Automatic chemical treatment system with liquid level sensor in chemical tank for calibration and chemical dispensing rate control

1. A wellbore chemical treating system, comprising:

a vessel for containing a treating chemical;

a first control valve in fluid communication between an outlet of the vessel and a well for selectively controlling the flow of the chemical from the vessel to the well;

a liquid level sensor disposed in the vessel; and

a controller in signal communication with the liquid level sensor and configured to operate the first control valve, the controller configured to adjust an operating time of first control valve based on differences between a predetermined rate of change in a liquid level and a measured rate of change in the liquid level in the vessel measured by the liquid level sensor over a selected period of time.

2. The system of claim 1 wherein the controller comprises a communication device configured to transmit signals from the liquid level sensor to a remote location.

3. The system of claim 2 wherein an operating time of the first control valve is remotely adjustable.

4. The system of claim 1 wherein the vessel comprises a pressure vessel closed to atmospheric pressure and a pressurized gas located in the pressure vessel, and wherein pressure exerted by the pressurized gas causes the chemical to flow from the pressure vessel to the well through the first control valve.

5. The system of claim 1 further comprising a fluid storage tank in hydraulic communication with the well through a second control valve, the second control valve in signal communication with the controller, and wherein the controller is configured to operate the second control valve to selectively enable flush fluid to enter the well.

6. The system of claim 5 wherein the controller is configured to operate the second control valve for time intervals corresponding to operating times of the first control valve.

7. A method for displacing treatment chemical in liquid form into a well, comprising:

at selected times displacing a selected amount of a treatment chemical into the interior of the well from a storage vessel;

automatically measuring an amount of the treatment chemical in the storage vessel over a selected period of time to determine a measured rate of change in the measured amount of the treatment chemical in the storage vessel; and

comparing a predetermined rate of change of an amount of the treatment chemical in the storage vessel to the measured rate of change in the measured amount of chemical in the storage vessel and adjusting the selected amount of displaced chemical at the selected times based on the comparison.

8. The method of claim 7 wherein the displacing the treatment chemical comprises:

applying compressed gas to an interior of the storage vessel to pressurize the chemical; and

at the selected times opening a valve disposed between the pressurized chemical and the interior of the well, thereby enabling the pressurized chemical to flow into the well.

9. The method of claim 8 further comprising reducing a pressure of the pressurized liquid to a selected amount above a pressure existing in the well.

10. The method of claim 7 further comprising stopping displacing the treatment chemical when an amount of fluid in the storage vessel falls below a selected threshold.

11. The method of claim 7 further comprising enabling a flush fluid to enter the well at selected times.

12. The method of claim 11 wherein the flush fluid selected entry times correspond to the times during which the treatment chemical is displaced into the well.