Subsurface storage of CO₂ – Injection well management during the operational phase

The project addresses the effects of CO₂-injection on rock properties, with a special focus on the injectivity. The injectivity is a measure of the “easiness” of injection (as the name suggest). The reservoir injectivity is studied with geochemical and geomechanical models. Rock samples from wells drilled at Svalbard are characterized and tested with respect to injectivity. Results from the project will form the basis for development of software tools and for guidelines for CO₂ injection.

So far INJECT has developed and continue to develop models for how a pore fluid may interact with the rock to enhance or reduce injectivity.

This applies in particular to models of hydraulic fracturing. The rock may fracture as a cause of pressure build-up during injection. Hydraulic fracturing may enhance the injectivity, which is a good thing. On the other hand, hydraulic fracturing can also lead to leakage, which will be a problem.

A model of hydraulic fracturing is developed in 2D and it is based on “bond”-strength. An extension of the model to 3D is in progress.
Hydrate sealing have focused on completion of non-equilibrium thermodynamics for nano- to micro scale modelling of hydrate phase transition kinetics (phase field theory). A PhD student at the University of Bergen started 2012, and has been conducting literature survey on modelling of cement/CO₂/water reactions as well as Hematite (rust)/CO₂/water.
Several activities are connected to the Longyearbyen CO₂ laboratory, which includes geomechanical testing and characterisation of the reservoir rocks. Geomechanical testing on cores from wells drilled at the storage site in Longyearbyen has been done at NGI. The primary focus in the study is to test the most important sealing formations (i.e Agardfjell and Rurikfjell, Helvetiafjell and Carolinefjell formations) with respect to geomechanical properties for the purpose of future geological storage of CO₂ at Longyearbyen. This work is performed in coordination with the LYB pilot, and some results are delivered in a separate report (NGI, 2012). Mineral characterisations of the same rocks are done at IFE. Additional sampling of the reservoir section in well Dh2, located about 7 km NW of the Adventdalen, has been performed to evaluate possible correlation/communication with well Dh4 in terms of lithology and Sr residual salt data (RSA data).

The work of the INJECT project will form the basis for decisions of how to build and operate the storage site.