Forming Multiple Deviated Wellbores

Abstract

A system includes a primary wellbore and a plurality of secondary wellbores. The primary wellbore includes a substantially vertical portion extending from a terranean surface to a predetermined location above a first target subterranean formation; a curved portion coupled to the substantially vertical portion and extending through the first target subterranean formation above a second target subterranean formation containing at least one of oil or gas; and a substantially horizontal portion coupled to the curved portion and extending through the first target subterranean formation and adjacent the second target subterranean formation. The plurality of secondary wellbores are coupled to the primary wellbore and extend angularly downward into the second target subterranean formation.

1 . A method comprising:
 forming a first wellbore portion from a terranean surface to a predetermined depth in or near a first target subterranean formation, the first wellbore portion having an upper section extending from the terranean surface downward in a substantially vertical manner for at least a portion of the depth to the first targeted subterranean formation;   forming a second wellbore portion coupled to the first wellbore portion, the second wellbore portion formed substantially horizontal to and in substantial entirety within the first target subterranean formation; and   forming a plurality of third wellbore portions comprising a plurality of deviated wellbores extending angularly downward into a lower second target subterranean formation from the second wellbore portion, the second target subterranean formation including at least one of oil or gas.   
     
     
         2 . The method of  claim 1 , wherein the first wellbore portion comprises a slanted wellbore from the terranean surface to the predetermined depth. 
     
     
         3 . The method of  claim 1 , wherein forming the upper vertical section of the first wellbore portion comprises drilling through one or more a geologic formations utilizing air as a drilling fluid. 
     
     
         4 . The method of  claim 1 , wherein forming the second wellbore portion comprises drilling through the first target subterranean formation utilizing air as a drilling fluid. 
     
     
         5 . The method of  claim 1 , wherein forming the plurality of third wellbore portions comprises drilling through the second target subterranean formation utilizing air as a drilling fluid. 
     
     
         6 . The method of  claim 1 , wherein forming the upper vertical section of the first wellbore portion comprises drilling through one or more a geologic formations utilizing foam as a drilling fluid. 
     
     
         7 . The method of  claim 1 , wherein forming the second wellbore portion comprises drilling through the first target subterranean formation utilizing foam as a drilling fluid. 
     
     
         8 . The method of  claim 1 , wherein forming the plurality of third wellbore portions comprises drilling through the second target subterranean formation utilizing foam as a drilling fluid. 
     
     
         9 . The method of  claim 1 , wherein the first target subterranean formation is directly adjacent the second target subterranean formation and between the terranean surface and the second target subterranean formation. 
     
     
         10 . The method of  claim 1 , wherein the plurality of deviated wellbores are formed from the second wellbore portion at a downward angle less than 90 degrees from horizontal. 
     
     
         11 . The method of  claim 1 , wherein forming a plurality of third wellbore portions comprising a plurality of deviated wellbores extending angularly into a second target subterranean formation from the second wellbore portion comprises forming a plurality of deviated wellbores extending angularly into the second target subterranean formation from the second wellbore portion and completely through the second target subterranean formation. 
     
     
         12 . The method of  claim 1 , wherein forming a plurality of third wellbore portions comprising a plurality of deviated wellbores extending angularly into a second target subterranean formation from the second wellbore portion comprises:
 forming a first group of deviated wellbores extending angularly into the second target subterranean formation; and   forming a second group of deviated wellbores extending angularly into the second target subterranean formation, the second group of deviated wellbores separated from the first group of deviated wellbores by a lateral offset.   
     
     
         13 . The method of  claim 12  further comprising determining the lateral offset between the first and second groups of deviated wellbores based at least in part on a predetermined fracture process or a predetermined stimulation process for the second target subterranean formation. 
     
     
         14 . The method of  claim 12 , wherein forming a first group of deviated wellbores extending angularly into the second target subterranean formation comprises forming a first group of deviated wellbores extending angularly into the second target subterranean formation at a first angle from horizontal; and
 forming a second group of deviated wellbores extending angularly into the second target subterranean formation comprises forming a second group of deviated wellbores extending angularly into the second target subterranean formation at a second angle distinct from the first angle.   
     
     
         15 . The method of  claim 14  further comprising determining the first and second angles based at least in part on a predetermined fracture process or a predetermined stimulation process for the second target subterranean formation. 
     
     
         16 . The method of  claim 1 , the plurality of deviated wellbores comprising a first plurality of deviated wellbores, the method further comprising:
 forming a fourth wellbore portion coupled to the first wellbore portion, the fourth wellbore portion radially offset from the second wellbore portion and formed substantially horizontal to and in substantial entirety within the first target subterranean formation; and   forming a second plurality of deviated wellbores extending angularly into the second target subterranean formation from the fourth wellbore portion.   
     
