PiPeline ground movement detection – retrofit to monitor unstable terrain

> continuous monitoring for geohazard prevention on the pipeline right-of-way in an inaccessible location

the challenge

Steep slopes and heavy rains resulting in ground movement put mountain pipeline routes at risk.

Pipelines crossing mountains are often more at risk from the weather and geohazards than from corrosion or third party damage. Two major pipelines in Peru are constantly at risk from geohazards. As operator, Compañía Operadora de Gas del Amazonas (COGA) is responsible for the integrity management of the 730 km natural gas (NG) pipeline, running from the upstream facilities at Malvinas to Lurín (south of Lima) and a parallel 560 km natural gas liquid (NGL) pipeline, on behalf of the owners, Transportadora de Gas del Perú (TgP).

The route is particularly challenging, with steep slopes and heavy rains causing soil movement. Between 2004 and 2006 the NGL pipeline experienced four ruptures. Three were due, at least in part, to soil instability, so COGA embarked on an integrity management program

combining established practices with new technologies to address, in particular, threats triggered by the environment.

Two particular sections of the pipeline right-of-way, situated in a remote and inaccessible area, were giving particular concern. To monitor these two critical pipeline sections, COGA installed Omnisens fiber optic ground movement monitoring. The advantages of this system were immediately apparent: it monitors strain and temperature all along the required lengths, continuously and automatically, identifying and locating soil movement events. It is ideal when the efficacy of other techniques is limited by weather conditions.

case study1

methodTo detect ground movement, the Omnisens system uses an optical fiber sensor cable (Strain Measurement Cable –SMC) installed in the vicinity of the pipeline. Small lateral and longitudinal movements, or a combination of the two, caused by a landslide, erosion or seismic activity, cause the strain monitoring cable to elongate.

Transmitted along the sensing cable, the location and amount of this strain (elongation) is calculated by the Omnisens interrogator installed in Pumping Station 2. The data is transferred via TCP/IP to the server at Lurin, several hundreds of kilometers distant, where it is accessed by the integrity engineers. Strain and temperature profiles are available for review.

The two lengths with heightened risk of ground movement, one of 700 m, the other of 300 m, were approximately 30 km apart. To monitor these sections in the most cost effective way, an existing fiber optic communication cable was used to transmit the light signal and data between the Omnisens integrator in Pumping Station 2 and the critical areas. The existing telecom cable was also used by the Omnisens system to monitor temperature, a useful indicator of erosional phenomenon. The only additional installation involved was the provision of a trench for the strain monitoring sensor. A 50 cm wide trench was dug within 2 to 3 meters of the main pipeline trench with the strain monitoring cable installed at a depth of about 1.0 m.

resultsCOGA were able to monitor continuously these two critical yet inaccessible lengths of the pipeline from hundreds of kilometers away.

For example: a strain event around KP126+100 was detected by the Omnisens system. The stress profile showed a peak at 8000 microstrain. Appropriate actions were taken and teams were sent to the correct location to investigate and take remedial action.

The strain detecting sensor is buried on the pipelineright-of-way, as a retrofit.Temperature changes detected by the telecoms cable are also continuously monitored.

~1m

Natural gas liquid pipelineNatural gas pipeline

~2.5m

Pipeline right of way

10000

6000

8000

4000

2000

0

-2000

KP125+400 KP125+600 KP125+800 KP126+000

Stra

in [m

icro

stra

in]

A soil stress profile showing the location of an event where the strain exceeds 8000 microstrain.

KP126+200

Optical fiber

Strain transfer layer

Stainless steel tube

50 cm wide trench forfiber optic sensing cable

case study2

Lima

160 km or 100 miles

Ica

Ayacucho

Pampa Melchorita MachuPicchu

Pumping Station 2

BOLIVIA

SOUTHPACIFICOCEAN

PERU

BRAZIL

Chiquintirca

Campo Malvinas

TGP

Omnisens system installation, showing how the two critical sections (A and B) more than 30 km apart, are monitored usinga single interrogator housed in pump station 2.

BKP125+400

PumpingStation

2

KP091+300 Kp091+000KP126+100

SMC SMC

Telecom OFC Telecom OFCTelecom OFCTelecom OFC

DITESTInterrogator

A 8 km25 km

Pipeline Pipeline

KP: Kilometer PointSMC: Strain Measurement Cable (GroundMovement Detection)Telecom OFC: Telecom Optical FiberCable (Telecommunication and temperature detection)

Sensing fiber cable (Strain)Temperature and return fiber(part of telecom optical fiber cable)

Display

OmnisensSystemServer

Data from DITEST is stored on a server in Lurin, where it is accessed by COGA integrity engineers.

TCP/IP Network

3

Do

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f: C

S-0

11(g

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d m

ove

men

t p

ipel

ine

RO

W C

OG

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references: John Malpartida Moya, Edward Francisco Oliveros Montes, Giancarlo Massucco De la Sota “Integration of Monitoring and Inspection Systems for Geohazard Assessment on Pipelines that cross Amazonian Jungles and the Andes.” Proceedings of the 2012 9th International Pipeline Conference September 24-28, 2012, Calgary, Alberta, Canada IPC2012-90501

DITEST is a trademark of Omnisens

conclusionCOGA developed the integrity managementsystem in line with the Peruvian national regulationfor hydrocarbon transmission, (DS 081-2007-EM)following the guidelines in API 1160 and ASMEB31.8S. The range of techniques used for the pipelineintegrity management is carefully evaluated andcomplimentary.

A soil/pipeline interaction model correlates the strain information from monitoring techniques and enables pipeline deformation to be estimated. All information is fed into a Geographic Information System, with the goal of completing the system risk assessment using a particular risk algorithm developed for the actual pipeline system.

By integrating inspections and monitoring systems, including the Omnisens Ground Movement Detection system, as part of Pipeline Integrity Management, the operator is able to act early in the chain of potentially critical events, mitigating and/or minimizing the possibility of failures. The risks to integrity of the system, people, the environment and the business are thus minimized.

Laying the strain sensing cable in its trench.

case study

omnisensContact us and details of local distributor can be found at:www.omnisens.comsales@omnisens.com

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