The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data a...The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data and drilling information,utilized sequence stratigraphy and seismic sedimentology as guidelines,and employed seismic interpretation methods to performed a division of deepsea stratigraphic sequences within the Romney 3D seismic survey area in the deep-water Taranaki Basin,New Zealand.Furthermore,it analyzed the characteristics of typical depositional systems and their associated controlling factors.The findings are as follows:(1)Based on seismic reflection termination relationships and seismic facies characteristics,four second-order sequence boundaries and nine thirdorder sequence boundaries were identified,resulting in the delineation of three second-order sequences and twelve third-order sequences in the basin.(2)Five seismic facies were recognized,corresponding to five typical sedimentary bodies:mass transport deposits(MTDs),deep-water channel,levee deposits,deltaic deposits,and pelagic deposits.However,due to the relatively thin sedimentary thickness of carbonate sediments,the seismic facies characteristics of carbonate sediments cannot be discerned in seismic data,but can be identified based on well data.Deltaic sediments mainly developed during the rift stage of the basin,while carbonate sediments formed during the transition from a passive to an active margin.Deep-water channel and levee deposits and MTDs emerged during the active margin stage,while pelagic deposits are ubiquitous in marine environments.(3)The uplift of New Zealand's interior and climate-driven erosion caused the resurgence of clastic sediments,which began to be transported to the deep sea,the seafloor topography would directly affect the movement path of sediment gravity flow,and sediment supply can affect the development and evolution of sedimentary systems.(4)Event deposits boundaries,such as erosional scour surfaces formed by channels and unconformities created by MTDs,can serve as boundaries for the division of deep-water stratigraphic sequences.This study proposes a method for delineating deep-water stratigraphic sequences using event deposits,particularly suitable under conditions where the influence of relative sea-level changes on deep-water deposits is relatively weak.This research not only enhances the understanding of deep-water depositional sequences but also provides a reference for studies on the evolution of deep-water deposition and its controlling factors in research areas with similar geological backgrounds worldwide.展开更多
Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysi...Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysis of the main source rocks,reservoirs,and vertical migration pathways within the Rovuma(RB)and Tanzania(TB)basins in East Africa utilizing drilling,logging,seismic,and geochemical data.The results indicate that the enhanced preservation conditions of the Lower Jurassic source rocks in the southwest could lead to the discovery of large natural gas fields in the southern TB and RB.The primary reservoir is a deep-water turbidite sandstone.Due to topographic differences,the expanse of the turbidite sandstones in the RB is significantly larger than those in Tanzania.The main vertical migration pathways are the western boundary fault zone of the Kerimbas Graben(WBFZ)and the Seagap fault zone(SFZ).In the RB,natural gas migrates vertically along the WBFZ and preferentially accumulates in the deep-water turbidite sandstones of the footwall under the control of the fluid potential.Conversely,in the southern TB,the deep natural gas first migrates upward along the SFZ,then moves along the shallow branch faults in the sandstones on both sides of the SFZ.展开更多
The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration.Based on the newly acquired high...The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration.Based on the newly acquired high-resolution 3D seismic,logging and core data of Pearl River Mouth Basin(PRMB),this paper dissected the shelf-edge delta to deep-water fan(SEDDF)depositional system in the Oligocene Zhuhai Formation of Paleogene in south subsag of Baiyun Sag,and revealed the complex coupling relationship from the continental shelf edge to deep-water fan sedimentation and its genetic mechanisms.The results show that during the deposition of the fourth to first members of the Zhuhai Formation,the scale of the SEDDF depositional system in the study area showed a pattern of first increasing and then decreasing,with deep-water fan developed in the third to first members and the largest plane distribution scale developed in the late stage of the second member.Based on the development of SEDDF depositional system along the source direction,three types of coupling relationships are divided,namely,deltas that are linked downdip to fans,deltas that lack downdip fans and fans that lack updip coeval deltas,with different depositional characteristics and genetic mechanisms.(1)Deltas that are linked downdip to fans:with the development of shelf-edge deltas in the shelf area and deep-water fans in the downdip slope area,and the strong source supply and relative sea level decline are the two key factors which control the development of this type of source-to-sink(S2S).The development of channels on the continental shelf edge is conducive to the formation of this type of S2S system even with weak source supply and high sea level.(2)Deltas that lack downdip fans:with the development of shelf edge deltas in shelf area,while deep water fans are not developed in the downdip slope area.The lack of“sources”and“channels”,and fluid transformation are the three main reasons for the formation of this type of S2S system.(3)Fans that lack updip coeval deltas:with the development of deep-water fans in continental slope area and the absence of updip coeval shelf edge deltas,which is jointly controlled by the coupling of fluid transformation at the shelf edge and the“channels”in the continental slope area.展开更多
It has been a challenge to distinguish between seismic anomalies caused by complex lithology and hydrocarbon reservoirs using conventional fluid identification techniques,leading to difficulties in accurately predicti...It has been a challenge to distinguish between seismic anomalies caused by complex lithology and hydrocarbon reservoirs using conventional fluid identification techniques,leading to difficulties in accurately predicting hydrocarbon-bearing properties and determining oil-water contacts in reservoirs.In this study,we built a petrophysical model tailored to the deep-water area of the Baiyun Sag in the eastern South China Sea based on seismic data and explored the feasibility of the tri-parameter direct inversion method in the fluid identification of complex lithology reservoirs,offering a more precise alternative to conventional techniques.Our research found that the fluid modulus can successfully eliminate seismic amplitude anomalies caused by lithological variations.Furthermore,the seismic databased direct inversion for fluid modulus can remove the cumulative errors caused by indirect inversion and the influence of porosity.We discovered that traditional methods using seismic amplitude anomalies were ineffective in detecting fluids,determining gas-water contacts,or delineating high-quality reservoirs.However,the fluid factor Kf,derived from solid-liquid decoupling,proved to be sensitive to the identification of hydrocarbon-bearing properties,distinguishing between high-quality and poor-quality gas zones.Our findings confirm the value of the fluid modulus in fluid identification and demonstrate that the tri-parameter direct inversion method can significantly enhance hydrocarbon exploration in deep-water areas,reducing associated risks.展开更多
