Invert Emulsion Research Articles

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.

Mitochondrial surface coating with artificial lipid membrane improves the transfer efficacy

Extracellular mitochondria are present and act as non-cell-autonomous signals to support energetic homeostasis. While mitochondria allograft is a promising approach in rescuing neurons, glia, and vascular cells in CNS injury and disease, there are profound limitations in cellular uptake of mitochondria together with the efficacy. Here, we modified mitochondria by coating them with cationic DOTAP mixed with DOPE via a modified inverted emulsion method to improve mitochondrial transfer and efficacy. We initially optimized the method using control microbeads and liposomes followed by using mitochondria isolated from intact cerebral cortex of male adult C57BL/6J mice. After the coating process, FACS analysis indicated that approximately 86% of mitochondria were covered by DOTAP/DOPE membrane. Moreover, the artificial membrane-coated mitochondria (AM-mito) shifted the zeta-potential toward positive surface charge, confirming successful coating of isolated mitochondria. Mitochondrial proteins (TOM40, ATP5a, ACADM, HSP60, COX IV) and membrane potentials were well maintained in AM-mito. Importantly, the coating improved mitochondrial internalization and neuroprotection in cultured neurons. Furthermore, intravenous infusion of AM-mito immediately after focal cerebral ischemia-reperfusion amplified cerebroprotection in vivo. Collectively, these findings indicate that mitochondrial surface coating with artificial lipid membrane is feasible and may improve the therapeutic efficacy of mitochondria allograft.

Probing the state of water in oil-based drilling fluids

Oil-based drilling fluids, also referred to as “invert emulsion drilling fluids”, have been widely accepted as mixtures of water-in-oil (W/O) emulsions and inorganic particles, in which the water droplet–particle interaction has not been considered. Probing the state of water plays an important role in optimizing the performance of oil-based drilling fluids. In this work, hydrophilic BaSO4 and hydrophobic polytetrafluoroethylene (PTFE) particles were added to W/O emulsions. The microstructures of the water droplets and particles in the oil phase were studied using an optical microscope. The state of water was characterized by T2 nuclear magnetic resonance (NMR) and low-temperature differential scanning calorimetry (LT-DSC). Finally, the state of water in actual invert emulsion drilling fluids was verified by two-dimensional T1-T2 NMR. The results showed that the water droplets bound to the hydrophilic BaSO4 particles formed hydrated particle aggregates in the oil phase, while the water droplets and hydrophobic PTFE particles were suspended individually in the oil phase. Thus, the so-called invert emulsion drilling fluids are in fact colloidal suspensions of hydrated particle aggregates in continuous oil phase, rather than W/O emulsions. The findings of this work provide new insights into the formulation and utilization of oil-based drilling fluids.

Improving the performance of invert emulsion drilling fluid using boron nitride and graphene nanoplatelets for drilling of unconventional high-temperature shale formations

Drilling in deep unconventional shale formations is one of the most complex and challenging tasks. The success of the drilling operation in these formations is greatly reliant on the drilling fluid used. Oil-based drilling fluid is extensively used for its excellent performance in drilling troublesome shale formations. However, the stability of conventional additives in oil-based drilling fluid at high temperatures limits their use. These deteriorate at high-temperature conditions and can cause severe drilling problems. This research study aims to improve the performance of oil-based drilling fluid by developing a hybrid nano-based invert emulsion drilling fluid using graphene nanoplatelets and boron nitride nanomaterials. An extensive and comprehensive experimental study is performed to investigate and quantify the effect of these nanomaterials on the rheological and filtration properties of oil-based drilling fluid. In addition to that, electrical stability and viscoelastic characteristics are also investigated. Characterisation of nanomaterials is performed to analyse the morphology and purity. The formulated hybrid nano-drilling fluid demonstrates the improved rheological properties with enhanced filtration characteristics. The nanomaterials with a concentration of 0.2 ppb improve the plastic viscosity and yield point by 17% and 36%, respectively. A maximum 60% reduction in filtrate loss is observed at 0.6 ppb. The nanomaterials also enhanced the viscoelastic properties and extended the linear viscoelastic range. Furthermore, the flow behaviour and rheological modelling are performed at varying temperatures (25–125 °C) and shear rates (0.1–1200 s−1). The obtained results suggest that the hybrid nano-drilling fluid exhibit non-Newtonian shear-thinning behaviour consistent with the Herschel–Bulkley model.

