Seminar Papers

Making infrastructure modifications to install launchers and receivers on gas gathering lines will typically cost 5-6 figures per line. The ability to pig gas gathering lines without making such modifications could offer flow assurance and corrosion prevention without the associated cost and downtime.

In this paper we describe the successful use of an elastomeric pig to dewater a gas gathering pipe in Colorado with no launcher or receiver, resulting in the complete restoration of flow in a pipe that had suffered from a differential due to water accumulation in low spots. The pig was inserted at a temporarily dropped spool and removed through a blowdown valve making use of its ability to be extruded through reduced bore piping.

Subsequent to risk based inspection (RBI) and corrosion assessment, it was highlighted that several operator pipelines in the North Sea required internal inspection to verify line conditions and to ensure that the pipelines were fit for purpose. It was recognised that some of these pipelines were not readily equipped for pigging operations and challenges existed to enable inspection of the lines. The most feasible means of obtaining detailed inspection data was to perform intelligent pigging (IP) operations, requiring the installation of temporary subsea launch/receive facilities, which were also used to allow pipeline cleaning using a combination of chemical applications, progressive pigging, and pipeline gauging before the IP tools were run.

Crack inspection of pipelines using conventional ultrasonic technology has become a standard application for in-line inspection (ILI) of liquid pipelines. Crack inspection tools have proven very successful for the detection of various types of cracks (e.g. SCC) or crack-like anomalies present in many pipelines worldwide. The first inspection tools were developed for axial crack inspection (UC), as most cracks or crack-like defects in pipelines are axially orientated. In some cases, however, circumferential cracking can occur prompting the development of tools for circumferential crack inspection (UCc). Standard crack inspection tools can be applied in most liquid pipelines transporting typical crude oils or products (e.g. diesel).

Over the years, specific inspection requirements came up that were not covered by the first tool generations. These requirements are related to different aspects of the inspection process ranging from tool-related characteristics to inspection-related challenges such as crack inspection in liquid gas. Consequently, those challenges are addressed by the latest tool developments allowing an inspection performance not possible before with regard to inspection speed and measuring resolution. In the paper, the achieved progress including enhanced depth sizing is described and illustrated by examples from inspection runs.

In-line inspection of offshore pipelines is a challenging task for several reasons, including:

• Many pipelines that were not designed to be piggable, now require inspection
• Change in operating conditions resulting in ultra-low flows and pipelines with bore restrictions
• Presence of in-line components including non-return valves, hot tap tees, etc.
• Demand for reduced operational impact as a result of pigging operations

Offshore pipelines distinguish themselves from onshore lines because external reference measurements and local repairs are often complex and challenging. Furthermore, inspecting offshore pipelines is often more demanding because of logistics, accessibility, and cost.

Consequently, tool performance, first run success, risk mitigation and operational impact are key factors to be considered when selecting an inspection solution. Additionally, in order to successfully execute these inspections, expertise from both the operator and inspection contractor, need to be combined in a multidisciplinary team that operates as ‘one team’ and establishes the confidence and trust in each other to make the correct decisions.

This paper will discuss a recent example of such a challenge: the successful inspection of a key Shell U.K. Limited (Shell) pipeline in the North Sea, which required a bespoke solution to overcome the pigging challenges associated with this pipeline.

The inspection of subsea pipelines, in particular - flowlines and gathering lines – has recently moved into the focus of offshore engineers. Contrary to most long-distance export pipelines many of these lines are unpiggable. While some of these lines can be inspected with tethered internal inspection tools the only inspection options until recently for the majority of the lines were visual testing, CP-surveys and local defect monitoring. With the MEC™-Combi Crawler system and the PECT inspection system it is now possible to gather integrity information to a level of accuracy that can be compared to in-line inspection, but is obtained by external scanning. This level of accuracy permits carrying out defect assessment based on inspection data. Case studies are presented for each inspection technique – Magnetic Eddy Current (MEC) and the Pulsed Eddy Current Technique (PECT) to show how the subsea inspection tools are adapted to fit the specific inspection task.

Traditionally, pipeline pigging has 2 extremes. At one end of the spectrum are cleaning pigs and at the other end are In-Line Inspection (ILI) tools or “intelligent pigs” and there is little that sits between. Cleaning pigs are basic tools that are frequently and easily deployed and carry little operational risk of lodging in the line, however, they gather little or no data. ILI tools are far more complex by design as the industry demands higher specification, greater accuracy and the ability to detect more types of pipeline defects. The consequence of this is larger tools needing specialist technicians, never mind the increased support and handling equipment as well as tight operating parameters and run scheduling. Operators have identified a need for tools in this middle ground of the 2 extremes and have encouraged the development of simple, easy to use and deploy inspection technology that uses advanced electromagnetic sensors integrated on to cleaning tools – or making the simple, smart.

Managing the long term integrity of a critical 10” subsea crude oil pipeline is dependent on being able to use the correct inspection technologies, however, the current structure of the pipeline does not allow for any in-line inspections. Consequently managing the short term integrity of the pipeline becomes a priority until the pipeline is made piggable. This paper describes where and how to investigate along the pipeline to determine the current internal condition of the pipeline.

A desktop feasibility study was completed in order to determine the locations and the confidence in the use of an external ultrasonic scanning survey (auto-UT) to determine the short term integrity of the pipeline. This comprised the following:

• Review of product composition and assessment of potential corrosion threats.
• Technical identification of the points along the length of the pipeline that is most susceptible to internal corrosion.
• Confidence in evaluating condition of pipeline based on auto-UT

In addition a review of the current sacrificial anode protection of the pipeline was completed to ensure that any investigative works completed would not result in any external corrosion issues.

