Oilfield Sewage Research Articles

Ordered mesoporous hairbrush-like nanocarbon assembled microfibers for solid-phase microextraction of benzene series in oilfield sewage.

The development of advanced functional nanomaterials for solid-phase microextraction (SPME) remains an imperative aspect of sample pretreatment. Herein, we introduce a novel SPME fiber consisting of graphene fibers modified with ordered mesoporous carbon nanotubes arrays (CNTAs) tailored for the determination of benzene series in oilfield wastewater, which is synthesized by an ionic liquid-assisted wet spinning process of graphene nanosheets, followed by a precisely controlled growth of metal-organic framework and subsequent pyrolysis treatment. The resulting robust microfiber structure resembles a "hairbrush" configuration, with a crumpled graphene fiber "stem" and high-order mesoporous CNTAs "hairs". This unique architecture significantly enhances the SPME capacity, as validated by gas chromatography-mass spectrometry. The hairbrush-like nanocarbon assembled microfibers possess structural characteristics, a high specific surface area, and numerous binding sites, offering efficient enrichment of benzene series compounds in oilfield wastewater, including benzene, ethylbenzene, m-xylene, p-xylene, and toluene. Our analysis demonstrates that these microfibers exhibit broad linear ranges (0.2-600μg L-1), low detection limits (0.005-0.03mg L-1), and excellent repeatability (3.2-5.5% for one fiber, 2.1-6.7% for fiber-to-fiber)for detection. When compared to commercial alternatives, these hairbrush-like nanocarbon-assembled microfibers exhibit significantly enhanced extraction efficiency for benzene series compounds.

Preparation of inorganic–organic composite coagulant and its mechanism in destroying emulsified oil in oilfield sewage

The complexity of oily sewage from oilfields has risen with the advancement of polymer flooding technology, thereby increasing the treatment challenge. In this study, a composite coagulant, PVPAM-PPFS, was proposed, inspired by octopus tentacles, with PVP as the backbone. FTIR, 1H NMR and Rg radius of gyration were used to characterize the functional groups and conformation of PVPAM-PPFS in aqueous environments. The composite coagulant exhibits facile dispersion in water. Upon hydrolysis of PVPAM-PPFS, numerous molecular chains resembling octopus tentacles are formed and confirmed through Atomic Force Microscopy (AFM). When applied to oily sewage in oilfields, PVPAM-PPFS demonstrates enhanced interaction with emulsified oil layers, capturing colloidal particles in water and thereby facilitating efficient separation of oil, water, and flocs. Lastly, the mechanism of PVPAM-PPFS was analyzed through a combination of coagulation experiments and detection of floc morphology. PVPAM-PPFS will better interact with colloidal particles in water through increased charge neutralization, bridging adsorption, and sweeping capabilities. Significantly, an enhanced crude oil recovery rate is observed from the recovered oil droplets following the disruption of the emulsion layer.

Oily wastewater treatment and reuse technology in low permeability oilfield

This paper takes Ordos Huaqing ultra-low permeability oilfield as the research object, analyzes the composition of the produced oily wastewater, and uses the treatment process of multiphase air flotation to shell filtration to quartz sand filtration to multi-effect evaporation to reuse the oily wastewater in the oilfield, analyzes the index changes of the purified oily wastewater. The results show that it has high oil content, salinity, sulfide, SS, sulfide and iron and manganese content. Through experimental combination and analysis of effluent quality, it is concluded that the process of multiphase air flotation→shell filtration→sand filtration→low temperature multi-effect evaporation is better, The average salinity of sewage in Huaqing oilfield used in the experiment is 2757 mg/L. and the dosage of polyaluminum chloride is 230 mg/L, polyacrylamide is 6 mg/L, the dissolved gas pressure of multiphase air flotation machine is 0.5 MPa, the reflux ratio of multiphase air flotation machine is 0.3, the dosage of defoamer is 5 mg/L, and the pH value is set at 5.5. The best treatment process of oilfield sewage and the best concentration of polyaluminum chloride and polyacrylamide are obtained. The research results provide theoretical data support for improving the treatment and reuse of oily wastewater in low permeability oilfield.

