Structural characteristics and deep-water hydrocarbon accumulation model of the Scotian Basin, Eastern Canada

Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is still insufficient, which constrains the oil and gas exploration in deep-water areas. Based on comprehensive data of magnetic anomalies, seismic survey, and drilling, this study determines the structure characteristics of the Scotian Basin and its hydrocarbon accumulation conditions in deep waters and evaluates the deep-water hydrocarbon exploration potential. The transform faults and basement structures in the northern basin control the sedimentary framework showing thick strata in east and thin strata in west of the basin. The bowl-shaped depression formed by thermal subsidence during the transitional phase and the confined environment (micro basins) caused by salt tectonics provide favorable conditions for the development of source rocks during the depression stage (also referred to as the depression period sequence) of the basin. The progradation of large shelf-margin deltas during the drift phase and steep continental slope provide favorable conditions for the deposition of slope-floor fans on continental margins of the basin. Moreover, the source-reservoir assemblage comprising the source rocks within the depression stage and the turbidite sandstones on the continental margin in the deep waters may form large deep-water turbidite sandstone reservoirs. This study will provide a valuable reference for the deep-water hydrocarbon exploration in the Scotian Basin.

Quantitative prediction model for the depth limit of oil accumulation in the deep carbonate rocks:A case study of Lower Ordovician in Tazhong area of Tarim Basin

With continuous hydrocarbon exploration extending to deeper basins,the deepest industrial oil accumulation was discovered below 8,200 m,revealing a new exploration field.Hence,the extent to which oil exploration can be extended,and the prediction of the depth limit of oil accumulation(DLOA),are issues that have attracted significant attention in petroleum geology.Since it is difficult to characterize the evolution of the physical properties of the marine carbonate reservoir with burial depth,and the deepest drilling still cannot reach the DLOA.Hence,the DLOA cannot be predicted by directly establishing the relationship between the ratio of drilling to the dry layer and the depth.In this study,by establishing the relationships between the porosity and the depth and dry layer ratio of the carbonate reservoir,the relationships between the depth and dry layer ratio were obtained collectively.The depth corresponding to a dry layer ratio of 100%is the DLOA.Based on this,a quantitative prediction model for the DLOA was finally built.The results indicate that the porosity of the carbonate reservoir,Lower Ordovician in Tazhong area of Tarim Basin,tends to decrease with burial depth,and manifests as an overall low porosity reservoir in deep layer.The critical porosity of the DLOA was 1.8%,which is the critical geological condition corresponding to a 100%dry layer ratio encountered in the reservoir.The depth of the DLOA was 9,000 m.This study provides a new method for DLOA prediction that is beneficial for a deeper understanding of oil accumulation,and is of great importance for scientific guidance on deep oil drilling.

Tectonic evolution and accumulation characteristics of Carboniferous shale gas in Yadu-Ziyun-Luodian aulacogen, Guizhou Province, South China

The Yadu-Ziyun-Luodian aulacogen(YZLA) developed into being NW-trending in the Late Paleozoic,and was considered as an important passive continental margin aulacogen in Guizhou Province, South China. This tectonic zone is considered a large intracontinental thrust-slip tectonic unit, which has undergone a long period of development. It was ultimately determined in the Yanshanian, where the typical Upper Paleozoic marine shales were deposited. In 2021, Well QSD-1 was deployed in the Liupanshui area at the northwest margin of the aulacogen, and obtained a daily shale gas flow of 11011 m3in the Carboniferous Dawuba Formation. It thus achieved a breakthrough in the invesgation of shale gas in the Lower Carboniferous in South China, revealing relatively good gas-bearing properties and broad exploration prospects of the aulacogen. Being different from the Lower Paleozoic strata in the Sichuan Basin and the Yichang area of the Middle Yangtze, the development of the Carboniferous Dawuba Formation in the aulacogen exhibits the following characteristics:(1) The Lower Carboniferous shale is thick and widely distributed, with interbedded shale and marlstone of virous thickness;(2) The total organic carbon(TOC) content of the shale in the Dawuba Formation ranges from 1% to 5%, with an average of 2%, and the thermal maturity of organic matter(Ro) varies from 1% to 4%, with an average of2.5%, indicating good hydrocarbon generation capacity;(3) The main shale in the aulacogen was formed during the fault subsidence stage from the Middle Devonian to the Early Permian. Although the strong compression and deformation during the late Indosinian-Himalayan played a certain role in destroying the formed shale gas reservoirs, comparative analysis suggests that the area covered by the current Triassic strata has a low degree of destruction. It therefore provides good conditions for shale gas preservation,which can be regarded as a favorable area for the next exploration.

Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

Numerical Simulations of Snow Accumulation in the Bogie Region of a Train Considering Snow Particle Rotation

To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains,an Euler‒Lagrange numerical approach is adopted.The study examines the effects of snow particle diameter and train speed on the ensuing dynamics.It is shown that considering snow particle rotational motion causes significant deviation in the particle trajectories with respect to non-rotating particles.Such a deviation increases with larger snow particle diameters and higher train speeds.The snow accumulation on the overall surface of the bogie increases,and the amount of snow on the vibration reduction device varies greatly.In certain conditions,the amount of accumulated snow can increase by several orders of magnitudes.

Mechanism of cross-level settlements and void accumulation of wide and conventional sleepers in railway ballast

The cross-level and twist irregularities are the most dangerous irregularity types that could cause wheel unloading with the risk of derailments and additional maintenance expenses.However,the mechanism of the irregularities initiation and development is unclear.The motivation of the present study was the previous experimental studies on the application of wide sleepers in the ballasted track.The long-term track geometry measurements with wide sleepers show an enormous reduction of the vertical longitudinal irregularities compared to the conventional track.However,wide sleepers had higher twist and cross-section level irregularities.The present paper aims to explain the phenomenon by discrete element method(DEM)modeling the development process of sleeper inhomogeneous support at cross-level depending on the sleeper form.The DEM simulations show that the maximal settlement intensity is up to 3.5 times lower for a wide sleeper in comparison with the conventional one.Nevertheless,the cross-level differential settlements are almost the same for both sleepers.The particle loading distribution after all loading cycles is concentrated on the smaller area,up to the half sleeper length,with fully unloaded zones under sleeper ends.Ballast flow limitation under the central part of the sleeper could improve the resilience of wide sleepers to the development of cross-level irregularities.The mechanism of initiation of the cross-level irregularity is proposed,which assumes the loss of sleeper support under sleeper ends.The further growth of inhomogeneous settlements along the sleeper is assumed as a result of the interaction of two processes:ballast flow due to dynamic impact during void closing and on the other side high pressure due to the concentration of the pressure under the middle part of the sleeper.The DEM simulation results support the assumption of the mechanism and agree with the experimental studies.

Distribution Characteristics and Accumulation Model for the Coal-formed Gas Generated from Permo-Carboniferous Coal Measures in Bohai Bay Basin, China: A Review

Coal-formed gas generated from the Permo-Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin,offshore eastern China.However,the proven gas reserves from this source rock remain low to date,and the distribution characteristics and accumulation model for the coal-formed gas are not clear.Here we review the coal-formed gas deposits formed from the Permo-Carboniferous coal measures in the Bohai Bay Basin.The accumulations are scattered,and dominated by middle-small sized gas fields,of which the proven reserves ranging from 0.002 to 149.4×108 m3 with an average of 44.30×108 m3 and a mid-point of 8.16×108 m3.The commercially valuable gas fields are mainly found in the central and southern parts of the basin.Vertically,the coal-formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic,among which the Paleogene and PermoCarboniferous are the main reservoir strata.According to the transporting pathway,filling mechanism and the relationship between source rocks and reservoir,the coal-formed gas accumulation model can be defined into three types:"Upward migrated,fault transported gas"accumulation model,"Laterally migrated,sandbody transported gas"accumulation model,and"Downward migrated,sub-source,fracture transported gas"accumulation model.Source rock distribution,thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal-formed gas.The fault activity and the configuration of fault and caprock control the vertical enrichment pattern.

