海水对下寒武统黑色页岩V矿化/富集的贡献

Early Cambrian black shales along the southern margin of the Yangtze Block are characterized by polymetallic mineralization in the lower part,including Ni-Mo sulfide ore,V ore,barite ore,phosphate ore,and"stone coal"(Fig.1a)[1,2],which were likely related to or at least coincident with the global ocean oxygenation event[3]and the radiation of early animals[4].The source of oreforming elements and the metallogenic mechanism of these polymetallic mineralization layers are highly debated.The models proposed include hydrothermal venting,seawater scavenging,and a combination of key mineralization factors such as terrigenous input,hydrothermal supply,seawater contribution,and impacts of clay mineral and organic matter(Fig.S1 online)[1].

In-situ U-Pb Dating of Quartz:A Preliminary Study

CHALLENGES AND RESEARCH PROGRESS Recent advancements in analytical capabilities and the precision of measuring instruments in in-situ laser ablation mass spectrometry(LA-MC-ICPMS)have markedly broad ened the utility of the U-Pb isotopic geochronometer.This progress has paved the way for accurately determining the ab solute ages of minerals with low uranium concentrations.In re cent years,in-situ U-Pb dating has witnessed rapid advance ments across diverse mineral types,encompassing calcite,dolo mite,fluorite,nacrite,anatase,and wolframite(Roberts et al.,2020).

Identification of sweet spots in shale-type and siltstone-type“shale oil systems”:A case study of the Chang 7 Member in Ordos Basin

Mid-high maturity shale oil is the most realistic field for the scale breakthrough of terrestrial shale oil production in China.Generally,three deficiencies hinder shale oil development in China:heavy oil density,small sweet spot areas,and poor distribution continuity.Thus,identifying the“sweet spots”in shale oil reservoirs is critical for the efficient exploration and development of terrestrial shale oil.This study targets the siltstone type(Class-Ⅱshale oil)and pure shale type(Class-Ⅲshale oil)of the Chang 7 Member in the Ordos Basin,and identifies three stratigraphic units,namely the hydrocarbon accumulation unit,hydrocarbon generation unit,and hydrocarbon retention unit,which together constitute the in-source“shale oil system”.The hydrocarbon accumulation unit is mainly siltstone,where the hydrocarbons are migrated from shales.It has favorable porethroat network connectivity with a pore connectivity ratio of 32–57%,being the siltstone-type sweet spots.The hydrocarbon generation unit is mainly composed of high-TOC mudstone/shale and is the main contributor to in-source hydrocarbon generation and expulsion.This unit has high three-dimensional connectivity(28–30%),as shown by the pore-throat network model,associated with vertical paths for hydrocarbon expulsion.The hydrocarbon retention unit is mainly composed of low-TOC mudstone/shale retaining self-generated and migrated hydrocarbons.The pore connectivity rate is 17–42%,and the pore-throat network connectivity direction is uneven.Light and low-carbon-number hydrocarbons are preferentially trapped or even sealed in small pores of the retention unit,forming the typical mudstone/shale-type sweet spots.In the process called shale oil intrasource migration,the oil migrates in source rocks causing component fractionation,which allows more shale oil to enrich in the hydrocarbon accumulation and retention units to form sweet spots,compared with the hydrocarbon generation unit.The migration paths include the one from mudstone/shale to siltstone interlayers and that from the high-TOC mudstone/shale intervals to the low-TOC intervals.The in-source accumulation of shale oil shows the differentiated enrichment model featuring“high-TOC mudstone/shale generating hydrocarbons,low-TOC mudstone/shale retaining hydrocarbons,siltstone accumulating hydrocarbons and multiple intra-source migration paths”.In the Ordos Basin,the organic-lean(TOC 1–3%)mudstone/shale intervals appear to be the sweet spots of shale oil,where there are abundant medium-short-chain hydrocarbons retained with high flowability.After fracturing stimulation,their production conditions may be even superior to those of siltstones.This proposed idea changes the previous strategy to look for sweet spots in high-TOC intervals derived from the shale gas industry.

