A review of reservoir damage during hydraulic fracturing of deep and ultra-deep reservoirs

Deep and ultra-deep reservoirs have gradually become the primary focus of hydrocarbon exploration as a result of a series of significant discoveries in deep hydrocarbon exploration worldwide.These reservoirs present unique challenges due to their deep burial depth(4500-8882 m),low matrix permeability,complex crustal stress conditions,high temperature and pressure(HTHP,150-200℃,105-155 MPa),coupled with high salinity of formation water.Consequently,the costs associated with their exploitation and development are exceptionally high.In deep and ultra-deep reservoirs,hydraulic fracturing is commonly used to achieve high and stable production.During hydraulic fracturing,a substantial volume of fluid is injected into the reservoir.However,statistical analysis reveals that the flowback rate is typically less than 30%,leaving the majority of the fluid trapped within the reservoir.Therefore,hydraulic fracturing in deep reservoirs not only enhances the reservoir permeability by creating artificial fractures but also damages reservoirs due to the fracturing fluids involved.The challenging“three-high”environment of a deep reservoir,characterized by high temperature,high pressure,and high salinity,exacerbates conventional forms of damage,including water sensitivity,retention of fracturing fluids,rock creep,and proppant breakage.In addition,specific damage mechanisms come into play,such as fracturing fluid decomposition at elevated temperatures and proppant diagenetic reactions at HTHP conditions.Presently,the foremost concern in deep oil and gas development lies in effectively assessing the damage inflicted on these reservoirs by hydraulic fracturing,comprehending the underlying mechanisms,and selecting appropriate solutions.It's noteworthy that the majority of existing studies on reservoir damage primarily focus on conventional reservoirs,with limited attention given to deep reservoirs and a lack of systematic summaries.In light of this,our approach entails initially summarizing the current knowledge pertaining to the types of fracturing fluids employed in deep and ultra-deep reservoirs.Subsequently,we delve into a systematic examination of the damage processes and mechanisms caused by fracturing fluids within the context of hydraulic fracturing in deep reservoirs,taking into account the unique reservoir characteristics of high temperature,high pressure,and high in-situ stress.In addition,we provide an overview of research progress related to high-temperature deep reservoir fracturing fluid and the damage of aqueous fracturing fluids to rock matrix,both artificial and natural fractures,and sand-packed fractures.We conclude by offering a summary of current research advancements and future directions,which hold significant potential for facilitating the efficient development of deep oil and gas reservoirs while effectively mitigating reservoir damage.

Deep Learning Shows Promise for Seasonal Prediction of Antarctic Sea Ice in a Rapid Decline Scenario

The rapidly changing Antarctic sea ice has garnered significant interest. To enhance the prediction skill for sea ice and respond to the Sea Ice Prediction Network-South's latest call, this study presents the reforecast results of Antarctic sea-ice area and extent from December to June of the coming year with a Convolutional Long Short-Term Memory(Conv LSTM)Network. The reforecast experiments demonstrate that Conv LSTM captures the interannual and interseasonal variability of Antarctic sea ice successfully, and performs better than the European Centre for Medium-Range Weather Forecasts. Based on this, we present the prediction from December 2023 to June 2024, indicating that the Antarctic sea ice will remain at lows, but may not create a new record low. This research highlights the promising application of deep learning in Antarctic sea-ice prediction.

Assessments of Data-Driven Deep Learning Models on One-Month Predictions of Pan-Arctic Sea Ice Thickness

In recent years,deep learning methods have gradually been applied to prediction tasks related to Arctic sea ice concentration,but relatively little research has been conducted for larger spatial and temporal scales,mainly due to the limited time coverage of observations and reanalysis data.Meanwhile,deep learning predictions of sea ice thickness(SIT)have yet to receive ample attention.In this study,two data-driven deep learning(DL)models are built based on the ConvLSTM and fully convolutional U-net(FC-Unet)algorithms and trained using CMIP6 historical simulations for transfer learning and fine-tuned using reanalysis/observations.These models enable monthly predictions of Arctic SIT without considering the complex physical processes involved.Through comprehensive assessments of prediction skills by season and region,the results suggest that using a broader set of CMIP6 data for transfer learning,as well as incorporating multiple climate variables as predictors,contribute to better prediction results,although both DL models can effectively predict the spatiotemporal features of SIT anomalies.Regarding the predicted SIT anomalies of the FC-Unet model,the spatial correlations with reanalysis reach an average level of 89%over all months,while the temporal anomaly correlation coefficients are close to unity in most cases.The models also demonstrate robust performances in predicting SIT and SIE during extreme events.The effectiveness and reliability of the proposed deep transfer learning models in predicting Arctic SIT can facilitate more accurate pan-Arctic predictions,aiding climate change research and real-time business applications.