Improvement of Emulsion Stability and Plugging Performance of Nanopores Using Modified Polystyrene Nanoparticles in Invert Emulsion Drilling Fluids.

Drilling fluid invasion and pressure transmission caused by the development of micropores and fractures in shale oil and gas formations are the major factors contributing to wellbore instability during drilling using oil-based drilling fluids (OBFs). In this study, a modified polystyrene latex (MPL) material was synthesized through emulsion polymerization and was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), particle size analysis, scanning electron microscopy (SEM) observations, and contact angle testing. The influence of the MPL on the stability of a water-in-oil emulsion was analyzed via sedimentation observations and electrical stability tests. The effects of the MPL on the plugging mechanism of white oil and water-in-oil emulsions were evaluated using 0.1–1.0 μm micro-porous filtration films. The experimental results revealed that the MPL has a favorable thermal stability, with an initial thermal decomposition temperature of 363°C, a median particle size (D50) of 233 nm, and a three-phase contact angle of 103.5°. The MPL can enhance the sedimentation stability of an emulsion to a considerable extent and can improve the electrical stability (ES) of the emulsion, which is conducive to the stability of OBFs. Due to the deformability of the MPL, it has a wide range of adaptations for micro-scale pores and fractures. In both the white oil and water-in-oil emulsions, the MPL can reduce the filtration loss through microporous membranes with pore sizes of 0.1–1.0 μm to within 10 ml. This paper details the methodology of the synthesis of nanomaterials that can effectively plug a formation’s nanopores and fractures; thereby, stabilizing OBFs.

Evaluating the influence of graphene nanoplatelets on the performance of invert emulsion drilling fluid in high-temperature wells

The oil-based mud is preferred to drill highly technical and challenging formations due to its superior performance. However, the inadequate chemical and thermal stability of conventional additives have greatly influenced the performance of oil-based mud at high-temperature conditions. Therefore, it is critical to design an oil-based mud with additives that withstand and improve its performance at high-temperature conditions. The nanoparticles have emerged as an alternative to the conventional additives that can significantly enhance the rheological and filtration characteristics of oil-based mud at high-temperature conditions. In this research study, a novel formulation of OBM enhanced with GNP is formulated, and its performance at high-temperature conditions is investigated. An extensive experimental study has been performed to study the effect of graphene nanoplatelets on the rheological and filtration properties along with flow behaviour, viscoelastic properties, electrical stability and barite sagging of oil-based mud at high temperatures. The graphene nanoplatelets are characterised to ascertain their purity and morphology. The result shows that the graphene nanoplatelets exhibited efficient performance and improved the rheological and filtration properties of oil-based mud. The plastic viscosity and yield point are improved by 11% and 42%, with a concentration of 0.3 ppb. Similarly, the gel strength and barite sagging tendency are enhanced by 14% and 2%, respectively. The filtration loss is also significantly decreased by up to 62% and 46%, with 0.5 ppb concentration at 100 and 120 °C. The addition of GNP results in the formation of a thin mud cake compared to the base mud sample. The rheological modelling recommends the shear-thinning behaviour of oil-based mud (n < 1), which is correlated with the Herschel–Bulkley model. An Artificial Neural Network model is developed to predict the viscosity of OBM based on the four input parameters (concentration of nanoparticles, temperature, shear rate and shear stress). The results demonstrate that graphene nanoplatelets have a favourable impact on the performance of oil-based mud. The addition of graphene nanoplatelets, even at small concatenation, has significantly improved the properties of oil-based mud at high-temperature.Graphical abstract

In-Situ Visualization and Characterization of Filter-Cake Deposition Using Time-Lapse Micro-CT Imaging

