China's Shale Gas Geological Investigation and Prospecting Have Made Significant Progress

Since 2015, the China Geological Survey has implemented a major program of ＂Geology Survey of Land Energy Mineral Resources＂. Till now, a total of billions of RMB have been invested and seven engineering projects have been established, all of which has greatly enhanced the geological survey and exploration of China＇s continental shale gas in an attempt to overcome the oil and gas shortage.

Present Situation of China's Shale Gas Exploration and Development

In recent years,with China＇s continuous investment in shale gas exploration and the continuous efforts of scientific workers,China’s shale gas exploration and development has achieved leap-forward development.In2011,China＇s State Council approved shale gas as a new mineral resource.In 2014,shale gas was first proved at geological reserves of 106.8 billion m^3.

2013 Production of China's Shale Gas Reaches 200 Million Cubic Meters and the First Transportation Pipeline Constructed

Results of the global shale gas resources show that minable resources of global shale gas are 187 trillion cubic meters （tern）, of which China accounts for 36 tcm （about 20% of the total amount）, which is mainly distributed in the Sichuan Basin, Yangtze Terrace, and Ordos Basin. From 2009 to 2012, China completed an accumulative number of 129 drilling wells related to shale gas, including 46 investigated vertical wells, 55 exploration wells and 28 evaluation wells, with 2012 production ranging from 25 million cubic meters （mcm） to 30 mcm.

Distribution characteristics, exploration and development, geological theories research progress and exploration directions of shale gas in China

The shale gas resources in China have great potential and the geological resources of shale gas is over 100×10^(12)m^(3),which includes about 20×10^(12)m^(3) of recoverable resources.Organic-rich shales can be divided into three types according to their sedimentary environments,namely marine,marine-continental transitional,and continental shales,which are distributed in 13 stratigraphic systems from the Mesoproterozoic to the Cenozoic.The Sichuan Basin and its surrounding areas have the highest geological resources of shale gas,and the commercial development of shale gas has been achieved in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in these areas,with a shale gas production of up to 20×10^(9)m^(3) in 2020.China has seen rapid shale gas exploration and development over the last five years,successively achieving breakthroughs and important findings in many areas and strata.The details are as follows.(1)Large-scale development of middle-shallow shale gas(burial depth:less than 3500 m)has been realized,with the productivity having rapidly increased;(2)breakthroughs have been constantly made in the development of deep shale gas(burial depth:3500-4500 m),and the ultradeep shale gas(burial depth:greater than 4500 m)is under testing;(3)breakthroughs have been made in the development of normal-pressure shale gas,and the assessment of the shale gas in complex tectonic areas is being accelerated;(4)shale gas has been frequently discovered in new areas and new strata,exhibiting a great prospect.Based on the exploration and development practice,three aspects of consensus have been gradually reached on the research progress in the geological theories of shale gas achieved in China.(1)in terms of deep-water fine-grained sediments,organic-rich shales are the base for the formation of shale gas;(2)in terms of high-quality reservoirs,the development of micro-nano organic matter-hosted pores serves as the core of shale gas accumulation;(3)in terms of preservation conditions,weak structural transformation,a moderate degree of thermal evolution,and a high pressure coefficient are the key to shale gas enrichment.As a type of important low-carbon fossil energy,shale gas will play an increasingly important role in achieving the strategic goals of peak carbon dioxide emissions and carbon neutrality.Based on the in-depth study of shale gas geological conditions and current exploration progress,three important directions for shale gas exploration in China in the next five years are put forward.

Pore Structure Heterogeneity of the Xiamaling Formation Shale Gas Reservoir in the Yanshan Area of China: Evaluation of Geological Controlling Factors

