Dr Elli-Maria Charalmpidou, Institute of Petroleum Engineering, School of Energy, Geoscience, Infrastructure and Society, Heriot-Watt University

Deformation processes and flow within stressed rocks: a non-conventional lab-scale approach
When Mar 04, 2019
from 02:00 PM to 03:00 PM
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Contact Phone +44 (0) 1865 273030
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Rock deformation processes are of crucial importance for most surface or subsurface engineering applications, in particular when these applications are related to the injection and production of fluids (e.g. geothermal energy extraction, oil and gas extraction, waste disposal or CO2 storage). There is a strong need for field studies to be complemented with lab-scale testing. The latter provides functional information on the mechanical behaviour of the tested material (e.g. E, G, ν). Furthermore, this sort of data are useful input parameters for modelling (e.g. FEM). However, these global measurements (average within the sample’s boundaries) cannot always reveal in detail the micro-processes occurring during frictional sliding and/or brittle faulting of a rock mass, in particular when the rock is heterogeneous – which is a quite common case in the reservoir scale.

Non-destructive full-field testing becomes of great importance to lab-testing since a variety of parameters can be investigated on the very same core. This is very practical especially for limited rock samples coming e.g. from a well. Furthermore, a combined use of non-destructive techniques – with different sensitivity and resolution – can provide 2D, 3D and 4D information and further explain the occurring micro-processes in a range of scales (from cm to 𝜇m). Extrapolating this knowledge to the reservoir scale leads to potentially fewer layers of uncertainty.

This talk will demonstrate how a combined use of non-destructive methods describe processes that take place during frictional sliding and brittle faulting in sedimentary rocks. Methods will include: a) Acoustic Emissions, their related source mechanisms and ultrasonic tomography – all linked to damage sensitivity; b) x-ray CT – related to density variations within the material; neutron tomography – sensitive to the presence of hydrogen and, thus, fluids containing it. Examples will focus on lab-deformed cores and cores with natural heterogeneities (including pre-existing fracture plains). The observed micro-processes on weakly cemented sands (natural and artificially cemented), sandstones, conglomerates and carbonates will be discussed. The correlation of these results can shed further light onto the hydro-chemo-mechanical behaviour of the tested materials (as compared to the conventional stress-strain measurements at the boundaries of the sample) and also offer more detailed information to exploration reservoir scale studies.