Repository for Oil and Gas Energy Research (ROGER)

Abstract:
Water scarcity has emerged as one of the most important global challenges of the twenty-first century. With rising demand for energy, and water being a critical input in energy production, the availability of water resources has put energy sustainable production under growing strain. While unconventional natural gas (especially shale gas) is seen as an important bridge for promoting the transition of energy system from high to low carbon, water availability is a significant constraint on the development of energy resources owing to the massive quantity of water used by the hydraulic fracturing. Against this background, our study aims to optimize the allocation of regionally scarce water resources for fostering integrated economic, social, and environmental growth in shale gas development plays. In light of the uncertainty inherent in the water supply management system for shale gas development, this work employed the Interval Two-stage Stochastic Programming (ITSP) to establish an optimal allocation model for water resources between wells jointly dispatched by surface water, underground water and reused water. The model predicted water scarcity, optimal water allocation, and the total benefit of the shale gas development water supply system under various scenarios. Furthermore, when compared to the Two-stage Stochastic Programming (TSP) model results, it was found that the ITSP model's interval value may present decision makers with more ideas and options than the TSP model. In addition, since the ITSP model is oblivious to the system risk issue, it incorporated robust optimization into the original ITSP model to build the Interval Two-stage Robust Stochastic Programming (ITRSP) model. Our findings were expressed as intervals that more accurately represent the actual optimal allocation of water resources, which also provided a broader decision-making space for decision makers in managing shale gas development water supply management schemes.

Abstract:
Brazil has the 10th largest shale gas reservoir, and the Paraná sedimentary basin has a potential area for shale gas production in the western portion of the São Paulo state. Despite that, the knowledge about the impacts of fracking on the local water resources is still limited. This study presents a novel reproducible method to compute the risk of water scarcity in areas with restricted or no shale gas development. Using geospatial numerical simulations under five scenarios from 500 to 2500 wells, we find that the fracking-related risk of water scarcity in the São Paulo state is low. For the 2013–2019 period, the long-term average seasonal water availability is between 0.05 and 1 Gm³ per water resources management unit, whereas fracking water demand would hardly overcome 6 Mm³ y−1. For instance, with 2500 wells, the fracking demand in Pontal do Paranapanema, the most prospective region for shale gas, would not overcome 3% of the yearly local water demand. The riskier areas are in Aguapeí and Baixo do Tietê water resources management units, during winter and autumn, and the most water-stressed area is São José dos Dourados. In regions and periods of low water availability, fracking operators can use adaptative strategies for shale gas production. In the context of imminent droughts, this research debates national energy security and casts doubt on the water efficiency and sustainability of the state's energy generation. At last, this research provides early insights to support shale gas and water policy, and future studies to further investigate relevant aspects to the Brazilian Water-Energy nexus.

Abstract:
Quantifying impacts of unconventional oil and gas production on water resources and aquatic habitats is critical for developing management approaches for mitigation. The study objective was to evaluate impacts of oil and gas production on groundwater and surface water and assess approaches to reduce these impacts using the Permian Basin as a case study. Water demand for hydraulic fracturing (HF) was compared to water supplies. We also examined contamination from surface spills. Results show that water demand for HF peaked in 2019, representing ~28% of water use in non-mining sectors. Most HF water was sourced from aquifers with ~1100 wells drilled in the Ogallala aquifer in 2019. The State monitoring network did not show regional groundwater depletion but was not sufficiently dense to address local impacts. Groundwater depletion is more critical in the western Delaware Basin within the Permian Basin because groundwater is connected to large flowing springs (e.g. San Solomon Springs) and to the Pecos River which has total dissolved solids ranging from ~3000 to 14,000 mg/L. Most produced water (70–80%) is disposed in shallow geologic units that could result in overpressuring and potential groundwater contamination from leakage through ~70,000 abandoned oil wells, including orphaned wells. While there is little evidence of leakage from abandoned wells, the state monitoring system was not designed to assess leakage from these wells. Oil spill counts totaled ~11,000 in the Permian (2009–2018). Approaches to mitigating adverse impacts on water management include reuse of PW for HF; however, there is an excess of PW in the Delaware Basin. Treatment and reuse in other sectors outside of oil and gas are also possibilities. Data gaps include reporting of water sources for HF, PW quality data required for assessing treatment and reuse, subsurface disposal capacity for accommodating PW, and spills from PW in Texas.

Abstract:
With the increasing consumption of energy in the world, shale gas, as a clean, efficient, and unconventional energy source, has been paid more and more attention. However, it should not be ignored that the process of shale gas exploitation will cause serious environmental pollution, especially water resource consumption and pollution. At present, the quantitative research on water resource cost of shale gas exploitation is rare. On the basis of summarizing the water resource consumption, pollution source in shale gas exploitation. This paper takes Chongqing Fuling national shale gas demonstration area as the research object, and cost measurement models are established from three aspects: water resource consumption, human body damage, and water quality decline. This paper innovatively calculates the water consumption cost of shale gas exploitation in Fuling, Chongqing. The calculation results show that the water consumption cost of Fuling shale gas in Chongqing is 93,639 Yuan per well. The research results provide theoretical basis and data support for enterprises to develop shale gas and the Chinese government to formulate shale gas development plan.

Abstract:
As the largest holder of shale gas resource estimates, China is actively promoting its shale gas development to steer its transitions to a low carbon energy system. The production of shale gas usually needs a large amount of water. According to our estimates, the direct water consumption is about 9700–37600m3/well, and the indirect water consumption is around 32,400–71,100 m3/well. Such a large amount of water consumption could have a serious impact on local human and ecosystem water consumption since China is a country with scarce and unevenly distributed water resources. Water scarcity footprint (WSF) of shale gas production in Chinese provinces is assessed to understand the impacts of shale gas production on local water consumption for other sectors. The results show that the average water pressure for shale gas production in China is higher compared with that of the U.S.. The average WSF in China is 16,574 m3 world. eq/106m3 gas while the WSF in the Barnett shale region in the U.S. is only around 2000 m3 world. eq/106m3 gas. 13 of 31 provinces have even higher WSF than the national average, in which the amount of shale gas resources accounts for about 20% of China's total. Shale gas exploitation in these 13 provinces might not be suitable or must be cautious from the perspective of WSF. The remaining 18 provinces have lower WSFs than the national average. A sustainable way for extracting shale gas in these 18 provinces needs to comprehensively consider WSF, the scale and speed of exploitation and the amount of local shale gas recoverable reserves.

Abstract:
The rise of unconventional oil and gas development in the form of hydraulic fracturing, or fracking, has drawn much attention from media, scholars, and policy makers, and Texas has frequently been the epicenter of this attention. This paper looks at fracking through a particular lens, that of an extraction process that relies heavily on water. This “water-energy nexus” has been studied in terms of the physical connections, but little research exists on how ordinary people might understand that nexus. This paper examines the effect of people's awareness of the water-energy nexus and county-level drought characteristics on their support for increased regulation of water issues associated with hydraulic fracturing. The analysis uses data from a Texas-based public opinion survey, and county-level data from the U.S. Drought Monitor and the Texas Railroad Commission. Multi-level modeling techniques are used to examine the impact of proximity, local water scarcity, and individual awareness of the water-energy nexus on people's willingness to support regulating aspects of water in hydraulic fracturing practices. The paper supports the hypothesis that individual awareness of the energy-water nexus and local water scarcity affects willingness to support greater regulation and concludes with some policy recommendations to improve policy transparency surrounding hydraulic fracturing.

