Patent ID: 7460438

Claim:
A method of downhole data communication in a producing well in which there is a flow path for a flow of produced product from the formation towards the surface, the data communication taking place between two locations in the flow path, at least one of which is downhole in the well, and the method comprising the steps of: collecting the produced product from the formation and causing or allowing the produced product to flow toward the surface; controlling a flow rate of the produced product at a first of the two locations in dependence on data to be transmitted; detecting, at the second of the two locations, the effect of said controlling of the flow rate of the produced product at the first location; and using the results of the detecting step to extract the data transmitted, wherein the step of controlling the flow rate of the produced product at the first of the two locations comprises modulating the flow rate so as to encode said data onto a carrier frequency that is below 0.1 Hz.