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《Bulletin of Mineralogy, Petrology and Geochemistry》
JOPC 2023 Vol.25 Number 5
2023, Vol.25 Num.5
Online: 2023-10-01
The 70th Anniversary Album of China University of Petroleum (Ⅰ)
0
2023 Vol. 25 (5): 0-Ⅰ [
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The 70th Anniversary Album of China University of Petroleum (Ⅰ)
959
ZHU Xiaomin, YE Lei, XIE Shuanghui, YANG Ke, QIN Yi
Sedimentary models and case study of sand-rich shallow-water delta in continental lacustrine basins with low accommodation
The sand-rich shallow delta in continental lacustrine basins with low accommodation is not only the research hotpoint in sedimentology,but also the attractive object in petroleum exploration. By tracking the research of shallow-water delta in low accommodation basins by domestic and foreign scholars,combined with the example of the Paleogene shallow-water delta in Wen'an slope of Baxian sag,the development conditions,sedimentary characteristics,sedimentary mechanism, and sedimentary models of shallow water delta in low accommodation basins are summarized. The development of a large shallow-water delta sedimentary system in low accommodation is controlled by relatively stable tectonic activities,gentle slopes(often less than 1°),periodic climates,open-flow lake basins,frequent fluctuations of the shallow-water environment,and high-speed and high-flux abundant sources. In the low accommodation,the shallow-water delta forms the oxidation color and the reduction color mudstones,which have strong biological disturbances,and sedimentary structures of strong hydrodynamic traction. The strong scouring action forms two kinds of intermittent positive rhythms of‘mud’ and‘mudless’. The river channel continues to extend to the center of the basin,forming deltas of dendritic,bandlike, and bird-foot shapes. The case study shows that the first Member of Shahejie Formation in Wen'an slope of Baxian sag is a low accommodation basin,and a large area of shallow-water delta is developed under the background of sufficient sediment supply. When the shallow-water delta is formed,the ratio of accomodation space and sediment supply(A/S) of the delta plain is the smallest, and the channel is mainly vertically-aggradated,so that the channel is stable and the bifurcation is rarely occurred. In the vertical direction,it is characterized by positive rhythms of‘mudless’,which is characterized by‘branch’ in the plane. In the inner front, the A/S is relatively increased, and the lateral migration of the channel is enhanced,causing the channel being bifurcated. In the vertical direction,positive rhythms of‘mud’ and‘mudless’ coexist,which is characterized by‘mesh’ in the plane. In the outer front, the A/S reaches the maximum; due to the dominance of lake waves,the subaqueous distributary channel is obviously sheeted,which is characterized by isolated sand body vertically and isolated channel or large area sheet sand on the plane.
2023 Vol. 25 (5): 959-975 [
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976
JI Hancheng, CHEN Liang, SUN Yushu, SHI Yanqing, XIANG Pengfei, YANG Zhibo
Ordovician lithofacies palaeogeography characteristics and their controlling effect on the reservoirs of buried hills in Yangshuiwu area,Jizhong Depression
In recent years,significant progress has been made in the exploration of oil and gas reserves in the buried hills of the Yangshuiwu area in the Jizhong Depression. However,the formation of reservoirs in inner buried hills is influenced by many complex factors,resulting in strong reservoir heterogeneity. Among these factors,lithofacies and palaeogeography obviously control the distribution of reservoirs in buried hills,which is helpful in guiding the exploration of oil and gas reserves. Based on studies of cores and thin sections,combined with drilling,logging,and oil and gas production data,it is believed that the Ordovician deposition in the Yangshuiwu area are tidal flat deposits,which consists of three sedimentary subfacies(subtidal zone,intertidal zone,and supratidal zone)and eight sedimentary microfacies. The frequent changes in sea levels caused the rapid variation in vertical sedimentary microfacies and it was characterized as an intertidal zone-subtidal zone. The dominant sedimentary microfacies in the plane direction are subtidal limestone flats,intertidal dolomitic limestone flats,limy dolomite flats,and limestone flats. The porosity of reservoirs in different sedimentary microfacies environments varied significantly. It is illustrated that some sedimentary microfacies,including the dolomite flat,limy dolomite flat,and dolomitic limestone flat in the intertidal zone-supratidal zone,control the distribution of favorable reservoirs.
