Method For Evaluating Hydraulic Fracturing

Abstract

A method for evaluating hydraulic fracturing places distinctive tracers in each of the fractured regions around a number of production wellbores. For example, these tracers can by carried in the fracking fluid. Preferably, the tracers are embedded in the proppant material carried by the fracking fluid to more accurately reflect the extent of the resulting fractures. An observation wellbore is then drilled to transect these fractured regions in series. As drilling progresses into each fractured region, the distinctive tracer for that fractured region can be recovered in the observation wellbore. This information can be used to determine the location and extent of the fractured regions. Gaps or regions of overlap between adjacent fractured regions can also be identified. In addition, the observation wellbore allows other types of evaluation of the fractured regions, such as visual inspection of fractures by camera.

We claim: 
     
         1 . A method for evaluating hydraulic fracturing in fractured regions around a plurality of production wellbores, said method comprising:
 placing distinctive tracers in each of the fractured regions;   drilling an observation wellbore to transect the fractured regions in series;   recovering the tracer for each fractured region in the observation wellbore as the observation wellbore is drilled into each fractured region; and   determining the extent of the fractured regions based on the recovered tracers in the observation wellbore.   
     
     
         2 . The method of  claim 1  further comprising identifying gaps between adjacent fractured regions based on the recovered tracers in the observation wellbore. 
     
     
         3 . The method of  claim 1  further comprising identifying regions of overlap between adjacent fractured regions based on the recovered tracers in the observation wellbore. 
     
     
         4 . The method of  claim 1  wherein the tracers are embedded in proppant material carried by fracking fluid used in hydraulic fracturing to produce the fractured regions. 
     
     
         5 . The method of  claim 1  wherein the fractured regions are aligned in a predetermined pattern. 
     
     
         6 . The method of  claim 5  wherein the fractured regions are in a linear arrangement. 
     
     
         7 . The method of  claim 1  wherein the observation wellbore is drilled to transect the fractured regions at varying distances from the production wellbores to observe the variation in fracture intensity. 
     
     
         8 . The method of  claim 1  further comprising providing a camera in the observation wellbore to enable visual inspection of fractures encountered in the fractured regions. 
     
     
         9 . The method of  claim 1  further comprising tracking the flow of subterranean fluids carrying the tracers, based on the recovered tracers in the observation wellbore. 
     
     
         10 . A method for evaluating hydraulic fracturing in fractured regions around a plurality of production wellbores, said method comprising:
 placing distinctive tracers in each of the fractured regions;   drilling an observation wellbore to transect the fractured regions in series;   recovering the tracer for each fractured region in the observation wellbore as the observation wellbore is drilled into each fractured region; and   identifying gaps and regions of overlap between adjacent fractured regions based on the recovered tracers in the observation wellbore.   
     
     
         11 . The method of  claim 10  wherein the tracers are embedded in proppant material carried by fracking fluid used in hydraulic fracturing to produce the fractured regions. 
     
     
         12 . The method of  claim 10  wherein the fractured regions are aligned in a predetermined pattern. 
     
     
         13 . The method of  claim 10  wherein the observation wellbore is drilled to transect the fractured regions at varying distances from the production wellbores to observe the variation in fracture intensity. 
     
     
         14 . The method of  claim 10  further comprising providing a camera in the observation wellbore to enable visual inspection of fractures encountered in the fractured regions. 
     
     
         15 . The method of  claim 10  further comprising tracking the flow of subterranean fluids carrying the tracers, based on the recovered tracers in the observation wellbore.