, Volume 36 Issue 3
    

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    油气勘探
  • Shi Baoheng and Xue Chao
    , 2009, 36(3): 1675-0.
    Abstract ( ) Download PDF ( ) Knowledge map Save
    Key scientific and technological problems tackling has promoted the rapid development of China’s natural gas industry. Studies of coal-formed gas theories, which were proposed in 1979 in China, have achieved great advance through four national major key scientific and technological problems tacklings during the "sixth five-year", "seventh five-year", "eighth five-year", and "ninth five-year" plans. The theories of natural gas origin, natural gas accumulation, natural gas (including coal-bed gas) enrichment have provided theoretical and scientific basis for the decision-making and deployment of gas exploration. The close combination of key problems tackling and actual production enhances the effects of exploration, and demonstrates the significance of the theoretical study of key scientific and technological problems tackling. In the 21st century, China’s gas industry enters the phase of rapid development, 12 large gas fields have been discovered and 6 large gas provinces formed, and the recent 30 years see the most proved gas reserves in the history of China. The key factors for the success of China’s gas industry in tackling key problems and rapid development are combination of theories and practices, innovation, and teamwork.
  • Dai Jinxing
    , 2009, 36(3): 1682-0.
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    Since its formation in China 30 years ago, the theory of coal-formed gas has not only opened a new field of coal-formed gas exploration, but also increased the proved reserves of coal-formed gas from 1/10 to 7/10 in the total gas of China; the nation’s proved gas reserves rise sharply from 2 264×108 m3 to 6.4×1012 m3; the annual production of gas rises from 137.34×108 m3 to 760×108 m3; and the nation’s coal-formed gas fields (reservoirs) increases from less than 10 (excluding Taiwan) to 124. After briefing the major developments of China’s coal-formed gas exploration, this paper concentrates on the exploration development of coal-formed gas in Ordos Basin, Tarim Basin and Sichuan Basin where large numbers of fields of coal-formed gas have been discovered. With data of carbon isotopes of alkane, it also demonstrates that some gas fields of controversial origin (Jingbian, Kekeya and Akemomu gas fields) are of, or predominantly, coal-formed gas, and that a few gas reservoirs (Wolonghe, Naxi, Hejiang gas fields) in the Xujiahe Formation coals of Sichuan Basin are oil-type gas.
  • Zhao Wenzhi; Wang Hongjun and Qian Kai
    , 2009, 36(3): 1686-0.
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    The concept of coal measures forming natural gas was proposed by German scholars in the 1940s. By the late 1970s, coal-formed gas accounted for almost 70% of the proved gas reserves in the world. Geological theory of coal-formed gas in China has gone through a process of introduction, absorption, innovation, development and forming into a system. The theoretical system, which covers coal-formed gas (conventional resource) and coalbed gas (non-conventional resource), includes gas source identification, coal-formed gas accumulation and distribution, as well as evaluation and prediction method. It has given good directions for the establishment and development of natural gas industry in China and accelerated the growth of reserves and production of natural gas in the past 30 years. It is also a successful case in satisfying the national need through combining major scientific and technological issues with practice closely.
  • Wang Tingbin
    , 2009, 36(3): 1712-0.
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    The growth of reserves and production was slow before 1982 in China. The tackling of key scientific and technological problems, started from early 1983, leads to the development of natural gas geological theories characteristic of China’s geology and establishes the exploration strategy of finding large and medium gas fields. Exploration and production technologies achieve great improvement and a large number of large gas fields with reserves of over 50BCM and over 100BCM are discovered in Ordos, Tarim, Sichuan, Songliao and other basins. This makes China’s natural gas production and reserves enter the high-speed developing stage. This indicates that tackling key scientific and technological problems in gas exploration is the main factor in increasing gas production and reserves. The current exploration situation shows that 80%-85% of natural gas resources remains unproved, gas-bearing areas are not determined in the Lower Paleozoic of Sichuan Basin and other places, and further exploration is needed in the deep areas of Songliao Basin.
  • Peng Ping’an; Zou Yanrong and Fu Jiamo
    , 2009, 36(3): 1713-0.
