Article pubs.acs.org/EF
Associating Copolymer Acrylamide/Diallyldimethylammonium Chloride/Butyl Acrylate/2-Acrylamido-2-methylpropanesulfonic Acid as a Tackifier in Clay-Free and Water-Based Drilling Fluids Xianmin Zhang,*,†,‡ Guancheng Jiang,†,‡ Yang Xuan,§ Le Wang,†,‡ and Xianbin Huang†,‡ †
State Key Laboratory of Petroleum Resources and Prospecting and ‡College of Petroleum Engineering, China University of Petroleum (Beijing), Beijing 102249, People’s Republic of China § Sinopec Research Institute of Petroleum Engineering, Beijing 100101, People’s Republic of China S Supporting Information *
ABSTRACT: Drilling fluids must possess optimal rheological properties, such as shear thinning and thixotropy, and the key materials to control these properties for clay-free and water-based drilling fluids (CFWBDFs) are organic polymers. To overcome the challenge, associating copolymer P(AM/DMDAAC/BA/AMPS) (ADBA) of acrylamide (AM), cationic monomer diallyldimethylammonium chloride (DMDAAC), hydrophobic monomer butyl acrylate (BA), and anionic monomer 2acrylamido-2-methylpropanesulfonic acid (AMPS) was synthesized. As a result of the intra-/intermolecular associations, a network structure was observed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. With increasing concentrations, the apparent viscosity (AV), viscoelasticity, and thixotropy of the aqueous solution were enhanced. The AV of the aqueous solution containing 0.6 wt % ADBA was 46 mPa s, more than double that of common tackifier potassium polyacrylamide (K-PAM). ADBA appeared as an excellent tackifier and possessed better rheological properties than KPAM. The laboratory test showed that ADBA effectively controlled the rheology and filtration loss of drilling fluids. Meanwhile, CFWBDFs with ADBA possessed better shear thinning than CFWBDFs with K-PAM. Therefore, the new copolymer had good potential for application in CFWBDFs.
1. INTRODUCTION Water-based drilling fluids (WBDFs) must possess optimal rheological properties as well as the ability to control fluid loss during the process of oil and gas well drilling.1 These properties could be effectively controlled by the network structure based on the bridging role between polymer and clay in common polymer WBDFs. However, in the clay-free and water-based drilling fluids (CFWBDFs), without clay, the network structure could not be made up by the common polymer itself. This work investigates hydrophobically associating zwitterionic polymer, and on the basis of associating interactions, such as hydrophobic association, electrostatic interactions, and hydrogen-bond interactions, the copolymer could possess a supramolecular network structure. Hydrophobically associating water-soluble polymers (HAWPs), with hydrophobic groups aggregating together in aqueous solutions, could form intra-/intermolecular associations, resulting in unique rheological characteristics.2,3 Therefore, such polymers have received widespread attention in recent years.4−8 Yamamoto et al. noted that “micelle nanostructures” are built up in polymer solutions via intra-/ intermolecular associations. Intramolecular associations result in the formation of unimolecular micelles.2 However, intermolecular associations could lead to a supramolecular network structure. The network structures are built up at an increasingly rapid rate as the concentration of polymer is increased. The associations are broken down when the solution is sheared and built up when the shear rate is reduced. This results in the reversible change of the buildup and breakdown © 2017 American Chemical Society
