Filtrate Volume Research Articles

Effects of Ultrasonic Oscillations on Colloidal Properties of Sulfonated Drilling Fluids

Summary The property development of drilling fluids strongly relies on the emergence of novelty additives and the formulation design of drilling fluids. Few studies focus on the influences of preparation technology on various properties of drilling fluids. At present, high-speed mechanical agitation is still the only method of formulating drilling fluids in the industrial community. In the paper, two kinds of sulfonated drilling fluids that were used frequently in China were prepared by the combination of high-power ultrasound and high-speed mechanical agitation. After the mechanical agitation, we exerted ultrasonic oscillations on the sulfonated drilling fluids and intensified the input of ultrasonic energy by increasing ultrasonic time or power. In addition, the superposition of mechanical agitation during ultrasonic oscillations could further help the sulfonated drilling fluids to absorb more ultrasonic energy when the time and power of ultrasonic oscillations remained unchanged. The effects of ultrasonic oscillations on the colloidal properties of sulfonated drilling fluids were investigated. The results show that the introduction of ultrasonic energy into sulfonated drilling fluids is able to cause the formation of thinner and denser mudcakes on borehole walls and further reduce the low temperature and low pressure (LTLP) and high temperature and high pressure (HTHP) filtrate volume. The HTHP accumulative filtrate volume within 30 minutes can be decreased by a maximum of 24.7%. Simultaneously, various Bingham-type rheological values, particularly yield point, get decreased. The ultrasonic improvement of filtration and rheological properties benefits from the formation of the stable colloidal structure of drilling fluids under acoustic cavitation. According to the total organic carbon (TOC) measurements, it is found that ultrasonic oscillations promote the adsorption of sulfonated additives on bentonite clays. The analysis of particle size and zeta potential also confirms that ultrasonic oscillations not only decrease the average clay particle size but also enhance the zeta potential absolute value. In our experimental range, all the colloidal properties acquire the continuing improvement with the increase in ultrasonic energy input, which cannot be achieved only through the high-speed mechanical agitation. Compared with our previous research works, the subject investigated in the paper is the given drilling fluid system, but not the bentonite suspension containing one single additive. It indicates that we take a step forward in the field application of ultrasound-assisted mud preparation technique.

Optimization of Water-Based Drilling Muds Using Dioscorea Villosa Starch: A Response Surface Methodology Approach

The need for environmentally friendly alternatives to water-based drilling fluids has prompted an investigation into the effects of Dioscorea villosa starch as a natural additive in the petroleum and gas industry. In this study, a design of experiments approach utilizing Response Surface Methodology (RSM) through Box-Behnken design (BBD) was employed to optimize the extraction of starch from wild yam (Dioscorea villosa) and formulate drilling muds. The regression model was used to determine the optimized parameters for starch extraction and the results showed a close agreement between the experimental and predicted values with a difference of only 1.295%. The responses considered in the design were plastic viscosity, yield point, apparent viscosity, filtrate volume, and filtercake thickness, with three factors being considered: bentonite, Dioscorea villosa starch, and temperature. The properties of the formulated water-based drilling muds enhanced with Dioscorea villosa starch were analyzed using ANOVA, and linear models were selected based on their significance. The findings suggest that the addition of Dioscorea villosa starch improves the filtration and rheological properties of the drilling muds, with optimal concentrations of 16.92g of bentonite, 3.85g of Dioscorea villosa starch, and a temperature of 81.90°F. Overall, the study demonstrates the potential of Dioscorea villosa starch as a natural additive in water-based drilling fluids, providing an eco-friendly alternative to chemical additives and offering potential environmental benefits.

Primary Investigation of Barite-Weighted Water-Based Drilling Fluid Properties.

