Produced Water Samples Research Articles

Microbial Diversity of the Produced Waters from the Oilfields in the Republic of Tatarstan (Russian Federation): Participation in Biocorrosion

A variety of microorganisms grow in oil reservoirs, where they participate in the biodegradation of oil and lead to changes in oil quality. Today, our knowledge about microbial processes in oil reservoirs is largely limited, and among the urgent tasks for the oil industry, monitoring and controlling microbial activity (including the activity of microbes responsible for biocorrosion) are important. In this work, we aimed to characterize the bacterial community structure of the produced waters from oilfields in the south of the Republic of Tatarstan (Russian Federation) using cultural and molecular methods of analysis. Bacteria from produced water samples from various oil wells were enriched, and 16S rRNA gene amplicon sequencing was used to assess the phylogenetic diversity of the bacterial communities. Thus, analysis of the bacterial communities revealed the presence of various members within the genera Desulfotomaculum, Clostridium, Acetobacterium, Desulfovibrio, Dethiosulfovibrio, Desulfomicrobium, Fusibacter, Dethiosulfatibacter, Thermovirga, Sphaerochaeta, and Desulfoplanes, but in different produced water samples. The role of the bacterial associations in biocorrosion was separately assessed in experiments on monitoring and stimulating biocorrosion. The bacterial community receiving additional nutrition was shown to have a higher corrosion potential, and scanning electron microscopy analysis confirmed changes in the surface of the metal coupons during immersion testing. The practical value of this research lies in identifying the potential contribution of microbial communities to oil pipeline corrosion.

Application of Ultra Fine Bubbles for Deoxygenation of Produced Water and Tap Water via Nitrogen Purging Scheme

In this study, we present our findings from examining a gas lift tower for produced and tap water de-oxygenation, applying the nitrogen purging at an ultra-fine bubble scale (18 μm average size). The experiments were conducted for produced water samples grafted with polyacrylamide concentration 300 ppm with a measured bulk viscosity of 5 mPa.s. Upon applying a series of experimental sets, 0 ppm DO was attained in all examined operational schemes (semi batch and once through) within various time limits, depending on the water level in the column. Considering the zero DO level as an objective function, the results showed an improvement of 5.7–14 folds in reaching the 0 ppm DO upon experimenting with the ultra-fine bubble purging in different schemes, compared with of the results obtained from the ordinary bubble size (mm scale). The results show that DO reached < 10 ppb within 23 minutes with nitrogen flowrate 3 L/min while DO reaching < 10 ppb within 28 minutes with nitrogen flowrate 5 L/min. Furthermore, implementing the ultra-fine bubble nitrogen purging was successful in running the de-oxygenation tower in a full continuous mode at a balanced inlet/outlet water flow rate. This has been done after reaching stability in the column operation (lasting around 1 hour for 422 L of examined water sample). The stable fine bubbles cloud in the column was quite efficient in treating water influent stream to be exited directly at 0 ppm DO within the same effluent flow rate. The treatment efficiency has shown an increase with increasing water level in the column, resulting in a denser layer/cloud of fine bubbles. This result suggests a unique approach/solution for the complete removal of DO from produced water, which is accounted effective to be adopted industrially

Classification of produced water samples using class-oriented chemometrics and comprehensive two-dimensional gas chromatography coupled to mass spectrometry

Produced water (PW) is a type of wastewater that arises during oil and gas production. Due to its potential environmental impact, PW is one of the most closely monitored forms of wastewater in the petroleum industry. The total oil and grease (TOG) content in the water is a crucial parameter for assessing the environmental impact of PW. Traditional methods for analyzing TOG in PW can be time-consuming and may not be compatible with green chemistry principles. In this study, an alternative method for classifying PW samples is proposed using a one-class classifier (OCC) model, which has proven useful for classification problems. To achieve this goal, headspace solid-phase microextraction (HS-SPME) combined with comprehensive two-dimensional gas chromatography (GC×GC) were employed to obtain TOG profiles from PW. A series of simulated PW samples containing TOG were generated using a mixture design comprising four petrochemicals at concentrations ranging from 10 mg L-1 to 50 mg L-1. The polydimethylsiloxane (PDMS) fiber showed the most representative extraction of analytes. The optimization of the HS-SPME method was performed using a Doehlert design with two variables, and the final conditions were set at 80 °C and 70 min for extraction temperature and time, respectively. A pixel-based data approach was used to implement data-driven soft independent modeling by class analogy (DD-SIMCA). Although DD-SIMCA is a developing area in GC×GC studies, the proposed model produced outstanding results with a sensitivity of 94.3 %, specificity of 95.0 %, and accuracy of 94.5 %, considering the complex and broad compositional range of the modeled mixtures. These findings demonstrated the effectiveness of the OCC model approach in classifying PW samples according to environmental regulations.

