Clay Swelling Research Articles

Inhibition Impact of Amino Acids on Swelling Clays: An Experimental and COSMO-RS Simulation Evaluation

The presence of swelling clays, namely, montmorillonite and illite-smectite mixed layer clays alike, significantly affects well stimulation processes, such as hydraulic fracturing. In this study, t...

Pore-Scale Water Vapor Condensation Behaviors in Shales: An Experimental Study

Water condensation in shales impacts its hydro-mechanical response. A mechanistic understanding of the pore-water system is made more challenging by significant anisotropy of pore architecture and nano-scale heterogeneity of pore surfaces. We probe the condensation response in two contrasting shales exposed to a vapor of contrast-matching water, as characterized by in situ ultra-small/small-angle neutron scattering (USANS/SANS) techniques under various relative humidities. One shale with a higher content of both kerogen and clay has rougher surfaces and higher anisotropy than the other shale (less clay and no kerogen) over length scales from 2.5 to 250 nm. Scanning electron microscopy with energy-dispersive spectrometry (SEM–EDS) analysis also confirms that the organic-rich shale presents more anisotropic microfabrics and higher heterogeneity compared to the other shale with less clay and no kerogen. USANS/SANS results show that water condensation effectively narrows the pore volume in the way of reducing the aspect ratio of non-equiaxed pores. For the shale with less clays and no kerogen under a relative humidity of 83%, a wetting film uniformly covers the pore-matrix interface over a wide range of length scale (1 nm–1.9 µm) without smoothing the surface roughness. In contrast, for the organic-rich and clay-rich shale with a strong wetting heterogeneity, condensation occurs at strongly curved hydrophilic asperities (1–10 nm) and smoothens the surface roughness. This is consistent with water vapor condensation behavior in a Vosges sandstone by Broseta et al. (Phys. Rev. Lett. 86:5313, 2001). Though well representing the condensation behavior of water vapor in mesopores/macropores (radii > 1 nm), USANS/SANS techniques could underestimate total water adsorption due to potential cation hydration and clay swelling in micropores (radii < 1 nm).

Influence of tailor-made TiO2/API bentonite nanocomposite on drilling mud performance: Towards enhanced drilling operations

A novel tailor-made TiO2 nanoparticles-bentonite (TNBT) nanocomposite-enhanced drilling mud was tested. The drilling mud showed excellent performance; (i) lubricity was enhanced, (ii) thin and well-intact mud cakes were created, (iii) coating was provided on shale and bentonite plugs, and (iv) clay and shale swelling were mitigated, hence these features ensured a platform for sustainable oil and gas well drilling. The synthesised TNBT nanocomposite followed the one-third bridging rule, i.e., these nanoparticles can bridge nanopore throats in shale pellets and American Petroleum Institute (API) standard bentonite pellets. The tailor-made TNBT nanoparticles were characterized by X-ray diffraction, and scanning electron microscopy. The coefficient of friction and filtrate loss of TNBT-enhanced muds were determined with a lubricity tester, and an API filter press, respectively. Additionally, shale and clay swellings were determined with a linear swell meter. The coefficient of friction was reduced after 0.8 g of TNBT was added to 350 ml drilling mud, resulting in a 35% enhancement in mud lubricity. The new mud also drastically mitigated the swelling in shale and clay when compared to conventional mud. The swelling inhibition was attributed to an increase in the mud viscosity and improved nanopore plugging characteristics, which resulted in less water infiltration. Thus, drilling mud supplemented with the tailor-made TiO2 nanoparticles-bentonite nanocomposite showed superior characteristics and a good potential for field operations.