Whole petroleum system and hydrocarbon accumulation model in shallow and medium strata in northern Songliao Basin,NE China

Based on the oil and gas exploration practice in the Songliao Basin,combined with the latest exploration and development data such as seismic,well logging and geochemistry,the basic geological conditions,oil and gas types and distribution characteristics,reservoir-forming dynamics,source-reservoir relationship and hydrocarbon accumulation model of the whole petroleum system in shallow and medium strata in the northern part of Songliao Basin are systematically studied.The shallow-medium strata in northern Songliao Basin have the conditions for the formation of whole petroleum system,with sufficient oil and gas sources,diverse reservoir types and well-developed transport system,forming a whole petroleum system centered on the source rocks of the Cretaceous Qingshankou Formation.Different types of oil and gas resources in the whole petroleum system are correlated with each other in terms of depositional system,lithologic association and physical property changes,and they,to a certain extent,have created the spatial framework with orderly symbiosis of shallow-medium conventional oil reservoirs,tight oil reservoirs and shale oil reservoirs in northern Songliao Basin.Vertically,the resources are endowed as conventional oil above source,shale oil/tight oil within source,and tight oil below source.Horizontally,conventional oil,tight oil,interlayer-type shale oil,and pure shale-type shale oil are developed in an orderly way,from the margin of the basin to the center of the depression.Three hydrocarbon accumulation models are recognized for the whole petroleum system in northern Songliao Basin,namely,buoyancy-driven charging of conventional oil above source,retention of shale oil within source,and pressure differential-driven charging of tight oil below source.

Tight gas charging and accumulation mechanisms and mathematical model

The gas-water distribution and production heterogeneity of tight gas reservoirs have been summarized from experimental and geological observations, but the charging and accumulation mechanisms have not been examined quantitatively by mathematical model. The tight gas charging and accumulation mechanisms were revealed from a combination of physical simulation of nuclear magnetic resonance coupling displacement, numerical simulation considering material and mechanical equilibria, as well as actual geological observation. The results show that gas migrates into tight rocks to preferentially form a gas saturation stabilization zone near the source-reservoir interface. When the gas source is insufficient, gas saturation reduction zone and uncharged zone are formed in sequence from the source-reservoir interface. The better the source rock conditions with more gas expulsion volume and higher overpressure, the thicker the gas saturation stabilization and reduction zones, and the higher the overall gas saturation. When the source rock conditions are limited, the better the tight reservoir conditions with higher porosity and permeability as well as larger pore throat, the thinner the gas saturation stabilization and reduction zones, but the gas saturation is high. The sweet spot of tight gas is developed in the high-quality reservoir near the source rock, which often corresponds to the gas saturation stabilization zone. The numerical simulation results by mathematical model agree well with the physical simulation results by nuclear magnetic resonance coupling displacement, and reasonably explain the gas-water distribution and production pattern of deep reservoirs in the Xujiaweizi fault depression of the Songliao Basin and tight gas reservoirs in the Linxing-Huangfu area of the Ordos Basin.

Preliminary Study on the Accumulation Characteristics of Mineral Elements in Potted Poa crymophila under Drought and Water Stress

[Objective] This study was conducted to explain the mechanism of the accumulation characteristics of mineral elements in alpine grassland plants. [Method] Cultivated alpine grassland plant, Poa crymophila, was treated with drought and wa- ter stress, and then the samples were collected and analyzed. [Result] Compared with the control group, under drought and water stress, multiple mineral elements tended to accumulate and increase, and there were significant differences in the contents of Cu, Mn, Ni and P （P〈0.05）. [Conclusion] Under drought and water stress, mineral elements in potted Poa crymophila tended to accumulate and in- crease, which is the adaption and response of Poa crymophila to drought and water stress, as well as the re-verification of the starvation effect hypothesis of mineral effects. The starvation effect of mineral elements is one of the endogenic forces for the accumulation and differentiation of mineral elements in grassland plants.

