摘要:In recent years, a series of large low and medium abundance oil and gas fields are discovered through exploration activities onshore China, which are commonly characterized by low porosity-permeability reservoirs, low oil/gas column height, multiple thin hydrocarbon layers, and distribution in overlapping and connection, and so on. The advantageous conditions for large-area accumulation of low-medium abundance hydrocarbon reservoirs include: (1) large (fan) delta sandbodies are developed in the hinterland of large flow-uncontrolled lake basins and they are alternated with source rocks extensively in a structure like “sandwiches”; (2) effective hydrocarbon source kitchens are extensively distributed, offering maximum contact chances with various sandbodies and hydrocarbon source rocks; (3) oil and gas columns are low in height, hydrocarbon layers are mainly of normal-low pressure, and requirements for seal rock are low; (4) reservoirs have strong inheterogeneity and gas reservoirs are badly connected; (5) the hydrocarbon desorption and expulsion under uplifting and unloading environments cause widely distributed hydrocarbon source rocks of coal measures to form large-area reservoirs; (6) deep basin areas and synclinal areas possess reservoir-forming dynamics. The areas with great exploration potential include the Paleozoic and Mesozoic in the Ordos Basin, the Xujiahe Formation in Dachuanzhong in the Sichuan basin, deep basin areas in the Songliao basin etc. The core techniques of improving exploration efficiency consist of the sweetspot prediction technique that focuses on fine characterization of reservoirs, the hydrocarbon layer protecting and high-speed drilling technique, and the rework technique for enhancing productivity.

摘要:Detailed geochemistry studies were conducted to investigate the origin of solid bitumens and hydrocarbon gases in the giant Puguang gas field. Two types of solid bitumens were recognized: low sulfur content, low reflectance (LSLR) solid bitumens in sandstone reservoirs in the Xujiahe Formation and high sulfur content, high reflectance (HSHR) solid bitumens in the carbonate reservoirs in the Lower Triassic Feixianguan and Upper Permian Changxing formations. Solid bitumens in the Upper Triassic Xujiahe Formation correlate well with extracts from the Upper Triassic to Jurassic non-marine source rocks in isotopic composition of the saturated and aromatic fractions and biomarker distribution. Solid bitumens in the Feixianguan and Changxing formations are distinctly different from extracts from the Cambrian and Silurian rocks but display reasonable correlation with extracts from the Upper Permian source rocks both in isotopic composition of the saturated and aromatic fractions and in biomarker distribution, suggesting that the Permian especially the Upper Permian Longtan Formation was the main source of solid bitumens in the carbonate reservoirs in the Feixianguan and Changxing formations in the Puguang gas field. Chemical and isotopic composition of natural gases indicates that the majority of hydrocarbon gases originated from sapropelic organic matter and was the products of thermal cracking of accumulated oils. This study indicates that source rock dominated by sapropelic organic matter existed in the Upper Permian and had made major contribution to the giant Puguang gas field, which has important implication for petroleum exploration in marine sequences in South China.