Abstract:
Water is one of the most important commodities in the world and plays an essential role in the hydrocarbon industry. With increased agricultural production, rapid industrialization, population growth and climate change, the world is facing an extreme water crisis in many regions. Coupled with a surge in energy demand and consumption, this has greatly influenced the hydrocarbon industry. With increasing stress on water resources, it is essential to examine how water is managed within the hydrocarbon industry and devise ways to utilize water more efficiently, especially within water scarce regions such as the Middle East. Augmented by the recent activities in the oil and gas industry, it can be seen that an economical and efficient hydraulic fracturing job has become crucial for the successful development of unconventional reservoirs. However, exploitation of unconventional reservoirs is heavily water-intensive as compared to conventional reservoirs. In this study, a comprehensive investigation that deals with quantification of changes with respect to the variation in prime contributors within a traditional fracture design process is presented. To understand the significance of key design parameters, factors that affect productivity within typical Middle Eastern shale gas reservoirs were analyzed through simple constrained cases. Investigations reveal that parameters such as fracture aperture, natural fracture distribution, fracturing fluid viscosity and Young’s modulus are crucial to the overall production and water requirement. Furthermore, an outline for resource management within a traditional fracture design process is presented along with potential challenges for the region. Enhancing existing methodologies and incorporating key parameters highlighted within this study can contribute to the overall value chain. In addition to ultimately assisting in the verification of modern best practices, this investigative approach will create a paradigm for future studies for the region to assist in a simplistic prediction of fracture propagation and associated response to augment water usage.

Abstract:
Unconventional oil and gas (UOG) production requires intensive freshwater consumption, but whether hydroclimate variation, which alters regional water availability, affects its activity and water footprint is still unknown. In this study, we investigate the temporal and spatial correlations of drought intensity with UOG activity and water consumption in Colorado over a 13-year period. We found that hydroclimate variation has a negligible or weak impact on the well number and water footprint of UOG production, and that monthly UOG water consumption in areas already under drought conditions could sustain up to >110% of municipal water usage at the county scale. By defining a new metric of drought-escaping distance, we show that drought climate could cover areas more than 500 miles from the well sites, preventing UOG producers from acquiring water from areas without water stress. This results in local water withdrawal that intensifies water scarcity and competition. Our study also quantifies the potential of UOG wastewater reuse to reduce regional water stress. Our findings underscore the importance of UOG production in water resource allocation in particular under drought conditions. Our research could provide new insights into understanding the effects of UOG production on regional water sustainability during drought periods in Colorado.

Abstract:
The increased water consumption for hydraulic fracturing and the volume of wastewater generated from shale gas and tight oil exploration are major environmental challenges associated with unconventional energy development. Recycling of the flowback and produced water for hydraulic fracturing is one of the solutions for reducing the water footprint of hydraulic fracturing and removing highly saline oil and gas wastewater. Here we investigated the implications of recycling saline wastewater for hydraulic fracturing by monitoring the natural gas production, flowback water volume, and the water quality of generated flowback water in shale gas wells from Changning gas field in Sichuan Basin, China. A comparison of two sets of shale gas wells, with six wells in each sub-group, from the same location in Changning gas field shows lower (~20%) natural gas production and higher flowback water volume (~18%) in wells that were fracked with recycled saline wastewater relative to wells that were fracked with fresh water after a year of production. Geochemical analysis suggests that hydraulic fracturing with saline wastewater increases the salinity of the wastewater and reduces the magnitude of water-shale rock interactions. In spite of the direct economic consequences in reduction in natural gas production from recycling of wastewater for hydraulic fracturing, in areas where water scarcity could become a limiting factor for future large-scale shale gas development, hydraulic fracturing with recycled flowback water can be more beneficial than utilization of limited freshwater resources, as long as the higher saline flowback water is fully recycled.

Abstract:
A large volume of water is required in shale gas development, especially for large-scale hydraulic fracturing in horizontal wells. This study focuses on 334 shale gas wells in the largest production field Fuling in China. Models are formulated to estimate the water use at each stage of the development process, including pre-drilling preparation, drilling and cementing, fracturing, gas testing, production testing. Domestic water used by employee community of shale gas companies are also fully considered. The results show that the average fracturing water use per well was 34,756.0 m3 in Fuling, which accounted for 98% of the total water use. By the end of 2017, the total fracturing water used in Fuling was 1.09 × 107 m3, and a total of 2.28 × 106 m3 of flowback fluid was achieved with 2.16 × 106 m3 of water reused. In addtion, the domestic water used by the employee community was found to be 2.19 × 106 m3, which was equivalent to the water saved from the flowback fluid. China’s special “development campaign” mode for shale gas extraction is the reason. The results improve the understanding of water use in China’s shale gas development and also provide important implications for water management.

Abstract:
Rapid growth in U.S. unconventional oil and gas made energy more available and affordable globally, but brought environmental concerns, especially related to water. We analyzed water-related sustainability of energy extraction focusing on: (a) meeting rapidly rising water demand for hydraulic fracturing (HF), and (b) managing rapidly growing volumes of water co-produced with oil and gas (produced water, PW). We analyzed historical (2009–2017) HF water and PW volumes in ~73,000 wells and projected future water volumes in major U.S. unconventional oil (semiarid regions) and gas (humid regions) plays. Results show a marked increase in HF water use, depleting groundwater in some semiarid regions (e.g. by ≤58 ft [18 m]/yr in Eagle Ford). PW from oil reservoirs (e.g. Permian) is ~15× higher than that from gas reservoirs (Marcellus). Water issues related to both HF water demand and PW supplies may be partially mitigated by closing the loop through reusing PW for HF of new wells. However, projected PW volumes exceed HF water demand in semiarid Bakken (2.1×) and Permian Midland (1.3×) and Delaware (3.7×) oil plays, with the Delaware accounting for ~50% of projected U.S. oil production. Therefore, water issues could constrain future energy production, particularly in semiarid oil plays.

Abstract:
Kondash et al. provide a valuable contribution to our understanding of water consumption and wastewater production from oil and gas production using hydraulic fracturing. Unfortunately, their claim that the water intensity of energy production using hydraulic fracturing has increased in all regions is incorrect. More comprehensive data show that, while the water intensity of production may have increased in regions such as the Permian basin, it has decreased by 74% in the Marcellus and by 19% in the Eagle Ford region. This error likely stems from an improper method for estimating energy production from wells: The authors use the median well to represent regional production, which systematically underestimates aggregate production volumes. Across all regions, aggregate data suggest that the water intensity of oil and natural gas production using hydraulic fracturing has increased by 19%. There also appears to be an error in estimates for water consumption in the Permian basin. Kondash et al. incorrectly claim that water intensity has increased in all regions, and several data errors are apparent. Kondash et al. incorrectly claim that water intensity has increased in all regions, and several data errors are apparent.