The shallow shelf delta/strand arenaceous-pelitic deposit region in the north of the Pearl River mouth basin, sitting on the northern continental shelf of the South China Sea, has already become an important oil produ...The shallow shelf delta/strand arenaceous-pelitic deposit region in the north of the Pearl River mouth basin, sitting on the northern continental shelf of the South China Sea, has already become an important oil production base in China. Recent researched has revealed that a great deal of deep-water fans of great petroleum potentiality exist on the Baiyun deep-water slope below the big paleo Pearl River and its large delta. Based on a mass of exploration wells and 2-D seismic data of the shallow shelf region, a interpretation of sequence stratigraphy confirmed the existence of deep-water fans. The cyclic falling of sea level, abundant detrital matter from the paleo Pearl River and the persistent geothermal subsidence in the Baiyun sag are the three prerequisites for the formation and development of deep-water fans. There are many in common between the deep-water shelf depositional system of the northern South China Sea and the exploration hotspots region on the two banks of the Atlantic. For example, both are located on passive continent margins, and persistent secular thermal subsidence and large paleo rivers have supplied abundant material sources and organic matter. More recently, the discovery of the big gas pool on the northern slope of the Baiyun sag confirms that the Lower Tertiary lacustrine facies in the Baiyun sag has a great potentiality of source rocks. The fans overlying the Lower Tertiary source rocks should become the main exploration areas for oil and gas resources.展开更多
Submarine canyon systems are sites for coarser clastic sediment accumulations in the deep-water domains, having the most potential for hydrocarbon reservoirs. Based on the interpretation of high resolution 2 D/3 D sei...Submarine canyon systems are sites for coarser clastic sediment accumulations in the deep-water domains, having the most potential for hydrocarbon reservoirs. Based on the interpretation of high resolution 2 D/3 D seismic and drilling data, depositional characteristics of three large deep-water canyon systems on the South China Sea northern margin have been analyzed. The Central Canyon System has a deep incision geomorphology extending from east to west, featured by distinct canyon segmentations, multi-provenance sediment supplies and multi-stage canyon fillings. The Pearl River Canyon System’s formation is closely related to the development of Pearl River Delta. Its vertical stacking and migrating canyon patterns have changed over time. The depositional architectures and evolution of the recent Penghu-Gaoping Canyon System respond to tectonic movements along the Taiwan-Luzon convergent continental margin. The main controlling factors of the formation and evolution of these three canyon systems include the tectonic setting, sediment supply, sea level change and paleo-geomorphology, among which the former two are dominant. The Penghu-Gaoping Canyon System formed along the subduction structural zone, directly indicating a typical tectonic origin. Numerous seismic data show that the Central Canyon and Pearl River Canyon systems are obviously affected by tectonics, associated local topography and sediment supply.展开更多
In order to optimize the design of a 12.5 m deepwater channel project and protect the ecological environment, it is necessary to study the habitat evaluation of species in the engineered area. A coupled eco-hydrodynam...In order to optimize the design of a 12.5 m deepwater channel project and protect the ecological environment, it is necessary to study the habitat evaluation of species in the engineered area. A coupled eco-hydrodynamic model, which combines a hydrodynamic model （ADCIRC） and a habitat suitability index （HSI） model is developed for target fish （Coilia nasus） and benthos （Corbicula fluminea） in the Yangtze River in order to predict the ecological changes and optimize the regulation scheme. Based on the existing research concerning the characteristics of Coilia nasus and Corbicula fluminea, the relationship between the target species and water environment factors is established. The verification results of tidal level, velocity and biological density show that the proposed coupling model performs well when predicting ecological suitability in the studied region. The results indicate a slight improvement in the potential habitat availability for the two species studied as the natural hydraulic conditions change after the deep-water channel regulation works.展开更多
Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration a...Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world.展开更多
Deep-water gravity flows are one of the most important sediment transport mechanisms on Earth. After 60 years of study, significant achievements have been made in terms of classification schemes, genetic mechanisms, a...Deep-water gravity flows are one of the most important sediment transport mechanisms on Earth. After 60 years of study, significant achievements have been made in terms of classification schemes, genetic mechanisms, and depositional models of deep-water gravity flows. The research history of deep-water gravity flows can be divided into five stages： incipience of turbidity current theory; formation of turbidity current theory; development of deep-water gravity flow theory; improvement and perfection of deep-water gravity flow theory; and comprehensive development of deep-water gravity flow theory. Currently, three primary classification schemes based on the sediment support mechanism, the rheology and transportation process, and the integration of sediment support mechanisms, rheology, sedimentary characteristics, and flow state are commonly used.Different types of deep-water gravity flow events form different types of gravity flow deposits. Sediment slump retransportation mainly forms muddy debris flows, sandy debris flows, and surge-like turbidity currents. Resuspension of deposits by storms leads to quasi-steady hyperpycnal turbidity currents （hyperpycnal flows）. Sustainable sediment supplies mainly generate muddy debris flows, sandy debris flows, and hyperpycnal flows. Deep-water fans, which are commonly controlled by debris flows and hyperpycnal flows, are triggered by sustainable sediment supply; in contrast, deep-water slope sedimentary deposits consist mainly of debris flows that are triggered by the retransportation of sediment slumps and deep-water fine-grained sedimentary deposits are derived primarily from fine- grained hyperpycnal flows that are triggered by the resuspension of storm deposits. Harmonization of classification schemes, transformation between different types of gravity flow deposit, and monitoring and reproduction of the sedimentary processes of deep-water gravity flows as well as a source-to-sink approach to document the evolution and deposition of deep-water gravity flows are the most important research aspects for future studies of deep-water gravity flows study in the future.展开更多
A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of ...A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.展开更多
Due to its structure,rock and mineral composition,fluid and other factors,the granite Buried Hill Reservoir is highly heterogeneous with a complex longitudinal structure and a reservoir space made up of a combination ...Due to its structure,rock and mineral composition,fluid and other factors,the granite Buried Hill Reservoir is highly heterogeneous with a complex longitudinal structure and a reservoir space made up of a combination of dissolution pores and fractures.This paper is based on current understanding of tectonic evolution in the northern part of the South China Sea,in conjunction with the seismic phase characteristics.It is determined that the meshed fault system was formed by three stages of movement-tectonic compression orogeny during the Indochinese epoch,strike-slip compression-tension during the Yanshanian Period,early fracture extension activation during the Himalayan-which controlled the distribution of the Buried Hill Reservoir.Drilling revealed two types of buried hills,faulted anticline and fault horst,their longitudinal structure and the reservoir space type being significantly different.The mineral composition,reservoir space and diagenetic characteristics of the reservoir rocks and minerals were analyzed by lithogeochemistry,micro section and logging etc.,it thus being determined that the Mesozoic rocks of the Songnan Low Uplift in the Qiongdongnan Basin are mainly composed of syenogranite,granodiorite,monzogranite,which is the material basis for the development of the Buried Hill Reservoir.The content of felsic and other brittle minerals is more than 70%,making it easy for it to be transformed into fractures.At the same time,the weathering resistance of granodiorite and monzogranite is weaker than that of syenogranite,which is easily weathered and destroyed,forming a thick sand gravel weathering zone.With increasing depth of burial,weathering and dissolution gradually weaken,the deep acidic fluid improving the reservoir property of internal fractures and expanding the vertical distribution range of the reservoirs.The research results lay a foundation for the exploration of Buried Hill in the deep-water area of the Qiongdongnan Basin.展开更多
Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in ...Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in the shadow zone of deep water. We propose a multiple-step fill inversion method to invert sound speed, density and attenuation in deep water. Based on a uniform liquid hMf-space bottom model, sound speed of the bottom is inverted by using the long range TL at low frequency obtained in an acoustic propagation experiment conducted in the South China Sea （SCS） in summer 2014. Meanwhile, bottom density is estimated combining with the Hamilton sediment empirical relationship. Attenuation coefficients at different frequencies are then estimated from the TL data in the shadow zones by using the known sound speed and density as a constraint condition. The nonlinear relationship between attenuation coefficient and frequency is given in the end. Tile inverted bottom parameters can be used to forecast the transmission loss in the deep water area of SCS very we//.展开更多
BSR （Bottom Simulating Reflector） occurs widely in the strata since the late Miocene in the deep-water area of the northern continental slope of South China Sea （SCS）. It is an important seismic reference mark whi...BSR （Bottom Simulating Reflector） occurs widely in the strata since the late Miocene in the deep-water area of the northern continental slope of South China Sea （SCS）. It is an important seismic reference mark which identifies the gas hydrate and its distribution influenced by the tectonic movements. Single-point basin modeling was conducted using 473 points in the study area. To discuss the relationships between the tectonic subsidence and BSR, the volume and rate of tectonic subsidence in each geological time have been simulated. The results show that there are three tectonic accelerate subsidence processes in the study area since the late Miocene, especially since 1.8Ma the tectonic subsidence accelerates more apparently. Since the Late Miocene to Pleistocene, the rate of tectonic subsidence in deep-water underwent a transformation from weak to strong. The ratio of tectonic subsidence to the total subsidence was relatively high （65-70%）. Through the superposition of the BSR developed areas and the contours of tectonic subsidence in this area, it was discovered that more than 80% of BSR tend to be distributed at the slope break or depression-uplift structural transfer zone and the average tectonic subsidence rate ranges from 70 m/Ma to 125 m/Ma.展开更多
Extensive transgression of lake water occurred during the Cretaceous Qingshankou Stage and the Nengjiang Stage in the Songliao basin, forming widespread deep-water deposits. Eleven types of microfacies of deep-water d...Extensive transgression of lake water occurred during the Cretaceous Qingshankou Stage and the Nengjiang Stage in the Songliao basin, forming widespread deep-water deposits. Eleven types of microfacies of deep-water deposits have been recognized in the continuous core rocks from the SKII, including mudstone of still water, marlite, dolostone, off shale, volcanic ashes, turbidite, slump sediment, tempestite, seismite, ostracoda limestone and sparry carbonate, which are divided into two types： microfacies generated due to gradually changing environments （Ⅰ） and microfacies generated due to geological events （Ⅱ）. Type Ⅰ is composed of some special fine grain sediments such as marlite, dolomite stone and oil shale as well as mudstone and Type Ⅱ is composed of some sediments related to geological events, such as volcanic ashes, turbiditie, slump sediment, tempestite, seismite, ostracoda limestone. The formation of sparry carbonate may be controlled by factors related to both environments and events. Generally, mudstone sediments of still water can be regarded as background sediments, and the rest sediments are all event sediments, which have unique forming models, which may reflect controlling effects of climatics and tectonics.展开更多
The deep-water area of the northern South China Sea, which has active and complicated tectonics, is rich in natural gas and gas hydrate. While the tectonic characteristics is different obviously between the east and t...The deep-water area of the northern South China Sea, which has active and complicated tectonics, is rich in natural gas and gas hydrate. While the tectonic characteristics is different obviously between the east and the west because of the special tectonic position and tectonic evolution process. In terms of submarine geomorphology, the eastern shelf-slope structure in Pearl River Mouth Basin is characterized by having wide sub-basins and narrow intervening highs, whereas the western （Qiongdongnan Basin） structure is characterized by narrow sub- basins and wide uplift. As to the structural features, the deep-water sags in the east are all structurally half- grabens, controlled by a series of south-dipping normal faults. While the west sags are mainly characterised by graben structures with faulting in both the south and north. With regards to the tectonic evolution, the east began neotectonic activity when the post-rifting stage had completed at the end of the Middle Miocene. In the Baiyun Sag, tectonic activity became strong and was characterised by rapid subsidence and obvious faulting. Whereas in the west, neotectonic activity began at the end of the Late Miocene with rapid deposition and weak fault activity.展开更多
The types,evolution processes,formation mechanisms,and depositional models of deep-water gravity flow deposits in a lacustrine rift basin are studied through core observation and systematic analysis.Massive transport ...The types,evolution processes,formation mechanisms,and depositional models of deep-water gravity flow deposits in a lacustrine rift basin are studied through core observation and systematic analysis.Massive transport of slide and slump,fluid transport of debris flow and turbidity currents are driven by gravity in deep-water lacustrine environment.The transformation between debris flow and turbidity current,and the transformation of turbidity current between supercritical and subcritical conditions are the main dynamic mechanisms of gravity flow deposits in a lake basin.The erosion of supercritical turbidity current controls the formation of gravity-flow channel.Debris flow deposition gives rise to tongue shape lobe rather than channel.Deep-water gravity flow deposits are of two origins,intrabasinal and extrabasinal.Intrabasinal gravity flow deposits occur as single tongue-shape lobe or fan of stacking multiple lobes.Extrabasinal gravity-flow deposits occur as sublacustrine fan with channel or single channel sand body.However,the nearshore subaqueous fan is characterized by fan of stacking multiple tongue shape lobes without channel.The differential diagenesis caused by differentiation in the nearshore subaqueous fan facies belt results in the formation of diagenetic trap.The extrabasinal gravity flow deposits are one of the important reasons for the abundant deep-water sand bodies in a lake basin.Slide mass-transport deposits form a very important type of lithologic trap near the delta front often ignored.The fine-grained sediment caused by flow transformation is the potential"sweet spot"of shale oil and gas.展开更多
