Application Of Drilling Fluid Research Articles

Synthesis of a Novel Modified Polysiloxane Filtrate Reducer and its Application in Water-Based Drilling Fluids

Synthesis of a Novel Modified Polysiloxane Filtrate Reducer and its Application in Water-Based Drilling Fluids

Development of Multiple Crosslinked Polymers and Its Application in Synthetic-Based Drilling Fluids.

This study addresses the performance challenges of Synthetic-Based Drilling Fluids (SBDF) in deep wells and high-temperature environments by engineering a novel multiple hydrogen-bonded crosslinked polymer, MBAH/nano-SiO2. Synthesized using methyl methacrylate (MMA), butyl methacrylate (BMA), acrylic acid (AA), N-hydroxyethyl acrylamide (HEAA), and nano-silica (nano-SiO2), the polymer improved crosslinking density, thermal properties, particle size distribution, and colloidal stability. The development of a 'weak gel' structure in W/O emulsions improved rheology and electrical stability (ES), with ES values reaching up to 775 V after aging at 180 °C. Moreover, the polymer's amphiphilic structure and the synergistic effect of nano-SiO2 increased emulsion film thickness and strength, further augmenting stability. The high-temperature and high-pressure filtration loss of SBDF was considerably reduced to 7.6 mL, benefiting well wall stability and reservoir damage control. This study provides crucial insights into optimizing multiple hydrogen-bonded crosslinked strategies and polymers in SBDF applications.

Study on the impact of weaving patterns of vibrating screen mesh on the performance of fluid flow through moving screens

Screen is a core component of the linear vibrating screen and is closely linked to the efficiency of drilling fluid recovery. This study aims to analyze the impact of different vibration frequencies and amplitudes on the fluid flow performance through screen with different weaving patterns. Analysis reveals that when the motion direction of the screen is opposite to the flow direction of the drilling fluid, higher screen velocity corresponds to increased drilling fluid permeation velocity and reduced pressure. Plain weave screen exhibits the highest fluid permeation velocity, maintaining the lowest negative pressure. Vortices concentrate mainly around the screen wires at the back of the screen, with herringbone twill weave screen showing improved vortex distribution compared to plain weave screen. Increasing vibration amplitude and frequency enhances screen motion, amplifying variations in pressure and pressure drop coefficients during the motion cycle. With increased amplitude and frequency, the average pressure drop coefficient of the screen rises, making it more challenging for drilling fluid to permeate through the screen. Herringbone twill weave screen demonstrate lower pressure drop coefficients than plain and twill weave screen, indicating superior drilling fluid permeation performance. Field experiments confirm that, compared to plain weave screen, drilling fluid filtered through herringbone twill weave screen results in significantly lower water content in cuttings. The findings of this study provide theoretical insights for the analysis and design of linear vibrating screen meshes in drilling fluid applications.

Research and application of low oil-water ratio organoclay-free oil-based drilling fluid technology

This paper introduces the formation and application of a low oil-water ratio organoclay-free oil-based drilling fluid. Shale oil and gas are important alternative energy sources. Due to the extremely complex geological conditions, oil-based drilling fluid technology is commonly used to reduce complexity. Although some achievements have been made, there are still problems such as unstable wellbore, difficult rheological control, and high cost. A stable and low-viscosity water-in-oil emulsion system was successfully prepared by using optimized fatty acid imidazolines emulsifier and alkyl alcohol ether wetting agent, which enabled the oil-based drilling fluid to have a larger solid and water phase capacity. On this basis, a special poly-fatty acid amide rheological modifier was used to assist in the regulation of rheological parameters, resulting in a low-viscosity and high-shear structure of the oil-based drilling fluid. This effectively ensured the efficiency of cuttings carrying while reducing the adverse effects of viscosity on Equivalent Circulating Density(ECD). The low oil-water ratio oil-based drilling fluid technology has been applied in a shale gas drilling platform in southern Sichuan, China, which greatly reduces the cost of oil-based drilling fluid while ensuring drilling efficiency.

