High Pressure And High Temperature Research Articles

Simulated Pressure-temperature Carbon Structure Map obtained through uniaxial compression of Bulk C60

Although the transformation from fullerene bulk into various functional carbon materials at high temperature and high pressure (HTHP) has been extensively explored experimentally, the understanding of the mechanism of structural transformations at atomic scale is still very poor. Based on the recently developed highly-accurate machine learning force field (MLFF), GAP-20, we performed a systematic study on the phase transformations of carbon structures. Various derived structures, such as C60 foams, sp2, sp3, and mixed sp2-sp3 amorphous carbon materials are formed at temperatures below 2500 K, while graphitic carbon, nano-graphitic carbon and diamond are formed at higher temperatures. These materials exhibit excellent mechanical properties and can be used for various applications. The activation energy of the transformation from amorphous carbon to diamond is found to be 2.42 eV, which explains the high stability of sp3 amorphous carbon materials observed recently [Nature, 2021, 599:599; Nature, 2021, 599:605]. The theoretical diagram obtained in this study provides a guidance for experimental synthesis of various functional carbon materials.

Experimental Study on the Application of Cellulosic Biopolymer for Enhanced Oil Recovery in Carbonate Cores under Harsh Conditions.

Polymer flooding is used to improve the viscosity of an injectant, thereby decreasing the mobility ratio and improving oil displacement efficiency in the reservoir. Thanks to their environmentally benign nature, natural polymers are receiving prodigious attention for enhanced oil recovery. Herein, the rheology and oil displacement properties of okra mucilage were investigated for its enhanced oil recovery potential at a high temperature and high pressure (HTHP) in carbonate cores. The cellulosic polysaccharide used in the study is composed of okra mucilage extracted from okra (Abelmoschus esculentus) via a hot water extraction process. The morphological property of okra mucilage was characterized with Fourier transform infrared (FTIR), while the thermal stability was investigated using a thermogravimetric analyzer (TGA). The rheological property of the okra mucilage was investigated for seawater salinity and high-temperature conditions using a TA rheometer. Finally, an oil displacement experiment of the okra mucilage was conducted in a high-temperature, high-pressure core flooding equipment. The TGA analysis of the biopolymer reveals that the polymeric solution was stable over a wide range of temperatures. The FTIR results depict that the mucilage is composed of galactose and rhamnose constituents, which are essentially found in polysaccharides. The polymer exhibited pseudoplastic behavior at varying shear rates. The viscosity of okra mucilage was slightly reduced when aged in seawater salinity and at a high temperature. Nonetheless, the cellulosic polysaccharide exemplified sufficiently good viscosity under high-temperature and high-salinity (HTHS) conditions. Finally, the oil recovery results from the carbonate core plug reveal that the okra mucilage recorded a 12.7% incremental oil recovery over waterflooding. The mechanism of its better displacement efficiency is elucidated.

Transparent diamond ceramics from diamond powder

Diamond possesses a unique combination of excellent optical, thermal, and mechanical properties, and is therefore an ideal transparent ceramic material for harsh and extreme environments. Due to its important applications in technology, transparent diamond ceramic (TDC) has been explored and prepared by chemical vapor deposition (CVD) or direct conversions of non-diamond carbon precursors at high pressure and high temperature (HPHT), but the preparation of large-size TDC with high mechanical strength remains a challenge. Here, we report for the first time, a transparent polycrystalline diamond ceramic from diamond powder with a transmittance of ∼60 % at wavelengths of 400–1600 nm. The analyses of phase composition, residual stress and microstructure evolution of the sintered samples with different sintering conditions indicate that compression at high temperatures (>2000 ⁰C) facilitates the deformation of diamond grains, allowing for densification and diamond-diamond bonding formation. The sintering pressure of the diamond powders with an optimized particle size distribution was dramatically reduced from 16 GPa to 10 GPa. Our results, based on successfully preparing centimeter-sized TDC, set the standard and the precedent for the large-scale preparation of larger TDC in proximity to industrial conditions.