Theory, Technology and Practice of Unconventional Petroleum Geology

0 INTRODUCTION The breakthroughs in unconventional petroleum have a great impact on world petroleum industry and innovation in petroleum geology(Dou et al,2022;Jia,2017;Zou et al.,2015b,2014a;Yerkin,2012;Pollastro,2007;Schmoker,1995).The exploration and development evolution from conventional petroleum to unconventional petroleum and more and more frequent industrial activities of exploring petroleum inside sources kitchen have deepened theoretical understanding of unconventional petroleum geology and promoted technical research and development(Jia et al.,2021,2017;Jin et al.,2021;Zhao W Z et al.,2020;Ma Y S et al.,2018,2012;Zou et al.,2018b,2016,2009;Dai et al.,2012).We have introduced and extended the theory of continuous hydrocarbon accumulation since 2008 and published several papers/books(in Chinese and English)with respect to unconventional petroleum geology since 2009,basically forming the theoretical framework for this discipline(Yang et al.,2022a,2021a,2019a,,2015a;Zou et al.,2019c,2017b,2014a,,2013a).In this paper,we present the background of unconventional petroleum geology,review the latest theoretical and technological progress in unconventional petroleum geology,introduce relevant thinking and practices in China,and explore the pathway of unconventional petroleum revolution and multi-energy coordinated development in super energy basins,hopefully to promote the unconventional petroleum geology and industry development.

中国为什么可以实现陆相“页岩油革命”?

陆相页岩油是保障国家石油供应安全和提升工业创新水平的战略接替资源.中国是陆相石油资源大国,占陆上石油资源总量的90%;也是陆相石油生产大国,陆相石油产量约占石油总产量的93%(贾承造等,2018;杨智和邹才能,2019).中国源岩层系发育多种类型非常规油气资源(图1),其中陆相页岩油是中国陆上未来剩余石油资源的主要接替领域.确立中国特色陆相页岩油理论技术攻关的科学问题,有利于推动实现中国陆相页岩油革命和石油工业持续发展.目前,中高成熟度页岩油在松辽、鄂尔多斯、渤海湾、准噶尔、四川等盆地已实现工业性突破与发展,中低成熟度页岩油已经开展大量前期基础理论与技术储备攻关,即将在鄂尔多斯、松辽等盆地进行工业性试验。

湖盆细粒重力流沉积作用过程及甜点层发育机制是什么?

陆相石油是中国石油储量和产量的主要贡献者,陆相石油的勘探对象经历了湖盆区外粗粒沉积储层为主、湖岸线附近粗-中粒沉积储层为主的常规石油,正在向湖盆区内细粒沉积储层为主的非常规页岩油气全面迈进(图1).深湖区发育的以粉砂、泥质粉砂、粉砂质泥、黏土和有机质为主的细粒重力流沉积物(粒径<0.0625 mm),是形成深水(湖)细粒沉积的重要搬运和沉积作用方式(Boulesteix et al.,2019),也是陆相页岩油气富集高产的重要储集甜点层类型(图1).深入研究湖盆细粒重力流体系沉积特征和发育机制,系统认识深湖环境细粒重力流体系沉积作用及演化,不仅对深入理解细粒重力流体系形成的特定地质条件及沉积作用过程、促进湖盆细粒重力流沉积学基础理论的创新发展,而且对湖盆区内页岩油气甜点层预测、富集区评价意义重大.