This work establishes and verifies a laboratory method for accurate, noninvasive, and nondestructive in-situ measurement of filter-cake, or mudcake, properties using high-resolution X-ray microcomputed tomography (micro-CT). Accurate in-situ characterization of mudcake properties is of vital importance for understanding mudcake deposition during mud-filtrate invasion and, more broadly, the deposition of filter cake during industrial filtration processes. The developed laboratory method involves the injection of pressurized drilling mud into a borehole located at the center of a cylindrical rock core sample. Radial mud-filtrate invasion is induced by maintaining the outside of the core sample at a lower pressure. Mudcake is deposited on the borehole wall while mud filtrate flows into the surrounding pore space of the core sample. Simultaneously, the core sample is continuously scanned using high-resolution X-ray micro-CT, allowing for three-dimensional (3D) in-situ visualization and characterization of the deposited mudcake. Analysis of experimental results is aided by a new set of filtration equations that are generalized for use with either water-based mud or invert emulsion drilling fluids, such as oil- or synthetic oil-based mud. Each experiment produces a time-series data set consisting of injected mud volume and the corresponding in-situ average mudcake thickness, porosity, and permeability. Results are presented for experiments involving injection of water- and synthetic oil-based drilling mud. We observe that experimental measurements agree well with modeled results when mudcake is thin compared to the size of the borehole—a condition that would be satisfied under most normal field conditions. Initial results also suggest that the developed method may be capable of providing accurate in-situ 3D measurements of local filter-cake properties during compressible cake filtration, which has significant implications for a wide range of industrial applications.

Viscoelastic and thermodynamic properties of highviscosity oil with different water cut

Dependencies of the viscoelastic and thermodynamic properties of high-viscosity oil from the oil-gathering reservoir of the N-Korenevskoye and Denisovskoye fields on the degree of water cut and temperature have been established. Under the conditions of shear deformations and at comparable temperatures, the nature of the processes of structure formation of oil at a low degree of water cut is due to phase transitions of paraffins, which is consistent with the experimental data described in the literature for non-watered oils, indicating the identity of the nature of intermolecular interactions between non-watered oil and oil with a low degree of water cut. The maximum effect of the thermal method for reducing the viscosity of oil with a low degree of water cut can be achieved when it is heated to the paraffin melting point T m *, determined using the ln(η) = f (1/T) dependence. The peculiarity of the rheological behavior of high-water-cut oil is due to an increase in the energy of intermolecular interaction, which in the entire temperature range is practically comparable to E act1 of low-water cut oil at T &lt;T m *, which is associated with the formationn of invert emulsions stabilized by interphase layers of asphaltene molecules. It is shown that an increase in temperature and shear deformations contribute to a decrease in the values of the effective viscosity of low and high water cut oil; however, the destruction of their colloidal structure does not occur in the entire range investigated. The loss of aggregate and kinetic stability of high-viscosity watered oil is achieved in the presence of a surfactant composition based on Sorbital C-20 and a sodium salt of alkylbenzenesulfonic acid, which causes the desorption of “natural stabilizers” from the oil-water interface and, as a consequence, the coalescence of water droplets.

Low Equivalent Circulating Density Organoclay-Free Invert Emulsion Drilling Fluids

AbstractHigh pressure and high temperature (HPHT) wells especially those with narrow pore/fracture pressure gradient margins present challenges in drilling. Maintaining optimum and low rheology for such wells becomes a challenge where a slight change in the bottom-hole pressure conditions can lead to nonproductive time. However, maintaining low viscosity profile for a drilling fluid can pose a dual challenge in terms of maintaining effective hole-cleaning and barite-sag resistance. This paper describes the formulation of 95pcf medium-density organoclay-free invert emulsion drilling fluids (OCIEF) with a low viscosity profile. The fluids gave lower plastic viscosity (PV), which ensured that the fluid presents low equivalent circulating density (ECD) contribution while drilling/circulating. These fluids were formulated with acid-soluble manganese tetroxide as weighting agent and a specially designed bridging-agent package. The fluids were hot rolled at 300 °F and their filtration and rheological properties were measured. The paper describes the static-aging, contamination, and high pressure/high temperature rheology measurements of the fluids at 300 °F. Particle plugging experiments were performed on the fluids to determine the invasion characteristics and the nondamaging nature of the fluids. These organoclay-free invert emulsion fluids (OCIEFs) were then field-trialed in different wells with good results. Field deployment of the 95pcf organoclay-free invert emulsion fluid helped to maintain the required hole stability in the high temperature and high pressure (HTHP) well. The well was displaced to 95pcf production screen test (PST) fluid and completed with a 4 ½ in. sand screen. The paper demonstrates the superior performance of the developed fluid in achieving the desired lab and field performance.

