Effective pipeline design and regular maintenance can assist in prolonging the lifespan of subsea pipelines, however the presence of marine vessels can significantly increase the risk of pipeline damage from anchor hazards. As noted in the Health and Safety Executive – Guideline for Pipeline Operators on Pipeline Anchor Hazards 2009. “Anchor hazards can pose a significant threat to pipeline integrity. The consequences of damage to a pipeline could include loss of life, injury, fire, explosion, loss of buoyancy around a vessel and major pollution”. This paper will describe state of the art pipeline isolation tooling that enables safe modification of pressurised subsea pipelines. Double Block and Bleed (DBB) isolation tools have been utilised to greatly reduce downtime, increase safety and maximise unplanned maintenance, providing cost-effective solutions to the end user. High integrity isolation methods, in compliance with international subsea system intervention and isolation guidelines (IMCA D 044 / IMCA D 006), that enable piggable and unpiggable pipeline systems to be isolated before any breaking of containment, will also be explained. This paper will discuss subsea pipeline damage scenarios and repair options available to ensure a safe isolation of the pipeline and contents in the event of an incident DNV GL type approved isolation technology enables the installation of a fail-safe, DBB isolation in the event of a midline defect. The paper will conclude with case studies highlighting challenging subsea pipeline repair scenarios successfully executed, without depressurising the entire pipeline system, and in some cases without shutting down or interrupting production.

Submarine pipelines are more often than before required to operate in harsh environments, especially for systems deployed in ultra-deep water. In order to minimize the installation tension due to the hanged section, they are installed empty and therefore the external pressure is often the prime load parameter for the design. New discoveries and associated technical challenges have generated important research and development endeavors in a wide range of disciplines in order to improve efficiency and reliability, but also keeping the risks associated with the new scenarios within an acceptable range. Some aspects that can be mentioned include, for instance, steel line grade improvements and manufacturing innovations of pipe products; more powerful lay vessels and development of new pipeline installation methods; determination of the mechanical behavior and the expected failure modes of concern for deep and long pipelines under combined loads; and the improved different design criteria like the DNV-OS-F101 (1) and API RP-1111 (2) codes. The intention of this paper is to review and compare three different pipeline design criteria well established in the oil and gas industry. The pipeline wall thickness design for pipe pressure containment (bursting), local buckling (system collapse) and propagating buckling for DNV-OS-F101 (1) and API RP-1111 (2) are discussed as well as the parameters used, definitions, safety philosophy and code limitations. A pipeline example is used to illustrate and compare the results.

Acoustic-induced vibration (AIV) and flow-induced vibration (FIV) are two common phenomena that can lead to vibration-induced fatigue failures in piping systems. Pipeline facility managers, operators, designers, and engineers are faced with identifying and mitigating the risks of AIV and FIV to avoid catastrophic instances of vibration-induced fatigue failures in their facilities. This paper identifies common challenges to conventional AIV/FIV analyses methods, and discusses advanced techniques available to address these challenges. Acoustic-induced vibrations are caused by the sound energy created by flow through pressure reducing devices like valves or restrictive orifice plates. This sound energy can cause the piping wall to vibrate, thus exciting, and possibly damaging, any nearby small-bore branch connections. Flow-induced vibrations are caused by pulsations induced by flow past dead legs in piping systems. These pulsations can create shaking forces that cause vibrations of piping, vessels, and equipment. The two phenomena will be compared and contrasted, while offering simple tips and best practices in identifying, evaluating, and solving these two common flow-induced issues. A field case study utilizing pulsation and vibration measurements between a line heater and inlet separator for a gas plant will be presented and discussed. The case presents an opportunity to investigate mainline and small-bore piping AIV/FIV risks in plants, provides example data of clear AIV and FIV phenomena, and identifies complex situations that require more rigorous analysis. Advanced techniques for analyzing and solving complex issues that are commonly found in piping systems will be explored. Further, the case highlights the benefits of early screening and preventive considerations of upset conditions when dealing with flow-induced pulsation and vibration issues. In this paper, the reader will gain an increased understanding of the importance of AIV/FIV in maintaining integrity of their facilities, and be provided with tools and knowledge to mitigate any risks that may be encountered.