The Qiongdongnan Basin has the first proprietary high-yield gas field in deep-water areas of China and makes the significant breakthroughs in oil and gas exploration.The central depression belt of deep-water area in t...The Qiongdongnan Basin has the first proprietary high-yield gas field in deep-water areas of China and makes the significant breakthroughs in oil and gas exploration.The central depression belt of deep-water area in the Qiongdongnan Basin is constituted by five sags,i.e.Ledong Sag,Lingshui Sag,Songnan Sag,Baodao Sag and Changchang Sag.It is a Cenozoic extensional basin with the basement of pre-Paleogene as a whole.The structural research in central depression belt of deep-water area in the Qiongdongnan Basin has the important meaning in solving the basic geological problems,and improving the exploration of oil and gas of this basin.The seismic interpretation and structural analysis in this article was operated with the 3D seismic of about 1.5×104 km2 and the 2D seismic of about 1×104 km.Eighteen sampling points were selected to calculate the fault activity rates of the No.2 Fault.The deposition rate was calculated by the ratio of residual formation thickness to deposition time scale.The paleo-geomorphic restoration was obtained by residual thickness method and impression method.The faults in the central depression belt of deep-water area of this basin were mainly developed during Paleogene,and chiefly trend in NE–SW,E–W and NW–SE directions.The architectures of these sags change regularly from east to west:the asymmetric grabens are developed in the Ledong Sag,western Lingshui Sag,eastern Baodao Sag,and western Changchang Sag;half-grabens are developed in the Songnan Sag,eastern Lingshui Sag,and eastern Changchang Sag.The tectonic evolution history in deep-water area of this basin can be divided into three stages,i.e.faulted-depression stage,thermal subsidence stage,and neotectonic stage.The Ledong-Lingshui sags,near the Red River Fault,developed large-scale sedimentary and subsidence by the uplift of Qinghai-Tibet Plateau during neotectonic stage.The Baodao-Changchang sags,near the northwest oceanic sub-basin,developed the large-scale magmatic activities and the transition of stress direction by the expansion of the South China Sea.The east sag belt and west sag belt of the deep-water area in the Qiongdongnan Basin,separated by the ancient Songnan bulge,present prominent differences in deposition filling,diaper genesis,and sag connectivity.The west sag belt has the advantages in high maturity,well-developed fluid diapirs and channel sand bodies,thus it has superior conditions for oil and gas migration and accumulation.The east sag belt is qualified by the abundant resources of oil and gas.The Paleogene of Songnan low bulge,located between the west sag belt and the east sag belt,is the exploration potential.The YL 8 area,located in the southwestern high part of the Songnan low bulge,is a favorable target for the future gas exploration.The Well 8-1-1 was drilled in August 2018 and obtained potential business discovery,and the Well YL8-3-1 was drilled in July 2019 and obtained the business discovery.展开更多
To overcome the current difficulties of high-precision machining and the high manufacturing and maintenance costs of spherical seals for deep-water drilling ball joints,a new spherical seal technique is proposed in th...To overcome the current difficulties of high-precision machining and the high manufacturing and maintenance costs of spherical seals for deep-water drilling ball joints,a new spherical seal technique is proposed in this paper.The spherical seal is mainly composed of silicone rubber and polytetrafluoroethylene(PTFE).Rational structural design makes the seal independent from the ball and other components,making it easy to replace if leakage occurs at its surface.PTFE can elastically deform over a certain deformation range,which guarantees that two sealing surfaces fit tightly together.O-Ring and PTFE elasticity makes up for any lack of accuracy during spherical machining and decreases the machining precision requirements for spherical surfaces.Using a finite element technique and nonlinear theory,the performance of the spherical seal under the influence of various factors is determined.The results show that the spherical seal designed in this paper exhibits excellent sealing performance under lowtemperature and high-pressure conditions.The spherical seal,a combination of an O-ring and PTFE,has the advantages of cheap manufacturing and maintenance costs and excellent sealing performance.展开更多
In recent years, the extraction of fossil resources, especially oil and gas in deep and ultra-deep water areas has been playing a more important role and been paid more attention to. For this reason, the working depth...In recent years, the extraction of fossil resources, especially oil and gas in deep and ultra-deep water areas has been playing a more important role and been paid more attention to. For this reason, the working depth of submarine pipelines, which are used for the transportation of oil and gas, has been increasing sharply. As the main failure pattern of deep-water pipelines, buckling and its propagation problem have drawn more attention of many research institutions and engineering units around the world. Based on the existing research, the summary of experiments and their outcomes of deep-water pipeline buckling failure is made in this paper. Research status and developing prospects of the experiments of buckling propagation and buckle arrestor are discussed in detail.展开更多
Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples(>3000 thin sections)from deep-water turbiditic sequences of the...Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples(>3000 thin sections)from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales,Australia.Based on these faunas,a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones.They are(in ascending order)the Paracordylodus gracilis Superbiozone(including the Prioniodus oepiki Biozone),Periodon flabellum Superbiozone(including the Oepikodus evae Biozone in the lower part),Periodon hankensis Biozone,Periodon aculeatus Superbiozone(including the Histiodella labiosa,Histiodella holodentata,Histiodella kristinae,Pygodus serra and Pygodus anserinus biozones)and the Periodon grandis Biozone.The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones.This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally.展开更多
基金the National Natural Science Foundation of China(Grant Nos.42077410 and 41872112).We acknowledge the insights and efforts of journal editor(Jie Hao)and three anonymous reviewers that improved the quality of the manuscript.
文摘The study of sequence stratigraphy often focuses on shallow marine and shelf-edge regions,while research on deep-sea stratigraphic sequences remains relatively weak.This study,based on highresolution 3D seismic data and drilling information,utilized sequence stratigraphy and seismic sedimentology as guidelines,and employed seismic interpretation methods to performed a division of deepsea stratigraphic sequences within the Romney 3D seismic survey area in the deep-water Taranaki Basin,New Zealand.Furthermore,it analyzed the characteristics of typical depositional systems and their associated controlling factors.The findings are as follows:(1)Based on seismic reflection termination relationships and seismic facies characteristics,four second-order sequence boundaries and nine thirdorder sequence boundaries were identified,resulting in the delineation of three second-order sequences and twelve third-order sequences in the basin.(2)Five seismic facies were recognized,corresponding to five typical sedimentary bodies:mass transport deposits(MTDs),deep-water channel,levee deposits,deltaic deposits,and pelagic deposits.However,due to the relatively thin sedimentary thickness of carbonate sediments,the seismic facies characteristics of carbonate sediments cannot be discerned in seismic data,but can be identified based on well data.Deltaic sediments mainly developed during the rift stage of the basin,while carbonate sediments formed during the transition from a passive to an active margin.Deep-water channel and levee deposits and MTDs emerged during the active margin stage,while pelagic deposits are ubiquitous in marine environments.(3)The uplift of New Zealand's interior and climate-driven erosion caused the resurgence of clastic sediments,which began to be transported to the deep sea,the seafloor topography would directly affect the movement path of sediment gravity flow,and sediment supply can affect the development and evolution of sedimentary systems.(4)Event deposits boundaries,such as erosional scour surfaces formed by channels and unconformities created by MTDs,can serve as boundaries for the division of deep-water stratigraphic sequences.This study proposes a method for delineating deep-water stratigraphic sequences using event deposits,particularly suitable under conditions where the influence of relative sea-level changes on deep-water deposits is relatively weak.This research not only enhances the understanding of deep-water depositional sequences but also provides a reference for studies on the evolution of deep-water deposition and its controlling factors in research areas with similar geological backgrounds worldwide.
