In the late 1970s,the theory of coal-formed gas began to take root,sprout,develop,and improve in China.After decades of development,a complete theoretical system was finally formed.The theory of coal-formed gas points...In the late 1970s,the theory of coal-formed gas began to take root,sprout,develop,and improve in China.After decades of development,a complete theoretical system was finally formed.The theory of coal-formed gas points out that coal measures are good gas source rocks,with gas as the main hydrocarbon generated and oil as the auxiliary.It has opened up a new exploration idea using coal-bearing humic organic matter as the gas source,transforming the theoretical guidance for natural gas exploration in China from“monism”(i.e.oil-type gas)to“dualism”(i.e.coal-formed gas and oil-type gas)and uncovering a new field of natural gas exploration.Before the establishment of the coal-formed gas theory,China was a gas-poor country with low proved gas initially-in-place(merely 2264.33×10^(8)m^(3))and production(137.3×10^(8)m^(3)/a),corresponding to a per capita annual consumption of only 14.37 m^(3).Guided by the theory of coal-formed gas,the natural gas industry of China has developed rapidly.By the end of 2023,China registered the cumulative proved gas initially-in-place of 20.90×10^(12)m^(3),an annual gas production of 2343×10^(8)m^(3),and a per capita domestic gas consumption reaching 167.36 m^(3).The cumulative proved reserves initially-in-place and production of natural gas were dominated by coal-formed gas.Owing to this advancement,China has transformed from a gas-poor country to the fourth largest gas producer in the world.The coal-formed gas theory and the tremendous achievements made in natural gas exploration in China under its guidance have promoted China from a gas-poor country to a major gas-producing country in the world.展开更多
In the global wave of energy transition and low-carbon development,China Petroleum Enterprise Association,together with the University of International Business and Economics,China University of Petroleum-Beijing,Sout...In the global wave of energy transition and low-carbon development,China Petroleum Enterprise Association,together with the University of International Business and Economics,China University of Petroleum-Beijing,Southwest Petroleum University,and other institutions,released four significant blue books on April 17:Annual Operating Report of China’s Natural Gas Industry Blue Book(2024-2025),China Oil&Gas Industry Development Analysis and Outlook Blue Book(2024-2025),China Low-Carbon Economy Development Report Blue Book(2024-2025),and Refined Oil and New Energy Development Report Blue Book(2024-2025).This series of blue books provides a comprehensive and high-level analysis of the development,issues,and trends in the oil and gas industry,offering a detailed depiction of the China Oil&Gas industry and its progress towards low-carbon development.展开更多
There are various types of natural gas resources in coal measures,making them major targets for natural gas exploration and development in China.In view of the particularity of the whole petroleum system of coal measu...There are various types of natural gas resources in coal measures,making them major targets for natural gas exploration and development in China.In view of the particularity of the whole petroleum system of coal measures and the reservoir-forming evolution of natural gas in coal,this study reveals the formation,enrichment characteristics and distribution laws of coal-rock gas by systematically reviewing the main types and geological characteristics of natural gas in the whole petroleum system of coal measures.First,natural gas in the whole petroleum system of coal measures is divided into two types,conventional gas and unconventional gas,according to its occurrence characteristics and accumulation mechanism,and into six types,distal detrital rock gas,special rock gas,distal/proximal tight sandstone gas,inner-source tight sandstone gas,shale gas,and coal-rock gas,according to its source and reservoir lithology.The natural gas present in coal-rock reservoirs is collectively referred to as coal-rock gas.Existing data indicate significant differences in the geological characteristics of coal-rock gas exploration and development between shallow and deep layers in the same area,with the transition depth boundary generally 1500-2000 m.Based on the current understanding of coal-rock gas and respecting the historical usage conventions of coalbed methane terminology,coal-rock gas can be divided into deep coal-rock gas and shallow coalbed methane according to burial depth.Second,according to the research concept of“full-process reservoir formation”in the theory of the whole petroleum system of coal measures,based on the formation and evolution of typical coal-rock gas reservoirs,coal-rock gas is further divided into four types:primary coal-rock gas,regenerated coal-rock gas,residual coal-rock gas,and bio coal-rock gas.The first two belong to deep coal-rock gas,while the latter two belong to shallow coal-rock gas.Third,research on the coal-rock gas reservoir formation and evolution shows that shallow coal-rock gas is mainly residual coal-rock gas or bio coal-rock gas formed after geological transformation of primary coal-rock gas,with the reservoir characteristics such as low reservoir pressure,low gas saturation,adsorbed gas in dominance,and gas production by drainage and depressurization,while deep coal-rock gas is mainly primary coal-rock gas and regenerated coal-rock gas,with the reservoir characteristics such as high reservoir pressure,high gas saturation,abundant free gas,and no or little water.In particular,the primary coal-rock gas is wide in distribution,large in resource quantity,and good in reservoir quality,making it the most favorable type of coal-rock gas for exploration and development.展开更多
Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the...Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the integrity of gas content within samples and are often constrained by estimation errors inherent in empirical formulas,which results in inaccurate gas content measurements.This study introduces a lightweight,in-situ pressure-and gas-preserved corer designed to collect coal samples under the pressure conditions at the sampling point,effectively preventing gas loss during transfer and significantly improving measurement accuracy.Additionally,a gas migration model for deep coal mines was developed to elucidate gas migration characteristics under pressure-preserved coring conditions.The model offers valuable insights for optimizing coring parameters,demonstrating that both minimizing the coring hole diameter and reducing the pressure difference between the coring-point pressure and the original pore pressure can effectively improve the precision of gas content measurements.Coring tests conducted at an experimental base validated the performance of the corer and its effectiveness in sample collection.Furthermore,successful horizontal coring tests conducted in an underground coal mine roadway demonstrated that the measured gas content using pressure-preserved coring was 34%higher than that obtained through open sampling methods.展开更多