Remote controlled, tethered isolation plugs and hot tap installed line-stop isolation tools are regularly used to provide fully proved double block isolations, enabling valve replacement or repairs without having to depressurise the entire pipeline. This type of isolation work scope could be described as conventional. Although, due to the safety criticality of any pipeline isolation, each application is engineered, tested and risk assessed against project specific parameters.

Isolation plugs are also used in unconventional, innovative ways throughout the pipeline life-cycle – from cradle to grave. This paper will describe case studies where isolation plugs have been used in non-standard ways to solve pipeline problems during the various phases of a pipeline’s life.

During the construction phase, isolation plugs are used to facilitate pipeline recovery in the event of a wet buckle. To enable recovery of large diameter or deep-water pipelines, the catenary section of pipeline to be recovered off the seabed usually requires to be dewatered. To dewater the catenary section, isolation plugs are deployed subsea, either via a diverless subsea launcher or via a pipeline retrieval tool with a cassette sleeve that contains the isolation plug.

During the operational phase, midline sectional replacement and repair may be required. In the case of an unpiggable defect, isolation plugs have been developed that can be pigged from either end of a pipeline towards each other, allowing the isolated section to be vented, cut out and replaced. To facilitate leak-testing following the repair an additional leak-test module is utilised and high-integrity pressure equalisation is used to safely unset the plugs.

Finally, for pipeline abandonment and decommissioning, isolation plugs are used to permanently plug and abandon pipelines. These isolation plugs can also be used to install a subsea bypass allowing platforms to be removed.

Pipeline pigging is a standard regular operational activity performed throughout the pipeline lifecycle and forms part of the Integrity Management System of a pipeline network. Typical examples of pigging applications include pre-commissioning, line-proving, cleaning, liquid removal, batching, inline inspection, inline isolation, and decommissioning. Key to all these activities is the ability to track the pigs in the pipeline, locate the pigs when necessary, and identify each pig when multiple pigs are in use at one time. More complex capabilities required are the ability to communicate, interrogate, and activate the pigs through the pipeline wall and induce sleep modes on transmitters, enabling battery life conservation during long operations.

Pig tracking can be performed by various methods—with devices fitted to the pig such as transmitters (electromagnetic or acoustic signal) or radioactive sources. External devices such as pipeline-fitted pig signaling devices, acoustic listening devices, or pressure pulse monitoring systems can also be used. The operational requirements and limitations of pigging activity will determine the best solution for tracking and monitoring.

Tracking of pigs in an offshore pipeline is challenging due to the environmental conditions. The pipelines tend to be constructed of thicker wall material (>15 mm) and are surrounded by large steel structures (platforms) as well as cyclic oscillating systems (pumps, turbines, etc.). Subsea sections may be covered for protection by rock dump, steel structures or buried below the seabed. These conditions provide challenges to transmitter tracking systems.

In the 1990s, T.D. Williamson designed and developed its proprietary inline isolation SmartPlug® tool, for isolation of a pressurized pipeline. The design requirements of this tool were that it could be pigged to an exact location, and once at the location, it could be remotely activated to effect the isolation. Once activated, it was essential that the system be remotely tested and monitored throughout the duration of the isolation, providing a safe controlled environment for the required works to be carried out. Communication capability at 100% was to be maintained throughout the operation. Due to the criticality of these design requirements, standard off-the-shelf transmitter systems were not found suitable for tracking the SmartPlug isolation tool.

Therefore, T.D. Williamson developed its own purpose-built system to support the SmartPlug tool, which was branded as the SmartTrack™ system.

In line inspections are commonly used to ensure safe operation of oil and gas pipelines. These inspections provide reliable information on the status of the pipeline’s integrity. Traditionally, gas pipelines are inspected using magnetic flux leakage (MFL) technology, and liquid pipelines are inspected using either MFL or ultrasonic wall measurement (UTWM) technology.

Recently, an additional technology has been introduced to the market, based on acoustic resonance technology (ART). This ART technology allows for the inspection of both liquid and gas pipelines with acoustic testing. The ART technology overcomes typical limitations of the prior state of art, such as limited wall thickness capability and speed (for MFL) and cleanliness criteria (for UTWM).

The authors will present the theoretical background of Acoustic Resonance Technology, and practical applications at a product level.

Furthermore, practical applications will be presented where the technology was applied in-field, in the North Sea area. Specifically; 2 occasions will be discussed of crude oil pipelines in the North Sea, which experience wax deposition to such a level that sufficient cleaning for UTWM inspections was not possible or cost-inhibitive.

Ice Pigging is a cleaning technique, mature in the water / wastewater industries, which is being developed for the Oil and Gas industry.

A high-solids ice slurry is pumped under pressure to deliver a wall shear stress on the pipe, cleaning it through physical abrasion. Made of just water and salt, ice pigs do their cleaning, unblocking, debris entraining and transport before melting back into their original components (commonly salt and water); offering a physical clean thousands of times more effective than flushing, without chemicals or risk of getting stuck.

The trails, which are the subject of this paper were commissioned by Royal Dutch Shell plc, using funding from their Gamechanger innovation program.

3D LASER SCANS are becoming increasingly popular for field verifications, and pipeline operators are demanding a corresponding ultra-high-resolution inline inspection technology capable of producing refined integrity calculations.

Ultimately, such an ultra-high-resolution inline inspection technology would lead to improved pipeline safety while simultaneously reducing the need for costly field verifications.

Hence, an ultra-high-resolution MFL technology with sensor spacing similar to that of a 3D laser scan has been developed.

In order to provide reliable inspection results using a ultra-high resolution MFL measurement system, a series of challenges had to be overcome:

• The extremely tight track spacing requires continuous data recording without any gaps in circumferential direction. This calls for accurate mechanical design to ensure each sensor stays exactly in its track, especially when passing welds.
• There can be a significant impact on the recorded data quality due to sensor placement on the yoke in relation to the magnetic field. Specific normalization efforts are required to ensure a uniform appearance of data for subsequent evaluation.
• The sheer amount of inspection data generated warrants the use of machine-based learning algorithms in data evaluation, reducing the ‘human factor’ impact.