基金financially supported by the National Natural Science Foundation of China(Grant No.42002150)the Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas,Yangtze University(Ministry of Education&Hubei Province,Grant No.UOG2024-12)+1 种基金the Open Foundation Project of the Key Laboratory of Polar Geology and Marine Mineral Resources(China University of Geosciences,Beijing,China),Ministry of Education(Grant No.PGMR-2023-201)the National Key Research Program of China(Grant No.2017ZX05032-002)。
文摘Compared to discrete continental marginal basins,the mechanisms of hydrocarbon migration and enrichment in transform continental marginal basins are poorly understood.In this study,we conducted a comprehensive analysis of the main source rocks,reservoirs,and vertical migration pathways within the Rovuma(RB)and Tanzania(TB)basins in East Africa utilizing drilling,logging,seismic,and geochemical data.The results indicate that the enhanced preservation conditions of the Lower Jurassic source rocks in the southwest could lead to the discovery of large natural gas fields in the southern TB and RB.The primary reservoir is a deep-water turbidite sandstone.Due to topographic differences,the expanse of the turbidite sandstones in the RB is significantly larger than those in Tanzania.The main vertical migration pathways are the western boundary fault zone of the Kerimbas Graben(WBFZ)and the Seagap fault zone(SFZ).In the RB,natural gas migrates vertically along the WBFZ and preferentially accumulates in the deep-water turbidite sandstones of the footwall under the control of the fluid potential.Conversely,in the southern TB,the deep natural gas first migrates upward along the SFZ,then moves along the shallow branch faults in the sandstones on both sides of the SFZ.
基金Supported by the National Natural Science Foundation of China(91528303)CNOOC Technology Project(2021-KT-YXKY-05).
文摘The coupling relationship between shelf-edge deltas and deep-water fan sand bodies is a hot and cutting-edge field of international sedimentology and deep-water oil and gas exploration.Based on the newly acquired high-resolution 3D seismic,logging and core data of Pearl River Mouth Basin(PRMB),this paper dissected the shelf-edge delta to deep-water fan(SEDDF)depositional system in the Oligocene Zhuhai Formation of Paleogene in south subsag of Baiyun Sag,and revealed the complex coupling relationship from the continental shelf edge to deep-water fan sedimentation and its genetic mechanisms.The results show that during the deposition of the fourth to first members of the Zhuhai Formation,the scale of the SEDDF depositional system in the study area showed a pattern of first increasing and then decreasing,with deep-water fan developed in the third to first members and the largest plane distribution scale developed in the late stage of the second member.Based on the development of SEDDF depositional system along the source direction,three types of coupling relationships are divided,namely,deltas that are linked downdip to fans,deltas that lack downdip fans and fans that lack updip coeval deltas,with different depositional characteristics and genetic mechanisms.(1)Deltas that are linked downdip to fans:with the development of shelf-edge deltas in the shelf area and deep-water fans in the downdip slope area,and the strong source supply and relative sea level decline are the two key factors which control the development of this type of source-to-sink(S2S).The development of channels on the continental shelf edge is conducive to the formation of this type of S2S system even with weak source supply and high sea level.(2)Deltas that lack downdip fans:with the development of shelf edge deltas in shelf area,while deep water fans are not developed in the downdip slope area.The lack of“sources”and“channels”,and fluid transformation are the three main reasons for the formation of this type of S2S system.(3)Fans that lack updip coeval deltas:with the development of deep-water fans in continental slope area and the absence of updip coeval shelf edge deltas,which is jointly controlled by the coupling of fluid transformation at the shelf edge and the“channels”in the continental slope area.
文摘It has been a challenge to distinguish between seismic anomalies caused by complex lithology and hydrocarbon reservoirs using conventional fluid identification techniques,leading to difficulties in accurately predicting hydrocarbon-bearing properties and determining oil-water contacts in reservoirs.In this study,we built a petrophysical model tailored to the deep-water area of the Baiyun Sag in the eastern South China Sea based on seismic data and explored the feasibility of the tri-parameter direct inversion method in the fluid identification of complex lithology reservoirs,offering a more precise alternative to conventional techniques.Our research found that the fluid modulus can successfully eliminate seismic amplitude anomalies caused by lithological variations.Furthermore,the seismic databased direct inversion for fluid modulus can remove the cumulative errors caused by indirect inversion and the influence of porosity.We discovered that traditional methods using seismic amplitude anomalies were ineffective in detecting fluids,determining gas-water contacts,or delineating high-quality reservoirs.However,the fluid factor Kf,derived from solid-liquid decoupling,proved to be sensitive to the identification of hydrocarbon-bearing properties,distinguishing between high-quality and poor-quality gas zones.Our findings confirm the value of the fluid modulus in fluid identification and demonstrate that the tri-parameter direct inversion method can significantly enhance hydrocarbon exploration in deep-water areas,reducing associated risks.
基金This study was supported by the project“the deep-water fan systems and petroleum resources in the South China Sea”(grant 40238060)sponsored by the Natural Science Foundation of China and the China National Offshore Oil Corporation.
