Oilfield Wastewater Research Articles

Corrosion-induced CaCO3 fouling in steel tube of oilfield wastewater treatment and the interfacial bonding mechanism: An experimental and theoretical investigation

Layered scale in a steel tube sample, obtained from an oilfield wastewater pipeline in northwestern China, is experimentally examined layer by layer. From the scale layer contacting with steel wall to the center hole (from the 1st to 4th layer), the organic content increases. The majority of 1st-layer is composed with iron oxides (corrosion products), while CaCO3 emerges in the 2nd layer, and its crystal structure transforms from aragonite to calcite as scale grows thicker from the 2nd to 4th layer. Then, FeCO3 and complex carbonate (Ca0.1Mg0.33Fe0.57CO3) are identified in the 3rd and 4th layers. The experiments indicate the corrosion products preferentially form before CaCO3 fouling. So, CaCO3 precipitates are likely to nucleate on the substrate of iron oxides (such as Fe2O3), which provides a newfound impetus to explore the interfacial bonding mechanism of Fe2O3@Fe(110) and CaCO3@Fe2O3(001). By combining MD and DFT approaches, it is demonstrated that two of three O atoms in Fe2O3 molecule have formed four O–Fe bonds with Fe(110), and those bond lengths are shorter than the one in bulk Fe2O3. And, totally seven bonds would form between CaCO3 and Fe2O3(001), in which three O–Ca, one Ca–Fe and three O–Fe bonds are included. For the bonded atoms, the former atom acts as charge acceptor, and the latter tends to be donor.

Study on oil and suspension solid removal from oil field wasted water by sedimentation

In order to remove oil and suspended solid in oilfield wastewater, Takacs model was improved and applied to the simulation of oil floating, the parameters of oil coagulation velocity were added. By this model, the accurate oil floating model and sludge sedimentation model were established. On the basis of this model, the experimental verification was carried out by the sample from the wasted water station. By the response surface method, the influence of flow rate, treatment fluid concentration and settling time and their interaction on oil removal rate and suspension removal rate were studied, and the important influence of time factor was determined. According to the pollution degree of oil field wasted water, based on the theory and experimental method of this paper, the treatment capacity and settling time of oil field wasted water could be optimized, which provides theoretical guidance for the improvement of settlement device and the industrial application in the oilfield.

Ag Deposition on N and B Co-doped TiO2 Nanoparticles: An Avenue for High-Efficiency Photocatalytic Degradation of Dye and Hydrocarbons in Oil-Contaminated Wastewater

Nowadays, the treatment of refractory wastewater such as oil-field wastewater has become one of the most concerning environmental problems. Using nanometer photocatalyst to treat wastewater under visible light is an alternative solution. In this study, N and B co-doped TiO2 particles with Ag surface modification (Ag/TNB) were prepared to improve the visible-light activity. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–VisDRS. The decomposition of Rh.B, and hydrocarbons in the oil-field wastewater under visible light was studied. The results showed that the presence of N, B and Ag improved the photocatalytic activity of TiO2. 98% of Rh.B was removed after 1 h photocatalysis at the conditions of pH 6 with the catalyst loading of 1 g/L. The COD value of oil-field wastewater was reduced by 54% after 2 h at the conditions of pH 8 with the catalyst loading of 2 g/L. The modified catalyst revealed its great potential in the practical application for environmental purification.

Anodic oxidation produces active chlorine to treat oilfield wastewater and prepare ferrate(VI)

This report describes an electrochemical method that encompasses the formation of active chlorine species and the synthesis of ferrate(Ⅵ). This process applies anodic oxidation to degrade oilfield wastewater pollutants, while simultaneously generating active chlorine from NaCl in the electrolyte. Ferrate(Ⅵ) is produced by utilizing the oxidizing properties of the active chlorine species in the presence of ferric ions, which are added after the electrolysis. The advantages of this method include (i) the relatively short electrolysis time required, (ii) the use of low current density conditions to produce active chlorine substances, and (iii) the formation of ferric hydroxide colloids, which can enhance the degradation of petroleum wastewater. The residual active chlorine in the system is used to synthesize ferrate(Ⅵ), which can help recycle waste. Specifically, the system achieves 89.4 % TOC reduction after 50 min of electrolysis with a current intensity of 1 A. Under the optimal dosage conditions (NaOH = 10 g·L−1, Fe(NO3)3 = 10 g·L−1), the concentration of ferrate(Ⅵ) produced after three hours of reaction is 1.08 mmol·L−1. The strategy described in this article demonstrates high efficiency towards removing organic pollutants in oilfield wastewater, and provides a waste resource recycling strategy.

