application of sol-gel transition of gellan and … p_68-78.pdf · on the drilling fluids...

Journal of Chemical Technology and Metallurgy, 53, 1, 2018

68

APPLICATION OF SOL-GEL TRANSITION OF GELLAN AND XANTHAN FOR ENHANCED OIL RECOVERY AND AS DRILLING FLUIDS

Zhanara Nurakhmetova1,2, Iskander Gussenov1,2, Vladimir Aseyev3, Vladimir Sigitov2, Sarkyt Kudaibergenov1,2

ABSTRACT

The behavior of natural polysaccharides such as gellan, xanthan and gellan-xanthan mixtures in model aqueous-salt solutions and real oilfield saline water is evaluated by means of viscosimetry and rheological experiments. The main attention is paid to the solution behavior of gellan because of its excellent gelling property in presence of low molecular mass salts. The results obtained show that the effectiveness of alkaline and alkaline earth metal salts in enhancement gellan gelation changes in the following order: BaСl2 > CaCl2 ≈ MgCl2 > KCl > NaCl.

The mechanical properties of gellan gels are studied in presence of alkaline, alkaline earth metal salts and in oilfield water. As a result, the Young modules and breaking stresses are found. The sol-gel transition of gellan and gellan-xanthan solutions inside of a sand pack model is demonstrated. The hydrodynamic behavior of 0.5 mass % gellan and 0.5 mass % gellan-xanthan solutions injected into the sand pack model of a high (20 D) and low (2 D) permeability is used to model the oil reservoirs in the process of enhanced oil recovery. The brine-initiated gelation of gellan and gellan-xanthan mixture is used for plugging of oil reservoir high-permeable channels and as a shut-off agent in polymer flooding technology. The influence of gellan and gellan-xanthan mixture together with bentonite on the drilling fluids rheological characteristics is evaluated for simulation of the drilling mud ability of importance for carrying up the drilled rock particles from the bottom hole of the well to the surface.

Keywords: gellan, xanthan, rheology, sol-gel transition, oil recovery, drilling fluids.

Received 17 May 2017Accepted 20 October 2017

Journal of Chemical Technology and Metallurgy, 53, 1, 2018, 68-78

1 Satbayev University, 22 Satbayev str., Almaty, Republic of Kazakhstan E-mail: [email protected] Institute of Polymer Materials and Technology 22 Satbayev str., Almaty, Republic of Kazakhstan E-mail: [email protected] Department of Polymer Chemistry, University of Helsinki Helsinki, Finland E-mail: [email protected]

INTRODUCTION

Low acyl gellan (LAG) which is produced by the bacterium Pseudomonas elodea consists of a tetrasac-charide repeating unit of D-glucose, D-glucuronic acid, D-glucose, and L-rhamnose [1 - 10]. The review by Mor-ris et al. [11] comprehensively considers the structure, rheology, gelation, topology, and application aspects of gellan. The coil-helix conformational and sol-gel phase transitions of gellan gums induced by temperature, salt addition, pH change etc. are the main subject of many

studies [12 - 17]. It is commonly accepted [2, 3, 5, 7-12, 18] that gellan gum exhibits a conformational change from a disordered state (single chain) to an ordered one (double helix) with decrease of temperature. The gelation is considered mediated by double-helix formation and their association enhanced in the presence of mono- and divalent alkaline and alkaline earth cations [19 - 22]. It is established [16] that the extent of aggregation and the effectiveness of promoting gel formation by ad-dition of ions is in correspondence with the line: Cs+

> Rb+ > K+ > Na+ > Li+. Divalent cations seem to bind

Zhanara Nurakhmetova, Iskander Gussenov, Vladimir Aseyev, Vladimir Sigitov, Sarkyt Kudaibergenov

69

directly to gellan macromolecules forming aggregates of gellan helices with the effectiveness of Ca2+ ˃ Mg2+

[18 - 25]. The main difference between the monovalent and divalent cations is that the monovalent cations shield the electrostatic repulsion between the COO- while the divalent cations, rather than by suppressing electrostatic repulsion, form interchain ionic bonds with carboxylic groups of the glucuronic acid units resulting in the ag-gregation of the double helices [26]. The sol-gel technol-ogy is an effective tool to design materials with unique chemical, physical and mechanical properties. The transition from a sol to a gel state proceeds with increase of disperse phase concentration or under the action of external factors (polymer concentration, temperature, time, medium pH, ionic strength, etc.). The rheological properties of deacylated gellan gel are superior to those of other common polysaccharide gels such as agar, k-carrageenan, and alginate at similar concentrations. The hardness, brittleness, and elasticity of gellan gel at 0.5 % is comparable to, and its stiffness is much higher than 1% k-carrageenan, 1.5 % agar, or 4.0 % gelatin gels [27]. Earlier [28 - 30] we have demonstrated for the first time that the gellan solution can successfully be used for enhanced oil recovery (EOR). Gellan has the remarkable property of plugging oil reservoir high drainage channels.

