System and method for measuring well flow rate

A method for determining a fluid flow rate from a fluid producing subterranean wellbore where a pump is provided to remove fluid from the wellbore, comprising the steps of:

• providing a mechanism for measuring a depth of a top of a column of fluid in an annulus of a subterranean wellbore;
• determining an annular area of at least the fluid containing portion of the wellbore as a function of depth;
• measuring the depth of the top of the column of fluid in the annulus over time while the pump is not operating;
• calculating an annular build-up flow rate over time as a function of the change in the depth of the top of the column of fluid while the pump is not operating and of the annular area;
• providing a standing valve leak rate greater than or equal to zero;
• calculating a reservoir flow rate as the difference between the annular build-up flow rate and standing valve leak rate;
• measuring the depth of the top of the column of fluid in the annulus over time while the pump is operating;
• calculating an annular drawn-down flow rate as a function of a change in the depth of the top of the column of fluid over time while the pump is operating and of the annular area;
• and,
• calculating a pump rate as the sum of an annular drawn-down flow rate and a reservoir flow rate.