The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stabili...The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins,were revealed.展开更多
Objective The production of coal fines is very common in the development of coalbed methane（CBM）in the eastern margin of the Ordos Basin,China.A large amount of produced coal fines seriously affect the productivity ...Objective The production of coal fines is very common in the development of coalbed methane（CBM）in the eastern margin of the Ordos Basin,China.A large amount of produced coal fines seriously affect the productivity of CBM wells（Wei Yingchun et al.,2013）.Therefore,the production problems of CBM wells caused by coal fines have attracted extensive attention.展开更多
To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 ...To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 coal outcrops. Additionally, detailed joint measurements of underground coal seams were taken at two coal mines. This study investigated the effects of seam thickness, lithology, and structure on joint development and established the relationship between joint development of coal and rock seams, which allowed predictions of predominant joint densities for the No.5 coal seam in the southeastern margin of the Ordos basin. The results show that outcrop and underground coal seams exhibit the same joint systems as rock seams. The joints are mainly upright. Predominant joints strike 55° on average, followed by joints striking 320°. The joint density of the coal seam is 18.7–22.5 times that of the sandstone seam at the same thickness. The predominant joint density of the No.5 coal seam, controlled by the structure, is 4–20 joints per meter. Joint densities exhibit high values at intersecting areas of faults and folds and decrease values in structurally stable areas. The permeability increases exponentially with increasing density of the predominant joints.展开更多
Compared with the United States,Australia,Canada,and other countries,China's coalbed methane reservoir is featured by low formation pressure,low permeability,low gas saturation,and strong heterogeneity,which not o...Compared with the United States,Australia,Canada,and other countries,China's coalbed methane reservoir is featured by low formation pressure,low permeability,low gas saturation,and strong heterogeneity,which not only increases the difficulty of reservoir stimulation but also restricts the single well production and the recovery efficiency of coalbed methane(CBM).In view of this,the research and application of horizontal drilling and completion technology of CBM at home and abroad are reviewed to provide references and theoretical supports for the advancement of the horizontal well engineering technology of CBM in China.This paper introduces a series of horizontal drilling and completion technologies(e.g.,the well type design,well structure optimization,well trajectory control,wellbore stability,completion optimization,reservoir protection,etc.).The advanced technologies and their adaptability,including screen pipe completion and stimulation with dual-layer tubular strings,radial horizontal well screen pipe completion and magnetic steering drilling,are dialectically discussed in this paper.In addition,a novel integrated engineering mode for the efficient and green development of deep CBM and coal through the underground“well factory”is proposed.The conclusions are as follows:(1)In view of the geological conditions and surface environment of the coal seam in China,the horizontal drilling and completion technologies of high rank coalbed methane should be further refined,and an integrated development for the coal measure gas is required;(2)More efforts should be made to strengthen the innovative research on horizontal drilling&completion technology for low-medium rank coals and the broken coal,so as to identify the efficient development mode for the complex coalbed methane reservoir;(3)When encountering major technical challenges during the green and efficient development of unconventional coal mines such as deep coal mines,low grade coal mines and thin coal seams in China,it is necessary to explore the development mode via in-situ conversion process based on underground“well factory”to realize the integrated green and efficient development of deep CBM and coal;(4)The high quality transformation with low-carbon and green energy in China will not only ensure national energy security,but also achieve the goal of“carbon peaking and carbon neutrality”.展开更多
A reporter for China’s Foreign Tradehas learned from the Ministry of theCoal Industry that China will takethe following steps to develop its coal industryduring the ninth five-Year plan period. 1. To regulate the pol...A reporter for China’s Foreign Tradehas learned from the Ministry of theCoal Industry that China will takethe following steps to develop its coal industryduring the ninth five-Year plan period. 1. To regulate the policy for buildupthe coal industry and to make a good job ofthe comprehensive development of buildinga number of key coal production bases.展开更多
基金The Scientific Research Project under contract No.CCL2021RCPS172KQNthe Formation Mechanism and Distribution Prediction of Cenozoic Marine Source rocks in Qiongdongnan and Pearl River Mouth Basin under contract No.2021-KT-YXKY01+3 种基金the Resource Potential,Accumulation Mechanism and Breakthrough Direction of Potential Oil-rich Sags in Offshore Basins of China under contract No.2021-KT-YXKY-03the National Natural Science Foundation of China(NSFC)under contract No.42372132the Open Foundation of Hebei Provincial Key Laboratory of Resource Survey and Researchthe National Natural Science Foundation of China(NSFC)under contract Nos 42072188,42272205。
文摘The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along with the control factors which impacted the development of thin coal seam groups in offshore lacustrine basins,were revealed.