Xanthan is one of the most extensively investigated polysaccharides produced by fermentation of a carbo-hydrate by naturally occurring bacterium Xanthomonas compestris. It is completely soluble in hot or cold water, hydrates quickly once dispersed and provides water binding resulting in very high viscosity solutions at a low concentration. These properties encourage its use as a thickener, a stabilizer, an emulsifier and a foaming agent. The industrial importance of xanthan is determined by its ability to control the rheology of water based systems. Even at low concentrations xanthan gum solutions show a high viscosity in comparison with other polysaccharide solutions. Xanthan gum solutions are highly pseudoplas-tic, i.e. even after high shear rates the initial viscosity is rebuilt immediately. Xanthan gum is mainly considered to be non-gelling and used for the control of viscosity due to the tenuous associations endowing it with weak-gel shear-thinning properties. Xanthan gum is used in many fields such as petroleum production, pipeline cleaning, enhanced oil recovery, textile printing and dyeing, ce-ramic glazes, slurry explosives and in cosmetics, in the

food and pharmaceutical industries [31]. Xanthan gum in water muds provides non-Newtonian mud rheology, which is required for efficient cuttings lifting in lower density muds. Xanthan is an anionic polymer with an average molecular mass of (1-2).106 Dalton, tolerance for salinity and pH independence (1 - 13). The tempera-ture tolerance varies with the water-phase components, but starts to degrade around from 93°C to 121°C [32, 33]. Xanthan interacts with other polysaccharides giving a synergistic increase of the solution viscosity, i.e. the observed viscosity is higher than the sum of the viscosi-ties of the pure components [34].

The behavior of aqueous solutions of gellan, xanthan and gellan-xanthan mixture under oil reservoir condi-tions and as drilling fluids is modelled in the course of the investigation presented. This is achieved by studying the viscosity, the rheology, the sol-gel phase transitions of the polysaccharides in presence of NaCl, KCl, MgCl2, CaCl2. and oilfield saline water containing 73 g L-1 of al-kaline and alkaline earth metal salts. The results obtained will provide to select the optimal concentrations of the polysaccharides to be injected into the oil reservoir for application in EOR and as drilling fluids.

EXPERIMENTAL

MaterialsFood grade low acyl gellan (LAG) (PubChem SID

135330201) purchased from “Zhejiang DSM Zhongken Biotechnology Co., Ltd.”, China, and xanthan gum purchased from “Xinjiang Fufeng Biotechnologies Co. Ltd”, China, were used without further purification. They were dispersed in distilled water at room temperature (25 ± 1°C) under vigorous magnetic stirring. Their concentrations selected for experiments varied from 0.2 to 1 wt.%. The salts NaCl, KCl, CaC12, MgCl2, and BaCl2 purchased from JSC “Reactive”, Russia, were used without further purification. The oilfield water from “Kumkol” oil reservoir with density of 1.05 g∙cm-3 and pH 6.68 contained Na+ and K+ of 22.5 g L-1, Ca2+ of 3.8 g L-1, Mg2+ of 0.85 g L-1 and Cl- of 43.9 g L-1. The total salinity was 73 g L-1.

MethodsThe reduced viscosity (ηsp/C) of aqueous gellan

solutions was measured using Ubbelohde viscometer at 25 ± 0.1oC. Its technical characteristics referred to a


70

capillary length of 90 mm, a capillary diameter of 0.86 mm, while the diapason of viscosity measurement in correspondence with Interstate Standard GOST 10028-81 was from 6 mm2 s-1 to 30 mm2 s-1. The rheological behavior of the polysaccharides aqueous solutions was monitored with Rheolab QC, Anton Paar (Austria) as a function of the polymer concentration, the salt types, pH and the temperature. The rheological measurements were carried out by C-DG42/SS/QC-LTD – Double Gap Cup compatible with LTD80. The results approximation was performed by the Ostwald-de Waele model aiming to determine the corresponding rheological and confor-mational characteristics. The model equation used was τ = К • уn where K was the consistency index, n was the nonlinearity index, while τ was the shear stress. The values of K and n of the Ostwald-de-Waele equation were found from the rheological data. The oilfield water total salinity was determined on SevenCompactTM S230 (Mettler-Toledo, Switzerland). Its elemental composi-tion was analyzed with a X-ray fluorescence analyzer (Epsilon 3 SW LTU, PANalytical, The Netherlands). A sand pack model of a permeability of 20 D and 2 D, re-spectively, was selected to test the behavior of gellan and gellan-xanthan solutions in porous media. The coreflood experiments were described in details in our previous paper [29]. The experiments with the sand pack model were carried out using UIC-C(2) (Russian Federation). The fluid loss indicator (W) was measured with the help of ВМ-6 (Russian Federation). The mud cake thickness (d) was measured by ВИКА ИВ-2 (Russian Federation).

