Application of seismic sedimentology in characterization of fluvial-deltaic reservoirs in Xihu sag, East China Sea shelf basin

The fluvial-deltaic reservoirs of the Oligocene Huagang Formation in the Xihu sag of the East China Sea shelf basin reflect rapid lateral change in sedimentary facies and poor morphology of conventional slice attributes,which bring difficulties to the reservoir prediction for subsequent exploration and development of lithologic reservoirs.The traditional seismic sedimentology technology is optimized by applying the characteristic technologies such as frequency-boosting interpretation,inversion-conventional–90°phase shift joint construction of seismic lithologic bodies,nonlinear slices,paleogeomorphology restoration,and multi-attribute fusion,to obtain typical slice attributes,which are conducive to geological form description and sedimentary interpretation.The Huagang Formation developed three types of sedimentary bodies:braided river,meandering river and shallow water delta,and the vertical sedimentary evolution was controlled by the mid-term base-level cycle and paleogeomorphology.In the early–middle stage of the mid-term base-level ascending cycle,braided channel deposits were dominant,and vertical superimposed sand bodies were developed.In the late stage of the ascending half-cycle and the early stage of the descending half-cycle,meandering river deposits were dominant,and isolated sand bodies were developed.In the middle–late stage of the descending half-cycle,shallow-water delta deposits were dominant,and migratory medium–thick sand bodies were developed.Restricted paleogeomorphology controlled the sand body distribution,while non-restricted paleogeomorphology had little effect on the sand body distribution.Based on reservoir characterization,the fault sealing type and reservoir updip pinch-out type structural lithological traps are proposed as the main directions for future exploration and development in the Xihu sag.

Coal petrology,sedimentology and depositional environment of the Parvadeh coais in the Upper Triassic,Tabas Block of Central-East Iran

Peat forming environment strongly influences the economic value of any coal seam and coal-bearing strata.Hence,pal-aeoenvironmental studies provide important information for coal resource exploration.In this context,detailed studies on selected coals from the Parvadeh Area,Iran,were conducted using sedimentology,coal petrology,X-ray diffraction(XRD),scanning electron microscopy-energy dispersive X-ray analyzer(SEM-EDX),and proximate analysis.The sedi-mentary facies above and below the coal seams are mainly marine or marine-influenced facies,supporting that the coal-forming mires in the Parvadeh Area developed in a paralic environment,where the base level must be closely related to sea level.Sulfur contents are moderate to high and mark the influence of brackish/marine water,especially during transgres-sion after peat growth in a lower delta plain environment.The peat-forming mires extended on coastal/delta plain lobes.The lower delta plain/coastal plain coals are characterized by lateral continuity and substantial thickness,whereas few coals possibly representing the upper delta plain are thin and more discontinuous.The detrital nature and composition of the numerous partings and the overall high ash yield in the coal seams indicate an active tectonic area with high rates of creation of accommodation space over peat growth.Coal petrology and coal facies analysis exhibits a permanently high water table within a forest swamp and mostly rheotrophic conditions,sometimes with connection to the seawater.Accord-ing to paleoenvironmental reconstructions,it seems that coal layers may be thicker,with less sulfur(pyrite),but more clastic minerals and partings toward the western part of the area.Although these coal seams presently have low economic potential for the mining operation,partly due to great depth,this humic,high-volatile to medium-volatile bituminous coal may be suitable for exploration of coal bed methane resources.

Subtle trap recognition based on seismic sedimentology- A case study from Shengli Oilfield

Seismic sedimentology is the study of sedimentary rocks and facies using seismic data. However, often the sedimentary body features can＇t be described quantitatively due to the limit of seismic resolution. High resolution inversion offsets this limitation and is applied to seismic sedimentology to identify subtle traps under complex geologic conditions, thereby widening the applicable range of seismic sedimentology. In this paper, based on seismic sedimentology, seismic phase-controlled nonlinear random inversion is used to predict the sandy conglomerate reservoir of Es3 in the Chezhen depression in Shengli Oilfield. Thickness and sedimentary microfacies maps of sandy conglomerate bodies in several stages are presented and several subtle traps were predicted and verified by drilling.

