Scholarly article on topic 'Water Requirements for Shale Gas Fracking in Fuling, Chongqing, Southwest China'

Water Requirements for Shale Gas Fracking in Fuling, Chongqing, Southwest China Academic research paper on "Earth and related environmental sciences"

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{"Hydraulic fracturing (fracking)" / "shale gas" / water / Fuling / Chongqing / China}

Abstract of research paper on Earth and related environmental sciences, author of scientific article — Hong Yang, Xianjin Huang, Qingyuan Yang, Jianjun Tu, Shengfeng Li, et al.

Abstract Techniques used to extract shale gas, hydraulic fracturing or fracking, do have draw-backs not least the large consumption of water. We provide the first estimate of water consumption in Chinese shale gas fracking. A case study from Fuling, Chongqing, Southwest China, shows that average water consumption is 27490 m3 per well, much higher (by 29%-160%) than in the USA. Data analysis indicates a significant correlation between water consumption and lateral length of wells (p<0.001, r2=0.47). Water usage for fracking can impact the local environment, and careful management will be required to avoid worsen the water stress.

Academic research paper on topic "Water Requirements for Shale Gas Fracking in Fuling, Chongqing, Southwest China"

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Energy Procedía 76 (2015) 106 - 112

European Geosciences Union General Assembly 2015, EGU Division Energy, Resources & Environment, ERE

Water Requirements for Shale Gas Fracking in Fuling, Chongqing,

Southwest China

Hong Yanga,b *, Xianjin Huanga, Qingyuan Yangc, Jianjun Tuc, Shengfeng Lia, Demin Yangd,e, Hong Xiad,e, Roger J. Flowerf, Julian R. Thompsonf

a School of Geographic and Oceanographic Science, Xianlin Campus, Nanjing University, Nanjing, 210023, China b CEES, Department of Biosciences, University of Oslo, Blindern, 0316, Oslo, Norway c School of Geographical Sciences, Southwest University, Chongqing, 400715, China d Key Laboratory for Shale Gas Resource & Exploration, Ministry of Land and Resources, Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China e Chongqing Engineering Research Center for Shale Gas Resource & Exploration, Chongqing Institute of Geology and Mineral Resources,

Chongqing 400042, China

f Environmental Change Research Centre / Wetland Research Unit, Department of Geography, UCL, London, WC1E 6BT, UK

Abstract

Techniques used to extract shale gas, hydraulic fracturing or fracking, do have draw-backs not least the large consumption of water. We provide the first estimate of water consumption in Chinese shale gas fracking. A case study from Fuling, Chongqing, Southwest China, shows that average water consumption is 27490 m3 per well, much higher (by 29%-160%) than in the USA. Data analysis indicates a significant correlation between water consumption and lateral length of wells (p<0.001, r2=0.47). Water usage for fracking can impact the local environment, and careful management will be required to avoid worsen the water stress.

© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-reviewunderresponsibilityof the GFZGermanResearchCentreforGeosciences Keywords: Hydraulic fracturing (fracking); shale gas; water; Fuling; Chongqing; China

* Corresponding author. Tel.: +0047 2285 4509; fax: +0047 2285 4438. E-mail address: hongyanghy@gmail.com

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the GFZ German Research Centre for Geosciences doi: 10.1016/j .egypro .2015.07. 862

1. Introduction

Energy plays a vital role in driving economic growth and providing for poverty alleviation in developing countries [1]. Coal still remains the dominant fuel in many developing nations and some more developed countries, yet coal burning is inefficient, disproportionately increases CO2 emissions to the atmosphere, exacerbates air pollution and threatens human health. For example, poor air quality and repeated major smog events are commonplace in China's growing cities [2]. Shifting energy usage to renewable resources or lower carbon fuels such as natural gas to meet demands for cleaner energy and climate impact reductions is now occurring in more and more countries. Shale gas, one of the unconventional natural gas sources, has rapidly developed in the USA during the last decade due to the widespread adoption of hydraulic fracturing or 'Tracking" [3]. This involves pumping large amounts of fluid at high pressure into the well to create fractures in the rock to propel sedimentary gas into the well cavity. The fracking fluid is a mixture of water, sand and less than 1% chemical additives. This technique has driven the shale gas boom in North America with, for example, production in the USA increasing 10-fold between 2001 and 2011 [4]. This has resulted in lower energy costs, allowed less reliance on fuel imports, created hundreds of thousands of jobs and stimulated growth in gross domestic product (GDP). The American shale gas boom has captured the attention of global policy makers, energy and natural resource managers, and environmental advocates.

As the largest CO2 emitter and a nation with severe air pollution problems, China has an increasing demand for renewable and low-carbon energy. According to an estimate from the U.S. Energy Information Administration (EIA), China has the world's largest shale gas reserves of 36.1 trillion m3 [5]. The Chinese government has adopted a number of policies to promote shale gas development. In the 12th Five Year Plan, China set a goal of producing shale gas at an annual rate of 6.5 billion m3 by 2015 [6]. By the mid of 2014 China had drilled more than 300 wells, producing 1.3 billion

shale gas [7].