Development of temperature- and salt-resistant viscosifier with dual skeleton structure of microcrosslinking and hydrophobic association structures and its application in water-based drilling fluids

In the process of developing deep oil and gas resources, the problem of high temperature and high salinity in deep strata has become a serious challenge faced by water-based drilling fluids. Under high temperature and high salinity conditions, drilling fluids must maintain good rheological properties to ensure safe and efficient drilling work. In this study, a temperature- and salt-resistant viscosifier (DASL) was synthesized using N, N-dimethylacrylamide, 2-Acrylamido-2-methylpropane sulfonic acid, sodium p-styrene sulfonate, and lauryl methacrylate as monomers with a double backbone structure of micro crosslinking and hydrophobic association structures. The results of pyrene fluorescence probe test and transmission electron microscopy observation showed that DASL has an obvious hydrophobic associative structure. Moreover, due to the presence of microcrosslinked structure, DASL exhibits good shear thinning property and thixotropy in aqueous solution. Under the conditions of 200 ℃ and 35 wt% NaCl, the apparent viscosity of the drilling fluid with 2 wt% DASL added was 24.5 mPa⸱s, and the filtration was only 9.2 mL. In addition, mechanism studies have shown that the dual skeleton structure of DASL improves its temperature and salt resistance. DASL can adsorb and bridge with bentonite particles, increase the internal friction and structural viscosity of the drilling fluid, enhance the internal mesh structure of the drilling fluid, improve the colloidal stability of the drilling fluid, and maintain a reasonable particle size distribution of the bentonite particles, which enable DASL to significantly increase the viscosity of the drilling fluid while reducing the filtration loss of the drilling fluid. This work demonstrates that polymers with dual skeleton structures of micro crosslinking and hydrophobic association have good application effects as temperature- and salt-resistant viscosifier for water-based drilling fluids.

Colloidal Properties of Polymer Amended Cyprus Bentonite for Water-Based Drilling Fluid Applications

In this work, we investigate the capability of a waste bentonite from the Polycanthos quarry in Cyprus, as a low-density solid additive to create colloids that are used in water-based drilling fluid systems (WBF) in drilling operations. Repurposing waste bentonite aligns with environmental sustainability and when properly processed can serve as a cost-effective solution to achieve the desired colloidal properties for WBF. Samples were obtained from waste stockpiles and were mechanically processed to a size < 63 μm. The material was activated with soda ash via three different methods investigating optimum soda ash percentage and curing time. Standard tests were performed for the rheological behavior and filtration properties and the results indicated that the quality of the activated clay dispersions improved slightly but the desired colloidal properties were not obtained. This can be attributed to the K+-rich clay and non-clay impurities that are inherent in the material so further amendment with xanthan gum polymer was conducted, at various concentrations. Results of this work show that with minor polymer addition, the material under investigation reaches the desired colloidal properties and qualifies according to API standards for WBF. Exploiting local waste clay material in WBF application leads to the development and sustainability of local resources thus contributing to the circular economy principle.

Experimental investigation on the sudden cooling effect of oil-based drilling fluid on the dynamic compressive behavior of deep shale reservoirs

Oil-based drilling fluids are widely used in deep drilling, and their cooling effect on shale reservoirs is critical for wellbore stability. To reveal the sudden cooling effect of oil-based drilling fluid on the dynamic compressive behavior of deep shale reservoirs, oil-based fluid cooling experiments were conducted on heated Longmaxi shale samples (25–200 °C) with five bedding orientations, followed by a series of dynamic compression tests using same incident energy. Anisotropic macroscopic thermal fractures occurred in the samples at 200 °C after oil-based fluid cooling, and the imbibed oil-based fluid entirely covered the bedding surfaces during cooling. The post-peak behavior of the dynamic stress-strain relationships of samples illustrated bedding- and temperature-dependent characteristics. Dynamic strength of the samples decreased with increasing temperature for each bedding orientation, and the dynamic strength versus bedding orientation showed a V-shaped curve at all temperatures. Anisotropic fragment degree of the samples was classified into three groups using debris screening analysis. Further, the dynamic strength reduction responses and the possible nature of dynamic strength anisotropy in shale reservoirs after oil-based drilling fluid cooling were discussed. This study helps to improve the oil-based drilling fluid application in shale reservoirs and understand the behavior of deep reservoirs during drilling.