“Exploring petroleum inside source kitchen”: Shale oil and gas in Sichuan Basin

The Sichuan Basin is rich in shale oil and gas resources,with favorable geological conditions that the other shale reservoirs in China cannot match.Thus,the basin is an ideal option for fully"exploring petroleum inside source kitchen"with respect to onshore shale oil and gas in China.This paper analyzes the characteristics of shale oil and gas resources in the United States and China,and points out that maturity plays an important role in controlling shale oil and gas composition.US shale oil and gas exhibit high proportions of light hydrocarbon and wet gas,whereas Chinese marine and transitional shale gas is mainly dry gas and continental shale oil is generally heavy.A comprehensive geological study of shale oil and gas in the Sichuan Basin reveals findings with respect to the following three aspects.First,there are multiple sets of organic-rich shale reservoirs of three types in the basin,such as the Cambrian Qiongzhusi Formation and Ordovician Wufeng Formation-Silurian Longmaxi Formation marine shale,Permian Longtan Formation transitional shale,Triassic Xujiahe Formation lake-swamp shale,and Jurassic lacustrine shale.Marine shale gas enrichment is mainly controlled by four elements:Deep-water shelf facies,moderate thermal evolution,calcium-rich and silicon-rich rock association,and closed roof/floor.Second,the"sweet section"is generally characterized by high total organic carbon,high gas content,large porosity,high brittle minerals content,high formation pressure,and the presence of lamellation/bedding and natural microfractures.Moreover,the"sweet area"is generally characterized by very thick organic-rich shale,moderate thermal evolution,good preservation conditions,and shallow burial depth,which are exemplified by the shale oil and gas in the Wufeng-Longmaxi Formation,Longtan Formation,and Daanzhai Member of the Ziliujing Formation.Third,the marine,transitional,and continental shale oil and gas resources in the Sichuan Basin account for 50%,25%,and 30%of the respective types of shale oil and gas geological resources in China,with great potential to become the cradle of the shale oil and gas industrial revolution in China.Following the"Conventional Daqing-Oil"(i.e.,the Daqing oilfield in the Songliao Basin)and the"Western Daqing-Oil&Gas"(i.e.,the Changqing oilfield in the Ordos Basin),the Southwest oil and gas field in the Sichuan Basin is expected to be built into a"Sichuan-Chongqing Daqing-Gas"in China.

Methods for Shale Gas Play Assessment: A Comparison between Silurian Longmaxi Shale and Mississippian Barnett Shale

Based on field work, organic geochemical analyses and experimental testing, a six-property assessment method for shale gas is proposed. These six properties include organic matter properies, lithofacies, petrophysical properties, gas content, brittleness and local stress field. Due to the features of continuous distribution over a large area and low resource abundance in shale plays, a sweet spot should have these following properties： （a） TOC〉2%; （b） brittle minerals content （〉40%） and clay minerals （〈30%）; （c） Ro （〉1.1%）; （d） porosity （〉2%） and permeability （〉0.000 1 mD）, and （e） effective thickness （30-50 m）. Applying these criteria in the Sichuan Basin, the Silurian Longmaxi shale consists of four prospecting sweet spots, including blocks of Changning, Weiyuan, Zhaotong and Fushnn-Yongchuan. Although these four blocks have some similarities, different features were usually observed. After comprehensive analyses using the six-property assessment method, the Fushun-Yongan Block ranks the most favorable sweet spot, followed by the Weiyuan Block. For the other two blocks, the Changning Block is better than the Zbaotong Block. By comparing with the Mississippian Barnett shale, characteristics that are crucial for a high-yielding in the Sichuan Basin include a high content of organic matter （TOC〉2.5%）, a moderate thermal maturity （Ro=0.4%-2%）, a high content of brittle minerals （quartz： 30%-45%）, a high gas content （〉2.5 m^3·t^-1）, and types I and II1 kerogen.

LA-ICPMS in-situ U-Pb Geochronology of Low-Uranium Carbonate Minerals and Its Application to Reservoir Diagenetic Evolution Studies

Reconstruction of the diagenetic evolution of reservoirs is one of the most significant tasks in oil and gas exploration and development.Assessing the accurate timing of diagenetic events is critical to better understand the process of reservoir evolution,but the isotope dating of diagenetic events is technically challenging.This paper uses three case studies in the sedimentary basins in China to demonstrate the promising application of recently developed LA-(MC)-ICPMS in-situ U-Pb geochronology.Our results show that the new U-Pb dating method provides a reliable and efficient chronological approach to determine the absolute ages of diagenetic events.For example,the U-Pb age data of the Cambrian carbonate reservoir in the Tarim Basin reveals three diagenetic events at 526±14,515±21,and 481±4.6 Ma,respectively.It is worth noting that microscopic observations are particularly important for improving the success rate of U-Pb dating.In addition,the recent progress and future prospects in the in-situ U-Pb dating method are also discussed in this study,suggesting that this method is currently hindered by the lack of international carbonate standards for data correction.

