Review of the Status quo of Unconventional oil and gas Exploration and Development
Abstract –This paper mainly introduce the concept of unconventional oil and gas, focuses on China’s tight oil, tight sandstone gas,
natural gas hydrate, shale gas, coal seam gas, oil sands and oil shale and other very unconventional oil and gas resources of the status
quo. Analysis a series of corresponding exploration and development technology, provided a exploration and development very
unconventional oil and gas resources in the process needs to be improved. Finally, the prospect of the development of unconventional
oil and gas resources of summary and outlook.
Keywords -Unconventional oil gas; Exploration technology; Development technology
Ⅰ. Introduction
Energy is an essential material basis for the survival and development of a country. The exploration and
exploitation of oil and gas resources is closely related to the national energy security and national economic
development. According to the National General Administration of customs statistics show that in 2012 China imported
2.71×108 tons of crude oil, an increase of 6.8%. According to the national development and Reform Commission
statistics, in 2012 China’s foreign oil dependency degree reached 56.4%, compared to 2011 and 2010 further rise, which
means since 1993, China became a net importer of crude oil, dependence on foreign oil in ten years increased 9 times.
According to the International Energy Agency analysis report shows that China’s crude oil demand growth in the future
if the same, oil import dependence will rise to 80% in 2035.
With the rapid development of China’s economy, the demand for oil and gas resources is also increasing, and the
exploration of conventional oil and gas resources has basically bottomed out. Therefore, unconventional oil and gas
exploration and development has become an important way to solve the current supply and demand contradiction.
China is unconventional oil and gas resources are rich, the development potential is very big. According to incomplete
statistics, the unconventional natural gas resources in the amount for 188×1012—196×1012m3, recoverable resources
amount to more than 45×1012 m3, dense oil can be recoverable resources amounted to 15×108t above1 (according to
song Yan, 2013). At the same time, the exploration and exploitation of unconventional oil and gas in China is becoming
more and more mature, and more and more unconventional oil and gas resources have been paid much attention. Can
say, the unconventional oil and gas resources is conventional oil and gas resources in the most appropriate
complementary resources, in the energy structure has a vital role, and will become the leading resource for the oil and
gas industry to replace the conventional oil and gas resources.
Ⅱ. Unconventional oil and gas research background
As is well known, oil and gas resources can be divided into conventional and unconventional oil and gas. China’s
oil industry has also experienced several different stages, that is, the conventional oil and gas exploration and
development stage, conventional and unconventional oil and gas development stage and unconventional oil and gas
exploration and development stage. So far, conventional oil and gas exploration in China has gone through more than
60 years, the reserves and production has passed its peak, is in the current breakthrough of both conventional and
unconventional oil and gas as a major strategic period and very unconventional oil and gas exploration and development
technology, oil and gas geology and oil and gas exploration main areas are to the field of unconventional oil and gas
migration.
Ⅲ. Unconventional oil and gas research connotation
Very unconventional oil and gas is refers to the traditional technology can not get natural industrial production,
need to use new technology to improve reservoir permeability and fluid viscosity to economic exploitation, continuous
or quasi continuous accumulation of oil and gas resources 2 (according to Zou, 2013). The former mainly refers to heavy
oil, heavy oil and deep oil, the latter mainly refers to coal bed gas, gas hydrate, deep natural gas and mineral oil and gas,
etc..
We can describe the relationship between conventional and non conventional resources with a triangular Pyramid
graph (Figure 1). At the top of the triangle Pyramid is the traditional resources, its development is easy, but the volume
is small. In the middle of the triangle, such as heavy oil, tight gas, has been a period of time development and
production of unconventional resources. It is currently emerging but technical challenges the most unconventional
resources including shale oil and natural gas hydrate, especially natural gas hydrate in all over the world contain a huge
amount of 13 (according to Jerome Rajnauth, 2012) in the bottom of the pyramid, we can find that the number of more
but the development of non conventional resources more difficult.
Figure 1 The Pyramid relationship between conventional and unconventional resources
(Holditch, 2008; Jerome Rajnauth, 2012)
Unconventional oil and gas resources are different from conventional oil and gas resources in the aspects of
hydrocarbon accumulation mechanism, occurrence state, distribution law and exploration and development. China’s
unconventional oil and gas resources are widely distributed, is very rich in reserves, a huge potential for development,
such as Eastern Bohai Bay Basin, central Ordos Basin and Sichuan Basin and the Western Tarim, quasi Junggar and
Turpan Hami basin. According to the research that, the unconventional oil and gas into the reservoir has the following
characteristics: (1) abundant reserves, widely distributed in the area; (2) unconventional oil and gas storage layer
heterogeneity strong; and (3) storage layer poor, low porosity and low permeability reservoirs.
