Petrophysical database for volcaniclastic rocks (CASP.IVR.1)

There is a need to characterise the petrophysical properties of a variety of volcaniclastic rocks in a consistent manner, so that injectivity rates, CO2 storage potential and sealing capacities can be adequately constrained. As the diagenetic histories of volcaniclastic rocks are complex it is essential to understand the relationship between mineralogy and permeability (and porosity) to determine the potential trade-off between higher reactivity and typically lower permeability with increasing volcanic rock fragments. In addition, the project will evaluate the mineral carbonation potential of the volcaniclastic rocks, which may be a benefit over conventional reservoirs.

Research programme

This project will compile a database of petrophysical properties for at least 100 volcaniclastic rocks with a variety of compositions (e.g. mafic v felsic, subalkaline v alkaline) and textures from different depositional settings (e.g. subaerial, submarine, rifts, subduction zones). The database will incorporate data from a variety of techniques (e.g. point–count data, Poro–Perm, MICP, QXRD) as well as published data where possible. The database will also include whole-rock geochemistry and quantify the abundance of elements (e.g. Ca2+, Mg2+, Fe2+) that will react with CO2 fluids, whilst SEM elemental phase maps (and tabulated data) will characterise textural relationships. A qualitative scheme will be developed to rank the likely impact of the various volcaniclastic rocks on CO2 injection, storage and/or seal capacity. The petrophysical data can be exported for modelling in, for example, Petrel reservoir engineering software, to constrain uncertainties in potential volcaniclastic reservoirs (not undertaken in this study).

Figure 1. Three representative photomircographs of volcaniclastic rocks from the CASP collection. Total Optical Porosities (TOP) calculated using the ImageJ software jPOR macro. Scale bars are 1 mm long.

Deliverables

Results will be delivered via a data release with associated presentation and a final technical report containing the following data for at least 100 volcaniclastic rock samples:

  • Sample information data table
  • Point-count data table
  • Porosity–Permeability data table
  • Qualitative X-ray Diffraction (QXRD) data table
  • Individual and summary Mercury Injection Capillary Pressure (MICP) data tables with CO2 column height data
  • An interactive Excel spreadsheet to adjust MICP parameters to reservoir conditions
  • X-ray Fluorescence (XRF) whole-rock major element data table
  • Inductively Coupled Plasma–Mass Spectrometry (ICP–MS) whole-rock trace element data table
  • Scanning Electron Microscopy–Backscattered Electron (SEM–BSE) and Secondary Electron (SE) imagery
  • Scanning Electron Microscopy–Energy Dispersive X-ray Spectrometry (SEM–EDS) data tables and elemental phase maps

The data will be delivered as individual tables, but also in a PostgreSQL database with a PostGIS extension. The technical report will also explore the interrelationships between the different data types.

Figure 2. A selection SEM-EDS elemental phase maps showing the concentration (brighter the colour the higher the concentration) and distribution of elements in a representative volcaniclastic rock from the CASP collection. Mg, Ca and Fe are liberated from highly reactive volcanic components by carbonic acid, which can then re-precipitate as various carbonate minerals clogging up pore space, but also locking away carbon for increased storage security. Al is shown to delineate mineral components.

Project duration

The project has a planned duration of 15 months.

Contact: Simon Passey for further information about this research and licensing options.

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