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The shelf‐margin deltas are the primary 'sources' of interest in siliceous submarine fan source‐to‐sink systems. However, less has yet to be discovered about the roles and effects of the shallow water platform situated on continental slopes. Using the Miocene sediments of the Ledong‐Lingshui Sag in the western part of the Qiongdongnan Basin (QDNB), this paper studies the YC35 coarse‐grained submarine fan that developed in the Meishan Formation (Fm.). The material sources, depositional characteristics, and developmental mechanisms of this fan were investigated. The restored palaeogeomorphology, based on high‐resolution 3D seismic data, shows that a shallow water platform exists. According to geochemical palaeoenvironmental data, the shallow water platform was ideal for forming carbonate deposits in the Meishan Fm., owing to the warm and humid palaeoclimate and the shifting trend in palaeowater depth. Based on the combined source tracing of heavy minerals, coherence slices, and seismic profiles, the shallow water platform and the Ningyuan River source on Hainan Island contributed to the YC35 coarse‐grained submarine fan. Compared to submarine fans formed during different periods, coarse‐grained fan stands out due to its distinct sedimentary structure, rock composition, and microlithological characteristics. Aside from not following the usual Bowmar sequence, there is an excess of gravel and no clear bedding or lamination. A large number of rock fragments, mostly granite and sedimentary rock (carbonatite), make up the rock composition. According to these results, the shallow water platform significantly affects submarine fan material composition. In addition, the attribute slice based on the root mean square reveals that shallow water platforms moderate peripheral deposition. We attribute the development and proximal supply of the shallow water platform to diapirism and forced regression. Our research provides novel insights and comprehension into the investigation of submarine fan sedimentary systems. [ABSTRACT FROM AUTHOR]

Large numbers of gas reservoirs have been discovered in overpressure basins. Fluid charging has a close relationship with paleo‐pressure evolution, affecting the migration of gas reservoirs. To study fluid charging and the related pressure system, we analyzed burial histories and fluid inclusion (PVTx) simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example. On the basis of fluid‐inclusion assemblages (FIAs), homogenization temperature (Th), final melting temperature (Tm, ice) and Raman spectroscopy in fluid inclusions, there are three stages of fluid charging: during the first and second stage, methane‐dominated fluid was charged at 2.2–1.7 Ma and 1.7–0.9 Ma, respectively. In the third stage, CO2‐rich hydrothermal fluid was charged since 0.9 Ma. It could be concluded from the well‐logging data that the disequilibrium compaction in the Yinggehai Fm., along with the fluid expansion and clay diagenesis in the Huangliu and Meishan formations, resulted in the overpressure in the Ledong slope zone. The evolution of paleo‐pressure was affected by the sedimentation rate of the Yinggehai Fm., as well as the hydrocarbon generation rate. Additionally, the Ledong Slope Zone is less affected by diapir activity than the nearby diapir area. Based on fluid inclusions, paleo‐pressure, basin modeling and geological background, the gas migration history of the Ledong Slope Zone can be divided into four stages: in the first stage, excess pressure was formed around 5 Ma; from 2.2 to 1.7 Ma, there was a reduction in the charging of hydrocarbon fluid and steadily increasing excess pressure; during the 1.7–0.9 Ma period a large amount of hydrocarbon was generated, excess pressure increasing significantly and hydraulic fractures forming in mudstones, With gas reservoirs developing in structural highs; since 0.9 Ma, CO2‐rich hydrothermal fluid accumulated in reservoirs adjacent to faults and the pressure coefficient remained stable. The research results are helpful in the study of fluid migration and accumulation mechanisms in overpressure basins. [ABSTRACT FROM AUTHOR]

Submarine channels act as the main conduits for the transport of sediment to deep‐water basins by sediment gravity flows. The interplay between fault‐related deformation and the initiation and development of the channels is poorly known. Here, we present the identification, formation and evolution of the Miocene slope‐parallel channel by employing 3D seismic reflection, wireline‐log and core data in the eastern slope of Yinggehai Basin, South China Sea. Based on the lengths and plan‐view shapes, a total of three different types of fault‐associated slope‐parallel depressions have been identified. The depressions were formed in the fault zone and controlled by the reactivation of the underlying older faults. Among them, Type‐1 depressions are short (<20 km) oval or circle shaped possessing only one depocenter. Type‐2 depressions are elongated (25–70 km), and usually have multiple depocenters. Type‐3 depressions, which are usually connected by slope‐perpendicular channels in the head and middle, are longer (more than 190 km) and connect shallow and deep‐water basins. The analysis of morphology, erosivity and material transport shows that Type‐3 depressions are fully fledged channels. Type‐1 and Type‐2 depressions are channel precursors representing the initial stage of channel evolution. With this motive, a model for the initiation and evolution of slope‐parallel submarine channels controlled by strike‐slip‐extensional faults is presented. Unlike the previous investigations which suggest that erosion takes place at the inception of submarine channel formation, the fault‐controlled slope‐parallel channel is mainly controlled by faulting and has no initial erosive base and does not develop levees. The depressions are extended and elongated by the continuous fault activity. It was not until the slope‐parallel depression connected with large‐scale slope‐perpendicular channels transporting materials into the depression via erosive turbidity currents that it evolved into a channel‐levee system. This study is of global importance for understanding submarine channel generation and evolution since the fault‐controlled slope‐parallel channels have been found in tectonic active basins worldwide. [ABSTRACT FROM AUTHOR]