Ilmenite Inclusion: A Solution towards Solid Sagging for Hematite-Based Invert Emulsion Mud

The sagging tendency of hematite in drilling mud is a common challenge occurring at high-pressure and high-temperature (HP/HT) applications. This work studies the performance of hematite-based invert emulsion mud for HP/HT conditions and provides a solution to prevent the hematite settlement using a combination of ilmenite with hematite. Practical mud formulation was utilized over a range of ilmenite/hematite ratios (0/100, 20/80, 40/60, and 50/50%) to study sagging behaviour. From the sag tests, the optimum combination proportion was determined. Thereafter, the density, emulsion stability, rheological and viscoelastic properties, and filtration conduct for the formulated mud were evaluated. The experiments were conditioned as per the standards of the American Petroleum Institute. The obtained results of sagging experiments indicated that including 50% of ilmenite mitigated the hematite settling and reduced the sag tendency towards the safe range. A slight drop (4%) in mud weight was noticed upon adding the ilmenite, whereas the emulsion stability was enhanced from 551 to 574 volts with the 50% ilmenite content. The rheology and viscoelasticity measurements showed that 50/50% combination improved the yield point (YP) by 50% with a trivial 1 cP increment on plastic viscosity (PV), hence enhancing the YP/PV ratio by 46%. Also, the gelling strength was enhanced resulting in flat rheology and better gel structure. The filtration behaviour of 50% ilmenite mud was improved compared to blank hematite as it resulted in 21, 15, and 17% reduction on the filtrated volume, filter cake weight, and thickness, respectively. This study provides a solution for hematite sagging issue at HP/HT using combined weighting agents, which contributes to enhancing the mud stability and avoiding several well control issues and related operational and technical challenges that eventually will economize the drilling cost and time.

Prediction of the Rheological Properties of Invert Emulsion Mud Using an Artificial Neural Network.

Successful drilling operations require optimum well planning to overcome the challenges associated with geological and environmental constraints. One of the main well design programs is the mud program, which plays a crucial role in each drilling operation. Researchers focus on modeling the rheological properties of the drilling fluid seeking for accurate and real-time predictions that confirm its crucial potential as a research point. However, only substantial studies have real impact on the literature. Several AI-based models have been proposed for estimating mud rheological properties. However, most of them suffer from non-being field applicable attractive due to using non-readily field parameters as input variables. Some other studies have not provided a comprehensive description of the model to replicate or reproduce results using other datasets. In this study, two novel robust artificial neural network (ANN) models for estimating invert emulsion mud plastic viscosity and yield point have been developed using actual field data based on 407 datasets. These datasets include mud plastic viscosity (PV), yield point (YP), mud temperature (T), marsh funnel viscosity (MF), and solid content. The mathematical base of each model has been provided to provide a clear means for models’ replicability. Results of the evaluation criteria depicted the outstanding performance and consistency of the proposed models over extant ANN models and empirical correlations. Statistical evaluation revealed that the plastic viscosity ANN model has a coefficient of determination (R2) of 98.82%, a root-mean-square error (RMSE) of 1.37, an average relative error (ARE) of 0.12, and an absolute average relative error of 2.69, while for yield point, this model has a coefficient of determination (R2) of 94%, a root-mean-square error (RMSE) of 0.76, an average relative error (ARE) of −0.67, and an absolute average relative error of 3.18.

Application of a Pickering Emulsified Polymeric Gel System as a Water Blocking Agent.

The conventional methods for controlling excess water production in oil/gas wells can be classified on the basis of the mechanism (pore-blocking mechanism and relative permeability modification) used. Gel systems developed on the basis of a pore-blocking mechanism completely block the pores and stop the flow of both oil and water, whereas a relative permeability modifier (RPM) only restricts the flow of a single phase of the fluid. The gel working on the basis of the pore-blocking mechanism is known as a total blocking gel. An invert emulsified (PAM–PEI) polymer gel is a relative permeability modifier system. The same invert emulsion system is tested as a total blocking gel system in this research work. The dual-injection technique (1st injection and 2nd injection) was used for this purpose. In this research work, the emulsion system was tested at a temperature of 105 °C. The core sections with drilled holes and fractures were used for the core flooding experiments, representing a highly fractured reservoir. The developed emulsified gel system was characterized using a dilution test, an inverted bottle test, microscopic images, and FTIR images. The emulsified polymer gel was tested using a core flooding experiment. After the 2nd injection, the postflood medical CT and micro-CT images of the core sections clearly showed the presence of two different phases in the core section, i.e., the oil phase and the gel phase. The core flooding experiment result indicates that the gel formed after the 2nd injection of the emulsion system can withstand a very high differential pressure, i.e., above 2000 psi. The gel did not allow any oil or water to be produced. Hence, the developed emulsified polymer gel system with the help of a dual-injection technique can be efficiently used as a total blocking gel for high-temperature reservoirs.