Methods for seismic sedimentology research on continental basins

In contrast to marine deposits, continental deposits in China are characterized by diverse sedimentary types, rapid changes in sedimentary facies, complex lithology, and thin, small sand bodies. In seismic sedimentology studies on continental lacustrine basins, new thinking and more detailed and effective technical means are needed to generate lithological data cubes and conduct seismic geo- morphologic analyses. Based on a series of tests and studies, this paper presents the concepts of time-equivalent seismic attributes and seismic sedimentary bodies and a ＂four-step approach＂ for the seismic sedimentologic study of conti- nental basins： Step 1, build a time-equivalent stratigraphic framework based on vertical analysis and horizontal corre- lation of lithofacies, electrofacies, seismic facies, and pale- ontological combinations; Step 2, further build a sedimentary facies model based on the analysis of single- well facies with outcrop, coring, and lab test data; Step 3, convert the seismic data into a lithological data cube reflecting different lithologies by means of seismic tech- niques; and Step 4, perform a time-equivalent attribute analysis and convert the planar attribute into a sedimentary facies map under the guidance of the sedimentary facies model. The whole process, highlighting the verification and calibration of geological data, is an iteration and feedback procedure of geoseismic data. The key technologies include the following： （1） a seismic data-lithology conversion technique applicable to complex lithology, which can convert the seismic reflection from interface types to rock layers; and （2） time-equivalent seismic unit analysis and a time- equivalent seismic attribute extraction technique. Finally, this paper demonstrates the validity of the approach with an example from the Qikou Sag in the Bohai Bay Basin and subsequent drilling results.

Unconventional Petroleum Sedimentology:A Key to Understanding Unconventional Hydrocarbon Accumulation

The commercial exploitation of unconventional petroleum resources(e.g.,shale oil/gas and tight oil/gas)has drastically changed the global energy structure within the past two decades.Sweet-spot intervals(areas),the most prolific unconventional hydrocarbon resources,generally consist of extraordinarily high organic matter(EHOM)deposits or closely associated sandstones/carbonate rocks.The formation of sweet-spot intervals(areas)is fundamentally controlled by their depositional and subsequent diagenetic settings,which result from the coupled sedimentation of global or regional geological events,such as tectonic activity,sea level(lake level)fluctuations,climate change,bottom water anoxia,volcanic activity,biotic mass extinction or radiation,and gravity flows during a certain geological period.Black shales with EHOM content and their associated high-quality reservoir rocks deposited by the coupling of major geological events provide not only a prerequisite for massive hydrocarbon generation but also abundant hydrocarbon storage space.The Ordovician-Silurian Wufeng-Longmaxi shale of the Sichuan Basin,Devonian Marcellus shale of the Appalachian Basin,Devonian-Carboniferous Bakken Formation of the Williston Basin,and Triassic Yanchang Formation of the Ordos Basin are four typical unconventional hydrocarbon systems selected as case studies herein.In each case,the formation of sweet-spot intervals for unconventional hydrocarbon resources was controlled by the coupled sedimentation of different global or regional geological events,collectively resulting in a favorable environment for the production,preservation,and accumulation of organic matter,as well as for the generation,migration,accumulation,and exploitation of hydrocarbons.Unconventional petroleum sedimentology,which focuses on coupled sedimentation during dramatic environmental changes driven by major geological events,is key to improve the understanding of the formation and distribution of sweet-spot intervals(areas)in unconventional petroleum systems.

