Chromium Triacetate Research Articles

Synthesis, characterization, and rheological behavior of HPG graft poly (AM-co-AMPS)/GO nanocomposite hydrogel system for enhanced oil recovery

The purpose of this study is to investigate the synthesis of graft copolymer nanocomposite based on hydroxypropyl guar (HPG) graft acrylamide (AM) and 2-acryloamido-2-methyl propane sulfonic acid (AMPS), reinforced with graphene oxide (GO), and study its suitability for the development of the copolymer-based hydrogel systems by chromium triacetate crosslinker to use in oil recovery applications. The characterization outcomes acknowledged the grafting of AM and AMPS onto HPG in the attendance of the GO. The uniform dispersion of GO at 0.1 wt.% was observed in the morphology analysis. Moreover, not only the viscosity but also, the storage and loss modulus of graft copolymer nanocomposites hydrogel improved by adding GO. The effect of graft copolymer nanocomposite and crosslinker concentrations on the performance of hydrogel was also evaluated and optimized by a rheological test. These results showed the outstanding performance of crosslinked hydrogel structure of HPG-g-poly (AM-co-AMPS)/GO, owing to the linking of AM with AMPS and grafting on the HPG chains and the surface of GO in attendance of chromium triacetate. This makes the copolymer hydrogel system more stable against salinity, shearing, and high temperatures. Therefore, this nanocomposite hydrogel system is potentially useful for oil recovery applications.

Preparation an Optimal Hydrogel of Water Shutoff for Iranian Oil Field

Presenting a suitable hydrogel for water shutoff in Iranian oil field is based on gelation time and gel strength. Rheological behavior of gel was the main purpose of this research. To determine the gelation time, thermal stability and gel strength a plan of bottle tests were conducted by using the central composite design method with two factors. The hydrogels composed of AN125VLM and chromium triacetate as copolymer and crosslinker, respectively were recorded for 8 weeks. Furthermore, the consistency modulus of the gels was measured by amplitude sweep tests using the Paar-Physica universal spectrometer, model MCR501. A hydrogel with 26,339 ppm concentration of copolymer and 0.12 ratio of crosslinker/copolymer and also gelation time of 2 days was selected as the optimal one. Also, it showed the maximum value of consistency modulus of 31,900 Pa among the other samples, tremendously, which showed the highest resistance against external stress. To ensure the gel strength among different effective parameters on the gel in porous media, a plan of rheological experiments were carried out. A 12 Run Plackett-Burman design was used for screening the eight parameters of NaCl, CaCl2, KCl and MgCl2 concentrations, temperature, pH, sodium lactate and nanoclay while keeping the optimal hydrogel component constant. Finally, it was found that temperature was the most effective parameter to control gelation time and also pH had negligible effect on the gelation time of this optimal gel.

Fabrication of a highly efficient new nanocomposite polymer gel for controlling the excess water production in petroleum reservoirs and increasing the performance of enhanced oil recovery processes

A new nanocomposite polymer gel is synthesized for reduction of excess water production in petroleum reservoirs at real operating conditions. This new nanocomposite gel contains SiO 2 nanoparticles, partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate. High pressure and high temperature tests using porous carbonate core are carried out to evaluate the effects of nanoparticles on the synthesized polymer gel performance. It is shown that the residual resistance factor ratio of water to oil using the synthesized polymer gel nanocomposite in this work is much higher than that of the ordinary polymer gels. The presented results confirm the high performance of the synthesized nanocomposite polymer gel for decreasing the water flow through porous carbonate bed. A mathematical model for description of oil and water flow behavior in the presence of synthesized nanocomposite polymer gel is also presented. The presented nano polymer gel leads to considerable cost saving in enhanced oil recovery (EOR) processes.

