Pipeline Monitoring – Locating leakages at oil and gas pipelines

Leaks occurring in underground pipelines constitute a substantial danger for both, human beings and the environment. Oil escaping from pipelines pollutes the earth and ground water.
Leaking gas creates the danger of fires and explosions. In addition, leaks bring about large economic losses. It is extremely important to locate leaks as soon as they occur and to be able to locate small leaks. Until now, monitoring systems have only reacted to large leaks and have not been able to pinpoint them accurately. Oil leaks cause temperature anomalies below the pipeline, whereas escaping gas induces a temperature decrease above the pipeline due to the easing of pressure.
Efficient leak location and the long-term monitoring of gas and oil pipelines can therefore be achieved by measuring the temperatures along a pipeline and observing how these temperatures vary over time. Optical-fibre, temperature-measuring technology presents new opportunities in this connection.
An optical-fibre, temperature-measuring cable is laid along a pipeline, enabling the temperatures in the ground to be measured simultaneously over long pipeline distances with a high degree of locational accuracy.
The sensor cable is completely passive electrically and can therefore by fitted to pipelines where a high risk of explosions exists.
The leakage-location principle by means of optical-fibre, temperature-measuring technology

Using optical-fibre, temperature measuring to monitor pipelines makes possible:

• The economical location of leakages and the long-term monitoring of pipelines

• The monitoring of pipeline sections up to 30 km long by means of a system

• The opportunity of linking individual systems to form an overall system to monitor longer sections if necessary

• The quantifying of leakage rates using model calculations

• It is not necessary to empty and clean the pipeline before inspecting it

• Shutting-down the pipeline is not necessary

• Small quantities of escaping oil can be exactly detected and located

• Damage can be identified in its early stages

The measuring system enables the temperature along a section of pipeline to be measured by using optical-fibre sensors. Temperature anomalies caused by leakages are identified via this system and the efficient location of leakages and long-term monitoring of gas and oil pipelines are thus made possible.
Read more:

• Distributed Temperature Sensing
• LNG and LPG Containment Integrity Monitoring Solutions

Distributed Temperature Sensing, the Motor for Tunnel Innovation and Safety in Croatia

Tunnels are sensitive traffic bottlenecks and consequently extraordinary vulnerable in case of accidents or fire blasts. Danger for life and enormous economic consequences ask also for technical solutions of prevention and limitation of damage.

LIOS Technology and its Croatian partner Tehnomobil have set a new standard for modern fire safety solutions for the road tunnel network in Croatia.

Croatia is located in South-Central Europe and shows diverse terrain, including: rolling hills in the continental north and northeast, densely wooded mountains and rocky coastlines on the Adriatic Sea. The highlight of Croatia's recent infrastructure developments is its rapidly growing highway network which puts focus on tunnels as well.

Tehnomobil’s excellent engineering and contracting background in traffic infrastructure and fire fighting industries perfectly match with LIOS Technology’s comprehensive experience in fire detection applications for tunnels and special hazard buildings with an impressive track record of more than 2000 installed fibre optic temperature sensing systems worldwide.

Best fire surveillance for more than 90 % of the road tunnels in Croatia

At present an impressive share of more than 90 % of the Croatian road tunnels are equipped with the fibre optic fire detection system by LIOS Technology. In 28 tunnels with in total 55 tunnel tubes the purely passive LIOS fibre optic line sensor cable has been installed by Tehnomobil for reliable and fast fire detection. Those tunnels with tube lengths ranging from 500m to almost 6000m were newly opened in recent years or re-opened after full refurbishments where the conventional line type fire detection system could be replaced by the fibre optic LIOS system. Within LIOS Technology’s long list of tunnel projects in Croatia it is worth to stress the tunnels Veliki Glozac and Brinje which received best scores at recent European tunnel safety rankings.

Read more:

• Optimum Safety in Tunnels and Special Hazard Buildings
• Distributed Temperature Sensing

Introduction to Distributed Temperature Sensing

Distributed Temperature Sensing Systems (DTS) are optoelectronic devices which measure temperatures by means of optical fibres functioning as linear sensors. Temperatures are recorded along the optical sensor cable, thus not at points, but as a continuous profile. A high accuracy of temperature determination is achieved over great distances.

Measuring Principle - Raman Effect
Physical measurement dimensions, such as temperature or pressure and tensile forces, can affect glass fibres and locally change the characteristics of light transmission in the fibre. As a result of the attenuation of the light in the quartz glass fibres through scattering, the location of an external physical effect can be determined so that the optical fibre can be employed as a linear sensor.