Molecular dynamics simulations of the colloidal interaction between smectite clay nanoparticles in liquid water

Colloidal interactions between clay nanoparticles have been studied extensively because of their strong influence on the hydrology and mechanics of many soils and sedimentary media. The predominant theory used to describe these interactions is the Derjaguin-Landau-Verwey-Overbeek (DLVO) model, a framework widely applied in colloidal and interfacial science that accurately predicts the interactions between charged surfaces across water films at distances greater than ~ 3 nm (i.e., ten water monolayers). Unfortunately, the DLVO model is inaccurate at the shorter interparticle distances that predominate in most subsurface environments. For example, it inherently cannot predict the existence of equilibrium states wherein clay particles adopt interparticle distances equal to the thickness of one, two, or three water monolayers. Molecular dynamics (MD) simulations have the potential to provide detailed information on the free energy of interaction between clay nanoparticles; however, they have only been used to examine clay swelling and aggregation at interparticle distances below 1 nm. We present the first MD simulation predictions of the free energy of interaction of smectite clay nanoparticles in the entire range of interparticle distances from the large interparticle distances where the DLVO model is accurate (>3 nm) to the short-range swelling states where non-DLVO interactions predominate (<1 nm). Our simulations examine a range of salinities (0.0 to 1.0 M NaCl) and counterion types (Na, K, Ca) and establish a detailed picture of the breakdown of the DLVO model. In particular, they confirm previous theoretical suggestions of the existence of a strong non-DLVO attraction with a range of ~ 3 nm arising from specific ion-clay Coulomb interactions in the electrical double layer.

Effects of swelling-clay and surface roughness on the wettability of transitional shale

Wettability in unconventional reservoirs is poorly understood. However, it plays a fundamental role in fluid-rock interactions, and an understanding of wetting behavior is essential for capillary seal assessments and hydrocarbon reserve estimation and recovery in clay-rich reservoirs. In this study, the wetting behavior of transitional Shanxi-Taiyuan shale from the southern North China basin was examined via the contact angle (CA) and spontaneous imbibition (SI) measurement methods. Under water-air-shale conditions, water-wet and neutral-wet behaviors were observed, whereas neutral-wet and oil-wet behaviors were observed under water-oil-shale conditions (Young's equation was used to convert the water-air-shale system to the water-oil-shale system). When the CA method was used, the shale was shown to be hydrophobic, whereas when the SI test was used, the shale was observed to be hydrophilic. The water-air CAs are negatively correlated with the total organic content (TOC), carbonate and clay mineral contents (excluding those of illite). Furthermore, iron-containing compounds, such as pyrite and siderite, were shown to decrease the water wetness. A linear negative correlation was found between the surface roughness and the CA value. The relationship between these parameters can be used to predict the CAs at different surface roughness values for a given sample. The contradictory wetting behaviors between the results of SI and CA methods can be explained by: (i) differences between the CAs formed under water-air-shale conditions and those formed under hydrocarbon-brine-shale conditions; (ii) differences in the surface roughness, which is dependent on the texture and mineralogy of the shale sample; and (iii) clay swelling after water sorption and the formation of microfractures due to water–rock interactions.

Graphene grafted with glucopyranose as a shale swelling inhibitor in water-based drilling mud

The current study reveals the glucopyranose modified graphene (Glu-Gr) properties as an efficient shale inhibitor. The dispersion recovery test and inhibition stability test were employed to assess the inhibition features of Glu-Gr. The Glu-Gr demonstrated better dispersion recovery and longer inhibition durability in comparison with traditional drilling mud. Various advanced characterization techniques were utilized to study the inhibition mechanism such as scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), energy dispersive X-Ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The hydrogen bonding helps to bind the hydroxyl groups of glucopyranose to the clay surface. The plugging, intercalation, and adsorption of Glu-Gr impede water molecules from entering the clay nanopores. Consequently, the Glu-Gr successfully mitigates the swelling of clay due to hydration.

Imidazolium-Based Ionic Liquids as Clay Swelling Inhibitors: Mechanism, Performance Evaluation, and Effect of Different Anions.

