Hydraulic fracturing process

Claim 2

In a process for fracturing a permeable, subterranean formation traversed by a well wherein a fracturing fluid comprised of a dispersion of particulate solid fluid loss reducing agent and particulate solid propping agent in a viscous carrier liquid is injected through the well and into contact with the formation at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, whereby said fluid loss reducing agent is deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said propping agent is deposited within the fracture at a location remote from the well, the improvement which comprises: following the injection of said fracturing fluid, treating the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture a particulate solid propping agent dispersed in a carrier liquid having a high fluid loss characteristic.

Claim 3

The process defined in claim 1 wherein the exposed faces of the formation are treated by injecting a solvent for said fluid loss reducing agent through the well and into contact with the formation.

Claim 4

The process defined in claim 2 wherein sufficient solvent is injected into said fracture to dissolve essentially all of the fluid loss reducing agent from the exposed faces of the formation.

Claim 5

The process defined in claim 2 wherein about 0.5 to 10 gallons of solvent is injected into the well per pound of said fluid loss reducing agent injected.

Claim 6

The process defined in claim 2 wherein said fluid loss reducing agent is soluble in oil and the solvent is an oil.

Claim 7

The process defined in claim 2 wherein said fluid loss reducing agent is soluble in acid and the solvent is an acid.

Claim 8

The process as defined in claim 2 wherein said fluid loss reducing agent is soluble in water and the solvent is water.

Claim 9

In a process for fracturing a permeable, subterranean formation traversed by a well wherein a fracturing fluid comprised of a dispersion of water-insoluble, oil-soluble, solid particles of fluid loss reducing agent and solid particles of propping agent in a viscous aqueous carrier liquid is injected through the well and into contact with the formation at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, whereby said fluid loss reducing agent is deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said propping agent is deposited within the fracture at a location remote from the well, the improvement which comprises: following the injection of said fracturing fluid, injecting through the well and into said fracture an oleaginous solvent in an amount sufficient to remove a substantial portion of said previously deposited fluid loss reducing agent from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture a particulate solid propping agent dispersed in a carrier liquid having a high fluid loss characteristic.

Claim 10

In a process for fracturing a permeable, subterranean formation traversed by a well wherein a fracturing fluid comprised of a dispersion of water-insoluble, oil-soluble, solid particles of fluid loss reducing agent and solid particles of propping agent in a viscous aqueous carrier liquid is injected through the well and into contact with the formation at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, whereby said fluid loss reducing agent is deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said propping agent is deposited within the fracture at a location remote from the well, the improvement which comprises: following the injection of said fracturing fluid, injecting through the well and into said fracture an oleaginous solvent in an amount sufficient to remove a substantial portion of said previously deposited fluid loss reducing agent from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture a particulate solid propping agent dispersed in a carrier liquid having a high fluid loss characteristic.

Claim 11

The process defined in claim 8 wherein said water-insoluble, readily oil-soluble fluid loss reducing agent is comprised of solid particles of paraffin wax or solid particles of a homogeneous mixture of paraffin wax and polymer.

Claim 12

The process as defined in claim 8 wherein sufficient oleaginous solvent is injected into said fracture to remove essentially all of the oil-soluble fluid loss reducing agent from the exposed faces of the formation.

Claim 13

In a process for fracturing a permeable, subterranean formation traversed by a well wherein a fracturing fluid comprised of a dispersion of solid particles of an oil and water-insoluble, acid-soluble fluid loss reducing agent and solid particles of propping agent in a viscous non-acidic carrier liquid is injected through the well and into contact with the formation at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, whereby said fluid loss reducing agent is deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said propping agent is deposited within the fracture at a location remote from the well, the improvement which comprises: following the injection of said fracturing fluid, injecting through the well and into said fracture an acid in an amount sufficient to remove a substantial portion of said previously deposited fluid loss reducing agent from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids in at least that part of the fracture adjacent to the well; and thereafter injecting through the well and into said fracture solid particles of propping agent dispersed in a carrier liquid having a High fluid loss characteristic.

Claim 14

In a process for fracturing a permeable, subterranean formation traversed by a well wherein a fracturing fluid comprised of a dispersion of solid particles of an oil and water-insoluble, acid-soluble fluid loss reducing agent and solid particles of propping agent in a viscous non-acidic carrier liquid is injected through the well and into contact with the formation at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, whereby said fluid loss reducing agent is deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said propping agent is deposited within the fracture at a location remote from the well, the improvement which comprises: following the injection of said fracturing fluid, injecting through the well and into said fracture an acid in an amount sufficient to remove a substantial portion of said previously deposited fluid loss reducing agent from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids in at least that part of the fracture adjacent to the well; and thereafter injecting through the well and into said fracture solid particles of propping agent dispersed in a carrier liquid having a High fluid loss characteristic.

Claim 15

The process defined in claim 11 wherein said oil and water-insoluble, acid-soluble fluid loss reducing agent is selected from the group consisting of carbonates of calcium, magnesium and barium.

Claim 16

The process defined in claim 11 wherein said acid is selected from the group consisting of hydrochloric acid, hydrofluoric acid and mixtures thereof.

Claim 17

The process defined in claim 11 wherein said acid is injected in an amount between about 10 and 100 percent of the amount of acid required to stoichiometrically react with the fluid loss reducing agent injected into the well.

Claim 18

The process defined in claim 11 wherein said carrier liquid having a high fluid loss characteristic is water.

