Methods and compositions for testing subterranean formations

A method of reducing the production of water from a subterranean formation subsequent to fracturing the formation, comprising:

• (a) providing an aqueous viscoelastic surfactant based hydraulic fracturing fluid comprising
• (i) an aqueous medium,
• (ii) an effective amount of a water soluble salt, and
• (iii) an effective amount of a thickener,
• (b) generating a viscous fluid comprising micelles, the micelles having hydrophobic and hydrophilic portions;
• (c) pumping the viscous fluid comprising wormlike or elongated micelles through a wellbore and into a formation at a pressure sufficient to fracture the formation, the formation having an aqueous zone containing water and a hydrocarbon zone;
• (d) admitting said micelles into the aqueous zone;
• (e) facilitating the breakdown of micelles within the hydrocarbon zone, thereby decreasing the viscosity of the fluid within the hydrocarbon zone to form a thinned fluid;
• (f) removing thinned fluid from the hydrocarbon zone of the formation;
• and
• (g) reducing the amount of water produced from the formation during the removing step.

A method of fracturing a subterranean formation comprising:

• (a) providing an aqueous viscoelastic surfactant based hydraulic fracturing fluid including a thickener comprising:
• (1) an aqueous medium;
• (2) an effective amount of an inorganic water soluble salt,
• (3) an effective amount of at least one thickener in the fluid, the thickener being at least one member selected from the group consisting of
• (i) an amine corresponding to the formula ##STR4## wherein R.sub.1 is at least about a C.sub.16 aliphatic group which may be branched or straight chained and which may be saturated or unsaturated, R.sub.2 and R.sub.3 are each independently, hydrogen or a C.sub.1 to about C.sub.6 aliphatic group which can be branched or straight chained, saturated or unsaturated and which may be substituted with a group that renders the R.sub.2 or R.sub.3 group more hydrophilic, or
• (ii) salts of the amine corresponding to the formula ##STR5## wherein R.sub.1, R.sub.2 and R.sub.3 are the same as defined herein and X.sup.- is an inorganic anion, or
• (iii) a quaternary ammonium salt of the amine corresponding to the formula ##STR6## wherein R.sub.1, R.sub.2, R.sub.3 and X.sup.- are the same as defined herein and R.sub.4 constitutes a group which has previously been set forth for R.sub.3, none of R.sub.1, R.sub.2, R.sub.3 or R.sub.4 are hydrogen, and the R.sub.2, R.sub.3 and R.sub.4 groups of the amine salt and quaternary ammonium salt may be formed into a heterocyclic 5- or 6-member ring structure which includes the nitrogen atom of the amine;
• (b) generating a viscous fluid comprising micelles;
• (c) pumping the viscous fluid comprising micelles through a wellbore and into a formation at a pressure sufficient to fracture the formation, the formation having an aqueous zone and a hydrocarbon zone, the aqueous zone comprising water;
• (d) facilitating entry of micelles into the aqueous zone;
• (e) structurally altering the micelles within the fluid in the hydrocarbon zone, thereby decreasing the viscosity of the fluid within the hydrocarbon zone;
• and
• (f) removing fluid from the hydrocarbon zone.

A method of reducing the amount of water produced from a subterranean formation following fracturing of the subterranean formation, the method comprising:

• (a) providing an aqueous viscoelastic surfactant based hydraulic fracturing fluid comprising:
• (1) an aqueous medium;
• (2) an effective amount of an water soluble salt, the salt being selected from the group of salts comprising ammonium chlorides, potassium chloride, sodium chloride, magnesium chloride, Mg-containing salts, Zn-containing salts, and calcium salts;
• (3) an effective amount of at least one thickener in the fluid, the thickener being at least one member selected from the group consisting of
• (i) an amine corresponding to the formula ##STR7## wherein R.sub.1 is at least about a C.sub.16 aliphatic group which may be branched or straight chained and which may be saturated or unsaturated, R.sub.2 and R.sub.3 are each independently, hydrogen or a C.sub.1 to about C.sub.6 aliphatic group which can be branched or straight chained, saturated or unsaturated and which may be substituted with a group that renders the R.sub.2 or R.sub.3 group more hydrophilic, or
• (ii) salts of the amine corresponding to the formula ##STR8## wherein R.sub.1, R.sub.2 and R.sub.3 are the same as defined herein and X.sup.- is an inorganic anion, or
• (iii) a quaternary ammonium salt of the amine corresponding to the formula ##STR9## wherein R.sub.1, R.sub.2, R.sub.3 and X.sup.- are the same as defined herein and R.sub.4 constitutes a group which has previously been set forth for R.sub.3, none of R.sub.1, R.sub.2, R.sub.3 or R.sub.4 are hydrogen, and the R.sub.2, R.sub.3 and R.sub.4 groups of the amine salt and quaternary ammonium salt may be formed into a heterocyclic 5- or 6-member ring structure which includes the nitrogen atom of the amine,
• (b) generating a viscous fluid comprising micelles;
• (c) pumping the viscous fluid through a wellbore and into the formation at a pressure sufficient to fracture the formation, the formation having at least one aqueous zone comprising water and at least one hydrocarbon zone containing oil or gas;
• (d) producing oil or gas from the subterranean formation;
• and
• (e) reducing the amount of connate water produced.

A method of fracturing a subterranean formation using a viscous fracturing fluid, comprising:

• (a) providing a concentrate at the ground surface, the concentrate comprising a thickening amount of a surfactant capable of forming micelles;
• (b) providing an aqueous fluid component;
• (c) providing a water soluble salt;
• (d) mixing the concentrate with the aqueous fluid component and water soluble salt to form a viscous fracturing fluid and pumping the viscous fracturing fluid into a wellbore.