Exploration and development of large gas fields is an important way for a country to rapidly develop its natural gas industry.From 1991 to 2020,China discovered 68 new large gas fields,boosting its annual gas output t...Exploration and development of large gas fields is an important way for a country to rapidly develop its natural gas industry.From 1991 to 2020,China discovered 68 new large gas fields,boosting its annual gas output to 1925×108m3in 2020,making it the fourth largest gas-producing country in the world.Based on 1696 molecular components and carbon isotopic composition data of alkane gas in 70 large gas fields in China,the characteristics of carbon isotopic composition of alkane gas in large gas fields in China were obtained.The lightest and average values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become heavier with increasing carbon number,while the heaviest values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become lighter with increasing carbon number.Theδ^(13)C_(1)values of large gas fields in China range from-71.2‰to-11.4‰(specifically,from-71.2‰to-56.4‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-18.9‰for coal-derived gas,and from-35.6‰to-11.4‰for abiogenic gas).Based on these data,theδ^(13)C_(1)chart of large gas fields in China was plotted.Moreover,theδ^(13)C_(1)values of natural gas in China range from-107.1‰to-8.9‰,specifically,from-1071%o to-55.1‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-13.3‰for coal-derived gas,and from-36.2‰to-8.9‰for abiogenic gas.Based on these data,theδ^(13)C_(1)chart of natural gas in China was plotted.展开更多
In 2024,China’s natural gas sector experienced robust growth in both supply and demand dynamics,as apparent consumption increased rapidly,reaching 426.05 billion m^(3),reflecting a 8.0%year-on-year surge.Domestic gas...In 2024,China’s natural gas sector experienced robust growth in both supply and demand dynamics,as apparent consumption increased rapidly,reaching 426.05 billion m^(3),reflecting a 8.0%year-on-year surge.Domestic gas increase in reserves and production persistently progressed,hitting a production volume of 249.27 billion m^(3) and achieving a six-year consecutive increment exceeding 13 billion m^(3).Imported natural gas continues to grow,with the combined volume of imported pipeline gas and imported LNG expected to reach 180.57 billion m^(3) in 2024,marking an 11.0%year-on-year increase.In 2025,China’s policy aimed at stabilizing growth will continue to exert its influence,maintaining a recovery trend in the national economy with steady progress.The natural gas market is expected to experience rapid growth,with demand primarily driven by industrial fuel and city gas,while the proportion of demand for power generation is anticipated to increase.The national natural gas demand growth rate is projected to be approximately 6%in 2025.展开更多
Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals th...Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals the fluid characteristics,gas accumulation control factors and accumulation modes in the Upper Paleozoic coal reservoirs.The study indicates findings in two aspects.First,the 1500-1800 m interval represents the critical transition zone between open fluid system in shallow-medium depths and closed fluid system in deep depths.The reservoirs above 1500 m reflect intense water invasion,with discrete pressure gradient distribution,and the presence of methane mixed with varying degrees of secondary biogenic gas,and they generally exhibit high water saturation and adsorbed gas undersaturation.The reservoirs deeper than 1800 m,with extremely low permeability,are self-sealed,and contains closed fluid systems formed jointly by the hydrodynamic lateral blocking and tight caprock confinement.Within these systems,surface runoff infiltration is weak,the degree of secondary fluid transformation is minimal,and the pressure gradient is relatively uniform.The adsorbed gas saturation exceeds 100%in most seams,and the free gas content primarily ranges from 1 m^(3)/t to 8 m^(3)/t(greater than 10 m^(3)/t in some seams).Second,the gas accumulation in deep coals is primarily controlled by coal quality,reservoir-caprock assemblage,and structural position governed storage,wettability and sealing properties,under the constraints of the underground temperature and pressure conditions.High-rank,low-ash yield coals with limestone and mudstone caprocks show superior gas accumulation potential.Positive structural highs and wide and gentle negative structural lows are favorable sites for gas enrichment,while slope belts of fold limbs exhibit relatively lower gas content.This research enhances understanding of gas accumulation mechanisms in coal reservoirs and provides effective parameter reference for precise zone evaluation and innovation of adaptive stimulation technologies for deep resources.展开更多
1.Introduction With the increasing demand for petroleum and natural gas resources,along with technological advancements in exploration and production,the primary frontier of oil and gas resources has shifted from conv...1.Introduction With the increasing demand for petroleum and natural gas resources,along with technological advancements in exploration and production,the primary frontier of oil and gas resources has shifted from conventional oil and gas development to the domains of“Two Deeps,One Unconventional,One Mature,”which include deep onshore,deepwater,unconventional resources,and mature oilfields[1].展开更多
A sensor,serving as a transducer,produces a quantifiable output in response to a predetermined input stimulus,which may be of a chemical or physical nature.The field of gas detection has experienced a substantial surg...A sensor,serving as a transducer,produces a quantifiable output in response to a predetermined input stimulus,which may be of a chemical or physical nature.The field of gas detection has experienced a substantial surge in research activity,attributable to the diverse functionalities and enhanced accessibility of advanced active materials.In this work,recent advances in gas sensors,specifically those utilizing Field Effect Transistors(FETs),are summarized,including device configurations,response characteristics,sensor materials,and application domains.In pursuing high-performance artificial olfactory systems,the evolution of FET gas sensors necessitates their synchronization with material advancements.These materials should have large surface areas to enhance gas adsorption,efficient conversion of gas input to detectable signals,and strong mechanical qualities.The exploration of gas-sensitive materials has covered diverse categories,such as organic semiconductor polymers,conductive organic compounds and polymers,metal oxides,metal-organic frameworks,and low-dimensional materials.The application of gas sensing technology holds significant promise in domains such as industrial safety,environmental monitoring,and medical diagnostics.This comprehensive review thoroughly examines recent progress,identifies prevailing technical challenges,and outlines prospects for gas detection technology utilizing field effect transistors.The primary aim is to provide a valuable reference for driving the development of the next generation of gas-sensitive monitoring and detection systems characterized by improved sensitivity,selectivity,and intelligence.展开更多