Drilling fluid is a critical component in drilling operation due to its various functions. It consists of many elements, and one of the main components is the weighting material which controls the mud density. The weighting material type and concentration have a significant impact on the drilling fluid properties. A common weighting material used in the oil and gas industry is barite. In this work, the impact of barite concentration on water-based drilling fluid was evaluated. The investigated drilling fluid properties are density, pH value, filtration behavior, and rheological parameters. An intense investigation was carried out to evaluate the impact of barite concentration on the filtration and filter cake sealing properties. The density and pH values were measured at room temperature, filtration test was performed at room temperature, and differential pressure was equal to 100 psi. The rheological parameters were determined after hot rolling for 16 h at a temperature of 250 °F. The results showed that both the density and pH value increased linearly with barite dosage. The filtration volume, filter cake thickness, and permeability increased with the incremental increase in barite dosage, and the exponential relationship was the best in describing the relation with barite concentration. However, the filter cake porosity had an inverse proportional relation with barite dosage. In the case of rheological properties, all the investigated properties including the plastic viscosity, yield point, ratio of yield point to plastic viscosity, and gel strength at two different times (i.e., 10 s and 10 min) increased in general as the barite concentration increased.

Aqueous drilling fluids systems incorporated with green nanoparticles and industrial spent caustic: Optimum rheology and filtration loss properties

Drilling fluids are one of the most significant components of drilling operations for proper functions including fluid loss reduction into the formation and outstanding rheological properties. The drilling fluids according to environmental regulations and governmental rules have to be friendly to the environment to lessen the negative effects on the environment and improve safety. In the current study, a cost-effective industrial alkali waste (spent caustic) was used as a pH controller along with the environmentally friendly uncoated and Chitosan-coated green magnetite nanoparticles (MNPs) in water-based drilling fluid systems. The study focuses on exploring the impact of the alkali waste compared to the conventional alkali (NaOH) on rheology and filtration loss properties. The flow models of the drilling fluid systems were examined. The results proved that the drilling fluid formulated with polymer-coated green MNPs and waste alkali exhibited higher rheological properties and lower mud cake thickness and filtration volume compared to the reference fluid, thus, the waste alkali could replace NaOH as a pH controller. The flow behavior of new fluids could be described precisely using the Herschel-Bulkley flow model. Whereas, the Bingham plastic flow model described the fluid systems incorporated with uncoated and polymer-coated green NPs and NaOH.

Application of machine learning to determine the shear stress and filtration loss properties of nano-based drilling fluid

A detailed understanding of the drilling fluid rheology and filtration properties is essential to assuring reduced fluid loss during the transport process. As per literature review, silica nanoparticle is an exceptional additive to enhance drilling fluid rheology and filtration properties enhancement. However, a correlation based on nano-SiO2-water-based drilling fluid that can quantify the rheology and filtration properties of nanofluids is not available. Thus, two data-driven machine learning approaches are proposed for prediction, i.e. artificial-neural-network and least-square-support-vector-machine (LSSVM). Parameters involved for the prediction of shear stress are SiO2 concentration, temperature, and shear rate, whereas SiO2 nanoparticle concentration, temperature, and time are the inputs to simulate filtration volume. A feed-forward multilayer perceptron is constructed and optimised using the Levenberg–Marquardt learning algorithm. The parameters for the LSSVM are optimised using Couple Simulated Annealing. The performance of each model is evaluated based on several statistical parameters. The predicted results achieved R2 (coefficient of determination) value higher than 0.99 and MAE (mean absolute error) and MAPE (mean absolute percentage error) value below 7% for both the models. The developed models are further validated with experimental data that reveals an excellent agreement between predicted and experimental data.

A Thermal-Responsive Zwitterionic Polymer Gel as a Filtrate Reducer for Water-Based Drilling Fluids.

It is crucial to address the performance deterioration of water-based drilling fluids (WDFs) in situations of excessive salinity and high temperature while extracting deep oil and gas deposits. The focus of research in the area of drilling fluid has always been on filter reducers that are temperature and salt resistant. In this study, a copolymer gel (PAND) was synthesized using acrylamide, N-isopropyl acrylamide, and 3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate through free-radical polymerization. The copolymer gel was then studied using FTIR, NMR, TGA, and element analysis. The PAND solution demonstrated temperature and salt stimulus response characteristics on rheology because of the hydrophobic association effect of temperature-sensitive monomers and the anti-polyelectrolyte action of zwitterionic monomers. Even in conditions with high temperatures (180 °C) and high salinities (30 wt% NaCl solution), the water-based drilling fluid with 1 wt% PAND displayed exceptional rheological and filtration properties. Zeta potential and scanning electron microscopy (SEM) were used to investigate the mechanism of filtration reduction. The results indicated that PAND could enhance bentonite particle colloidal stability, prevent bentonite particle aggregation, and form a compact mud cake, all of which are crucial for reducing the filtration volume of water-based drilling fluid. The PAND exhibit excellent potential for application in deep and ultra-deep drilling engineering, and this research may offer new thoughts on the use of zwitterionic polymer gel in the development of smart water-based drilling fluid.