Lithostratigraphy,Sedimentology,and Provenance of the Balfour Formation(Beaufort Group) in the Fort Beaufort-Alice Area,Eastern Cape Province,South Africa

The Balfour Formation has a pronounced lithological variation that is characterized by alternating sandstone- and mudstone-dominated members. The sandstone-dominated Oudeberg and Barberskrans Members are composed of lithofacies that range from intraformationai conglomerates to fine-grained sediments, whereas the mudstone-dominated members （Daggaboersnek, Elandsberg, and Palingkloof） are dominated by the facies Fm and FI. Petrography, geochemistry, and a paleocurrent analysis indicated that the source rock of the Balfour Formation was to south east and the rocks had a transitional/dissected magmatic arc signature. The sandstones-rich members were deposited by seasonal and ephemeral high-energy, low-sinuous streams, and the fine-grained-rich members were formed by ephemeral meandering streams. The paleoclimates have been equated to present temperate climates; they were semiarid becoming arid towards the top of the Balfour Formation. This has been determined by reconstructing the paleolatitude of the Karoo Basin, geochemistry, paleontology, sedimentary structures, and other rock properties, like color.

Sedimentology and Ichnology of Upper Montney Formation Tight Gas Reservoir, Northeastern British Columbia, Western Canada Sedimentary Basin

Several decades of conventional oil and gas production in Western Canada Sedimentary Basin (WCSB) have resulted in maturity of the basin, and attention is shifting to alternative hydrocarbon reservoir system, such as tight gas reservoir of the Montney Formation, which consists of siltstone with subordinate interlaminated very fine-grained sandstone. The Montney Formation resource play is one of Canada’s prime unconventional hydrocarbon reservoir, with reserve estimate in British Columbia (Natural Gas reserve = 271 TCF), Liquefied Natural Gas (LNG = 12,647 million barrels), and oil reserve (29 million barrels). Based on sedimentological and ichnological criteria, five lithofacies associations were identified in the study interval: Lithofacies F-1 (organic rich, wavy to parallel laminated, black colored siltstone);Lithofacies F-2 (very fine-grained sandstone interbedded with siltstone);Lithofacies F-3A (bioturbated silty-sandstone attributed to the Skolithos ichnofacies);Lithofacies F-3B (bioturbated siltstone attributed to Cruziana ichnofacies);Lithofacies F-4 (dolomitic, very fine-grained sandstone);and Lithofacies F-5 (massive siltstone). The depositional environments interpreted for the Montney Formation in the study area are lower shoreface through proximal offshore to distal offshore settings. Rock-Eval data (hydrogen Index and Oxygen Index) shows that Montney sediments contains mostly gas prone Type III/IV with subordinate Type II kerogen, TOC ranges from 0.39 - 3.54 wt% with a rare spike of 10.9 wt% TOC along the Montney/Doig boundary. Vitrinite reflectance data and Tmax show that thermal maturity of the Montney Formation is in the realm of “peak gas” generation window. Despite the economic significance of the Montney unconventional “resource-play”, however, the location and predictability of the best reservoir interval remain conjectural in part because the lithologic variability of the optimum reservoir lithologies has not been adequately characterized. This study presents lithofacies and ichnofacies analyses of the Montney Formation coupled with Rock-Eval geochemistry to interpret the sedimentology, ichnology, and reservoir potential of the Montney Formation tight gas reservoir in Fort St. John study area (T86N, R23W and T74N, R13W), northeastern British Columbia, western Canada.

Some problems on dynamical sedimentology in sea area near Huanghe Seaport

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Thin-interbedded reservoirs prediction based on seismic sedimentology

Interference of thin-interbedded layers in seismic reflections has great negative impact on thin-interbedded reservoirs prediction.To deal with this,two novel methods are proposed that can predict the thin-interbedded reservoirs distribution through strata slices by suppressing the interference of adjacent layer with the help of seismic sedimentology.The plane distribution of single sand bodies in thin-interbedded reservoirs can be clarified.(1)The minimum interference frequency slicing method,uses the amplitude-frequency attribute estimated by wavelet transform to find a constant seismic frequency with the minimum influence on the stratal slice of target layer,and then an optimal slice corresponding the constant frequency mentioned above can be obtained.(2)The superimposed slicing method can calculate multiple interference coefficients of reservoir and adjacent layers of target geological body,and obtain superimposed slice by weighted stacking the multiple stratal slices of neighboring layers and target layer.The two proposed methods were used to predict the distribution of the target oil layers of 6 m thick in three sets of thin-interbedded reservoirs of Triassic Kelamayi Formation in the Fengnan area of Junggar Basin,Northwestern China.A comparison with drilling data and conventional stratal slices shows that the two methods can predict the distribution of single sand bodies in thin-interbedded reservoirs more accurately.