At present, China’s investment in the industrialization of the exploration and development of unconventional oil
and gas resources are mainly the following categories:
A. Tight oil
Tight oil the main reservoir space, there are two, one is in the interlayer of the source rocks of carbonate rock and
clastic rock, and the second is adjacent source rocks of the dense layer 3 (according to Zou , 2012). Dense oil in China
are widely distributed, generally divided into three types: continental sandstone reservoir (such as Ordos Basin,
Yanchang Formation reservoir, Lake phase carbonate reservoir (such as the Sichuan Basin in the area of Daanzhai
reservoir) and marl fractured reservoir (such as Jiuquan Basin in Qingxi sag, reservoir).
B. Oil sands
Oil sands, also known as tar sands, is composed of quartz sand, asphalt, clay, minerals, water, etc. the mixture and
asphalt content for 10-18%, sulfur content can be more than 7%, an extremely complex mixtures of hydrocarbons and
carbon can be integrated processing oil from 14 (according to Deborah Gordon, 2012). Its relative density is greater than
0.95 under the temperature of oil layer.
Oil sand is the main source of unconventional oil resources, which plays an important role in the world energy
supply. According to the U.S. Geological Survey (USGS) in 2004, the world’s oil sand oil recoverable resources is about
6510×108 barrels, accounting for 32% of the world’s total oil resources can be mined. At present, the research and
development of oil sand, all over the world are accelerating, along with the development of exploration and
development technology, the proportion of global hydrocarbon energy will continue to increase. In recent years, Shell,
BP, Exxon, Mobil and other major oil companies to actively invest in the field of oil sands, increase the exploration and
development of oil sands. In particular, Canada, whose oil sands exploration has entered a large-scale commercial
development, has become the world’s second largest oil reserves after Saudi Arabia 4 (according to Zhai Guangming,
2008).
Little oil sand resources in China, mainly distributed in the Western quasi Junggar basin, Tarim Basin, Qaidam
Basin, Ordos Basin and Songliao basin etc., especially in Junggar basin, northwestern margin of the Fengcheng area
found China’s first large oil sands mine 5 (according to Tong, 2014).
C. Oil shale
Oil shale and oil shale can be called, is a high ash content and low calorific value of fossil fuel, containing
insoluble in organic solvents, by retorting and shale oil and shale semi coke. The oil shale resource evaluation results
show that China’s oil shale resources total ranked fourth in the world, of which can be taken out of oil shale resources
about 119.79×1012m3, the distribution layer is mainly of Cenozoic, Mesozoic strata, the regional distribution of the main
in the eastern region, Qinghai Tibet region and the central region 6 (according to Lei, 2008).
D. Dense gas
Dense gas refers to the permeability is less than 0.5 milli Darcy’s natural gas resources, mainly occur in low
porosity and low permeability reservoir, gas bearing saturation is low, including tight sandstone gas, volcanic gas,
carbonate rock gas. Tight sandstone gas reservoir in the basin of the world, the large amount of resources, has been
found in the dense gas basin of about 70. In the United States, this kind of gas reservoir and is often referred to as low
permeability gas reservoirs of 7 (according to Zhao Jing Zhou, 2012), the first in tight oil and gas field progress, and
then rely on in horizontal wells and fracturing of the main technology in the coal seam to seam gas can become a new
growth point 8(according to Zhangkang, 2013). The United States is the most successful country in the development of
tight gas, and then China.
Tight sandstone gas reservoirs are widely distributed in China, such as Ordos, Sichuan, Songliao, Bohai Bay,
Qaidam Basin, Tarim Basin and Junggar basin. Tight sandstone gas development in Ordos Basin is well developed, and
the tight sandstone gas fields, such as Surig, Yulin, North and bull, are also in the northern part of the basin. Especially
Sulige gas field, is currently China’s largest gas field, development potential is very broad, with support of the Sulige
gas field development, tight sandstone gas gradually become an important part of China’s natural gas exploration and
production.
E. Natural gas hydrate
Natural gas hydrate is a crystalline compound formed from natural gas and water under certain conditions similar
to ice, non stoichiometric and cage crystalline compound, due to its appearance as ice, and in the event of a fire burning,
so also known as combustible ice, ice and gas solid gas, main components for methane. Methane hydrates trapped in the
lattice of frozen water, its natural state is not the chemical bonds between methane and water 15 (according to Schumann
Jon, 2012). Natural gas hydrate is mainly characterized by the high energy density, per unit volume of gas hydrate
decomposition can probably release 160 per unit volume of methane gas, its energy density is 2 to 5 times the
conventional natural gas.