Short-Term Postoperative Outcome of Baerveldt Glaucoma Implant with Two Tubes Inserted into the Vitreous Cavity

Here, we report a new surgical technique designed to increase filtration volume and reduce intraocular pressure (IOP) in glaucoma and its one-year outcome. Two tubes were created from a single Baerveldt glaucoma implant (BI) by folding the tube in a U-shape and incising only the outer edge of the stretched loop tip. The tubes were placed into the vitreous cavity via the pars plana through a long scleral tunnel, without a scleral valve or graft patch. Twenty eyes of 18 patients with neovascular glaucoma were included. This technique was performed in 10 eyes of 10 patients (double group), and outcomes were compared to 10 eyes of eight patients in which a single tube BI was inserted (single group). The primary outcome measures included IOP, supplemental medical therapy score (SMTS), and intraoperative and postoperative complications before and after surgery at 12 months. The mean IOP (SMTS) were 32.0 ± 11.33 mmHg (4.1) in the double group and 29.7 ± 6.31 mmHg (5.7) in the single group, preoperatively reduced to 11.8 ± 2.70 mmHg (0.2) (63% reduction, p < 0.004) and 14.2 ± 4.05 mmHg (1.1) (52% reduction, p < 0.002) after 12 months, respectively. SMTS showed 95% (p = 0.005) and 89% (p = 0.005) reductions, respectively. Although there was no significant difference in IOP between the two groups at 12 months (p = 0.16), there were significant differences in the SMTS between the two groups before, and 6 and 12 months after, surgery (p = 0.01, 0.04 and 0.04, respectively). A reduction in the SMTS suggests that increasing filtration volume by placing two tubes has the potential to further reduce IOP as compared with a single tube.

Sulfonated sodium tannin and AM/AMPS copolymer complex as an anti-temperature viscosity reducer for water-based drilling fluid

ABSTRACT Viscosity reducer is used to reduce the high viscosity of drilling fluid containing bentonite as a continuous phase. However, the viscosity of drilling fluid increases and the rheology of the drilling fluid deteriorates at high temperature, causing problems such as reduction in rate of penetration and bit balling. As a core component, drilling fluids with bad rheology seriously affect the further development of drilling engineering, especially at high temperatures. Therefore, there is an urgent need for viscosity reducer suitable for high temperature. In this study, a high temperature-resistant viscosity reducer for water-based drilling fluid was prepared. The rheological parameters of drilling fluids containing 0, 0.5, 1, 1.5 wt% viscosity reducer after aging at different temperatures were evaluated. The results showed that the rheological parameters, such as apparent viscosity, yield point, plastic viscosity, and gel strength decreased within 200℃. Otherwise, filtration volume of 1.8 and 2.2 g/cm3 compound drilling fluids containing 1 wt% viscosity reducer was less than 10 ml. And its resistance to Na+ contamination reached saturation, that is, 36% NaCl solutions. The mechanism of viscosity reduction was also investigated by Fourier transform infrared and X-ray diffraction. Viscosity reducer adsorbed on the clay particles and destroyed the network structure formed by the clay particles while releasing free water.

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.