A method of fracturing a subterranean formation using a viscoelastic surfactant having micelles which are capable of selective formation or dissipation depending upon the polarity of the environment, comprising

• (a) providing a concentrate at the ground surface, the concentrate comprising an effective amount of at least one thickener in the fluid, the thickener being at least one member selected from the group consisting of ##STR10## wherein R.sub.1 is at least about a C.sub.16 aliphatic group which may be branched or straight chained and which may be saturated or unsaturated, R.sub.2 and R.sub.3 are each independently, hydrogen or a C.sub.1 to about C.sub.6 aliphatic group which can be branched or straight chained, saturated or unsaturated and which may be substituted with a group that renders the R.sub.2 or R.sub.3 group more hydrophilic, or
• (B) salts of the amine corresponding to the formula ##STR11## wherein R.sub.1, R.sub.2 and R.sub.3 are the same as defined herein and X.sup.- is an inorganic anion, or
• (C) a quaternary ammonium salt of the amine corresponding to the formula ##STR12## wherein R.sub.1, R.sub.2, R.sub.3 and X.sup.- are the same as defined herein and R.sub.4 constitutes a group which has previously been set forth for R.sub.3, none of R.sub.1, R.sub.2, R.sub.3 or R.sub.4 are hydrogen, and the R.sub.2, R.sub.3 and R.sub.4 groups of the amine salt and quaternary ammonium salt may be formed into a heterocyclic 5- or 6-member ring structure which includes the nitrogen atom of the amine, and
• (b) providing an aqueous fluid component;
• and
• (c) blending the concentrate with the aqueous fluid component above the ground surface to form a viscous fracturing fluid while substantially simultaneously pumping the viscous fracturing fluid below the surface of the ground into a wellbore.

A method of fracturing a formation, comprising:

• (a) providing a thickening amount of a surfactant capable of forming micelles and an aqueous medium;
• (b) generating a viscous fluid;
• (c) pumping the viscous fluid through a wellbore and into a formation at a pressure sufficient to fracture the formation, the formation having a hydrocarbon-bearing zone;
• and
• (d) facilitating a decrease in viscosity of the viscous fluid within the hydrocarbon-bearing zone.

A method of fracturing a formation penetrated by a wellbore using a viscoelastic surfactant fluid, comprising:

• (a) providing a viscoelastic surfactant fluid comprising
• (i) a thickening amount of a surfactant capable of forming micelles;
• and
• (ii) an aqueous medium;
• (b) generating a viscoelastic surfactant fluid containing micelles, the micelles having a micellar structure of hydrophilic and hydrophobic portions;
• (c) pumping the viscoelastic surfactant fluid containing micelles through a wellbore and into a formation at a pressure sufficient to fracture the formation, the formation having a hydrocarbon-bearing zone and an aqueous zone;
• (d) facilitating a decrease in viscosity of the viscoelastic surfactant fluid within the hydrocarbon-bearing zone;
• (e) maintaining integrity of the micelles within the aqueous zone;
• (f) thereby reducing the production of connate water from the formation after fracturing, and also reducing the amount of fluid loss into the formation during the pumping step.

A method of fracturing a formation penetrated by a well using a viscoelastic fluid, comprising:

• (a) providing a viscoelastic fluid comprising a surfactant capable of forming elongated micelles comprising
• (i) an aqueous liquid;
• (ii) a viscoelastic surfactant having a cationic surfactant ion, and
• (b) generating a viscoelastic fluid containing micelles;
• (c) pumping the viscoelastic fluid containing micelles through a wellbore and into a formation at a pressure sufficient to fracture the formation, the formation having a hydrocarbon-bearing zone and an aqueous zone;
• (d) facilitating a decrease in viscosity of the viscoelastic fluid within the hydrocarbon-bearing zone;
• (e) maintaining for some period of time the integrity of micellar structures within the aqueous zone;
• (f) thereby reducing the production of water from the formation upon placing the well back on production.

A method of reversibly altering the viscosity of an aqueous fracturing fluid to reduce the production of connate water subsequent to fracturing a well, the method comprising:

• (a) contacting the aqueous fracturing fluid with a viscoelastic surfactant based fracturing fluid comprising a surfactant capable of forming wormlike micelles;
• (b) increasing the viscosity of the aqueous fracturing fluid;
• (c) pumping the fracturing fluid into the well;
• (d) decreasing the viscosity of the aqueous fracturing fluid containing the viscoelastic surfactant by contacting the aqueous fracturing fluid having increased viscosity with hydrocarbons or substituted hydrocarbons;
• (e) contacting the aqueous fracturing fluid with aqueous subterranean fluids;
• and
• (f) reducing the production of water from the well.

A method of increasing the size of a fracture formed in a subterranean formation, comprising:

• (a) contacting an aqueous fracturing fluid with a thickening amount of a viscoelastic surfactant capable of forming a structured fluid;
• (b) increasing the viscosity of the aqueous fracturing fluid;
• (c) pumping the aqueous fracturing fluid into a formation penetrated by a well, the formation having a fracture face;
• (d) fracturing the formation at the fracture face;
• (e) contacting the aqueous fracturing fluid with the formation fracture face, wherein fluid loss into the formation fracture face is reduced;
• and
• (f) providing a greater volume of aqueous fluid with which to fracture the formation as a result of reduced fluid loss.