Flow allocation in drill bits

Abstract

A method for designing a drill bit comprising modeling a domain between a drill bit and a surrounding wellbore. A region is defined within each of a plurality of flow paths through which fluid travels through the domain. An allocation of flow among the plurality of flow paths through the domain is determined and the drill bit is modified such that the allocation of flow is substantially uniform among the plurality of flow paths. A drill bit comprises a bit body having a plurality of blades projecting there from, wherein at least one blade has a greater length than at least one other blade. A plurality of nozzles, or ports, are disposed on the body and a plurality of junk slots are formed between adjacent blades so that the flow of fluid through each of the plurality of junk slots is substantially uniform.

1 . A method for designing a drill bit, comprising: 
 modeling a domain between a drill bit having a first design and a surrounding wellbore;    defining a plurality of regions, wherein one of the plurality of regions is disposed within each of a plurality of flow paths through which fluid travels through the domain;    determining an allocation of flow among the plurality of flow paths through the domain; and    modifying the first design of the drill bit such that the allocation of flow is substantially uniform among the plurality of flow paths.    
   
   
       2 . The method of  claim 1  wherein the plurality of regions are disposed within junk slots.  
   
   
       3 . The method of  claim 1  wherein the first design is modified by adjusting a nozzle or port parameter.  
   
   
       4 . The method of  claim 3  wherein the nozzle or port parameter is an angular orientation, position, size, or seat depth.  
   
   
       5 . The method of  claim 1  wherein the first design is modified by changing the number of nozzles or ports.  
   
   
       6 . The method of  claim 1  wherein the first design is modified by adjusting a bit geometry parameter.  
   
   
       7 . The method of  claim 6  wherein the bit geometry parameter is a blade size, blade shape, or bit body geometry.  
   
   
       8 . The method of  claim 1  wherein the flow allocation is determined based on a fluidic property of fluid moving through the plurality of regions.  
   
   
       9 . The method of  claim 8  wherein the fluidic property is a volumetric flow rate, mass flow rate, or net flow rate.  
   
   
       10 . The method of  claim 1  further comprising: 
 modeling a modified domain between a drill bit having a modified design and the surrounding wellbore;    defining a plurality of regions within the modified domain, wherein each region is disposed within each of a plurality of flow paths through which fluid travels through the modified domain;    determining an allocation of flow among the plurality of flow paths through which fluid travels through the modified domain; and    selecting a bit design based on a comparison of the allocation of flow among the flow paths in the modified domain and the allocation of flow among the flow paths in the unmodified domain.    
   
   
       11 . The method of  claim 1  further comprising generating a visual representation of the allocation of flow among the flow paths.  
   
   
       12 . A drill bit comprising: 
 a bit body having a plurality of blades projecting there from, wherein at least one blade has a greater length than at least one other blade;    a plurality of nozzles or ports disposed on said body; and    a plurality of junk slots formed between adjacent blades, wherein said junk slots provide a passageway for the flow of the fluid from said plurality of nozzles or ports, wherein bit design parameters are such that the flow of fluid through each of the plurality of junk slots is substantially uniform.    
   
   
       13 . The drill bit of  claim 12  wherein the bit design parameters comprise a nozzle or port parameter or a bit geometry parameter.  
   
   
       14 . The drill bit of  claim 12  wherein at least one of said plurality of nozzles or ports has nozzle or port parameter that is different than a nozzle or port parameter of another of said plurality of nozzles or ports.  
   
   
       15 . The drill bit of  claim 12  wherein the nozzle or port parameter comprises at least one of, quantity, design, size, radial location, axial location, angular orientation, seat depth, and arrangement.  
   
   
       16 . The drill bit of  claim 12  wherein at least one of said junk slots has a greater number of said plurality of nozzles or ports positioned there within than are positioned within another of said plurality of junk slots.  
   
   
       17 . The drill bit of  claim 12  wherein at least one of said plurality of blades has more material at an upper portion of the blade, extends farther toward a central bit axis, or has a greater thickness than another of said plurality of blades.  
   
   
       18 . The drill bit of  claim 12  wherein said plurality of nozzles or ports comprises a number of nozzles or ports equal to the number of said plurality of blades.  
   
   
       19 . A drill bit of  claim 12  further comprising: 
 a central bit axis through the bit body; and wherein the plurality of blades extending from said bit body, wherein said plurality of blades comprises at least one primary blade and at least one secondary blade, wherein at least one of the primary blades extends closer to the central bit axis than at least one of the secondary blade.    
   
   
       20 . The drill bit of  claim 19  wherein said plurality of nozzles or ports comprises at least one primary nozzle or port and at least one secondary nozzle or port.  
   
   
       21 . The drill bit of  claim 19  wherein the at least one primary nozzle or port is located closer to the bit central axis than the at least one secondary nozzle or port.  
   
   
       22 . The drill bit of  claim 19  wherein the at least one primary nozzle or port has a smaller angular orientation than the at least one secondary nozzle or port.  
   
   
       23 . The drill bit of  claim 19  wherein the at least one primary nozzle or port has a shorter seat depth than the at least one secondary nozzle or port.