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Deep‐water massive sandstones (DWMS) are characterized by large volumes of sand accumulations which are considered as potential reservoir intervals in deep‐marine environments. Lithological variations and bed thickness statistics are used to interpret the distribution of massive sandstones in a deep‐marine fan‐lobe system. These massive sandstones are interpreted based on lithological heterogeneities and detailed facies analysis in seventeen exposed sections of the Late Palaeogene deposits in Sabah, NW Borneo. Sedimentary logs containing details of lithology textures and structures were used to recognize nine sedimentary facies of DWMS. These lithofacies were then grouped into three sedimentary facies associations: (1) massive facies association with basal part of turbiditic Bouma sequence, (2) massive facies association having soft‐sediment deformation structures, and (3) massive facies association with erosional features. The facies analysis portrays inner to middle submarine fan deposition and was later applied to reconstruct the distribution of a channel‐lobe complex. Individual sandstone bed thicknesses vary from 1 m to more than 8 m and the number of massive sandstones in submarine lobes range from less than 10% to more than 50%. The thicknesses of massive sandstones in channels are more than 8 m, whereas distal lobes have thicknesses from 1–2 m only. These sandstones are concentrated in channels, proximal and medial lobe settings that can also be verified from calculating the average of all maximum thickness of massive sand intervals that is, 8.91 m. The lithological heterogeneities and the processes associated with the deposition of these massive sandstones are vital for potential hydrocarbon reservoirs in the deep‐marine environments around the globe. [ABSTRACT FROM AUTHOR]

Lithologic variations in deep-water slope channel systems provide critical insight into sedimentary processes on deep-water slopes, and are a key control on natural resource distribution and connectivity in subsurface reservoirs associated with ancient deep-water systems. While many studies have described these variations at outcrop-scale along depositional strike (across-channel), few have focused on documenting along-depositional-dip changes due to: (1) the dearth of along-slope perspectives afforded by outcrops; or (2) limited resolution and coverage of subsurface data sets. In this study, slope channel elements (≤30 m thick; ≤400 m wide) and composite channelform bodies composed of ≥2 stacked channel elements (channel complexes and channel systems; >30 m thick; >400 m wide) were characterized along a 50-km-long depositional-dip-oriented outcrop belt of the Campanian-Maastrichtian Tres Pasos Formation (Chile) to constrain longitudinal changes in channel fill character and stacking patterns. Results show that channel elements become more sandstone-rich downdip. Outcrop observations are supported by channel element net-to-gross ratios (measures of sandstone proportion), which increase downdip. Sandstone-prone channel elements within channel complexes and channel systems are more prevalent downdip; however, variability in lateral and vertical offset between successive channel elements downdip results in a poor correlation between net-to-gross values and paleoslope position when composite channelform bodies are considered. These findings suggest that the along-slope distribution of coarse-grained sediment in channel systems is tied to the degree of coarse-grained sediment bypass and erosion that occurs along a slope. The results of this study provide a detailed perspective into downdip changes in slope channel fill and stacking patterns, and help clarify aspects of analogous subsurface reservoirs, including sandstone proportion trends for several scales of deep-water slope channel architecture. • Deep-water slope channel systems are analyzed using outcrop and subsurface data • Sandstone content in studied slope channel systems is found to increase downslope • Sandstone content is linked to sand-rich sediment bypass/deposition along a slope • Channel fill stacking is linked to autogenic processes and local slope morphology • Study findings provide insight into the properties of analogous reservoir units [ABSTRACT FROM AUTHOR]