Despite smaller CO2 emissions compared to coal and oil, shale gas extraction by fracking is associated with a number of environmental risks. These include the large consumption of water, the potential for contamination of water resources, possible enhancement of seismic events, and venting and leaking of methane, a gas with more than 70 times the global-warming potential of CO2 [4,8,9]. Increased use of shale gas fracking in China may intensify competition for water between the gas industry and other industrial, agricultural and domestic sectors in already water scarce areas [10]. Without proper treatment, excess flow-back water from fracking may add to existing pollution of China's water and soil resources. This may furth er endanger human health and damage ecosystems [11]. Many of Chinese shale gas wells are located near earthquake fault zones, for example the Sichuan Basin (including Sichuan and Chongqing), so risk of increased seismicity needs careful attention [12,13].

Several studies have recognised the challenges associated with the demands for water from China's shale gas industry [10,14-17]. However, there has been no sound scientific assessment of potential rates of water consumption due to lack of data from direct measurement or estimates from the gas industry. The current study is the first attempt to extend our knowledge about water consumption by shale gas fracking in China. It is based on water consumption and shale gas production data obtained from Fuling, Chongqing, Southwest China. In the study, we explore (i) the water consumption of China's shale gas fracking (ii) the differences in fracking-related water consumption between Fuling and American shale gas wells.

2. Method

2.1 Research area

This study selected the Fuling shale gas industry as a case study area. Fuling is in the centre of Chongqing, southwest China (Fig. 1). It is characterized by a subtropical monsoon climate. Mean annual temperature is around 16.5oC and on average it receives approximately 1150 mm of precipitation each year [18]. The area has a mountainous and hilly landscape over which the dominant (41%% of the area) natural vegetation is subtropical evergreen broadleaved forest and warm coniferous forest. Approximately 35%% of the area has been cleared for farmland. The dominant crops including rice, maize, wheat, and mustard and agricultural activities are predominantly small scale. The Wu River, the largest southern tributary of Yangtze River, crosses into the Fuling district and provides the source of water for many of the region's shale gas wells.

The Fuling shale gas field is China's first commercial shale gas development. It draws gas from one of the major geological depositional centres in the Longmaxi Formation, southern China's marine shale formation [19]. The maximum thickness of shale deposits (total organic carbon >0.5%) in the area is 120 m. By the end of 2014, nearly 150 wells had been drilled and around 1.0 billion m3 of gas were produced from the Fuling shale gas field, almost 75°% of the national shale gas production [20]. It is estimated that annual shale gas production in Fuling could reach nearly 7 billion m3 by 2017 [21].

2.2 Data collection and statistical analysis

Data describing water use during shale gas fracking in Fuling were recorded by well operators and subsequently collected for 32 wells by the Chongqing Institute of Geology and Mineral Resources. These data were supplemented by information provided in journal papers and industrial reports. Analysis focussed on establishing the range of fracking-related water consumption and, using correlation analysis undertaken using R [22], the factors influencing the variability in water use between different wells.

3. Results and Discussion

Water consumption between individual shale gas wells in Fuling varies widely. The largest and smallest volumes of water employed during fracking operations were 3096 m3 and 46140 m3, respectively. Approximately 80% of wells consumed between 20000 and 40000 m3 of water (Fig. 2). The mean and median water consumption per well were 27490 m3 and 28800 m3, respectively. To minimize the influence of outliers on correlation analysis, an outlier

Legend

o 50 100 km

Rivers

Fig. 1. The location of Fuling, Chongqing, Southwest China.

test was carried out [23] and as a result one outlier (the well associated with the smallest water consumption) was removed. Linear correlation analysis indicated a significant positive correlation between water consumption and lateral sub-surface length of the well (p<0.001, r2=0.47).

I-1-1-1-1-1

0 10000 20000 30000 40000 50000 Water consumption of shale gas tracking (m3)

Fig. 2. Histogram showing water consumption by shale gas fracking in Fuling, Chongqing, Southwest China.

Compared with published water consumption figures for American shale wells [24-26], wells in Fuling required between 29% and 160% more water (Table 1). This greater water consumption is assumed to be due to the greater burial depth of Fuling shale gas reserves (3000-5000 m) compared to those in the USA (mainly 800-2000 m) [27]. China's less mature fracking techniques are also assumed to increase water consumption [10].

Table 1. Comparison ofwater consumption of shale gas wells in the USA and China.

Shale gas play State/Province, Country Water consumption (m3) Source

Woodford Oklahoma, USA 16000 [24]

Barnett Texas, USA 10600 [25]

Haynesville Texas, USA 21500 [25]

Eagle Ford Texas, USA 16100 [25]

Niobrara Colorado, USA 13000 [26]

Fuling Chongqing, China 27490 T his st udy

There are large variations in initial gas production of each well. In addition, the rate at which production declines varies between wells following different trajectories for example the scaling decline [28] or hyperbolic decline [29,30]. Based on data from the Chinese shale gas wells, gas productions calculated from P90, P50, P10 probabilities of typical curves, using the uncertainty analysis method, are 68213, 119985 and 133679 m3 day-1, respectively [30]. Gas production estimated using conventional certainty analysis is 95115 m3 day-1, close to the P50 value. Therefore in this study we used a shale gas production figure of119985 m3 day-1 for high-quality wells in subsequent analysis.

