2013 Vol. 31, No. 05
Display Method:
2013, 31(05): 757-772.
Abstract:
Basin-range system, as a new geological unit or entity, has been accepted and studied in geosciences. Based on reviews on the past research advances, three rules are brought forward for basin-range classification, which includes plate tectonic unit (location), tectonic geodynamical regime, and paleogeographical or tectonic-sedimentary attributes of source-sink systems. There are three basin-range types, intracontinent, continent margin (continent-ocean) and intraocean, and further fourteen sub-typies can be presented in the classification scheme. Then a research frame of basin-range system sedimentology is stated and discussed, in which the tectonic-stratigraphic unit and isochronal stratigraphic framework, provenance tracing and source-sink system, and integrated depositional records and paleotectonic-paleoclimatic evolution are three important research basises; and the depositional system (tract) and integrated tectonic-paleogeography is research core; and the basin-range evolution geodynamics is an subject target of basin-range system sedimentology. As a case study of intracontinent basin-range system in eastern North China, the research shows that the most prominent basin-range system occurred in north North China during Jurassic-early Early Cretaceous due to collision and uplift process between Siberia block and North China-Mongolia one. However, a coexistent source-sink system related to the Su-Lu orogen has weak influences on sedimentary paleogeography of the North China. As another case study of continent margin basin-range system in Tarim area, northwest China, the research basicially reveals differential geological records, reflecting passive and arc-related continent margin basin-range systems, respectively coexisted between west South Tianshan and east one. Finally, in order to deepen the basin-range geodynamics, it is especially suggested to pay attention to academic researches of the provenance tracing and source-sink system and the integrated depositional records and paleotectonic-paleoclimatic evolution.
Basin-range system, as a new geological unit or entity, has been accepted and studied in geosciences. Based on reviews on the past research advances, three rules are brought forward for basin-range classification, which includes plate tectonic unit (location), tectonic geodynamical regime, and paleogeographical or tectonic-sedimentary attributes of source-sink systems. There are three basin-range types, intracontinent, continent margin (continent-ocean) and intraocean, and further fourteen sub-typies can be presented in the classification scheme. Then a research frame of basin-range system sedimentology is stated and discussed, in which the tectonic-stratigraphic unit and isochronal stratigraphic framework, provenance tracing and source-sink system, and integrated depositional records and paleotectonic-paleoclimatic evolution are three important research basises; and the depositional system (tract) and integrated tectonic-paleogeography is research core; and the basin-range evolution geodynamics is an subject target of basin-range system sedimentology. As a case study of intracontinent basin-range system in eastern North China, the research shows that the most prominent basin-range system occurred in north North China during Jurassic-early Early Cretaceous due to collision and uplift process between Siberia block and North China-Mongolia one. However, a coexistent source-sink system related to the Su-Lu orogen has weak influences on sedimentary paleogeography of the North China. As another case study of continent margin basin-range system in Tarim area, northwest China, the research basicially reveals differential geological records, reflecting passive and arc-related continent margin basin-range systems, respectively coexisted between west South Tianshan and east one. Finally, in order to deepen the basin-range geodynamics, it is especially suggested to pay attention to academic researches of the provenance tracing and source-sink system and the integrated depositional records and paleotectonic-paleoclimatic evolution.
2013, 31(05): 782-797.
Abstract:
Classifications for various depositional systems have been the general attention of sedimentary geologists. In recent years, sedimentologists have emphasized increasingly on the texture-genetic classification of deltaic depositional system which are the focus and hot issue for sedimentology study and hydrocarbon exploration and development. This paper aims to review the development of the study for deltaic depositional system, points out the problems, demonstrates the specific meaning and scheme of texture-genetic classification for deltaic deposits systematically, and illustrates the advantages of this type of method. Simultaneously, a method of facies mapping which indicates the characteristics of texture-genetic classification for deltas is proposed with the related specific issues in this paper. Based on the principles of high resolution sequence stratigraphy and layer correlation droved by depositional facies, this mapping method emphasizes identifying depositional facies type by litho-facies assemblages and vertical successions. In order to reflect the grain size, distribution and sedimentary genesis of sand-body and represent the reservoir prediction adequately, multi-parameters from lithology, well logs and seismic are nested during mapping.
Classifications for various depositional systems have been the general attention of sedimentary geologists. In recent years, sedimentologists have emphasized increasingly on the texture-genetic classification of deltaic depositional system which are the focus and hot issue for sedimentology study and hydrocarbon exploration and development. This paper aims to review the development of the study for deltaic depositional system, points out the problems, demonstrates the specific meaning and scheme of texture-genetic classification for deltaic deposits systematically, and illustrates the advantages of this type of method. Simultaneously, a method of facies mapping which indicates the characteristics of texture-genetic classification for deltas is proposed with the related specific issues in this paper. Based on the principles of high resolution sequence stratigraphy and layer correlation droved by depositional facies, this mapping method emphasizes identifying depositional facies type by litho-facies assemblages and vertical successions. In order to reflect the grain size, distribution and sedimentary genesis of sand-body and represent the reservoir prediction adequately, multi-parameters from lithology, well logs and seismic are nested during mapping.
2013, 31(05): 807-823.
Abstract:
Microbial carbonates are important oil & gas reservoir rocks, as well as the main rock types in China old strata. Microbial carbonates can be divided into stromatolites, thrombolite，dendrolite and other two types. The reservoir pore systems are closely related to microbialite sedimentary process, and mostly affected by structures and textures of microbialites. Framework and fenestral vugs are the main types of reservoir space. From Middle-Neo Proterozoic to Mesozoic, microbial carbonates reservoirs are discovered globally in various oil & gas fields, so that their petroleum resource potential is great.The researches on rock types,litofacies texture, depositional models and favorable facies zones of microbial reservoir, are well worth deep study in future.
Microbial carbonates are important oil & gas reservoir rocks, as well as the main rock types in China old strata. Microbial carbonates can be divided into stromatolites, thrombolite，dendrolite and other two types. The reservoir pore systems are closely related to microbialite sedimentary process, and mostly affected by structures and textures of microbialites. Framework and fenestral vugs are the main types of reservoir space. From Middle-Neo Proterozoic to Mesozoic, microbial carbonates reservoirs are discovered globally in various oil & gas fields, so that their petroleum resource potential is great.The researches on rock types,litofacies texture, depositional models and favorable facies zones of microbial reservoir, are well worth deep study in future.