Optical fibres are made from doped quartz glass. Quartz glass is a form of silicon dioxide (SiO2) with amorphous solid structure. Thermal effects induce lattice oscillations within the solid. When light falls onto these thermally excited molecular oscillations, an interaction occurs between the light particles (photons) and the electrons of the molecule. Light scattering, also known as Raman scattering, occurs in the optical fibre. Unlike incident light, this scattered light undergoes a spectral shift by an amount equivalent to the resonance frequency of the lattice oscillation.

The light scattered back from the fibre optic therefore contains three different spectral shares:

• the Rayleigh scattering with the wavelength of the laser source used,
• the Stokes line components with the higher wavelength in which photons are generated, and
• the Anti-Stokes line components with a lower wavelength than the Rayleigh scattering, in which photons are destroyed.

The intensity of the so-called Anti-Stokes band is temperature-dependent, while the so-called Stokes band is practically independent of temperature. The local temperature of the optical fibre is derived from the ratio of the Anti-Stokes and Stokes light intensities.

Measuring Principle - OFDR Technology
Latest DTS evaluation units deploy the method of Optical Frequency Domain Reflectometry (OFDR) . The OFDR system provides information on the local characteristic when the backscatter signal detected during the entire measurement time is measured as a function of frequency in a complex fashion, and then subjected to Fourier transformation. The essential benefits of OFDR technology are the quasi continuous wave mode employed by the laser and the narrow-band detection of the optical back scatter signal, whereby a significantly higher signal to noise ratio is achieved than with conventional pulse technology (OTDR). This technical benefit allows the use of affordable semiconductor laser diodes and electronic assemblies for signal averaging.

The optical frequency domain reflectometry has been developed as a high-resolution measurement process for the characterisation of optical wave guides with length dimensions of just a few millimetres. In contrast, its application for the Raman backscatter measurement was introduced and patented by the company LIOS Technology.

Schematic system set up
The temperature measuring system consists of a controller (frequency generator, laser source, optical module, HF mixer, receiver and micro-processor unit) and a quartz glass fibre (fibre optic) as line-shaped temperature sensor.

The design is three-channel, since an additional reference channel is required besides the two measurement channels (Anti-Stokes and Stokes). Corresponding to the OFDR system, the power output of the laser runs through the sinus-shaped frequency starting from a starting frequency in the kilohertz range through the ending frequency in the high megahertz range within a measurement time interval with the help of the High Frequency (HF) modulator. The resulting frequency shift is a direct measurement of the local resolution of the reflectometer. The frequency-modulated laser light is connected to the fibre optic-sensor via the optical module.

The continuously back-scattered Raman light is spectrally filtered in the optical module and converted into electrical signals by means of photo detectors. Then the measurement signals are amplified and mixed in the Low Frequency spectral range (LF range). The Fourier transformation of the averaged LF signals results in the two Raman backscatter curves. The amplitudes of these backscatter curves are proportional to the intensity of the Raman scattering of the viewed location. The fibre temperature along the sensor cable results from the amplitude ratio of the two measurement channels.


High Reliability and Industrial Strength

The semiconductor laser diode has been thoroughly type tested according the Telcordia GR-468 standard. It fulfils telecom standards with a medium lifetime of more than 25 years. The entire system was comprehensively evaluated by various independent international bodies (e.g. the VdS, the association of German asset insurers) including EMC tests as well as endurance tests at accelerated aging environments. Field data of the huge installed base prove the exceptional high reliability of the controllers.

Read more...

Intelligent Well Completion - Special Focus on "World Oil" magazine

Right from the oil industry’s begin­ning, people wanted to know more about the reservoirs that they were exploiting. This included having a more sound un­derstanding about reservoir behaviour and obtaining knowledge on how to optimize hydrocarbon recovery. As it was, and still is, impossible to look directly into a res­ervoir, other ways to obtain information about it needed to be investigated. Direct surface measurements were helpful and are still required today, but downhole sensing quickly became an important topic for reservoir monitoring.

The first sensors were for pressure measurements and then temperature. Nowadays, micro-sensing images a whole ground section in 3D. A lot of in­formation can be derived from relatively easy temperature measurements along the borehole. The advances in fibre op­tics and packaging, and the experience gained over the last five to 10 years, has enabled the industry to deliver low-cost DTS systems. An additional factor has been further development of industry standards and electronics, enabling per­sonnel to build an architecture that al­lows data flow from the well to the pro­duction technologist’s desk.