Acetylation of Cellulose Nanocrystals Extracted from Cotton for Drilling Fluid Application: Structural and Thermal Characterization

In petroleum exploration, cellulose derivatives such as carboxymethylcellulose (CMC) are frequently used in drilling, cementing and fracturing fluids. However, under extreme drilling conditions, these additives have limited performance. In this regard, cellulose nanocrystals particles (CNCs) which are also derived from cellulose material are a suitable candidate due to their shear thinning rheology and thixotropy properties, even at low concentrations, among so many properties thanks to their crystalline structure and their nanometric dimensions.In this work, hydrolyzed fibers from industrial cotton are acetylated using acetic anhydride and sulfuric acid as catalysts, with the aim to modify surface properties of the obtained CNCs without changing their fiber structure and morphology. FTIR analysis pointed out the acetylation success of the obtained nanocrystals whose dimensions were found to be unaltered by the modification process. SEM images of cotton nanocrystal indicate that CNCcsurface modification preserves the nanoscale dimensions of the nanoparticles. Also, TGA analysis showed thermal stability for the acetylated CNCc.

Application of Novel Magnetic Surfactant-Based Drilling Fluids for Clay Swelling Inhibition

Water-based drilling fluids are widely employed in the oilfield industry for the efficient and smooth drilling of wellbore reservoirs. In this study, a novel drilling formulation was prepared by mixing a magnetic surfactant in the base mud formulation. Several drilling fluid tests were conducted, which include steady shear and dynamic rheology, filtration, clay sedimentation, clay swelling, and particle size distribution analysis. Different analytical techniques─XRD, FTIR, and TGA analyses─were performed to study the interactions of magnetic surfactant with the clay platelets. The experimental results of the surfactant-modified formulations were compared to the base mud formulation. Thermal gravimetric analysis of the surfactant-modified mud showed improved thermal stability compared to the base mud. FTIR analysis results of the base mud and surfactant-modified mud were compared. In the steady shear rheology experiments, the flow curves of the base mud and surfactant-modified mud showed that the addition of surfactant in the base mud affects the shear stress of formulation. The shear stress data of rheology was fitted to the Herschel–Bulkley model, and model parameters trends were assessed with and without the addition of surfactant in the base mud. Shale inhibition tests showed that the incorporation of magnetic surfactant minimized the clay hydration of swelling, thus proving a superior shale inhibitor. The particle size analysis showed that the average particle size of clay particles increased with the increasing concentration of the magnetic surfactant. The linear swelling analysis of clay showed that the rate of swelling was 90% in the surfactant-modified mud as compared to the swelling rate in deionized water. According to the zeta potential, the combination of surfactants significantly affects the electrokinetic behavior of dispersion. Further, the XRD proved that the interlayer spacing of clay increasing while interacting with magnetic surfactant molecules indicates the ability of magnetic surfactant as a shale swelling and hydration inhibitor for water-based drilling formulations.

The Development and Application of Novel Water-Based Drilling Fluid for Complex Pressure System Formation in the South China Sea

The Y oilfield reservoir is characterized by ultra-depleted reservoir and multiple pressure systems in each well section. If conventional PLUS/KCL drilling fluid is used in directional drilling, the following problems are found: the rheological stability of drilling fluid is not sufficient, resulting in increased viscosity and thickening after aging, and the single plugging material may cause loss-circulation when the drilling differential pressure is more than 26 MPa, resulting in poor reservoir protection effects. To solve the above problems, based on the conventional PLUS/KCL drilling fluid formula, a PLUS/KCL drilling fluid system suitable for directional drilling in multi-pressure systems was formed by optimizing the addition of a treating agent to improve the rheological stability of the drilling fluid, optimizing the plugging agent and compound combination to improve plugging ability, and optimizing the particle size distribution of a temporary plugging agent to improve the reservoir protection effect. The laboratory test evaluation showed that the optimized PLUS/KCL drilling fluid had fine plugging pressure capacity, and the intrusion depth was only 4.1 cm on the natural core at 120 °C/35 MPa/12 h, effectively reducing the risk of loss-circulation. The permeability recovery rate of the core after cutting off the polluted end was more than 90%, indicating that the reservoir protection effect was good. The drilling fluid performance was stable, and the cuttings rolling recovery rate was over 90%. Field application showed that the optimized PLUS/KCL drilling fluid was used without any loss-circulation or wellbore instability, and the production of all wells was over-matched, effectively solving the problem of ensuring drilling safety and reducing reservoir damage under the differential pressure of multiple pressure systems.