Sedimentology of the Redang Island Coral Reefs Environment

A study on the sedimentology of the Redang Island coral reefs environment was conducted. Sediments were collected on board UNIPERTAMA VII during the pre and post monsoon seasons. Twenty and seven sediments samples were collected using a Smith McIntyre grab on board UNI PERTAMA VII and put in labelled plastic bags then brought back to the laboratory for analysis. The sediments were analyzed for their sedimentological characteristics （mean size, skewness, standard deviation and kurtosis） using dry sieving method. Results showed that the highest mean size value of the sediments during the pre and post monsoons seasons are 2.14 ~ and 2.37 O. respectively and the lowest are -0.40 q~ and -0.10 ~, respectively. Based on the results, sediments can be classified as medium sand （34%）, poorly sorted （67%）, strongly negative skewed （36%） and extremely leptokurtic （56%） during the pre monsoon season, while during the post monsoon season sediments can be classified as medium sand （38%）, poorly sorted （73%）, strongly negative skewed （41%） and very leptokurtic （62%）. Results revealed that the sediments in the whole study area are relatively coarse. No relationship was observed between mean size and other sedimentological characteristics （R2= 0.05 pre-monsoon. R2 =0.0017 post monsoon） with seasons.

Sedimentology, Structure and Depositional Environments of the Subsurface Cretaceous, North Sinai, Egypt Using Well Logs

A complete set of well logs was used to study the sedimentology, structural and depositional environments of the subsurface Cretaceous rocks of northern Sinai, as a promising hydrocarbon province in Egypt. The sedimentological interpretations of well logs show sedimentary sequence of the Early Cretaceous, represented by the Neocomian, Aptian and Albian, which is composed mainly of shales and marls with minor carbonate and sandstone intercalations. Based on the Th/K ratios, the argillaceous sediments are composed of illite, montmorillonite and micas with little amounts of glauconite and chlorite. The environmental interpretations revealed sedimentological environments vary from estuarine to lagoonal and backreef of the Barremian-Aptian rocks, and from continental to estuarine in the Aptian-Albian. By contrast, the Late Cretaceous rocks, represented by the Cenomanian, Turonian, Santonian and Maastrichtian, are mainly composed of carbonates with few shale and marl intercalations. This sequence was accumulated under lagoonal to neritic and bathyal environments. The structural interpretations of well logs show that the Cretaceous section attains a wide range of dip magnitudes and dispersed azimuths all over the study area, which is probably attributed to tectonic and sedimentological processes. The inherited structural complexities indicate possible rejuvenations along old fault planes and rotation of the faulted blocks.

Late Cretaceous-Paleogene Formation of the Bekrit Syncline, Middle Atlas, Morocco: Sedimentology, Geochemistry, Palynology and Paleoenvironments

Globally, the Paleogene period experienced several events marking the Paleocene-Eocene transition which is especially to one of the hottest periods that the Earth has ever known (Paleocene-Eocene Thermal Maximum, PETM), followed by the biological crisis that affected benthic foraminifera. The Bekrit Syncline, subject of this study, shows three Formations of range from the Cretaceous to the Eocene ages (the El Koubbat, Irbzer and Bekrit-Timahdite Formations). Sedimentological, palynological and geochemical analyses of collected samples, in the Bekrit syncline, were studied to determine the paleogeographic and paleoenvironmental conditions of the Middle Atlas. The carbonate rocks were analyzed by microscopic study and geochemical analysis by X-ray Fluorescence (XF) and Inductively Coupled Plasma Spectrometry (ICP). The results obtained highlight the sedimentary events that took place during the Paleogene. Thus, the Maastrichtian is characterized by a closed euxinic marine environment shared by a more open and oxidizing environment. On the other hand, the Paleocene was a restricted marine environment with evaporitic sedimentation, while the Eocene sees the installation of a carbonate platform with a bioclastic Shoal.