2013, 31(05): 824-833.
Abstract:
The tectonic events and climatic changes during the formation and evolution of the Tibetan Plateau could be recorded in the sedimentary succession in adjacent basins. Qaidam Basin, which is located in the northern sector of Tibetan Plateau, preserves a set of thick and continuous Cenozoic sediments. These sediments are the reliable materials for investigation on tectonic evolution of the Tibetan Plateau. Here, we present an integrated study of the Cenozoic sediments from outcrops and drilling well cores. The results indicate that Qaidam Basin has recorded three phases of tectonic evolution. The details can be described as follows. (1) The red coarse detrital sediments of Lulehe Formation which are characterized by low abundances of (Zircon, Tourmaline Rutile) minerals and low heavy mineral stability index. These sediments recorded an event of orogenic movement and tectonic uplift in the whole basin scale, which can be explained as the farfield effects of India-Eurasia collision. Furthermore, after this orogenic event, the region of Altyn and East Kunlun areas was rapidly denudated and flattened, and then became to depositional areas since Middle-Late Eocene. Therefore, it is concluded that Qaidam, Tarim and Hoh Xil Basins may have been parts of a single topographic depression at that time. (2) The Shang Ganchaigou Formation and Xia Youshashan Formation coarse sediments in front of the Altyn Mountains formed in response to the uplift of the Altyn area, whereas the dominated fine-grain sediments with high heavy mineral stability index of other vegions of the Qaiclam Basin can be interpreted as delta-lake facies, suggesting a stage of quiet tectonic background. This quiet setting can be caused by the large-amplitude lateral extrusion along the sinistral strike-slip Altyn Tagh Fault which accommodated the continuing indentation of India into Eurasia. (3) The Shang Youshashan Formation and Shizigou Formation upward-coarsening sediments with low heavy mineral stability index were deposited in high-gradient depositional systems. These sediments recorded the event of crustal shortening and thickening and the intense, rapid uplift of the whole northern Tibetan Plateau. Furthermore, the integrated provenance analysis results indicate the Cenozoic source compositions for the Northern Qaidam Basin did not have significant changes over time.
The tectonic events and climatic changes during the formation and evolution of the Tibetan Plateau could be recorded in the sedimentary succession in adjacent basins. Qaidam Basin, which is located in the northern sector of Tibetan Plateau, preserves a set of thick and continuous Cenozoic sediments. These sediments are the reliable materials for investigation on tectonic evolution of the Tibetan Plateau. Here, we present an integrated study of the Cenozoic sediments from outcrops and drilling well cores. The results indicate that Qaidam Basin has recorded three phases of tectonic evolution. The details can be described as follows. (1) The red coarse detrital sediments of Lulehe Formation which are characterized by low abundances of (Zircon, Tourmaline Rutile) minerals and low heavy mineral stability index. These sediments recorded an event of orogenic movement and tectonic uplift in the whole basin scale, which can be explained as the farfield effects of India-Eurasia collision. Furthermore, after this orogenic event, the region of Altyn and East Kunlun areas was rapidly denudated and flattened, and then became to depositional areas since Middle-Late Eocene. Therefore, it is concluded that Qaidam, Tarim and Hoh Xil Basins may have been parts of a single topographic depression at that time. (2) The Shang Ganchaigou Formation and Xia Youshashan Formation coarse sediments in front of the Altyn Mountains formed in response to the uplift of the Altyn area, whereas the dominated fine-grain sediments with high heavy mineral stability index of other vegions of the Qaiclam Basin can be interpreted as delta-lake facies, suggesting a stage of quiet tectonic background. This quiet setting can be caused by the large-amplitude lateral extrusion along the sinistral strike-slip Altyn Tagh Fault which accommodated the continuing indentation of India into Eurasia. (3) The Shang Youshashan Formation and Shizigou Formation upward-coarsening sediments with low heavy mineral stability index were deposited in high-gradient depositional systems. These sediments recorded the event of crustal shortening and thickening and the intense, rapid uplift of the whole northern Tibetan Plateau. Furthermore, the integrated provenance analysis results indicate the Cenozoic source compositions for the Northern Qaidam Basin did not have significant changes over time.
2013, 31(05): 845-855.
Abstract:
The shallow marine regions consisting of the Bohai, Yellow and East China Seas represent a typical wide continental shelf environment with abundant terrestrial sediment supply. Here, a variety of sedimentary records have been formed during the Holocene period. The Holocene sedimentary systems developed here have unique characteristics in terms of spatial distribution, material composition, Sedimentation rate and the timing of accumulation, which are related to active sediment transport processes induced by tides, shelf circulations and sediment gravity flow. The sedimentary records thus formed tend to be high resolution slices, i.e., each record has a resolution of <102 years and covers a part of the Holocene period. In the field of process-product relationship study, the mid-Holocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, the Holocene mud deposits off the Zhejiang-Fujian coasts and theother mud areas over the region are of importance. These systems may be understood by identifying the material supply (from both sea bed reworking during the sea level rise event and river discharges), transport-accumulation processes, the formation of the sediment sequences and the future evolution of the sedimentary systems, for which numerical modeling becomes increasingly important.
The shallow marine regions consisting of the Bohai, Yellow and East China Seas represent a typical wide continental shelf environment with abundant terrestrial sediment supply. Here, a variety of sedimentary records have been formed during the Holocene period. The Holocene sedimentary systems developed here have unique characteristics in terms of spatial distribution, material composition, Sedimentation rate and the timing of accumulation, which are related to active sediment transport processes induced by tides, shelf circulations and sediment gravity flow. The sedimentary records thus formed tend to be high resolution slices, i.e., each record has a resolution of <102 years and covers a part of the Holocene period. In the field of process-product relationship study, the mid-Holocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, the Holocene mud deposits off the Zhejiang-Fujian coasts and theother mud areas over the region are of importance. These systems may be understood by identifying the material supply (from both sea bed reworking during the sea level rise event and river discharges), transport-accumulation processes, the formation of the sediment sequences and the future evolution of the sedimentary systems, for which numerical modeling becomes increasingly important.