Reservoir characteristics and formation model of Upper Carboniferous bauxite series in eastern Ordos Basin,NW China

Through core observation,thin section identification,X-ray diffraction analysis,scanning electron microscopy,and low-temperature nitrogen adsorption and isothermal adsorption experiments,the lithology and pore characteristics of the Upper Carboniferous bauxite series in eastern Ordos Basin were analyzed to reveal the formation and evolution process of the bauxite reservoirs.A petrological nomenclature and classification scheme for bauxitic rocks based on three units(aluminum hydroxides,iron minerals and clay minerals)is proposed.It is found that bauxitic mudstone is in the form of dense massive and clastic structures,while the(clayey)bauxite is of dense massive,pisolite,oolite,porous soil and clastic structures.Both bauxitic mudstone and bauxite reservoirs develop dissolution pores,intercrystalline pores,and microfractures as the dominant gas storage space,with the porosity less than 10% and mesopores in dominance.The bauxite series in the North China Craton can be divided into five sections,i.e.,ferrilite(Shanxi-style iron ore,section A),bauxitic mudstone(section B),bauxite(section C),bauxite mudstone(debris-containing,section D)and dark mudstone-coal section(section E).The burrow/funnel filling,lenticular,layered/massive bauxite deposits occur separately in the karst platforms,gentle slopes and low-lying areas.The karst platforms and gentle slopes are conducive to surface water leaching,with strong karstification,well-developed pores,large reservoir thickness and good physical properties,but poor strata continuity.The low-lying areas have poor physical properties but relatively continuous and stable reservoirs.The gas enrichment in bauxites is jointly controlled by source rock,reservoir rock and fractures.This recognition provides geological basis for the exploration and development of natural gas in the Upper Carboniferous in the study area and similar bauxite systems.

Characteristics of Cd uptake and accumulation in two Cd accumulator oilseed rape species

Two pot experiments were conducted under greenhouse conditions to investigate the characteristics of Cd uptake and accumulation by two Cd accumulator oilseed rape varieties and one Indian mustard grown on a loamy soil that had been artificially contaminated by different amounts of CdSO\-4(0, 20, 40, 60, 80, 100 mg/kg soil). The relationship between shoot Cd uptake of the two oilseed rape cultivars and the soil Cd concentrations could be simulated via quadratic equations. The curve showed that maximum shoot Cd uptake of Indian mustard was 314.7 μg/pot at soil Cd concentration of 87.8 mg/kg, while maximum uptake of the variety Xikou Huazi was 543.3 μg/pot at soil Cd concentration of 69.1 mg/kg and that of the variety Zhongyou Za-1hao was 576.7 μg/pot at soil Cd concentration of 84.0 mg/kg, suggesting that shoot Cd uptake ability of the two Cd accumulator oilseed rapes was significantly higher than that of the Indian mustard. Xikou Huazi had higher phytoremediation potential for Cd contaminated soil. Shoot Cd accumulation ability of the two Cd accumulator oilseed rapes was correspond and Cd was easier translocated to the shoot than hyperaccumulator Indian mustard as comparation plant. Shoot Cd distribution pattern showed consistent and significant reduction from older leaves to younger ones of two oilseed rapes and Indian mustard. Cd uptake by oilseed rapes in growth prophase was higher than that of growth anaphase.

Geological characteristics and accumulation mechanisms of the "continuous" tight gas reservoirs of the Xu2 Member in the middle-south transition region,Sichuan Basin,China

＂Continuous＂ tight gas reservoirs are those reservoirs which develop in widespread tight sandstones with a continuous distribution of natural gas. In this paper, we summarize the geological features of the source rocks and ＂＇continuous＂ tight gas reservoirs in the Xujiahe Formation of the middle- south transition region, Sichuan Basin. The source rocks of the Xul Member and reservoir rocks of the Xu2 Member are thick （Xul Member： 40 m, Xu2 Member： 120 m） and are distributed continuously in this study area. The results of drilled wells show that the widespread sandstone reservoirs of the Xu2 Member are charged with natural gas. Therefore, the natural gas reservoirs of the Xu2 Member in the middle-south transition region are ＂continuous＂ tight gas reservoirs. The accumulation of ＂continuous＂ tight gas reservoirs is controlled by an adequate driving force of the pressure differences between source rocks and reservoirs, which is demonstrated by a ＂one-dimensional＂ physical simulation experiment. In this simulation, the natural gas of＂continuous＂ tight gas reservoirs moves tbrward with no preferential petroleum migration pathways （PPMP）, and the natural gas saturation of＂continuous＂ tight gas reservoirs is higher than that of conventional reservoirs.

