A review of the current options for the treatment and safe disposal of drill cuttings

Characteristics of heavy metal migration during pyrolysis of typical oily wastes and environmental risk assessment of pyrolysis residues

Solid-phase residues from pyrolysis of oily wastes (OS) are widely used due to their rich pore structure and strong adsorption capacity. In this study, pyrolysis residues (OS-P) were obtained from the pyrolysis treatment of four typical OS in Karamay, Xinjiang. The results indicate that the crystalline substances in OS-P mainly were SiO2, BaSO4, and graphite. The heavy metals of OS-P were higher than that of OS in the following order: Zn > Cu > Ni > Cr > Pb > Cd. The results of the improvement of Community Bureau of Reference (BCR) sequential extraction showed that the proportion of Cu, Ni and Cr in OS1-P in the residual fraction was higher than that of the other three OS. The residual fraction of Cu, Ni, and Cr in OS1-P increased from 16.0 %, 30.0 %, and 11.0 % to 66.1 %, 81.9 %, and 89.2 %, respectively. After pyrolysis treatment, the leaching concentration of heavy metals in the residue was reduced. Referring to the requirements for heavy metal control limits (GB 4284-2018), all heavy metals in OS-P showed low risk. Their potential ecological risk indices were 4.11, 3.13, 4.87 and 5.35, respectively, indicating that the potential ecological hazards of heavy metals from OS-P were slight. There was no significant effect on the histopathological changes of kidney, lung, liver, ovary and testis of mice, showing that the rational use of OS-P in production will not produce toxic effects on target animals. Based on risk assessment and safety evaluation, the application of OS-P is controllable, safe and reliable for resource utilization.

Laser-upgraded coal tar for smart pavements in road and bridge monitoring applications

The implementation of an intelligent road network system requires many sensors for acquiring data from roads, bridges, and vehicles, thereby enabling comprehensive monitoring and regulation of road networks. Given this large number of required sensors, the sensors must be cost-effective, dependable, and environmentally friendly. Here, we show a laser upgrading strategy for coal tar, a low-value byproduct of coal distillation, to manufacture flexible strain-gauge sensors with maximum gauge factors of 15.20 and 254.17 for tension and compression respectively. Furthermore, we completely designed the supporting processes of sensor placement, data acquisition, processing, wireless communication, and information decoding to demonstrate the application of our sensors in traffic and bridge vibration monitoring. Our novel strategy of using lasers to upgrade coal tar for use as a sensor not only achieves the goal of turning waste into a resource but also provides an approach to satisfy large-scale application requirements for enabling intelligent road networks.

Disposal of drilling waste in salt mines in China

A lot of drilling wastes are produced during oil/gas exploration and exploitation in China. Many countries have built and successfully run projects to dispose of wastes in salt mines, which fully demonstrates the feasibility and superiority of this technology. The application prospects of using salt mines to dispose of drilling wastes is comprehensively evaluated from many aspects. It is concluded that this technology has broad application prospects in China. The scientific and technical problems that need to be solved in order to successfully use this technology are systematically summarized, and some practical suggestions are put forward to improve relevant laws and policies. Considering the geological conditions of salt mines and the requirements of laws and regulations in China, a set of perfect and more advanced Chinese schemes has been proposed.

Construction of Shale Gas Oil-Based Drilling Cuttings Degrading Bacterial Consortium and Their Degradation Characteristics

Oil-based drilling cuttings (OBDCs) contain petroleum hydrocarbons with complex compositions and high concentrations, which have highly carcinogenic, teratogenic, and mutagenic properties. In this study, three highly efficient petroleum hydrocarbon-degrading bacteria were screened from OBDCs of different shale gas wells in Chongqing, China, and identified as Rhodococcus sp. and Dietzia sp. Because of their ability to degrade hydrocarbons of various chain lengths, a new method was proposed for degrading petroleum hydrocarbons in shale gas OBDCs by combining different bacterial species. Results showed that the bacterial consortium, consisting of the three strains, exhibited the highest degradation rate for petroleum hydrocarbons, capable of degrading 74.38% of long-chain alkanes and 93.57% of short-chain alkanes, respectively. Moreover, the petroleum hydrocarbon degradation performance of the bacterial consortium in actual OBDCs could reach 90.60% in the optimal conditions, and the degradation kinetic process followed a first-order kinetic model. This study provides a certain technical reserve for the bioremediation of shale gas OBDCs.

Human health risk assessment of volatile organic compounds in oil-based drill cuttings of shale gas

Waste oil-based drill cuttings contain dioxins and volatile organic compounds (VOCs), which have the potential to cause serious health effects in humans. Therefore, this paper took oil-based drill cuttings (OBDCs) as the research object and carried out the testing of VOCs and dioxins content by using GC-MS and HRGCS-HRMS and comprehensively evaluated the content, composition and distribution pattern of VOCs and dioxins and the risk to human health posed by the two pollutants in OBDCs. The results showed that the VOCs did not exceed the emission limits in ESPPI (GB 31571-2015), but it is vital to recognise that 1,2-dichloropropane has the potential to cause cancer risk, with soil and groundwater risk control values of 662.95 mg·kg-1 and 0.066 mg·kg-1, respectively. Benzene, 1,2-dichloropropane and 8 other VOCs pose a non-carcinogenic risk to humans. The levels of polychlorinated dibenzofurans (PCDFs) exceeded those of polychlorinated dibenzo-p-dioxins (PCDDs), which accounted for 95.76 percent of the total PCDD/Fs, 2,3,4,7,8-P5CDF (56.00%), 2,3,7,8-T4CDF (9.20%), 1,2,3,6,7,8-H6CDF (8.80%) and 1,2,3,7,8-P5CDF (8.00%) were the main contributing monomers. The findings of the assessment on exposure risk indicate that there is a respiratory risk to oil-based drill cuttings dioxins for adults and children exceeded the World Health Organisation (WHO) acceptable daily intake (ADI) (1-4 pgTEQ/kg/d). Finally, three aspects of solid waste pre-treatment prior to incineration, the incineration process and post incineration were used to reduce the environmental and human health risks from dioxins.

Oil well drill cuttings and sunflower cake: effects on sunflower crop and soil chemical attributes

Onshore oil well drill cuttings and sunflower cake from biodiesel production require an appropriate destination to reduce the risks of environmental contamination. The aim of this study was to evaluate the potential use of the combination of different doses of these wastes on the growth of sunflower plants (Helianthus annus L.) and on soil chemical attributes after cultivation, making it possible to recommend safe application doses. Sunflower plants, cultivar Neon, were cultivated in a greenhouse for 80 days in Planossolo Háplico (Ultisol) as the main substrate. The design used was completely randomized, in a 6 × 6 factorial arrangement, composed of five doses of sunflower cake (2, 4, 8, 16 and 32 Mg ha-1) and five doses of drill cuttings (5, 15, 30, 45 and 60 Mg ha-1) and an experimental control using only Ultisol After cultivation, soil chemical attributes and the parameters height (H), stem diameter (D), and dry mass (DMAP) and nutrient contents in the aerial part of the plants were analyzed. Sunflower cake dose of 32 Mg ha-1 limited the germination of sunflower plants. In sunflower plants, the highest contents of calcium (Ca), magnesium (Mg), phosphorus (P) and potassium (K) were verified when the sunflower cake doses were associated with drill cuttings doses >45 Mg ha-1. The mixture between sunflower cake and drill cuttings in the proportion of 16:45 Mg ha-1, respectively, promoted higher H, D and DMAP of sunflower plants, as well as a considerable improvement in soil fertility, without causing significant increments in sodium content in the soil after cultivation.HighlightsInadequate disposal of agro-industrial wastes represents loss of raw material and energy.Drill cuttings and sunflower cake wastes enable improvements in soil fertility attributes.The combination of sunflower cake and drill cuttings contributed to sunflower growth and nutrient contents.The mixture of drill cuttings and sunflower cake has potential for use as agricultural input.