RESULTS AND DISCUSSION

Gellan and XanthanGellan is an anionic extracellular bacterial polysaccha-

ride discovered in 1978 [30]. The structural formula of gellan consisting of tetrasaccharide repeating units: 1,3-linked β-D-glucose, 1,4-linked β-D-glucoronic acid, 1,4-linked β-D-glucose, and 1,4-linked α-L-rhamnose is shown in Fig. 1.

The application aspects of gellan in oil industry, to our knowledge, have not been described yet. Xanthan gum is also a microbial exopolysaccharide produced by bacterium Xanthomonas campestis. It consists of repeated pentasaccharide units composed of two D-glucopyranosyl units, two mannopyrasonyl units and D-glucopyranosyluronic acid in the molar ratio of 2.8:2.0:2.0 (Fig. 2). Xanthan is widely used in oil

recovery, fracturing, pipeline cleaning and oil well drilling [32 - 34].

Influence of alkaline, alkaline earth metal ions and oilfield water on the viscosity, the gel formation and the morphology of gellan

The viscosimetric measurements were performed with 0.2 mass % gellan because the reduced viscosity of 0.5 mass % gellan is extremely high and difficult to

Fig. 1. The repeating monomeric unit of gellan gum.

Fig. 2. The primary structure of xanthan.

Fig. 3. Dependence of the reduced viscosity of 0.2 mass % gellan on the ionic strength of the solution adjusted by ad-dition of oilfield water salinity of 73 g.L-1 (1), CaCl2 (2), BaCl2 (3), MgCl2 (4). The arrows indicate the start of the gelation process (temperature of 25oC).


71

measure. The dependence of the reduced viscosity of 0.2 mass % gellan on the ionic strength of the solution adjusted by addition of BaСl2, CaCl2, MgCl2 and oilfield water of salinity of 73 g L-1 is shown in Fig. 3. Accord-ing to viscosimetric data [35] the salts effect gelation enhancement changes in the following line: BaСl2 > CaCl2 ≈ MgCl2 > oilfild water. This is in good agree-

ment with the results for gellan [36].One of the remarkable properties of gellan is its abil-

ity to undergo sol-gel phase transitions in oilfield brine water of Kumkol oil reservoir of total salinity of 73 g L-1 containing mono- and divalent cations, such as Na+, K+, Ca2+ and Mg2+ [29, 37]. The addition of 10 vol.% - 40 vol.% oilfield saline water to an aqueous gellan solution causes gel formation (a sol-gel transition), while the presence of 50 vol. % - 90 vol. % oilfield saline water leads to gellan precipitation (Fig. 4).

As mentioned above gellan gelation is related to the acceleration of the charge-shielding effect by monova-lent ions and the “bridging” effect of the divalent one. In combination, they give the double helix structure stabilized additionally by hydrogen bonds [38]. Both mono- and divalent cations present in oilfield water are associated with the surface of gellan double helix. It is assumed that the phase separation of gellan in high saline oilfield water may be due to the synergistic “salting out” effect of the mono- and divalent cations. Gellan sol-gel transition in oilfield water may promote enhanced oil recovery from the saline reservoirs. The morphology of gellan gels formed in the presence of NaCl, KCl, MgCl2 and CaCl2 refers to micron-sized strands forming a continuous network (Fig. 5).

Mechanical properties of gellan gelThe strain-stress data of gellan gels obtained in the

course of the compression tests is shown in Table 1. The

Fig. 4. Illustration of the samples referring to an initial 0.5 mass % aqueous solution of gellan (0), a sol-gel transition (1-4) and formation of liquid and dense solid phases (5-9) in presence of oilfield water salinity of 73 g L-1. The oilfield water content is 0 (0), 10(1), 20(2), 30(3), 40(4), 50(5), 60(6), 70(7), 80(8) and 90 vol.% (9). Vtotal = 5 mL, Ctotal = 0.5 mass %.

Fig. 5. SEM images of gellan gels formed in presence of NaCl, KCl, MgCl2 and CaCl2.

Table 1. Mechanical properties of gellan gel induced by addition of individual salts and oilfield saline water.

No. Gellan gels induced by salt addition

Young’s modulus, 10-2 N m-2

Fracture stress, %

1 NaCl 7,84 26,1 2 KCl 8,45 31,7 3 MgCl2 9,01 31,7 4 CaCl2 9,36 32,0 6 Oilfield saline water 9,54 33,1


72

values of the Young’s modulus and breaking stress are included as well.

The mechanical parameters of gellan gel increase as a function of the additive as follows: oilfield water > CaCl2 > MgCl2 > KCl > NaCl. They coincide well with the viscosity and rheology data. As seen from Table 1, the values of the Young’s modulus and breaking stress of gellan gel formed in oilfield water are higher than those obtained in individual salts presence. This may be due to the synergistic effect of the monovalent and divalent cations contained in the saline water. The good mechanical properties of gellan gel in oilfield water provide plugging of the high permeable channels in an oil reservoir (Fig. 6).