The first complete mitogenome of Acharax sp.(Protobranchia,Solemyida,Solemyidae):comparisons with other Solemyidae bivalves and deep-sea adaptive characteristics

Solemyidae is an ancient group of protobranch bivalves,and most solemyids are symbiotic with chemoautotrophic and gill-hosted bacteria,enabling them to survive in unusual habitats such as deepsea chemosynthetic environments.However,evolution of the mitogenomes in this family and their phylogenetic relationships remain poorly understood.The complete mitogenome of Acharax sp.was determined and compared with other available mitogenomes of solemyids.The mitogenome of Acharax sp.is 18970 bp in length and consists of 13 protein-coding genes,2 ribosomal RNA genes,and 22 transfer RNA genes.The gene arrangement was identical to those of other sequenced solemyids.For the present five mitogenomes of Solemyidae species,all protein-coding genes were initiated with the typical ATD(ATA,ATG,and ATT)codon and terminated with the TAA/TAG codon.Furthermore,the incomplete termination codon was detected.The Ka/Ks ratio analyses indicated that 13 protein-coding genes of five Solemyidae mitogenomes suffered strong purifying selection.Compared to 45 existing shallow water equivalents,the 18 available mitogenomes from the deep-sea,including the Acharax sp.in this study,show significantly more nonpolar amino acids in the 13 protein-coding genes,which indicates the adaptation to the deep-sea environment.The phylogenetic tree based on 48 Bivalvia complete mitogenomes provided further information to support the scientific classification of protobranchs.The relationships among Solemyidae were assessed based on 2 mitochondrial(16S rRNA and COX1)and 3 nuclear(18S rRNA,28S rRNA,and histone H3)gene sequences from 17 in-group species.The two genera Acharax and Solemya formed a monophyletic clade each,and Acharax sp.clustered with previously reported Acharax bivalves with high support values.

A numerical study of the South China Sea deep circulation and its relation to the Luzon Strait transport

A fine-resolution MOM code is used to study the South China Sea basin-scale circulationand its relation to the mass transport through the Luzon Strait. The model domain includes the South China Sea, part of the East China Sea, and part of the Philippine Sea so that the currents in the vicinity of the Luzon Strait are free to evolve. In addition, all channels between the South China Sea and the Indonesian seas are closed so that the focus is on the Luzon Strait transport. The model is driven by specified Philippine Sea currents and by surface heat and salt flux conditions. For simplicity, no wind-stress is applied at the surface.The simulated Luzon Strait transport and the South China Sea circulation feature a sandwich vertical structure from the surface to the bottom. The Philippine Sea water is simulated to enter the South China Sea at the surface and in the deep ocean and is carried to the southern basin by western boundary currents. At the intermediate depth, the net Luzon Strait transport is out of the South China Sea and is fed by a western boundary current flowing to the north at the base of the thermocline. Corresponding to the western boundary currents, the basin circulation of the South China Sea is cyclonic gyres at the surface and in the abyss but an anti-cyclonic gyre at the intermediate depth. The vorticity balance of the gyre circulation is between the vortex stretching and the meridional change of the planetary vorticity. Based on these facts, it is hypothesized that the Luzon Strait transports are determined by the diapycnal mixing inside the entire South China Sea. The South China Sea plays the role of a 'mixing mill' that mixes the surface and deep waters to return them to the Luzon Strait at the intermediate depth. The gyre structures are consistent with the Stommel and Arons theory (1960), which suggests that the mixing-induced circulation inside the South China Sea should be cyclonic gyres at the surface and at the bottom but an anti-cyclonic gyre at the intermediate depth. The simulated gyre circulation at the intermediate depth has been confirmed by the dynamic height calculation based on the Levitus hydrography data. The sandwich transports in the Luzon Strait are consistent with recent hydrographical observations.Model results suggest that the Kuroshio tends to form a loop current in the northeastern South China Sea. The simulated Kuroshio Loop Current is generated by the pressure head at the Pacific side of the Luzon Strait and is enhanced by the β-plane effects. The β - plane appears to be of paramount importance to the South China Sea circulation and to the Luzon Strait transports. Without the β-plane, theLuzon Strait transports would be greatly reduced and the South China Sea circulation would be complete-ly different.