Blowdown is a planned or unplanned release of pressurized natural gas from stations, equipment (vessels) or pipelines. In high pressure pipelines, the blowdown leads to low temperatures within the fluid and high vent rates due to larger gas inventory volumes. Blowdown is a hazardous operation, and for this reason several methods have been proposed to improve the accuracy in the estimation of the blowdown rate and the blowdown time in pipelines. In general, these approaches include either physical volume or pipe models with numerical and analytical methods of solution. For instance, a very simple approach for the estimation of the blowdown time is presented by American Gas Association (AGA); this approach can be used a as first-approximation to verify the size of the blowdown stack/valve. Another well-known simple method to predict gas-line blowdown times was presented by Weiss, Botros and Jungowski (WBJ) (1988); this method involves the application of correction factors that regards the pipeline as a volume. However, due to the transient nature of the blowdown and the proven accuracy of their formulation, in recent years transient simulations have been performed using commercial simulation software. This work compares simplified approaches and an acknowledged transient method integrating significant effects of fluid mechanics (quasi-steady flow for one phase), heat and mass transfer and rigorous thermodynamics. This transient method is extensively used by process design engineers since it is included as a calculation tool or utility in commercial simulation software. Experimental data taken from acknowledged literature allows estimating the level of accuracy of these approaches. Due to the complexity and sometimes non-availability of the transient models included in commercial simulation software, a novel and innovative simplified hybrid approach is presented in this work. This approach includes novel and improved correlations as well as numerical solutions of a physical model that can be easily translated into a computational code or sequentially structured in a spreadsheet. This method allows for estimating relevant variables associated to the pressure – time computation and the optimal sizing of blowdown stack/valves in gas pipelines, based on recommended gas blowdown times; these times were estimated considering a balance between the maximum permissible blowdown duration and the minimum wall and fluid temperatures that can safely be contained in the pipeline. Finally, comparisons between the results obtained by using commercial software and the novel approach are presented, showing a fair level of accuracy of this method (7.6 % maximum error percentage) considering its simplicity with regard to the transient modelling.

This paper describes the results of pressure vessel fracture test which called West Jefferson and/or partial gas burst testing using Grade API X65 linepipe steel with high Charpy energy that exhibits inverse facture in the Drop Weight Tear Test (DWTT). A series of pressure vessel fracture tests which is as part of an ongoing effort by the High-strength Line Pipe committee (HLP) of the Iron and Steel Institute of Japan (ISIJ) was carried out at low temperature in order to investigate brittle-to-ductile transition behavior and to compare to DWTT fracture behavior. Two different materials on Fracture Appearance Transition Temperature (FATT) property were used in these tests. One is −60 degree C and the other is −25 to −30 degree C which is defined as 85 % shear area fraction (SA) in the standard pressed notch DWTT (PN-DWTT). The dimensions of the test pipes were 24inches (609.6 mm) in outside diameter (OD), 19.1 mm in wall thickness (WT). In each test, the test pipe is cooled by using liquid nitrogen in the cooling baths. Two cooling baths are set up separately on the two sides of the test vessel, making it possible to obtain fracture behaviors under two different test temperatures in one burst test. The test vessel was also instrumented with pressure transducers, thermocouples and timing wires to obtain the pressure at the fracture onset, temperature and crack propagation velocity, respectively. Some informative observations to discuss appropriate evaluation method for material resistance to brittle facture propagation for high toughness linepipe materials are obtained in the test. When the pipe burst test temperatures are higher than the PN-DWTT transition temperature, ductile cracks were initiated from the initial notch and propagated with short distance in ductile manner. When the pipe burst test temperatures were lower than the PN-DWTT transition temperature, brittle cracks were initiated from the initial notch and propagated through cooling bath. However, the initiated ductile crack at lower than the transition temperature was not changed to brittle manner. This means inverse facture occurred in the PN-DWTT is a particular problem caused by the API DWTT testing method. Furthermore, results for the pipes tested indicated that inverse facture occurred in PN-DWTT at the temperature above the 85 % FATT may not affect the arrestability against the brittle fracture propagation and it is closely related with the location of brittle fracture initiation origin in the fracture appearance of PN-DWTT.

