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Article

Imidazoline-Based Fatty Acid Derivatives as Novel Shale Inhibitors for Water-Based Drilling Fluids

by
Ioana Gabriela Stan
1,
Mihail Tudose
1,
Alina Petronela Prundurel
1,
Gheorghe Branoiu
1,
Liviu Dumitrache
1,
Silvian Suditu
1,
Doru Bogdan Stoica
1,*,
Emil Zaharia
2 and
Rami Doukeh
1,*
1
Well Drilling, Extraction and Transport of Hydrocarbons Department, Petroleum-Gas University of Ploiesti, 100680 Ploiesti, Romania
2
Atica Chemicals SRL, 202 Căzănești Str., 240414 Râmnicu Vâlcea, Romania
*
Authors to whom correspondence should be addressed.
Appl. Sci. 2025, 15(20), 11050; https://doi.org/10.3390/app152011050
Submission received: 20 September 2025 / Revised: 9 October 2025 / Accepted: 13 October 2025 / Published: 15 October 2025
(This article belongs to the Topic Exploitation and Underground Storage of Oil and Gas)
Browse Figures
Versions Notes

Abstract

Water-based drilling fluids (WBMs) are widely applied in petroleum engineering due to their lower cost and reduced environmental impact compared to oil-based muds. However, their performance is severely limited in shale formations, where hydration and swelling of clay minerals lead to wellbore instability. In this study, two novel imidazoline-type inhibitors were synthesized from fatty acids: A-Lin (derived from linoleic acid) and A-Lau (derived from lauric acid). The synthesis involved amidation followed by cyclization, and the products were characterized using FTIR and TGA. Their performance as shale hydration inhibitors was evaluated in WBM formulations and compared with commercial additives (Amine NF and Glycol). The FTIR spectra confirmed successful imidazoline ring formation, while TGA demonstrated good thermal stability up to 150 °C, with A-Lin exhibiting superior resistance due to its unsaturated structure. Rheological tests showed that the synthesized additives reduced plastic viscosity, thereby improving cuttings transport efficiency. Swelling tests revealed that A-Lin achieved the lowest final swelling (6.3%), outperforming both commercial inhibitors and the saturated A-Lau analogue. Furthermore, A-Lin provided the best lubricity coefficient (0.148), reducing torque and drag during drilling. Overall, A-Lin demonstrated strong potential as an efficient, thermally stable, and environmentally compatible shale inhibitor for advanced WBM formulations. Compared to conventional inhibitors such as KCl, glycol, and amine-based additives, A-Lin uniquely combines superior swelling inhibition, enhanced lubricity, and good thermal stability, highlighting its novelty as an imidazoline derivative derived from renewable fatty acids

1. Introduction

Oil and gas drilling operations are fundamental to the development of global energy resources, as their efficiency and safety strongly impact production continuity [1]. Drilling fluids represent a key component in this process, ensuring wellbore stability, controlling formation pressures, transporting drilled cuttings to the surface, and cooling and lubricating the drill bit [2,3]. Over the years, significant technological progress has enhanced the performance of these fluids, making them indispensable for modern well construction and cost-effective drilling [4].
Two major categories of drilling fluids are commonly employed: oil-based muds (OBMs) [5] and water-based muds (WBMs) [6]. OBMs, typically composed of diesel and other petroleum derivatives, exhibit excellent technical performance and strong resistance to shale hydration [7,8]. Nevertheless, their high toxicity, elevated operational and disposal costs, and strict environmental regulations have limited their desirability in modern drilling practice [9]. By contrast, WBMs have gained wide acceptance due to their low cost, ease of formulation, and more environmentally friendly profile, currently accounting for the majority of drilling fluid applications [10,11].
Despite these advantages, WBMs face significant challenges when drilling through shale formations. The interaction between water and clay-rich shales often results in hydration, swelling, and dispersion of clay minerals, leading to serious wellbore instability problems [12,13]. These destabilizing mechanisms can compromise drilling safety, reduce efficiency, and increase operational costs. To mitigate such risks, the incorporation of shale inhibitors into WBMs has become a central strategy for improving wellbore stability [14]. Recent advances in chemical inhibitors provide promising approaches to suppressing shale hydration and enhancing the performance of WBMs [15].
Conventional shale inhibitors in water-based drilling fluids are primarily divided into inorganic salts and organic polymers. Inorganic salts such as potassium chloride (KCl) [16], ammonium chloride (NH4Cl) [17], calcium chloride (CaCl2) [18], sodium chloride (NaCl) [19] and tetramethylammonium chloride [(CH3)4NCl] [20] have long been applied to suppress clay swelling and hydration. However, the use of salts, particularly KCl at elevated concentrations, raises concerns related to toxicity and environmental impact [21]. At the same time, high concentrations of chloride anions have been shown to markedly reduce the water uptake capacity of smectite clays, thereby influencing the hydration and swelling behavior of shale [22].
Organic inhibitors, including polyethylene glycol (PEG) [23], polyacrylamide (PAM) [24], partially hydrolyzed polyacrylamide (PHPA) [25], polyamides, and xanthan gum, provide an alternative route to stabilizing shale [26]. While they improve fluid–shale compatibility, these materials often exhibit insufficient resistance under high-temperature drilling conditions, limiting their applicability in deep or high-pressure reservoirs [27].
To overcome the limitations of conventional inorganic salts and organic polymers, a variety of novel inhibitors have been developed in recent years. These include small-molecule ammonium salts, polyhydroxy organic amines, modified surfactants, nanocomposites, and polymeric systems, each designed to enhance inhibition efficiency and stability under harsh downhole conditions. For instance, Wang et al. (2024) [28] reported that the small-molecule ammonium inhibitor TEE-2 achieved strong shale hydration control (anti-swelling rate 84.94%, linear swelling 29.34% at 0.5%) through adsorption and stabilization of clay layers. Similarly, Du et al. (2020) [29] synthesized a polyhydroxy organic amine inhibitor, N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (THEED), via an amination–condensation route. At 2 wt%, THEED achieved a shale rolling recovery of 89.6% and reduced linear swelling to 4.74 mm, significantly outperforming conventional KCl and quaternary ammonium salts. In another study, Barati et al. (2017) [30] evaluated tallow amine ethoxylate (KETALO15) as a shale stabilizer in WBMs, showing comparable inhibition performance to 2 wt% KCl, with improved cuttings recovery and reduced bentonite swelling at both low (26 °C) and elevated (65 °C) temperatures. Beyond amines, composite materials have also shown promising results. The polypropylene–nanosilica composite modified with (3-aminopropyl) triethoxysilane (PNSC + NH2) exhibited superior shale inhibition, reducing clay swelling to 28% after 36 h and achieving a shale recovery rate of 75.3 wt% at 1.5 w/v%, significantly outperforming KCl and KCl + HPAM systems [31]. Likewise, Xian et al. (2021) [32] reported that ammonium adipate solution AAS-8 (adipic acid + tetraethylenepentamine, 1:2) reduced clay swelling to 59.61% at 0.1% concentration through electrostatic adsorption and hydrogen bonding. More recently, Tian et al. (2024) [33] synthesized a novel polyionic polymer inhibitor (TIL-NH2) via free radical polymerization, combining imidazole cationic rings and primary amine groups. At only 0.9% dosage, TIL-NH2 achieved over 85% shale hydration inhibition with excellent thermal stability (>300 °C), demonstrating superior performance compared to conventional inhibitors. Finally, Zhong et al. (2016) [34] reported that the novel diamine 4,4′-methylenebis-cyclohexanamine (MBCA) provided superior shale inhibition to polyether diamine, maintaining effectiveness up to 200 °C with a linear swelling rate of only 10.38%.
Building on these advances, the present work reports the synthesis and evaluation of two novel imidazoline-based inhibitors derived from fatty acids, namely A-Lin (from linoleic acid) and A-Lau (from lauric acid). Their structural features were characterized using FTIR and TGA analyses, while their performance as anti-swelling additives in water-based drilling fluids was systematically compared with that of conventional commercial inhibitors (Amine NF and Glycol). Particular attention was given to their thermal stability, rheological behavior, lubricity, and shale inhibition efficiency, with the aim of identifying environmentally compatible alternatives capable of enhancing the performance of WBMs under demanding drilling conditions.

