Properties Of Oil-based Drilling Fluids Research Articles

A comprehensive study of the effect of multi-walled carbon nanotubes as an additive on the properties of oil-based drilling fluids

A comprehensive study of the effect of multi-walled carbon nanotubes as an additive on the properties of oil-based drilling fluids

An Amphiphilic Multiblock Polymer as a High-Temperature Gelling Agent for Oil-Based Drilling Fluids and Its Mechanism of Action.

Oil-based drilling fluids are widely used in challenging wells such as those with large displacements, deepwater and ultra-deepwater wells, deep wells, and ultra-deep wells due to their excellent temperature resistance, inhibition properties, and lubrication. However, there is a challenging issue of rheological deterioration of drilling fluids under high-temperature conditions. In this study, a dual-amphiphilic segmented high-temperature-resistant gelling agent (HTR-GA) was synthesized using poly fatty acids and polyether amines as raw materials. Experimental results showed that the initial decomposition temperature of HTR-GA was 374 °C, indicating good thermal stability. After adding HTR-GA, the emulsion coalescence voltage increased for emulsions with different oil-to-water ratios. HTR-GA could construct a weak gel structure in oil-based drilling fluids, significantly enhancing the shear-thinning and thixotropic properties of oil-based drilling fluids under high-temperature conditions. Using HTR-GA as the core, a set of oil-based drilling fluid systems with good rheological properties, a density of 2.2 g/cm3, and temperature resistance up to 220 °C were constructed. After aging for 24 h at 220 °C, the dynamic shear force exceeded 10 Pa, and G' exceeded 7 Pa, while after aging for 96 h at 220 °C, the dynamic shear force exceeded 4 Pa, and G″ reached 7 Pa. The synthesized compound HTR-GA has been empirically validated to significantly augment the rheological properties of oil-based drilling fluids, particularly under high-temperature conditions, showcasing impressive thermal stability with a resistance threshold of up to 220 °C. This notable enhancement provides critical technical reinforcement for progressive exploration endeavors in deep and ultra-deep well formations, specifically employing oil-based drilling fluids.

A New Approach for Predicting the Rheological Properties of Oil-Based Drilling Fluids under High Temperature and High Pressure Based on a Parameter-Free Method

Under different temperatures and pressures, the physical parameters of drilling fluid will change, resulting in inaccurate drilling hydraulic calculations. Aiming to address the problem of the traditional rheological prediction method needing to first determine the rheological model, this paper proposed a method for first predicting the readings of the rheometer and then determining the rheological model. The model established in this paper adopted a parameter-free method, which expands the application range of the model. Rheology experiments were carried out on the three types of oil-based drilling fluids collected at the well site. The model in this paper was verified based on the experimental data. The results showed that, compared with the traditional drilling fluid rheological prediction method, the model established in this paper had a better prediction effect, with an average error of 4.85%, and the average error reduction ranges from 3.8% to 8.3%. The model established in this paper is able to provide theoretical support for accurate hydraulic calculation.

Experimental study of the effect of crystalline aluminum oxide nanofibers on the properties of oil-based drilling fluids

This work presents first-of-its kind research on the effect of alumina nanofibers (ANF) on drilling emulsions. ANF is a new generation crystalline nanofiber material with ultra-high mechanical strength and stability. From a physicochemical point of view, the material constitutes alumina nanofibers with a unidirectional dispersed structure and a faceted surface. Such characteristics provide ANF with a wide range of possibilities for interacting with various polymer matrices, as well as with ceramic and metallic materials. A number of characteristics and properties, such as viscosity, rheology, structure formation, filtration and antifriction properties, clay swelling kinetics, and stability of oil-based drilling fluids (OBDF) modified with aluminum oxide nanofibers, have been studied. These studies have demonstrated the positive effect of nanofibers on all functional characteristics of drilling fluids. It was found that nanofibers significantly change the rheological characteristics, reduce filtration losses, and reduce the coefficient of friction of drilling fluids without significantly degrading their colloidal stability in the concentration range not exceeding 1 wt%. The addition of ANF doubles the effective viscosity and yield strength, reduces filtration losses by a factor of 2.5, reduces the coefficient of friction by almost two times, and does not impair the colloidal and thermal stability of oil-based drilling fluids. This paves the way for the use of this material as the most promising one in drilling fluid development.