Integration of Real-Time Chemical Sensors for Deep Sea Research

There is a great demand for in-situ real-time chemical sensors in the oceanographic research, to measure the chemical components under the deep sea. The ISE (Ion Selective Electrode) is commonly used as a detecting part of deep-sea electro-chemical sensors. The paper highlights the solidification and micromation of the working and reference electrodes. The sensors of pH and H 2S with a thermal probe are accomplished after the solution of configuration of electrodes and signal processing. The sensor system has been tested successfully in the cruise of DY105-12, 14 sponsored by China Ocean Mineral Research and Exploitation Association(COMRA).

Study on low-temperature lipase of psychrophilic bacterium 2-5-10-1 isolated from deep sea of Southern Ocean

A strain of psychrophilic bacterium, 2-5-10-1, which produces low-temperature lipase, is isolated from the deep sea of Prydz Bay in Southern Ocean. The highest lipase secretion of this strain is observed at 5 degreesC and this temperature is also for optimal growth. Tween 80 and olive oil enhance secretion of lipase. The optimal temperature and pH for lipase activity are 35 degreesC and 7.5 degreesC respectively. At 0degreesC, the lipase still has 37% relative enzyme activity. The lipase shows high thermolability, more than 50% activity lost after incubation at 60 degreesC for 15 min. EDTA has no effect on lipase activity, indicating the lipase activity is independent of divalent cation. In contrast, the lipase activity is inhibited drastically by Cu2+ and Zn2+.

New perspective of Miocene marine hydrocarbon source rocks in deep-water area in Qiongdongnan Basin of northern South China Sea

Drilling wells reveal that the organic matter abundance of Miocene marine source rocks in shallow water area of the Qiongdongnan Basin is relatively low with poor hydrocarbon generation poten- tial. However, in some drilling wells of deep water area close to the central depression belt, Miocene marine source rocks with better organic matter abundance and hydrocarbon generation have been found, which have achieved better source rock standard based on the analysis of geochemical charac- teristics. Although there are no exploratory wells in deep water area of the research region, through the comparative analysis of geochemical data of several typical exploratory wells respectively from shallow water area in the basin, central depression belt margin in deep-water area of the basin and Site 1148 of deep sea drilling in the South China Sea Basin, it reveals that the tendency of the quality of source rocks becomes positive gradually from delta to bathyal environment, which then becomes negative as in deep oceanic environment. Owing to the lack of terrestrial organic matter input, the important controlling factors of Miocene marine source rocks in the Qiongdongnan Basin are ocean productivity and preservation conditions of organic matter. The element geochemistry data indicate that the tendency of the paleoproductivity and the preservation conditions of organic matter become positive as water depth increase from shallow area to bathyal area close to central depression belt. So it is speculated that there must exist high quality source rocks in the central depression area where the preservation conditions of organic matter are much better. Besides, in theory, in oxygen-poor zone of oceanic environment at the water depth 400–1 000 m, the preservation conditions of organic matter are well thus forming high-quality marine source rocks. The result- ing speculation, it is reasonable to consider that there are high hydrocarbon generation potential source rocks in bathyal environment of the Qiongdongnan Basin, especially at the water depth 400– 1 000 m.