2. Materials and Methods

2.1. Materials

Lauric acid (≥95%, Merck KGaA, Darmstadt, Germany), linoleic acid (≥98%, Merck), Diethylenetriamine (DETA) (99%, Merck), toluene (Chemical Company, Iași, România ≥98%), sodium carbonate anhydrous (≥99%), and potassium chloride (≥99%, Thermo Scientific, Waltham, MA, USA) were used as received without further purification. Additional commercial additives, including defoamer (anti-foaming agent), bactericide, amine NF, and glycol (commonly applied as anti-hydrate agents), were supplied by Newpark Romania (Ploiești, Romania). Barite (BaSO4, weighting material) was obtained from RUA Bulgaria. All chemicals were of analytical grade.

2.2. Synthesis of the Anti-Swelling Additive

The synthesis of the anti-swelling active compounds was carried out in a 500 mL three-neck round-bottom flask equipped with a Vigreux distillation column, a modified Dean–Stark apparatus fitted with a thermometer to monitor the azeotropic boiling mixture, a condenser for reflux, and a magnetic stirrer operating at 1500 rpm. The reaction temperature was controlled using an external thermostat, with a thermocouple immersed in the reaction medium for precise monitoring under atmospheric pressure, as shown in Supplementary Figure S1.
In a typical procedure, linoleic acid (0.5 mol, ~140 g) and diethylenetriamine (DETA) (0.5 mol, ~52 g) were charged into the flask along with 100 mL of toluene, used as an entrainer to facilitate water removal and drive the condensation reaction. The mixture was heated to 120 °C, at which point the water formed during the reaction co-distilled with toluene as an azeotrope (bp ~84 °C) [35] and was collected in the Dean–Stark trap. The reaction was continued for 4 h under vigorous stirring until the collected water volume stabilized at 6.5 mL, corresponding to the completion of the first amidation stage [36].
The overall synthetic pathway, including amidation with DETA followed by intramolecular cyclization to form the imidazoline ring, is illustrated in Figure 1, which shows the preparation of A-Lin (from linoleic acid) and A-Lau (from lauric acid).
Following this, toluene was removed by distillation, and the reaction setup was reassembled. The temperature was then raised to 225 °C, and the mixture was stirred for an additional 3 h to induce the cyclization to an imidazoline structure (reaction scheme, Figure 1), affording the final product, designated as A-Lin.
An analogous synthesis of A-Lau was conducted using lauric acid and diethylenetriamine (DETA) at a 1:1 molar ratio. The reaction was carried out in a 500 mL three-neck round-bottom flask equipped with a Vigreux distillation column, Dean–Stark trap, reflux condenser, and magnetic stirring (1500 rpm). Lauric acid (0.5 mol, 100.2 g), DETA (0.5 mol, ~52.0 g), and toluene (100 mL) were introduced into the system. The mixture was heated to 120 °C under atmospheric pressure to promote the amidation reaction while continuously removing water by azeotropic distillation.
The endpoint of the amidation stage was defined by stabilization of the collected water volume at 6.5 mL for at least one hour, which was considered sufficient to establish a total amidation time of 4 h. Subsequently, toluene was removed by distillation, the reaction setup was reassembled, and the temperature was increased to 225 °C to induce cyclization. The endpoint of the cyclization stage was determined by the cessation of water evolution for at least 30 min, and the successful formation of the imidazoline ring was confirmed by the appearance of the characteristic C=N stretching band in the FTIR spectrum.

2.3. Preparation of Water-Based Drilling Fluids

Four formulations of water-based drilling muds (WBMs) were prepared according to the compositions listed in Table 1. For the base formulation, 917 mL of tap water was mixed for one minute with 0.5 g of caustic soda in order to increase pH. After that, 0.5 g of sodium carbonate was mixed for another minute, followed by the addition of 70 g of potassium chloride, mixed for two minutes. One milliliter of defoamer was mixed for one minute and then one milliliter of bactericide for one minute.
Depending on the formulation, commercial inhibitors (Amine NF, Glycol) or synthesized additives (A-Lin, A-Lau) were incorporated as shown in the table, and each was mixed for an additional 2 min. For filtrate control, 3 g of xanthan gum was added and mixed for 5 min, while 10 g of PAC LV was added for rheology control and mixed for 5 min. Finally, 202 g of barite was introduced as weighting agent to reach the target density, followed by mixing for 42 min.
All formulations were prepared at ambient temperature using a Hamilton Beach mixer (50 min, speed setting 2), followed by high-shear homogenization with a Silverson mixer (6000 rpm, 10 min) to ensure uniform dispersion of all components.
After preparation and initial testing, the four formulations were subjected to shale inhibition evaluation using a Dynamic Linear Swell Meter (OFITE) for 70 h. Shale wafers were prepared from 15 g of shale cuttings (<500 μm) obtained from the X Rosetti formation (depth 2917 m). The cuttings were pressed under 6000 psi (~41 MPa) for 30 min in a compactor cell press to achieve a molding density of 2.6 g/cm3. The wafers were shaped with a 28 mm diameter and conditioned for 24 h prior to testing. Swelling measurements were carried out at (20–23) °C, and the swelling reduction efficiency of each formulation was compared to assess the relative performance of the synthesized additives against commercial benchmarks.

