To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D sei...To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.展开更多
Fluvial systems play a crucial role in coastal and riverine ecosystems, making it essential to understand their responses to sea level changes for preserving biodiversity and managing natural resources. The evolution ...Fluvial systems play a crucial role in coastal and riverine ecosystems, making it essential to understand their responses to sea level changes for preserving biodiversity and managing natural resources. The evolution of the modern Indus River Delta offers a rare opportunity to study the interplay between sea level fluctuations, tectonism, sediment supply, and the corresponding fluvial responses. This study employs the ‘SedSim' stratigraphic forward model to simulate the delta's evolution from 200 kyr to the next5 kyr, drawing on data from field observations, Landsat imagery, digital elevation models, and previous studies. The model consists of 205 layers, each representing a 1-kyr time step, covering the last two glacial-interglacial cycles. Between 200 kyr and 130 kyr, during a lowstand period, sedimentation on the delta plain continued due to partial flow from the Indus River. During the last interglacial(130–60 kyr), rising sea levels led to peak sediment deposition, characteristic of a highstand phase. From 60 kyr to 18 kyr, sea levels dropped to their lowest during the Last Glacial Maximum(LGM), resulting in extensive erosion and minimal deposition on the delta plain. From 18 kyr to the present, rapidly rising sea levels, coupled with intensified monsoon activity, increased sedimentation rates and triggered avulsion and aggradation processes. The model accurately predicted depositional thickness across the delta plain, indicating a maximum of ca. 200 m at the shoreline platform, ca. 175 m in the northeastern delta, and ca. 100 m in the central delta. The study underscores the delta's vulnerability to future sea level rise, which–at a projected rate of 1 m/kyr–could significantly influence the densely populated, low-lying delta plain. These findings offer valuable insights into the geomorphic evolution of the Indus Delta and emphasize the socioeconomic implications of sea level change, underscoring the importance of proactive management and adaptation strategies.展开更多
The challenge of this work is to provide new data on the lithostratigraphy and tectono-stratigraphic evolution of two units belonging to the ophiolitic Ligurian-Piedmont zone of the Western Alps,i.e.the Albergian unit...The challenge of this work is to provide new data on the lithostratigraphy and tectono-stratigraphic evolution of two units belonging to the ophiolitic Ligurian-Piedmont zone of the Western Alps,i.e.the Albergian unit and the Lago Nero unit,exposed in the upper Susa and Chisone valleys(Northwestern Italy).展开更多
Stratigraphic correlations are essential for the fine-scale characterization of reservoirs.However,conventional data-driven methods that rely solely on log data struggle to construct isochronous stratigraphic framewor...Stratigraphic correlations are essential for the fine-scale characterization of reservoirs.However,conventional data-driven methods that rely solely on log data struggle to construct isochronous stratigraphic frameworks for complex sedimentary environments and multi-source geological settings.In response,this study proposed an intelligent,automatic,log-seismic integrated stratigraphic correlation method that incorporates wavelet frequency-division transform(WFT)and dynamic time warping(DTW)(also referred to as the WFT-DTW method).This approach integrates seismic data as constraints into stratigraphic correlations,enabling accurate tracking of the seismic marker horizons through WFT.Under the constraints of framework construction,a DTW algorithm was introduced to correlate sublayer boundaries automatically.The effectiveness of the proposed method was verified through a stratigraphic correlation experiment on the SA0 Formation of the Xingshugang block in the Lasaxing oilfield,the Songliao Basin,China.In this block,the target layer exhibits sublayer thicknesses ranging from 5 m to 8 m,an average sandstone thickness of 2.1 m,and pronounced heterogeneity.The verification using 1760 layers in 160 post-test wells indicates that the WFT-DTW method intelligently compared sublayers in zones with underdeveloped faults and distinct marker horizons.As a result,the posterior correlation of 1682 layers was performed,with a coincidence rate of up to 95.6%.The proposed method can complement manual correlation efforts while also providing valuable technical support for the lithologic and sand body characterization of reservoirs.展开更多