According to China's Shale Gas Development Plan [6], to meet the annual shale gas production target of 6.5 billion m3

by the end of 2015, some 148 wells will be required. Based on the results from this study around 4 million m3 water will be needed for fracking. To meet the gas production target of 60-100 billion m3 by the end of 2020, 1370-2283 new wells will be required; accordingly 38-63 million

m3 water will be consumed. Chongqing recently released the shale gas development plan which proposed targets of 10 and 20 billion m3 by 2017 and 2020, respectively [21]. These would require 6.3 and 12.6 million m3 water for fracking, respectively.

Water for fracking can be taken from a number of different sources: local streams, rivers or lakes, groundwater, or more remote sources with water being transported to wells by road or pipeline. For the wells near the Wu River, river water has been used. In more remote areas that lack readily accessible local supplies, water has to be transported by trucks leading to substantially increased road traffic between water sources and well sites. Reusing flow-back and water produced during the fracking process may reduce the freshwater demand. However, less than 10% of fracking fluid returns to the surface as flow-back water in the Fuling area.

Environmentally sensitive development of current fracking techniques is one of the biggest challenges for shale

gas exploration, especially for China where greater burial depth requires more water [9]. One option is to utilise non-freshwater sources, for example brackish water or waste water [26]. Although provincial-wide water use for shale gas extraction may not yet represent a major challenge for water resources, local impacts in areas such as Fuling, which will depend upon on maintaining water availability and sharing this resource with other developing uses for water, may lead to conflicts if the water requirements of different sectors cannot be met.

This study has focused on Fuling, while there may be spatial variations in fracking-related water consumption due to different geological conditions, depths of vertical and lateral well shafts and hacking times [31]. Our results highlight the importance of research on water demand in other countries with large shale gas reserves such as Poland, Argentina and South Africa. We have assumed that shale gas production is from the new wells drilled each year, and the estimate of gas production over time is based on the P50 of typical curves for uncertainty analysis. There are uncertainties in the estimates of shale gas production in the long-term and it can be argued that shale gas production from individual wells will decline rather quickly [28,30,32]. It is also important to recognise that this current study has focussed on water consumption during fracking operations alone. Other stages of shale gas exploration and use, for example the construction of well infrastructures, gas processing, and the transport and distribution of gas, will require additional water. A life cycle estimate of water consumption will therefore be needed for a more accurate estimate of total water demands of the shale gas industry development [33].

In addition to the demands upon water resources for shale gas exploration, there are other challenges facing the sustainable development of Chinese shale gas resources. Fracking produces waste water containing brines, heavy metals, radionuclides and organic pollutants [4]. Without proper treatment and strict environmental monitoring, the discharge of this waste into the environment has the potential to cause major impacts with implications for ecosystems and human beings [11]. Furthermore, Chongqing is near an active seismic region and several large earthquakes have occurred in the Sichuan Basin including the 8.0 Ms Wenchuan earthquake (May 12, 2008) and the Ms 7.0 Lushan earthquake (April 20, 2013). The potential earthquake threat of expanding shale gas development is an area of major public concern [12,13]. Shale gas pads and related road and pipeline construction will encroach on farmland, forests and grassland. The loss of natural vegetation may increase habitat fragmentation with implications for conservation of engendered species, threaten ecosystem service delivery [34] and so intensify current rates of land use change [35,36]. The Sichuan Basin is one of China 'rice bowls' and los s of farmland will affect crop production. Reduced vegetation cover and consequent enhanced soil erosion and siltation, particularly for Yangtze reservoirs, are already major problems [37,38] and may be exacerbated by shale gas well expansion. Methane emissions are another major challenge to the lower-carbon benefits of shale gas. Some studies have identified considerable leakage of methane during the extraction and transport of shale gas which impact the net carbon benefit of using shale gas as a strategy to reduce greenhouse gas emissions. [9]. The integrity of engineered structures including drilling equipment and pipelines is also a concern. Without in situ measurements and routine monitoring, it is difficult to estimate the risk of methane leakage from Chinese shale gas wells and associated infrastructure.

Balancing economic development, energy demands and environmental protection is a major dilemma for all governments, especially those in developing countries. Shale gas is one of the key solutions that has been advocated to cut China's increasing CO2 emissions and to clean its polluted air. Achieving these goals does, however, require reconciliation, in a quantitative manner, of the environmental impacts of shale gas development. Compared to the USA, Chinese shale gas extraction operations are relatively poorly developed. The chances of freshwater pollution and other environmental problems are higher whilst monitoring programmes are largely insufficient. China's newly introduced Environmental Protection Law does provides the legal weapons to protect the nations fragile ecosystems [39] but strict enforcement of this legislation will be essential if the environmental impacts from shale gas fracking are to be minimized [40].

Acknowledgements

Fieldwork was greatly assisted by support from by Fuling Environmental Protection Bureau and SinoPec Oilfield Service Jianghan Corporation. We acknowledge BIARI funding.

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