Abstract:
Shale gas extraction has attracted great attention, especially in China, following its energy transition toward decarbonization, while the fast-expanding shale gas industry faces serious challenges related to water scarcity and water contamination. Quantitative investigations of the impacts of shale gas production on water scarcity and water contamination contribute to public awareness that shale gas production will worsen the water resource shortage. This paper presents a comprehensive water footprint (WF) assessment to improve understanding of the water sustainability and availability in shale gas industry. A detailed process water footprint model was used to quantify precisely the potential water consumption and environmental impacts. The full water use chain in the shale gas industry was examined, from the water used for well drilling and equipment maintenance, to the injection of hydraulic fracturing fluids and the disposal of the produced water. The results indicate that the historical water consumption ranged from 633.23 m3/segment to 2,292.90 m3/segment, totaling nearly 4.54 × 106 m3 for 120 wells. The projections of the estimated total WF for the constructed production period 2018–2020 and stable production period 2021–2030 were 3.30 × 107 m3/year and 5.21 × 107 m3/year in the Changning play, accounting for 10.12% and 15.98% of the average annual runoff of the Changning River, respectively, and 3.19 × 108 m3/year and 6.38 × 108 m3/year in all of the plays in China, accounting for 0.25% and 0.50% of the total national industrial water consumption in China in 2017 (1.28 × 1011 m3), respectively. The grey WF was the main contributor, accounting for 94.50% to the total WF, suggesting that water quality issues should be highly emphasized and that this footprint has a significant impact on the pollution of the water bodies near shale gas sites. These findings provide a valuable insight in understanding water consumption process in shale gas industry that can be employed to develop water resource and wastewater treatment management strategies and indicate that water resource contamination will restrict shale gas development and different effective alternative forms of management strategies, laws or regulations regarding water resources should be implemented to alleviate water resource and environmental burdens.

Abstract:
The method of hydraulic fracturing used to exploit unconventional shale gas has raised public concerns over the volumes of freshwater that are extracted for injection operations as well as the volumes of wastewater generated as a by-product of gas production. Using data from the British Columbia Oil and Gas Commission, this paper examines the volumes of produced and injected water from hydraulically fractured gas wells in Northeastern British Columbia. The two major producing shale gas basins in the province are the Montney and the Horn River. In this study, these are divided into several sub-basins based on existing geological and reservoir engineering applications. For each sub-basin the average volumes of wastewater- and injected water per well are calculated and then normalized to cumulative gas production. Ratios of injected water: gas production and wastewater: gas production are then applied to estimated volumes of remaining gas reserves in each sub-basin in order to calculate a total water footprint of future exploitation. These extrapolated water footprints were further elaborated into three scenarios of wastewater recycling rates: 0, 40, and 100% re-use. This study also compares the quality and quantity of wastewater produced from hydraulically fractured wells to their conventional counterparts in the province. Based on these calculations, the total future freshwater withdrawal and wastewater production volumes for all basins range from 1.65 to 3 billion, and 0 to 1.35 billion cubic metres, respectively. Volumes of freshwater withdrawal are relatively modest compared to other industries when considering the size of Northeastern British Columbia and the time-scale of extraction. In general, hydraulically fractured wells in Northeastern British Columbia produce volumes of wastewater that are equal to or lower than those required for injection. Unconventional gas wells often produce far less wastewater than their conventional counterparts.

Abstract:
This paper explores how a novel and water-intensive method of energy production – high-volume hydraulic fracturing (a.k.a., “fracking” or “fracing”) – has taken hold in a river basin that is over-appropriated, is managed via a water governance regime that did not anticipate hydraulic fracturing's idiosyncrasies, and where public concern about dedicating freshwater to hydrocarbon production is high. Via a grounded examination of hydraulic fracturing water use in Colorado’s busiest oilfield and most crowded river basin, I argue that the practice has come to exist – and persist – despite these countervailing forces because it is an ephemeral energy-water assemblage. It is always in motion, is tough to monitor, and emerges only to disappear and reemerge again. This shape-shifting capacity distinguishes hydraulic fracturing from better-known energy-water couplings such as the hydroelectric dam and from historical surface irrigation practices in the American West. It also has consequences. While the uncritical energy-water literature suggests that these energy-water relations have been sufficiently characterized by volumetric gallons-per-well estimates, and the physical ephemerality of the hydraulic fracturing assemblage keeps its on-the-ground complexities elusive, an abridged and uncomplicated picture of hydraulic fracturing endures in the academic literature and public discourse. The partial understandings that result make this assemblage simpler to produce and reproduce. This study responds to calls for more nuanced analyses of energy-water relations. It also contributes to assemblage theory by examining the relationship between instability and stability in the lives of an assemblage, which underscores the importance of processes of disassembly and reassembly within assemblage-style analyses.

Abstract:
Hydraulic fracturing (HF) operations have transformed the unconventional energy industry, leading to a global increase in hydrocarbon production. Despite this, only the US, China, Canada and Argentina currently dominate production of unconventional resources, with the majority of shale basins globally remaining unprofitable to develop. An important gap in current water-energy nexus research, which this study addresses, is the assessment of potential water use to satisfy HF procedures in emergent plays. This work presents a screening tool for assessing first-order estimates of water impacts in undeveloped shale plays, testing the approach in the transboundary Eagle Ford (EF) play in northeast Mexico. We couple surface water and groundwater stress indicators derived from global hydrological variables to depict a baseline water stress index. Relative water stress is mapped for proposed blocks to be leased by the Mexican government in the future. We simulate four HF scenarios to assess new total water stress indicators for each block, considering shale production schemes using representative well drilling density (well lateral length(s) per unit area) and HF water intensity (HF water volume per unit lateral length) from existing EF development in Texas. Results suggest that the most feasible management scenario would consider the drilling of ∼1360 new unconventional wells/yr with projected HF water use of ∼57 Mm3/yr (0.7% of the total water withdrawals). The remaining scenarios will largely affect groundwater resources. Though applied to the EF in Mexico, this screening tool can assess water use constraints in emerging unconventional plays globally.

Abstract:
The potential water demand for fracturing fluids along with the possible flowback and produced water production is assessed for the Dutch Posidonia shale. Total water demand estimated for 25 years of the field development using historic data from the U.S. plays varies between 12.2 and 36.9 Mm3. The maximal annual water consumption of 0.95–2.88 Mm3 is expected in the peak years of shale gas production. These figures are much lower than the availability of any potential water sources, which include drinking water, fresh and brackish groundwater, river water, effluents of wastewater treatment plants (WWTP) and sea water. River water is considered the most promising water source for fracturing fluids in the Dutch Posidonia shale based on its availability (>6·104 Mm3/year) and quality (only bacterial composition needs to be controlled). Total wastewater production for the whole period of the field development is estimated between 6.6 and 48.0 Mm3. Wastewater recycling can cover significant part of the source water demand for fracturing fluid. However, high mineral content of the wastewater as well as temporal and spatial discrepancies between wastewater production and water demand will form obstacles for wastewater recycling. The assessment framework developed in this study may be applied for other shale gas fields with high uncertainties regarding subsurface properties, connate formation water characteristics and future legislative framework.