To understand hydrocarbon migration in terms of the mechanisms, accumulations and exploration targets, it is essential to correctly identify and characterize the carrier systems that control fluid-migration history and oil/gas reservoir formation. The Yinggehai Basin in China is an important area for natural gas exploration and production. However, due to the argillaceous sand sedimentary environment and the absence of faults from the Neogene thermal subsidence period, traditional migration pathways are absent in the Yinggehai Basin, posing significant challenges to target evaluation in this area. Exploration shows that most of the existing gas reservoirs are associated with vertical migration. In this work, coherence cube and curvature seismic techniques are used in the central diapir zone of the Yinggehai Basin to identify diapir-associated fractures and regional stress. Together with geological analysis, two categories of carrier system are discussed in detail to explain the complex migration and accumulation patterns that have puzzled the area. Diapirs have five evolutionary phases, i.e., pressurization, piercing, equilibrium, release and collapse, which have different fracture development patterns, leading to different mechanisms of hydrocarbon migration and accumulation. The carbon isotopes of gaseous hydrocarbons in DF shallow layers and mid-deep layers have an inverted order distribution, indicating mixed accumulation with different maturity, whereas in the mid-deep layers of the diapir-affected areas, there is a single accumulation with low maturity. Early diapiric activity allowed the natural gas produced from deep source rocks to migrate upward along the diapiric carrier system and accumulate in suitable traps to form gas reservoirs. For regional-stress related fractures, the gradual loss of overpressure and fluids from deep to shallow in high-pressure fractures results in the gas accumulation time of deep traps in the regional stress-related carrier system being relatively late and the gas accumulation time of shallow traps being relatively early. [ABSTRACT FROM AUTHOR]

The Yinggehai Basin is a typical high temperature and high pressure (HTHP) gas-bearing basin. The pressure coefficient exceeds 2.2 in deeply-buried Miocene reservoirs in the Ledong Slope, a nondiapir zone in the Yinggehai Basin. Determining the overpressure mechanisms and predicting the pore pressure are key issues for natural gas exploration and development in the Ledong Slope. In this paper, overpressure mechanisms were investigated according to the analysis of vertical effective stress-logging responses and geological evaluations, and the pore pressure was predicted using the Bowers method. The loading-unloading crossplots indicated that the overpressure that existed in reservoirs mainly consists of two types: neighbor-source and allo-source overpressure. The neighbor-source overpressure is mainly caused by the pressure transmission from the adjacent mudstone to the reservoir, with a pressure coefficient less than 1.5 ~ 1.6. The high-magnitude overpressure points with pressure coefficients greater than 1.6 show a typical unloading response, indicating elevated sandstone pressures rather than in situ mudstone pressures, which are most likely to be generated by overpressure vertical transfer. The high-magnitude overpressure fluid generated by the high mature ultradeep buried N1s source rock migrated to the shallower reservoirs via hidden faults/microfractures, which led to the vertical transfer of overpressure. Vertically transferred overpressure was generated at 1.5 ~0.2 Ma, which is beneficial for the preservation of overpressure in lenticular sandbodies. The estimated pore pressure by the Bowers method is in good agreement with the measured pressure and provides a meaningful reference for predrilling pressure prediction in nondiapir or diapir zones in the Yinggehai Basin. [ABSTRACT FROM AUTHOR]