Designing Smart drilling fluids using modified nano silica to improve drilling operations in Geothermal wells

High pressure and high temperature (HPHT) conditions in geothermal wells have necessitated the need to develop thermally stable geothermal drilling mud systems to combat potential drilling complications. This is because mud fluids degrade under HPHT conditions due to high temperature effects. This study therefore aims to establish the optimum concentration of a cationic surfactant that would successfully modify the surface of silica nanoparticles and thereafter, evaluate the performance of modified nano silica as a rheological and filtration property enhancer in water-based muds (WBMs). The surface of silica nanoparticle was successfully modified by adding Hexadecyltrimethylammonium bromide (CTAB) to silica solution. Different mud formulations containing modified nano silica with varying zeta potential values, SNP3 -S2, SNP3 -S4, SNP3 -S5, SNP3 -S6, and SNP3 -S7 with -17.7 mV, 20 mV, 28.2 mV, 35.4 mV, and 37.1 mV respectively were investigated. Results showed that modified nano silica with the highest absolute value of zeta potential enhanced drilling mud rheology as temperature increased from 149°C to 232 °C. The optimal amount of CTAB was found to be between 1.0 and 2.0 wt.%. Filtration loss was reduced by 11.4, 17.6, and 29.5% on average for mud samples SNP3-S5, SNP3-S6, and SNP3-S7, respectively, at all temperatures. Mud cake thickness was reduced by 19.9, 11.6, and 28.7% on average by mud samples SNP3-S5, SNP3-S6, and SNP3-S7 respectively at all temperatures.

Experiment on Gas–Liquid Sulfur Relative Permeability under High-Temperature High-Pressure Sour Gas Reservoir Condition

In the development of high temperature sour gas reservoirs, gas–liquid sulfur two phase percolations exist, which have a significant impact on the gas permeability and gas well productivity. There are currently few reports on experimental studies on gas–liquid sulfur relative permeability. This study improves the experimental equipment and process, and it proposes an experimental method for measuring the gas–liquid sulfur relative permeability curve. Several typical core samples from a sour gas reservoir in Sichuan Basin, China were selected for experimental study, and the gas–liquid sulfur relative permeability under high temperature and high pressure (HTHP) was measured. The results show that, first, the critical flowing saturation of liquid sulfur was 40%, and the gas–liquid sulfur co-flow zone was narrow. With the increase in the liquid sulfur saturation, the gas relative permeability decreased rapidly. Second, the better the physical properties of the core, the greater the damage of liquid sulfur to the core properties. The residual liquid sulfur saturation of the fractured core was higher than matrix core, and as liquid sulfur saturation increased, so did the damage to gas permeability. Third, temperature had an effect on the gas–liquid sulfur relative permeability. Gas relative permeability decreased as the temperature rose, while the liquid sulfur relative permeability remained essentially constant. Fourth, the rock effective stress had a significant impact on the gas–liquid sulfur relative permeability. The relative permeability of gas and liquid sulfur decreased as the effective stress increased, and the fractured core was more sensitive to stress.

Pseudointerpenetrating network nanocomposite hydrogel for temporary plugging in fractured reservoirs

Nanomaterial-enhanced hydrogels have attracted considerable attention as temporary plugging agents for lost circulation control due to their improved strength under high temperature and high pressure (HTHP) conditions compared to conventional hydrogels. In this study, a pseudointerpenetrating network nanocomposite hydrogel (PINNG), which was composed of temperature-resistant polyacrylamide (TSPAM), polyethyleneimine (PEI) and cellulose nanofibrils (CNFs), was proposed. CNF with a fibrous structure exhibited a more significant effect on the rheological behavior and mechanical strength of the hydrogel than nanosilica (nano-SiO2). The reversible CNF network endowed the gelant with increased zero-shear viscosity and significant thixotropy. Furthermore, the presence of CNF noticeably improved the strength of PINNG, and the elastic modulus of PINNG was 1232% greater than that of the blank sample. According to analyses of Fourier transform infrared spectroscopy (FTIR), thermogravimetry-derivative thermogravimetry (TG–DTG) and scanning electron microscopy (SEM), it can be deduced that the strengthening mechanism of CNF was mainly related to physical filling, physical crosslinking, and especially the formation of a pseudointerpenetrating network structure with the crosslinked polymer chains. Due to the strengthening effect of CNF, PINNG exhibited a better pressure-bearing performance than the blank sample and the nano-SiO2 composite sample under 140 °C for the core with 2 mm of fracture width. Additionally, the favorable degradability of the PINNG system demonstrated that PINNG exhibited great potential in the application of lost circulation control as a temporary plugging agent.