Emulsions of glycerol in olefin: A critical evaluation for application in oil well drilling fluids

Drilling in ultra-deep waters presents a series of difficulties and specificities, related to well depth, water depth, high pressures and saline formations found in the pre-salt basins. In addition, there is still a need to use fluids that meet environmental legislation for cleaning and disposal of cuttings in the sea. In view of these requirements, the invert emulsion fluids, of brine in olefin, are promising and have been extensively used for this application. These fluids need to maintain their rheological properties throughout the drilling, also considering the temperature variation, in order to minimize the formation of hydrates, interaction with clay areas, interaction with saline zones and damages to the permeable rock. The hypothesis of this research is that the substitution of brine by glycerol in the drilling fluid can lead to the following advantages: (a) maintenance of rheological properties; (b) mitigation of interactions with clay and saline areas; (c) no formation of hydrates, due to absence of water in the fluid; and (d) introduction of a new economic effectiveness for glycerol waste disposal. For this, crude glycerol was used to replace saturated NaCl brine in the invert emulsion drilling fluid. The interaction with saline and clay-rich zones was investigated by evaluating the interaction of the dispersed phase and the continuous phase using clay and salt plugs. Among the main results, crude glycerol obtained as a by-product of biodiesel was compatible with commercial additives used in drilling fluids based on brine in olefin emulsions, demonstrating feasibility of immediate application in drilling fluids, in view of the maintenance of rheological properties, reduction of filtrate volume and lower reactivity with salt and clay areas. Thus, the article presents a new composition of drilling fluid for ultra-deep waters, with the potential to minimize damage to the rock formation, through the use of a waste from the biodiesel production industry, without the need of previous treatments.

Sagging Prevention for Hematite-Based Invert Emulsion Mud

Abstract The solids sagging in high-pressure high-temperature (HP/HT) reservoirs is a common challenge associated with hematite drilling fluids. This study provides a solution to hematite sagging in invert emulsion mud for HP/HT wells, which involves the combination of Micromax (Mn3O4) with hematite. The particles of both weighting agents were characterized to address their mineralogical features. A field formulation of the mud was used over a range of Micromax/hematite ratios (0/100, 20/80, and 30/70%) in laboratory experiments to address the sag performance and determine the optimal combination ratio. Then, density, emulsion stability, rheology, viscoelasticity, and filtration performance for the formulated mud were addressed. The tests were conditioned to 500 psi and 350 °F. The acquired results of sag tests indicated that incorporation of 30% Micromax solved the hematite sagging issue and brought the sag tendency within the recommended safe range. An insignificant reduction in mud density was observed upon the inclusion of Micromax, while the emulsion stability was obviously improved from 551 to 614 volts with the 30% Micromax mixture. The recommended 30/70% combination had almost no effect on plastic viscosity and yield point since they were increased by one unit, but the gel strength was improved resulting in flat rheology and better solids suspension capacity. The filtration behavior of the formulation with 30% Micromax was enhanced compared to pure hematite as it resulted in 10% and 14% reduction of the filtrate volume and filter-cake thickness, respectively. This study contributes to improve and economize the drilling cost and time by formulating a stabilized and distinguished-performance drilling mud using combined weighting agents at HP/HT.

Investigation of magnetite-based invert emulsion mud at high pressure high temperature

Investigation of magnetite-based invert emulsion mud at high pressure high temperature

Rheological investigation of pickering invert emulsion system for conformance control in high temperature reservoirs