Rheology of gellan, xanthan and gellan-xanthan solutions

A comprehensive information on the rheological properties of gellan, xanthan and gellan-xanthan mixture as a function of the temperature and the salt content is required to predict the polysaccharides behavior in the oil reservoir and as drilling mud. The shear stress-shear rate curves of 0.5 mass % gellan solution on the tem-perature show pseudoplastic behavior in the temperature interval between 25oC and 55oC (Fig. 7a). Newtonian flow of gellan solution is realized at 60oC - 70oC. The step-wise transformation of gellan solution from pseu-

doplastic behavior to Newtonian one may be explained by “melting” of gellan double stranded structure and formation of gellan macromolecules in a random coil conformation at a higher temperature. The 0.5 % xanthan solution belongs to a typical viscoplastic liquid in the temperature range of 25oC - 40oC. However, it transforms to a pseudoplastic liquid between 40oC and 65oC. The gellan-xanthan mixture behaves as a pseudoplastic liquid in the whole temperature interval of 25oC - 70oC due to the formation of interpolymer complexes between gellan and xanthan stabilized by hydrogen bonds.

The dependences of the shear stress on the shear rate for gellan and gellan-xanthan solutions in presence of NaCl, KCl, CaC12, MgCl2 and oilfield water are shown in Fig. 8. The increase of the shear stress as a function of the shear rate follows the line: oilfield water > CaC12 > MgCl2 > KCl > NaCl (Fig. 8a). This sequence is in a good agreement with the salts effect on enhancing gellan gelation. It is seen that the effect of oilfield water is more substantial compared to that of the individual salts. This may be due to the combined effect of alkaline and alkaline earth metal ions on the coil-helix conformation of gellan. In case of the gellan-xanthan (2:1) mixture, the shear stress increases as follows: CaC12 > KCl > NaCl > MgCl2 (Fig. 8b). The gradually transformation of the gellan-xanthan mixture from a pseudoplastic to a viscoplastic liquid in the presence of salts is supposed to result from the formation of ternary polymer metal complexes.

Fig. 6. Mechanical properties of gellan gel formed in oilfield water salinity of 73 g/L.

Fig. 7. Shear stress-shear rate curves of 0.5 mass % gellan (a), xanthan (b) and gellan-xanthan (2:1) (c) solutions in the temperature interval of 25oC - 70oC.


73

Behavior of gellan solution in a sand pack modelGellan’s ability to viscosify and gelate in saline me-

dia is its specific feature. Its advantages in comparison with those of poly(acrylamide) [39] traditionally used for EOR refer to: 1) production on the ground of renew-able source of raw materials (biomass for instance); 2) requirements of a low injectable concentration; 3) provision of high oil recovery effectiveness; 4) ecologi-cal friendliness due to biodegradability. In this respect, it is also of interest to study the gellan solution flow behavior in a sand pack model. It is expected that the gellan solution in the course of injection into oil reservoir undergoes a coil-helix conformation and sol-gel phase transitions. Initially, the pumping of an aqueous solution of gellan into the injection well is easy because of the low viscosity of the polymer solution. Further, the gel slug formed upon the contact with underground saline medium starts to plug the high-permeable channels with-out touching the less-permeable hydrocarbon-productive zones (Fig. 9).

Subsequently, the injected water (or water flooding) penetrates as much as possible into the less permeable zones so that oil is displaced from these poorly swept zones. The sand pack model of an absolute gas perme-ability and a pore volume of 20 D and 47 cm3 (porosity - 38 %), respectively, is initially saturated with brine water of salinity of 73 g∙L-1. The brine saturated sand pack is flooded by crude oil with viscosity of 1.218 mPa s and density of 0.772 g cm-3. As a result, the initial oil and water saturation became equal to 73.2 % and 26.7 %, respectively. The temperature of the sand pack model is kept at 62°C during the whole filtration experiments. Water flooding is simulated by injection of brine into the sand pack model under the flow rate of 0.5 cm3∙min-1. After pumping of 2 pore volumes (1 pore volume is equal to 50 cm3) of water through the model, the oil displacement coefficient becomes equal to 49 %. After water flooding completion, 0.5 mass % gellan solution is injected into the sand pack under the same flow rate. The hydrodynamic behavior of the gellan solution within the sand pack model is visualized by the dependence of the injection pressure versus the pumped volume (Fig. 10). As seen from Fig. 10a, after injection of 40 cm3 of gellan solution the injection pressure sharply increases up to 0.47 MPa, while it dramatically decreases down to 0.2 MPa after injection of 50 cm3 of gellan solution. This behavior is interpreted as follows. When the gellan solu-tion penetrates the high permeable channels (or pores) it contacts with brine and the gelation process is enhanced. The formation of gel particles within the pores decreases the permeability and increases the injection pressure. The injection of 10 cm3 - 40 cm3 of gellan solution into the

Fig. 8. Shear stress-shear rate curves of 0.5 mass % gellan (a), 0.5 mass % xanthan (b), 0.5 mass % gellan-xanthan (2:1) solutions (c), of an ionic strength µ = 0.01 adjusted by addition of NaCl (1), KCl (2), MgCl2 (3), CaC12 (4) and oilfield water (5).

