Produced Water Samples Research Articles

Geochemical Characteristics of Water Produced from Coalbed Methane Wells in the Southern Qinshui Basin and Construction of an Associated Model: Implications for Coalbed Methane Co-Production

The geochemical characteristics of water produced from coalbed methane (CBM) wells contain rich information about the associated geology, environment, and production. This study was conducted in the Southern Qinshui Basin, where produced water samples were collected from 10 typical CBM wells and their ionic compositions and water quality parameters were tested. The differences in the chemical characteristics of the produced water between different producing coal seams and between single-seam production wells (SPWs) and multi-seam co-production wells (MCWs) were compared, and the geochemical formation process of the produced water was revealed. The following conclusions were obtained: (1) the water produced samples that were mainly Na-HCO3-type and were generally weakly alkaline and moderately mineralized. The water produced from No. 15 coal seam was more enriched in SO4, Ca, and Mg compared to that of No. 3 coal seam, and the variations were more intense, reflecting a more complex water chemistry formation. (2) The ionic data of the water produced from MCWs do not lie between the coal seams of SPWs, nor do they satisfy the linear relationship between the ionic compositions of SPWs, reflecting the differences in the water sources between MCWs and SPWs. Water from MCWs tends to communicate with active water sources outside the coal seams, and the produced water contains small amounts of Cl and total dissolved solids, thus inhibiting the pressure reduction efficiency and limiting the effect of CBM co-production. (3) Based on a principal component analysis of the ionic compositions, two characteristic components were extracted, and these represented two types of hydrochemical formation processes. The first type is pyrite oxidation and carbonate dissolution, and its opposite represents sulfate reduction. The second type reflects the groundwater retention and confinement characteristics, and its opposite represents active groundwater or stronger recharge conditions. (4) A geochemical formation model of the water produced from CBM wells in the study area was constructed. Cation exchange adsorption and sulfate reduction were found to be the main water–rock interactions in the coal measure, and they determine the overall water quality of the produced water. Recharge has a relatively significant influence on water produced from MCWs. Pyrite oxidation exists in the water produced from No. 15 coal seam of the Taiyuan Formation, and the higher sulfur content in the coal contributes to this reaction. The results of the study will assist in deepening our understanding of the geochemical formation mechanisms of water produced from CBM wells, and they provide the main reasons for the poor CBM co-production effect from the Shanxi and Taiyuan Formations.

Automated filtering scripts based on accurate mass applied to comprehensive two-dimensional gas chromatography coupled to high resolution mass spectrometry for group-type analysis of naphthenic acids

In this work, it is reported the detailed evaluation of filtering scripts for comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry (GC×GC–HRMS). Automated scripts were built to perform group-type analysis of naphthenic acids (NAs) in complex mixtures, like produced water (PW) samples. The logical operations were based on high-resolution mass spectral information acquired by using electron ionization (EI) and chemical ionization in the positive mode (PCI). The most common derivatization methods were carefully evaluated for group-type analysis. The performance of the scripts was evaluated using the rank metric (RM), wherein the sum-normalized absolute difference was calculated for true positives versus false positives. The best performing approach for qualitative analysis was attained by combining the derivatization with N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) with EI due to the high intensity and characteristic pseudo-molecular ions (even-electron [M-57]+). The data obtained supported the development of selective scripts, exhibiting accuracy values above 98 % and 88 % for the reference and unknown PW samples, respectively. The retention pattern of GC×GC was also used as a discriminant parameter for ambiguous identification, highlighting the synergy between GC×GC and HRMS. The proposed scripts are an interesting alternative to profile 154 classes of MTBSTFA-derived NAs, which considerably reduced the time spent in manual data curation and annotation, while improving the reliability of the results. This is an important step to aid in the development of standard methods for the study and regulation of water-soluble compounds found in PW samples.