摘要:The Tahe Oilfield is a complex petroleum reservoir of Ordovician carbonate formation and made up of spatially overlapping fracture-cavity units. The oilfield is controlled by a cave system resulting from structure-karst cyclic sedimentation. Due to significant heterogeneity of the reservoir, the distribution of oil and water is complicated. Horizontally, a fresh water zone due to meteoric water can be found in the north part of the Akekule uplift. A marginal freshening zone caused by water released from mudstone compaction is found at the bottom of the southern slope. Located in a cross-formational flow discharge zone caused by centripetal and the centrifugal flows, the main part of the Tahe Oilfield, featuring high salinity and concentrations of Cl- and K++Na+, is favorable for accumulation of hydrocarbon. Three types of formation water in the Tahe Ordovician reservoir are identified: (1) residual water at the bottom of the cave after oil and gas displacement, (2) residual water in fractures/pores around the cave after oil and gas displacement, and (3) interlayer water below reservoirs. The cave system is the main reservoir space, which consists of the main cave, branch caves and depressions between caves. Taking Cave System S48 in the Ordovician reservoir as an example, the paper analyzes the fluid distribution and exploitation performance in the cave system. Owing to evaporation of groundwater during cross-formational flow, the central part of the main cave, where oil layers are thick and there is a high degree of displacement, is characterized by high salinity and Br- concentration. With high potential and a long stable production period, most wells in the central part of the main cave have a long water-free oil production period. Even after water breakthrough, the water content has a slow or stepwise increase and the hydrochemistral characteristics of the produced water in the central part of the main cave are uniform. From the center to the edge of the main cave, displacement and enrichment of oil/gas become weaker, residual water increases, and the salinity and concentration of Br- decrease. At the edge of the main cave, although the wells have a high deliverability at the beginning with a short stable production period and water-free production period. After water breakthrough, the pressure and deliverability drop quickly, and the water content rises quickly. The hydrochemistral characteristics of the produced water are relatively uniform. Wells in the branch caves have a relatively low deliverability at the beginning, with a short stable production period. Water breakthrough appears quickly and then the pressure and deliverability drop quickly. The salinity and concentrations of Cl- and K++Na+ are usually fluctuant or descend slowly in the produced water. Wells in low areas of ancient karst have a low deliverability and a short stable production period. The yield drops quickly and the water content is high, while the characteristics of the produced water may vary significantly well to well. The salinity and concentrations of Cl- and K++Na+ in the produced water are usually fluctuant with a precipitous decline.

摘要:By analyzing the characteristics of development, structural evolution and reservoir beds of the residual carbonate strata, this study shows that the residual carbonate strata in the Yingmaili low uplift are favorable oil and gas accumulation series in the Tabei (northern Tarim uplift) uplift. There are different patterns of hydrocarbon accumulation on the northern and southern slopes of the Yingmaili low uplift. The north-south differentiation of oil reservoirs were caused by different lithologies of the residual carbonate strata and the key constraints on the development of the reservoir beds. The Mesozoic terrestrial organic matter in the Kuqa depression and the Palaeozoic marine organic matter in the Manjiaer sag of the Northern depression are the major hydrocarbon source rocks for the northern slope and southern slope respectively. The hydrocarbon accumulation on the northern and southern slopes is controlled by differences in maturity and thermal evolution history of these two kinds of organic matter. On the southern slope, the oil accumulation formed in the early stage was destroyed completely, and the period from the late Hercynian to the Himalayian is the most important time for hydrocarbon accumulation. However, the time of hydrocarbon accumulation on the northern slope began 5 Ma B.P. Carbonate inner buried anticlines reservoirs are present on the southern slope, while weathered crust and paleo-buried hill karst carbonate reservoirs are present on the northern slope. The northern and southern slopes had different controlling factors of hydrocarbon accumulation respectively. Fracture growth in the reservoir beds is the most important controlling factor on the southern slope; while hydrocarbon accumulation on the northern slope is controlled by weathered crust and cap rock.

摘要:There are significant differences in type and distribution between marine source rock and continental source rock. According to the lithology, the Cambrian-Ordovician source rock in the Tarim basin is divided into two types: the carbonate source rock and the mud source rock. The two sets of source rocks are developed mainly in three sets of formations, Lower-Middle Cambrian carbonate source rock and mud source rock, Lower-Middle Ordovician mud source rock and Upper Ordovician lime mud source rock. The stratigraphic and areal distributions of the source rocks are controlled by the altitude and the sedimentary facies respectively. The mud source rock is developed in slope-semi deep sea environment. The source rock developed in the slope sedimentary environment is related with the anoxic environment and the one developed in semi deep sea has a close relationship with the up-flowing sea water. The carbonate source rock is developed mainly in platform slope of highstand systems tract and it is usually intimately associated with the salt rock. The Lower-Middle Cambrian carbonate source rock is developed mainly in the Bachu, Tazhong, Tangguzibasi and Yingmaili areas. The Lower-Middle Cambrian mud source rock is mainly developed in the areas east of the line of Kunan 1-Tadong 1. The Lower-Middle Ordovician mud source rock is developed mainly in the east slope of the Manjiaer depression. The carbonate source rock of Early Ordovician is developed mainly in the platform slope of highstand systems tract, such as the south margin of Tabei, the north slope of Tazhong, the Bachu area and Keping area.

