Figure 5- 18 Schematic Diagram of Global Shale Gas Exploration and Development Situation
I. Present Situation of Shale Gas Exploration and Development
1. Present situation of shale gas exploration and development in North America
North America is the earliest area where shale gas was discovered in the world. 182 1 year, 1 shale gas well was drilled in Devonian shale in the eastern United States, which opened the prelude to the development of world natural gas industry. 19 14 discovered the first shale gas field-Dasha gas field. 198 1 year, george mitchell, who is known as the father of Barnett shale gas, carried out large-scale fracturing on Well C. w. slay 1 in Barnett shale and achieved success, thus achieving a real breakthrough in shale gas development. Compared with the world oil discovery, shale gas was discovered nearly 40 years earlier. By the end of 2009, North America was still the most successful area for shale gas exploration and development in the world. Gas-bearing shale was found in Paleozoic and Mesozoic strata in about 50 basins, and shale gas was produced in nearly 10 basins, with more than 50,000 development wells with a depth of 2500-4500m；. In 2009, the output was 1000× 108m3, accounting for 12% of the total natural gas production in North America, which made North America enter a new era of natural gas prosperity.
(1) Early exploration and development stage of shale gas (182 1 ~ 1975)
182 1 year, a well was drilled in the Devonian Dunkirk shale in the Appalachian basin in the eastern United States, with a depth of only 2 1m, and natural gas was obtained from the Devonian Perrysbury Formation Dunkirk shale, with a depth of 8.23m m. This well became the first shale gas well in North America and the first commercial shale gas well in the world. The natural gas produced by this well meets the lighting and part of life in Fredonia, and it was supplied to 1858 for 37 years. With the increasing demand for natural gas in the United States, the exploration and development of shale gas once heated up, and a lot of shallow drilling was carried out on Devonian black shale. 1863, low-yield gas flow was found in Devonian and Mississippi shale in Illinois basin in the eastern United States. 1870 to 1900 The exploration and development scope covers the eastern states or regions of the United States, such as new york, Pennsylvania, Ohio, Kentucky and Virginia. 19 14 years, when Devonian Ohio shale was drilled in Appalachian basin, the high-yield gas flow with daily gas production of 2.83× 104m3 was obtained, and the world's first shale gas field, BigSandy gas field, was discovered. 1926 the gas-bearing range of the large sandy gas field expanded from the east to the west of the Appalachian basin, which was known to the world at that time. At present, about 1 10,000 wells have been drilled in large sandy gas fields. In 2008, the average daily gas production of the highest single well was 283 1.2m3, and the gas production was 15.2× 108 m3, making it the 20th gas field in the United States (EIA, 2009, quoted from the US Department of Energy, etc.). BigSandy gas field is an important achievement in early exploration and development of shale gas.
(2) Key stage of shale gas geological theory and exploration and development technology (1975 ~ 1989)
Before the middle of the 20th century, the exploration and development of shale gas in the United States were mainly concentrated in the Appalachian, Michigan and Illinois basins in the eastern region, with Devonian and Mississippi black shale as the target beds. Except for the Ohio shale sandy gas field in Appalachian basin and the antrim shale gas field in Michigan basin, a large number of other wells have no commercial gas flow or only low-yield gas flow, which makes it impossible to carry out large-scale commercial development. In view of the above difficulties, and in response to the oil crisis that has already occurred, since the late 1970s, the US Department of Energy and other government agencies and related enterprises have invested a lot of money to start the research project on shale gas geological theory and exploration and development technology (ESGP) for the eastern United States, and carried out a series of theoretical and technical studies from geology and geochemistry to gas reservoir engineering, which confirmed the gas production capacity and huge resource potential of black shale in the eastern region represented by Devonian and Mississippi systems in the Appalachian Basin, and formalized shale gas resources.