Clay swelling is one of the challenges faced by the oil industry. Water-based drilling fluids (WBDF) are commonly used in drilling operations. The selection of WBDF depends on its performance to improve rheology, hydration properties, and fluid loss control. However, WBDF may result in clay swelling in shale formations during drilling. In this work, the impact of imidazolium-based ionic liquids on the clay swelling was investigated. The studied ionic liquids have a common cation group, 1-allyl-3-methyllimidozium, but differ in anions (bromide, iodide, chloride, and dicyanamide). The inhibition behavior of ionic liquids was assessed by linear swell test, inhibition test, capillary suction test, rheology, filtration, contact angle measurement, scanning electron microscopy, and X-ray diffraction (XRD). It was observed that the ionic liquids with different anions reduced the clay swelling. Ionic liquids having a dicyanamide anion showed slightly better swelling inhibition performance compared to other inhibitors. Scanning electron microscopy images showed the water tendency to damage the clay structure, displaying asymmetrical cavities and sharp edges. Nevertheless, the addition of an ionic liquid to sodium bentonite (clay) exhibited fewer cavities and a smooth and dense surface. XRD results showed the increase in d-spacing, demonstrating the intercalation of ionic liquids in interlayers of clay. The results showed that the clay swelling does not strongly depend on the type of anion in imidazolium-based ILs. However, the type of anion in imidazolium-based ILs influences the rheological properties. The performance of ionic liquids was compared with that of the commonly used clay inhibitor (sodium silicate) in the oil and gas industry. ILs showed improved performance compared to sodium silicate. The studied ionic liquids can be an attractive alternative for commercial clay inhibitors as their impact on the other properties of the drilling fluids was less compared to commercial inhibitors.

Experimental Investigation of Inhibitive Drilling Fluids Performance: Case Studies from United States Shale Basins

Shale formations are attractive prospects due to their potential in oil and gas production. Some of the largest shale formations in the mainland US, such as the Tuscaloosa Marine Shale (TMS), have reserves estimated to be around 7 billion barrels. Despite their huge potential, shale formations present major concerns for drilling operators. These prospects have unique challenges because of all their alteration and incompatibility issues with drilling and completion fluids. Most shale formations undergo numerous chemical and physical alterations, making their interaction with the drilling and completion fluid systems very complex to understand. In this study, a high-pressure, high-temperature (HPHT) drilling simulator was used to mimic real time drilling operations to investigate the performance of inhibitive drilling fluid systems in two major shale formations (Eagle Ford Shale and Tuscaloosa Marine Shale). A series of drilling experiments using the drilling simulator and clay swelling tests were conducted to evaluate the drilling performance of the KCl drilling fluid and cesium formate brine systems and their effectiveness in minimizing drilling concerns. Cylindrical cores were used to mimic vertical wellbores. It was found that the inhibitive muds systems (KCl and cesium formate) provided improved drilling performance compared to conventional fluid systems. Among the inhibitive systems, the cesium formate brine showed the best drilling performances due to its low swelling rate and improved drilling performance.

Forecasting of the technological parameters of the oil displacement with the various mineral content water in the clay storage collector

A multicomponent hydrodynamic model of the process of oil displacement with water with different mineralogical composition in clay-containing collectors is proposed on the basis of combination of equations of continuity, filtration law and equation of state, equation of salt concentration in water and equation of saturation between phases which enables prediction of process parameters of oil displacement with fresh and formation waters with and without consideration of clay swelling.

