The assessment of mineral resources and their explored reserves are closely related to factors such as the degree of exploration, depth of study and progress of technology. The assessment made at different time may vary in the prediction of resources potential and estimation of the reserves. The assessment of resources and the classification and calculation of reserves presently used in China are approaching the conventional methods used internationally, but there are still some differences, so that some discrepancy may occur in the comparison. China has made assessment and prediction of the five energy resources, coal, oil, natural gas, uranium and geotherm, in different forms and time, and has thus acquired a systematic understanding of their resources.

2.1.1.1 Status of Resources

(1) Coal

According to the resources prediction made in the 1980s, the total resources for coal are 5.06 trillion tons. Among them, about 4.45 trillion tons are located at vertical depths shallower than 1,800 m, which are less than those of the former USSR (6.8 trillion tons) and more than those of the USA (3.6 trillion tons), ranking second in the world in a comparison with resources at similar depths.

By the end of 1997, the accumulative explored geological reserves of coal reached 1,033.398 billion tons, accounting for 20.4% of the total resources. Among them, reserves by detailed exploration reached 252,584 million tons, making up 24.4% of the explored reserves. The accumulative coal output was 26,125 million tons, and the retained reserves by detailed exploration were 230,452 million tons (64.6% of which already used), ranking third in the world (after the CIS and USA).

The distribution of coal resources is widespread but uneven: rich in the north and west while poor in the south and east. The regions with resources exceeding 1,000 billion tons consist of Xinjiang (1,621 billion tons) and Inner Mongolia (1,205.3 billion tons), and those exceeding 100 billion tons include Shanxi, Shaanxi, Gansu, Ningxia, Guizhou, Hebei, Shandong, Henan and Anhui. The accumulative resources of the above regions reach 4,811.3 billion tons, accounting for 95.1% of the total resources.

The present retained reserves of coal are concentrated in the following 12 provinces or regions: Shanxi (257.8 billion tons), Inner Mongolia (224.7 billion tons), Shaanxi (161.9 billion tons), Xinjiang, Gansu, Ningxia, Heilongjiang, Hebei, Shandong, Henan, Guizhou and Yunnan. They have accumulative explored reserves of 963.7 billion tons, making up 96.1% of the total explored reserves.

(2) Oil and gas

It is estimated based on the resources assessment made in the early 1990s that the total resources are 93 billion tons for conventional oil and 38 trillion cubic meters for conventional gas, and calculated ultimate recoverable resources are 14 billion tons for the former and 10.5 trillion cubic meters for the latter. Besides, according to other research results, the resources of the unconventional coalbed methane are estimated to reach 32.64 trillion cubic meters for burial depths shallower than 2,000 m, and the prospective geological reserves of shale oil are about 14.2 billion tons. The sedimentary basins in the South China Seas also have very good potential for oil and gas.

Up to the end of 1997, the accumulative explored recoverable reserves of oil amounted to 5.5 billion tons, accounting for 39.3% of the total recoverable resources, whereas the accumulative production of oil was 3,172 million tons, with the remaining recoverable reserves of 2,327 million tons, ranking 11th in the world. The accumulative explored recoverable reserves of natural gas were 1.05 trillion cubic meters, accounting for 7.95% of the total ultimate recoverable conventional gas resources, whereas the accumulative production of gas was 247.564 billion cubic meters, with the remaining recoverable reserves of 805.2 billion cubic meters, ranking 24th in the world.

The distribution of oil and gas is uneven, relatively concentrated in a number of large basins. The oil resources in eastern China (Northeast China, North China and the Yangtze-Huaihe area, with an amount of 36.34 billion tons) comprise 39% of the total; those in western and central China (24.789 billion tons) and the shelf regions (24.675 billion tons) account for 26.7% and 26.5% respectively; and the southern regions occupy only a small proportion. As for the natural gas resources, the central regions (11.36 trillion cubic meters) comprise 29.95% of the total; the western regions (10.78 trillion cubic meters), 28.4%; and the shelf regions (8.39 trillion cubic meters), 22.1% of the total. The 13 basins and sea areas, Bohai Bay, Songliao, Tarim, Junggar, Turpan-Hami, Ordos, Qaidam, Sichuan, Bohai Sea, East China Sea Shelf, Pearl River Mouth, Yinggehai-Qiongdongnan and Beibu Gulf, making up only 8.66% of the total number of the basins, have oil resources of 75.04 billion tons and gas resources of 30.7 trillion cubic meters, accounting for 80.7% and 80.86% respectively of the total resources.

Distribution of the explored reserves of oil and gas has a similar feature with that of resources, i.e., the reserves are also concentrated in some large oilfields (> 100 million tons) and gas fields (>30 billion cubic meters). Geographically, for oil: 79% in the eastern regions, 15.6% in the central and western regions, 4.7% in the shelf regions, and only a small proportion in other regions; for gas: 67.2% in the central and western regions, 16.74% in the shelf regions, and 15.64% in the eastern regions. The 7.23% large oilfields have explored reserves comprising 58.6% of the total reserves, and the 6.2% large gas fields have explored reserves amounting to 43.9% of the total.

(3) Uranium

According to the research results and prediction made by some specialists, the uranium resources of China amount to 1 to 2 million tons. More than 200 uranium regions have been explored with substantial reserves of uranium proved.

