Method for Determining Spacing of Hydraulic Fractures in a Rock Formation

Abstract

Methods of the present disclosure include determining an expected trajectory of induced fractures in a rock formation, analyzing net pressure associated with the induced fractures, and determining at least one of spacing of induced fractures and a property of the induced fractures based on the net pressure. Computer-readable medium containing the method are also disclosed. Other related methods are also disclosed.

1 . A method comprising:
 determining an expected trajectory of induced fractures;   analyzing net pressure associated with the induced fractures; and   determining at least one of spacing of induced fractures and a property of the induced fractures based on the net pressure.   
     
     
         2 . The method of  claim 1 , wherein determining an expected trajectory of induced factures comprises:
 analyzing stresses prior to inducing fracturing;   modeling a trajectory of a first fracture;   determining effects on the stresses based on the modeled trajectory of the first fracture; and   modeling a trajectory of a subsequent fracture based on the effects on the stresses caused by the first fracture.   
     
     
         3 . The method of  claim 2 , further comprising decreasing the spacing of induced fractures based at least on the modeling of the first and subsequent fractures. 
     
     
         4 . The method of  claim 1 , further comprising determining a maximum horizontal stress. 
     
     
         5 . The method of  claim 1 , wherein the property of the induced fractures includes an expected trajectory of a subsequently induced fracture. 
     
     
         6 . The method of  claim 1 , wherein the net pressure is determined by at least one of surface pressures or down-hole pressures during fracturing. 
     
     
         7 . A method of optimizing fracture spacing comprising:
 propagating an initial fracture;   measuring pressure associated with propagating the initial fracture;   determining a minimum spacing required to prevent a second fracture from intersecting the initial fracture; and   propagating the second fracture at least the minimum spacing distance away from the initial fracture.   
     
     
         8 . The method of optimizing fracture spacing of  claim 7 , further comprising:
 measuring pressure associated with propagating the second fracture;   determining a second minimum spacing required to prevent a third fracture from intersecting the second fracture; and   propagating the third fracture at least the second minimum spacing distance away from the second fracture.   
     
     
         9 . The method of optimizing fracture spacing of  claim 8 , wherein determining the second minimum spacing is based at least on the pressure associated with propagating the second fracture. 
     
     
         10 . The method of optimizing fracture spacing of  claim 7 , wherein the second fracture is propagated at a distance sufficient to allow a third fracture to be propagated between the first and the second fractures. 
     
     
         11 . The method of optimizing fracture spacing of  claim 10 , further comprising:
 determining spacing required to prevent the third fracture from intersecting the first and second fractures based at least on the pressure associated with propagating the first and the second fractures; and   determining a decreased distance between a fourth and the second fracture based at least on the spacing required to prevent the third fracture intersecting the first and second fractures and the pressure associated with propagating the second fracture.   
     
     
         12 . The method of optimizing fracture spacing of  claim 7 , wherein determining the minimum spacing comprises:
 modeling stresses caused by the first fracture based at least on the pressure associated with propagating the first fracture; and   modeling a trajectory of the second fracture based on the modeled stresses.   
     
     
         13 . The method of optimizing fracture spacing of  claim 7 , wherein determining the minimum spacing comprises modeling at least one of an attraction zone and a repulsion zone associated with the first fracture based at least on net pressure, in-situ stress contrast, or average angle of deviation from a trajectory of the first fracture. 
     
     
         14 . The method of optimizing fracture spacing of  claim 13 , wherein the minimum spacing is outside of the attraction zone associated with the first fracture. 
     
     
         15 . The method of optimizing fracture spacing of  claim 13 , wherein determining the minimum spacing further comprises modeling a stress reversal region. 
     
     
         16 . A method of optimizing fracture spacing comprising:
 analyzing stresses associated with a first set of at least one fractures associated with a first well;   analyzing stresses associated with a second set of at least one fractures associated with a second well; and   determining spacing of a fracture associated with a third well such that the fracture associated with the third well does not intersect with the first set and the second set of fractures, the third well running between the first and second wells.   
     
     
         17 . The method of optimizing fracture spacing of  claim 16 , wherein determining spacing of the fracture associated with the third well comprises:
 modeling the stresses associated with the first and the second set of fractures;   modeling a trajectory of the fracture associated with the third well.   
     
     
         18 . The method of optimizing fracture spacing of  claim 16 , wherein analyzing stresses associated with the first set of at least one fractures is based at least on net pressure of propagating the first set of at least one fractures. 
     
     
         19 . The method of optimizing fracture spacing of  claim 16 , wherein the first set and the second set of fractures comprise at least two fractures and are spaced such that the fracture associated with the third well is substantially between a first and a second fracture of the first set of fractures and between a first and a second fracture of the second set of fractures. 
     
     
         20 . The method of optimizing fracture spacing of  claim 19 , further comprising determining a decreased distance between a third and the second fracture of the first set of fractures and a third and the second fracture of the second set of fractures based at least on the spacing required to prevent the fracture associated with the third well from intersecting the first and the second set of fractures, the distance determined such that a second fracture associated with the third well may be propagated between the second and the third fractures of the first set of fractures and the second and the third fractures of the second set of fractures without intersecting the first or the second set of fractures. 
     
     
         21 . A method of determining maximum horizontal pressure comprising:
 measuring an actual pressure during each stage of fracturing of a rock formation;   determining a theoretical expected pressure during each stage of fracturing of the rock formation;   determining a maximum horizontal pressure of the rock formation based at least on a comparison of the theoretical expected pressure and the measured actual pressure.