A simulation study of the effect of clay swelling on fracture generation and porosity change in shales under stress anisotropy

The simulation study of the effect of clay swelling on fracture generation and porosity change in shale rocks is of great significance for applying hydraulic fracturing in the development of shale reservoirs in the petroleum industry. However, previous simulations did not consider the heterogeneous characteristics of shales. Besides, it is not clear how the swelling stresses are distributed owing to swelling inside shales. In this paper, we employ a discrete element method (DEM) modeling, which is combined with the CT images and MATLAB coding, to predict the effect of clay swelling on fracture generation and porosity change in shales under stress anisotropy. We are able to successfully simulate the effect of clay swelling on fracture generation and porosity change in heterogeneous shales under stress anisotropy by employing the discrete element method (DEM) modeling. Clay content is the key factor in fracture generation and the resulted porosity change. For shales with high clay content, clay swelling has contributions to the recovery of shale's porosity. The von Mises stress maps show that the stress inside the model is highly anisotropic and the maximum effective stresses concentrate on the fractures' areas. The larger the pressure is applied to the sample, the larger the von Mises stress can be observed. Stress anisotropy is a positive factor in fracture generation in the process of water-shale interaction. The degree of the clay swelling and the heterogeneity of samples are two factors that could influence the results.

Evaluation of Clay Hydration and Swelling Inhibition Using Quaternary Ammonium Dicationic Surfactant with Phenyl Linker.

Water-based drilling fluids are extensively used for drilling oil and gas wells. However, water-based muds cause clay swelling, which severely affects the stability of wellbore. Due to two adsorption positions, it is expected that cationic gemini surfactants can reduce the clay swelling. In this work, quaternary ammonium dicationic gemini surfactants containing phenyl linkers and different counterions (Cl− and Br−) were synthesized, and the effect of variation in counterions on swelling and hydration properties of shales was studied. Numerous water-based drilling fluid formulations were prepared with different concentrations of surfactants to study the swelling inhibition capacity of surfactants. The performance of surfactant-containing drilling muds was evaluated by comparing them with base drilling mud, and sodium silicate drilling mud. Various experimental techniques were employed to study drilling mud characteristics such as rheology and filtration. The inhibition properties of drilling mud formulations were determined by linear swelling experiment, capillary suction time test, particle size distribution measurement, wettability measurements, and X-ray Diffraction (XRD). Experimental results showed that surfactant-based formulation containing bromide counterion exhibited superior rheological properties as compared to other investigated formulations. The filtration test showed that the gemini surfactant with chloride counterion had higher filtrate loss compared to all other formulations. The bentonite swelling was significantly reduced with increasing the concentration of dicationic surfactants as inhibitors, and maximum reduction in the linear swelling rate was observed by using a formulation containing surfactant with chloride counterion. The lowest capillary suction timer (CST) was obtained in the formulation containing surfactant with chloride counterion as less CST indicated the enhanced inhibition capacity. The particle size measurement showed that average bentonite particle size increased upon the addition of surfactants depicting the inhibition capacity. The increase in basal spacing obtained from XRD analysis showed the intercalation of gemini surfactants in interlayers of bentonite. The contact angle measurements were performed to study the wettability of the bentonite film surface, and the results showed that hydrophobicity increased by incorporating the surfactants to the drilling fluid.

Compression of Na-Montmorillonite Swelling Clay Interlayer Is Influenced by Fluid Polarity: A Steered Molecular Dynamics Study.

The compressive responses of an interlayer of the dry sodium-montmorillonite (Na-MMT) swelling clay as well as the clay intercalated with organic fluids of a wide range of dielectric constants from 110 (formamide) to 20 (acetone) are quantitatively evaluated using steered molecular dynamics simulations. Representative dry clay and clay with fluid (clay-fluid) molecular models are constructed, and the stress-strain relationships upon compression of these models are studied using constant force steered molecular dynamics (SMD) simulations. Our results show that the polarity of the fluids and the amount of the fluid molecules in the clay interlayer play a significant role in the interlayer spacing, interlayer volume, interlayer strain, interlayer modulus, nonbonded interactions, and conformation of the fluid molecules upon externally applied stresses. The clay interlayer responses upon compression are essential for the development of multiscale modeling of swelling clays and prediction of the reliable compressive behavior, which are critical for the accurate analysis and economical design of the infrastructures in swelling clay areas and the densification of clays for ceramics manufacturing.