Investigation of Poly(MM-EM-BM) as Nanosealing Materials in Oil-Based Drilling Fluids: Synthesis and Evaluation.

Nanosealing technology has become the key to overcoming the wellbore instability problem in deep and ultradeep shale formations. In this Article, the terpolymer poly(MM-EM-BM) was synthesized from methyl methacrylate, ethyl methacrylate, and butyl methacrylate by a Michael addition reaction. The poly(MM-EM-BM) nanoparticles were investigated by Fourier transform infrared spectroscopy, laser scattering analysis, and thermogravimetric analysis. The results imply that the particle size range of poly(MM-EM-BM) is between 33.90 and 135.62 nm and the average diameter is about 85.95 nm at room temperature, which can maintain excellent stability at 382.75 °C. The effects of poly(MM-EM-BM) on the properties of oil-based drilling fluids (OBDFs) were ascertained through experiments on the rheological performance, electrical stability, and high-temperature and high-pressure (HTHP) filtration loss. The results suggested that when the amount of added poly(MM-EM-BM) increases, the apparent viscosity, plastic viscosity, dynamic shear force, and demulsification voltage of the drilling fluids will increase correspondingly; in contrast, the HTHP filtration loss gradually decreased. When poly(MM-EM-BM) is added at 0.75%, the kinetic-to-plastic ratio of the drilling fluids is 0.24 and the filtration loss is 0.6 mL, showing excellent overall performance. The drilling fluids have a good rock-carrying ability and water loss wall-building property. The sealing performance and mechanism of poly(MM-EM-BM) were researched by the method of a sealing performance test under high temperature. The results indicated that the more poly(MM-EM-BM) used, the higher the sealing efficiency of the mud cake and the core as the sealing medium. When poly(MM-EM-BM) was added at 0.75%, the sealing rates of the mud cake and the core as the sealing medium reached the maximum sealing rates of 40.30% and 91.48%, respectively. When poly(MM-EM-BM) enters the core nanopore joint for a certain distance under formation pressure, a tight sealing layer will be formed to effectively prevent the entry of filtrate. Poly(MM-EM-BM) as a potential oil-based nanosealing agent is expected to solve the problem caused by wellbore instability in shale horizontal wells.

Experimental study of the effect of adding nanoparticles on the rheological properties of oil-based drilling fluids

A systematic study of the effect of nanoparticles of various concentrations and sizes on the rheological properties of various oil-based drilling fluids with nanoparticle additives has been carried out. The concentration of nanoparticles in drilling emulsions varied from 0.25 to 2 wt%, and the average size of nanoparticles ranged from 18 to 100 nm. As a result of numerous laboratory experiments, formulations and technology for the preparation of stable oil-based drilling fluids with additives of nanoparticles have been developed. The effect of nanoparticles on the viscosity and rheological properties of these drilling fluids has been studied.

Effect of Hydrophobic Iron Oxide Nanoparticles on the Properties of Oil-Based Drilling Fluid