摘要:With a comprehensive study on the petrology, geology and geochemistry of some Ordovician granule limestone samples in the Tahe Oilfield of the Tarim Basin, two stages of burial dissolution were put forward as an in-source dissolution and out-source dissolution based on macro-microcosmic petrology and geochemistry features. The main differences in the two stages are in the origin and moving pass of acid fluids. Geochemical evidence indicates that burial dissolution fluids might be ingredients of organic acids, CO2 and H2S associated with organic matter maturation and hydrocarbon decomposition, and the in-source fluid came from organic matter in the granule limestone itself, but the out-source was mainly from other argillaceous carbonate rocks far away. So, the forming of a burial dissolution reservoir resulted from both in-source and the out-source dissolutions. The granule limestone firstly formed unattached pinholes under in-source dissolution in situ, and afterwards suffered wider dissolution with out-source fluids moving along unconformities, seams, faults and associate fissures. The second stage was much more important, and the mineral composition in the stratum and heat convection of the fluid were also important in forming favorable reservoirs.

摘要:Ordovician fracture-cavity carbonate reservoir beds are the major type of producing formations in the Tahe oilfield, Tarim Basin. The seismic responses of these beds clearly changes depending on the different distance of the fracture-cavity reservoir bed from the top of the section. The seismic reflection becomes weak or is absent when the fracture-cavity reservoir beds are less than 20 ms below the top Ordovician. The effect on top Ordovician reflection became weaker with deeper burial of fracture-cavity reservoir beds but the developed deep fracture-cavity reservoir beds caused stronger reflection in the interior of the Ordovician. This interior reflection can be divided into strong long-axis, irregular and bead string reflections, and was present 80 ms below the top Ordovician. Aimed at understanding reflection characteristics, the spectral decomposition technique, which uses frequency to “tune-in” bed thickness, was used to predict Ordovician fracture-cavity carbonate formations in the Tahe oilfield. Through finely adjusting the processing parameters of spectral decomposition, it was found that the slice at 30 Hz of the tuned data cube can best represent reservoir bed development. Two large N-S-trending strong reflection belts in the mid-western part of the study area along wells TK440-TK427-TK417B and in the eastern part along wells TK404-TK409 were observed distinctly on the 30 Hz slice and 4-D time-frequency data cube carving. A small N-S trending reflection belt in the southern part along wells T403-TK446B was also clearly identified. The predicted reservoir bed development area coincides with the fracture-cavities connection area confirmed by drilling pressure testing results. Deep karst cavities occur basically in three reservoir bed-development belts identified by the Ordovician interior strong reflection. Spectral decomposition proved to be a useful technique in identifying fracture-cavity reservoir beds.

摘要:At present, shallow gases have received much attention due to low cost in exploration and production. Low-mature gases, as one significant origin to shallow gas, turns to be an important research topic. The present understanding of low-mature gases is confined within some geological cases, and few laboratory studies have been reported. Therefore, the potential and characters of low-mature gases are not clear up to now. Here, two premature samples (one coal and the other shale) were pyrolyzed in a gold confined system. The gaseous components including hydrocarbon gases and non-hydrocarbon gases were analyzed. Based on kinetic modeling, the formation of low-mature gases was modeled. The results showed that during low mature stage, about 178 mL/gTOC gas was generated from the shale and 100 mL/gTOC from the coal. Two third to three fourth of the generated gases are non-hydrocarbon gases such as H2S and CO2. The total yields of C1–5 for the two samples are almost the same, 30–40 mL/gTOC, but individual gaseous hydrocarbon is different. The shale has much lower C1 but higher C2–5, whereas the coal has higher C1 but lower C2–5. Hydrocarbon gases formed during low-mature stage are very wet. The stable carbon isotope ratios of methane range from ?40‰ to ?50‰ (PDB), in good consistence with empiric criterion for low-mature gases summed up by the previous researchers. The generation characters suggest that the low-mature gases could be accumulated to form an economic gas reservoir, but most of them occur only as associated gases.

摘要:The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub-salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation, and the supra-salt sequence composed of continental clastics of the Upper-Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement-involved imbricated thrust belt, basement-involved and salt-detached superimposed deformed belt, buried salt-related detached belt, duplex, piling triangle zone and pop-up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower-Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower-Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.

