CO₂ permeability along fragmented shale interfaces

The integrity of the interface between cement and caprock is a crucial barrier towards leakage from CO₂ storage reservoirs. It is present both in active and abandoned wellbores. The quality of zonal isolation along this interface has normally been studied using defect-free shale rocks, even when it is known that shale fragments/fractures during drilling operations. The fragmenting is caused by a combination of chemical and mechanical effects, such as mud type, mud circulation rate, drillstring rotation and the lack of filter cake formation on the low-permeability shale wall.

To ensure that realistic data on the permeability of the cement-caprock interface in wells can be gathered, this project will use existing experimental equipment available at SINTEF to create shale cylinders with more relevant state of the rock interface, cement them, quantify the quality of the cement bond, and flood CO₂ through the composite samples.

This will give information on: (i) how to minimize fragmenting (e.g. by optimizing circulation rate, drillstring rotation speed or the angle with which the shale is penetrated), (ii) how cement can be optimized to seal against the fragmented shale interface, (iii) how to reliably predict leakage rates through wells penetrating CO₂ storage reservoirs.