Micro-heterogeneity is an integral parameter of the pore structure of shale gas reservoir and it forms an essential basis for setting and adjusting development parameters.In this study,scanning electron microscopy,high-pressure mercury intrusion and low-temperature nitrogen adsorption experiments were used to qualitatively and quantitatively characterize the pore structure of black shale from the third member of the Xiamaling Formation in the Yanshan area.The pore heterogeneity was studied using fractal theory,and the controlling factors of pore development and heterogeneity were evaluated in combination with geochemical parameters,mineral composition,and geological evolution history.The results show that the pore structure of the reservoir was intricate and complicated.Moreover,various types of micro-nano scale pores such as dissolution pores,intergranular pores,interlayer pores,and micro-cracks are well developed in member 3 of the Xiamaling Formation.The average porosity was found to be 6.30%,and the mean value of the average pore size was 4.78 nm.Micropores and transition pores provided most of the storage space.Pore development was significantly affected by the region and was mainly related to the total organic carbon content,vitrinite reflectance and mineral composition.The fractal dimension,which characterizes the heterogeneity,is 2.66 on average,indicating that the pore structure is highly heterogeneous.Fractal dimension is positively correlated with maturity and clay mineral content,while it is negatively correlated with brittle mineral content and average pore size.These results indicate that pore heterogeneity is closely related to thermal history and material composition.Combined with the geological background of this area,it was found that the pore heterogeneity was mainly controlled by the Jurassic magmatism.The more intense the magma intrusion,the stronger the pore heterogeneity.The pore structure and its heterogeneity characteristics present today are a general reflection of the superimposed geological processes of sedimentary-diagenetic-late transformation.The influence of magmatic intrusion on the reservoir is the main geological factor that should be considered for detailed evaluation of the Xiamaling Formation shale gas reservoir in the Yanshan area.

Prospect Conceiving of Joint Research and Development of Shale Gas and Coalbed Methane in China

Inspired by successful development of shale gas in USA and influenced by hydrocarbon resources shortage currently, China has strengthened shale gas research and accelerated its exploration process. In order to enrich coalbed methane (CBM) and shale gas geological theory and promote their development process, this paper compared shale gas with CBM in accumulation, distribution, reservoir and production. It expatiated on the background and significance of the combined research and development, and analyzed the geological foundation and future prospects. Our investigation demonstrated that there are many sets of coal-bearing strata in Shanxi formation of Permian system in Ordos in North China, Longtan formation of Upper Permian and Xujiahe formation of Upper Triassic in Southern Yangtze region, Xishanyao formation of Middle Jurassic in Turpan-Hami Basin and Junggar Basin in Northwest China, and Shahezi formation of Cretaceous in Songliao Basin in northeast China. In these regions, shales which are interbeded with coal seams have the characters of big thickness, continuous distribution, high content of organic matter, good parent material and high maturity, accord with the basic geological conditions to format shale gas and CBM reservoir and composite gas reservoir, thus form appropriate regions and layers to carry out joint research and exploration with good prospects for development.

Occurrence and influence of residual gas released by crush methods on pore structure in Longmaxi shale in Yangtze Plate, Southern China

The composition of gas released under vacuum by crushing from the gas shale of Longmaxi Formation in Upper Yangtze Plate,Southern China was systematically investigated in this study.The effect of residual gas release on pore structures was checked using low-pressure nitrogen adsorption techniques.The influence of particle size on the determination of pore structure characteristics was considered.Using the Frenkel-Halsey-Hill method from low-pressure nitrogen adsorption data,the fractal dimensions were identified at relative pressures of 0‒0.5 and 0.5‒1 as D1 and D2,respectively,and the evolution of fractal features related to gas release was also discussed.The results showed that a variety component of residual gas was released from all shale samples,containing hydrocarbon gas of CH4(29.58%‒92.53%),C2H6(0.97%‒2.89%),C3H8(0.01%‒0.65%),and also some non-hydrocarbon gas such as CO2(3.54%‒67.09%)and N2(1.88%‒8.07%).The total yield of residual gas was in a range from 6.1μL/g to 17.0μL/g related to rock weight.The geochemical and mineralogical analysis suggested that the residual gas yield was positively correlated with quartz(R^2=0.5480)content.The residual gas released shale sample has a higher surface area of 17.20‒25.03 m^2/g and the nitrogen adsorption capacity in a range of 27.32‒40.86 ml/g that is relatively higher than the original samples(with 9.22‒16.30 m^2/g and 10.84‒17.55 ml/g).Clearer hysteresis loop was observed for the original shale sample in nitrogen adsorption-desorption isotherms than residual gas released sample.Pore structure analysis showed that the proportions of micro-,meso-and macropores were changed as micropores decreased while meso-and macropores increased.The fractal dimensions D1 were in range from 2.5466 to 2.6117 and D2 from 2.6998 to 2.7119 for the residual gas released shale,which is smaller than the original shale.This factor may indicate that the pore in residual gas released shale was more homogeneous than the original shale.The results indicated that both residual gas and their pore space have few contributions to shale gas production and effective reservoir evaluation.The larger fragments samples of granular rather than powdery smaller than 60 mesh fraction of shale seem to be better for performing effective pore structure analysis to the Longmaxi shale.

