Offshore oil and gas production is increasingly growing popular globally. Produced water (PW), which is the largest byproduct of oil and gas production, is a complex mixture of dissolved and ...undissolved organic and inorganic substances. PW contributes considerably to oil pollution in the offshore petroleum and gas industry owing to the organic substances, which mainly include hydrocarbons; this is a major concern to researchers because of the long-term adverse effects on the ecosystem. Since the development of offshore petroleum and gas industry, the PW treatment process has been classified into pretreatment, standard-reaching treatment, and advanced purification treatment based on the characteristics of PW and has been coupled with the environmental, economic, and regulatory considerations. The mechanism, design principle, application, and development of conventional technologies for PW treatment, such as gravity and enhanced gravity sedimentation, hydrocyclone, gas flotation, and medium filtration, are summarized in this study. Novel methods for further application, such as tubular separation, combined fibers coalescence, and membrane separation, are also discussed. Enhancement of treatment with multiple physical fields and environmentally friendly chemical agents, coupled with information control technology, would be the preferred PW treatment approach in the future. Moreover, the PW treatment system should be green, efficient, secure, and intelligent to satisfy the large-scale, unmanned, and abyssal exploration of offshore oil and gas production in the future.
Classical offshore gas field platforms with connecting bridges in the South China Sea and the standby ship beside the platforms. Functions of three platforms in the figure are well drilling and workover, gas production, and accommodation of personnel Display omitted
•Produced water (PW) has danger or potential danger to the ocean environment.•Oil and suspend solid removal were two important steps for PW treatment.•PW management is based on fundamental characteristics, regulations and standards.•Intellectualization and automation will be the development trend for this industry.•Physical devices coupled with chemical agents are the realistic treatment process.
Improving the produced fluid yield is an effective measure for realizing the crude oil production capacity of offshore platforms. However, for offshore platforms employed in production, using the ...narrow space of the platform to expand the produced water treatment system is a significant problem. In this study, a highly efficient pre-treatment core tube was coupled with the main cavity and secondary cavities (MCSCs) based on a vane-type tubular separator and a cub-mother cyclone. The optimal inlet Reynolds number and processing capacity were determined according to the structure size of the MCSC, and the MCSC was applied to achieve highly efficient pre-treatment of produced water in a heavy oilfield in the Bohai Sea. The comprehensive evaluation indicators FA and FV were better than those used by current technology. When the influent oil content fluctuated around 2000 mg/L (average of 1772.81 mg/L), the oil content in the effluent was stable and below 200 mg/L (average of 106.44 mg/L), and the separation efficiency was nearly 94%. Compared to those of the current corrugated plate interceptor on the platform, the floor space was reduced by more than 60% and the separation efficiency increased by up to 65%.
As of 2022, China has achieved a crude oil processing capacity of 918 million tons, leading to a notable escalation in the production of refinery wastewater. The composition of refinery wastewater is ...intricate and diverse, posing a substantial challenge to its treatment. In order to facilitate appropriate discharge or reuse, an exhaustive separation process is imperative for refinery wastewater. Conventional pre-treatment processes typically employ inclined plate separators and dissolved air flotation (DAF) for the removal of oil and suspended solids (SS), while sequencing batch reactor (SBR), oxidation ditch, or biological aerated filter (BAF) are employed for the biological treatment process. However, these approaches encounter challenges such as a large spatial footprint, suboptimal treatment efficiency, and high energy consumption. In response to these challenges, this study introduces a novel integrated apparatus consisting of a high-efficiency oil remover (HEOR), coalescence oil remover (COR), and an airlift-enhanced loop bioreactor (AELR). A pilot-scale test was conducted to evaluate the performance of this integrated system in practical field applications. The pilot-scale tests reveal that, without the addition of chemical agents, the petroleum removal efficiency of “HEOR + COR” system was 1.2 times that of DAF. Compared with the SBR system, AELR's volume loading was increased by 1.56 times. The effluent quality achieved in the pilot-scale tests attained parity with that the original process. The “HEOR + COR + AELR” system exhibited energy and carbon emissions reduction of 28% and 30% compared to the “DAF + SBR” system, respectively. Therefore, the operating costs was reduced by approximate 1 Chinese Yuan (CNY) per ton of treated water. This technological advancement serves as a valuable reference for the implementation of low-carbon treatment of refinery wastewater.
•"CHEOR + COR + AELR" system is introduced for pollutant removal.•The new system reduces costs by 1 CNY/t compared to "DAF + SBR".•The carbon emissions of the new system is just 70% of "DAF + SBR".
