• Basic definitions
• Shale Gas / Resources and Production
• Shale Gas / Mainstream technologies, advantages and disadvantages
• Shale Gas / Research and innovations
• References
• Photo gallery

The most detailed state of shale gas resources by countries is given in the following fundamental sources [5, 10-11]. According to the authors, as of the last update (dated September 24, 2015), there are 7 576.6 Tcf in the world or about 215 Tcm of “Unproved technically recoverable resources” of shale gas, which is comparable to the global reserves of traditional natural gas (Fig. 1). Between the first (2011) and second (2013) issues of the «Technically Recoverable Shale Oil and Shale Gas Resources» [5,10], data on the resources of several countries were updated or added, including, for example, the resources of Egypt and Russia have been added, the resources of Venezuela, Algeria, Canada, Ukraine, India and Pakistan have significantly increased. In turn, the resources of Mexico, Poland, Libya and South Africa have decreased.

Fig. 6. Distribution of resources and volumes of shale gas production by countries of the world

According to these sources, the largest (over 500 Tcf) reserves are found in China (1 115.2), Argentina (801.5), Algeria (706.9), the USA (622.5) and Canada (572.9). The top 10 countries in terms of shale gas reserves also include Mexico, Australia, South Africa, Russia and Brazil. A total of 46 countries are mentioned, of which 14 - European countries, 8 countries from Asia and Pacific and South Asia, 13 - Middle East and Africa, 8 - South America & Caribbean, and finally 3 from North America. Most of the shale gas resources are concentrated in North America - 1,685 and Asia and Pacific - 1,607 Tcf. In [5], detailed information is presented on 137 shale formations and prospective shale basins for most of those noted in Fig. 6 countries.

In detail, and most importantly, largely on the basis of real practice, shale gas resources have been investigated in the United States. A simplified map of the main shale plays of the USA is presented in fig. 7 based on [12]. It also provides data on resources, active basin areas, shale layer depth and rock porosity, as well as lists of companies involved in the exploration and production of shale gas.

Fig. 7. Shale Gas Plays in the United States of America

Despite the apparent simplicity of the process, keeping in mind that it should be carried out underground, at great depths and in layers of relatively small thickness, we are talking about an exceptional engineering breakthrough, technologies that are similar in nature to surgical or jewellery operations. Here, at each stage, knowledge of a large number of related disciplines is required, from purely technical, for example, simple (or vice versa, not simple) fittings, shut-off valves and flexible hoses that can withstand hydraulic shock and not collapse faster than rock, to chemical fillers and cracking bases in materials science. More detailed information about fracking for different levels of understanding, including historical information, video resources, and major equipment suppliers, can be found, for example, in [40–46]. Additional important information about this process is presented in [46] or on the websites of the main developers of this technology - the American companies Halliburton and Schlumberger [47-48].

Various drilling sensors, special tools, for example, whipstocks, bottomhole, drill bits, turbodrills turbines, drilling mud motors, have been widely used to implement Directional Drilling. Maintaining the bending radius of the borehole pipe and its diameter (usually at least 100 ft radius per 1-inch of pipe diameter) or diameter-to-wall thickness ratio (D / T) is important. Modern directional drilling technologies in their configuration contain rotary steerable systems and sophisticated software that allows for accurate placement of wells and automate drilling processes [47]. Currently, directional drilling is widely used not only for the production of shale gas or oil, but to increase the production of traditional hydrocarbons. According to [49], in the USA the number of horizontal wells has steadily increased, and by 2018 had exceeded the number of vertical wells.

As already noted above, special fluids are used to ensure hydraulic fracturing. The requirements for them, as well as a list of the most frequently applicable, are contained in [36,50-52]. Hydraulic fracturing fluids are an environmental vulnerability of the technology, since many of them contain deleterious and toxic chemicals, so special attention is paid to the development of special harmless compounds. The selection of proppants is also important for hydraulic fracturing [53–55]. Their main function is to maintain the cracks formed during hydraulic fracturing in the open state. Thus, the proppants on the one hand should have high strength and hardness, and on the other hand, should easily move together with the fluid to the edges of the cracks during hydraulic fracturing. In addition, they must have a strict fractional composition. The proppant size is usually 0.1–2.38 mm [55]. Proppants are usually made of silica sand, which is much cheaper than other options, from ceramics (lightweight, intermediate density, high density ceramic proppant), as well as modified compositions, primarily resin coated proppants. According to [54], silicon proppants prevail in the US market, their share is 80%, polymer coated and ceramic proppants each have 10% of the market. In 2015, 37.5 million tons of this was used in the USA. The largest producer of ceramic proppants in the world is China [54].

In industrial practice, hydraulic fracturing is carried out by specialized service companies with their own staff of specialists and equipment. According to [56] in the USA, the effectiveness of such specialization has significantly increased in recent years, as evidenced by the increase in the number of fracked wells per active crew. This also indicates a high level of cooperation between various additional services - equipment suppliers, suppliers of consumables (proppants, fluids, pipes, etc.), repair services, etc.

