4D geomechanics

Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea

A. Jaramillo, M. D. Mangriotis, C. MacBeth

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Since production-induced stress changes in the reservoir lead to deformation and velocity variations in the overburden, understanding the geomechanical behaviour of the caprock has become important for reservoir characterisation. We utilise a semi-analytical Geertsma approach that linearly relates subsurface displacements to geomechanical compacting reservoirs, to invert for reservoir pressure changes from 4D time-strains measured within the overburden shales (Heather, Kimmeridge Clay and Kromer Knoll Gr.) from the Shearwater Field. This solution aims to recover average R-factors from a scaling process where the inverted pressure and the pressure from the simulator predictions are statistically analysed. We validate the technique by generating multiple simulations for several ranges of mechanical properties and forward modelling the inversion results; we found that average R-factor of 4-5 for the shales closely matches both distributions of pressure change. We also demonstrate that the R-values recovered from this method are a function of mechanical properties and lithology, which have significant impact on the computation of realistic time-shift from predicted vertical strain. The inversion method has shown to be an adequate analytical approach for strain and pressure modelling of the reservoir and overburden caprock at Shearwater, improving the current understanding of how shales deformation occur in geomechanically active reservoirs.

Original languageEnglish
Title of host publication81st EAGE Conference and Exhibition 2019
PublisherEAGE Publishing BV
ISBN (Electronic)9789462822894
Publication statusPublished - 3 Jun 2019
Event81st EAGE Conference and Exhibition 2019 - London, United Kingdom
Duration: 3 Jun 20196 Jun 2019

Conference

Conference81st EAGE Conference and Exhibition 2019
CountryUnited Kingdom
CityLondon
Period3/06/196/06/19

Fingerprint

R388
Geomechanics
North Sea
shales
geomechanics
overburden
mechanical property
Mechanical properties
mechanical properties
Lithology
inversions
stress change
reservoir characterization
compacting
forward modeling
lithology
simulator
Simulators
simulators
clays

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Jaramillo, A., Mangriotis, M. D., & MacBeth, C. (2019). 4D geomechanics: Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea. In 81st EAGE Conference and Exhibition 2019 EAGE Publishing BV.
Jaramillo, A. ; Mangriotis, M. D. ; MacBeth, C. / 4D geomechanics : Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea. 81st EAGE Conference and Exhibition 2019. EAGE Publishing BV, 2019.
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Jaramillo, A, Mangriotis, MD & MacBeth, C 2019, 4D geomechanics: Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea. in 81st EAGE Conference and Exhibition 2019. EAGE Publishing BV, 81st EAGE Conference and Exhibition 2019, London, United Kingdom, 3/06/19.

4D geomechanics : Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea. / Jaramillo, A.; Mangriotis, M. D.; MacBeth, C.

81st EAGE Conference and Exhibition 2019. EAGE Publishing BV, 2019.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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AU - Jaramillo, A.

AU - Mangriotis, M. D.

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PY - 2019/6/3

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N2 - Since production-induced stress changes in the reservoir lead to deformation and velocity variations in the overburden, understanding the geomechanical behaviour of the caprock has become important for reservoir characterisation. We utilise a semi-analytical Geertsma approach that linearly relates subsurface displacements to geomechanical compacting reservoirs, to invert for reservoir pressure changes from 4D time-strains measured within the overburden shales (Heather, Kimmeridge Clay and Kromer Knoll Gr.) from the Shearwater Field. This solution aims to recover average R-factors from a scaling process where the inverted pressure and the pressure from the simulator predictions are statistically analysed. We validate the technique by generating multiple simulations for several ranges of mechanical properties and forward modelling the inversion results; we found that average R-factor of 4-5 for the shales closely matches both distributions of pressure change. We also demonstrate that the R-values recovered from this method are a function of mechanical properties and lithology, which have significant impact on the computation of realistic time-shift from predicted vertical strain. The inversion method has shown to be an adequate analytical approach for strain and pressure modelling of the reservoir and overburden caprock at Shearwater, improving the current understanding of how shales deformation occur in geomechanically active reservoirs.

AB - Since production-induced stress changes in the reservoir lead to deformation and velocity variations in the overburden, understanding the geomechanical behaviour of the caprock has become important for reservoir characterisation. We utilise a semi-analytical Geertsma approach that linearly relates subsurface displacements to geomechanical compacting reservoirs, to invert for reservoir pressure changes from 4D time-strains measured within the overburden shales (Heather, Kimmeridge Clay and Kromer Knoll Gr.) from the Shearwater Field. This solution aims to recover average R-factors from a scaling process where the inverted pressure and the pressure from the simulator predictions are statistically analysed. We validate the technique by generating multiple simulations for several ranges of mechanical properties and forward modelling the inversion results; we found that average R-factor of 4-5 for the shales closely matches both distributions of pressure change. We also demonstrate that the R-values recovered from this method are a function of mechanical properties and lithology, which have significant impact on the computation of realistic time-shift from predicted vertical strain. The inversion method has shown to be an adequate analytical approach for strain and pressure modelling of the reservoir and overburden caprock at Shearwater, improving the current understanding of how shales deformation occur in geomechanically active reservoirs.

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Jaramillo A, Mangriotis MD, MacBeth C. 4D geomechanics: Inverting for shales R-factors using seismic time-strains in the shearwater field, central North Sea. In 81st EAGE Conference and Exhibition 2019. EAGE Publishing BV. 2019