WELL TESTING
A method of well testing to determine properties of oil and gas wells 8 comprises: applying oscillations to the flow rate and/or pressure at multiple wells 8 wherein the oscillations applied at different wells of the multiple wells are at different test frequencies; receiving measurements of flow rate in flows downstream of a production header that combines the flows from the multiple wells 8, and/or receiving measurements of pressure and/or temperature from individual wells 8; carrying out a frequency analysis of the pressure, flow rate and/or temperature measurements to determine pressure, flow rate and/or temperature variations induced by the applied oscillations; and determining properties of the different wells 8 of the multiple wells 8 based on the results of the frequency analysis at the test frequencies for the wells 8.