The provenance of microorganisms adapted to extreme salinity, extreme temperature, and toxic metals within the Montney shale formation.

Introduction Shale oil reservoirs are hypothesized to be sterile due to the extremely high temperature, pressure and salinity within these formations (Evans et al. 2018). High concentrations of toxic metals also pose challenges that demand specific microbial adaptions (Boyd and Barkay 2012, White and Gadd 1998, Ben Fekih et al. 2018). While some microorganisms are introduced into and are selected for within shale formations during hydraulic fracturing, the possibility that certain microorganisms are pre-existing inhabitants of these formations is less clear. Here, we followed the microbial diversity of input and output fluids injected into a Montney formation shale reservoir to assess the distribution and transport of microbial populations during hydraulic fracturing. Enrichment cultures distinguished various metabolisms in the microbial populations found in different sample types, and adaptations allowing them to colonize such niches. Material and methods Fracturing fluid, drilling muds (3302 m, 3350 m and 3400 m depths), shale cuttings (rinsed from the drillings muds), shale core plugs and produced water samples (12-month period) were sampled from a Montney shale oil reservoir. Microbial community compositions were analyzed by amplicon sequencing. Metal content was analyzed by inductively coupled plasma-mass spectrophotometry. High salinity enrichments at 90°C of the drilling muds or rinsed shale samples were set up in triplicate and amended with glucose and guar gum (a mannose/galactose-based polymer used during hydraulic fracturing). Sugars were measured through spectrophotometric assays. Metagenomic analyses were performed to assess microbial gene content. Results/Discussion Provenance of microorganisms from the Montney shale formation Provenance of microorganisms from the Montney shale formation Input fluids (fracturing fluid, drilling muds) were revealed to be the likely source of most of the microbial diversity. However, some microorganisms were only detected in the subsurface samples. ASVs affiliated with Aurantimonas, Caminicella, BRH-c8a (Family Desulfallas) and Geotoga exhibited occurrence patterns consistent with being derived from subsurface shale formations. Geotoga has only ever been reported from oil reservoirs (Semenova et al. 2020). Analysis of produced water revealed ASVs from these groups increasing in abundance during hydraulic fracturing operations, suggesting selective pressure from oil reservoir conditions (e.g., toxic metal presence, input of saline water, temperature and pressure fluctuations). Incubations set up from drilling muds showed a preference for glucose while incubations of the rinsed shale cuttings showed a microbial preference for guar gum (i.e., mannose production; Fig. 0), reinforcing the presence of different populations being derived from surface and subsurface samples. Adaptations for life in Montney shale Adaptations for life in Montney shale When considering adaptations of microorganisms for environmental conditions found in oil reservoirs, it is relevant to note the presence of toxic metals such as arsenic, cadmium and mercury. Levels of all three metals were found to vary over time within the 28-day shale microbial enrichments and 12-month produced water time course analyses (Suppl. material 1). Metagenomics revealed various genes for the internalization and metabolism of all three metals within the shale microbiome (i.e., arsenate reductases, arsenite transporters, metallothioneins, mercuric reductases). In conclusion, the results of this study suggest that shale reservoirs thus might not be sterile environments, and host microorganisms are able to contend with major perturbations.

Ion and Stable Isotope Geochemistry of Produced Water in Coalbed Methane Wells in the Tiefa Basin.