Three partial gas pipe burst tests were conducted to assess the brittle-to-ductile transition temperature and brittle fracture arrestability of a heavy-walled TMCP line-pipe steel. This steel had a very high Charpy energy (400 J) which is typical of many modern line-pipe steels. In standard pressed-notch DWTT specimen tests this material exhibited abnormal fracture appearance (ductile fracture from the pressed notch prior to brittle fracture starting) that occurs with many high Charpy energy steels. Such behavior gives an invalid test by API RP 5L3, which makes the transition temperature difficult to determine. The first burst test was conducted in a manner that is typical of a traditional West Jefferson (partial gas vessel) burst tests. The crack was initiated in the center of the cooled vessel (with a partial air gap), but an unusual result occurred. In this test a ductile fracture just barely started from each crack tip, but one of the endcaps blew off. The pipe rocketed into the wall of a containment building. The opposite endcap impacted the wall of the building and brittle fractures started there with one coming back to the center of the vessel. The implication from this test was that perhaps initiation of the brittle fracture in the base metal gives different results than if the initial crack came from a brittle location. The second burst test used a modified West-Jefferson Burst Test procedure. The modification involved cutting a short length of pipe at the center of the vessel and rotating the seam weld to the line of crack propagation. The HAZ of the axial seam weld had a higher dynamic transition temperature. The initiation flaw was across one of the center girth welds so that one side of the initial through-wall crack had the crack tip in the base metal while the other side initiated in the seam weld HAZ. On the base metal side, the crack had about 220 mm of crack growth before reaching steady-state shear area, i.e., the shear area gradually decreased as the fracture speed was increasing. On the other side, a brittle fracture was started in the HAZ as expected, and once it crossed the other central girth weld into the base metal, the fracture immediately transformed to a lower shear area percent. These results along with those from the first burst test suggest that the DWTT specimen should have a brittle weld metal in the starter notch region to ensure the arrestability of the material. The final burst test was at a warmer temperature. There was a short length of crack propagation with higher shear area percent, which quickly turned to ductile fracture and arrested. In addition various modified DWTTs were conducted and results were analyzed using an alternative brittle fracture arrest criterion to predict pipe brittle fracture arrestability.

Tough market conditions have seen the price of oil drop which with the subsequent uncertainty surrounding the industry have seen the oil and gas industry concentrate on reducing the cost of designing, installing and operating pipelines. A critical process for the industry is the procurement, manufacture and installation of appropriate linepipe. The method of installation is often dictated by the pipe size and the water depth that the pipe is to be laid in, however there are times when the choice of lay method is due to vessel availability and relative costs for each technique. In early 2014, Tata Steel successfully manufactured and delivered 16"OD × 0.875”WT X65 submerged arc welded longitudinal (SAWL) linepipe for installation via the reel lay method. Notable features about this fact were the size, which represents the thickest 16” external diameter UOE pipe yet delivered by Tata Steel, and that this was to be the first UOE pipe to be installed by the reel lay method in the North Sea. The ability to manufacture small diameter thickwall linepipe was only possible due to recent operational developments including an established tooling programme and a fully validated Finite Element (FE) model of the UOE process, along with years of experience of integrating these tools into the manufacturing process. This paper discusses the manufacturing challenges for small diameter thickwall linepipe, and how with the aid of modelling tools, innovative thinking and previous experience in supplying small diameter thickwall linepipe into two reel-installed projects, the pipe was manufactured and delivered with the properties shown to be compliant with DNV OS-F101 Supplementary Requirement P.

A proprietary fibre optic sensing technology has been developed and is capable of simultaneously utilising an existing fibre optic communication cable as an integrity-testing sensing cable, thus providing continuous, real-time monitoring of the fibre cable and any structure near the cable (ie., ground, tunnels, ducts, pipes, buildings, equipment, vessels, etc.). With this system, simultaneous fibre optic communications and real-time vibration monitoring was demonstrated using a wavelength multiplexed fibre system for a channel bandwidth of 500 MHz over 18 km of standard singlemode fibre. Real-time vibration monitoring was also demonstrated using standard singlemode and multimode fibre over lengths of 28 km and 53 km, respectively. Trials of the system are currently underway in Australia and the first commercial field installation with this capability is to be completed in mid-1998 in Indonesia. This paper highlights the benefits and potential of this dual-capacity system and details results obtained to-date.