of the supramolecular structure along with the change of the shear rate. The network structure leads to special rheological properties, such as viscoelasticity, high viscosity at a low shear rate, shear thinning (or thickening), thixotropy (or antithixotropy), etc. Meanwhile, the electrostatic interactions between positive and negative groups could enhance the structure and these special rheological properties. As a result of the special rheological performance associated with these materials, HAWPs have extensive applications in oilfields, such as enhanced oil recovery.9,10 Meanwhile, as a result of the shear-thinning behavior, the polymers can effectively control the rheology of WBDFs and improve drilling efficiency. Near the drill bit, the shear rate is high (between 10 000 and 100 000 s−1) and the viscosity of the drilling fluids is very low, which, thus, makes maximal utilization of water horsepower. However, in an annular space, the shear rate is reduced (between 10 and 250 s−1) and the drilling fluids possess enough viscosity for effective carrying cuttings and weighting materials. Meanwhile, the network structure can bind free water, and the “micelle nanostructures” can plug cracks developing around the wellbore during drilling. Previous studies show the use of HAWPs to control filtration of drilling fluids.11,12 Mao et al. used a hydrophobically associated polymer-based nanosilica composite as a filtrate reducer, Received: October 10, 2016 Revised: March 31, 2017 Published: April 3, 2017 4655
DOI: 10.1021/acs.energyfuels.6b02599 Energy Fuels 2017, 31, 4655−4662
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Energy & Fuels Table 1. Elemental Analysis of the Copolymer polymer composition C (wt %)
N (wt %)
S (wt %)
H (wt %)
AM
DMDAAC
BA
AMPS
yield (%)
43.34
13.38
3.319
6.159
7.86
0.35
0.2
1
84.5
demonstrating improved filtration loss control and wellbore stability.12 The hydrophobically associating zwitterionic polymer P(AM/DMDAAC/BA/AMPS) (ADBA) was synthesized and characterized in this paper.13−15 The monomer acrylamide (AM), hydrophobic monomer butyl acrylate (BA), cationic monomer diallyldimethylammonium chloride (DMDAAC), and anionic monomer 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were used in the reaction. The heteroatoms in all of the monomers can generate hydrogen bonds in aqueous solution. Additionally, the presence of positive and negative groups in the zwitterionic polymer results in a buildup of electrostatic interactions. A five-carbon ring is formed in the polymer because of the monomer DMDAAC, which provides a hydrophobic group, and the hydrophobic monomer BA, which contains an appropriate hydrophobic chain. The interactions in the polymer can be defined on the basis of the electrostatic groups, hydrogen bonds, and hydrophobic groups. This was beneficial to the buildup of the network and the control of the properties of the polymer solution, such as viscoelasticity and filtration control, as well as those of WBDFs with the new polymer.
molar ratio of AM/DMDAAC/BA/AMPS was about 7.86:0.35:0.2:1, and the probable reaction schema was presented as Scheme 1.
Scheme 1. Probable Reaction Schema of the Copolymer (ADBA)
2. EXPERIMENTAL SECTION 2.1. Materials. The monomer AM (99% purity), hydrophobic monomer BA (99% purity), cationic monomer DMDAAC (60%, w/w, aqueous solution), anionic monomer AMPS (99% purity), cetyltrimethylammonium bromide (CTAB, 99% purity), sodium hydroxide (NaOH, 97% purity), and initiators for the synthesis of sodium bisulfite (NaHSO3. analytical purity) and potassium persulfate (KPS, analytical purity) were from Energy Chemical, Shanghai, China. The water used was deionized water. WBDF additives, such as barite, emulsified asphalt, potassium chloride (KCl), potassium humate (KHm), calcium carbonate, modified starch, lubricant, humic acid derivative (RSTF), common tackifier potassium polyacrylamide (KPAM), etc., were purchased from Shida Bocheng Technology Co., Ltd., Beijing, China. 2.2. Experimental Procedure. 