Numerical analysis of flow field and separation characteristics in an oilfield sewage separation device

A novel oilfield high-oil-recovery water injection treatment device, the hydrocyclone oil removal device, was developed to treat oilfield sewage in the oil phase. It addresses the problems of high oil content in oilfield sewage, direct discharge of contaminants to the environment, and reduction of formation water absorption capacity by reinjection formation. An experimental verification and numerical simulation of the device were carried out to analyze its mechanism and influencing factors. An analysis of the flow path, phase distribution, velocity distribution, and pressure distribution of oil and water revealed the oil removal mechanism of the hydrocyclone oil removal device: automatic separation of oil and water could be realized by using the physical properties of the fluid, the special structure of the equipment, and the appropriate operating parameters. The influence of the inlet oil concentration, flow, pressure, and oil droplet size on the separation efficiency was investigated. The inlet flow, pressure, and the oil droplet size were found to be directly proportional to the separation efficiency, and the oil concentration was found to be inversely proportional to the separation efficiency. These results could further the efficient application of the high-oil-recovery water injection treatment device. The research results also have important engineering value for the efficient treatment and recycling of oil and gas field wastewater.

A reusable Fe3O4/GO-COOH nanoadsorbent for Ca2+ and Cu2+ removal from oilfield wastewater

Oilfield wastewater contains a large number of metal ions (such as Ca2+ and Cu2+). Reinjection in oil wells without treatment would affect oil recovery. To remove Ca2+ and Cu2+ ions, we prepared a reusable Fe3O4/GO-COOH nanoadsorbent by the magnetization and carboxylation of graphene oxide (GO). The Ca2+ and Cu2+ removal percents of the nanoadsorbent reached 78.4% and 51% at 60 min, respectively. After five adsorption/desorption cycles, the nanoadsorbent retained high recovery rates (82.1% for Ca2+ and 91.8% for Cu2+) and removal percents (72.3% for Ca2+ and 49.33% for Cu2+). In the simulated indoor oil recovery test, oilfield wastewater treated with Fe3O4/GO-COOH could enhance oil recovery (EOR) by 11.0% compared with untreated oilfield wastewater. The novel magnetic nanoadsorbent could not only adsorb metal ions in oilfield wastewater effectively to enhance oil recovery (EOR) but could also be quickly recycled and reused, which shows promising application prospects in oil exploitation.

Oxidation of sulfur ions in oilfield wastewater by montmorillonite loaded Mn catalyzed hydrogen peroxide oxidation

Oxidation of sulfur ions in oilfield wastewater by montmorillonite loaded Mn catalyzed hydrogen peroxide oxidation

Formation and treatment features of oil-fields waste water

The oil-fields development and operation can be associated with high water consumption and waste water emission. Most of the pollutants come from drilling and formation waters. At the same time, a significant proportion of solid dispersed pollutants is accounted for drilling waste water. Formation waters are the main source of oil contaminants. The technological processes of oil-field waste water treatment are based on gravity separation. In the context of increasing the environmental requirements for production activities, especially in the regions with low average annual temperatures and, accordingly, slow processes of ecosystems’ self-cleaning, the problem of environment reliable protection arises. Gravity separation methods cannot provide the required quality of waste water treatment. Modern achievements in the field of baromembrane technologies and high salinity of waste water make it most effective and expedient to use membrane and electrochemical methods of waste water treatment.

Catalytic Ozonation with Activated Carbon for Degradation of Polyacrylamide in Wastewater

With the development of tertiary oil, the technology of polymer oil displacement has been widely used. The treatment of the oilfield wastewater become harder, owing to the extensive use of the polyacrylamide (PAM) in oil displacement. This experiment explored the modified activated carbon surface properties on the removal rate of PAM, under the conditions of the temperature 50 °C, the ozone concentration 5 L/min, the reaction time 1 h . The activated carbon(AC) was modified by copper, iron, nitrogen-containing compound. And the turbidity method was used to analyze the PAM concentration. The experimental results showed that the best modifier was ethylenediamine, which had less nitrogen; the optimum modification conditions of cupric nitrate were the calcination temperature 500 °C, maceration 15 mL; the optimum modification conditions of iron nitrate were the calcination temperature 550 °C, maceration 20 mL.

Corrosion inhibition of triazines in sulfur-containing oilfield wastewater

Corrosion inhibition of triazines in sulfur-containing oilfield wastewater

Efficient Treatment and Microbial Community Variation of High-Salinity Oilfield Wastewater Using Combined Biochemistry Technology and Constructed Wetland

Efficient Treatment and Microbial Community Variation of High-Salinity Oilfield Wastewater Using Combined Biochemistry Technology and Constructed Wetland

Efficient Pollutants Removal and Microbial Flexibility Under High-Salt Gradient of an Oilfield Wastewater Treatment System

Efficient Pollutants Removal and Microbial Flexibility Under High-Salt Gradient of an Oilfield Wastewater Treatment System

