Estimation of Formation Properties by Analyzing Response to Pressure Changes in a Wellbore

Abstract

A system and method for estimating properties of a hydrocarbon-producing formation includes varying the pressure in one or more first wellbores and analyzing the effect of the pressure variations in one or more second wellbores. The analysis may be accomplished by applying the pressure variations at varying timescales to enable the testing of multiple paths through the formation at the same time. The analysis may be used to estimate properties of the formation and a field that includes multiple well sites or potential well sites. The analysis may be used to enhance the operation of one or more of the wells and to identify potential future well sites.

We claim: 
     
         1 . A method for estimating the properties of a geological formation near a wellbore, the method comprising:
 operating an artificial lift system at a first rate for a first time period to apply a reduced pressure to the wellbore;   operating the artificial lift system at a second rate for a second time period;   monitoring the change of a fluid level in the wellbore over the second time period to estimate a property of the geological formation.   
     
     
         2 . The method of  claim 1 , wherein monitoring the change of a fluid level in the wellbore over the second time period to estimate a property of the wellbore comprises estimating a property selected from the group consisting of formation pressure, permeability, and recoverable reserve. 
     
     
         3 . The method of  claim 1 , further comprising operating the artificial lift system at a third rate during a third time period following the second time period and monitoring the change of a fluid level in the wellbore to estimate a second property of the geological formation. 
     
     
         4 . The method of  claim 1  wherein monitoring the change in fluid level is comprises measuring the fluid height or the measuring pressure of the fluid in the wellbore. 
     
     
         5 . The method of  claim 1 , wherein monitoring the change of a fluid level comprises measuring the level of fluid in the wellbore using a contact sensor. 
     
     
         6 . The method of  claim 1 , wherein monitoring the change of a fluid level comprises measuring the level of fluid in the wellbore using a non-contact sensor. 
     
     
         7 . The method of  claim 1 , further comprising operating an artificial lift system at a third rate from a third time to a fourth time, and monitoring the change in fluid level from the third time to the fourth time to determine a second property of the wellbore. 
     
     
         8 . The method of  claim 1 , further comprising comparing an estimated property of the formation estimated at the second time to the estimated property of the formation estimated at a third time to verify the estimation. 
     
     
         9 . A method for estimating the properties of a geological formation near a first wellbore, the method comprising:
 operating an artificial lift system in a second wellbore for a first time period at a first pressure;   altering the pressure of the second wellbore for a second time period;   monitoring and analyzing a change of a fluid level in the first wellbore during the second time period to estimate a property of the formation.   
     
     
         10 . The method of  claim 9 , wherein altering the pressure of the second wellbore for a second time period comprises increasing the static pressure in the second wellbore using a pressure regulator. 
     
     
         11 . The method of  claim 9 , wherein altering the pressure of the second wellbore for a second time period comprises increasing the pump rate of a submersible pump in the second wellbore. 
     
     
         12 . The method of  claim 9 , wherein monitoring and analyzing a change of the fluid level in the first wellbore during the second time period to estimate a property of the formation comprises estimating a property selected from the group consisting of the porosity of the formation, the density of a fluid from the formation, the resistivity to flow of the formation, formation permeability, and the recoverable reserve of the formation. 
     
     
         13 . The method of  claim 11 , wherein monitoring and analyzing a change of the fluid level in the first wellbore during the second time period to estimate a property of the formation comprises estimating the extent to the first wellbore and second wellbore are fluidly coupled to the same geological formation. 
     
     
         14 . The method of  claim 11 , further comprising monitoring and analyzing a second change of fluid in a third wellbore during the second time period to determine a property of the formation. 
     
     
         15 . The method of  claim 14 , further comprising estimating the extent to which the first wellbore, second wellbore, and third wellbore are coupled through the formation. 
     
     
         16 . A system for mapping the properties of a geological formation, the system comprising:
 a first wellbore having a pressure adjustment device deployable in a first wellbore;   a sensor for monitoring the fluid level in a second wellbore;   a controller that is operable to communicate with the pressure adjustment device and the sensor, the controller including a memory having instructions for:
 varying the pressure in the first wellbore from a first time period to a second time period; 
 analyzing the change of a fluid level in the second wellbore over the second time period in response to the change in pressure in the first wellbore; and 
 estimating a property of a geological formation between the first wellbore and second wellbore based on said analyzing. 
   
     
     
         17 . The system of  claim 16 , wherein the pressure adjustment device comprises a submersible pump and wherein varying the pressure comprises changing the pump rate of the submersible pump. 
     
     
         18 . The system of  claim 17 , wherein changing the pump rate of the submersible pump comprises stopping the pump. 
     
     
         19 . The system of  claim 16 , wherein estimating a property of the geological formation comprises estimating a property selected from the group consisting of the porosity of the formation, the density of a fluid extracted from the formation, the resistivity to flow of the formation, the formation pressure, the formation permeability, and the formation's recoverable reserve. 
     
     
         20 . The system of  claim 16  further comprising a second sensor deployable in a third wellbore and operable to monitor the fluid level in the third wellbore and a second pressure adjustment device for varying the pressure in the third wellbore, wherein the memory further comprises instructions for:
 varying the pressure in third wellbore using the second pressure adjustment device from a third period to a fourth time period; 
 analyzing the change of a fluid level in the third wellbore over the second time period in response to the change in pressure in the first wellbore; 
 analyzing the change of a fluid level in the second wellbore over the fourth time period in response to the change in pressure in the third wellbore; and 
 estimating a property of a geological formation between the first wellbore and third wellbore and between the second wellbore and third wellbore based on said analyzing.