In addition to presenting solutions for the above listed technical challenges, this paper will also provide insight into how pipeline integrity management will benefit from ultra-high-resolution MFL inline inspection results.

A 28" sub-sea pipeline supplying gas to Hong Kong was damaged by an anchor drag 278km from Hong Kong in 90m of water. The damage involved two subsea Pipeline End Manifolds (PLEM) and also dented the pipeline adjacent to the North PLEM. This paper details the repair of the damage using a combination of non-piggable and piggable isolation tools.

A model to examine pigging and inspection of gas networks with multiple pipelines, connections and customers is presented in this paper. A case study of a typical gas system with multiple lines, connections and off-takes is presented to demonstrate the use of such a model for planning and executing real life operations. A gas flow rate is provided into the network to the various users of the network or grid. Each customer has a requirement for both a minimum pressure and a minimum flow that cannot be disrupted without agreement or penalty to the operating company. Additionally, inspection or ILI tools must be run within certain velocity constraints to allow reliable data to be achieved. Due to the complexity of the system, there is a risk that the pig could stall in the line as flow is diverted as a result of the pigs own differential pressure. Manipulation of valves and flows must be planned and performed carefully so as not to disrupt the demands of the various customers in the network. Excessive pressure drop across closed valves is undesirable if they are to be opened during the operation. Pigging the system is onerous due to the need to balance the requirements of the pigs and the demands of the customers. The pig run time or expected arrival time with transient events such as valves opening, changes in flows, disruption to customers and other transient events is calculated. The paper presents the model and its use to optimise pigging programs in gas networks.

Pipelines manufactured from corrosion-resistant alloys (CRA) are becoming more common in special applications, in particular with offshore pipelines which are in many cases exposed to a harsh and highly corrosive environment. For many years the inspection of CRA pipelines (solid CRA, clad and lined pipe) was not a high priority. Due to the special composition of these types of line pipe it also posed specific challenges to in-line inspection methods as compared to the inspection of common line pipe.

In this article, the different types of CRA line pipe and the relevant characteristics regarding in-line inspection (metal loss inspection, crack inspection) are described. Typical damage mechanisms (e.g. pitting corrosion) that may develop during operation are illustrated and the specific capabilities that are available for ultrasonic in-line inspection as well as the limitations are explained. Several examples from inspection runs in CRA pipelines are presented demonstrating that reliable in-line inspections with good data quality are feasible to a wide extent.

The Congo River crossing (CRX) pipeline system was built to bring associated gases from various fields to a liquefied natural gas (LNG) processing plant in Soyo, Angola. The pipeline system runs a distance of approximately 140 km from the processing plant to the South Nemba platform located offshore Cabinda via two satellite pigging platforms [north pigging platform (NPP) and south pigging platform (SPP)], which provide the location for a drilled conduit that crosses the Congo River.

The pipeline system comprises four segments (A, B, C, and W), running from the South Nemba platform to the Angola LNG (ALNG) terminal in Soyo.

A service company was contracted to perform pre-commissioning services on each segment independently (flood, clean, gauge, caliper survey, hydrotest) before the close-in spools and subsea structures were installed.

Once all segments were completed and tied in, a global leak test was conducted before commencing dewatering operations. Each segment was bulk dewatered followed by final dewatering and vacuum drying before being packed with nitrogen in preparation for first gas.

During the various campaigns, each segment experienced incidents/problems, ranging from stuck centraliser tools, leaking hot stabs, vessel delays, etc., resulting in major delays to the overall project. The pre-commissioning work was successfully completed in early 2016.

Pipeline Engineering opened a Service Centre within the city of Aberdeen, Scotland in 2008 to offer a pigging tool management and tool refurbishment service to the North Sea Pipeline Operators for their routine pigging tools.

Routine pigging tools are used by the pipeline operators to carry out cleaning operations within the production pipelines without impacting on production flow or revenues.

The Aberdeen Service Centre receipts the pigging tools from the customer post run, and then conducts a full service which comprises of cleaning, stripping, inspection, spares replacement, refurbishment, and final testing. The pigging tools are then ready to be utilised on another routine cleaning run.

Once the pigging tool has been fully serviced, a detailed refurbishment report is submitted to the customer, providing visibility on the pigging tools condition and information of the service work carried out by Pipeline Engineering. This pigging tool management and tool refurbishment service has helped customers make large savings on their annual pigging tool costs, whilst also receiving the required engineering expertise to optimise their pigging operations.

The Aberdeen Service Centre has a pigging tool tracking system in place for each customer which highlights their full pigging tool fleet location, condition, configuration, last test date, run details and GA details. This information was previously submitted to the customer on a weekly basis, along with a summary report of all activities. The customers used this system on a regular basis to monitor their pigging tool logistics, and to advise the platform personnel on what the next pigging requirement were to be.

In Q3 of 2016, Pipeline Engineering has upgraded their pigging tool management service to their customers by introducing an Online Pigging Tool Management System. This online management system, with a personalised customer log in, helps each customer improve visibility of their pigging tool fleet whilst providing the option to remotely access the data via a mobile phone or tablet app. Having such up to date data at hand reduces the customers and/or platforms time spent sourcing the required information via the previous method of emails or saved folders.

As the Oil and Gas industry operates 24/7, Pipeline Engineering has created an excellent solution to provide continual all year support to the pigging industry.

This paper describes the optimisation process for cleaning tool maintenance via some customer case studies, demonstrates the software functionality and describes the benefits of having the data at your fingertips.

