Well in a geological structure

Abstract

A well () in a geological structure, the well () comprising a first casing string () with a second casing string () partially inside, and a third casing string () partially inside the second casing string (). A first inter-casing annulus () is defined between the first () and second casing strings (), and a second inter-casing annulus () is defined between the second () and third casing strings (). A primary fluid flow control device (), such as a wirelessly controllable valve, on the second casing provides () fluid communication between the first inter-casing annulus () and the second inter-casing annulus (); and a secondary fluid flow control device (), such as a second wirelessly controllable valve, on the third casing string () provides fluid communication between the second inter-casing annulus () and a bore of the third casing (). In the event of a 'blow-out', a kill fluid can then be introduced into an annulus and the fluid flow control devices used to allow the kill fluid to cascade down the well to control it. Accordingly, the time taken to drill a relief well may be mitigated or obviated which can reduce the time and cost to control the well and can mitigate environmental impact of hydrocarbon loss caused by the blow-out.