The Potential Water Quality Impacts of Shale Gas Exploitation

2020 ◽  
Author(s):  
Hsiao-Yuan Tammy Hsu ◽  
Fred Worrall ◽  
Andy Aplin
Keyword(s):  
Chemical Composition ◽  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Fluid Composition ◽  
Potential Contribution ◽  
Sources Of Information ◽  
Geothermal Waters ◽  
Rock Interaction ◽  
The Uk

<p>     The potential development of shale gas has brought with it several concerns about environmental impacts, these include: induced seismicity, air pollution, and groundwater contamination. During hydraulic fracturing for shale gas, large volumes of oxic and acidic water are injected into the gas-bearing formations. The injected fluids contain a range of additives and will mix and react with the in-situ groundwater and shale rock with the potential to drive water-rock interactions; release metal contaminants; alter the permeability of the bedrock; with each of these affecting the transport and recovery of water, hydrocarbons, and contamination. The purpose of this study is to understand the geochemical processes and inorganic metals release during hydraulic fracturing to assess the potential contribution of fluid-rock interaction for the composition of produced waters and alteration of shale mechanical properties.<br>     The study has: <br>i) Statistically analysed the chemical composition of hydraulic fracturing in USGS dataset to create prior distributions for the prediction of the salinity and chemical composition of flowback fluids in the UK. <br>ii) Statistically analysed the composition and controls on geothermal waters in the UK. Deep geothermal waters are an analogue for the in-situ groundwater composition with which injected fracking fluids will react and mix.<br>iii) Both sources of information have assisted in the design of the high pressure, high temperature experiments that will simulate the fracking fluid processes<br>iv) Undertaken sequential extraction of target shales to understand the data from existing batch experiments undertaker</p><p>     Future work will include isotope proxy and mineralogical texture studies to predict flowback fluid composition and the post-frack condition of the shale.</p>

Fracture Initiation and Propagation in a Deep Shale Gas Reservoir Subject to an Alternating-Fluid-Injection Hydraulic-Fracturing Treatment

SPE Journal ◽  
2019 ◽  
Vol 24 (04) ◽  
pp. 1839-1855 ◽  
Author(s):  
Bing Hou ◽  
Zhi Chang ◽  
Weineng Fu ◽  
Yeerfulati Muhadasi ◽  
Mian Chen
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Fracture Initiation ◽  
Fluid Injection ◽  
Hydraulic Fractures ◽  
Stress Difference ◽  
Gas Reservoirs ◽  
Complex Fracture ◽  
Initiation And Propagation

Summary Deep shale gas reservoirs are characterized by high in-situ stresses, a high horizontal-stress difference (12 MPa), development of bedding seams and natural fractures, and stronger plasticity than shallow shale. All of these factors hinder the extension of hydraulic fractures and the formation of complex fracture networks. Conventional hydraulic-fracturing techniques (that use a single fluid, such as guar fluid or slickwater) do not account for the initiation and propagation of primary fractures and the formation of secondary fractures induced by the primary fractures. For this reason, we proposed an alternating-fluid-injection hydraulic-fracturing treatment. True triaxial hydraulic-fracturing tests were conducted on shale outcrop specimens excavated from the Shallow Silurian Longmaxi Formation to study the initiation and propagation of hydraulic fractures while the specimens were subjected to an alternating fluid injection with guar fluid and slickwater. The initiation and propagation of fractures in the specimens were monitored using an acoustic-emission (AE) system connected to a visual display. The results revealed that the guar fluid and slickwater each played a different role in hydraulic fracturing. At a high in-situ stress difference, the guar fluid tended to open the transverse fractures, whereas the slickwater tended to activate the bedding planes as a result of the temporary blocking effect of the guar fluid. On the basis of the development of fractures around the initiation point, the initiation patterns were classified into three categories: (1) transverse-fracture initiation, (2) bedding-seam initiation, and (3) natural-fracture initiation. Each of these fracture-initiation patterns had a different propagation mode. The alternating-fluid-injection treatment exploited the advantages of the two fracturing fluids to form a large complex fracture network in deep shale gas reservoirs; therefore, we concluded that this method is an efficient way to enhance the stimulated reservoir volume compared with conventional hydraulic-fracturing technologies.