A long 778 km high pressure, submarine pipeline supplying natural gas will serve multiple combined cycle gas turbine peaking units on the Pacific Rim. The gas supply flow into the pipeline is constant, but the power plant will primarily operate during daylight hours or in certain situations, operate in a two-shift mode. So the pipeline essentially serves as an increasing pressure, gas storage vessel during the night, and pressure falls off during the day as the gas is fired. Hence, the gas letdown receiving station presented many critical design challenges. Among these were the need for constant plant service pressure control, especially during individual power generator unit startup, shutdown, and upset conditions. In addition, there was a very severe noise attenuation requirement and high gas flow rangeability was required. This complex, integrated gas pressure, control valve letdown system and its operation is described in detail.

PETRONAS Gas Berhad (PGB), a listed partly-owned subsidiary of PETRONAS is undertaking the Peninsular Gas Utilization Project - Stage III (PGU III). The PGU III Sector 2 & 3 project extends from Lumut, Perak to Pauh, Perlis on the West Coast of Peninsular Malaysia, with two laterals, the Gurun Lateral and the Penang Lateral. The Penang Lateral is further divided into the Prai Lateral, Gelugor Mainline and the Gelugor Tenaga National Berhad (TNB) Meter Station project individually. This paper will focus its’ discussion on the technical and engineering challenges faced in the design of the Gelugor Mainline Project. The Gelugor Mainline consist of about 7 km NPS 24 gas pipeline which runs from TNB Prai Power Plant of the mainline to TNB Gelugor Power Plant on the Penang Island. The pipeline is planned to operate at high pressure. The pipeline route traverses complex terrain with varied seabed lithology with depth up to 16m. The pipeline will cross active shipping lane, zones of live electrical cables, extensive system of submarine pipeline, mudbank and areas susceptible to mass gravity flows. There is also an area subjected to future development with an expected 170 kN/m 2 distributed load with 3 m covers required which is an expressway and Light Rapid Transportation (LRT) system, the proposed development of a “Vision City” is also a few meters away from the pipeline. The pipeline also passes by an environmentally sensitive area that includes the rearing of caged fishing activities. It is essential for the project team to determine and investigate the variable risks to the pipeline in order to take appropriate evasive and mitigating action in design. This required comprehensive survey activities in the busy shipping straits. The paper will explore and detail out its’ study starting from the description of the design concept to the varied environmental challenges. This paper aims to describe the route selection process, the pipeline design process and outline some of the specialist techniques employed in the design construction of the Gelugor Mainline, Penang, Malaysia. In nearly every major project a drive for cost and risk reduction results in a number of new ideas with varying degree of impact. Hence, the following areas will be elaborated and presented in greater details: • Pipeline Design. • Pipe-lay vessel. • Pipeline installation methodology.