FlexIQ™ is a complete offering in the arena of flexible riser integrity management from the strategic alliance of INTECSEA and Innospection. This partnership looks to redefine the approach to flexible riser integrity management by offering the best in inspection and computational simulation techniques as part of an Integrity Management Framework. This, in turn, leads to a significant improvement in understanding operational risk and enables a fully integrated service for inspection, analysis and data management. An overview and benefits of the offering will be presented:

• Risk-based integrity management and inspection planning
• State-of-the-art annulus testing of flexible risers
• Visual and MEC-FIT™ Inspection
• Dynamic riser simulation using detailed, multi-layered finite element models with FLEXAS™
• Intervention planning and construction management
• Life of field riser analysis and model updates

Safe operation of pipelines carrying corrosive products or in a corrosive environment requires (i) an understanding of the corrosion threats, (ii) the ability to estimate corrosion growth rates (CGR) of features; and (iii) the ability to apply these rates to plan future inspections, repairs and replacements. Reducing uncertainties in corrosion behaviour will therefore result in safer, more cost efficient operation.

This paper provides:

• An overview of methods used in the industry for estimating CGRs (e.g. coupons, corrosion modelling, box matching and signal matching).
• A discussion of the challenges involved with Magnetic Flux Leakage (MFL) signal matching; and how advances in pattern recognition and data pre-processing, now allow full automated matching of signal data from repeat inspections.
• A comparison of different ways of using CGRs (e.g. feature specific rates, maxima, upper bounds, segmented rates) and a methodology for selecting the best method, to ensure safety while minimising repair and re-inspection requirements.
• Case studies demonstrating the efficacy of using signal matching and a tailored CGR application method.

It is now widely acknowledged within the oil and gas industry that operational (production) pigging is a key frontline O&M activity for controlling internal corrosion in upstream production pipelines. Within MACAW we are at the forefront of this battle, helping operators with the development of corrosion management strategies and in the implementation of effective corrosion control schemes.

In this technical paper we provide a Corrosion Engineer’s perspective on developing corrosion management systems for oil and gas pipeline assets, highlighting organisational and technical challenges and the importance of operational pigging (i.e. utilisation of production pigs and ILI tools) and how this fits within an overall corrosion management strategy. More specifically, for the most common internal corrosion threats, we discuss possible mitigation strategies and their implementation (e.g. the identification of correct pigging tools and treatment frequencies for the application of biocides to control microbiologically influenced corrosion).

Based on actual results obtained through assessments and investigations conducted on a wide range of pipelines, the impact and effectiveness of typical current operating practices are critically reviewed. Suggestions and recommendations are then put forward for discussion with regard to improvements and/or alternative pigging strategies which may be beneficial in combating a range of different internal pipeline corrosion threats.

Intelligent inline inspections (ILI) are widely used to guarantee a safe operation of pipelines. The inline inspection provides reliable data in an economic way. Ultrasonic (UT) is currently the most accurate and reliable In-Line Inspection technology available in the market. These UT ILI Tools record data while travelling through the entire pipeline from Launcher to Receiver. In most cases, the Pipeline Operator does not need to make major adjustments to their pipeline. Nevertheless, pipeline operators may have to adjust medium flow rates to accommodate optimum inline inspection conditions, e.g. down to 1m/s.

NDT Global recently introduced the latest generation of UT tools - EVO SERIES 1.0. This generation offers highest inspection velocities of up to 4m/s. This high speed tools overcome reduction of flow rates for intelligent inspection runs. In addition, highest axial resolution available at the market (0.75mm) and circumferential resolution of 4mm provide excellent input for accurate pressure calculations, e.g. based on Riverbottom and crack depth profiles or even 3D Finite element modeling.

The authors will present basic background information about ultrasound inspection technologies. Theoretical aspects of EVO Series 1.0 tools are discussed for crack and wall thickness inspections followed by a case study performed in a real pipeline. Furthermore, EVO generation offers capabilities of combining different technologies in one tool. One single inspection tool with corrosion and crack transducers enables pipeline operators to operate their system safe with a minimized impact while inspection.

Nearly half of the world`s oil or gas pipelines have until recently been considered “un-piggable”.

This term is used when a pipeline cannot be inspected with a free-swimming in-line inspection tool without a need to modify the tool or the line to be inspected. Typical examples are for instance missing launching and receiving facilities, diameter variations, tight bends, low pressure and flow conditions or high pressure and high temperature environments, onshore or offshore.

In this paper the typical issues regarding the inspection of challenging pipelines will be discussed. A new concept will be introduced, the so-called “toolbox approach”. The driving idea behind the concept is based on having a large variety of services with all the required technologies, including magnetic flux leakage (MFL), eddy current or ultrasound, enabling tailor made solutions to be packaged utilizing exactly the right technical resources for a specific inspection and integrity challenge.

But it is not limited to a technology perspective. It also uses market information to identify mid- and long term market needs as well as special operational procedures.

In addition it must be stated that this type of work relies heavily on the expertise and experience of the crew involved, because of the often extremely complex boundary conditions and operational parameters encountered during the job performance.

Several case studies will be presented to illustrate this approach and address the major issues of successfully inspecting pipelines previously considered “unpiggable”, with a special focus on accessibility, negotiability and propulsion.

To effectively and regularly pig pipelines, a versatile technology is required that could be seamlessly implemented with the ability to navigate variable geometry all whilst being both operationally and cost effective.

Pipelines are the carriers of high value materials, critical to the success of the operation. Pipelines and pipe networks new and old, multi-bore and straight require care and maintenance to ensure that they are kept in good condition for fulfilling the aforementioned purposes. Collections of unwelcome bodies and /or restrictions to flow can prove to be very dangerous to the surrounding environment.

Aubin has developed EVO-Pig which alongside Pipeline Gels help remove unwanted bodies and debris from pipelines, ensuring flow conditions are optimised, maintaining production and pipeline integrity. EVO-Pig is a low cost option when compared to traditional mechanical pigging operations. Combined with the simplicity of the design premise and ease of operation, the technology offers a low risk option to pipeline pigging. Shape memory technology, enables the hydraulically or pneumatically driven flexible pig to easily move through changes in pipeline diameter and bends in the pipeline with the added benefit of not needing to be received.