摘要:The Triassic in the Longmengshan foreland basin is rich in oil and gas resources. Its reservoirs feature low-porosity, low-permeability, small pore throat, high water saturation, and strong heterogeneity. The existence of abnormally high pressure and various reservoir-cap combinations developed at different times provide favorable conditions for trapping oil and gas. Taking the theory of petroleum systems as a guide, and beginning with research on tectonics, sedimentary history, distribution and evolution of source rocks, reservoir evolution, hydraulic force distribution, and hydrocarbon migration, analysis and study of static factors like source rocks, reservoirs and cap rocks, and dynamic factors such as hydrocarbon generation, migration, and accumulation revealed the characteristics of the Upper Triassic petroleum system in western Sichuan province. The deep-basin gas in the central hydrocarbon kitchen of the Upper Triassic, structural-lithological combination traps on the surrounding slopes, and the structural traps of the Indo-Chinese–Yangshan paleohighs, are potential plays. The relatively well- developed fault zones in the southern segment of the Longmengshan foothill belt are favorable Jurassic gas plays. Pengshan-Xinjin, Qiongxi, and Dayi are recent exploration targets for Jurassic oil/gas reservoirs.

摘要:The paper studies CO2 degassing and controlling factors under the condition of contact metamorphism in the Shuangshan area, southern Tan–Lu fault belt and the method of calculating the amount of CO2 degassing. The results show that the amount of CO2 degassing is controlled by the characteristics of the country rocks, including the thermal conductivity, penetrability, porosity and connectivity. Compositions, size and depth of intrusive rock also have an important influence on CO2 degassing, i.e., they generated numerous cracks in the country rocks, and thus allowed the easy flow and accumulation of fluids. The amount of CO2 flux in contact metamorphism is calculated quantitatively based on the metamorphic reaction and time–integrated fluid flux. The value (0.729–2.446×104 mol/cm2) of CO2 flux suggests that CO2 was provided mainly by the contact metamorphic reaction. The generation and releasing of CO2 are positively correlated with the degree of metamorphism, and XCO2 in fluids gradually increases from dolomite zone to calcite zone, but in the zone of grossular, fluid flux is the largest and XCO2 sharply decreases due to involvement of magmatic water. This study presents evidence that a large amount of industrial–scale CO2 can be produced during contact metamorphism. On the basis of theoretical and practical studies, a cone model has been proposed to response CO2 degassing for the contact metamorphism, and it can be used to explore CO2 accumulations beyond the oil–gas basins. This model can also be applied to the study of inorganic genesis of CO2 accumulations.

摘要:Sichuan Basin is one of the structurally stable and gas-rich basins, being regarded as one of China’s important natural gas industry bases. Puguang and Jiannan gas fields, located in the eastern Sichuan Basin are two large fields with gas derived from Permian and Lower Triassic marine carbonate. The genesis of marine carbonate natural gas was examined using carbon isotope composition and hydrocarbon components of natural gas samples from the eastern and western Sichuan Basin, and compared with that of acidolysis gas derived from marine source rock in the eastern Sichuan Basin. It is concluded that the natural gas in the marine carbonate reservoir originated from pyrolysis of the earlier crude oil and light-oil, and then mixed with kerogen pyrolysis gas of the Permian and Lower Silurian source rock.

摘要:More than 40 years have been passed since exploration and development of oil-gas began in the Bohai Bay Basin. Though we have faced with many difficulties during our exploration, exciting discoveries in petroleum-rich sags have been made in recent years. Studies show that the petroleum-rich sags are characterized by multiple sets of oil-gas accumulation in the pre-Eogene to Neogene strata in profile and large-area connection or superimposition of oil-gas reservoirs in different strata. Therefore, petroleum-rich sags continue to be a focus of future oil-gas exploration in the Bohai Bay Basin. There is still a great potential of petroleum resources. Inshore and offshore areas, onshore stratigraphic reservoirs, high-precision exploration in old oilfields, reservoirs inside buried hills, and volcanic reservoirs will contribute a lot in increasing the annual oil-gas production and reserves in the basin.