2013, 31(05): 856-866.
Abstract:
The Upper Permian in southwestern China was developed with abundant coal resources, and is divided into three formations including Emeishan Basalt Formation, Longtan Formation (lower and middle memberss of Xuanwei Formation or Wujiaping Formation) and Changxing Formation (upper member of Xuanwei Formation or Wangjiazhai Formation) from bottom to top. The sequence stratigraphy, paleogeography, and coal accumulation of the Late Permian in this region have been studied based on outcrop and borehole sections. According to regional unconformities, sedimentary facies reversal surface, base of incised valley fill sandstones, and distribution of marine limestone beds which reflects variation of the transgressions, we have subdivided the Later Permian into 3 third-order sequences and related lowstand, transgressive, highstand systems tracts. Sequence 1 corresponds to the intervals of early Wujiaping stage, and is distributed mainly in the northeastern Sichuan, eastern Yunnan and western and eastern Guizhou. Sequence 2 corresponds to the middle Wujiaping stage, and Sequence 3 corresponds to late Wujiaping stage though Changxing stage. Both Sequence 2 and Sequence 3 are all distributed in the whole region of southwestern China. The vertical and lateral variation of facies in three sequences reveals a overall transgression pattern of palaeogeography. From bottom (Sequence 1) to top (Sequence 3) and from west to east, there was a variation in facies units from fluvial plain, through tidal-delta combination, to shallow marine. In these three sequences，depositional environments are all deeper in the east, and shallower in the west, with the transgressive pulse of advancing from east to west. The coal-forming environments are swamps developed from fluvial overbank, interdistibutary bay, lagoon-tidal flat environments, while the favorable coal-forming environment is the interdistributary bay of the delta plain. In the three sequences, with the overall westward transgression, beneficial coal-forming environments and coal-accumulating centers migrated to the west, towards the Khangdian Oldland.
The Upper Permian in southwestern China was developed with abundant coal resources, and is divided into three formations including Emeishan Basalt Formation, Longtan Formation (lower and middle memberss of Xuanwei Formation or Wujiaping Formation) and Changxing Formation (upper member of Xuanwei Formation or Wangjiazhai Formation) from bottom to top. The sequence stratigraphy, paleogeography, and coal accumulation of the Late Permian in this region have been studied based on outcrop and borehole sections. According to regional unconformities, sedimentary facies reversal surface, base of incised valley fill sandstones, and distribution of marine limestone beds which reflects variation of the transgressions, we have subdivided the Later Permian into 3 third-order sequences and related lowstand, transgressive, highstand systems tracts. Sequence 1 corresponds to the intervals of early Wujiaping stage, and is distributed mainly in the northeastern Sichuan, eastern Yunnan and western and eastern Guizhou. Sequence 2 corresponds to the middle Wujiaping stage, and Sequence 3 corresponds to late Wujiaping stage though Changxing stage. Both Sequence 2 and Sequence 3 are all distributed in the whole region of southwestern China. The vertical and lateral variation of facies in three sequences reveals a overall transgression pattern of palaeogeography. From bottom (Sequence 1) to top (Sequence 3) and from west to east, there was a variation in facies units from fluvial plain, through tidal-delta combination, to shallow marine. In these three sequences，depositional environments are all deeper in the east, and shallower in the west, with the transgressive pulse of advancing from east to west. The coal-forming environments are swamps developed from fluvial overbank, interdistibutary bay, lagoon-tidal flat environments, while the favorable coal-forming environment is the interdistributary bay of the delta plain. In the three sequences, with the overall westward transgression, beneficial coal-forming environments and coal-accumulating centers migrated to the west, towards the Khangdian Oldland.
2013, 31(05): 889-897.
Abstract:
Under the guide of modern sedimentology and seismic sedimentology, combined with the comprehensive analysis of core data from more than ten wells and geophysical data, Qingshankou Formation is divided into 3 long-term cycles and 6 medium-term cycles in Qijia area, Songliao Basin. The 3 long-term cycles, SQ1, SQ2 and SQ3 correspond to the members，Qing Ⅰ, Qing Ⅱ and Qing Ⅲ, and the time scale of medium-term cycle is about 0.5~1.5 Ma, with thickness ranging from 45 m to 116 m. Shallow-water delta which consists of high-maturity fine-grained sandstone is mainly developed in Qingshankou Formation, and erosion surface reflecting stronge flow action, parallel beddings and long-scale cross beddings are well developed. Distributary channel sandstone is well developed in the shallow-water delta sedimentary system, with single channel thickness about several meters. The accumulative thickness of distributary channels can reach to tens of meters with a large distributing area, extending to the center of lacustrine basin over tens of kilometers. The development of subaqueous distributary channel of shallow-water delta is closely related to the base level (lake level) change. In the early stage of rising semi-cycle and the late stage of falling semi-cycle, the fluviation is significant and the channel sandstone which can extend towards the center of lacustrine basin more than 50 kilometers is well developed, with large accumulative thickness of compound sandbody (17~28 m) and high sandstone to strata ration (78%~88%). In the late stage of rising semi-cycle and the early stage of falling semi-cycle, the lake level rises and the fluviation becomes weak, resulting in the extending distance of distributary channel less than 30 kilometers with small accumulative thickness of compound sandbody (5~12 m) and low sandstone to strata ration (22%~45%). Delta front can be divided into inner front and outer front. The subaqueous distributary channel in inner front has good continuity and extends further, whereas the subaqueous distributary channel in outer front has poor continuity and sheet sand is well developed. Two typical sedimetanry models of shallow-water delta, delat plain well developed in humid climate and detla front well developed in arid climate, are established in Qijia area, Songliao Basin. Stratal slices from seismic sedimentology are applied to display the branchlike sandstone dispersal pattern of shallow-water delta and the characteristics of widely distribution. This study also points out that the detla front channel sandstone which is near to oil source and faults would be the favorable exploration targets.