Abstract:
The primary challenges of petroleum industries are to provide a secure quantity and quality of water resources and how to manage the generated wastewater adequately. Appropriate application of water treatment systems would play a substantial role in drilling operations. Therefore, wastewater management and controlling the amount of produced hazardous materials should be significantly taken into consideration. The objective of this extensive study is to calculate the required water for the waterflooding, polymer flooding, and hydraulic fracturing performances, and subsequently, the percentage of fresh water saving in a shale oil reservoir was calculated accordingly. First of all, the required water and treated water for each well were calculated, and then, the percentage of saving water was averagely calculated. As a result, the percentage of fresh water saving for waterflooding, polymer flooding, and hydraulic fracturing were 71.5%, 70%, and 83.7%, respectively. It was indicated that most of the injected water was treated again and reinjected in the fracturing operations. Furthermore, the total volume of required water for the drilling of Pazanan oilfield’s wells was approximately 125 million gallons that indicated the treatment processes provided about 95 million gallons of this volume. Consequently, the average volume of fresh water saving was relatively 70% which was clarified the accuracy of wastewater separation and purification in the treatment system.

Abstract:
Natural gas (NG) from shale formations (or shale gas) is an unconventional energy resource whose potential environmental impacts are still not adequately assessed. Hence, this study performs a Life Cycle Assessment (LCA) of shale gas considering a gas well under appraisal in Burgos, Spain. An attributional model was developed, considering the NG pre-production and production phases in the system boundaries, considering 1 MJ of processed NG as a functional unit. Results were obtained through the CML-IA baseline method (developed by the Center of Environmental Science of Leiden University) and showed that well design, drilling and casing, hydraulic fracturing, NG production, gathering, and processing are critical processes. To better address the environmental impacts, a comparison with similar studies was carried out, as well as a sensitivity and an uncertainty analysis using Monte Carlo simulation (MCS). The model was found to be particularly sensitive to water usage in hydraulic fracturing and to the number of workovers with hydraulic fracturing. Limited data availability for shale gas exploration still poses a challenge for an accurate LCA. Even though shale gas remains controversial, it still can be considered as a strategic energy resource, requiring a precautionary approach when considering its exploitation and exploration.

Abstract:
Vaca Muerta is the major region in South America where horizontal drilling and hydraulic fracturing techniques are used to extract unconventional shale oil and gas. Despite the growing interest in the Vaca Muerta resources, there is only a limited understanding of the impacts that their extraction could have on local water resources. This study uses a water balance model to investigate the hydrological implication of unconventional oil and gas extraction in this region. We find that, with current rates of extraction, water scarcity is observed for four months a year. We also find that water consumption per fractured well increased 2.5 times in the period 2012-2016 and produced water from unconventional shale formation sharply increased from roughly zero to 1.15×106 m3 y-1 in the 2009-2017 period. Our projections estimate that in this region future water consumption for unconventional oil and gas extraction will increase 2.2 times in the 2017-2024 period reaching 7.40×106 m3 y-1. The consequent exhacerbation of current water scarcity will likely lead to competition with irrigated agriculture, the greatest water consumer in this semiard region. Produced water recycling, domestic wastewater reuse, brackish groundwater use, and waterless unconventional oil and gas extraction technologies are some of the strategies that could be adopted to meet future additional water demand. Our results estimate the likely range of water consumption and production from hydraulic fracturing operations in the Vaca Muerta region under current and future conditions. These results could be used to make informed decisions for the sustainable water management in this semiarid region of Argentina.

Abstract:
Australia has significant quantities of technically recoverable shale gas and the potential to become a major producer of natural gas from these unconventional resources. However, the hydrocarbon extraction process from shale formations involves heavy drilling and hydraulic fracturing. Both these activities consume a considerable volume of water, which impacts local communities and the environment. This paper proposes a combinatorial methodology that incorporates multi-criteria decision-making and system dynamics to select the best water resources, and then investigate the regional impact of consuming those resources over the long-term. The methodology is described through a case study on the Beetaloo Basin, Northern Territory – a prospective shale gas resources deposit. The results show that the produced water and fresh groundwater are appropriate options for the basin, and appropriate scenarios can prevent the over-extraction of fresh groundwater, maximise the reuse of water, and minimise aquifer disturbance. The proposed methodology is designed to support petroleum companies when making decisions about which water resources to use in shale mining operations to balance various factors affecting the system.

Abstract:
This work proposes an optimization approach for designing efficient water networks for the shale gas production through the recycle and reuse of wastewater streams reducing the freshwater consumption and effluents considering economic and environmental goals. The economic objective function aims to minimize the total annual cost for the water network including the costs associated with storage, treatment and disposal (capital cost) as well as freshwater cost, treatment cost and transportation costs. The environmental objective is addressed to deal with the minimization of the environmental impact associated with the discharged concentration of total dissolved solids in the wastewater streams and the freshwater consumption through an environmental function that represents the benefit for removing pollutants using the eco-indicator 99 methodology. The methodology requires a given scheduling for the completion phases of the target wells to be properly implemented by the available hydraulic fracturing crews during a time horizon. The model formulation is configured to determine the optimal sizes for the equipment involved by the project, particularly the sizes for storage and treatment units are quantified by the optimization process. A case study is solved to evaluate the effectiveness of the proposed optimization approach.Graphical abstract Open image in new window

Abstract:
Research Highlight

Abstract:
Access to water, in sufficient quantities and of sufficient quality is vital for human health. The United Nations Committee on Economic, Social and Cultural Rights (in General Comment 15, drafted 2002) argued that access to water was a condition for the enjoyment of the right to an adequate standard of living, inextricably related to the right to the highest attainable standard of health, and thus a human right. On 28 July 2010 the United Nations General Assembly declared safe and clean drinking water and sanitation a human right essential to the full enjoyment of life and all other human rights. This paper charts the international legal development of the right to water and its relevance to discussions surrounding the growth of unconventional energy and its heavy reliance on water. We consider key data from the country with arguably the most mature and extensive industry, the USA, and highlight the implications for water usage and water rights. We conclude that, given the weight of testimony of local people from our research, along with data from scientific literature, non-governmental organization (NGO) and other policy reports, that the right to water for residents living near fracking sites is likely to be severely curtailed. Even so, from the data presented here, we argue that the major issue regarding water use is the shifting of the resource from society to industry and the demonstrable lack of supply-side price signal that would demand that the industry reduce or stabilize its water demand per unit of energy produced. Thus, in the US context alone, there is considerable evidence that the human right to water will be seriously undermined by the growth of the unconventional oil and gas industry, and given its spread around the globe this could soon become a global human rights issue.

