Environmental Risk Assessment for Exploration and Extraction Processes of Unconventional Hydrocarbon Deposits of Shale Gas and Tight Gas: Pomeranian and Carpathian Region Case Study as Largest Onshore Oilfields

All Shale Gas reservoirs are not the same. There are no typical Tight Gas reservoirs. These two statements can be found numerous times in the literature on shale gas and tight gas reservoirs. The one common aspect of developing these unconventional resources is that wells in both must be ‘hydraulically fractured’ in order to produce commercial amounts of gas. Operator challenges and objectives to be accomplished during each phase of the Asset Life Cycle (Exploration, Appraisal, Development, Production, and Rejuvenation) of both shale gas and tight gas are similar. Drilling, well design, completion methods and hydraulic fracturing are somewhat similar; but formation evaluation, reservoir analysis, and some of the production techniques are quite different. Much of the experience in shale and tight gas has been developed in the US and in Canada, to a lesser extent; and most of the technologies that have been developed by operators and service companies are transferable to other parts of the world. However, the infrastructure, including equipment and service company availability, governmental regulations, logistics, processing, environmental considerations, and pricing are not the same as in the US. This may impact the rate of the technology transfer as well as the selection of some of the technology. This paper is focused on operations challenges, technologies, and experience associated with shale and tight gas projects. It is likely that environmental concerns and the drive to reduce development costs of tight and shale gas reservoirs will drive new approaches to the development of these reservoirs in China, Latin America, Middle East, North Africa, and other parts of the world.

Theory and practice of unconventional gas exploration in carrier beds: Insight from the breakthrough of new type of shale gas and tight gas in Sichuan Basin, SW China

“All Shale Gas reservoirs are not the same” and “there are no typical Tight Gas reservoirs,” are two statements found numerous times in the literature on shale gas and tight gas reservoirs. The one common aspect of developing these unconventional resources is that wells in both must be ‘hydraulically fractured’ in order to produce commercial amounts of gas. Operator challenges during each phase of the asset life cycle (Exploration, Appraisal, Development, Production, and Rejuvenation) of both shale gas and tight gas are similar. Drilling, well design, completion methods and hydraulic fracturing are similar; but reservoir analysis and formation evaluation techniques are quite different. Much of the experience in shale and tight gas has been developed in the U.S.; and most of the technologies that have been developed by operators and service companies are transferable to Middle East, North Africa and other parts of the world. However, the infrastructure, including equipment and service company availability, governmental regulations, logistics, processing, environmental considerations, and pricing are not the same as in the U.S.; which may impact the rate of the technology transfer as well as the selection of the technology. It is likely that environmental concerns and the drive to reduce development costs of tight and shale gas reservoirs will drive a new “factory” approach to the development of these two types of developments. Whilst shale gas and tight gas reservoirs are no longer considered to be ‘unusual’ projects by investors in the U.S., elsewhere they are regularly referred to as “unconventional resources”. As a subsequence of the technical, logistical and cost challenges mentioned above, shale and tight gas reservoirs require special attention in terms of economic analysis. The economics of producing shale gas and tight gas reservoirs will be discussed in this workshop, with case studies that can demonstrate the challenges of evaluating the commercial viability of projects.

Crossplots of porosity vs. permeability from various North American basins show that there is a continuum between conventional, tight and shale gas reservoirs. This is significant as some of the key issues, particularly in shale and tight gas reservoirs, are having good estimates of storage and flow capacity. The crossplots include data from the Fayettville, Barnett, Ohio and Marcellus shales in the United States; Horn River and soft shales in Canada, tight gas Nikanassin formation in Canada and several conventional North American gas reservoirs. The data used in the crossplots have been obtained from plugs, crushed samples and drill cuttings. The results permit integration of the storage and potential gas deliverability for determining flow units and other important characteristics such as brittleness and/or ductility, hydraulic fracturing alternatives, effect of water saturation and mud filtrate; and differentiation between viscous and diffusion dominated flow. Examples of simulation at the pore throat level, from which it is possible to estimate petrophysical, rock-fluid interaction and rock mechanics properties, are presented. The storage and flow capacity in the case of stacked layers, or lateral variations of conventional, tight and shale gas formations, are discussed in detail. The data suggest that permeability determinations from crushed shale samples might be pessimistic as they do not take into account the possible presence of microfractures and pores in organic matter within shale matrix. It is concluded that crossplots of porosity vs. permeability are very powerful for distinguishing and evaluating storage and flow capacities of conventional, tight and shale gas reservoirs. The concept of flow units in shales and tight gas, and its differentiation from conventional formations, should prove powerful in future simulation work.