The formation of natural gas hydrates in the low temperature and high pressure conditions, it is generally
distributed in the deep sea sediment and cold permafrost. The alpine zone, high latitude area of frozen soil with
conducive to the formation of natural gas hydrate, such as the Qinghai Tibet Plateau of China, South China Sea and the
high latitude permafrost zone, the South China Sea resources with the greatest potential can be said that natural gas
hydrate is China’s natural gas reserve resources library, the energy of our country in the future has a important influence
9 (according to Zou, 2010).
However, due to the natural gas hydrate is a very unstable substances, mining and control methods of improper
cause geological disasters in the process of drilling, even with today’s technology, it is difficult to achieve commercial
development.
F. Shale gas
Shale gas refers to exist in shale of tiny pores, cracks and minerals, organic matter on the surface of the natural gas
in a free and adsorbed form, its main composition is methane is a kind of efficient and clean energy resources, mainly
used for gas, heating, power generation, automotive fuel and chemical production. Its characteristics are mainly four
points: a wide range of distribution, large thickness, long mining life, and organic matter content is generally more than
2%. Global shale gas resources of about 456 trillion cubic meters, equivalent to the total amount of coal-bed methane
and tight gas, mainly in China, North America, Central Asia, the Middle East and North Africa and other regions.
China’s shale gas resources potential, mainly in the offshore and onshore marine basin.
Distribution, the lower Paleozoic in southern China Paleozoic marine shale, North China marine shale, Tarim
Basin Cambrian – Ordovician Marine shale, Songliao Basin in Cretaceous lacustrine shale, Junggar Basin on the second
Triassic – Jurassic lacustrine facies shale and Ordos Basin Triassic lacustrine shale has a wide range, thickness, maturity
high, fully equipped with shale gas reservoir basic geological conditions, which in Southeast Sichuan Jiao Shi Ba
anticline belt Longmaxi group was the most prominent, becoming China’s first shale gas exploration and development
of the demonstration zone, by the end of 2015 will be built with an annual output of 50 million capacity.
G. Coal bed gas
Coal bed methane is a very unconventional natural gas in coal bed with the adsorption state. The methane content
is more than 90%, and it is the most realistic energy to take over 10 (according to Che Changbo, 2008). Since the 80’s in
twentieth Century, our country has begun the exploration of coal bed gas. China’s CBM resources are rich, rapid
development, is the world in addition to Russia and Canada, the third largest coal-bed methane reserves. Mainly in
North, northwest, northeast, Yunnan and South China is the main coal accumulating area, which in North China and
northwest poly coal region mainly. Secondly, for the South China Poly coal region, northeast poly coal region of CBM
resources low 11 (according to Zhang Jie, 2004). Along with the development of coal bed gas development technology,
the industry has a good prospect in China.
Ⅳ. Unconventional oil and gas exploration and development technology
With the deepening of geological knowledge, the geological theory has been continuously innovative, which
provides a solid scientific theory and technology for the exploration of unconventional oil and gas exploration. At
present, coalbed methane and shale gas resources amount larger, and the amount of conventional oil and natural gas
resources close, can form a large-scale production base, will be in the future an important supplement to the energy of
oil and natural gas, the development is an important strategy to sustainable development of oil and gas. In recent years,
unconventional oil and gas in resource exploration and development has achieved rapid development, mainly depends
on the following technologies:
A. Natural gas development technology
At present, the technology is divided into seven categories, namely coal geophysical recognition of coal seam
drilling and completion technology, pinnate branching drilling technology and drainage gas technology, horizontal well
drilling technology, horizontal well piecewise fracturing technology, drainage gas recovery technology, low set
transmission processing technology. These technologies can greatly improve the reservoir physical properties, pore
structure and pore structure, and reduce the impact of reservoir heterogeneity.
B. Tight gas production technology
Means of the exploitation of tight gas is relatively abundant, mainly reflected in the following aspects: tight
sandstone gas reservoir fine description technology and very unconventional natural gas seismic exploration and
development technology, cluster wells, horizontal wells and pinnate horizontal well drilling technology, multiwell,
multilayer fracturing reconstruction of production technology, high precision 3D seismic technology, ground heating,
low pressure gas gathering, mixed phase measurement technique. Also, the use of the above technology can improve the
reservoir structure, improve the recovery rate, increase the gas production.
