Among the principal challenges of the twenty-first century are how to secure access to clean water for drinking and agriculture, and how to provide sufficient energy for a growing and hopefully more prosperous population, while coping with the threat of climate change. The economics and social aspects of these challenges have a common scientific underpinning: flow in porous media. The majority of the world's freshwater resides underground in aquifers; most of our energy comes from oil and gas extracted from porous rock; and one promising method to reduce atmospheric emissions of carbon dioxide is to collect it from major sources, such as fossil-fuel burning power stations, and inject it deep underground into saline aquifers or depleted hydrocarbon reservoirs. Indeed, global-scale carbon dioxide storage is necessary if we are to avoid dangerous climate change. In any event, the understanding and management of fresh water, oil and gas recovery and carbon dioxide storage all rely on quantifying how fluids flow through porous rocks.

The emphasis in this book is on multiphase flow and applications in hydrocarbon recovery, geological carbon dioxide storage and contaminant transport, as mentioned above. However, the basic principles are relevant to many other applications in science and engineering, including in fuel cells, membranes and biological systems.

The material will focus on the physics of fluid displacement at the pore scale in geological systems, meaning that we will be concerned with the scale of the interstices between solid grains, or the size of void spaces in the rock that is typically of the order of microns (μm). It is the behaviour at this scale that plays a key role in determining the overall movement of the fluids and how much can be recovered.

In combination with the huge practical applications that drive the science, two recent advances have transformed our understanding of how fluids move at the pore scale: the development of methods to image rocks, the pore space and the fluids within them, in three dimensions at a resolution from nanometres to centimetres; and the availability for good public-domain software for solving flow and transport problems.