Metal-Organic Frameworks(MOFs)have emerged as promising materials for gas adsorption and separation due to their exceptional surface area,tunable porosity,and versatility in functionalization.This paper explores the m...Metal-Organic Frameworks(MOFs)have emerged as promising materials for gas adsorption and separation due to their exceptional surface area,tunable porosity,and versatility in functionalization.This paper explores the mechanisms of gas adsorption in MOFs,including physical adsorption,chemisorption,and synergistic effects,which contribute to their efficiency in capturing and separating gases.The applications of MOFs in key areas such as carbon dioxide capture,hydrogen storage,natural gas separation,and air purification are discussed,highlighting their potential to address pressing environmental and energy challenges.Additionally,the use of MOFs in selective gas separation,membranes,and adsorption-based technologies like Pressure Swing Adsorption(PSA)and Vacuum Swing Adsorption(VSA)is explored,emphasizing their advantages over traditional materials.Despite challenges related to scalability,stability,and cost,MOFs hold great promise for advancing gas separation technologies in the near future,offering more efficient,sustainable,and environmentally friendly solutions.展开更多
The supply of energy is a severe challenge for every country,particularly those that are industrially developed and highly populated.Natural gas is among the most essential energy sources due to its reasonably low cos...The supply of energy is a severe challenge for every country,particularly those that are industrially developed and highly populated.Natural gas is among the most essential energy sources due to its reasonably low cost and high heating value.One of the elements of a sustainable energy supply is underground gas storage(UGS).UGS systems consist of a cushion gas(base gas)and a working gas.The cushion gas is injected into a reservoir to sustain the pressure and remain there until the period of storage ends,while the working gas is the main gas to be stored and produced.Unlike prior studies on fully depleted fields,our research emphasizes the potential of UGS in the presence of remaining oil and integrates key concepts,such as enhanced oil recovery and CO_(2)sequestration.A simulation study was conducted using Qatari Advanced Simulator for Reservoirs software to determine the feasibility of a UGS system in a partially depleted oil reservoir.N_(2) and CO_(2)gases were considered and analyzed over short,medium,and long injection/withdrawal cycles to investigate their potential as cushion gases for natural gas storage in a partially depleted oil reservoir.It was found that using CO_(2)as a cushion gas produces 32%,57%,and 90%of CH_(4) according to short-,medium-,and long-term energy storage scenarios,respectively,with the CH_(4) production higher than when using N2.This study sheds light on the feasibility of implementing underground gas storage systems in partially depleted oil reservoirs.展开更多
Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.Americ...Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.America’s“natural gas independence”has reshaped the global natural gas market,creating a new pattern of“supply shifting westward and consumption shifting eastward”.展开更多
In 2024,China’s natural gas industry continues to show a positive trend.In the field of exploration and development,a large ultra-deep water and ultra-shallow gas field has been discovered,further enhancing the uniqu...In 2024,China’s natural gas industry continues to show a positive trend.In the field of exploration and development,a large ultra-deep water and ultra-shallow gas field has been discovered,further enhancing the unique deep-water complex oil and gas exploration and development technology system independently developed by China.Remarkable achievements have been made in offshore development,including the commissioning of Deep Sea No.1 PhaseⅡ,the first deep-water high-pressure gas field.Additionally,the establishment of the Daji gas field,the first onshore coal rock gas field with an oil and gas equivalent of one million tons,provides strong support for domestic natural gas production.In terms of infrastructure construction,the entire China-Russia east-route natural gas pipeline has been completed,the Xinjiang section of the West Fourth Line is now operational,the Southern Xinjiang Gas Pipeline project has been fully launched,and five new or expanded LNG receiving terminals have been added,increasing the annual receiving capacity by 21.10 million tons.In the field of related equipment manufacturing,China successfully delivered the first vessel of its largest LNG transportation ship construction project,the Greenergy Ocean,and successfully launched its first large-scale floating natural gas liquefaction facility,the NGUYA FLNG.In terms of market supply and demand,natural gas consumption exceeded 400 billion m^(3) for the first time,with apparent consumption reaching 412.43 billion m^(3),an increase of 24.9 billion m^(3) year-on-year,reflecting a growth rate of 6.4%.The total supply reached 424.3 billion m^(3),an increase of 27.5 billion m^(3) year-on-year,with a growth rate of 7.5%.In terms of regulatory policy,China has once again issued a natural gas utilization policy aimed at further guiding the orderly and efficient development of the natural gas market.展开更多
Accurate identification of natural gas origin is fundamental to the theoretical research on natural gas geosciences and the exploration deployment and resource potential assessment of oil and gas.Since the 1970s,Acade...Accurate identification of natural gas origin is fundamental to the theoretical research on natural gas geosciences and the exploration deployment and resource potential assessment of oil and gas.Since the 1970s,Academician Dai Jinxing has developed a comprehensive system for natural gas origin determination,grounded in geochemical theory and practice,and based on the integrated analysis of stable isotopic compositions,molecular composition,light hydrocarbon fingerprints,and geological context.This paper systematically reviews the core framework established by him and his team according to related references and application results,focusing on the conceptual design and technical pathways of key diagnostic diagrams such asδ^(13)C_(1)-C_(1)/(C_(2)+C_(3)),δ^(13)C_(1)-δ^(13)C_(2)-δ^(13)C_(3),δ^(13)CCO_(2)versus CO_(2)content,and the C7light hydrocarbon ternary plot.We evaluate the applicability and innovation of these tools in distinguishing between oil-type gas,coal-derived gas,microbial gas,and abiogenic gas,as well as in identifying mixed-source gases and multi-stage charging systems.The findings suggest that this identification system has significantly advanced natural gas geochemical interpretation in China,shifting from single-indicator analyses to multi-parameter integration and from qualitative assessments to systematic graphical identification,and has also exerted considerable influence on international research in natural gas geochemistry.The structured overview of the development trajectory of natural gas origin discrimination methodologies provides a technical support for natural gas geological theory and practice and offers a scientific foundation for the academic evaluation and application of related achievements.展开更多