A portable tool for colorimetric detection of corrosion inhibitors using paper-based analytical devices

In this work, we report a complete and portable analytical instrumentation dedicated to the colorimetric analysis of corrosion inhibitors. The construction of the analytical tool was planned based on carousel architecture and it involves a simple combination of a 3D-printed holder containing eight circular zones and an Arduino microcontroller photoelectric sensor. In addition, paper-based analytical devices (PAD) were manufactured in the form of microzones using manual cutting and assembled in the 3D printed holder for performing colorimetric measurements of quaternary amines in wastewater samples from the petroleum industry. A blue dye was used as a model color and the obtained pixels responses through the proposed analytical tool and well-known smartphone-based analysis revealed similar colorimetric intensities, thus clearly demonstrating the high performance of the 3D-printed analytical instrumentation. The target colorimetric reaction occurs via the interaction of ammonium quaternary present in corrosion inhibitors composition with the chromogen 3′, 3″, 5′, 5″ – tetrabromophenolphthalein-ethyl-ester (TBPE) in an acidic medium. Detailed optimization of the colorimetric reaction involving the ammonium quaternary was successfully performed, as well as the evaluation of possible physical–chemical interferences (pH, carbonate levels, and temperature) mostly usual in produced water from petroleum pipelines. Recovery studies of ammonium quaternary in real produced water samples exhibited acceptable performance (88 to 121%). Thus, the obtained results successfully demonstrated that the proposed 3D-printed analytical system associated with PADs offers a huge potential to be used for colorimetric detection of corrosion inhibitors in wastewater samples and it can be used in the point-of-need involving the petroleum industry field.

Produced Water Deoxygenation: Investigation of Nitrogen Purging scheme– Parametric Study – Part1

Produced water (PW) is water that comes out of the well with the crude oil during crude oil production. The quality of produced water varies significantly based on the geochemistry of the producing formation, the type of hydrocarbon produced, and the characteristics of the producing well. A well-known obstacle hindering the re-use of the produced water, in different sectors, is the high content of dissolved oxygen (DO) as it can cause corrosion and polymer degradation. In this study, we report the experimental investigations for de-oxygenating samples of PW collected from Omani oil fields via a gas lift unpacked and packed column. Two types of packing (polyethylene rushing rings and spherical glass balls) were used. Upon treating the PW samples grafted with different concentration of polyacrylamide; 100-500 ppm, through different purging techniques at various N2 throughputs, a considerable reduction in the content of the dissolved oxygen (from saturation level to less than 1 ppm) was detected in the first duration (3 minutes). Upon examining purging durations up to 300 minutes, the DO removal efficiency was slightly improved; however, residues of DO (approaching 0.5 ppm) was left unremoved which indicates the necessity for elaborating another approach for treating the shallow DO levels.

From water analysis to scale and corrosion control improvements: A Permian Basin example

Oil and gas production and geothermal energy exploitation generate large volumes of produced water (PW), which is causing various operational challenges including environmental sustainability, scale, corrosion, and other economic and safety issues. Using the Permian Basin as an example, this study traced the PW sources and developed a new procedure for scale and corrosion management improvements based on the PW compositions from U.S. Geological Survey National Produced Waters Geochemical Database (USGS PWGD). Both correlations between the major ions and Br− and between the water isotopes (δD versus δ18O) showed that most PW samples evolved from seawater, and a group samples from foreign sources were detected. The downhole pH, CO2% and calcite saturation index (SI) at surface were predicted by assuming PW is at equilibrium with calcite at downhole conditions. The SI values of barite, halite, and gypsum were also predicted. A dosage of 1 mg/L of NTMP (nitrilotris(methylene phosphonic acid)) was recommended to control such scale formations for >95% Permian wells. Furthermore, this study incorporated a mechanistic corrosion module to calculate the corrosion rate, which correlated well with the measured Mn2+ concentration. Such good correlation suggested that Mn2+ concentration can be utilized as a proxy for the steel corrosion. This recommended procedure has been shown to provide vital information for formation water source evolution analysis and scale and corrosion management improvements based on produced water composition with nonideal data.

