Method for monitoring or tracing operations in well boreholes

Abstract

The present invention relates to methods for monitoring or tracing a job operation performed in a borehole, such as well boreholes traversing a geological formation. In one embodiment, the methods of the invention include (a) disposing into the borehole, in alternate stages, a neutron absorber during the performance of the job operation; (b) logging the borehole with an instrument capable of measuring a neutron capture in and around the borehole after performance of the job operation; and (c) monitoring or tracing the job operation performed in the borehole by comparing the measured neutron capture with a baseline neutron capture in and around the borehole. The methods of the present invention pose small or no risk from a heath safety and environment perspective and are useful for monitoring or tracing hydraulic fracturing, cementing operation in well boreholes, production logging or subsurface location downhole collars, float shoes and other jewellery.

What is claimed is: 
     
         1 . A method for monitoring or tracing a job operation performed in a borehole, the method comprising:
 (a) disposing into the borehole a neutron absorber during the performance of the job operation;   (b) logging the borehole with an instrument capable of measuring a neutron capture in and wound the borehole after performance of the job operation; and   (c) monitoring or tracing the job operation performed in the borehole by comparing the measured neutron capture with a baseline neutron capture in and around the borehole,   wherein the neutron absorber is disposed into the borehole in alternate stages.   
     
     
         2 . The method of  claim 1 , wherein said method further comprises measuring a gamma radiation response in and around the borehole, and said monitoring or tracing of the job operation is obtained by comparing the measured neutron capture and gamma radiation with a baseline neutron capture and gamma radiation in and around the borehole. 
     
     
         3 . The method of  claim 2 , wherein said method further comprises measuring a natural gamma radiation response in and around the borehole, and said monitoring or tracing of the job operation is obtained by comparing the measured neutron capture and natural gamma radiation with a baseline neutron capture and natural gamma radiation in and around the borehole. 
     
     
         4 . The method of  claim 1 , wherein the instrument is a logging tool, said logging tool including a neutron source and a neutron detector. 
     
     
         5 . The method of  claim 2 , wherein the instrument is a logging tool, said logging tool including a neutron source, a neutron detector and a neutron gamma detector. 
     
     
         6 . The method of  claim 3 , where the instrument is a logging tool, said logging tool including a neutron source, a neutron detector, a neutron gamma detector, and a natural gamma detector. 
     
     
         7 . The method of  claim 5 , wherein the neutron source comprises a geophysical accelerator or a chemical source of neutrons. 
     
     
         8 . The method of  claim 1  characterized in that mid baseline neutron capture is obtained by measuring the neutron capture in and around the borehole before performance of the job operation in the borehole. 
     
     
         9 . The method of  claim 1 , wherein the neutron absorber is added to a fluid carrier used in the performance of the job operation, and wherein said method is a method for monitoring and tracing the fluid used in the job operation. 
     
     
         10 . The method of  claim 10 , wherein said fluid is selected from the group consisting of: proppant slurry, hydraulic fluid, and cement. 
     
     
         11 . The method  claim 1 , wherein the neutron absorber is cadmium, boron or a combination thereof. 
     
     
         12 . The method of  claim 1 , wherein the neutron absorber is boron carbide. 
     
     
         13 . The method of  claim 1 , wherein said job operation is hydraulic fracturing. 
     
     
         14 . The method of  claim 1 , wherein said job operation is cementing operation in well boreholes. 
     
     
         15 . The method of  claim 1 , wherein said job operation is production logging or subsurface location of borehole jewellery. 
     
     
         16 . The method of  claim 1 , wherein the disposing of stage in which the neutron absorber is disposed into the borehole be followed by a stage in which the neutron absorber is not disposed into the well borehole. 
     
     
         17 . A method of profiling, monitoring or tracing the relative depth of fractures created in a formation during hydraulic fracturing of a borehole, the method comprising:
 (a) disposing into die borehole a neutron absorber during die hydraulic fracturing of the borehole;   (b) measuring a neutron capture in and around the borehole after the hydraulic fracturing;   (c) measuring a gamma radiation response in ad around the borehole after the hydraulic fracturing; and   (d) profiling, monitoring or tracing the relative depth of fractures created by the hydraulic fracturing by comparing the measured neutron capture and gamma radiation with a baseline neutron capture and gamma radiation in and around the borehole.