基金financially supported by the National Natural Science Foundation of China(grants No.41402134 and 41272181)
文摘Objective The production of coal fines is very common in the development of coalbed methane（CBM）in the eastern margin of the Ordos Basin,China.A large amount of produced coal fines seriously affect the productivity of CBM wells（Wei Yingchun et al.,2013）.Therefore,the production problems of CBM wells caused by coal fines have attracted extensive attention.
基金Financial support for this work, provided by the National Science and Technology Major Project (No. 2011ZX05034-001)
文摘To predict joint development characteristics of coal seams, joint characteristics of rock seams from 88field stations were observed and comparisons were made between joint characteristics of coal and rock seams at 10 coal outcrops. Additionally, detailed joint measurements of underground coal seams were taken at two coal mines. This study investigated the effects of seam thickness, lithology, and structure on joint development and established the relationship between joint development of coal and rock seams, which allowed predictions of predominant joint densities for the No.5 coal seam in the southeastern margin of the Ordos basin. The results show that outcrop and underground coal seams exhibit the same joint systems as rock seams. The joints are mainly upright. Predominant joints strike 55° on average, followed by joints striking 320°. The joint density of the coal seam is 18.7–22.5 times that of the sandstone seam at the same thickness. The predominant joint density of the No.5 coal seam, controlled by the structure, is 4–20 joints per meter. Joint densities exhibit high values at intersecting areas of faults and folds and decrease values in structurally stable areas. The permeability increases exponentially with increasing density of the predominant joints.
基金Key Project of Natural Science Foundation of China(NSFC)"Basic Research on three-dimensional design&construction of an underground well factory with complex structures"(No.:52234002),and Innovative Research Group Project of NSFC“Basic Research on Drilling and Completion of Critical Oil and Gas Wells”(No.:51821092).
文摘Compared with the United States,Australia,Canada,and other countries,China's coalbed methane reservoir is featured by low formation pressure,low permeability,low gas saturation,and strong heterogeneity,which not only increases the difficulty of reservoir stimulation but also restricts the single well production and the recovery efficiency of coalbed methane(CBM).In view of this,the research and application of horizontal drilling and completion technology of CBM at home and abroad are reviewed to provide references and theoretical supports for the advancement of the horizontal well engineering technology of CBM in China.This paper introduces a series of horizontal drilling and completion technologies(e.g.,the well type design,well structure optimization,well trajectory control,wellbore stability,completion optimization,reservoir protection,etc.).The advanced technologies and their adaptability,including screen pipe completion and stimulation with dual-layer tubular strings,radial horizontal well screen pipe completion and magnetic steering drilling,are dialectically discussed in this paper.In addition,a novel integrated engineering mode for the efficient and green development of deep CBM and coal through the underground“well factory”is proposed.The conclusions are as follows:(1)In view of the geological conditions and surface environment of the coal seam in China,the horizontal drilling and completion technologies of high rank coalbed methane should be further refined,and an integrated development for the coal measure gas is required;(2)More efforts should be made to strengthen the innovative research on horizontal drilling&completion technology for low-medium rank coals and the broken coal,so as to identify the efficient development mode for the complex coalbed methane reservoir;(3)When encountering major technical challenges during the green and efficient development of unconventional coal mines such as deep coal mines,low grade coal mines and thin coal seams in China,it is necessary to explore the development mode via in-situ conversion process based on underground“well factory”to realize the integrated green and efficient development of deep CBM and coal;(4)The high quality transformation with low-carbon and green energy in China will not only ensure national energy security,but also achieve the goal of“carbon peaking and carbon neutrality”.
文摘A reporter for China’s Foreign Tradehas learned from the Ministry of theCoal Industry that China will takethe following steps to develop its coal industryduring the ninth five-Year plan period. 1. To regulate the policy for buildupthe coal industry and to make a good job ofthe comprehensive development of buildinga number of key coal production bases.