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    Hydrocarbon-generation kinetics is of applicable significance in the study of coal-derived gas pool formation. Its research progress in recent years includes: in combination with geothermal history, it is used as a tool to evaluate source rocks dynamically and depict the change of source kitchen with geological time; according to the carbon isotope fractionation kinetics, a more precise model of identifying coal-derived gas is developed, which contains the kinetic relationship among gas compounds; the combination of compositional kinetics and carbon isotopic kinetics leads to the study method of accumulation processes of coal-derived gases, which is constrained precisely by multi kinetic indices; with the reservoir records, generation kinetics is used to study the whole gas life including generation, charge and alteration. The problems that need investigation are generation kinetics of coal-derived gas at low maturity, pressure effects on gas generation, minerals and water influences, and kinetics of residual soluble organic matter at high maturity.
  • Zou Caineng; Tao Shizhen; Zhu Rukai; Yuan Xuanjun; Li Wei; Zhang Guangya; Zhang Xiangxiang; Gao Xiaohui; Liu Liuhong; Xu Chunchun; Song Jiarong and Guohui
    , 2009, 36(3): 1714-0.
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    The comprehensive analysis of geological setting, accumulation condition, trapping mechanism and distribution regularity of oil-gas of the Upper Triassic in Sichuan Basin reveals that the gas accumulation in Xujiahe Formation is a layered lithologic giant gas province. Coal source rocks in layers expelled hydrocarbon evaporatively. Under the setting of the episodic fold-thrusting and compression in the boundary orogen, multi-sources charged quickly and formed a coarse deltaic environment with a large-scale delta plain and a small-scale delta front. In gentle structures, Darcy and non-Darcy flow mechanisms coexist because of the limited buoyancy of low permeability sandstone, thus forming the coexisting oil-gas-water system. This paper classifies the diagenetic facies quantitatively using compaction percentage, cementation percentage and corrosion percentage, and defines eight diagenetic subfacies and twenty diagenetic microfacies. Besides, the origin of diagenetic facies is analyzed by using Ro and formation water parameter. This kind of giant gas province originated mainly from stable large-scale continental depressions, gentle foreland slopes and paralic facies in central China. It is characterized by large-area layered distribution, no obvious trap and cap formation, large-scale resource, low-abundance reserves, and difficult to exploit.
  • Zhang Shuichang; Mi Jingkui; Liu Liuhong and Tao Shizhen
    , 2009, 36(3): 1716-0.
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    The distribution of coal gas pools is controlled by many geological factors in China. The accumulation and pool-forming process of coal measures gas is studied from aspects of structure, source rock evolution, reservoir, pool-forming history, etc. The comparison results show that there are many similarities in geology between the Upper Paleozoic gas pools in Ordos Basin and the Upper Triassic Xujiahe Formation gas pools in Sichuan Basin, and the difference of the gas pools features in the two basins is caused by different structural evolutions and pool-forming processes. In Ordos Basin, water shoved by gas migrated from lower to higher positions in the formation process of the gas pools, and the abnormality of low gas reservoir pressure was caused by the water and gas reversal. In Sichuan Basin, structural traps controlled the gas pools distribution in Xujiahe Formation, lithologic gas pools was found locally, and the main factors for the abnormally high pressure are the quick deposition due to undercompaction, the hydrocarbon generation of source rocks and the structural compression during the Himalayan period.
  • Zhong Ningning and Chen Gongyang
    , 2009, 36(3): 1717-0.
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    The key controls on the gas and oil preferences of coal-bearing strata are discussed from the relationship of material foundation between coal formation and hydrocarbon generation, the variation of the initial gas to oil ratio (GOR) of organic matter in coal-bearing strata, and the feature of coal-bearing sequence related to the formation and evolution of source rocks. The density occurrence pattern of maceral compositions, the effect of GOR redistribution of coal measures in the processes of coalification, and the change of sequence base levels are the key factors for the coal measures being oil-prone or gas-prone. The maceral compositions of major coal-bearing sequences (coal basins) in China can be classified into three patterns, vitrinite liptinite/sapropel assemblage, vitrinite inertinite assemblage and transitional assemblage (intergradation), which represent oil-prone, gas-prone and transitional coal measures, respectively. Due to the control of sequence base level change, the latter two patterns are common. It is natural that gas prone is characteristic of most of the major coal-bearing sequences in China.