During the same period (1980s-early 1990s), GTI focused on the resource potential of shale gas in the United States and enhanced oil recovery technology. From 65438 to 0980, the American government promulgated and implemented the tax subsidy policy of Article 29 of the Energy Unexpected Profit Act, which played an important role in promoting the development of shale gas in the United States. During this period, Appalachia, Michigan and other basins have achieved large-scale development of shale gas and steady growth of production (Figure 5- 19). It is particularly noteworthy that George P.Mitchell, the father of shale gas revolution, drilled MEC 1C by virtue of 18 years of shale gas mining technology research and exploration and development practice. Well W.Slay 198 1 year, Mississippi shale in Fort Worth basin in south-central United States, nitrogen foam fracturing. The industrial exploitation of Barnett shale gas was successfully realized, and the shale gas field in the east of Newark (1982) was discovered, which quickly pushed the shale gas producing area from the eastern United States to the south-central region. Cumulative gas production of mec1c. W.Slay is 600×104m3 from 198 1 to 1993; 1995 is subjected to large-scale gel secondary fracturing again, and gas production is 82×104m3 in two and a half years; 1998 shut in the well again and carry out the third sand fracturing. In recent 10 years, the cumulative gas production is 2850× 104m3, and the daily gas production is still around 0.9× 104m3. At present, the shale gas field in the east of Newark is the largest gas field in the United States. The proven recoverable reserves of natural gas are 7400× 108m3, and the natural gas output in 2008 is 460.2× 108m3. From 1979 to 1990, the shale gas production in the United States increased by 2.5 times.
(3) Great development stage of shale gas (1990 ~ 2000)
From 1990 to 10 in 2000, shale gas became the most active natural gas development target in the United States. With the progress of drilling and completion technology, the breakthrough of large-scale hydraulic fracturing technology and the large-scale construction of gas pipelines, large-scale shale gas exploitation has been realized in Ohio, New Albany, Barnett and Lewis in Fort Worth basin, and the shale gas production in the United States has increased significantly. By 2000, there were 28,000 shale gas wells, and the annual shale gas output exceeded 100×65438+.
Figure 5- 19 Annual shale gas production change in the United States
(4) Rapid development stage of shale gas (2000-2006)
With the popularization and application of horizontal well drilling and completion, large-scale hydraulic fracturing and repeated fracturing, and the large-scale development of barnett shale gas in Fort Worth Basin, shale gas development in the United States has entered a rapid development stage. In 200 1 year, the number of wells in barnett shale gas area of Fort Worth Basin exceeded 1000, and the annual gas production reached 38.2× 108m3. In 2004, Southwest Energy Company discovered Fayetteville shale gas area in Akoma Basin, and the annual output of barnett shale gas in Fort Worth Basin exceeded 100× 108m3 (. In the five years from 2000 to 2006, the shale gas production in the United States doubled again, with the annual output exceeding 200× 108m3.
(5) High-speed development stage of shale gas (2007-present)
In recent years, with the innovation of shale gas geological understanding, the continuous breakthrough of horizontal well drilling and completion, large-scale hydraulic fracturing, graded fracturing and multi-well synchronous fracturing, and the large-scale popularization and application of "factory-style" batch production operation mode, shale gas in North America has entered a high-speed development stage, surpassing tight sandstone gas and coalbed methane. At present, shale gas has been found in 46 sets of shale in more than 50 basins in the eastern, south-central and southwestern United States and western Canada, covering almost all marine source rocks in North America (Figure 5-20). Shales with annual shale gas output exceeding 50× 108m3 include Woodford(52× 108m3), Montney(62× 108m3), Haynesville (93× 108m3) and Fayettville (/kloc-0). The development depth of shale gas has deepened from the early180 ~ 2,000m to 2,500 ~ 4,500m. When a single basin reaches 6000m, the number of production wells has increased by 3,500 ~ 4,500 (by 10% ~ 15%) in recent years, reaching more than 50,000 in 2009. Breakthroughs in hydraulic fracturing and other technologies have reduced the cost of reservoir reconstruction by 65% and increased the ultimate oil recovery by 20%. In the past 10 years, the shale gas production in the United States has increased by nearly 10 times, and has doubled every year in recent years. Canada made a breakthrough in shale gas production in 2007, since it carried out the pilot test of shale gas research and exploration and development in West Canada Basin Group in 2000. In 2009, the above-mentioned output of shale gas in North America reached 65,438+0,000× 65,438+008m3 (including 930× 108m3 in the United States and 70× 108m3 in Canada), and the output of a large number of small and medium-sized companies was not included (ARI, 2065,438+)
Figure 5-20 Distribution Map of Main Gas-bearing Shales in North America
Figure 5-2 1 Gas Production Statistics of Major Shales in North America
2. Present situation of shale gas exploration and development in China
Shale gas is not new in China (Wang Lansheng et al., 2009). Since natural gas was first discovered in Qiong 1 well in Sichuan Basin in 1667, especially since 1960s, shale gas or shale fractured gas reservoirs have been continuously discovered in almost all oil-bearing basins such as Songliao, Bohai Bay, Sichuan, Ordos and Qaidam. Well Wei-5, which was drilled in Weiyuan Structure 1966 in Sichuan Basin, obtained 2.46× 104m3 daily gas from the shale of Qianzhusi Formation of Cambrian in 2795 ~ 2798m, which became a typical shale gas production well discovered in China in the early days. Since 2000, the China government and related enterprises have attached great importance to the exploration and development of shale gas and paid close attention to the development trend of shale gas in North America. In recent years, the exploration and development of shale gas has been put on the important agenda.
