Oil shale resources in China and their utilization

XU Zhi, ZHU Jianwei,2*, DONG Qingshui,2and SUN Pingchang

1.CollegeofEarthSciences,JilinUniversity,Changchun130061,China;2.KeyLaboratoryofOilshaleandCoexistentEnergyMineralsofJilinProvince,JilinUniversity,Changchun130061,China



Oil shale resources in China and their utilization

XU Zhi1, ZHU Jianwei1,2*, DONG Qingshui1,2and SUN Pingchang1

1.CollegeofEarthSciences,JilinUniversity,Changchun130061,China;2.KeyLaboratoryofOilshaleandCoexistentEnergyMineralsofJilinProvince,JilinUniversity,Changchun130061,China

Abstract:The unconventional oil and gas resources presented in oil shales have meant these potential sources of hydrocarbons, which has become a research focus. China contains abundant oil shale resources, ranking fourth in the world, with ca.7 254.48×108t within 24 provinces, including 48 basins and 81 oil shale deposits. About 48% of the total oil shale resources are concentrated in the eastern resource region, with a further 22% in the central resource region. 65% of the total quantity of oil shale resources is present at depths of 0--500 m, with 17% of the total resources being defined as high-quality oil shales yielding more than 10% oil by weight. Chinese oil shale resources are generally hosted by Mesozoic sediments that account for 78% of the total resources. In terms of the geographical distribution of these resources, some 45% are located in plain regions, and different oil shale basins have various characteristics. The oil shale resources in China represent a highly prospective future source of hydrocarbons. These resources having potential use not only in power generation and oil refining but also in agriculture, metal and chemical productions, and environmental protection.

Key words:China; oil shale; resources; distribution; utilization

1Introduction

The oil shales in China are usually light gray to dark brown rocks in lithology, containing combustible solid organic material and high ash (inorganic mineral material) concentrations yielding shale oil by low-temperature distillation. The amount of oil generated from these shales is generally >3.5% by weight. These oil shales contain a variety of organic material, including polymeric kerogens (humosapropelic and saprohumolic) insoluble in organic solvents, as well as asphalt soluble in organic solvents (Liuetal., 2006). The ash within the shales is dominated by quartz, kaolin, and clay, among other minerals (Lietal., 2013). Oil shales generally have joulerific values of >4.18 MJ/kg and thickness of ≥0.7 m (Liu & Liu, 2005), and are generally used for power generation and oil refining, though their advances in exploration and processing technology mean to have potential use in the chemical, agriculture, and environmental protection industries (Liu & Liu, 2006; Qianetal., 2003).

2Oil shale resources in China

The Ministry of Land and Resources of the China launched a nationwide oil shale resource assessment (i.e., the National Oil Shale Resource Evaluation) between 2004 and 2006. Based on this assessment and other data from previous studies and exploration (Wang & Xu, 1992; Hendrixetal., 1995; Zhaoetal., 1991; Liu, 1999; Wangetal., 2005; Knutsonetal., 1990), a new evaluation of oil shale resources was undertaken by the Geological Survey of China in 2009. This project separated China into five main oil shale resource region, namely the Eastern, Western, Central, Southern, and Qinghai-Tibet regionsetal., 2006)(Fig.1). The oil shales in these regions were evaluated based on parameters such as oil shale resource, oil quality, chronostratigraphy, geography and depth.

Fig.1　Distribution of oil shale resources in China

The National Oil Shale Resource Evaluation indicates that the oil shales in China are distributed in 24 provinces, 48 basins, and 81 oil shale deposits (Fig.1). The 2010 update to this evaluation indicates total oil shale resources of 7 254.48×108t, with ca. 1 185.63×108t of discovered resources and 6 068.85×108t of potential resources. About 48% of the total oil shale resources are located in the Eastern resource area, with other resources (in decreasing order of size) located in the Central and Qinghai-Tibet regions, with the lowest amount of resources (3%) present in the Southern resource region (Fig.2a). Oil shale deposits in China are generally located in plains areas (45% of resources), and partly in the loess tableland and plateau areas. The fact that the majority of the resources are located in areas of plains or loess tableland makes the development and utilization of oil shale easier (Fig.2b). Oil shale resources in China are also generally hosted in Mesozoic sediments, comprising some 78% of the total resources (Fig.2c). The oil shales generally yield 3.5%--5% oil by weight, comprising about 46% of the total oil shale resources known in China. Higher-yielding oil shales, which generate 5%--10% and >10% oil by weight, comprise some 37% and 17% of total oil shale resources in China, respectively (Fig.2d). In addition, 65% of the total oil shale resources is located at depths of 0--500 (Fig.2e), and deposits with lower stripping ratios are suitable for open-cut mining (e.g. in Fushun Basin), whereas deeper deposits (e.g. in Huadian Basin) have higher stripping ratios and are suitable for underground mining.