2.4. Characterization and Testing of the Anti-Swelling Additives

The synthesized anti-swelling additives were characterized using Fourier-transform infrared spectroscopy (FTIR). Spectra were recorded on a Shimadzu IRAffinity-1S spectrometer (Kyoto, Japan) equipped with a GladiATR-10 accessory, enabling attenuated total reflectance (ATR) measurements. FTIR spectra were collected over the wavenumber range of 700–4000 cm−1 at a resolution of 4 cm−1, with 45 scans per sample. Approximately 5–10 mg of powdered sample was directly applied to the ATR crystal to ensure full surface coverage, as illustrated in Supplementary Figure S2.
Thermal stability was investigated by thermogravimetric analysis (TGA) using a METTLER TOLEDO TGA/IST system (Greifensee, Switzerland). Samples of A-Lau (51.316 mg) and A-Lin (41.368 mg) were heated from 30 to 550 °C under nitrogen (30 mL/min) at a heating rate of 10 °C/min (Figure S3). For practical relevance to drilling operations, the interpretation of thermal stability was focused on the 30–400 °C interval.
Mineralogical analysis was performed using X-ray diffraction (XRD) with a D8 Advance diffractometer (Bruker-AXS, Karlsruhe, Germany) operating with Cu-Kα radiation (λ = 1.54 Å), equipped with a nickel filter, θ-θ geometry, and a Bragg–Brentano configuration. XRD measurements were carried out under the following conditions: 40 kV, 40 mA, a step size of 0.1°, a scan speed of 0.1° per 5 s, and a 2θ scan range from 5° to 60°.
The alkalinity of the drilling fluid was determined to quantify the bicarbonate (HCO3−), carbonate (CO32−), and hydroxyl (OH−) ions, following the API Recommended Practice 13B. The procedure employed 0.02 N sulfuric acid as titrant, with phenolphthalein and bromocresol green as pH indicators. The concentrations of calcium and magnesium ions, which define the hardness of the drilling fluid, were also measured according to API RP 13B-1 [37].
The titration was performed using standardized disodium ethylenediaminetetraacetate dihydrate (EDTA) as the complexing agent, a buffer solution containing ammonium chloride and ammonium hydroxide, and calmagite (Calver II) [37] as the color indicator. The chloride (Cl−) content of the filtrate was determined by argentometric titration using 1 N silver nitrate as titrant, potassium chromate as the endpoint indicator, and 0.02 N sulfuric acid with phenolphthalein for pH adjustment, in accordance with API RP 13B-1 [37]. All titrations were performed on filtrate samples of the drilling fluids at ambient temperature.
In addition to spectroscopic and thermal analyses, the physicochemical and rheological properties of the prepared water-based drilling fluids (WBMs) were systematically evaluated. Measurements included mud weight (g/cm3) for density determination and pH for acidity/alkalinity assessment. Rheological behavior was characterized using a Fann viscometer at 49 °C, with dial readings recorded at 600, 300, 200, 100, 6, and 3 rpm. Gel strength values were determined after 10 s and 10 min (Gels 10″/10′) to assess thixotropic recovery. From these data, plastic viscosity (PV) and yield point (YP) were calculated to describe the flow behavior and carrying capacity of the fluids. Filtration performance was assessed according to the API standard filtrate volume (mL), while the mud cake thickness (mm) was measured to evaluate filter-cake buildup. The lubricity coefficient was determined to estimate the friction-reduction potential of the fluid. Finally the inhibition performance of A-Lin and A-Lau as anti-swelling additives was assessed by linear swelling tests performed on a Dynamic Linear Meter with Compactor and Computer made by Ofite. This method offers a simple, low-cost, and widely adopted laboratory approach to evaluate the efficiency of shale hydration inhibitors [29,38].
The ionic composition of the drilling fluids was also determined to assess the effect of the synthesized additives on the aqueous chemistry of WBMs. Standard analytical procedures were used to quantify calcium (Ca2+), magnesium (Mg2+), and chloride (Cl−) ions, as well as bicarbonate (HCO3−), carbonate (CO32−), and hydroxyl (OH−) species. Monitoring these parameters is essential, as ionic equilibria strongly influence shale hydration, dispersion, and fluid stability. Variations in ion content provided further insight into the inhibition mechanisms of A-Lin and A-Lau compared with the commercial benchmarks (amine NF and glycol).
In order to comprehensively evaluate performance, the inhibition efficiency of the synthesized additives (A-Lin and A-Lau) was compared with that of conventional commercial inhibitors, namely amine NF and glycol, which are widely used in water-based drilling fluid formulations.

3. Results and Discussion

3.1. FTIR Spectral Analysis

Figure 2 presents the FTIR spectra of the synthesized products A-Lin (derived from linoleic acid) and A-Lau (derived from lauric acid). Both spectra show a broad absorption band at 3290 cm−1, attributed to N–H stretching vibrations, confirming the incorporation of amine functionalities through amidation and subsequent cyclization [28,33,39]. A distinct band at 3075 cm−1, observed only in A-Lin, corresponds to C=C stretching vibrations, reflecting the unsaturation characteristic of linoleic acid [40].
Strong absorptions at 2925 and 2850 cm−1 are assigned to the asymmetric and symmetric stretching of aliphatic C–H groups from the long fatty acid chains [39,41]. The band at 1648 cm−1 is characteristic of C=O stretching, likely associated with residual intermediates prior to complete cyclization [39]. A well-defined absorption at 1590 cm−1 corresponds to C=N stretching, consistent with the formation of the imidazoline ring, while the peak at 1460 cm−1 represents N–H bending vibrations, confirming amide bond formation [33,42]. Additional features include the band at 1250 cm−1, attributed to C=O stretching of secondary amides [39], and the band near 1050 cm−1, assigned to C–N stretching vibrations [43].
Notably, A-Lin exhibits an additional weak feature near 1590 cm−1, which can be attributed to C=C stretching vibrations of the unsaturated linoleic acid chain [40], distinguishing it from the saturated A-Lau product. In both spectra a well-defined band at 1590 cm−1 is assigned to C=N stretching of the imidazoline ring. For A-Lin, a minor overlap with C=C is plausible due to the =C–H band at 3075 cm−1 (present only in A-Lin), yet the comparable 1590 cm−1 response in A-Lau (which lacks C=C), together with the accompanying C–N (~1050 cm−1) and N–H bending (1460 cm−1) bands and the absence of the precursor acid C=O (~1705 cm−1), indicates that this band is dominated by C=N in both inhibitors, confirming imidazoline ring formation. Overall, the FTIR results validate the successful synthesis of the imidazoline structures through amidation and cyclization, with spectral differences reflecting the structural nature of the precursor fatty acids (saturated vs. unsaturated).

