NCCS Webinar Invitations 28 October 2021

Cement bond push-out tests with exposure to CO2

28 October 2121
13.00 - 13.30

Presenter:

Nils Opedal, SINTEF

Description

The experimental method known as the push-out test was used to assess the shear bond strength for well cement, in contact with rock formations. This is a critical parameter needed for models for planning well construction and abandonment, as cement is used as barrier between the well and the surrounding subsurface formations.

In the work detailed here, we looked at the effect of exposure to different mixtures of CO2 and brine on the cement bond strength. This interface is already the weakest link in well integrity; for CO2 injection wells, as well as for plugged legacy oil and gas wells, it is thus of the utmost importance to quantify any additional weakening as a result of exposure to CO2. This exposure could occur near the well or inside it in case of an unwanted leakage event (also known as sustained casing pressure, if occurring inside the well).

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Effects of plastic deformation on
poroelastic pore pressure coefficients

28 October 2021
13.30 - 14.00

Presenter:

Marcin Duda, NTNU

Description

This presentation contains extracts from our work on the relationship between the undrained pore pressure response to stress changes and plastification of a transversely isotropic (TI) medium, such as shales.

We present results of laboratory experiments indicating strong correlation between the values of the poroelastic parameters and the ratio between elastic and total axial strains, a relationship that can prove to be very useful in modelling of pore pressure response in shales in the direct proximity of faults.

Finally, we show a case of transition of unloading-induced pore pressure change from negative to positive values in the constant mean stress conditions, as well as gradual deviation of shale behavior from the one expected for a medium with purely elastic TI symmetry.