Under the guide of modern sedimentology and seismic sedimentology, combined with the comprehensive analysis of core data from more than ten wells and geophysical data, Qingshankou Formation is divided into 3 long-term cycles and 6 medium-term cycles in Qijia area, Songliao Basin. The 3 long-term cycles, SQ1, SQ2 and SQ3 correspond to the members，Qing Ⅰ, Qing Ⅱ and Qing Ⅲ, and the time scale of medium-term cycle is about 0.5~1.5 Ma, with thickness ranging from 45 m to 116 m. Shallow-water delta which consists of high-maturity fine-grained sandstone is mainly developed in Qingshankou Formation, and erosion surface reflecting stronge flow action, parallel beddings and long-scale cross beddings are well developed. Distributary channel sandstone is well developed in the shallow-water delta sedimentary system, with single channel thickness about several meters. The accumulative thickness of distributary channels can reach to tens of meters with a large distributing area, extending to the center of lacustrine basin over tens of kilometers. The development of subaqueous distributary channel of shallow-water delta is closely related to the base level (lake level) change. In the early stage of rising semi-cycle and the late stage of falling semi-cycle, the fluviation is significant and the channel sandstone which can extend towards the center of lacustrine basin more than 50 kilometers is well developed, with large accumulative thickness of compound sandbody (17~28 m) and high sandstone to strata ration (78%~88%). In the late stage of rising semi-cycle and the early stage of falling semi-cycle, the lake level rises and the fluviation becomes weak, resulting in the extending distance of distributary channel less than 30 kilometers with small accumulative thickness of compound sandbody (5~12 m) and low sandstone to strata ration (22%~45%). Delta front can be divided into inner front and outer front. The subaqueous distributary channel in inner front has good continuity and extends further, whereas the subaqueous distributary channel in outer front has poor continuity and sheet sand is well developed. Two typical sedimetanry models of shallow-water delta, delat plain well developed in humid climate and detla front well developed in arid climate, are established in Qijia area, Songliao Basin. Stratal slices from seismic sedimentology are applied to display the branchlike sandstone dispersal pattern of shallow-water delta and the characteristics of widely distribution. This study also points out that the detla front channel sandstone which is near to oil source and faults would be the favorable exploration targets.
2013, 31(05): 907-919.
Abstract:
The Tarim Basin contains extensive carbonate platform deposits of the Ordovician System, with more than three thousand kilometers of rimmed carbonate platform margins. Comprehensive analysis of seismic, borehole and outcrop data reveals that the Ordovician carbonate system in the basin can be divided into four composite sequences defined by major unconformities. Ten sequence consists of a regional depositional cycle from transgression with an onlapping transgressive systems tract (TST) to regression with a prograding highstand systems tract (HST), and can be further subdivided into eight third-order sequences based on subordinate discontinuous boundaries at the carbonate platform marginal zones. Constrained by the marginal slope of the early-rifted Manjiaer aulacogen, the carbonate platform margins of the Lower and Middle Ordovician that prograded eastward in an arcuate belt extending generally north-south across the northern part of the basin. The development of the Tazhong uplift resulted in an extensive unconformity between the Middle and the Upper Ordovician in the south-central basin, and subsequently constrained the formation of an isolate carbonate platform, with their margins controlled by marginal thrust-fault belts of the paleo-uplift during the Late Ordovician. In the northern basin, the Late Ordovician carbonate platform margin developed around the marginal slope of the Tabei paleouplift. The transgressive regressive cycles of the carbonate system are comparable and seem to have occurred simultaneously across the entire basin, suggesting that the cyclic sequence architecture was fundamentally controlled by eustatic fluctuations. The reef shoal facies complexes that developed along the platform margins, with paleokarst development at unconformities, constitute the major reservoir of large petroleum reserves in the basin.
The Tarim Basin contains extensive carbonate platform deposits of the Ordovician System, with more than three thousand kilometers of rimmed carbonate platform margins. Comprehensive analysis of seismic, borehole and outcrop data reveals that the Ordovician carbonate system in the basin can be divided into four composite sequences defined by major unconformities. Ten sequence consists of a regional depositional cycle from transgression with an onlapping transgressive systems tract (TST) to regression with a prograding highstand systems tract (HST), and can be further subdivided into eight third-order sequences based on subordinate discontinuous boundaries at the carbonate platform marginal zones. Constrained by the marginal slope of the early-rifted Manjiaer aulacogen, the carbonate platform margins of the Lower and Middle Ordovician that prograded eastward in an arcuate belt extending generally north-south across the northern part of the basin. The development of the Tazhong uplift resulted in an extensive unconformity between the Middle and the Upper Ordovician in the south-central basin, and subsequently constrained the formation of an isolate carbonate platform, with their margins controlled by marginal thrust-fault belts of the paleo-uplift during the Late Ordovician. In the northern basin, the Late Ordovician carbonate platform margin developed around the marginal slope of the Tabei paleouplift. The transgressive regressive cycles of the carbonate system are comparable and seem to have occurred simultaneously across the entire basin, suggesting that the cyclic sequence architecture was fundamentally controlled by eustatic fluctuations. The reef shoal facies complexes that developed along the platform margins, with paleokarst development at unconformities, constitute the major reservoir of large petroleum reserves in the basin.
2013, 31(05): 928-938.
Abstract:
Deep-water deposit of Ch7 member, in Trssic Yanchang Formation, is widely distributed in the center of Ordos basin. Study on particle size, sedimentary textures and structures and organic geochemistry shows that sedimentary rock in deep water can be summed up as four types, i.e. oil-shale lithofacies, dark-mudstone lithofacies, siltstone-mudstone lithofacies and sandstone lithofacies. The oil-shale lithofacies is characterized by high organic carbon content and good type of organic matter, with higher value of resistivity and natural gamma, clear negative anomalies of SP curves, and the curves of acoustic interval transit times varies sharply; dark-mudstone lithofacies characterized by being rich with organic carbon, mid-low value of resistivity, midhigh value of natural gamma and high value of density and acoustic interval transit times; siltstone-mudstone lithofacies by mid value of resistivity, low natural gamma, high density and sharply varied curves of acoustic interval transit time, with mud content ranges about 20~70%；and sandstone lithofacies by low value of resistivity and acoustic interval transit time, and natural gamma, with mud content lower than 20%. The shape of different lithofacies are defined and configuration difference of lithofacies at deepwater slope and lake bottom plain is illustrated in detail. It is pointed out that deep-water rock has great significance for unconventional oil and gas resources. For example oil shale lithofacies and dark-mudstone lithofacies, as the main source rock of Mesozoic, contribute greatly for the formation of large scale reserviors in Ordos basin; the deepwater sandstone lithofacies provides extensive spaces for large-scale tight oil; and deepwater siltstone-mudstone and oil shale lithofacies is the important accommodation for shale oil and has the potential of economic value.