Design and Strength Analysis of A Spherical Connector for Lifting Subsystem in Deep Sea Mining System

A flexible connector of lifting pipes in a deep sea mining system is designed. The buttress thread （ based on API standard） is used and foreign experience in connector design is referred to. With this kind of connector, the lifting pipe wiU only bear the axial force, free of moment. The strength of the connector is analyzed in detail, including the connecting strength of the buttress thread, the dynamic load of the pipe system, pressures inside and outside of the pipe, the lateral stress of the pipe wall and so on. Especially, a geometric model is built for 3-D contact stress analysis. The distribution graph of contact stress is presented. It is indicated that the strength of the spherical connector meets the demand.

Deepwater Ventilation and Stratification in the Neogene South China Sea

Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea （SCS） since the Early Miocene. The results indicate that 3 lithostratigraphic units, respectively corresponding to 21-17 Ma, 15-10 Ma, and 10-5 Ma with positive red parameter （a^＊） marking the red brown sediment color represent 3 periods of deep water ventilation. The first 2 periods show a closer link to contemporary production of the Antarctic Bottom Water （AABW） and Northern Component Water（NCW）, indicating a free connection of deep waters between the SCS and the open ocean before 10 Ma.After 10 Ma, red parameter dropped but stayed higher than the modern value （a^＊=0）, the CaCO3 percentage difference between Site 1148 from a lower deepwater setting and Site 1146 from an upper deepwater setting enlarged significantly, and benthic species which prefer oxygen-rich bottom conditions dramatically decreased. Coupled with a major negative excursion of benthic δ^13Cat ～10 Ma,these parameters may denote a weakening in the control of the SCS deep water by the open ocean.Probably they mark the birth of a local deep water due to shallow waterways or rise of sill depths during the course of sea basin closing from south to east by the west-moving Philippine Arc after the end of SCS seafloor spreading at 16-15 Ma. However, it took another 5 Ma before the dissolved oxygen approached close to the modern level. Although the oxygen level continued to stabilize, several Pacific Bottom Water （PBW） and Pacific Deep Water （PDW） marker species rapidly increased since ～6 Ma,followed by a dramatic escalation in planktonic fragmentation which indicates high dissolution especially after ～5 Ma. The period of 5-3 Ma saw the strongest stratified deepwater in the then SCS, as indicated by up to 40﹪ CaCO3 difference between Sites 1148 and 1146. Apart from a strengthening PDW as a result of global cooling and ice cap buildup on northern high latitudes, a deepening sea basin due to stronger subduction eastward may also have triggered the influx of more corrosive waters from the deep western Pacific. Since 3 Ma, the evolution of the SCS deep water entered a modern phase, as characterized by relative stable 10﹪ CaCO3 difference between the two sites and increase in infaunal benthic species which prefer a low oxygenated environment. The subsequent reduction of PBW and PDW marker species at about 1.2 Ma and 0.9 Ma and another significant negative excursion of benthic δ^13Cto a Neogene minimum at ～0.9 Ma together convey a clear message that the PBW largely disappeared and the PDW considerably weakened in the Mid-Pleistocene SCS. Therefore, the true modern mode SCS deep water started to form only during the ＂Mid-Pleistocene climatic transition＂ probably due to the rise of sill depths under the Bashi Strait.

Screening and Phylogenetic Analysis of Deep-Sea Bacteria Capable of Metabolizing Lignin-Derived Aromatic Compounds

Lignin is one of the most abundant biomasses in nature. It is composed of aromatic moieties and has great potential for use in the production of chemical alternatives to petroleum products. Because of increasing interest in biocatalysis, the potential for industrial application of microbial metabolism of lignin-derived compounds has gained considerable recent attention. Functional screenings of culturable bacteria isolated from sediments and sunken wood collected from the deep sea revealed the existence of a number of previously unidentified bacteria capable of metabolizing lignin-related aromatic compounds. Of the 510 isolates obtained in the present study, 208 completely or partially metabolized these compounds. The 208 isolates were classified into diverse phyla, including Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria. Among the 208 isolates, 61 unique 16S rRNA gene sequences were detected including previously unidentified marine lineage isolates. The metabolites of the isolates were analysed using liquid chromatography/mass spectrometry (LC/MS) or gas chromatography/mass spectrometry (GC/MS). Most of the representative 61 isolates non-oxidatively decarboxylated the substrates to produce the corresponding aromatic vinyl monomers, which are used as feed stocks for bio-based plastics production. Oxidative metabolism of the lignin-related compounds for assimilation was frequently observed. Our study showed that the deep-sea environment contains an abundance of microorganisms capable of both non-oxidative and oxidative bioconversion of lignin-derived aromatic compounds. The ability for bio-conversion of aromatic compounds found in this study will facilitate the development of future biotechnological applications.