Improving the filtration properties for manganese tetroxide mud utilizing perlite particles to drill wide-range permeability sandstone formation

A required feature of any drilling formulation is to mitigate the formation damage by having an excellent filtration and filter cake properties. The key factor for preventing and limiting formation damage is to improve the sealing qualities of the planned drilling fluid. In this study, a new novel filtration agent called “perlite” was introduced for improving the manganese tetroxide mud cake ability for better sealing features. The perlite particles were loaded to formulation containing the manganese tetroxide as weighting agent. The water-based drilling mud was designed at high densities (14.25 and 17.2 ppg). Perlite was added in varied concentrations to reach the optimum performance. The filtration test conducted at reservoir temperature of 250 °F and a differential pressure of 300 psi to form the filter cake. The tests were performed using sandstone cores with two different permeability categories (low and high permeabilities) as the filtration media. This gave the full picture of perlite performance as implemented for different formation properties and considering the drilling fluid properties. The formed filter cake structure and chemical composition was evaluated using scanning electron energy-dispersive X-ray (SEM–EDS). The presented results illustrated how the perlite was compatible to be added to the manganese tetroxide weighting agents in the same formulation. In addition, it has the capacity to improve the filter cake's sealing qualities, lowering the filtration volume by 41% and the filter cake internal and external layers permeability by 58% and 25%, respectively. Moreover, the EDS analysis showed that the perlite particles are concentrated generally in the internal layer of the filter cake.

Silver Nanowires Coated Nitrocellulose Paper for High-Efficiency Electromagnetic Interference Shielding.

A thin and conductive coating on an environmentally friendly polymer is imperative for protecting sensitive electronic devices. In this regard, a series of silver nanowires (AgNWs) coated nitrocellulose (NC) papers are fabricated by a simple and fast processed vacuum-assisted filtration method by varying filtrate volume to address electromagnetic interference. Their structural and EMI shielding performance is analyzed. The submicron thick and the lighter paper reveal the conductive AgNWs interwoven on the rough NC surface, making a 2D in-planar structure. Due to a strongly interconnected network, the coated paper displays an exceptional electrical conductivity of 8603 S/m. Despite having a minimum AgNW coating thickness of ∼0.69 μm and an area density of 0.041 mg/cm2, an ultrahigh EMI shielding effectiveness (SE) of about 69.4 dB (a specific EMI SE (SE/t) of 1005797 dB/cm) in the entire X-band (8-12 GHz) region is achieved. The effective material parameters, extracted using plane-wave theory, indicate that AgNWs form closed current loops resulting in magnetic losses. These AgNWs coated NC papers synthesized by a simple procedure are promising EMI shielding materials for current emerging electronic devices.

Use of surfactants for efficient removal of calcium phosphate particles from water

Today, softening of water in offices and private homes is mainly carried out by the ion exchange method, despite its significant negative impact on the hydrosphere. The development of alternative safe technologies in this field is extremely relevant today. Such an alternative can be considered the use of effective reagents that transfer hardness ions into the solid phase.
 The use of phosphates as such reagents allows, depending on the conditions, to reduce the residual hardness of water to the level of 0.1 mg-eq/dm3 or less. An important problem of this technology is the efficiency of separating the solid phase from the mother liquor. This step can be implemented by advocating or filtering. Using model calcium solutions treated with appropriate doses of sodium phosphate and flocculants, the most effective of them in settling processes were selected. As flocculants, polyacrylamide was used - as a nonionic flocculant, Magnofloc - 336 from Ciba - as an anionic flocculant, Zetag - 7692 from Ciba - as a cationic flocculant.
 The flocculant Magnofloc - 336 turned out to be the most effective in settling highly dispersed particles of calcium phosphate. At a flocculant concentration of 30 mg/dm3 for 10 min of settling, the apparent volume of the solid phase decreases to 30 % of the initial volume of the suspension and stabilizes at this value. Other types of flocculants and other doses were less effective.
 A somewhat different situation is observed when separating the solid phase by filtration. The greatest influence on the filtration rate is caused by the temperature, the hydrogen index and the ratio between the components. Only temperatures below 20 °C significantly affect the rate of filtration. This is especially noticeable at a temperature of 5 °C. At this temperature, the volume of filtrate is 8-20 minutes behind the volume of filtrate of distilled water. At 15 °C, this difference is smaller, and at temperatures above 20 °C, the curves generally overlap. In the pH range of 5-9, there is no significant effect on the filtration rate. Only in a strongly alkaline environment do the necessary filtering times increase significantly, which, in our opinion, is due to the formation of a significant number of amorphous particles of various composition, which can block the pores of the filters. With the stoichiometric ratio of the components, the curve of the change in the filtration rate practically coincides with the curve of the change in the filtration rate of distilled water under the same conditions. When the ratio changes both downward and upward, the conditions for filtering the suspension deteriorate. And the more the ratio differs from stoichiometry, the more developed the structure of the solid phase is and the worse its separation from the liquid phase is. As the ratio between the components changes, so does the pH of the zero charge of the solid particles. If the stoichiometric ratio of the components is at pH 8.15, then when the ratio decreases to 0.5, it decreases to pH 7.41, and when it increases to 2, it increases to pH 8.64. A change in the ratio of components affects not only the sign of the surface charge, but also its magnitude, which cannot help but affect the efficiency of solid phase separation. The type and dosage of flocculants determined to be most effective in settling do not always provide the same effect in filtration. Suspensions without the addition of flocculants have the highest filtration speed. The study of the effect of flocculants at their concentrations of 10 and 30 mg/dm3 showed that none of its different types and at their different concentrations contributes to an increase in the filtration rate. Obviously, significant doses of flocculants contribute to the rapid calming of the porous medium of the filters and cause a decrease in the rate of transport of the liquid phase.
 The obtained results make it possible to determine effective reagents for removing calcium ions from natural waters and the optimal conditions for their use and serve as a basis for the development of effective and environmentally safe technologies for softening natural waters.