AbstractLately, nanoparticles (NPs) have shown the potential to improve the performance of oil well fluids significantly. Several studies have reported the ability of NPs to produce improved properties of both water and oil-based drilling fluids. In this study, hydrophobic iron oxide NPs were synthesized by thermal decomposition of iron pentacarbonyl in an inert atmosphere, and its performance was tested in the oil-based drilling fluid with 90/10 oil-to-water ratio (base fluid). Oil-based drilling fluids treated with nanofluids were formulated by adding 0.5 wt% and 1.0 wt% iron oxide NPs in hexane solution to the base drilling fluid. The base fluid and the nanofluid-treated drilling fluids were evaluated by characterizing their rheological properties at different temperatures, viscoelastic properties, lubricity, filtrate loss, static and dynamic settling, and separation properties. Results showed that 0.5 wt% iron oxide dispersed in hexane reduced the high pressure high temperature (HPHT) filtrate loss by 70%, filter cake thickness by 55%, and the coefficient of friction by 39%. Moreover, the nanofluid based drilling fluid reduced the free oil layer caused by syneresis during aging at high temperature by 16.3% compared to the base fluid. This study has shown that hydrophobic iron oxide NPs have the potential to improve the properties of oil-based drilling fluid.

Novel Spherical Polymer Sealing Agent for Oil-Based Drilling Fluids to Overcome Borehole Instability Problem in Low Permeability Reservoirs

Due to borehole instability problem in low permeability formations, a new type of spherical polymer sealing agent (OLBS) for oil-based drilling fluids was prepared via suspension polymerization, and the sealing effect of polymer sealing agent on low permeability cores was evaluated. The results indicated that OLBS had no influence on the rheological properties of oil-based drilling fluids. The core displacement experiments indicated that OLBS could reduce the core permeability by a significant amount, and thus stop fluid invasion into the formations, so OLBS could provide an excellent sealing effect and improve wellbore strength. Using this polymer sealing agent to plug the low permeability formations is a very powerful approach to address borehole instability problem in troublesome low permeability formations. This sealing agent is suitable for the drilling of long sections of horizontal laterals. In the future, the oil-based drilling fluids containing OLBS might hold great promise to resolve borehole instability problem in low permeability formations.

Synergistically using layered and fibrous organoclays to enhance the rheological properties of oil-based drilling fluids

Layered organo-montmorillonite (OMt) is widely used as the rheological additives in oil-based drilling fluids. Recently, fibrous organoclays, such as organo-palygorskite, had been reported as the rheological agent in oil-based drilling fluids. These organoclays showed different rheological properties and mechanisms. In this work, the joint use of OMt and OPal in oil-based drilling fluids was investigated. The optimized organoclays were prepared according to the previous reports and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal analysis. The rheological properties of mixed organoclays at different mass ratios were tested in comparison with the single organoclay. Viscous flow behavior, viscosity and thixotropy were summarized. The synergetic use of OMt and OPal could improve the rheological properties of oil-based drilling fluids, even aged at 200 °C. The optimal mass ratio of OMt to OPal was 1:1. The rheological mechanism of mixed OMt and OPal in oil was concluded based on the X-ray diffraction results of organoclay/oil gels. The presence of fibrous OPal enhanced the network structure of layered OMt and prevented the network structure from collapse by interlacing among the nanolayers.

Study on the effect of polymeric rheology modifier on the rheological properties of oil-based drilling fluids

A new type of polymeric rheology modifier was synthesized by suspension polymerization, and the effect of rheology modifier on the rheological properties of oil-based drilling fluids was investigated. The results indicated that the obtained polymer had good capacity of improvement of shearing force of oil-based drilling fluids under high temperature and high pressure conditions. Moreover, the obtained polymer can improve the stability of oil-based drilling fluids greatly. As a result, the obtained polymer is a good rheology modifier for oil-based drilling fluids, and it can optimize oil-based drilling fluid system with good rheological properties, good static suspension ability for cuttings and environmental protection function. It can play an essential role in safe drilling jobs and improvement of drilling efficiency.

