Hydraulic Fracturing with Strong, Lightweight, Low Profile Diverters

Abstract

Low profile diverters for, and the use of such diverters in, fracing operations to stimulate production of oil and gas are capable of seating against and temporarily sealing perforations, even when frac fluid is being pumped at high rates and pressures, or in horizontal or highly deviated well bores, where conventional ball sealers cannot be reliably used because of high flow rates and pressures.

What is claimed is: 
     
         1 . A method of stimulating production of hydrocarbons from a well having a casing through which has been formed a plurality of perforations, the method comprising:
 pumping into the wellbore under pressure a hydraulic fracture fluid containing proppant or an acid;   after pumping a predetermined amount of the hydraulic fracture fluid containing proppant or acid into the well bore, introducing into the flow of hydraulic fracture fluid entering the well bore, without stopping pumping, a predetermined number of diverters for seating against a portion, but not all, of the plurality of perforations to obstruct and temporarily seal them, thereby diverting the hydraulic fracture fluid containing proppant or acid toward the remaining ones of the plurality of perforations not being obstructed; and   continuing to pump the hydraulic fracture fluid containing proppant or acid under pressure into the well bore;   wherein each of the diverters has, when seated on one of the plurality of perforations, a first surface facing the perforation opening and a second surface facing generally in the direction of a center line of the well bore, the area of the first surface being greater than the area of the perforation opening, and wherein each of the diverters, when seated, presents a cross-sectional area to the flow of hydraulic fracture fluid containing proppant or acid through the well bore during pumping that is substantially smaller than the first and the second surface areas.   
     
     
         2 . The method of  claim 1 , the pumping of hydraulic fracture fluid containing proppant or acid continues without interruption when introducing the diverters into the flow of hydraulic fracture fluid. 
     
     
         3 . The method of  claim 1 , wherein, when one of the plurality of diverters is seated on one of the plurality of perforations, it is held in place by pressure of the hydraulic fracture fluid within the well bore acting against the second surface of the diverter. 
     
     
         4 . The method of  claim 1 , wherein the permeability of the subterranean formation adjacent to each of the plurality of stimulated perforations that are being at least partially obstructed and temporarily sealed by the predetermined number of diverters is greater than the permeability of the subterranean formation adjacent to each of the remaining ones of the plurality of perforations that are not being obstructed by a diverter. 
     
     
         5 . The method of  claim 1 , wherein each of the plurality of diverters has a shape substantially similar to the shape of an object chosen from a group consisting essentially of a discus, erythrocyte, saucer, disk, and wafer. 
     
     
         6 . The method of  claim 1 , wherein each of the plurality of diverters is hollow. 
     
     
         7 . The method of  claim 1 , wherein each of the plurality of diverters is capable of withstanding a differential pressure of at least 5,000 pounds per square inch without failing. 
     
     
         8 . The method of  claim 1 , wherein each of the plurality of diverters is capable of withstanding a differential pressure of at least 7500 pounds per square inch without failing. 
     
     
         9 . The method of  claim 1 , wherein each of the plurality of diverters is capable of withstanding a differential pressure of at least 10,000 pounds per square inch. 
     
     
         10 . The method of  claim 1 , wherein each of the plurality of diverters, when seated on one of the plurality of perforations, presents a cross-sectional area to the flow of hydraulic fracture fluid through the well bore during pumping that is 25% or less than the cross-sectional area presented by a ball-shaped diverter seated on the one of the plurality of perforations. 
     
     
         11 . The method of  claim 1  wherein the permeability of the subterranean formation adjacent to those of the plurality of perforations being obstructed and temporarily sealed by the diverters is greater than the permeability of the remaining ones of the plurality of perforations not being obstructed and temporarily sealed by the diverters. 
     