The potential geochemical information in the produced water of coalbed methane (CBM) wells is conducive to the exploration and development of CBM in the case that the produced water is primitive formation water. A total of 58 produced water samples collected from 13 CBM wells in the Daxing Mine, Tiefa Basin, were investigated. Ionic composition tests and stable isotope analysis were conducted to explore the geochemical characteristics and sources of produced water as well as the method for determining whether the produced water is primitive formation water. The results suggest that the fracking fluid for CBM stimulations is the main factor affecting the ion change of the produced water in the initial stage of drainage. The concentrations of Cl- and Ca2+ + Mg2+ could be taken as the indices to identify whether the produced water is primitive formation water. When the Cl- concentration is lower than 20 mEq/L and the Ca2+ + Mg2+ concentration is lower than 1 mEq/L, the produced water is close to the pristine formation water. Biogenic methanogenic activity may result in a high δ13CDIC and high concentrations of HCO3- in the pristine formation water in the Tiefa Basin. The data of δD and δ18O in the study area suggest that the formation water might come from atmospheric precipitation, which is later affected by evaporation and the water-rock reaction. The hydrogen isotope values in the produced water derived from the lower coal group display a substantial elevation compared to those from the upper coal group. This disparity in the hydrogen isotope composition presents an opportunity to utilize δD in produced water as a tool for distinguishing the formation water between these two groups.

Fence-Line Spectroscopic Measurements Suggest Carry-Over of Salt-Laden Aerosols into Flare Systems Is Common.

Pollutant emissions from gas flares in the upstream oil and gas (UOG) industry can be exacerbated by aerosols of coproduced liquid hydrocarbons and formation water that survive separation and enter the flare. Of noteworthy concern is the potential impact of salt-laden aerosols, since the associated chlorine may adversely affect combustion and emissions. Here, we use a novel approach to remotely detect carry-over of salt-laden aerosols into field-operational flares via flame emission spectroscopy targeting two of the most abundant species in produced water samples, sodium and potassium. Ninety-five UOG flares were examined during field campaigns in the Bakken (U.S.A. and Canada) and Amazon (Ecuador) basins. For the first time, carry-over of salt species into flares is definitively detected and further found to be concerningly common, with 74% of studied flares having detectable sodium and/or potassium signatures. Additional analysis reveals that carry-over strongly correlates with reported flared gas volume (positive) and well age (negative), but carry-over was also observed in flares linked to older wells and those flaring relatively little gas. Given the scale of global UOG flaring and the risk of salt-laden aerosols affecting emissions, these findings emphasize the need to review separation standards and re-evaluate pollutant emissions from flares experiencing carry-over.

Synergistic cotreatment of cooling tower blowdown and produced waters: Modeling strategies for a comprehensive wastewater treatment simulation

Cooling tower blowdown from thermoelectric power plants and produced water from hydraulic fracturing may soften when mixed due to the complimentary chemistry of the two wastewaters. The potential benefit of low effort softening warrants the investigation of a cotreatment process concerning these industrial wastewaters. The synergy is expected to lessen chemical demand for softening and further enable sustainable practices such as designing for a zero-liquid discharge (ZLD) process. The treatment process may then provide a treated effluent suitable for use as blowdown makeup. In this study, the feasibility and effectiveness of a cotreatment train is explored through simulation of chemical softening, filtration, reverse osmosis (RO), multi-effect distillation (MED), and electrolysis unit operations within a comprehensive process model. Innovative modeling strategies are necessary to result in a meaningful process model when considering the significant complexity of the water chemistry for this treatment train. Through the methodology described in this work, a feasible process design is presented as a base case for treatment of experimentally characterized blowdown and produced water samples obtained in the northern Appalachian region. Thereafter, the base case also establishes a platform for more detailed process analyses of different scenarios in future work. Detailed descriptions of modeling methodologies, process design decisions, and simulation results are provided as a perspective on comprehensive modeling of multi-technology treatment trains for complex feedwaters. With the results of the cotreatment simulation, it is determined that the total water recovery of the process may serve to completely makeup the blowdown rate and partially make up the evaporative losses of a theoretical thermoelectric plant's water demand. This complete recovery is evaluated to require 18,343.531 kW of a chemical energy equivalent, 1184.971 kW of electricity, and 68,126.291MJh−1 of power plant steam to result in 408.532m3h−1 of treated water effluent at a quality of approximately 0.135gL−1 total dissolved solids for the base case design.