Physical and chemical characterization of drill cuttings: A review

Drill cuttings comprise a mixture of rocks generated during drilling activities of exploration and production of oil and gas. These residues' properties are variable, depending on several drilling parameters and drilled rock composition. Many scientific studies have been published regarding the characterization of these residues. Articles summarizing these residues' characteristics and toxicity data are poorly explored in the literature. This work reviews the principal methods used to characterize drill cuttings and data about these residues' properties. Some authors have reported the large content of Zn in drill cuttings. These cuttings can be associated with base fluids (as olefins, varying from C11 to C18), and some time crude oil (high range of TPH, unresolved complex mixtures, and PAH compounds). Acute and chronic toxicity tests have shown negative impacts of different types of fluids, the components of these fluids, and cuttings on other marine organisms.

Dynamic response of microbial communities to thermally remediated oil-bearing drilling waste in wheat soil

The primary objective of our study was to mix thermally remediated oil-bearing drilling waste (TRODW) with farmland soil during wheat planting and explore the response of microbial phospholipid fatty acid (PLFA) communities as well as the feasibility of returning TRODW to farmland. Based on environmental protection requirements and the dynamic response of wheat soil, this paper not only provides a method combining multiple models for mutual verification but also provides valuable and exploratory information for the remediation and reuse of oily solid waste. Our research found that salt damage mainly originated from sodium ions and chloride ions that inhibited the development of microbial PLFA communities in the treated soils at the initial stage. When salt damage declined, TRODW improved the levels of phosphorus, potassium, hydrolysable nitrogen and soil moisture, increasing the soil health status and promoting the development of microbial PLFA communities even when the addition ratio reached 10%. Moreover, the influences of petroleum hydrocarbons and heavy metal ions on microbial PLFA community development were not significant. Therefore, when salt damage is controlled effectively and the oil content in TRODW is no more than 3‰, it is potentially feasible to return TRODW to farmland.

Physical-chemical characterization and leaching studies involving drill cuttings generated in oil and gas pre-salt drilling activities

This work describes characterization and leaching studies of pre-salt drill cuttings from offshore oil and gas exploration in ultradeep waters. The metals Fe, Al, and Ba were present in the highest concentrations in drill cuttings (30000 mg kg^-1, 32600 mg kg^-1, and 33000 mg kg^-1 respectively). The most significant contents of Ba, Al, Fe, Cu, Pb, Mn, Si, and Zn were found in cuttings containing non-aqueous fluids (NADF), but the highest concentrations of Ni and Cr were found in samples containing aqueous fluids (WBDF). The content of total petroleum hydrocarbons (TPHs) in the samples with WBDF fluids ranged from < 5.58 to 15.76 mg Kg^-1 while the TPH content of the samples with NADF ranged from 28.46 to 47.16 mg Kg^-1. Data on the content of unresolved complex mixtures (UCMs) and sheen tests indicated probable contamination of some cutting samples with oil. Most samples showed some degree of contamination by polycyclic aromatic hydrocarbons (PAHs). The metals present in the highest concentrations in saline and aqueous leachates were Si and Ba. The metals Cd, Cu, Ni, and Zn were present in varied concentrations in the saline leachates, and the metals Si, Ba, Cu, and Zn were found in the aqueous leachates.

Treatment of drilling fluid waste during oil and gas drilling: a review

Oil and gas exploration and development provide important energy sources for the world, and drilling fluid is an essential engineering material for oil and gas exploration and development. During the drilling of oil wells, drilling fluids are eventually discarded as waste products after many cycles. Abandoned drilling fluid constitutes one of the largest wastes generated during oil and gas exploration and development. Drilling fluid contains many chemicals, which turn into pollutants during use. Furthermore, when drilling is carried out to reach reservoir, the drilling fluid becomes contaminated with crude oil. It may also mix with groundwater containing salts and heavy metals. The resulting pollutants and harmful substances threaten the environment, humans, animals, and plants. The variety and complexity of drilling fluid waste have increased in recent years. Various countries and regions are paying more attention to the ecological environment, and effective methods are urgently needed to solve problems associated with of environmental pollution caused by drilling fluid wastes. At present, various physical, chemical, and biological methods have been proposed for the treatment of drilling fluid wastes: safe landfilling, stabilization/solidification treatment, physicochemical treatment, thermal treatment, supercritical fluid treatment, bioremediation, etc. All of these methods show promising characteristics, and they each have advantages and limitations; thus, treatment methods need to be selected according to the actual application scenarios. This critical overview is based on an extensive literature review, and it summarizes and expounds on the current drilling fluid waste treatment technologies and proposes views future potential and outlook.

Regional distribution, properties, treatment technologies, and resource utilization of oil-based drilling cuttings: A review

Oil-based drilling cuttings (OBDC) are hazardous wastes produced during the extensive use of oil-based drilling mud in oil and gas exploration and development. They have strong mutagenic, carcinogenic, and teratogenic effects and need to be properly disposed of to avoid damaging the natural environment. This paper reviews the recent research progress on the regional distribution, properties, treatment technologies, and resource utilization of OBDC. The advantages and disadvantages of different technologies for removing petroleum pollutants from OBDC were comprehensively analyzed, and required future developments in treatment technologies were proposed.

The pozzolanic activity of calcined oil-based drilling cuttings-aluminosilicate composites

In order to reduce the environmental impact of shale gas production and towards the attenuation of artificial pozzolanic materials production cost, new oil-based drilling cuttings (OBDCs) pozzolanic materials have been introduced. After calcination, the chemical composition and the pozzolanic activity of oil-based drilling cuttings residue (OBDCRs) were investigated. The combination of X-ray diffraction (XRD), thermogravimetric analysis (TG), and Fourier transform infrared (FTIR) techniques shed light on impacts of pretreatment, calcination temperature, and Ba²⁺ on minerals' structure and pozzolanic activity. The results showed that, after high temperature calcination, the components of Si or Al in the OBDCRs particle surface and structure were activated and recombined to produce corresponding activity. Ba²⁺ could promote the pozzolanic activity of OBDCRs. The 28-day-compressive strength of OBDCRs was bigger than 31.33Mpa, and the compression strength ratios of cement mortar were bigger than 65%. Therefore, the pozzolanic reactivity of the treated OBDCs was competitive with that of conventional shale, which indicates that the heat treatment of OBDCs produces a cement substitute without any secondary pollution.

Comparative life cycle assessment of cement, sintered bricks and non-sintered bricks manufacturing using water-based drilling cuttings from shale gas production in the Sichuan Basin, China

This study determined the environmental impacts of three recycling pathways for water-based drilling cuttings (WDC), namely cement, sintered bricks, and non-sintered bricks, based on the life cycle assessment (LCA) method. A life cycle inventory was developed with based on the resource utilization of 1t drilling cuttings as the functional unit, and a sensitivity analysis was conducted to identify the essential materials and energy consumption. The results showed that the sequence of the environmental impact index for the three recycling pathways was cement, non-sintered brick and sintered brick. Primary energy demand and direct emissions were the main reasons for this difference. Direct emissions, electricity, and binder were the largest contributors to the inventory of cement, sintered bricks, and non-sintered bricks, accounting for 54%, 33.4%, and 62.1% of the environmental impact burden, respectively. Furthermore, a 5% reduction in direct emissions, electricity, and binder decreased the integrated impact index by approximately 2.67%, 3.04%, and 3.38% for cement, sintered bricks, and non-sintered bricks, respectively. Based on the LCA results, strategies for reducing emissions and conserving energy were proposed. These results provide a useful reference for creating a sustainable system for recycling water-based drilling cuttings.