摘要:It is concluded that there are three hydrocarbon generation and accumulation processes in northeastern Sichuan on the basis of the characteristics of solid bitumen, gas-light oils-heavy oils, homogenization temperature of fluid inclusions and diagenesis for beach- and reef-facies dolomite gas-bearing reservoirs in the Puguang Gas Field, northeastern Sichuan Basin, southern China. The first hydrocarbon generation and accumulation episode occurred in the Indosinian movement (late Middle Triassic). The sapropelic source rocks of the O3w (Upper Ordovician Wufeng Formation)-S1l (Lower Silurian Longmaxi Formation) were buried at depths of 2500 m to 3000 m with the paleogeothermal temperature ranging from 70°C to 95°C, which yielded heavy oil with lower maturity. At the same time, intercrystalline pores, framework pores and corrosion caused by organic acid were formed within the organic reef facies of P2ch (Upper Permian Changxing Formation). And the first stage of hydrocarbon reservoir occurred, the level of surface porosity of residual solid bitumen {solid bitumen/ (solid bitumen + residual porosity)} was higher than 60%. The second episode occurred during the Middle Yanshanian movement (late Middle Jurassic). During that period, the mixed organic source rocks were deposited in an intra-platform sag during the Permian and sapropelic source rocks of O3w-S1l experienced a peak stage of crude oil or light oil and gas generation because they were buried at depths of 3500 m to 6800 m with paleogeothermal temperatures of 96-168°C. At that time, the level of surface porosity of residual solid bitumen of the T1f shoal facies reservoirs was between 25% and 35%, and the homogenization temperatures of the first and second stages of fluid inclusions varied from 100°C to 150°C. The third episode occurred during the Late Yanshanian (Late Cretaceous) to the Himalayan movement. The hydrocarbon reservoirs formed during the T1f and P2ch had the deepest burial of 7700 m to 8700 m and paleogeotemperatures of 177°C to 220°C. They could be cracked into dry gas (methane), and the same with the source rocks of the Permian and O3w-S1l because they all reached the pyrolysis stage under such conditions. Consequently, the present natural gas (methane) reservoirs were developed.

摘要:The Songpan-Aba area, similar to those basins on the Yangtze block, following the rifting and separation of the Yangtze block, gradually developed into a passive marginal basin on a passive continent margin in Early Paleozoic, and later, with the Qinling-Qilian oceanic crust subduction and ocean closure, the Caledonides were formed and the foreland basin was superimposed upon. Being influenced by the Paleo-Tethyan extension, intra-continental rifting-margin basins were formed in Late Paleozoic. Following the formation of peripheral orogenic belt, the Upper Triassic again superimposed the foreland basin. The Mesozoic and Cenozoic overprinted the faulted basin, forming the Qinghai-Tibet Plateau domes. Hydrocarbon source rock in the Early Paleozoic passive basin, the Upper Paleozoic platform carbonates and the Triassic mudstones comprise the main source-reservoir-cap combination. Each layer of this area is at the advanced stage of diagenetic evolution, being entered the middle and late diagenetic stages, and anadiagenetic stage. Besides the highly matured Triassic and Permian in Zoigê and Hongyuan, almost all the area is at the early stage of over maturatation, generating much methane. This area has the potential for oil and gas.

摘要:Inspired from the anomaly of low pressure in the middle and deep reservoir of the Paleogene in the Jiyang depression, this paper discusses theoriticall “water consumption” of the principal mineral alteration during the diagenetic stage. The preliminary research result shows that “water consumption” of mineral alteration in the diagenetic stage can make formation water greatly decrease. Relevant formations will be in the stage of low pressure without supply of exterior liquid. Pressure differences between the relevant formations and wall rocks make hydrocarbons enter easily to form the effective reservoir.