Research Progress of Elastomer Materials and Application of Elastomers in Drilling Fluid.

An elastomer is a material that undergoes large deformation under force and quickly recovers its approximate initial shape and size after withdrawing the external force. Furthermore, an elastomer can heal itself and increase volume when in contact with certain liquids. They have been widely used as sealing elements and packers in different oil drilling and development operations. With the development of drilling fluids, elastomer materials have also been gradually used as drilling fluid additives in drilling engineering practices. According to the material type classification, elastomer materials can be divided into polyurethane elastomer, epoxy elastomer, nanocomposite elastomer, rubber elastomer, etc. According to the function classification, elastomers can be divided into self-healing elastomers, expansion elastomers, etc. This paper systematically introduces the research progress of elastomer materials based on material type classification and functional classification. Combined with the requirements for drilling fluid additives in drilling fluid application practice, the application prospects of elastomer materials in drilling fluid plugging, fluid loss reduction, and lubrication are discussed. Oil-absorbing expansion and water-absorbing expansion elastomer materials, such as polyurethane, can be used as lost circulation materials, and enter the downhole to absorb water or absorb oil to expand, forming an overall high-strength elastomer to plug the leakage channel. When graphene/nano-composite material is used as a fluid loss additive, flexibility and elasticity facilitate the elastomer particles to enter the pores of the filter cake under the action of differential pressure, block a part of the larger pores, and thus, reduce the water loss, while it would not greatly change the rheology of drilling fluid. As a lubricating material, elastic graphite can form a protective film on the borehole wall, smooth the borehole wall, behaving like a scaly film, so that the sliding friction between the metal surface of the drill pipe and the casing becomes the sliding friction between the graphite flakes, thereby reducing the friction of the drilling fluid. Self-healing elastomers can be healed after being damaged by external forces, making drilling fluid technology more intelligent. The research and application of elastomer materials in the field of drilling fluid will promote the ability of drilling fluid to cope with complex formation changes, which is of great significance in the engineering development of oil and gas wells.

Cellulose nanofibrils as rheology modifier and fluid loss additive in water-based drilling fluids: Rheological properties, rheological modeling, and filtration mechanisms

This study aims to improve the rheological and filtration properties of water-based drilling fluids (WDFs) by using cellulose nanofibrils (CNFs), which are the critical parameters in drilling operation. Results showed that the incorporation of CNFs in WDFs effectively improved the rheological and filtration properties. The lathy and flexible CNFs was entangled with bentonite (BT) to form the intertwined CNFs-BT network structure in WDFs, leading to an enhanced viscosity, gel behavior, and temperature stability of WDFs. WDFs containing CNFs showed the superior rheological properties, including the yield stress, anti-deformation capacity and structural restructuring capacity, suggesting an increased capacity to transport the cuttings to the surface. The excellent shear-thinning behavior was due to the orientation movement of CNFs along the shear force. Moreover, the nanosized CNFs resulted in the low permeable filter cakes, leading to less fluid loss volume and final filtration rate. We revealed the fundamental insights into the rheological and filtration properties of WDFs containing CNFs, paving the way for the application of new eco-friendly drilling fluid. Data availabilityData will be made available on request.