Distribution and Accumulation Characteristics of Heavy Metals in Sediments in Southern Sea Area of Huludao City, China

The southern sea area of the Huludao City, Liaoning Province might be polluted by heavy metals because it is close to the Jinzhou Bay, one of the heaviest sea area polluted by heavy metals in China. The undisturbed modem sediment core can be used to analyze the accumulation and source of the pollutants using 137Cs and 21pbex. Thirty-five samples of surface sediment and two core sedi- ments were collected from the southern sea area of Huludao City. The concentrations of copper （Cu）, lead （Pb）, chrome （Cr）, zinc （Zn）, arsenic （As） and mercury （Hg） in the surface sediments as well as Cu, Pb, Zn, Cr, 137Cs and 2~~pbex in the core sediments were deter- mined to research the spatial distribution and accumulation characteristics, and to analyze the sources and the potential risks of heavy metals. The results show that the pollution levels of Zn and Hg are serious, and 26 stations are at moderate or heavy ecological risks. The concentrations of the heavy metals increase from east to west, as well as from open sea to offshore marine area. The concentrations of heavy metals are not high in the sediments adjacent to the Jinzhou Bay, and the influence caused by the seawater exchange with the Jinzhou Bay is little. The concentrations of the heavy metals in the core sediments show low-high-low characteristic, and it coincides with the pollution history of Huludao City. The atmospheric deposition of heavy metals from the Huludao Zinc Plant is likely to be the main source of pollution without direct discharge of wastewater. The high concentrations of heavy metals appear on the upper sediment of 20 cm. The shallow sediment with high heavy metal contents might be exposed to surface when it was disturbed by the ocean engineering and big storm surge, then cause risk to the safety of aouaculture and human honlthy.

Hydrocarbon accumulation characteristics of beachbar sandstones in the southern slope of the Dongying Sag, Jiyang Depression, Bohai Bay Basin, China

A number of beach-bar sandstone reservoir beds are developed in the upper fourth member of the Eocene Shahejie Formation （Es4s） on the southern slope of the Dongying Sag.Based on the analysis of seismic and logging data,with characterization and petrographic studies of core and cutting samples,this paper analyzes the hydrocarbon accumulation characteristics in two typical blocks of the Boxing and Wangjiagang oilfields,especially reservoir bed heterogeneity and migration conditions that influence oil and gas distribution,calculates the index of reservoir bed quality （IRQ） with a mathematical method,and discusses the relationship between driving force and resistance of hydrocarbon accumulation.Taking into account the characteristics of thin interbeds in beach-bar sandstones,an experimental model simulated the characteristics of hydrocarbon migration and accumulation in thin interbedded sandstones with reservoir bed heterogeneity.The results showed that hydrocarbon distribution and properties were extremely non-uniform.Reservoir bed and migration conditions controlled hydrocarbon accumulation in beach-bar sandstones.IRQ is above 0.4 in the main hydrocarbon region.Sand body distribution,structural configuration and fault systems controlled the direction of regional migration and location of hydrocarbon accumulation.Simulation experiments indicated that the change of driving force for hydrocarbon migration affected selective accumulation mechanisms.Hydrocarbon moved vertically along fault zones to the reservoir and resulted in the distribution of hydrocarbon in the reservoir.Two kinds of hydrocarbon accumulation models exist in the study area.One is a hydrocarbon accumulation model controlled by reservoir bed heterogeneity and the second is a hydrocarbon accumulation model controlled by a complex migration system with faults connecting sandbodies.Finally,different exploration strategies should be adopted for the detailed exploration for beach-bar sandstone reservoirs according to different geological backgrounds.