Tectonic evolution of the Huangling dome and its control effect on shale gas preservation in the north margin of the Yangtze Block, South China

Significant breakthroughs of shale gas exploration have been made in Lower Cambrian and Sinian shale in the north margin of the Yangtze Block,South China.The drill wells with industrial gas flow located in the southern margin of the Huangling dome.Base on the geological survey,2D seismic,geochronological and drill wells data,the tectonic evolution history of Huangling dome was studied,and its control effect on the preservation condition of shale gas was discussed.The result shows that the Huangling dome might undergo four tectonic stages:(1)About 800 Ma,granite intrusion in the Huangling dome basement,primarily of granites replaced metamorphism rocks;(2)800-200 Ma,no significant tectonic movement with slowly buried history;(3)From 200 Ma,multi-phase uplift and the sedimentary rocks was eroded in the core of the Huangling dome.Shale gas in the Cambrian and Sinian strata was well preserved in the margin of the Huangling dome as the following reasons:(1)The Sinian shale was buried about 7.8 km indepth during Middle Jurassic,source rocks have a suitable thermal maturity for shale gas;(2)The rigid basement of the Huangling dome was mainly composed by homogeneity granite,without intensive deformation.As the main challenges of the widely distributed Lower Cambrian and Sinian shale are highmaturity and intensive deformation,a geological unit with a dome probably is a favorable zone for the old age shale gas.Therefore,it indicates that the adjacent zone of the Xuefengshan,Shennongjia and Hannan are the geological units with a dome and probably have potentials for the exploration of shale in the Lower Cambrian and Sinian.

The Openness Degree Study of the Jiaoshiba Shale Gas, Sichuan Basin, China–Potential Factor Responsible for Reversed Isotope Series

Objective Reversed alkane δ;C and δ;H values in many prolific shale plays all over the world have aroused much attention in the study of the formation mechanism of reversed isotope series in alkanes in the past few years（Zou Caineng et al., 2016）. Although many researchers have put forward different hypotheses, the mechanism has not been well understood yet. The openness degree of oil and gas system

Controlling factors of marine shale gas differential enrichment in southern China

Based on the exploration and development practice of marine shale gas in Fuling, Weiyuan, Changning, Luzhou and Southeast Chongqing in southern China, combined with experiments and analysis, six factors controlling differential enrichment of marine shale gas are summarized as follows:(1) The more appropriate thermal evolution and the higher the abundance of organic matter, the higher the adsorption and total gas content of shale will be.(2) Kerogen pyrolysis and liquid hydrocarbon cracking provide most of the marine shale gas.(3) The specific surface area and pore volume of organic matter rich shale increased first and then decreased with the increase of thermal evolution degree of organic shale. At Ro between 2.23% and 3.33%, the shale reservoirs are mainly oil-wet, which is conducive to the enrichment of shale gas.(4) The thicker the roof and floor, the higher the shale gas content. The longer the last tectonic uplift time and the greater the uplift amplitude, the greater the loss of shale gas will be.(5) The buried depth and dip angle of the stratum have different controlling and coupling effects on shale gas in different tectonic positions, resulting in two differential enrichment models of shale gas.(6) The effective and comprehensive matching of source, reservoir and preservation conditions determines the quality of shale gas accumulation. Good match of effective gas generating amount and time, moderate pore evolution and good preservation conditions in space and time is essential for the enrichment of shale gas.

Gas Occurrence and Accumulation Characteristics of Cambrian–Ordovician Shales in the Tarim Basin, Northwest China