Synthesis of a Low-Molecular-Weight Filtrate Reducer and Its Mechanism for Improving High Temperature Resistance of Water-Based Drilling Fluid Gel System.

During the exploitation of deep and ultradeep oil and gas resources, the high-temperature problem of deep reservoirs has become a major challenge for water-based drilling fluids. In this study, a novel high-temperature-resistant filtrate reducer (LDMS) with low molecular weight was synthesized using N, N-dimethylacrylamide; sodium p-styrene sulfonate; and maleic anhydride, which can maintain the performance of a drilling fluid gel system under high temperature. Unlike the conventional high-temperature-resistant polymer filtrate reducer, LDMS does not significantly increase the viscosity and yield point of the drilling fluid gel systems. After aging at 210 °C, the filtrate volume of a drilling fluid with 2 wt% LDMS was only 8.0 mL. The mechanism of LDMS was studied by particle size distribution of a drilling fluid gel system, Zeta potential change, adsorption experiment, change of bentonite interlayer spacing, filter cake scanning electron microscope, and related theoretical analysis. The mechanism study revealed that LDMS could be adsorbed on the surface of bentonite particles in large quantities and intercalated into the interlayer of bentonite. Thus, it can improve the hydration degree of bentonite particles and the colloidal stability of the drilling fluid gel system, maintain the content of fine particles in the drilling fluid gel system, form a compact mud cake, and significantly reduce the filtrate volume of the drilling fluid gel system. Therefore, this work will promote the application of a low-molecular-weight polymer filtrate reducer in high-temperature-resistant water-based drilling fluid gel systems.

Improving filter cake sealing properties for high-density ilmenite drilling fluid

Drilling fluids must be cautiously designed to form an impermeable filter cake layer that diminishes the intensity of solid and mud invasion during drilling of a well. Inability to abate solid and mud invasion can cause adverse effects on the productivity of the drilled well. As a result, a variety of additives have been proposed for improving filter cake's sealing properties, which are also utilized to control fluid filtration. This work investigates the role an amorphous volcanic glass (perlite), a novel filtration agent, to amend the quality of filter cake layer that formed using ilmenite (FeTiO3) drilling fluid. The characteristics of the filter cake were evaluated in terms of the filtration behavior, filter cake thickness, permeability and porosity. In order to accomplish this aim, several concentrations of perlite particles were loaded to the Ilmenite weighted drilling fluid. The tests were conducted under high-pressure high-temperature environment according to API standards. The results of the drilling fluid (containing perlite) were compared with a reference drilling fluid (zero concentration of perlite). It is observed that the perlite containing formulation has improved filtration properties. The flake-shaped perlite particles blocked the filter cake pores and accordingly produced an impermeable filter cake. There was a drastic drop in the filter cake overall permeability after adding perlite concentration of 3 lb/bbl, from 6.09 × 10−3 Darcy to 1.46 × 10−3 Darcy and a significant drop (55%) in the associated filtration volume from 18.5 cm3 to 8.5 cm3. Moreover, perlite-based filter cake lowered the pore size of the filter cake and decreased the filter cake thickness by 45%.