The economic performance of drilling and natural gas production in the United States, including elements of horizontal drilling and hydraulic fracturing, are discussed in more detail in [57], which was prepared by IHS Global Inc. by order of U.S. Energy Information Administration. The total profitability of any production is always determined by the ratio on the one hand of the value of capital and operating costs, and on the other hand of external economic factors dictating the price of demand for products. The preamble to this publication notes that the availability of information on these costs is significantly lower compared to information on price and productivity dynamics and poses a certain problem, especially when it is necessary to carefully evaluate future market trends.

For typical U.S. onshore wells in the USA, in [57] five key cost categories were identified that define more than 75% of the total cost of drilling and completing wells. Among them, equipment costs, including frac pumps, account for the largest share, at about 24%. The remaining key costs are concentrated in a relatively narrow percentage range from 11 to 15% and include - Rig and drilling fluid, Casing and cement, Proppant, Completion fluids and flow back. The average drilling and completion costs for the five studied onshore plays (Eagle Ford, Bakken, Marcellus, Midland and Delaware) averaged $6 million per well, rising to almost $10 million per well in some years [57]. Directional drilling cost parameters are set at the following levels (by the end of 2018) - for Drilling Cost per Total Depth - $100-150 per foot and for Completion Cost per Lateral Foot - an average of about $500 per foot. More detailed information is presented in the appendix to [57] - IHS Oil and Gas Upstream Cost Study (Commission by EIA).

In [58], the costs of shale hydrocarbon production in the long term were studied based on modelling supply and demand scenarios, including the latest corrective U.S. Energy Information Administration (latest EIA cost data) data. According to the authors, production costs will remain moderate until 2040, and cost variation will range from $2.5 / MMBtu to $6.0 / MMBtu in 2040. This research also explains the significant gap in the cost of producing shale hydrocarbons in the United States and other regions of the world.

Publication [59] provides data on the cost of drilling for shale gas production in China in the Sichuan Basin. It was noted that by mid-2015, the average cost of drilling a horizontal well was between $11.3 – $12.9 million, with a significant downward trend in costs. The structure of shale gas well cost is as follows - drilling and completion 5.3, fracturing - 3.9, steel - 1.2, drilling and completion labour - 0.9, fracturing labour - 0.2 (all in million U.S. dollars).

The problem of resolving a large number of environmental claims is of crucial importance for the development of shale technologies, in particular fracturing. A general list of environmental impacts of hydraulic fracturing technologies can be easily found, for example, in [36, 37, 60]. High levels of fresh water consumption, groundwater pollution with hazardous chemicals, soil and surface water pollution with insufficiently efficient recycling of the injected fluid stand out among them. It should be noted here that when considering this list it is necessary to separate the general environmental problems of the extraction and use of fossil fuels and those specific ones that are directly related to the peculiarities of the production of shale hydrocarbons. In this sense it is hardly worth focusing on issues related to air emissions, such as methane, issues related to land use, personnel safety or climate change, since all this is no less inherent in the extraction of traditional fossil fuels. But the problems of using large volumes of water, various hazardous chemicals and inducing seismicity seem fair.

Increased water consumption during fracking is determined by the very essence of the technological operation, which is based on hydraulic action. According to [61], in the most developed shale region of the USA, Pennsylvania (Marcellus), the average consumption of water injected for hydrofracturing was 3 million gallons per well, sometimes reaching a maximum of 8.3 million gallons. Water brought onsite ranged from 30 to 100%, an average of 84%, and recovery of injected water averaged only 10%, sometimes rising to a maximum of 57%. According to the author of the article in [62], the expenses of the oil and gas industry for water supply can reach 15%, which is not often taken into account in the initial costs. This is one of the most pressing issues because treatment and disposal of large volumes of wastewater used after cracking is a very expensive operation. Moreover, the purification of recycled water is required not only due to the addition of proppants and chemicals, but also because many deposits contain heavy metals and naturally occurring radioactive materials [36]. The latter, however, is also characteristic of deposits of traditional hydrocarbons. Since most of the fields are far from existing treatment facilities, and often even in areas with minimal infrastructure, it is clear that the construction of additional treatment facilities is extremely undesirable for oil and gas companies, sometimes beyond the margins of project profitability. Obviously, one of the reasons for stopping shale production in Europe is precisely connected with this problem, or rather with the problem in the difference between the legislation on wastewater in the USA (where, in particular, its deep underground injection is allowed) and the EU, where wastewater treatment is always required by law [36]. The use of alternative fracking options with the substitution of water for, for example, liquefied petroleum gas and liquefied carbon dioxide, in addition to serious financial and technological problems, pose new environmental impact problems, including increased fire and explosion hazards or risk of significant carbon dioxide leaks [36]. Perhaps membrane cleaning technologies may have good prospects [64], especially if these are mobile service complexes.