Boron removal from synthetic brines and oilfield produced waters using aluminum electrocoagulation

High boron (B) levels in oil and gas produced waters prevent its beneficial reuse as irrigation water without proper treatment. Aluminum (Al) electrocoagulation (EC) is a promising technology for B removal, but further research and development is needed to optimize EC for use in removing B from produced waters. To this end, B removal by adsorption onto insoluble aluminum hydroxide solids, generated by EC in simulated brines (up to 50,000 mg/L NaCl) and real oilfield produced waters, was studied. B removal during EC was greater than when aluminum hydroxide solids formed by EC were subsequently exposed to B containing solutions. Working parameters affecting B removal during the EC process, including current, total dissolved solid (TDS), temperature, pH, scale-forming cations and organic matter, were investigated to explore ways to achieve higher B removal. Boron removal increased with increased current loading and time, and with the concomitant increased Al solids concentration. However, too high a current loading limited B removal because of a change in the structure of the aluminum hydroxide solids. Higher TDS decreased B removal slightly, but lower TDS concentrations limited the use of higher current loadings. Temperature increased during EC treatment, particularly at higher current loadings, and this inhibited B removal due to an accelerated aggregation of amorphous Al solids into larger, denser, and presumably more crystalline particles. The best B removal occurred at pH 8, corresponding to a slightly positive zeta potential for aluminum hydroxide and a small but significant fraction of negatively charged B species. Scale-forming cations such as Ba2+ and Sr2+ had no obvious effect on the EC process. The presence of high concentrations of Mg2+ and Ca2+ resulted in low bulk pH values during the EC process and greater formation of solid products, but B removal did not decrease during a pH-controlled (pH = 8) EC process with these divalent cations present. Two produced water samples collected from oilfields in Kansas, US were treated using EC for 1 h, resulting in up to ~70 % B removal from solution with a current loading of 6.67 A/L, and up to 78 % with 13.33 A/L.

Determination of naphthenic acids in produced water by using microchip electrophoresis with integrated contactless conductivity detection

This study reports for the first time the use of a microchip electrophoresis (ME) device with integrated capacitively coupled contactless conductivity detection (C4D) to analyze naphthenic acids in produced water. A mixture containing 9-anthracenecarboxylic, 1-naphthoic, and benzoic acids was separated and detected using a running buffer composed of 10 mmol L−1 carbonate buffer (pH = 10.2). The separation was achieved within ca. 140 s with baseline resolution greater than 2 and efficiency values ranging from 1.9 × 105 to 2.4 × 105 plates m−1. The developed methodology provided linear correlation with determination coefficients greater than 0.992 for the concentration ranges between 50 and 250 µmol L−1 for benzoic and 9-anthracenecarboxylic acids, and between 50 and 200 µmol L−1 for 1-naphthoic acid. The achieved limit of detection values varied between 4.7 and 7.7 µmol L−1. The proposed methodology revealed satisfactory repeatability with RSD values for a sequence of eight injections between 5.5 and 7.7% for peak areas and lower than 1% for migration times. In addition, inter-day precision was evaluated for sixteen injections (a sequence of four injections performed during four days), and the RSD values were lower than 11.5 and 4.9% for peak areas and migration time, respectively. Five produced water samples were analyzed, and it was possible to detect and quantify 9-anthracenecarboxylic acid. The concentrations ranged from 1.05 to 2.24 mmol L−1 with recovery values between 90.8 and 96.0%. ME-C4D demonstrated satisfactory analytical performance for determining naphthenic acids in produced water for the first time, which is useful for petroleum or oil industry investigation.

The Microbial Community and Functional Potential in the Midland Basin Reveal a Community Dominated by Both Thiosulfate and Sulfate-Reducing Microorganisms.