High-pressure and high-temperature synthesis of stable SxCo3.6Ni0.4Sb12 skutterudite compounds

Compared to Te, Ni is found in abundance in the earth's crust. At the same time, the mechanical properties of Ni atom-substituted skutterudite are significantly improved. In this study, a series of S-filled Ni-substituted skutterudite compounds were synthesized by a high-pressure and high-temperature (HPHT) method in the synthesis pressure range of 1.0–3.0 GPa. The phase composition, microscopic morphology, and electrothermal transmission properties of the SxCo3.6Ni0.4Sb12 (x = 0, 0.05, 0.10, 0.20) samples were systematically characterized. Phase composition analysis showed that the introduction of S atoms into the intrinsic pores of skutterudite can improve the solid solution limit of Ni atoms in the Co sites of skutterudite. The filling limit of S increased with the synthetic pressure. Moreover, microscopic morphology analysis revealed that the filling of S atoms inhibited the growth of grains. A large number of lattice fringes in different directions were found in the sample, containing abundant microstructures such as lattice distortions and dislocation defects. Compared with the synthesized samples, S0.05Co3.6Ni0.4Sb12 synthesized at 1.0 GPa had a maximum room temperature power factor of 7.98 × 10−4 Wm−1K−2. The electrical properties of S0.05Co3.6Ni0.4Sb12 samples stored for 6 months without any protective measures were tested at room temperature. No obvious changes in performance were observed, which proved that the HPHT method can synthesize stable samples. After several thermal cycles, the electrical properties of the S0.05Co3.6Ni0.4Sb12 sample was tested for variable temperature, and it was found that the sample still had good stability. How the substitution of S atoms with Ni atoms reduces the lattice thermal conductivity can be explained by fitting the Callaway model. The S0.05Co3.6Ni0.4Sb12 sample synthesized at 1.0 GPa had a maximum zT value of 0.46 at the test temperature of 773 K, which decreased to 0.43 after multiple thermal cycles at the same temperature.

A Review on Geothermal Energy and HPHT Packers for Geothermal Applications

Energy is an essential component for prosperity, economic growth, and development and has become a basic necessity for humans, but at the same time, it has an impact on the environment. Therefore, it is believed that, in the coming future, renewable energy will play an important part in fulfilling the energy demand. In that respect, geothermal energy will be vital as it is a continuous source of energy that is not affected by metrological conditions and can be used in power generation or domestic heating. Many countries around the globe are actively producing energy from geothermal resources. However, the extraction of the heat from the subsurface comes with challenges such as subsurface environment, wellbore instability, corrosion, loss of circulation, and cementing operation. However, one of the most challenging and critical tasks is the zonal isolation of the geothermal well. A packer is a tool that is used for the zonal isolation of a well, and at high pressure and high temperature (HPHT) conditions, which is common for geothermal wells. Most of the components of packers fail, causing well integrity issues. This paper gives a review of the forces acting on packers, testing standards, problems encountered by a packer in the HPHT subsurface environment, and designs to overcome those problems.

Improving the Weak Gel Structure of an Oil-Based Drilling Fluid by Using a Polyamide Wax.

Oil-based drilling fluids (OBDFs) are widely used, but there are common problems associated with them, such as low yield point and poor cutting–carrying and hole cleaning ability. In this paper, a polyamide wax (TQ-1) was synthesized from dimeric acid and 1,6-hexanediamine to improve the weak gel structure of OBDFs. The TQ-1 was characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Then the effect of the TQ-1 on the stability of the water-in-oil emulsion was studied by sedimentation observation, stability analysis, an electrical stability test, and particle size measurement. The effect of the TQ-1 on the rheological properties of the water-in-oil emulsion was analyzed by viscosity vs. shear rate test and the three-interval thixotropic test. Finally, the performance of the TQ-1 in OBDFs was comprehensively evaluated. The experimental results showed that the initial thermal decomposition temperature of the TQ-1 was 195 °C, indicating that the TQ-1 had good thermal stability. After adding the TQ-1, the emulsion became more stable since the emulsion stability index (TSI) value decreased when the emulsions were placed for a period of time and the demulsification voltage was increased. The TQ-1 could form a weak gel structure in the water-in-oil emulsions, which made the emulsions show excellent shear thinning and thixotropy. TQ-1 can improve the demulsification voltage of OBDFs, greatly improve the yield point and gel strength, and largely reduce the sedimentation factor (SF). In addition, TQ-1 has good compatibility with OBDFs, and in our study the high-temperature and high-pressure (HTHP) filtration decreased slightly after adding the TQ-1. According to theoretical analysis, the mechanism of TQ-1 of improving the weak gel structure of OBDFs is that the polar amide group can form a spatial network structure in nonpolar solvents through hydrogen bonding.