Chemical and Reactive Transport Processes Associated with Hydraulic Fracturing of Unconventional Oil/Gas Shales

Hydraulic fracturing of unconventional oil/gas shales has changed the energy landscape of the U.S. Recovery of hydrocarbons from tight, hydraulically fractured shales is a highly inefficient process, with estimated recoveries of <25% for natural gas and <5% for oil. This review focuses on the complex chemical interactions of additives in hydraulic fracturing fluid (HFF) with minerals and organic matter in oil/gas shales. These interactions are intended to increase hydrocarbon recovery by increasing porosities and permeabilities of tight shales. However, fluid-shale interactions result in the dissolution of shale minerals and the release and transport of chemical components. They also result in mineral precipitation in the shale matrix, which can reduce permeability, porosity, and hydrocarbon recovery. Competition between mineral dissolution and mineral precipitation processes influences the amounts of oil and gas recovered. We review the temporal/spatial origins and distribution of unconventional oil/gas shales from mudstones and shales, followed by discussion of their global and U.S. distributions and compositional differences from different U.S. sedimentary basins. We discuss the major types of chemical additives in HFF with their intended purposes, including drilling muds. Fracture distribution, porosity, permeability, and the identity and molecular-level speciation of minerals and organic matter in oil/gas shales throughout the hydraulic fracturing process are discussed. Also discussed are analysis methods used in characterizing oil/gas shales before and after hydraulic fracturing, including permeametry and porosimetry measurements, X-ray diffraction/Rietveld refinement, X-ray computed tomography, scanning/transmission electron microscopy, and laboratory- and synchrotron-based imaging/spectroscopic methods. Reactive transport and spatial scaling are discussed in some detail in order to relate fundamental molecular-scale processes to fluid transport. Our review concludes with a discussion of potential environmental impacts of hydraulic fracturing and important knowledge gaps that must be bridged to achieve improved mechanistic understanding of fluid transport in oil/gas shales.

Oil-Based Mud Waste as a Filler Material in LDPE Composites: Evaluation of Mechanical Properties

Traditionally, the drilling waste generated in oil and gas exploration operations, including spent drilling fluid, is disposed of or treated by several methods, including burial pits, landfill sites and various thermal treatments. This study investigates drilling waste valorisation and its use as filler in polymer composites. The effect of the poor particle/polymer interfacial adhesion bonding of the suspended clay in oil-based mud (OBM) slurry and the LDPE matrix is believed to be the main reason behind the poor thermo-mechanical and mechanical properties of low-density polyethylene (LDPE)/OBM slurry nanocomposites. The thermo-mechanical and mechanical performances of LDPE)/OBM slurry nanocomposites without the clay surface treatment and without using compatibilizer are evaluated and discussed. In our previous studies, it has been observed that adding thermally treated reclaimed clay from OBM waste in powder form improves both the thermal and mechanical properties of LDPE nanocomposites. However, incorporating OBM clay in slurry form in the LDPE matrix can decrease the thermal stability remarkably, which was reported recently, and thereby has increased the interest to identify the mechanical response of the composite material after adding this filler. The results show the severe deterioration of the tensile and flexural properties of the LDPE/OBM slurry composites compared to those properties of the LDPE/MMT nanocomposites in this study. It is hypothesised, based on the observation of the different test results in this study, that this deterioration in the mechanical properties of the materials was associated with the poor Van der Waals force between the polymer molecules/clay platelets and the applied force. The decohesion between the matrix and OBM slurry nanoparticles under stress conditions generated stress concentration through the void area between the matrix and nanoparticles, resulting in sample failure. Interfacial adhesion bonding appears to be a key factor influencing the mechanical properties of the manufactured nanocomposite materials.

Utilizing shale gas drilling cuttings as admixture in cement mortars: a case study in Fuling, Chongqing, China

Huge amount of water-based drilling cuttings (WDC) is generated during the drilling and exploitation of shale gas. In this study, WDC powder was used as a replacement of cement at different mass fraction (0, 10%, 30%, and 50%) to prepare cement mortars. The mechanical properties, water absorption, and heavy metals leaching of the mortars were then investigated along with the corresponding microstructures. The results showed that a higher porosity was formed within the WDC-blended mortars. For instance, the porosity of the control specimen was 16.7%, while the porosity increased to 20.6%, 21.4%, and 25.0% for the mortars blended with 10%, 30%, and 50% WDC, respectively. Therefore, the mechanical properties of the mortars decreased and their water absorption increased with the increase of WDC replacement ratio. For example, the compressive strength of the mortars blended with 10% and 30% WDC decreased from 33.11 MPa of the control specimen to 29.33 MPa and 21.48 MPa, respectively. Nevertheless, the blended mortars still satisfied the M20 strength grade according to the Chinese standard (JGJ/T 98-2010). The compressive strength of the mortar blended with 50% WDC was 11.33 MPa and then satisfied the M10 strength grade. The leaching test indicated that the water quality of leachates from the mortars blended with lower than 30% WDC remained as Grade I according to the Chinese standard (GB 3838-2002); the water quality of leachate from the mortar blended with 50% WDC was classified as Grade III, which, however, would not cause a safety issue to the environment.

The effect of amendment addition drill cuttings on heavy metals accumulation in soils and plants: Experimental study and artificial network simulation

A greenhouse experiment was carried out to evaluate the influence of drill cuttings addition on the accumulation of heavy metals in soil, in plant biomass (Trifolium pretense L.) cultivated on soils with the addition of this type of waste. The transfer and transformation of heavy metals in the soil with drill cuttings- Trifolium pretense L were discussed. Drilling waste in the amount of 2.5%, 5%, 10% and 15% of dry weight were added to acidic soil. The concentrations of heavy metals in the soil and plant materials were determined by an inductively coupled plasma mass spectrometry method. Results indicated that drilling wastes addition had a positive influence on the growth of Trifolium pretense L. However, the concentrations of heavy metals increased in the prepared mixtures along with the dose of drilling wastes. The drilling wastes addition also changed the metal accumulation capacity in plant parts. Nevertheless, the concentrations of heavy metals in soils and above-ground parts of plants did not exceed the permissible values in respective legal standards. The values of the heavy metals bioconcentration coefficient in Trifolium pretense L at the highest dose of drill cuttings were as follows: in the above-ground parts Cd>Cu>Ni>Cr>Pb>Zn, in roots Cd>Ni>Cr>Zn>Pb>Cu. An artificial neural network model was developed in order to predict the concentration of heavy metals in the plants cultivated on the soils polluted with drill cuttings. The input (drill cuttings dose, pH, organic matter content) and the output data (concentration of heavy metals in the shoot cover) were simulated using an artificial neural network program. The results of this study indicate that an artificial neural network trained for experimental measurements can be successfully employed to rapidly predict the heavy metal content in clover. The artificial neural network achieved coefficients of correlation over 90%.

