This is a part of the continuing series of technical talks that I post on Sundays, and which can be found by clicking on the tech talk link at the top of the main page. Gradually these are getting a little more technical, so I would suggest if you are new to these that you start at the beginning and work your way up.

Having recently written about sandstones and permeability, and then about water flooding, I want to go on, this time to talk about carbonate rocks, as the general topic and secondary porosity, with some comments at the end on formations in chalk and the problems that this can bring to places such as Ekofisk. (Added for clarity - when I talk about carbonates I mean calcium carbonate and the related rocks such as limestone, chalk and dolomite, to name but three.) I again want to emphasize that, life being what it is, the true situation is often a bit more complex than I describe in this simplistic overview, and that I am very grateful when folk give more specific information about some of their experiences in the field.