C. Coal bed methane extraction technology
World coal seam gas of mining technology has been very mature, the mining methods generally have two, one is
the conventional natural gas fields with the same mining method in the coal mining, drill and various mining wells, such
as vertical wells, horizontal wells and multi branch horizontal well. By using the poor drainage of coal bed gas reservoir
and underground pressure can also be used in fracturing, CO2 injection stimulation measures to improve the production.
Another is the use of coal mine production and return roadway and later combined coal bed gas extraction in coal
mining area. However, due to the complex geological structure, the impact of the multi period tectonic activity, the coal
seam permeability and the formation pressure is lower, which brings some difficulty to the exploitation. But through the
development, China’s coal-bed methane exploration technology is increasingly mature, techniques have been developed
to achieve a breakthrough (e.g. pinnate horizontal well development technology and nitrogen injection, carbon dioxide
gas mining production technology), and constantly improve the production, coal seam gas is in period of rapid
development.
D. Oil sand mining technology
At present, the separation technology of oil sand oil in China is mature. Oil sands mining method is divided for
open pit mining and in-situ mining, open-pit mining technology is more mature, low cost, high recovery rate of asphalt,
but generally require oil sand layer thickness is larger, buried with a depth of less than l00m, oil content of more than
8%. In situ mining method is suitable for the deep buried oil sand mine, the mining cost is higher. In addition, in the
process of the oil placer mines, environmental protection is very important, due to need a lot of water extraction and
separation, separation after the waste sand and sewage processing must keep up with.
E. Shale gas recovery technology
At present, the exploitation of shale gas mainly uses “in directional and horizontal wells” and “fracking”
technology 16 (according to Anthony Andrews, et al., 2009), can effectively improve the shale gas production of single
well, two techniques have greatly promoted the development and production of shale gas, the cracking seam channel of
shale gas reservoir has been effective development and improve the shale gas in single well production.
F. Natural gas hydrate exploitation technology
At present, the exploitation of natural gas hydrate technology is still in experimental stage, mainly using thermal
desorption method, the high temperature of the water is injected into the methane hydrate occurs, the methane
analytical. The frozen soil under the methane hydrate mining technology has been relatively mature, and oceanic
methane hydrate resources development and utilization of technology is still in the exploration.
G. Rock oil shale mining technology
The exploitation and utilization of oil shale has nearly 200 years, refining shale oil technology is very mature,
mainly through the ground dry distillation of oil shale. For the technology of oil shale, general depth should be less than
l00m, using open-pit mining and mining in two ways, more than 100m need by underground retorting technology to
extract oil shale.
Ⅴ. Summary and Outlook
With the very unconventional oil and gas mining technology increasingly mature, the exploration and development
will gradually occupy the dominant position of the oil and gas production. Therefore, we must in the three aspects of
technological innovation, environmental protection, and other personnel reserve give attention to:
A. The relative lack of China’s oil and gas resources, the need to vigorously strengthen the unconventional oil and gas
development to continue to actively carry out international exchanges and cooperation, fully absorb the international
advanced technology and methods, do take people long to make up our own weaknesses. Successful development of
shale oil and gas, coal bed methane and other non conventional resources, providing a mature technology and
experience for reference, our country in conventional oil and gas exploration, has also been in horizontal well drilling,
fracturing and other aspects also accumulated some experience, have a certain technical base 12 (according to Ma
Yongsheng, 2012). So, through the very unconventional oil and gas storage layer recognition, geological reservoir
research, horizontal well fracturing, oil shale and tar sands technology key technology introduction and improved based
on, in a relatively short period of time for the geological characteristics of China’s unconventional exploration and
development of technology, to pave the way for a large-scale development.
B. Unconventional oil and gas resources in the development and use of the process, there is a high cost, environmental
pollution and other issues. High cost, including the cost of the pre technological research and development, and the cost
of exploration and exploitation, which is the highest, which affects the sustainable development of unconventional oil
and gas resources. Unconventional oil and gas resources are complex in geological structure, which has special
technical requirements in the process of exploration and exploitation. Environmental pollution, such as oil sands in the
process of smelting and use may affect groundwater quality, destroy the surface vegetation, consume a lot of energy, the
release of greenhouse gases, etc.. The United States has a potential environmental threat in the exploitation of shale gas
17 (according to Grushevenko Dmitry, Grushevenko Ekaterina, 2012). Part of the chemical substances such as fracturing
fluid, benzene and other involved in the development of shale gas in the process of entering the environment and cause
pollution 18 (according to Clifford A.Lipscomb, et al., 2012). Shale gas in the production process of consumption of
water, groundwater pollution, air pollution and destruction of ecological environment and other issues, so, to protect the
water quality is very important topic, is to ensure that the key to the sustainable development of shale gas 19 (according
to Stephen A. Holditch 2013).