Release characteristics of polycyclic aromatic hydrocarbons (PAHs) leaching from oil-based drilling cuttings

Drilling cuttings, the primary byproduct from the exploration and mining of shale gas, are potentially hazardous wastes that are associated with the serious depletion of land resources and environmental safety problems. In this work, the distribution of polycyclic aromatic hydrocarbons (PAHs) in oil-based residues of shale gas drilling cuttings was studied. Furthermore, a column leaching test was carried out to investigate the leaching behaviour of PAHs. The results showed that (1) the concentrations of 4-ring PAHs were highest among the PAH concentrations detected from the oil-based residues, and the concentration of PAHs decreased with increasing particle size of the residues. (2) The PAH concentration in leachates from all the tested residues differed during the leaching process, and the cumulative amount of each leached PAH accounted for 1.50-3.20% of the total PAHs. (3) The first-order diffusion model (FRDM) was the most applicable model for describing the leaching characteristics of the PAHs, and the leaching rate was initially controlled by surface wash-off and then by diffusion.

Emissions of BTEXs, NMHC, PAHs, and PCDD/Fs from Co-processing of Oil-based Drilling Cuttings in Brick Kilns

Oil-based drilling cuttings (OBDC) produced from shale gas development is a hazardous waste that have high calorific values and should be disposed of properly. Burning bricks with OBDC is a promising co-disposal method; however, organic pollutants emitted during this process have not received sufficient attention. In this study, the composition and combustion characteristics of OBDC were determined, and the emissions of typical organic pollutants when burning bricks with the addition of OBDC were investigated; these included benzene series compounds (BTEXs), non-methane total hydrocarbons (NMHC), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The results showed that OBDC comprised large amounts of alkanes and aromatic hydrocarbons, and combusted mainly in the temperature range of 145-450 °C with an ignition temperature of 145 °C. The co-processing 10% OBDC increased the concentrations of toluene, NMHC, and PAHs in the flue gases by ∼1000%, ∼500%, and 200%, respectively, compared to the control experiment; however, their emission concentrations were within the limits set by the Integrated emission standards of air pollutants of Chongqing. It is worth noting that 26.443 ng/Nm³ PCDD/Fs with a total toxicity of 0.709 ng I-TEQ/Nm³ was generated from the co-processing 10% OBDC, which was ascribed to the high content of chlorine and aromatic hydrocarbons in the OBDC-promoted PCDD/Fs formed during the burning and cooling processes. Though PCDD/Fs in flue gas exceeded the 0.5 ng I-TEQ/Nm³ limit prescribed in the Pollution control standard for hazardous wastes incineration of China, the realistic emission of PCDD/Fs is expected to meet with this emission limit after desulfurization treatment as PCDD/Fs can be absorbed by gypsum. It is recommended that a lower amount of OBDC is added to reduce PCDD/F formation at the source and to take more efficient air pollution control system in order to reach a stricter emission limit of 0.1 ng I-TEQ/Nm³ in EU and USA. Cycling flue gas may also be an effective method to reduce other organic pollutants. Under these conditions, co-processing OBDC in brick kilns can be achieved without serious environmental pollution, making it a potential method for disposal and utilization.

Waste management in the mining industry of metals ores, coal, oil and natural gas - A review

Waste generated due to mining activity poses a serious issue due to the large amounts generated, even up to 65 billion tons per year, and is often associated with the risk posed by its storage and environmental management. This work aims to review waste management in the mining industry of metals ores, coal, oil and natural gas. It includes an analysis and discussion on the possibilities for reuse of certain types of wastes generated from mining activity, and discusses the benefits, disadvantages and the impact of waste management on the environment. The article presents current methods of waste management arising during the extraction and processing of raw materials and the threats resulting from its application. Furthermore, the potential methods of mining waste management are discussed through an in-depth characterization of the properties and composition of various types of rocks. The presented work addresses not only the issues of more sustainable management of waste from the mining industry, but also responds to the current efforts to implement the assumptions of a circular economy, which is aimed at closing the loop. The methods of recycling by-products and treating waste as a resource more and more often not only meet environmental expectations, but also become a legal requirement. In this respect, the presented work can serve as a valuable support in decision-making about waste management.

The fate of waste drilling fluids from oil & gas industry activities in the exploration and production operations

Operational discharges from oil and gas exploration industry, accidental spillage, or improperly disposed drilling wastes has serious detrimental effects on human and the environment. The water- and oil-based fluids wastes are generated every year all over the world and remain a serious challenge in compliance with the requirements of zero discharge for the oil and gas industry. To meet environmental regulations, sustainable and effective waste management is critical yet mostly missing in the oil and gas industry. This work aims to provide the current state of art in drilling waste (drill cuttings and drilling fluids). An overview of the drilling fluid waste is first provided followed by its characteristics, environmental concerned constituents in this waste stream are then explored while considering the current waste management efforts. Environmental and regulatory issues regarding drilling waste and the shortcomings of regulations are also discussed. The work sums up with a perspective future trends on drilling waste management, opportunities and challenges ahead including the potential for recycling and re-use of waste drilling fluids and cuttings for commercial products development. There are opportunities for waste valorisation especially in raw materials recovery for valuable products utilisation rather than incurring burden to the environment.

Using prototypes to enable development of commercially viable field scale contaminated site remediation processes

Soil structure was damaged from solvents and localised heating after a large fire which had potential to limit bioremediation of an industrial site. Laboratory prototypes (biopile, bioflushing, bioreactor, slurry reactor) for treating the site contamination were developed. After successful laboratory testing (96% removal of main contaminant, phenol), the bioflushing prototype was then applied in the field. Field prototype removed 95% phenol using a small scale 2000 L bioreactor. Field trial was then scaled to commercial clean-up. Intensive soil grid sampling after 600 days treatment revealed hotspots of solvents remaining as well as the heterogeneity in the subsurface, however overall concentrations were substantially decreased below the initial assessment. The process decreased initial soil phenol concentrations of approximately 500 mg/kg (pre-treatment area average) to 75 mg/kg across the most contaminated areas. Phenol toxicity increased with depth and is linked to increasing oxygen deficit. The study demonstrated the prototyping process enabling site clean-up and scaling for bioremediation at the industrial site, provided certainty for site owner on treatment elements and achieving improved environmental and commercial outcomes.

Volatilization behavior of polycyclic aromatic hydrocarbons from the oil-based residues of shale drill cuttings

Shale gas, an emerging oil-bearing and pillar industry at home and abroad, has a very large impact on economic development and industry, but the resulting emerging pollutants pose a serious threat to the environment. Drilling cuttings, the primary byproduct of the exploration and mining of shale gas, are potentially hazardous types of waste that seriously deplete land resources and pose environmental safety problems. In this paper, a long-term static volatilization experiment was conducted to study the volatilization of polycyclic aromatic hydrocarbons (PAHs) in the oil-based residue of shale gas drill cuttings. Furthermore, the effects of some relevant environmental factors controlling the volatilization behavior were evaluated, including different particle sizes, temperatures and illuminances. The results showed that (1) the volatilization concentrations of PAHs gradually increased with prolonged volatilization time. PAHs with smaller ring numbers were present at the highest concentrations among the detected PAHs, and they were more readily volatilized and could be detected earlier. (2) The C-history method was found to significantly describe the kinetic process of the volatilization of PAHs. (3) Different environmental factors had different effects on the volatilization of PAHs. We found that increasing the temperature and illuminance and decreasing the particle size increased volatility. Through canonical correspondence analysis, PAHs volatilization was found to be a complex process, so volatilization tests under simulated environmental conditions are of scientific and environmental interest.

