The Xujiahe Formation in Sichuan Basin has a large amount of tight gas resources and rich reserves, but its production rate is low. The development mechanism of favorable reservoirs and the enrichment and high-yield laws of hydrocarbons remain unclear, which is particularly important for the study of hydrocarbon accumulation models of deep tight gas reservoirs. Through a large number of core observation, analysis and testing, well data and other studies, the authors established an isochronous sequence stratigraphic framework, carried out the study of reservoir characteristics, clarified the formation mechanism of favorable reservoirs, summarized the patterns of hydrocarbon enrichment and high-yield, and established evolution models of the second member of Xujiahe Formation (T3x2 Member) in the Xinchang structural belt of the Western Sichuan Depression. Four main understandings were obtained: (i) From bottom to top, the T3x2 Member can be divided into 1 long-term cycle, 3 medium-term cycles, and 16–20 short-term cycles in total; (ii) Favorable reservoirs can be classified into two types, namely the layer-cake type with horizontal fractures and massive-bedding type with horizontal fractures; (iii) Layer-cake reservoirs are generally medium-coarse grained, quartz-rich with favorable pore structures, whereas massive-bedding-type reservoirs are mostly medium-grained, feldspar-rich with moderate pore structures; (iv) High-quality reservoirs are mainly high-energy sedimentary facies, which develop residual intergranular pores and dissolution pores, and differential densification is the key to the formation of favorable reservoirs. This study established a hydrocarbon enrichment and high-yield evolutionary model characterized by the sequence of “early reservoir formation → compaction → overpressure hydrocarbon charging → late structural reworking”, and clarified that targeting traps formed during hydrocarbon accumulation constitutes the core exploration target, while delineating sweet spots modified by late structural adjustment is the key for development deployment.

The Late Oligocene Huagang Formation in the Xihu Depression, East China Sea Shelf Basin, records typical braided river delta deposits. However, the influence of astronomical forcing on sand-body distribution remains unclear. Based on core, logging, and seismic data, subaqueous distributary channels of braided river deltas were identified and multi-scale lake-level fluctuations were reconstructed. The main findings findings are: (1) The upper Huagang Formation records stable 1.2 Myr long obliquity cycles and 405 kyr long-eccentricity cycles. A 5.6 Myr floating astronomical time scale (ATS) was established using the stable 405 kyr eccentricity signal. (2) DYNOT analysis shows that both million-year and 100,000-year lake-level variations are astronomically driven. The 1.2 Myr cycle controls 3rd-order lake-level changes, influencing deltaic facies belts, while the 405 kyr cycle governs 4th-order fluctuations, affecting sand-body stacking patterns. (3) Obliquity and eccentricity cycles also jointly modulate climate. A high-obliquity, low-eccentricity mode reflects a warmer, wetter climate with lower lake levels, where sand bodies occur in tangential or superimposed patterns. A high obliquity, high eccentricity mode reflects a colder, drier climate with higher lake levels, where sand bodies are isolated. This study provides new theoretical insights for high-resolution reservoir characterization and development of braided river delta reservoirs.

The Late Eocene Huizhou-A sandy conglomeratic system in the Pearl River Mouth Basin presents a highly heterogeneous reservoir system shaped by intense synsedimentary fault activity and variable depositional processes. Utilizing 3D seismic interpretation, well log analysis, and core calibration, this study reconstructs the tectono-sedimentary evolution, facies distribution, and diagenetic modifications controlling reservoir quality. Results show that the best reservoir quality is not confined to proximal fan-delta coarse-grained deposits near steep boundary faults, but occurs mainly in fan-delta front and braided-river-delta deposits, especially braided- and turbidite-channel microfacies. These reservoirs benefit from better sorting, favorable grain size, and higher textural maturity, whereas proximal clastic-flow deposits are poorer due to heterogeneity, poor sorting, and compaction. Reservoir quality is also depth-dependent: upper Enping reservoirs are mainly controlled by maturity, while lower Enping reservoirs are more influenced by grain size. Semi-quantitative analysis identifies the 7–11 km transport-distance zone as the optimal fairway for vertically stacked high-quality reservoirs. This approach not only guides exploration and development in the Huizhou Sag but also offers a transferable predictive model for similar steep slope lacustrine rift basins with comparable tectono-sedimentary settings worldwide.