Fig.2　Characteristics of distribution of oil shale in China(Liu et al., 2006)

Chinese oil shale resources are located in 48 individual basins, some of which (e.g., the Fushun, Maoming, and Huadian basins) have undergone some development, whereas others with huge oil shale potential (e.g., the Songliao, Ordos, and Junggar basins) remain undeveloped. All of these resources have different characteristics, as evaluated using five main parameters (oil shale resource, oil content, and the chronostratigraphy, geography and depth of the resource).

3Current utilization of oil shale in China

The 2014 China Energy Statistical Yearbook indicates that the demand for oil in China will continue to increase in the foreseeable future and that China will also increasingly become dependent on foreign oil. Total oil imports of China were about 3.1×108t in 2014, and oil prices and importation are increasingly influenced by international events. This situation should be remedied by changing the structure of Chinese energy usage to reduce dependence on foreign energy. One possibility is the utilization of oil shales as a supplement to conventional oil in an approach that could provide the basis for meeting Chinese demand for oil using domestic resources (Youetal., 2004; Liu & Liu, 2005; Yeetal., 2010; Maetal., 2012).

Current technology, combined with the early stage development and utilization of oil shale, means that the main application for these resources is combustion during power generation, for retorting oil, and in the refining of paraffin. These current uses are highly polluting and have a low rate of utilization. However, new advances in oil shale technology and research have focused on the utilization of oil shale within a recycling economy rather than purely focusing on refining or power generation. This has meant an expansion in the possible use of oil shales beyond the three traditional areas of petrochemicals, electricity generation, and refining, to new potential areas of application in the agriculture, metals, and chemicals industries as well as in environmental protection. This has led to the development of a new and comprehensive multi-field and multi-directional oil shale utilization model that is dominated by traditional uses but is also supplemented by new areas of use. This model is also designed to enable the efficient and environmentally friendly utilization of oil shales (Fig.3).

Fig.3　Diagram of utilization model of oil shale in China

3.1Traditional uses

3.1.1Distillation and refining of oil shales, and In-Ground Processing

Currently there have been three main methods used in China to exploit oil shales, including outcrop mining, underground mining, and combined exploitation. The distillation of oil from oil shales is controlled by the carbonization temperature (low temperature= 450℃-550℃,moderate temperature=700℃, high temperature=900℃), oil-shale particle size (block=20--60 mm, particle=1--20 mm, powder=<1 mm), heating method (gas heated or solid heated carriers), and heating rate. Previous research suggested that oil shale retorting can be completed at temperatures above 600℃(Hilger, 2003). Fushun-typeinsitucarbonization of oil shale has also been developed in China, with technological developments yielding possible processing of up to 100--200 t/d of oil shale at utilization and recovery rates of 80% and 70%, respectively. Thisinsituprocessing yields shale oil that can be directly used as a liquid fuel or further processed to generate gasoline, kerosene, diesel, petroleum coke, and other chemical products (Lietal., 2012). There are currently some 10 oil-shale production plants in China that produced 7×105t of shale oil in 2012. In addition, an oil shale in-ground conversion process (ICP) is currently being used in field experiments in the Songliao Basin with feasibility testing in collaboration with Shell, though the quality and thickness of oil shale in this area means that this ICP method is not ideal and is not currently being used on an industrial scale.