The use of emulsified gel system in high temperature reservoirs is a promising technique for deep reservoir conformance control. The successful implementation of emulsified gel system for conformance control is mainly dependent on emulsion stability. The emulsion system was designed in a way so that it will only breaks once it reaches the desired depth/zone of interest. The gelation time is very much dependent on the emulsion stability. The flow properties of the emulsion system, which is one of its important physical attributes help to determine the gelation time. In this research study the invert pickering emulsion system was developed for conformance control in high temperature reservoirs. The effect of various variables such as different type of mixing method, salinity, type of emulsifier and temperature was studied. The emulsion systems were prepared using three different mixing methods denoted as M1, M2 and M3. Five different aqueous phase with different salinity were used and their effect on the emulsion systems gelation time was studied. The effect of four different emulsifiers i.e., Cloisite 20, Claytone II, Claytone HY and Claytone ER was evaluated. The emulsion systems were also tested at two different temperatures of 80 °C and 95 °C (ambient pressure conditions). In total fifteen different emulsion systems were prepared and tested. The emulsion system with highest salinity and Cloisite 20 as emulsifier was found to be with the longest gelation time of 24306 s (at 80 °C). At 95 °C, the Cloisite 20 as emulsifier and aqueous phase in field mixing water provided highest gelation time of 3362 s. The emulsion system with lowest salinity and Claytone HY as emulsifier was found to be with the lowest gelation time of 1684 s. Increase in temperature tends to decrease the gelation time of the developed emulsified gel system. The emulsion prepared with mixing method 3 (M3) and Cloisite 20 as emulsifier provided a gelation time of 5040 s at 80 °C but the gelation time of the same system is decreased to 3362 s at 95 °C. The effect of mixing method on the gelation time was also studied. Emulsion system prepared with mixing method 1 (M1) gives the gelation time of 7020 s whereas the same emulsion system prepared with the mixing method 3 (M3) gives gelation time of 5040 s. • The research article presents emulsified pickering emulsion system. • The emulsion system is invert emulsion stabilized with organoclay particles. • The effect of different emulsifiers, salinity and temperature was studied. • Three mixing methods for emulsion preparation were tested for their effect on gelation behavior.

Developing a Thermally Stable Ester-Based Drilling Fluid for Offshore Drilling Operations by Using Aluminum Oxide Nanorods

Esters were found to be promising alternatives to oil, as a constituent of drilling fluids, due to their biodegradability and bioaccumulation attributes. In this study, we used ethyl octanoate ester (EO) as a low molecular weight synthetic oil for formulating an ester-based drilling fluid (EBDF). Aluminum oxide nanorods (nanoparticles) were introduced as a Pickering emulsion stabilizer. Like the commercial emulsifiers, they showed that they stabilized the invert emulsion drilling fluid in our study. The rheological and filtration properties of the EBDF were tested at normal pressure and three temperatures: low temperature deepwater (LT) conditions of 2.6 °C, normal pressure and normal temperature (NPNT) conditions of 26.8 °C, and elevated temperature conditions of 70 °C. To enhance the stability and filtration properties of the drilling fluid, aluminum oxide nanoparticles (NPs) were used. An optimum concentration of 1 wt% was found to provide superior rheological performance and higher stability than samples without NPs at NPNT, LT, and elevated temperature conditions. Steadier gel rheology was exhibited at elevated temperature conditions, and a slow rate of an increasing trend occurred at the lower temperatures, with increasing NP concentrations up to 1.5 wt%. Filtration loss tests presented a reduction of fluid loss with increasing the NP concentration. The results demonstrate that a reduction of up to 45% was achieved with the addition of 1 wt% NP. These results show that nano-enhancement of ethyl octanoate drilling fluids would suffice to provide a wider range of operational temperatures for deepwater drilling operations by providing better thermal stability at elevated temperatures and maintaining stability at lower temperatures.