The depositional architectures of continuous translation point bars (TPBs) in single meandering channel belts are increasingly being identified with modern seismic data imaging, yet they remain poorly characterized. This study uses 3D seismic and well-logging data to assess the spatial distribution patterns of depositional thickness and sand fraction of continuous TPBs, and discusses the factors that control the differences in sedimentary characteristics among the different TPBs. In the eastern Shaleitian Uplift of the Bohai Bay Basin, five translation point bars with counter-point bars (TPB1–TPB5) were recorded, two of them (TPB1 and TPB2) being built by a combination of downstream migration and rotation, the others only by translation (TPB3–TPB5). Regardless of whether TPBs undergo apex rotation, the bar thickness of TPBs shows a strong positive correlation with the sinuosity variation (R2 = 0.80), as increased sinuosity in a channel segment leads to deeper scour along the outsides of river bends. Along the flow direction, a declining bar sand fraction of pure TPBs links to diminished flow transportation capacity (TPB3–TPB4). Apex rotation resulted in the bar sand fraction rapidly decreasing in TPB1 and abnormally increasing in TPB2 along the flow direction, through enhanced localized scouring. In an area with significant slope changes, the sand fraction of a TPB tends to respond to the slope gradient (TPB5). This research illustrates the depositional architectures of continuous TPBs under different controlling factors, providing significant implications for characterizing the sand distribution and reservoir heterogeneity in subsurface translation point bars.

Classical sequence stratigraphic model exhibit certain limitations in constructing stratigraphic frameworks and predicting sediment transport, as real-world stratigraphic architecture and sediment dispersal are governed by a multitude of factors. Based on data from the Qiongdongnan Basin, 15 models were conducted using DionisosFlow to analyze the influences of sediment supply, sea-level fluctuations, and hydrodynamic processes on shelf-margin architecture and sediment partitioning. The results indicate that: (1) The progradation of the shelf margin was primarily controlled by sediment supply and hydrodynamic processes, showing a weak correlation with sea-level fluctuations. Under high sediment flux, wave-dominated conditions promoted shelf progradation, whereas fluvial-dominated processes had an inhibitory effect. (2) The lateral variability in shelf-margin architecture responded to all three factors, with sediment supply and hydrodynamic processes exerting a more significant influence. (3) The efficiency of deep-water sediment transport exhibited only a weak correlation with the amplitude of sea-level change, which was far less significant compared to other controlling factors. The use of forward-modeling scenarios to examine multiple control factors on shelf-margin architecture and sediment partitioning indicates that accounting more for uncertainty in stratal interpretation and prediction from seismic profiles and outcrops within sequence stratigraphy controlled by multiple factors could enhance the evaluation of subsurface accuracy.

The Late Eocene Pinghu Formation, located in the Xihu Sag of the East China Sea shelf basin, is a significant coal-bearing formation that offers a prime opportunity to delve into the sedimentary mechanisms underlying coal seam formation. By leveraging core and well logging data, the vertical evolution of the Pinghu Formation, from a tide-influenced delta to a river-dominated delta, has been meticulously delineated. The Astronomical Time Scale of the Pinghu Formation has been reconstructed through the application of Time Series Analysis. The research findings reveal that the development of thin coal seams within the Pinghu Formation is predominantly governed by tidal and orbital parameters. Specifically, orbital parameters serve as the driving force behind coal seam formation, while tidal forces exert a protective influence on coal seam preservation. Under the assumed monsoon-response framework, thin coal seams are primarily consistent with Pmin and Omin (precession and obliquity minimum) cycles, and they secondly form during Pmin and Omax (precession minimum and obliquity maximum) cycles. The sedimentary environment provides the essential backdrop for coal seam deposition, while orbital parameters may have modulated the transport of water and heat by monsoons to peat plants. Significance testing indicates that orbital forcing plays a primary role in controlling coal-seam development, whereas the influence of depositional systems is comparatively weaker. This likely suggests that coal seams exhibit a degree of selectivity in recording astronomical cyclicities under different depositional settings, rather than uniformly preserving a single combination of orbital forcing parameters. This study holds significance in enhancing our comprehension of the deposition mechanisms of multi-layer thin coal seams, thereby contributing valuable insights to the field of coal seam sedimentology.