Modelling coupled processes in bentonite: recent results from the UK's contribution to the Äspö EBS Task Force

2012 ◽  
Vol 76 (8) ◽  
pp. 3033-3043 ◽  
Author(s):  
D. Holton ◽  
S. Baxter ◽  
A. R. Hoch
Keyword(s):  
Large Scale ◽  
Task Force ◽  
Fractured Rock ◽  
Coupled Processes ◽  
Spent Fuel ◽  
Rock Interaction ◽  
Waste Container ◽  
Buffer Material ◽  
The Uk

AbstractA range of potential concepts for the geological disposal of high level wastes and spent fuel are being studied and considered in the UK. These include concepts that use bentonite as a buffer material around the waste containers. The bentonite will be required to fulfil certain safety functions, the most important being (1) to protect the waste containers from detrimental thermal, hydraulic, mechanical and chemical processes; and (2) to retard the release of radionuclides from any waste container that fails. The bentonite should have a low permeability and a high sorption capacity.These safety functions could be challenged by certain features, events and processes (FEPs) that may occur during the evolution of the disposal system. A consideration of how these FEPs may affect the safety functions can be used to identify and to prioritize the important areas for research on bentonite. We identify these important areas (which include hydration of compacted bentonite, illitization and erosion of bentonite), and describe how they are being investigated in current international research on bentonite.The Äspö EBS Task Force is a collaborative international project designed to carry out research on bentonite. In 2011, the Nuclear Decommissioning Authority Radioactive Waste Management Directorate joined the EBS Task Force partly to benefit from its collective experience. The work of the EBS Task Force is split into two research subareas: (1) the THM subarea, which includes tasks to understand homogenization of bentonite as it resaturates, to investigate the hydraulic interaction between bentonite and fractured rock, and to model in situ experiments; and (2) the THC subarea, which includes tasks to investigate the issue of understanding transport through bentonite, and to model in situ experiments. In particular, the bentonite rock interaction experiment is a large-scale in situ experiment concerned with understanding groundwater exchange across bentonite rock interfaces, with the objective of establishing better understanding of bentonite wetting. In this paper, we describe our work to model the spatial and temporal resaturation of bentonite buffer in a fractured host rock.

scholarly journals Effect of Shale Anisotropy on Hydration and Its Implications for Water Uptake

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4225
Author(s):  
Yunhu Lu ◽  
Lingping Zeng ◽  
Yan Jin ◽  
Guanglei Chen ◽  
Junfan Ren ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Water Uptake ◽  
Rock Interaction ◽  
Longmaxi Formation ◽  
Fracture Width ◽  
Flowback Water ◽  
Bedding Planes ◽  
Before And After ◽  
Shale Anisotropy

Water uptake induced by fluid–rock interaction plays a significant role in the recovery of flowback water during hydraulic fracturing. However, the existing accounts fail to fully acknowledge the significance of shale anisotropy on water uptake typically under in situ reservoir temperature. Thus we investigated the shale-hydration anisotropy using two sets of shale samples from the Longmaxi Formation in Sichuan Basin, China, which are designated to imbibe water parallel and perpendicular to shale bedding planes. All the samples were immersed in distilled water for one to five days at 80 °C or 120 °C. Furthermore, samples’ topographical and elemental variations before and after hydration were quantified using energy-dispersive spectroscopy–field-emission scanning electron microscopy. Our results show that shale anisotropy and imbibition time strongly affect the width of pre-existing micro-fracture in hydrated samples. For imbibition parallel to lamination, the width of pre-existing micro-fracture initially decreases and leads to crack-healing. Subsequently, the crack surfaces slightly collapse and the micro-fracture width is enlarged. In contrast, imbibition perpendicular to lamination does not generate new micro-fracture. Our results imply that during the flowback process of hydraulic fracturing fluid, the shale permeability parallel to bedding planes likely decreases first then increases, thereby promoting the water uptake.