Numerical simulatim of rainwater accumulation and flow characteristics over windshield of high-speed trains

In this paper, a Euler-Lagrangian particle/fluid film/VOF coupled multiphase flow model is presented. Numerical simulations are conducted, and the rainwater accumulation and flow characteristics over two types of windshields are studied based on the presented model. The results show that an uneven water film is formed over the windshield, with rain water accumulation occurring for the concave windshield but not for the convex windshield. At low speeds, the average fluid-film thickness for a concave windshield is larger than that of a convex windshield;however, a minor difference occurs between these two values at high speeds, and a critical velocity is observed for the two types of windshields. When the train velocity is less than the critical velocity, the fluid film at the lower part of the windshield and the train nose flows downward, and beyond the critical velocity, the fluid film over the entire windshield and train nose flows upward.

Studies on the Photosynthetic Characteristics andAssimilate's Accumulation and Transformation inHeavy Panicle Type of Rice

Using 18 indica rice varieties with different panicle weight, the photosynthetic characteristics and assimilate's accumulation and transformation in heavy panicle type of rice(HPT)were studied. The results showed that the net photosynthetic rate of the flag leaf in HPT after heading was obviously higher than that in medium panicle type(MPT)and light panicle type(LPT). The reason for the high net photosynthetic rate in HPT was the increase of Rubisco activities and chlorophyll content, and keeping high assimilate ability to CO2 under high and low light intensity, high temperature and low CO2 content, and light midday depression and wide adaptability to environmental conditions. The high net photosynthetic rate of HPT might be also the results of its excellent stomatal characteristics and higher total quantity of stomatal opening degrees(stomatal density X stomatal opening degrees). There was a large amount of dry matter production after heading and obvious high assimilate's transformation to panicle in HPT.

Structural Characteristics and their Significance for Hydrocarbon Accumulation in the Northern Slope of the Central Sichuan Paleo-uplift

Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.

Reservoir characteristics and hydrocarbon accumulation of Carboniferous volcanic weathered crust of Zhongguai high area in the western Junggar Basin, China

Based on the drilling,cores,logs,seismic,laboratory analysis and so on,reservoir characteristics and hydrocarbon accumulation of Carboniferous volcanic weathered crust in Zhongguai high area are studied.Volcanic rocks were formed in an island arc environment.The lithology is mainly andesite and tuff;Reservoir spaces are mainly secondary pore,fracture and their combination forms,fractures have a better effect on reservoir seepage;There are four layer structures of volcanic weathered crust,weathered clay layer,strongly weathered zone,weakly weathered zone and unweathered zone and strongly weathered zone is the best,which is the main reservoir development zone;The development of reservoir is mainly affected by weathering-leaching,lithology and lithofacies,and fault(fracture);Effective reservoirs could reach to 480 m thickness(high quality reservoirs are within 240 m).Carboniferous volcanic reservoirs are distributed along three zones,which are near the fault zone,high structural part,favorable lithofacies development zone,and one plane,which is near the unconformity.

Formation conditions and accumulation characteristics of Bozhong 19-6 large condensate gas field in offshore Bohai Bay Basin

Based on the study of natural gas resource, low buried hill trap formation mechanism, high quality reservoir control factors and natural gas preservation conditions, the formation conditions and reservoir accumulation characteristics of Bozhong 19-6 large condensate gas field were summarized. Large gas generation potential of multiple sets of thick humic-sapropelic source rocks in high maturity stage in Bozhong depression was the basis of large gas field formation. The multi-stage tectonic evolution since Indosinian period formed large-scale buried hill traps. The Tanlu fault activity formed multi-type reservoirs, and buried hill metamorphic rock of Archean and sand-conglomerate of Kongdian Formation were high-quality reservoirs. Thick overpressure lacustrine mudstone and weak neotectonic movement provided good preservation conditions. Bozhong 19-6 gas reservoir was a condensate gas reservoir with very high condensate oil content, and the gas origin was humic-sapropelic and kerogen-cracking gas, and the gas field had large gas thickness, high gas column characteristics and the accumulation process was first oil and then gas. The buried hill reservoir was a massive reservoir and the Kongdian reservoir was a stratified reservoir. The gas field had multi-channel hydrocarbon intense charge from overpressure source rocks, atmospheric-weak overpressure reservoir favorable for accumulation, thick overpressure mudstone caprock favorable for preservation, and natural gas ultra-late rapid accumulation model.