Preparation of inorganic nanocomposite coagulant and its application in oilfield sewage treatment

Carbon nanotubes (CNTs), as a new type of carbon material with complete molecular structure, have great application potential in the field of nanocomposites. In this study, carbon nanotubes were first surface modified to give them good hydrophilicity. Subsequently, the nanocomposite coagulant (PASS-T) with different modified CNTs (m-CNTs) contents was prepared by alkaline titration method. The CNT, m-CNT, PASS and PASS-T were characterized by FTIR, XRD and XRF. Then the coagulant was applied to oily sewage, and the coagulation results showed that the PASS-T (0.1%) had the best oil reduction rate (92%) and turbidity reduction rate (97%). Appropriate addition of m-CNT can increase the local concentration of coagulant at the molecular level, making the flocs of oily sewage larger. It can be found by SEM that PASS-T produces large and knotted flocs in oily sewage. Finally, the residual turbidity and oil removal rate of the different coagulants were statistically analyzed.

Preparation of a cationic block copolymer composite coagulant TP(AM-DAC-PPFS) and its coagulation performance for treating oilfield sewage

Efficient purification of oily sewage, recycling, and standard discharge have become key issues for the sustainable development of oil fields. In this study, the surface of PPFS was organically modified by a silane coupling agent. Then, covalently bonded cationic block inorganic-organic composite coagulant was prepared by chosen sodium polyacrylate as the template. This unique structure significantly enhances the positive charge and molecular chain length of the coagulant, thus improving its ability to perform charge neutralisation, adsorption bridging, and sweep coagulation. The characteristic functional groups and thermophysical properties of the composite coagulant were analysed by FTIR and thermogravimetric analysis. The transformation of random copolymers to block copolymers was determined by 1 H NMR, thus confirming the successful synthesis of the cationic block structures. The turbidity removal and oil removal properties of oily sewage were investigated by coagulation experiment. The Zeta potential, dynamic and static light scattering, and field emission scanning electron microscopy (SEM) were used to study the effect of composite coagulants on the microscopic morphology and coagulation of flocs. Finally, the coagulation mechanism of the compound coagulant was analyzed with the dynamic change of the particle size of the flocs. The cationic block structure in TP(AM-DAC-PPFS) can effectively neutralise the negative charges on the surface of impurity particles and emulsified oil. The optimal dosage of TP(AM-DAC-PPFS) was 30 mg·L−1, at which the turbidity and oil removal rates can reach 98.3% and 93.8%, respectively.

Effect of Sulfate-Reducing Bacteria on the Production of Iron Sulfides

Using Fourier transform infrared spectroscopy (FTIR) to identify the sulfate-reducing bacteria (SRB) in Daqing Oilfield sewage. The growth curve of SRB and the adsorption ability of extracellular polymeric substances (EPS) to the Fe2+ were combined to explore iron sulfide generation. X-ray diffraction (XRD) results showed that different species of SRB produce iron sulfides, mainly composed of mackinawite. The growth characteristics of SRB affected the formation of iron sulfides and had a negative charge. Various SRB growth trends were different. The growth of the bacterium in an exponential phase or log phase can be described by the greater concentration of inoculation. And smooth growth trends were contributed to the formation of FeS. At the same time, sulfur-rich, like FeS2, was easily formed when S2− (or S2 2−) played a major role compared with the protein and polysaccharide functional groups in the negatively charged EPS at the process of Fe2+ adsorption.

Effect of hydrophobically associating polymeric aluminum-polymer dual coagulant on coagulation of oily sewage from oilfields

Whether the oilfield sewage index can reach the reinjection specification is a crucial issue that is urgently need to be solved in polymer flooding systems. Thus the coagulability and floc morphology development of dual coagulants was systematically studied in different pH oily wastewaters. Acidification improved the deprotonation ability of coagulant. Hydrophobic associative polyaluminum silicate-poly dimethyl diallyl ammonium chloride (PASSC-PD) resolved the problem of excessive acid addition. The dual coagulants prepared not only preserved the high charge density of polyaluminum silicate (PASS) itself but also made it have the hydrophobic association and strong bridging ability. Besides, PASSC-PD was compared with hydrophobic associative polyaluminum silicate (PASS-C), PASS, and poly dimethyl diallyl ammonium chloride (PDMDAAC) pertaining to the polymer flooding oily sewage of Daqing Oilfield. The coagulation result demonstrated that PASSC-PD exhibited more advantageous turbidity and oil removal efficiencies than PASS-C, PASS, and PDMDAAC. The floc morphology result showed that adding dual coagulant made the petal-like floc of oily sewage larger at the pH value of 6. Furthermore relevant results evidenced that the coagulant had more successful fruits of turbidity removal of 96.5% and oil removal of 96.3% under weak acid conditions. These can satisfy the reinjection condition of oily sewage.