2023 Vol. 25 (5): 976-991 [
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992
GONG Chenglin, XU Changgui, GUAN Dayong, WANG Qiming, LI Dongwei
Sequence stratigraphic model of Bozhong subbasin during a syn-rift to post-rift transition and its controls on regionally extensive sublacustrine fans
The marked difference in sequence stratigraphy between lacustrine and marine basins requires the establishment of sequence stratigraphic model with function of predicting sublacustrine fans,aiming to a better prediction of areally extensive sublacustrine fans in the Oligocene Dongying Formation of the Bozhong subbasin. Five unconformities and four maximum flooding surfaces are recognized,based on seismic and borehole datasets. They divide the Oligocene Dongying Formation into four third-order sequences,each of which contains an expanding systems tract(retrogradational to aggradational parasequences)and regressive systems tract(progradational parasequences),resulting in an expanding-regressive sequence model. Regionally extensive channelized sublacustrine fans(
i.e.
,channel-lobe complexes)are composed of feeder channels and terminational fans,which consist of lobe axes,lobe fringes,and lobe distal fringes. They are mainly seen to occur in expanding systems tracts immediately above the sequence boundaries,and mainly occur on the gentle slope in front of syndepositional slope-break zones. They represent comprehensive responses to high sediment supply and vigorous sediment-gravity flows under humid climatic conditions,and to syndepositional slope-break zones. Regionally extensive channelized sublacustrine fans,coupled to favorable hydrocarbon-accumulation conditions,can form big subtle traps,which are the most favorable exploration targets of Oligocene Dongying Formation of the Bozhong subbasin. Regionally extensive non-channelized sublacustrine fans(
i.e.
,mass-transport complexes)contain mass-transport deposits and sandy debrites. They mainly seen to occur in regressive systems tracts immediately above the maximum flooding surfaces,and mainly occur on the steep slope in front of syndepositional slope-break zones or the hanging wall of boundary faults. They represent comprehensive responses to low sediment supply and diluted sediment-gravity flows under arid climatic conditions and to the mass-wasting processes induced by high relief gradients and other triggers. Regionally extensive non-channelized sublacustrine fans,coupled to other favorable hydrocarbon-accumulation conditions,can form big subtle traps,which are the favorable exploration targets of Oligocene Dongying Formation of the Bozhong subbasin.
2023 Vol. 25 (5): 992-1010 [
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1011
WANG Junhui, XIAN Benzhong
Revisiting the concept of alluvial river grade
Grade refers to the state of a river where sediment is conveyed without net deposition or net erosion but completely bypassed through the river. The concept of grade is fundamental to geomorphology,geology and stratigraphy,because it represents the critical condition between river aggradation and degradation. According to conventional views,rivers will spontaneously approach the theoretical graded profile and finally reach it,given constant external forcings such as stable base level and steady sediment supply. The conventional notion of grade is valid for local scale of the alluvial system,but not for system scale of the whole alluvial system from a source-to-sink perspective. This is because the conventional notion seldom considers the free boundary condition of the alluvial system(
i.e.
,the upper and lower boundary of the alluvial system can move freely). For example,extension of the alluvial system by delta progradation at the downstream end of the river is inevitably accompanied by alluvial aggradation. This indicates that in moving boundary conditions,the necessary condition for the alluvial river to attain the state of grade at system scale is base level fall rather than base level standstill. Physical and numerical experiments further verified that the alluvial river can reach system-scale grade by three ways. (1)Forced grade,which can be realized in fixed downstream boundary conditions,for example,the downstream end of the alluvial river cannot extend freely by extreme deep basin water depth. In this case,the alluvial river grades to stationary base level. (2)Autogenic grade,which is realized in full moving boundary conditions and the basin floor slope equals that of the alluvial system. In this case,constant rate of base level fall is necessary. (3)Allogenic grade,which is realized in full moving boundary conditions and the basin floor slope is steeper than that of the alluvial system. In this case,slowing down of the base level fall in a particular pattern is necessary. Genetic stratigraphy which highlights the stacking process of strata should fully take the three ways of grade into account,by which the interpretation of stacking of strata will be clearer.