Silica oxygen isotope record of core PC10 diatoms from the Bransfield Strait,Antarctica and its application in sedimentology

51 diatom samples taken from the piston core PC10 in the Bransfield Strait of West Antarctica were determined by using silica oxygen isotope analysis.The diatom based results reveal that the 753 cm long core PC10 was deposited in the area in the last 112 5 ka B.P., representing 1 5 oxygen isotopic stages and including one incomplete glacial/interglacial cycle and a postglacial period. The sedimentation rate in interglacial period seems to be a little higher than that in glacial, owing to the more terrigenous supply by ice rafting during the interglacial stages.

Sedimentology and Mineralogy of Surface Formations of the Mossendjo Area (Republic of Congo): Paleoenvironmental and Paleoclimatic Implications

Studies undertaken at several sites in the Congolese basin and in the Chaillu massif are helping to reinterpret the sedimentological formations known as cover formations, which are widely exposed in Central Africa. This article presents the results of granulometric, morphoscopic, mineralogical and chemical analyzes obtained at three sites in the Chaillu. Gronulometric analysis indicates that the sands at the three sites are rated medium to high. The cumulative curves are essentially sigmoidal with regular and spreading slopes. This facies indicates that the deposition took place due to a banal and moderate variation in the competence of the carrier current. The morphoscopy of the quartz grains shows that they are mainly angular and shiny. These data reflect a relatively close source and transport by water. The synthesis of lithological, granulometric, petrographic and geochemical analyzes allowed us to highlight three episodes of deposits in the Mossendjo area: the first is characterized by a channel-type fluvial system marked by deposits from the hospital borehole and from the station;the second, which is alluvial, corresponds to the clogging of the channel. These two alluvial phases are overcome by a third, fluvial, channel-type episode, the end of which is marked by the establishment of the yellow formation. The vertical and lateral organization at the outcrop of this yellow formation has the same characteristics as those described earlier and in the sub-region where it was attributed to the wind-generated cover formation. This study thus highlights the existence of a wet phase during which two fluvial systems of non-contemporary channel types developed which overlap.

MY WORK ON PIONEERING NEW FRONTIERS IN SEDIMENTOLOGY

In 1953, I graduated from a university and completed curricular courses for a post-graduate program in 1956.

Sedimentary Characteristics,Ages,and Environmental Significance of Gravel Deposits and Loess in Shandong,Eastern China:Regional Response to Global Change Since the Last Glacial Period

Investigation of rarely studied gravel layers found in the loess in Shandong Province,eastern China,reveals the fabric characteristics of two gravel layers(G1,G2)and the sedimentary characteristics of loess at the typical and well-preserved Heiyu section(HY),where,to determine the paleoclimatic changes during Marine Isotope Stage 3a.Optically stimulated luminescence dates of the HY formation range from 0.26±0.02 ka to 39.00±2.00 ka.In addition,the ages of G1 and G2 were estimated using the Bayesian model to be 39.60-40.50 and 29.00-29.50 ka.G1 and G2 are mainly composed of fine and medium gravel,both of which were subangular to subrounded limestone,with gravel directions to NE and E.The average flow velocity,average depth,and flood peak flow of G1 are 1.10 m/s,0.49 m,and 37.04 m^(3)/s,respectively,calculated using the flow energy method,whereas those of G2 are 0.98 m/s,0.38 m,and 18.38 m^(3)/s,respectively.Analysis of climate proxy indices show that the sedimentary environment of the gravel and loess in HY might be a regional response to global change.

