Inhibiting Microbial Activity in a Subsurface Formation

Abstract

Systems and methods for injecting a microbial inhibitor into a subsurface formation include a downhole tool including a tool body; a tank disposed within the tool body configured to contain a microbial inhibitor fluid; an injection nozzle fluidly connected to the tank. The injection nozzle can extend from an outer surface of the tool body. An injection pump is coupled to the tank to pump the microbial inhibitor fluid from the tank through the injection nozzle. A sensor is configured to measure a microbial concentration, a hydrogen concentration, or both. An onboard computer system disposed within the tool body is configured to operate the injection pump and the injection nozzle to inject the microbial inhibitor fluid into the subsurface formation in response to measurements from the sensor.

What is claimed is: 
     
         1 . A downhole tool for injecting a microbial inhibitor into a subsurface formation, the downhole tool comprising:
 a tool body;   one or more tanks disposed within the tool body, the one or more tanks configured to contain a microbial inhibitor fluid;   one or more injection nozzles fluidly connected to the one or more tanks, the one or more injection nozzles extending from an outer surface of the tool body;   one or more injection pumps fluidly coupled to the one or more tanks and operable to pump the microbial inhibitor fluid from the one or more tanks through the one or more injection nozzles;   one or more sensors configured to measure a microbial concentration, a hydrogen concentration, or both; and   an onboard computer system disposed within the tool body configured to operate the one or more injection pumps and the one or more injection nozzles to inject the microbial inhibitor fluid into a subsurface formation in response to measurements from the one or more sensors.   
     
     
         2 . The downhole tool of  claim 1 , wherein the one or more injection nozzles comprise sharp tips to penetrate the subsurface formation to inject the microbial inhibitor fluid directly into the subsurface formation. 
     
     
         3 . The downhole tool of  claim 1 , wherein the one or more injection nozzles are attached to one or more hydraulic actuators, the one or more hydraulic actuators operable to move the one or more injection nozzles from a retracted position to an extended position to insert the one or more injection nozzles into the subsurface formation. 
     
     
         4 . The downhole tool of  claim 1 , wherein the one or more sensors comprise a Clark-type hydrogen sensor comprising an internal reference electrode and a sensing anode. 
     
     
         5 . The downhole tool of  claim 4 , wherein the Clark-type hydrogen sensor is electrically coupled with a picoammeter to measure an oxidation current. 
     
     
         6 . The downhole tool of  claim 1 , wherein the onboard computer system is a first onboard computer system, and the downhole tool further comprises a second onboard computer system configured to operate the one or more sensors to determine a microbial concentration level,
 wherein the tool body comprises a downhole portion and an uphole portion, the downhole portion comprises the one or more tanks, the one or more injection pumps, and the first onboard computer system, and the uphole portion comprises the one or more sensors, and the second onboard computer system, and   wherein the first onboard computer system and the second onboard computer system are configured to communicate over a wireless communications network.   
     
     
         7 . The downhole tool of  claim 1 , wherein the one or more injection pumps comprise pressure piston pumps. 
     
     
         8 . The downhole tool of  claim 1 , wherein the onboard computer system is further configured to determine an amount, a rate, and a frequency to inject the microbial inhibitor fluid into the subsurface formation based on the measurements from the one or more sensors. 
     
     
         9 . The downhole tool of  claim 1 , wherein the one or more sensors extend from the outer surface of the tool body toward walls of a wellbore. 
     
     
         10 . A method for operating a downhole tool to inject a microbial inhibitor in a subsurface formation, the method comprising:
 extending one or more injection nozzles from the downhole tool into the subsurface formation; and   injecting a microbial inhibitor into the subsurface formation by operating one or more injection pumps to pump the microbial inhibitor from one or more tanks within the downhole tool through the one or more injection nozzles into the subsurface formation.   
     
     
         11 . The method of  claim 10 , further comprising: measuring a microbial concentration or a hydrogen concentration in a wellbore of the subsurface formation using one or more sensors of the downhole tool. 
     
     
         12 . The method of  claim 11 , further comprising in response to determining that the microbial concentration exceeds a threshold microbial concentration or determining that the hydrogen concentration falls below a threshold hydrogen concentration, injecting the microbial inhibitor into the subsurface formation. 
     
     
         13 . The method of  claim 12 , further comprising determining an amount, a rate, and a frequency to inject the microbial inhibitor into the subsurface formation based on measurements from the one or more sensors. 
     
     
         14 . The method of  claim 11 , wherein the one or more sensors comprise a Clark-type hydrogen sensor comprising:
 an internal reference electrode;   a sensing anode; and   a picoammeter electrically coupled to the internal reference electrode and the sensing anode and operable to measure an oxidation current.   
     
     
         15 . The method of  claim 10 , wherein extending the one or more injection nozzles comprises operating a hydraulic system coupled to the one or more injection nozzles to extend the one or more injection nozzles from a retracted position near an outer surface of the downhole tool to an extended position away from the outer surface of the downhole tool to insert the one or more injection nozzles into the subsurface formation. 
     
     
         16 . The method of  claim 10 , wherein the one or more injection pumps comprise pressure piston pumps. 
     
     
         17 . A downhole tool for injecting a microbial inhibitor into a subsurface formation, the downhole tool comprising:
 a tool body;   a tank disposed within the tool body configured to contain a microbial inhibitor fluid;   an injection nozzle fluidly connected to the tank, the injection nozzle extending from an outer surface of the tool body;   an injection pump fluidly coupled to the tank and operable to pump the microbial inhibitor fluid from the tank through the injection nozzle; and   a sensor operable to measure a microbial concentration, a hydrogen concentration, or both.   
     
     
         18 . The downhole tool of  claim 17 , further comprising:
 a first onboard computer system configured to control the injection pump and the injection nozzle to inject the microbial inhibitor fluid into a subsurface formation; and   a second onboard computer system configured to operate the sensor to determine a microbial concentration level, a hydrogen concentration, or both.   
     
     
         19 . The downhole tool of  claim 18 , wherein the first onboard computer system and the second onboard computer system each comprise a field programmable gated array. 
     
     
         20 . The downhole tool of  claim 19 , wherein the injection nozzle is attached to a hydraulic actuator, the hydraulic actuator operable to move the injection nozzle from a retracted position to an extended position to insert the injection nozzle into the subsurface formation.