The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major inter...The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major interval in the Jianyang Block of the Tianfu gas field in the basin,is characterized by considerable buried depth,tight reservoirs,and strong heterogeneity.By using cast thin section,X-ray diffraction(XRD),scanning electron microscopy(SEM),fluid inclusion thermometry,and core analysis,the reservoir rock types,dominant diageneses,diagenetic history,and controls on high-graded reservoirs were investigated.It is found that the Xu4 Member in Jianyang mainly consists of lithic feldspar sandstones and feldspar lithic sandstones,followed by lithic quartz sandstones.High-energy hydrodynamic conditions in the microfacies of underwater distributary channels and mouth bars are beneficial to the preservation of primary pores and the occurrence of secondary pores,and there are no significant differences in petrophysical properties between these two microfacies.Compaction and calcareous cementation are the dominant controls on reservoir porosity decrease in the Xujiahe Formation;corrosion is the major contributor to porosity increase by generating secondary dissolved pores,e.g.intragranular dissolved pores and intergranular dissolved pores,as major reservoir space in the study area.Fracture zones around the faults inside the Xujiahe Formation(fourth‒order faults)are favorable for proximal tight gas accumulation,preservation,and production.The research findings have been successfully applied to explore the Xujiahe Formation in the slope zone of the Sichuan foreland basin.They can be referential for other similar tight sandstone gas accumulations.展开更多
BACKGROUND Emphysematous gastritis(EG)is a rare and serious condition that has fatal consequences.Although its clinical presentation is not specific,radiological imaging is characterized by intramural gastric gas.Defe...BACKGROUND Emphysematous gastritis(EG)is a rare and serious condition that has fatal consequences.Although its clinical presentation is not specific,radiological imaging is characterized by intramural gastric gas.Defects in the stomach mucosal barrier and invasion of gas-producing organisms are believed to be the cause.CASE SUMMARY An 88-year-old male with multiple comorbidities presented to our center with abdominal pain and increased stoma output as chief complaints.Upon further investigation he was found to have EG.Despite the high mortality risk without intervention,the patient and family declined operative intervention.CONCLUSION This case report underscored the challenges of managing a critically ill elderly patient with a history of multiple comorbidities and extensive abdominal surgeries and highlighted the successful use of conservative measures in treating EG.展开更多
The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations...The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.展开更多
Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some sho...Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.展开更多
Coal measures are significant hydrocarbon source rocks and reservoirs in petroliferous basins.Many large gas fields and coalbed methane fields globally are originated from coal-measure source rocks or accumulated in c...Coal measures are significant hydrocarbon source rocks and reservoirs in petroliferous basins.Many large gas fields and coalbed methane fields globally are originated from coal-measure source rocks or accumulated in coal rocks.Inspired by the discovery of shale oil and gas,and guided by“the overall exploration concept of considering coal rock as reservoir”,breakthroughs in the exploration and development of coal-rock gas have been achieved in deep coal seams with favorable preservation conditions,thereby opening up a new development frontier for the unconventional gas in coal-rock reservoirs.Based on the data from exploration and development practices,a systematic study on the accumulation mechanism of coal-rock gas has been conducted.The mechanisms of“three fields”controlling coal-rock gas accumulation are revealed.It is confirmed that the coal-rock gas is different from CBM in accumulation process.The whole petroleum systems in the Carboniferous–Permian transitional facies coal measures of the eastern margin of the Ordos Basin and in the Jurassic continental facies coal measures of the Junggar Basin are characterized,and the key research directions for further developing the whole petroleum system theory of coal measures are proposed.Coal rocks,compared to shale,possess intense hydrocarbon generation potential,strong adsorption capacity,dual-medium reservoir properties,and partial or weak oil and gas self-sealing capacity.Additionally,unlike other unconventional gas such as shale gas and tight gas,coal-rock gas exhibits more complex accumulation characteristics,and its accumulation requires a certain coal-rock play form lithological and structural traps.Coal-rock gas also has the characteristics of conventional fractured gas reservoirs.Compared with the basic theory and model of the whole petroleum system established based on detrital rock formations,coal measures have distinct characteristics and differences in coal-rock reservoirs and source-reservoir coupling.The whole petroleum system of coal measures is composed of various types of coal-measure hydrocarbon plays with coal(and dark shale)in coal measures as source rock and reservoir,and with adjacent tight layers as reservoirs or cap or transport layers.Under the action of source-reservoir coupling,coal-rock gas is accumulated in coal-rock reservoirs with good preservation conditions,tight oil/gas is accumulated in tight layers,conventional oil/gas is accumulated in traps far away from sources,and coalbed methane is accumulated in coal-rock reservoirs damaged by later geological processes.The proposed whole petroleum system of coal measures represents a novel type of whole petroleum system.展开更多
基金Supported by the National Natural Science Foundation of China(42372165)Science and Technology Special Project of PetroChina Oil&Gas and New Energy Company(2023YQX10101)+1 种基金Project of the Ministry of Natural Resources of China(QGYQZYPJ2022-1)China National Petroleum Corporation Science and Technology Project(2024DJ93)。
文摘In the late 1970s,the theory of coal-formed gas began to take root,sprout,develop,and improve in China.After decades of development,a complete theoretical system was finally formed.The theory of coal-formed gas points out that coal measures are good gas source rocks,with gas as the main hydrocarbon generated and oil as the auxiliary.It has opened up a new exploration idea using coal-bearing humic organic matter as the gas source,transforming the theoretical guidance for natural gas exploration in China from“monism”(i.e.oil-type gas)to“dualism”(i.e.coal-formed gas and oil-type gas)and uncovering a new field of natural gas exploration.Before the establishment of the coal-formed gas theory,China was a gas-poor country with low proved gas initially-in-place(merely 2264.33×10^(8)m^(3))and production(137.3×10^(8)m^(3)/a),corresponding to a per capita annual consumption of only 14.37 m^(3).Guided by the theory of coal-formed gas,the natural gas industry of China has developed rapidly.By the end of 2023,China registered the cumulative proved gas initially-in-place of 20.90×10^(12)m^(3),an annual gas production of 2343×10^(8)m^(3),and a per capita domestic gas consumption reaching 167.36 m^(3).The cumulative proved reserves initially-in-place and production of natural gas were dominated by coal-formed gas.Owing to this advancement,China has transformed from a gas-poor country to the fourth largest gas producer in the world.The coal-formed gas theory and the tremendous achievements made in natural gas exploration in China under its guidance have promoted China from a gas-poor country to a major gas-producing country in the world.
