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

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

Water ◽

10.3390/w12040941 ◽

2020 ◽

Vol 12 (4) ◽

pp. 941 ◽

Cited By ~ 2

Author(s):

Dirk Mallants ◽

Elise Bekele ◽

Wolfgang Schmid ◽

Konrad Miotlinski ◽

Andrew Taylor ◽

...

Keyword(s):

Coal Seam ◽

Hydraulic Fracturing ◽

Shallow Groundwater ◽

Solute Concentration ◽

Coal Seam Gas ◽

Transport Modelling ◽

Environmental Concentrations ◽

Modelling Framework ◽

Recharge Rates ◽

Migration Pathways

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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Field trials of the use of hydrated bentonite for decommissioning oil and gas wells

The APPEA Journal ◽

10.1071/aj15067 ◽

2016 ◽

Vol 56 (2) ◽

pp. 561 ◽

Cited By ~ 1

Author(s):

Brian Towler ◽

Mahshid Firouzi ◽

Amin Mortezapour ◽

Paul Hywel-Evans

Keyword(s):

Coal Seam ◽

Oil And Gas ◽

Laboratory Data ◽

Field Trials ◽

Gas Wells ◽

Coal Seam Gas ◽

Water Wells ◽

The Us ◽

Oil And Gas Wells ◽

The Many

Bentonite is widely used for plugging shallow water wells in the US. In the past 15 years Chevron has been plugging oil and gas wells with bentonite in the San Joaquin Basin in California, and has successfully plugged about 10,000 wells. In several previous publications the authors’ research team has reported laboratory data to predict pressure containment using bentonite to underpin the fundamentals for plugging both oil and gas wells. The authors propose bentonite as an alternative medium for decommissioning coal seam gas wells in Queensland. Gas producing companies in Queensland are proposing to drill and produce about 40,000 coal seam gas wells in the state, and all of these will have to be plugged eventually. Water wells are shallow and are usually plugged with coarse granulated bentonite that is simply poured down the hole and hydrated. The authors propose a process for compressing bentonite into cylinders of various shapes, which promises to improve the use of bentonite for plugging deeper wells. Oil and gas wells are presently plugged and abandoned with cement. Bentonite has a number of advantages when plugging oil and gas wells. It is cheaper and easier to deploy and it is more reliable than cement. In this extended abstract the application of bentonite for plugging conventional oil and gas and coal seam gas wells will be discussed. The many field trials will be reviewed and the fundamental theory for plugging wells with bentonite will be outlined.

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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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Stress Changes and Coal Failure Analysis in Coal Seam Gas Wells Accounting for Matrix Shrinkage: An Example from Bowen Basin, East Australia

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

10.15530/ap-urtec-2019-198309 ◽

2019 ◽

Author(s):

Mohammadreza Zare Reisabadi ◽

Manouchehr Haghighi ◽

Abbas Khaksar

Keyword(s):

Coal Seam ◽

Failure Analysis ◽

Gas Wells ◽

Coal Seam Gas ◽

Matrix Shrinkage ◽

Stress Changes

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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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