After many years in development, Discovery™ subsea pipeline CT (computed tomography) technology is now fully operational and field proven, having successfully completed hundreds of subsea pipeline inspection scans.

Discovery™ is externally deployed and can scan through any type of pipeline, including flexibles and pipe-in-pipe systems, and through any type of coating. The scan results provide high resolution tomographic images of the pipeline walls to 1mm resolution, as well as characterizing pipeline contents to determine the amount and type of deposits present.

The inspection is carried out online with no disruption to normal pipeline operations.

This paper will describe how Discovery™ is used to help in mapping a pipelines contents to assist with operational pigging, and also how it is used to verify and accurately size defects picked up during ILI campaigns.

Pigging tools for pipelines are typically dominated by cleaning pigs at one end of the spectrum and intelligent pigs at the other. The cleaning pigs are simple, low cost tools that are deployed by onsite technicians and pose little operational risk to the pipeline Operator. Their simple design and construction, especially with foam pigs, mean there is little risk of them getting stuck in the line, mobilisation costs are low and they can be deployment & retrieved with standard facilities. Intelligent pigs on the other hand are complex tools that need to carry the NDT sensors and electronics / power modules in a configuration that allows for optimum inspection capability while maintaining good Piggability. The use of Intelligent pigs require significantly more planning in terms of logistics and operations, the use of specialist personnel for deployment and the processing of data.

The impact to production and the cost of inline inspection is significant and subsequently ILI tools are only deployed in a pipeline ever few years so data can be infrequent.

I2i Pipelines have pioneered the development and integration of advanced electromagnetic inspection sensors onto conventional cleaning tools for the regular inspection of pipelines. The innovative pigs bring together the best capabilities of both types of tools, the ease of use, the low risk and the low cost of a cleaning tool design coupled with the advanced NDT sensors normally associated with more expensive ILI tools. The result is a fully capable range of inspection tool that can be deployed regularly by onsite engineers to inspect pipelines for corrosion and cracking, trend inspection data and capture any changing conditions within the pipeline.

This paper will look into the technical challenges, applications and operational advantages of deploying inspection technology with routine cleaning operations.

As older fields become uneconomic, technology improves, business models change, and offshore assets, such as platforms, cease to be productive and are decommissioned.

In many cases, the existing pipeline network around these platforms is repurposed or reconfigured to suit current needs. Productive wells can be tied in to the existing network, and unproductive assets can be bypassed. Although the platforms are most often specific in purpose, the pipelines are generalists by nature. And prolonging the life of this type of asset is almost always profitable.

This paper explores the consequences of decommissioning – as part of pipeline repurposing – through a series of North Sea projects involving pipeline isolation conducted over the last seven years.

The ILI industry still lacks a suitable inspection technology for CRA-lined pipelines, i.e. pipes with a mechanically bonded inner pipe of a corrosion resistant alloy inside of a ferritic steel pipe carrying the hoop stress. Neither the existing UT technology is able to inspect through the interface of a CRA and a ferritic steel component, nor is the current MFL technology able to sufficiently magnetise the ferritic steel pipe in order to inspect this type of pipe.

The current contribution investigates the possibility of Magnetic Eddy Current (MEC) to carry out such an inspection. A prototype internal inspection tool has been devised. Several types of sample defects have been produced into the ferritic steel carrier pipe as well as into the CRA-inner pipe. The defect types anticipate the integrity issues that an internal inspection tool would need to address. Several pull tests under controlled speeds have been carried out. The results are presented. Influences of tool speed, magnetisation level and eddy current parameter are investigated. Special attention is drawn to the distinction of different defect types.

The MEC technology was found to be a suitable inspection technique for CRA-lines pipes. This is achieved through several adaptations for this particular task. The particular challenges for the internal inspection of CRA-lines pipes are underlined. The technology may also fill other existing inspection gaps, like the inspection of heavy walled small diameter gas pipelines.

The use of high-bypass de-sanding pigs, either in isolation or in conjunction with traditional brush pigs, has been proven as an effective new method for mobilising and removing both waxy and particulate debris.

This case study will discuss the execution and findings of an operational cleaning campaign targeted at the removal of both waxy and particulate debris from an ultra-deepwater oil production pipeline in West Africa. The campaign utilised traditional brush pigs as well as high-bypass de-sanding pigs to remove debris for the purpose of reducing the risk of under-deposit corrosion.

The focus of the paper will be on the high-bypass de-sanding pig; its design, function and operation, and how it complemented the capabilities of more traditional brush tools.

The paper will describe the cleaning requirements and the tool types engineered for the operation, including the difficulties of design for the pipeline geometry and operating conditions.

The global market conditions influence the extraction of resources onshore as well as offshore, whereby particularly offshore exploration pipelines need to cope with high temperatures and pressures as well as products containing corrosive elements. This leads to potentially higher corrosion rates in a high temperature environment. Pipelines made of ferritic steels are susceptible to corrosion attack, especially if specific types of medium are transported in the line or the pipe is situated in a critical environment.

The industry is addressing this issue through various means, also including the development of new materials and pipe types. More and more corrosion resistant materials like stainless steel are used, e.g. duplex steels or different types of corrosion resistant alloy (CRA) pipes. Over the past 30 years thousands of kilometers of CRA pipelines are laid and there is still a growing demand.

However, in the carbon steel but also in the CRA layer different types of defects and/or features can appear, whereby the ILI technologies so far focus on carbon steel pipes.

This paper will give an overview of state-of-the-art ILI technologies to inspect mechanically and metallurgically bonded CRA pipes. The challenges for inspection of the carbon steel and the CRA layer, for different ILI technologies will be presented.