3.2. Thermal Stability Analysis (TGA-DTG)

To assess downhole applicability under high-temperature conditions, the thermal stability of the synthesized inhibitors (A-Lin and A-Lau) was evaluated by thermogravimetric analysis (TGA-DTG), and the results are presented in Figure 3. The TG curves reveal three main thermal domains. In the low-temperature region (30–140 °C), both samples exhibited a minor mass loss of ~1.5% at ~140 °C, attributed to desorption of physisorbed water and trace volatiles, consistent with the presence of polar groups (–NH) prone to moisture uptake [33].
The gradual mass loss observed between 140 and 220 °C can be attributed to the onset of cleavage of terminal C–NH2 bonds, which are thermally less stable compared to the compound’s backbone.
The derivative thermogravimetric (DTG) curves indicate that the slight weight loss below 150 °C (approximately 1.63%) corresponds mainly to the desorption of physically adsorbed water and volatiles, with a negligible difference of 0.122% compared to the mass loss at 140 °C. This confirms that the inhibitors remain structurally stable up to around 150 °C. The actual chemical decomposition (cleavage of terminal amine groups) clearly begins beyond ~180 °C, reaching a distinct DTG peak at approximately 210 °C, consistent with the study by Worzakowska et al. [44], which reported comparable thermal behavior for imidazoline-based hybrids under inert conditions, showing the onset of decomposition above 180 °C and a major DTG peak around 200–208 °C. This clarification demonstrates that both inhibitors remain stable up to 150 °C, the upper safe temperature limit for drilling applications, whereas higher temperatures correspond to a stage of progressive degradation rather than sudden breakdown.
This process is typically accompanied by the release of ammonia and low-molecular-weight fragments, reflecting the progressive decomposition of amino functionalities rather than abrupt chain scission [45].
In the high-temperature range (220–400 °C), pronounced decomposition of the molecular backbone occurred, with cumulative mass losses of ~51.4% for A-Lin and ~68.5% for A-Lau at 400 °C. The higher residual mass of A-Lin (~48.6%) compared to A-Lau (~31.5%) suggests enhanced thermal resistance, plausibly linked to the unsaturated linoleic-derived chain, which can favor cyclization and char formation, thereby delaying volatilization relative to the saturated lauric-derived analogue. Overall, both inhibitors remain largely stable up to ~150 °C with only minor weight loss, supporting their suitability for moderate-to-high-temperature WBMs, while the onset of substantive degradation beyond ~210 °C indicates limitations for prolonged exposure. Nevertheless, A-Lin demonstrated a broader thermal safety margin than A-Lau, making it the more promising candidate for use in hotter drilling environments or extended high-temperature operations.

3.3. XRD Analysis of the X Rosetti Shale

The mineralogical composition of the shale sample collected from the X Rosetti formation was characterized by X-ray diffraction (XRD), as illustrated in Figure 4. The diffractogram exhibits distinct crystalline reflections corresponding to several major and minor mineral phases. Characteristic peaks were identified for quartz at 2θ = 23.5°, 26.8°, and 35.1°, associated with the (100), (112), and (110) planes [46,47], respectively; for calcite at 31.2°, 39.3°, 43.1°, 47.4°, and 49°, corresponding to the (006), (113), (202), (116), and (018) planes [48,49,50]; and for montmorillonite at 6.5°, 19.9°, and 29.6°, related to the (001), (110), and (005) planes [51,52]. Additional reflections were observed for illite (001) at 9.6° [53], kaolinite (110) at 21° and kaolinite (001) at 12.6° [54], barite (002) and (210) at 26° and 28.5° [55] and dolomite (110) at 36.2° [56], confirming the heterogeneous and complex nature of the argillaceous matrix.
Quantitative phase analysis revealed that the shale is predominantly composed of calcite (≈30%) and montmorillonite (≈25%), followed by quartz (≈19%), illite (≈9%), kaolinite (≈4%), barite (≈4%), Sylvite (≈4%), and dolomite (≈1%). The coexistence of highly expansive montmorillonite with non-expanding illite layers indicates a moderate-to-high swelling potential, which is consistent with the behavior observed in linear swelling tests. The relatively high proportion of carbonates (mainly calcite and dolomite) enhances the mechanical rigidity of the rock and contributes to ionic buffering capacity during exposure to water-based drilling fluids.
Based on literature data for shales with comparable montmorillonite–illite ratios, the cation-exchange capacity (CEC) of the studied formation is estimated at 25–35 meq per 100 g, corresponding to a moderate ion-exchange activity [57,58,59]. Overall, the mineralogical profile demonstrates a balanced assemblage of expandable and non-expandable clay minerals, carbonates, and siliceous components, confirming that the X Rosetti shale represents a moderately reactive formation suitable for evaluating the inhibition efficiency of the synthesized imidazoline-based additives.

3.4. Analysis of Drilling Fluid Properties and Swelling Performance

The physicochemical and rheological parameters of the four WBM formulations (Table 2) indicate that all mud systems were prepared with comparable density (1.20 g/cm3), ensuring a uniform baseline for evaluation. The pH values ranged from 9.20 to 9.72, confirming the alkaline nature of the fluids, which is favorable for shale inhibition. Rheological measurements reveal moderate differences: A-Lin and A-Lau exhibited slightly lower Fann readings at high shear rates (600 rpm: 47 and 50, respectively) compared to Amine NF (60) and Glycol (56), indicating reduced apparent viscosity. This is further supported by the lower plastic viscosity (14 and 16 cP for A-Lin and A-Lau, respectively) relative to the commercial additives, which may enhance cuttings transport efficiency while reducing pumping energy requirements.
The fluid loss data reinforce the superior sealing effect of A-Lin and A-Lau. API filtrate values increased from 5.6 mL (Amine NF) to 8.4 mL (A-Lin), with slightly thicker mud cakes (0.8 mm for A-Lin vs. 0.5 mm for others).
The most decisive comparison lies in the swelling tests (Figure 5). The linear swelling curves demonstrate that shale wafers exposed to A-Lin exhibited the lowest final swelling (~6.3%) after 70 h, outperforming both the commercial inhibitors (Amine NF: 6.7%; Glycol: 7.7%) and the structurally similar A-Lau (7.0%). This superior inhibition can be attributed to the unsaturated structure of linoleic acid in A-Lin, which likely enhances adsorption on clay surfaces and promotes partial hydrophobic interactions, thereby reducing water ingress into the clay interlayers. By contrast, A-Lau, derived from saturated lauric acid, displayed higher swelling and less efficient inhibition.
The lubricity coefficients of all systems were in the range 0.154–0.195, with A-Lin exhibiting the lowest value (0.148), indicating enhanced friction reduction relative to commercial benchmarks. This property, combined with its superior swelling inhibition, suggests that A-Lin can provide dual benefits: improved shale stability and reduced torque and drag in drilling operations.
Taken together, these results demonstrate that while commercial inhibitors (Amine NF and Glycol) provide balanced rheological performance and acceptable inhibition, the synthesized A-Lin derivative exhibits a more favorable combination of thermal stability, shale inhibition, and lubricity. Therefore, A-Lin shows strong potential as an efficient and environmentally compatible alternative inhibitor for WBMs under demanding drilling conditions.
Previous studies have demonstrated that imidazoline- and imidazolium-based compounds effectively suppress shale hydration by adsorbing onto clay surfaces, reducing water ingress, and enhancing fluid–rock compatibility. For example, imidazolium ionic liquids markedly decreased clay swelling and improved shale stability in WBMs [60,61], while polymeric inhibitors containing imidazolium units provided improved inhibition efficiency and operational stability [26]. Such findings support our conclusion that the imidazoline derivative A-Lin, owing to its structural similarity, is expected to significantly enhance wellbore stability while lowering torque and drag, thereby facilitating smoother drilling in shale-rich intervals. This advantage aligns with recent reports of environmentally friendly inhibitors designed to replace high-dosage KCl systems [21].
Although the synthesized imidazoline-based inhibitors are expected to be environmentally benign due to their fatty acid backbone, this study did not include direct measurements of toxicity or biodegradability. This limitation will be addressed in future work through standardized eco-toxicological and biodegradation assessments.