Fig. 9. Photos of an aqueous solution of gellan prior to (a) and after (b) contacting reservoir brine of 73 g L-1 salinity.


74

sand pack saturated by brine and oil is accompanied by displacement of oil-containing liquid (samples no. 1 - 4 in the inset).

An accumulation of gel particles inside the high per-meable channels and hence severe plugging of the sand pack model takes place with the introduction of 40 cm3 to 50 cm3 of the injected gellan solution. The plugging is accompanied by lack of squeezed liquid (sample no.5 in the inset). Some of the gellan gel generated inside of the porous media is displaced out of the model after injection of 50 cm3 - 60 cm3 of gellan solution. The breakthrough of gel plug leads to sharp decrease of the injection pressure together with continuous displace-ment of oil and water mixture from the sand pack model (samples no. 7 - 10 in the inset). The permeability of the porous media and the gellan concentration play a crucial role in the plugging mechanism. When the permeability of the porous media is extremely high (for instance, 20 D) the gelation of gellan takes place only once causing a sharp increase and a decrease of pressure. A periodic increase and decrease of the injection pressure (pressure oscillation) is observed for the sand pack model of a lower permeability (Fig. 10b). For example, an oscilla-tion behavior of 0.5 mass % gellan solution is detected inside the sand pack model of a permeability of 2 D. The hydrodynamic behavior of 0.5 mass % gellan solution presented in Fig. 10b may be explained in the follow-ing way. When the gellan solution penetrates the brine saturated sand pack model, it preferentially occupies the high permeable channels and plugs them (the injection

pressure increases). The accumulation of gel particles attained leads to the plugging of new channels. When they are reached by the solution, it flows into them (the injection pressure decreases). Thus, the permanent plug-ging of the different channels by the gellan gel leads to constant redirection of the gellan solution to pores of lower and lower permeability. This step-wise plugging of high and low permeable channels is responsible for the periodic increase and decrease of the injection pressure.

Behavior of the gellan and xanthan (2:1) mixture in a sand pack model

The injection of 0.5 % gellan-xanthan solution into sand pack model is conducted at a flow rate of 0.1 cm3

min-1. In the course of injection the injection pressure increases up to its maximal value - 1 MPa confirming the high ability of the gellan-xanthan mixture to plug the pores space (Fig. 11, curve 1). To simulate the water flow towards the producing well, a further injection of water into the core sample is conducted from the oppo-site side of the injected polymer. Curve 2 of the Fig. 11 shows that the water flow rate increase does not lead to a substantial increase of the injection pressure. During the last step, at a flow rate of 1cm3 min-1, the injection pressure increases up to 0.15 MPa. These results indicate the ability of gellan-xanthan (2:1) mixture to plug high permeable pore channels. However, the mixture is less effective in creating high resistance to water filtration. The results of the polymer flooding experiment are sum-marized in Table 2. The gellan-xanthan (2:1) mixture

Fig. 10. Variation of the injection pressure during the filtration of 0.5 mass % gellan solution through a sand pack model of a permeability of 20 D (a) and 2 D (b). The pore volume is equal to 50 cm3, the temperature is 55 °C, while the flow rate is 0.5 cm3 min-1.


75

plugs pore spaces less effectively than the gellan solu-tion itself, so mixing of xanthan with gellan does not provide an improvement of oil displacement and does not increase the resistance to the water flow. Moreo-ver, the hydrodynamic behavior of the gellan-xanthan mixture does not favor the transfer of big volumes of the solution deeply into the reservoir. This is verified by the gradual increase of the injection pressure up to 1 MPa during the injection of the mixture into the core sample, whereas the pressure increases only up to 0.15 MPa in case of gellan injection. The subsequent water

injection reveals that pure gellan plugs more effectively high permeable channels.