Colloidal dispersion gels for in-depth permeability modification

In this study, we describe the synthesis, characterization and evaluation of colloidal dispersion gels (CDGs) to be used as in-situ fluid diversion. The chemical stability of CDGs was improved by modifying the polymer mixture. The CDGs were synthesized by free radical crosslinking polymerization using 2-acrylamido-2-methylpropane sulfonic acid (AMPS), Acrylic acid (AAc), partially hydrolyzed polyacrylamide (HPAM) and chromium triacetate crosslinker. The effect of crosslinker/polymer concentration, salinity, gelation time, rheological behavior, particle size distribution of CDGs, also their thermo-chemical stabilities and resistance/residual resistance factor (RRF) were investigated.

Effect of Inorganic Polymer Gel Systems on Residual Resistance Factor in Fractured Core Model

Excessive water production through fractures become an important problem in oil exploration of fractured reservoirs. For this purpose, polymer gels were prepared by crosslinking of aqueous solutions of polymer and crosslinker for the purpose of water management in high water cut fractured reservoirs. A copolymer of sulfonated polyacrylamide was used as polymer and chromium triacetate (Cr(OAc)3) and aluminum nitrate nonahydrate (Al(NO3)3.9H2O) were used as inorganic crosslinkers at 90oC. Two quadratic models were presented for the two inorganic polymer gel systems to predict the gelation time by using a central composite design which showed highly significant results. The results also showed that polymer concentration was the main effect on gelation time. Increasing polymer concentration leads to accelerate the gelation process and then decrease of gelation time. Based on the gelation time and strength of three dimensional structure of polymer gel, the selected polymer gels of Cr(OAc)3 and Al(NO3)3.9H2O were applied to study the performance of polymer gel system in fractured core with the same polymer concentration of 37071 ppm and the crosslinker concentration of 13096 ppm and 2707 ppm, respectively. Also, the gelation time of these polymer gels was determined 12 h and 34 h, respectively. For this purpose, the coreflooding test was carried out to measure the output flow rate before and after polymer gel treatment in order to calculate the Residual Resistance Factor (RRF). As a result, after polymer gel treatment, the output flow rate decreased intensively and by increasing injection pressure, the RRF decreased gradually. The polymer gels of Cr(OAc)3 and Al(NO3)3.9H2O in the fracture were renitent up to 70 and 60 bar against the water pressure drop, while these polymer gels were renitent up to 60 and 40 bar against the oil pressure drop, respectively. The polymer gel of Cr(OAc)3 demonstrated higher residual resistance factor than the polymer gel of Al(NO3)3.9H2O.

Effect of Network Parameters of Preformed Particle Gel on Structural Strength for Water Management

Summary Preformed particle gel (PPG) is an appropriate solution for conformance control and water management in low permeability reservoirs. In this paper, the network parameters of PPGs are evaluated through swelling tests and rheology and by determining their role in maintaining structural strength. Several PPG hydrogels were prepared by varying the concentrations of polyacrylamide and chromium triacetate [Cr(OAc)3] as copolymer and crosslinker, respectively, using a central composite design. The characterization of these hydrogels was performed using a scanning electron microscope (SEM), electron dispersion X-ray (EDX), and environmental scanning electron microscope (ESEM). The correlation between reaction conditions and the network parameters of polymer networks, such as the molecular weight of the polymer chain between two neighboring crosslinks (Mc¯), the crosslink density, and the size fraction, have been determined. In addition, swelling of the hydrogels took place through the Fickian diffusion mechanism. Structural states of Laponite dispersions strongly depend on concentration and ionic strength. Based on the rheological tests, the dynamic modulus of the PPG was strongly dependent on the initial concentration and resulting network parameters of the hydrogel. The results showed an effective interaction between Mc¯ and the elastic modulus of the gel network. Through the optimization of the network parameters, the appropriate composition was presented on the basis of the factors of strength (complex modulus of 4×104 Pa in the plateau region), the formation of a 3D network, and the preservation of the viscoelastic structure in the presence of Na+, Ca2+, and Mg2+, at a salt sensitivity of 0.5. In addition, the optimum sample structure was confirmed on the basis of microscopic images. Based on the coreflooding data, the optimal PPG showed a disproportionate permeability reduction (DPR) index of 17.01 and indicated the dual performance of these materials against water and oil. Also, the permeability diagrams of the core showed wettability of the oil-wet core could shift to more water-wet after PPG injection. To summarize this research, we present the determination and analyses of the network parameters as a novel technique for predicting the performance of hydrogels in porous media, and for investigating their strength under harsh reservoir conditions. In other words, determination of the network parameters can be used to ensure the success of the gel performance in porous media.