Analysis of naphthenic acids in produced water samples by capillary electrophoresis-mass spectrometry.

A capillary electrophoresis-mass spectrometry method was used to analyze naphthenic acids in produced water samples. It was possible to detect cyclopentanecarboxylic, benzoic, cyclohexanebutyric, 1-naphthoic, decanoic, 3,5-dimethyladamantane-1-carboxylic, 9-anthracenecarboxylic, and pentadecanoic acids within ca. 13min using a buffer composed of 40mmol/L ammonium hydroxide, 32mmol/L acetic acid and 20% v/v isopropyl alcohol, pH 8.6. The proposed method showed good repeatability, with relative standard deviation (RSD) values of 6.6% for the sum of the peak areas and less than 2% for the analysis time. In the interday analysis, the RSD values for the sum of the peak areas and migration time were 10.3% and 10%, respectively. The developed method demonstrated linear behavior in the concentration range between 5 and 50mg/L for benzoic, decanoic, 3,5-dimethyladamantane-1-carboxylic and 9-anthracenecarboxylic acids, and between 10 and 50mg/L for cyclopentanecarboxylic, cyclohexanebutyric, 1- naphthoic, and pentadecanoic acids. The detection limits values ranged from 0.31 to 1.64mg/L. Six produced water samples were analyzed and it was possible to identify and quantify cyclopentanecarboxylic, benzoic, cyclohexanebutyric, and decanoic acids. The concentrations varied between 4.8 and 98.9mg/L, proving effective in the application of complex samples.

Public Health Risk Assessment of Treated and Untreated Produce Water Effluent

Discharge of produced water into the aquatic environment may release chemicals that are highly toxic to sensitive marine species even at low concentrations, causing bio-degeneration/transformation of the biota. Some metals and hydrocarbons may accumulate in sediments, bio-accumulate in bottom living biological communities which may pose threat to humans and animals. Physicochemical quality of untreated and treated produced water were assessed.Toxicity and pollution levels as well as human health risk assessment of treated and untreated produced water were also determined to ascertain the level of environmental safety vis-à-vis effects of treatment, in order to identify potential environmental concerns from existing treatment practices. Microbial density and concentration of eight heavy metals in produced water samples were assessed following standard procedures and different indices were used to assess the health risk.Concentration (in mg/L) of iron was 6.9 (untreated) and 0.001 (treated wastewater), arsenic 0.001 for both untreated and treated wastewater, zinc (0.002 for both untreated and treated wastewater), mercury (0.001 for both untreated and treated wastewater), chromium (0.001 for both untreated and treated wastewater), cadmium (1.1 for untreated and 0.001 for treated wastewater), lead (0.9 for untreated and 0.001 for treated wastewater) and nickel (0.005 for both untreated and treated wastewater). Further, statistical analysis showed correlation between physicochemical parameters of untreated and treated wastewater as well as heavy metal concentrations. Health risk assessment showed major potential non-carcinogenic risk was via ingestion, with led as the main contributor. Overall non-carcinogenic risk evaluation of produced water showed that humans are not susceptible. Similarly, chromium was the major contributor to the carcinogenic health risk but values for lethal average daily doses and cumulative carcinogenic risk were within permissible limits.

Solar desalination of oilfield brines using nanogel materials

The oil and gas industry is currently facing an environmental and economic challenge with the production of water from their wells. In this paper, a novel solution to these challenges is proposed by implementing solar absorbing hydrogels to aid in the desalination of this brine. The hydrogel uses poly(vinyl alcohol) as its backbone and insulator and is crosslinked with polypyrrole as the solar absorber. Internal features show improved fluid flow into the hydrogel which are supported by swelling tests. Dimensions of this hydrogel can affect the overall performance. Data shows that hydrogels with a thickness of at least 2 cm have the highest desalination rate. To apply it to oilfield brines, a lab-stock brine with a TDS concentration of 230,000 ppm was used as well as untreated produced water samples collected from select geological formations. Lab-stock brines showed desalination rates nearly 2.5 times higher when these hydrogels were used and field samples showed desalination rates up to 4.5 times higher. Condensed water samples showed greater than 99% decreases in major ions present in the water.