Study on hydrodynamic characteristics and backwashing efficiency of three types turbines of axial dynamic backwashing technology for oilfield wastewater filter

Study on hydrodynamic characteristics and backwashing efficiency of three types turbines of axial dynamic backwashing technology for oilfield wastewater filter

Oilfield wastewater treatment

Installations for the treatment of oilfield wastewater have been developed. The article presents a solution of hydrocyclone installations for the treatment of oilfield wastewater based on the use of swirling flows. Due to the centrifugal forces in the hydrocyclone and the turbulent movement of water, the armor shells of oil droplets are destroyed, they are enlarged, and the monodispersity increases. The forces acting in the hydrocyclone are considered, and the efficiency of centrifugal forces in separating solid particles is estimated. The main parameters and requirements for the quality of oilfield wastewater are given, recommended for calculation in the development of new and improving existing oilfield wastewater treatment plants for oil reservoir flooding, which allows increasing oil recovery by 1,5-2 times. Improving the systems of field preparation of products includes both the development of new effective technical means, including hydrocyclones, and the improvement of traditionally used equipment. Gidrocyclone can be used as the main element in the wastewater treatment system, provided that the regime is observed, in which there is no over-dispersion of the remaining oil in the water, (water in oil). Thus, the device implements a mechanism for separating light (oil, gas) and heavier fractions (sediment, water, oil). To protect the environment from reservoir water pollution, the following measures are necessary: ensuring deep treatment of oilfield wastewater; extensive use of anti-corrosion coatings and chemical reagents for corrosion protection of oil-producing equipment; full use of waste water obtained in the field in the reservoir pressure maintenance system; monitoring of the state of surface water and the quality of waste water used in the reservoir pressure maintenance system.

Heterogeneous degradation of oil field additives by Cu(II) complex‐activated persulfate oxidation

AbstractIn this work, bentonite‐supported Cu(II) complex (B@Cu(II)L) was prepared by a one‐pot method and used as a heterogeneous catalyst for evaluating its catalytic activity in oxidation degradation of hydroxypropyl guar gum (HPGG) in oilfield wastewater. All of the reaction parameters effected degradation efficiency, such as Na2S2O8 concentration, catalyst amount, reaction temperature, and pH value, were investigated in detail. The results showed that the absolute viscosity of HPGG solution can be decreased from 15 to 1.48 mm2/s in presence of 15% Na2S2O8 (mass ratio to HPGG) and 1.5 g/L B@Cu(II)L at 45°C and pH = 10. It was also found that the chemical oxygen demand of HPGG solution catalyzed by B@Cu(II)L decreased from 4,080 to 584 mg/L after 240 min under the optimum experimental conditions. The catalytic activity of supported bivalent copper complexes over bentonite was gradually decreased due to the loss of the active copper.

Removal of Ca2+ and Mg2+ from oilfield wastewater using reusable PEG/Fe3O4/GO-NH2 nanoadsorbents and its efficiency for oil recovery

The high salinity of oilfield-produced water caused by the presence of metal ions, such as Ca2+ and Mg2+, has a significantly adverse effect on oil recovery. It is crucial to remove these metal ions efficiently before the oilfield wastewater is reinjected down into the oil wells. To address this issue, we prepared a PEG/Fe3O4/GO-NH2 nanoadsorbent by aminating GO, incorporating magnetic Fe3O4 nanoparticles and coating with PEG (PEG = poly(ethylene glycol); GO-NH2 = aminated graphene oxide). We investigated the removal ratios of the nanoadsorbent for Ca2+ and Mg2+. The respective removal ratios for Ca2+ and Mg2+ reached 69.8 % and 61.1 % at 10 min, indicating that the nanoadsorbent was capable of efficiently removing Ca2+ and Mg2+. We also evaluated the reusability of the nanoadsorbent by recycling and reusing it 5 times. At the fifth recycling run, the nanoadsorbent retained relatively high reuse rates (79.1 % for Ca2+, 69.5 % for Mg2+) and removal ratios (69.5 % for Ca2+, 64.3 % for Mg2+), suggesting that the nanoadsorbent possessed relatively high reusability. Oilfield wastewater treated with the nanoadsorbent was employed for oil recovery in core displacement experiments. The oil recovery efficiency significantly increased by 11.8 % compared with untreated oilfield wastewater. Therefore, the PEG/Fe3O4/GO-NH2 nanoadsorbent exhibits considerable potential for the treatment of oilfield wastewater to enhance oil recovery.

Study on Reutilization of Pyrolytic Residues of Oily Sludge.