Examination of disproportionate permeability reduction mechanism on rupture of hydrogels performance

In this paper, the overall performance of a disproportionate permeability reduction mechanism for a sulfonated polyacrylamide copolymer and the chromium triacetate crosslinker was investigated. A home-built gel filtration system was used for visual inspections and evaluations of the hydrogel performance. The experiments were conducted based on rheological test plans, energy-dispersive X-ray spectroscopy, and scanning electron microscope. Accordingly, quadratic equations based on the polymer and crosslinker concentrations were presented predicting the rupture pressure gradient of the hydrogel and the hydrogel output due to the oil and water injection through the hydrogel. It was indicated that the polymer concentration was the main effect on the rupture pressure gradient of the hydrogel and hydrogel output. Moreover, under constant concentration of crosslinker, increasing polymer concentration showed an increase in rupture pressure gradient and output of the hydrogel due to the increase of elastic modulus of hydrogel network and its strength as a viscoelastic material. As the hydrogel structure illustrated no rupture during the gel filtration experiments, a mechanism presented justifying the disproportionate permeability reduction phenomenon which in that under constant condition, the oil permeability through hydrogel was greater than the water permeability.

Numerical modeling and experimental investigation of inorganic and organic crosslinkers effects on polymer gel properties

Hydrogel treatment is one of the most important chemical methods to reduce excessive water in mature reservoirs. In this study, four hydrogel systems were studied for applying in water shutoff treatments. The hydrogel systems consisted of sulfonated polyacrylamide and chromium triacetate, aluminum nitrate nonahydrate (both as inorganic crosslinkers), polyethyleneimine, and hexamethylenetetramine (both as organic crosslinkers). The effects of polymer and crosslinker concentrations and their interactions on gelation and syneresis times were determined using the central composite design method. Based on the results values, four investigated samples of the hydrogel systems were selected for further rheological and thermal stability investigations. Among the four selected hydrogels, the polyethyleneimine one retained its structure under strains below 2050%. Thus, this system was recommended to use under different reservoir conditions (up to 110 °C). Moreover, it was found that gelation time and gel strength could be controlled by both adjusting polymer and crosslinker concentrations and choosing the right crosslinker type. The results of the study might be used in selecting the proper type of crosslinker in hydrogels based on their gelation time, syneresis time, deformation strength, and thermal stability for specific operating conditions.

Colloidal dispersion gels based on sulfonated polyacrylamide and chromium triacetate for harsh-environment

The aim of this study was to outline the preparation of colloidal dispersion gels (CDGs) based on sulfonated polyacrylamide (SPA) and chromium triacetate and investigating their stability in harsh conditions. The effect of crosslinker, polymer concentration, salinity, and gelation time and temperature on the formation, rheological behavior and size distribution of CDGs and also their thermo-chemical stabilities were investigated. It was found that the shear viscosity and size of CDGs decreased with increasing of preparation time. Dynamic light scattering and scanning electron microscopy evaluations showed that the size of CDGs particles decreased with increasing of the Cr3+ concentration. In addition, SPA solution had yield stress, while CDGs did not. The elevation of temperature inhibits while the salinity does not disturb the formation of CDGs. In the systems with lower polymer concentration, CDGs were formed. Conversely, in the systems with higher polymer concentration, bulk gels were formed. After aging, CDG sample had a minimal viscosity loss, indicating its exceptional thermo-chemical stability.