The oil and gas pipelines are spread around the world in all nations as complex networks. The increased usage of gas is rapidly increasing this network. These networks are generally made from various diameters of pipes. The pipelines are serviced on as required basis, using pig launcher and receivers to suit the pipe diameter. Pigs of different types may be launched in different sequences, to clean the pipes and to obtain various data related to pipe condition and location. The pig launching and receiving process uses rapid pressure changes in the launcher and receiver and some magnitude of impact may be experienced by the unit. This process also requires frequent access to the launcher/receiver unit. To have an efficient and cost effective usage of the launcher/receiver unit, it is essential to have a door mechanism, which is safe, robust, capable of the above loading conditions, requires minimum service and is easy to use. PECO has recently developed & designed a door, which incorporates ail the above requirements. The door was put to high pressure testing and the test results were so encouraging that PECO named it SafeLock ® Closure. The design was developed with gas pipelines in mind. However it is equally applicable to vessels, exchangers and other metal openings where quick, frequent and easy access is required. Safety has been the prime concern through out the design and development process of this closure. Therefore the final product has resulted in a very safe closure. The initial design of the SafeLock ® door / closure used a spring load to make it easy in operation. This was removed in the later design. The segmental blocks, usually called C-ring segments, are operated to move in and out of the shell-sub annulus. The closure opening and closing is performed by the use of a single lever arm. This way only one person can operate (open and close) the door / closure. For opening and closing, the lever-arm needs to be rotated less than 40 degree angle. The rotation direction of the lever arm in closing is reverse of that in opening. The door / head can be fully retrieved from the shell-sub and rest by the side of the launcher/receiver to provide complete access to the opening. This door / closure provides quick access to launcher / receiver, pig traps, meter provers, filter vessel, scrubber, scraper, manway to pressure vessel, etc. This closure can be mounted in the vertical or horizontal position. During change of filter elements, launching a pig, quick access to container under pressure, this closure door is designed to provide a safe and fast service. The construction, operation, design details and application of the new closure door are included in this paper and explained with the help of the design diagrams and photographs.

High power and high capacity turbo-compressor systems frequently sustain acoustically induced vibrations. Higher order acoustic modes generated by turbo-compressors often couple selectively with structural pipe resonances producing significant increase in pipe wall vibration. In some instances, these coincidences generate high local stress levels that fatigue pipe shell or pipe attachments. In order to judge the level of dynamic strain and stress in piping systems, elaborate theories are employed. However, these are frequently not practical and relatively difficult to use in industrial applications, for example, in troubleshooting process. First, the accuracy of predicted results depends on assumed boundary conditions. The boundary conditions for on-site cases are rarely known and always difficult to estimate. Second, strains and stresses are complex and often difficult to determine, since they vary in space and time and may be caused by a multimode frequency excitation. Therefore, the strain and stress can only be predicted in reasonable bounds through laborious sensitivity and error analyses, which add further complexity to the already convoluted mathematical predictions. The correct stress level prediction in a structure, by means of directly measured vibrational velocity levels, is very desirable. Therefore, accurate mapping of the vibrational field is necessary. Since the mapping or evaluating of complex vibrational fields is very tedious and expensive using conventional technology (ample number of strain gauges or accelerometers), an alternative technique has been developed: wide field pulsed holographic interferometry. This method provides three dimensional field images of vibrating structures allowing extraction of the actual vibrational responses (displacement and velocity), and calculation of dynamic strain and stress information. These are described by their gradient, peak and phase values obtained from the holograms documenting vibrational fields. This paper describes empirical verification of the wide field pulsed holographic technology which is used to predict a service life of the complex piping structure subjected to multimode frequency excitation. The experimental work was carried out on a sample thin wall vessel, which was either empty or partially filled with water and excited by the hammer or shaker. Through the conversion of vibrational response levels into strain (and stress level), and verification of the conversion against strain gauge measurement results, the technology is proven as a diagnostic tool. It is concluded that there are many advantages of using holography to evaluate complex vibrational fields. They include: i) ‘instant’ results, ii) non-intrusive nature (i.e. the machinery subject to testing can operate without interruptions), iii) satisfactory accuracy, iv) complete and permanent records, and v) significant savings of time and money due to reducing the analysis effort and implementation of suitable recommendations.

Terminals are an integral part of a pipeline system. Typically, petroleum products are transported from an initiating terminal to various delivery terminals along the pipeline. Operation safety is paramount in transporting petroleum products in the pipeline industry. Safety can affect the performance and economics of a pipeline system. While effective operation safety requires well-trained operators, operational procedures, and compliance with regulatory requirements, the best way to ensure operation safety is to implement safety systems during the design stage of the pipeline system. A pressure relief system is an important component of an engineered safety system. This system is intended to prevent catastrophic failure of the transport system due to overpressure conditions that can occur under abnormal operating conditions. This paper discusses pressure surge relief as it applies to the design of pipeline terminals. Different pressure surge relief devices such as pressure relief valves and pressure surge vessels are considered and their advantages and disadvantages are discussed. The effects of transport rates, piping configurations, and other equipment operation, such as pumps and valves, on pressure surge relief system, are evaluated. One of the primary objectives of this paper is to discuss pressure surge events, device simulations, and key parameters to consider when selecting a pressure surge relief system for a terminal design to ensure that the piping system and hydraulic components remain safe during abnormal operating conditions. Although the analyses presented in this paper are applicable across a broad range of operating conditions and equipment and devices in terminal system designs, it is not possible to cover all situations. As such, sound engineering principles and engineering judgment should always be applied in an engineering design.