Recent exploration has revealed the coexistence of coalbed methane (CBM), shale gas, and tight sandstone gas within the coal-bearing strata of the Paleozoic marine–continental transitional sedimentary environment in the Qinshui Basin, China. These three unconventional gas resources are exploration targets within coal seams, but current research primarily focuses on CBM. Hence, this study integrated investigation into the characteristics of CBM, shale gas, and tight gas reservoirs using core samples, logging data, and laboratory tests from Carboniferous–Permian strata in the southern Qinshui Basin. It clarifies the formation and evolution of coal measures gas; establishes a symbiotic combination model of CBM, tight gas, and shale gas; and discusses the coexistence mechanism of coal measures gas and the geological factors affecting symbiotic enrichment. Within the study area, source rocks, primarily composed of coal seams and organic-rich shales, are widespread and highly developed, serving not only as source rocks, but also as reservoirs with exceptionally low porosity and permeability. Interbedded sandstone forms tight reservoirs alongside coal and shales, with short migration distances conducive to free gas charging. Following the sedimentation of upper Carboniferous Taiyuan Formation–lower Permian Shanxi Formation (C3t-P1s) coal-bearing strata, two main gas generation episodes and one continuous gas expulsion process occurred, resulting in independent CBM, tight gas, and shale gas reservoirs. Due to the intricate relationship between source rock and reservoir configuration, tectonic uplift, and the influence of natural fractures, the three kinds of gas (CBM, tight gas, and shale gas) can coexist in various combinations. Gas migration and accumulation are influenced by variations in strata temperature and pressure due to changes in coal seam burial depth, leading to dynamic exchange equilibrium between different gas-bearing systems. Moreover, tectonic uplift has created fracture systems in tight reservoirs, facilitating gas migration and accumulation. Considering the relative positioning of thin coal seams, nearby cap rocks, and gas-bearing systems, the CBM symbiotic combination model can be categorized into three types: (1) a combination of sandstone, shale, and one or multiple coal seams form a double-source and three-reservoir gas reservoir; (2) two sets of shale or a single set of coal seams interleaved create a double-source and double-reservoir gas reservoir; and (3) the development of shale or coal seams results in a single-source and double-reservoir gas reservoir combination. Among them, the first two modes together account for 82.5%. This study will enhance unconventional gas utilization and provide a theoretical foundation for understanding the compatibility of superimposed gas-bearing systems in coal measure strata.

Summary With the rapid growth of gas consumption in China, it is particularly important to accelerate the pace of domestic gas exploration. In recent years, tight gas exploration has entered a rapid development stage. As one of three major gas producing basins in China, mangy significant breakthroughs in the tight sand gas exploration of middle and shallow layers has been made in the central and western parts of the Sichuan basin in recent years. In this paper, the near-surface multiple time windows Q compensation technology introduced mainly includes the micro-logging constrained tomographic static correction technology and multiple time windows Q compensation technology based on a modified centroid frequency shift method. It is applied to process the seismic data acquisited from the central parts of the Sichuan Basin to explore tight sand gas reservoirs in shallow layers. The application results show that the near-surface multiple time windows Q compensation technology can effectively improve the resolution of seismic data and highlight the amplitude characteristics of channel sands. The application of the technology has positive significance for exploring shallow tight sand gas reservoirs.

Veterinary medicinal products (VMPs) and their metabolites are complex, biologically active molecules, which are produced in large quantities and have a high potential to be released in the environment. During the marketing authorisation procedure of a VMP, a product-based environmental risk assessment (ERA) has to be provided for all new applications, including generics. When a risk to the environment cannot be excluded, the applicant may propose risk mitigation measures (RMMs). The result of the ERA of VMPs is part of the benefit/risk analysis. When the VMP presents a risk to the environment and no RMMs can mitigate this risk, the benefit/risk balance may be negative, resulting in a refusal of marketing authorisation. The potential environmental risk related to its particular use (indication, target animals, administration route, etc.) is just one of the several indicators of the environmental impact of VMPs on the environment. In a more holistic approach, emissions to the environment during the entire lifecycle of VMPs should be considered. Besides this, VMPs can be extremely toxic for non-target organisms and may have long-term effects on ecosystems. For example, antiparasitics (used in aquaculture and for pasture animals), were mainly designed as insecticides and as such are extremely toxic to invertebrates. Because of this extreme toxicity, environmental concerns for this group of compounds cannot be ignored, especially when they are released directly into the environment, as is the case in aquaculture. The effect of antiparasitics such as ivermectin on dung fauna and dung pat degradation has been shown in field experiments. Another group of compounds which have environmental concerns are antimicrobials. Antimicrobials are toxic for phytoplankton and terrestrial plants; however, the main concerns for these compounds are related to the development of antimicrobial resistance in the receiving compartments. Besides these ‘expected’ effects, non-expected effects may also occur, which are not dealt with within the standard ERA. After the devastating effect of diclofenac-containing VMPs on the vulture populations in South East Asia, public concern was raised on the effects of these VMPs on birds nesting in the European Union (EU). An “ad hoc” risk assessment in relation to the use of VMPs containing diclofenac in the EU showed that serious effects on populations of vultures and other necrophagous birds cannot be excluded. Several possible risk mitigation measures were proposed (including banning the product). Veterinary medicines have been shown to occur widely in manure and soil, but they also enter ground and surface water. Compared to human medicines, the amount of monitoring data available is very limited. Effects on the environment are formally part of the pharmacovigilance system of veterinary medicines, but it is very unlikely that the effects are detected via this system. Therefore, it is important to review the environmental risk of existing VMPs which were granted marketing authorisation before the ERA guidelines were adopted.