     
         17 . The method of  claim 1 , wherein the second target subterranean formation comprises a hydrocarbon bearing shale formation. 
     
     
         18 . The method of  claim 1 , wherein at least one of the first wellbore portion, the second wellbore portion, and the plurality of deviated wellbores are formed by rotary drilling equipment. 
     
     
         19 . The method of  claim 1 , wherein forming a plurality of deviated wellbores extending angularly into a second target subterranean formation from the second wellbore portion comprises forming a plurality of deviated wellbores extending downwardly into a second target subterranean formation from the second wellbore portion and angularly offset from horizontal and vertical. 
     
     
         20 . A system comprising:
 a primary wellbore comprising:
 a substantially vertical portion extending from a terranean surface to a predetermined location above a first target subterranean formation; 
 a curved portion coupled to the substantially vertical portion and extending through the first target subterranean formation above a second target subterranean formation containing at least one of oil or gas; and 
 a substantially horizontal portion coupled to the curved portion and extending through the first target subterranean formation and adjacent the second target subterranean formation; and 
   a plurality of secondary wellbores coupled to the primary wellbore and extending angularly downward into the second target subterranean formation.   
     
     
         21 . The system of  claim 20 , wherein the substantially vertical portion of the primary wellbore is formed by drilling through one or more a geologic formations utilizing air as a drilling fluid. 
     
     
         22 . The system of  claim 20 , wherein the substantially horizontal portion of the primary wellbore is formed by drilling through one or more a geologic formations utilizing air as a drilling fluid. 
     
     
         23 . The system of  claim 20 , wherein at least one of the plurality of secondary wellbores is formed by drilling through one or more a geologic formations utilizing air as a drilling fluid. 
     
     
         24 . The system of  claim 20 , wherein the substantially vertical portion of the primary wellbore is formed by drilling through one or more a geologic formations utilizing foam as a drilling fluid. 
     
     
         25 . The system of  claim 20 , wherein the substantially horizontal portion of the primary wellbore is formed by drilling through one or more a geologic formations utilizing foam as a drilling fluid. 
     
     
         26 . The system of  claim 20 , wherein at least one of the plurality of secondary wellbores is formed by drilling through one or more a geologic formations utilizing foam as a drilling fluid. 
     
     
         27 . The system of  claim 20 , wherein the first target subterranean formation is directly adjacent the second target subterranean formation and between the terranean surface and the second target subterranean formation. 
     
     
         28 . The system of  claim 20 , wherein the plurality of secondary wellbores are coupled to the substantially horizontal portion of the primary wellbore. 
     
     
         29 . The system of  claim 28 , wherein the plurality of secondary wellbores are formed from the substantially horizontal portion at a downward angle less than 90 degrees from horizontal. 
     
     
         30 . The system of  claim 20 , wherein at least one of the plurality of secondary wellbores extends completely through the second target subterranean formation. 
     
     
         31 . The system of  claim 20 , wherein the plurality of secondary wellbores comprise:
 a first group of secondary wellbores extending angularly downward into the second target subterranean formation; and   a second group of secondary wellbores extending angularly downward into the second target subterranean formation, the second group of secondary wellbores separated from the first group of secondary wellbores within the second target subterranean formation by a lateral offset.   
     
     
         32 . The system of  claim 31 , wherein the lateral offset between the first and second groups of secondary wellbores is based at least in part on a predetermined fracture process or a predetermined stimulation process of the second target subterranean formation. 
     
     
         33 . The system of  claim 31 , wherein the first group of secondary wellbores extend angularly downward into the second target subterranean formation at a first angle from horizontal and the second group of secondary wellbores extend angularly downward into the second target subterranean formation at a second angle from horizontal, the second angle distinct from the first angle. 
     
     
         34 . The system of  claim 33 , wherein the first and second angles are determined based at least in part on a predetermined fracture process or a predetermined stimulation process of the second target subterranean formation. 
     
     
         35 . The system of  claim 20 , the curved portion comprising a first curved portion, the system further comprising:
 a second curved portion coupled to the substantially vertical portion and radially offset from the first curved portion around the substantially vertical portion, the second curved portion extending through the first target subterranean formation above the second target subterranean formation;   a second substantially horizontal portion coupled to the second curved portion and extending through the first target subterranean formation and adjacent the second target subterranean formation; and   a second plurality of secondary wellbores extending angularly downward into the second target subterranean formation from the second substantially horizontal portion.   
     
     
         36 . The system of  claim 20 , wherein the second target subterranean formation comprises a hydrocarbon bearing shale formation. 
     
     
         37 . The system of  claim 20 , wherein at least one of the primary wellbore and the plurality of secondary wellbores are formed by rotary drilling equipment.