China's uranium resources are unevenly distributed. Up to the present uranium deposits have been found in 23 provinces or regions, but they are concentrated in Jiangxi, Guangdong, Guizhou, Hunan, Guangxi, Xinjiang, Liaoning, Yunnan, Hebei, Inner Mongolia, Zhejiang and Gansu, and especially abundant in Jiangxi, Hunan, Guangdong and Guangxi.

(4) Geothermals

As predicted by geologists, China's geothermal resources total 2.1192¡Á1020 kJ, equivalent to heat generated by 7.2310¡Á1012 tons of standard coal. The total geothermal resources stored in 15 sedimentary basins (Northern North China, Southern North China, Songliao, northern Jiangsu, Ordos, Fenhe,Weihe, Jianghan, Leiqiong, Sichuan, Chuxiong, Hexi Corridor, Qaidam, Junggar and Turpan-Hami) at depths shallower than 2,000 m amount to 4.0184¡Á1019 kJ, equivalent to heat generated by 1.3711¡Á1012 tons of standard coal.

By the end of 1996, the total explored recoverable geothermal water in China amounted to 2,523,800 m3/d (c. 921 million m3/a), with usable heat energy of 4,333.89 MW. The heat energy it can supply per year was equivalent to heat generated by 4.660¡Á106 tons of standard coal. Among the resources, the Grade-B recoverable geothermal water amounted to 784,000 m3/d, with usable heat energy of 735.68 MW.

The geothermal resources are also unevenly distributed. The southwestern regions (2,204.45 MW) comprise 51.87%; North China (734.72 MW), 16.95%; the central-southern regions (687.75 MW), 15.87%; and the northeast and northwest regions, 2.52% and 3.57% respectively.

2.1.1.2Characteristics of Resources

(1) Coal

China's coals are characterized by a distribution of multiple ages, distinct zoning, great variety and rather deep burial depths. Medium-grade metamorphic coals are mainly distributed in the Late Paleozoic, medium- to low-grade metamorphic coals in the Mesozoic, and mainly low-grade metamorphic lignite in the Tertiary. Geographically, the areas north of the Tianshan-Yinshan Mountains are dominated by distribution of lignite and low-grade metamorphic coals, while in the areas south of the Tianshan-Yinshan Mountains and north of the Kunlun-Qinling-Dabie Mountains are distributed bituminous coals and anthracite of various metamorphic grades, and minor lignite. The extensive southern regions are dominated by high-grade metamorphic coals. In terms of the variety of coals, high-quality power-genera-ting coal is the most abundant, accounting for 72.9% of the retained reserves; high-quality coking coal and anthracite have a relatively small proportion of 25.4%. There is a diversity of associated minerals in the coal fields, which can be used for multiple purpose. The reserves of coals buried deeper than 1,000 m comprise 53.2% of the total, those suitable for opencast mining only 4.1%, and high-grade metamorphic coals have small reserves.

(2) Oil and gas

China's petroleum is dominated by a continental origin, and generated in relatively young strata. Meso-Cenozoic petroleum resources comprise 86.28% of the total, and the explored geological reserves are also mainly distributed in the Meso-Cenozoic strata. As for the natural gas resources, 49.19% occur in the Meso-Cenozoic strata, and 50.18% in the Paleozoic, reflecting that a large proportion of gas is generated in marine sediments. The complicated geological conditions in China have resulted in diversity of resources quality and oil/gas fields. Among the petroleum resources, conventional oil comprises 87.1%, oil in low-permeability reservoirs 6.1%, viscous oil 2.0%, and immature oil 4.8%. The oil/gas fields so far discovered are mainly medium-sized and small ones, and mostly structural oil/gas fields, including anticlinal and fault-block ones. The physical geographic conditions for the resources distribution are also very complicated, 43.3% of the oil resources and 66.7% of the gas resources are distributed in such areas as sea beaches, swamps, deserts, mountains and loess highland. 23.26% of petroleum resources are buried at depths of 3,500~4,500 m, and a substantial portion deeper than 4,500 m (e.g. the Tarim Basin).

(3) Uranium

The uranium deposits that have been explored are dominated by the granite, volcanic, sandstone and C-Si-mudstone types. They are mainly of medium and low grades, with a great proportion of ores having a uranium content of 0.05£¥~0.3%. The ores are mainly of a monocrystal composition; only a very few deposits are found to be associated with other metals. The deposits are usually medium or small in size. The orebodies are mostly buried within 500 m of depth. The mineralization mainly occurred in the Mesozoic and Cenozoic, concentrated in the time interval of 87~45 Ma. The metallogenetic sequence is generally as follows: the migmatite type, pegmatite type, granite type, C-Si-mudstone type and sandstone type. In terms of origin, the uranium deposits can be divided into the endogenic (magmatic and hydrothermal), exogenic (diagenetic and epigenic illuviation) and polygenic types.

(4) Geothermals

China's geothermal resources consist of two types, geothermal springs in tectonically uplifted areas and underground thermal water in sedimentary basins. They are dominated by medium (90~150¡æ) and low (<90¡æ) temperatures, which account for 99.7% of the total resources. The geothermal fields are mainly medium to small in size, comprising 92.8% of the total, but the usable thermal energy only accounts for 24.13% of the total.