Reprinted from: World Oil,  May 2007 issue, pgs 37–44.


Read more:

	Download complete "World Oil" article on permanent downhole temperature sensing
	Oil and gas well optimisation and reservoir performance improvement

Integrated Condition Monitoring for High Voltage Cables: Direct link to SCADA / substation automation

The intrinsic temperature measuring system DTS based on LIOS Technology’s design, with fibre optic sensors either installed within the power cable’s cross section (FIMT - Fibre in metal tube ) or attached to the exterior of the cable, makes it possible to record the temperature profile along an entire cable route continuously, and to pinpoint the exact location of hot spots within a metre.

Most commonly the measured temperature profile data is transmitted via standard interfaces from systems of the DTS as required, and be either displayed or further processed by PC, PLC or SCADA systems. As a result of the increasing demands placed on the ability to network and integrate measuring systems into management systems, LIOS offers network components that summarise DTS data from several DTS units and transport or convert it to the required network standards and protocols like Modbus, DNP3, IEC60870-5 or XML based data interfaces (e.g. POSC).

Equipped with the Embedded Communication Module (ECM) the Distributed Temperature Sensing (DTS) evaluation unit is accessible by Ethernet/ LAN, holds its own IP address and is compatible with DHCP.
The on-board storage facility of measurement data provides automatic buffering of network break downs. It can handle multiple protocols, so the DTS can be directly linked to PLC or SCADA systems and communicates in various industrial protocol standards providing measured data and customised alarm information.
Hereby, the evaluation unit communicates as a TCP /IP server with several clients.

Features of the embedded communication module of the LIOS DTS controller:

• Configuration and operation of the DTS via two independent channels:
  
  
  • RS232
  • Ethernet TCP/IP
  
  
• Onboard storage of measurement data
  
  
  • Buffers up to 72 hours of measurement data and initiates data transfer automatically after communication link was re-established
  • Individual file access to measurement data through CHARON_02 (onboard data storage 1 GB)
  
  
• Allows to operate individual Plug-In-Interfaces for customer specific protocol solutions
  
  
  • The DTS can communicate in parallel with its proprietary protocol and one or more customer specific protocols like DNP3, IEC60870-5-104, IEC61850, POSC WITSML, Modbus (Master/Slave) etc.
  • Individual assignments for protocols and client addresses (IP) possible
  
  
• Ethernet communication to and from clients with high bandwidth
• Module comes with built-in user configurable Firewall and enables reliable operation even in WAN’s
• Secure data transmission and individual authorisation according TLS- Standard (RFC 2246)

The most common industrial protocols used in electrical systems worldwide are introduced in the following section. However, also other protocol standards are available or can be implemented for the ECM. Please contact us in case of questions.

MODBUS
The MODBUS protocol was published by Modicon in 1979. It is a quite simple single master – multiple slave protocol widely used in general purpose SCADA applications. It provides binary (bit) and 16-bit integer data, but no floating point values, polled by the master, i.e. the slave cannot send data spontaneously. The protocol specification is openly published and royalty-free. In the DTS ECM, TCP/IP is used as transport layer.

IEC 60870-5
IEC 60870-5 provides a communication profile for sending basic Telecontrol messages between systems. It was developed by the IEC Technical Committee 57 (Working Group 03) as a protocol standard for Telecontrol, Teleprotection, and associated telecommunications for electric power systems. The result of this work is IEC 60870-5. The protocol provides inter alia bit, integer and floating point data with or without time stamps. Data is transmitted from controlled stations (slaves) either by polling or spontaneously. In the ECM the IEC 60870-5-104 companion standard, defining standard TCP/IP connections as transport layer, is used.

DNP3
DNP3 (Distributed Networking Protocol) is an open standard managed by the DNP User Group. Initially; the DNP3 protocol was developed by Westronic (now GE-Harris) in 1993. It is widely used in electrical systems worldwide, including North and South America, the UK, Southeast Asia, South Africa, Australia, and New Zealand. It has gained wider use beyond electrical utilities, e.g. for water supply as well. The DNP3 protocol is also referenced in IEEE Std. 1379-2000, which recommends a set of best practices for implementing modern SCADA Master-RTU/IED communication links.
The protocol provides bit, integer and floating point data and time stamps. Data is transmitted from the outstation (slave) either by polling or spontaneously. The ECM uses TCP/IP as transport layer, but even in this mode the DNP3 protocol additionally uses its own protocol stack for synchronisation and error checking. This provides extra security.

