S.M. Shah

Three-dimensional imaging of porous media using confocal laser scanning microscopy

In the last decade, imaging techniques capable of reconstructing three‐dimensional (3‐D) pore‐scale model have played a pivotal role in the study of fluid flow through complex porous media. In this study, we present advances in the application of confocal laser scanning microscopy (CLSM) to image, reconstruct and characterize complex porous geological materials with hydrocarbon reservoir and CO2 storage potential. CLSM has a unique capability of producing 3‐D thin optical sections of a material, with a wide field of view and submicron resolution in the lateral and axial planes. However, CLSM is limited in the depth (z‐dimension) that can be imaged in porous materials. In this study, we introduce a ‘grind and slice’ technique to overcome this limitation. We discuss the practical and technical aspects of the confocal imaging technique with application to complex rock samples including Mt. Gambier and Ketton carbonates. We then describe the complete workflow of image processing to filtering and segmenting the raw 3‐D confocal volumetric data into pores and grains. Finally, we use the resulting 3‐D pore‐scale binarized confocal data obtained to quantitatively determine petrophysical pore‐scale properties such as total porosity, macro‐ and microporosity and single‐phase permeability using lattice Boltzmann (LB) simulations, validated by experiments.

Preparation of microporous rock samples for confocal laser scanning microscopy

In this paper we describe an improved sample-preparation technique for applying confocal laser scanning microscopy to image the void space of porous geological media, particularly various kinds of carbonate rocks with significant microporosity. We have improved the existing sample-preparation technique for confocal imaging by introducing a positive-pressure application step. This additional step helps to force the fluorescent-doped epoxy mixture inside the submicron pores (the microporosity) which make up a significant fraction of the total porosity of the carbonate rocks being characterized using confocal laser scanning microscopy. We also provide additional technical details and discuss practical aspects important to consider when imaging carbonate rock samples using this technique.