2.2.1. Synthesis of the Copolymer. The copolymer (ADBA) was prepared by free-radical emulsion polymerization.16,17 During the reaction, the surfactant CTAB was used to solubilize BA into emulsions. The reaction was carried out in a 300 mL beaker equipped with a thermometer and a mechanical stirrer. The reactants including 36 mmol of AMPS and 2.7 mmol of CTAB in deionized water, 281.7 mmol of AM, 7.8 mmol of BA, and 15.5 mmol of DMDAAC were added to the reactor. NaOH was used to adjust pH to a value of 7−8, and 120 mL of deionized water was used in all. The solution was stirred continuously for 0.5 h under a stream of highpurity nitrogen to remove trapped air. Redox initiators (0.3 mmol of NaHSO3 and 0.3 mmol of K2S2O8) were added. The reactor was heated from ambient temperature to 50 °C using a thermostatic water bath and was then kept at 50 °C for 4 h. Then, a gel-like copolymer was obtained. The gel-like mixture was cut into smaller chunks, washed by ethanol and acetone to remove surfactants and unreacted monomers, and dried in a vacuum oven to evaporate water, ethanol, and acetone. The final product was crushed by a crushing machine. At last, white powder was obtained (26.19 g and yield of 84.5%). The elemental analysis of the copolymer was measured through a VARIO EL III elemental analyzer (Germany), and the result was presented as Table 1.18 The
2.2.2. Characterization of the Copolymer. 2.2.2.1. Experimental Nuclear Magnetic Resonance (NMR) Elucidation. A Bruker Avance 400 spectrometer and a Bruker Avance III 400 MHz WB solid-state NMR spectrometer (Bruker, Switzerland) were used to record the 1H NMR spectrum with D2O as the solvent and the solid-state 13C NMR spectrum, respectively.19−21 2.2.2.2. Molecular Weight Measurement. The molecular weights of ADBA and K-PAM were measured through gel permeation chromatography with multi-angle laser light scattering (GPC− MALLS, Wyatt, Santa Barbara, CA, U.S.A.) with the ASTRA 5.0 software. The elution solvent was deionized water, and dn/dc was 0.130 mL g−1.22 2.2.2.3. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The morphologies of ADBA and K-PAM were observed through Hitachi SU8010 SEM and Tecnai F20 TEM. The polymers were diluted in deionized water to a concentration of 500 ppm. Several drops of this aqueous solution were dripped onto the slide, dried, and then metal-sprayed for 15 min for SEM. Several drops were dripped onto the carbon-coated copper TEM grids and dried for TEM. 2.2.2.4. Viscosity Measurement. The viscosity of the polymer solution and drilling fluids was measured using a six-speed, Fann 35type ZNN-D6 viscometer (Haitongda Company, Shandong, China), according to American Petroleum Institute (API) specifications. The rheological parameters, such as the apparent viscosity (AV), plastic viscosity (PV), and yield point (YP), of the copolymer solution and the drilling fluids were determined by rotation rates of 600 and 300 rpm at room temperature. AV, PV, and YP were calculated from θ600 and θ300 as eqs 1−3.23
AV = 0.5θ600
(mPa s)
PV = θ600 − θ300 4656
(mPa s)
(1) (2) DOI: 10.1021/acs.energyfuels.6b02599 Energy Fuels 2017, 31, 4655−4662
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Figure 1. 1H NMR spectrum of ADBA.
Figure 2. 13C NMR spectrum of ADBA.
YP = 0.5(2θ300 − θ600)
(Pa)
2.2.2.6. Viscoelasticity Measurements. The viscoelasticities of the aqueous polymer solutions were measured with a angular velocity sweep from 0.1 to 100 rad s−1 at a shear stress of 0.3 Pa. 2.2.2.7. API Filtration Loss Measurements. The filtration loss of the drilling fluids was measured with a ZNZ-D3-type medium-pressure filtration apparatus (Qingdao Bairuida Machinery Corporation, China) according to API specifications.
(3)
2.2.2.5. Rheological Measurements. The shear-thinning behavior of solutions was studied by rheological measurements carried out on a HAAKE MARS III (Thermo Scientific, Germany) with the software HAAKE RheoWin. The 0.2, 0.4, and 0.6 wt % ADBA and 0.4 wt % KPAM solutions without bubbles were tested at 25.0 ± 0.1 °C. To eliminate the influence of shear, the solutions were allowed to rest until the cylinder reached the measuring position before the measurement. During the experiment, the shear rate was varied in the range of 10−1000 s−1 and the maximum wait time was 20 s at each shear rate step. The thixotropic properties of these polymer solutions were measured in a shear rate range of 10−1000 s−1 and then 1000− 10 s−1.