Human pharmaceuticals in surface waters: Implementation of a prioritization methodology and application to the French situation

Human and veterinary antibiotics enter the environment through wastewater effluent, agricultural use of manure and treated sewage for fertilizer, and leakage from waste storage facilities. This antibiotic pollution may exert selective pressure on bacteria to develop drug resistance, which is especially concerning if it develops in pathogenic bacteria. A new study weighs known bacterial antibiotic sensitivities against the backdrop of antibiotic concentrations measured in the environment and suggests that resistance in clinically relevant bacteria may not be kept in check by current risk assessment action levels [EHP 120(8):1100–1106; Tello et al.]. Ciprofloxacin, erythromycin, and tetracycline were selected for the analysis from among the approximately 150 compounds for which minimum inhibitory concentrations (MICs) have been reported for different bacteria. An MIC is the amount of antibiotic needed to inhibit bacterial growth. Each of the three antibiotics affects a wide range of bacteria and represents a distinct class of antibiotics used in humans and animals. Concentrations of each antibiotic in various environmental compartments, or media, had been documented previously. Current guidelines for environmental risk assessment reflect the phase I action limits of the International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products. This program, which evaluates the safety of veterinary drugs, calls for environmental risk assessment of antibiotics whose concentrations exceed 1 ppb in aquatic compartments or 100 ppb in terrestrial compartments. These guidelines have been implemented in regulations in the United States, Europe, Japan, and Australia. www.jasonschneider.com The researchers compared information on antibiotic levels in the environment with information on the MICs of clinically relevant bacteria to determine if current levels of antibiotic pollution might be high enough to promote the development of resistance. Within aquatic compartments, only a small fraction of the 27 bacterial genera included in the study were predicted to be affected by environmental concentrations of antibiotics, and results suggested that the phase I action level would protect against resistance. However, current levels of antibiotic pollution in terrestrial compartments—particularly in river sediments, liquid manure, and farmed soil—may be high enough to favor the evolution of bacterial resistance. The conclusions may be limited by long-term selective pressure and by the fact that MIC tests do not represent environmental conditions. Furthermore, the authors did not address bioavailability or the potential influences of antibiotic mixtures, metals, or disinfectants. Nevertheless, the potential for antibiotic pollution to increase antibiotic resistance in clinically relevant bacteria has important implications for public health and environmental health policy, and the authors demonstrate a possible framework for answering important outstanding questions about the environmental impact of antibiotics.

Review of the scientific evidence to support environmental risk assessment of shale gas development in the UK

In contrast to human health risk assessment, there are no definitive guidelines for environmental risk assessment of cosmetic products. The objective of this study was to perform an in-depth analysis of ten modeling environmental tools and to establish the best rationale to assess the impact on environmental safety considering the recent global pandemic scenario and the evolution of the consumer mindset. A literature analysis was performed for the ten modeling environmental tools, and when possible, each was downloaded for comparison. Chesar was the tool that proved to be the easiest to enter data, and it has the more straightforward and direct application steps; thus, it was chosen for the initial assessment of ingredients that demonstrate potential environmental hazards. For high-level tools, it was not possible to establish a comparison for choice, as the models are private and have little data in the literature. Even so, for a more detailed assessment after the first initial assessment via Chesar, iSTREEM could be used. This study delivers important knowledge about the modeling tools and how to establish a rationale for environmental risk assessment. Keywords: environmental modeling tools, environmental risk assessment, cosmetic products, environmental impact, formulation