摘要:Migration fractionation diagnosis is complicated in rifted basins where migration distance is generally short and lateral migration in sandy beds and vertical migration along faults are co-existed. Quantitative data from GC-MS analysis makes it possible to distinguish lateral and vertical migration effects. Oils discovered from the Jiaolige oilfield, eastern Lujiapu Depression are derived from single source rock with similar maturity, which is an ideal case to study the migration fractionation effects. Compositional differences among oils are largely caused by the migration fractionation either laterally in sand beds or vertically along the faults. Subtle maturity differences are assessed by the classic saturated hydrocarbon parameters which have certain influence on nitrogen compounds. In a certain maturity range, the ratios of shield and semi-shield isomers to the exposed isomers of alkylcarbazoles change with maturity in an opposite direction with migration fractionation, which may conceal the migration influence. However, migration and maturation have the same effects on absolute concentrations of alkylated carbazoles and benzocarbazole [a]/([a]+[c]) ratios, which provides an ideal tool for migration direction assessment. Continuous variations among different samples reflect increased migration distance in sandy beds, while abrupt changes may indicate the change of migration conduit systems. Integrated both geochemical interpretation and geological constrains, not only migration direction can be determined, but also the conduit systems through the sandy beds or the faults can be recognized.

摘要:Extensive organic-matter (OM) rich facies (black shales) occur in the Ordo-Silurian boundary successions in the Yangtze area, South China. To investigate the redox changes of the Yangtze Sea during the Ordo-Silurian transition, two OM sections (Wangjiawan in Yichang, Hubei Province, and Sanjiaguan in Zhangjiajie, Hunan Province) straddling the Ordo-Silurian boundary are studied. The measurements finished in this study include contents of the total organic carbon (TOC), pyrite sulphur, and different species of Fe, including dithionite-extractable Fe (FeD), pyrite Fe (FeP), HCl-extractable Fe (FeH), and total Fe (FeT), in black shales, as well as other redox proxies, such as the S/C ratio, the ratio between highly reactive Fe (FeHR = FeD + FeP) and FeT, and the FeP/(FeP + FeH) ratio, known as the degree of pyritization (DOP). In the Wangjiawan section, the Middle Ashgill sediments have high FeHR/FeT ratios (0.20–0.77; avg. 0.45), high DOP values (0.21–0.72; avg. 0.54), and a relatively constant sulfur content independent of the organic carbon content. By the contrast, the mid-early Hirnantian deposits generally have low FeHR/FeT ratios (0.10–0.35; avg. 0.21), low DOP values (0.11–0.40; avg. 0.28), and S/C values are clustering on the normal marine value (S/C = 0.36). The late Hirnantian and early Rhuddanian deposits, similar to those of the Middle Ashgill deposits, are characterized by high FeHR/FeT ratios (0.32–0.49; avg. 0.41), high DOP values (0.46–0.68; avg. 0.53) and fairly constant sulfur contents. These data suggest the occurrences of marine anoxia on the Yangtze Sea shelf during intervals of the Mid Ashgill, Late Hirnantian and Early Rhuddanian, and ventilated and oxygenated marine conditions during the mid-early Hirnantian time. The mid-early Hirnantian ventilated event was concomitant with the global glacial period, likely resulted from the glacio-eustatic sea-level fall and subsequent circulation of cold, dense oxygenated waters upon the shelf seabed. Accordingly, the abrupt change from oxygenated to anoxic marine waters from the late Hirnantian and the early Rhuddanian were resulted from the post-glacial rise of eustatic sea level. Combined with the data from Sanjiaguan section near the subemergent highland, salinity stratification of water columns are strongly evidenced by very low S/C ratios ( 0.00–0.08, avg. 0.02), low FeHR/FeT ratios (0.10–0.37, avg. 0.27), low DOP values (0.01–0.27, avg. 0.10), and TOC contents (0.72%–4.27%, avg. 2.55%). Under this circumstance, the anoxic water columns could have formed beneath the halocline, above which desalinized waters formed. In the Wangjiawan section, TOC contents are generally high (0.94–9.32%, avg. 4.44%), but low (0.35%–2.12%, avg. 1.29%) in the mid-early Hirnantian that is coincident with the oceanic oxic stage, together with relation of the organic contents to the stratal thickness, suggesting that the accumulation of the organic matter was mainly controlled by the oxygen levels of the water columns; on the other hand, productivity and depositional rate may also have played a role in the organic accumulation and preservation.