3. RESULTS AND DISCUSSION 3.1. Characterization of ADBA. 3.1.1. NMR Spectrum of ADBA. The 1H and 13C NMR spectra of ADBA were shown in Figures 1 and 2, respectively. In Figures 1 and 2, several characteristic peaks were seen in the spectrum of ADBA because of different monomers. −CH2−CH−CO− and −CH− 4657
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Energy & Fuels CO− in AM, BA, or AMPS were at the regions of 1.22−1.67 and 2.27−1.89 ppm, respectively. CH3− in BA and AMPS appeared at 0.74 and 1.32 ppm, respectively. −CH2−N+ and CH3−N+ in DMDAAC were observed at the region of 3.01− 2.78 ppm. The peak at 3.04 ppm was for −CH2−SO3− in AMPS.19−21 As seen in Figure 2, the region of 57.5−0 ppm was for alkyl−alkyl, and the peaks at 54, 43, and 31 ppm were for −CH−alkyl, −CH2−alkyl, and CH3−alkyl, respectively. The region of 66.5−57.5 ppm was for −CH2−O in BA and alkyl−N in DMDAAC, and the peak at 73.6 ppm was for C−N in AMPS. The peak at 180 ppm was for −CO−N and − CO− O−. Meanwhile, there was no peak at the region of 100−150 ppm, indicating that there was no monomer.19 Thus, the 1H and 13C NMR spectra show that the polymer is a P(AM/ DMDAAC/BA/AMPS) copolymer. 3.1.2. Molecular Characteristics of the Copolymer. Molecular weight possesses a great influence on the viscosity of the polymer; thus, the molecular weights of the copolymer ADBA and K-PAM were measured. The calculation procedure was described in Figure S1 of the Supporting Information, and the results were shown in Table 2. The weight-average
Figure 4. TEM images of the different parts of ADBA and K-PAM: (a) chains in ADBA, (b) cross chains in ADBA, and (c) clear chain in KPAM.
Table 2. Molecular Characteristics of the Samples ADBA K-PAM a
Rna (nm)
Rw (nm)
Mnb (×106)
Mw (×106)
Mw/Mn
56.0 120.8
65.5 143.4
0.5180 1.423
1.024 2.006
1.977 1.410
Number-average radius moments. weight.
b
Number-average molecular
molecular weights (Mw) of both ADBA and K-PAM were over 106. However, the Mw and weight-average radius moments (Rw) of ADBA were almost half of those of K-PAM. In the polymer solvation process, swelling occurred first and then solvation. A low molecular weight was advantageous to the polymer solubility. 3.1.3. Analysis of the Morphology. The aggregation structures of ADBA and K-PAM were studied by SEM and TEM.24,25 The SEM images of the polymers were shown in Figure 3, and TEM images were shown in Figure 4. Figure 3a
Figure 5. TEM image of the copolymer.
polymer was tested by F20 TEM. The results were shown in Table 3. Oxygen and carbon atoms were observed in both the Table 3. Element Contents of the Branched and Main Chains branched chain (Figure 5a)
main chain (Figure 5b)
element
weight (%)
atomic (%)
CK NK OK CK OK
91.60 4.22 4.16 96.14 3.85
93.13 3.68 3.18 97.07 2.92
branched and main chains. Additionally, nitrogen was also observed in the branched chain. The presence of the heteroatoms was beneficial for the formation of hydrogen bonds. On the other hand, the presence of NaOH resulted in the generation of −COO− from AM and BA. The negatively charged −COO− ions formed electrostatic interactions with positive groups N+(CH2)2(CH3)2. The hydrogen bonds and electrostatic interactions together resulted in the buildup of the network structure. However, there were only intermolecular forces and hydrogen-bond interactions between the heteroatoms and the network structure could not be made up in KPAM. The dynamic physical cross-linking network structure was built up by the combined effect of electrostatic interactions between the positive and negative groups in the polymer, the interactions between the hydrophobic groups, and the hydrogen bonds.
Figure 3. SEM images of ADBA and K-PAM: (a) ADBA and (b) KPAM.
shows the network structure in copolymer ADBA, while the polymer K-PAM particulates were gathered together in Figure 3b. As seen in Figure 4, the chains in the polymer ADBA were obvious (Figure 4a) and linked together to build up a network structure (Figure 4b). However, the polymer K-PAM presented a clear chain structure in Figure 4c. To further study the mechanism by which the network structure was built up, the elementary composition of the branched chains (Figure 5a) and main chains (Figure 5b) of the 4658
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Energy & Fuels 3.2. Rheological Behavior of Polymer Solution. The influence of hydrophobic composition on the solution behavior of polyacrylamides has already been studied by several authors.26−28 Hydrophobic associations can increase the solution viscosity and lead to particular rheological properties (i.e., shear-thinning behavior, viscoelasticity, etc.). 3.2.1. Influence of Concentrations. Figure 6 illustrates the effects of copolymer ADBA and K-PAM concentrations on the
substantially increased the viscosity of the solution in accordance with the literature.29−31 3.2.2. Influence of the Shear Rate. The shear rate can induce variations in molecular conformations and hydrophobic aggregation behavior. The influence of the shear rate on the viscosities of 0.2, 0.4, and 0.6 wt % polymer ADBA and 0.4 wt % K-PAM solutions was investigated, and the results were shown in Figure 8. It is apparent that all of the polymer solution
Figure 6. Dependence of the appeared viscosity upon polymer concentrations for the copolymer at 25 °C.