Abstract:
Shale gas is likely to play a major role in China's transition away from coal. In addition to technological and infrastructural constraints, the main challenges to China's sustainable shale gas development are sufficient shale gas production, water availability, and adequate wastewater management. Here we present, for the first time, actual data of shale gas production and its water footprint from the Weiyuan gas field, one of the major gas fields in Sichuan Basin. We show that shale gas production rates during the first 12 months (24 million m3 per well) are similar to gas production rates in U.S. shale basins. The amount of water used for hydraulic fracturing (34,000 m3 per well) and the volume of flowback and produced (FP) water in the first 12 months (19,800 m3 per well) in Sichuan Basin are also similar to the current water footprints of hydraulic fracturing in U.S. basins. We present salinity data of the FP water (5000 to 40,000 mgCl/L) in Sichuan Basin and the treatment operations, which include sedimentation, dilution with fresh water, and recycling of the FP water for hydraulic fracturing. We utilize the water use data, empirical decline rates of shale gas and FP water productions in Sichuan Basin to generate two prediction models for water use for hydraulic fracturing and FP water production upon achieving China's goals to generate 100 billion m3 of shale gas by 2030. The first model utilizes the current water use and FP production data, and the second assumes a yearly 5% intensification of the hydraulic fracturing process. The predicted water use for hydraulic fracturing in 2030 (50–65 million m3 per year), FP water production (50–55 million m3 per year), and fresh water dilution of FP water (25 million m3 per year) constitute a water footprint that is much smaller than current water consumption and wastewater generation for coal mining, but higher than those of conventional gas production in China. Given estimates for water availability in Sichuan Basin, our predictions suggest that water might not be a limiting factor for future large-scale shale gas development in Sichuan Basin.

Abstract:
The environmental impacts of a typical hydraulic fracturing operation for shale gas recovery were evaluated using life cycle assessment, with energy demands for well drilling and fracturing determined from GHGfrack model. Dominant environmental impacts stem from well construction, which are >63% in all categories (e.g., global warming and eutrophication), and mainly due to diesel fuel combustion and steel production. The relative impacts related to water use (i.e., fracturing fluid components, water/wastewater transportation, and wastewater disposal) are relatively small, ranging from 5 to 22% of total impacts in all categories; freshwater consumption for fracturing is also a small fraction of available water resources for the shale play considered. The impacts of replacing slickwater with CO2 or CH4-foam fracturing fluid (≤10 vol % water) were evaluated; total impacts decrease <12%, and relative impacts related to water use decrease to 2–9% of total impacts. Hence, switching to a foam-based fracturing fluid can substantially decrease water-related impacts (>60%) but has only marginal effects on total environmental impacts. Changes in lateral well length, produced to fresh-water ratios, fracturing fluid composition, and LCA control volume do not change these findings. More benefits could potentially be realized by considering water versus foam-related impacts of ecological health and energy production.

Abstract:
Food system and energy planners have given scant attention to the impacts on agrifood systems of a particular form of energy productionfrackingand its implications for planning and regulation. Impacts include those related to water availability and quality; land quality, use, and value; wildlife; labor costs; infrastructure and services; and the implications of boom and bust dynamics of these for the sustainability of agriculture and food systems. Planning is challenged by competing frames of economic and environmental benefits, lack of capacity, power imbalances, and sometimes state policy. This review maps research on these linkages, identifies elements of successful planning, and offers directions for future research.

Abstract:
The hydraulic fracturing boom in Texas required massive water flows. Beginning in the summer of 2011, water became scarce as a prolonged heat wave and subsequent severe drought spread across the state. Oil and gas producers working in drought areas needed to purchase expensive local water or transport water from a non-drought county far from the drill site. In response to decreased water availability in drought areas, these producers completed fewer wells and completed wells that used less water. This decrease in well-level water use had a measurable effect on the amount of oil and gas produced by wells completed during exceptional conditions.

Abstract:
Demand for high-volume, short duration water withdrawals could create water stress to aquatic organisms in Fayetteville Shale streams sourced for hydraulic fracturing fluids. We estimated potential water stress using permitted water withdrawal volumes and actual water withdrawals compared to monthly median, low, and high streamflows. Risk for biological stress was considered at 20% of long-term median and 10% of high- and low-flow thresholds. Future well build-out projections estimated potential for continued stress. Most water was permitted from small, free-flowing streams and “frack” ponds (dammed streams). Permitted 12-h pumping volumes exceeded median streamflow at 50% of withdrawal sites in June, when flows were low. Daily water usage, from operator disclosures, compared to median streamflow showed possible water stress in 7–51% of catchments from June–November, respectively. If 100% of produced water was recycled, per-well water use declined by 25%, reducing threshold exceedance by 10%. Future water stress was predicted to occur in fewer catchments important for drinking water and species of conservation concern due to the decline in new well installations and increased use of recycled water. Accessible and precise withdrawal and streamflow data are critical moving forward to assess and mitigate water stress in streams that experience high-volume withdrawals.

Abstract:
The development of shale gas resources is subject to technical challenges and markedly affected by volatile markets that can undermine the development of new projects. Consequently, stakeholders can greatly benefit from decision-making support tools that integrate the complexity of the system along with the uncertainties inherent to the problem. Accordingly, a general methodology is proposed in this work for the evaluation of integrated shale gas and water supply chains. First, key parametric uncertainties are identified from a candidate pool via a global sensitivity analysis based on a deterministic optimization model. Then, a two-stage stochastic model is developed considering only the key uncertain parameters in the problem. Moreover, the merits of modeling uncertainty and implementing the stochastic solution approach are evaluated using the expected value of perfect information and the value of the stochastic solution metrics. Furthermore, the conditional value-at-risk approach was implemented to evaluate different risk-aversion levels and the corresponding impacts on the shale gas development plan. The proposed methodology is illustrated through two real-world case studies involving six and eighth potential well-pad locations and two options of well-pad layouts. This article is protected by copyright. All rights reserved.

Abstract:
Shale gas production is a water and energy-intensive process that has expanded rapidly in the United States in recent years. This study compared the life cycle water consumption and greenhouse gas emissions from hydraulic fracturing in the Barnett region of Texas, located in one of the most drought prone regions of the United States. Four wastewater treatment scenarios were compared for produced water management in the Barnett region. For each scenario, the cradle-to-gate life cycle global warming potential and water scarcity footprint was estimated per mega joule of gas produced. The results show a trade-off between water and carbon impacts, because energy is required for treatment of water. A reduction of 49 percent in total water consumed or a 28 percent reduction in the water scarcity footprint in the shale gas production process can be achieved at a cost of a 38 percent increase in global warming potential, if the wastewater management shifted from business as usual to complete desalination and reuse of produced water. The results are discussed in the context of wastewater management options available in Texas.

Abstract:
Shale deposits are globally abundant and widespread. Extraction of shale oil and shale gas is generally performed through water-intensive hydraulic fracturing. Despite recent work on its environmental impacts, it remains unclear where and to what extent shale resource extraction could compete with other water needs. Here we consider the global distribution of known shale deposits suitable for oil and gas extraction and develop a water balance model to quantify their impacts on local water availability for other human uses and ecosystem functions. We find that 31–44% of the world's shale deposits are located in areas where water stress would either emerge or be exacerbated as a result of shale oil or gas extraction; 20% of shale deposits are in areas affected by groundwater depletion and 30% in irrigated land. In these regions shale oil and shale gas production would likely compete for local water resources with agriculture, environmental flows, and other water needs. By adopting a hydrologic perspective that considers water availability and demand together, decision makers and local communities can better understand the water and food security implications of shale resource development.