4. Conclusions

The synthesized inhibitors A-Lin and A-Lau demonstrated effective shale hydration control in WBMs. A-Lin outperformed all tested additives, reducing swelling to 6.3% and achieving the lowest lubricity coefficient (0.148), compared with A-Lau (7.0%), Amine NF (6.7%) and Glycol (7.7%). FTIR and TGA analyses confirmed the imidazoline structure and stability up to ~150 °C, with A-Lin showing superior resistance. Overall, A-Lin represents a promising eco-friendly alternative to conventional shale inhibitors, combining thermal stability, inhibition efficiency, and improved lubricity.
Taken together, these findings confirm the potential of A-Lin as a practical and sustainable drilling fluid additive. Its performance at moderate concentrations indicates a potential to reduce reliance on high-dosage KCl, thereby lowering the environmental footprint of drilling fluids while simultaneously enhancing drilling efficiency and promoting safer, more sustainable shale operations.
This study demonstrates for the first time that fatty acid–derived imidazoline inhibitors, particularly A-Lin, provide a novel alternative to conventional shale inhibitors by combining strong shale inhibition, improved lubricity, and enhanced thermal stability, thereby offering both technical and environmental advantages over existing additives.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/app152011050/s1, Figure S1: Experimental setup for the synthesis of anti-swelling imidazoline derivatives (A-Lin and A-Lau) via amidation and cyclization with diethylenetriamine (DETA); Figure S2: Experimental setup for the synthesis and FTIR analysis of anti-edema additives using the Shimadzu IRAffinity-1S spectrometer (Kyoto, Japan), equipped with a GladiATR-10 accessory (PIKE Technologies); Figure S3: Experimental setup for thermal stability analysis using the METTLER TOLEDO TGA/IST system (Greifensee, Switzerland), equipped with a nitrogen flow controller (30 mL/min). The instrument software interface showing the programmed heating profile is also presented.

Author Contributions

Conceptualization, R.D., I.G.S. and E.Z.; methodology, R.D., E.Z. and I.G.S.; validation, R.D. and D.B.S.; formal analysis, R.D., M.T. and D.B.S.; investigation, L.D., S.S., A.P.P. and G.B.; resources, R.D. and A.P.P.; data curation, R.D. and D.B.S.; writing—original draft preparation, R.D. and D.B.S.; writing—review and editing, R.D.; visualization, D.B.S., I.G.S., M.T. and R.D.; supervision G.B. and I.G.S.; project administration, R.D. All authors have read and agreed to the published version of the manuscript.

Funding

The authors thankfully acknowledge the Petroleum-Gas University of Ploiesti, Romania for the financial support, project GO-GICS “Study of possibilities for increasing the efficiency of well drilling by using high-performance drilling fluid systems” number 30780/11 December 2024.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