The middle sub-member (Es3z) within the third member (Es3) of the Eocene Shahejie formation is the main source of the generation and accumulation of hydrocarbons in the lacustrine deltas of Bonan depression. Exploration and research work in different blocks is carried out separately. Types of sedimentary facies, and their vertical and lateral evolution in Es3z are not studied in detail. To fill this knowledge gap, we did a detailed analysis of facies and lithological characteristics through integrative studies of cores, well logs and seismic data. Identification of sedimentary structures and lithology of the reservoir zone from cores are calibrated with high-quality well logs and seismic data. Depositional facies in Es3z reservoirs are identified through analysis of sedimentary structures, grain size, log's trends and seismic sections. Es3z was deposited in the fan delta front setting where five facies associations are found, among them distributary channels consisting of MCS, CSg, PCSs, MS, RCL, WCS, PBSs, RCS and GBS lithofacies, natural levee containing DFs, and furthermore, sheet sand are associated to CBS and SSM lithofacies. GM, GGM and DGM lithofacies are related to inter-distributary deposits, whereas mouth bars consist of PLS, CS and CFS. Depositional history, flow direction of the sediments, and facies distribution are investigated through detailed facies mapping and cross-section profiling to show that the sediments were sourced from southeast to northwest. We found thicker succession of sedimentary profiles towards north and north-west directions. Belt distributary channel deposits, covering a wide range of areas, act as potential reservoirs along with mouth bar deposits, while mudstones in interdistributary channels act as a good source and seal rocks. The methodology adopted has great potential to explore the reservoirs of fan delta front in lacustrine deltas. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new workflow integrating intelligent inversion and lithology model is proposed. • This method improves the seismic resolution and prediction of tight sandbodies. • The results provide reliable geological information for horizontal well drilling. Lacustrine gravity-flow deposits are common in sedimentary basins, and sand bodies formed in the basin center mingled with organic rich mudstone may form excellent tight reservoirs of hydrocarbons. However, the complex architecture and intensive heterogeneities of lacustrine gravity-flow deposits commonly pose great risks for hydrocarbon exploration and development. To address this problem, a new workflow for predicting tight sandstone is proposed in this work. The workflow combines well log analysis, intelligent seismic inversion and 3D geological modelling to improve the prediction effectiveness of tight sandstone and sedimentary facies. The original 3D seismic data was firstly decomposed into three components with low, middle and high frequencies to improve the resolution of seismic inversion, and a nonlinear relationship between well logs and the decomposed 3D seismic data was then established by using an algorithm of support vector machine. A 3D lithofacies model was subsequently established integrating well logs and the seismic inversion result. The distribution of sand thickness was imaged relying on the lithofacies model. Correlations between the actual and predicted sand thickness based on the seismic attributes and the seismic inversion result was improved from 0.66 to 0.79. The prediction of sand bodies was further improved through the 3D lithofacies modelling, especially for these thin sandstone layers. Sedimentary facies of the Chang_7 member in the Qingcheng Oilfield, Ordos Basin, were characterized based on the distribution of sand bodies. Fan-shaped sand bodies are mapped in each zone of the Chang_7 member, revealing that the entire Chang_7 successions are of sub-lacustrine fan in origin. The Chang_7 member mainly contains six sedimentary architectural elements: main channel, branch channel, lobe, lobe edge, slump body and inter lobe/inter channel. The distribution of sedimentary facies is different in different zones, and appears to be largely related to the change of base-level. A horizontal well was designed according to the prediction of sand bodies, which show a higher probability of drilling into sandstone by approximately 10% compared with that of other horizontal wells. [ABSTRACT FROM AUTHOR]

The Zagórnik-Rzyki studied section includes the upper part of the Veřovice Fm and the lower part of the Lhoty Fm (Aptian–Albian), which are small fragments of the much thicker sedimentary succession of the Silesian Nappe (Polish Outer Carpathians). Logged section gives a good insight into the relatively proximal but muddy submarine fan environment with at least partially confined nature and widely distributed facies of heterolithic deposits and banded sandstone. Three distinguished facies associations represent a gradual lateral shift toward the depositional lobe flank in a relatively proximal setting, away from the main sediment distribution pathways. The studied heterolithic deposits show various internal sedimentary structures (muddy ripples, draped ripples, low-amplitude bed-waves, low-angle laminated bedforms, small lenticular bedforms and plane-parallel laminated mudstone) considered as a record of the dynamic of sedimentary processes on a submarine depositional lobe flank environment. Despite the predominance of finning upward grain size trends (wanning flow deposits), sedimentary structures in the heterolithic deposits may stack in a varied order, also forming coarsening upward trend (waxing flow deposits), bi-gradational trend (waxing to wanning flow deposits), and complex trends (deposits with multiple waxing to wanning flow pulses) indicating record of hyperpycnal flows. Lack of hybrid event beds despite the occurrence of transitional flow deposits is evidence that even in mud-dominated to mixed sand-mud submarine turbidite systems, the flow transformation from fully turbulent to cohesive laminar behaviour is incomplete in relatively proximal depositional environment. Instead, a variety of facies banded sandstone and heterolithic deposits may represent a significant fragment of the sedimentary record in the proximal depositional lobe flank setting. [ABSTRACT FROM AUTHOR]