Abstract:
Shale gas development has been heralded as a game changer that has had, and will continue to have, repercussions for energy scenarios around the world, and natural gas has been hailed as the transition fuel to a low carbon future. Shale gas production—made feasible and economical by advances in hydraulic fracturing—offers a solution in the face of increased demand, instability in key producing regions, and societal aversion to the risks of nuclear energy. This “golden future,” however, has come into conflict with increasing concerns over water. This paper examines policy and regulatory frameworks around hydraulic fracturing in Texas and Spain in order to consider the trade-offs—particularly at the expense of water security—that may occur as decision-makers pursue improvements in energy security. We compare regulatory, institutional, and cultural contexts in order to understand and evaluate the robustness of these frameworks to prevent the reduction in water security as a consequence of the pursuit of energy security. Paucity of data is discussed. We also consider questions such as disclosure of information to the public about water use or the chemical composition of frac fluids and public opinion about hydraulic fracturing. Lessons are drawn that may assist policymakers who seek to guarantee water security while pursuing energy security.

Abstract:
Approximately 81% of the nation's energy demands are supported by hydrocarbons, largely in part to the relatively recent exploration of oil and gas from unconventional shale energy reserves. The extraction of shale energy requires technological ingenuity, such as hydraulic fracturing and horizontal drilling, and significant freshwater resources to successfully recover the previously sequestered hydrocarbons from low porosity formations. As unconventional oil and gas development continues to expand to meet the growing energy demands, it becomes increasingly more important to understand the potential environmental implications and to practice proper environmental stewardship. For example, concerns over water usage and the related consequences have dramatically increased due to the demand for water used in hydraulic fracturing, the increased volumes of wastewater being produced, and the need to dispose of or reuse the wastewater without compromising the surface and subsurface environments. As such, this chapter will cover the life cycle of water in oil and gas development (conventional and unconventional), including water use and waste production in the drilling, stimulation, and production phases; the current waste management strategies and challenges within the various treatment modalities; and the widespread implications of the varying forms of waste management.

Abstract:
This study identifies five data input categories essential to quantifying water use and the environmental impacts via water use metrics (i.e., Water Footprints) when evaluating water use during upstream unconventional oil and gas. Published water use metrics, which included provisions for addressing each of the five categories, were selected for evaluation. The selected metrics were compared and evaluated against data parameters defined within each of the input categories. Finally, a decision tree for method selection, which differentiates between assessment mechanisms, impact indicator, and result units, is presented to facilitate method selection of future studies of water use in unconventional oil and gas development.

Abstract:
Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the entire life cycle of the well based on its suitability for re-fracturing to stimulate their long and lateral horizontal wells. According to our data, sourcing, storage, transportation, treatment, and disposal of this large volume of water could account for up to 10% of overall drilling and completion costs. With increasingly stringent regulations governing the use of fresh water and growing challenges associated with storage and use of produced and flowback water in hydraulic fracturing, finding alternative sources of fracturing fluid is already a hot debate among both the scientific community and industry experts. On the other hand, waterless fracturing technology providers claim their technology can solve the concerns of water availability for shale development. This study reviews high-level technical issues and opportunities in this challenging and growing market and evaluates key economic drivers behind water management practices such as waterless fracturing technologies, based on a given shale gas play in the United States and experience gained in Canada. Water costs are analyzed under a variety of scenarios with and without the use of (fresh) water. The results are complemented by surveys from several oil and gas operators. Our economic analysis shows that fresh water usage offers the greatest economic return. In regions where water sourcing is a challenge, however, the short-term economic advantage of using non-fresh water-based fracturing outweighs the capital costs required by waterless fracturing methods. Until waterless methods are cost competitive, recycled water usage with low treatment offers a similar net present value (NPV) to that of sourcing freshwater via truck, for instance.

Abstract:
Water resources development and landscape alteration exert marked impacts on water-cycle dynamics, including areas subjected to hydraulic fracturing (HF) for exploitation of unconventional oil and gas resources found in shale or tight sandstones. Here we apply a conceptual framework for linking baseflow analysis to changes in water demands from different sectors (e.g. oil/gas extraction, irrigation, and municipal consumption) and climatic variability in the semiarid Eagle Ford play in Texas, USA. We hypothesize that, in water-limited regions, baseflow (Qb) changes are partly due (along with climate variability) to groundwater abstraction. For a more realistic assessment, the analysis was conducted in two different sets of unregulated catchments, located outside and inside the Eagle Ford play. Three periods were considered in the analysis related to HF activities: pre-development (1980-2000), moderate (2001-2008) and intensive (2009-2015) periods. Results indicate that in the Eagle Ford play region, temporal changes in baseflow cannot be directly related to the increase in hydraulic fracturing. Instead, substantial baseflow declines during the intensive period of hydraulic fracturing represent the aggregated effects from the combination of: (1) a historical exceptional drought during 2011-2012; (2) increased groundwater-based irrigation; and (3) an intensive hydraulic fracturing activity. (C) 2017 Elsevier B.V. All rights reserved.

Abstract:
Production of oil from shale and tight reservoirs accounted for almost 50% of 2016 total U.S. production and is projected to continue growing. The objective of our analysis was to quantify the water outlook for future shale oil development using the Eagle Ford Shale as a case study. We developed a water outlook model that projects water use for hydraulic fracturing (HF) and flowback and produced water (FP) volumes based on expected energy prices; historical oil, natural gas, and water-production decline data per well; projected well spacing; and well economics. The number of wells projected to be drilled in the Eagle Ford through 2045 is almost linearly related to oil price, ranging from 20,000 wells at $30/barrel (bbl) oil to 97,000 wells at $100/bbl oil. Projected FP water volumes range from 20% to 40% of HF across the play. Our base reference oil price of $50/bbl would result in 40,000 additional wells and related HF of 265×109 gal and FP of 85×109gal. The presented water outlooks for HF and FP water volumes can be used to assess future water sourcing and wastewater disposal or reuse, and to inform policy discussions.