To solve the problem of productivity decline resulted from plugging of screen by natural gas hydrate in the Shenhu area， South China Sea， the internal and external flow fields of Helmholtz and organ-pipe nozzles were simulated numerically using computational fluid dynamics （CFD）. The fluid field velocity and gas content were used as the main criteria to investigate the performance of plug removal by two types of cavitation jet nozzles in natural gas hydrate reservoirs. Moreover， a screen with simulated plugging by mud-sand deposits of natural gas hydrate in the Shenhu area was prepared to verify the actual effect and evaluate the performance of nozzles. The study results show that under natural gas hydrate reservoir conditions， the organ-pipe nozzle exhibits slower velocity decay， generates more bubbles in the external flow field， and delivers superior cavitation performance to the Helmholtz nozzle. The nozzle structure has apparent impacts on the pressure on the screen exterior after plug removal， in terms of which the organ-pipe nozzle outperforms the Helmholtz nozzle by achieving an 18.1% greater plug removal effect. Moreover， the organ-pipe nozzle enables a screen permeability 32.5% higher than the Helmholtz nozzle. The study results provide a reference for plug removal of natural gas hydrate by cavitation jet.

The Erlian Basin, a significant continental sedimentary basin in northeastern China, is renowned for its abundant hydrocarbon resources. Extensive research has been conducted on its sedimentary sequences, hydrocarbon accumulation, and geodynamic background. However, previous tectonic units classifications of the Erlian Basin predominantly reflect its post-Cenozoic tectonic framework, neglecting the Early Cretaceous period. This oversight fails to explain recent petroleum discoveries in the Wulanhua area of the Ondor Sum Uplift. In this study, geological, well log, seismic, gravity, and magnetic data, along with large, deep fault distributions and the regional geology of the Erlian Basin, were utilized to analyze its basement characteristics and propose a new tectonic division. Our findings reveal that the Erlian Basin's basement exhibits composite characteristics, resulting in a north-south zonation of basin depressions. Consequently, the basin's tectonic units were divided into northern, central, and southern depressions, delineated by two major deep faults: Xilinhot and Chifeng-Kaiyuan. This revised tectonic division clarifies the Early Cretaceous tectonic framework, enhances the basin's hydrocarbon exploration potential, and will guide future exploration efforts. Our study identifies nine favorable sags within the Erlian Basin with significant hydrocarbon potential.

The significance of tectonics in shaping sequence stratigraphy within continental rift basins, especially those with extensional strike-slip composite characteristics, cannot be overstated. These basins, often repositories of rich oil and gas reserves, are defined by their intricate fault systems and dynamic tectonic interplay. Despite their economic importance, the tectono-sequence characteristics of these basins remain underexplored, affecting the understanding and prediction of petroleum systems. This study presents a comprehensive tectono-sequence analysis of the Miaoxi'nan sub-sag in the eastern Bohai Bay Basin, a continental lacustrine sag intersected by the eastern branch of the Tan-Lu fault zone. By integrating extensive 3D seismic data, wireline logs, and previous research, we establish a detailed tectono-sequence framework and unravel the complex interplay of geometric and kinematic characteristics within the extensional strike-slip fault system that governs the evolution of the basin. Our investigation reveals a multi-tiered sequence stratigraphic structure comprising two first-order, 4 sorder, and seven third-order sequences. The west sub-branch of the East branch of the Tan-Lu fault zone (EBTLFZ) is identified as a strike-slip fault with a predominantly south-north strike, while the east sub-branch exhibits characteristics of a persistent tension-shear strike-slip fault zone. The study also shows a transitional fault strike of the rifting system from a multi-directional orientation at the base to a northeast-northeast-east direction, corresponding with different tectonic stages that have directed fault activities and sedimentary deformation. Additionally, both the extensional and strike-slip fault systems of the sag have experienced segmental growth evolution, influencing the westward and northward migration patterns of the basin's depocenter and subsiding center. Overall, the sequence development within the Miaoxi'nan sub-sag is predominantly regulated by the first- and second-order extensional faults, with the EB-TLFZ sub-branch faults providing further adjustment. This study provides vital insights into the tectono-sequence dynamics of extensional strike-slip composite basins, with implications for future hydrocarbon exploration and exploitation.