Compaction is regarded as central to the reduction of reservoir physical properties. The thermal compaction process controlled by a basin's heat flow and the static compaction caused by overload on rocks are both important factors controlling the compaction strength. However, porosity loss resulting from thermal and static compaction has not been distinguished. The Baiyun Sag in the Pearl River Mouth Basin in the northern part of the South China Sea with high heat flows and a variable geothermal gradient is an ideal setting for studying the characteristics and mechanisms of the thermal compaction process. The characteristics of compaction and the effect of thermal fluid activities on reservoir physical properties are carried out, based on the observation and identification of sandstone thin sections under a microscope, the measurement and simulation of the temperatures and trapping pressures of fluid inclusions, and the calculation of the compaction porosity loss as well. The result shows that the compaction mode of sandstone reservoirs in the Zhuhai Formation is dominated by static compaction in the LGR (the low geothermal gradient region), whereas the diagenetic process of the Zhuhai Formation in the MGR (the moderate geothermal gradient region) and HGR (the high geothermal gradient region) is affected not only by the static compaction effect but also by the thermal compaction effect caused by abnormal formation temperature and pressure conditions. The porosity loss caused by the thermal compaction ranges from 5.5% to 11.2% with an average of 7.9% and from 4.6% to 16.6% with an average of 10.2% in the MGR and HGR, respectively. The porosity loss caused by the static compaction ranges from 15.9% to 20.8% with an average of 19.4% and from 8.4% to 15.8% with an average of 12.8% in the MGR and HGR, respectively. [ABSTRACT FROM AUTHOR]

Various deep‐water deposits developed in the Yinggehai Basin and Qiongdongnan Basin (Ying‐Qiong Basin) in the northern South China Sea, making the two basins significantly hydrocarbon‐producing areas and ideal for studying the genetic mechanism and sedimentary characteristics of deep‐water clastic rocks. Using cores, image well logging, heavy mineral assemblages, and seismic data, we thoroughly studied the geometry, tectonic background, driving mechanism, and source‐to‐sink process of deep‐water deposits in the study area. The results showed that: (1) there were five genetic mechanisms of deep‐water clastic rock, i.e., slides, slumps, debris flows, turbidity currents, and bottom currents. (2) The sliding deposits were distributed from the delta front to the continental slope toe. The slumping deposits were mainly distributed at the continental slope toe or the basin's central area, far from the delta front. The turbidity deposits were widely developed in the deep‐water area, but with huge differences in thickness. The bottom currents mainly reworked previous deposits far from the slope. (3) Slip and extension along the preexisting fault zone were the main structural factors that drive the axial channel formation at the slope foot. (4) The sand‐rich gravity sediment flows in the Ying‐Qiong basin were primarily caused by the direct supply of terrigenous debris into the marine environment over the slope break. [ABSTRACT FROM AUTHOR]

Cohesion and friction coefficients are fundamental parameters of granular materials used in analogue experiments. Our six models, comprising two sets of quartz sand with a 0–3 mm thickness of basal glass beads, illustrate that accretionary wedges with high basal friction have relatively larger slope angles and heights, shorter wedge lengths, and larger numbers of faults with smaller spacings and displacements than wedges with low basal friction. It should be noted that the differences in the geometry and evolution of the two sets of homogeneous quartz sands are not distinct; however, the differences are substantial when the models have low basal friction of the glass beads. In particular, there are two different tendencies of growth in wedge height with progressive shortening, that is, progressive growth of wedge height with high basal friction and steady‐state growth of wedge height with basal glass beads. We thus infer that the wedge geometries in our experiments are preferentially controlled by the low basal friction achieved with glass beads. In particular, the basal décollement (even when thin) has a significant influence on the location and development of accretionary wedges, in contrast to the physical properties of brittle materials (e.g., friction coefficient and cohesion). [ABSTRACT FROM AUTHOR]

Vinyl acetate is polymerized in the living way under the irradiation of blue light-emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2-(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well-regulated molecular weight and narrow molecular weight distribution (Ð < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix-assisteed laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). [ABSTRACT FROM AUTHOR]

Diselenide-containing polymers are facilely synthesized from polymers prepared by atom transfer radical polymerization (ATRP). Benefiting from the ATRP technology, this protocol provides a flexible route for controlling the polymer structure, which allows for a great variety of architectures of selenium-containing polymer materials for applications in various fields. The oxidative and reductive responsive behavior of the obtained diselenide-containing polymers is also investigated. [ABSTRACT FROM AUTHOR]