Novel gemini surfactant as a clay stabilizing additive in fracturing fluids for unconventional tight sandstones: Mechanism and performance

The effect of clay particles on reservoir performance and nearby formations depends on its swelling properties, cation exchange capacity, and morphology. In this study, a novel synthesized gemini surfactant is used as an additive in fracturing fluid to stabilize the clays in an unconventional tight sandstone rock fracturing. The effect of clay swelling on the tensile strength of the tight sandstone rock is quantified using breakdown pressure experiments. Petrophysical alterations are evaluated using coreflooding experiments. Micro computerized tomography, scanning electron microscope, and nuclear magnetic resonance tests were done before and after each coreflooding experiment to evaluate the formation damage. Similar experiments were carried out without any clay stabilizer (deionized water) and with different commercial clay stabilizers used in fracturing fluids (3 wt % NaCl, and 3 wt % KCl), to compare and evaluate their clay swelling capacities with gemini surfactant. Scioto sandstone samples with average liquid permeability around 0.3 mD and average porosity around 14–16% were used. The X-ray diffraction analysis showed the presence of illite, chlorite, and kaolinite clays in the studied Scioto sandstone samples. Breakdown pressure measurement test results showed that the use of novel gemini surfactant solution as clay stabilizing additive resulted in a significantly lower fracture pressure compared to the deionized water, 3 wt % NaCl, and 3 wt % KCl solutions. Breakdown pressure with gemini surfactant was 746 psia, with 3 wt% KCl was 797 psia, with 3 wt% NaCl was 845 psia, and deionized water showed very higher breakdown pressure of 905.9 psia. The reduction in breakdown pressure is attributed to the clay stabilization capacity of the novel gemini surfactant. Permeability measurements from the coreflooding experiments also confirmed the clay stabilization capacity of the gemini surfactant. Micro computerized tomography and nuclear magnetic resonance showed that the rock samples saturated with deionized water, 3 wt % NaCl, and 3 wt % KCl resulted in the reduced porosity due to the swelling of illite, while the gemini surfactant maintained the porosity due to clay stabilization.

A laboratory study of a novel bio-based nonionic surfactant to mitigate clay swelling

This study reports the applicability of quillaja saponin (QS) as a vigorous and environmentally friendly shale swelling inhibitor. QS is a natural surfactant, which is extracted from herbal sources. The inhibition strength of this surfactant was assessed through various experiments, such as sedimentation, inhibition, filtration, particle size, Scanning Electron Microscope (SEM) images, and cutting recovery. Data obtained from these tests illustrated that QS greatly inhibits clays from swelling. The optimal concentration for QS in this intend was 10 g/L. Compatibility of this surfactant with other common additives was also investigated, which showed that it is totally compatible. Finally, the potential inhibition mechanism was assessed through thermal gravimetric analysis (TGA), zeta potential, and contact angle measurement experiments. Surface coating, and wettability alteration of clay particles to the oil-wet state was recognized as the most probable mechanism.

Low salinity waterflooding: Surface roughening and pore size alteration implications

Multiple mechanisms of low salinity waterflooding (LSW) orchestrate the increase of oil recovery. One proposed mechanism is surface roughening which alters the wettability in pores. However, clay swelling that generates surface roughening also simultaneously reduces the pore size. Therefore, we study the implication of surface roughening and pore size of the rock that leads to oil recovery in LSW at different brine compositions and clay contents. We measure the incremental oil recovery due to brine dilution sequences by using a modified-Amott imbibition cell. The results suggest that oil recovery due to brine dilution is minimal when the cores have clay content above 20%. The pore size alteration effects compete with surface roughening. We find that the presence of divalent ions hinders the clay swelling. This implies a smaller pore size alteration and the least amount of surface roughening. In addition, the evolutions of deduced pore size distribution through T2 NMR confirm the results of LSW imbibition. Further, zeta potential measurements on the sandstone suspension provide the surface-charge to understand the oil recovery mechanism. This research suggests that the pore size alteration and surface roughening are important mechanisms for incremental oil recovery in sandstone during LSW operation. These findings might aid the rational design of LSW in the future.