Application of Poly(caffeic acid) for the Extraction of Critical Rare Earth Elements.

Poly(caffeic acid) was synthesized and utilized for the extraction and determination of rare earth elements (REEs), thorium, and uranium. Oxidative polymerization of caffeic acid, a low-cost plant-based material, in the presence of ethylenediamine produced a granular, air-stable, and cross-linked polymer. The polymer is highly oxygenated and together with the amino group from ethylenediamine efficiently coordinates and preconcentrates these critical elements from aqueous media. Extraction was dependent on solution pH, amount of sorbent, and extraction time, while the concentration and flow rate of the desorption solution governed the recovery efficiency. Removal and recovery efficiencies greater than 98 and 90%, respectively, and low levels of detection ranging from 0.1 to 2.9 ng/L were achieved. Determination of these strategic elements in the presence of potentially interfering ions as well as in complex matrices such as well water and produced water samples also was demonstrated. The capacity of poly(caffeic acid) was determined with lanthanum as a representative REE to be 161.7 mg/g, establishing the promise of poly(caffeic acid) for larger-scale extractions in addition to the ability to screen sources for the presence of REEs.

Oilfield produced water assessment from onshore treatment facilities in Niger Delta: Water quality susceptibility and suitability for soil irrigation

The abundance of natural fossil fuel in the Niger Delta of Nigeria has instituted generation of oilfield produced water (PW) in large volume. This constitutes environmental pollution when discharged outside the permissible limit given by Nigerian Upstream Petroleum Regulatory Commission (NUPRC). PW can be used for soil irrigation if its constituents are remediated after treatment. This research assessed the physicochemical properties of untreated and treated samples of oilfield PW from Awoba, Imo River and Kolo creek oil fields of Niger Delta using electrometric, argentometric, colorimetric, titration, atomic absorption spectroscopy, APHA and HACH standard methods. Oil-treatment facilities effectiveness was investigated by comparing laboratory results for treated-PW with the permissible regulatory values of NUPRC. The pH, salinity hazard, sodium hazard, boron, chloride, TDS, carbonate and nitrate of treated-PW were measured to check the suitability of treated-PW quality for soil irrigation. Measured values were compared with the permissible standard of US EPA. Sodium adsorption ratio (SAR) and electric conductivity (EC) were used to determine the level of sodium and salinity hazards respectively. The results indicated that none of the untreated-PW samples complied with NUPRC permissible limit. Physicochemical properties of treated-PW revealed samples to be close to or within approved NUPRC standards except in few cases. All the measured parameters of treated-PW from Awoba and Imo River oil fields conformed to the US EPA standard value except their ECs and SAR of Imo River oil field which measured 2.46 and 2.93 ds m−1, and 2.57 respectively. However, all other parameters measured for treated-PW from Kolo creek oil field did not conform to the standard except pH and nitrate which measured 7.7 and 4.86 mg/L respectively. In conclusion, oil treatment facilities should be more robust to degrade a wide range of recalcitrant compounds in PW pollutants in order to minimize the impacts of toxic compounds in PW on the environment.

