The seismic attributes of water-rich sandstone contain much information about the rock's physical properties and seismic wave parameters. They are commonly used to predict the rock's physical properties (e.g. porosity). However, the seismic attributes of water-rich sandstone are affected by porosity, water saturation and thickness. To eliminate the influence of thickness on the porosity prediction of water-rich sandstone and improve the accuracy of the porosity prediction, the authors propose a Lambert W-R transform method to isolate the contribution of thickness and porosity from seismic attributes. First, a rock physical model is used to calculate the equivalent elastic parameters of water-rich sandstones with different porosity values and water saturation levels. Second, the seismic attribute dataset of water-rich sandstone is established by forward modelling the seismic response of the wedge-shaped water-rich sandstone model, and the selection of sensitive physical properties is completed. Then, the transformation parameters (zeta R-Ah(s) and eta R-Ah(s)) are obtained by Lambert W-R transformation, which is exponentially related to instantaneous amplitude. zeta R-Ah(s) and eta AhRs are sensitive to thickness and porosity, respectively. Finally, an interpretative template for porosity prediction of water-rich sandstone is established by cross-plot analysis (zeta R-Ah(s) and eta R-Ah(s)) and verified by a practical case. The verification results show that the porosity predicted by the interpretation template is consistent with drilling fluid consumption. However, it is lower than the porosity of logging constrained P-wave impedance inversion.

SignificaneThe analysis of source-to-sink system is a comprehensive study of tectonic geology, sedimentology, and sequence stratigraphy. Because of its integral, dynamic, and semiquantitative-quantitative characteristics, it has attracted widespread attention.ProgressThis review first introduces the key issues of the deep-time source-to-sink systems (pre-Quaternary systems), which include the quantitative characterization of sediment mass balance and the control of the transport process on the sediment. Due to the lack of stratigraphic records and the difficulty in obtaining parameters, the research is still challenging.Second, it reviews the quantitation methods of deep-time source-to-sink systems that can be classified into three categories, namely, geochronology, uniformitarianism, and sedimentology. By obtaining information such as geomorphological parameters, hydraulic parameters, erosion rates, and sediment flux, various methods establish the quantitative relationships between "sources" and "sinks" and then rebuild the sedimentary basin infilling history. This article introduces the principles and related parameters of different methods and then compares the advantages and limitations to provide a reference for future research. It is believed that geochronology is widely used, and the core lies in provenance analysis. The key to uniformitarianism is the analogy of geological background and the selection of geological parameters. The sedimentology is controlled by multiple variables, and the tectonic-climate background and research scale need to be considered comprehensively.Conclusions and ProspectsFinally, this review states the development of quantitative analysis of deep-time source-to-sink systems. Under the guidance of the important idea of "the present is the key to the past", the research needs to focus on the provenance systems, sediment routing systems, sediment dispersal, and redistributive process, and coupling relationship between various parameters. Research also needs to pay attention to quantitative analysis at multiple timescales and multidisciplinary dynamic analysis. Compared with continental margin source-to-sink systems, continental lacustrine source-to-sink system patterns and prediction models need to be further improved.

源-汇系统是目前国内外地球科学领域的研究热点,对于含油气盆地古地理重建以及源储预测评价有着重要的指导作用.本文以准噶尔盆地二叠系为研究对象,通过基于盆地地质大剖面的构造-层序特征分析、定年数据的物源体系演化分析和沉积过程约束的正演模拟等方法,深化了对准噶尔盆地二叠纪古地理格局的认识,探讨了二叠纪源-汇系统演化特征与二叠系源储分布规律.早二叠世为盆地断陷发育期,以石炭系为主物源,除东南部发育海相-海陆过渡相沉积外,总体以近物源扇三角洲-湖相沉积体系为主,多断陷的沉积格局控制了玛湖等凹陷优质烃源岩的分布,与火山岩相关的扇三角洲前缘砂体与混积云质岩构成有利储集体;中二叠世为盆地断-拗转换期,物源年龄开始趋于复杂,沉积中心、沉降中心较早二叠世明显向盆内迁移,早期断陷趋于连通,盆地西部仍以近物源的扇三角洲群-湖相沉积体系为主,东南部则转换为远物源三角洲群-湖盆沉积体系,在盆地中部发育连片分布的规模烃源岩,可与同期(扇)三角洲前缘形成良好的源储组合;晚二叠世进入盆地拗陷发育期,物源供给范围更广,物源年龄进一步复杂化,大型浅水湖盆发育远物源为主的退覆型河流-三角洲沉积体系,为盆地规模油气成藏奠定了储层基础.