Spontaneous imbibition in igneous rocks: effect of KCl concentration, confining pressure, and imbibition direction

Understanding spontaneous imbibition helps to determine the fracturing fluid volume and optimize the flowback design. At present, many studies have mainly focused on shale, but few on igneous rocks. As such, in this study, imbibition experiments were conducted on igneous rocks. The effects of KCl concentration, confining pressure, and imbibition direction on the spontaneous imbibition were systematically investigated. This study then introduces a new imbibition capacity index. The results show that KCl concentration has certain inhibitory effects on igneous rock imbibition, which reduce the absorption of clay minerals to liquid. Different imbibition directions result in distinct imbibition volumes. The co-current imbibition process is similar to fluid leak-off, but this rule is not satisfied in countercurrent imbibition, the n of which is fitted as 0.1.0.3. Increasing the confining pressure will slightly decrease the imbibition capacity of igneous rock. Rock imbibition causes a decrease in the surface hardness and physical properties of igneous rock, and increasing the KCl concentration in the fluid will effectively hinder clay swelling.

Inhibitive properties comparison of different polyamino acids in water-based drilling fluids

In drilling fluid industry, few shale inhibitors commonly used can simultaneously meet the requirements of strong inhibition and environmental performance. In our previous study, polyamino acid materials showed great potential to be used as environmental-friendly and efficient shale inhibitors. Herein, four polyamino acids with different functional groups, polyglycine (PGly), polyglutamic acid (PGlu), polylysine (PLys), and polyarginine (PArg), were successfully synthesized to study the influence of amino acid composition on inhibition performance. Results indicated that PGly and PGlu mainly exerted their inhibition by decreasing the clay swelling degree, while PLys and PArg mainly showed their inhibition on decreasing the clay dispersion degree. In detail, PGly and PGlu could enter the interlayer region of sodium bentonite (Na-BT) and decrease the interlayer spacing, which could reduce the Na-BT swelling degree to 83.8% and 85.8%, respectively. However, their inhibition on shale dispersion at high temperatures was not satisfactory. Meanwhile, PLys and PArg displayed superior thermal stability and could improve the shale recovery to 66.85% and 74.45% at 150 °C. They could strongly adsorb onto the surface of Na-BT particles, encapsulate them, and decrease the ζ potential to −2.06 and −15.9 mV, thus forming stable aggregates. Compared with PGly and PGlu, PLys and PArg would cause limited change of the interlayer spacing of Na-BT. In all, PArg was preferred to be used as a biodegradable and effective shale inhibitor at high-temperature wells. In the future, different polyamino acid combinations can be designed as more highly effective inhibitors for water-based drilling fluids.

Multiple Approaches to Quantifying the Effective Porosity of Lacustrine Shale Oil Reservoirs in Bohai Bay Basin, East China