Influences of surfactants on the structures and properties of organo-palygorskite in oil-based drilling fluids

Organo-palygorskite (OPal) is a potential rheological additive in oil-based drilling fluids. This work aims to reveal the influences of surfactants on the structures and properties of OPal in oil-based drilling fluids. Firstly, palygorskite was organically modified by three quaternary ammonium salts with different lipophilicity. The crystal structures and morphologies of OPal samples were characterized by X-ray diffraction and scanning electron microscope. Organic surfactants coated on the surface of palygorskite. Gel volume tests were used to indicate the compatibility between OPal and oil. Viscosity tests were applied to characterize the gel strength and ability of gel formation. The contents of different components of OPal/oil fluids and OPal/oil gels were obtained by mass analysis. Optical microscopy testified the dispersity of OPal/oil fluids. X-Ray diffraction was also applied to characterize the gel structure of OPal/oil. Better lipophilicity of surfactants lead to better dispersity of OPal in oil. However, excellent dispersity of can't automatically contribute to high viscosity and gel strength. A little polarity is beneficial for promoting the rheological properties of oil-based drilling fluids. Temperature rising facilitates the disaggregation of OPal in oil, but high temperature may result in thermal decomposition of surfactants on the surface of palygorskite.

Organoclay influence on high pressure-high temperature volumetric properties of oil-based drilling fluids

Two organoclays, commonly used in the formulation of drilling fluids, were dispersed in a mineral oil. Organoclay mass fraction ranged from 0.01 to 0.05. PVT data for the mineral oil and all the suspensions studied were obtained by using a high pressure vibrating tube densimeter, in a temperature range comprised between 40 and 140°C and pressures up to 1200bar. The main objective of this work was to study the influence of organoclay nature and concentration on the density of organoclay suspensions in a wide range of pressure and temperature. A Tait-like equation fitted the volumetric behavior of these suspensions fairly well. Organoclay addition to the liquid matrix yielded a significant increase in density values in the whole range of temperature and pressure tested. The expansive volumetric behavior of these suspensions is essentially influenced by organoclay nature and dampened by increasing pressure.

Rheological properties of organo-palygorskite in oil-based drilling fluids aged at different temperatures

Aiming to develop a new excellent rheological additive for use in oil-based drilling fluids, palygorskite (Pal) was organically modified with three cationic surfactants using wet method. The surfactants were octadecyl trimethyl ammonium chloride (C18-A), benzyl dimethyl octadecyl ammonium chloride (C18-B) and dimethyl dioctadecyl ammonium chloride (DC18). The structure and properties of organo-palygorskite (OPal) and its use in oil-based drilling fluids were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), thermal analysis, gel volume and rheological tests. Surfactant-modification did not change the crystal structure of Pal, but changed the aggregation of Pal fibers. Surfactants mainly coated on the surface of Pal. But the details were influenced by the molecular scale of surfactants and the coating level. The scale of polar heads of surfactants being smaller than the channels' scale is expected. Surface modification decreased the particle size of Pal and loosened the arrangement of Pal fibers. The thermal stability of OPal decreased as follows: C18-A-Pal>C18-B-Pal>DC18-Pal, as well as the thermal stability of corresponding oil-based drilling fluids. Particularly, C18-A-Pal fluids could bear heat of 200°C. OPal could increase the viscosity of oil-based drilling fluids well. In addition, the oil-based drilling fluids containing OPal showed excellent thixotropy aged above 150°C. Temperatures below 150°C increased the rheological properties of oil-based drilling fluids while high temperature helped to disperse the OPal particles and fibers. The rheological properties of oil-based drilling fluids containing OPal were influenced by surfactants nature (polar head scale of surfactant cation, Hydrophilic-Lipophilic Balance (HLB) value, molecular conformation), coating level and temperature. The rheological properties of OPal fluids indicated that OPal was very suitable for oil-based drilling fluids.

