Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

The aetiology of neurodegenerative diseases (ND) seems to involve susceptibility genes and environmental factors. Toxic metals are considered major environmental pollutants. Following our study of a case of multiple sclerosis (MS) improvement due to removal of aluminium (Al) and other toxic metals, we have examined the possible relationship between Al intoxication and ND. We used the slow intravenous treatment with the chelating agent EDTA (calcium disodium ethylene diamine tetraacetic acid) (chelation test) to remove Al and detected it in the urine collected from the patients for 12 hours. Patients affected by MS represented 85.6% of total ND. Al was present in 44.8% of cases comprehensive of ND and healthy patients. Al levels were significantly higher in ND patients than in healthy subjects. We here show that treatment of patients affected by Al burden with ten EDTA chelation therapies (EDTA intravenous administration once a week) was able to significantly reduce Al intoxication.

Chelating agents such as ethylenediaminetetraacetic acid (EDTA) and hydroxy ethylene diamine triacetic acid (HEDTA) have been used as stand-alone stimulation fluids. These fluids can be used to stimulate water injectors, oil, or gas producers. In this study, an analytical model was developed to describe the flow of HEDTA and EDTA chelating agents and propagation inside calcite formations. The analytical model can be used as a pre-design tool before the treatments. The developed model can be used to predict the volume of the chelant required to create wormholes in calcite formations at different temperatures. The temperature affects the diffusion coefficient of the chelating agent, wormholing rate, and wormhole shape and size. The dissolving power of different forms of HEDTA can be determined using the model. The optimum injection rate based on optimum wormholing conditions was identified. Also, the model can be used to predict the wormholing rate of different chelating agents in calcite formations. The analytical model can be used to predict the performance of the chelating agent in calcite stimulation. The volume of chelating agent required to stimulate calcite formation per foot thickness was determined using the developed model. The optimum injection rate was determined for different chelating agents using the model, and the results were compared with experimental results from previous work and there was a good agreement between the measured and the predicted values. The model can be used to determine the best stimulation fluid based on the temperature and fracture pressure of the target zones.

Different fluids have been introduced in the oil industry to be used as alternatives to HCl. Chelating agents such as EDTA (ethylenediaminetetraaceticacid), and HEDTA (hydroxy ethylene diamine triacetic acid) have been used as stand-alone stimulation fluids. These fluids can be used to stimulate water injectors, oil, or gas producers, therefore, the effect of the type of reservoir fluid on the stimulation process should be investigated.In this study, an analytical model was developed to describe the flow of HEDTA and EDTA chelating agents and propagation inside carbonate formations. The analytical model can be used as a pre-design tool before the treatments. The developed model can be used to predict the volume of the chelant solution required to create wormholes in calciteformations at different temperatures. The temperature affects the diffusion coefficient of the chelating agent, wormholing rate, and wormhole shape and size. The dissolving power of different forms of HEDTA chelating agent can be determined using the model. The optimum injection rate based on optimum wormholing conditions was identified for the chelating agents. Also, the model can be used to predict the wormholing rate of different chelating agents in carbonate formations.The analytical model can be used to predict the performance of the chelating agent in carbonate stimulation. The volume of chelating agent required to stimulate carbonate formation per foot thickness was determined using the developed model. The optimum injection rate was determined for different chelating agents using the model and the results were compared with experimental results from previous work and there was a good agreement between the measured and the predicted values. The model can be used to determine the best stimulation fluid based on the temperature and fracture pressure of the target zones.

Phenylethyl resorcinol smartLipids for skin brightening – Increased loading & chemical stability

Thermal inactivation of rabies and several other rhabdoviruses was studied using virus suspended in several different diluents. Rabies serogroup viruses were more stable than Kern Canyon or vesicular stomatitis viruses. Limited studies of two fish rhabdoviruses requiring low temperatures (less than 33 C) for replication indicated that they were not markedly more thermolabile than rabies virus. Bovine serum protein components in complex cell culture media stabilized virus at 56 C, but at temperatures of less than or equal to 37 C, sodium tris (hydroxymethyl)-aminomethane (NT) buffer containing ethylenediaminetetraacetic acid (EDTA) (NTE) was a much more efficient stabilizer of virus infectivity. Chelating agents EDTA and ethyleneglycol-bis-(beta-aminoethyl ether)tetraacetic acid were equally efficient in protection of rabies virus infectivity; the effect of each was lost when excess Ca2+ was added. Bovine serum in NT or NTE buffers produced a thermostabilizing effect at 37 C not provided by the same serum concentration in complex cell culture media. Bovine serum was more efficient than EDTA in stabilizing virus infectivity during repeated cycles of freezing and thawing.

