System and method for modeling shale discontinuity

Abstract

A method and system of locating discontinuities in a reservoir are provided. The method includes identifying a plurality of injection and production sites in the reservoir, injecting fluid into selected injection sites in accordance with an injection schedule, monitoring an output at the production sites, determining a time delay between the injection sites and the production sites based on the monitored output, and determining a location of discontinuities based on the determined time delay.

1 . A method of locating discontinuities in a reservoir, comprising:
 identifying a plurality of injection and production sites in the reservoir;   injecting fluid into selected injection sites in accordance with an injection schedule;   monitoring an output at the production sites;   determining a time delay between the selected injection sites and the production sites based on the monitored output; and   determining a location of discontinuities based on the determined time delay.   
     
     
         2 . The method according to  claim 1 , wherein determining the time delay comprises determining the time delay using a forward/backward iterative procedure. 
     
     
         3 . The method according to  claim 1 , wherein determining the location of discontinuities comprises using a tomographic method and the determined time delay. 
     
     
         4 . The method according to  claim 3 , wherein using the tomographic method includes reconstructing an interior velocity model with a rock formation based on measured arrival times between a transmitter and a receiver. 
     
     
         5 . The method according to  claim 4 , wherein the velocity model captures physical properties of a region of the rock formation where a transmitted signal propagates, the transmitted signal including a seismic wave, an acoustic wave, or a fluid pressure wave. 
     
     
         6 . The method according to  claim 1 , further comprising closing selected production sites that are in a common layer with the selected injection sites to force the injected fluid to flow between different layers. 
     
     
         7 . The method according to  claim 1 , wherein determining the time delay between the injection sites and the production sites based on the monitored output comprises:
 calculating a first time delay based on initial locations of discontinuities that are based on initial reservoir model;   determining whether or not a difference between the calculated first time delay and a measured time delay is smaller than a set threshold;   if the difference is smaller than the set threshold, then the initial reservoir model is used to determine the locations of the discontinuities.   
     
     
         8 . The method according to  claim 7 , wherein determining the time delay further comprises:
 if the difference is greater than the set threshold, updating the initial reservoir model based on the difference;   calculating a second time delay based on the updated reservoir model; and   determining whether or not a difference between the second time delay based on the updated reservoir model and the measured time delay is smaller than the threshold.   
     
     
         9 . The method according to  claim 8 , wherein the updating of reservoir model, the calculating of the second time delay and the determining whether or not the difference between the calculated second time delay based on the updated reservoir model is repeated until the difference between the calculated second time delay and the measured time delay is smaller than the set threshold. 
     
     
         10 . The method according to  claim 7 , the set threshold is equal to approximately one percent to 5 percent of the measured time delay. 
     
     
         11 . A system for locating discontinuities in a reservoir, comprising:
 a processor configured to:   determine a time delay between injection sites and production sites in a the reservoir based on monitored output at the production sites from injecting fluid to selected injection sites in accordance with an injection schedule; and   determine a location of discontinuities based on the determined time delay.   
     
     
         12 . The system according to  claim 11 , wherein the processor is configured to determine the time delay using forward/backward iterative procedure. 
     
     
         13 . The system according to  claim 11 , wherein the processor is configured to determine the location of discontinuities using a tomographic method and the determined time delay. 
     
     
         14 . The system according to  claim 13 , wherein the tomographic method includes reconstructing an interior velocity model with a rock formation based on measured arrival times between a transmitter and a receiver. 
     
     
         15 . The system according to  claim 14 , wherein the velocity model captures physical properties of a region of the rock formation where a transmitted signal propagates, the transmitted signal including a seismic wave, an acoustic wave, or a fluid pressure wave. 
     
     
         16 . The system according to  claim 1 , wherein the processor is configured to:
 calculate a first time delay based on initial locations of discontinuities that are based on initial reservoir model;   determine whether or not a difference between the calculated first time delay and a measured time delay is smaller than a set threshold;   if the difference is smaller than the set threshold, then the initial reservoir model is used to determine the locations of the discontinuities.   
     
     
         17 . The system according to  claim 16 , wherein the processor is configured to:
 update the initial reservoir model based on the difference, if the difference is greater than the set threshold;   calculate a second time delay based on the updated reservoir model; and   determine whether or not a difference between the second time delay based on the updated reservoir model and the measured time delay is smaller than the threshold.   
     
     
         18 . The system according to  claim 17 , wherein the processor is configured to repeat the updating of reservoir model, the calculating of the second time delay and the determining whether or not the difference between the calculated second time delay based on the updated reservoir model until the difference between the calculated second time delay and the measured time delay is smaller than the set threshold. 
     
     
         19 . The system according to  claim 16 , the set threshold is equal to approximately one percent to 5 percent of the measured time delay.