Property of concrete made of recycled shale gas drilling cuttings

Exploration and development of shale gas generate a lot of water-based drilling cuttings (WDC), which can then be used in concrete engineering. This work studied mix ratio optimization, mechanical properties, leaching characteristics and the microstructure of the WDC concrete. The results showed that the pH and COD values of these WDC were slightly above 9.0 and 60, respectively. All other indices satisfied the first grade standard of Chinese standard GB8978. On the other hand, a moderate amount of WDC can be improved concrete properties, especially its workability and compressive strength. When the water-binder ratio is 0.52 and the sand ratio is 41%, we can obtain C25 strength grade and 130 ~ 140 mm slump grade concrete by adding high efficiency water reducing agent and fly ash. XRD and SEM analysis showed that the silica and aluminum oxide in WDC reacted with calcium hydroxide to form secondary hydration products: C-S-H gel and ettringite, which are conducive to the formation of concrete strength and solidified the heavy metals and other contaminants. EDX analysis found it is known that the hydration products in WDC concrete can bind metal elements well. The environmental leaching test shows that the recycled WDC added to concrete products as aggregate and admixture is very environmentally friendly and sustainable.

Particular pollutants, physical properties, and environmental performance of porous ceramsite materials containing oil-based drilling cuttings residues

The mineral compositions of oil-based drilling cutting residues (ODCRs) were similar to that of clay, which could be used as raw materials for ceramsite. In this study, the maximum addition of ODCRs and the optimum calcination conditions were studied by single factor experiment. The microstructure, phase composition, and element distribution of ceramsite were studied by means of SEM, XRD and EDS. The ceramsite, with a 40% ODCRs content, was calcined at 1000 °C for 2 h. After cooling down, the ceramsite had good physical properties, including low density, low water absorption, and high compressive strength. The bulk density was 850-970 kg/m³, the water absorption was 2.1-10%, and the cylinder compressive strength was 6-11.8 MPa. And most of the heavy metals in ODCRs were effectively solidified. The organic toxic substances were completely burned. The leaching amount of harmful elements met the requirements of Chinese standards. The ceramsite would avoid secondary pollution to the environment. So the ceramsite made from ODCRs can not only improve the processing speed of ODCRs, but also be used as building materials, greening materials, industrial filter materials, etc., and increase its environmental and social benefits.

Effect of Oily Sludge Treatment with Molten Blast Furnace Slag on the Mineral Phase Reconstruction of Water-Quenched Slag Properties

Blast furnace slag, which is the main by-product of the ironmaking process discharged at 1450 °C, contains high-quality sensible heat, while oily sludge is the main solid waste produced in the process of gas exploration, storage, and transportation. The energy and resource utilization of blast furnace slag is complementary to the environmentally friendly treatment of oily sludge, which has provided a new idea for the multi-factor synergistic cycle and energy transformation of the two wastes. The pyrolysis of the oily sludge with the molten blast furnace slag was conducted in the current paper. Results showed that the oily sludge was rapidly pyrolyzed, and the heavy metal elements in the oily sludge were solidified. The solidification rate of the heavy metals exceeds 90%, except for vanadium. The reconstituted water-quenched blast furnace slag still has good activity, and it will not affect the further use of the slag after pyrolysis (BFS-P).

Leaching behavior of polycyclic aromatic hydrocarbons (PAHs) from oil-based residues of shale gas drill cuttings

Cuttings are the main solid residues which are generated from drilling operations. Due to the presence of heavy and radioactive elements, the environment risk posed by cuttings has attracted increasing attention. In this work, a short-term static immersion experiment was carried out to investigate the leaching of polycyclic aromatic hydrocarbons (PAHs) from oil-based residues of shale gas drilling cuttings. Furthermore, the effects of some relevant environmental factors controlling the leaching behavior were evaluated, including the different particle sizes, pH, extraction time, solid-to-liquid (S/L) ratio and dissolved organic matter (DOM) concentration. The results showed that (1) the concentrations of leached PAHs gradually increased with prolonged leaching time, but the cumulative amount of PAHs released during leaching was less than 3% of the total. (2) The Elovich, parabolic diffusion and power function models were found to fit the experimental data better than the first-order kinetic equation, indicating that the leaching of PAHs was controlled by the coupling of diffusion and chemical reactions at the source surface. (3) Different environmental factors had different impacts on the leaching of PAHs: the shaking time and presence of DOM increased leachability, the particle size and S/L ratio decreased leachability, and the pH did not affect the leachability of PAHs. Therefore, PAHs leaching was a complex process, and it is of scientific and environmental interest to conduct the leaching tests under the simulated environmental conditions.

Enhanced biodegradation and valorization of drilling wastewater via simultaneous production of biosurfactants and polyhydroxyalkanoates by Pseudomonas citronellolis SJTE-3

Pseudomonas citronellolis SJTE-3 was isolated as a highly efficient microorganism for biodegradation and valorization of drilling fluids (DF) wastewater. The strain metabolised DF and oily mud exhibiting up to 93%, 86%, 85% and 88% of chemical oxygen demand (COD), n-dodecane, n-tetradecane and naphthalene removal efficiency respectively. Enhanced bioconversion was enabled through production of biosurfactants that reduced the surface tension of water by 53% and resulted in 43.3% emulsification index (E24), while synthesizing 24% of dry cell weight (DCW) as medium-chain-length polyhydroxyalkanoates (PHA). Expression from the main pathways for alkanes and naphthalene biodegradation as well as biosurfactants and PHA biosynthesis revealed that although the alkanes and naphthalene biodegradation routes were actively expressed even at stationary phase, PHA production was stimulated at late stationary phase and putisolvin could comprise the biosurfactant synthesized. The bioconversion of toxic petrochemical residues to added-value thermoelastomers and biosurfactants indicate the high industrial significance of P. citronellolis SJTE-3.

Risk assessment of human exposure to heavy metals, polycyclic aromatic hydrocarbons, and radionuclides in oil-based drilling cutting residues used for roadbed materials in Chongqing, China

Oil-based drilling cutting residues (OBDCRs) contain many kinds of carcinogenic contaminants, such as heavy metal elements, polycyclic aromatic hydrocarbons (PAHs), and natural radioactive materials (NORMs), which are great risks for the environment and human health. This study investigated the chemical composition, the radioactive strength, the heavy metal contents, and the org matter contents in OBDCRs and estimated the health risks due to exposure to heavy metals, PAHs, and radionuclides in OBDCRs used for roadbed materials. From the measurements, it was found that the content values of benzopyrene (a), diphenylanthracene (a, h), and petroleum hydrocarbons exceeded the standard limit. The content values of Cu, Zn, As, and Ni were higher than 50% of the standard limit. If OBDCRs were directly used to make roadbed materials, the total carcinogenic risk values (CR_n) of As, benzoanthracene (a), benzopyrene (a), and dibenzoanthracene (a, h) were all higher than 10^-6. The average absorbed dose rate was higher than 80 nGy/h. There were greater risks of carcinogenic environment and potential harms to human health. To reduce the health risks, it is necessary to consider the strategy of the utilization of OBDCRs, the working time, and the service life of the recycled OBDCRs and establish a legal standard and liability for the utilization of OBDCRs as solid waste resources.

Using water-based drilling cuttings from shale gas development to manufacture sintered bricks: a case study in the southern Sichuan Basin, China

Large amounts of water-based drilling cuttings (WDC) would be generated during the drilling of shale gas wells, which would occupy land resources and pose significant threat to soil and groundwater environment. The aim of this study was to assess the feasibility of using WDC as a replacement of natural clay to prepare sintered bricks. To determine the optimum preparation condition, the weight loss on ignition, bulk density, water absorption, and compressive strength of the samples were tested. Meanwhile, the environmental performance of the final products was evaluated and micro-analysis was conducted via X-ray diffraction and scanning electron microscopy. The results showed that using WDC to manufacture sintered bricks was technically feasible, but the physical mechanical performance would significantly decrease with the increase of the replacement ratio because of the presence of less silica and excessive calcium. The addition of waste glass and fly ash could promote the generation of molten glassy phase and form the crystal particle bonding structure, which would contribute to the physical-mechanical performance of WDC sintered bricks. Some mineral components in raw materials decomposed and formed minerals with better thermal stability during the sintering process. Under the optimum preparation conditions (mass ratio of WDC: waste glass: fly ash at 40:20:40, sintering temperature at 900 °C, and insulation time at 2 h), the physical-mechanical and environmental performance of WDC sintered bricks could meet the requirements of corresponding Chinese standards and ASTM standards. Thus, in this study, an effective solution to recycle WDC from shale gas development is provided.

