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Papers by Dr Snehalata Agashe

La presente invention concerne un fluide de fracturation comprenant : de l'eau ; un sel solub... more La presente invention concerne un fluide de fracturation comprenant : de l'eau ; un sel soluble dans l'eau ; et un tensioactif viscoelastique. Le tensioactif viscoelastique augmente la viscosite du fluide de fracturation, la viscosite etant augmentee au moins jusqu'a une viscosite suffisante pour qu'un agent de soutenement soit en suspension dans le fluide de fracturation ; et ledit tensioactif viscoelastique est au moins a une concentration suffisante de sorte que le tensioactif viscoelastique forme spontanement des micelles. La presente invention concerne egalement un procede de fracturation d'une formation souterraine qui consiste : a introduire le fluide de fracturation dans un puits, le puits penetrant dans la formation souterraine ; et a creer une ou plusieurs fractures au sein de la formation souterraine a l'aide du fluide de fracturation.

L'invention concerne un procede d'entretien d'un puits de forage dans une formation s... more L'invention concerne un procede d'entretien d'un puits de forage dans une formation souterraine, qui comprend la preparation d'un fluide d'entretien de puits de forage comprenant (i) un agent de fracture, un precurseur d'agent de fracture ou des combinaisons de ceux-ci, l'agent de fracture comprenant un acide de sucre et (ii) un fluide a base aqueuse, et la mise en contact du fluide d'entretien de puits de forage avec un gâteau de filtration dans le puits de forage et/ou la formation souterraine.

Organically crosslinked polymer (OCP) systems are well-known sealants used for water shutoff in c... more Organically crosslinked polymer (OCP) systems are well-known sealants used for water shutoff in conformance applications. However, in multizone treatments with significant differences in permeability, a diverter is essential to divert the sealant to shut off less-permeable zones. This paper investigates the use of a relative permeability modifier (RPM) as a diverter for the sealant. This solution is most effective at shutting off zones in cases where multiple water-bearing strata with different permeability are encountered. The sealant is proven to be effective, even at 400°F. Two sandpacks of different permeabilities were formulated. All diversion tests were performed at room temperature and without any backpressure. The RPM adsorbed to the high-permeability zone more than the low-permeability zone. Once adsorbed, the RPM hindered flow of the water-based sealant in the high-permeability zone and diverted it to the low-permeability zone. With higher flow rates, the effect of diversion was lower because more sealant in the low-permeability pack provided resistance for further penetration of the sealant. The RPM and sealant were mixed at different ratios and tested under high-pressure/high-temperature (HP/HT) conditions to observe the effect of mixing on the gelation time for the sealant. The effect of the RPM on gelation time for the sealant was insignificant, provided the polymer and crosslinker concentration of the sealant was constant. RPMs have been widely applied to decrease the permeability to water in oil and gas wells. RPMs have also been used for acid diversion. The current study shows a new application of using RPMs as a diverter for sealants. This investigation will help increase the potential areas where multizone shutoff using a sealant treatment can be used.

Synthetic polymers have long been used as fluid-loss additives (FLAs) in hydraulic cement slurrie... more Synthetic polymers have long been used as fluid-loss additives (FLAs) in hydraulic cement slurries for cementing subterranean zones. Typically used synthetic polymeric materials include N,N-dimethylacrylamide and sulfonated acrylamide monomers, which are preferred for high temperature applications. However, as these materials are less environmentally acceptable, the search for more environmentally acceptable chemical increases. Although preferred materials are biopolymers, they sometimes impart high slurry viscosity at ambient temperature, and cause thinning and settling of the cement slurries at elevated temperatures. Thus, there is a need for an additive composition that is environmentally acceptable and performs better over a wide temperature range. This paper presents a novel idea of using a combination of two biopolymers, a hydrophobically modified (HM) biopolymer and a hydroxypropyl derivative of cyclodextrin (DCY) for controlling fluid loss, while imparting better cement slurry properties, stability, and viscosity. HM biopolymer as an FLA by itself causes excessive surface slurry viscosification at ambient temperature. However, when DCY was added into the cement slurry, optimum slurry viscosities were observed at ambient temperature, thus avoiding pumping issues. Laboratory experiments showed that the fluid-loss control was excellent, but the viscosity of cement slurry was high at ambient temperature when the HM biopolymer was used as a FLA by itself. The addition of DCY reduced the surface viscosity without compromising fluid-loss control and without affecting other properties. Studies conducted at elevated temperatures revealed that the HM biopolymer was left intact to maintain the cement slurry viscosity at that temperature, thereby helping prevent settling issues. Also, no significant effect on compressive strength development and thickening time of the cement slurry was observed with the addition of DCY molecules. The results of laboratory experimentation at ambient and elevated temperatures support the formation of in-situ inclusion complex formation of DCY molecules with the HM biopolymer.