Deep-water deposit of Ch7 member, in Trssic Yanchang Formation, is widely distributed in the center of Ordos basin. Study on particle size, sedimentary textures and structures and organic geochemistry shows that sedimentary rock in deep water can be summed up as four types, i.e. oil-shale lithofacies, dark-mudstone lithofacies, siltstone-mudstone lithofacies and sandstone lithofacies. The oil-shale lithofacies is characterized by high organic carbon content and good type of organic matter, with higher value of resistivity and natural gamma, clear negative anomalies of SP curves, and the curves of acoustic interval transit times varies sharply; dark-mudstone lithofacies characterized by being rich with organic carbon, mid-low value of resistivity, midhigh value of natural gamma and high value of density and acoustic interval transit times; siltstone-mudstone lithofacies by mid value of resistivity, low natural gamma, high density and sharply varied curves of acoustic interval transit time, with mud content ranges about 20~70%；and sandstone lithofacies by low value of resistivity and acoustic interval transit time, and natural gamma, with mud content lower than 20%. The shape of different lithofacies are defined and configuration difference of lithofacies at deepwater slope and lake bottom plain is illustrated in detail. It is pointed out that deep-water rock has great significance for unconventional oil and gas resources. For example oil shale lithofacies and dark-mudstone lithofacies, as the main source rock of Mesozoic, contribute greatly for the formation of large scale reserviors in Ordos basin; the deepwater sandstone lithofacies provides extensive spaces for large-scale tight oil; and deepwater siltstone-mudstone and oil shale lithofacies is the important accommodation for shale oil and has the potential of economic value.
2013, 31(05): 751-756.
Abstract:
Master Ye Lianjun is the first Editor-in-Chief of the journal of “Acta Sedimentologica Sinica”. He set up not only the journal, but also sedimentology of China. The main chain of the sedimentary ore forming theory includes three links: sources of ore-forming materials, ore-forming processes, and mine forecast. “Theory of imbibitions of terrestrial weathering products” emphasized the sources of ore-forming materials; “theory of physical enrichment for genesis of industrial phosphorite deposits”, “theory of composite-process and poly-episodic aspect of sedimentary mineral deposits”, and “theory of biomineralization” emphasized the ore-forming processes; and “historic-geological significance of sedimentary ore genetic epochs” emphasized the way of mine forecast. The foundation for Master Ye Lianjun to achieve his innovation is state-in-art observation and deeply thought. We should learn from him doing our best to observe carefully, good at in-time summary, dare to challenge old idea, and think ahead.
Master Ye Lianjun is the first Editor-in-Chief of the journal of “Acta Sedimentologica Sinica”. He set up not only the journal, but also sedimentology of China. The main chain of the sedimentary ore forming theory includes three links: sources of ore-forming materials, ore-forming processes, and mine forecast. “Theory of imbibitions of terrestrial weathering products” emphasized the sources of ore-forming materials; “theory of physical enrichment for genesis of industrial phosphorite deposits”, “theory of composite-process and poly-episodic aspect of sedimentary mineral deposits”, and “theory of biomineralization” emphasized the ore-forming processes; and “historic-geological significance of sedimentary ore genetic epochs” emphasized the way of mine forecast. The foundation for Master Ye Lianjun to achieve his innovation is state-in-art observation and deeply thought. We should learn from him doing our best to observe carefully, good at in-time summary, dare to challenge old idea, and think ahead.
2013, 31(05): 773-781.
Abstract:
The Lower Permian Lucaogou Formation in Santanghu area, Xinjiang, NW China contains new types of sedimentary deposits mantle-originated hydroclastites and hydrothermal exhalites, which are characterized by a subsurface source. The rocks occur as mm-laminae with a great total thickness and have a variety of composition, texture, and structures. They contain abundant mantle-originated hydrothermal minerals and microscopic hydroclastic magmatic fragments, and can be classified into five types on the basis of sediment source and grain composition, sedimentary texture and structure, and interpreted forming mechanisms: 1) fall-out phreatomagmatic hydroclastite, formed by fall out of fine magmatic ash generated by hydroclastic explosion; 2) surge phreatomagmatic hydroclastite, formed by base surge of coarse magmatic fragments generated by hydroclastic explosion; 3) hydrothermal exhalite, formed by chemical precipitation from hydrothermal exhalative fluids and containing typical minerals associated with "black and white smokers"; 4) peperite composed of admixtures of hydroclastic, hydrothermal, and normal lacustrine chemical sediments; and 5) microbialite composed of biogenic minerals produced by thermophilic and toxin-loving microbes. All these rocks were deposited in a starved lake in an intracontinental rift basin. The grain composition suggests that hydroclastic and hydrothermal processes were originated from a great depth and related to mantle-derived magmas. The interlamination of these rocks suggests that hydroclastic, hydrothermal, and normal lacustrine processes were alternating and episodic.
The Lower Permian Lucaogou Formation in Santanghu area, Xinjiang, NW China contains new types of sedimentary deposits mantle-originated hydroclastites and hydrothermal exhalites, which are characterized by a subsurface source. The rocks occur as mm-laminae with a great total thickness and have a variety of composition, texture, and structures. They contain abundant mantle-originated hydrothermal minerals and microscopic hydroclastic magmatic fragments, and can be classified into five types on the basis of sediment source and grain composition, sedimentary texture and structure, and interpreted forming mechanisms: 1) fall-out phreatomagmatic hydroclastite, formed by fall out of fine magmatic ash generated by hydroclastic explosion; 2) surge phreatomagmatic hydroclastite, formed by base surge of coarse magmatic fragments generated by hydroclastic explosion; 3) hydrothermal exhalite, formed by chemical precipitation from hydrothermal exhalative fluids and containing typical minerals associated with "black and white smokers"; 4) peperite composed of admixtures of hydroclastic, hydrothermal, and normal lacustrine chemical sediments; and 5) microbialite composed of biogenic minerals produced by thermophilic and toxin-loving microbes. All these rocks were deposited in a starved lake in an intracontinental rift basin. The grain composition suggests that hydroclastic and hydrothermal processes were originated from a great depth and related to mantle-derived magmas. The interlamination of these rocks suggests that hydroclastic, hydrothermal, and normal lacustrine processes were alternating and episodic.