Abstract:
Mexico's government enacted an energy reform in 2013 that aims to foster competitiveness and private investment throughout the energy sector value chain. As part of this reform, it is expected that extraction of oil and gas via hydraulic fracturing will increase in five shale basins (e.g. Burgos, Sabinas, Tampico, Tuxpan, and Veracruz). Because hydraulic fracturing is a water-intensive activity, it is relevant to assess the potential water availability for this activity in Mexico. This research aims to quantify the water availability for hydraulic fracturing in Mexico and identify its spatial distribution along the five shale basins. The methodology consisted of a multilayer geospatial analysis that overlays the water availability in the watersheds and aquifers with the different types of shale resources areas (e.g. oil and associated gas, wet gas and condensate, and dry gas) in the five shale basins. The aquifers and watersheds in Mexico are classified in four zones depending on average annual water availability. Three scenarios were examined based on different impact level on watersheds and aquifers from hydraulic fracturing. For the most conservative scenario analyzed, the results showed that the water available could be used to extract between 8.15 and 70.42 Quadrillion British thermal units (Quads) of energy in the typical 20-30 year lifetime of the hydraulic fracturing wells that could be supplied with the annual water availability overlaying the shale areas, with an average across estimates of around 18.05 Quads. However, geographic variation in water availability could represent a challenge for extracting the shale reserves. Most of the water available is located closer to the Gulf of Mexico, but the areas with the larger recoverable shale reserves coincide with less water availability in Northern Mexico. New water management techniques (such as recycling and re-use), more efficient fracturing methods, shifts in usage patterns, or other water sources need to be identified to allocate water for hydraulic fracturing without affecting current users (e.g. municipal, irrigation, industrial, and environmental flows).

Abstract:
Water use for oil and gas development (i.e., hydraulic fracturing) is a concern in semiarid basins where water supply is often stressed to meet demands, and oil and gas production can exacerbate the situation. Understanding the impacts of water use for hydraulic fracturing (HF) on water availability in semiarid regions is critical for management and regulatory decisions. In the current work, we quantify water use for HF at several scales from municipal to state-wide using the IHS Enerdeq database for the South Platte Basin. In addition, we estimate produced water (a by-product of oil and gas production), using data from the Colorado Oil and Gas Conservation Commission to explore reuse scenarios. The South Platte River Basin, located in northeastern Colorado, encompasses the Denver-Metro area. The basin has one of the most productive oil and gas shale formations in Colorado, with much of the production occurring in Weld County. The basin has experienced higher horizontal drilling rates coupled with an increasing population. Results show water use for horizontal and vertical wells averages 11,000 and 1,000m(3), respectively. Water use for HF in the South Platte Basin totaled 0.63% of the basin's 2014 total water demand. For Weld County, water use for HF was 2.4% of total demand, and for the city of Greeley, water use was 7% of total demand. Produced water totaled 9.4Mm(3) in the basin for 2014, which represents 42% of the total water used for HF.

Abstract:
Scientists and water users are concerned about the potential impact on water resources, particularly during low-flow periods, of freshwater withdrawals for hydraulic fracturing (fracking). Therefore, the objective of this paper is to assess the potential impact of hydraulic fracturing on water resources in the Muskingum watershed of Eastern Ohio, USA, especially due to the trend of increased withdrawals for hydraulic fracking during drought years. The Statistical Downscaling Model (SDSM) was used to generate 30 years of plausible future daily weather series in order to capture the possible dry periods. The data generated were incorporated in the Soil and Water Assessment Tool (SWAT) to examine the level of impact due to fracking at various scales. Analyses showed that water withdrawal due to hydraulic fracking had a noticeable impact, especially during low-flow periods. Clear changes in the 7-day minimum flows were detected among baseline, current and future scenarios when the worst-case scenario was implemented. The headwater streams in the sub-watersheds were highly affected, with significant decrease in 7-day low flows. The flow alteration in hydrologically-based (7Q10, i.e. 7-day 10-year low flow) or biologically-based (4B3 and 1B3) design flows due to hydraulic fracking increased with decrease in the drainage area, indicating that the relative impact may not be as great for higher order streams. Nevertheless, change in the annual mean flow was limited to 10%.

Abstract:
This paper is the first of a two-part series designed to assess and summarize extant knowledge regarding hydraulic fracturing water and wastewater management practices using a comparative, multidisciplinary approach. To provide context for both papers, the water and wastewater practices are summarized for the four focus plays: Montney, Duvernay, Barnett, and Marcellus. In Alberta and British Columbia, which host the less-studied Duvernay and Montney plays, play-scale unconventional water and wastewater data are extracted and combined from three databases: FracFocus.ca, geoSCOUT, and AccuMap. A reasonable picture of hydraulic fracturing water use and practices in western Canada emerges from the over 4,000 wells studied. From late 2011 to early 2014, the average number of fracturing stages reported increased from 7 to over 14, while reported cumulative water use approached approximately 15 million m3 in 2013, the first year for which full data in all three databases was available. The majority of wells consuming 10,000 to 50,000 m3 of water are slickwater type, located largely in the two target plays; however, several wells using >50,000 m3 of water appear in the Horn River Formation in BC. While it is possible to identify in the databases wastewater treatment facilities and deep wastewater injection wells, it is at present difficult to constrain wastewater disposal practices and chemistry in Alberta and British Columbia. The analysis points to the need for further coordination between academics, industry, and governmental agencies to develop publicly available, searchable databases that carefully document water sourcing, wastewater recycling/reuse/disposal, and chemistry, in order to properly form hydraulic fracturing water management strategies.

Abstract:
This study develops a multi-level programming model from a life cycle perspective for performing shale-gas supply chain system. A set of leader-follower-interactive objectives with emphases of environmental, economic and energy concerns are incorporated into the synergistic optimization process, named MGU-MEM-MWL model. The upper-level model quantitatively investigates the life-cycle greenhouse gas (GHG) emissions as controlled by the environmental sector. The middle-level one focuses exclusively on system benefits as determined by the energy sector. The lower-level one aims to recycle water to minimize the life-cycle water supply as required by the enterprises. The capabilities and effectiveness of the developed model are illustrated through real-world case studies of the Barnett, Marcellus, Fayetteville, and Haynesville Shales in the US. An improved multi-level interactive solution algorithm based on satisfactory degree is then presented to improve computational efficiency. Results indicate that: (a) the end-use phase (i.e., gas utilization for electricity generation) would not only dominate the life-cycle GHG emissions, but also account for 76.1% of the life-cycle system profits; (b) operations associated with well hydraulic fracturing would be the largest contributor to the life-cycle freshwater consumption when gas use is not considered, and a majority of freshwater withdrawal would be supplied by surface water; (c) nearly 95% of flowback water would be recycled for hydraulic fracturing activities and only about 5% of flowback water would be treated via CWT facilities in the Marcellus, while most of the wastewater generated from the drilling, fracturing and production operations would be treated via underground injection control wells in the other shale plays. Moreover, the performance of the MGU-MEM-MWL model is enhanced by comparing with the three bi-level programs and the multi-objective approach. Results demonstrate that the MGU-MEM-MWL decisions would provide much comprehensive and systematic policies when considering the hierarchical structure within the shale-gas system.

Abstract:
Since the early 2000s, oil and natural gas production in the United States have been transformed through technological innovation. Hydraulic fracturing, combined with advanced directional drilling techniques, made it possible to economically extract oil and gas resources previously inaccessible. The resulting surge in production increased domestic energy supplies and brought economic benefits to many areas of the United States. The growth in domestic oil and gas production also raised concerns about potential impacts to human health and the environment, including potential effects on the quality and quantity of drinking water resources. Some residents living close to oil and gas production wells have investigated changes in the quality of drinking water and assert that hydraulic fracturing is responsible for these changes. Other concerns include competition for water between hydraulic fracturing activities and other water users, especially in areas of the country experiencing drought, and the disposal of wastewater generated from hydraulic fracturing. This investigation synthesizes available scientific literature and data to assess the potential for hydraulic fracturing for oil and gas to change the quality or quantity of drinking water resources, and identifies factors affecting the frequency or severity of potential changes. This investigation can be used by federal, tribal, state, and local officials; industry; and the public to better understand and address any vulnerabilities of drinking water resources to hydraulic fracturing activities.