     
         12 . A method of stimulating production of hydrocarbons from a well bore having a casing, the method comprising:
 establishing within the well bore a plurality of frac stages isolatable from each other; and   for each of the plurality of frac stages,
 forming a plurality of perforations in the casing along a first section of the well bore; 
 pumping into the wellbore under pressure the predetermined amount of a hydraulic fracture fluid containing proppant or acid; and 
 after a predetermined amount of hydraulic fracture fluid containing proppant or acid has been pumped into the well bore, introducing into the flow of hydraulic fracture fluid containing proppant or acid entering the well bore, without stopping pumping, a batch of diverters, the batch of diverters containing fewer diverters than the number of perforations in the plurality of perforations for seating against a portion, but not all, of the plurality of perforations to temporarily obstruct and seal them at least partially, thereby diverting the hydraulic fracture fluid containing proppant or acid toward the remaining ones of the plurality of perforations not being obstructed for fracturing the subterranean formation adjacent to them; and 
 continuing to pump the hydraulic fracture fluid containing proppant or acid under pressure into the well bore; 
   wherein each of the plurality of diverters has, when seated on one of the plurality of perforations, a first surface facing the perforation opening and a second surface facing generally in the direction of a center line of the well bore, the area of the first surface being greater than the area of the perforation opening, and wherein each of the diverters, when seated, presents a cross-sectional area to hydraulic fracture fluid flowing through the well bore during pumping that is substantially smaller than the first and the second surface areas.   
     
     
         13 . The method of  claim 12 , wherein each of the plurality of diverters has a shape substantially similar to the shape of an object chosen from a group consisting essentially of a discus, erythrocyte, saucer, disk, and wafer. 
     
     
         14 . The method of  claim 12 , wherein each of the plurality of diverters is hollow. 
     
     
         15 . The method of  claim 12 , wherein each of the plurality of diverters is capable of withstanding a differential pressure of at least 5,000 pounds per square inch. 
     
     
         16 . The method of  claim 12 , wherein each of the plurality of diverters, when seated on one of the plurality of perforations, presents a cross-sectional area to the flow of hydraulic fracture fluid through the well bore during pumping that is 25% or less than the cross-sectional area presented by a ball-shaped diverter seated on the one of the plurality of perforations. 
     
     
         17 . The method of  claim 12  wherein the permeability of the subterranean formation adjacent to those of the plurality of perforations being obstructed and temporarily sealed by the diverters is greater than the permeability of the remaining ones of the plurality of perforations not being obstructed and temporarily sealed by the diverters. 
     
     
         18 . A diverter for obstructing and temporarily sealing at least a portion of a perforation of a predetermined size or smaller in casing of a well bore in a subterranean formation during hydraulic fracturing, the diverter comprising an impermeable body having a cross-sectional maximum thickness that is substantially smaller than its maximum width or maximum length, the thickness being measured along a first axis, the length along a second axis and the width along a third axis, the first, second and third axes being mutually orthogonal;
 wherein the maximum width and length are sufficient for the diverter to obstruct and temporarily seal the perforation; and wherein the maximum thickness is sufficiently small to avoid the diverter, when seated on a perforation, from being removed from the perforation by hydraulic fracture fluid flowing past the diverter to other perforations in the casing not sealed with a diverter when the hydraulic fracture fluid is flowing into the well bore at or below a predetermined maximum rate.   
     
     
         19 . The diverter of  claim 18 , wherein the impermeable body is shaped as a discus, a saucer, a disk, a wafer, or an erythrocyte. 
     
     
         20 . The diverter of  claim 18 , wherein the diverter is capable of withstanding a differential pressure of at least 5,000 pounds per square inch. 
     
     
         21 . A non-spherical diverter for obstructing and temporarily sealing a perforation in a well casing in a subterranean formation during hydraulic fracturing, the diverter comprising an impermeable body that, when seated on a perforation, has a first surface generally facing the perforation opening and a second surface facing generally in the opposite direction, toward a center line of the well, the area of the second surface being greater than the area of the perforation opening; wherein the body, when seated on a perforation, presents a cross-sectional area to a flow of hydraulic fracture fluid through the well that is substantially smaller than the first and the second surface areas. 
     
     
         22 . The diverter of  claim 21  wherein the cross-sectional area presented to a flow of hydraulic fracture by the diverter when it is seated on a perforation does not exceed 25% of that presented by a spherically shaped diverter having a diameter of not less than the maximum width and the maximum length when seated on the perforation. 
     
     
         23 . The diverter of  claim 21 , wherein the diverter has a shape substantially similar to the shape of an object chosen from a group consisting essentially of a discus, erythrocyte, saucer, disk, and wafer. 
     
     
         24 . The diverter of  claim 21 , wherein the body of the diverter is relatively rigid and does not fail when subject to a differential pressure of at least 5,000 psi. 
     
     
         25 . The diverter of  claim 21 , wherein the body has coating on its surface that is flexible to enhance sealing of the perforations. 
     
     
         26 . The diverter of  claim 21 , wherein the second surface of the body is flat. 
     
     
         27 . The diverter of  claim 18 , wherein the second surface of the body is curved.