Laponite-polymer composite as a rheology modifier and filtration loss reducer for water-based drilling fluids at high temperature

In the process of deep oil and gas drilling, high temperature and high amounts of salt will greatly deteriorate the rheological properties of water-based drilling fluids (WBDFs), increase the fluid loss of drilling fluids, and seriously threaten the safety of operations. It is urgent to develop new high-temperature and salt-resistant drilling fluid additives. In this study, a novel organic-inorganic polymer nanocomposite (P-RD') was synthesized by combining laponite and polymer, and its chemical structure and properties were characterized and evaluated by various experimental methods. The results show that P-RD' forms a spatial network structure in aqueous solution, and has good clay adsorption capacity and pore and crack sealing ability. At 180 °C and 15 wt% NaCl, it has good rheological stability to WBDFs, the American Petroleum Institute (API) filtration loss is only 7.1 mL, and the high temperature and high pressure (HTHP) filtration loss is controlled at 29.2 mL. P-RD' has dual functions, which can effectively strengthen the temperature and salt resistance of WBDFs, and is expected to be used as a rheology modifier and filtration loss reducer in high-temperature deep well drilling.

Accurate in situ measurements of thermoelectric transport properties at high pressure and high temperature.

Regulating electron structure and electron-phonon coupling by means of pressure and temperature is an effective way to optimize thermoelectric properties. However, in situ testing of thermoelectric transport performance under pressure and temperature is hindered by technical constraints that obscure the intrinsic effects of pressure and temperature on thermoelectric properties. In the present study, a new reliable assembly was developed for testing the in situ thermoelectric transport performance of materials at high pressure and high temperature (HPHT). This reduces the influence of thermal effects on the test results and improves the success rate of in situ experiments at HPHT. The Seebeck coefficient and electrical resistivity of α-Cu2Se were measured under HPHT, and the former was found to increase with increasing pressure and temperature; for the latter, although an increase in the pressure acted to lower the electrical resistivity, an increase in the temperature acted to increase it. On increasing pressure from 0.8 to 3GPa at 333K, the optimal power factor of α-Cu2Se was increased by ∼76% from 2.36 × 10-4-4.15 × 10-4Wm-1K-2, and the higher pressure meant that α-Cu2Se had its maximum power factor at lower temperature. The present work is particularly important for understanding the thermoelectric mechanism under HPHT.

Preparation of titanium-tantalum-oxygen composite thermoelectric ceramics through high-pressure and high-temperature method

Because of its high stability and low cost, titanium oxide is a very promising thermoelectric material. Improvement of its thermoelectric performance is limited by the strong correlations among conductivity, Seebeck coefficient, and thermal conductivity. It is therefore important to optimize at least two of these three parameters. This paper provides a new idea for the synergistic optimization of the conductivity and thermal conductivity of titanium oxide. Under high temperature and high pressure, the elementary substance Ta can reduce TiO2 to Magnèli phase titanium oxide (mainly Ti8O15), which greatly increases its conductivity. At the same time, the submicron tantalum oxide (Ta2O5) generated during the reaction process can effectively reduce the lattice thermal conductivity and total thermal conductivity, and realize the synergistic optimization of the conductivity and thermal conductivity of the material. The titanium-tantalum-oxygen composite thermoelectric ceramics prepared by the high-pressure and high-temperature (HPHT) method have good thermoelectric and mechanical properties. The maximum zT value of the material at 973 K is 0.176, and its Vickers hardness is 11.14.

Tin disulfide with bright near-IR luminescence centers obtained at high pressures

In this work, the high-pressure and high-temperature (HPHT) method was applied to obtain crystalline tin disulfide (${\mathrm{SnS}}_{2}$). The synthesis was performed in a sulfur-tin-carbon growth system by placing the reaction mixture of sulfur and tin in a graphite capsule. The synthesized ${\mathrm{SnS}}_{2}$ demonstrated to be a highly crystalline $2H$-polytypic form suitable for mechanical exfoliation of atomically thin films. The crystals reveal strong near-IR photoluminescence attributed to a new luminescence center in ${\mathrm{SnS}}_{2}$. At 5 K, this center is characterized by a narrow zero-phonon line at 885 nm and phonon sideband whose structure is governed by ${\mathrm{SnS}}_{2}$ phonon density of states. Based on $\mathit{ab}$ initio calculations, the center is attributed to carbon in the tin sublattice. The side product of the HPHT synthesis is the diamond phase containing optically active tin-vacancy centers (${\mathrm{SnV}}^{\ensuremath{-}}$).