The ideal sensor embedded in power cables: Fibre In Metal Tube (FIMT)

The optical fibre serves as the distributed temperature sensor for LIOS DTS systems and is typically surrounded by a protective layer. It is preferably encased in a stainless steel tube which significantly increases the mechanical stability of the sensor. Fibre encapsulated in stainless steel tube or short “Fibre In Metal Tube (FIMT)” is a hermetically sealed rugged construction for very long lengths of optical fibres. Furthermore, it is particularly effective in protecting against the hydrostatic pressures, high temperature effects and corrosive environments.
The inside of the FIMT metallic tube may lined with gel to ensure that the sensor cable remains permanently water-proof. This viscous gel protects the fibres from many environmental concerns, prevents damage from microbending conditions and helps to minimize the forces applied during spooling and deployment.
An important parameter to consider with FIMT is the Excess Fibre Length. It is defined by the percentage of excess fibre loaded into the metal tube during processing to relieve induced stresses directly related to the differing thermal coefficient of expansions of each material contained in the construction. FIMT is exposed to drastic and often rapid changes in temperature and pressure, so the Excess Fibre Length must be considered to ensure continuous, robust performance across all operational conditions.
FIMT constructions contain individual or multiple fibres (single mode or multi mode) and are available in sizes ranging from 1 mm to 3 mm outer diameter, variations in effective wall thickness are possible as well. FIMT serves as the core for various fibre optic sensor cable constructions or may be integrated into high voltage cable designs directly.
The FIMT is manufactured from a special stainless steel strip. During the manufacturing process this strip is formed to a tube and welded along its length. The stainless steel tubes must be hermetically sealed for all applications. For this reason the complete weld seam is subjected to a leak proof test by means of eddy current. By means of a drawing process the desired final diameter is attained on the one hand and an increase in strength through cold conversion on the other. During the manufacturing process the optical fibres are inserted into the tube. They are clearly differentiated by means of a specific colour code. At the end of the production process the tubes are subjected to a complete optical attenuation measurement and then documented for back-tracing. Additionally, each length produced is subjected to a weld penetration test, each weld seam undergoes a leak test, and the Excess Fibre Length is checked.
LIOS offers a variety of FIMT constructions perfectly suitable for distributed temperature sensing applications along power cable transmission systems.

DTS support for Steam Assisted Gravity Drainage (SAGD)

Accurate, continual, and real-time temperature reading along the well path can give you valuable information about the condition of both the reservoir and downhole completion provided by LIOS distributed temperature sensing (DTS). This enables you to adjust parameters and schedule maintenance for maximum hydrocarbon production and minimize downtime.

[caption id="" align="aligncenter" width="500" caption="DTS support for Steam Assisted Gravity Drainage (SAGD)"][/caption]

DTS Temperature readings allow you to:

• Enhance oil and gas recovery
• Increase production yields
• Track well production changes over time
• Reduce frequency of well interventions
• Improve reservoir management strategies
• Supply in-flow distribution along the reservoir
• Detect early water, steam (SAGD), or gas breakthrough and its location
• Observe steam flooding performance
• Verify and allocate cross flow
• Determine skin factor
• Check integrity of casing and completion
• Monitor and optimize gas lift valve operation
• Detect stuck or leaky valves, perforation inflow, porous insulation, wax deposits, hydrate precipitation, etc.

Read more: DTS Condition Monitoring in Oil & Gas Exploration

Reliable Energy Supply for the city of Graz, Austria

In order to improve the energy supply for the city of Graz, CCC GmbH Berlin installed new cable connections across the town between the transformer stations of Graz-South and Graz-West. The entire underground engineering, i.e. the joint base installation mand complete trenching construction was built by STEWEAG-STEG GmbH. The new cable installation is one of the city’s main transmission lines and is heavily loaded. In order to optimize the transmission performance and to guarantee its secure reliability, the cable installation has been equipped with large scale cross-bonding systems at its sheath. In addition, by the help of the LIOS Distributed Temperature Sensing (DTS) system, the level of backup capacity can be assessed. These optical fibres can monitor the cable temperature along the trench and have been integrated into the sheath area of the cable.

