A Generic Method for Predicting Environmental Concentrations of Hydraulic Fracturing Chemicals in Soil and Shallow Groundwater

Source-pathway-receptor analyses involving solute migration pathways through soil and shallow groundwater are typically undertaken to assess how people and the environment could come into contact with chemicals associated with coal seam gas operations. For the potential short-term and long-term release of coal seam gas fluids from storage ponds, solute concentration and dilution factors have been calculated using a water flow and solute transport modelling framework for an unsaturated zone-shallow groundwater system. Uncertainty about dilution factors was quantified for a range of system parameters: (i) leakage rates from storage ponds combined with recharge rates, (ii) a broad combination of soil and groundwater properties, and (iii) a series of increasing travel distances through soil and groundwater. Calculated dilution factors in the soil increased from sand to loam soil and increased with an increasing recharge rate, while dilution decreased for a decreasing leak rate and leak duration. In groundwater, dilution factors increase with increasing aquifer hydraulic conductivity and riverbed conductance. For a hypothetical leak duration of three years, the combined soil and groundwater dilution factors are larger than 6980 for more than 99.97% of bores that are likely to be farther than 100 m from the source. Dilution factors were more sensitive to uncertainty in leak rates than recharge rates. Based on this dilution factor, a comparison of groundwater predicted environmental concentrations and predicted no-effect concentrations for a subset of hydraulic fracturing chemicals used in Australia revealed that for all but two of the evaluated chemicals the estimated groundwater concentration (for a hypothetical water bore at 100 m from the solute source) is smaller than the no-effect concentration for the protection of aquatic ecosystems.

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Probabilistic Groundwater Flow, Particle Tracking and Uncertainty Analysis for Environmental Receptor Vulnerability Assessment of a Coal Seam Gas Project

Water ◽

10.3390/w12113177 ◽

2020 ◽

Vol 12 (11) ◽

pp. 3177

Author(s):

Dennis Gonzalez ◽

Sreekanth Janardhanan ◽

Daniel E. Pagendam ◽

Daniel W. Gladish

Keyword(s):

Risk Assessment ◽

Coal Seam ◽

Groundwater Flow ◽

Contaminant Transport ◽

Particle Tracking ◽

Gas Wells ◽

Coal Seam Gas ◽

Transport Pathway ◽

Transport Modelling ◽

Contamination Risk

The production of coalbed methane, or coal seam gas (CSG) in Australia increased 250-fold since the 1990s to around 1502 petajoules in 2019 and continues to expand. Groundwater flow in the aquifers intersected by gas wells could potentially facilitate a transport pathway for migration of contaminants or poorer quality water from deeper formations. While regulatory and mitigation mechanisms are put in place to minimize the risks, quantitative environmental impact assessments are also undertaken. When many gas wells are drilled in a wide area where many potential receptors are also spatially distributed, potential source-receptor combinations are too numerous to undertake detailed contamination risk assessment using contaminant transport modelling. However, valuable information can be gleaned from the analysis of groundwater flow directions and velocities to inform and prioritise contamination risk assessment and can precede computationally challenging stochastic contaminant transport modelling. A probabilistic particle tracking approach was developed as a computationally efficient screening analysis of contamination pathways for a planned CSG development near Narrabri in northern New South Wales, Australia. Particle tracking was run iteratively with a numerical groundwater flow model across a range of plausible parameter sets to generate an ensemble of estimated flow paths through the main Great Artesian Basin aquifer in the area. Spatial patterns of path lines and spatial relationships with potential receptors including neighbouring groundwater extraction wells and hydrologically connected ecological systems were analysed. Particle velocities ranged from 0.5 to 11 m/year and trajectories indicated dedicated contaminant transport modeling would be ideally focused at the local scale where wells are near potential receptors. The results of this type of analysis can inform the design of monitoring strategies and direct new data collection to reduce uncertainty and improve the effectiveness of adaptive management strategies and early detection of impacts.

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Quantifying the Influence of Three Dimensionality on Hydraulic Fracturing in Coal Seam Gas Wells

Proceedings of the SPE/AAPG/SEG Asia Pacific Unconventional Resources Technology Conference ◽

10.15530/ap-urtec-2019-198203 ◽

2019 ◽

Author(s):

Christopher R. Leonardi ◽

Thomas Flottmann ◽

Vibhas J. Pandey ◽

Raymond J. Johnson Jr.