Chemical Demulsification of Oil-in-Water Emulsion from Gas Condensate Field

Produced water, also known as oily wastewater, is one of the major wastes in the oil and gas industry. During the hydrocarbon production, formation of emulsion takes place such as oil-in-water emulsion which has a huge financial effect on the sector. Oil and gas industry seeks highly effective and reasonable demulsifying chemicals to separate the oil-in-water emulsions into water and crude oil. Thus, in this publication, resin alkoxylate, cationic polyamine, cationic surfactant and ethylene oxide/propylene oxide (EO/PO) block copolymers are utilized to resolve the oil-in-water emulsion from a gas condensate field. According to the findings of preliminary screening, a unique demulsifier DB was formulated by incorporating resin alkoxylate and cationic surfactant at an optimal weight percentage ratio. Demulsification efficiency (De) of 96 % based on measurement of turbidity was attained after treating the oil-in-water (O/W) emulsion with demulsifier DB at a dosage of 7 ppm. To determine the demulsifier's efficiency further, the oil-in-water content (OiW) of the produced water was evaluated after the treatment with demulsifier DB. Oil removal efficiency (ORe) of 90% was achieved as the formulated demulsifier DB reduced the oil-in-water content (OiW) of O/W emulsion from 1008.3 ppm to 97.1 ppm within 15 minutes at the dosage of 7 ppm. Furthermore, interfacial tension (IFT) and Turbiscan analysis were performed to further study the demulsification process of blank sample and the addition of the demulsifier DB at the optimized dosage of 7 ppm. At demulsifier DB dosage of 7 ppm, the interfacial tension between oil and water reduced significantly compared to blank sample from 24.98 mN/m to 9.38 mN/m. The produced water sample after treatment with 7 ppm of demulsifier DB resulted in a significant increase of Turbiscan Stability Index (TSI) value of 8 which indicates the rate at which the separation of oil and water occurred. The attained results of IFT and Turbiscan analysis further validate that mixed surfactant system is more efficient than single surfactant system. By combining surfactants with different functional groups, mixed surfactant systems can exhibit greater surface activity than single surfactants.

Effective Biocorrosive Control in Oil Industry Facilities: 16S rRNA Gene Metabarcoding for Monitoring Microbial Communities in Produced Water.

Microbiologically influenced corrosion (MIC) or biocorrosion is a complex biological and physicochemical process, Strategies for monitoring MIC are frequently based on microbial cultivation methods, while microbiological molecular methods (MMM) are not well-established in the oil industry in Brazil. Thus, there is a high demand for the development of effective protocols for monitoring biocorrosion with MMM. The main aim of our study was to analyze the physico-chemi- cal features of microbial communities occurring in produced water (PW) and in enrichment cultures in oil pipelines of the petroleum industry. In order to obtain strictly comparable results, the same samples were used for both culturing and metabarcoding. PW samples displayed higher phylogenetic diversity of bacteria and archaea whereas PW enrichments cultures showed higher dominance of bacterial MIC-associated genera. All samples had a core community composed of 19 distinct genera, with MIC-associated Desulfovibrio as the dominant genus. We observed significant associations between the PW and cultured PW samples, with a greater number of associations found between the cultured sulfate-reducing bacteria (SRB) samples and the uncultured PW samples. When evaluating the correlation between the physicochemical characteristics of the environment and the microbiota of the uncultivated samples, we suggest that the occurrence of anaerobic digestion metabolism can be characterized by well-defined phases. Therefore, the detection of microorganisms in uncultured PW by metabarcoding, along with physi-cochemical characterization, can be a more efficient method compared to the culturing method, as it is a less laborious and cost-effective method for monitoring MIC microbial agents in oil industry facilities.

Oxidation treatment of shale gas produced water: Molecular changes in dissolved organic matter composition and toxicity evaluation

Produced water (PW) is the largest waste stream generated by hydraulic fracturing in an unconventional shale gas reservoir. Oxidation processes (OPs) are frequently used as advanced treatment method in highly complicated water matrix treatments. However, the degradation efficiency is the main focus of research, organic compounds and their toxicity have not been properly explored. Here, we obtained the characterization and transformation of dissolved organic matters of PW samples from the first shale gas field of China by two selected OPs using FT-ICR MS. CHO, CHON, CHOS, and CHONS heterocyclic compounds associated with lignins/CRAM-like, aliphatic/proteins, and carbohydrates compounds were the major organic compounds identified. Electrochemical Fe2+/HClO oxidation preferentially removed aromatic structures, unsaturated hydrocarbons, and tannin compounds with a double-bond equivalence (DBE) value below 7 to more saturated compounds. Nevertheless, Fe (VI) degradation manifested in CHOS compounds with low DBE values, especially single bond compounds. Oxygen- and Sulfur-containing substances, primarily O4–11, S1O3-S1O12, N1S1O4, and N2S1O10 classes, were the main recalcitrant components in OPs. The toxicity assessment showed that the free-radical-formed Fe2+/HClO oxidation could cause significant DNA damage. Therefore, the toxicity response byproducts need spcial attention when conducting OPs. Our results led to discussions on designing appropriate treatment strategies and the development of PW discharge or reuse standards.