  • Luo Xia; Sun Fenjin; Shao Mingli; Wang Zhihong; Zeng Fuying; Zhao Zehui; Xia Li and He Feng
    , 2009, 36(3): 1718-0.
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    The composition and carbon isotope composition of about 150 natural gas samples reveals that natural gases of deep strata in Songliao Basin are derived from multiple sources and the coal-formed gases are widely distributed in the basin. Several gas fields show features of coal-formed gas or contain coal-formed gases, with δ13C2 being larger than -28‰ and δ13CMCC6 being larger than -22‰, such as Shengping gas field in the north of the basin, Xiaohelong and Xiaochengzi gas fields in the south. Organic matter of source rocks in the deep strata is dominantly Type Ⅲ, with a small portion of Type Ⅱ. The average TOC of source rocks in the Shahezi (K1sh) Formation is 1.99%. Sedimentary facies studies of single wells, which penetrated coals of the Shahezi Formation, indicate that these coals are developed in peat swamps of deltaic plain, depressions between fan deltas, coastal shallow lakes, flooding plain etc, and structures are mainly distributed in the boundary of fault depressions, especially in their slope, some in the center of lakes.
  • Zhu Guangyou; Zhang Shuichang; Chen Ling; Yang Haijun; Yang Wenjing; Zhang Bin and Su Jin
    , 2009, 36(3): 1720-0.
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    The formation mechanism of deep effective reservoirs is elaborated based on the analysis of the conditions for forming natural gas accumulations in deep Kuqa Depression. Natural gas charging is closely related to the formation of effective sandstone reservoirs in the deep zone: reservoirs which capture oil and gas in the early period are of better quality during the long burial period; reservoirs which do not capture oil and gas in the early period is compact after deep burial because of compaction. Oil and gas charging before the reservoir is deeply buried significantly inhibits mechanical compaction and fracture closure as well as densification, so the effective pores and fractures will be preserved. The formation conditions of large gas fields in Kuqa Depression are as follows: sufficient coal gas source; great gas generation potential of high-evolution Jurassic source rocks; secondary pores and micro-fissures developed in deep sandstone reservoirs; wide distribution of gypsum-salt cap rock with large thickness; good association of source-reservoir-cap in space; well developed hydrocarbon migration pathways of dominantly faults; high expulsion efficiency; big migration and accumulation coefficient and deep or ultra-deep traps developed below salt structures.
  • Jin Qiang; Song Guoqi and Wang Li
    , 2009, 36(3): 1721-0.
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    Coal-derived gas from the Carboniferous Permian coal-measures is discovered in east Linqing Depression and Jiyang Depression in the Shengli Oilfield. Investigation on the distribution, characteristics, structure and thermal evolution of the coal-measure source rock reveals that there are obvious differences in hydrocarbon generation histories in five structural units including high, uplift, lower uplift, slope and deep sag. The active energy of primary and secondary generations and other parameters from the thermal simulations of coal samples were calculated and associated with the burial histories of the five structural units, establishing the quantitative relations of coal-derived gas generation and geological times. There are 5 coal-derived gas generation models: no generation in the high area at middle-late stage; no generation in the uplift area at late stage; mature to highly mature generation in the lower uplift at late stage; mature to highly mature generation in the slope at late stage; over-mature generation in the deep sag at late stage. Highly mature gas source kitchens are developed in eastern sag of Linqing Depression, southern slope of Huimin Sag, Luojia slope of Zhanhua Sag, eastern slope of Chezhen Sag, and northern slope of Chengdong Uplift; the slopes and their surrounding areas are the most favorable areas for coal-derived gas.
  • Li Jian; Jiang Zhenglong; Luo Xia; Wang Dongliang and Han Zhongxi
    , 2009, 36(3): 1722-0.