文摘The shallow shelf delta/strand arenaceous-pelitic deposit region in the north of the Pearl River mouth basin, sitting on the northern continental shelf of the South China Sea, has already become an important oil production base in China. Recent researched has revealed that a great deal of deep-water fans of great petroleum potentiality exist on the Baiyun deep-water slope below the big paleo Pearl River and its large delta. Based on a mass of exploration wells and 2-D seismic data of the shallow shelf region, a interpretation of sequence stratigraphy confirmed the existence of deep-water fans. The cyclic falling of sea level, abundant detrital matter from the paleo Pearl River and the persistent geothermal subsidence in the Baiyun sag are the three prerequisites for the formation and development of deep-water fans. There are many in common between the deep-water shelf depositional system of the northern South China Sea and the exploration hotspots region on the two banks of the Atlantic. For example, both are located on passive continent margins, and persistent secular thermal subsidence and large paleo rivers have supplied abundant material sources and organic matter. More recently, the discovery of the big gas pool on the northern slope of the Baiyun sag confirms that the Lower Tertiary lacustrine facies in the Baiyun sag has a great potentiality of source rocks. The fans overlying the Lower Tertiary source rocks should become the main exploration areas for oil and gas resources.
基金supported by the China-ASEAN Maritime Cooperation Fund Project (No. 12120100500017001)the National Natural Science Foundation of China (Nos. 41976067,41830537,41606074)+1 种基金the Fundamental Research Funds for the Central Universities,China University of Geosciences (Wuhan)(No. CUG170659)the Programme of Introducing Talents of Discipline to Universities (No. B14031)。
文摘Submarine canyon systems are sites for coarser clastic sediment accumulations in the deep-water domains, having the most potential for hydrocarbon reservoirs. Based on the interpretation of high resolution 2 D/3 D seismic and drilling data, depositional characteristics of three large deep-water canyon systems on the South China Sea northern margin have been analyzed. The Central Canyon System has a deep incision geomorphology extending from east to west, featured by distinct canyon segmentations, multi-provenance sediment supplies and multi-stage canyon fillings. The Pearl River Canyon System’s formation is closely related to the development of Pearl River Delta. Its vertical stacking and migrating canyon patterns have changed over time. The depositional architectures and evolution of the recent Penghu-Gaoping Canyon System respond to tectonic movements along the Taiwan-Luzon convergent continental margin. The main controlling factors of the formation and evolution of these three canyon systems include the tectonic setting, sediment supply, sea level change and paleo-geomorphology, among which the former two are dominant. The Penghu-Gaoping Canyon System formed along the subduction structural zone, directly indicating a typical tectonic origin. Numerous seismic data show that the Central Canyon and Pearl River Canyon systems are obviously affected by tectonics, associated local topography and sediment supply.
基金The National Natural Science Foundation of China(No.51209040,51279134)the Natural Science Foundation of Jiangsu Province(No.BK2012341)
文摘In order to optimize the design of a 12.5 m deepwater channel project and protect the ecological environment, it is necessary to study the habitat evaluation of species in the engineered area. A coupled eco-hydrodynamic model, which combines a hydrodynamic model （ADCIRC） and a habitat suitability index （HSI） model is developed for target fish （Coilia nasus） and benthos （Corbicula fluminea） in the Yangtze River in order to predict the ecological changes and optimize the regulation scheme. Based on the existing research concerning the characteristics of Coilia nasus and Corbicula fluminea, the relationship between the target species and water environment factors is established. The verification results of tidal level, velocity and biological density show that the proposed coupling model performs well when predicting ecological suitability in the studied region. The results indicate a slight improvement in the potential habitat availability for the two species studied as the natural hydraulic conditions change after the deep-water channel regulation works.
基金The National Natural Science Foundation of China under contract Nos 42077410 and 41872112。
文摘Deep-water channel systems are important petroleum reservoirs,and many have been discovered worldwide.Understanding deep-water channel sedimentary elements and evolution is helpful for deep-sea petroleum exploration and development.Based on high-resolution 3D seismic data,the Miocene channel system in the deep-water Taranaki Basin,New Zealand,was analyzed by using seismic interpretation techniques such as interlayer attribute extraction and strata slicing.The channel system was divided into five composite channels(CC-I to CC-V)according to four secondary level channel boundaries,and sedimentary elements such as channels,slump deposits,inner levees,mass transport deposits,and hemipelagic drape deposits were identified in the channel system.The morphological characteristics of several composite channels exhibited stark variances,and the overall morphology of the composite channels changed from relatively straight to highly sinuous to relatively straight.The evolution of the composite channels involved a gradual and repeated process of erosion and filling,and the composite channels could be divided into three evolutionary stages:initial erosion-filling,later erosion-filling(multistage),and channel abandonment.The middle Miocene channel system may have formed as a consequence of combined regional tectonic activity and global climatic change,and its intricate morphological alterations may have been influenced by the channel's ability to self-regulate and gravity flow properties.When studying the sedimentary evolution of a large-scale deep-water channel system in the Taranaki Basin during the Oligocene-Miocene,which transitioned from a passive margin to plate convergence,it can be understood how tectonic activity affected the channel and can also provide a theoretical reference for the evolution of the deepwater channels in areas with similar tectonic conversion environments around the world.
基金National Natural Science Foundation of China (Grant No.U1262203)the National Science and Technology Special Grant (Grant No.2011ZX05006-003)the Fundamental Research Funds for the Central Universities (Grant No.14CX06070A)
文摘Deep-water gravity flows are one of the most important sediment transport mechanisms on Earth. After 60 years of study, significant achievements have been made in terms of classification schemes, genetic mechanisms, and depositional models of deep-water gravity flows. The research history of deep-water gravity flows can be divided into five stages： incipience of turbidity current theory; formation of turbidity current theory; development of deep-water gravity flow theory; improvement and perfection of deep-water gravity flow theory; and comprehensive development of deep-water gravity flow theory. Currently, three primary classification schemes based on the sediment support mechanism, the rheology and transportation process, and the integration of sediment support mechanisms, rheology, sedimentary characteristics, and flow state are commonly used.Different types of deep-water gravity flow events form different types of gravity flow deposits. Sediment slump retransportation mainly forms muddy debris flows, sandy debris flows, and surge-like turbidity currents. Resuspension of deposits by storms leads to quasi-steady hyperpycnal turbidity currents （hyperpycnal flows）. Sustainable sediment supplies mainly generate muddy debris flows, sandy debris flows, and hyperpycnal flows. Deep-water fans, which are commonly controlled by debris flows and hyperpycnal flows, are triggered by sustainable sediment supply; in contrast, deep-water slope sedimentary deposits consist mainly of debris flows that are triggered by the retransportation of sediment slumps and deep-water fine-grained sedimentary deposits are derived primarily from fine- grained hyperpycnal flows that are triggered by the resuspension of storm deposits. Harmonization of classification schemes, transformation between different types of gravity flow deposit, and monitoring and reproduction of the sedimentary processes of deep-water gravity flows as well as a source-to-sink approach to document the evolution and deposition of deep-water gravity flows are the most important research aspects for future studies of deep-water gravity flows study in the future.