Influence of dispersed phase on the rheological

behavior of gellan solutionsEvaluation of the influence of bentonite on rheo-

logical characteristics of gellan solution is necessary for simulation of drilling mud ability to carry up drilled rock particles from the bottomhole of the well to the surface. Influence of dispersed phase on the rheologi-cal and conformational characteristics of 0.5 mass % gellan solution in the presence of bentonite was studied by rotational viscometry. Addition of bentonite leads to increase of pH value from 6.4 to 10.0. Shear stress versus shear rate curves of the colloid systems were processed by the model of Ostwald–de Waele. The low value of n is characteristic for high pseudoplasticity. It is commonly accepted that the pseudoplastic liquids with n < 0.3 are more effective as drilling fluids because they provide the effective borehole cleaning with minimal well pressure loss. The value of n depends on the ability of system to form the hydrogen bonds in solutions for evaluation of internal uniformity; the consistency index K indicates the strength of hydrogen bonds. The rheological parameters obtained for 0.5 mass % gellan in the presence of benton-ite are summarized in Table 3. The values of correlation coefficient (R2) show, that the model of Ostwald-de Waele better describes the rheological behavior of gellan

Fig. 11. Time dependent changing of injection pressure in the course of injection of 0.5 % gellan-xanthan (2:1) mixture (1) and reservoir water (2).

Table 2. Oil displacement efficiency of water flooding and gellan-xanthan flooding.Step Type of injection Oil displacement

coefficient, % 1 Water flooding 52 2 Injection of 0.5% gellan-xanthan (2:1)mixture 58 (increment 6%)* 3 Injection of water after injection of 0.5% gellan-

xanthan (2:1) mixture 58 (increment 0%)

*Increment of oil displacement coefficient is equal to 6 % obtained in lab conditions.

Table 3. Rheological parameters of gellan solution in the presence of bentonite at 25°C.Сbentonite,

% Сgellan, %

Rheological parameters

Model of Ostwald-de Waele, after 1 min

Model of Ostwald-de Waele, after 10 min

K, Pa·sn n R2 K, Pa·sn n R2 0 0.5 0.371 0.829 0.958 0.43 0.739 0.968 2 0.5 8.038 0.243 0.997 9.69 0.242 0.999 4 0.5 9.754 0.218 0.992 11.36 0.263 0.986 6 0.5 10.781 0.288 0.989 12.38 0.247 0.964 8 0.5 11.445 0.298 0.972 9.50 0.192 0.693


76

solution and the colloid-dispersed systems gellan-ben-tonite excepting for 8 mass % of bentonite concentration. When the bentonite concentration is equal to 8 mass % or more the Ostwald-de Waele model cannot properly describe the rheological behavior of the systems due to formation of micro- and macrogels.

Influence of dispersed phase on the rheological behavior of gellan-xanthan (2:1) mixture

For the mixture of gellan-xanthan the formation of strong hydrogen bonds between two macromolecules is expected leading to high values of K while the value of n is slightly changed (Table 4).

Analysis of the results shows that all solutions form a good filter cake with the thickness d = 0.5 mm but the best result was obtained for gellan-xanthan (2:1) mixture (the sample No.5) due to less fluid loss indicator (W) (Table 5). The decrease of the filtration index and pseudoplastic behavior of the gellan-xanthan mixture (2:1) is probably connected with complexation of gellan with both xanthan and bentonite and stabilization of the formed structure by hydrogen bonds.

CONCLUSIONS

The sol-gel phase transition of gellan in model aque-ous-salt solutions and in oilfield saline water was studied. It was shown that addition of 10 - 40 vol.% oilfield saline water to 0.5 mass % aqueous gellan solution causes the gel formation while addition of 50-90 vol.% oilfield saline water leads to formation of liquid and dense solid phases. The rheology of 0.5 mass % gellan solution at temperature interval of 25 - 55oC is pseudoplastic. The Newtonian flow of 0.5 mass % gellan solution is real-ized at 60 - 70oC. Step-by-step transformation of gellan solution from pseudoplastic character to Newtonian may be explained by “melting” of double stranded structure of gellan and existing of gellan macromolecules in random coil conformation at higher temperature. Both shear stress and effective viscosity of gellan including the Young’s modulus and breaking stress are changed in the following order: Oilfield water > CaC12 > MgCl2 > KCl > NaCl. The highest gelation efficiency of oilfield water in comparison with individual salts may be due to synergistic “salting out” effect of both monovalent

Table 4. Rheological parameters of gellan-xanthan (2:1) mixture in the presence of bentonite at 25°C.

Сbentonite, %

Сgellan-xanthan, %

Rheological parameters Model of Ostwald–de Waele,

after 1 min Model of Ostwald–de Waele,

after 10 min K, Pa·sn n R2 K, Pa·sn n R2

0 0.5 0,985 0,324 0,986 0,619 0,416 0,989 2 0.5 1,556 0,390 0,979 2,125 0,347 0,986 4 0.5 2,569 0,348 0,985 2,481 0,396 0,965 6 0.5 2,749 0,341 0,983 4,032 0,289 0,993

No. Composition of drilling fluids*, % Characteristics of drilling fluids Сtotal Сgellan/

Сxanthan Сbentonite

CKCl рH Funnel

viscosity, sec/qt

W, сm3 d, mm

1 0,5 1:3 1 2 9,7 41 10 0,5 2 0,5 1:3 1.25 2 9,7 41 10 0,5 3 0,5 1:3 3 3 9,8 39 10 0,5 4 0,5 1:2 0,5 3 9,4 30 10 0,5 5 0,5 2:1 1,75 0,045 9,8 36 5,6 0,5

* The rest is water

Table 5. Composition and properties of drilling fluids based on gellan-xanthan mixtures.