Challenges in stratigraphic modeling arise from underground uncertainty.While borehole exploration is reliable,it remains sparse due to economic and site constraints.Electrical resistivity tomography(ERT)as a cost-eff...Challenges in stratigraphic modeling arise from underground uncertainty.While borehole exploration is reliable,it remains sparse due to economic and site constraints.Electrical resistivity tomography(ERT)as a cost-effective geophysical technique can acquire high-density data;however,uncertainty and nonuniqueness inherent in ERT impede its usage for stratigraphy identification.This paper integrates ERT and onsite observations for the first time to propose a novel method for characterizing stratigraphic profiles.The method consists of two steps:(1)ERT for prior knowledge:ERT data are processed by soft clustering using the Gaussian mixture model,followed by probability smoothing to quantify its depthdependent uncertainty;and(2)Observations for calibration:a spatial sequential Bayesian updating(SSBU)algorithm is developed to update the prior knowledge based on likelihoods derived from onsite observations,namely topsoil and boreholes.The effectiveness of the proposed method is validated through its application to a real slope site in Foshan,China.Comparative analysis with advanced borehole-driven methods highlights the superiority of incorporating ERT data in stratigraphic modeling,in terms of prediction accuracy at borehole locations and sensitivity to borehole data.Informed by ERT,reduced sensitivity to boreholes provides a fundamental solution to the longstanding challenge of sparse measurements.The paper further discusses the impact of ERT uncertainty on the proposed model using time-lapse measurements,the impact of model resolution,and applicability in engineering projects.This study,as a breakthrough in stratigraphic modeling,bridges gaps in combining geophysical and geotechnical data to address measurement sparsity and paves the way for more economical geotechnical exploration.展开更多
Shaw's method used to correlate 40 sections across the Permo-Triassic boundary in South China is applied in the paper. Two steps are adopted to get an Integral Composite Section (ICS) by synthesizing these data : ...Shaw's method used to correlate 40 sections across the Permo-Triassic boundary in South China is applied in the paper. Two steps are adopted to get an Integral Composite Section (ICS) by synthesizing these data : First , South China is divided into five areas and composite section developed for each area . Then the second step . the Changxing composite section is regarded as a composite standard (CSRS) while the ICS is produced by matching the CSRS with composite sections of the other areas. Three biozones in the Changxingian and two biozones in the Griesbachian can be discerned on the basis of computing Z values in the ICS. These biozones are marked by the Z values which quantitatively represent their time ranges ; therefore , they may increase accuracy of stratigraphic time correlation . The mass extinction at the end of the Permian is an abrupt event that is supported by the relative rate of extinction near the P/T boundary . About 90% of invertebrate species died out by the end of the Permian . The duration of the mass extinction is rather short ,approximately 0.018Ma .展开更多
Late Paleozoic strata in northeastern China are distributed in a zonal pattern around the old-land on the Jiamusi-Mongolia Block. They are composed of active deposits in the regular distributed tectonic lithofacies zo...Late Paleozoic strata in northeastern China are distributed in a zonal pattern around the old-land on the Jiamusi-Mongolia Block. They are composed of active deposits in the regular distributed tectonic lithofacies zones. This indicates that the late Paleozoic strata belong to continental margin deposits. According to the strong conformability of the sedimentary strata in the same continental margin and distinct differences among the three continental margins, three stratigraphical regions of the Jiamusi-Mongolia Stratigraphical Province are recognized along the northern, southern and eastern margins of the Jiamusi-Mongolia Block, named respectively as Xing＇an Stratigraphical Region, Inner Mongolia grass-Songhua River Stratigraphical Region and Baoqing-Hunchun Stra- tigraphical Region. Due to the characteristics of continental margin deposits and active sediments, the strata can be correlated on the level of formation by the methods of analysing the rock association in the same stratigraphic region. Therefore, some revisions of the lithologieal formations of the late Paleozoic strata in northeastern China have been made, and a new chart of lithostratigraphic correlation has been proposed. Furthermore, the present stratigraphic framework is setting on the International Stratigraphic Chart on the level of stage, after comprehen- sive researches to lithostratigraphy, biostratigraphy and chronostratigraphy, especially the conodont biostratigra- phy and isotopic ages of volcanic rocks obtained in recent years.展开更多
The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-r...The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-resolution sequences are divided based on the above results. The study shows that the stratigraphic base-level cyclic method is an efficient way in the determination of the high-resolution sequences, especially in the classification of tbe terrestrial and transitional depositional succession.展开更多
The International Commission on Stratigraphy(ICS)has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of...The International Commission on Stratigraphy(ICS)has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries.The primary objective of ICS is to define precisely a global standard set of timecorrelative units(Systems,Series,and Stages)for stratigraphic successions worldwide.These units are,in turn,the basis for the Periods,Epochs and Ages of the Geological Time Scale.Setting an international global standard is fundamental for expressing geological knowledge.It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked,equated and collated.This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.展开更多