Author Emil Zaharia was employed by the company Atica Chemicals SRL. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Deville, J.P. Chapter 4—Drilling fluids. In Fluid Chemistry, Drilling and Completion; Wang, Q., Ed.; Gulf Professional Publishing: Oxford, UK, 2022; pp. 115–185. [Google Scholar] [CrossRef]
  2. Bendi, A.; Raja, M.; Vashisth, C.; Kaur, P.; Udayasri, A.; Mech, D.; Swamy, T.N.V.R.L.; Raghav, N. Drilling fluids: Score years of trends, innovations and implications in research. J. Mol. Liq. 2024, 413, 125891. [Google Scholar] [CrossRef]
  3. Mahmoud, H.; Mohammed, A.A.A.; Nasser, M.S.; Hussein, I.A.; El-Naas, M.H. Green drilling fluid additives for a sustainable hole-cleaning performance: A comprehensive review. Emergent Mater. 2024, 7, 387–402. [Google Scholar] [CrossRef]
  4. Yang, J.; Dong, T.; Yi, J.; Jiang, G. Development of Multiple Crosslinked Polymers and Its Application in Synthetic-Based Drilling Fluids. Gels 2024, 10, 120. [Google Scholar] [CrossRef] [PubMed]
  5. Davison, J.M.; Jones, M.; Shuchart, C.E.; Gerard, C. Oil-Based Muds for Reservoir Drilling: Their Performance and Cleanup Characteristics. SPE Drill. Complet. 2001, 16, 127–134. [Google Scholar] [CrossRef]
  6. Ali, I.; Ahmad, M.; Ganat, T. Development of a new formulation for enhancing the rheological and filtration characteristics of low-solids WBMs. J. Pet. Sci. Eng. 2021, 205, 108921. [Google Scholar] [CrossRef]
  7. Jamrozik, A.; Protasova, E.; Gonet, A.; Bilstad, T.; Żurek, R. Characteristics of oil based muds and influence on the environment. AGH Drill. Oil Gas 2016, 33, 681–691. [Google Scholar] [CrossRef]
  8. Dye, W.; d’Augereau, K.; Hansen, N.; Otto, M.; Shoults, L.; Leaper, R.; Clapper, D.; Xiang, T. New Water-Based Mud Balances High-Performance Drilling and Environmental Compliance. SPE Drill. Complet. 2006, 21, 255–267. [Google Scholar] [CrossRef]
  9. Khashay, M.; Zirak, M.; Sheng, J.J.; Ganat, T.; Esmaeilnezhad, E. Elevated temperature and pressure performance of water based drilling mud with green synthesized zinc oxide nanoparticles and biodegradable polymer. Sci. Rep. 2025, 15, 11930. [Google Scholar] [CrossRef]
  10. Hosseini, S.E.; Nowrouzi, I.; Shahbazi, K.; Kamari, M.; Mohammadi, A.H.; Manshad, A.K. An investigation into shale swelling inhibition properties of dodecyltrimethylammonium chloride (DTAC) for water-based drilling fluids. Geoenergy Sci. Eng. 2023, 223, 211465. [Google Scholar] [CrossRef]
  11. Rana, A.; Arfaj, M.K.; Saleh, T.A. Advanced developments in shale inhibitors for oil production with low environmental footprints—A review. Fuel 2019, 247, 237–249. [Google Scholar] [CrossRef]
  12. Li, Y.; Xia, C.; Liu, X. Water-based drilling fluids containing hydrophobic nanoparticles for minimizing shale hydration and formation damage. Heliyon 2023, 9, e22990. [Google Scholar] [CrossRef]
  13. Jia, H.; Huang, P.; Wang, Q.; Han, Y.; Wang, S.; Zhang, F.; Pan, W.; Lv, K. Investigation of inhibition mechanism of three deep eutectic solvents as potential shale inhibitors in water-based drilling fluids. Fuel 2019, 244, 403–411. [Google Scholar] [CrossRef]
  14. Hawkes, C.D.; McLellan, P.; Maurer, W.; Ruan, C. Wellbore Instability in Shales: A Review of Fundamental Principles, Physico-Chemical Mechanisms in Mud-Shale Interaction and GRI-Funded Research; Gas Research Institute: Chicago, IL, USA, 2000. [Google Scholar]
  15. Saleh, T.A. Advanced trends of shale inhibitors for enhanced properties of water-based drilling fluid. Upstream Oil Gas Technol. 2022, 8, 100069. [Google Scholar] [CrossRef]
  16. Shi, X.; Wang, L.; Guo, J.; Su, Q.; Zhuo, X. Effects of inhibitor KCl on shale expansibility and mechanical properties. Petroleum 2019, 5, 407–412. [Google Scholar] [CrossRef]
  17. Buslaev, G.; Lavrik, A. Comparative Study of Efficiency of Hydrate Inhibitors Based on Ammonium Salts and Polyvinylpyrrolidone. Int. J. Eng. 2026, 39, 898–905. [Google Scholar] [CrossRef]
  18. Retnanto, A.; Yrac, R.; Shaikh, A.; Alagha, R.; Alsulaiti, F.; Chagouri, T. Experimental evaluation of corrosion inhibitors for completion fluids in the petroleum production systems. J. Pet. Explor. Prod. Technol. 2024, 14, 331–342. [Google Scholar] [CrossRef]
  19. Shenoy, S.; Gilmore, T.; Twynam, A.J.; Patel, A.; Mason, S.; Kubala, G.; Vidick, B.; Parlar, M. Guidelines for Shale Inhibition During Openhole Gravel Packing with Water-Based Fluids. SPE Drill. Complet. 2008, 23, 80–87. [Google Scholar] [CrossRef]
  20. Bavoh, C.B.; Md Yuha, Y.B.; Tay, W.H.; Ofei, T.N.; Lal, B.; Mukhtar, H. Experimental and modelling of the impact of quaternary ammonium salts/ionic liquid on the rheological and hydrate inhibition properties of xanthan gum water-based muds for drilling gas hydrate-bearing rocks. J. Pet. Sci. Eng. 2019, 183, 106468. [Google Scholar] [CrossRef]
  21. Tian, Y.; Liu, X.; Liu, Y.; Dong, H.; Zhang, G.; Su, B.; Liu, X.; Hu, Y.; Huang, J.; Lu, Z. Research and Performance Evaluation of Environmentally Friendly Shale Inhibitor TIL-NH2 for Shale Gas Horizontal Wells. Molecules 2024, 29, 5950. [Google Scholar] [CrossRef]
  22. Fink, J. Petroleum Engineer’s Guide to Oil Field Chemicals and Fluids; Gulf Professional Publishing: Oxford, UK, 2021. [Google Scholar] [CrossRef]
  23. Huang, D.-C.; Xie, G.; Peng, N.-Y.; Zou, J.-G.; Xu, Y.; Deng, M.-Y.; Du, W.-C.; Xiao, Y.-R.; Huang, J.-J.; Luo, P.-Y. Synergistic inhibition of polyethylene glycol and potassium chloride in water-based drilling fluids. Pet. Sci. 2021, 18, 827–838. [Google Scholar] [CrossRef]
  24. Koh, J.K.; Lai, C.W.; Johan, M.R.; Gan, S.S.; Chua, W.W. Recent advances of modified polyacrylamide in drilling technology. J. Pet. Sci. Eng. 2022, 215, 110566. [Google Scholar] [CrossRef]
  25. Sid, A.N.; Kouini, B.; Bezzekhami, M.A.; Toumi, S.; Ouchak, K.; Benfarhat, S.; Tahraoui, H.; Kebir, M.; Amrane, A.; Assadi, A.A.; et al. Optimization of Partially Hydrolyzed Polyacrylamide (HPAM) Utilized in Water-Based Mud While Drilling. Processes 2023, 11, 1133. [Google Scholar] [CrossRef]
  26. Li, Q.; Zhu, D.-Y.; Zhuang, G.-Z.; Li, X.-L. Advanced development of chemical inhibitors in water-based drilling fluids to improve shale stability: A review. Pet. Sci. 2025, 22, 1977–1996. [Google Scholar] [CrossRef]
  27. Zhu, W.; Zheng, X. Effective Modified Xanthan Gum Fluid Loss Agent for High-Temperature Water-Based Drilling Fluid and the Filtration Control Mechanism. ACS Omega 2021, 6, 23788–23801. [Google Scholar] [CrossRef]
  28. Wang, Q.; He, H.; Zhao, Y.; Rui, J.; Jiang, R.; Slaný, M.; Chen, G.; Gu, X. Preparation and Performance Evaluation of Small-Molecule Ammonium as a Shale Hydration Inhibitor. Minerals 2024, 14, 1117. [Google Scholar] [CrossRef]
  29. Du, W.; Wang, X.; Chen, G.; Zhang, J.; Slaný, M. Synthesis, Property and Mechanism Analysis of a Novel Polyhydroxy Organic Amine Shale Hydration Inhibitor. Minerals 2020, 10, 128. [Google Scholar] [CrossRef]
  30. Barati, P.; Shahbazi, K.; Kamari, M.; Aghajafari, A. Shale hydration inhibition characteristics and mechanism of a new amine-based additive in water-based drilling fluids. Petroleum 2017, 3, 476–482. [Google Scholar] [CrossRef]
  31. Oseh, J.O.; Norddin, M.N.A.M.; Muhamad, H.N.; Ismail, I.; Gbadamosi, A.O.; Agi, A.; Ismail, A.R.; Blkoor, S.O. Influence of (3–Aminopropyl) triethoxysilane on entrapped polypropylene at nanosilica composite for shale swelling and hydration inhibition. J. Pet. Sci. Eng. 2020, 194, 107560. [Google Scholar] [CrossRef]
  32. Xian, S.; Chen, S.; Lian, Y.; Du, W.; Song, Z.; Chen, G. Preparation and Evaluation of Ammonium Adipate Solutions as Inhibitors of Shale Rock Swelling. Minerals 2021, 11, 1013. [Google Scholar] [CrossRef]
  33. Tian, Y.; Liu, X.; Liu, Y.; Dong, H.; Zhang, G.; Su, B.; Huang, J. Preparation and Mechanism of Shale Inhibitor TIL-NH2 for Shale Gas Horizontal Wells. Molecules 2024, 29, 3403. [Google Scholar] [CrossRef]
  34. Zhong, H.; Qiu, Z.; Tang, Z.; Zhang, X.; Xu, J.; Huang, W. Study of 4, 4′-methylenebis-cyclohexanamine as a high temperature-resistant shale inhibitor. J. Mater. Sci. 2016, 51, 7585–7597. [Google Scholar] [CrossRef]
  35. Isac-García, J.; Dobado, J.A.; Calvo-Flores, F.G.; Martínez-García, H. Chapter 4—Basic Laboratory Operations. In Experimental Organic Chemistry; Isac-García, J., Dobado, J.A., Calvo-Flores, F.G., Martínez-García, H., Eds.; Academic Press: Cambridge, MA, USA, 2016; pp. 71–144. [Google Scholar]
  36. Wongwanichkangwarn, I.; Limtrakul, S.; Vatanatham, T.; Ramachandran, P.A. Amidation Reaction System: Kinetic Studies and Improvement by Product Removal. ACS Omega 2021, 6, 30451–30464. [Google Scholar] [CrossRef]
  37. API RP 13B-1; Recommended Practice for Field Testing Water-Based Drilling Fluids. American Petroleum Institute: Washington, DC, USA, 2000.
