Sensing sub-assembly and method of operating a hydraulic fracturing system

Abstract

A sensing sub-assembly for use with a drilling assembly that includes a cylindrical body including an internal flow channel extending therethrough. The internal flow channel is configured to channel a first fluid therethrough. A recessed cavity is also defined therein. The recessed cavity is coupled in flow communication with an ambient environment exterior of the cylindrical body, and a second fluid flows within the ambient environment. The recessed cavity is configured to receive a continuous stream of the second fluid therethrough. At least one sensor is coupled to the cylindrical body, and the at least one sensor is configured to determine characteristics of the second fluid in the continuous stream that flows through the recessed cavity.

What is claimed is: 
     
         1 . A sensing sub-assembly for use with a drilling assembly, said sensing sub-assembly comprising:
 a cylindrical body comprising:
 an internal flow channel extending therethrough, said internal flow channel configured to channel a first fluid therethrough; and 
 a recessed cavity defined therein, said recessed cavity coupled in flow communication with an ambient environment exterior of said cylindrical body, wherein a second fluid flows within the ambient environment, and said recessed cavity is configured to receive a continuous stream of the second fluid therethrough; and 
   at least one sensor coupled to said cylindrical body, said at least one sensor configured to determine characteristics of the second fluid in the continuous stream that flows through said recessed cavity.   
     
     
         2 . The sensing sub-assembly in accordance with  claim 1 , wherein said cylindrical body further comprises a flow inlet and a flow outlet defined therein, wherein said flow inlet is configured to channel the continuous stream of the second fluid into said recessed cavity, and said flow outlet is configured to discharge the continuous stream of the second fluid from said recessed cavity. 
     
     
         3 . The sensing sub-assembly in accordance with  claim 1 , wherein said at least one sensor comprises a first pair of sensors comprising a first sensor and a second sensor, said first sensor positioned for determining characteristics of the first fluid within said internal flow channel, and said second sensor positioned for determining characteristics of the second fluid within said recessed cavity. 
     
     
         4 . The sensing sub-assembly in accordance with  claim 3 , wherein said at least one sensor comprises a second pair of sensors, said first pair of sensors configured to operate at a different frequency than said second pair of sensors. 
     
     
         5 . The sensing sub-assembly in accordance with  claim 4 , wherein said second pair of sensors comprises a third sensor and a fourth sensor, said third sensor positioned for determining characteristics of the first fluid within said internal flow channel, and said fourth sensor positioned for determining characteristics of the second fluid within said recessed cavity. 
     
     
         6 . The sensing sub-assembly in accordance with  claim 4 , wherein said second pair of sensors comprises a fifth sensor and a sixth sensor, said fifth sensor and said sixth sensor longitudinally spaced from each other within said recessed cavity. 
     
     
         7 . The sensing sub-assembly in accordance with  claim 1 , wherein said recessed cavity is defined by a circumferential indent extending about said cylindrical body such that said recessed cavity is exposed to the ambient environment. 
     
     
         8 . The sensing sub-assembly in accordance with  claim 7 , wherein said cylindrical body further comprises a plurality of longitudinal members arranged circumferentially within said circumferential indent. 
     
     
         9 . The sensing sub-assembly in accordance with  claim 8 , wherein said at least one sensor is circumferentially offset from adjacent pairs of longitudinal members of said plurality of longitudinal members. 
     
     
         10 . The sensing sub-assembly in accordance with  claim 1 , wherein said at least one sensor comprises at least one of an ultrasound sensor and an acoustic sensor. 
     
     
         11 . A method of operating a hydraulic fracturing system, said method comprising:
 advancing a drilling assembly within a subterranean rock formation, wherein the drilling assembly is configured to discharge a first fluid into the subterranean rock formation, and wherein a second fluid flows past an exterior of the drilling assembly;   channeling a continuous stream of the second fluid through at least a portion of the drilling assembly; and   determining characteristics of the second fluid in the continuous stream channeled through the drilling assembly.   
     
     
         12 . The method in accordance with  claim 11  further comprising identifying fracture initiation locations within the subterranean rock formation based on the characteristics of the second fluid in the continuous stream. 
     
     
         13 . The method in accordance with  claim 12 , wherein identifying fracture initiation locations comprises:
 determining, with a first sensor of a first pair of sensors, characteristics of the first fluid;   determining, with a second sensor of the first pair of sensors, characteristics of the second fluid in the continuous stream; and   comparing the characteristics of the first fluid to the characteristics of the second fluid in the continuous stream.   
     
     
         14 . The method in accordance with  claim 13  further comprising operating the first sensor and the second sensor at the same frequency. 
     
     
         15 . The method in accordance with  claim 14 , wherein operating the first sensor and the second sensor comprises operating the first sensor and the second sensor at a frequency defined within a range between and including about 100 kilohertz and 20 megahertz. 
     
     
         16 . The method in accordance with  claim 13  further comprising determining, with a second pair of sensors, characteristics of the second fluid in the continuous stream, wherein the first pair of sensors are configured to operate at a first frequency and the second pair of sensors are configured to operate at a second frequency different from the first frequency. 
     
     
         17 . The method in accordance with  claim 16  further comprising operating the second pair of sensors at the second frequency defined within a range between and including about 10 kilohertz and about 20 kilohertz. 
     
     
         18 . The method in accordance with  claim 13  further comprising:
 determining, with a third sensor of a third pair of sensors, characteristics of the first fluid; and 
 determining, with a fourth sensor of the third pair of sensors, characteristics of the second fluid in the continuous stream, wherein the first pair of sensors are configured to operate at a first frequency and the third pair of sensors are configured to operate at a third frequency different from the first frequency. 
 
     
     
         19 . The method in accordance with  claim 11 , wherein determining characteristics of the second fluid comprises determining characteristics of the second fluid with at least one of an ultrasound signal and an acoustic signal. 
     
     
         20 . The method in accordance with  claim 19 , wherein determining characteristics of the second fluid comprises determining a hydrocarbon content of the second fluid based on changes in sound speed of the at least one of the ultrasound signal and the acoustic signal through the second fluid.