Verification of inspection results is a challenge to the industry. This is notable in situations of offshore pipelines which are a challenge to access and repair. It is essential that operators have accurate and reliable information on their pipeline condition to enable informed decisions with regards to maintaining and ensuring the ongoing integrity of their assets.

The case study presented in this paper is based on data collected on the condition of a large diameter crude oil pipeline which has undergone several in-line inspections, corrosion investigations and integrity assessments.

In order to verify the results of these in-line inspections and subsequent assessments, automated ultrasonic infield inspection results were utilised. A combined technology review and assessment was then completed to determine the accuracy of the measured metal loss features and corrosion rates identified by in-line inspection surveys.

This paper aims to highlight the results of this investigation and the subsequent benefits of utilising in-line inspection tools as part of an ongoing integrity management strategy.

There can be many flow assurance challenges that may result in reduced production through a production system such as paraffin wax, asphaltenes, salts & scales, sand, hydrates and corrosion products. The presence of deposits in a pipeline can lead to accelerated corrosion as well as restricting flow resulting in production rates that are less than the capacity of the system. In order to successfully inspect a pipeline using in-line inspection tools thorough cleaning of the line is required to avoid data loss during the inspection. In addition to the presence of deposits causing issues while the system is in production the presence of deposits can be problematic during decommissioning.

The first step in any cleaning operation is to gain an understanding where the deposits / restrictions are located in the pipeline along with the chemistry of the deposit. Once the amount and location of deposits are known a custom cleaning program can be developed to clean the pipeline.

The oil and gas industry worldwide is reliant on the long term reliability of pipelines, predominantly rigid pipelines as the safest and most efficient means for the transportation of hydrocarbons.

Pipeline operators need peace of mind that should a pipeline fail their processes and contingency plans are fully qualified and ready to respond to an emergency scenario.

There are two distinct damage scenarios that need to be considered, the first is operational damage caused by corrosion or erosion. This damage tends to occur slowly over a long timescale so regular inspection of the pipeline can monitor the condition and ensure planned maintenance is carried out.

The second damage scenario is through external impact, caused by an anchor drag, dropped object or landslide. With this scenario there will be no warning and the damage could breach the pipeline, introducing an unpiggable bore restriction at minimum or stopping pipeline flow completely.

This presentation will discuss recent advancements in isolation technology which have been developed to enable the installation of safety critical double block and bleed isolations when an unpiggable midline defect exists.

Significant savings can be achieved by having the required equipment ready for deployment in the event of a pipeline failure. The primary objective of an Emergency Pipeline Repair System is to facilitate a rapid and safe repair ensuring pipeline production can be resumed as soon as possible, minimising environmental and commercial impact.

The presentation will include a case study featuring STATS supply of emergency response isolation plugs from 32" to 38" developed for Qatargas. These fully engineered isolation systems were designed and manufactured to meet the clients specification and are now maintained in a state of readiness close to the operator’s asset, to ensure rapid response to an emergency repair.

Internal long axial corrosion is the most common corrosion type in offshore crude oil and water injection pipelines. It has frequently a complex shape that ranges from a smooth uniform wall thickness reduction to a rugged surface with varying depths.

Long axial corrosion anomalies can be reliably detected and sized by means of ultrasonic in-line inspection (UT ILI). The rough surface of the corrosion can lead to outliers in the gathered ILI data. Accordingly, an elaborated filtering and re-processing of the inspection data is crucial for a consistent data assessment.

The inspection report usually provides maximum anomaly dimensions (total length, peak depth, etc.) and does not sufficiently describe the complex shape of corrosion anomalies. Therefore, methods based on corrosion depth profile (river-bottom profile, RBP) have to be applied for pressure capacity assessment. In addition, corrosion growth rates are ideally obtained by comparing RBPs of consecutive inspections.

This paper outlines the main results of a recent joint industry project that provides guidance to the assessment of long axial corrosion based on UT ILI results. It involves the determination of RBPs, the calculation of the safe operating pressure, the determination of corrosion growth rates and the extrapolation of the future pressure capacity. Compared to other assessment methods which are also based on RBP, the presented assessment approach accounts for a higher probability of failure associated with a higher number of corroded sections in a pipeline.

Chevron North Sea Limited (CNSL) operates more than 25 pipelines across three operated assets in the UK North Sea – Alba, Captain and Erskine.

Processes adopted by CNSL for effective management of pipeline integrity and reliability include a combination of online data collection, fluids sampling, corrosion risk assessment, remnant life modelling, and physical inspection techniques for the measurement of pipeline condition.

This paper discusses the input that in-line inspection (ILI) can have into an overall pipeline integrity management strategy. The following key points will be discussed: The importance of combining knowledge relating to active corrosion mechanisms together with an understanding of the capabilities and limitations of available in-line inspection technology. How ILI results can be used to review the effectiveness of corrosion management strategies and support remaining life assessment. How to select an appropriate re-inspection interval.

Case studies will be used to provide a practical insight into how this is achieved within CNSL.

Pigging operations often present monitoring challenges that are difficult to predict prior to launch. These include confirming launch, monitoring pig progress at strategic locations and confirmation of the pig’s arrival, often under adverse conditions. Accurately locating a stuck pig as well as quantifying the associated debris transported into the receiver can also be problematic.

Using a combination of different non-intrusive pig monitoring, signalling and data communications equipment, an operator can mitigate against these risks for even the most difficult or lengthy pigging operations.

Drawing on experiences gained throughout a diverse project history, this paper provides insights into reliable and novel monitoring methods available to an operator engaged in pigging operations. Descriptions of real life projects utilising using a variety of non-intrusive technologies will be discussed.

This paper focuses on the technology and logistical challenges for a long-distance, deepwater pipeline precommissioning and inspection project.

