Rate control sequence for diversion treatment

Abstract

A flow rate control sequence for modulating the flow rate at the surface, so as to increase and/or reduce the rate of flow at specific times and increments so that the flow rate of the diverter material downhole is correspondingly reduced or increased such that it enters dominant fractures and avoids entry of marginal fractures. To achieve this, a diversion plan may be developed involving a plurality of planning stages. These stages may include a first overall planning stage, a second downhole planning stage taking into account downhole rate schedule, and the third surface planning stage taking into account parameters at the surface which may impact a diversion plan. Each of these planning stages may be updated or revised based on the results and constraints of other planning stages

What is claimed is: 
     
         1 . A method comprising:
 determining a current flow rate distribution for fractures in a wellbore, the fractures comprising a dominant fracture and a marginal fracture, the dominant fracture receiving fluid at a higher rate from the wellbore than the marginal fracture;   determining a desired flow rate distribution for the fractures in the wellbore; and   determining a flow rate control sequence for injecting a fluid comprising a carrier fluid and a diverter material into an entrance of the wellbore at a surface of the earth to deliver the diverter material into the dominant fracture and avoid delivery of the diverter material into the marginal fracture to transition from the current flow rate distribution to the desired flow rate distribution.   
     
     
         2 . The method of  claim 1 , wherein
 the flow rate control sequence comprises a flow rate decrease adjustment at the entrance of the wellbore such that the diverter material enters the dominant fracture as the divert material passes by the dominant fracture and a flow rate increase adjustment at the entrance of the wellbore such that the diverter material avoids entry into the marginal fracture as the diverter material passes by the marginal fracture without substantially entering the marginal fracture, thereby delivering at least a portion of the diverter material into the dominant fracture at least partially blocking the dominant fracture and avoiding substantial delivery of the diverter material into the marginal fracture.   
     
     
         3 . The method of  claim 1  further comprising:
 determining an amount of a diverter material required to at least partially block the dominant fracture to achieve the desired flow rate distribution. 
 
     
     
         4 . The method of  claim 1  further comprising:
 estimating a concentration of diverter material that enters the dominant fracture based on a transport efficiency of the diverter material in the carrier fluid, the transport efficiency being based on a difference in flow rate between the diverter material and the carrier fluid. 
 
     
     
         5 . The method of  claim 4  wherein the estimating is further based on at least one member selected from the group of a perforation property, perforation orientation, and a diverter material property. 
     
     
         6 . The method of  claim 4  wherein the transport efficiency is defined by the formula: 
       
         
           
             
               
                 R 
                 i 
               
               = 
               
                 
                   
                     C 
                     i 
                   
                    
                   
                     Q 
                     i 
                   
                 
                 
                   
                     C 
                     up 
                   
                    
                   
                     Q 
                     up 
                   
                 
               
             
           
         
         wherein R i  is transport efficiency, 
         C i  is the concentration of the diverter material that will enter into a fracture i, 
         C up  is the concentration upstream of a fracture i, 
         Q i  is the volumetric flow rate of the diverter material into a fracture i, 
         Q up  is the volumetric flow rate of the diverter material upstream of a fracture i, 
         wherein fracture i comprises at least the dominant fracture. 
       
     
     
         7 . The method of  claim 4 , wherein the flow rate sequence comprises determining a flow rate of the diverter material upstream from the dominant fracture for delivering at least a portion of the diverter material into the dominant fracture. 
     
     
         8 . The method of  claim 7 , wherein the dominant fracture is a first dominant fracture, and the wellbore further comprises a second dominant fracture, the second dominant fracture being downstream from the first dominant fracture, each of the first and second dominant fractures receiving fluid at a higher rate from the wellbore than the marginal fracture,
 the determining the flow rate sequence further comprises determining a second flow rate of the fluid upstream from a second dominant fracture but downstream from the first dominant fracture for delivering at least a portion of the diverter material to the second dominant fracture at least partially blocking the second dominant fracture.   
     
     
         9 . The method of  claim 4 , further comprising updating at least one of the rate control sequence or the amount of diverter material required to block the dominant fracture based on the estimated concentration of diverter material that enters the dominant fracture. 
     
     
         10 . The method of  claim 4  wherein the wellbore comprises a plurality of dominant fractures and a plurality of marginal fractures, each of the plurality of dominant fractures receiving fluid at a higher rate from the wellbore than the marginal fractures, and
 the method comprising determining a rate control sequence for each of the plurality of dominant fractures and each of the plurality of marginal fractures, the rate control sequence comprising a flow rate decrease adjustment at the entrance of the wellbore such that a portion of the diverter material enters each of the plurality of dominant fractures as the diverter material passes by each of the plurality of the dominant fractures and a flow rate increase adjustment at the entrance of the wellbore such that the diverter material avoids entry into each of the marginal fractures as the diverter material passes by each of the marginal fractures. 
 