2023 Vol. 25 (5): 1011-1031 [
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1032
LI Wei, YUE Dali, WANG Wurong, GAO Jian, Wu Shenghe, WANG Nansu, LIU Jingyang, ZHANG Jiajia
Depositional models of braided rivers: characteristics of sedimentary evolution and architecture
Braided river deposits are important components of continental sedimentary basins,and the important reservoirs for hydrocarbon,uranium and other mineral resources. In the past three decades,the study of braided rivers has made great progress in the deposit features,evolution and sedimentary architecture. It has high theoretical significance and industrial value to review previous researches and to forecast the development direction. Generally,braided rivers can be divided into relatively stable and classical ones,according to the variety of sedimentary architecture and the evolution rate of landform. There is no significant distinction between geomorphic features of the two kinds of braided rivers. Their formation and evolution processes are basically similar,mainly consisting of four developmental stages: (i)formation of transverse unit bars with limited relief from an initially featureless bed;(ii)channel development around bars and in some cases dissecting transverse unit bars;(iii)formation of relatively simpler compound bars;and(iv)amalgamation of these simpler compound bars into more complex compound bars. Nevertheless,characteristics of their inner architecture show significant differences. The mid-channel bars in relatively-stable braided rivers are usually composed of a set of vertically accretionary sandbodies and falling silt layers. In terms of the classical braided rivers,erosion/incision surfaces and chutes are in a heavy density. There are no clear boundaries between the bars and channels,and so the bars and channels are stacked on each other and forming a pan-connected sandbody. A large number of studies on the sedimentary architecture of braided rivers have been performed,which shows a growing trend of studying the various sedimentary models of braided rivers,and of exploring their major controls,evolution process and formation mechanism by integrating fluvial dynamics and sedimentology.
2023 Vol. 25 (5): 1032-1048 [
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1049
ZHANG Zili, LI Qi, ZHU Xiaomin, TAN Mingxuan, ZHANG Ruifeng, CAO Lanzhu, LI Fengxun, SHAN Shuaiqiang
Sedimentary and seismic responses characteristics of gravity flow sublacustrine fans in lacustrine rift basin: case study on the Paleogene Shahejie Formation in Baxian sag,Bohai Bay Basin
Abundant sublacustrine fan(SLF)gravity flow deposits are developed in various tectonic evolution stages of lacustrine rift basins. Through 3D seismic fine interpretation combined with drilling/logging analysis,the genetic type and distribution of gravity flow fans in lacustrine rift basins are discussed and the depositional models are summarized for the Shahejie Formation of the Baxian Sag,Bohai Bay Basin. The research shows that three genetic types include slumping-,flood-,and storm-induced gravity flow SLF are developed in the Paleogene Shahejie Formation,and can be further divided into five specific types. Based on the sediment source of gravity flow SLF,bottom structures of the sag on the sediment transport path,and plane distribution characteristics between them,it can be divided into three plane combination types: provenance area-fault steep slope zone-SLF,(progradational)delta-slope break zone-SLF,underwater low bulge(beach bar)-SLF. Four depositional models are established including storm gravity flow SLF in the initial rift period,flood SLF in the strong rift period,flood SLF in the stable rift period,and slump SLF in the post rift return period. The study shows that gravity flow SLF deposits of different genetic types are developed in each tectonic evolution stage of lacustrine rift basin. The triggering mechanism of gravity flow SLF is mainly related to delta instability in slope area,paroxysmal flood and lake wave action. The architecture and distribution of gravity flow SLF are controlled by fault activity and bottom structures of the sag,and its size is mainly controlled by triggering mechanism. The gravity flow SLF wrapped by dark mudstone and oil shale formed in deep and semideep lake has good source reservoir cap rock configuration and oil/gas accumulation conditions,which is a sweet spot for oil and gas exploration. Seismic slice analysis based on well data can effectively guide the exploration of thin sandstone sheets.