Cyclostratigraphic studies enable to reconstruct the geological timescales of many marine formations. However, these investigations are still lacking a precise astronomical tuning in lacustrine environments, particularly in the Middle Jurassic, due to the paucity of biological traces and the lack of data. In this study, detailed spectral analyses of natural gamma ray (GR) logging data were conducted on the lacustrine Sha-1 member from two wells in the Sichuan Basin, southwestern China. Core data samples were calibrated to test the lithological changes for proceeding with cyclostratigraphic analysis with more confidence. The spectral analysis and evolutionary spectral analysis of the GR logs reveal that the wavelength ratios of the stratigraphic cycles are-20:5:2:1, being consistent with the period ratios of astronomical cycles (long eccentricity, short eccentricity, obliquity, and precession). Correlation coefficient (COCO) analyses were applied to quantitatively measure the fitting of the witnessed sedimentary cycles to astronomical periods and provide a possible sedimentation rate range. The results show that astronomical time scale of the studied interval comprises 58.4-60.6 m cycles, representing the 405 kyr eccentricity cycles, and 14.9-16.6 m cycles, representing the-100 kyr eccentricity cycles. This study reveals a-2.43 Myr duration for the Sha-1 member. Sedimentary noise modeling reveals that long-term million-year period (1.2 Myr) astronomical forcing may have been a significant driver of lake-level changes in the Sichuan Basin. Moreover, high-frequency (405 kyr scale) lake-level variations associated with the mid-term base-level cycles (4th-order sequences) were linked to climato-eustatic changes. This study suggests comparison between parameters of cyclostratigraphic records and sequence stratigraphic base-level cycles in lacustrine sediments. The stratigraphic surfaces of mid-term base-level cycles correspond to minima-405 kyr-long eccentricity cycle curve and high values of DYNOT (dynamic noise after orbital tuning). Integrating cyclostratigraphy with the base-level cycles is, therefore, a vital approach for defining the short-term oscillations of lake-level, and proved to be a useful tool for characterizing thin-bedded lacustrine reservoirs.

Many modern paralic depositional systems are characterized by complicated morphologies mixed with the river, tide, and wave processes. However, the prediction of hydrodynamic processes within their ancient counterparts is challenging from the subsurface data due to the limitation of resolution and coverage. This study illustrates an integrated work on the mixed-energy paralic deposits of the lower Miocene Zhujiang Formation in the western shelf of the Pearl River Mouth Basin, northern South China Sea. Through a synthesis of grain size and heavy mineral analysis, well-based facies interpretation, and seismic stratigraphic study, it generally shows a vertical change from the dominance of tidal strait deltas and tide-influenced deltas to a river-dominated delta with the wave-dominated shelf throughout three members, in response to the evolution from semi-closed to open marine settings. Tidal, river, and wave signals were recognized from the mixed-energy paralic deposits, albeit with alternative interpretations and non-negligible limitations. Tidal processes, which were interpreted from grain size distribution unmixing and statistical heavy mineral comparison, intensified towards the distal reach in the Member 2, and they generally declined after the drowning of paleo-Highs in the Member 1-2. Fluvial processes, which were reflected by heavy mineral evidence and sedimentary response, significantly enhanced from Member 2 to Member 1-1 with more extensive drainages and increased sediment supply, despite the long-term transgression. The presence of large-scale shoreline-parallel shelf sand ridges in the Member 1-1 was mostly controlled by the wind-driven Guangdong Coast Currents and intrusion of the South China Sea Branch of Kuroshio Current, which were coupled with the maximum East Asian Monson intensity and the Indonesian Seaway shoaling before the final closure. We demonstrated that a multidisciplinary approach presented can be effectively used to assess the changes in hydrodynamic processes of mixed-energy depositional systems, which unravel more paleogeographic, paleoclimatic, and paleoceanographic information from depositional records.