Influence of the surfactants' nature on the structure and rheology of organo-montmorillonite in oil-based drilling fluids

Aiming to select appropriate organo-montmorillonites (OMt) for the use in oil-based drilling fluids, the influences of surfactants' nature on the structure of OMt, structure and rheology of OMt in oil-based drilling fluids were studied in this work. X-ray diffraction (XRD) results indicated a tendency that bigger modifiers resulted in higher basal spacing and more ordered internal arrangement. Scanning electron microscope (SEM) images testified a trend that modifiers with bigger size and low Hydrophile-Lipophile Balance (HLB) value resulted in more OMt lamellaes (thickness of ca. 50nm) scattered. Contact angle tests demonstrated that lipophilicity of OMt was influenced by the HLB values of surfactants. XRD results of OMt in oil-based drilling fluids indicated a tendency that surfactants with bigger size and low HLB values led to easier exfoliation in oil. OMt modified with small size and high HLB values obviously shrank while OMt modified with bigger size and low HLB values kept exfoliation above 180°C. The rheological flow model of OMt in oil-based drilling fluids was very different from the surfactants' size and polarity. Exfoliation of OMt in oil improved the rheological properties of oil-based drilling fluids, such as viscosity and thixotropy. Thixotropy of oil-based drilling fluids benefited from the exfoliation of OMt in oil while excessive exfoliation was harmful to increasing viscosity.

Applied properties of oil-based drilling fluids with montmorillonites modified by cationic and anionic surfactants

Montmorillonites modified by cationic surfactants have been used in oil-based drilling fluids for a period of time, while few studies focused on the use of montmorillonites modified by both cationic and anionic surfactants in oil-based drilling fluids. Compared with cationic surfactants, anionic surfactants have an advantage in thermal stability. Here, two parts of work were described. First, montmorillonites were modified by cationic and anionic surfactants through mechanochemistry. The structure and properties of organomontmorillonites were studied by X-ray diffraction, thermal analysis, contact angles and dispersion. Second, the applet properties including thixotropy, viscosity properties, gel properties and filtration loss resistance of oil-based drilling fluids with organomontmorillonites as additives were further studied at both room temperature (25°C) and higher temperatures (200–220°C). Characterizations indicated that cationic and anionic surfactants had intercalated into the interlayer spaces of montmorillonites, and the cationic–anionic organomontmorillonites had high surface polarity, better thermal stability and dispersion in high polar solvent than cationic organomontmorillonites. The properties of oil-based drilling fluids under both room and high temperatures showed that cationic and anionic organomontmorillonites performed better thixotropy, and had better rheological properties and less filtration loss than cationic organomontmorillonites in different oil–water ratio oil-based drilling fluids. The novel cationic and anionic organomontmorillonites have the potential to be widely applied in oil-based drilling fluids.

Study on the Effect of Humic Acid Acetamide on the Rheological Properties of Diesel Oil-Based Drilling Fluids

A new kind of humic acid acetamide compoud was synthesized by chemical modification of humic acid with octadecylamine, and the effect of humic acid acetamide on the rheological properties of oil-based drilling fluids was investigated. The results indicated that the humic acid acetamide had excellent dispersing property, and good capacity of depressing fluid loss. Moreover, the humic acid acetamide had better property of depressing fluid loss than oxidated asphalt. As a result, this humic acid acetamide is an excellent fluid loss agent for diesel oil-based drilling fluids, and is an good alternative to oxidated asphalt.

Preparation of a Novel Nano-Polymer as Plugging and Filtration Loss Agent for Oil-Based Drilling Fluids

Oil-based drilling fluids and synthetic based drilling fluids are frequently used in shale-gas plays when wellbore stability is necessary. In this paper, a novel nano-polymer, as a plugging agent in oil-based drilling fluid, was prepared and characterized by Fourier transform infrared (FTIR), thermo-gravimetric analyses (TGA) and scanning electron microscopy (SEM). The rheological properties, high temperature-high pressure (HTHP) filtration properties and permeability plugging properties of oil-based drilling fluids were greatly improved by adding the nano-polymer, due to its nanometer size and the compact layer formed on the surface of the core.