The Permian Basin is the highest producing oil and gas reservoir in the United States. Hydrocarbon resources in this region are often accessed by unconventional extraction methods, including horizontal drilling and hydraulic fracturing. Despite the importance of the Permian Basin, there is no publicly available microbiological data from this region. We completed an analysis of Permian produced water samples to understand the dynamics present in hydraulically fractured wells in this region. We analyzed produced water samples taken from 10 wells in the Permian region of the Midland Basin using geochemical measurements, 16S rRNA gene sequencing, and metagenomic sequencing. Compared to other regions, we found that Permian Basin produced water was characterized by higher sulfate and lower total dissolved solids (TDS) concentrations, with a median of 1,110 mg/L and 107,000 mg/L. Additionally, geochemical measurements revealed the presence of frac hits, or interwell communication events where an established well is affected by the pumping of fracturing fluid into a new well. The occurrence of frac hits was supported by correlations between the microbiome and the geochemical parameters. Our 16S rRNA gene sequencing identified a produced water microbiome characterized by anaerobic, halophilic, and sulfur reducing taxa. Interestingly, sulfate and thiosulfate reducing taxa including Halanaerobium, Orenia, Marinobacter, and Desulfohalobium were the most prevalent microbiota in most wells. We further investigated the metabolic potential of microorganisms in the Permian Basin with metagenomic sequencing. We recovered 15 metagenome assembled genomes (MAGs) from seven different samples representing 6 unique well sites. These MAGs corroborated the high presence of sulfate and thiosulfate reducing genes across all wells, especially from key taxa including Halanaerobium and Orenia. The observed microbiome composition and metabolic capabilities in conjunction with the high sulfate concentrations demonstrate a high potential for hydrogen sulfide production in the Permian Basin. Additionally, evidence of frac hits suggests the possibility for the exchange of microbial cells and/or genetic information between wells. This exchange would increase the likelihood of hydrogen sulfide production and has implications for the oil and gas industry. IMPORTANCE The Permian Basin is the largest producing oil and gas region in the United States and plays a critical role supplying national energy needs. Previous work in other basins has demonstrated that the geochemistry and microbiology of hydrocarbon regions can have a major impact on well infrastructure and production. Despite that, little work has been done to understand the complex dynamics present in the Permian Basin. This study characterizes and analyzes 10 unique wells and one groundwater sample in the Permian Basin using geochemical and microbial techniques. Across all wells we found a high number of classic and thiosulfate reducers, suggesting that hydrogen sulfide production may be especially prevalent in the Permian Basin. Additionally, our analysis revealed a biogeochemical signal impacted by the presence of frac hits, or interwell communication events where an established well is affected by the pumping of fracturing fluid into a new well. This information can be utilized by the oil and gas industry to improve oil recovery efforts and minimize commercial and environmental costs.

Dissolved organic matter within oil and gas associated wastewaters from U.S. unconventional petroleum plays: Comparisons and consequences for disposal and reuse

Wastewater generated during petroleum extraction (produced water) may contain high concentrations of dissolved organics due to their intimate association with organic-rich source rocks, expelled petroleum, and organic additives to fluids used for hydraulic fracturing of unconventional (e.g., shale) reservoirs. Dissolved organic matter (DOM) within produced water represents a challenge for treatment prior to beneficial reuse. High salinities characteristic of produced water, often 10× greater than seawater, coupled to the complex DOM ensemble create analytical obstacles with typical methods. Excitation-emission matrix spectroscopy (EEMS) can rapidly characterize the fluorescent component of DOM with little impact from matrix effects. We applied EEMS to evaluate DOM composition in 18 produced water samples from six North American unconventional petroleum plays. Represented reservoirs include the Eagle Ford Shale (Gulf Coast Basin), Wolfcamp/Cline Shales (Permian Basin), Marcellus Shale and Utica/Point Pleasant (Appalachian Basin), Niobrara Chalk (Denver-Julesburg Basin), and the Bakken Formation (Williston Basin). Results indicate that the relative chromophoric DOM composition in unconventional produced water may distinguish different lithologies, thermal maturity of resource types (e.g., heavy oil vs. dry gas), and fracturing fluid compositions, but is generally insensitive to salinity and DOM concentration. These results are discussed with perspective toward DOM influence on geochemical processes and the potential for targeted organic compound treatment for the reuse of produced water.

Profiling organic acids in produced water samples using vacuum-assisted sorbent extraction and gas chromatography coupled to Fourier transform Orbitrap mass spectrometry

In this article, we describe the preliminary findings obtained with headspace vacuum-assisted sorbent extraction (VASE) as an alternative for sample preparation in the analysis of organic acids in produced water (PW). VASE is a headspace technique that combines the use of high-capacity sorbent traps and low-pressure conditions. Method development included extraction parameters and thermal desorption conditions. Multivariate optimization using design of experiments (DOE) was performed for variable screening and method optimization. A microwave-assisted derivatization protocol was proposed to convert the organic acids into its corresponding methyl esters (ME). The reaction was conducted in-sample prior to VASE extraction, and had the advantage of dismissing the use of organic solvents. The isolated fraction was analyzed by gas chromatography coupled to high resolution mass spectrometry (GC-HRMS). Quantitative analysis exhibited a linear range from 1 to 100 µg L-1. The reported detection limits ranged from 0.001 to 0.070 µg L-1 using the model acids. The method was successfully applied for qualitative analysis of PW samples. It was possible to detect important classes, such as hydrocarbons, oxygen- and nitrogen- containing compounds. Several NAs species with different double-bond equivalent (DBE) values and carbon numbers could be found in both samples. The greenness of the analytical method was also evaluated, exhibiting better environmental metrics when compared with traditional liquid–liquid extraction.