Spectroscopic Study of the 3107 cm−1 and 3143 cm−1 H-Related Defects in Type Ib Diamonds

Hydrogen-related infrared absorption bands in natural diamonds have been extensively investigated and widely used to identify natural, treated, and synthetic diamonds grown by high pressure and high temperature (HPHT) and chemical vapor deposition (CVD) techniques. However, the evolutional behavior of the hydrogen-related defects and the relationship between the hydrogen-related and nitrogen-related defects in natural and HPHT-treated Ib diamonds are unclear. In this article, the hydrogen-related defects, particularly the infrared absorption bands of 3107 cm−1 and 3143 cm−1 in natural type Ib diamonds and HPHT-treated natural diamonds, were systematically investigated using spectroscopic techniques. It was found that the 1405 cm−1 absorption intensity was directly proportional to the 3107 cm−1 absorption intensity; the 3143 cm−1 absorption intensity increased with the increase in the 3107 cm−1 absorption intensity, but there was no strict linear relationship between them. The 3143 cm−1 band was not only related to the intensity of the 3107 cm−1 but also related to the value of NC/NA in natural diamonds. When the value of NC/NA was less than one, the 3143 cm−1 band was more pronounced. After high-temperature annealing, the absorption intensities of the 3107 cm−1 and 3143 cm−1 in natural type Ib diamonds became stronger. However, in HPHT synthetic diamonds, only a 3107 cm−1 defect was introduced with the increase in the A centers in the diamonds. The difference and the detectability of the 3143 cm−1 and 3107 cm−1 bands investigated could be efficiently used to identify natural type Ib diamonds from their counterparts, including the synthetic diamonds and the HPHT-treated diamonds.

Strain-induced strengthening in superconducting β-Mo2C through high pressure and high temperature

High-strain-induced microstructural refinement and dislocations are critical for the strengthening of metallic materials; however, this is difficult to achieve in ceramic materials due to their unique bonding characteristics and electronic structure. Here, a series of β-Mo2C bulk ceramics are consolidated by the high pressure and high temperature (HPHT) strategy. Our results demonstrate that high strain-induced grain plastic deformation at high pressure produces a lamellar sub-grain structure with high-density dislocations, and that the dislocations at the lath-like grain boundaries eventually evolve into low-angle grain boundaries. The mechanical properties, superconducting behavior, and onset of oxidation of the specimens are investigated. It is found that superconductivity and hardness arise from the high density of states at the Fermi level, while the high intrinsic hardness is attributed to the strong hybridization between Mo-4d orbitals and C-2p orbitals. Furthermore, strain-induced defect structure (dislocations and low-angle grain boundaries) mainly mainly enhances the intrinsic structure of β-Mo2C.

Pipeline element for upheaval buckling analysis of submarine pipelines with geometric-imperfections under high temperature high pressure

Submarine pipeline is used for transporting oil from wells to resource storage facilities. The oil inside the pipeline is heated and pressured for long-distance transportation, making the pipeline under high temperature and high pressure (HTHP). The pipeline is usually placed inside a trench where surrounding soil restraints its longitudinal expansion. The pipeline is not perfectly straight, but with geometric imperfections, so the upheaval buckling may be triggered when the accumulated compression force has reached its buckling strength. It is not easy to conduct a geometrically nonlinear analysis for the pipeline because of the nonlinear soil–pipeline interactions (SPIs). This paper proposes a new line element aiming for the geometrically nonlinear large deformation analysis of the pipeline under HTHP. The axial expansion force due to high working temperature and pressure is included in the element formulation. Furthermore, a Gauss–Legendre integral method is employed to consider continuously distributed nonlinear SPIs in both lateral and longitudinal directions. Since the pipeline might exhibit large deflections, the analysis adopts the Updated-Lagrangian approach to establish the equilibrium conditions. A Newton–Raphson procedure is developed to execute the analysis. Detailed element formulations are given. Six groups of examples are provided to examine the robustness of the numerical method.