77

and divalent cations present in saline water. The brine-initiated gelation of gellan may be used for plugging of the high-permeable channels of oil reservoir and as a shut-off agent in polymer flooding technology. The gellan-xanthan and gellan-xanthan-bentonite systems are suitable for the formulation of drilling fluids.

AcknowledgementsAuthors thank the Ministry of Education and Sci-

ence of the Republic of Kazakhstan for financial support (Grant No.4410/GF4 2015-2017).

REFERENCES

1. M. Akutu, K. Kubota, K. Nakamura, Light scatter-ing, sound velocity and viscoelastic behaviour of aqueous gellan solutions, Progress in Colloid and Polymer Science, 114, 1999, 56-61.

2. M. Emako, T. Tomohisa, A. Peter, N. Katsuyoshi, Effects of sodium chloride and calcium chloride on the interaction between gellan gum and konjac glucomannan, Journal Agricultural Food Chemistry, 44, 1996, 2486-2495.

3. Sh. Kanesaka, T. Watanabe, Sh. Matsukawa, Binding effect of Cu2+ as a trigger on the sol-to-gel and the coil-to-helix transition processes of polysaccharide, gellan gum, Biomacromolecules, 5, 2004, 863-868.

4. S. Khandker, N. Katsuyoshi, Chain release behavior of gellan gels, Progress in Colloid and Polymer Science, 136, 2009, 177-186.

5. K. Kohei, H. Junichi, M. Shiro, Effects of monova-lent cation and anion species on the conformation of gellan chains in aqueous systems, Carbohydrate Polymers, 61, 2005, 168–173.

6. T. Masakuni, T. Takeshi, T. Yukihiro, K. Teruko, Molecular origin for rheological characteristics of native gellan gum, Colloid and Polymer Science, 287, 2009, 1445-1454.

7. F. Mazen, M. Milas, M. Rinaudo, Conformational transition of native and modified gellan, Interna-tional Journal Biological Macromolecules, 26, 1999, 109-118.

8. T. Natakeyama, K, Nakamura, M. Takahashi, H. Ha-takeyama, Phase transitions of gellan-water systems, Prog. Colloid Polym. Sci., 114, 1999, 98-101.

9. R. Takahashi, M. Akutu, K. Kubota, K. Nakamura, Characterization of gellan gum in aqueous NaCl solution, Progress in Colloid and Polymer Science, 114, 1999, 1-7.

10. Y. Yuguchi, H. Urakawa, S. Kitamura, I. Wataoka, K. Kajiwara, The sol-gel transition of gellan gum aqueous solutions in the presence of various metal salts, Progress in Colloid and Polymer Science, 114, 1999, 41-47.

11. E. Morris, N. Katsuyoshi, M. Rinaudo, Gelation of gellan – A review, Food Hydrocolloids, 28, 2012, 373-411.

12. H. Fukada, K. Takahashi, S. Kitamura, Y. Yuguchi, H. Urakawa, K. Kajiwara, Termodynamics and structural aspect of the gelling process in the gel-lan gum/metal salt aqueous solutions, Journal of Thermal Analyss Calorimetry, 70, 2002, 797-806.

13. F. Jennifer, H. Robin, S. Fotios, T. Ian, Self- struc-turing foods based on acid-sensitive low and high acyl mixed gellan systems to impact on satiety, Food Hydrocolloids 35, 2014, 522-530.

14. D. Mariella, D. Pasquale, C, Vittorio, Solution and gelling properties of gellan benzyl esters, Macro-molecules 32, 1999, 7109-7115.

15. S. Matsukawa, Z. Huang, T. Watanabe, Structural change of polymer chains of gellan monitored by circular dichroism, Progress in Colloid and Polymer Science, 114, 1999, 92-97.

16. E. Miyoshi, K. Nishinari, Non-Newtonian flow be-havior of gellan gum aqueous solutions, Progress in Colloid and Polymer Science, 277, 1999, 727-734.

17. T. Tuan-Chew, F. Wan-Teck, L. Min-Tze, M. Azhar, Comparative assessment of rheological properties of gelatin or gellan in maize starch - egg white compos-ite gels, Journal of King Saud University – Science, 4, 2014, 311-322.

18. E. Ogawa, H. Matsuzawa, M. Iwahashi, Conforma-tional transition of gellan gum of sodium, lithium and potassium types in aqueous solutions, Food Hydrocolloids, 16, 2002, 1-9.