Synthesis of antibacterial polyaluminium silicate sulfate /sepiolitenano composite coagulant for oilfield sewage treatment

The utilization of a large amount of anionic polyacrylamide (APAM) and sodium alkyl benzene sulfonate can induce the emulsified oil to acquire a stable emulsified colloid system in polymer flooding oily wastewater. However, for the traditional inorganic coagulants, such as polyaluminum, polyiron, etc., a relatively large number of bacteria will breed after oily sewage is treated for a specific period of time. Along these lines, in work, a new type of antibacterial polymeric aluminum silicate sulfate/sepiolite coagulant (PASS-H) was synthesized by using grafting hydrophobic antibacterial monomers in combination with coagulants composed of sepiolite as the base material for improving oily sewage purification. The structure and the surface morphology of the copolymer were systematically characterized, indicating that PASS-H was successfully synthesized. In addition, the coagulation performance of the polyaluminum silicate sulfate (PASS), modified sepiolite, and PASS-H during the treatment of polymer-containing oily wastewater was compared. In the coagulation experiments, PASS-H exhibited excellent turbidity, oil removal, and antibacterial properties. At 60 mg/L, the turbidity, oil removal rate, Zeta potentialand maximum floc size were 98%, 95%, 1.59 mv, and 26 μm, respectively. The mechanism of coagulation was thoroughly investigated based on the order of dosing, the tested water pH, Zeta potential, floc size, and the impact of the floc morphology on the coagulation. The coagulation behavior of the separate addition of the modified sepiolite and PASS was weaker than that induced by the one-time addition of PASS-H. Moreover, the enhanced charge neutralization, bridging adsorption, sweeping, and adsorption played a synergistic role in reducing the total amount of PASS-H and improving the coagulation ability. The introduction of antimicrobial monomers in PASS-H can also effectively inhibit the regeneration of sulfate-reducing bacteria (SRB) in the water. Finally, the residual turbidity and oil removal rate of the different coagulants were statistically analyzed. The extracted results have practical significance for both cost reduction and efficiency increase in large-scale applications.

Integration of a novel distributed water and energy system in the oilfield

The oil production process in union stations requires consuming a lot of energy, and sewage at high temperature will be produced simultaneously. Realizing the benefits of energy saving that waste heat utilization can bring to the oil field, this article first describes a novel integrated water separation and treatment process (IWSTP) with energy-saving effects. Based on the integrated process, the oilfield distributed heat station system is a good choice for utilizing waste heat from sewage. The heat pump is also considered as indispensable equipment for recovering the low-temperature waste heat of oilfield sewage. Next, a mixed integer linear programming model considering energy and technical constraints is developed to optimize the oilfield water treatment process to minimize annual total cost, which determines the selection and capacity of the required equipment. Taking an oilfield in China as an example, the validity and applicability of this model are demonstrated. The results show that the optimized scheme saves 14.08% of the economic cost compared with the traditional energy supply scheme. Finally, the impact of energy price fluctuation on the design results is analyzed.

Application of Oilfield Sewage Treatment Technology in Water Injection Technology

Application of Oilfield Sewage Treatment Technology in Water Injection Technology

Magnetic Hyperbranched Molecular Materials for Treatment of Oily Sewage Containing Polymer in Oilfield Compound Flooding.

With the continuous improvement in oilfield development and the application of tertiary oil recovery technology, the water content of oilfield-produced fluids has gradually increased, and a large number of oilfield sewage with complex components has also been produced after oil–water separation, and effective treatment is urgently needed. ASP flooding sewage contains alkali, various surfactants, polymers, microemulsion oil droplets, and solid impurities, which are difficult to be effectively treated by traditional water treatment agents and methods. In this study, aminopropyl triethoxysilane (APTES) was used to modify the nano-Fe3O4 coated with tetraethyl silicate (TEOS). The product was used as the ferromagnetic nano-core for the iterative reaction of Michael addition and ester amidation to synthesize a magnetic hyperbranched polyamide amine, and its performance in the treatment of ASP flooding wastewater was evaluated experimentally. For the preparation of APTES-modified Fe3O4@SiO2 (FOSN) product, TEOS was coated over Fe3O4 in an ethanol aqueous solution environment and then APTES was added dropwise. The first-generation branched product (1-FSMN) was obtained by the reaction of FOSN and methyl acrylate graft product (FOSN-M) with ethylenediamine, and the highest yield was 93.7%. The highest yield of the second-generation branched product (2-FSMN) was 91.6%. In this study, a composite flooding wastewater sample from a block in the Bohai oilfield was taken. The suspended solids content was 143 mg/L, the oil content was 921.09 mg/L, the turbidity was 135 NTU, and the zeta potential was −47 mV. The third-generation hyperbranched polymer (3-FSMN) and its quaternary ammonium salt (3-FSMN-Q) performed best in the appropriate dosage range, with the highest oil removal rate of 97%, suspended solid removal rate of 90.3%, turbidity reduction rate of 86.6% and zeta potential reduction rate of 88%. For 3-FSMN and its quaternary ammonium salt, the gravity/magnetic PAC compound treatment experiment was carried out. In the settlement time of only 5 min, 3-FSMN/PAC and 3-FSMN-Q/PAC can achieve the maximum oil removal rate of 87.1% and suspended solids removal rate of 87.3% for polymer containing wastewater from ASP flooding, and 86.3 and 86.0% for 120 mg/L. Its treatment capacity was much better than that of common treatment agent combination (CPAM/PAC).