Experimental study on invasion law of oil rim in condensate gas reservoir with bottom water and oil rim

The condensate gas reservoir with bottom water and oil-rim faces the invasion of oil-rim and bottom water in the process of depleted gas production. In order to explore the invasion mechanism and distribution of oil-rim for a better coping strategy, the long-core displacement apparatus was modified for X-CT scan withstanding high temperature and high pressure (HTHP). From 56.58 to 47 MPa, the oil-gas contact rose fast and gradually slowed down, and the corresponding invasion volume accounted for 82.98% of the total invasion volume. From 47 to 8.8 MPa, the watercut soared to 98% and the invasion rate tended to stagnate. Finally, oil-rim oil was left completely in the reservoir pores and the recovery of condensate oil was only 30.27%. The paper revealed the damage of excessive pressure drop to condensate and oil-rim, and discussed its influencing factors and various pressure control methods. The modified apparatus filled the gap of obtaining oil saturation by X-CT scan under stable HTHP, which had a general application prospect in subsequent optimization and core displacement experiments where oil distribution needed to be observed under HTHP.

Effect of Hematite Dosage on Water-Based Drilling Fluid and Filter Cake Properties

Abstract Drilling deep wells became common in the oil and gas sector as a result of the high demand for energy in the world. This type of wells is not trivial to drill as a result several challenges that they encounter, such as harsh conditions represented by high-pressure and high-temperature (HPHT), and the high hydrostatic column required to prevent the kick. Therefore, advanced materials are desired and accordingly higher concentration of weighting material is required to drill such resources. In this work, a systematic investigation of the hematite concentration effect on the water-based drilling fluid properties is performed. Three doses were overloaded to a constant drill fluid recipe. Then, the drilling fluid properties including density, viscosities, filtration, and filter cake properties were evaluated. The viscosities were assessed at the temperature of 120 °F, before and after aging in a hot rolling oven for 16 h at 250 °F and 500 psi. The American Petroleum Institute filtration test was performed at ambient temperature and 100 psi. The results showed that the hematite concentration has proportional relation to the apparent viscosity, plastic viscosity, and yield point before and after the hot rolling. The YP/PV ratio was decreased as the hematite dose increased in the drilling fluid. Similarly, the gel strengths at 10 s and 10 min were increased as the concentration of hematite increased. The filter cake thinness, filtration volume, and filter cake permeability were also amplified as the hematite concentration increased, where the filter cake porosity was almost kept constant. In addition, several correlations were drawn as a function of the hematite dosage for the examined drilling properties.

Graphene nanoplatelets reinforced cement as a solution to leaky wellbores reinforcing weak points in hydrated Portland cement with graphene nanoparticles improves mechanical and chemical durability of wellbore cements

To improve the performance of wellbore cement under subsurface environments, graphene nanoplatelets (GNPs) were added in various percentages to Class-H cement slurry. Microstructural characterization of cement slurries cured at 90 °C and 95% RH indicates that GNP modifies the microstructure of hydrated cement by reinforcing pore spaces. As a result, the mechanical properties, such as Young's modulus and axial peak stress, obtained from high temperature triaxial compression tests are significantly improved based on different percentages of added GNPs. Furthermore, the hydrated 1 × 2inch GNP- Portland cement cores tested under simulated deep wellbore conditions of high-temperature and high pressure (HTHP), appear to have a ductile-like behavior, when compared to a typical brittle nature of Portland cement pastes. From our observations and published data on graphene resistance to fracture, GNP addition to cement is evidently enhancing the flexibility of cement. These improvements would reduce the risks associated with wellbore cement deterioration and a consequent leakage in fossil fuel production, geothermal energy production, CO2 storage as well as long-term sealing materials in plugging and abandonment of all wellbores at the end of their service life.

Polysaccharide derivative as an additive in Olefin-Based drilling fluid

The search for drilling fluids of low environmental impact and high performance has increased and became of utmost importance over the years. In this study, a hydrophobically modified polysaccharide was obtained from the reaction of carboxymethylcellulose (CMC) with dodecylamine (DDA) in water and evaluated as a new green additive in an olefin-based fluid. FTIR and 1H NMR spectra revealed the presence of amide groups on the CMA-DDA derivative, demonstrating that the reaction was successful. Unlike the polysaccharide precursor, the product showed turbidity in water, due to association between hydrophobic groups inserted onto CMC chains. The formation of polymer aggregates in water was confirmed by DLS. The rheological measurements in water and saline medium also corroborated to DLS data, as the viscosity of the derivative was higher than that of CMC. Confocal microscopy indicated that the hydrophobically modified CMC contributes to the inverse emulsion stability. CMC-DDA behaved as an efficient rheological modifier on olefin-based drilling fluids, besides of contributing to reduce filtrate loss under high temperature and high pressure (HTHP) conditions.