2023 Vol. 25 (5): 1049-1068 [
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1069
PENG Yang, STEEL J.Ronald, GONG Chenglin, WEI Xiaojie, SHENG Lina
A review on tidal depositional processes and characteristics
Tidal deposits not only play a significant role in reconstruction of palaeogeographic sedimentary environments and palaeoclimate,but also are important reservoirs in oil and gas exploration. Tides,characterized by periodic fluctuations in the water level accompanied by horizontal water flows,arise from the gravitational attractions between the Earth,Moon,and Sun. Tidal currents exhibit distinctive characteristics compared to other currents,as they show systematic changes in flow direction and velocity with intervening slack-water periods within each tidal cycle. The characteristic features of tidal currents have a profound influence on sediment transport and depositional processes. Tidal processes can form a variety of sedimentary structures or features,including tidal rhythmites,flaser-wavy-lenticular bedding,tidal bundles,reactivation surfaces,compound cross bedding,bidirectional cross bedding,double mud drapes,fluid mud deposits,
etc.
These sedimentary structures or features occur in various tidal depositional environments and are controlled by tidal depositional processes,resulting in complex stratigraphic architectures within the depositional systems. In oil and gas exploration,it is crucial to conduct detailed characterization of the rock record and infer associated sedimentary processes in order to enhance predictions regarding the distribution of corresponding sedimentary facies and main sandbodies. This paper provides a comprehensive review of tide generation with controlling factors,tidal depositional processes,sedimentary structures,and their depositional environments. The aim is to improve understanding of recent research progress in tidal depositional systems and offer scientific guidance for oil and gas exploration and development.
2023 Vol. 25 (5): 1069-1089 [
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GE Zhiyuan, XU Hongxiang
Hydraulic and sedimentary responses of turbidity current to structurally-controlled topography
As one of the main sedimentary processes on Earth,turbidity current is responsible for transporting significant amounts of terrigenous sediments,such as mud,sand and organic carbon,into deep water environments. Traditional depositional models of turbidite systems mainly focus on deep-water areas with planar topography. However,slope areas and various tectonic basins hosting turbidite sedimentation often have complex topographic characteristics. Recent studies of turbidite systems based on outcrop observations,numerical and physical simulations as well as in-situ monitoring,have revealed the hydraulic responses of turbidity current to complex topography,namely flow reflection,deflection and hydraulic jump. However,due to the difficulties of acquiring hydraulic parameters of turbidity current,and the topographic complexities of various structures,a gap still remains between our understanding of the hydraulic response of turbidity current to local topographies and large-scale sediment distribution patterns in structurally-controlled basins. Thus,the studies of turbidity current responses to various topographic settings are still largely model driven,with both similarities and variations present among different models. Taking folding topography as an example,at topographic highs,the gravitational potential energy of turbidity current tends to increase,and the turbidity current reflects and accumulates sediments in the upstream direction;while at a topographic low,gravitational potential energy of turbidity current tends to decrease and the turbidity current experiences hydraulic jumps and drop sediments in the downstream direction. In other cases,due to topographic variations,the sedimentary characteristics of turbidites vary in different tectonic settings. In summary,although significant progress has been made on understanding turbidity current responses to structurally-controlled topography,most studies are still qualitative and semi-quantitative in nature with static or oversimplified topography. Future studies,especially case anatomy combined with quantitative methods,such as in-situ monitoring and simulation,are imperative to enhance our understanding of the topic.
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1118
LAI Jin, LI Hongbin, ZHANG Mei, BAI Meimei, ZHAO Yidi, FAN Qixuan, PANG Xiaojiao, WANG Guiwen
Advances in well logging geology in the era of unconventional hydrocarbon resources
Comprehensive and advanced demands are raised for well logging geology in the era of unconventional oil and gas resources,and new and comprehensive theory and technical systems are urgently to be developed in order to solve the problems in the well logging geology for unconventional oil and gas resources. This paper compares the differences of geological characteristics between conventional and unconventional hydrocarbon resources. Furthermore the matched well log series are introduced,and then the main contents in well log evaluation of unconventional hydrocarbon resources are summarized,in addition,the key points and processes of well log evaluation are clarified. The well log evaluation of source rocks,the related theorical and technical systems as well as their application in resource “sweet spot”optimization are summarized. The LithoScanner is used to determine the mineral content and total organic carbon(TOC)content,and the image log is used for picking out sedimentary structure such as lamina,and then the lithofacies can be determined using well logs. The evaluation of bedding parallel fractures in unconventional hydrocarbon resources is an important,and the integration of conventional well logs and image logs can pick out the fractures in a single well. The evaluation and prediction of geological “sweet spots”should pay attention to the well log responses and comprehensive evaluation of lithofacies,bedding parallel fracture and calculation of reservoir parameters. Lastly the importance of in situ stress fields and brittleness index are emphasized in terms of evaluation and prediction of engineering “sweet spots”. The integration of various resolution geological data,well log data and artificial intelligence will promote the continuous innovations on well logging geology.