  38. Stephens, M.; Gomez-Nava, S.; Churan, M. AADE-09-NTCE-11-04: Laboratory Methods to Assess Shale Reactivity with Drilling Fluids. In Proceedings of the AADE National Technical Conference and Exhibition, New Orleans, LA, USA, 21–23 April 2009. [Google Scholar]
  39. Peng, S.Y.; Jiang, Z.N.; Li, Y.R.; Dong, C.F.; Liu, H.F.; Zhang, G.A. A new exceptional imidazoline derivative corrosion inhibitor for carbon steel in supercritical CO2 environment. Corros. Sci. 2025, 245, 112663. [Google Scholar] [CrossRef]
  40. Abdullah, B.M.; Salih, N.; Salimon, J. Optimization of the chemoenzymatic mono-epoxidation of linoleic acid using D-optimal design. J. Saudi Chem. Soc. 2014, 18, 276–287. [Google Scholar] [CrossRef]
  41. Lazorenko, G.; Kasprzhitskii, A.; Yavna, V. Synthesis and structural characterization of betaine- and imidazoline-based organoclays. Chem. Phys. Lett. 2018, 692, 264–270. [Google Scholar] [CrossRef]
  42. Muktiarti, N.; Ditama, I.; Soegijono, B. Characterization of imidazoline derivates synthesized from soybean oil fatty acids as corrosion inhibitors on mild steel. AIP Conf. Proc. 2020, 2242, 020023. [Google Scholar] [CrossRef]
  43. Chang, N.; Liu, K.; Zhao, Y.; Deng, Y.; Ge, H. Inhibition Performance and Mechanism of Poly(Citric Acid–Glutamic Acid) on Carbon Steel Corrosion in Simulated Seawater. Appl. Sci. 2024, 14, 9465. [Google Scholar] [CrossRef]
  44. Worzakowska, M.; Sztanke, M.; Rzymowska, J.; Sztanke, K. Thermal Decomposition Path—Studied by the Simultaneous Thermogravimetry Coupled with Fourier Transform Infrared Spectroscopy and Quadrupole Mass Spectrometry—Of Imidazoline/Dimethyl Succinate Hybrids and Their Biological Characterization. Materials 2023, 16, 4638. [Google Scholar] [CrossRef]
  45. Li, L.; Guan, C.; Zhang, A.; Chen, D.; Qing, Z. Thermal stabilities and the thermal degradation kinetics of polyimides. Polym. Degrad. Stab. 2004, 84, 369–373. [Google Scholar] [CrossRef]
  46. Kharya, A.; Sachan, H.K.; Tiwari, S.K.; Singhal, S.; Singh, P.C.; Rai, S.; Kumar, S.; Mehta, M.; Gautam, P.K.R. New occurrence of albitite from Nubra valley, Ladakh: Characterization from mineralogy and whole rock geochemistry. Curr. Sci. 2016, 111, 1531–1535. [Google Scholar] [CrossRef]
  47. Zhang, C.; Xu, Z.; Hu, Y.; He, J.; Tian, M.; Zhou, J.; Zhou, Q.; Chen, S.; Chen, D.; Chen, P.; et al. Novel Insights into the Hydroxylation Behaviors of α-Quartz (101) Surface and its Effects on the Adsorption of Sodium Oleate. Minerals 2019, 9, 450. [Google Scholar] [CrossRef]
  48. Zhao, T.; Xu, C.; Ma, Y.; Zeng, Y.; Wang, N. Study on preparation and structure of chrysanthemum-shaped micron calcium carbonate based on inverse microemulsion. Micro Nano Lett. 2020, 15, 1151–1155. [Google Scholar] [CrossRef]
  49. Kaczmarek, S.E.; Gregg, J.M.; Bish, D.L.; Machel, H.G.; Fouke, B.W. Dolomite, very high-magnesium calcite, and microbes—Implications for the microbial model of dolomitization. In Characterization and Modeling of Carbonates–Mountjoy Symposium 1; Society for Sedimentary Geology: Tulsa, OK, USA, 2017; Volume 109. [Google Scholar] [CrossRef]
  50. Al-Jaroudi, S.S.; Ul-Hamid, A.; Mohammed, A.-R.I.; Saner, S. Use of X-ray powder diffraction for quantitative analysis of carbonate rock reservoir samples. Powder Technol. 2007, 175, 115–121. [Google Scholar] [CrossRef]
  51. Damian, G.; Damian, F.; Szakács, Z.; Iepure, G.; Aştefanei, D. Mineralogical and Physico-Chemical Characterization of the Oraşu-Nou (Romania) Bentonite Resources. Minerals 2021, 11, 938. [Google Scholar] [CrossRef]
  52. Borralleras, P.; Segura, I.; Aranda, M.A.G.; Aguado, A. Influence of experimental procedure on d-spacing measurement by XRD of montmorillonite clay pastes containing PCE-based superplasticizer. Cem. Concr. Res. 2019, 116, 266–272. [Google Scholar] [CrossRef]
  53. Liu, R.; Mei, X.; Zhang, J.; Zhao, D.-b. Characteristics of clay minerals in sediments of Hemudu area, Zhejiang, China in Holocene and their environmental significance. China Geol. 2019, 2, 8–15. [Google Scholar] [CrossRef]
  54. Belachew, N.; Hinsene, H. Preparation of cationic surfactant-modified kaolin for enhanced adsorption of hexavalent chromium from aqueous solution. Appl. Water Sci. 2019, 10, 38. [Google Scholar] [CrossRef]
  55. Sanad, M.M.S.; Rashad, M.M. Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore. Int. J. Miner. Metall. Mater. 2016, 23, 991–1000. [Google Scholar] [CrossRef]
  56. Medina-Carrasco, S.; Valverde, J.M. In situ XRD analysis of dolomite calcination under CO2 in a humid environment. CrystEngComm 2020, 22, 6502–6516. [Google Scholar] [CrossRef]
  57. Saidian, M.; Godinez, L.J.; Prasad, M. Effect of clay and organic matter on nitrogen adsorption specific surface area and cation exchange capacity in shales (mudrocks). J. Nat. Gas Sci. Eng. 2016, 33, 1095–1106. [Google Scholar] [CrossRef]
  58. Rao, B.H.; Reddy, P.S.; Mohanty, B.; Reddy, K.R. Combined effect of mineralogical and chemical parameters on swelling behaviour of expansive soils. Sci. Rep. 2021, 11, 16562. [Google Scholar] [CrossRef]
  59. Alagoz, E.; Mengen, A.E. Shale Characterization Methods Using XRD, CEC, and LSM: Experimental Findings. Pet. Petrochem. Eng. J. 2024, 8, 1–10. [Google Scholar] [CrossRef]
  60. Ahmed Khan, R.; Murtaza, M.; Abdulraheem, A.; Kamal, M.S.; Mahmoud, M. Imidazolium-Based Ionic Liquids as Clay Swelling Inhibitors: Mechanism, Performance Evaluation, and Effect of Different Anions. ACS Omega 2020, 5, 26682–26696. [Google Scholar] [CrossRef]
  61. Dai, Z.; Sun, J.; Xiu, Z.; Huang, X.; Lv, K.; Liu, J.; Sun, Y.; Dong, X. Preparation and Performance Evaluation of Ionic Liquid Copolymer Shale Inhibitor for Drilling Fluid Gel System. Gels 2024, 10, 96. [Google Scholar] [CrossRef]
Applsci 15 11050 g001
Figure 1. Synthesis pathway of imidazoline derivatives (A-Lin from linoleic acid and A-Lau from lauric acid) via amidation and cyclization with diethylenetriamine (DETA).
Figure 1. Synthesis pathway of imidazoline derivatives (A-Lin from linoleic acid and A-Lau from lauric acid) via amidation and cyclization with diethylenetriamine (DETA).
Applsci 15 11050 g001
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Figure 2. FTIR spectra of the synthesized imidazoline derivatives A-Lin (from linoleic acid) and A-Lau (from lauric acid).
Figure 2. FTIR spectra of the synthesized imidazoline derivatives A-Lin (from linoleic acid) and A-Lau (from lauric acid).
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Figure 3. Thermogravimetric (TGA) curves of A-Lin and A-Lau showing their thermal stability profiles.
Figure 3. Thermogravimetric (TGA) curves of A-Lin and A-Lau showing their thermal stability profiles.
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Figure 4. XRD pattern of the X Rosetti shale.
Figure 4. XRD pattern of the X Rosetti shale.
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Figure 5. Time-Dependent Swelling of Shale Exposed to A-Lin, A-Lau, Glycol and Amine-Type Inhibitors.
Figure 5. Time-Dependent Swelling of Shale Exposed to A-Lin, A-Lau, Glycol and Amine-Type Inhibitors.
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Table 1. Composition of WBM formulations.
Table 1. Composition of WBM formulations.
ProductsWBM 1 (Amine NF)WBM 2 (Glycol)WBM 3 (A-Lau)WBM 4 (A-Lin)
Tap water (mL)917917917917
Caustic soda (g)0.50.50.50.5
Sodium carbonate (g)0.50.50.50.5
Potassium chloride (g)70707070
Defoamer (mL)1111
Bactericide (mL)1111
Amine NF (g)20–––
Glycol (g)–20––
A-Lau (g)––20–
A-Lin (g)–––20
PAC LV (g)10101010
Xanthan gum (g)3333
Barite (g)202202202202
Table 2. Physicochemical and rheological properties of WBM formulations containing commercial and synthesized inhibitors.
Table 2. Physicochemical and rheological properties of WBM formulations containing commercial and synthesized inhibitors.
ParametersWBM 1
Amine NF		WBM 2
Glycol		WBM 3
A-Lau		WBM 4
A-Lin
Mud weight (g/cm3)1.201.201.201.20
pH9.209.4510.239.72
Fann 600 rpm @ 49 °C60566047
Fann 300 rpm @ 49 °C41403833
Fann 200 rpm @ 49 °C30332927
Fann 100 rpm @ 49 °C21221919
Fann 6 rpm @ 49 °C6556
Fann 3 rpm @ 49 °C5445
Gels 10″/10′5/65/64/55/6
Plastic Viscosity (cP)19162214
Yield Point (lb/100 ft2)22241619
API Filtrate (mL)5.66.06.48.4
Mud Cake (mm)0.50.50.50.8
Bicarbonate (mg/L)122122244122
Carbonate (mg/L)600720720720
Hydroxyl (mg/L)0000
Calcium (mg/L)160160160160
Chlorides (mg/L)33,00033,00033,00033,000
Magnesium (mg/L)48484848
Lubricity coefficient0.1950.1920.1540.148
Swell %6.77.77.06.3
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Stan, I.G.; Tudose, M.; Prundurel, A.P.; Branoiu, G.; Dumitrache, L.; Suditu, S.; Stoica, D.B.; Zaharia, E.; Doukeh, R. Imidazoline-Based Fatty Acid Derivatives as Novel Shale Inhibitors for Water-Based Drilling Fluids. Appl. Sci. 2025, 15, 11050. https://doi.org/10.3390/app152011050