     
     
         11 . The method of  claim 10  wherein the dominant fractures and marginal fractures have perforations arranged in clusters, the flow rate control sequence being based on clusters of the dominant or marginal fractures. 
     
     
         12 . The method of  claim 4 , further comprising determining a concentration of the diverter material injected into the entrance of the wellbore at the surface of the earth based on an effect on the concentration of the diverter as it transports from the surface to at least one of the dominant fracture or the marginal fracture. 
     
     
         13 . The method of  claim 4 , further comprising determining the rate control sequence based on a translational time delay, the translational time delay comprising the time it takes for flow rate change at the entrance of the wellbore to translate to a flow rate change of the diverter material as it passes at least one of the dominant fracture or the marginal fracture in the wellbore. 
     
     
         14 . The method of  claim 4 , wherein the diverter material is injected into the entrance of the wellbore at the surface by pump equipment,
 the method further comprising determining the rate control sequence further based on a delay in a rate command change input to the pump equipment and a change in rate being actuated by the pump equipment to the diverter material injected at the surface.   
     
     
         15 . The method of  claim 1 , wherein the diverter material is injected in the form of a pill. 
     
     
         16 . The method of  claim 1 , wherein the fluid is injected by an electric pump. 
     
     
         17 . The method of  claim 1 , carrying out an injection of diverter material based on the determined flow rate control sequence. 
     
     
         18 . A system comprising:
 one or more processors; and   a memory storing instructions to:   determining a desired flow rate distribution for fractures in a wellbore, the fractures comprising a dominant fracture and a marginal fracture, the dominant fracture receiving fluid at a higher rate from the wellbore than the marginal fracture; and   determining a flow rate control sequence for injecting a fluid comprising a carrier fluid and a diverter material into an entrance of the wellbore at a surface of the earth to deliver the diverter material into the dominant fracture and avoid delivery of the diverter material into the marginal fracture to achieve the desired flow rate distribution.   
     
     
         19 . The system of  claim 18  wherein
 the flow rate control sequence comprises a flow rate decrease adjustment at the entrance of the wellbore such that the diverter material enters the dominant fracture as the divert material passes by the dominant fracture and a flow rate increase adjustment at the entrance of the wellbore such that the diverter material avoids entry into the marginal fracture as the diverter material passes by the marginal fracture without substantially entering the marginal fracture, thereby delivering at least a portion of the diverter material into the dominant fracture at least partially blocking the dominant fracture and avoiding substantial delivery of the diverter material into the marginal fracture. 
 
     
     
         20 . The system of  claim 18  further comprising:
 estimating a concentration of diverter material that enters the dominant fracture based on a transport efficiency of the diverter material in the carrier fluid, the transport efficiency being based on a difference in flow rate between the diverter material and the carrier fluid. 
 
     
     
         21 . The method of  claim 18 , further comprising determining a concentration of the diverter material injected into the entrance of the wellbore at the surface of the earth based on an effect on the concentration of the diverter as it transports from the surface to at least one of the dominant fracture or the marginal fracture. 
     
     
         22 . A non-transitory computer readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to:
 determining a desired flow rate distribution for fractures in a wellbore, the fractures comprising a dominant fracture and a marginal fracture, the dominant fracture receiving fluid at a higher rate from the wellbore than the marginal fracture; and   determining a flow rate control sequence for injecting a fluid comprising a carrier fluid and a diverter material into an entrance of the wellbore at a surface of the earth to deliver the diverter material into the dominant fracture and avoid delivery of the diverter material into the marginal fracture to achieve the desired flow rate distribution.   
     
     
         23 . The non-transitory computer readable medium of  claim 22 , wherein
 the flow rate control sequence comprises a flow rate decrease adjustment at the entrance of the wellbore such that the diverter material enters the dominant fracture as the divert material passes by the dominant fracture and a flow rate increase adjustment at the entrance of the wellbore such that the diverter material avoids entry into the marginal fracture as the diverter material passes by the marginal fracture without substantially entering the marginal fracture, thereby delivering at least a portion of the diverter material into the dominant fracture at least partially blocking the dominant fracture and avoiding substantial delivery of the diverter material into the marginal fracture.   
     
     
         24 . The non-transitory computer readable medium of  claim 22  further comprising:
 estimating a concentration of diverter material that enters the dominant fracture based on a transport efficiency of the diverter material in the carrier fluid, the transport efficiency being based on a difference in flow rate between the diverter material and the carrier fluid.