2023 Vol. 25 (5): 1118-1138 [
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YE Lei, ZHU Xiaomin, XIE Shuanghui, YANG Ke, ZHANG Meizhou, QIN Yi
Restoration methods of sedimentary palaeogeomorphology and applications: a case study of the First Member of Paleogene Shahejie Formation in Raoyang sag
The restoration of sedimentary palaeogeomorphology,an important aspect of source-sink system analysis,is helpful for the reconstruction of the sediment transport path system. It is crucial to study the distribution and evolution of ancient drainage systems, sedimentary systems and reservoir development in sedimentary basins. This paper summarizes the common methods and research progress of palaeogeomorphology restoration. The residual thickness method,impression method,back stripping and filling method,sedimentology method,sequence stratigraphy method,and geophysics method, etc., are the common methods used to restore sedimentary palaeogeomorphology. In the process of palaeogeomorphology restoration,the factors such as tectonic subsidence differences,compaction,stratum erosion and palaeowater depth should be considered to restore the original sedimentary thickness and quantitatively restore the sedimentary palaeogeomorphology. In the future,the study of palaeogeomorphology will gradually develop in the direction of multidisciplinary theory intersection,multi-method comprehensive analysis and multi-data application verification. The Lixian slope in the Raoyang sag was NNE-trending,west-uplifting and east-dipping,and south-gentle and north-steep before the deposition of the First Member of the Paleogene Shahejie Formation. From west to east,it is devided into the uplift area,slope area and trough area. The distribution of sand bodies was obviously controlled by the geomorphology. The slope area was controlled by two slope breaks,and the sandy sediments were more easily developed in the gentle slope zone. The multiple sets of NE-trending normal faults in the trough area led to the semi-graben geomorphology,which limits the development and distribution of sand bodies. It is easier to accumulate sandy sediments in the lower terrain and near the faults. These sand bodies that are continuously distributed in the plane can be regarded as potentially favorable reservoirs.
2023 Vol. 25 (5): 1139-1155 [
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1156
PANG Xiaojiao, WANG Guiwen, KUANG Lichun, ZHAO Fei, LI Hongbin, HAN Zongyan, BAI Tianyu, LAI Jin
Logging evaluation of lithofacies and their assemblage under control of sedimentary environment:a case study of the Qingshankou Formation in Gulong sag,Songliao Basin
The bottom section the Qing 1 and Qing 2 Members of the Qingshankou Formation(Q1~Q2)in the Gulong Sag of Songliao Basin consists of typical high-organic-carbon shales with vast resource potential. The division and characterization of lithofacies play an important role in the evaluation of shale oil sweet spots. It's challenging to recognize lithofacies in a single well. In this study,core photos,thin sections,XRD as well as element data are used to detect the geological characteristic of the reservoir. Besides,LithoScanner and Schlumberger's fullbore formation microimager(FMI)are used to achieve the continuous identification and division of the lithofacies. The result shows that the lithology of the study area mainly consists of four types,including clayey shale,felsic shale,shell limestone,and dolomite. Various-scale laminated structures include millimeter-scale laminations,centimeter-scale bedding,and decimeter-scale structureless laminations. Consequently,ten types of lithofacies were then obtained by coupling lithology and lamina structure. Laminated and bedded clayey shales and laminated and bedded felsic shales are predominant,while massive shell limestone and dolomite mostly occur as thin interlayers,with massive shales occasionally developed. It is clear that the lithofacies assemblages under the control of stratigraphic cycles can be divided into five types. Laminated clayey shale interbedded with layered clayey shale is the most common type in study area. The Qingshankou Formation as a whole was deposited in a freshwater lake basin with a relatively strong reducing environment,with water depth reaching its maximum in the Q7 member and gradually decreasing afterward. There are slight variations in sedimentary environments within different subunits. The predominant lithofacies type varies with water depth,with laminated clayey shales dominating during high-water conditions and bedded felsic shales predominating during low-water conditions. The classification and rapid identification of lithofacies and lithofacies assemblage types provide insight into the shale oil exploration and development and guide for the prediction of shale oil geological sweet spots and engineering sweet spots.