Modified Laponite synthesized with special wettability as a multifunctional additive in oil-based drilling fluids

In this study, Modified Laponite with lyophobic wettability was synthesized as a multi-functional additive to solve instability of emulsions, rheological deterioration, and wellbore instability of oil-based drilling fluid. Properties and its influence on emulsion stability, rheological behavior and plugging property were investigated. The results showed that Modified Laponite was in a shape of sheet layer and had micro-meter length and nano-meter thickness which was in match with the diameter of shale pores. And it was proved to be resistant to approximately 450 °C by thermogravimetric analysis measurement. Mechanism analysis revealed that Modified Laponite could stable the oil-based drilling fluid through four sections. Firstly, Modified Laponite with lyophobic wettability could promote its existence in the interface of brine/mineral oil. Secondly, Modified Laponite could decrease the interfacial tension from 32.8 to 13.5 mN/m to maintain the emulsion particles in a small size for a long time then to ensure the emulsion stability. Thirdly, Modified Laponite could enhance the shear-thinning rheological behavior which could maintain the rheological stability and enhance the sedimentation stability in ultra-deep reservoirs with high temperature and high pressure conditions. Fourthly, Modified Laponite could plug the shale pores effectively by preventing pressure transmission and enhancing shale compressive strength, and decrease the filtration volume of oil-based drilling fluid from 7.4 mL to 2.6 mL after aging at 180 °C for 16 h to stable the wellbore. Therefore, Modified Laponite was a multifunctional additive to stable the emulsion, enhance the rheological stability and strength the wellbore stability, which could ensure the application of oil-based drilling fluid in drilling process of ultra-deep reservoirs.

Gel Stability of Calcium Bentonite Suspension in Brine and Its Application in Water-Based Drilling Fluids.

With the development of the oil industry and the increasingly complex drilling environment, the performance of drilling fluids has to be constantly improved. In order to solve the problem of bentonite dispersion and hydration in a saline medium, a drilling fluid additive with good performance and acceptable cost was sought. The effects of several water-soluble polymers, such as cellulose polymers, synthetic polymers and natural polymers, on the rheology and gel suspension stability of calcium-based bentonite were compared in this study. Among the examined polymers, the xanthan gum biopolymer (XC) was the least negatively affected in the saline medium used. However, its high price limits its industrial application in oil and gas drilling fluids. In this study, a salt-tolerant polymer, modified vegetable gum (MVG), was prepared by a cross-linking modification of a natural plant gum, which is abundant and cheap. Then, a salt-tolerant polymer mixture called SNV was prepared, composed of the salt-resistant natural polymer MVG and the biopolymer XC. The salt tolerance and slurry ability of SNV and common water-soluble polymers were evaluated and compared. We then selected the most suitable Herschel–Bulkley model to fit the rheological curve of the SNV–bentonite aqueous suspension system. SNV improved the rheological properties of the calcium-based bentonite slurry and the dispersion stability of bentonite. In an SNV concentration of 0.35%, the apparent viscosity (AV) of the base slurry increased from 2 mPa·s to 32 mPa·s, and the low shear reading value at 3 rpm increased from 0 dia to 5 dia. This could greatly improve the viscosity and cutting carrying capacity of the bentonite drilling fluid. The bentonite drilling fluid prepared with SNV could be directly slurried with brine and even seawater; this means that when drilling in ocean, coastal saline water and high-salinity-surface saline water areas, the slurry preparation cost and preparation time can be conveniently reduced.

Dimer fatty acid and fatty amide effects on the properties of synthetic-based drilling fluids

This paper mainly deals with the analysis of chemical modification on a dimer of fat acid to evaluate the effect on synthetic drilling fluids. The performance of drilling fluids in the deepwater fields is negatively impacted by the elevation of rheological parameters. A required property of the drilling fluid is a minimal sensitivity of the rheological properties with respect to temperature, leading to a flat-rheology system. A proposed fatty amide was synthesized via condensation reaction between saturated dimer fatty acid and diethanolamine. In this reaction, it was used N,N′-dicyclohexylcarbodiimide as coupling agent and 4-dimethylaminopyridine as catalyst. The synthesized material was characterized by FTIR, 13C NMR, solubility tests and surface tension. Next, the precursor dimer fatty acid and the synthesized fatty amide were initially applied on a visual stability test in invert emulsion systems before application in synthetic drilling fluids. Spectroscopic analyses confirmed that fatty amide was successfully synthesized. Surface tension measurements showed that both dimer fatty acid and the fatty amide amide have not surfactant properties. However, when both products were applied in synthetic drilling fluids, electrical stability and HPHT filtration tests proved the ability to stabilize emulsion systems, probably, as network agents. In addition, the drilling fluids containing dimer fatty acid and fatty amide presented minimal viscosity sensitivity in the temperature range of 4–49 °C, at ambient pressure and 344 bar, leading to flat-rheology synthetic drilling fluids.

