Downhole Ball Dropping Systems and Methods with Redundant Ball Dropping Capability

Abstract

A downhole ball dropping system operable to be positioned in a well. The system includes a tool string having a flow path. First and second ball dropper assemblies are interconnected in the tool string. The first ball dropper assembly releasably retains a first ball and the second ball dropper assembly releasably retains a second ball. A sensor is operable to detect deployment of the first ball and is operable to generate a signal to prevent release of the second ball from the second ball dropper assembly.

What is claimed is: 
     
         1 . A downhole ball dropping system operable to be positioned in a well, the system comprising:
 a tool string having a flow path;   a first ball dropper assembly interconnected in the tool string, the first ball dropper assembly releasably retaining a first ball;   a second ball dropper assembly interconnected in the tool string, the second ball dropper assembly releasably retaining a second ball; and   a sensor operable to detect deployment of the first ball and operable to generate a signal to prevent release of the second ball from the second ball dropper assembly.   
     
     
         2 . The downhole ball dropping system as recited in  claim 1  wherein the second ball dropper assembly is positioned downhole of the first ball dropper assembly. 
     
     
         3 . The downhole ball dropping system as recited in  claim 1  wherein the second ball dropper assembly is circumferentially positioned relative to the first ball dropper assembly. 
     
     
         4 . The downhole ball dropping system as recited in  claim 1  wherein the sensor is operable to detect the first ball passing through the flow path after release thereof by the first ball dropper assembly. 
     
     
         5 . The downhole ball dropping system as recited in  claim 4  wherein the first ball further comprises a magnetic device and wherein the sensor detects a change in a magnetic field. 
     
     
         6 . The downhole ball dropping system as recited in  claim 4  wherein the first ball further comprises an RFID tag and wherein the sensor further comprises an RFID reader. 
     
     
         7 . The downhole ball dropping system as recited in  claim 1  wherein the sensor is operable to detect release of the first ball from first ball dropper assembly. 
     
     
         8 . A downhole ball dropping method comprising:
 positioning a downhole ball dropping system in a well, the downhole ball dropping system including a tool string having a flow path, a first ball dropper assembly interconnected in the tool string and releasably retaining a first ball and a second ball dropper assembly interconnected in the tool string and releasably retaining a second ball;   sending a deployment signal to the first ball dropper assembly to release the first ball;   detecting deployment of the first ball with a downhole sensor; and   generating a deactivation signal from the downhole sensor to prevent release of the second ball from the second ball dropper assembly.   
     
     
         9 . The downhole ball dropping method as recited in  claim 8  wherein sending the deployment signal to the first ball dropper assembly to release the first ball further comprises sending a deployment signal selected from the group consisting of a mechanical signal, a pressure signal, an acoustic signal, an optical signal, an electrical signal, a temperature signal, a displacement signal, a time delay signal and combinations thereof. 
     
     
         10 . The downhole ball dropping method as recited in  claim 8  wherein detecting deployment of the first ball with the downhole sensor further comprises detecting the first ball passing through the flow path after release thereof by the first ball dropper assembly. 
     
     
         11 . The downhole ball dropping method as recited in  claim 10  wherein detecting the first ball passing through the flow path after release thereof by the first ball dropper assembly further comprises detecting a change in a magnetic field. 
     
     
         12 . The downhole ball dropping method as recited in  claim 10  wherein detecting the first ball passing through the flow path after release thereof by the first ball dropper assembly further comprises detecting an RFID tag. 
     
     
         13 . The downhole ball dropping method as recited in  claim 8  wherein detecting deployment of the first ball with the downhole sensor further comprises detecting release of the first ball from first ball dropper assembly. 
     
     
         14 . A downhole ball dropping system operable to be positioned in a well, the system comprising:
 a tool string having a flow path;   a first ball dropper assembly interconnected in the tool string, the first ball dropper assembly releasably retaining a first ball;   a first actuation assembly operably associated with the first ball dropper assembly, the first actuation assembly operated responsive to a deployment signal of a first type;   a second ball dropper assembly interconnected in the tool string, the second ball dropper assembly releasably retaining a second ball; and   a second actuation assembly operably associated with the second ball dropper assembly, the second actuation assembly operated responsive to a deployment signal of a second type,   wherein, the deployment signal of the second type is different from the deployment signal of the first type, thereby providing independent and redundant ball deployment capability.   
     
     
         15 . The downhole ball dropping system as recited in  claim 14  wherein the second ball dropper assembly is positioned downhole of the first ball dropper assembly. 
     
     
         16 . The downhole ball dropping system as recited in  claim 14  wherein the second ball dropper assembly is circumferentially positioned relative to the first ball dropper assembly. 
     
     
         17 . The downhole ball dropping system as recited in  claim 14  wherein the deployment signal of the first type and the deployment signal of the second type are each selected from the group consisting of a mechanical signal, a pressure signal, an acoustic signal, an optical signal, an electrical signal, a temperature signal, a displacement signal, a time delay signal and combinations thereof 
     
     
         18 . A downhole ball dropping method comprising:
 positioning a downhole ball dropping system in a well, the downhole ball dropping system including a tool string having a flow path, a first ball dropper assembly interconnected in the tool string and releasably retaining a first ball and a second ball dropper assembly interconnected in the tool string and releasably retaining a second ball;   sending a deployment signal of a first type to the first ball dropper assembly to release the first ball;   determining deployment of the first ball failed; and   sending a deployment signal of a second type to the second ball dropper assembly to release the second ball,   wherein, the deployment signal of the second type is different from the deployment signal of the first type, thereby providing independent and redundant ball deployment capability.   
     
     
         19 . The downhole ball dropping method as recited in  claim 18  wherein determining deployment of the first ball failed further comprises determining deployment of the first ball failed with a downhole sensor. 
     
     
         20 . The downhole ball dropping method as recited in  claim 18  wherein sending the deployment signal of the first type and sending the deployment signal of the second type each further comprises sending a deployment signal selected from the group consisting of a mechanical signal, a pressure signal, an acoustic signal, an optical signal, an electrical signal, a temperature signal, a displacement signal, a time delay signal and combinations thereof