Ultra-high Resolution Distributed Strain Sensing based on Phase-OTDR

This paper describes the method of identifying typical defects of bored cast-in-situ piles when instrumenting using Distributed Optical Fiber Strain Sensing (DOFSS). The DOFSS technology is based on Brillouin Optical Time Domain Analyses (BOTDA), which has the advantage of recording continuous strain profile as opposed to the conventional discrete based sensors such as Vibrating Wire strain gauges. In pile instrumentation particularly, obtaining distributed strain profile is important when analysing the load-transfer and shaft friction of a pile, as well as detecting any anomalies in the strain regime. Features such as defective pile shaft necking, discontinuity of concrete, intrusion of foreign matter and improper toe formation due to contamination of concrete at base with soil particles, among others, may cause the pile to fail. In this study, a new technique of detecting such defects is proposed using DOFSS technology which can potentially supplement the existing non-destructive test (NDT) methods. Discussion on the performance of instrumented piles by means of maintained load test are also presented

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Distributed Strain Sensing in der Geotechnik - Teil 2

Bautechnik ◽

10.1002/bate.201800039 ◽

2018 ◽

Vol 95 (9) ◽

pp. 653-657

Author(s):

Arne Kindler ◽

Stephan Großwig ◽

Thomas Pfeiffer

Keyword(s):

Strain Sensing ◽

Distributed Strain

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Apodised fibre Bragg grating arrays for quasi-distributed strain sensing

Conference Proceedings. LEOS'98. 11th Annual Meeting. IEEE Lasers and Electro-Optics Society 1998 Annual Meeting (Cat. No.98CH36243) ◽

10.1109/leos.1998.737898 ◽

2002 ◽

Author(s):

K.E. Chisholm ◽

L.A. Everall ◽

J.A.R. Williams ◽

L. Zhang ◽

I. Bennion

Keyword(s):

Bragg Grating ◽

Fibre Bragg Grating ◽

Strain Sensing ◽

Distributed Strain

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Novel Near-Wellbore Fracture Diagnosis for Unconventional Wells Using High-Resolution Distributed Strain Sensing during Production

SPE Journal ◽

10.2118/205394-pa ◽

2021 ◽

pp. 1-10

Author(s):

Ge Jin ◽

Gustavo Ugueto ◽

Magdalena Wojtaszek ◽

Artur Guzik ◽

Dana Jurick ◽

...

Keyword(s):

Oil And Gas ◽

Fiber Optic ◽

Fracture Network ◽

Production Performance ◽

Hydraulic Fractures ◽

Fracture Aperture ◽

Strain Sensing ◽

Extensional Strain ◽

Cluster Efficiency ◽

Distributed Strain

Summary The characteristics of hydraulic fractures in the near-wellbore region contain critical information related to the production performance of unconventional wells. We demonstrate a novel application of a fiber-optic-based distributed strain sensing (DSS) technology to measure and characterize near-wellbore fractures and perforation cluster efficiency during production. Distributed fiber-optic-based strain measurements are made based on the frequency shift of the Rayleigh scatter spectrum, which is linearly dependent on strain and temperature changes of the sensing fiber. Strain changes along the wellbore are continuously measured during the shut-in and reopening operations of a well. After removing temperature effects, extensional strain changes can be observed at locations around the perforation cluster during a shut-in period. We interpret that the observed strain changes are caused by near-wellbore fracture aperture changes caused by pressure increases within the near-wellbore fracture network. The depth locations of the measured strain changes correlate well with distributed acoustic sensing (DAS) acoustic intensity measurements that were measured during the stimulation of the well. The shape and magnitude of the strain changes differ significantly between two completion designs in the same well. Different dependencies between strain and borehole pressure can be observed at most of the perforation clusters between the shut-in and reopening periods. We assess that this new type of distributed fiber-optic measurement method can significantly improve understanding of near-wellbore hydraulic fracture characteristics and the relationships between stimulation and production from unconventional oil and gas wells.

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