Coalbed methane, tight and shale gas are three important unconventional gas resources in China. ‘‘According to data from the Ministry of Land and Resources, at the end of 2013, China had 11, 12 and 25 trillion cubic meters, respectively of remaining technically recoverable resources of coalbed methane, tight gas and shale gas which are still in the early stage of development’’. (Source CNPC and ARA International Limited). China is developing its shale gas exploration and exploitation strategies for economic reasons and social aspects (so-called ‘‘shale gas revolution’’). Huge shale gas reserves provide a reliable source for sustaining China’s economic development and contributing to China’s ‘‘Energiewende’’. Zhao et al. (2015a) analyze the strategic measures and advantages for a safe and vigorous development of shale gas in China and review the developments of hydraulic fracturing technologies in China. Economic exploitation for shale gas is highly dependent on the complexity of the fracture network caused by hydraulic fracturing technology, so it is necessary to accurately assess the effect of the fracture network on gas flow behavior and productivity (Li et al. 2015c). This thematic issue is particularly dedicated to recent researches in unconventional gas resources in China related to the reservoirs indicated in Fig. 1 in order to substitute coal by ‘‘clean’’ gas energy resources as a transitional technology towards renewable energy resources. The thematic issue compiles theoretical, experimental as well as field studies in China. Different reservoir types are under investigation such as tight and shale gas reservoirs as well as coal mines with coalbed methane resources. Fundamental aspects on process understanding in unconventional gas reservoirs as well as the international context of research and technology deployment are discussed in this volume. Tight gas reservoirs have become an important resource for the world’s gas supply. Such reservoirs have very low permeability (usually below 0.1 mD) and show a strong stress sensitivity to fluid transport properties and a considerable productivity decline during the production process due to decreasing reservoir pressure as well as increasing effective stress. In an experimental study by Albrecht and Reitenbach (2015) several measurement series were performed on plugs from the North-German Rotliegend tight gas reservoirs to determine the effects of changing stress and pore pressure conditions on reservoir & Olaf Kolditz olaf.kolditz@ufz.de

Tight gas has revolutionized the energy picture in North America. The US energy information agency states that the tight gas and oil in the USA has boosted the production of natural gas by around 35% in recent years. This has reduced the need for gas imports. Thousands of meters underground, tight gas trapped in microscopic pores of very dense rocks requires hydraulic fracturing to fracture the rock and releases the gas into the well, known as tight gas. Environmental impact of producing tight gas has caused concerns related to air emissions, water contamination and disposal of waste generated by the tight gas production. There are also concerns related to the possibility of methane escaping into the air during tight gas production and development of this resource class causing minor earth tremors. The advancements in the drilling technologies have recently enabled greater volume of gas to be produce from a single drilling site. This reduces the operational footprint, which is directly proportional to emission profile of tight gas resource. There is a knowledge gap in understanding of Green House Gas (GHG- CO2 equivalent) footprint of tight gas’ resource development because of lack of operational constraints in previous environmental impact assessment of this resource. The objective of this study is to add value and reduce the scientific gap with respect to understanding of tight gas’ resource development techniques, related environmental, and land impact. There remain concerns about development of tight gas related to chemical and methane release into the local water and air, seismic events because of hydraulic fracturing and waste disposal. In order to understand this phenomenon better the work establishes the tight gas production foundation by in depth understanding of 1) Features of Tight gas reservoirs; 2) Geological environment, deposition and generation of tight gas resource; 3) Field development techniques of tight gas resource including construction, production and processing. The work then uses methodology of accounting input and out parameters of cradle to grave tight gas system boundary throughout its life cycle and understands previous GHG (CO2 equivalent) number of tight gas resource development. The work does systematic analysis and summarizes the previously published life cycle analysis to understand further the potential environmental impacts of resource development of tight gas. This will help hydrocarbon exploration and production operators to optimize the operations of tight gas production by better understanding of each sub block of tight gas field development in terms of C02 numbers by using low carbon technologies thus reducing the potential impacts.

As part of the AU$86.3 million ‘Towards a New Energy Future’ package, the Australian Government has committed AU$30.4 million to undertake the Geological and Bioregional Assessments Program. This program aims to encourage sustainable gas development through a series independent scientific studies into the potential environmental impacts of shale and tight gas exploration and production. These studies, conducted by Geoscience Australia and CSIRO, supported by the Bureau of Meteorology and managed by the Department of the Environment and Energy, will focus on three basins (regions) that are prospective, but underexplored for shale and tight gas. The program seeks to encourage exploration to bring new gas resources to the East Coast Gas Market within the next 5–10 years, increase the understanding of the potential environmental impacts posed by gas developments and increase the efficiency of assessment, monitoring and ongoing regulation, including improved data capture and reporting. The Cooper Basin and the Isa Superbasin have been selected for investigation with a third basin expected to be announced by mid-2018. The program will be delivered in three stages over 4 years and will investigate areas prospective for shale and tight gas within these regions. This independent, transparent, science-based approach aims to assist in building community understanding of, and confidence in, the capacity for safe and environmentally sustainable unconventional gas developments.

Chapter 9 - Tight Oil and Gas