(1) Basic Geological Research of Shale Gas
From June 2008 to October 2008 10, China petroleum exploration and development research institute drilled the first shale gas geological well in China-Changxin 1 well, obtained a lot of shale gas geological information, and made a clear judgment on the shale gas prospect in the southern Sichuan basin and the upper Yangtze region.
In June 5438+February, 2009, the Ministry of Land and Resources and China Geo University drilled a geological survey well-Yu Ye 1 in the east of Sichuan Basin, and explored the shale gas exploration prospect in areas where shale strata are widely exposed and high-steep structures are complex.
On July 20 10, China Petroleum Exploration and Development Research Institute and China Petroleum Southwest Oil and Gas Field Company comprehensively applied new technologies, such as gamma ray spectrometer, element capture instrument, ground penetrating radar and land laser three-dimensional full information scanner, to carry out the geological survey and actual measurement of Paleozoic shale outcrops in southern China, and established the first digital standard profile of marine shale strata in China in Changning area, Sichuan Basin-the shale stratigraphic profile of Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Shuanghe, Changning.
(2) International cooperation and exploration and development
In 2006, China Petroleum and American Xintian Petroleum Company held the first international symposium on shale gas, and in 2007, a joint study on shale gas potential and development feasibility in Weiyuan area was further carried out. In 2008, the Ministry of Land and Resources established the shale gas resource potential and favorable area optimization projects in key areas of China in the special project of national strategic oil and gas resources investigation and evaluation. Domestic oil companies, such as China Petroleum, began to conduct extensive exchanges and constituency evaluation with companies such as Dan Wen, ExxonMobil, ConocoPhillips and Shell.
In 2009, China Petroleum organized experts from the United States, Norway and other countries to participate in the international symposium on shale gas, started the first international cooperation exploration and development project of shale gas in China with Shell in Fushun-Yongchuan block of Sichuan Basin, and took the lead in developing China shale gas industrial production pilot zone in Weiyuan-Changning and Zhaotong of Sichuan Basin.
During US President Barack Obama's visit to China in June 5438+065438+ 10, 2009, he signed a Memorandum of Understanding on Cooperation in Shale Gas Field with China. 20 10 China Petrochemical and BP began to jointly exploit shale gas in Kaili, Guizhou and Huangqiao, northern Jiangsu. China Petroleum cooperates with ConocoPhillips and Statoil to carry out shale gas prospect assessment and exploration and development in the south-central Sichuan Basin. 20 10 Sichuan Wei-20 1 Well achieved high-yield gas flow in Cambrian and Silurian shales, realizing the first industrialization breakthrough of shale gas in China.
The Ministry of Land and Resources, petroleum enterprises, relevant scientific research institutes and schools have carried out the construction of shale gas resources investigation and constituency evaluation demonstration area in the Yangtze River area of China. The goal is to conduct a comprehensive and systematic investigation and evaluation of shale gas resources in China in the next 10 year, and select 20 ~ 30 favorable exploration and development zones in China by 2020 to form a certain shale gas production capacity.