The chelating agent EDTA (ethylenediaminetetraacetic acid) is a compound of massive use world wide with household and industrial applications, being one of the anthropogenic compounds with highest concentrations in inland European waters. In this review, the applications of EDTA and its behavior once it has been released into the environment are described. At a laboratory scale, degradation of EDTA has been achieved; however, in natural environments studies detect poor biodegradability. It is concluded that EDTA behaves as a persistent substance in the environment and that its contribution to heavy metals bioavailability and remobilization processes in the environment is a major concern.

Location and magnitude of formation damage due to iron precipitation during acidizing carbonate rocks

Hydraulic fracturing operations require large amount of water which, in some cases, could reach six million gallons per treatment. Fresh water, from surface and subsurface sources, is usually used to formulate the fracturing fluid. The use of produced water in hydraulic fracturing has gained increased attention in the last few years, as it would solve fresh water acquisition challenges and reduces its disposal costs. However, produced water usually contains high amounts of total dissolved solids (TDS) that prevents its compatibility with fracturing fluid additives and negatively affects the fracturing fluid rheology. This paper investigates the effect of different chelating agents on the use of high-TDS produced water in high pH borate-crosslinked gels used in hydraulic fracturing fluids. Samples of field-produced water were analyzed for different ion concentrations. Synthetic water was prepared with different amounts of Na, K, Ca, and Mg salts. The fracturing fluid was formulated using natural guar polymer, borate-based crosslinker, biocide, surfactant, clay controller, scale inhibitor, and pH buffer. Five chelating agents tested in this study included HEDTA, GLDA, di-sodium EDTA, di-ammonium EDTA, and sodium gluconate. Compatibility tests of the fluid system at 180ºF were conducted at different ion concentrations. Apparent viscosity of the fracturing fluid was measured using a high-pressure high-temperature rotational rheometer. All rheology tests were conducted at a temperature of 180ºF and were conducted according to API 13m procedure with a three-hour test duration. Results indicated the potentiality of high-TDS water to cause precipitate and, hence, formation damage. However, the use of chelating agents has reduced the precipitation of divalent cations and enabled the formulation of fracturing fluid at higher Ca and Mg concentrations. The use of 2.5 wt% of HEDTA has enabled the formulation of the fracturing fluid using synthetic produced water that contains TDS of 101,000 ppm with Ca and Mg concentrations of 2,500 and 200 ppm, respectively. The fracturing fluid showed an average viscosity of 150 cp at 100 s-1 despite the high-TDS and high-hardness environment. The use of GLDA reduced the Ca and Mg ion precipitation; however, its chelation effect was found to be limited to certain concentrations. Some chelating agents showed the ability to chelate the boron ion and/or reduce the system's pH value. Consequently, viscosity measurements indicated the breaking of the fluid viscosity after the addition of the chelating agent. This paper presents the use of chelating agents to maximize the effectiveness of produced water for hydraulic fracturing operations. Successful use of chelating agents would reduce produced water disposal costs and improve the environment by reducing the consumption of fresh water.

Chapter 5 - Chelate-assisted phytoremediation

O percarbonato de sódio (PCS) é um oxidante com aplicação recente para a remediação de solos e água subterrâneas. Por ser um composto à base de peróxido de hidrogênio, o PCS possui potencial para degradar uma grande variedade de contaminantes, mas ainda é relativamente pouco conhecido e estudado. Esse trabalho apresenta uma revisão das suas principais propriedades, reações e fatores que interferem na sua aplicação na remediação ambiental. Os estudos de diversos autores foram compilados para levantar informações sobre reações com diferentes tipos de contaminantes, dosagens, uso de ativadores e quelantes. O PCS apresenta capacidade de degradar de forma eficiente alguns hidrocarbonetos aromáticos, incluindo benzeno, hidrocarbonetos policíclicos aromáticos e solventes clorados, entre outros. Verificou-se que o uso de ativadores propiciou a geração do radical hidroxila com maior velocidade e intensidade. Outras espécies reativas de oxigênio, como os radicais hidroperoxila e o ânion superóxido, também são formadas e auxiliam na degradação dos contaminantes, apesar de não possuírem o mesmo potencial de oxidação do radical hidroxila. Diferentes ativadores são citados na literatura como eficientes, como Fe(II) e Fe(III). O uso de agentes quelantes também resulta em maior eficiência, principalmente o ácido citrico, ácido oxálico e EDDS (ácido etilenodiamino-N,N’-dissuccínico – C10H16N2O8). No entanto, a análise dos estudos publicados torna evidente que as condições para obtenção de bons resultados são extremamente dependentes das condições específicas da área, como íons dissolvidos, presença de matéria orgânica e interações com diferentes minerais. Além disso, existe um número reduzido de informações sobre a interação do PCS com diferentes minerais e solos.