Low-temperature thermal desorption and secure landfill for oil-based drill cuttings management: Pollution control, human health risk, and probabilistic cost assessment

Oil-based drill cuttings (OBDCs) were managed in two scenarios including low-temperature thermal desorption (LTTD) and secure landfill through a case study. The removal of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in OBDCs by LTTD under different conditions was investigated. Probabilistic human health risk assessment was performed to quantify the health risk posed to waste management workers under the two scenarios, while the associated costs were also analyzed. The results show that LTTD at 300 °C for >20 min could remove 96.27% of PAHs in OBDCs but its removal effect on heavy metals was not significant. It was found that cancer risks posed by PAHs in both securely landfilled and LTTD-treated OBDCs were not significant (<1e-06); however, significant cancer risks (7.95e-05-9.45e-05) were identified for exposure to toxic heavy metals. Increased health risk was observed as a result of exposure to LTTD treatment residues compared to securely landfilled OBDCs. Inhalation of chromium(VI) and oral ingestion of arsenic in OBDCs were critical exposure routes. Both cancer and non-cancer risks in the secure landfill scenario were negligible. The cost analysis results suggest that LTTD combined with stabilization/solidification could be more economically attractive than secure landfill for the handling of OBDCs.

Genotoxicity detection of oil-containing drill cuttings by Comet assay based on a demersal marine fish Mugilogobius chulae

An enormous amount of oil-containing drill cuttings have been produced by the marine oil and gas industry. The environmental impacts of discharged drilling waste have been extensively studied. However, there is still an urgent need to develop alternative methods to identify the genotoxicity of untreated and treated drill waste in a timely manner before it is discharged. In this study, we developed a relatively rapid, sensitive, and accurate genotoxicity-detection method using Comet assay and the marine benthic goby Mugilogobius chulae. This goby is sensitive to a standard toxicant mitomycin C (MMC). The optimal exposure period for genotoxicity detection using M. chulae was determined. Three genotoxic indices (tail length (TL), tail DNA content (TD), and tail moment (TM)) were used to assess the effectiveness of high-temperature treatment of oil-contaminated waste. Untreated oil-containing drill cuttings exhibited the highest genotoxicity to goby cells. Genotoxicity was dramatically reduced after thermal treatment of drill cuttings at 350 °C and 500 °C. TD and TM exhibited significant correlation with the concentration of total petroleum hydrocarbons (TPHs)/total polycyclic aromatic hydrocarbons (PAHs) according to Pearson and Mantel correlation analyses (P values were <0.05). Using redundancy analysis (RDA) and variation partition analysis (VPA), the genotoxic effects of the drill cuttings were ascribed to total alkanes and specific groups of PAHs. In conclusion, this newly established biological model has the potential to be widely used to detect the genetic damage of untreated or treated oil-containing drill cuttings discharged into the marine environment.

Life cycle assessment of low-temperature thermal desorption-based technologies for drill cuttings treatment

The life cycle impacts of treatment of typical oil-based drill cuttings (OBDCs) using three low-temperature thermal desorption (LTTD)-based systems, including thermomechanical cuttings cleaner (TCC), screw-type dryer (STD), and rotary drum dryer (RDD), were explored with a case study in British Columbia, Canada. Two energy supply scenarios, including diesel generator-based onsite (scenario i) and hydropower-based offsite (scenario ii) treatments, were considered in the assessment. The results show that RDD generated the lowest life cycle impacts in terms of damages to human health, ecosystems, and resources in scenario i. TCC-scenario ii generated the lowest impacts among all assessed cases, suggesting that using renewable energy can greatly reduce the impacts of LTTD-based OBDCs treatment. Also, net environmental benefits could be achieved considering the reuse of recovered oil, and the highest net environmental benefits were obtained in TCC-scenario ii. The process contribution analysis found that thermal desorption process accounted for 80-95 % of impacts in almost all impact categories. Energy consumption contours and linear regression models were also developed to help drilling waste managers estimate the life cycle impacts of using hydropower-driven TCC to treat OBDCs with different water and oil contents.

Oil-based mud waste reclamation and utilisation in low-density polyethylene composites

Oil-based mud (OBM) waste from the oil and gas exploration industry can be valorised to tailor-made reclaimed clay-reinforced low-density polyethylene (LDPE) nanocomposites. This study aims to fill the information gap in the literature and to provide opportunities to explore the effective recovery and recycling techniques of the resources present in the OBM waste stream. Elemental analysis using inductively coupled plasma-optical emission spectrometry (ICP-OES) and X-ray fluorescence analysis, chemical structural analysis by Fourier transform infrared (FTIR) spectroscopy, and morphological analysis of LDPE/organo-modified montmorillonite (LDPE/MMT) and LDPE/OBM slurry nanocomposites by scanning electron microscopy (SEM) have been conducted. Further analysis including calorimetry, thermogravimetry, spectroscopy, microscopy, energy dispersive X-ray analysis and X-ray diffraction (XRD) was carried out to evaluate the thermo-chemical characteristics of OBM waste and OBM clay-reinforced LDPE nanocomposites, confirming the presence of different clay minerals including inorganic salts in OBM slurry powder. The microscopic analysis revealed that the distance between polymer matrix and OBM slurry filler is less than that of MMT, which suggests better interfacial adhesion of OBM slurry compared with the adhesion between MMT and LDPE matrix. This was also confirmed by XRD analysis, which showed the superior delamination structure OBM slurry compared with the structure of MMT. There is a trend noticeable for both of these fillers that the nanocomposites with higher percentage filler contents (7.5 and 10.0 wt% in this case) were indicated to act as a thermal conductive material. The heat capacity values of nanocomposites decreased about 33% in LDPE with 7.5 wt% MMT and about 17% in LDPE with 10.0 wt% OBM slurry. It was also noted, for both nanocomposites, that the residue remaining after 1000°C increases with the incremental wt% of fillers in the nanocomposites. There is a big difference in residue amount (in %) left after thermogravimetric analysis in the two nanocomposites, indicating that OBM slurry may have significant influence in decomposing LDPE matrix; this might be an interesting area to explore in the future. The results provide insight and opportunity to manufacture waste-derived renewable nanocomposites with enhanced structural and thermal properties.

Effect of drill cuttings addition on physicochemical and chemical properties of soil and red clover (Trifolium pretense L.) growth

The most economical method of drill cuttings disposal may be their application in land reclamation which allows for the wastes recovery. However, the wastes application into the soil should ensure that the quality of the environment would not be deteriorated. These investigations were aimed at identifying the effect of drill cuttings, which were the mixture of different types of drilling wastes, on the physicochemical properties of acidic soil and growth of red clover (Trifolium pratense L.). The experimental design comprised 5 treatments, which differed in a dose of the drill cuttings: 0% (control), 2.5%, 5%, 10% and 15% of dry weight. A six-week pot experiment was conducted to determine the influence of the wastes on the plant growth. The results showed that the drill cuttings addition significantly changed the chemical and physicochemical properties of the soil, such as: electrical conductivity (EC), pH, base saturation, content of carbonate, alkaline cations (Ca2+, Na+, K+, Mg2+), organic matter, total organic carbon (TOC), and available phosphorus form. However, the most important factors that influenced the growth of red clover were pH, base saturation, content of Mg2+ and plant available phosphorus. The red clover biomass was increased from 1.5 to 2.5 times depending on the dose of wastes. We concluded that the examined wastes can be used for reclamation of the acid and unfertile degraded soils, but the amount of wastes should not exceed 5% of the soil, because the highest total clover biomass was observed just at this dose.