Effectiveness of foam-gel formulation in homogenizing the CO2 front during subsurface sequestration

Underground sequestration of carbon dioxide uniformly all over the designated geo-formation requires use of sealant formulation in large volume. Thin channels, cracks or fractures that otherwise would have allowed a by-pass of CO2 needs to be sealed a priori. Use of a mobile hydrogel formulation that gets crosslinked over time inside the channel may be used as a sealant. Introduction of gas phase in the form of small bubbles during placement may reduce the density of the formulation, help in reaching the hard-to-reach places near the caprock, and reduce the material cost of the treatment. The surfactant and the polymer in the aqueous phase may help in stabilizing the bubbles till the cross-linked network becomes immobile for blocking unwanted flow. The paper addresses the effectiveness of foam-gel layer in sealing reservoir fractures. Partially hydrolyzed polyacrylamide was crosslinked by chromium triacetate in presence of alpha olefin sulfonate as surfactant. The introduction of gas bubbles using a fluidic arrangement, the self-alignment of bubbles on a petridish, and the alignment under the confinement of a thin channel respectively are studied here. The stability of the composite film during shut-in period, and when subjected to water or CO2 pressure were evaluated. The rupture process and the hindered flow of injected phase at the post-rupture stage were characterized. Laser based volumetric images and the pressure gradients along the channel helped in ascertaining the flow path, and intrinsic flow resistances. The foam gel layer could withstand a CO2 pressure gradient of 0.7 kg/cm2 over a length of 30.48 cm without rupture. When the pressure exceeded the rupture pressure, an aperture equivalent to 1/10th of the distance between the two walls opened up for hindered flow of CO2.

Chromium(III) cross-linked poly(acylamide co-2-acrylamido-2-methyl-1-propanesulfonic acid) hydrogels, prepared by frontal polymerization in aqueous solutions

Polyelectrolyte hydrogels based on copolymers of acrylamide with 2-acrylamido-2-methylpropanesulfonic acid were prepared by frontal copolymerization in dilute aqueous solutions of the monomers using ammonium persulfate as initiator chromium triacetate as cross-linking agent. The influence of the monomer molar ratio, initiator and cross-linker concentration on the possibility of performing the copolymerization and monomer reactivity ratios in the frontal mode, and on the characteristics of the obtained hydrogels was examined.

Rheological and transport properties of sulfonated polyacrylamide hydrogels for water shutoff in porous media

In this research, an optimal hydrogel, based on sulfonated polyacrylamide, was synthesized by statistical design of experiments using central composite method. This new hydrogel composed of sulfonated polyacrylamide (AN125VLM) and chromium triacetate as copolymer and crosslinker, respectively. The bottle and rheological tests were conducted to investigate the gelation time, thermal stability, gel strength and also ultimate elastic modulus, complex modulus, and yield stress. It was found that copolymer concentration had the main effect in both rheological and transport properties of hydrogels. The sample prepared at optimum condition, i.e. copolymer concentration of 26,340 ppm and crosslinker/copolymer ratio of 0.12, had an ultimate elastic modulus of 29.9 kPa, yield stress of 800 Pa, and complex modulus of 32 kPa. A coreflooding test through fracture was carried out to examine the optimum gel performance in a porous media. A value of 483 for the residual resistance factor ratio of water to oil confirmed the high ability of the hydrogel in reducing the relative permeability of water to oil in fractured media. Copyright © 2014 John Wiley & Sons, Ltd.

