Method of stimulating oil and gas wells using deformable proppants

Abstract

A method of fracturing using deformable proppants minimizes proppant pack damage, without compromising the fracturing fluid's proppant transport properties during pumping, by use of deformable proppants. Selection of proppant is dependent upon the mechanical properties of the formation rock. The strength of the deformable proppant is dependent upon the modulus of the formation rock being treated such that the proppant is capable of providing, at the very least, a minimum level of conductivity in in-situ stress environments. The maximum elastic modulus of the deformable proppant is less than the minimum modulus of the formation rock which is being treated. The method is particularly applicable in fracturing operations of subterranean reservoirs such as those comprised primarily of coal, chalk, limestone, dolomite, shale, siltstone, diatomite, etc.

1 . A method of stimulating a subterranean formation comprising:
 (a) introducing particulates into the subterranean formation at a pressure sufficient to create or enlarge fractures in the formation, wherein the particulates consist essentially of deformable proppants having an apparent specific gravity less than or equal to 2.45;   (b) creating a partial monolayer of said particulates in the created or enlarged fractures; and   (c) allowing the subterranean formation to close on the created partial monolayer such that the energy of the closure stress is absorbed by the particulates and not by the face of the rock;   wherein the fracture containing the partial monolayer of particulates is capable of providing at least a minimum level of conductivity at in-situ reservoir stress conditions between from 100 psi to 15,000 psi.   
     
     
         2 . The method of  claim 1 , wherein at least one of the following conditions prevail:
 (i) at least some of the particulates are non-spherical;   (ii) the particulates are a mixture of different deformable proppants;   (iii) at least some of the particulates are a substantially spherical or beaded proppant of a copolymer; or   (iv) the particulates are transported into the formation in a carrier fluid.   
     
     
         3 . The method of  claim 2 , wherein the particulates are transported into the formation in a carrier fluid. 
     
     
         4 . The method of  claim 3 , wherein the carrier fluid is salt water, fresh water, a liquid hydrocarbon or a gas. 
     
     
         5 . The method of  claim 4 , wherein the carrier fluid further contains at least one member selected from the group consisting of gelling agents, cross-linking agents, gel breakers, curable resins, hardening agents, solvents, surfactants, foaming agents, demulsifiers, buffers, clay stabilizers and acids. 
     
     
         6 . The method of  claim 3 , wherein the particulates are substantially neutrally buoyant in the carrier fluid. 
     
     
         7 . The method of  claim 2 , wherein at least some of the particulates are non-spherical. 
     
     
         8 . The method of  claim 7 , wherein at least some of the particulates are elongated, tapered, egg, tear drop or oval shape. 
     
     
         9 . The method of  claim 7 , wherein at least some of the particulates are cubic, bar-shaped, cylindrical or multi-faceted. 
     
     
         10 . The method of  claim 2 , wherein the particulates are a mixture of different deformable proppants. 
     
     
         11 . The method of  claim 2 , wherein at least some of the particulates are a substantially spherical or beaded proppant of a copolymer. 
     
     
         12 . The method of  claim 11 , wherein the copolymer is reacted with a crosslinker. 
     
     
         13 . The method of  claim 12 , wherein at least some of the particulates are a terpolymer. 
     
     
         14 . A method of stimulating a subterranean formation comprising:
 (a) introducing into the subterranean formation a fracturing fluid at a pressure above the fracturing pressure of the subterranean formation, wherein the fracturing fluid contains particulates having a modulus less than the modulus of the rock of the subterranean formation, and creating a partial monolayer in the formation, wherein the particulates consist essentially of deformable proppants having an apparent specific gravity between from about 1.0 and about 1.2; and   (b) allowing the subterranean formation to close such that the energy of the closure stress is absorbed by the deformable proppants and not by the face of the rock;   wherein the fracture containing the partial monolayer of deformable proppants is capable of providing at least a minimum level of conductivity at in-situ reservoir conditions.   
     
     
         15 . The method of  claim 14 , wherein at least one of the following conditions prevail:
 (i) at least some of the deformable proppants are non-spherical;   (ii) the deformable proppants are a mixture of different deformable proppants;   (iii) at least some of the deformable proppants are a substantially spherical or beaded proppant of a copolymer; or   (iv) the fracturing fluid contains salt water, fresh water, liquid hydrocarbons or a gas.   
     
     
         16 . The method of  claim 15 , wherein the fracturing fluid contains salt water, fresh water, liquid hydrocarbons or a gas. 
     
     
         17 . The method of  claim 16 , wherein the gas is nitrogen. 
     
     
         18 . The method of  claim 16 , wherein the fracturing fluid further contains at least one member selected from the group consisting of gelling agents, cross-linking agents, gel breakers, curable resins, hardening agents, solvents, surfactants, foaming agents, demulsifiers, buffers, clay stabilizers and acids. 
     
     
         19 . The method of  claim 16 , wherein the deformable proppants are substantially neutrally buoyant in the carrier fluid. 
     
     
         20 . The method of  claim 15 , wherein at least some of the deformable proppants are non-spherical. 
     
     
         21 . The method of  claim 15 , wherein the deformable proppants are a mixture of different deformable proppants; 
     
     
         22 . The method of  claim 15 , wherein at least some of the deformable proppants are a substantially spherical or beaded proppant of a copolymer. 
     
     
         23 . The method of  claim 22 , wherein the copolymer is reacted with a crosslinker. 
     
     
         24 . A method of fracturing a subterranean formation surrounding an oil or gas well which comprises:
 (a) introducing into the subterranean formation a deformable proppant, wherein the deformable proppant consists essentially of:
 (i) an aggregate of an organic lightweight material having an apparent specific gravity less than or equal to 2.45 and a weight modifying agent, wherein the organic lightweight material is a polymeric material selected from the group consisting of polystyrene, a styrene-divinylbenzene copolymer, a polyacrylate, a polyalkylacrylate, a polyacrylate ester, a polyalkyl acrylate ester, a modified starch, a polyepoxide, a polyurethane, a polyisocyanate, a phenol formaldehyde resin, a furan resin and a melamine formaldehyde resin; or 
 (ii) an aggregate of an organic lightweight material having an apparent specific gravity less than or equal to 2.45 and a weight modifying agent, the aggregate having a coating or modifying agent which increases the resistance of the aggregate to deformation; 
   wherein the modulus of the deformable proppant is less than the modulus of the rock of the subterranean formation; and   (b) allowing the subterranean formation to close such that the energy of the closure stress is absorbed by the deformable proppant and not by the face of the rock.   
     
     
         25 . A method of stimulating a subterranean formation susceptible to fines generation and minimizing damage from the spalling of fines to a proppant pack within the formation comprising:
 (a) introducing into the subterranean formation at a pressure above the fracturing pressure of the subterranean formation a fluid containing deformable particulates;   (b) creating or enlarging a fracture in the formation, wherein a proppant pack of the deformable particulates is deposited in the fracture, wherein the deformable particulates of the proppant pack consist essentially of either:
 (i) deformable particulates having an apparent specific gravity less than or equal to 2.45; or 
 (ii) deformable particulates having an apparent specific gravity less than or equal to 2.45 having a coating or modifying agent which increases the resistance of the deformable particulates to deformation; 
   wherein the modulus of the deformable particulates is less than the modulus of the rock of the subterranean formation, the particulates being capable of providing at least a minimum level of conductivity; and   (c) allowing the subterranean formation to close such that the energy of the closure stress is absorbed by the deformable particulates of the proppant pack and not by the face of the rock;   wherein fines is minimized and damage to the proppant pack from the spalling of fines is minimized by the presence of the deformable particulates.