Petrobras Transporte S.A. – TRANSPETRO’s Gas Pipeline System, composed by 7.3 thousand kilometers, 135 delivery stations and 21 compressor stations, has a very seasonally dependent operation. Highly linked with the Brazilian energy grid, during the dry season of the year a large part of the 77.3 million cubic meters of natural gas daily transportation are used to generate around 6.4 gigawatts to power the country. Additionally, the ever increasing number of power plants and distribution companies around the country demand more and more gas to be offered to supply the system. Among the different sources of natural gas available, the LNG is the most flexible for such seasonal operation. In order to support this current demand and to attend future demands, the regasification ability of Baía de Guanabara LNG Terminal was increased in December 2012, by changing the regasification vessel that supplies the southeast portion of the gas pipeline network, from 14 to 20 million cubic meters per day. To prepare to receive the new ship, some tests were performed to determine the operational limits on system survival time without LNG supply during vessel exchange. This assessment involved two different issues. The ship change operation occurred during a period of high consumption, when the LNG terminal was needed to sustain the network inventory. A long period without this supply, caused by the exchange of LNG vessel, would affect the deliveries. On the other hand, the new ship’s commissioning curve would introduce a large amount of natural gas into the system during a short period of time, demanding that the deliveries absorbed such volume. Four planning scenarios were assessed based on some expected pipeline supply and delivery conditions. The work was important as a reference for future changes on operating supply units of TRANSPETRO gas pipeline system, showing the importance of pipeline simulation both as a planning tool for pipeline logistic problems and as operational support.

Increases in export pipeline development can result in a corresponding increase in marine transportation activities and the potential to escalate adverse interactions with marine wildlife. Ship traffic introduces risks of vessel strikes as well as the amount of underwater noise produced in the marine environment. Growing public and scientific concern over the potential effects of increasing ship traffic on marine wildlife mean that even terrestrially-based pipeline projects need to start considering the effects of shipping in developing environmental mitigation programs for their export operations. Northern Gateway is proposing to construct and operate twin pipelines between Alberta and British Columbia, and an associated tank and marine terminal for export operations. While Northern Gateway will not own or operate any of the tankers, they have committed to implementing a comprehensive marine mitigation, monitoring and research program, including measures to reduce ship strikes and effects of underwater noise on marine mammals. Vessel strikes can cause severe or fatal injuries. Higher relative risk exists where shipping traffic overlaps with increased densities of marine mammals. Vessel speed has been positively correlated with the degree of risk and injury; consequently, Northern Gateway has set maximum year-round speed restrictions of 10–12 knots for all Project-related tankers calling at the marine terminal, with further restrictions of 8–10 knots in key areas. Other large vessels in this region currently travel at speeds of 16–21 knots. Mandatory speed restrictions will also reduce the Project’s contribution to underwater noise. Effects of underwater noise on marine mammals include temporary habitat avoidance, reduced feeding efficiency, behavioural change, increased stress, and communication masking. Acoustic modeling conducted for the project predicted that reducing vessel speeds from 15 to 9.6 knots would decrease underwater noise input by nearly 12 dB, making the zone of ensonification 2–3 times smaller than in the absence of mitigations. Purpose-built escort tugs will use best commercially-available noise-quieting technology and speed restriction areas will be refined through six-years of surveys and a quantitative vessel strike analysis. Vessel traffic is not unique to Northern Gateway; however, through minimizing their incremental contribution, they hope to serve as an industry example. This approach to minimizing effects of routine marine export operations is unique in the shipping industry in Canada and the United States. If other proponents were to adopt similar types of measures, Northern Gateway believes that the marine environment would see some net benefits in terms of a reduction in adverse effects on marine mammals.