2013, 31(05): 798-806.
Abstract:
The method of sequence stratigraphy marks a new revolution of sedimentary geology. It uses multiple subjects to form a sedimentary model to interpret evolution and stratigraphic structure of sedimentary basin for oil and gas exploration based on analysis of autocycle and allocycle. Sequence stratigraphy is useful to decrease the risks of reservoir prediction. The main types of sedimentary sandbodies of deep-water lake basin are progressive sandstones from delta front to slope, gravity flow sandstones including turbidite channel, basin floor fan and debris flow sandstones. The distribution of non-channellized turbidite sandstones has closely relation with basin slope and systems tract evolution. There are developed sliding turbidite from delta front to slope in high-gradient areas, and developed basin floor fan turbidite in other areas during early transgressive and late regressive period. The rebuilding of sequence and systems tracts and analysis of sedimentary mechanism would increase predicting ability of reservoirs and decrease risks of reservoir prediction. These turbidite sandstones have low porosity and low permeability, with very fine grains on thin section observation. There are median sorting and poor rounding in grains. The clastic contents are quartz, quartz sandstone, and minor feldspar and calcite. The cements are mainly calcite. They belong to low-porosity and lowpermeability reservoirs which could be as exploration targets of fracture reservoirs and unconventional resources.
The method of sequence stratigraphy marks a new revolution of sedimentary geology. It uses multiple subjects to form a sedimentary model to interpret evolution and stratigraphic structure of sedimentary basin for oil and gas exploration based on analysis of autocycle and allocycle. Sequence stratigraphy is useful to decrease the risks of reservoir prediction. The main types of sedimentary sandbodies of deep-water lake basin are progressive sandstones from delta front to slope, gravity flow sandstones including turbidite channel, basin floor fan and debris flow sandstones. The distribution of non-channellized turbidite sandstones has closely relation with basin slope and systems tract evolution. There are developed sliding turbidite from delta front to slope in high-gradient areas, and developed basin floor fan turbidite in other areas during early transgressive and late regressive period. The rebuilding of sequence and systems tracts and analysis of sedimentary mechanism would increase predicting ability of reservoirs and decrease risks of reservoir prediction. These turbidite sandstones have low porosity and low permeability, with very fine grains on thin section observation. There are median sorting and poor rounding in grains. The clastic contents are quartz, quartz sandstone, and minor feldspar and calcite. The cements are mainly calcite. They belong to low-porosity and lowpermeability reservoirs which could be as exploration targets of fracture reservoirs and unconventional resources.
2013, 31(05): 834-844.
Abstract:
The northeastern Jiangxi region lies in the southeastern part of the Jiangnan sub-basin in the Nanhua rift systems. Recent results of research from the regional geological survey have disclosed that the Nanhua strata of the Neoproterozoic in the Jiangnan sub-basin consist of the rift wedge-shaped sedimentary strata which are overlapped upon the metamorphic basement. More precisely, the continental volcanic rocks and volcaniclastic rocks from the Taoyuan Formation occur in the lowermost horizons of the wedge-shaped strata, representing the onset of a new round sedimentary cycle in the Jiangnan sub-basin of the Nanhua rift systems. The rhyolite samples collected from the Taoyuan Formation give a SHRIMP U-Pb age of 8 039 Ma for the crystalline zircons, an initial age of the Neoproterozoic basin in northeastern Jiangxi. The sedimentary facies analysis indicates that the sedimentation of the wedgeshaped strata in the Jiangnan sub-basin is mainly composed of: (1) continental volcanic rocks association; (2) alluvial-diluvial facies and fluvial-lacustrine facies association; (3) littoral-neritic facies to the bathyal facies association, and (4) tillite facies association. Comparing with the other sub-basins in southeastern margin of Yangtze Block, the sedimentation of the Jiangnan sub-basin is predominated by continental facies other than marine facies, but both of them bears a striking resemblance in sedimentary succession, all went through a onlap process from continental facies to marine facies, representing the sedimentary evolution of the typical rift basin following the breakup of the South China palaeocontinent during the Nanhuan of the Neoproterozoic.
The northeastern Jiangxi region lies in the southeastern part of the Jiangnan sub-basin in the Nanhua rift systems. Recent results of research from the regional geological survey have disclosed that the Nanhua strata of the Neoproterozoic in the Jiangnan sub-basin consist of the rift wedge-shaped sedimentary strata which are overlapped upon the metamorphic basement. More precisely, the continental volcanic rocks and volcaniclastic rocks from the Taoyuan Formation occur in the lowermost horizons of the wedge-shaped strata, representing the onset of a new round sedimentary cycle in the Jiangnan sub-basin of the Nanhua rift systems. The rhyolite samples collected from the Taoyuan Formation give a SHRIMP U-Pb age of 8 039 Ma for the crystalline zircons, an initial age of the Neoproterozoic basin in northeastern Jiangxi. The sedimentary facies analysis indicates that the sedimentation of the wedgeshaped strata in the Jiangnan sub-basin is mainly composed of: (1) continental volcanic rocks association; (2) alluvial-diluvial facies and fluvial-lacustrine facies association; (3) littoral-neritic facies to the bathyal facies association, and (4) tillite facies association. Comparing with the other sub-basins in southeastern margin of Yangtze Block, the sedimentation of the Jiangnan sub-basin is predominated by continental facies other than marine facies, but both of them bears a striking resemblance in sedimentary succession, all went through a onlap process from continental facies to marine facies, representing the sedimentary evolution of the typical rift basin following the breakup of the South China palaeocontinent during the Nanhuan of the Neoproterozoic.
2013, 31(05): 878-888.