In a word, drawing lessons from the experience of shale gas exploration and development in North America and extensive international exchanges and cooperation, China has carried out the construction of pilot zones for shale gas industrialization exploration and development in Paleozoic marine shale strata in many southern regions, and is carrying out basic research and preliminary evaluation of shale gas in Yangtze, Ordos, Tarim, Bohai Bay and Songliao basins or regions. Using geological analogy, the shale gas resource potential in China is predicted. China's shale gas exploration and development and related research started late and is still in its infancy.
3. Present situation of shale gas exploration and development in other areas
Since 2005, shale gas exploration and development has gradually expanded from North America to the whole world. In 2007, Europe launched the six-year European Shale Gas Project (GASH), which was funded by the industry and assisted by the German National Geological Laboratory, with the aim of evaluating the shale gas resources in Europe and optimizing the basin. At present, shale rich in organic matter has been found in five basins, and the shale gas resources are preliminarily estimated to be 30×10/2m3 (ari, 20 10). At least 40 companies including ExxonMobil, Dan Wen, Total, ConocoPhillips and Shell are looking for shale gas in Europe (Vello et al., 2009). From 2009 to 20 10, companies such as Statoil, Chesapeake and Sasol jointly evaluated the shale gas prospects in South Africa and obtained the right to explore shale gas resources in Karoo Basin. Australian Beach Oil Company has discovered organic shale in 7 basins in Oceania, which has great potential for early evaluation. It plans to develop shale gas in Cooper Basin, and has made a single-well industrial breakthrough in New Zealand. Many countries in Asia have carried out investigations and pilot tests on shale gas resources, and the exploration and development of shale gas in China has achieved remarkable results.
Second, the global shale gas resource potential
It is predicted (Rogne, 1997) (Li Jianzhong et al., 2009; Rogner, 1997), the global shale gas resource is 456.2×10/2m3 (Table 5- 1 1), which is equivalent to coalbed methane (256×1kloc). Shale gas resources are mainly distributed in North America, Central Asia and China, the Middle East and North Africa, Latin America and the former Soviet Union. At present, in addition to the United States and Canada, China, Australia, Germany, France, Sweden, Poland and other countries are also carrying out research, exploration and development of shale gas.
Table 5- 1 1 Global Distribution of Shale Gas Resources
Globally, except for sub-Saharan Africa, there may be less shale gas resources in Europe. So far, only North America has conducted commercial exploration and development, and there is a reliable reserve conclusion. Nevertheless, according to experience, Rogner's (1997) estimation of global shale gas resources is conservative (AEI, 2009). Take North America as an example. In 2008, Tristone Capital evaluated nine shale gas areas, including Barnett, Deep Bossier, Haynesville, Fayetteville, Woodford, Marcellus, Montney, HornRiver(Muskwa) and UticaGothic in Canada. If the risk factors are not taken into account, the recoverable resources in these nine areas reach 265,438+0× 65,438+0,065,438+0.2m3 (anonymous, 2008, quoted from Vello et al., 2009). Recently, Advanced Resources International (2009) evaluated the resources of seven shale gas basins in North America, including barnett, Fayetteville, Woodford, marcellus, Haynesville, Monteny and Horn River. Its original shale gas resources are about146×1012m3, and its recoverable resources are 20×10/2m3. Among them, the original shale gas resources of five shale gas basins in the United States, such as Barnett, Fayetteville, Woodford, marcellus and Haynesville, reached107×1012m3, and the recoverable resources were13×10.
According to the resource evaluation results of Canadian Unconventional Natural Gas Association (CSUG), the original shale gas resources in Canada are more than 42.5×1012m3 (Dawson, 2008, 2009, quoted from Chalmsar et al., 2008), which exceeds the conventional natural gas resources in Canada12× 6544. Among them, BC province has the largest shale gas resources, reaching more than 28× 10 12m3. Kuuskraa(2009) estimated that the original shale gas resources in Montney and Horn River basins were 39× 10 12m3, and the recoverable resources were 7×10/2m3.
Third, the shale gas resource potential in China.