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    Carboniferous and Jurassic coal-measure rocks with their relative coal-formed gas are developed in Junggar Basin. Carboniferous source rocks have high organic material abundance, Type Ⅲ organic material, and high maturity. Jurassic source rocks are widely distributed with big thickness and great maturity variety. The Middle and Lower Jurassic are the predominant sources of natural gas, and the potential is large. Carboniferous coal-formed gas is dry gas, its carbon isotope is heavy, the methane carbon isotope composition is about -30‰, the ethane carbon isotope composition is above -28‰, the carbon isotope series is positive (δ13C1<δ13C2<δ13C3<δ13C4). Gas reservoir is self-generating and self-preserving. Gas from the Jurassic source rocks has wide distribution and is wet. Methane carbon isotope composition varies greatly, and the carbon isotope reversal of butane and propane is common, reflecting that natural gas has different maturity and the mixing of different-maturity natural gas originated from the same source results in the light isotopic values of heavy hydrocarbons. The potential of the Carboniferous rocks is huge, and is the major exploration area. Gas from the Jurassic source rocks is distributed widely and the southern margin of the basin is a favorable area.
  • Liu Dehan; Xiao Xianming; Tian Hui; Yang Chun; Hu Anping and Song Zhiguang
    , 2009, 36(3): 1724-0.
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    Many giant gas fields of different origins have been discovered in China, including gases cracked from crude oil, high maturity kerogens and coal-formed gas. These gas fields can be well distinguished based on the petrology of reservoir bitumen and fluid inclusions and the composition of inclusion gas determined by the laser Raman. The oil-cracking gas reservoir is characterized by pyrobitumen with an intermediate phase structure and complicated types of fluid inclusions including gas inclusions, solid bitumen inclusions, aqueous inclusions, even their combination. Under high temperature and high pressure, the methane inclusion from the oil-cracking gas reservoir contains some H2S, CO2, heavy hydrocarbons and bitumen, and immiscible inclusions containing sulphur occur in some reservoirs. There is usually no the intermediate phase pyrobitumen in the gas reservoirs of coal and high maturity kerogen origins because the gases are migrated and accumulated from sources elsewhere, and the fluid inclusions for these gas fields are low abundant and their types are simple, mainly methane inclusions without bitumen and heavy hydrocarbons.
  • Zhang Wenzheng; Yang Hua; Xie Liqin; Huang Sijing and Yang Yihua
    , 2009, 36(3): 1725-0.
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    An experimental device and flowchart were designed to carry out experiments simulating dissolution of anorthites, pyroxenes and amphiboles in acetic acid solution under different temperature and pressure conditions. Anorthites, pyroxenes and amphiboles all show features of erosion and dissolution, with Ca displaying the highest dissolution and Al and Si displaying the lowest dissolution among the major constituent elements. With increase in temperature, the dissolution rates of elements like Ca, Si, and Mg as well as the total dissolution amount of minerals can be remarkably increased, exhibiting a positive temperature effect. However, the dissolution of Al appears to be special, at 50-75 ℃ its dissolution coefficient is higher than that of Si, exhibiting a positive temperature effect, while at 100-125 ℃ its dissolution amount turns out to be low, exhibiting a negative temperature effect. Precipitation can mainly account for the low dissolution of Al at high temperatures. Complexation of acetic acid appears to be favorable for Al migration during the dissolution of alumosilicates at the lower temperature rock-forming stage, but cannot account for Al migration at the higher temperature rock-forming stage.
  • 油气田开发
  • Li Baozhu; Zhu Zhongqian; Xia Jing and Ma Caiqin
    , 2009, 36(3): 1726-0.