Highlights

• 110 kV high-voltage power cables between transformer stations Graz-South and Graz-West
• 3 cable lines with a length of 3,2 km each (total 9,6 km cable),one of which is equipped for the entire distance of 3,2 km with integrated optical fibres in a steel tube integrated in the copper screen of the HV-cable for temperature monitoring (DTS)
• 18 sets of accessories
• Cross-bonding system in order to maximize transmission performance
• During the planning period numerous calculations for currentcarrying capacity were carried out in order to judge the influenceof crossing long-distance heating lines.
• Direct DTS data interface for temperature and operational data into the overall SCADA system of STEWEAG-STEG (Fernwirkanlage STEWEAG-STEG) using protocol IEC 60870-5-104

Setting Standards for Highly Reliable DTS Performance

LIOS Technology GmbH is the leading manufacturer of industrial DTS systems with an impressive track record of more than 2000 installations in permanent operation. Its current DTS product series was carefully designed and thoroughly tested targeting reliable performance and smooth operation in industrial environments.
This was imposingly endorsed by the latest statistical field analysis in respect of a mean time between failures (MTBF) evaluation. Adapted from field data of our installed base of the current DTS product series an excellent MTBF figure of 28 years was reached.

High reliability is also a result of the unique optical frequency-domain reflectometry (OFDR) technology of the LIOS DTS systems. In contrast to time-domain technology using pulsed lasers with high peak powers, the LIOS OFDR DTS uses a quasi-continuous laser with low peak power resulting in a nonexistent wear out of the laser unit or any other fatigue of other optical components. The exceptional reliability favors the deployment of the LIOS DTS systems in all remote, safety-relevant and industrial applications.

Success story for permanent downhole sensing - Maximize your ROI with DTS

Technology is the key driver in the quest for greater efficiency. In the oil and gas industry, there is keen interest and high demand for low-cost, reliable, and easily installable systems to enhance downhole production and recovery.

“Installation of LIOS DTS in the Darat Field in Brunei has proven to increase the value of the wells from our customer significantly because of early detection of faulty gas lift valves, resulting in quick repair and increased production.”

Lt Col (B) Mahmod Yakop (Founder & Managing Director, AMRTUR Corporation Sdn. Bhd)

In a co-operation between Shell International Exploration and Production (SIEP) and LIOS Technology GmbH (LIOS) the feasibility and economical added value of permanent downhole temperature sensing have been successfully demonstrated in a number of recently deployed on- and offshore projects in Brunei BSP. This shows that once certain maturity and robustness in a technology has evolved and an agreement on standards has been implemented low-cost equipment can be designed, manufactured, and deployed even for low-cost wells. The applied design and working practices enable permanent in-well sensing for a large-scale role out. Additionally, a common database has been developed and successfully deployed. The reservoir engineers in BSP have now full access to the low-cost DTS installed wells around the clock, every day of the year.

Offshore Europe 2009 - Meet us in Aberdeen - 8-11 September 2009

LIOS Technology will be exhibiting at Offshore Europe 2009, from 8 till 11 September in Aberdeen, German Pavilion. In this show, we proudly present our full range and latest Distributed Temperature Sensing (DTS) systems for Oil & Gas applications.

See the latest information about our new HT SAGD application (high temperature steam assisted gravity drainage) for Oil & Gas including our new hydrogen resistant fibre rated 300 degree C and our latest auto calibration system.

Please contact us directly at oil@downhole-monitoring.com for more information or to make an appointment.

Visitors are invited to stop by the LIOS stand  No. 1397 b.
LIOS staff will be on hand to answer questions and discuss particular challenges.

Please register for free admission at  http://www.offshore-europe.co.uk/LIOSTechnology

Read more at our  Downhole Monitoring website.

Join us in Cologne - LIOS Festive Head Office Opening Event

LIOS Technology GmbH – Linear Optical Sensors has inaugurated its new head office building at Seiler Höfe, Cologne, Germany with a festive opening event on 27 May 2009. The Power-GEN / POWERGRID Europe trade fair which was held in Cologne this year served as an appropriate occasion for LIOS’ official launch party. The joyful gathering was well attended by customers and partners of LIOS coming from all parts of Europe, Asia and Oceania.

The 1912/13 built warehouses for cable and wire products were recently refurbished and converted into modern office and production space building the ideal showcase for LIOS’ innovative online condition monitoring solutions utilized in modern power management.