1. Distribution characteristics of organic-rich shale
China marine organic-rich shale is widely distributed and thick, and mainly developed in the Paleozoic Doushantuo Formation (Z2), Qianzhusi Formation (1), Dachengsi Formation (O 1), Wufeng Formation-Longmaxi Formation (O3-S 1) and Luofu Formation (D2). The most developed shales are distributed from the top of the Lower Cambrian and Upper Ordovician to the bottom of the Lower Silurian, especially in the Yangtze Craton.
(1) Lower Cambrian marine shale
The middle and upper Yangtze region is well developed, and the organic matter type is sapropelic mixed type. Seen from the sedimentary environment, the marine shale of the Lower Cambrian is most developed in the three deep-water shelf areas of East Sichuan-West Hubei, South Sichuan and Hunan-Guizhou, with an average thickness of 100m and an average TOC value of about 8%. The marine shale of Lower Cambrian in Sichuan Basin is developed in the whole basin, mainly siliceous shale, carbonaceous shale, silty shale and black shale, with an average thickness of 1.39m and an average TOC value of 1.0% ~ 5.5%. Shale buried in the south of the basin is shallower than 4000m. ..
(2) Upper Ordovician-Lower Silurian marine shale
Widely distributed in southeastern Sichuan, northeastern Sichuan, western Hubei, eastern Chongqing and the middle and lower reaches of the Yangtze River. The main types are black shale, carbonaceous shale, black graptolite shale and calcareous shale, with an average thickness of 1.20m and an average TOC value of about 4%. Kerogen is sapropelic. Upper Ordovician-Lower Silurian marine shale in Sichuan Basin is well developed in southern and eastern Sichuan. According to the statistics of marine shale from Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation in Shuanghe, Changning, Sichuan Basin, the thickness of black shale from Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation in southern Sichuan is more than 308 meters, and the organic matter type is sapropelic, with an average TOC of 2.94% and a maximum TOC of 8.75%.
(3) Carbonaceous shale of marine and lacustrine coal measures.
Such rocks are widely distributed in North China, South China and Tarim Basin (Table 5- 13). The northern part is mainly developed in Tianshan-Mengxing Trough. The thickness of Shanxi Formation-Taiyuan Formation-benxi formation shale in Ordos Basin is 40 ~ 120 m, and the thickness of single layer is not large, mostly alternating with coal seam, tight sandstone and even thin limestone. The maximum thickness of Carboniferous Dishuiquan Formation carbonaceous shale in Junggar Basin is 249 meters, and the cumulative thickness of Permian Lucaogou Formation black shale exceeds 200 meters ... The maximum thickness of Carboniferous Longtan Formation (P2) in southern China is 670 meters, and its distribution area is about 30×104 ~ 50×104km2. Among them, the shale thickness of the upper Permian Longtan Formation in Yunnan, Guizhou and Guangxi is 20 ~ 60m, that of the upper Permian shale in Sichuan Basin is 10 ~ 125m, that of central and southwestern Sichuan is 80 ~1/0m, and that of northwest, north and northeast Sichuan is thinner, mostly less than. Mesozoic-Cenozoic lacustrine coal-series carbonaceous shale is mainly developed in depressed and faulted lacustrine basins, such as Jurassic in Ordos basin and Junggar basin, Upper Triassic in Sichuan basin and Jurassic in Turpan-Hami basin, with a thickness of 50-400 m and a maximum thickness of1000 m. ..
Table 5- 12 Distribution of Marine Shales in China
Table 5- 13 Land-sea interaction and distribution of coal-bearing carbonaceous shale in China
Generally speaking, China marine and Mesozoic lacustrine carbonaceous shale, except the upper Yangtze and Yunnan, Guizhou and Guangxi regions, has a small single-layer thickness, often interbedded with coal, tight sandstone and even limestone, and the average single-layer thickness is generally less than 15m. It will be a great challenge to develop this thin coal shale gas alone, and it is an effective new development method to jointly develop multi-purpose layers such as shale gas, tight gas and coalbed methane.