Synergistic effects of compost, cow bile and bacterial culture on bioremediation of hydrocarbon-contaminated drill mud waste

Bioremediation has gained global prominence as an effective method for treating hydrocarbon-contaminated drill mud waste (HCDW). However, the problem of low nutrient content, bioavailability and microbial presence remain largely unresolved. In this study, the synergistic effects of compost, cow bile and bacterial culture on the degradation rate of HCDW was investigated. A homogenized HCDW sample (80 kg) obtained from 25 different drill mud tanks was divided into 20 portions (4 kg each) and each adjusted to 1.4% nitrogen content + 20 ml cow bile (i.e., basic treatment). Pure cultures of Brevibacterium casei (Bc) and Bacillus zhangzhouensi (Bz) and their mixture (BcBz) were subsequently added to 12 of the amended HCDW (basic) to undergo a 6-week incubation. A portion of the unamended HCDW (2 kg) was used as control. Initial pH, electrical conductivity and surface tension values of the HCDW were 8.83, 2.34 mS/cm and 36.5 mN/m, respectively. Corresponding values for total petroleum hydrocarbon (TPH), total nitrogen and total plate count bacteria were 165 g/kg, 0.04% and 4.4 × 10² cfu/ml. The treatments led to a substantial reduction in TPH (p < 0.05) while the control had no significant effect (p > 0.05). TPH reduction after the experimental period occurred in the order: basic + BcBz (99.7%) > basic + Bz (99.5%) > basic + Bc (99.2%) > basic (95.2%) > control (0.06%). Multiple regression analysis revealed significant effect of total plate count, pH, CN ratio and electrical conductivity (R² = 0.87, p = 0.05) on the degradation of TPH in the HCDW. The study demonstrates strong interactive effects of compost, cow bile and bacteria culture on the remediation of HCDW, which can be applied to boost the efficiency of the bioremediation technique.

Formulation of Bio-Based Washing Agent and Its Application for Removal of Petroleum Hydrocarbons From Drill Cuttings Before Bioremediation

Drill cuttings from petroleum exploration and production sites can cause diverse environmental problems. Total petroleum hydrocarbons (TPHs) are a major pollutant from the use of polyolefin-based mud. As an alternative to incineration, this study investigated the application of surfactant-enhanced washing technology prior to bioremediation. The washing step was necessary because the initial TPH concentrations were quite high at approximately 15% (w/w). Washing agents were formulated by varying the concentration of lipopeptide biosurfactant (in foamate or cell-free broth), Dehydol LS7TH (fatty alcohol ethoxylate 7EO, oleochemical surfactant) and butanol (as a lipophilic linker) at different salinities. The most efficient formula produced a Winsor Type I microemulsion (oil-in-water microemulsion) with polyolefin and contained only 20% (v/v) foamate and 2% (v/v) Dehydol LS7TH in water. Due to the synergistic behavior between the anionic lipopeptides and non-ionic Dehydol LS7TH, the formula efficiently removed 92% of the TPHs from the drill cuttings when applied in a jar test. To reduce the cost, the concentrations of each surfactant should be reduced; thus, the formula was optimized by the simplex lattice mixture design. In addition, cell-free broth, at a pH of 10, containing 3.0 g/L lipopeptides was applied instead of foamate because it was easy to prepare. The optimized formula removed 81.2% of the TPHs and contained 72.0% cell-free broth and 1.4% Dehydol LS7TH in water. A 20-kg soil washing system was later tested where the petroleum removal efficiency decreased to 70.7% due to polyolefin redeposition during separation of the washing solution. The remaining TPHs (4.5%) in the washed drilled cuttings were further degraded by a mixture of Marinobacter salsuginis RK5, Microbacterium saccharophilum RK15 and Gordonia amicalis JC11. To promote TPH biodegradation, biochar and fertilizer were applied along with bacterial consortia in a microcosm experiment. After 49-day incubation, the TPHs were reduced to 0.9% by both physical and biological mechanisms, while the TPHs in the unamended samples remained unaffected. With the use of the formulated bio-based washing agent and bioremediation approach, the on-site treatment of drill cuttings could be conducted with an acceptable cost and low environmental impacts.

Selecting the best stabilization/solidification method for the treatment of oil-contaminated soils using simple and applied best-worst multi-criteria decision-making method

Oil-contaminated soils resulted from drilling activities can cause significant damages to the environment, especially for living organisms. Treatment and management of these soils are the necessity for environmental protection. The present study investigates the field study of seven oil-contaminated soils treated by different stabilization/solidification (S/S) methods, and the selection of the best treated site and treatment method. In this study, first, the ratios of consumed binders to the contaminated soils (w/w) and the treatment times for each unit of treated soils were evaluated. The ratios of consumed binders to the contaminated soils were between 6 and 10% and the treatment times for each unit of treated soils were between 4.1 and 18.5 min/m³. Physicochemical characteristics of treated soils were also determined. Although S/S methods didn't change the water content of treated soils, they increased the porosity of soils. Unexpectedly, the cement-based S/S methods didn't increase the pH of the treated soils. The highest and the lowest leaching of petroleum hydrocarbons was belonging to S/S using diatomaceous earth (DE) and the combination of Portland cement, sodium silicate and DE (CS-DE), respectively. The best acid neutralization capacity was obtained for soils treated using the combination of Portland cement and sodium silicate (CS). Based on the best-worst multi-criteria decision-making method (BWM-MCDM), the soils treated using CS-DE was select as the best. The BWM-MCDM can be used as an effective tool for the selection of the best alternative in all areas of environmental decontamination.

A Comprehensive Guide to Different Fracturing Technologies: A Review

Hydraulic fracturing has made the production of gas more economical. Shale gas possesses the potential to arise as a main natural gas source worldwide. It has been assessed that the top 42 countries, including the U.S., are predicted to own 7299 trillion cubic feet (tcf) of technically recoverable shale gas resources. The main goal of this paper is to serve as a guide of different shale gas extraction methods. The significance of these methods and possible pros and cons are determined. Each technique was explained with the support of literature review. Specifically, this paper revealed that some fracking methods such as pulsed arc electrohydraulic discharges (PAED), plasma stimulation and fracturing technology (PSF), thermal (cryogenic) fracturing, enhanced bacterial methanogenesis, and heating of rock mass are at the concept stage for conventional and other unconventional resources. Thus, these found to be significant for stimulating natural gas wells, which provides very good production results. This paper also discovered that fracking remains the recommended technique used by the oil and gas industries.

Preparation of non-sintered lightweight aggregates through co-mechanochemical treatment of oil-contaminated drill cuttings, circulation fluidized bed combustion fly ash, and quicklime

This work investigates the feasibility of co-mechanochemical treatment of oil-contaminated drill cuttings (OCDC), circulation fluidized bed combustion (CFBC) fly ash, and quicklime to prepare non-sintered lightweight aggregates (NSLWAs). The NSLWAs with high cylinder compressive strength and low water absorption could be obtained under the condition of optimal water addition and appropriate steam-curing temperature, as well as steam-curing time. Co-mechanochemical treatment could enhance the pozzolanic reactivity of CFBC fly ash effectively, which is beneficial to the strength development of NSLWAs. Moreover, co-mechanochemical treatment also can degrade the petroleum hydrocarbon of OCDC, greatly reducing the leaching concentrations of total petroleum hydrocarbons (TPH) of NSLWAs. The final leaching concentrations of TPH are much lower than the requirements of Chinese National Standard GB 31571-2015. Graphical abstract.