An effective porosity is defined as the ratio of volume of interconnected pore space to total volume of a porous sample. It controls the magnitude of fluid flow and is a key parameter in the assessment of recoverable resources. However, its accurate measurement in tight formations is challenging, due to their complex pore structure and lithofacies heterogeneity. In this study, porosities of sixteen lacustrine shale samples from the second Member of the Kongdian Formation (Ek2) in the Cangdong Sag, Bohai Bay Basin were measured and compared using multiple methods and sample sizes to compare and contrast the effective porosity results. The methods included helium pycnometry (HP; cubes of 1 cm3 and grains at 500-841 μm), water immersion porosimetry (WIP; cubes), mercury intrusion porosimetry (MIP; cubes), and nuclear magnetic resonance (NMR; cubes). Finally, samples were completely sealed using paraffin for bulk density measurements to evaluate the extent of potential clay swelling in shale samples involving probing fluids. Results from the HP, WIP, and MIP methods for skeletal density, bulk density, and effective porosity with cubic samples were compared. While very similar skeletal densities were found for all three methods, a lower bulk density, and therefore lower porosity, from the MIP approach can be attributed to the experimental conditions (e.g., vacuum efficiency, applied pressure, wettability of water/helium vs. mercury) and the probable presence of pores with diameters larger than 50 μm not measurable by MIP. Furthermore, the HP porosity of granular samples with 500-841 μm grain sizes can be regarded as approaching the total porosity. The complicated relationship between WIP and NMR porosities may result from the heat-induced volatilization of moisture in pores during NMR tests, and countercurrent imbibition of water replacing the residual hydrocarbons during the saturation process for sample preparation in both tests. The swelling behavior of the lacustrine Ek2 shale with water is not significant because of the low content of expansive clay minerals. In summary, the WIP and HP methods are recommended for effective porosity measurement, whereas the NMR and MIP methods are invaluable for the measurement of pore-size distribution, with additional information on the effective porosity.

Poly(Oxyethylene)-amidoamine Based Gemini Cationic Surfactants with Hydrophilic Spacers as Clay Stabilizers

Water-based drilling fluids cause severe formation damage upon interaction with clay-based formations. Therefore, clay inhibitors are commonly used in the oil and gas industry to prevent clay swell...

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ФОРМИАТА НАТРИЯ НА ТЕРМОСТОЙКОСТЬ КРАХМАЛСОДЕРЖАЩЕГО ГЛИНИСТОГО БУРОВОГО РАСТВОРА

Актуальность работы обусловлена необходимостью сохранения свойств буровых растворов, содержащих крахмальные реагенты, в условиях высокой минерализации и длительного воздействия повышенных температур. Цель: экспериментально определить температурный интервал и оптимальные концентрации эффективного применения формиата натрия в составе буровых растворов, содержащих крахмальные реагенты. Объекты: крахмалсодержащий глинистый буровой раствор с разными концентрациями натриевых солей (хлорида натрия и формиата натрия). Методы: определение фильтрационных и реологических параметров согласно ГОСТ 33213-2014 (ISO 10414-1:2008) после старения буровых растворов при повышенных температурах с использованием термоячеек; проведение опытов методом построения матрицы центрального композиционного планирования и математической обработки результатов экспериментальных данных. Результаты. Проведен сравнительный анализ свойств глинистых буровых растворов, содержащих крахмальный реагент, с использованием хлорида натрия NaCl и формиата натрия HCOONa, после длительного нахождения системы в условиях высоких температур. Показано, что природа соли оказывает значительное влияние на термостойкость крахмалсодержащего бурового раствора: хлорид натрия не обеспечивает термостабильности раствора; формиат натрия позволяет обеспечить термостойкость крахмалсодержащего бурового раствора до 140–160 °С. Получены уравнения регрессии второго порядка, описывающие зависимость показателя фильтрации и реологических параметров крахмалсодержащего глинистого бурового раствора от температуры и концентрации формиата натрия. Установлено, что термостойкость крахмального реагента при совместном применении с формиатом натрия повышается вследствие высокой растворимости соли, которая подавляет гидратацию полисахарида и, соответственно, замедляет его гидролиз при воздействии высоких температур. Выявлено, что эффективная концентрация натриевой соли муравьиной кислоты как термостабилизатора в составе крахмалсодержащего бурового раствора зависит от температуры применения системы: при низких концентрациях соли термостойкость обеспечивается в диапазоне 100–133 °С за счет хорошей активности крахмала; при высоких концентрациях соли – в диапазоне 133–160 °С – за счет низкого содержания свободной воды в системе вследствие высокой растворимости формиата натрия. Показано, что формиат натрия не предотвращает набухание глин, а наоборот, способен оказывать на них пептизирующее действие.