Synthesis of a new high temperature and salt resistant zwitterionic filtrate reducer and its application in water-based drilling fluid

To overcome the negative effects of high temperature and salt pollution on the performance of drilling fluid in deep and ultra-deep wells, it is imperative to develop a high- temperature-and salt-resistant filtrate reducer. A zwitterionic quaternary copolymer (DADN) of N, N-dimethylacrylamide (DMAA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), diallyl dimethyl ammonium chloride (DMDAAC), and N-vinylcaprolactam (NVCL) was synthesized in an aqueous solution by free radical copolymerization reaction. The composition, structure, and thermal stability of the copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), Gel Permeation Chromatography (GPC), elemental analysis and thermogravimetric analysis (TGA), respectively. Furthermore, the filtration loss reduction performance of DADN was evaluated according to the American Petroleum Institute (API) standard. The mechanisms of filtrate loss reduction and salt resistance were revealed based on the transmission electron microscopy (TEM) analysis, adsorption isotherm and zeta potential analysis for the water-based drilling fluid (WBDF) containing DADN, and the scanning electron microscopy (SEM) analysis, energy-dispersive spectrometry (EDS) analysis and Brunner–Emmet–Teller (BET) analysis for the corresponding filter cake. The results showed that the thermal decomposition of DADN mainly happened over 298 ℃. Meanwhile, DADN exhibited the most outstanding filtration loss reduction ability compared to three commercially filtrate reducers (Driscal D, CMC and PAC-Lv). Specifically, the filtration losses of Driscal D/WBDF, CMC/WBDF and PAC-Lv/WBDF were 18.2, 31.2 and 24.8 mL after hot rolling at 220 °C for 16 h, respectively, while the filtration loss of DADN was only 6.5 mL. It was found that 2% DADN showed excellent filtration loss reduction ability at 220 °C and 15% NaCl. As confirmed by the SEM, EDS and adsorption isotherm results, strong adsorption of DADN on bentonite was obtained even under a high temperature and high-salinity environment. In particular, in the high-salinity environment, a firm “star network” structure formed by bentonite/DADN was observed by TEM, significantly improving the colloidal stability and filter cake compactness of WBDF.

Rheological Property Measurement and Application of Formate-Based Drilling Fluids at Elevated Temperatures: A Review

Rheological Property Measurement and Application of Formate-Based Drilling Fluids at Elevated Temperatures: A Review

Reduction of formation damage in horizontal wellbores by application of nano-enhanced drilling fluids: Experimental and modeling study