3.1.2Power generation from shale-oil combustion

Electricity generation using organic-rich oil shale and shale oil extracted from char products is an important use for oil shales. This process avoids the “oil shale to shale oil” conversion, enabling a more favorable mode of combustion. In addition, use of circulating fluidized bed combustion technology has greatly improved the utilization rate of oil shales (Youetal., 2004), with some 69% of the world’s production of oil shale being used for power generation. Chinese power generation from oil shales includes a low-ratio oil shale circulating fluidized bed boiler that is currently being used in Huadian in Jilin Province and has an evaporation rate of 65 t/h. This boiler has a combustion efficiency that can reach 98.45%--98.74%, has a thermal efficiency of about 87.4%--87.9%, and can be adapted for coal use as well as incorporating environmental protection processes. There are three other small oil-shale power plants in China with a total generating capacity of 30 MW (Lietal., 2012).

3.1.3Building materials generated from oil shale ash

Burning or retorting results in the production of 60%--80% shale ash, primarily as oil shales contain high contents of incombustible minerals. These oil shale ashes can be used in various ways according to their material compositions and properties. The majority of Chinese oil shales are clay-dominated, rather than the generally calcareous oil shales found elsewhere, meaning that oil shale ash produced in China could be used as a building material to make bricks, cement, concrete, and other materials. There are several shale ash cement and brick factories that produce some 90×104t of cement and 33×107bricks in the areas around Liaoning, Fushun, Gansu, Yaojie, Wangqing and other areas (Li, 2012).

3.2Areas for innovation

The utilization of oil shale has been improved by the extension of the use of this resource to other areas such as the agricultural, metal, and chemical industries, and the production of environmental protection materials. The organic matter, minerals, and trace elements present in oil shales and the associated ash are all essential substances for soil and agriculture. This, combined with the presence of acid-generating elements, nitrogen oxides, and alkaline elements in oil shales, means that this material can be converted into agricultural fertilizers and soil conditioners. Black-shale-type oil shales in the Southern resource area are associated with polymetallic mineralization, are enriched in elements such as Ni and Mo, and contain SiO2, AlO3, Fe2O3, CaO, MgO, SO3, other trace and rare earth elements, and heavy metals. These characteristics mean that this material is suitable for the production of silica (silicon dioxide), alumina, oil shale waxes, organic acids, and other chemical products, and it can also be used in base metal production (Jietal., 2010). In addition, oil shale ashes processed at high temperatures are highly porous and contain many active adsorption groups, meaning they are ideal for use in the handling of sewage and waste gases (Shawabkehetal., 2004; Jia, 2012).

These new areas of innovation not only solve some of the issues around oil shale ash disposal and shortages in key metals and minerals, but can also significantly contribute to environmental protection programs. Consequently, there exists a need to combine the variable characteristics of Chinese oil shale resources with appropriate processes and technologies in order to optimize the utilization of these resources in a way that balances economic efficiency and environmental protection (Cheetal., 2008; Sun, 2007).

4Conclusions

The National Oil Shale Resource Evaluation indicates that the oil shales in China are located in 24 provinces or autonomous regions, 48 basins, and 81 oil shale deposits. Prior to 2010, the Chinese oil shale resources were thought to be 7 254.48×108t, comprising discovered (1 185.63×108t) and potential (6 068.85×108t) oil shale resources, the majority of which are located in the Eastern and Central resource regions. The majority of these oil shale resources are hosted in the Mesozoic and Cenozoic sediments and are generally high in quality, with some 17% of the resources yielding >10% oil by weight. Most of these resources are present at shallow depths (<500 m) in plains areas of China.

The traditional areas of oil shale development and utilization are chemical refining, power generation, and construction material production, all of which have dominated oil shale use to date. However, advances in exploration technology and processes have meant that oil shales can now be used in the agricultural, metal, and chemical industries as well as in the production of new environmental protection materials. In summary, China has developed new methods that allow the comprehensive utilization of oil shales in a program that is dominated by traditional uses but is supplemented by new and innovative uses for these resources.

Acknowledgements

We thank the staff of the Key Laboratory of Oil Shale and Coexistent Energy Minerals of Jilin Province, for their advice and assistance during the time of collecting and displaying data．

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doi:10.3969/j.issn.1673-9736.2015.01.07

*Corresponding author(Email:zhujw@jlu.edu.cn)

Article ID: 1673-9736(2015)01-0048-07

Received 25 October 2015, accepted 28 December 2015

Supported by the Ministry of Education of China Grants (OSR-1-03)