Abstract:
Development of shale gas resources is expected to play an important role in China's projected transition to a low-carbon energy future. The question arises whether the availability of water could limit this development. The paper considers a range of scenarios to define the demand for water needed to accommodate China's projected shale gas production through 2020. Based on data from the gas field at Fuling, the first large-scale shale gas field in China, it is concluded that the water intensity for shale gas development in China (water demand per unit lateral length) is likely to exceed that in the US by about 50%. Fuling field would require a total of 39.9–132.9 Mm3 of water to achieve full development of its shale gas, with well spacing assumed to vary between 300 and 1000 m. To achieve the 2020 production goal set by Sinopec, the key Chinese developer, water consumption is projected to peak at 7.22 Mm3 in 2018. Maximum water consumption would account for 1% and 3%, respectively, of the available water resource and annual water use in the Fuling district. To achieve China's nationwide shale gas production goal set for 2020, water consumption is projected to peak at 15.03 Mm3 in 2019 in a high-use scenario. It is concluded that supplies of water are adequate to meet demand in Fuling and most projected shale plays in China, with the exception of localized regions in the Tarim and Jungger Basins.

Abstract:
Many of the environmental impacts associated with hydraulic fracturing of unconventional gas wells are tied to the large volumes of water that such operations require. Efforts to develop non-aqueous alternatives have focused on carbon dioxide as a tunable working fluid even though the full environmental and production impacts of a switch away from water have yet to be quantified. Here we report on a life cycle analysis of using either water or CO2 for gas production in the Marcellus shale. The results show that CO2-based fluids, as currently conceived, could reduce greenhouse gas emissions by 400% (with sequestration credit) and water consumption by 80% when compared to conventional water-based fluids. These benefits are offset by a 44% increase in net energy use when compared to slickwater fracturing as well as logistical barriers resulting from the need to move and store large volumes of CO2. Scenario analyses explore the outlook for CO2, which under best-case conditions could eventually reduce life cycle energy, water, and GHG burdens associated with fracturing. To achieve these benefits, it will be necessary to reduce CO2 sourcing and transport burdens and to realize opportunities for improved energy recovery, averted water quality impacts, and carbon storage.

Abstract:
This study presents an integrated probabilistic framework by combining Monte Carlo Simulation with a gas transport model of a horizontal well with multi-fracturing stages to assess shale gas resources in the Wangyinpu Formation of the Xiuwu Basin, China. Modeling results suggest that the 30-year cumulative production of a single horizontal well is predicted at a likely value of 3.50 × 108 m3 with a maximum of 6.78 × 109 m3. Potential shale gas production from a “sweet spot” area is estimated at a range of 1.13 × 1010–1.76 × 1013 m3 with a likely value of 8.24 × 1011 m3. Sensitivity analysis indicates that the gas production rate and cumulative gas production of a single horizontal well are most sensitive to the relative volume occupied by kerogen in the bulk volume of the shale, gas desorption rate, number of fracturing stages, and permeability of the stimulated zone. Assessment of water demand for horizontal well drilling and hydraulic fracturing suggests that shale gas development at the Xiuwu Basin will not likely cause regional water-supply stress because of abundant water resources in the region. The probabilistic approach presented in this study can provide valuable information for planning shale gas development and can also be applied to other shale gas reservoirs.

Abstract:
Sustainable water management is paramount to ensuring continued access to fresh water resources. Some states have chosen to use analytical solutions to predict pumping-induced drawdowns and the reduction in groundwater baseflow to streams in an effort to predict negative impacts associated with high volume groundwater withdrawals (HVGWs). In line with this approach, the State of Michigan has developed the Water Withdrawal Assessment Tool (WWAT), which estimates streamflow depletion to evaluate whether a proposed HVGW activity will have an adverse impact on stream ecology. To assess the tool's performance, this study compared calculations for streamflow depletion estimated using the Hunt (1999) solution, as implemented in the WWAT, with those of a numerical groundwater flow model developed in MODFLOW for two different locations in Michigan where HVGW wells have been permitted. In addition, sensitivity and uncertainty analyses were conducted. The results showed that the WWAT, in general, provides a conservative estimate of stream depletion. However, to obtain a more accurate estimate, the type of aquifer (unconfined versus semi-confined) needs to be taken into account. The most critical parameters are the storativity, S, and the streambed conductance, λ. Since S has a fixed value of 0.01 in the WWAT, the role of streambed conductance becomes paramount. Given the paucity of information regarding λ, its estimation merits additional scrutiny.

Abstract:
Colorado has recently experienced a significant increase in unconventional oil and gas development, with the greatest concentration of activity occurring in Weld and Garfield counties. Water for oil and gas development has received much attention mainly because water resources are limited in these regions and development is taking place closer to populated areas than it did in the past. Publicly available datasets for the period 2011–2014 were used to identify water acquisition strategies and sources of water used for oil and gas. In addition, the annual average water used in these two counties was quantified and compared to their total water withdrawals. The analysis also quantified the water needed for different well types, along with the flowback water that is retrieved. Weld and Garfield counties are dissimilar in respect to development practices for water acquisition, preferred well type and the fate of flowback water. But at the same time, this difference displays how geological characteristics, water availability, and administration localities are the key elements along with economics in the decision making process within the oil and gas sector. This effort also revealed data challenges regarding accessibility and reliability of reported information, and the need for additional data. Improving the understanding of the unconventional oil and gas sector’s water use will help identify possible effects and tradeoffs on the local/regional level, which could diminish the conflicting perspectives that shape the water-energy discussions. This would complement the ability to make informed water resources planning and management decisions that are environmentally and socially acceptable.

Abstract:
A major concern associated with current shale-gas extraction is high consumption of water resources. However, decision-making problems regarding water consumption and shale-gas extraction have not yet been solved through systematic approaches. This study develops a new bilevel optimization problem based on goals at two different levels: minimization of water demands at the lower level and maximization of system benefit at the upper level. The model is used to solve a real-world case across Pennsylvania and West Virginia. Results show that surface water would be the largest contributor to gas production (with over 80.00% from 2015 to 2030) and groundwater occupies for the least proportion (with less than 2.00% from 2015 to 2030) in both districts over the planning span. Comparative analysis between the proposed model and conventional single-level models indicates that the bilevel model could provide coordinated schemes to comprehensively attain the goals from both water resources authorities and energy sectors. Sensitivity analysis shows that the change of water use of per unit gas production (WU) has significant effects upon system benefit, gas production and pollutants (i.e., barium, chloride and bromide) discharge, but not significantly changes water demands.