Reduction of Heavy Hydrocarbons from Oilfield Produced Water

This paper presents attempts to reduce the concentration of organic pollutants in oilfield produced wastewater before its discharge into natural water bodies or reinjection into the wells. The contaminant content was significantly decreased by wastewater treatment, based on solid phase adsorption, photocatalytic degradation of organic molecules and chemical oxidation of oily compounds. The study was conducted with real wastewater, which is in practice released in the environment. The produced water samples, taken from four sampling points in the oilfield site, were analyzed for physicochemical (temperature, redox potential (Eh), conductivity, pH, dissolved oxygen) and specific (chemical oxygen demand (COD), total oily hydrocarbons (TOH), phenols) parameters, cations (Ca2+, Mg2+, Na+, K+) and anions (Cl−, HCO3−, SO42−, S2−), in order to determine the initial water status. The organic contaminants in oilfield produced water showed COD of 39–58 mg/L, TOH of 152–363 mg/L and phenols of 0.07–0.21 mg/L. The TOH was chosen as a suitable parameter for the evaluation of the treatment method efficiency. The adsorption on activated charcoal decreased the TOH levels up to 52 mg/L, which corresponds to 85% removal of oily compounds. Chemical oxidation, carried out with Ca(ClO)2 in a concentration of 400 mg/L for 1 h at room temperature, showed TOH removal in the range of 80–94% for different wastewater samples. The use of 300 mg/L TiO2 or ZnO under UV irradiation for 12 h led to TOH removal of 25–78% and 82–92%, respectively. Both photocatalysts were characterized by using X-ray diffraction, reflectance UV-vis spectroscopy and scanning electron microscopy. The crystal forms anatase and wurtzite for TiO2 and ZnO, respectively, were found. The estimated band gap of 3.48 eV for direct transition in TiO2 and 3.25 eV for ZnO agrees well with that reported in the literature. Higher photodegradation of organic compounds was observed for ZnO, indicating that it absorbed more light photons than TiO2 did. A mechanism for photocatalytic degradation over a more efficient photocatalyst, ZnO, was proposed based on the GC-MS analysis of raw water and treated effluents produced for 6 and 12 h.

Evaluation of petroleum as extractor fluid in liquid-liquid extraction to reduce the oil and grease content of oilfield produced water

This work aims to evaluate the use of petroleum as a solvent in the liquid-liquid extraction of oil and grease content from oilfied produced water. Initially, tests were performed with synthetic effluent, using cyclohexanecarboxylic acid as model compound through the study of physical-chemical parameters: pH, temperature, stirring speed and time, petroleum type and concentration, and initial concentration of naphthenic acids. Afterwards, the process was evaluated for the removal of oil and grease content from a real oilfield produced water sample. The pH and petroleum concentration proved to be significantly influential in removing cyclohexanecarboxylic acid from the synthetic produced water (ANOVA). The greater the amount of petroleum present, the greater the efficiency. By acidifying the synthetic effluent, the efficiency of removing these naphthenic acids from the synthetic produced water was increased. Response surface methodology (RSM) evaluated these two factors. On the other hand, the initial concentration of cyclohexanecarboxylic acid and petroleum type did not presented great influence on the obtained results, indicating robustness of the process. The methodology carried out with synthetic effluent proved to be efficient in removing the oil and grease content from real effluent (≈ 60% of removal at pH range 2–5).