All aspects of water supply in regions rich in shale resources were studied in detail in [63], as well as, for example, in [64-65]. Key disappointing findings from [63]: “38 percent of shale resources are in areas that are either arid or experiencing severe or extremely high water shortages; 19 percent are in areas with high or extremely high seasonal variability; and 15% are in places subject to severe or very severe drought”.  The most problematic countries of the top twenty countries with large reserves of shale gas, according to [63], are Algeria, Libya, Egypt, which are assigned to the most problematic category Arid & Low Water Use. Reserves leader China, as well as Mexico, South Africa, and India are categorized as High water stress level, and Pakistan as Extremely high. Thus, almost half of the countries in the top twenty have or will have problems with the water supply of shale gas production processes. A similar picture emerged when considering regions rich in shale oil reserves. To protect groundwater from contaminated process water, there are sufficiently reliable technological methods, including special multilevel protection of the well with a steel casing and cement layers [64], therefore leakages are possible only in emergency cases in violation of technical regulations.

It is difficult to deny the influence of fracking on the indication of seismicity on the basis of several serious statistical facts set forth, for example, in [66]. However, it is apparently not yet possible to establish clear quantitative parameters for such an effect. In [66], it was demonstrated that between 2010 and 2013, an average of 100 earthquakes of magnitude 3.0 occurred in the middle and eastern parts of the United States, which is more frequent than between 1970 and 2000, when an average of 20 similar shocks were recorded yearly. The second fact noted by the researchers is that seismicity increased in the regions where wastewater was pumped into deep burial wells after hydrocracking. Finally, the third fact - an earthquake with a magnitude of 5.6 points that occurred in Oklahoma in 2011 - one of the factors of which was the removal of wastewater [66]. However, only a small number of over 30,000 wastewater discharges affect seismicity in the region. To manage emerging risks, U.S. Geological Survey researchers conducted the study of geological and other data to create a quantitative risk management model called "the traffic-light system". However, this will inevitably require a revision of the regulatory framework for wastewater disposal, aimed solely at protecting drinking water sources, but not at earthquake safety [66].

Obviously, the latest source of information on induced seismicity may be a study by the United Kingdom's Oil and Gas Authority (OGA), on the basis of which the UK government cancelled permissions for hydraulic fracturing operations [38–39]. Moreover, the reason for this was not so much the earthquakes themselves, but the impossibility to predict the scale of possible earthquakes.

Source: Advanced Energy Technologies

In both cases, the largest number of patent applications was filed in the United States. The top ten also included WIPO, CNIPA (China), EPO, CIPO (Canada), IP Australia, IMPI (Mexico), INPI (Brazil), Rospatent (Russia) patent offices. IPO (Great Britain) and INPI (Argentina) entered the top 10 lists for Directional Drilling and Hydraulic Fracturing, respectively. Perhaps the main difference between the two diagrams is that a lot of patent applications are registered in the Chinese office related to the subject of Hydraulic Fracturing (second line in the list).

A substantially different picture emerges when considering the residency of applicants. As follows from fig. 13 and 14, the vast majority of patent applications were submitted by US residents - in 68% and 61%, respectively.

Fig. 13-14. The distribution of applicants by residency. Left - Directional Drilling, Right - Hydraulic Fracturing.

Source: Advanced Energy Technologies

Residents of China, Canada and the Netherlands were also quite active, and together with US residents, formed the three leaders in groups. For a patent selection related to Directional Drilling, the least non-residents were patented in the United States (19% of non-residents of the total number of applicants). In CNIPA (China) 75% of non-residents were patented, and in EPO, CIPO (Canada), IP Australia, IMPI (Mexico), INPI (Brazil), Rospatent (Russia) – from 85% to 100%.

Hydraulic Fracturing is characterized by approximately the same picture, however, in CNIPA (China) the number of non-residents was significantly smaller – only 31%.
The problems to which the patent solutions of the applicants were aimed in their patent applications are shown in Fig.15-16.

Fig. 15-16. Left - The main problems of patent applications on the subject of Directional Drilling. Right - The main problems of patent applications related to Hydraulic Fracturing.

AOP – administrative and organisational problems; EB – Ecological balance; EGWC - Energy, gas or water consumption; EPM– Environmental protection measures; HCEI – High CAPEX / Exploration and Infrastructure; HCEP– High CAPEX / Equipment production; HCG– High costs in general; HOOC– High OPEX / Operation and consumables; HORR– High OPEX / Repair and replacement; LEE - Low Efficiency / Exploration; LEG– Low efficiency in general; LEMP– Low efficiency / Main processes; LESP  – Low efficiency / Secondary processes; UP– Unclear problem
Source: Advanced Energy Technologies

Table 1. Distribution of shares of patent applications by elements of the technological chain of shale hydrocarbon production

Source: Advanced Energy Technologies

Table 2. Top 10 Applicants in the field of Directional Drilling

Source: Advanced Energy Technologies

Table 3. Top 10 Applicants in the field of Hydraulic Fracturing

Source: Advanced Energy Technologies

In the examined patent selection, the most frequently encountered subgroups of the International Patent Classification are directly related to Directional Drilling and Hydraulic Fracturing: Е21В 43/26 Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells .Methods for stimulating production ..by forming crevices or fractures; and C09K 08/62 Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations .Compositions for stimulating production by acting on the underground formation and Compositions for forming crevices or fractures.

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