Gelation Rheology and Water Absorption Behavior of Semi-Interpenetrating Polymer Networks of Polyacrylamide and Carboxymethyl Cellulose

Gelation rheology and swelling behavior of novel semi-interpenetrating polymer network (semi-IPN) hydrogels based on polyacrylamide are described. These hydrogels were prepared by solution cross-linking of partially hydrolyzed polyacrylamide and carboxymethyl cellulose (CMC), using chromium triacetate. Effects of CMC content on the gelation process and swelling behavior in tap water and different electrolyte solutions were investigated. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the semi-IPN gels increased with increasing CMC content. Enhancement of storage modulus was more than two times for the semi-IPN gels containing 50 wt% CMC. It was also found that increasing the CMC content decreased the loss factor, indicating that the elastic properties of this gelling system increase more strongly than the viscous properties. The swelling ratio of the semi-IPN gels in tap water, NaCl and CaCl2 solutions, and synthetic oil reservoir water slightly decreased as the concentration of the CMC increased. The improved storage modulus and slightly decreased swelling capacity in oil reservoir water make these semi-IPN hydrogels potentially good candidates for excess water treatment in oil recovery applications.

Swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions: comparison of theoretical and experimental results

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/sodium montmorillonite with chromium triacetate as ionic cross-linker. The effect of montmorillonite content on equilibrium swelling in NaCl and CaCl2 solutions, ultimate storage modulus and effective cross-link density was evaluated. The limiting storage modulus of the nanocomposite (NC) hydrogels dropped by increasing montmorillonite content up to 1,000 ppm, and then it increased by further montmorillonite loading. A mechanism is proposed for the formation of PAMPS/Na+-MMT/Cr3+ NC hydrogels. According to this mechanism, the drop in limiting storage modulus of the NC gels at low Na+-MMT concentration is due to ionic interactions between the negative layers of sodium montmorillonite and Cr3+, leading to decreased cross-link density. However, the increase of the limiting storage modulus of the NC gels at high clay concentration results from the strong interactions between the polyacrylamide chains and clay platelets. The equilibrium swelling ratio of the NC networks decreased with increase of montmorillonite content in both aqueous NaCl and CaCl2 solutions. In addition, the experimental swelling data of these NC hydrogels were described by a modified Flory–Rehner theory. The modified model was sensitive to montmorillonite concentration and it described adequately the swelling data for NC gels in NaCl solutions. Nevertheless, theoretical predictions showed some deviations from experimental results for swelling of NC hydrogels in CaCl2 solutions.

Study on the Dynamic Rheometry and Swelling Properties of the Polyacrylamide/Laponite Nanocomposite Hydrogels in Electrolyte Media

Polyacrylamide/laponite/chromium triacetate nanocomposite (NC) hydrogels were prepared by incorporation of the laponite nanoparticles in partially hydrolyzed polyacrylamide followed by cross-linking of their aqueous solutions with chromium triacetate. Influence of nanoparticle, cross-linker, polymer concentrations, and gelation media (water) temperature, salinity, and rheometer frequency on the viscoelastic behavior of the NC hydrogels were studied by probing the network properties. In addition, swelling behaviors of these NC gels in tap and oil reservoir water were evaluated. According to dynamic rheometry of the gelation process, the limiting storage modulus of the NC gels increased with increasing laponite content. The addition of laponite into the polyacrylamide gelling system increased their viscous properties more strongly than the elastic properties. The ultimate elastic modulus of the NC gels increased with increasing water salinity and temperature. Increasing rheometer frequency during gelation retarded the sol–gel transition and decreased the ultimate elastic modulus. The equilibrium swelling ratio of the NC hydrogels in tap water decreased with increasing laponite content. The salt sensitivity of the NC gels in oil reservoir water slightly decreased with increasing laponite content. These results suggest the superiority of the hydrolyzed polyacrylamide (HPAM)/chromium acetate/laponite NC hydrogels for water shut-off applications in oil reservoirs as compared with unfilled HPAM gels.