Compositional Analysis of Conventional and Unconventional Permian Basin-Produced Waters: A Simple Tool for Predicting Major Ion Composition

Summary Treatment methods for produced water (PW) are significantly affected by a high concentration of total dissolved solids (TDS), a summation of dissolved organic and inorganic compositions. Understanding the constituents of TDS to eliminate or prevent chemical reactions is critical in the design optimization of the treatment processes. In this paper, two PW geochemical data sets generated from conventional and unconventional reservoirs in the Permian Basin were analyzed to correlate constituents with TDS. Compositional data sets from over 115,000 PW samples originally reported by the U.S. Geological Survey (USGS) and 45 oil and gas operations were analyzed. Data preprocessing, culling, systematized- and meta-analysis, and statistical techniques were adapted to associate the data. Subcompositional geochemical data were transformed into isometric log ratios and are presented in bivariate and multivariate plots. Results indicate that Na+ and Ca2+ were the dominant cations and Cl− was the dominant anion. No observable trend differences in the Na+, Cl−, Ca2+, Mg+, and SO42− concentrations between PW from conventional and unconventional wells were registered. Variations in the isometric log ratio of Na/Cl and Ca/SO4 with TDS revealed that Na/Cl was nearly constant over the range of TDS, suggesting mineral buffering or a lack of significant water/rock reactions involving Na and Cl, and that Ca/SO4 increased with TDS, indicating that low-salinity fluids may have dissolved anhydrite producing a value near zero, with Ca gain and/or SO4 loss with increasing salinity. In all 10 counties and 8 formations investigated in this work, the ln (Ca/SO4) denotes Ca gain/SO4 loss relative to their composition in anhydrite or Permian seawater. Likely mechanisms leading to elevated ln (Ca/SO4) include sulfate reduction, dolomitization of calcite, Na/Ca cation exchange, albitization, and anhydrite precipitation from Ca-rich fluids. Results from this work are important as it is revealed that Ca/SO4 and Na/Cl can potentially be predicted from PW TDS concentrations. This information was combined to create a reservoir or location-specific model to estimate Na, Cl, Ca, and SO4 concentrations in Permian Basin PW, a powerful tool to improve treatment and reuse options in areas with few direct data.

Biodesalination and treatment of raw hypersaline produced water samples using indigenous wastewater algal consortia

Indigenous microalgae consortia present in domestic wastewater, were acclimatized to three real produced water (PW) samples collected from different oil fields. PW, a byproduct of oil mining and extraction, is hypersaline and toxic. Therefore, progressive adaptation mechanism was applied for acclimatization in a steadily decreasing dilutions of PW. After acclimatization, algae consortia were used for biodesalination and treatment of PW. The acclimatization lag phase was longer when the dilutions were reduced. The predominant species present in the consortia were Chlorella. One PW sample (onshore with largest initial salinity) showed the earliest adaptation (13 days) at lowest dilution. Chloride and salinity removal efficiencies of 25% and 22% were achieved, respectively, along with significant decrease in total dissolved solids (TDS) and conductivity in the different samples. The same PW sample showed highest removal of chloride (25%, from initial 53 g/L to final 40 g/L) and COD (44%). Another PW sample showed highest removal of salinity (22%), electrical conductivity (9%), TDS (20%) and total organic carbon (26%), as well as highest increase in alkalinity (86%). Removal efficiencies were minimum in the last PW sample which also showed less adaptability to the same dilution ratio of other two PW samples.

Characterization of produced water and surrounding surface water in the Permian Basin, the United States

A thorough understanding of produced water (PW) quality is critical to advance the knowledge and tools for effective PW management, treatment, risk assessment, and feasibility for beneficial reuse outside the oil and gas industry. This study provides the first step to better understand PW quality to develop beneficial reuse programs that are protective of human health and the environment. In total, 46 PW samples from unconventional operations in the Permian Basin and ten surface water samples from the Pecos River in New Mexico were collected for quantitative target analyses of more than 300 constituents. Water quality analyses of Pecos River samples could provide context and baseline information for the potential discharge and reuse of treated PW in this area. Temporal PW and river water quality changes were monitored for eight months in 2020. PW samples had total dissolved solids (TDS) concentrations ranging from 100,800–201,500 mg/L. Various mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances were detected at different concentrations. Chemical characterization of organic compounds found in Pecos River water showed no evidence of PW origin. Isometric log-ratio Na-Cl-Br analysis showed the salinity in the Pecos River samples appeared to be linked to an increase in natural shallow brine inputs. This study outlines baseline analytical information to advance PW research by describing PW and surrounding surface water quality in the Permian Basin that will assist in determining management strategies, treatment methods, potential beneficial reuse applications, and potential environmental impacts specific to intended beneficial use of treated PW.