Provenance studies involving regional-scale drainages that traverse lithostructurally complex terranes are challenging, especially if similar-aged zircon populations are distributed across source areas. In this paper, we study the late Eocene succession of the Beibuwan Basin in the northwestern part of the South China Sea, which is near the junction of the Yangtze, Cathaysia, and Indochina Blocks. We apply a zircon-based multiproxy approach that integrates U-Pb dating, Hf isotopes, and U-Pb/fission track double dating, and sedimentological evidence to understand source-to-sink pathways. Detrital zircon geochronology analysis reveals significant spatial provenance variation between western and northern samples, with unimodal and multimodal age peaks, respectively. Although both samples contain a large amount of Caledonian ages, provenance determination is uncertain based on the statistical analysis of age distributions alone. Compared with northern samples, combined zircon Hf isotope and fission track analysis suggest that western samples may have been sourced from the Song Chay Massif in the Yangtze Block, rather than from the nearby Yunkai Massif in the Cathaysia Block, as indicated by previous studies. Seismic stratigraphic studies indicate the existence of a large-scale axial deltaic clinoform in western areas, which may be linked to the development of an extensive palaeodrainage originating from the Song Chay Massif in the northwest. This southeast-flowing palaeodrainage was potentially a precursor to the palaeo-Red River and Pearl River tributaries. These findings validate that zircon-based multiproxy analyses effectively resolve provenance complexities in diverse regions, but emphasise that integration of sedimentological evidence is important to further refine the source-to-sink model.

The controls on cross-shelf deltaic architecture variability and high-frequency clinoform development along continental margins remain inadequately explored. Recently acquired high-resolution seismic data from the passive continental margin in the northwestern South China Sea offer an opportunity to investigate the intra-sequence architecture and shelf-edge trajectories of the early Pleistocene (2.6 to 1.8 Ma) succession in detail. Five high-frequency sequences, with an average duration of similar to 160 kyr in duration (4th-order sequences), exhibit distinct intra-sequence architectures and are related to four shelf-edge trajectory types: descending, slightly ascending, steeply ascending, and backstepping. The observed correlation between shelf-edge trajectories and intra-sequence architectures under high-frequency sea-level fluctuations reflects the dynamic interplay between accommodation and sediment supply, underscoring their potential as predictive tools in depositional process analysis. The stratal variability of early Pleistocene shelf-margin clinoforms documented in this study is controlled by a combination of factors, including sea-level fluctuations, climate, sediment supply, and tectonics. The reduced dominance of falling-stage systems tracts during the early Pleistocene compared to the late Pleistocene is attributed to the lower amplitude and more symmetrical nature of sea-level changes, which restricted the dominance of falling-stage systems tracts. The well-preserved transgressive and regressive units reflect sufficient sediment supply and paced accommodation creation. Our results emphasize that the local variations in high-frequency sequence architecture were shaped by multiple factors beyond sea-level changes in the early Pleistocene shelf-margin. Local factors such as tectonism and sediment supply can complicate the correlation of seismic sequences, even across relatively short distances.

The hangingwall dip-slope settings are important components of rift basins, being able to influence offshore sedimentation, but a few studies have examined their properties. Their reactivation of growth faults can contribute to re-shape basin geometry influencing the associated stratigraphic successions. This paper investigates the structural evolution of a hangingwall dip-slope setting to explore the development of multiphase rifts that imprint tectonic properties and stress field migration by utilizing seismic, well-log, and core data from the Xihu Sag, East China Sea Shelf Basin. Three composite sequences (CS1-3) are defined within the Eocene synrift deposits, along with three third-order sequences in CS3. We have reconstructed the evolution of two tectonic phases: rift phase 1 and rift phase 2. Furthermore, we identified two stages within each phase: rift initiation and rift development 1 for rift phase 1, and rift development 2 and rift termination for rift phase 2. However, an immediate decrease in fault activity was recorded in the rift phase 2. Alterations in the stress field throughout intermittent rift phases led to differences in tectono-stratigraphic structures. In rift phase 1, expansion occurred from small isolated depocenters to larger systems, while rift phase 2 experienced contraction. Concurrently, basin geometry evolved from wedge-shaped half-grabens to dish-like geometries. The tectonic change caused sediment overfilling to starvation in rift phase 1 and sediment starvation to balance filling in rift phase 2. This contribution provides insights into hangingwall dip-slope dynamics and rift basin depositional systems.