Weatherford Pipeline and Specialty Services (P&SS) performed this work on behalf of Noble Energy Inc., a major oil and gas exploration and production company. Its subsidiary, Noble Energy Mediterranean Ltd., contracted directly with Weatherford P&SS as part of their development of a subsea gas production and transportation system connecting the deepwater Tamar Gas Field to an offshore receiving and processing platform linked to the existing Mari-B Platform in the Mediterranean sea.

Gas production from the Tamar Reservoir is designed to occur through five high flow rate subsea wells into the subsea gathering system, which consists of an infield flowline from each well to a subsea manifold. From the subsea manifold, dual subsea pipelines will transport Tamar production approximately 149km to the Tamar Offshore Receiving and Processing Platform where the gas will be processed. The processed gas will then be delivered to the existing Ashdod Onshore Terminal (AOT) for gas sales into the Israel Natural Gas Line (INGL) system.

The inspection of pipelines through high levels of coating remains a challenging task. In particular offshore pipelines often require a thick coating for various purposes. Usually it is a combination of mechanical impact and corrosion protection. Hence the configurations can be quite different. The external inspection of subsea pipelines and risers often complement or substitute an internal inspection by pigging.

An overview of available technologies is presented. The limitation of the technologies and their physical origins are discussed. A systematic investigation in improving the capabilities was done. Most of the principles are based on some kind of eddy current technique. Several case studies of inspection through a thick coating are presented. In one case risers had to be inspected through as much as 12mm of coating and with a wall thickness of 25mm. The high stand-off measurement usually conflicts with a high resolution of the scanned surface. Metal loss defects as small as 10 mm and as shallow as 10% have been found. In a different project a wire disorganisation of a flexible pipe had to be detected through a coating of 9 mm. In this case it was possible to show, how a regular signal pattern and its distortion by defects can lead to a sensitive detection of defects through a coating.

In the last 4 years more than 800 inspections have been completed on & off-shore with the latest generation MFL ILI technology, capturing information on tens of thousands of kilometres of pipe, and generating a significant volume of dig verification data.

In collaboration with Oil & Gas pipeline operators around the world this growing dig verification database has been utilized to improve software models, algorithms, & analysis processes to validate and further enhance system detection, sizing, & reporting capabilities.

This paper focuses on the recent collaboration between ExxonMobil and PII, to investigate system capabilities with respect to “Pinholes”, to address a known threat to a specific pipeline in the United Kingdom.

This paper will describe the:

• Evolution of the "Pinhole" specification that captured the interest of ExxonMobil.
• Use of Finite Element models to predict entitlement for characterization of "Pinhole" type defects
• Detail of and results from the ExxonMobil sponsored test program that was conducted in early 2013
• The in-line inspection, analysis report, and dig verification that followed for the pipeline in question.

Internal corrosion can lead to production reduction as corrosion by-products accumulate in the pipeline and, in the event of a through-wall failure, can cause extensive hazard to people and damage to asset and the environment.

Corrosion inhibitors have proven to be very effective at reducing the overall corrosion rate when added to the pipeline product in small amounts. The inhibitors are generally introduced into the pipeline by injection, either as slug treatment or continuous injection, or most commonly as batch treatment employing a chemical column between two pigs.

Operators are looking for alternative treatment options. This may include the application of corrosion inhibitors by an innovative “spray pig” technology.

Mechanical interlocking products guarantee strict adherence to procedure and thus avoid human error. They are particularly useful for operations that are generally recognized as highly dangerous, such as pigging. Interlocks are a cost-effective measure that results in extremely high safety levels.

Traditionally however, interlocks function as independent and stand-alone safety systems. But as advanced digital technology now enables us to combine process control and safety instrumented functions within a common automation infrastructure, wouldn’t it be better to integrate operator procedures, such as those safeguarded by mechanical interlocks, with the Distributed Control System (DCS) and Safety Instrumented System (SIS) as well?

As the overall infrastructure in the oil and gas industry is aging there is an increasing demand to assess the integrity of all existing assets. As a result pipeline inspection using In-Line Inspection (ILI) tools has become the standard for pipelines that can be considered piggable. Many of the world's pipelines were however never designed to be pigged, the so-called unpiggable pipelines.

To operators these unpiggable pipelines are equally important to the overall integrity of the pipeline system and suitable inspection solutions are therefore required. Although alternatives like direct assessment and spot checks using in-field, non-destructive testing exist, the most valuable information can only be obtained from the inside of the pipeline using in-line inspection devices.

Typical challenges involve access (no pig traps installed), operating conditions as well as the pipeline geometry. Due to the individual challenges arising from pipelines deemed to be unpiggable a wide variety of tailored solutions has been developed in recent years.

One of ROSEN's recent developments is the extremely short Bi-Di Inline-Inspection tools. Their bi-directional design, passage capabilities and wide range of operating conditions provide great flexibility to operators, thus minimizing the operational impact and required pipeline modifications. Applications include ILI of tanker loading/unloading pipelines, gathering pipelines, branch connections, risers and flare lines.

This paper will discuss the continued development of ILI solutions specifically designed to close the gap between piggable and unpiggable pipelines by discussing their challenges, practical application, case studies, and the future of additional research and development.

In 2005, Total were planning to carry out an inspection of two 32” gas and condensate pipelines running 92 km from the South Pars field in the Persian Gulf to the shore terminal at Assaluyeh in Iran. The pipelines were overdue for inspection but it was known that hard scale deposits were present in the line which would present significant difficulties to the passage of either MFL or Ultrasonic tools. Total were therefore planning to carry out an acid clean of Sea Line 1 to remove the scale prior to the use of the inspection pigs. Our company was asked if we could run a multi-channel caliper tool through the line to measure the thickness and the distribution of deposits and to provide the information to the pipeline engineers to allow them to optimise the acid clean. In due course we successfully carried out the caliper run and from the data, we were able to map of the distribution of the scale and an estimate of the total volume of the deposits. From this information, Total were able to determine the quantity of acid required and optimise the soak time to ensure all of the scale was removed. Following the acid clean, we were asked to return and run the caliper to confirm that all of the deposits had been removed. In fact when we did the run we found that some of the thickest deposits had not been removed so a mechanical cleaning pig was used to remove the remaining deposits allowing the MFL inspection to be carried out.