Rheological and swelling behavior of semi‐interpenetrating networks of polyacrylamide and scleroglucan

AbstractPreparation and characterization of novel semi‐interpenetrating polymer network (semi‐IPN) hydrogels based on partially hydrolyzed polyacrylamide (HPAM) and scleroglucan solution crosslinked with chromium triacetate are described. Effects of scleroglucan concentration on the gelation process and swelling behavior of synthesized hydrogels in different media were investigated using dynamic rheometery and swelling tests, respectively. Oscillatory shear rheology showed that the limiting storage modulus of the semi‐IPN gels increased with increase in scleroglucan concentration. It was also found that the viscous energy dissipating properties of the semi‐IPN gels decreased with increase in the crosslinker concentration of the gelation system. In addition, the loss factor slightly decreased by increasing the scleroglucan content, indicating that the viscous properties of this gelling system decreased more than its elastic properties. The swelling tests showed that the equilibrium swelling ratio (ESR) of the semi‐IPN networks decreased with increase in scleroglucan content, due to the decrease of ionic groups of polyelectrolyte hydrogel. However, the semi‐IPN gels showed lower salt sensitivity in synthetic oil reservoir water as compared with HPAM gels. Therefore, these semi‐IPN hydrogels may be considered potentially good candidates for enhanced oil recovery (EOR) applications. Copyright © 2009 John Wiley & Sons, Ltd.

Gelation and Swelling Behavior of Semi-Interpenetrating Polymer Network Hydrogels Based on Polyacrylamide and Poly(vinyl alcohol)

Novel semi-Interpenetrating Polymer Network (semi-IPN) hydrogels based on partially Hydrolyzed Polyacrylamide (HPAM) and Poly(Vinyl Alcohol) (PVA) were prepared by solution crosslinking using chromium triacetate. Effects of PVA content on the gelation process and swelling behavior in tap water and different electrolyte solutions were investigated. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the semi-IPN gels decreased with increasing PVA content. It was also found that increasing the PVA content increases the loss factor, indicating that the viscous properties of this gelling system increase more strongly than the elastic properties. The swelling ratio of the semi-IPN gels in tap water decreased as the concentration of the PVA increased. However, the semi-IPN gels showed lower salt sensitivity factor in synthetic oil reservoir water as compared with HPAM gels. Therefore, they are potentially good candidates for enhanced oil recovery applications.

Effect of montmorillonite on gelation and swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide/sodium montmorillonite with chromium triacetate. The gelation process and effects of clay content and ionic strength on swelling behavior were investigated. X-ray diffraction patterns indicated that exfoliated type of microstructure was formed. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the nanocomposite (NC) gels decreased with increasing clay content up to 1000 ppm, but it increased by further increase of Na +-montmorillonite concentration. It was also found that with increasing the clay content, the viscous energy dissipation properties of the nanocomposite gels increased. The swelling ratio of nanocomposite gels in tap water decreased as the concentration of the clay increased. However, nanocomposite gels showed higher resistance against syneresis in electrolyte solutions as compared with unfilled gels. Therefore, they are potentially good candidates for enhanced oil recovery applications.

Preparation and Swelling Behavior of Partially Hydrolyzed Polyacrylamide Nanocomposite Hydrogels in Electrolyte Solutions

In this research, nanocomposite hydrogels were prepared by cross‐linking of partially hydrolyzed polyacrylamide/sodium montmorillonite aqueous solutions with chromium triacetate. The gelation process and influence of nanoclay content and salt concentration on swelling behavior were investigated. Study of gelation behavior using dynamic rheometry method showed that increasing the nanoclay content decreases the storage modulus, due to the partial adsorption of polymer chains onto the clay surface and ionic interaction between negative layers of sodium montmorillonite and Cr.3+ By increasing the cross‐linker concentration of the gelation system, the viscous energy dissipation properties of the nanocomposite gel decreases. Swelling ratio of the nanocomposite gels in distilled water decreased as the concentration of the nanoclay increased. However, nanocomposite gels showed lower salt sensitivity in electrolyte media compared with unfilled gels.