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    Kela 2 gas field in Tarim Basin is a rare large-scale full-contained, super-pressured dry gas field in the world, and its development is extremely complicated. After detailed technological research breakthrough, the development concept of drilling few high-production-rate wells is formed, that is, the main producing wells use 177.8 mm (7 in) diameter tubing in order to make full use of the formation energy. The fine 3D geological model of huge thick sandstone reservoirs is built constrained by the lateral reservoir prediction data, sedimentary facies data and so on. And the development mechanism of the super-pressured gas reservoirs has been studied based on this model. The rock deformation effect must be included in the deliverability evaluation. A material balance equation for super-pressured gas reservoirs with aquifer drive is derived for the dynamic reserves calculation, and the reserves derived from the conventional pressure drawdown method is 1.5 to 2.1 times the actual dynamic reserves. A temperature correction method is formed to solve the decline of the wellhead pressure build-up curves of super-pressured gas wells at the later stage, and this method is verified to be credible.
  • 石油工程
  • Zhang Yi; Xian Baoan; Zhao Qingbo; Zhou Weidong and Sun Ping
    , 2009, 36(3): 1727-0.
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    Aerated under-balanced technology is one of the commonly used technologies in coalbed methane (CBM) drilling for protecting the coal seams from pollution. Based on the characteristics of the aerated under-balanced drilling (UBD) for CBM pinnate horizontal wells, the mathematical models for calculating multiphase flow pressure drops both in horizontal wells and in vertical wells are optimized, and the solution to bottom hole under-pressure value and its calculating flow diagram are also proposed. With the established models and the data from a CBM field of Qinshui Basin, the bottom hole under-pressure values were calculated under different gas injection pressures, different gas injection rates, and different mud flow rates. The analysis shows that when the gas injection pressure is constant, the bottom hole under-pressure value increases with the increase of mud flow rate, and the bigger the annular gas injection rate, the smaller the bottom hole under-pressure value; under the optimum gas injection pressure, the bottom hole under-pressure value decreases as the annular gas injection rate increases when the mud flow rate is constant, and the bottom hole under-pressure value increases with mud flow rate when the gas injection rate is constant. By using the calculating models and methods, the optimal parameters of annular gas injection could be acquired according to field requirements of under-balanced drilling.
  • 资源评价与管理
  • Luo Dongkun; Chu Wangtao; Wu Xiaodong and Li Weichao
    , 2009, 36(3): 1728-0.
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    The coalbed methane (CBM) development activities in China are concentrated in the regions with low-permeability coal reservoirs. There are two kinds of drilling technologies: one is the conventional vertical well technology, the other is multi-branch horizontal well technology. Based on these two technologies, firstly, without taking account of the production capacity replacement and aiming at the same well-control area, the economic benefits between the development plan with whole vertical wells and the one with entire multi-branch horizontal wells were compared; and then the comparison of the economic benefits between the whole-vertical-well development plan and the mixed-well-type one was also made, considering the production capacity replacement and aiming at the same designed production capacity. IPP and NPV methods were used to calculate the economic evaluation indices of application of each plan in different CBM prospects, and the technical and economic potentialities of these two technologies were analyzed. The conventional vertical well technology can realize certain economic benefits and it is the preferred technology now, even for some time in the future; the multi-branch horizontal well technology is more suitable for low permeability coal reservoirs and can increase CBM production in these reservoirs, but the risk is high due to high drilling investment, and it cannot be popularized soon until the drilling equipment and technicians are localized gradually.
  • 学术讨论
  • Xu Yongchang; Wang Xiaofeng and Shi Baoguang
    , 2009, 36(3): 1729-0.
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    In the late 1980s, the concept of bio-thermo-catalytic transitional zone gas and early-thermogenic gas were proposed. It was believed that medium- and large-sized gas fields can be formed not only at the high evolution stage of organic matter but also at the low mature stage (i.e. 0.4%≤Ro<0.6%). According to recent researches, the thermal evolution level of low-mature gas should be 0.4%≤Ro<0.8%. Low-mature gas can be identified through four characteristics, including carbon isotopic composition of methane and ethane, light hydrocarbon parameter, geological background and source rock. This paper demonstrates that the Urengoy gas field in west Siberian Basin and gas-bearing areas in the Turpan-Hami Basin belong to the type of low-mature gas, and points out that low-mature gas is mainly related to coal measures. Low-mature gas can be said to be an extension of coal-formed gas. China has great coal resources, and the coal of Ro<0.9% accounts for more than 60%, suggesting that low-mature gas have a good prospect in China.