System and Method for Determining Pump Intake Pressure or Reservoir Pressure in an Oil and Gas Well

Abstract

A system includes a controller and a system of valves connected to pipes collecting the well casing gas produced from a casing annulus of the producing well. A pressure sensor measures the pressure of the well casing gas in the casing annulus. The system determines a well casing gas flow rate by measuring a build-up pressure of the well casing gas in a casing annulus when a valve from the casing annulus is closed. A fluid level in the casing of the well is determined using a pressure wave created in the well casing gas using the controller and the one or more valves. A fluid gradient correction factor is found using an actual fluid level in the casing. The controller calculates the pressure using the gas flow rate, the fluid level and the fluid gradient correction factor.

What is claimed is: 
     
         1 . A method for calculating a pressure at a producing well having a fluid level and a well casing gas, the method comprising:
 determining a well casing gas flow rate at the surface of the well by measuring a well casing gas build up pressure in a casing annulus when a valve from the casing annulus is closed;   determining a fluid level in a casing of the well from the surface using a pressure wave created in the well casing gas;   determining a fluid gradient correction factor using an actual fluid level in the casing; and   calculating the pressure using the well casing gas flow rate, the fluid level and the fluid gradient correction factor.   
     
     
         2 . The method of  claim 1 , wherein the pressure is a pump intake pressure. 
     
     
         3 . The method of  claim 1 , wherein the pressure is at any datum in the well. 
     
     
         4 . The method of  claim 1 , wherein the well casing gas flow rate is determined from a plurality of well casing gas flow rate measurements taken over a period of time. 
     
     
         5 . The method of  claim 1 , wherein determining the well casing gas flow rate and the fluid level is done by a combination of valves and a controller associated with the producing well. 
     
     
         6 . The method of  claim 5 , wherein the combination of valves and the controller are permanently mounted to the well. 
     
     
         7 . The method of  claim 5 , wherein the data processing is done remotely from the producing well. 
     
     
         8 . The method of  claim 1 , wherein a factor K is used to calculate the flow rate of the well casing gas. 
     
     
         9 . The method of  claim 1 , wherein the actual fluid level is a fluid level determined without adding gas in the fluid column below the fluid level. 
     
     
         10 . A system for determining a pressure in a producing well having a well casing gas and a well fluid therein, the system comprising:
 a controller associated with the producing well;   one or more valves connected to pipes collecting the well casing gas produced from a casing annulus of the producing well, the one or more valves controlled by the controller; and   a pressure sensor measuring the pressure of the well casing gas in the casing annulus;   wherein the system determines a well casing gas flow rate by measuring a build-up pressure of the well casing gas in a casing annulus when a valve to the casing annulus is closed, the system further determines a fluid level in the casing of the well from using a pressure wave caused in the well casing gas using the controller and the one or more valves, and the system further determines a fluid gradient correction factor using a measured fluid level in the casing; and   further wherein the controller calculates the pressure using the well casing gas flow rate, the fluid level and the fluid gradient correction factor.   
     
     
         11 . The system of  claim 10 , wherein the pressure is a pump intake pressure. 
     
     
         12 . The system of  claim 10 , wherein the pressure is at any datum in the well. 
     
     
         13 . The system of  claim 10 , wherein the well casing gas flow rate is determined from a plurality of well casing gas flow rate measurements taken over a period of time. 
     
     
         14 . The system of  claim 10 , wherein the controller is remote from the producing well. 
     
     
         15 . The system of  claim 14 , wherein the combination of valves and the controller are permanently mounted to the well. 
     
     
         16 . The system of  claim 14 , wherein the combination of valves and the controller are on a mobile platform. 
     
     
         17 . The system of  claim 10 , wherein a factor K is used to calculate the well casing gas flow rate of the well casing gas. 
     
     
         18 . The system of  claim 10 , wherein the actual fluid level is a fluid level determined without adding gas in the fluid column below the fluid level. 
     
     
         19 . A method for calculating a pressure at a producing well having a fluid level and a well casing gas, the method comprising:
 measuring a well casing gas build up pressure in a casing annulus when a valve from the casing annulus is closed;   calculating a well casing gas flow rate at the surface of the well using the well casing gas build up pressure and a factor K based on a ratio of specific heats of the well casing gas;   creating a pressure wave in well casing gas in the casing annulus;   calculating a fluid level in a casing of the well from the surface using the pressure wave created in the well casing gas;   determining a fluid gradient correction factor using an actual fluid level in the casing using a reference curve; and   calculating the pressure using the well casing gas flow rate, the fluid level and the fluid gradient correction factor.   
     
     
         20 . The system of  claim 19 , wherein the actual fluid level is a fluid level determined without adding gas in the fluid column below the fluid level.