The internal architecture of deep-water channels is highly complex. Previous research has primarily emphasized the sedimentary processes governing channel migration, yet the linkage between sediment-source mechanisms and migration patterns—particularly their vertical evolution—remains insufficiently understood. Drawing on 3D seismic data, well logs, and core analyses, this study delineates the channel architecture within the deep-water succession of the Niger Delta Basin. Furthermore, by correlating high-frequency sea-level fluctuations with the formation timing of structural units, we explore how sea-level changes influence the spatial distribution and evolutionary dynamics of submarine fan systems. This study investigated the bottom-up evolution of two channel-lobe systems—the East Channel System (ECS) and West Channel System (WCS) within the stratigraphic succession, identifying two principal channel migration styles: expansive migration and downstream migration. In the ECS, migration was primarily characterized by a combination of downstream and expansive patterns. In contrast, the WCS displayed intermittent downstream migration, accompanied by some irregular migration. Correlation of sea-level variation curves with corresponding core photographs indicates that the ECS developed during a fourth-order sea-level. Its lower lobe and upper channel intervals each correspond to two complete five-stage sea-level cycles. In this system, debris flows and high-density turbidity currents produced stronger lateral erosion and channel migration, giving rise to the expansive migration style. Conversely, the WCS formed during a four-stage sea-level rise, with its lobe and channel sections likewise corresponding to two complete five-stage sea-level cycles. Here, sedimentation dominated by high- and low-density turbidity currents promoted enhanced erosion and migration along the flow direction, resulting in the predominance of downstream migration patterns. The ECS and WCS together constitute a complete three-tiered stratigraphic sequence representing two lobe–channel systems. This configuration deviates to some extent from the conventional understanding of the spatial distribution of debris flows, lobate channels, main channels, and deep-sea mud deposits. Consequently, during intervals of frequent sea-level fluctuation, deep-water sedimentary components within the continental slope region can partially record the signals of fourth- and even fifth-order sea-level variations, facilitated by a stable tectonic framework and favorable sediment preservation conditions. These findings offer valuable insights for reconstructing regional sedimentary processes and interpreting sea-level evolution.

Recent studies of two-phase non-coaxial analogue experiments and natural rifts suggest that the pre-existing faults that form in the first-phase rift could strongly influence the fault development during a subsequent phase of extension. However, related models from natural examples are still lacking. Here we compare the fault geometry and evolution with different pre-existing fault arrays in two adjacent areas (Xijiang and Lufeng sags) from the Pearl River Mouth Basin in the South China Sea. This basin has experienced two-phase rifting including the middle Eocene rift phase 1 (NW-SE extension) and a late Eocene-early Oligocene rift phase 2 (N-S extension). The Xijiang Sag developed an approximately NE-striking listric fault system, while the Lufeng Sag formed complex structure is composed of six major faults with various orientations. We demonstrate that the first-phase fault network in the Xijiang Sag is a colinear listric fault system, while that in the Lufeng Sag comprises two sets of (non-colinear) faults. In the Xijiang Sag, the second-phase fault network consists of the reactivated first-phase faults, newly formed faults abutting against or cross-cutting the pre-existing reactivated faults or occurring between the pre-existing faults. In contrast, in the Lufeng Sag, the second-phase faults include partially reactivated first-phase non-colinear faults and new non-colinear faults. The influence of first-phase faults on second-phase faults is manifested in several distinctive ways. Two sets of major non-colinear faults led to the development of more complicated oblique faults in the Lufeng Sag. The development of the second-phase faults is the result of a combination of geometry and heterogeneity of pre-existing fabrics, variation of extension direction and local perturbations set up by the geometry of pre-existing faults.