文摘In the global wave of energy transition and low-carbon development,China Petroleum Enterprise Association,together with the University of International Business and Economics,China University of Petroleum-Beijing,Southwest Petroleum University,and other institutions,released four significant blue books on April 17:Annual Operating Report of China’s Natural Gas Industry Blue Book(2024-2025),China Oil&Gas Industry Development Analysis and Outlook Blue Book(2024-2025),China Low-Carbon Economy Development Report Blue Book(2024-2025),and Refined Oil and New Energy Development Report Blue Book(2024-2025).This series of blue books provides a comprehensive and high-level analysis of the development,issues,and trends in the oil and gas industry,offering a detailed depiction of the China Oil&Gas industry and its progress towards low-carbon development.
基金Supported by the National Science and Technology Major Project for New Oil and Gas Exploration and Development(2025ZD1404200)Forward-looking and Fundamental Project of PetroChina Company Limited(2024DJ23)Scientific Research and Technology Development Project of PetroChina Research Institute of Petroleum Exploration&Development(2024vzz).
文摘There are various types of natural gas resources in coal measures,making them major targets for natural gas exploration and development in China.In view of the particularity of the whole petroleum system of coal measures and the reservoir-forming evolution of natural gas in coal,this study reveals the formation,enrichment characteristics and distribution laws of coal-rock gas by systematically reviewing the main types and geological characteristics of natural gas in the whole petroleum system of coal measures.First,natural gas in the whole petroleum system of coal measures is divided into two types,conventional gas and unconventional gas,according to its occurrence characteristics and accumulation mechanism,and into six types,distal detrital rock gas,special rock gas,distal/proximal tight sandstone gas,inner-source tight sandstone gas,shale gas,and coal-rock gas,according to its source and reservoir lithology.The natural gas present in coal-rock reservoirs is collectively referred to as coal-rock gas.Existing data indicate significant differences in the geological characteristics of coal-rock gas exploration and development between shallow and deep layers in the same area,with the transition depth boundary generally 1500-2000 m.Based on the current understanding of coal-rock gas and respecting the historical usage conventions of coalbed methane terminology,coal-rock gas can be divided into deep coal-rock gas and shallow coalbed methane according to burial depth.Second,according to the research concept of“full-process reservoir formation”in the theory of the whole petroleum system of coal measures,based on the formation and evolution of typical coal-rock gas reservoirs,coal-rock gas is further divided into four types:primary coal-rock gas,regenerated coal-rock gas,residual coal-rock gas,and bio coal-rock gas.The first two belong to deep coal-rock gas,while the latter two belong to shallow coal-rock gas.Third,research on the coal-rock gas reservoir formation and evolution shows that shallow coal-rock gas is mainly residual coal-rock gas or bio coal-rock gas formed after geological transformation of primary coal-rock gas,with the reservoir characteristics such as low reservoir pressure,low gas saturation,adsorbed gas in dominance,and gas production by drainage and depressurization,while deep coal-rock gas is mainly primary coal-rock gas and regenerated coal-rock gas,with the reservoir characteristics such as high reservoir pressure,high gas saturation,abundant free gas,and no or little water.In particular,the primary coal-rock gas is wide in distribution,large in resource quantity,and good in reservoir quality,making it the most favorable type of coal-rock gas for exploration and development.
基金supported by the National Natural Science Foundation of China(Nos.51827901,42477191,and 52304033)the Fundamental Research Funds for the Central Universities(No.YJ202449)+1 种基金the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(No.SKLGME022009)the China Postdoctoral Science Foundation(No.2023M742446).
文摘Gas content serves as a critical indicator for assessing the resource potential of deep coal mines and forecasting coal mine gas outburst risks.However,existing sampling technologies face challenges in maintaining the integrity of gas content within samples and are often constrained by estimation errors inherent in empirical formulas,which results in inaccurate gas content measurements.This study introduces a lightweight,in-situ pressure-and gas-preserved corer designed to collect coal samples under the pressure conditions at the sampling point,effectively preventing gas loss during transfer and significantly improving measurement accuracy.Additionally,a gas migration model for deep coal mines was developed to elucidate gas migration characteristics under pressure-preserved coring conditions.The model offers valuable insights for optimizing coring parameters,demonstrating that both minimizing the coring hole diameter and reducing the pressure difference between the coring-point pressure and the original pore pressure can effectively improve the precision of gas content measurements.Coring tests conducted at an experimental base validated the performance of the corer and its effectiveness in sample collection.Furthermore,successful horizontal coring tests conducted in an underground coal mine roadway demonstrated that the measured gas content using pressure-preserved coring was 34%higher than that obtained through open sampling methods.
基金Supported by the National Natural Science Foundation of China(41472120)General Project of National Natural Science Foundation of China(42272188)+1 种基金Special Fund of PetroChina and New Energy Branch(2023YQX10101)Petrochemical Joint Fund of Fund Committee(U20B6001)。
文摘Exploration and development of large gas fields is an important way for a country to rapidly develop its natural gas industry.From 1991 to 2020,China discovered 68 new large gas fields,boosting its annual gas output to 1925×108m3in 2020,making it the fourth largest gas-producing country in the world.Based on 1696 molecular components and carbon isotopic composition data of alkane gas in 70 large gas fields in China,the characteristics of carbon isotopic composition of alkane gas in large gas fields in China were obtained.The lightest and average values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become heavier with increasing carbon number,while the heaviest values ofδ^(13)C_(1),δ13C2,δ13C3andδ13C4become lighter with increasing carbon number.Theδ^(13)C_(1)values of large gas fields in China range from-71.2‰to-11.4‰(specifically,from-71.2‰to-56.4‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-18.9‰for coal-derived gas,and from-35.6‰to-11.4‰for abiogenic gas).Based on these data,theδ^(13)C_(1)chart of large gas fields in China was plotted.Moreover,theδ^(13)C_(1)values of natural gas in China range from-107.1‰to-8.9‰,specifically,from-1071%o to-55.1‰for bacterial gas,from-54.4‰to-21.6‰for oil-related gas,from-49.3‰to-13.3‰for coal-derived gas,and from-36.2‰to-8.9‰for abiogenic gas.Based on these data,theδ^(13)C_(1)chart of natural gas in China was plotted.