Abstract:
A study of reservoir modeling is present with 3D seismic and logging data by applying of multi-point statistical modeling, and by the combination of seismic and logging data. The results indicate that the combination of seismic and logging data can reduce uncertainty of reservoir modeling. The study includes the quality control of seismic data, the combination of soft and hard data, the application of multi-point modeling, the making of training image, and the selection of curves for sand body probability making. At last, the result obtained by the combination of 3D seismic and logging data makes a contrast with the result by only logging data. Seismic shale content cross sections are used as a criterion for these analysis and contrast, which include 3 levels: ① contrast of distributions of sand and shale for upper part and low part of the reservoir, ② contrast of distributions of sand and shale for different wells and their neighboring areas, ③ contrast of among well logging sand prediction cross sections, and both well logging and seismic sand prediction cross sections, produced by different random seeds. As a result of this paper, multi-point statistical modeling constrained by 3D seismic data obviously increases reasonableness of sand prediction inter-wells, and reduces uncertainty of reservoir modeling.
A study of reservoir modeling is present with 3D seismic and logging data by applying of multi-point statistical modeling, and by the combination of seismic and logging data. The results indicate that the combination of seismic and logging data can reduce uncertainty of reservoir modeling. The study includes the quality control of seismic data, the combination of soft and hard data, the application of multi-point modeling, the making of training image, and the selection of curves for sand body probability making. At last, the result obtained by the combination of 3D seismic and logging data makes a contrast with the result by only logging data. Seismic shale content cross sections are used as a criterion for these analysis and contrast, which include 3 levels: ① contrast of distributions of sand and shale for upper part and low part of the reservoir, ② contrast of distributions of sand and shale for different wells and their neighboring areas, ③ contrast of among well logging sand prediction cross sections, and both well logging and seismic sand prediction cross sections, produced by different random seeds. As a result of this paper, multi-point statistical modeling constrained by 3D seismic data obviously increases reasonableness of sand prediction inter-wells, and reduces uncertainty of reservoir modeling.
2013, 31(05): 898-906.
Abstract:
The types and lithology characters of Permian dolomitic clastic rocks in northwestern Junggar Basin are investigated by means of petrologic analysis, Xray indentification, carbon and oxygen isotope geochemistry and element geochemistry analysis, also analyzed Dolomization mechanism, Established dolomitization model. dolomitic clastic rocks in study areas include dolomitic mudstone, dolomitic siltstone, dolomitic tuffaceous siltstone, dolomitic tuffaceous shale,ect. And dolostones which are formed through dolomitization by replacing lacutrine plaster and siliceous (tuffaceous) components mainly consist of powderfine dolomites with automorphic or hypidiomorphic crystals, while residual calcite and late filled calcite cement commonly exist. The ratio of V/ Ni(1.2～4.8)content of Sr(95.5～782.2 μg/g)Mg/Ca(0.5～3.0),the degree of order(0.36~0.98)δ18OPDB(14.8‰～3.2‰)and δ13CPDB(1‰～5.2‰)all have larger variation range. The dolomitic rocks in this area mainly formed in a relatively weak hydrodynamic conditions, deep, peaceful, salt and lowsalt semiclosed terrestrial bay environment, have a characteristic of several stages and various causes. During Permian periods, in the researching zone the tectonics is complex, fault development, subtropical hot climate and frequent volcanic which provide favourable source of Mg2+ and permeability channel for the rich magnesium fluid fast flow. Comprehensive research show that these dolomitic rocks have three kinds of genetic types: Penecontemporaneous dolomitization, buried dolomitization, hydrothermal dolomitization.
The types and lithology characters of Permian dolomitic clastic rocks in northwestern Junggar Basin are investigated by means of petrologic analysis, Xray indentification, carbon and oxygen isotope geochemistry and element geochemistry analysis, also analyzed Dolomization mechanism, Established dolomitization model. dolomitic clastic rocks in study areas include dolomitic mudstone, dolomitic siltstone, dolomitic tuffaceous siltstone, dolomitic tuffaceous shale,ect. And dolostones which are formed through dolomitization by replacing lacutrine plaster and siliceous (tuffaceous) components mainly consist of powderfine dolomites with automorphic or hypidiomorphic crystals, while residual calcite and late filled calcite cement commonly exist. The ratio of V/ Ni(1.2～4.8)content of Sr(95.5～782.2 μg/g)Mg/Ca(0.5～3.0),the degree of order(0.36~0.98)δ18OPDB(14.8‰～3.2‰)and δ13CPDB(1‰～5.2‰)all have larger variation range. The dolomitic rocks in this area mainly formed in a relatively weak hydrodynamic conditions, deep, peaceful, salt and lowsalt semiclosed terrestrial bay environment, have a characteristic of several stages and various causes. During Permian periods, in the researching zone the tectonics is complex, fault development, subtropical hot climate and frequent volcanic which provide favourable source of Mg2+ and permeability channel for the rich magnesium fluid fast flow. Comprehensive research show that these dolomitic rocks have three kinds of genetic types: Penecontemporaneous dolomitization, buried dolomitization, hydrothermal dolomitization.
2013, 31(05): 920-927.
Abstract:
In the Upper Cretaceous, Nenjiang Formation have been formed a progradation-retrogradation type stratigraphy in the second lacustrine flooding Period, according to the tectonic unconformity, sedimentary unconformity, lake flooding surface and regressive surface and so on, which totals eleven sequence boundaries, the Nenjiang Formation was divided into one secondorder sequence, two third-order sequences and ten fouth-order sequences, restored the sedimentary filling evolution histories in the fourth-order sequence stratigraphic framework. During the first member of the Nenjiang Formation deposition, the SB07 the maximum flooding surface was formed on the top of strata, which resulted in the retrogradation sequence has the characteristic of low-angle retrogradation delta sediment with the lake level constantly rise, meanwhile the large scale turbidite channels and turbidite fans are observed in the delta front. By uplifting the basin during the second-order and fifth-order member of Nenjiang Formation deposition, developed a series east to west into the area of high-angel delta is characterized by the deposition of retrograding sequences, because of the slumping in the delta front slopes, the forepart of lacustrine zone discovered a series of slump turbidite fan bodies. Retrograding sequences usually incurred the direction 90o change of the deposition material source, its the mainly difference compare with progradation sequence, whereas the structure of progradation sequence and sedimentary characteristics indicated that the oil shale (at the bottom of the Nenjing second member) is formed in the process of shrinking lake, not in maximum lake flooding through to the sea invasion.