Unraveling the Complex Composition of Produced Water by Specialized Extraction Methodologies.

Produced water (PW), a waste byproduct of oil and gas extraction, is a complex mixture containing numerous organic solubles and elemental species; these constituents range from polycyclic aromatic hydrocarbons to naturally occurring radioactive materials. Identification of these compounds is critical in developing reuse and disposal protocols to minimize environmental contamination and health risks. In this study, versatile extraction methodologies were investigated for the untargeted analysis of PW. Thin-film solid-phase microextraction with hydrophilic-lipophilic balance particles was utilized for the extraction of organic solubles from eight PW samples from the Permian Basin and Eagle Ford formation in Texas. Gas chromatography-mass spectrometry analysis found a total of 266 different organic constituents including 1,4-dioxane, atrazine, pyridine, and PAHs. The elemental composition of PW was evaluated using dispersive solid-phase extraction followed by inductively coupled plasma-mass spectrometry, utilizing a new coordinating sorbent, poly(pyrrole-1-carboxylic acid). This confirmed the presence of 29 elements including rare earth elements, as well as hazardous metals such as Cr, Cd, Pb, and U. Utilizing chemometric analysis, both approaches facilitated the discrimination of each PW sample based on their geochemical origin with a prediction accuracy above 90% using partial least-squares-discriminant analysis, paving the way for PW origin tracing in the environment.

Toxicological characterization of produced water from the Permian Basin

Produced water (PW) is a hypersaline waste stream generated from the shale oil and gas industry, consisting of numerous anthropogenic and geogenic compounds. Despite prior geochemical characterization, the comprehensive toxicity assessment is lacking for evaluating treatment technologies and the beneficial use of PW. In this study, a suite of in vitro toxicity assays using various aquatic organisms (luminescent bacterium Vibrio fischeri, fish gill cell line RTgill-W1, and microalgae Scenedesmus obliquus) were developed to investigate the toxicological characterizations of PW from the Permian Basin. The exposure to PW, PW inorganic fraction (PW-IF), and PW salt control (PW-SC) at 30−50% dilutions caused significant toxicological effects in all model species, revealing the high salinity was the foremost toxicological driver in PW. In addition, the toxicity level of PW was usually higher than that of PW-IF, suggesting that organic contaminants might also play a critical role in PW toxicity. When comparing the observed toxicity with associated chemical characterizations in different PW samples, strong correlations were found between them since higher concentrations of contaminants could generally result in higher toxicity towards exposed organisms. Furthermore, the toxicity results from the pretreated PW indicated that those in vitro toxicity assays had different sensitives to the chemical components present in PW. As expected, the combination of multiple pretreatments could lead to a more significant decrease in toxicity compared to the single pretreatment since the mixture of contaminants in PW might exhibit synergistic toxicity. Overall, the current work is expected to enhance our understanding of the potential toxicological impacts of PW to aquatic ecosystems and the relationships between the chemical profiles and observed toxicity in PW, which might be conducive to the establishment of monitoring, remediation, treatment, and reuse protocols for PW.

Immobilized Algae for Produced Water Treatment and Desalination

Produced water (PW) is the effluent generated during oil mining and extraction. On average, for every barrel of oil, 4-5 barrels of PW are generated worldwide. The presence of various contaminants in PW makes it toxic. Disposal of untreated PW into oceans and water bodies can cause adverse effects on human health and the environment. Taking into account the large volumes of it being generated, and its effects on the environment, proper treatment is required before reuse or disposal. Microalgal treatment is an effective method for the bioremediation and biodesalination of produced water when acclimatized algal biomass is used for the treatment. However, harvesting this acclimatized high-value algal biomass for reuse and recycling, and the reuse or disposal of produced water is challenging. Thus, the immobilization of microalgae into polymer matrices will be beneficial in solving both problems. Different polymers, both natural and synthetic are used as matrices for immobilizing cells. In this study, experiments were done with alginate and chitosan matrices to immobilize algae. Microalgae enriched and grown in wastewater were acclimatized to three different produced water samples by progressive adaptation in a steadily increasing ratio of produced water. The algae which could adapt and grow in the highest ratio in minimum time were immobilized and used for bioremediation of produced water. The study also evaluated the stability of the matrix in produced water and the treatment efficiency. The results of the study led to the conclusion that produced water is highly toxic for the stability of alginate and chitosan matrices. A more stable matrix has to be determined and experimented with for immobilizing algae and treatment of produced water.