Lacustrine shale is mainly distributed in continental oil and gas basins with the widest sedimentary range (Table 5- 14). Statistics show that at present, more than 80% of oil and gas reserves in China come from lacustrine source rocks. Thick lacustrine organic-rich shale was deposited in Mesozoic-Cenozoic depression basins such as Songliao and Ordos and Cenozoic fault basins in Bohai Bay. For example, Nenjiang Formation and Qingshankou Formation in Songliao Basin are well developed. Nenjiang Formation is distributed stably in the whole basin, and the thickness of the central depression is more than 250 meters. The first member of Qingshankou Formation is almost all black shale in the central depression, with a thickness of 60-80 m, kerogen type I-II and Ro value of 0.9%- 1.8%.
Table 5- 14 Distribution of lacustrine shale in China
The Chang 7 member of Yanchang Formation in Ordos Basin is mainly composed of deep lacustrine deposits. The average thickness of organic-rich shale is 20 ~ 40m, the distribution area is over 4× 104km2, the average organic carbon content is as high as 14%, the kerogen type is Ⅰ-Ⅱ, and the Ro value is 0.6% ~ 1.2%. Recently, a large number of tight oil have been discovered in this lacustrine shale formation. The oil layer is a compact siltstone interlayer with a thickness of 10 ~ 20m, a porosity of 10.2% and a permeability of 0.2 1× 10-3 μm 2. There are nearly 200 industrial oil and gas wells with an average output of 8.6t/d, which is very similar to the tight oil found in Bakken shale in Willis-Burton Basin in North America. Bakken shale is a kind of shale rich in organic matter, the thickness is less than 15m, the TOC value is as high as 14% ~ 18%, and the Ro value is 1. 1% ~ 1.3%. The porosity of the main reservoir is 10% ~ 13%, the permeability is less than 1× 10-3μm2, the thickness is 5 ~ 15m, and the area is about 75563km2. In 2008, USGS estimated that the geological resources of shale oil were 24 1× 6538.
2. Potential of shale gas resources in China.
Many scholars or institutions have predicted the shale gas resource potential in China, and the overall evaluation is optimistic (Zou Cai et al., 2010a; Li Jianzhong et al., 2009; Liu Chenglin et al., 2004; Zhu Hua et al., 2009).
The exploration and development of shale gas in China is still in the primary stage, and the information that can be used to predict the potential of shale gas resources is very limited. Although the development scale and shale quality of organic-rich shale in different regions of China are broadly similar, the formation and enrichment of shale gas in different regions are different due to the complex geological conditions in China, especially the tectonic evolution, sedimentary environment and thermal evolution process. Paleozoic marine organic-rich shale in China has a wide distribution range, large continuous thickness and high organic content, but it has a high degree of evolution and many structural changes. Mesozoic and Cenozoic lacustrine organic-rich shales vary widely in lateral direction, and are mainly composed of thick mudstone or interbedded sandstone and mudstone, with moderate organic abundance and low thermal maturity.
Based on geological analogy, the shale gas resource potential in China is predicted. The favorable area of Paleozoic marine organic-rich shale in China is 63×104 ~ 90×104km2, and that of Mesozoic and Cenozoic lacustrine organic-rich shale is 23×104 ~ 33×104km2, with an effective thickness of 20 ~ 300m. Ro value is 0.8% ~ 4.5%. It is preliminarily predicted that the shale gas resources in China are 30×1012 ~100×10/2m3. Shale gas technology and economically recoverable resources in China need further study.
There are three particularities in the comparison between shale gas in China and shale gas in North America: First, marine shale has a high degree of thermal evolution (Ro value is 2.5% ~ 5.0%) and strong tectonic activity, so it is necessary to find areas with favorable preservation conditions and avoid outcrops and fault damage areas; Second, the thermal evolution of lacustrine shale is low and its distribution is heterogeneous, so effective development needs targeted technology; Third, the ground is complex, such as mountains and hills, and it is buried deeply (1000 ~ 6000 m), so adaptive technology is needed to reduce the cost. Therefore, the exploration and development of shale gas in China should pay attention to the special geological conditions such as complex surface, buried depth and later preservation, such as the deep buried marine shale in Tarim Basin, the problems of preservation and mountain surface development in some southern areas. Therefore, it is necessary to strengthen the optimization and economic evaluation of favorable areas.