Reuse of Produced Water from the Petroleum Industry: Case Studies from the Intermountain-West Region, USA

The produced water (PW) volume in the Intermountain-West (I-WEST) region is about 600 million m3 in 2021. More than one-third of the PW is injected for disposal, which can be a waste of water, considering the water scarcity in the I-WEST region. In this work, we analyzed the potential for the reuse of PW in the I-WEST region. The PW composition and volume in different basins in the I-WEST region were analyzed. The regulations for drinking water, domestic use, irrigation, livestock watering, aquatic, surface water discharge, groundwater discharge, hydraulic fracture, and hydrogen (H2) production were summarized. We identified the appropriate treatments depending on the PW composition and water standards. We also analyzed each PW treatment’s water recovery, energy demand, and cost. We selected the samples of PW from the Raton Basin, San Juan Basin, and Permian Basin to assess the potential reuse of PW in the I-WEST region. The comparison between PW composition and water standards shows that the regulations are not designed for the reuse of PW because the constituents in water regulations do not match the constituents in PW. The low-salinity PW can be treated for agricultural use with relatively low cost and high water recovery, while the high-salinity PW is more suitable for hydraulic fracturing. The treatment cost (including operation, maintenance, energy, labor, and disposal cost) ranges from $0.11/bbl to $1.01/bbl, depending on the PW composition and targeted water standards. The reuse of PW for H2 production is a promising usage purpose. Due to the high demand for fresh water in H2 production, the reuse of PW can alleviate the stress of water scarcity in the I-WEST region. This work provides guidance for the reuse of PW in the I-WEST region.

Multi-elemental analysis of free water obtained from water in oil emulsions from Niger Delta Region using ICP-OES

Disposal of produced water obtained from crude oil could be challenging and tough because of the effect it has on the environment. Produced water contains high levels of salt and toxic substances which must be treated before re-use or disposal to reduce their impact on the environment, people and assets. Hence, the characterization of produced water for its chemical composition is essential. This study presents the determination of heavy metals (Co, Cu, Pb, Fe, Zn, Ni, and Cd) in produced water obtained from crude oil emulsion samples via inductively coupled plasma optical emission spectrometry (ICP-OES). The samples were subjected to treatment prior to analysis. The analytical curve obtained from the calibration gave excellent correlation coefficients ranging from 0.9995- 1.000 and the recovery values obtained were very good (95% - 105%). The result of the heavy metal analysis in μg/l (Co: <DL to 14.3, Cu: 114.1 to 1553.2, Fe: 492.1 to 1576.4, Ni: 52.3 to 174.5, Pb: <DL to 15.1, Zn: 92.4 to 432.9, Cd: 2.3 to 4.4) indicates that the concentrations of the metals evaluated in the produced water samples were above the recommended discharge limit ( Zn - 1.0 mg/L, Co - 0.02 mg/L, Fe - 1.0 mg/L, Cu - 0.02 mg/L, Cd - 0.01 mg/L, Ni - 0.03 mg/L and Pb - 0.05 mg/L).