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Gas Wells ◽

Coal Seam Gas

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Vertical gas migration associated with coal seam gas production

The APPEA Journal ◽

10.1071/aj15108 ◽

2016 ◽

Vol 56 (2) ◽

pp. 602

Author(s):

Ludovic Ricard ◽

Julian Strand

Keyword(s):

Coal Seam ◽

Risk Evaluation ◽

Critical Role ◽

Gas Production ◽

Mitigation Strategies ◽

Gas Migration ◽

Coal Seam Gas ◽

Gas Reservoirs ◽

Gas Leakage ◽

Migration Pathways

Gas migration outside coal seam gas reservoirs has been identified as a risk associated with CSG production. While such an event has not been reported or scientifically associated with CSG production, understanding the physical mechanism of the vertical migration in the overburden involved should gas leakage occur would improve mitigation strategies and risk evaluation. In this extended abstract, a series of key modelling scenarios of gas migration above the reservoir are developed. Interpretation of the scenarios highlights that: the seal/leakage nature of the overburden strongly impacts gas migration and volume of gas leaked; when leakage does occur, the leaked volume represents a very small portion of the original gas in place and volume of gas produced; the connectivity of the overburden plays a critical role on the gas migration pathways and volume of gas leaked; and, residual gas saturation, and relative permeability hysteresis provide means to trap the mobile gas, significantly reducing the volume of gas leaked reaching shallower formations.

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Numerical modelling of fracturing effect stimulated by pulsating hydraulic fracturing in coal seam gas reservoir

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2017.08.016 ◽

2017 ◽

Vol 46 ◽

pp. 651-663 ◽

Cited By ~ 8

Author(s):

Chunchi Ma ◽

Yupeng Jiang ◽

Huilin Xing ◽

Tianbin Li

Keyword(s):

Numerical Modelling ◽

Coal Seam ◽

Hydraulic Fracturing ◽

Coal Seam Gas ◽

Gas Reservoir

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In vitro cytotoxicity assessment of a hydraulic fracturing fluid

Environmental Chemistry ◽

10.1071/en14010 ◽

2015 ◽

Vol 12 (3) ◽

pp. 286 ◽

Cited By ~ 5

Author(s):

Madeleine E. Payne ◽

Heather F. Chapman ◽

Janet Cumming ◽

Frederic D. L. Leusch

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Human Health ◽

Produced Water ◽

Coal Seam Gas ◽

Fracturing Fluid ◽

Human Health Risks ◽

Fracturing Fluids ◽

Hydraulic Fracturing Fluid

Environmental context Hydraulic fracturing fluids, used in large volumes by the coal seam gas mining industry, are potentially present in the environment either in underground formations or in mine wastewater (produced water). Previous studies of the human health and environmental effects of this practice have been limited because they use only desktop methods and have not considered combined mixture toxicity. We use a novel in vitro method for toxicity assessment, and describe the toxicity of a hydraulic fracturing fluid on a human gastrointestinal cell line. Abstract Hydraulic fracturing fluids are chemical mixtures used to enhance oil and gas extraction. There are concerns that fracturing fluids are hazardous and that their release into the environment – by direct injection to coal and shale formations or as residue in produced water – may have effects on ecosystems, water quality and public health. This study aimed to characterise the acute cytotoxicity of a hydraulic fracturing fluid using a human gastrointestinal cell line and, using this data, contribute to the understanding of potential human health risks posed by coal seam gas (CSG) extraction in Queensland, Australia. Previous published research on the health effects of hydraulic fracturing fluids has been limited to desktop studies of individual chemicals. As such, this study is one of the first attempts to characterise the toxicity of a hydraulic fracturing mixture using laboratory methods. The fracturing fluid was determined to be cytotoxic, with half maximal inhibitory concentrations (IC50) values across mixture variations ranging between 25 and 51mM. When used by industry, these fracturing fluids would be at concentrations of over 200mM before injection into the coal seam. A 5-fold dilution would be sufficient to reduce the toxicity of the fluids to below the detection limit of the assay. It is unlikely that human exposure would occur at these high (‘before use’) concentrations and likely that the fluids would be diluted during use. Thus, it can be inferred that the level of acute risk to human health associated with the use of these fracturing fluids is low. However, a thorough exposure assessment and additional chronic and targeted toxicity assessments are required to conclusively determine human health risks.