In Situ Sequestration of a Hydraulic Fracturing Fluid in Longmaxi Shale Gas Formation in the Sichuan Basin

2019 ◽  
Vol 33 (8) ◽  
pp. 6983-6994 ◽  
Author(s):  
Bin Yang ◽  
Hao Zhang ◽  
Yili Kang ◽  
Lijun You ◽  
Jiping She ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Fracturing Fluid ◽  
Gas Formation ◽  
Longmaxi Shale ◽  
The Sichuan Basin ◽  
Hydraulic Fracturing Fluid

scholarly journals Fracking bad language – hydraulic fracturing and earthquake risks

2021 ◽  
Vol 4 (2) ◽  
pp. 303-327
Author(s):  
Jennifer J. Roberts ◽  
Clare E. Bond ◽  
Zoe K. Shipton
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Perceived Risk ◽  
Induced Seismicity ◽  
Earthquake Risk ◽  
Public Concern ◽  
Public Events ◽  
Risk Magnitude ◽  
The Uk ◽  
Survey Responses

Abstract. Hydraulic fracturing, or fracking, is a borehole stimulation technique used to enhance permeability in geological resource management, including the extraction of shale gas. The process of hydraulic fracturing can induce seismicity. The potential to induce seismicity is a topic of widespread interest and public concern, particularly in the UK where seismicity induced by hydraulic fracturing has halted shale gas operations and triggered moratoria. Prior to 2018, there seemed to be a disconnect between the conclusions of expert groups about the risk of adverse impacts from hydraulic-fracturing-induced seismicity and the reported level of public concern about hydraulic fracturing induced seismicity. Furthermore, a range of terminology was used to describe the induced seismicity (including tremors, earthquakes, seismic events, and micro-earthquakes) which could indicate the level of perceived risk. Using the UK as a case study, we examine the conclusions of expert-led public-facing reports on the risk (likelihood and impact) of seismicity induced by hydraulic fracturing for shale gas published between 2012 and 2018 and the terminology used in these reports. We compare these to results from studies conducted in the same time period that explored views of the UK public on hydraulic fracturing and seismicity. Furthermore, we surveyed participants at professional and public events on shale gas held throughout 2014 asking the same question that was used in a series of surveys of the UK public in the period 2012–2016, i.e. “do you associate shale gas with earthquakes?”. We asked our participants to provide the reasoning for the answer they gave. By examining the rationale provided for their answers, we find that an apparent polarisation of views amongst experts was actually the result of different interpretations of the language used to describe seismicity. Responses are confounded by the ambiguity of the language around earthquake risk, magnitude, and scale. We find that different terms are used in the survey responses to describe earthquakes, often in an attempt to express the risk (magnitude, shaking, and potential for adverse impact) presented by the earthquake, but that these terms are poorly defined and ambiguous and do not translate into everyday language usage. Such “bad language” around fracking has led to challenges in understanding, perceiving, and communicating risks around hydraulic-fracturing-induced seismicity. We call for multi-method approaches to understand the perceived risks around geoenergy resources and suggest that developing and adopting a shared language framework to describe earthquakes would alleviate miscommunication and misperceptions. Our findings are relevant to any applications that present – or are perceived to present – the risk of induced seismicity. More broadly, our work is relevant to any topics of public interest where language ambiguities muddle risk communication.

The effect of gravity on the shape and direction of vertical hydraulic fractures

2020 ◽  
Vol 60 (2) ◽  
pp. 668
Author(s):  
Saeed Salimzadeh
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Hydraulic Fracture ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Gas Reservoirs ◽  
Unconventional Gas Reservoirs ◽  
Fracture Fluid ◽  
Fracture Opening

Australia has great potential for shale gas development that can reshape the future of energy in the country. Hydraulic fracturing has been proven as an efficient method to improve recovery from unconventional gas reservoirs. Shale gas hydraulic fracturing is a very complex, multi-physics process, and numerical modelling to design and predict the growth of hydraulic fractures is gaining a lot of interest around the world. The initiation and propagation direction of hydraulic fractures are controlled by in-situ rock stresses, local natural fractures and larger faults. In the propagation of vertical hydraulic fractures, the fracture footprint may extend tens to hundreds of metres, over which the in-situ stresses vary due to gravity and the weight of the rock layers. Proppants, which are added to the hydraulic fracturing fluid to retain the fracture opening after depressurisation, add additional complexity to the propagation mechanics. Proppant distribution can affect the hydraulic fracture propagation by altering the hydraulic fracture fluid viscosity and by blocking the hydraulic fracture fluid flow. In this study, the effect of gravitational forces on proppant distribution and fracture footprint in vertically oriented hydraulic fractures are investigated using a robust finite element code and the results are discussed.

