phase flow were determined to 3.42 m/s for an 8 (eight) inch riser pipe. After thorough analysis of the two phase flow regime in each of the individual exit configurations, the third and the fourth exit configurations were seen to have flow properties that ensures easy flow within the production system as well as ensure lower computational cost. Convergence (Iterations), total pressure, static pressure, velocity and pressure drop were used as criteria matrix for selecting ideal riser exit geometry, and the third exit geometry was adjudged the ideal exit geometry of all the geometries. The flow in the third riser exit configuration was modelled as a two phase flow. From the results of the two phase flow analysis, it was concluded that the third riser configuration be used in industrial applications to ensure free flow of crude oil and gas from the oil well during oil production.

Further Computational Investigations Into Aero-Engine Bearing Chamber Off-Take Flows

2010 ◽  
Author(s):  
Adam Robinson ◽  
Carol Eastwick ◽  
Herve´ Morvan
Keyword(s):  
Experimental Work ◽  
Symmetry Plane ◽  
Two Phase ◽  
Pipe System ◽  
Aero Engine ◽  
Gravity Driven ◽  
Computational Fluid Dynamics Cfd ◽  
Modelling Assumptions ◽  
Static Head ◽  
Engine Bearing

Within an aero-engine bearing chamber oil is provided to components to lubricate and cool. This oil must be efficiently removed (scavenged) from the chamber to ensure it does not overheat and degrade. Bearing chambers typically contain a sump section with an exit pipe leading to a scavenge pump. In this paper a simplified geometry of a sump section, here simply made of a radial off-take port on a walled inclined plane, is analysed computationally. This paper follows on work presented within GT2008-50634. In the previous paper it was shown that simple gravity draining from a static head of liquid cold be modelled accurately, for what was akin to a deep sump situation fond in integrated gear boxes for example. The work within this paper will show that the draining of flow perpendicular to a moving film can be modelled. This situation is similar to the arrangements found in transmission bearing chambers. The case modelled is of a walled gravity driven film running down a plane with a circular off-take port, this replicates experimental work similar to that reported in GT2008-50632. The commercial computational fluid dynamics (CFD) code, Fluent 6 [1] has been employed for modelling, sing the Volume of Fluid (VOF) approach of Hirt and Nichols [2, 3] to capture the physics of both the film motion and the two phase flow in the scavenge pipe system. Surface tension [4] and a sharpening algorithm [5] are used to complement the representation of the free surface and associated effects. This initial CFD investigation is supported and validated with experimental work, which is only depicted briefly here as it is mainly sued to support the CFD methodology. The case has been modelled in full as well as with the use of a symmetry plane running down the centre of the plane parallel to the channel walls. This paper includes details of the meshing methodology, the boundary conditions sued, which will be shown to be of critical importance to accurate modelling, and the modelling assumptions. Finally, insight into the flow patterns observed for the cases modelled are summarised. The paper further reinforces that CFD is a promising approach to analysing bearing chamber scavenge flows although it can still be relatively costly.

Offshore pipeline buried in Indian coastal clay: buckling behaviour analysis

2021 ◽  
pp. 1-16
Author(s):  
Debtanu Seth ◽  
Bappaditya Manna ◽  
J. T. Shahu ◽  
Tiago Fazeres-Ferradosa ◽  
Francisco Taveira-Pinto ◽  
...  
Keyword(s):  
Behaviour Analysis ◽  
Offshore Pipeline
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