Journal of Polymer Research

This work reports one-step synthesis process of LiOH-castor oil based polyurethane foam (PU) by c... more This work reports one-step synthesis process of LiOH-castor oil based polyurethane foam (PU) by completely replacing synthetic polyol. The reaction involved reacting varying weight percentage of lithium hydroxide with castor oil along with isocyanate. The successfully synthesized stable PU foams were characterized for density, sol fraction, cellular morphology, polymer phase morphologies and thermo-mechanical properties. The properties of the LiOH-castor oil based PU foams were compared with the conventional PU foam. Flexibility of the synthesized foams was observed to be lower than conventional PU foam for 0.05%, 0.1% and 0.5% LiOH due to the presence of closed cells with pin holes. Whereas, presence of open cellular structure in 0.3% LiOH-castor oil based PU foams showed flexible nature. Sol fraction of all the synthesized foams was found low (~ 5%) indicating improved reactivity. Thermal conductivity, glass transition temperature, thermal stability and mechanical properties of the synthesized PU foams suggest the possibility of replacing conventional PU foams for various applications.

Using solid particulate additives is becoming difficult because of strict health, safety, and env... more Using solid particulate additives is becoming difficult because of strict health, safety, and environmental (HSE) concerns and green operation initiatives taken by operators. When solid particulates are used as additives for downhole treatments, they are generally batch-mixed into the gelled fluid as long as the viscosity of the fluid is sufficient to prevent settling of the particles. It is possible that solid particles could settle and block the blending equipment; hence, an additional blender is required at location to mix such solid additives so that the main or primary blender remains functional throughout the job for subsequent mixing of other treatment fluids. Using the additional blender requires additional logistics, man power, and associated costs to the operator. Therefore, it is usually recommended to use liquid additives in the field to help avoid problems associated with using solids and related additional equipment issues. This paper describes the systematic approach used for the development of a non-aqueous suspension fluid for suspending varied-sized (8 to 40 mesh; ~2400 to ~400 μ particles of a particulate diverter with a specific gravity of 1.29 g/cm3. The developed suspension is stable at ambient temperatures for more than 30 days. It remains free flowing for more than 30 days, even at 40°F, and the solid particles do not settle, even at slightly higher temperatures, such as 100°F. The chemical score index (CSI) of the formulation is 120, which shows that the suspension is environmentally acceptable. Performance of the suspension was evaluated through core flow experiments with brown sandstone core samples, which indicated that the fluid containing the newly developed suspension of the diverter particles did not cause formation damage to the samples used.

An array of fluid-Loss additives (FLAs) are available for use in hydraulic cement slurries for ce... more An array of fluid-Loss additives (FLAs) are available for use in hydraulic cement slurries for cementing subterranean zones. Synthetic polymers based on N,N-dimethylacrylamide and sulfonated acrylamide derivative polymers are generally used for high temperature applications. These polymers are typically less environmentally acceptable than biopolymers. Biopolymers used as FLAs sometimes impart high slurry viscosity at ambient temperature, but lead to thinning and settling of the cement slurries at elevated temperatures. Therefore, there is a need for an additive composition that is environmentally acceptable and performs better at elevated temperatures. This paper describes a novel approach using a combination of a hydrophobically modified (HM) biopolymer and a derivatized cyclodextrin as an environmentally acceptable FLA system. Cyclodextrin (CD) is a cyclic oligosaccharide molecule with a hydrophobic cavity. CD binds selectively to hydrophobic molecules or parts of molecules that ...