Improving oil mechanism of polymer gel fracturing fluid based on filtration displacement

In contrast to the field effect of guar gum fracturing fluid, the polymer gel fracturing fluid causes a different production phenomenon. There is a lag between fracturing and the occurrence of oil production; however, the period of higher oil production is extended. In this study, the filtration displacement of the polymer gel fracturing fluid improves the fracturing effect was put forward. The claim is verified by comparing the difference in the mechanism by which the polymer gel and guar gum fracturing fluids increase oil production. Experiments were conducted to determine the influence of permeability and filtration pressure on the filtration volume of the polymer gel fracturing fluid and the remaining oil saturation in the filtration displacement area. The field effect of the polymer gel fracturing fluid was analyzed. The results indicated that the filtration displacement of the polymer gel fracturing fluid can help improve the remaining oil distribution in reservoirs in the upper, lower, and front areas of the fracture, which may help extract the remaining oil under the pressure difference of the subsequent production and displacement function of flooding agents. The filtration pressure difference was controlled according to the permeabilities of fracturing reservoirs to ensure that the oil displaced by polymer gel fracturing fluid could flow back to the fracture after being displaced. A new method of injecting the pre-displacement agent before fracturing the reservoir, namely the “fracturing after displacement”, was proposed. This method can help further exploit the remaining oil in the reservoir near the well production end, thereby improving the fracturing effect. Field applications also show that the fracture construction effect of the polymer gel is better than that of the guar gum fracturing fluid, owing to better filtration performance.

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

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

Chemical evidence for the tradeoff-in-the-nephron hypothesis to explain secondary hyperparathyroidism.

BackgroundSecondary hyperparathyroidism (SHPT) complicates advanced chronic kidney disease (CKD) and causes skeletal and other morbidity. In animal models of CKD, SHPT was prevented and reversed by reduction of dietary phosphate in proportion to GFR, but the phenomena underlying these observations are not understood. The tradeoff-in-the-nephron hypothesis states that as GFR falls, the phosphate concentration in the distal convoluted tubule ([P]DCT]) rises, reduces the ionized calcium concentration in that segment ([Ca++]DCT), and thereby induces increased secretion of parathyroid hormone (PTH) to maintain normal calcium reabsorption. In patients with CKD, we previously documented correlations between [PTH] and phosphate excreted per volume of filtrate (EP/Ccr), a surrogate for [P]DCT. In the present investigation, we estimated [P]DCT from physiologic considerations and measurements of phosphaturia, and sought evidence for a specific chemical phenomenon by which increased [P]DCT could lower [Ca++]DCT and raise [PTH].Methods and findingsWe studied 28 patients (“CKD”) with eGFR of 14–49 mL/min/1.73m2 (mean 29.9 ± 9.5) and 27 controls (“CTRL”) with eGFR > 60 mL/min/1.73m2 (mean 86.2 ± 10.2). In each subject, total [Ca]DCT and [P]DCT were deduced from relevant laboratory data. The Joint Expert Speciation System (JESS) was used to calculate [Ca++]DCT and concentrations of related chemical species under the assumption that a solid phase of amorphous calcium phosphate (Ca3(PO4)2 (am., s.)) could precipitate. Regressions of [PTH] on eGFR, [P]DCT, and [Ca++]DCT were then examined. At filtrate pH of 6.8 and 7.0, [P]DCT was found to be the sole determinant of [Ca++]DCT, and precipitation of Ca3(PO4)2 (am., s.) appeared to mediate this result. At pH 6.6, total [Ca]DCT was the principal determinant of [Ca++]DCT, [P]DCT was a minor determinant, and precipitation of Ca3(PO4)2 (am., s.) was predicted in no CKD and five CTRL. In CKD, at all three pH values, [PTH] varied directly with [P]DCT and inversely with [Ca++]DCT, and a reduced [Ca++]DCT was identified at which [PTH] rose unequivocally. Relationships of [PTH] to [Ca++]DCT and to eGFR resembled each other closely.ConclusionsAs [P]DCT increases, chemical speciation calculations predict reduction of [Ca++]DCT through precipitation of Ca3(PO4)2 (am., s.). [PTH] appears to rise unequivocally if [Ca++]DCT falls sufficiently. These results support the tradeoff-in-the-nephron hypothesis, and they explain why proportional phosphate restriction prevented and reversed SHPT in experimental CKD. Whether equally stringent treatment can be as efficacious in humans warrants investigation.