Effect of polyisobutylenesuccinimide on low-temperature rheology and dispersibility of clay particles in mineral oil

In the process of deepwater drilling, maintaining proper low-temperature rheological properties of oil-based drilling fluids and controlling the viscosity of clay dispersions in nonpolar solvents are of great importance. In this work, a dichain polyisobutylenesuccinimide with sufficient viscosity lowering performance was synthesized. The effects of polyisobutylenesuccinimide on low-temperature rheology and dispersibility of organoclay particles in mineral oil were investigated by rheological measurements, sedimentation experiments, optical microscopic observation and transmission electron microscopy. The results indicate that the polyisobutylenesuccinimide is an effective rheological modifier and dispersant at low temperatures in nonpolar solvents. The dispersion mechanism was investigated by Fourier transform infrared spectroscopy, adsorption measurements and X-ray diffraction. The results suggest that the polyisobutylenesuccinimide molecules adsorb on the surface of organoclay particles by hydrogen bonding interactions. The combination of steric stabilization and modification of the Hamaker constant of the particles leads to stable organoclay dispersions. In contrast, polyisobutylenesuccinimide has no significant impact on the long-term dispersibility of unmodified montmorillonite in mineral oil, because of the lower surface coverage.

Rheological properties of oil-based drilling fluids at high temperature and high pressure

The rheological properties of two kinds of oil-based drilling fluids with typically composition were studied at pressures up to 138 MPa and temperatures up to 204 °C using the RheoChan 7400 Rheometer. The experimental results show that the apparent viscosity, plastic viscosity and yield point decrease with the increase of temperature, and increase with the increase of pressure. The effect of pressure on the apparent viscosity, plastic viscosity and yield point is considerable at ambient temperature. However, this effect gradually reduces with the increase of temperature. The major factor influencing the rheological properties of oil-based drilling fluids is temperature instead of pressure in the deep sections of oil wells. On the basis of numerous experiments, the model for predict the apparent viscosity, plastic viscosity and yield point of oil-based drilling fluids at high temperature and pressure was established using the method of regressive analysis. It is confirmed that the calculated data are in good agreement with the measured data, and the correlation coefficients are more than 0.98. The model is convenient for use and suitable for the application in drilling operations.

Adjuvants for intravaginal immunization

Aiming to develop a new excellent rheological additive for use in oil-based drilling fluids, palygorskite (Pal) was organically modified with three cationic surfactants using wet method. The surfactants were octadecyl trimethyl ammonium chloride (C18-A), benzyl dimethyl octadecyl ammonium chloride (C18-B) and dimethyl dioctadecyl ammonium chloride (DC18). The structure and properties of organo-palygorskite (OPal) and its use in oil-based drilling fluids were characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), thermal analysis, gel volume and rheological tests. Surfactant-modification did not change the crystal structure of Pal, but changed the aggregation of Pal fibers. Surfactants mainly coated on the surface of Pal. But the details were influenced by the molecular scale of surfactants and the coating level. The scale of polar heads of surfactants being smaller than the channels' scale is expected. Surface modification decreased the particle size of Pal and loosened the arrangement of Pal fibers. The thermal stability of OPal decreased as follows: C18-A-Pal > C18-B-Pal > DC18-Pal, as well as the thermal stability of corresponding oil-based drilling fluids. Particularly, C18-A-Pal fluids could bear heat of 200 °C. OPal could increase the viscosity of oil-based drilling fluids well. In addition, the oil-based drilling fluids containing OPal showed excellent thixotropy aged above 150 °C. Temperatures below 150 °C increased the rheological properties of oil-based drilling fluids while high temperature helped to disperse the OPal particles and fibers. The rheological properties of oil-based drilling fluids containing OPal were influenced by surfactants nature (polar head scale of surfactant cation, Hydrophilic-Lipophilic Balance (HLB) value, molecular conformation), coating level and temperature. The rheological properties of OPal fluids indicated that OPal was very suitable for oil-based drilling fluids.