Claim 19

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into said formation, a fracturing fluid comprised of a dispersion of sand and solid particles of an oil-soluble, water-insoluble fluid loss reducing agent comprised of petroleum wax in a viscous aqueous carrier liquid, said particles of fluid loss reducing agent having a size within the range of about 0.5 to 50 microns, whereby said particles of fluid loss reducing agent are deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said sand is deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture about 0.5 to 10 gallons of a hydrocarbon oil per pound of said fluid loss reducing agent injected into the well, whereby a substantial portion of said previously deposited fluid loss reducing agent is removed from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in a carrier liquid having a high fluid loss characteristic, whereby said sand is deposited in the fracture adjacent to the well without substantially extending the fracture further into the formation.

Claim 20

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into said formation, a fracturing fluid comprised of a dispersion of sand and solid particles of an oil-soluble, water-insoluble fluid loss reducing agent comprised of petroleum wax in a viscous aqueous carrier liquid, said particles of fluid loss reducing agent having a size within the range of about 0.5 to 50 microns, whereby said particles of fluid loss reducing agent are deposited on the exposed faces of the formation to reduce the loss of fracturing fluid thereto and said sand is deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture about 0.5 to 10 gallons of a hydrocarbon oil per pound of said fluid loss reducing agent injected into the well, whereby a substantial portion of said previously deposited fluid loss reducing agent is removed from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in a carrier liquid having a high fluid loss characteristic, whereby said sand is deposited in the fracture adjacent to the well without substantially extending the fracture further into the formation.

Claim 21

The process defined in claim 16 wherein said oil soluble, solid fluid loss reducing agent consists of particles of a homogeneous solid solution of paraffin wax and polymer.

Claim 22

The method defined in claim 16 wherein the carrier liquid having a high fluid loss characteristic is hydrocarbon oil.

Claim 23

The method defined in claim 16 wherein said carrier liquid having a high fluid loss characteristic is an aqueous liquid.

Claim 24

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, a fracturing fluid comprised of a viscous, non-acidic carrier liquid having dispersed therein sand and solid particles of calcium carbonate, said particles of calcium carbonate having a size within the range of about 0.5 to 50 microns, whereby said particles of calcium carbonate are deposited on the exposed faces of the fracture to reduce the loss of fracturing fluid to said formation and said sand particles are deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture an acid selected from the group consisting of hydrochloric acid, hydrofluoric acid and mixtures thereof, said acid being injected in an amount between about 10 and 100 percent of the amount of acid required to stoichiometrically react with the calcium carbonate injected into the well, whereby a substantial portion of said calcium carbonate is removed From the exposed faces of the formation so as to increase the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in an aqueous carrier liquid having a high fluid loss characteristic whereby sand particles are deposited in the fracture adjacent to the well without substantially extending the depth of the fractures into the formation.

Claim 25

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, a fracturing fluid comprised of a viscous, non-acidic carrier liquid having dispersed therein sand and solid particles of calcium carbonate, said particles of calcium carbonate having a size within the range of about 0.5 to 50 microns, whereby said particles of calcium carbonate are deposited on the exposed faces of the fracture to reduce the loss of fracturing fluid to said formation and said sand particles are deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture an acid selected from the group consisting of hydrochloric acid, hydrofluoric acid and mixtures thereof, said acid being injected in an amount between about 10 and 100 percent of the amount of acid required to stoichiometrically react with the calcium carbonate injected into the well, whereby a substantial portion of said calcium carbonate is removed From the exposed faces of the formation so as to increase the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in an aqueous carrier liquid having a high fluid loss characteristic whereby sand particles are deposited in the fracture adjacent to the well without substantially extending the depth of the fractures into the formation.

Claim 26

The process defined in claim 20 wherein the non-acidic carrier liquid having a high fluid loss characteristic is water.

Claim 27

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, a fracturing fluid comprised of a dispersion of sand and a water-soluble, oil-insoluble fluid loss reducing agent having a size within the range of about 0.5 to 50 microns in a viscous, non-aqueous carrier liquid, whereby said fluid loss reducing agent is deposited on the exposed faces of the fracture to reduce the loss of fracturing fluid to said formation and said sand particles are deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture 0.5 to 10 gallons of water per pound of said fluid loss reducing agent injected into the well, whereby a substantial portion of said previously deposited fluid loss reducing agent is removed from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in a carrier liquid having a high fluid loss characteristic, whereby said sand is deposited in the fracture adjacent to the well without substantially extending the fracture further into the formation.

Claim 28

A process for fracturing a permeable, subterranean formation traversed by a well comprising: injecting through the well and into said formation, at a pressure and volume flow rate sufficient to form a fracture and to extend said fracture a substantial distance into the formation, a fracturing fluid comprised of a dispersion of sand and a water-soluble, oil-insoluble fluid loss reducing agent having a size within the range of about 0.5 to 50 microns in a viscous, non-aqueous carrier liquid, whereby said fluid loss reducing agent is deposited on the exposed faces of the fracture to reduce the loss of fracturing fluid to said formation and said sand particles are deposited within the fracture at a location remote from the well; next injecting through the well and into said fracture 0.5 to 10 gallons of water per pound of said fluid loss reducing agent injected into the well, whereby a substantial portion of said previously deposited fluid loss reducing agent is removed from the exposed faces of the formation so as to substantially restore the permeability of the formation to subsequently injected fluids; and thereafter injecting through the well and into said fracture, at a volume flow rate essentially the same as that used to form and extend the fracture, solid particles of sand dispersed in a carrier liquid having a high fluid loss characteristic, whereby said sand is deposited in the fracture adjacent to the well without substantially extending the fracture further into the formation.

Claim 29

The method defined in claim 22 wherein said fluid loss reducing agent is calcium chloride.

Claim 30

The method defined in claim 22 wherein a small slug of an amphoteric solvent is injected immediately following the first fracturing treatment.