文摘In 2024,China’s natural gas sector experienced robust growth in both supply and demand dynamics,as apparent consumption increased rapidly,reaching 426.05 billion m^(3),reflecting a 8.0%year-on-year surge.Domestic gas increase in reserves and production persistently progressed,hitting a production volume of 249.27 billion m^(3) and achieving a six-year consecutive increment exceeding 13 billion m^(3).Imported natural gas continues to grow,with the combined volume of imported pipeline gas and imported LNG expected to reach 180.57 billion m^(3) in 2024,marking an 11.0%year-on-year increase.In 2025,China’s policy aimed at stabilizing growth will continue to exert its influence,maintaining a recovery trend in the national economy with steady progress.The natural gas market is expected to experience rapid growth,with demand primarily driven by industrial fuel and city gas,while the proportion of demand for power generation is anticipated to increase.The national natural gas demand growth rate is projected to be approximately 6%in 2025.
基金Supported by the National Natural Science Foundation of China(42130802,42272200)CNPC Science and Technology Major Project(2023ZZ18)+1 种基金PetroChina Changqing Oilfield Major Science and Technology Project(2023DZZ01)Technology Project of PetroChina Coalbed Methane Company Limited(2023-KJ-18)。
文摘Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals the fluid characteristics,gas accumulation control factors and accumulation modes in the Upper Paleozoic coal reservoirs.The study indicates findings in two aspects.First,the 1500-1800 m interval represents the critical transition zone between open fluid system in shallow-medium depths and closed fluid system in deep depths.The reservoirs above 1500 m reflect intense water invasion,with discrete pressure gradient distribution,and the presence of methane mixed with varying degrees of secondary biogenic gas,and they generally exhibit high water saturation and adsorbed gas undersaturation.The reservoirs deeper than 1800 m,with extremely low permeability,are self-sealed,and contains closed fluid systems formed jointly by the hydrodynamic lateral blocking and tight caprock confinement.Within these systems,surface runoff infiltration is weak,the degree of secondary fluid transformation is minimal,and the pressure gradient is relatively uniform.The adsorbed gas saturation exceeds 100%in most seams,and the free gas content primarily ranges from 1 m^(3)/t to 8 m^(3)/t(greater than 10 m^(3)/t in some seams).Second,the gas accumulation in deep coals is primarily controlled by coal quality,reservoir-caprock assemblage,and structural position governed storage,wettability and sealing properties,under the constraints of the underground temperature and pressure conditions.High-rank,low-ash yield coals with limestone and mudstone caprocks show superior gas accumulation potential.Positive structural highs and wide and gentle negative structural lows are favorable sites for gas enrichment,while slope belts of fold limbs exhibit relatively lower gas content.This research enhances understanding of gas accumulation mechanisms in coal reservoirs and provides effective parameter reference for precise zone evaluation and innovation of adaptive stimulation technologies for deep resources.
基金the Science Foundation of China University of Petroleum,Beijing(Grant No.2462024YJRC021)the National Natural Science Foundation of China(Grant No.U24B2031 and 52104013).
文摘1.Introduction With the increasing demand for petroleum and natural gas resources,along with technological advancements in exploration and production,the primary frontier of oil and gas resources has shifted from conventional oil and gas development to the domains of“Two Deeps,One Unconventional,One Mature,”which include deep onshore,deepwater,unconventional resources,and mature oilfields[1].
基金supported by the National Key R&D Program of China(No.2023YFC3707201)the National Natural Science Foundation of China(No.52320105003)+2 种基金the Informatization Plan of Chinese Academy of Sciences(No.CAS-WX2023PY-0103)the Fundamental Research Funds for the Central Universities(No.E3ET1803)sponsored by the Alliance of International Science Organizations(ANSO)scholarship for young talents.
文摘A sensor,serving as a transducer,produces a quantifiable output in response to a predetermined input stimulus,which may be of a chemical or physical nature.The field of gas detection has experienced a substantial surge in research activity,attributable to the diverse functionalities and enhanced accessibility of advanced active materials.In this work,recent advances in gas sensors,specifically those utilizing Field Effect Transistors(FETs),are summarized,including device configurations,response characteristics,sensor materials,and application domains.In pursuing high-performance artificial olfactory systems,the evolution of FET gas sensors necessitates their synchronization with material advancements.These materials should have large surface areas to enhance gas adsorption,efficient conversion of gas input to detectable signals,and strong mechanical qualities.The exploration of gas-sensitive materials has covered diverse categories,such as organic semiconductor polymers,conductive organic compounds and polymers,metal oxides,metal-organic frameworks,and low-dimensional materials.The application of gas sensing technology holds significant promise in domains such as industrial safety,environmental monitoring,and medical diagnostics.This comprehensive review thoroughly examines recent progress,identifies prevailing technical challenges,and outlines prospects for gas detection technology utilizing field effect transistors.The primary aim is to provide a valuable reference for driving the development of the next generation of gas-sensitive monitoring and detection systems characterized by improved sensitivity,selectivity,and intelligence.
文摘Metal-Organic Frameworks(MOFs)have emerged as promising materials for gas adsorption and separation due to their exceptional surface area,tunable porosity,and versatility in functionalization.This paper explores the mechanisms of gas adsorption in MOFs,including physical adsorption,chemisorption,and synergistic effects,which contribute to their efficiency in capturing and separating gases.The applications of MOFs in key areas such as carbon dioxide capture,hydrogen storage,natural gas separation,and air purification are discussed,highlighting their potential to address pressing environmental and energy challenges.Additionally,the use of MOFs in selective gas separation,membranes,and adsorption-based technologies like Pressure Swing Adsorption(PSA)and Vacuum Swing Adsorption(VSA)is explored,emphasizing their advantages over traditional materials.Despite challenges related to scalability,stability,and cost,MOFs hold great promise for advancing gas separation technologies in the near future,offering more efficient,sustainable,and environmentally friendly solutions.