Application of 9-component S-wave 3D seismic data to study sedimentary facies and reservoirs in a biogasbearing area:A case study on the Pleistocene Qigequan Formation in Taidong area,Sanhu Depression,Qaidam Basin,NW China

To solve the problems in restoring sedimentary facies and predicting reservoirs in loose gas-bearing sediment,based on seismic sedimentologic analysis of the first 9-component S-wave 3D seismic dataset of China,a fourth-order isochronous stratigraphic framework was set up and then sedimentary facies and reservoirs in the Pleistocene Qigequan Formation in Taidong area of Qaidam Basin were studied by seismic geomorphology and seismic lithology.The study method and thought are as following.Firstly,techniques of phase rotation,frequency decomposition and fusion,and stratal slicing were applied to the 9-component S-wave seismic data to restore sedimentary facies of major marker beds based on sedimentary models reflected by satellite images.Then,techniques of seismic attribute extraction,principal component analysis,and random fitting were applied to calculate the reservoir thickness and physical parameters of a key sandbody,and the results are satisfactory and confirmed by blind testing wells.Study results reveal that the dominant sedimentary facies in the Qigequan Formation within the study area are delta front and shallow lake.The RGB fused slices indicate that there are two cycles with three sets of underwater distributary channel systems in one period.Among them,sandstones in the distributary channels of middle-low Qigequan Formation are thick and broad with superior physical properties,which are favorable reservoirs.The reservoir permeability is also affected by diagenesis.Distributary channel sandstone reservoirs extend further to the west of Sebei-1 gas field,which provides a basis to expand exploration to the western peripheral area.

Palaeogene Sandstones of the Manika Plateau in Kolwezi (DR Congo): Sedimentological and Geochemical Characterization, Provenance, Palaeoalteration and Tectonic Context

This work presents a study of the Paleogene sandstones of the Manika plateau in Kolwezi, DR Congo. These sandstones belong to the “Grès polymorphes” group, which together with the overlying “Sables ocre” makes up the Kalahari Supergroup. Sedimentological and geochemical analyses have enabled us to characterize these sandstones and determine their origin, the conditions of their formation and the tectonic context in which they were developed. The results show that the sandstones are quartz arenites with a high level of mineralogical, textural and chemical maturity. They are recycled sandstones, formed in an intracratonic sedimentary basin, in the context of a passive continental margin, after a long fluvial transport of sediments. These sandstones initially come from intense alteration of magmatic rocks with felsic composition, mainly tonalite-trondhjemite-granodiorite (TTG) complexes, in hot, humid palaeoclimatic conditions and oxidizing environments.

Geological Interpretation and Identification of Albian-Aged Petroleum Prospects in Block A, San Pedro Margin (Côte d’Ivoire)

The study aims to identify Albian-age oil prospects in Block A of the San Pedro margin, Côte d’Ivoire, by conducting a detailed geological interpretation. The objective is to confirm the presence of oil reservoirs trapped by favorable geological structures, identifiable through geophysical and seismic methods. The methodological approach is based on a combined analysis of studies and seismic data. Drilling data from well PA, including well logs and end-of-well reports, were used to characterize the lithological formations encountered, particularly those of the Albian. 3D seismic profiles were interpreted to identify structures conducive to hydrocarbon accumulation. Isochrone, isovelocity, and isobath maps were developed to refine the interpretation. Sedimentological analyses revealed five sandy/gritty levels between 2610 m and 3100 m, interspersed with clay, limestone, and siltstone beds. The seismic profiles highlighted two main prospects. These prospects exhibit favorable geological structures, including normal faults and structural traps that provide oil traps.

Seismic Sedimentology and Its Application in Shallow Sea Area,Gentle Slope Belt of Chengning Uplift

Seismic sedimentology is a new frontier inter-discipline subject, and shows good prospect and potentiality in reservoir deposition research with seismic data and geophysics technologies. We made seismic sedimentology research of shallow sea area, gentle slope belt of Chengning （埕宁） uplift, Bohalwan （渤海湾） basin. In shallow sea area with sparse well coverage, it was difficult to characterize the reservoir architecture with the traditional method based on wells. A new method to resolve the above problems is built： （1） information on plane and in section is inter-ealibrated with each other; （2） recognize the isochronic surfaces by frequency decomposition and interpret the depositional character with technology of stratal slicing; （3） make a comprehensive research with the stratal slice interpreta- tion and the dissection of well group. The depositional model of this area is built and used in the architecture analysis of area without wells. The architecture description reveals that the sedimentary character of pan-connection sand bodies in braided rivers is the reason for high water cut of the new horizontal wells. .