Pyrolytic residues of oily sludge are a kind of hazardous solid waste produced by high-temperature pyrolysis of oily sludge, which still contains a certain amount of mineral oil; improper disposal can cause secondary pollution. In order to reutilize the pyrolytic residues of oily sludge, the pyrolytic carbon in pyrolytic residues is recovered by a combination of physical flotation and chemical separation, and they are used for the treatment of oilfield wastewater and adsorption of oil. The results showed that the purity of the pyrolytic carbon is 95.93%; many pores of different sizes are distributed on the surface, with mainly mesoporous distribution. Specific surface area, pore volume, and average pore diameter reach 454.47 m2/g, 0.61 cm3/g, and 6.91 nm, respectively. Adsorption effect of pyrolytic carbon on COD and oil in oilfield wastewater is better than that of activated carbon at the same condition. With regard to adsorption on diesel and crude oil, the initial instantaneous adsorption rate of pyrolytic carbon is 3.8 times and 1.86 times faster than that of activated carbon, respectively. When pyrolytic carbon reaches saturated adsorption, cumulative adsorption of activated carbon on diesel and crude oil is much lower than that of pyrolytic carbon.

Hierarchical WO3@Cu(OH)2 nanorod arrays grown on copper mesh with superwetting and self-cleaning properties for high-performance oil/water separation

To realize highly efficient oil/water separation of inorganic metallic membranes for potential industrial application, hierarchical WO3@Cu(OH)2 nanorod arrays (NRA) were grown on copper mesh surfaces by combination of facile chemical oxidation and hydrothermal deposition. The WO3@Cu(OH)2 NRA-coated mesh was endowed with superhydrophilic, underwater superoleophobic and photocatalytically-driven self-cleaning functionalities to effectively separate oil and water from kerosene/water mixture, oilfield wastewater, and surfactant-stabilized emulsion. Results demonstrated that the water flux of surfactant-stabilized emulsion was up to 1.29 kL m−2 h−1 and the oil residues in filtrate was about 50 mg L−1. The visible-light-driven self-cleaning ability of the as-fabricated mesh was verified by the restored superwettability upon 80-min irradiation of visible light. Meanwhile, the WO3@Cu(OH)2 NRA coatings on copper mesh surfaces was found to maintain high stability and durability under extreme environment conditions, such as immersion tests in salt, acidic and alkaline solutions, high temperature and mechanical abrasion tests. With the inherent merits of high separation efficiency photocatalytically-activated self-cleaning and high stability, the as-fabricated WO3@Cu(OH)2 NRA-coated copper mesh is a potentially promising type of inorganic membranes for the treatment of oily wastewater in practical industrial fields.

Experimental study on filtration effect of oilfield sewage based on new polyurethane modified materials.

In the process of oilfield wastewater treatment, the polymer-modified materials with special wettability have been recognized by many scholars for their high filtration efficiency and good adsorption effect. In this paper, we used micro-computed tomography scanning and infrared scanning technology to further explore the internal structure and surface chemistry of polyurethane modified materials and then established an experimental platform for the filtration performance of polyurethane modified materials. The change of suspended solids concentration and oil content in the sewage was tested under different filtration rate, filter layer thickness, and water quality. The results showed that the porosity of the filter material and the oil-absorbing material was 65.85% and 56.03% respectively, and the difference in the number of oxygen-containing functional groups on the surface of these two materials indicated different adsorption force for sewage impurities. And the polyurethane modified materials had good filtration performance. Through these experiments, we demonstrated that the quality of water filtrated by the polyurethane modified materials met the requirements of the 'National Comprehensive Wastewater Discharge Standards', and the filtration efficiency for suspended particles and oils in oily sewage was higher than 80%. These materials have important practical significance for the harmless treatment of oily sewage.

Treatment of alkali/surfactant/polymer flooding oilfield wastewater with polytetrafluoroethylene microfiltration membrane: Performance and membrane fouling

Polytetrafluoroethylene (PTFE) membrane has been used in the treatment of actual alkali/surfactant/polymer (ASP) flooding oilfield wastewater. However, limited information is available regarding the mechanisms of membrane fouling. Here, the membrane fouling mechanisms were analyzed by studying the membrane fouling resistance, pore blocking models, interfacial energies of foulant-membrane and foulant-foulant and contribution of major foulant to membrane fouling, which was supplemented by microscopic characterizations. The results showed that the organic foulants (anionic polyacrylamide (APAM) and crude oil) appeared on the fouled membrane. The form of membrane fouling was mainly cake layer, based on the calculation of membrane fouling resistance and the fitting of classical models. Moreover, APAM, which had a higher mass transfer rate and lower energy barrier with the membrane (141.32 kT), produced a “shielding” effect on crude oil fouling on the hydrophobic PTFE membrane, showing that PTFE membrane has great potential in ASP wastewater treatment. Additionally, the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory verified that membrane fouling at the early stage of the microfiltration process was more serious than the later stage, resulting in the TMP reaching 50 kPa in a short time. This finding could be useful for mitigating membrane fouling and optimizing cleaning methods.