Evaluation of the self-assembled functional PPFS-P-AM composite for treating oilfield sewage

Oilfield sewage has a complex composition with large amounts of emulsified oils, polymers and surfactants. Efficient coagulants are required to purify such sewage to meet emissions standards. In this study, oxidized FeSO4·7H2O and NaHCO3were condensed by basic titration and polyferric sulfate phosphate (PPFS) was prepared by the addition of NaH2PO4·2H2O to improve its charge and stability. In addition, by adding modified palygorskite and cationic amylum, a functional polyferric sulfate phosphate, palygorskite and cationic amylum copolymer (PPFS-P-AM) composite coagulant was synthesized through self-assembly, and then used to treat oilfield sewage. The characteristic functional groups and crystal forms of the coagulant were characterized by FTIR and XRD. The zeta potential and radius of gyration (Rh) indicate that the introduction of palygorskite and cationic amylum enhance the charge neutralization and bridging adsorption abilities, respectively. The optimal dosage of cationic amylum is 5% in 80 mg·L−1 PPFS-P-AM, which provides turbidity and oil removal rates of 98% and 94%, respectively. Observation by SEM shows that the micro-morphology of PPFS-P-AM flocs has adendritic distribution with a reticular macromolecular structure that provides good sweeping performance during the sedimentation process. Finally, an analysis of its properties and performance reveals the mechanism by which PPFS-P-AM coagulates oilfield sewage. PPFS-P-AM provides better coagulation than the other studied coagulants via the synergistic effects of reinforced charge neutralization, bridging adsorption and sweeping.

High-Temperature-Resistant, Low-Concentration Water-Controlling Composite Cross-Linked Polyacrylamide Weak Gel System Prepared from Oilfield Sewage.

The polyacrylamide weak gel is an effective system to block a high-permeability layer, realize water control, and enhance oil recovery. However, its application is limited by poor temperature resistance and high polymer dosage. In this paper, an inorganic–organic composite cross-linking agent was synthesized by using Cr(III) and phenolic resin. The composite cross-linking agent can cross-link low concentrations of polyacrylamide to obtain a high-temperature-resistant weak gel system in oilfield sewage. By adjusting the ratio of Cr(III), phenolic resin, and polyacrylamide, an optimum formula MF-7 can be obtained according to the gel strength. Results from evaluation experiments show that the strength of MF-7 can reach H grade even at polyacrylamide concentrations as low as 0.3%. The temperature resistance of the weak gel system is up to 100 °C, and no syneresis occurs after 330 h at 95 °C. Scanning electron microscopy (SEM) results show that MF-7 has a three-dimensional network structure with spherical nodes. The spherical node is composed of polyacrylamide, and its structure size is completely matched with the hydrodynamic radius of the used polyacrylamide. When combined with the network structure formed by Cr(III), the dense cross-linking network structure with nodes can greatly improve the strength and thermal stability of the gel system. The higher the molecular weight of the polyacrylamide used, the higher the strength of the gel obtained. Overall, the composite cross-linking agent can synergistically improve the mechanical properties of the gel, and this weak gel system formed by oilfield sewage is more economical and tolerant.

Zwitterionic Polymer Hairy Coating onto Mesh toward Easy Oil/Water Separation.