Characteristics,Types,and Prospects of Geological Sweet Sections in Giant Continental Shale Oil Provinces in China

“Sweet sections”in giant shale oil provinces are preferential fields that primarily support China to increase the reserves and production of continental shale oil.Based on the study of the geological conditions of shale oil in the continental basins in China,it was found that the shale stratum in major oil generation windows generally has higher degrees of oil and gas accumulation,and mostly contains oil.Hydrocarbon generation and reservoir capacities are the two key parameters for evaluating and optimizing favorable shale oil provinces.The evaluation index(volume of shale stratum multiplied by total organic carbon(TOC)multiplied by total porosity)for the giant continental shale oil provinces is also proposed.It is optimized that the Upper Triassic Chang 7 Member in the southcentral Ordos Basin,Lower Cretaceous Qing 1 Member in the Gulong-Changling Sag in the Songliao Basin,Middle-Lower Permian in the Junggar Basin,Da’anzhai Member of the Ziliujing Formation of Lower Jurassic in the central and northern Sichuan Basin,and Paleogene oil-rich sag in the Bohai Bay Basin are the five giant continental shale oil provinces.The word“geological sweet sections”in continental shale oil provinces of China refers to favorable shale intervals which are relatively rich in oil,with superior physical properties,and more easily modified and developed commercially under applicable economic and technological conditions.After evaluation,there are mainly two types of“geological sweet sections”of giant continental shale oil developed onshore in China.One type of“geological sweet sections”is generally mudstone with optimal physical properties or a thin tight reservoir,to which the shale oil migrates a short distance.They are medium-to-high-mature zones with a thin sandy shale stratum in the Chang 7 Member in the Ordos Basin,mixed shale stratum in the mediummature Lucaogou Formation in the Jimsar Sag,and multi-layered mixed Paleogene shale stratum in the Bohai Bay Basin.The other type of“geological sweet sections”is generally shale oil residing in various shale reservoir spaces.This type was developed in the Qing 1 Member in the Gulong Sag and Da’anzhai Member in the north-central Sichuan Basin.Free shale oil mainly occurs in shale,sandycarbonate lamina,micro-lamella structure,and micro-fractures.Layers with lamina,lamination,and micro-fractures are generally shale oil“geological sweet sections.”Starting from field tests and the construction of the“geological sweet sections”in giant continental shale oil provinces,the shale oil industry has been rapidly developing and will become an important supplement to domestic oil production in China.

Fluid Mobility Evaluation of Tight Sandstones in Chang 7 Member of Yanchang Formation, Ordos Basin

Fluid mobility has been important topic for unconventional reservoir evaluation.The tight sandstones in Chang 7 Member of the Ordos Basin has been selected to investigate the fluid mobility based on the application of core flooding-NMR combined method and core centrifugation-NMR combined method,and the porous structure is studied using optical microscope,field emission scanning electron microscope(FE-SEM),CT and mercury injection.Our results include:(i)Feldsparrock fragments dissolution pores,calcite dissolution pores,clay mineral dissolution pores,intergranular dissolution expansion pores,inter-granular pores,intra-kaolinite pores,and intra-illite/smectite mixed layer pores are developed in Chang 7 tight sandstones;3D CT pore structure shows that the pore connectivity is positively related to physical properties,and the overall storage space is connected by the throat with diameter between 0.2 and 0.3μm.The percentage of storage space connected by throats with diameter less than 100 nm can reach more than 35%.(ii)Movable fluid saturation of Chang 7 tight sandstones is between 10%and 70%,and movable oil saturation is between 10%and 50%.Movable fluid saturation may cause misunderstanding when used to evaluate fluid mobility,so it is recommended to use movable fluid porosity in the evaluation of fluid mobility.The porosity ranging from 5%to 8%is the inflection point of the fluidity and pore structure.For samples with porosity less than 8%,the movable fluid porosity is generally less than 5%.Moreover,the movable fluid is mainly concentrated in the storage space with a throat diameter of 0.1 to 1μm.For samples with porosity greater than 8%,the porosity of the movable fluid is more than 5%,and the movable fluid is mainly concentrated in the storage space with a throat diameter of 0.2 to 2μm.(iii)The movable fluid saturation measured by core flooding-NMR combined method is generally higher than that measured by core centrifugation-NMR combined method.The former can evaluate the mobility of the oil-water two-phase fluid in samples,while the latter can better reflect the pore structure and directly evaluate the movable fluid in the pore system controlled by different throat diameters.All these results will provide valuable reference for fluid mobility evaluation in tight reservoirs.