The transport of diluent (i.e. condensate blend) and/or diluted bitumen (i.e. dilbit) using buried pipelines is common practice. Aerial surveys are conducted on a regular basis as a part of the leak detection strategy at Enbridge Pipelines. During these surveys, the pilot flies over the right-of-way to visually inspect the pipeline for leakage along the pipeline corridor. Beyond visual inspection, the detection of proximal indicators of leakage by using remote sensors mounted on the aircraft is proposed in order to further enhance visual aerial leak detection methods. These sensors are designed to detect volatile organic compounds (VOCs) which are expected to evolve, even from small liquid leaks within the shallow subsurface and subsequently reach the atmosphere. If these VOCs can be detected in the local atmosphere in the vicinity of a leak during aerial surveys, then small liquid leaks may be more easily identified, characterized and remediated. This study is aimed to characterize and model VOC movement through soil to quantify the amount of VOC concentration expected to diffuse into the atmosphere within the vicinity of leakage. The experimental study consisted of the characterization of three organic fluids, and one type of soil material representative of that used in pipeline construction. Two types of dilbit with different viscosities, as well as a typical diluent (i.e. condensate), were used because these types of organic fluids are commonly transported using pipelines. Batch laboratory tests were conducted using glass screw top vessels in order to determine the concentration and organic species evolving from these fluids. Headspace VOC and other gas species were characterized after 24 hours following the addition of the fluid to the sealed vessel. Custom designed laboratory-based columns were constructed, based upon scaled down field dimensions, and were used to simulate fluid leakage. Fluid was injected at the base of each column, over which porous media was suspended. Each test characterized the migration of VOCs through the porous medium, VOC breakthrough at the surface and data allowed the calculation of VOC flux into the overlying headspace. Columns were operated under closed and flow through modes. Data obtained from the laboratory experiments defined bounding parameters for numerical simulations comprising of decoupled subsurface and atmospheric models. Subsurface modelling of the experimentally simulated leakage event was refined and validated using experimental data and a larger scale field leak scenario was modeled. Data from the laboratory testing and subsurface numerical simulations was used to construct atmospheric dispersion models of a potential field leak simulation. All atmospheric dispersion modelling used a Gaussian Dispersion Model within the Polair Software package (Odotech Inc.).

The oil and gas industry has three major segments: upstream, midstream and downstream. Upstream is frequently referred to as exploration & production. The midstream segment involves transportation, storage and marketing of oil and gas products. Transportation options may vary from small connector pipelines to massive cargo vessels covering trans-ocean routes. Most oil types may be transported in their original condition, while natural gas needs to be either compressed or liquefied for transmission. Storage helps to balance fluctuations between supply and demand of energy products. Downstream covers the refining and processing of hydrocarbons into usable products. Each segment has facilities to support one or various processes. Terminals include pipeline, rail, trucks and cargo transmission which imply a complex model to cover the whole facility to evaluate risk and reliability with all processes and functions involved. Before addressing the logistics of each midstream component the reliability of the involved assets needs to be evaluated. First to be considered is terminal location with respect to upstream and downstream. Onshore and maritime terminals have several components in common and two main processes may coexist (storage and distribution). All terminal components represent circuits with a specific sub process or function. Some circuits have a serial arrangement so they are highly dependent on each other’s reliability. Also some circuits develop parallel processes with null or low impact on the terminal main process; however they may influence the facility risk in terms of probability of failure and consequences. Support and auxiliary circuits play an important role in terminal reliability since they could affect performance and continuity. There are circuits thought of as transmission and logistics elements, and that reliability is highly dependent on mechanical integrity to perform a specific function. Maritime terminals may have a circuit of SPM (Single Point Mooring) buoys for loading or uploading product. The analysis model has to include every circuit to cover any possible arrangement and configuration. The model is supported by a processes mapper that allows the user to define serial, parallel and support processes based on a logistics scheme in terms of reliability and mechanical integrity. The developed model provides results to support decision making for product transmission and distribution and addresses the importance of terminals in terms of risk and reliability for logistics planning. The terminals model is supported by 16 algorithms that may be used according to operator needs by simply activating or deactivating circuits to obtain values for probabilities of failure that predict any potential service interruption.