A zwitterionic polymeric hair-coated stainless steel mesh membrane is fabricated, which demonstrates efficient separation of oil/water mixtures and emulsions. The hairy coating of poly(divinylbenzene-co-vinylbenzene chloride) is generated by precipitation cationic polymerization, and subsequently grafting a zwitterionic polymer layer by atom transfer radical polymerization of sulfobetaine methacrylate. The microstructure of the hairy coating is tunable from an array of individual nanofibers to porous networks by interweaving of the hairs. The long-range attraction of zwitterionic polymers with water renders the coated mesh with excellent superhydrophilic and underwater superoleophobic performance. The coated mesh is highly antifouling to avoid the prehydration in conventional methods. Moreover, the microstructure is demonstrated to be responsible for the high separation efficiency of oil/water emulsion. Therefore, separation of oil/water mixtures and emulsions becomes easier by the coated mesh, which is promising in industrial oil field sewage treatment.

Study on rare earth elements, heavy metals and organic contents in the soil of oil exploration site at Matruh Governorate, Egypt

Soil is an issue material for sustainable economic and development plans; besides it considers the most valuable natural resource in all fields of citizens' life. This study is carried out to assess the impacts of heavy metals and some organic constituents on the soil, and consequently on its pollution, in a sampling point left behind the exploration activities in a site subjected to oil and gas exploration nearby Matruh Governorate, Egypt. Moreover, it is trying to evaluate the contents of some added-value rare earth in the same area. Samples were collected from ten points in a bore at different depths starting at 13,000 feet with increasing down distance every 50 feet. The study area is located within latitude 30° 48′ to 36° 889 ̋ S and longitudes 26° 59′ to 16° 406 ̋ E. Geographically, Matruh is part of the Great Western Desert.Rare Earth Elements (REEs), Heavy Metals (HMs) and organic constituents in the soil samples were analyzed based on Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Fourier transform infrared spectroscopy (FT-IR). Geoaccumulation Index (Igeo), Enrichment factor (EF) and Pearson Correlation Coefficients (R) were calculated to consider the soil pollution in the studied point. Also, to evaluate the abundance of REEs and to follow the relations between those elements.The study illustrated that: the most organic soil pollutants in the oil field sewage were aliphatic and aromatic hydrocarbon, phenols, organic sulfide aliphatic acid and others. Based on the geoaccumulation Index (Igeo) and Enrichment Factor (EF) classifications, the soil quality of the studied site can be classified, in general, as class 0, (uncontaminated) to class 6, (extremely contaminated). Moreover, The potentiality of the rare earth should be subjected to intensive studies to decide their economical mining and element processing.

Application of Nanocellulose in Oilfield Chemistry.

The preparation and classification of nanocellulose are briefly introduced, and the modification of nanocellulose and the application of modified nanocellulose in oilfield chemistry are reviewed. The principles and methods of surface modification, including surface adsorption, oxidation, acetylation, silanization, etherification, and polymer grafting, are summarized. Meanwhile, this paper focuses on the application of nanocellulose research progress in drilling fluid, enhanced oil recovery, and oilfield sewage treatment. In addition, the application issues and natural advantages of nanocellulose are analyzed, and suggestions and ideas on how to expand its application are put forward. Finally, the development and potential application of nanocellulose in oilfield chemistry are proposed.

Study on the oxidation treatment of sodium sulfide by sodium persulfate

In view of a large amount of sulfur ions contained in oilfield sewage, finding an efficient method for desulfurization to reduce the sulfide content of sulfide in oilfield sewage has become one of the topics urgently studied by oilfield workers. In this paper, the oxidation method is used to treat sulfur ions in oilfield sewage, and it is oxidized to harmless elemental sulfur or high-priced sulate. The effects of pH, molar ratio, reaction time, temperature and concentration on the removal rate of sulfur ions were investigated. The optimal reaction conditions were determined that the initial concentration of simulated water was 75 mg/L, pH=8, the molar ratio of sodium persulfate and sodium sulfide was 1.2: 1, the reaction time was 30 minutes. The maximum removal rate of sulfur ions by sodium sulfate can reach 96.11% at 35°C.

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.

Simulation Analysis of Sedimentation Separation of Suspended Solids Sewage in Oil Field Based on COMSOL

After oil and water separation, the produced sewage needs to be treated in a series of ways and injected into the ground if it reaches the discharge standard in oilfields. Sedimentation separation is one of the most important process. In order to study the law of settlement, a set of settlement simulation device was set up, and the raw wastewater was extracted from the oil production plant for settlement experiment, and the relevant data were gathered. Comsol software is used to model and analyse the model. Through comparing the calculation results with the experimental data, the velocity and concentration of liquid-solid two-phase medium change rules are concluded, which lays a foundation for further research on efficient treatment of oilfield sewage.

Analysis of Sedimentation Technology for Oilfield Sewage Treatment

Analysis of Sedimentation Technology for Oilfield Sewage Treatment