Coal measure metallogeny:Metallogenic system and implication for resource and environment

Coal,coal measure gas,coal conversion to oil and gas,and coal-based new materials are reliable guarantees for stable energy supply and economic and social development in China.The coal-dominated resource endowment and the economic and social development stage determine the irreplaceable position of coal resources in the energy system.Coal measure resources,including aggregated or dispersed solids,liquid and gaseous multitype energies,and metal as well as nonmetallic minerals,are the products of multisphere interaction and metallogenetic materials generation,migration,and accumulation.Coal measures record rich deep-time geological information of transitional and terrestrial peat bogs,which is a crucial carrier to reveal ecosystem evolution,significant organic carbon sequestration,atmospheric O_(2)/CO_(2)variation,and wildfire events.Coal measure evolution is accompanied by the migration and transformation of various materials during diagenesis-metamorphism,forming differentiated coal compositions besides properties and various mineral resources in its adjacent strata.The enrichment condition,occurrence state,and separation potential are the premise for level-by-level use and efficient development of coal measure resources.Coal measure metallogeny is based on the metallogenic system of multiple energy and mineral resources in coal measures and their environmental effects.Fully understanding coal measure metallogeny is beneficial for promoting the coal transition from fuel to raw materials and strengthening its attribute of multiple mineral resources.The metallogeny comprises various aspects,including:(1)the symbiosis mechanism,co-exploration and co-mining conditions of various resources;(2)the source-sink system of ore-forming materials;(3)the differential carbon accumulation and hydrogen enrichment effect;(4)organic(coal and hydrocarbon)and inorganic(mineral)interactions;and(5)combination of minerals naturally enrichment during the metallogenic process and artificial enrichment during the ore processing process.The coal measure metallogeny belongs to the geoscience disciplines,and studies the types,formation,distribution,enrichment mechanisms,evaluation methods,and development strategies of resources related to coal measures.The key scientific problems include geological records related to mineral enrichment processes,metallogenic mechanisms,resource distribution,occurrence evaluation,and accurate development.Developing coal measure metallogeny is significant in improving the critical mineral metallogenic theory,revealing various deep-time earth systems and realizing the national energy transformation and high-quality development.

What are the Lacustrine Fine-Grained Gravity Flow Sedimentation Process and the Genetic Mechanism of Sweet Sections for Shale Oil?

0 INTRODUCTION Oil in continental Basins is the main contributor to petroleum reserves and production in China.The exploration targets of the oil in continental Basins have experienced a transformation from conventional oil,whose reservoirs are mainly composed of coarse-grained deposits outside the lacustrine basin,and coarse-medium-grained sediments deposited near the shoreline of the lacustrine basin.

Why Can China Realize the Continental“Shale Oil Revolution”?

0 INTRODUCTION Continental shale oil is a strategic alternative resource to ensure the safety of national oil supply and improve the level of industrial innovation.China is a large country of continental oil resources,accounting for 90%of the total onshore oil resources;and China is also a major producer of continental oil,accounting for about 93%of the total oil production(Yang et al.,2019;Jia et al.,2018).