In this research study, 27 ichnospecies belonging to 18 ichnogenera are described for the first time from the lower Miocene Tiaret Marl Formation (north-western Algeria), which consists of thin-to medium-bedded sandstones and marlstones, representing deep-sea fan facies. The sandstones contain the following ichnotaxa: Cardioichnus isp., cf. Chondrites isp., Ophiomorpha isp., Ophiomorpha annulata, Ophiomorpha rudis , Palaeophycus isp., cf. Planolites isp., Planolites montanus, Zoophycos isp., Tisoa siphonalis , Helminthorhaphe isp., Scolicia isp., Scolicia prisca, Scolicia vertebralis , Cosmorhaphe isp., Desmograpton isp., Gordia isp., Helminthopsis isp., Nereites isp. , Tubulichnium cf. incertum , Urohelminthoida appendiculata, cf. Megagrapton isp., Paleodictyon minimum, P. strozzii, P. majus, P. (Glenedictyum) miocenicum and P. maximum. The given ichnoassemblage is recorded for the first time from the Miocene of Algeria and assigned to the Nereites ichnofacies, which is typical of marine bathyal depth. • The lower Miocene Tiaret Marl Formation has been divided into 2 units. • The environment corresponds to deep-sea fan. • Several trace fossils from Tiaret Marl Formation are recorded for the first time from Algeria. • The studied ichnoassemblage corresponds to the Nereites ichnofacies. [ABSTRACT FROM AUTHOR]

The morphodynamics of supercritical density flows have a large impact on the dispersal of sediment and the resulting depositional architecture. Coarse-grained delta-foreset deposits represent ideal field examples of deposition by supercritical density flows on steep slopes. Field examples were studied in the Eocene Sant Llorenç del Munt fan-delta complex at the southeastern margin of the Ebro Foreland Basin (NE Spain). The fan-delta slope deposits, which are dominated by marlstones and fine-grained sandstones, include coarser-grained facies that indicate deposition by supercritical density flows. The formation of the perched lobes is interpreted as related to the expansion of supercritical density flows on the delta slope. Deposits of supercritical density flows form 2-4.5 m thick lobes, which are perched on the delta foreset. Lobes are bounded at the base and top by erosional surfaces that are characterized by long-wavelength geometries with irregularly spaced scours. Internally, the lobes are organized into 0.5-3 m thick lobe elements that pinch-out upslope and show backstepping stacking in dip sections and compensational stacking in strike sections. Lobe deposits include conglomerates, pebbly sandstones and sandstones and display lateral grain-size fining both in downflow direction and in across flow sections. Beds typically onlap the downslope dipping erosion surfaces at the base of a lobe or lobe element, respectively. Proximal lobe deposits are characterized by amalgamated scour fills, displaying backset cross-stratification or concentric stratification. Some scours are infilled by structureless sandstone or marlstone, containing pebble-sized clasts and large sandstone slabs derived from the underlying beds, and are commonly associated with laterally more extensive erosional surfaces. Amalgamated scours with backsets are interpreted as related to the occurrence of hydraulic jumps. Extensive scoured surfaces are interpreted as indicating phases of bypass. Downslope the scour fills pass into more sheet-like beds with sinusoidal or subhorizontal stratification, indicating deposition by antidunes. These antidune deposits dominate the more distal parts of the lobe deposits. [ABSTRACT FROM AUTHOR]