Oil pollution from produced water in the offshore petroleum industry is one of the most serious marine pollutants worldwide, and efficient separation technology is crucial for the control of oil ...pollutant emission. Medium coalescence is an efficient oil-water separation technology, but its theory is lacking and the development is slow. In this work, the microscopic mechanism of fiber coalescence was revealed, and found that the effective collision positions were the three-phase contact line and the exposed fiber surface. Further, a theoretical model for calculating the separation performance of a fiber bed was established. For a given inlet droplet size distribution and bed geometric parameters, the outlet droplet size distribution and the total separation efficiency of the fiber bed can be predicted. Then, an Ω-shaped woven method composed of oil-wet fibers and oil-phobic fibers was designed and the separation performance of the fiber beds prepared by the method and the influence law of various parameters were clarified through macroscopic experiment. Finally, the novel technology achieved its first engineering application on an offshore platform, with the average oil content of the outlet was less than 25 mg/L, which could reform the current treatment process of produced water.
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•Effective collisions occur on three-phase contact line and exposed fiber surface.•Fusion by precursor film on oil-wet fiber but by liquid bridge on oil-phobic fiber.•A new theoretical model for predicting separation performance of a fiber bed.•The Ω woven structure combining oil-wet fibers and oil-phobic fibers.•Successfully applied to the deep purification of offshore oily wastewater.
Offshore oil production, which is a significant source of petroleum, has recently caused extensive concern. Produced water (PW) is the highest-volume byproduct of oil and gas production. The organic ...pollutants dominated by hydrocarbons, namely oil, in PW are the major concerns to researchers because of the adverse effects to the marine ecosystem. In industrial processes, the oil is needed to be separated by individual or cooperative use of separation technologies, such as gravity settlement, enhanced gravity settlement, and hydrocyclones. However, these conventional technologies cannot reach the separation requirements in a compact space under extreme conditions, such as emulsification and large volumes of PW. To improve the treatment efficiency, decrease the occupation of space, the practical use of a full-scale PW treatment process was proposed and investigated in the Bohai Sea, China. The oil content of PW after treatment with the full-scale process was less than 20 mg·L-1, alongside a reduction in the chemical dosage concentration (over 40% and 60% for reverse demulsifier and water clarifier, respectively) compared with the conventional process. Besides, an increase in the amount of produced liquid and PW of over 50% and 40% was achieved, respectively, generating a 30000 m3·a-1 growth in oil production in this single wellhead platform. The organic compounds and relative concentrations of these compounds were analyzed in this full-scale practical application. Hydrocarbons were the major organic pollutants in PW. Approximately 100 kinds of organic compounds that were detected in the influent of the process were reduced to 8 in the effluent with a separation efficiency over 90%, which made the PW cleaner to the marine environment. The simultaneous separation of alkanes and slightly soluble organics in PW can be explained by rotation and internal circulation, which provides a possible mechanism by which slightly soluble materials in major phase could be transferred from major phase to dispersed phased, in which the materials have a significantly higher solubility. This study provided an attractive strategy to answer the ecological menace caused by the hydrocarbon exploitation in offshore oilfields, to the benefit of both the economy and the environment.
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•An industrial full-scale practice of an offshore platform was investigated.•Organic characteristics of PW were systematically analyzed.•Organic pollutants in PW were dominated by hydrocarbons.•Alkanes and soluble organics can be separated simultaneously.
The development of an efficient and sustainable separation method for oily wastewater has become a major challenge for industrial development and environmental protection. In this work, the simple ...special wettability particle preparation method and the hybrid filters construction strategy was reported for enhanced oil/water separation efficiency. Two special wettability quartz sands mixed in a certain proportion could destroy the balance of dispersed droplets in the oil-water emulsion, induce the coalescence of dispersed droplets, and purify the oil-water emulsion by the tortuous channel in the filter. Based on the coupling effect of “size sieving” and “coalescence separation”, the special wettability particle hybrid filter with a mass ratio of 3:1 had good droplet coalescence ability, and the separation efficiency of various kinds of oil-water emulsions can reached more than 98%. The hybrid filters exhibited robust mechanical and chemical stability, excellent durability, which enable them to be competent for oil/water separation in multitasking and complex environment.
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•The superhydrophilic and superhydrophobic quartz sands hybrid filter was reported.•The screening and coalescence mechanism were used to achieve rapid demulsification.•The hybrid filter possesses excellent oil/water separation efficiency (＞98%).
•A novel type of static micromixer is designed by experiment and CFD simulation.•Coupled ejector and swirl shear mixer.•The mixing effect of the novel static micromixer is better.•The novel static ...mixer is expected to replace the dynamic high shear mixer.
