October2006

www.sintef.com

SINTEF Petroleum Research

StrategyWe use 2D (thin section) and 3D (μCT) grain scale image data to perform distinct element model (DEM) simulation of static and dynamic rock behaviour, including the computation of stress-strain behaviour and of stress-dependent wave velocities. We have developed a poromechanical model that combines the effect of pressurised fluids with pore scale deformation.

Experiments on glass beads

Controlled laboratory experiments on uncemented glass beads demonstrated that the distinct element model (PFC - Particle Flow Code - by Itasca) largely reproduces experimental behaviour, both in terms of static loading response and wave velocities.

PETЯUS - Petrophysics Under StressA Research Program at SINTEF Petroleum Research 2002-06

Main objectiveTo predict the stress dependency of mechanical and petrophysical rock properties.

Main deliverableA numerical laboratory that is based on a particle scale description of rocks (from petrographical analysis). This permits the computation of mechanical and petrophysical rock properties as function of external stress and pore pressure.

Thin section image

Sandstone Cross section (mCT) Grain partitioning DEM representation

2D DEM

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Senior Scientist R. M. Holt and Research Scientist L. Li

Strain localization

We have used DEM to study strain localization in 2D cemented granular media. The upper picture shows shear bands that were developed at low confinement. Below we see a horizontal compaction band formed at high confining pressure. The green and red lines represent intergranular tensile and shear bond failures while black dots indicate intragranular failures.

Bergen OfficeVisiting address: HøyteknologisenteretThormøhlensgt. 55, 5008 BergenPhone: +47 55 54 39 00Fax: +47 55 54 39 05

Stavanger OfficeVisiting address: Rogaland KunnskapsparkProf. Olav Hanssens vei 7A, 4068 StavangerPhone: +47 51 87 44 00Fax: +47 51 87 44 01

Houston OfficeVisiting address: 11999 Katy Freeway,Suite 490, Houston TX 77079, USAPhone:281-854-2589 (extension #214) Fax: 281-854-2588

SINTEF Petroleumsforskning AS

SINTEF Petroleum Research

Main Office:Postal address: NO-7465 Trondheim, Norway Visiting address: S.P. Andersens vei 15BPhone: +47 73 59 11 00Fax: +47 73 59 11 02E-mail: info@iku.sintef.no

CalibrationA calibration strategy for cemented granular materials has been developed based on controlled experiments on epoxy cemented glass beads. An important part of the calibration process is the estimation of bond strength from a needle scratch test, which was developed as part of this research project.

Contact persons: Rune Martin Holt, rune.holt@sintef.noIdar Larsen, idar.larsen@sintef.noLiming Li, liming.li@sintef.no

Publications11 scientific Papers have been published (8 of them refereed) fully or partly based on results from the PETЯUS project. One PhD Thesis at NTNU has been completed with support from PETЯUS.

The PETЯUS project was supported by The Norwegian Research Council, ConocoPhillips, Norsk Hydro, Petrobrãs, Shell, and Statoil.

Long term deformationUse of a time-dependent contact law between the particles permits estimation of long term deformation properties (creep) based on short term laboratory tests.

Stress-dependent permeabilityAs part of the PETЯUS project we have also performed experimental studies of stress-dependent permeability. The experiments were carried out at isotropic and anisotropic stress conditions. Both external stress and pore pressure were varied during the tests. The NMR response under stress was also investigated.

Needle scratch test Corresponding DEM simulation