Sequence boundary is studied in detail in reference to the Permian Guadalupian Lopingian boundary, based on high resolution correlation of conodont zones. A conceptual synchronous stratigraphic boundary, corresponding...Sequence boundary is studied in detail in reference to the Permian Guadalupian Lopingian boundary, based on high resolution correlation of conodont zones. A conceptual synchronous stratigraphic boundary, corresponding to the age of the sequence boundary dated in the conformable portion of the sequence boundary, is defined as the sequence chronostratigraphic boundary (SCB). The sequence boundary is proved to be dual in nature in regards to tin-synchrony and diachroneity of stratigraphic boundaries. The merits of the sequence boundary in stratigraphic subdivision, correlation and classification are elucidated in comparison with the lithostratigraphic boundary, the biostratigraphic boundary and the traditional approach of the global stratotype section and point (GSSP ). By integrating the virtues of the sequence boundary and the GSSP, it is proposed that the GSSP should be established in the conformable portion of the related sequence boundary. The boundary established in light of this approach is defined as the best natural boundary. The analysis of the sequence boundary leads to the conclusion that sequence stratigraphy is a regional and transitional stratigraphic system between local lithostratigraphy and global chronostratigraphy. Therefore, a new tripartite stratigraphic classification scheme is tentatively proposed.展开更多
There are a number of small -scale brown coal basins in the central part of Yunnan. The coal-bearing strata are made up of alluvialfan-lacustrine-swamp genetic Seguences’ On the basis of the detialedgenatic stratigra...There are a number of small -scale brown coal basins in the central part of Yunnan. The coal-bearing strata are made up of alluvialfan-lacustrine-swamp genetic Seguences’ On the basis of the detialedgenatic stratigraphic analyses with some basins, three types of chronestratigraphic interfaces and second grade or the geneticstratigraphic units are defined. This paper reveals inherent relationswith regrad to the genetic stratigraphic evolution and coal formation of the small-scale fault basins’展开更多
The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for t...The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for the protection and documentation of stratigraphic sections includes:(1)marked tablets showing the standardized bed,member and formation divisions and,where applicable,standardized meter intervals for future investigations;(2)a monument or other on-site interpretive information;and(3)field guides for different audiences summarizing its importance with maps and detailed descriptions.In particular,the ten Global Stratotype Sections and Points(GSSPs)established in southern China are well preserved and managed;and some are now within tourist-friendly educational national geoparks.We suggest that other national stratigraphic commissions might incorporate some of the experiences from China’s current efforts to preserve and standardize important reference sections for Earth history research.展开更多
In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift successio...In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift succession in Qiongdongnan Basin, northern South China Sea, was built using seismic profiles, complemented by well logs and cores. One first-order and three second-order sequences were identified on the basis of basin-scale unconformities, and seven third-order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin. Through unconformity analysis and backstripping procedure, the Paleogene synrift tectonic evolution of deep- water area of Qiongdongnan Basin was proved to be episodic, which can be divided into rifting stage-I, rifting stage-II and rifting stage-III. Episodic rifting resulted in the formation of various types of struc- tural slope break belts, which controlled different architectures and internal makeup of sequences. This study enhances the understanding of the control of tectonic evolution on sequence stratigraphic pat- terns and establishes relevant patterns in a typical rift basin, and further proposes the favorable sand- stone reservoirs developing in different sequence stratigraphic patterns, which will be pretty helpful for subtle pool exploration in deepwater area of petroliferous basins.展开更多
The onshore oil and gas exploration has stepped into a new stage in China, with equal attention paid to both stratigraphic and subtle reservoirs and structural reservoirs. In the past few years, the increases in oil r...The onshore oil and gas exploration has stepped into a new stage in China, with equal attention paid to both stratigraphic and subtle reservoirs and structural reservoirs. In the past few years, the increases in oil reserves in most basins were found mainly in the stratigraphic and subtle reservoirs. Latest resource evaluation shows that the onshore stratigraphic and subtle reservoirs in China account for 42% of the total remaining resource, the highest in the four major exploration regions. Therefore, these reservoirs will be the most practical, potential and prevalent fields for long-lasting oil and gas exploration in onshore China. Among PetroChina's annual oil geologic reserves of 4.3 × 108t^4.6× 108t, the stratigraphic and subtle reservoirs account for more than 50%. In such basins as Songliao, Ordos, Bohai Bay, Junggar, Tarim, Sichuan and Erlian basins, stratigraphic and subtle reservoirs with geologic reserves ranging from 5×107t to 3×108t were discovered, including Ansai, Jing'an, Daqingzijing, Liuxi, well-21 area in Shinan, and Hadexun. Stratigraphic and subtle reservoirs in the four types of inland basins differ from each other in the formation conditions and the distribution patterns. While continental basins are controlled by unconformity surface, maximum flooding surface and fracture surface, the Paleozoic marine basins are influenced by paleouplift, unconformity surface, and fluctuation of the sea level. Through exploration practices and research, PetroChina has formed its own technique series focused on 3-D seismics and sequence stratigraphy.展开更多