Figure 8. Viscosity versus shear rate curves for ADBA and K-PAM solutions with various concentrations at 25 °C.
viscosities of the polymer solutions. With increasing concentrations, the viscosities of both ADBA and K-PAM solutions increased. Meanwhile, the ADBA solution viscosity increased much higher than that of K-PAM, although Mw of ADBA was less than that of K-PAM. When the ADBA concentration was 0.6 wt %, the apparent viscosity was 46 mPa s, more than double that of K-PAM. Therefore, ADBA was a good tackifier. The margin was narrow when the concentration was less than 0.3 wt % and wide over 0.3 wt %. At low concentrations, the isolated molecule (Figure 7a) exhibited a strong tendency for
exhibited shear-thinning properties. With an increasing shear rate, the viscosities of the polymer solutions decreased, which indicated that the intra-/intermolecular interactions were broken down to varying degrees. In addition, concentrations of polymer solutions had a positive effect on viscosities. This implied that intra-/intermolecular interactions in the aqueous polymer solutions with a high concentration were enhanced, which could be attributed to the fact that the interactions, which were broken down under shear, were easier to build up at high concentrations. The viscosity of 0.4 wt % ADBA solution was always larger than the viscosity of 0.4 wt % KPAM solution. Meanwhile, the viscosity of the solution containing 0.2 wt % ADBA was close to the viscosity of 0.4 wt % K-PAM solution at a low shear rate while lower than that of K-PAM solution at a high shear rate. This indicated that the polymer ADBA possessed better shear thinning than K-PAM. This was due to the supramolecular network structure in the ADBA made from the associating interactions, such as hydrophobic association, electrostatic, and hydrogen-bond interactions, while there were only hydrogen-bond interactions in the polymer K-PAM, which could not make up the network structure. 3.2.3. Thixotropy of the Solution. Figure 9 illustrates the flow curves of the polymer solutions containing various concentrations of ADBA and 0.4 wt % K-PAM. The thixotropic loops were formed between the ascending and descending curves in aqueous solutions. The thixotropic behavior was associated with the shear thinning and reversible associations under shearing. The associations, such as electrostatic interactions, associative interactions between the hydrophobic groups, and hydrogen-bond interactions, were broken down upon shearing and rebuilt at rest.32 Additionally, there was a hysteresis between breakdown and rebuild of the associations.
Figure 7. Schematic diagram of the various concentration regimes for polymers (the associating blocks were red, and the polymer chains were black): (a) isolated molecule, (b) intramolecular associations, and (c) intermolecular associations.
intramolecular associations to form unimolecular micelles (Figure 7b). This resulted in a slight increase in the hydrodynamic radius, and the viscosity increased slightly. As the concentration was increased, the chains underwent intermolecular associations and the viscosity of the polymer solution increased rapidly. Over a certain concentration, intermolecular hydrophobic associations were dominant (Figure 7c). This led to the buildup of the network structure and the increase in the hydrodynamic volume, which 4659
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Figure 9. Flow curves (T = 25 °C) of 0.2, 0.4, and 0.6 wt % ADBA and 0.4 wt % K-PAM solutions.
Figure 10. Variation of the dynamic modulus as a function of angular velocity for polymer solution with different concentrations measured at a shear stress of 0.3 Pa and T = 25 °C.