基金support provided by Hamad bin Khalifa University,Qatar Foundation,Qatar(210028127).
文摘The supply of energy is a severe challenge for every country,particularly those that are industrially developed and highly populated.Natural gas is among the most essential energy sources due to its reasonably low cost and high heating value.One of the elements of a sustainable energy supply is underground gas storage(UGS).UGS systems consist of a cushion gas(base gas)and a working gas.The cushion gas is injected into a reservoir to sustain the pressure and remain there until the period of storage ends,while the working gas is the main gas to be stored and produced.Unlike prior studies on fully depleted fields,our research emphasizes the potential of UGS in the presence of remaining oil and integrates key concepts,such as enhanced oil recovery and CO_(2)sequestration.A simulation study was conducted using Qatari Advanced Simulator for Reservoirs software to determine the feasibility of a UGS system in a partially depleted oil reservoir.N_(2) and CO_(2)gases were considered and analyzed over short,medium,and long injection/withdrawal cycles to investigate their potential as cushion gases for natural gas storage in a partially depleted oil reservoir.It was found that using CO_(2)as a cushion gas produces 32%,57%,and 90%of CH_(4) according to short-,medium-,and long-term energy storage scenarios,respectively,with the CH_(4) production higher than when using N2.This study sheds light on the feasibility of implementing underground gas storage systems in partially depleted oil reservoirs.
文摘Since 2011,America has maintained its position as the world’s largest natural gas producer.Since 2017,America has consistently experienced a surplus in natural gas supply,becoming a net exporter of natural gas.America’s“natural gas independence”has reshaped the global natural gas market,creating a new pattern of“supply shifting westward and consumption shifting eastward”.
文摘In 2024,China’s natural gas industry continues to show a positive trend.In the field of exploration and development,a large ultra-deep water and ultra-shallow gas field has been discovered,further enhancing the unique deep-water complex oil and gas exploration and development technology system independently developed by China.Remarkable achievements have been made in offshore development,including the commissioning of Deep Sea No.1 PhaseⅡ,the first deep-water high-pressure gas field.Additionally,the establishment of the Daji gas field,the first onshore coal rock gas field with an oil and gas equivalent of one million tons,provides strong support for domestic natural gas production.In terms of infrastructure construction,the entire China-Russia east-route natural gas pipeline has been completed,the Xinjiang section of the West Fourth Line is now operational,the Southern Xinjiang Gas Pipeline project has been fully launched,and five new or expanded LNG receiving terminals have been added,increasing the annual receiving capacity by 21.10 million tons.In the field of related equipment manufacturing,China successfully delivered the first vessel of its largest LNG transportation ship construction project,the Greenergy Ocean,and successfully launched its first large-scale floating natural gas liquefaction facility,the NGUYA FLNG.In terms of market supply and demand,natural gas consumption exceeded 400 billion m^(3) for the first time,with apparent consumption reaching 412.43 billion m^(3),an increase of 24.9 billion m^(3) year-on-year,reflecting a growth rate of 6.4%.The total supply reached 424.3 billion m^(3),an increase of 27.5 billion m^(3) year-on-year,with a growth rate of 7.5%.In terms of regulatory policy,China has once again issued a natural gas utilization policy aimed at further guiding the orderly and efficient development of the natural gas market.
基金Supported by the“14th Five-Year Plan”Prospective and Basic Research Project of CNP)(2021DJ0502)Open Project of Key Laboratory of Shale Gas Resource Exploration(Chongqing Institute of Geology and Mineral Resources),Ministry of Natural Resources(KLSGE-2023)National Natural Science Foundation of China(42172149,U2244209)。
文摘Accurate identification of natural gas origin is fundamental to the theoretical research on natural gas geosciences and the exploration deployment and resource potential assessment of oil and gas.Since the 1970s,Academician Dai Jinxing has developed a comprehensive system for natural gas origin determination,grounded in geochemical theory and practice,and based on the integrated analysis of stable isotopic compositions,molecular composition,light hydrocarbon fingerprints,and geological context.This paper systematically reviews the core framework established by him and his team according to related references and application results,focusing on the conceptual design and technical pathways of key diagnostic diagrams such asδ^(13)C_(1)-C_(1)/(C_(2)+C_(3)),δ^(13)C_(1)-δ^(13)C_(2)-δ^(13)C_(3),δ^(13)CCO_(2)versus CO_(2)content,and the C7light hydrocarbon ternary plot.We evaluate the applicability and innovation of these tools in distinguishing between oil-type gas,coal-derived gas,microbial gas,and abiogenic gas,as well as in identifying mixed-source gases and multi-stage charging systems.The findings suggest that this identification system has significantly advanced natural gas geochemical interpretation in China,shifting from single-indicator analyses to multi-parameter integration and from qualitative assessments to systematic graphical identification,and has also exerted considerable influence on international research in natural gas geochemistry.The structured overview of the development trajectory of natural gas origin discrimination methodologies provides a technical support for natural gas geological theory and practice and offers a scientific foundation for the academic evaluation and application of related achievements.
基金supported by the China National Petroleum Corporation Science and Technology Project(Study on genesis mechanism and distribution law of high quality reservoir of the fourth Member of Xujiahe Formation in middle and west Sichuan area,20230301-23)。
文摘The Triassic Xujiahe Formation in the slope zone of the Sichuan foreland basin is a new field of continental tight gas exploration in recent years.The fourth member of the Xujiahe Formation(Xu4 Member),the major interval in the Jianyang Block of the Tianfu gas field in the basin,is characterized by considerable buried depth,tight reservoirs,and strong heterogeneity.By using cast thin section,X-ray diffraction(XRD),scanning electron microscopy(SEM),fluid inclusion thermometry,and core analysis,the reservoir rock types,dominant diageneses,diagenetic history,and controls on high-graded reservoirs were investigated.It is found that the Xu4 Member in Jianyang mainly consists of lithic feldspar sandstones and feldspar lithic sandstones,followed by lithic quartz sandstones.High-energy hydrodynamic conditions in the microfacies of underwater distributary channels and mouth bars are beneficial to the preservation of primary pores and the occurrence of secondary pores,and there are no significant differences in petrophysical properties between these two microfacies.Compaction and calcareous cementation are the dominant controls on reservoir porosity decrease in the Xujiahe Formation;corrosion is the major contributor to porosity increase by generating secondary dissolved pores,e.g.intragranular dissolved pores and intergranular dissolved pores,as major reservoir space in the study area.Fracture zones around the faults inside the Xujiahe Formation(fourth‒order faults)are favorable for proximal tight gas accumulation,preservation,and production.The research findings have been successfully applied to explore the Xujiahe Formation in the slope zone of the Sichuan foreland basin.They can be referential for other similar tight sandstone gas accumulations.