C. China should strengthen the regulation and control of unconventional oil and gas resources development, the
development of its future development and the corresponding stage of the development of scientific planning, orderly
development and utilization. We should also strengthen the development and utilization of non conventional energy
financial support and preferential subsidies to promote its smooth development. In addition, it is necessary to establish
and plan the training system of the personnel training system, which is composed of the research and technical experts,
so as to ensure the reasonable development of unconventional oil and gas resources.
ACKNOWLEDGMENT
In the process of writing this paper, thanks to He Sheng, Xie Xi Nong, Xu Sihuang three professors of good
guidance, in this together to express my gratitude!
REFERENCES
[1] Song Yan, Jiang Lin, Ma Zhi. The formation of unconventional oil and gas reservoir and its distribution characteristics [J]. Journal of
palaeogeography, 2013, 15 (5): 605-614.
[2] Zou Caineng, Zhang Guosheng, et al. Unconventional oil and gas concepts, characteristics, potential and technology – and unconventional oil and
gas geology [J].Petroleum Exploration and Development,2013, 40 (4): 385 – 399
[3] Zou Caineng,Zhu Rukai, Wu Songtao. Characteristics and mechanisms of conventional and unconventional oil and gas accumulation – and the
prospect of China’s tight oil and tight gas as an example [J]. Petroleum Journal, 2012, 33 (2): 173-187.
[4] Zhai Guangming. Some considerations on unconventional oil and gas exploration and development [J]. Natural Gas Industry, 2008, 28 (12): 1-3.
[5] Tong Xiaoguang, Guo Jianyu, Wang Zhaoming. Unconventional oil and gas geology theory and technology progress [J]. Frontier Geology, 2014,
21 (1): 9-20.
[6] Lei Qun, Wang Hongyan, Zhao Qun. Current situation and suggestion of unconventional oil and gas exploration and development in China and
abroad [J]. Natural Gas Industry, 2008, 28 (12): 7-10.
[7] Zhao Jingzhou. Unconventional oil and gas related concepts, classification and resource potential [J]. Natural Gas and Earth Sciences, 2012,23
(3): 393 – 406
[8] Zhang Kang, China’s unconventional oil and gas development of diversified thinking [J]. Energy, 2013, (8): 84 – 87
[9] Zou Caineng,Zhang Guangya, Tao Shizhen. The geological characteristics, the important discovery and unconventional petroleum geology in the
global petroleum exploration field [J].Petroleum Exploration and Development,2010, 37 (2): 129-145.
[10] Che Changbo, Yang Hulin, Li Fubing. Unconventional oil and gas resources exploration and development policy considerations [J]. Natural Gas
Industry, 2008, 28 (12): 4-6
[11] Zhang Jie, Jin Zhijun, Zhang Jinchuan. Potential and distribution of unconventional oil and gas resources in China [J]. Petroleum and
Petrochemical today, 2004,12 (10): 17 – 19.
[12] Ma Yongsheng,Feng Jianhui, Mou Zehui. Unconventional oil gas resource potential and exploration progress in China Petrochemical [J]. China
Engineering Science, 2012, 14 (6): 22-30.
[13]Jerome Rajnauth, 2012. Is It Time to Focus on Unconventional Resources. Advances in Petroleum Exploration and Development, 4(2): 37–45.
doi: 10. 3968/j. aped. 1925543820120402. 778
[14]Deborah Gordon, 2012. Understanding Unconventional Oil. The Global Think Tank, 1–21.
[15]Jon Schumann, Shapour Vossoughi, 2012. Unconventional Gas Resources in the U.S.A.. AIP Conference Proceedings, 1453(1): 301–306. doi: 10.
1063/1. 4711191
[16]Anthony Andrews, et al., 2009. Unconventional Gas Shales: Development, Technology, and Policy Issues. Congressional Research Service, 1–44.
[17]Ekaterina Grushevenko, Dmitry Grushevenko, 2012. Unconventional Oil Potential Tends to Change the World Oil Market. Energy Science and
Technology, 4(1): 68–74. doi: 10. 3968/j. est. 1923847920120401. 178
[18]Clifford A. Lipscomb, et al., 2012. Unconventional Shale Gas Development and Real Estate Valuation Issues. Review of Regional Studies, 42(2):
161–175.
[19]Stephen A. Holditch, 2013. Unconventional Oil and Gas Resource Development – Let’s do it right. Elsevier, 1(2): 2–8. doi: 10. 1016/j. juogr.
2013. 05. 001