In 2006 we were invited back to carry out the pre-cleaning caliper survey of the second pipeline – Sea Line 2. Foam pigs had been run through this pipeline but no hard bodied pigs. We therefore offered a smart gauging pig to run in the line first to get an idea of the size and location of the major restrictions before running our caliper tool.

However, when the gauging pig was run, it was severely damaged and the rear disc stack was completely stripped off the pig and left in the line (Figure 1). Clearly the restriction in this line was much more severe than in Sea Line 1. Fortunately the pig had not been completely stuck in the line and by measuring the damage we were able to figure out the key design parameters of a caliper pig which should be able to get through the restriction in the bend at the bottom of the riser.

With help from the engineers at Propipe, a caliper pig was produced and much to our relief, it passed through the line without a hitch. Once again, data from the caliper run was used to produce a mapping of the scale deposits and this time the post cleaning caliper run showed that the deposits had been successfully removed.

Several of the world’s oil and gas facilities are experiencing aging production infrastructure. Operators are now applying greater focus to integrity management and more frequent inspections. Internal visual inspection is one method for the inspection of pipeline systems. Challenges exist with this method related to camera tools and receiving a clear image as well as performing swift inspections to keep disruption of production to a minimum.

When a major operator on the Norwegian continental shelf required effective inspection of several flexible production risers, it became apparent that the existing technology did not provide the required image quality and operational effectiveness. This lead to the development of an inspection camera tool that combines existing technology used for inspection of drilling risers and blowout preventers (BOPs) with a commonly used deployment vehicle (pig) design.

The tool enables single inspection runs to acquire digital images in a high-pressure environment. It incorporates high resolution, wide-angle 185/360° images, powerful lighting, and customized software with digital unwrapping and advanced digital filtering.

The tool body has a bidirectional pig design and is launched and controlled using a high-tensile-strength control cable. An effective stripper unit mounted on a regular pig launcher helps ensure a safe launch and control of the tool. The visual inspection tool is normally launched in clear fluid, but other driving media can also be used.

Within pipeline systems, this camera tool enables inspection for abnormalities, corrosion, coating, functions, and other features. Operators can use this technology to improve and expedite the decision-making process, leading to time savings, reduced costs, and increased offshore safety.

When it comes to a fast, non-intrusive, complete and meaningful inspection of an offshore pipeline in-line inspection (ILI) has been the method of choice for several decades now. However, not all pipelines, piping or other tubular structures can be inspected with in-line inspection tools (pigs). The method is usually limited to looping flow lines or export pipelines, specifically designed for ILI operation. The remaining structures are often summarized under the buzzword “non-piggable”.

The typical ILI viewpoint is to consider the piggability under either the aspect of pipeline design or pipeline operation. Typical piggability issues in pipelines under pipeline design aspects are launching/receiving facilities, bends, and internal obstructions. The other aspects are operations-related. ILI may be impossible due to too high/low flow, too high temperature and other. In both cases ILI solutions can still be conceived and realised by either changing the pipeline or by adapting the pig. The latter is the technically more interesting solution for service providing companies. ILI providers are busy in designing and already offer tools for multiple diameters, for bi-directional operation and tools with special insertion techniques. Also there are many solutions available that use a cable operated tool and/or a crawler type tool. Discussions on solutions for unpiggable pipelines usually focus on these types of solutions.

There still remains an area of inspection tasks that can be summarized under “Not at all piggable”. For either technical or financial reasons, a pig-like solution may still remain unfeasible. In some cases the involved technical risk may also convince the involved parties to refrain from any ILI adaptation. In these cases either key-hole solutions or external inspection may remain the only option. The distinction between a key-hole solution and a pig-based inspection can be made by the aim to reach a 100% coverage in the latter case. For other inspection types a lower inspection coverage is usually accepted.

Acoustic pipeline pig tracking, simply put, is the attachment of a battery powered acoustic pinger to a pipeline pig; the acoustic signal generated by the pinger travels through the pipeline and into the surrounding water and is subsequently tracked with a suitable receiver system.

Receivers consist of a hydrophone, essentially an aquatic microphone tuned to the frequencies of interest, and some sort of user interface which displays, or more often plays back downshifted audio of the ping.

The hydrophones attached to receivers can be either omni-directional or directional depending on the task at hand. For tracking from a surface vessel, omni-directional is often the obvious choice. However, when precise locating of the pinger is required, a directional hydrophone can be used.

The energy emitted by the acoustic pinger are acoustic tones, often only a few milliseconds long and outside the range of human hearing, typically between 10kHz and 40kHz.

Acoustic pig tracking itself is not a new field. For decades pinger suppliers have supplied pinger equipment to offshore pipeline construction companies and pipeline operators alike. These pingers, when properly mounted on pipeline pigs, have provided these basic offshore pig tracking functions.

Despite this list of strong positive features, acoustic pig tracking has a somewhat spotty record of reliability in the field. Over the years CDI has had the opportunity to speak with many of the end-users of acoustic equipment. Anecdotal end user experiences have varied widely, with some firms having good experiences and others having complete failures.

Some of the failures of the systems are no doubt due to a lack of understanding and training of the operator; user error. This is not uncommon when infrequently used systems are put into the hands of end users. However, user error cannot account for all of the failures experienced by otherwise competent operators. There are some subtle underlying technical problems with existing acoustic pig tracking systems.

Perhaps greatest among these is multipathing.