2023 Vol. 25 (5): 1156-1175 [
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1176
CUI Hang, ZHU Shifa, GAO Yishan, DONG Yao
Review of fluid flow types,chronological methods and geological applications in siliciclastic reservoirs
Fluid flow is an important medium controlling material evolution and energy exchange,and is closely related to rock composition,metal mineralization,and hydrocarbon reservoir accumulation in sedimentary basins,and therefore has high significance for exploration and practical application. By summarizing the previous research achievements and combining with the typical case studies,the fluid flow types,chronological methods and geological applications in siliciclastic reservoirs were reviewed. Finally,the existing problems and prospects of diagenetic fluid chronology were summarized. In general,fluid flow of clastic rocks can be classified into several main types: connate water,meteoric water,water from dehydration of minerals,fluid related to thermal evolution of source rocks,and deep hydrothermal fluid. The composition characteristics of different types of fluid flow and the main influencing diagenetic stages vary,but they are generally controlled by a variety of factors including tectonic activity,tectonothermal events,sedimentation,transport systems,and burial history. For diagenetic fluid chronology,the authors summarized the principles,main characteristics,sample requirements,applicable diagenetic fluid types about mineral observation method,fluid inclusion, calcite mineral dating(isotopic dilution method,ESR method,LA-ICP-MS method),authigenic illite
40
K/
40
Ar and
39
Ar/
40
Ar dating,potassium feldspar overgrowth
40
K/
40
Ar and
39
Ar/
40
Ar dating,organic-rich sediment Re-Os dating and other analytical techniques. Moreover,the geological application of diagenetic fluid chronology for determining the sedimentary age of strata,recovering the evolutionary history of diagenesis,determining the precise time of brittle tectonic activity,and determining the timing of hydrocarbon charging was summarized.
2023 Vol. 25 (5): 1176-1198 [
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1199
SUN Haitao, HUANG Xiaojie, YANG Liu, FAN Guozhang, HUANG Xiaojuan, WANG Hongping, ZHONG Dakang, ZHOU Siyu
Spherulite-dendritic crystal characteristics and its genesis of the Lower Cretaceous lacustrine carbonate rocks in Santos Basin,Brazil
The Lower Cretaceous Barra Velha Formation in Santos Basin,Brazil,consists of lacustrine carbonate components with spherical,dendritic and shrub structures,but their origin has not been unified yet. Based on the analysis of drilling core and thin section data,combined with geochemical data and regional tectonic background,this paper analyzes the characteristics of various components,classification, and depositional environments of these carbonate rocks. The research shows that spherical crystals with cross extinction under orthogonal light developed in the Barra Velha Formation,also including fan-shaped crystals,dendriform crystals and dendritic crystals with undulatory extinction. The micritic limestone,spherical crystal and dendritic crystal formed an upper vertical sequence. Trace elements,carbon and oxygen isotopes,and clumped isotopes,suggest a high-salinity and high-temperature fluid condition when the spherulite-dendritic crystals were deposited. In combination with regional tectonic background of the Santos Basin,this paper proposes the spherical crystal-dendritic particles were caused by the hydrothermal fluid connected by the deep large faults,and the saline minerals charge supplied by the frequent seawater transgression. This model better explains the characteristics of the rapid growth of spherulite-dendritic particles,and provides a new theoretical basis for the genesis and distribution of carbonate reservoirs in this basin.
2023 Vol. 25 (5): 1199-1210 [
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