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Induced stress evolution of hydraulic fracturing in an inclined soft coal seam gas reservoir near a fault

Journal of Natural Gas Science and Engineering ◽

10.1016/j.jngse.2021.103794 ◽

2021 ◽

Vol 88 ◽

pp. 103794

Author(s):

Qianting Hu ◽

Zhizhong Jiang ◽

Quangui Li ◽

Wenbin Wu ◽

Qingguo Wang ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Stress Evolution ◽

Coal Seam Gas ◽

Gas Reservoir ◽

Soft Coal ◽

Induced Stress ◽

Soft Coal Seam

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Utilising current technologies to understand permeability, stress azimuths and magnitudes and their impact on hydraulic fracturing success

The APPEA Journal ◽

10.1071/aj09100 ◽

2010 ◽

Vol 50 (2) ◽

pp. 736 ◽

Cited By ~ 2

Author(s):

Raymond Johnson ◽

Brent Glassborow ◽

Jeremy Meyer ◽

Michael Scott ◽

Ashish Datey ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Limited Area ◽

Supporting Evidence ◽

Coal Seam Gas ◽

Structural Setting ◽

Data Process ◽

Petroleum Wells ◽

Well Data ◽

Sonic Logging

In coal seam gas exploration and appraisal, stress and permeability are often inter-related and play a large role in deliverability, particularly affecting hydraulic fracturing effectiveness. Generally, the structural setting for a coal seam gas (CSG) play can be defined by indirect data such as petroleum wells, core wells, or seismic data; however, the viability of a structure to be highly conducive to CSG development also requires direct measurements to fully define the effects associated with this interdependency of stress and permeability. Unfortunately, this interdependency may not be as apparent during the exploration phase as within the planning, execution and evaluation of a hydraulic fracturing program. We will present data from a limited area of the Surat Basin, in the Walloon coal measures, where initial regional and well data were available to allow drilling to evaluate a small, localised, structural setting for CSG development. While some permeability data were encouraging in the initial program, subsequent drilling indicated that permeability might become variable across this structure. Thus, further investigations were made and included novel, cross-dipole sonic logging in combination with acoustic and more advanced resistivity imaging logs. These data indicated that the stress and permeability azimuths may be aligned to take advantage of hydraulic fracturing. Thus, a hydraulic fracturing program was initiated in this area incorporating diagnostics to understand the potential benefit of this technology. The results of this program, while localised, do indicate that a potential pitfall can exist in some environments where the stress magnitudes along with stress and dominant permeability axes are not ideally positioned to take advantage of hydraulic fracturing. We will show how the data in this case were acquired, evaluated and integrated to support the overall understanding and interpretation of the results. Due to space constraints, this paper focusses primarily on the overall data process and is unable to elaborate fully on all diagnostics used and the fullness of their determinations; however, adequate supporting evidence is supplied in order to illustrate the problems in executing and achieving effective stimulation in similar structural settings.

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Applications of Indirect Hydraulic Fracturing to Improve Coal Seam Gas Drainage for the Surat and Bowen Basins, Australia

10.15530/ap-urtec-2021-208375 ◽

2021 ◽

Author(s):

Raymond Leslie Johnson ◽

Honja Miharisoa Ramanandraibe ◽

Ayrton Ribeiro ◽

Matthew Ramsay ◽

Kaa Tipene ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Coal Seam Gas ◽

Gas Drainage

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Environmental issues associated with coal seam gas recovery: managing the fracking boom

Environmental Chemistry ◽

10.1071/en12136 ◽

2012 ◽

Vol 9 (5) ◽

pp. 425 ◽

Cited By ~ 17

Author(s):

Graeme E. Batley ◽

Rai S. Kookana

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

New Technology ◽

Surface Water Quality ◽

Environmental Issues ◽

Ecological Risks ◽

Coal Seam Gas ◽

Gas Recovery ◽

Lack Of Information ◽

Energy Needs

Environmental context Coal seam gas reserves are likely to make a major contribution to future energy needs. However, the new technology for exploiting these reserves, termed hydraulic fracturing, raises several environmental issues. We discuss the research required to assess the ecological risks from gas recovery. Abstract Coal seam gas reserves represent a major contribution to energy needs, however, gas recovery by hydraulic fracturing (fracking or fraccing), requires management to minimise any environmental effects. Although the industry is adapting where possible to more benign fracking chemicals, there is still a lack of information on exposure to natural and added chemicals, and their fate and ecotoxicity in both the discharged produced and flow-back waters. Geogenic contaminants mobilised from the coal seams during fracking may add to the mixture of chemicals with the potential to affect both ground and surface water quality. The research needs to better assess the ecological risks from gas recovery are discussed.

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