The Tarim Basin is located in northwestern China and is the biggest basin in China with huge oil and gas resources. Especially the Lower to Middle Cambrian and Middle to Upper Ordovician possess the major marine source rocks in the Tarim Basin and have large shale gas resource potential. The Cambrian–Ordovician shales were mainly deposited in basin–slope facies with thicknesses between 30–180 m. For shales buried shallower than 4500 m, there is high organic matter abundance with TOC（total organic carbon） mainly between 1.0% and 6.0%, favorable organic matter of Type I and Type II, and high thermal maturity with RoE as 1.3%–2.75%. The mineral composition of these Cambrian–Ordovician shale samples is mainly quartz and carbonate minerals while the clay minerals content is mostly lower than 30%, because these samples include siliceous and calcareous shale and marlstone. The Cambrian and Ordovician shales are compacted with mean porosity of 4% and 3%, permeability of 0.0003×10^（-3）–0.09×10^（-3） μm^2 and 0.0002×10^（-3）–0.11×10^（-3） μm^2, and density of 2.30 g/m^3 and 2.55 g/m^3, respectively. The pores in the shale samples show good connectivity and are mainly mesopore in size. Different genetic types of pores can be observed such as intercrystal, intergranular, dissolved, organic matter and shrinkage joint. The reservoir bed properties are controlled by mineral composition and diagenesis. The maximum adsorption amount to methane of these shales is 1.15–7.36 cm^3/g, with main affecting factors being organic matter abundance, porosity and thermal maturity. The accumulation characteristics of natural gas within these shales are jointly controlled by sedimentation, diagenesis, hydrocarbon generation conditions, reservoir bed properties and the occurrence process of natural gas. The natural gas underwent short-distance migration and accumulation, in-place accumulation in the early stage, and adjustment and modification in the later stage. Finally, the Yulin（well Y1） and Tazhong（well T1） areas are identified as the targets for shale gas exploration in the Tarim Basin.

A New Discovery on the Deformation Behavior of Shale Gas Reservoirs Affecting Pore Morphology in the Juhugeng Coal Mining Area of Qinghai Province, Northwest China

Objective The Juhugeng mining area in Qinghai Province of northwest China has attracted wide attention among geologists for it hosts typical coal measure gases.The shale gas reservoirs were reformed by intensive structural movements during geological periods,

Progress and Challenges of Shale Gas Exploration and Development in China

China is abandant in shale gas resources. Encouraged by the successful development of shale gas resources in the U. S., China began its shale gas research and exploration activity about 10 years ago. This paper briefed the history, state quo and future of shale gas development in the country. Factors that constrain the shale gas industry there include technology limitations, attitude of the government, environmental concerns and etc. The future of the shale gas industry in China depends heavily on how well these issues are dealt.

Fracturing Technology and DevelopmentProblems of Shale Gas Resource in China

Development of shale gas in North America has come into commercialized production. China with rich shale gas resourcesstarted lately in developing. Several factors, such as the complicated geological structure and incomplete technology, do influencethe progress of shale gas development. This paper introduce the mature technologies in North America, including the choice offracture fluid, the horizontal well fracturing technology, the monitoring technology in the later period. Bidding exploration rightin earlier stage, infrastructure, environment, are all main points in shale gas developing in China.

Geological characterization and exploration potential of shale gas in the Carboniferous Jiusi Formation,northern Guizhou and Yunnan provinces,SW China

Dark mudstones and shales of the Carboniferous Jiusi Formation are widely developed in northern Guizhou and Yunnan provinces, SW China. However, the distribution, reservoir characterization, and exploration potential of organic-rich shales in this area are yet to be quantified, thus limiting the prospect of shale gas in this area. This study investigates the basic geological conditions of Jiusi shale gas, using core data, well-logs, and some other test data, obtaining the following results. The organic-rich shales are mainly composed of deltaic-to-shallow-shelf deposits, with thickness ranging from 0 to 450 m, and above 350 m around the subsidence center. The organic matter is mainly type Ⅱ kerogen with TOC content of mostly 1%–2%, indicating a moderate maturity. The argillaceous shale reservoirs are indicative of strong heterogeneity, high clay minerals content, low porosity, low permeability, high specific surface area, and relatively developed secondary porosity. The gas-log anomaly intervals obtained from the survey wells have a cumulative thickness that is apparently greater than 200 m, and a few shale intervals showing high desorbed and adsorbed gas contents. Due to complex structures in the study area, conditions responsible for shale gas occurrence and trapping are generally moderate. However, areas having wide and gentle folds with moderate depth of burial reveals relatively favorable conditions of hydrocarbon traps. In contrast with typical marine-continental transitional shales, the Jiusi shale have better geological conditions for shale gas preservation. The analysis of the geological framework and hydrocarbon potential of Carboniferous Jiusi Formation provide more insight for the exploration of Carboniferous shale gas in southern China.