In the Upper Cretaceous, Nenjiang Formation have been formed a progradation-retrogradation type stratigraphy in the second lacustrine flooding Period, according to the tectonic unconformity, sedimentary unconformity, lake flooding surface and regressive surface and so on, which totals eleven sequence boundaries, the Nenjiang Formation was divided into one secondorder sequence, two third-order sequences and ten fouth-order sequences, restored the sedimentary filling evolution histories in the fourth-order sequence stratigraphic framework. During the first member of the Nenjiang Formation deposition, the SB07 the maximum flooding surface was formed on the top of strata, which resulted in the retrogradation sequence has the characteristic of low-angle retrogradation delta sediment with the lake level constantly rise, meanwhile the large scale turbidite channels and turbidite fans are observed in the delta front. By uplifting the basin during the second-order and fifth-order member of Nenjiang Formation deposition, developed a series east to west into the area of high-angel delta is characterized by the deposition of retrograding sequences, because of the slumping in the delta front slopes, the forepart of lacustrine zone discovered a series of slump turbidite fan bodies. Retrograding sequences usually incurred the direction 90o change of the deposition material source, its the mainly difference compare with progradation sequence, whereas the structure of progradation sequence and sedimentary characteristics indicated that the oil shale (at the bottom of the Nenjing second member) is formed in the process of shrinking lake, not in maximum lake flooding through to the sea invasion.
2013, 31(05): 867-877.
Abstract:
Digital outcrop modelling is a method of imaging outcrop as a series of polygons viewable with 3D visualization technology, on to which digital geological information (e.g., outcrop sections) may be stacked. The technique achieves a digital outcrop model (DOM) from which comprehensive measurements and interpretation may be undertaken. A DOM is able to incorporate 3D data from ground-based laser scanner, remote-sensing imagery, high precision grayscale photographs, ground-penetrating radar and other all geo-digital sources. The use of DOM in combination with traditional sedimentological field data helped improve the accuracy and efficiency of meandering delta plain sand body characterisation and consequently also improved the qualitative and quantitative assessment of data for the purpose of reservoir modelling. We used the DOM to measure and precisely describe the distribution characteristics of channel sands of the Quliu delta plain in the Ordos Basin. In order to provide the basis for a comparative reservoir model, the 3D distribution model can be quality controlled through the measurement of the characteristics of channel sand reservoir in varied sites and predicting the morphological characteristics of ground sand in the outcrop area by groundpenetrating radar. The DOM shows: (1) Tanjiahe section channel forms; these sandstone bodies form elongate lenses with a flat upper surface, a width of 192 m and a maximum thickness of about 14 m of the most biggest channel body sand. The boundary between channel and surrounding rocks is clear.Four stages of deposition are identified within the sandstone bodies indicating a complex positive rhythm. (2) Branch channels to the meandering river are isolated on the delta plain. These sandstone bodies show lateral migration and vertical stacking which is accurately described in the 3D DOM. The horizontal width of the multi-period superimposed channels of the sandstone bodies are 192.4 m, 32.54 m, 41.83 m and 79.97 m, thickness are 14 m, 4.52 m, 3.85 m and 5.66 m giving a width to thickness ratio of 12:1. (3) Through analysis of typical reservoir performance of the sand bodies encountered, reservoir properties can be assigned to different parts of the DOM. The delta plain branch channel sandstones are classified as poor quality. In the main channel sands the highest quality reservoir would be found in the lower part of the channel which then decreases upward. The lowest quality reservoir is found in the two channel wings. Reservoir quality is best at the thickest part of the sandstone body in every period channel where it achieves a porosity of 8% and a permeability of 0.13 mD. Building of a DOM integrated with geo-data is an effective method to quantitatively analyse outcrop analogues including the 3D spatial characteristics of potential reservoir elements which can be acquired accurately. The DOM can also provide the basis of comparative studies on reservoirs in the exploitation of oil and gas.
Digital outcrop modelling is a method of imaging outcrop as a series of polygons viewable with 3D visualization technology, on to which digital geological information (e.g., outcrop sections) may be stacked. The technique achieves a digital outcrop model (DOM) from which comprehensive measurements and interpretation may be undertaken. A DOM is able to incorporate 3D data from ground-based laser scanner, remote-sensing imagery, high precision grayscale photographs, ground-penetrating radar and other all geo-digital sources. The use of DOM in combination with traditional sedimentological field data helped improve the accuracy and efficiency of meandering delta plain sand body characterisation and consequently also improved the qualitative and quantitative assessment of data for the purpose of reservoir modelling. We used the DOM to measure and precisely describe the distribution characteristics of channel sands of the Quliu delta plain in the Ordos Basin. In order to provide the basis for a comparative reservoir model, the 3D distribution model can be quality controlled through the measurement of the characteristics of channel sand reservoir in varied sites and predicting the morphological characteristics of ground sand in the outcrop area by groundpenetrating radar. The DOM shows: (1) Tanjiahe section channel forms; these sandstone bodies form elongate lenses with a flat upper surface, a width of 192 m and a maximum thickness of about 14 m of the most biggest channel body sand. The boundary between channel and surrounding rocks is clear.Four stages of deposition are identified within the sandstone bodies indicating a complex positive rhythm. (2) Branch channels to the meandering river are isolated on the delta plain. These sandstone bodies show lateral migration and vertical stacking which is accurately described in the 3D DOM. The horizontal width of the multi-period superimposed channels of the sandstone bodies are 192.4 m, 32.54 m, 41.83 m and 79.97 m, thickness are 14 m, 4.52 m, 3.85 m and 5.66 m giving a width to thickness ratio of 12:1. (3) Through analysis of typical reservoir performance of the sand bodies encountered, reservoir properties can be assigned to different parts of the DOM. The delta plain branch channel sandstones are classified as poor quality. In the main channel sands the highest quality reservoir would be found in the lower part of the channel which then decreases upward. The lowest quality reservoir is found in the two channel wings. Reservoir quality is best at the thickest part of the sandstone body in every period channel where it achieves a porosity of 8% and a permeability of 0.13 mD. Building of a DOM integrated with geo-data is an effective method to quantitatively analyse outcrop analogues including the 3D spatial characteristics of potential reservoir elements which can be acquired accurately. The DOM can also provide the basis of comparative studies on reservoirs in the exploitation of oil and gas.