19. G. Hans, S. Olav, Gelation of Gellan Gum, Carbo-hydrate Polymers, 7, 1987, 371-393.

20. D. Lin, L. Xinxing, T. Zhen, Critical behavior at sol-gel transition in gellan gum aqueous solutions


78

with KCl and CaCl2 of different concentrations, Carbohydrate Polymers, 81, 2010, 207-212.

21. M. Nickerson, A. Paulson, A. Speers, Rheological properties of gellan solutions: effect of calcium ions and temperature on pre-sol formation, Food Hydrocolloids, 17, 2003, 577-583.

22. M. Nickerson, A. Paulson, F. Hallett, Pre-gel solu-tion properties of gellan polysaccharides: Effect of potassium and calcium ions on chain associations, Food Research International, 41, 2008, 462-471.

23. T. Juming, A. Marvin, Z. Yanyin, Compression strength and deformation of gellan gels formed with mono- and divalent cations, Carbohydrate Polymers, 29, 1996, 11-16.

24. A. Masahiko, O. Yuko, N. Takayuki, J. Phys. Chem., 104, 2000, 6755-6760.

25. Y. Nitta, R. Takahashi, K. Nishinari, Viscoelasticity and phase separation of aqueous Na-type gellan solution, Biomacromolecules, 11, 2010, 187-191.

26. I. Camelin, C. Lacroix, C. Paquin, H. Prevost, R. Cachon, C. Divies, Effect of chelatants on gellan gel rheological properties and setting temperature for immobilization of living bifidobacteria, Biotech-nology Progress, 9, 1993, 291-297.

27. S. Kudaibergenov, R. Ibragimov, I. Gusenov, G. Tatykhanova, Zh. Ibraeva, Zh. Adilov, A. Sag-indykov, Potential application of gellan for polymer flooding technology, The International Journal of Transport & Logistics, 2012, 47-51.

28. S. Kudaibergenov, Zh. Adilov, N. Nuraje, A. Sag-indykov, G. Tatykhanova, R. Ibragimov, I. Gusenov, Laboratory test for enhanced oil recovery with gel-lan, International Journal of Biological and Chemi-cal Sciences, 4, 2012, 58-68.

29. S. Kudaibergenov, N. Nuraje, Zh. Adilov, D. Abilkhairov, R. Ibragimov, I. Gusenov, A. Sag-indykov, Plugging behavior of gellan in porous saline media, Journal of Applied Polymer Science, 132, 2015, 41256.

30. C. Norman, J. Lucia, L. Strappa, Successful pilot project of water conformance in a mature field,

Vizcacheras, Argentina, EAGE 67th Conference & Exhibition, Madrid, Spain, 13 - 16 June, 2005, 1-17.

31. P. Fitzpatrick, J. Meadows, I. Ratcliffe, P. Willams, Control of the properties of xanthan/glucomannan mixed gels by varying xanthan fine structure, Car-bohydrate Polymers, 92, 2013, 1018-1025.

32. J. Lee, Y. Kim, K. Song, Transient rheological behav-ior of natural polysaccharide xanthan gum solutions in start-up shear flow fields: An experimental study using a strain-controlled rheometer, Korea-Australia Rheology Journal, 27, 2015, 227-239.

33. D. Petri, Xanthan gum: A versatile biopolymer for biomedical and technological applications, Journal of Applied Polymer Science, 132, 2015, 42035.

34. M. Ghannam, B. Abu-Jdayila, N. Esmailb, Flow behavior comparison of xanthan and alcoflood polymers aqueous solutions, American Journal of Oil and Chemical Technologies, 1, 2013, 1-11.

35. R, Ibragimov, I, Gusenov, G, Tatykhanova, Zh. Adilov, N. Nuraje, S. Kudaibergenov, Study of gellan for polymer flooding, Journal of Dispersion Science and Technology, 34, 2013, 1-8.

36. S. Matsukawa, Z. Tang, T. Watanabe, Hydrogen-bonding behavior of gellan in solution during structural change observed by 1H NMR and circular dichroism methods, Progress in Colloid and Polymer Science, 114, 1999, 15-25.

37. I. Gussenov, R. Ibragimov, S. Kudaibergenov, D. Abilkhairov, D. Kudaibergenov, Application of polymer gellan for injectivity profile leveling. SPE Annual Caspian Technical Conference and Exhibi-tion, 12-14 November, 2014, Astana, Kazakhstan.

DOI: http://dx.doi.org/10.2118/172299-MS.38. E. Miyoshi, K. Nishinari, Rheological and thermal

properties near the sol–gel transition of gellan gum aqueous solutions, Progress in Colloid and Polymer Science, 114, 1999, 68-82.

39. D. Wever, F. Picchioni, A. Broekhuis, Polymers for enhanced oil recovery: A paradigm for structure-property relationship in aqueous solution, Progress in Colloid and Polymer Science, 36, 2011, 1558-1628.

application of sol-gel transition of gellan and … p_68-78.pdf · on the drilling fluids...

Documents