Effect of EDTA on the metastable zone width of ADP

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

The presence of cationic pollutant metals in municipal wastewater effluent is a concern because stringent discharge requirements cannot always be met with conventional treatment methods. Attempts to improve metal removal are often unsuccessful because a significant fraction of the cationic metals are complexed by the synthetic chelating agent ethylenediamine tetraacetic acid (EDTA). To identify practical approaches for improving metal removal, an analytical method for measuring metal-EDTA complexes was used to survey metal speciation at a series of wastewater treatment plants. Following these analyses, bench-scale experiments were conducted. The survey data indicated that pollutant metal-EDTA complexes account for a significant fraction of the dissolved metals in wastewater. The bench-scale studies indicated that ferric chloride addition improves the removal of copper and zinc by approximately 20%. To test the results of the bench-scale experiments, a full-scale experiment was conducted by interrupting chemical addition at a municipal wastewater treatment plant that normally adds ferric chloride during primary treatment. Results indicated that ferric chloride addition had a slight impact on metal speciation but no effect on metals removal. The lack of an effect was attributed to changes in metal speciation that occurred during primary treatment irrespective of ferric chloride addition. This title belongs to WERF Research Report Series ISBN: 9781843396949 (Print) ISBN: 9781780404387 (eBook)

This paper describes laboratory and modeling work to utilize high-sulfate pit brine and calcium chloride solutions as a means to the permeability of water producing zones. The study included compatibility tests, coreflood experiments, and scale prediction to calculate SI and SA at surface and reservoir conditions. The pit brine contains sulfate ions at 120,250 mg/L and its TDS is nearly 400,000 mg/L. Three solutions that contained calcium chloride at 10, 20, and 30 wt% were prepared. Coreflood tests were conducted using carbonate core of 100 to 1,100 md. Tests were conduced at 200°F (reservoir temperature) and overburden pressure of 2,000 psi. Most coreflood tests were conducted at 1 cm3/min. The pressure drop across the cores was monitored during these tests. Compatibility tests indicated instantaneous precipitation of calcium sulfate when pit water and calcium chloride brines are mixed. Scale predictions are done for 10, 20 and 30 wt% CaCl2 brines with pit brine. The maximum super-saturation at 200°F for CaSO4 occurs at 45, 60 and 70 vol% of pit brine for 10, 20 and 30 wt% of CaCl2, respectively. Predictedmaximum anhydrite is nearly 55, 81 and 97 g/L for the three CaCl2 brines, respectively. Coreflood tests indicated that maximum core plugging occurs when pit brines is injected into cores saturated with CaCl2 brines. The degree of core damage depends on the injection rate. Core flood results were explained in terms of thermodynamics and viscous fingering effects, which occur when a less viscous fluid displaces a more viscous fluid in porous media. Water production is a serious concern for oil and gas companies. On one hand, there is a cost required to lift this water, and to perform separation, treatment, and then disposal. In addition, water production causes scale, corrosion and emulsion problems. Therefore, every effort should be made to minimize excessive water production.Currenttechniques that rely on chemicals (cross-linked polymers) are expensive and in some cases these chemicals are not environmentally friendly. The technique described in this paper is simple, and utilizes simple and green chemistry. It can be used to plug water-producing zones in carbonate and sandstone reservoirs. This paper introduces a simple, effective technique that can be used to reduce the flow into high permeability zones. This technique can be used to minimize drill string sticking that occurs during drilling and reduce the amount of produced water during production Coreflood tests indicated that this technique is very effective in reducing the permeability of reservoir cores.

Carbonate reservoirs have complex pore structures and serious heterogeneity, which increase the difficulty to achieve efficient oilfield development. Conventional core plugs cannot accurately depict the heterogeneity characteristics that may beyond the scale of plugs. Thus, whole core experiments are conducted to better study this issue. The methodologies involved in this study include experimental study, outcrop observation, statistical analysis, and numerical modeling. 18 whole core sections are collected from a giant cretaceous carbonate reservoir located in the Middle East, and the OOIP of this carbonate is 4000 MM bbls. We conducted 3D CT, whole core experiments, and plug experiments for the total of 18 sections of the core. Furthermore, numerical simulation is conducted to better evaluate the impact of heterogeneity. After integrating results from all these methodologies and technologies, 2D and 3D CT images, horizontal permeability, vertical permeability, and density of whole core, horizontal plug, and vertical plug are obtained. Then, pore structure visualization and experimental results are combined, and analysis was carefully conducted. Results show that whole core can better depict the reservoir heterogeneity, and some interesting observations were found, such as when the permeability of the core section is low, permeability of whole core is greater than that of plugs; whereas when the permeability of the core section is high, permeability of whole core is lower than that of plugs. Simulation results indicate that heterogeneity is one of the major factors determining the performance of carbonate reservoirs. This study offers detailed evidence to support engineers and geologists for better understanding the heterogeneity and optimizing production plan on the carbonate reservoir.