ChemistrySelect, Apr 2, 2020

La presente invention concerne un fluide de fracturation comprenant : de l'eau ; un sel solub... more La presente invention concerne un fluide de fracturation comprenant : de l'eau ; un sel soluble dans l'eau ; et un tensioactif viscoelastique. Le tensioactif viscoelastique augmente la viscosite du fluide de fracturation, la viscosite etant augmentee au moins jusqu'a une viscosite suffisante pour qu'un agent de soutenement soit en suspension dans le fluide de fracturation ; et ledit tensioactif viscoelastique est au moins a une concentration suffisante de sorte que le tensioactif viscoelastique forme spontanement des micelles. La presente invention concerne egalement un procede de fracturation d'une formation souterraine qui consiste : a introduire le fluide de fracturation dans un puits, le puits penetrant dans la formation souterraine ; et a creer une ou plusieurs fractures au sein de la formation souterraine a l'aide du fluide de fracturation.

L'invention concerne un procede d'entretien d'un puits de forage dans une formation s... more L'invention concerne un procede d'entretien d'un puits de forage dans une formation souterraine, qui comprend la preparation d'un fluide d'entretien de puits de forage comprenant (i) un agent de fracture, un precurseur d'agent de fracture ou des combinaisons de ceux-ci, l'agent de fracture comprenant un acide de sucre et (ii) un fluide a base aqueuse, et la mise en contact du fluide d'entretien de puits de forage avec un gâteau de filtration dans le puits de forage et/ou la formation souterraine.

Organically crosslinked polymer (OCP) systems are well-known sealants used for water shutoff in c... more Organically crosslinked polymer (OCP) systems are well-known sealants used for water shutoff in conformance applications. However, in multizone treatments with significant differences in permeability, a diverter is essential to divert the sealant to shut off less-permeable zones. This paper investigates the use of a relative permeability modifier (RPM) as a diverter for the sealant. This solution is most effective at shutting off zones in cases where multiple water-bearing strata with different permeability are encountered. The sealant is proven to be effective, even at 400°F. Two sandpacks of different permeabilities were formulated. All diversion tests were performed at room temperature and without any backpressure. The RPM adsorbed to the high-permeability zone more than the low-permeability zone. Once adsorbed, the RPM hindered flow of the water-based sealant in the high-permeability zone and diverted it to the low-permeability zone. With higher flow rates, the effect of diversion was lower because more sealant in the low-permeability pack provided resistance for further penetration of the sealant. The RPM and sealant were mixed at different ratios and tested under high-pressure/high-temperature (HP/HT) conditions to observe the effect of mixing on the gelation time for the sealant. The effect of the RPM on gelation time for the sealant was insignificant, provided the polymer and crosslinker concentration of the sealant was constant. RPMs have been widely applied to decrease the permeability to water in oil and gas wells. RPMs have also been used for acid diversion. The current study shows a new application of using RPMs as a diverter for sealants. This investigation will help increase the potential areas where multizone shutoff using a sealant treatment can be used.

Synthetic polymers have long been used as fluid-loss additives (FLAs) in hydraulic cement slurrie... more Synthetic polymers have long been used as fluid-loss additives (FLAs) in hydraulic cement slurries for cementing subterranean zones. Typically used synthetic polymeric materials include N,N-dimethylacrylamide and sulfonated acrylamide monomers, which are preferred for high temperature applications. However, as these materials are less environmentally acceptable, the search for more environmentally acceptable chemical increases. Although preferred materials are biopolymers, they sometimes impart high slurry viscosity at ambient temperature, and cause thinning and settling of the cement slurries at elevated temperatures. Thus, there is a need for an additive composition that is environmentally acceptable and performs better over a wide temperature range. This paper presents a novel idea of using a combination of two biopolymers, a hydrophobically modified (HM) biopolymer and a hydroxypropyl derivative of cyclodextrin (DCY) for controlling fluid loss, while imparting better cement slurry properties, stability, and viscosity. HM biopolymer as an FLA by itself causes excessive surface slurry viscosification at ambient temperature. However, when DCY was added into the cement slurry, optimum slurry viscosities were observed at ambient temperature, thus avoiding pumping issues. Laboratory experiments showed that the fluid-loss control was excellent, but the viscosity of cement slurry was high at ambient temperature when the HM biopolymer was used as a FLA by itself. The addition of DCY reduced the surface viscosity without compromising fluid-loss control and without affecting other properties. Studies conducted at elevated temperatures revealed that the HM biopolymer was left intact to maintain the cement slurry viscosity at that temperature, thereby helping prevent settling issues. Also, no significant effect on compressive strength development and thickening time of the cement slurry was observed with the addition of DCY molecules. The results of laboratory experimentation at ambient and elevated temperatures support the formation of in-situ inclusion complex formation of DCY molecules with the HM biopolymer.

