Method of removing wellbore fluid from well and water removal well

Abstract

A method for removal of fluid from a subterranean formation is provided, the method including the steps of: providing a wellbore from the surface to within the formation: providing a pump in the wellbore capable of removing fluid from the wellbore to a surface location; establishing a pump performance function as pump curves; measuring at least one variable that establishes where the pump is operating on the pump curve; determining the differential pressure across the pump from the measured variable and the digital power and the flow rate; determining the suction side pressure from the differential pressure across the pump and the vertical height of the annular fluid column of the fluid column above the pump; determining the suction side fluid level from the suction side pressure and the fluid density.

What is claimed is: 
     
         1 . A method for removal of fluid from a subterranean formation comprising the steps of:
 providing a wellbore from the surface to within the formation:   providing a pump in the wellbore capable of removing fluid from the wellbore to a surface location;   establishing a pump performance function as pump curves;   measuring at least one variable that establishes where the pump is operating on the pump curve;   determining a differential pressure across the pump from the at least one measured variable;   determining a pressure of liquid pumped by the electric driven pump at a know height of the annular fluid column above the suction of the electric driven pump;   determining a height of the annular fluid column of liquid above the suction of the pump from the differential pressure across the pump, the know height of the annular fluid column above the suction of the electric driven pump, and the pressure of liquid pumped by the electric driven pump at a know height of the annular fluid column above the suction of the electric driven pump.   
     
     
         2 . The method of  claim 1  further comprising the step of selecting a target height of the annular fluid column of liquid above the suction of the pump to which the pump is to maintain. 
     
     
         3 . The method of  claim 2  further comprising the step of adjusting the output flow rate of the pump to a flow rate which maintains the level of fluid in the wellbore essentially at the target height of the annular fluid column of liquid above the suction of the pump. 
     
     
         4 . The method of  claim 3  wherein the electric pump is a variable speed electric pump and the step of adjusting the output flow rate of the pump is accomplished by adjusting the frequence of electricity to the variable speed electrical pump. 
     
     
         5 . The method of  claim 1  further comprising measuring the pressure in an annulus of the wellbore and determining the height of the annular fluid column of liquid above the suction of the pump from the differential pressure across the pump, the know height of the annular fluid column above the suction of the electric driven pump, and the pressure of liquid pumped by the electric driven pump at a know height of the annular fluid column above the suction of the electric driven pump, and the pressuer in the annulus of the wellbore. 
     
     
         6 . The method of  claim 1  further comprising the step of determining the height of the annular fluid column of liquid above the suction of the pump by independent means in order to calibrate the calculation of the height of the annular fluid column of liquid above the suction of the pump. 
     
     
         7 . The method of  claim 1  further comprising the step of producing methane from the subterranean formation. 
     
     
         8 . The method of  claim 1  wherein the subterranean formation is a coal containing formation. 
     
     
         9 . A wellbore comprising:
 an electric driven pump;   a current measuring device effective to measure the current to the electric driven pump and produce a signal corresponding to the current   a pressure measuring device effective to measure the pressure of liquid pumped by the electric driven pump and produce a signal corresponding to this pressure:   a memory device containing relationships between current, and the head produced by the pump; and   a controller to control the electric driven pump to maintain a predetermined height of the annular fluid column of liquid above the suction of the pump according to the relationship between the current, the variable frequency, and the head produced by the pump and the measured pressure of liquid pumped by the electric driven pump.   
     
     
         10 . The wellbore of  claim 9  further comprising a sensor for measuring methane flow rate from the wellbore wherein the controller resets the predetermined height of the annular fluid column of liquid above the suction of the pump to maximize net profit. 
     
     
         11 . The wellbore of  claim 9  wherein the pump is a variable speed electric driven pump, and the controller controls the frequency of alternating current to the variable speed electric driven pump. 
     
     
         12 . The wellbore of  claim 9  further comprising a control valve in the wellbore fluid production line from the electric driven pump wherein the controller controls the position of the control valve. 
     
     
         13 . The wellbore of  claim 9  further comprising:
 a recycle line from the discharge of the electric driven pump back to the suction of the electric driven pump; 
 a control valve in the recycle line; wherein the controller controls the control valve in the recycle line to maintain the height of the annular fluid column of liquid above the suction of the pump. 
 
     
     
         14 . The wellbore of  claim 13  wherein the controller also controls the valve in the recycle line to maintain a predetermined minimum flow rate of liquids through the electric driven pump.