Filter Cake Breaker Evaluation Scaled Up From Laboratory to Field Conditions

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 199260, “Filter Cake Breaker Evaluation for Water Injectors: Scale Up From Laboratory to Field Deployment,” by Pavithiran Chandran, SPE, Arunesh Kumar, SPE, and Iain Cameron, BP, et al., prepared for the 2020 SPE International Conference and Exhibition on Formation Damage Control, Lafayette, Louisiana, 19–21 February. The paper has not been peer reviewed. The complete paper describes the test procedures adopted for evaluating various filter cake breaker formulations and the work conducted to develop the systems to be ready for use in two North Sea fields (Field A and Field B). Water injection wells were planned to provide pressure support to oil producers in the two fields, and water-based drilling fluids were selected to drill the reservoir sections for both. The average permeability is 1000 md for Field A and 50–100 md for Field B. A laboratory study was commissioned to evaluate and optimize filter cake breaker systems for use in water injectors to efficiently remove external and internal filter cake to attain matrix injection without the need for backflow to clean the sandface. Introduction Field A was commissioned to drill 18 producers and seven water injectors from a semisubmersible drilling rig. Most of the injector wells are high-inclination, long openhole sections. Fluid density of 1.24–1.48 specific gravity (SG) (10.3–12.3 ppg) was required for wellbore stability. The Field B development plan included drilling 26 producers and 10 water injectors with an average injection rate target of 40,000 B/D of treated, produced water per well. Most wells are high-inclination to reduce the risk of direct fracture communication between wells. Injectivity indexes of 10–30 BWPD/psi were anticipated. The ability to include backflow/gas-lift capacity in the injector wells to assist cleanup was not included in the operational plan; therefore, direct injection was the preferred design standard. The injection interval in Field A features high-permeability (approximately 1000-md) zones; the Field B injection interval is considered a low-to-mid-permeability (approximately 100-md) zone. Injection of warm produced water into naturally occurring fractures in Field B injector wells yields poorer performance than when cooler fluids such as seawater are used. Higher downhole temperature and longer fluid residence time in the wellbore on Field B could increase the temperature of the injection fluid and thermally contract the natural fractures. Poor initial injectivity with produced water was identified as a potential risk on these wells, because this could lead to subsequent complications with seawater injection into these zones. Reservoir Drilling Fluid (RDF) Design and Selection Water-based RDF was chosen to drill the reservoir section of the water injectors on the basis of its ability to reduce operational complexity in terms of fluids preparation, displacement design, and screen running issues. RDF fluids typically contain a brine phase to achieve required density, xanthan polymer for viscosity, starch for filtration control, sized calcium carbonates for a bridging package, and specialized chemicals to address specific well challenges such as shale inhibitors and lubricants. Water-based RDF is more amenable than invert emulsion fluids to stimulation treatments for cleanup of filter cake and remediation of near-wellbore damage. However, water-based fluids can pose other operational issues such as increased torque and drag and potential for differential sticking, especially while drilling long horizontal wells, as was planned for both fields. A lubricant was included in the fluid used on Field B to manage torque-and-drag issues.

Study the suitability of neem seed oil for formulation of eco-friendly oil based drilling fluid

The present work intended to develop an invert emulsion drilling mud from biodegradable neem seed oil as an alternative to conventional diesel-based drilling mud. This would present comparable properties and performances with API standard requirements, ecologically friendly and at a low cost. Biodiesel produced from non-edible neem oil was used as the continuous phase in an invert emulsion-based drilling mud. Different tests to investigate the applicability of the mud for drilling applications were conducted. The rheological and lubricity tests results indicate that the neem oil biodiesel-based drilling muds are comparable with conventional diesel-based drilling muds. The produced biodiesel shows a significantly better flash point of 168 °C than the traditional diesel flash point of 70 °C; indicating better fire safety than the conventional diesel. The lubricity and rheological data indicate the formulated mud with neem seed oil biodiesel fair reasonably well with conventional diesel and within the API requirements. In general, the preliminary results show that neem oil biodiesel is a potential alternative to conventional organic oil in formulating oil-based drilling mud in terms of technical and environmental analysis.

Optimization of invert emulsion oil-based drilling fluids performance through heterocyclic imidazoline-based emulsifiers

In this work six structurally related imidazoline oligomers based on the reaction of liner polyamine with saturated and unsaturated long alkyl chains (C18 oleic and stearic) fatty acids were prepared, followed by a quaternization reaction to produce new conventional and gemini imidazolinium quaternary salts. The chemical structures of prepared amphiphiles were confirmed via spectroscopic methods and elemental microanalysis, also, the prepared emulsifier’s characterization has been studied through static interfacial tension, visual and microscopic examination of prepared emulsification systems. The static interfacial tension measurements show a high ability to reduce interfacial tension values between diesel oil and water. The visual and microscopic examination gave evidence of a multilayer interface around emulsion particles and an increase of emulsion droplets size as a function of time with acceptable emulsion stability and phase separation. For both oil-based mud cost and diesel oil toxicity, this article brings to light many important aspects of designing new emulsifiers for low toxicity invert emulsion muds with lower diesel oil content. The prepared emulsifiers were mixed to be investigated and evaluated as primary emulsifiers package to formulate the invert emulsion oil-based muds (IEOBMs). The electrical stability, rheological properties, and filter loss were evaluated before and after hot roller aging and compared with the reference mud sample formulated from the commercial-grade emulsifiers. The experimental investigations conducted based on the Herschel-Bulkley rheological model showed good rheological behavior compared to the reference mud sample, high resistance to the deformation that occurred to prepared mud systems due to hot roller aging, good electrical stability, and high pressure-high temperature filtration loss values.