Journal of Polymer Research

This work reports one-step synthesis process of LiOH-castor oil based polyurethane foam (PU) by c... more This work reports one-step synthesis process of LiOH-castor oil based polyurethane foam (PU) by completely replacing synthetic polyol. The reaction involved reacting varying weight percentage of lithium hydroxide with castor oil along with isocyanate. The successfully synthesized stable PU foams were characterized for density, sol fraction, cellular morphology, polymer phase morphologies and thermo-mechanical properties. The properties of the LiOH-castor oil based PU foams were compared with the conventional PU foam. Flexibility of the synthesized foams was observed to be lower than conventional PU foam for 0.05%, 0.1% and 0.5% LiOH due to the presence of closed cells with pin holes. Whereas, presence of open cellular structure in 0.3% LiOH-castor oil based PU foams showed flexible nature. Sol fraction of all the synthesized foams was found low (~ 5%) indicating improved reactivity. Thermal conductivity, glass transition temperature, thermal stability and mechanical properties of the synthesized PU foams suggest the possibility of replacing conventional PU foams for various applications.

Using solid particulate additives is becoming difficult because of strict health, safety, and env... more Using solid particulate additives is becoming difficult because of strict health, safety, and environmental (HSE) concerns and green operation initiatives taken by operators. When solid particulates are used as additives for downhole treatments, they are generally batch-mixed into the gelled fluid as long as the viscosity of the fluid is sufficient to prevent settling of the particles. It is possible that solid particles could settle and block the blending equipment; hence, an additional blender is required at location to mix such solid additives so that the main or primary blender remains functional throughout the job for subsequent mixing of other treatment fluids. Using the additional blender requires additional logistics, man power, and associated costs to the operator. Therefore, it is usually recommended to use liquid additives in the field to help avoid problems associated with using solids and related additional equipment issues. This paper describes the systematic approach used for the development of a non-aqueous suspension fluid for suspending varied-sized (8 to 40 mesh; ~2400 to ~400 μ particles of a particulate diverter with a specific gravity of 1.29 g/cm3. The developed suspension is stable at ambient temperatures for more than 30 days. It remains free flowing for more than 30 days, even at 40°F, and the solid particles do not settle, even at slightly higher temperatures, such as 100°F. The chemical score index (CSI) of the formulation is 120, which shows that the suspension is environmentally acceptable. Performance of the suspension was evaluated through core flow experiments with brown sandstone core samples, which indicated that the fluid containing the newly developed suspension of the diverter particles did not cause formation damage to the samples used.

An array of fluid-Loss additives (FLAs) are available for use in hydraulic cement slurries for ce... more An array of fluid-Loss additives (FLAs) are available for use in hydraulic cement slurries for cementing subterranean zones. Synthetic polymers based on N,N-dimethylacrylamide and sulfonated acrylamide derivative polymers are generally used for high temperature applications. These polymers are typically less environmentally acceptable than biopolymers. Biopolymers used as FLAs sometimes impart high slurry viscosity at ambient temperature, but lead to thinning and settling of the cement slurries at elevated temperatures. Therefore, there is a need for an additive composition that is environmentally acceptable and performs better at elevated temperatures. This paper describes a novel approach using a combination of a hydrophobically modified (HM) biopolymer and a derivatized cyclodextrin as an environmentally acceptable FLA system. Cyclodextrin (CD) is a cyclic oligosaccharide molecule with a hydrophobic cavity. CD binds selectively to hydrophobic molecules or parts of molecules that ...

ChemistrySelect, Apr 2, 2020