With the increasing concentrations, the areas of thixotropic loops of aqueous polymer solutions increased, indicating that the thixotropic property was enhanced. Meanwhile, there were only hydrogen-bond interactions in K-PAM, and the thixotropic property was less. The area of thixotropic loops of the 0.4 wt % K-PAM solution was similar to the area containing 0.2 wt % ADBA. Polymers with good shear thinning and thixotropy are favorable for the control of the rheology in drilling fluids. The shear rate in the drill pipe is high, and the viscosity of the drilling fluids could be very low. This lowers resistance and prompts waterpower near the bit nozzle fully used. While, in the annular space, the shear rate is low and thixotropic structures were rebuilt. The drilling fluids could possess enough viscosity to effectively carry cuttings. Therefore, drilling fluids, which exhibit good shear-thinning and thixotropy behavior, could improve the drilling rate. 3.2.4. Viscoelasticity of Solutions. The viscoelasticities of various ADBA concentrations and 0.4 wt % K-PAM aqueous solutions were investigated, and the results were shown in Figure 10.33 With increasing concentrations of ADBA, the storage modulus (G′) and loss modulus (G″) of the polymer solution increased. Both G′ and G″ increased first and then reduced with increasing angular velocity, and G′ increased larger than G″ at first and then decreased larger than G″. There was a certain angular velocity range, where G′ was larger than G″ in the ADBA solution, indicating that the dominant property was elasticity while viscosity at other angular velocities. The elastic range of the 0.2 wt % ADBA aqueous polymer solution was only near 10 rad s−1, and the range increased over 0.2 wt %. Meanwhile, with increasing concentrations, the angular velocity value at which the main performance changed from elasticity to viscosity increased. At lower angular velocity, the associations, which were broken down, produced a strong tendency for intermolecular associations. Thus, G′ was enhanced. However, over a certain angular velocity, the network structure of the polymer was broken down and the viscosity behavior was dominant. With increasing concentrations, the associations were enhanced and the angular velocity value at which the main performance changed from elasticity to viscosity increased. It could be attributed to the fact that it required larger angular velocities to
make the network structure break down. However, the 0.4 wt % K-PAM solutions without a network structure did not possess the elasticity property during all of the angular velocity range tested.
4. APPLICATION IN WBDFS The polymer was investigated in the laboratory for application in drilling fluids and compared to K-PAM. Using other drilling fluid additives, a CFWBDF with a density of 1.20 g cm−3 was prepared, and the formulation was shown in Table 4. Table 4. Drilling Fluid Formulation component (g L−1)
1
2
3
ADBA K-PAM fresh water KHm KCl RSTF emulsified asphalt modified starch calcium carbonate lubricant barite
2
4
6
815 24 48 24 24 24 16 12 215
815 24 48 24 24 24 16 12 215
815 24 48 24 24 24 16 12 215
4 6 815 24 48 24 24 24 16 12 215
Formulations 1, 2, and 3 were with the new copolymer, and the concentrations were 2, 4, and 6 g L−1, respectively, while formulation 4 was with 6 g L−1 K-PAM as the comparison. All drilling fluids were aged at 90 °C for 16 h. Then, the properties of drilling fluids, such as rheological properties and API filtration, were measured at 60 °C, while the high-pressure and high-temperature (HTHP) filtration was measured at 90 °C. The results were shown in Table 5. Meanwhile, the rheological properties of formulations 2 and 4 were measured through HAAKE MARS III at 90 °C. After hot rolling, there was no precipitation in all drilling fluids, indicating that the drilling fluids were stable and the copolymer possessed good compatibility with other additives. Table 5 shows that properties of various drilling fluids after hot rolling. With increasing copolymer concentrations, the 4660
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groups, and hydrogen-bond interactions. However, only with hydrogen-bond interactions, the polymer K-PAM displayed a line through TEM. The copolymer was a good tackifier. The viscosity of the polymer solution increased with the increasing concentrations, and the increasing margin was wide above 0.3 wt %. When the concentration was 0.6 wt %, the apparent viscosity was near 46 mPa s. Meanwhile, the polymer solution exhibited good viscoelasticity and shear thinning. The buildup and breakdown of the associations occurred reversibly with the changing shear rate, resulting in a thixotropic behavior. With increasing concentrations, the areas of thixotropic loops and G′ and G″ increased, indicating that the thixotropic behavior and viscoelasticity of the copolymer were enhanced. However, without the network structure, the solution containing 0.4 wt % K-PAM possessed less shear-thinning and thixotropic behavior than that with ADBA. The copolymer ADBA, with the network structure, could effectively control the rheology and filtration of CFWBDFs. The CFWBDF with ADBA possessed better rheology behavior and filtration loss control performances than that with K-PAM. Thus, the copolymer possessed good potential for application in CFWBDFs.