基金The National Major Project of Science and Technology of China under contract No.2011ZX05025-002-03
文摘A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.
文摘Due to its structure,rock and mineral composition,fluid and other factors,the granite Buried Hill Reservoir is highly heterogeneous with a complex longitudinal structure and a reservoir space made up of a combination of dissolution pores and fractures.This paper is based on current understanding of tectonic evolution in the northern part of the South China Sea,in conjunction with the seismic phase characteristics.It is determined that the meshed fault system was formed by three stages of movement-tectonic compression orogeny during the Indochinese epoch,strike-slip compression-tension during the Yanshanian Period,early fracture extension activation during the Himalayan-which controlled the distribution of the Buried Hill Reservoir.Drilling revealed two types of buried hills,faulted anticline and fault horst,their longitudinal structure and the reservoir space type being significantly different.The mineral composition,reservoir space and diagenetic characteristics of the reservoir rocks and minerals were analyzed by lithogeochemistry,micro section and logging etc.,it thus being determined that the Mesozoic rocks of the Songnan Low Uplift in the Qiongdongnan Basin are mainly composed of syenogranite,granodiorite,monzogranite,which is the material basis for the development of the Buried Hill Reservoir.The content of felsic and other brittle minerals is more than 70%,making it easy for it to be transformed into fractures.At the same time,the weathering resistance of granodiorite and monzogranite is weaker than that of syenogranite,which is easily weathered and destroyed,forming a thick sand gravel weathering zone.With increasing depth of burial,weathering and dissolution gradually weaken,the deep acidic fluid improving the reservoir property of internal fractures and expanding the vertical distribution range of the reservoirs.The research results lay a foundation for the exploration of Buried Hill in the deep-water area of the Qiongdongnan Basin.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434012,41561144006,11174312 and 11404366
文摘Bottom acoustic parameters play an important role in sound field prediction. Acoustic parameters in deep water are not well understood. Bottom acoustic parameters are sensitive to the transmission-loss （TL） data in the shadow zone of deep water. We propose a multiple-step fill inversion method to invert sound speed, density and attenuation in deep water. Based on a uniform liquid hMf-space bottom model, sound speed of the bottom is inverted by using the long range TL at low frequency obtained in an acoustic propagation experiment conducted in the South China Sea （SCS） in summer 2014. Meanwhile, bottom density is estimated combining with the Hamilton sediment empirical relationship. Attenuation coefficients at different frequencies are then estimated from the TL data in the shadow zones by using the known sound speed and density as a constraint condition. The nonlinear relationship between attenuation coefficient and frequency is given in the end. Tile inverted bottom parameters can be used to forecast the transmission loss in the deep water area of SCS very we//.
基金supported by the National 973 Basic Research Program (Grant No. 2009CB219502)National Natural Science Foundation of China (Grant No. 41072084)
文摘BSR （Bottom Simulating Reflector） occurs widely in the strata since the late Miocene in the deep-water area of the northern continental slope of South China Sea （SCS）. It is an important seismic reference mark which identifies the gas hydrate and its distribution influenced by the tectonic movements. Single-point basin modeling was conducted using 473 points in the study area. To discuss the relationships between the tectonic subsidence and BSR, the volume and rate of tectonic subsidence in each geological time have been simulated. The results show that there are three tectonic accelerate subsidence processes in the study area since the late Miocene, especially since 1.8Ma the tectonic subsidence accelerates more apparently. Since the Late Miocene to Pleistocene, the rate of tectonic subsidence in deep-water underwent a transformation from weak to strong. The ratio of tectonic subsidence to the total subsidence was relatively high （65-70%）. Through the superposition of the BSR developed areas and the contours of tectonic subsidence in this area, it was discovered that more than 80% of BSR tend to be distributed at the slope break or depression-uplift structural transfer zone and the average tectonic subsidence rate ranges from 70 m/Ma to 125 m/Ma.
文摘Extensive transgression of lake water occurred during the Cretaceous Qingshankou Stage and the Nengjiang Stage in the Songliao basin, forming widespread deep-water deposits. Eleven types of microfacies of deep-water deposits have been recognized in the continuous core rocks from the SKII, including mudstone of still water, marlite, dolostone, off shale, volcanic ashes, turbidite, slump sediment, tempestite, seismite, ostracoda limestone and sparry carbonate, which are divided into two types： microfacies generated due to gradually changing environments （Ⅰ） and microfacies generated due to geological events （Ⅱ）. Type Ⅰ is composed of some special fine grain sediments such as marlite, dolomite stone and oil shale as well as mudstone and Type Ⅱ is composed of some sediments related to geological events, such as volcanic ashes, turbiditie, slump sediment, tempestite, seismite, ostracoda limestone. The formation of sparry carbonate may be controlled by factors related to both environments and events. Generally, mudstone sediments of still water can be regarded as background sediments, and the rest sediments are all event sediments, which have unique forming models, which may reflect controlling effects of climatics and tectonics.
基金The National Basic Research Program(973 Program)of China under contract No.2009CB219401Science and Technology Program of Guangzhou under contract No.201505041038084+2 种基金the Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)under contract No.PLN1401the Key Laboratory of Gas Hydrate,Ministry of Land and Resources under contract No.SHW(2014)-DX-01the State Key Laboratory Breeding Base of Nuclear Resources and Environment,East China Institute of Technology under contract No.NRE1302
文摘The deep-water area of the northern South China Sea, which has active and complicated tectonics, is rich in natural gas and gas hydrate. While the tectonic characteristics is different obviously between the east and the west because of the special tectonic position and tectonic evolution process. In terms of submarine geomorphology, the eastern shelf-slope structure in Pearl River Mouth Basin is characterized by having wide sub-basins and narrow intervening highs, whereas the western （Qiongdongnan Basin） structure is characterized by narrow sub- basins and wide uplift. As to the structural features, the deep-water sags in the east are all structurally half- grabens, controlled by a series of south-dipping normal faults. While the west sags are mainly characterised by graben structures with faulting in both the south and north. With regards to the tectonic evolution, the east began neotectonic activity when the post-rifting stage had completed at the end of the Middle Miocene. In the Baiyun Sag, tectonic activity became strong and was characterised by rapid subsidence and obvious faulting. Whereas in the west, neotectonic activity began at the end of the Late Miocene with rapid deposition and weak fault activity.