One of the basic challenges during drilling horizontal wellbores is the damage induced by invasion of mud filtrate into the formation. Addition of nanoparticles to drilling fluids has been recognized as a measure of control and reduction of filtrate invasion, which is the primary mechanism of the aforementioned formation damage. Despite notable advances in composing Nano-enhanced drilling fluids, the role of nanoparticle hydrophobicity on performance of the fluids has not been well studied. This study is based on a combined experimental-numerical methodology. In the experimental section, a procedure to find the optimum composition of Nano-enhanced water-based samples, containing nanoparticles of hydrophilic/hydrophobic silica and lipophilic clay to minimize the formation damage associated with mud circulation is recommended. The main idea was to investigate the effect of hydrophobicity of nanoparticles on damage reduction and furthermore, discover how other properties such as types/concentration of nanoparticles/micro-sized additives, temperature and pressure would affect functionality and characteristics of drilling fluids. In order to more accurately and practically investigate any probable enhancements in performance of fluid samples a particular radial filtration setup was designed and used; then, functionality of mud samples was examined on grain packed porous media at radial flooding flow condition. Results revealed that samples containing 0.2 wt. % hydrophobic nanosilica had the best functionality with returned permeability of 68.4% and 51.1% for the cases of water saturated and oil saturated porous media, respectively. In the modeling section, mass balance and momentum equations were solved simultaneously by using elapsed time data. Permeability as well as thickness of mud cake formed on the wellbore wall were evaluated and compared for different Nano-enhanced mud samples. Results showed that nano-enhanced drilling fluid samples generated thinner mud cakes with lower permeability values during quite shorter period of time. Results of this work might be helpful to better understand the behavior of nano-enhanced drilling fluids in radial porous systems at different conditions of nanoparticles hydrophobicity and applicable to minimize the induced formation damage during drilling of the horizontal section of a production well. • A combined experimental-numerical methodology is used to evaluate any possible enhancement in characteristics of drilling fluid, mud cake and damaging potential. • The effects of hydrophobicity of nanoparticles along with types/concentration of nanoparticles/ micro-sized additives, temperature and pressure on characteristics of drilling fluids are investigated. • A particular radial filtration setup is designed and used to more precisely evaluate the damaging potential of mud samples and to measure permeability recovery after mud filtrate invasion. • Samples containing 0.2 wt. % hydrophobic nanosilica had the best functionality with return permeability of 68.4% and 51.1% in water-saturated and oil-saturated porous media, respectively. • In the modeling section, mass balance and momentum equations are solved simultaneously; permeability and thickness of filter cake are evaluated and compared for each of mud samples.

Rheological investigation of polymer/clay dispersions as potential drilling fluids

The rheological properties of poly(ethylene glycol)(PEG)/Laponite® RD (Lap) and poly(propylene glycol)(PPG)/Lap aqueous dispersions, with 2% polymer and different clay concentrations, were investigated at 25 °C in order to establish the optimal composition to formulate a system applicable as drilling fluid. Some of the most important parameters, such as low shear rate viscosity, plastic viscosity, yield stress and flow behavior index, were determined and discussed. The PEG/Lap and PPG/Lap dispersions containing more than 2.55% and 3.10% clay, respectively, could be considered in the formulation of drilling fluids. The yield point value of dispersions, which is suitable for drilling fluid applications, increased while their plastic viscosity decreased in the presence of NaCl. By addition of NaCl, the complex viscosity of these samples becomes independent of temperature in the range 10 °C – 65 °C. Zeta potential value decreases as the Lap concentration increases up to about 3% clay and, higher clay content no longer affects it. • Laponite® RD (Lap) aqueous dispersions in presence of PEG or PPG were investigated. • Rheological results suggest Lap suitability for drilling fluids. • Effect of salt and temperature on viscoelastic properties was evaluated. • Zeta potential as function of clay content and polymer structure was analysed. • Structure of Lap dispersions in presence/absence of PEG or PPG was discussed.

Characterization of Local Clay for Drilling Mud Production

Oil companies’dealing with drilling operations in Nigeria often spends millions of dollars in importation of bentonite for its operations as a result of its importance and high demand. As a result of this, attempt to source for local substitute has been initiated, which if successful would save the nation from this huge capital flight. In this study, a sample of Umuna local clay deposit was evaluated for drilling fluid application. The viscosity and filtration loss was analyzed and it’s far below that of the imported bentonite. The properties of the local clay was improved by addingmaterials such as HV-CMC, Drispac polymer and bentonite extenders to the formulated mud to enhance its viscosity and filtration loss Also the shearing speed was increased, but the used speed is limited to practical shearing speed. Theclay yield and characterization of the beneficiated samples show that the treated local clay is slightly comparable to the imported bentonite. The Calcium Exchange Capacity (CEC) result for the clay samples fall within the 70 – 150 Meq/100g. This result further suggests that the analyzed clay is of montimorillonite family, with traces of illite which is good for drilling mud production. The obtained results from this study indicates that the filtration loss and plastic viscosity for the analyzed clay samples were generally far from comparing with the imported bentonite, but through beneficiation, they were able to compare with the imported bentonite.