Under subsea conditions, the transportation of ‘waxy’ crude oil through pipelines is accompanied by the precipitation and deposition of higher paraffinic compounds as solids (waxes) onto the cooler surfaces of the pipeline. Wax deposition is more pronounced during shut down of a pipeline since the fluid is held at static conditions. In this study, the static cooling of wax–solvent mixtures in a cylindrical vessel was modeled as a moving boundary formulation involving liquid–solid phase transformation. The deposition process during the transient cooling was treated as a partial freezing/solidification process. Also, the effect of the mixture composition and the cooling rate on the Wax Precipitation Temperature (WPT) or the solubility curve of the wax–solvent mixture was taken into consideration when the bulk liquid phase temperature was lowered below the WAT of the initial mixture composition. The predictions for the transient temperature profiles in the liquid and the deposit region, and the location of the liquid–deposit interface were validated with recently reported experimental results [19]. The predictions were also compared with the predictions for the gelling behavior of wax–solvent mixtures under static cooling reported by Bidmus [19]. The predictions for the temperature profile at seven thermocouple locations and the location of the liquid–deposit interface were in agreement with the experimental results and signified the important role of the solubility curve. The mathematical model presented was based on heat transfer considerations and regarded the deposition process to be thermally driven.

In order to safely extend the life of damaged in-service components, Fitness-For-Service (FFS) assessments are used to evaluate structural integrity. These FFS assessments largely depend upon the quality of the inspection data. Compared to traditional inspection methods such as pit gauge or ultrasonic techniques, laser profilometry provides faster results with higher resolution and accuracy. Improved inspection data enables more precise FFS assessments and leads to fewer unnecessary repairs and non-conservative assessments. This paper examines how laser profilometry measurements were taken of several corrosion areas on the exterior shell of a pressure vessel in order to complete a FFS assessment equivalent to an API 579 Level 2 assessment. The results of the FFS assessment show how laser profilometry data may be used in a detailed structural integrity analysis to consider a vessel safe for continued use. A discussion of how laser profilometry data could also be used for an API 579 Level 3 assessment, using finite element analysis, in areas not acceptable for Level 1, or 2 assessments is included.

The pipeline pigging operation for emptying purposes is a common practice in the petroleum and gas transport industry. The emptying operation is employed for removal of the pipeline liquid products and substitution for an inert gas like nitrogen. This operation is necessary before pipeline maintenance or hydrostatic test procedures. The emptying operation applied for oil pipelines usually demands large volumes of nitrogen because of the pressure difference that is necessary to maintain the pig in a velocity that guarantee an efficient and safe operation. The nitrogen that is originally stored inside cryogenic vessels in liquid phase is pumped and vaporized to be injected into the pig launcher, after heating the gas. The gas injection and expansion inside the pipeline propel the pig, delivering the product that was in the pipeline at the receiver station. It is common to cut the nitrogen injection in a certain instant of the operation, before the pig reaches its destination. From then on, the expansion of the gas is able to finish the operation alone. A dynamic simulator called DESLOCAN2 was developed by SIMDUT/PUC-Rio to simulate the pig motion during emptying operations with nitrogen in TRANSPETRO crude oil and refined products pipelines. In the operation planning phase the simulator is used to evaluate the gas mass flow rate, the inlet gas pressure and the nitrogen cut instant that can propel the pig to its destination with a minimum volume of nitrogen. The outlet liquid pressure is calculated using two simultaneous controllers: outlet flow rate based on maximum pig velocity and minimum outlet pressure that avoids slack line condition. The dynamic simulator also can be used as a forecast monitor of the pipeline pigging operation given the current inlet gas and outlet liquid conditions, allowing the visualization of actual and forecasted pipeline pressure profile, the pig velocity and position, the accumulative gas inside the pipeline and the volume of product removed. The main objectives of this paper are: Present the mathematical modeling and considerations built in the simulator; Validate the model’s main hypothesis; Present the gained experience on building the model and planning an emptying operation of an existing pipeline: OSBAT 24.