Effects and recovery of larvae of the cold-water coral Lophelia pertusa (Desmophyllum pertusum) exposed to suspended bentonite, barite and drill cuttings

Fossil fuel drilling operations create sediment plumes and release waste materials into the ocean. These operations sometimes occur close to sensitive marine ecosystems, such as cold-water corals. While there have been several studies on the effects of energy industry activities on adult corals, there is very little information on potential impacts to their early life history stages. Larval stages of many marine organisms, including cold-water corals use cilia as a means of feeding and swimming, and if these structures become clogged with suspended particulates, the larvae may sink and be lost to the system. The objective of this study was to understand the response of Lophelia pertusa larvae to a different drilling waste components, and assess post-exposure recovery. Larvae of two ages (eight and 21 days) were exposed to a range of concentrations of bentonite, barite and drill cuttings. Larval sensitivity was assessed using the concentration at which 50% of the larvae showed behavioral effects (EC₅₀) or lethal effects (LC₅₀). Larvae showed greatest sensitivity to bentonite, followed by barite and drill cuttings, and also showed age-related responses that differed among the test materials. Post exposure recovery was variable across materials, with larvae exposed to bentonite having the lowest recovery rates. Understanding the vulnerability of early life history stages to human activities can help inform management strategies to preserve reproductive capacity of important marine ecosystems.

Physicochemical characteristics of oil-based cuttings from pretreatment in shale gas well sites

Understanding the physicochemical characteristics of oil-based cuttings (OBCs) is an important foundation for subsequent treatment and management. The macro- and microscopic properties of white oil-based cuttings (WOBCs) and diesel-based cuttings (DBCs) after the different pretreatment steps have been assessed using scanning electron microscopy. The organic and inorganic compositions of OBCs have been analyzed using X-ray diffraction, Fourier-transform infrared spectrometry, and gas chromatography-mass spectrometry. Inorganic matter (SiO₂, BaSO₄, and CaCO₃), alkanes, aromatic compounds, and water were the main components of OBCs. The organic content (26.14%) and alkane content of the WOBCs were higher than that of the DBCs, whereas for the inorganic content (70.87%), the reverse was true. The macro- and micromorphologies of OBCs were quite different because their oil and water contents were different. The oil contents of OBCs decreased in the order A1 (14.64%) > A3 (12.67%) > A2 (11.06%) and B1 (9.19%) > B3 (8.94%) > B2 (4.66%); the water contents decreased in the order A1 (2.99%) > A3 (2.19%) > A2 (1.09%) and B1 (2.30%) > B3 (1.87%) > B2 (1.09%). Moreover, a skid-mounted treatment technology for OBCs was proposed. The results can be a scientific guidance for the treatment and management of OBCs.

Continuous supercritical water oxidation treatment of oil-based drill cuttings using municipal sewage sludge as diluent

Oil-based drill cuttings (OBDC) is a characteristic hazardous waste that is generated in oil and gas exploration. In this study, two typical OBDCs from shale gas fields were treated in a continuous supercritical water oxidation (SCWO) for the first time. Because both heat value and ash content (AC) in the OBDCs were well beyond the capacity of continuous operation, municipal sewage sludge (MSS) was innovatively adapted as the diluent. A mixed sludge with OBDC addition levels of 10%, 20%, and 30% was tested using a novel SCWO reactor. Mean residence times of reactants in different reaction zones were specifically calculated. Results indicated the organic carbon removal efficiency could reach up to 98.44%. Eight detected heavy metals were found to be almost completely removed into solid products, and the concentrations in liquid products were all below the discharge limits. It was also found that the SCWO reactor exhibited good anti-plugging and anti-corrosion performance. The AC in the feedstock was up to 28.58%. To the best of our knowledge, this has, hitherto, not been achieved in a continuous SCWO operation. This study provides a new approach for harmlessly and completely degrading OBDC, and is also helpful for the industrialization of SCWO technology.

Chemical attributes of soil and growth of castor beans fertilized with drilling gravel from oil wells and castor pie

The extraction of oil from onshore wells and the production of biodiesel from castor bean crops have grown in recent years, resulting in the production of large volumes of drill cuttings from these wells and castor pie, which can be harmful to the environment. The objective of this work was to evaluate the influence of a combination of different doses of drill cuttings and castor pie on the chemical attributes of a Planosol and on the dry mass production of the aerial part (DMAP) and dry mass of roots (DMR) of castor bean crops (Ricinus communis L.), cultivar BRS-149 Nordestina. The experimental design was a randomized block with a factorial 6 × 6, consisting of five castor pie doses (2, 4, 8, 16, and 32 Mg ha-1); five drill cuttings doses (5, 15, 30, 45, and 60 Mg ha-1) and an experimental control using only soil samples, with three repetitions. The soil used as the main substrate was collected at 0.0-0.2 m depth in a Planosol. The mixture of the topsoil layer with the experimental doses was performed using a mixer for 5 min, and the samples were distributed in 8 dm3 pots; each pot corresponded to an experimental unit. The mixture of cuttings from drill wells and castor pie with a 30: 16 Mg ha-1 ratio, provided favorable chemical conditions for castor bean crop development; however, drill cuttings doses >30 Mg ha-1 can cause soil salinization, and negatively affect the development of castor bean crops.

Remediation of oil-based drill cuttings using low-temperature thermal desorption: Performance and kinetics modeling

A bench-scale apparatus was used for the low-temperature thermal desorption (LTTD) treatment of oil-based drill cuttings (OBDCs). The effects of treatment temperature, treatment duration, sand/OBDCs mixing ratio, and initial oil content on the LTTD treatment performance were investigated. It was found that the petroleum hydrocarbons (PHCs) were barely left in the high-oil-content drill cuttings after LTTD (at 300 °C for 20 min), and thus the overall soil health was improved. The desorption kinetics models of PHCs under various conditions were established, and it was found that the LTTD of OBDCs followed nonlinear least-squares exponential kinetics (adjusted R² > 0.9). The energy consumption models of LTTD treatment under different temperatures were also developed. The modeling results are of practical guiding significance and useful for designing effective LTTD treatment systems of OBDCs.

Co-pyrolysis of metal contaminated oily waste for oil recovery and heavy metal immobilization

The treatment of metal-contaminated oily waste was investigated by using an approach of co-pyrolysis with hog fuel in a fixed bed reactor. Both oil recovery and heavy metal immobilization were evaluated. Three experimental factors, including pyrolysis temperature, reaction time, and hog fuel addition in the feedstock, were examined to find their effects on the treatment performance. Metal immobilization in the solid char obtained from co-pyrolysis was examined from its speciation characteristics. A higher pyrolysis temperature led to a decreased oil recovery but more non-bioavailable metal species in the char residue. This is also evident from the calculated risk index (RI) for eco-toxicity assessment, with RI of 34.6 and 117.1 at 600 °C and 400 °C, respectively. The addition of hog fuel into oily waste for co-pyrolysis also led to increased metal immobilization but a decreased overall oil recovery. A low temperature co-pyrolysis (400 °C) by adding 20% of hog fuel was found as the most effective oily waste disposal strategy with satisfactory oil recovery and an acceptable risk index of 54.1.