Evaluation of Selected Chemicals used for Oil and Gas Production and Their Toxic Effects on the Niger Delta Fresh Water Tilapia Guineensis

There are projections of continuous increase in the world’s energy demand, which might result to increase in oil and gas exploration and production activities. Nigeria for instance, runs a mono-economy that largely depends on the revenues from her rich oil and gas deposits. Oil and gas exploration and production activities are expected to increase over the years in Nigeria to meet her economic needs, as well as the global energy need. However, oil and gas production activities are associated with environmental concerns, especially with respect to management of the kind of wastes it generates. A major waste generated during oil and gas completion and production operations is the Produced Water (composed of water, different production chemicals and other constituents). This study is focused on evaluation of the toxic effects of selected production chemicals on the Niger Delta freshwater Tilapia guineensis. Among the chemicals evaluated include: SPECTRUS NX1173 (Biocide), FLOGARD MS 6208 (Corrosion inhibitor), ELIMINOX (Oxygen scavenger) and EC9017A (anti-foam), while Tilapia guineensis was used as the bioindicator. Whereas there are past researches on the individual chemicals and confirmation that they are toxic in nature, there are no adequate researches on the comparative toxicity effects of these chemicals, especially on the Niger Delta environment. Produced water samples were simulated in the laboratory using the production chemicals (at different concentrations) and 2000ml of freshwater sample for each experimental setup. The fishes were acclimatized for ten days using same freshwater sample, those that survived were selected for the experiment. The mortality and survival rate of the test organism was monitored at a constant interval of one (1) hour for Ninety-six (96) hours and the percentage mortality of the test organism recorded for all the chemicals at different concentrations ranged from 100% to 10%. The lethal concentration (LC50) calculated for each of the chemicals are as follows: Corrosion inhibitor 0.002%, biocide 0.003%, oxygen scavenger 0.01% and defoamer 0.176%. The corrosion inhibitor was the most toxic as there was 100% mortality of the Tilapia guineensis within 24 hours of the test period, while the defoamer was the least toxic as there were more survival of the test organism at the end of the test period. The test results indicated that all the production chemicals used in this research were toxic, their lethal concentrations differed from one chemical to the other, and the corrosion inhibitor and biocide had the highest toxicity effect on the organisms. The research findings could be used as a basis by the Nigerian regulatory agencies for possible review of currently approved completion and production chemicals for oil and gas activities, as well as produced water disposal options, especially discharge in water bodies in the Niger Delta.

The impact of bacterial diversity on resistance to biocides in oilfields

Extreme conditions and the availability of determinate substrates in oil fields promote the growth of a specific microbiome. Sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB) are usually found in these places and can harm important processes due to increases in corrosion rates, biofouling and reservoir biosouring. Biocides such as glutaraldehyde, dibromo-nitrilopropionamide (DBNPA), tetrakis (hydroxymethyl) phosphonium sulfate (THPS) and alkyl dimethyl benzyl ammonium chloride (ADBAC) are commonly used in oil fields to mitigate uncontrolled microbial growth. The aim of this work was to evaluate the differences among microbiome compositions and their resistance to standard biocides in four different Brazilian produced water samples, two from a Southeast Brazil offshore oil field and two from different Northeast Brazil onshore oil fields. Microbiome evaluations were carried out through 16S rRNA amplicon sequencing. To evaluate the biocidal resistance, the Minimum Inhibitory Concentration (MIC) of the standard biocides were analyzed using enriched consortia of SRB and APB from the produced water samples. The data showed important differences in terms of taxonomy but similar functional characterization, indicating the high diversity of the microbiomes. The APB and SRB consortia demonstrated varying resistance levels against the biocides. These results will help to customize biocidal treatments in oil fields.