Upper Paleozoic Marine Shale Characteristics and Exploration Prospects in the Northwestern Guizhong Depression,South China

Multiple sets of organic-rich shales developed in the Upper Paleozoic of the northwestern Guizhong Depression in South China. However, the exploration of these shales is presently at a relatively immature stage. The Upper Paleozoic shales in the northwestern Guizhong Depression, including the Middle Devonian Luofu shale, the Nabiao shale, and the Lower Carboniferous Yanguan shale, were investigated in this study. Mineral composition analysis, organic matter analysis(including total organic carbon(TOC) content, maceral of kerogen and the vitrinite reflection(Ro)), pore characteristic analysis(including porosity and permeability, pore type identification by SEM, and pore size distribution by nitrogen sorption), methane isothermal sorption test were conducted, and the distribution and thickness of the shales were determined, Then the characteristics of the two target shales were illustrated and compared. The results show that the Upper Paleozoic shales have favorable organic matter conditions(mainly moderate to high TOC content, type Ⅰ and Ⅱ_1 kerogen and high to over maturity), good fracability potential(brittleness index(BI) > 40%), multiple pore types, stable distribution and effective thickness, and good methane sorption capacity. Therefore, the Upper Paleozoic shales in the northern Guizhong Depression have good shale gas potential and exploration prospects. Moreover, the average TOC content, average BI, thickness of the organic-rich shale(TOC > 2.0 wt%) and the shale gas resources of the Middle Devonian shales are better than those of the Lower Carboniferous shale. The Middle Devonian shales have better shale gas potential and exploration prospects than the Lower Carboniferous shales.

Protoconodont fossils for refining the Cambrian bottom and the contribution to shale gas formation along the southwest margin of Yangtze Block

It has been an intense debate on the exact boundary between Ediacaran and Cambrian in the southwest Yangtze Block.The calibration of this critical boundary has a remarkable influence on the further investigation of the break-up of the Rodinia Supercontinent,the early life evolution,and the mechanism of the phosphorite deposit.Ediacaran and Cambrian strata and fossils are widely distributed in Anning,Yunnan Province in China.In recent years,the Xiaowaitoushan Member from the Lower Yuhucun Formation has been studied.Through this interval with continuous collections,the first appearance datums(FADs)of the protoconodont(Fomitchella cf.inchoate Yang et He,Protohertzina cf.anabarica Missarzhevsky)and globular embryos fossil(Olivooides sp.)earlier than these in the Lower Cambrian strata of the Meishucun Formation were discovered.This discovery indicates that the Xiaowaitoushan Member has included more FADs than the previously discovered single FAD of Anabarites primitivus Qian et Jiang,and the Ediacaran–Cambrian boundary in southwest China should be replaced below the Point“A”of the Meishucun Formation in Yunnan Province.The Point“B”of the Meishucun Formation is younger than the suggested age 541 Ma of the Ediacaran–Cambrian boundary and can no longer reference the Global Boundary Stratotype Section and Point(GSSP)correlation in southwest China.It can be suggested based on the previous stratigraphy and palaeontology studies from northern Sichuan and southern Shaanxi and the FAD of the globular embryos fossils that the Ediacaran‒Cambrian boundary in the southwest Yangtze Block should be placed at the base of the Xiaowaitoushan Member;other phosphorite strata refer to Xiaowaitoushan Member.The discovery of the FADs of the shelly fossils in the Xiaowaitoushan Member provides new evidence for the global correlation of the Ediacaran–Cambrian boundary in the southwest Yangtze Block.The conodont discoloration index(CAI)of the specimens in Anning is between 2 and 3,which indicates that the organic matter in Xiaowaitoushan Member is matured and has high potential to form a shale gas reservoir.

Geochemical and microbial characters of sediment from the gas hydrate area in the Taixinan Basin, South China Sea

