Interaction between solid, liquid and biological components of the natural porous media - an experimental approach

The subsurface porous media is typically composed of solid, liquid and biological components. The storage capacity and deliverability of the resources through this media is mainly dictated by the interaction between these components and by the by-products of the complex interactions. For example, when a sand grain is coated by a micrometre-scale very fine grained material (such as detrital clay), other blocky minerals cannot precipitate on the grain. This simple process keeps the pore network open and allows fluids to flow through the pores. Although this relationship is well known, the clay coating mechanism is not fully understood. Over few decades, electrostatic forces are accepted to be the main process of attaching micrometre-scale clay particles to sand grains. Recent observations, however, show that biological control (mostly biofilms) has a significant input to the process and should be investigated in detail.

This PhD study targets the commonly overlooked component of porous media and investigates the interaction of biofilms with other components with an experimental approach. By doing this, the study aims to develop a better understanding of the evolution of the porous media, which in turn provide a valuable input to resource management, exploration and infrastructure design.

The study will investigate the topic in various scales ranging from molecular to microscopic to regional/basinal scale as outline below.

* The interaction of biofilms with two selected solid components of the porous media (sand grain and clay particles) and the contribution of important ecological factors (e.g. pH, salinity, TOC) will be investigated by controlled laboratory experiments using naturally-derived microbial communities. The community composition associated with sand grains (biofilm) and liquid phase (free-living) will be analysed by DNA sequencing (using phylogenetic marker genes).

* The sand-clay-biofilm interaction will be assessed by imaging techniques (e.g. confocal-laser scanning and scanning electron microscopy). The results from laboratory experiment, will be used to characterised sand-clay-biofilm interaction in various natural environments (including recent surface and ancient subsurface examples) using similar analytical techniques.

* The spatial distribution of clay coated grains in reservoirs (basin scale) and the controls on this distribution will be studied in the context of sedimentology and pore-scale reservoir quality evolution.