文摘BACKGROUND Emphysematous gastritis(EG)is a rare and serious condition that has fatal consequences.Although its clinical presentation is not specific,radiological imaging is characterized by intramural gastric gas.Defects in the stomach mucosal barrier and invasion of gas-producing organisms are believed to be the cause.CASE SUMMARY An 88-year-old male with multiple comorbidities presented to our center with abdominal pain and increased stoma output as chief complaints.Upon further investigation he was found to have EG.Despite the high mortality risk without intervention,the patient and family declined operative intervention.CONCLUSION This case report underscored the challenges of managing a critically ill elderly patient with a history of multiple comorbidities and extensive abdominal surgeries and highlighted the successful use of conservative measures in treating EG.
基金financially supported by the National Natural Science Foundation of China(Nos.41772132,41502157,41530314)the key project of the National Science&Technology(No.2016ZX05043-001)+1 种基金the Fundamental Research Funds for the Central Universities(No.2652019095)the China Postdoctoral Science Foundation(No.2021M692998)。
文摘The composition and sedimentary controlling effect of the coal measure gas-bearing(CMG)system of the Jurassic Xishanyao Formation in the southern margin of the Junggar Basin(SJB)are analysed based on core observations,sample tests,and logging data.The results show that the lithological associations of the SJB can be classified into 6 types based on sediment supply strengths and sealing abilities,while the gas shows of CMG reservoirs vary greatly among different lithological associations.Due to the diversified coal-forming environment and multistage coal accumulation,superimposed CMG systems are generally developed in the SJB,and their types include:superimposed unattached CMG systems,multilayer unified CMG systems,and superimposed mixed CMG systems.Furthermore,sedimentary controls on the vertical and regional distributions of different types of CMG systems are discussed according to the sedimentary facies of single wells and well cross-sections and the corresponding data of well log,gas logging,and gas contents.Shore shallow lake environments in the Fukang,Miquan,and northern Liuhuanggou areas were favourable for forming superimposed unattached CMG systems.Braided river environments in the Houxia and the southern Liuhuanggou areas usually formed multilayer unified CMG systems.Braided river delta environments in the Manasi,Hutubi,and eastern Sikeshu areas generally developed multilayer unified CMG systems and superimposed mixed CMG systems.For different types of superimposed CMG systems,the number of gas-bearing units,coal seam gas content,vertical hydraulic connectivity and lateral continuity vary considerably,which makes it necessary to tailor the CMG co-production plan to the type of CMG system.
基金supported by the Natural Science Foundation of China(Grant No.42302170)National Postdoctoral Innovative Talent Support Program(Grant No.BX20220062)+3 种基金CNPC Innovation Found(Grant No.2022DQ02-0104)National Science Foundation of Heilongjiang Province of China(Grant No.YQ2023D001)Postdoctoral Science Foundation of Heilongjiang Province of China(Grant No.LBH-Z22091)the Natural Science Foundation of Shandong Province(Grant No.ZR2022YQ30).
文摘Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.
基金Supported by the PetroChina Basic Project(2024DJ23)CNPC Science Research and Technology Development Project(2021DJ0101)。
文摘Coal measures are significant hydrocarbon source rocks and reservoirs in petroliferous basins.Many large gas fields and coalbed methane fields globally are originated from coal-measure source rocks or accumulated in coal rocks.Inspired by the discovery of shale oil and gas,and guided by“the overall exploration concept of considering coal rock as reservoir”,breakthroughs in the exploration and development of coal-rock gas have been achieved in deep coal seams with favorable preservation conditions,thereby opening up a new development frontier for the unconventional gas in coal-rock reservoirs.Based on the data from exploration and development practices,a systematic study on the accumulation mechanism of coal-rock gas has been conducted.The mechanisms of“three fields”controlling coal-rock gas accumulation are revealed.It is confirmed that the coal-rock gas is different from CBM in accumulation process.The whole petroleum systems in the Carboniferous–Permian transitional facies coal measures of the eastern margin of the Ordos Basin and in the Jurassic continental facies coal measures of the Junggar Basin are characterized,and the key research directions for further developing the whole petroleum system theory of coal measures are proposed.Coal rocks,compared to shale,possess intense hydrocarbon generation potential,strong adsorption capacity,dual-medium reservoir properties,and partial or weak oil and gas self-sealing capacity.Additionally,unlike other unconventional gas such as shale gas and tight gas,coal-rock gas exhibits more complex accumulation characteristics,and its accumulation requires a certain coal-rock play form lithological and structural traps.Coal-rock gas also has the characteristics of conventional fractured gas reservoirs.Compared with the basic theory and model of the whole petroleum system established based on detrital rock formations,coal measures have distinct characteristics and differences in coal-rock reservoirs and source-reservoir coupling.The whole petroleum system of coal measures is composed of various types of coal-measure hydrocarbon plays with coal(and dark shale)in coal measures as source rock and reservoir,and with adjacent tight layers as reservoirs or cap or transport layers.Under the action of source-reservoir coupling,coal-rock gas is accumulated in coal-rock reservoirs with good preservation conditions,tight oil/gas is accumulated in tight layers,conventional oil/gas is accumulated in traps far away from sources,and coalbed methane is accumulated in coal-rock reservoirs damaged by later geological processes.The proposed whole petroleum system of coal measures represents a novel type of whole petroleum system.