Deep waters warming in the Nordic seas from 1972 to 2013

The warming of deep waters in the Nordic seas is identified based on observations during Chinese 5th Arctic Expedition in 2012 and historical hydrographic data. The most obvious and earliest warming occurrs in the Greenland Basin （GB） and shows a coincident accelerated trend between depths 2000 and 3500 m. The ob-servations at a depth of 3000 m in the GB reveal that the potential temperature had increased from ？1.30°C in the early 1970s to ？0.93°C in 2013, with an increase of about 0.37°C （the maximum spatial deviation is 0.06°C） in the past more than 40 years. This remarkable change results in that deep waters in the center of the Lofton Basin （LB） has been colder than that in the GB since the year 2007. As for the Norwegian Basin （NB）, only a slight trend of warming have been shown at a depth around 2000 m since the early 1980s, and the warming amplitude at deeper waters is just slightly above the maximum spatial deviation, implying no obvious trend of warming near the bottom. The water exchange rate of the Greenland Basin is estimated to be 86% for the period from 1982 to 2013, meaning that the residence time of the Greenland Sea deep water （GSDW） is about 35 years. As the weakening of deep-reaching convection is going on, the abyssal Nordic seas are playing a role of heat reservoir in the subarctic region and this may cause a positive feedback on the deep-sea warming in both the Arctic Ocean and the Nordic seas.

Deep Sea AUV Navigation Using Multiple Acoustic Beacons

Navigation is a critical requirement for the operation of Autonomous Underwater Vehicles（AUVs）.To estimate the vehicle position,we present an algorithm using an extended Kalman filter（EKF） to integrate dead-reckoning position with acoustic ranges from multiple beacons pre-deployed in the operating environment.Owing to high latency,variable sound speed multipath transmissions and unreliability in acoustic measurements,outlier recognition techniques are proposed as well.The navigation algorithm has been tested by the recorded data of deep sea AUV during field operations in a variety of environments.Our results show the improved performance over prior techniques based on position computation.

Deep-Sea Geohazards in the South China Sea

Various geological processes and features that might inflict hazards identified in the South China Sea by using new technologies and methods.These features include submarine landslides,pockmark fields,shallow free gas,gas hydrates,mud diapirs and earthquake tsunami,which are widely distributed in the continental slope and reefal islands of the South China Sea.Although the study and assessment of geohazards in the South China Sea came into operation only recently,advances in various aspects are evolving at full speed to comply with National Marine Strategy and‘the Belt and Road’Policy.The characteristics of geohazards in deep-water seafloor of the South China Sea are summarized based on new scientific advances.This progress is aimed to aid ongoing deep-water drilling activities and decrease geological risks in ocean development.

Influence of simulating deep-sea environmental factors on cathodic performance of seawater battery

A metal-dissolved oxygen seawater battery(SWB)uses metal and dissolved oxygen as the reactants,and it is ideal for use as a long-time low-power distributed power supply in deep sea,due to its advantages of open structure in service without electrolyte.However,several simulating deep-sea environmental factors,such as flow rate,dissolved oxygen concentration,and temperature of seawater may af fect the oxygen reduction reaction(ORR)rate and the stability of electrochemically modified polyacrylonitrile-based carbon fiber brush(MPAN-CFB)cathode,which was studied by steady-state polarization and galvanostatic discharge methods.In addition,the scales formed on MPAN-CFB surface were characterized by SEM and XRD.Results show that the ORR rate increased quickly with the increase of the seawater flow rate up to 3 cm/s,and then gradually stabilized.Moreover,the ORR rate was largely af fected by dissolved oxygen concentration,and the concentration of>3 mg/L was favorable.Compared with surface layer temperature of 15℃,the low temperature of deep sea(4℃)has a negligible ef fect on ORR rate.When the working current is too high,it will lead to the formation of CaCO_3 scales(aragonite)of at the cathodic surface,resulting in the decrease of ORR rate,and consequently the damage to the long-time stability of MPAN-CFB.