The development of high-performance static mixers is a critical research topic in process intensification in the process industry. This research combines computational fluid dynamics simulation and experimental testing to design a new type of static micromixer: First, a variable-diameter swirl shear mixer was designed and its structure was optimized. Measured by Malvern laser particle size analyzer, the median particle size decreased from 41 μm to 29 μm in the designed micromixer compared to that of traditional static mixers. Subsequently, the dispersed phase injection method was upgraded to a jet injection method, and the static micromixer was designed with a combination of an ejector and a variable-diameter swirl shear mixer. The median particle size of the dispersed droplets further decreased to 23 μm, achieving a dispersion effect at 2100−2400 rpm of the dynamic high-shear mixer. The micromixer greatly improved the static mixing effect and may replace dynamic high-shear mixers in the future.
The treatment of electric desalting wastewater with a high oil content and strong emulsification is one of the most difficult problems in refineries. An industrial pilot study was carried out using ...swirling flotation coupled with medium coalescence. The self-adaptive structure was designed for swirling flotation and the coalescence medium was a combination of fibers and granules. The effects of the flow rate, gas injection mode, gas flow rate, and the depth of the medium bed on the separation performance were investigated. Under optimum operating conditions, when the inlet oil content is 400–2500 mg/L, the oil removal efficiency of the swirling flotation is 90% and the total oil removal efficiency is up to 98.63%. The oil content, suspended solids content, and chemical oxygen demand (COD) of the effluent can be stabilized below 30 mg/L, 15 mg/L, and 700 mg/L, respectively, which meets the requirements for discharge to a downstream treatment plant. This study provides a new technical idea for the treatment of electric desalting wastewater with the advantages of a high operation elasticity, a rapid treatment process, and a high efficiency.
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•The characteristics of EDW in refineries were comprehensively investigated.•A technique of using swirling flotation coupled with medium coalescence was proposed.•The optimal operating parameters for the technique were optimized by an industrial pilot.•The study provides a new technical concept for treatment of EDW with high efficiency.
Refinery wastewater is not only large in volume but also complex in composition. It requires multi-stage treatment to achieve discharge or reuse targets. Pretreatment plays an important role as a ...front-end treatment. In conventional pretreatment technologies, petroleum removal and suspension removal are carried out through inclined plate settlement combined with two-stage air flotation. This poses problems such as high energy and chemical consumption and large outputs of hazardous waste. In this study, a short-process physical pretreatment technology is designed in conjunction with combined fiber coalescer (CFC) and granular media filter (GMF). The results of the pilot test show that with no added chemicals, the treated refinery wastewater is clear and translucent, and the petroleum and suspended solids content could be reduced to less than 20 mg/L, which falls within the acceptable range of the biochemical influent index. This process could greatly reduce the generation and emission of scum and volatile organic compounds (VOCs) and provides a new technique for the low-carbon pretreatment of refinery wastewater.
•Refinery wastewater could be treated by media coalescence.•Media coalescence could replace inclined plate and two-stage air flotation.•The treatment effect of media coalescence is more stable.•Media coalescence is more efficient, economical and environmentally friendly.
Produced water (PW) of the liquid phase is the largest volume by-product from the process of offshore oil and gas production, and compact and efficient treatment methods are brought into focus. The ...PW, condensate oil, and floccule in the liquid phase all require treatment to satisfy the requirements of the standards. The liquid phase volume from offshore gas fields is typically not as large as that from offshore oil fields. The presence of the floccule and severity of emulsification, however, cause higher levels of treatment difficulty. Ecological damage to the ocean and some other potential hazards can be caused if PW discharged into the ocean contains oil that exceeds the concentrations of the value, of which ranges from 15 mg/L to 50 mg/L according to different standards. Condensate oil phase pipes may also be corroded if the oil phase is not well treated. This study examines a pilot system with the capacity of 0.5 m3/h, that includes pre-, PW, and condensate oil treatments performed at an industrial offshore gas field platform on the South China Sea. The water and oil phases were transparent in appearance. The concentration of oil in the PW discharged to the ocean was less than 50% of the value of the relative standards. The concentration of water in the condensate oil was lower than 200 mg/L, which satisfied the requirement of this platform for transportation by submarine pipelines. The accumulative floccule in the liquid phase was also gathered using a filter bag that proceeded a virtuous circle due to the avoidance of the accumulation of the floccule. This pilot system provides a novel solution method for the liquid phase from offshore gas fields containing highly emulsified PW, condensate oil, and floccule, which diffuses between the PW and the condensate oil.
•A pilot system for liquid phase on an offshore platform was investigated.•Separability was determined by size and Zeta potential distribution.•Oil content in PW was 50% lower than the value in relevant standard.
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