The true picture of environmental DNA, a case study in harvested fishponds

The application of environmental DNA (eDNA) metabarcoding has revolutionised large scale biodiversity monitoring of aquatic ecosystems. Validation studies have been performed mainly in laboratories and mesocosm experiments, however large-scale field experiments are necessary to verify the robustness of eDNA based monitoring for more specific applications and different environmental conditions. Here, eDNA samples were collected from three fishponds with high fish density and broad species diversity during summer and autumn. This sampling design included a large number of spatial replicates evenly spaced across the pond surface and samples from the inflow, while pooled samples were used to test the effect of filtration volumes on detectability. Most common species were detected using eDNA, but rare species were often missed out under these high stocking densities. Average read counts and site occupancy positively correlated strongly with species abundance and biomass, with the exception of samples affected by PCR inhibition. Higher diversity detections were observed in autumn compared to summer samplings and in running compared to standing water. Fish communities detected in pooled samples reflect the overall community structure, and the species detectability increases with higher filtration volumes. This work highlights how eDNA based surveys can be optimised based on sampling conditions to achieve the highest overall detection, which has important implications for applying this method to aid management and policy initiatives.

Use of synthetic calcium carbonate particles as an additive in water-based drilling fluids

The design and formulation of drilling fluids are essential for a successful drilling operation performance. In this work, the incorporation of calcium carbonate particles (CaCO3) as a novel additive of water-based drilling fluids (WBMs) was evaluated. CaCO3 particles were synthesized by the precipitation method and characterized in terms of morphological, thermal and structural properties. WBM systems were prepared containing three different viscosifier additives such us xanthan gum, (XGD), guar gum (GG) or corona gum (GEC). The addition of CaCO3 particles on the rheological, filtration, thermal and structural properties of WBMs was investigated. It was found that fluids containing XGD and CaCO3 particles exhibited significant improvements on their functional properties. This behavior was mainly attributed to surface interactions between bentonite with polymers, as well as bentonite with CaCO3. For all systems, the addition of particles resulted in a reduction in the volume of filtrate. Moreover, the Sisko and Herschel Bulkley model were employed in order to describe theoretical the rheological behaviour.

Primary Investigation of Ilmenite Dosage Effect on the Water-Based Drilling Fluid Properties

Abstract A high-density mud is required for deep drilling operations to keep formation pressure under control and avoid the kick. The high-density mud showed several challenges including sagging issues, undesirable rheology parameters, and higher possibility of inducing formation damage. Ilmenite is a weighting material that is used to increase the density of the drilling fluid. The effect of ilmenite dosage on the density of drilling fluid, rheological parameters, filtration, and filter cake qualities was explored in this study. Three different models were used to match the rheological properties including the Bingham model, the power-law model, and the Herschel–Bulkley model. The results showed that the prepared drilling mud density was correlated exactly with the amount of ilmenite added to the formulation. Similarly, the viscosity parameters were increased as ilmenite dosage increased. Even so, the results show that the rheological behavior seems to exhibit perfect matching using the three models, Herschel–Bulkley model was showing the highest accuracy compared to the other investigated models. Notably, the filtration behavior was dominated greatly by ilmenite dosage. The filtration volume and filter cake increased drastically as the ilmenite concentration increased. Correspondingly, the filter cake permeability was increased as the ilmenite concentration increased. Meanwhile, the dense packing of ilmenite particles at high concentrations produced lower filter cake porosity. Correlations were found with excellent accuracy between the ilmenite dosage and the filtration volume and filter cake properties.