The deep mantle upwelling beneath the northwestern South China Sea:Insights from the time-varying residual subsidence in the Qiongdongnan Basin

Deep hot mantle upwelling is widely revealed around the Qiongdongnan Basin on the northwestern South China Sea margin. However, when and how it influenced the hyper-extended basin is unclear.To resolve these issues, a detailed analysis of the Cenozoic time-varying residual subsidence derived by subtracting the predicted subsidence from the backstripped subsidence was performed along a new seismic reflection line in the western Qiongdongnan Basin. For the first time, a method is proposed to calculate the time-varying strain rates constrained by the faults growth rates, on basis of which, the predicted basement subsidence is obtained with a basin-and lithosphere-scale coupled finite extension model, and the backstripped subsidence is accurately recovered with a modified technique of backstripping to eliminate the effects of later episodes of rifting on earlier sediment thickness. Results show no residual subsidence in 45–28.4 Ma. But after 28.4 Ma, negative residual subsidence occurred, reached and remained ca. -1000 m during 23–11.6 Ma, and reduced dramatically after 11.6 Ma. In the syn-rift period(45–23 Ma), the residual subsidence is ca. -1000 m, however in the post-rift period(23–0 Ma),it is positive of ca. 300 to 1300 m increasing southeastwards. These results suggest that the syn-rift subsidence deficit commenced at 28.4 Ma, while the post-rift excess subsidence occurred after 11.6 Ma.Combined with previous studies, it is inferred that the opposite residual subsidence in the syn-and post-rift periods with similar large wavelengths(>10^(2) km) and km-scale amplitudes are the results of transient dynamic topography induced by deep mantle upwelling beneath the central QDNB, which started to influence the basin at ca. 28.4 Ma, continued into the Middle Miocene, and decayed at ca.11.6 Ma. The initial mantle upwelling with significant dynamic uplift had precipitated considerable continental extension and faulting in the Late Oligocene(28.4–23 Ma). After ca. 11.6 Ma, strong mantle upwelling probably occurred beneath the Leizhou–Hainan area to form vast basaltic lava flow.

Seismic stratigraphy of the Qiongdongnan deep sea channel system,northwest South China Sea

Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4–8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.

Design of Low-Power Data Logger of Deep Sea for Long-Term Field Observation

This paper describes the implementation of a data logger for the real-time in-situ monitoring of hydrothermal systems. A compact mechanical structure ensures the security and reliability of data logger when used under deep sea. The data logger is a battery powered instrument, which can connect chemical sensors （pH electrode, H2S electrode, H2 electrode） and temperature sensors. In order to achieve major energy savings, dynamic power management is implemented in hardware design and software design. The working current of the data logger in idle mode and active mode is 15 μA and 1.44 mA respectively, which greatly extends the working time of battery. The data logger has been successftdly tested in the first Sino-American Cooperative Deep Submergence Project from August 13 to September 3, 2005.

Deep-water Fan Systems and Petroleum Resources on the Northern Slope of the South China Sea

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.

Experiment and Simulation for Articulated Lifting Subsystem of 1000 m Deep Sea Mining System

The experiment system of 1000 m deep sea mining system is built up with the similarity theory. Sine mechanism is used to simulate mining ship to generate lateral shock excitation by ocean wave. Simulation and experiment of spherical joint connecting deep sea mining system has been done in band six marine conditions. The results indicate that the moment of spherical joint connecting deep sea mining is smaller than that of the thread connected ones, the lifting pipe of sphelical joint is ＂flexible pipe＂. The flexural torque of the articulated lifting pipe system in pump and buffer is generally periodic variation with some irregularity, the value is stable on 60 N·S, and it is obviously smaller than that of the fixed lifting pipe system; The total displacement exhibits cyclic variation pattern, and the periodicity of them is longer than that of sea current. The results of experiment and simulation are basically consistent. And the analysis in the paper offers theoretical foundation of 1000 m deep sea mining system in China.