scholarly journals Fracking bad language: Hydraulic fracturing and earthquake risks

2020 ◽  
Author(s):  
Jennifer J. Roberts ◽  
Clare E. Bond ◽  
Zoe K. Shipton
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Earthquake Risk ◽  
Public Events ◽  
Well Stimulation ◽  
Communication Challenges ◽  
Risk Magnitude ◽  
Industry Policy ◽  
The Uk ◽  
Public Views

Abstract. Hydraulic fracturing, fracking, is a well stimulation technique used to enhance permeability to aid geological resource management, including the extraction of shale gas. The process of hydraulic fracturing can induce seismicity and the risk of seismicity is a topic of widespread interest and is often reported to be an issue of public concern regarding hydraulic fracturing. This is particularly the case in the UK, where seismicity induced by hydraulic fracturing has halted shale gas operations, and triggered moratoria. However, there seems a disconnect between the level of risk and concern around seismicity caused by shale gas operations as perceived by publics and that reported by expert groups (from industry, policy, and academia), which could manifest in the terminology used to describe the seismic events (tremors, earthquakes, micro-earthquakes). In this paper, we examine the conclusions on induced seismicity and hydraulic fracturing from expert-led public facing reports on shale gas published between 2012 and 2018 and the terminology used in these reports. We compare these to results from studies conducted in the same time period that explore public views on hydraulic fracturing and seismicity. Further, we surveyed participants at professional and public events on shale gas held throughout 2014 to elicit whether they associate shale gas with earthquakes. We use the same question that was used in a series of surveys of the UK publics in the period 2012–2016, but we asked our participants to provide the reasoning for the answer they gave. By examining the rationale provided for their answers we find that an apparent polarisation of views amongst experts is an artefact and in fact responses are confounded by ambiguity of language around earthquake risk, magnitude, and scale. We find that different terms are used to describe earthquakes, often in an attempt to express the magnitude, shaking, or risk presented by the earthquake, but that these terms are poorly defined and ambiguous and do not translate into everyday language usage. Such “fracking bad language” has led to challenges in the perception and communication of risks around earthquakes and hydraulic fracturing, and leaves language susceptible to emotional loading and misinterpretation. We call for multi-method approaches to understand perceived risks around geoenergy resources, and suggest that adopting a shared language framework to describe earthquakes would alleviate miscommunication and misperceptions. This work is relevant for a range of applications where risks are challenging to conceptualise and poorly constrained; particularly those of public interest where language inconsistency can exacerbate communication challenges and can have widespread consequence.

Structural Studies on Mitotic Spindle Fibres

1978 ◽  
Vol 36 (3) ◽  
pp. 615-626
Author(s):  
J.R. Mcintosh
Keyword(s):  
Chemical Composition ◽  
Mitotic Spindle ◽  
Structural Studies ◽  
Mitotic Apparatus ◽  
Chemical Studies ◽  
Medical Interest ◽  
Spindle Fibres

The mitotic apparatus is a structure of obvious biological and medical interest, but it has proved to be a difficult cellular machine to understand. The chemical composition of the spindle is only slightly elucidated, largely because of the difficulties in preparing useful isolates of the structure. Chemical studies of the mitotic spindle have been reviewed elsewhere (Mcintosh, 1977), and will not be discussed further here. One would think that structural studies on the mitotic apparatus (MA) in situ would be straightforward, but even with this approach there is some disagreement in the results obtained with various methods and by different investigators. In this paper I will review briefly the approaches which have been used in structural studies of the MA, pointing out the strengths and problems of each approach. I will summarize the principal findings of the different methods, and identify what seem to be fruitful avenues for further work.

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