The Taixinan Basin is one of the most potential gas hydrate bearing areas in the South China Sea and abundant gas hydrates have been discovered during expedition in 2013. In this study, geochemical and microbial methods are combinedly used to characterize the sediments from a shallow piston Core DH_CL_11（gas hydrate free） and a gas hydrate-bearing drilling Core GMGS2-16 in this basin. Geochemical analyses indicate that anaerobic oxidation of methane（AOM） which is speculated to be linked to the ongoing gas hydrate dissociation is taking place in Core DH_CL_11 at deep. For Core GMGS2-16, AOM related to past episodes of methane seepage are suggested to dominate during its diagenetic process; while the relatively enriched δ18O bulk-sediment values indicate that methane involved in AOM might be released from the ＂episodic dissociation＂ of gas hydrate.Microbial analyses indicate that the predominant phyla in the bacterial communities are Firmicutes and Proteobacteria（Gammaproteobacteria and Epsilonproteobacteria）, while the dominant taxa in the archaeal communities are Marine_Benthic_Group_B（MBGB）, Halobacteria, Thermoplasmata, Methanobacteria,Methanomicrobia, Group C3 and MCG. Under parallel experimental operations, comparable dominant members（Firmicutes and MBGB） are found in the piston Core DH_CL_11 and the near surface layer of the long drilling Core GMGS2-16. Moreover, these members have been found predominant in other known gas hydrate bearing cores, and the dominant of MBGB has even been found significantly related to gas hydrate occurrence. Therefore,a high possibility for the existing of gas hydrate underlying Core DH_CL_11 is inferred, which is consistent with the geochemical analyses. In all, combined geochemical and microbiological analyses are more informative in characterizing sediments from gas hydrate-associated areas in the South China Sea.

The influence factors of gas-bearing and geological characteristics of Niutitang Formation shale in the southern margin of Xuefeng Mountain ancient uplift: A case of Well Huangdi 1

In order to evaluate the geological characteristics and gas-bearing factors of Niutitang Formation within the Lower Cambrian of northern Guizhou,the Huangping area located at the southern edge of the ancient uplift belt of Xuefeng Mountain was selected as the target area,and Well Huangdi 1 was drilled for the geological survey of shale gas.Through geological background analysis and well logging and laboratory analysis such as organic geochemical test,gas content analysis,isothermal adsorption,and specific surface area experiments on Well Huangdi 1,the results show that the Niutitang Formation is a deep-water shelf,trough-like folds and thrust fault.The thickness of black shale is 119.95 m,of which carbonaceous shale is 89.6 m.The average value of organic carbon content is 3.55%,kerogen vitrinite reflectance value is 2.37% and kerogen type is sapropel-type.The brittle mineral content is 51%(quartz 38%),clay mineral content is 38.3%.The value of porosity and permeability are 0.5%and 0.0014 mD,which the reservoir of the Niutitang Formation belongs to low permeability with characteristics of ultra-low porosity.The gas content is 0.09‒1.31 m^3/t with a high-value area and a second high-value area.By comparing with the geological parameters of adjacent wells in the adjacent area,the accumulation model of“sediment control zone,Ro control zone,structure controlling reservoir”in the study area is proposed.Therefore,deep-water shelf-slope facies,Ro is between high maturity-early stage of overmaturity and well-preserved zones in the Niutitang Formation in this area are favorable direction for the next step of shale gas exploration.

Major progress in the natural gas exploration and development in the past seven decades in China

China has made significant progress in the exploration and development of natural gas in the past 70 years,from the gas-poor country to the world’s sixth largest gas production country.In 1949,the annual gas output in China was 1117×104 m3,the proved gas reserves were 3.85×108 m3,and the average annual gas consumption and available reserves of per person were 0.0206 m3 and 0.7107 m3,respectively.By 2018,the average domestic annual gas production per person was 114.8576 m3 and the reserves were 12011.08 m3,and the average domestic annual gas production and reserves per person in the past 70 years increased by 5575 times and 16900 times,respectively.The exploration and development of large gas fields is the main way to rapidly develop the natural gas industry.72 large gas fields have been discovered in China so far,mainly distributed in three basins,Sichuan(25),Ordos(13)and Tarim(10).In 2018,the total gas production of the large gas fields in these three basins was 1039.26×108 m3,accounting for 65%of the total gas production in China.By the end of 2018,the cumulative proved gas reserves of the 72 large gas fields had amounted to 124504×108 m3,accounting for 75%of the total national gas reserves(16.7×1012 m3).New theories of natural gas have promoted the development of China’s natural gas industry faster.Since 1979,the new theory of coal-derived gas has boosted the discovery of gas fields mainly from coal-measure source rocks in China.In 2018,the gas production of large coal-derived gas fields in China accounted for 50.93%and 75.47%of the total national gas production and total gas production of large gas fields,respectively.Guided by shale gas theories,shale gas fields such as Fuling,Changning,Weiyuan and Weirong have been discovered.In 2018,the total proved geological reserves of shale gas were 10455.67×108 m3,and the annual gas production was 108.8×108 m3,demonstrating a good prospect of shale gas in China.