AMA Style

Stan IG, Tudose M, Prundurel AP, Branoiu G, Dumitrache L, Suditu S, Stoica DB, Zaharia E, Doukeh R. Imidazoline-Based Fatty Acid Derivatives as Novel Shale Inhibitors for Water-Based Drilling Fluids. Applied Sciences. 2025; 15(20):11050. https://doi.org/10.3390/app152011050

Chicago/Turabian Style

Stan, Ioana Gabriela, Mihail Tudose, Alina Petronela Prundurel, Gheorghe Branoiu, Liviu Dumitrache, Silvian Suditu, Doru Bogdan Stoica, Emil Zaharia, and Rami Doukeh. 2025. "Imidazoline-Based Fatty Acid Derivatives as Novel Shale Inhibitors for Water-Based Drilling Fluids" Applied Sciences 15, no. 20: 11050. https://doi.org/10.3390/app152011050

APA Style

Stan, I. G., Tudose, M., Prundurel, A. P., Branoiu, G., Dumitrache, L., Suditu, S., Stoica, D. B., Zaharia, E., & Doukeh, R. (2025). Imidazoline-Based Fatty Acid Derivatives as Novel Shale Inhibitors for Water-Based Drilling Fluids. Applied Sciences, 15(20), 11050. https://doi.org/10.3390/app152011050

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