Table 5. Drilling Fluid Properties aging time (h) aging temperature (°C) pH density (g cm−3) PV (mPa s) YP (Pa) gel10″/gel10′ (Pa) API filtration (mL) HTHP filtration at 90 °C (mL)
1
2
3
4
16 90 8 1.20 8 2.5 0.5/0.5 2.4 7.4
16 90 8 1.20 13 3.5 1/2 2.0 6.8
16 90 8 1.20 19 4 1.5/3 1.8 6.4
16 90 8 1.20 15 3 1/2 2.4 7.6
viscosities and gel strengths of CFWBDFs increased and the filtration reduced. Additionally, the rheological property of drilling fluid with 4 g L−1 new copolymer was close to that with 6 g L−1 K-PAM, and the HTHP filtration loss was less than that with 6 g L−1 K-PAM, indicating that the new copolymer possessed better rheology behavior and filtration loss control performances than K-PAM. This would be attributed to the associations and network structure in the copolymer. Figure 11 shows the rheological properties of formulation 2 and 4 at different shear rates under 90 °C. With increasing
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.energyfuels.6b02599. Molecular weight calculation procedure of ADBA and KPAM (PDF)
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AUTHOR INFORMATION
Corresponding Author
*Telephone: 010-89732239. E-mail: zhangxianmin2007@126. com. ORCID
Xianmin Zhang: 0000-0003-2538-092X Notes
The authors declare no competing financial interest.
■
Figure 11. Viscosity versus shear rate curves for formulations 2 and 4 at 90 °C.
ACKNOWLEDGMENTS This work was performed with financial support from the National Natural Science Foundation of China (Grants 51521063 and 51474231) and the National Major Scientific and Technological Special Project (Grant 2016ZX05022-001001-001).
shear rates, the viscosity of both drilling fluids reduced. The viscosity of formulation 2 was higher than that of formulation 4 at low shear rates while lower when the shear rates were high (near 1000 s−1). This illustrated that formulation 2 possessed better shear thinning than formulation 4. With great shear thinning, the drilling fluids could take full advantage of waterpower near the bit nozzle and effectively carry cuttings and weighting materials in the annular space. Good rheology behavior was conducive to effective carrying cuttings and weighting materials. Meanwhile, the network structure promoted the formation of a compacted filter cake, resulting in lower fluid loss, which contributed to the wellbore stability.
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REFERENCES
(1) Mahto, V.; Sharma, V. P. Rheological study of a water based oil well drilling fluid. J. Pet. Sci. Eng. 2004, 45 (1), 123−128. (2) Yamamoto, H.; Tomatsu, I.; Hashidzume, A.; Morishima, Y. Associative properties in water of copolymers of sodium 2(acrylamido)-2-methylpropanesulfonate and methacrylamides substituted with alkyl groups of varying lengths. Macromolecules 2000, 33 (21), 7852−7861. (3) Taylor, K. C.; Nasr-El-Din, H. A. Water-soluble hydrophobically associating polymers for improved oil recovery: A literature review. J. Pet. Sci. Eng. 1998, 19 (3), 265−280. (4) Xue, W.; Hamley, I. W.; Castelletto, V.; Olmsted, P. D. Synthesis and characterization of hydrophobically modified polyacrylamides and some observations on rheological properties. Eur. Polym. J. 2004, 40 (1), 47−56.
5. CONCLUSION A new associating polymer ADBA was synthesized, and the molar ratio of AM/DMDAAC/BA/AMPS was 7.86:0.35:0.2:1. Meanwhile, a network structure was observed through SEM and TEM. The structure was built up from associations, such as electrostatic interactions, interactions between the hydrophobic 4661
DOI: 10.1021/acs.energyfuels.6b02599 Energy Fuels 2017, 31, 4655−4662
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DOI: 10.1021/acs.energyfuels.6b02599 Energy Fuels 2017, 31, 4655−4662