摘要:The distribution of the Jurassic coal measures in the northern Qaidam Basin is obviously controlled by the regional structures. Based on the existing data of coalfield exploration and combined with the analysis of coalfield basement structures, features of the main faults, and the distribution of coal measures, this paper brings forward a scheme of coalfield tectonic divisional units and the definition of the coal-controlling structural styles in the northern Qaidam Basin. The structure control of the distribution of coal measures is further discussed. Several stages of regional tectonic activities since the Indosinian has led to the distribution of coal measures into the characteristics of zonation from the north to south and block from east to west. The results indicate that the structural deformations are the most intense in the front of the three uplifted belts, which are characterized by the combination of thrusts. The coal measures are uplifted to the shallow formations, and are easy to be exploited, but the scale of mines is small because of serious damages by the coal distribution. On the contrary, the stress and strain are weak in the three depressions, with the coal-controlling structural styles being mainly the thrust-fold and thrust-monocline combinations. The distribution of coals in the depressions is relatively stable. The shallower part of the depression will become the key areas for exploration and development of coal resources in the northern Qaidam Basin.

摘要:Coal is China’s dominant energy resource. Coal geological exploration is the basis of sustainable development of coal industry. Since the late 1990s, the advances in Chinese coal geology and exploration techniques have been shown in the following aspects. (1) The basic research of coal geology has changed from traditional geological studies to earth system science; (2) Breakthroughs have been achieved in integrated exploration techniques for coal resources; (3) Evaluation of coal and coalbed methane resources provides important basis for macropolicy making for China’s coal industry and construction of large coal bases; (4) Significant advances have been made in using information technology in coal geological exploration and 3S (GPS, GIS, RS) technology. For the present and a period of time in the future, major tasks of Chinese coal geological technology are as follows: (1) solving resources replacement problem in eastern China and geological problems of deep mining; (2) solving problem of integrated coal exploration of complex regions in energy bases of central China, and resources problems induced by coal exploitation; (3) making efforts to enhance the level of geological research and resources evaluation of coal-accumulation basins in western China; (4) strengthening geological research of clean coal technologies; (5) strengthening geological research of the problems in modern coal mining and safe production; (6) promoting information technology in coal resources and major geological investigations.

摘要:Formation of coal seam and coal-rich zone is an integrated result of a series of factors in coal accumulation process. The coal accumulation system is an architectural aggregation of coal accumulation factors. It can be classified into 4 levels: the global coal accumulation super-system, the coal accumulation domain mega-system, the coal accumulation basin system, and the coal seam or coal seam set sub-system. The coal accumulation process is an open, dynamic, and grey system, and is meanwhile a system with such natures as aggregation, relevance, entirety, purpose-orientated, hierarchy, and environment adaptability. In this paper, we take coal accumulation process as a system to study origin of coal seam and coal-rich zone; and we will discuss a methodology of the systematic analysis of coal accumulation process. As an example, the Ordos coal basin was investigated to elucidate the application of the method of the coal accumulation system analysis.

摘要:Based on the systematic analysis of the coal gangue in Weibei Coalfield, such as petrologic characteristics, chemical composition, nutrient elements, deleterious elements, and the transformation, and compared with the soil element content background values of Loess Plateau and national harmful materials controlling standards, we conclude that the coal gangue in the Weibei Coalfield has huge potential to be used as clay fertilizer.

摘要:To promote the rational development and use of clean coal resources in China, data on the regional and age distribution of sulfur, arsenic and other harmful elements in Chinese coal was broadly collected, tested for content, and analyzed. Coal in northwestern China is characterized by low to extremely low levels of sulfur; the coal of the Taiyuan Formation in northern China mainly has high-sulfur content; that of the Shanxi Formation is mainly characterized by low sulfur coal; and the Late Permian coal in southern China has overall higher sulfur content; other regions have low sulfur coal. The average content of harmful trace elements in the bulk of China’s coal is similar to the corresponding content in the coal of the North America and the rest of the world, whereas the content of various elements (Hg, Sb and Se) is different in magnitude to the corresponding percentage in the crust. The average content of the elements Cr, Se, Co, Be, U, Br in Late Permian coal in S China ranks first in the country whereas the average content of Hg and Cl in the coals of Late Carboniferous to Early Permian age in N China are the highest. The average content of Mn in Early and Middle Jurassic coal is higher in NW China. The high content of harmful elements in some coal should cause particular concern both in the development and utilization of coal.