In order to clarify the evolution characteristics of the fault system in Wushi Sag, Beibuwan Basin, the author basing on 3D seismic date in Wushi Sag, combining with the changes of the regional stress field, analyzed the characteristics and evolution law of fault system, established the rotation of the extension-detachment fault development model controlled by the oblique extensional block in Wushi Sag, and studied its control effect on hydrocarbon accumulation. The study shows that; from the Paleocene to the Early Eocene, the extensional stress field is nearly perpendicular to the existing north-east trending faults. During this period, the faults are mainly characterized by extensional evolution; from the Mid-Late Eocene to the Oligocene, the extensional stress field rotates clockwise and intersects the pre-existing north-east fault at an acute angle, which mankes the early fault was activated, and due to the thick plastic oil shale at the top and bottom of the second member of the Liushagang, the faults shows the extension-slip evolution characteristics under the joint control of oblique tension and plastic formation; as the stress continues to rotate, the up fault of the detachment fault develops a tension-torsional adjustment fault, forming a floweriness structural. The developing extensional faults in the sag control the spread of Eocene hydrocarbon source rock and large reservoir collectives; extension-slip faults control the difference of the structural zone and the formation of the trap groups, among them, the throw side of slip zone shows the "anticlinal rise", the gas-oil convergence background is superior, and it is the most favorable enrichment area in the Wushi Sag. This result has guiding significance for gas-oil exploration and zone optimization in Wushi Sag. [ABSTRACT FROM AUTHOR]

The Yinggehai Basin is an important Cenozoic gas bearing basin in the South China Sea. With the gradual improvement of gas exploration and over-development in shallow layers, deep overpressured layers have become the main target for natural gas exploration. There are no large-scale faults in the strata above the Meishan Formation in the central depression, and hydraulic fracturing caused by overpressure in mudstone cap rocks is the key factor for the vertical differential distribution of gas. In this paper, based on the leak-off data, pore fluid pressure, and rock mechanics parameters, the Fault Analysis Seal Technology (FAST) method is used to analyze the hydraulic fracture risk of the main mudstones in the central depression. The results show that the blocks in the diapir zone have been subjected to hydraulic fracturing in the Huangliu cap rocks during the whole geological history, and the blocks in the slope zone which is a little distant from the diapirs has a lower overall risk of hydraulic fracture than the diapir zone. In geological history, the cap rocks in slope zone remained closed for a longer time than in diapir zone and being characterized by the hydraulic fracture risk decreases with the distance from the diapirs. These evaluation results are consistent with enrichment of natural gas, which accumulated in both the Yinggehai Formation and Huangliu Formation of the diapir zone, but it only accumulated in the the Huangliu Formations of the slope zone. The most reasonable explanation for the difference of the gas reservoir distribution is that the diapirs promote the development of hydraulic fractures: (1) diapirism transfers deep overpressure to shallow layers; (2) the small fault and fractures induced by diapir activities weakened the cap rock and reduced the critical condition for the natural hydraulic fractures. These effects make the diapir zone more prone to hydraulic fracturing, which are the fundamental reasons for the difference in gas enrichment between the diapir zone and the slope zone. [ABSTRACT FROM AUTHOR]

The Yinggehai Basin is a strongly overpressured basin without large-scale faults in the Central Depression Zone. The hydraulic seal capacity of the caprocks over geological history has been the key factor controlling the vertical distribution characteristics of oil and gas. Based on leak-off data, rock mechanics tests and measured pore pressure data, this paper analyses the potential of natural hydraulic fracturing with the fault analysis seal technology (FAST) methodology for caprocks C1 (caprock of the Huangliu Formation) and C2 (caprock of the Meishan Formation) of the diapir belt in the north Central Depression Zone and determines the failure mode and gas sealing capacity of the two caprocks. The results show that gas leakage occurred continuously in both C1 and C2 in the diapir zone (DZ) throughout geological time. However, far from the diapir zone (FDZ), hydraulic leakage occurred only in caprock C2 while no leakage occurred in caprock C1 over geological time. These results are consistent with the gas accumulation that occurred in both the Yinggehai Formation and Huangliu Formation in the DZ but only in the Huangliu Formation in the FDZ. A relatively reasonable explanation is that diapirism promoted natural hydraulic fracture development via the following effects: (i) Diapirism transfers deep overpressure to shallow layers and increases the pressure gradient; (ii) The high-angle fractures associated with diapirism reduce the critical stress condition for the occurrence of natural hydraulic fracturing; and (iii) Diapirism results in the formation of dome structures in shallow layers, causing more shallow burial of caprock in the DZ than the FDZ. Shallowly buried caprocks, which have a relatively lower hydraulic fracture pressure, facilitate gas migration. These effects promoted natural hydraulic fracturing in the DZ, which is the main reason for the difference in the vertical distribution of gas reservoirs between the DZ and FDZ. • The main highlights are as follows: • The stress regime in the north Central Depression Zone of Yinggehai Basin is investigated. • The diapirism can promote the hydraulic fracturing in the overpressure basin. • The relationship between gas distribution and the risk of natural hydraulic fracturing in geologic history is analysed. [ABSTRACT FROM AUTHOR]