The prediction of sand body is a key focus in evaluating reservoir distribution, playing a crucial role in oil and gas exploration and development. To clarify the development characteristics of the sand body in the Huangyan structural belt of the Xihu Sag and effectively identify the hidden channel, a new approach is proposed. This approach incorporates a Convolutional Block Attention Module (CBAM) into a Convolutional Neural Network (CNN). Well logging and seismic data were used to predict the distribution of sand body in the lower section of the Huagang Formation (H12). Firstly, based on known sand-stratum ratio data and well-side seismic data, the seismic attributes that are sensitive to the reservoir response are preferred through correlation analysis, which are used to construct a Polynomial Linear Regression (PLR) model to obtain the preliminary sand distribution prediction results. Secondly, the grid is divided according to this result. Then, three sample selection methods, namely proportional, fixed-range, and random, are used to construct three sample sets in conjunction with the geologic model guide. Finally, CBAM-CNN, CNN, Random Forest (RF), Support Vector Machines (SVM), and Backpropagation Neural Network (BPNN) are utilized for sand body prediction. The results indicate that when using the same model, the sample set selected by the fixed-range selection method yielded the best prediction outcome. When using the same sample set, the CBAM-CNN model outperformed the others. Among various strategies, training the CBAM-CNN model with the sample set derived from the fixed-range selection method led to the highest test set R2 of 0.913. The results of the sand body distribution indicate that fine river channels are more continuous, and reservoir boundaries are clearer, significantly outperforming other schemes. This outcome can serve as a guide for further reservoir delineation.

This study proposes a microwave heating energy supplement technology for gas hydrate reservoir. The microwave radiation simulation model of the leaky coaxial antenna is established by HFSS. Based on the simulation results of microwave antenna structure parameters on the radiation performance, the optimized shape, angle, length, width and fillet of the slot are rectangle, 80 degrees, 38 mm, 12 mm and 2 mm, respectively. To compare the heating performance of microwave antenna before and after optimization, a microwave heating simulation model for hydrate reservoir is developed, which is validated by experimental results. The comparison results illustrate that, after microwave heating 10 h with the optimized antenna structure, the average temperature within a 1-m radius of natural gas hydrate reservoir increases to 10.613 degrees C, which is about 5.5 degrees C higher than that before the optimization. The aforementioned results suggest that the optimized microwave antenna structure significantly increases the temperature of the hydrate reservoir, providing the necessary energy to drive hydrate decomposition. The proposed microwave energy supplementation technique holds promise for advancing the efficient development of natural gas hydrates, the further investigation of effect of which on gas production within hydrate reservoirs is needed for future application.

Abstract The investigation into microwave heating technology for enhancing gas production from hydrate reservoir has attracted wide attention. However, the initial microwave heating device structure still has limitations of low average temperature and uneven temperature distribution in the reservoir during microwave heating. This study has established the microwave heating simulation model, which is validated by the reservoir microwave heating experiment results. Based on the simulation results of microwave heating model, the optimized structure parameters of microwave heating device are obtained: the slots distribution method is cross-distribution, the slot shape is rectangle, the slot angle is 75°, and the slot length is 30 mm. Following microwave heating with the optimized structure for 10 hours, the average temperature within the 1-meter radius of the reservoir rises from 2 °C to 9.52 °C, the maximum temperature in the reservoir is 58.21 °C, and the temperature standard deviation is 9.15 °C. The results mentioned above indicate that the optimized structure can well increase the temperature in the gas hydrate reservoir and the temperature distribution is uniform. This study will further promote the application of microwave heating technology in the actual exploitation of natural gas hydrate.

The Miocene Zhujiang Formation is one of the most productive oil and gas-bearing strata in the Pearl River Mouth Basin (PRMB), South China Sea. The disagreement of the stratigraphic scheme and the lack of high-precision stratigraphic scheme and mechanism understanding have seriously constrained the further deepening exploration of the rocky oil and gas reservoirs. Based on the analysis of the Gamma ray series, lithologic sequence variations, the cyclostratigraphy, and sequence stratigraphy of wells A1 and B2 were in the Zhujiang Formation analyzed. The 4 third-order sequences and 17 fourth-order sequences were identified, 19 long eccentricity cycles were also obtained and significant Myr-obliquity signals were identified. An astronomical time scale was established with the formation time of the Baiyun movement (23.8 Ma) as the boundary time of the Zhujiang Formation-Zhuhai Formation. In addition, tectonic subsidence analysis was also performed. The results suggest that 1.2-Myr obliquity and tectonics were the main factors of the third-order sea-level fluctuations and the third-order sequences in the PRMB, and long eccentricity played a role in the development of the fourth-order sequences. The main drivers of stratigraphy may also differ at different stages of basin evolution. The combination of cyclostratigraphy, sequence stratigraphy, and tectonic subsidence is useful for establishing an objective delineation and understanding the driving mechanism of the sequence stratigraphy.