Method of hydraulic fracturing to reduce unwanted water productions
A method of hydraulically fracturing a hydrocarbon-bearing subterranean formation ensures that the conductivity of water inflow below the productive zone of the subterranean formation is reduced. The method consists of two principal steps. In the first step, a fracture in and below the productive zone of the formation is initiated by introducing into the subterranean formation a fluid, free of a proppant, such as salt water, fresh water, brine, liquid hydrocarbon, and/or nitrogen or other gases. The proppant-free fluid may further be weighted. In the second step, a proppant laden slurry is introduced into the subterranean formation which contains a relatively lightweight density proppant. Either the fluid density of the proppant-free fluid is greater than the fluid density of the proppant laden slurry or the viscosity of the proppant-free fluid is greater than the viscosity of the proppant laden slurry. The method limits undesirable fracture height growth in the hydrocarbon-bearing subterranean formation during the fracturing.
1 . A method of hydraulically fracturing a hydrocarbon-bearing subterranean formation which comprises:
(a) introducing a proppant-free fluid into the subterranean formation for a time and at an injection rate sufficient to initiate fracturing;
(b) introducing into the subterranean formation a proppant laden slurry containing relatively lightweight density proppant;
wherein at least one of the following conditions prevail:
(i.) the fluid density of the proppant-free fluid is greater than the fluid density of the proppant laden slurry; or
(ii) the viscosity of the proppant-free fluid is greater than the viscosity of the proppant laden slurry.
2 . The method of claim 1 , wherein the density of the relatively lightweight density proppant is less than or equal to 3.25 g/cc.
3 . The method of claim 2 , wherein the relatively light density proppant is an ultra lightweight density proppant having a density less than or equal to 2.25 g/cc.
4 . The method of claim 3 , wherein the density of the ultra lightweight density proppant is less than or equal to 1.75 g/cc.
5 . The method of claim 4 , wherein the density of the ultra lightweight density proppant is less than or equal to 1.25 g/cc.
6 . The method of claim 1 , wherein the relatively lightweight density proppant is selected from ceramics, resin coated ceramics, glass microspheres, sintered bauxite, resin-coated sintered bauxite, aluminum pellets, aluminum needles, nylon pellets, ground or crushed shells of nuts, seed shells crushed fruit pits, or processed wood materials or a mixture thereof.
7 . The method of claim 1 , wherein the relatively lightweight density proppant is a selectively configured porous particulate or a well treating aggregate.
8 . The method of claim 1 , wherein the fracture in the subterranean formation is initiated by a fluid which contains a breaker, surfactant, biocide, gelling agent, curable resin, hardening agent, solvent, foaming agent, demulsifier, buffer, clay stabilizer, acid, or a mixture thereof.
9 . The method of claim 1 , wherein the fracture in the subterranean formation is initiated by a fluid which comprises salt water, fresh water, liquid hydrocarbon, and/or nitrogen or other gases.
10 . The method of claim 1 , wherein the fluid introduced to the formation in step (a) is weighted.
11 . The method of claim 10 , wherein the weighted fluid introduced to the formation in step (a) further comprises a water control additive.
12 . The method of claim 10 , wherein the weighted fluid introduced to the formation in step (a) further comprises a relative permeability modifier.
13 . A method of limiting undesirable fracture height growth in a hydrocarbon-bearing subterranean formation during hydraulic fracturing, the method comprising:
(a) initiating a hydraulic fracture that grows below the productive zone of the formation by pumping a dense liquid into the formation for a time sufficient for the liquid to migrate to the lower extremities of the initiated fracture by gravity segregation
(b) introducing into the formation a proppant laden slurry containing a relatively lightweight density proppant, the density and/or viscosity of the relatively lightweight density proppant being less than the density and/or viscosity of the liquid of step (a); and
(c) allowing the proppant slurry to override (by density differential) the liquid pumped into the formation in step (a) for a time sufficient so as to separate the proppant slurry from the liquid pumped into the formation in step (a).
14 . The method of claim 13 , wherein the density of the relatively lightweight density proppant is less than or equal to 3.25 g/cc.
15 . The method of claim 14 , wherein the relatively lightweight density proppant is an ultra lightweight density proppant having a density less than or equal to 2.25 g/cc.
16 . The method of claim 15 , wherein the density of the ultra lightweight density proppant is less than or equal to 1.75 g/cc.
17 . The method of claim 16 , wherein the density of the ultra lightweight density proppant is less than or equal to 1.25 g/cc.
18 . The method of claim 13 , wherein the relatively lightweight density proppant is selected from ceramics, resin coated ceramics, glass microspheres, sintered bauxite, resin-coated sintered bauxite, aluminum pellets, aluminum needles, nylon pellets, ground or crushed shells of nuts, seed shells crushed fruit pits or processed wood materials or a mixture thereof.
19 . The method of claim 13 , wherein the relatively lightweight density proppant is a selectively configured porous particulate or a well treating aggregate.
20 . The method of claim 13 , wherein the fracture in the subterranean formation is initiated by a fluid which contains a breaker, surfactant, biocide, gelling agent, curable resin, hardening agent, solvent, foaming agent, demulsifier, buffer, clay stabilizer, acid, or a mixture thereof.
21 - 33 . (canceled)