Combined chlorine dioxide–membrane distillation for the treatment of produced water

Membrane distillation (MD) is a promising technique for desalinating hypersaline brine, such as produced water (PW). To date, fouling and scaling have remained as major challenges for MD implementation. In this study, chlorine dioxide combined with induced air floatation (ClO2-IAF) was systematically investigated as a pretreatment prior to MD. First, the ClO2 generation based on sodium chlorite and hydrochloric acid was optimized to maximize the on-demand ClO2 production. The maximum production yield of 18.4% was obtained with 4 wt.% NaClO2 and 20 wt.% HCl solutions, with a molar ratio of 1:1.25. Then, two real PW samples were pretreated, and removal efficiencies for total suspended solids (TSS), turbidity, iron, and total organic carbon (TOC) were comprehensively studied by varying the ClO2 dosage between 6 and 91 mg/L. The ClO2-IAF pretreatment displayed TSS and turbidity removals above 90% and TOC removal close to 55%. The PW constituents such as benzene, toluene, ethylbenzene, xylene (BTEX), and total petroleum hydrocarbons (TPH) were analyzed and quantified throughout the cascade of the treatments. The volatiles like BTEX were mainly removed by air floatation, while saturated hydrocarbons such as TPH were retained by the hydrophobic membrane. The MD long-term stability without any in-place cleaning was evaluated, and the membrane withstood for twenty two days without wetting, suggesting that optimizing oxidation pretreatment is critical for mitigating the fouling in MD. Results suggest that organic fouling in PW could be effectively reduced by the pretreatment, but further treatment is required to mitigate the scaling, which resulted in MD wetting.

Comparison of microbial community structures between oil and water phases in a low-permeability reservoir after water flooding

The application of Microbial Enhanced Oil Recovery relies heavily on the microorganisms in oil wells. However, due to the difficulties in separating bacteria from oil samples, studies on bacterial communities in oil samples are limited. In this study, oil and produced water samples from the same well were collected from the western oilfield of the Ordos Basin, and DNA extraction was effective. Full-length 16S rRNA genes were sequenced using PacBio to study the impact of water flooding on the microbial community structure and the potential biochemical functions of bacteria in a low-permeability reservoir. The results showed that water flooding decreased the temperature and salinity while increasing the dissolved oxygen in the tested oil well. It has influence on the reservoir community. Nitrate-reducing bacteria such as Bradyrhizobium and Methylovirgula are enriched in the reservoir. Nitrate and nitrite can be used as electron acceptors by denitrification to produce N2, which can inhibit the growth of sulfate-reducing bacteria. Additionally, bacteria strains such as Flexistipes and Marinobacter can use hydrocarbons as energy source to degrade crude oil and change its properties. The study demonstrated the presence of a large number of advantageous bacteria in low-permeability reservoirs after water flooding, providing a biological foundation for the application of microbial enhanced oil recovery.

Quantitative Identification of Water Sources of Coalbed Methane Wells, Based on the Hydrogen and Oxygen Isotopes of Produced Water—A Case of the Zhijin Block, South China

The quantitative identification of water sources is an important prerequisite for objectively evaluating the degree of aquifer interference and predicting the production potential of coalbed methane (CBM) wells. However, this issue has not been solved yet, and water sources are far from being completely understood. Stable water isotopes are important carriers of water source information, which can be used to identify the water sources for CBM wells. Taking the Zhijin block in the Western Guizhou Province as an example, the produced water samples were collected from CBM wells. The relationships between the stable isotopic compositions of the produced water samples and the production data were quantitatively analyzed. The following main conclusions were obtained. (1) The δD and δ18O values of the produced water samples were between −73.37‰ and −27.56‰ (average −56.30‰) and between −11.04‰ and −5.93‰ (average −9.23‰), respectively. The water samples have D-drift characteristics, showing the dual properties of atmospheric precipitation genesis and water–rock interaction modification of the produced water. An index d was constructed to enable the quantitative characterization of the degree of D-drift of the produced water. (2) The stable isotopic compositions of produced water showed the control of the water sources on the CBM productivity. The probability of being susceptible to aquifer interference increased with the increasing span of the producing seam combination, reflected in the lowering δD and δ18O values and the decreasing gas productivity. (3) Three types of water, namely, static water, dynamic water, and mixed water, were identified. The characteristic values of the isotopic compositions of the static and dynamic water were determined. Accordingly, a quantitative identification method for the produced water sources was constructed, based on their stable isotopic compositions. The identification results have a clear correlation with the gas production, and the output of the static water contributes to the efficient CBM production. The method for the quantitative identification of the water sources proposed in this study, can help to improve the CBM development efficiency and optimize the drainage technology.