基金Supported by the National Natural Science Foundation of China(41802127,U1762217)China National Science and Technology Major Project(2016ZX05006-003)。
文摘The types,evolution processes,formation mechanisms,and depositional models of deep-water gravity flow deposits in a lacustrine rift basin are studied through core observation and systematic analysis.Massive transport of slide and slump,fluid transport of debris flow and turbidity currents are driven by gravity in deep-water lacustrine environment.The transformation between debris flow and turbidity current,and the transformation of turbidity current between supercritical and subcritical conditions are the main dynamic mechanisms of gravity flow deposits in a lake basin.The erosion of supercritical turbidity current controls the formation of gravity-flow channel.Debris flow deposition gives rise to tongue shape lobe rather than channel.Deep-water gravity flow deposits are of two origins,intrabasinal and extrabasinal.Intrabasinal gravity flow deposits occur as single tongue-shape lobe or fan of stacking multiple lobes.Extrabasinal gravity-flow deposits occur as sublacustrine fan with channel or single channel sand body.However,the nearshore subaqueous fan is characterized by fan of stacking multiple tongue shape lobes without channel.The differential diagenesis caused by differentiation in the nearshore subaqueous fan facies belt results in the formation of diagenetic trap.The extrabasinal gravity flow deposits are one of the important reasons for the abundant deep-water sand bodies in a lake basin.Slide mass-transport deposits form a very important type of lithologic trap near the delta front often ignored.The fine-grained sediment caused by flow transformation is the potential"sweet spot"of shale oil and gas.
基金The National Natural Science Foundation of China under contract No.91528303the National Science and Technology Major Project under contract Nos 2016ZX05026,2011ZX05025 and 2008ZX05025the National Basic Research Program(973 Program)of China under contract No.2009CB219400
文摘The Qiongdongnan Basin has the first proprietary high-yield gas field in deep-water areas of China and makes the significant breakthroughs in oil and gas exploration.The central depression belt of deep-water area in the Qiongdongnan Basin is constituted by five sags,i.e.Ledong Sag,Lingshui Sag,Songnan Sag,Baodao Sag and Changchang Sag.It is a Cenozoic extensional basin with the basement of pre-Paleogene as a whole.The structural research in central depression belt of deep-water area in the Qiongdongnan Basin has the important meaning in solving the basic geological problems,and improving the exploration of oil and gas of this basin.The seismic interpretation and structural analysis in this article was operated with the 3D seismic of about 1.5×104 km2 and the 2D seismic of about 1×104 km.Eighteen sampling points were selected to calculate the fault activity rates of the No.2 Fault.The deposition rate was calculated by the ratio of residual formation thickness to deposition time scale.The paleo-geomorphic restoration was obtained by residual thickness method and impression method.The faults in the central depression belt of deep-water area of this basin were mainly developed during Paleogene,and chiefly trend in NE–SW,E–W and NW–SE directions.The architectures of these sags change regularly from east to west:the asymmetric grabens are developed in the Ledong Sag,western Lingshui Sag,eastern Baodao Sag,and western Changchang Sag;half-grabens are developed in the Songnan Sag,eastern Lingshui Sag,and eastern Changchang Sag.The tectonic evolution history in deep-water area of this basin can be divided into three stages,i.e.faulted-depression stage,thermal subsidence stage,and neotectonic stage.The Ledong-Lingshui sags,near the Red River Fault,developed large-scale sedimentary and subsidence by the uplift of Qinghai-Tibet Plateau during neotectonic stage.The Baodao-Changchang sags,near the northwest oceanic sub-basin,developed the large-scale magmatic activities and the transition of stress direction by the expansion of the South China Sea.The east sag belt and west sag belt of the deep-water area in the Qiongdongnan Basin,separated by the ancient Songnan bulge,present prominent differences in deposition filling,diaper genesis,and sag connectivity.The west sag belt has the advantages in high maturity,well-developed fluid diapirs and channel sand bodies,thus it has superior conditions for oil and gas migration and accumulation.The east sag belt is qualified by the abundant resources of oil and gas.The Paleogene of Songnan low bulge,located between the west sag belt and the east sag belt,is the exploration potential.The YL 8 area,located in the southwestern high part of the Songnan low bulge,is a favorable target for the future gas exploration.The Well 8-1-1 was drilled in August 2018 and obtained potential business discovery,and the Well YL8-3-1 was drilled in July 2019 and obtained the business discovery.
文摘To overcome the current difficulties of high-precision machining and the high manufacturing and maintenance costs of spherical seals for deep-water drilling ball joints,a new spherical seal technique is proposed in this paper.The spherical seal is mainly composed of silicone rubber and polytetrafluoroethylene(PTFE).Rational structural design makes the seal independent from the ball and other components,making it easy to replace if leakage occurs at its surface.PTFE can elastically deform over a certain deformation range,which guarantees that two sealing surfaces fit tightly together.O-Ring and PTFE elasticity makes up for any lack of accuracy during spherical machining and decreases the machining precision requirements for spherical surfaces.Using a finite element technique and nonlinear theory,the performance of the spherical seal under the influence of various factors is determined.The results show that the spherical seal designed in this paper exhibits excellent sealing performance under lowtemperature and high-pressure conditions.The spherical seal,a combination of an O-ring and PTFE,has the advantages of cheap manufacturing and maintenance costs and excellent sealing performance.
基金Supported by the National Natural Science Foundation of China(No.51239008)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.51321065)the National Basic Research Program of China(“973”Program,No.2014CB046805)
文摘In recent years, the extraction of fossil resources, especially oil and gas in deep and ultra-deep water areas has been playing a more important role and been paid more attention to. For this reason, the working depth of submarine pipelines, which are used for the transportation of oil and gas, has been increasing sharply. As the main failure pattern of deep-water pipelines, buckling and its propagation problem have drawn more attention of many research institutions and engineering units around the world. Based on the existing research, the summary of experiments and their outcomes of deep-water pipeline buckling failure is made in this paper. Research status and developing prospects of the experiments of buckling propagation and buckle arrestor are discussed in detail.
文摘Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples(>3000 thin sections)from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales,Australia.Based on these faunas,a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones.They are(in ascending order)the Paracordylodus gracilis Superbiozone(including the Prioniodus oepiki Biozone),Periodon flabellum Superbiozone(including the Oepikodus evae Biozone in the lower part),Periodon hankensis Biozone,Periodon aculeatus Superbiozone(including the Histiodella labiosa,Histiodella holodentata,Histiodella kristinae,Pygodus serra and Pygodus anserinus biozones)and the Periodon grandis Biozone.The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones.This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally.