More and more attention has been paid to the sedimentary forward modeling (SFM) since the study on the sedimentology is targeted toward quantification, process orientation and systematization. This review first stated the main input and output data of the current sedimentary forward modeling and sorted out the determination methods of the input parameters. Then it reviewed the classification methods of the sedimentary forward modeling, and the classification principles included principle of simulation, number of simulation processes, types of simulation results, simulation dimension, simulation scale, data fidelity and source region covering source-sink system. Subsequently, it introduced the sedimentary forward modeling methods for the different sedimentary systems of clastic series, including hillside landform, river and deep-draft waterway, delta, lobe and landslide. It also described some classic simulation programs for the individual series, indicated the sedimentary characteristics of this series to be essentially simulated and their corresponding principles of simulation and covered multiple simulation methods as much as possible to expand the understanding of the sedimentary forward modeling. Finally, it looked into the development of the sedimentary forward modeling believed it would be targeted toward the three-dimension visualization, multi-process integration and multi-discipline integration, proposed to strengthen the training of compound talents in computer, mathematics, mechanics and geosciences; strengthened the experimental study on the sedimentary forward modeling hypothesis to study the sedimentation theory; tried multiple simulation methods and shifted the application foremost to the research and development foremost.

被动大陆边缘依据地貌可分为平直型与S型,前人对其控制作用的研究多集中在三角洲发育与深水沉积物输入量2个方面,而对于峡谷和海底扇的影响以及坡折的作用仍然缺乏定量化的系统研究.采用沉积正演方法,研究S型与平直型被动大陆边缘上的沉积体系特征的异同点,系统对比了沉积体系分布、沉积物配置关系、层序格架发育、演化特征,以及河流和浊积水道特征.研究表明,S型边缘三角洲欠发育,进积为主,加积为辅,峡谷内可见明显凹岸侵蚀,海底扇为沉积物主要卸载区域,总体受海平面升降影响小;而平直型边缘三角洲高度发育,加积为主,进积为辅,峡谷中上部被三角洲沉积覆盖,海底扇几乎不发育,总体受海平面升降影响大.进一步研究表明,陆架坡折导致沉积物在陆架之上贮存少,向深水区搬运多,而陆坡坡折导致沉积物在陆坡上贮存少,在峡谷口大量卸载.

The debate on the submarine canyon origin between the upslope erosion model dominated by retrogressive mass failures and the downslope erosion model controlled by gravity flows has not been fully settled. However, this debate is critical for explaining submarine canyon evolution. This study combines susceptibility mapping and stratigraphic forward modeling (SFM) to examine the origin and evolution of submarine canyons under various fluvial discharge and morphologies. The SFM work consists of dozens of hypothetical numerical experiments based on typical passive margin bathymetry with half bathymetry occupied by an incipient canyon and associated river mouth topography, and another half bathymetry by steep slopes without canyons. Evolution characteristics in both plan and cross-section views are analyzed, and the impacts of fluvial and morphological features on canyon evolution are tested.The results indicate that the submarine canyons retreat landward, tributaries develop on the canyon outer banks, and blind canyons grow landward to capture small gullies and form shelf-incising canyons. The upslope pattern is dominant regardless of changes in fluvial discharge and morphologies. The locations of tiny gullies on steep slopes determine the distribution and growth direction of submarine canyons, whereas fluvial conditions and morphology parameters affect the canyon dimensions. High fluvial discharge and high canyon sidewall slope angle promote tributary development and canyon erosion. High canyon sinuosity leads to an asymmetrical distribution of tributaries on canyon outer banks whereas high regional slope angle increases the canyon length and decreases the canyon spacing.This study settles the debate between the upslope and downslope erosion models. In addition, it refines the up slope model by highlighting the importance of small-scale gullies and testing the influence of fluvial and morphological conditions on canyon evolution. The conclusions could promote the understanding of submarine canyons and assist in reservoir exploration and hazards prevention.(c) 2021 Elsevier B.V. All rights reserved.

Morphology is one of the principal driving forces governing the sedimentology and evolution of delta‐canyon‐fan systems. However, quantified and systematic studies of morphological controls are still very limited. This study applied hydraulic‐based stratigraphic forward modelling to investigate the impacts of morphological parameters on sediment budget partitioning and channel network of delta‐canyon‐fan systems on passive margins. A total of six sets of stratigraphic forward models are built using 47 initial bathymetries with six varying morphological parameters: shelf gradient; shelf width; slope gradient; canyon sinuosity; canyon depth; and basin gradient. The quantified relationships between morphological parameters and sedimentological parameters (dimensions, deposition/erosion volume/area, number of tributaries and slope channels) are investigated. The causes behind the relationships are explored by analyzing the response of qualified sedimentary features to morphological controls, such as grain‐size distribution, channel migration and sequence stratigraphic frame. The results suggest that low shelf gradient, low shelf width, high canyon gradient and low canyon sinuosity are beneficial for sediment budget partitioning into deep basins and turbidity currents to flow inside canyons. Low canyon depth also promotes sediment delivery but results in more channels on canyon flanks. For the delta, channel lateral migration increases then decreases with increasing shelf gradient due to the gradient threshold in determining channel sinuosity; delta size increases then stops increasing with increasing shelf width due to the shelf width threshold in determining the balance between accommodation and sediment supply. For the canyon, low canyon gradient, high canyon sinuosity and low canyon depth have similar effects on canyons, all resulting in significant channel translation and canyon widening but less canyon head retrogradation. This study improves the knowledge of controlling factors and sediment transport regime of a delta–canyon–fan system. Moreover, the observed relationships could provide semi‐quantitative guidelines to predict the dimensions of delta–canyon–fan systems and the distribution of hydrocarbon reservoirs.

Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions. The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multiprocess and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability. Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelfincised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.

The present work simulated a hypothetical 4D delta-canyon-fan depositional system using stratigraphic forward modelling (SFM) to: 1) investigate the differences and linkages of the sea-level control on the evolution of each sub-environment; 2) explain the evolution under the constraints of sea-level change from the perspective of channel activities. The SFM approach LECODE applied in this study combines an open-channel flow approach with a non-uniform sediment transport algorithm, with former to simulate water dynamics of turbidity currents and river flows and latter to simulate the transportation, deposition, and erosion of sediments. The input data is calibrated via sensitivity analysis and survey of analogue records. The results are compared with three sets of actual seismic data as verification. After introducing the general characteristics of the model, this study compares the influence of sea-level change on the delta, canyon, and fan, respectively, by analysing stratigraphic framework, the architecture of channel-levee complex, channel distribution and migration, sedimentation/erosion rate, and peak velocity. Moreover, a higher sediment supply case and a lower sediment supply case are compared to test the situation when sediment supply is less dominant. Finally, the influence of sea-level change on channel migration is discussed and the system evolution, especially the canyon evolution, is explained from the view of channel activities. The results show that sea-level control will be weakened from the delta to the fan via the canyon along with sediment transport. With higher sediment supply, the weakening is stronger. With lower sediment supply, the whole system is more sensitive to the sea-level change and this sensitivity lasts longer. The channel migration is more influenced by local topography, even adjacent topography, rather than sea-level change. The inner bank erosion near the canyon head is directly related to the shelf morphology. The translation and asymmetrical distribution of turbidity channels result in the translation and asymmetrical erosion of canyon bends. The insights extracted from this study could discriminate sea-level control on submarine canyon and fan instead of regarding them as an entirety of ultimate sink in source-to-sink research. Also, the integrated investigation with both qualified perspectives and quantified data could refine sequence stratigraphic concepts and provide a prototype for hydrocarbon exploration on high-sediment-supply river-fed delta-canyon-fan systems.

Sedimentary characteristics and genesis of a sandy, topset-dominated braided river delta from Huangqihai Lake were investigated using trenching and a ground penetrating radar survey. Ten lithofacies types were identified with assistance of grain size distribution to record a broad range of depositional processes within an overall coarsening upward sequence. Four distinct architectural elements, including channel fill, compound bar, sand sheet, and river mouth bar, built up this delta. No obvious foreset can be identified in this braided river delta. A gentle slope (0.2°) and shallow basin (<10 m deep), young age (~25 years), and low sediment supply caused by human disturbance and semi-arid climate, are believed to allow this type of topset-dominated delta to form.

This study built a 3-dimensional stratigraphic forward modeling for deepwater turbidity system from river mouth to abyssal basin via sinuous canyon in geological time-scale. The model is based on the bathymetry of Perth Canyon, Western Australia. Then this study observed the sedimentary evolution and patterns in space. Finally the possible controlling parameters are tested including inflow variables and bathymetry variables. The results show the favorable reservoirs rich in coarse sediments are located in canyon and canyon-fan transition zones. The deposition of channel and splay is more random and hard to predict because of frequent migration. The gradient on each part, depocenter migration and sediment supply no matter if concentration changes are the main controlling reasons. The sinuosity and slope gradient influences the asymmetry degree in canyon bends but will not affect submarine fan prominently. The side wall gradient and depth in canyon determines condense degree and natural levee height. It provides an important test bed for uncertainty modeling and these patterns will improve understanding of transportation and impact of depositional variables on architectures. It demonstrates that for deepwater reservoir prediction without adequate data this method and the calibration through constructing synthetic seismic data can provide new insights and reduce unnecessary investment.

According to the cores, outcrops, seismic data and wire-line logs, the main influences exerted by slope gradient on sedimentation of lacustrine delta are as follows: 6 kinds of microfacies assemblages are recognized in the elaborate development area and 3 sequences of these assemblages are identified in the well correlation along provenance; the bars-rich delta front is developed in steep slope while the river-rich delta front in gentle slope. The exploration and development experience indicate the reservoirs formed in steep area are favorable for well-connected sandbodies and high sand-bearing ratios.