To improve the success rate of locating hydrocarbon reservoirs in pre-Cenozoic inland compressional basins, taking the Early Yanshanian succession of eastern Yihezhuang salient as an example, this paper studied the se...To improve the success rate of locating hydrocarbon reservoirs in pre-Cenozoic inland compressional basins, taking the Early Yanshanian succession of eastern Yihezhuang salient as an example, this paper studied the sedimentary facies and sequence stratigraphic patterns. First, through seismic profiles, well logs, cores and outcrops, the sequence framework was established and internal sedimentary facies were identified. Further, according to analysis of single-wells and connecting-wells, the vertical evolution and horizontal distribution of sedimentation inside the sequence frameworks were discussed. The following results were acquired:(1) meandering river characterized by dual structures superposing each other was developed, and the dual structures can be further divided into three kinds;(2) the entire Early Yanshanian succession was interpreted as one first-order sequence, composed of three third-order sequences, including SQ-Fz1, SQ-Fz2 and SQ-St from bottom to top. Each third-order sequence can be further divided into three system tracts;(3) in different system tracts, different types of dual structures developed separately, and sedimentary bodies showed different horizontal distribution scales and vertical superposition patterns. Finally, the model of sequence stratigraphic patterns was established. This study enhanced the use of sequence stratigraphy to inland tectonically active basins, and would be helpful to predict reservoirs in pre-Cenozoic residual basins.展开更多
This paper presents a unique and formal method of quantifying the similarity or distance between sedimentary facies successions from measured sections in outcrop or drilled wells and demonstrates its first application...This paper presents a unique and formal method of quantifying the similarity or distance between sedimentary facies successions from measured sections in outcrop or drilled wells and demonstrates its first application in inverse stratigraphic modeling. A sedimentary facies succession is represented with a string of symbols, or facies codes in its natural vertical order, in which each symbol brings with it one attribute such as thickness for the facies. These strings are called attributed strings. A similarity measure is defined between the attributed strings based on a syntactic pattern-recognition technique. A dynamic programming algorithm is used to calculate the similarity. Inverse stratigraphic modeling aims to generate quantitative 3D facies models based on forward stratigraphic modeling that honors observed datasets. One of the key techniques in inverse stratigraphic modeling is how to quantify the similarity or distance between simulated and observed sedimentary facies successions at data locations in order for the forward model to condition the simulation results to the observed dataset such as measured sections or drilled wells. This quantification technique comparing sedimentary successions is demonstrated in the form of a cost function based on the defined distance in our inverse stratigraphic modeling implemented with forward modeling optimization.展开更多
Taking member one of Yingcheng Formation of Cretaceous in Xudong area, Xushen Gas Field of Songliao Basin for an example and aimed at the diachronous problem generally existed in vol- canic reservoir division, firstly...Taking member one of Yingcheng Formation of Cretaceous in Xudong area, Xushen Gas Field of Songliao Basin for an example and aimed at the diachronous problem generally existed in vol- canic reservoir division, firstly advanced the method of two steps and two unites in the researches of volcanic reservoir finely division that guided by the method that sources controlled and founded the stratigraphic trellis. In this process, volcanic edifices and bodies were identified and traced. The results indicated that aimed strata in study areas could be carved up to six layers of YCII1, YCII2, YCII-II, YCIIlI, YCIII2 and YCIIII from the top to the bottom. Analyzing causes and firmly united of well data and seismic data could achieve fine stratigraphic division of volcanic reservoir. Surfaces of layers and volcanic bodies were basically unanimous in side direction. Stratum inclination gradually reduced with the distances increased from craters. The results of volcanic reservoir division had preferable con- sistency with lithologies and volcanic lithofacies and dynamic development data. The researches offered a useful method to stratigraphic division of volcanic reservoir and it had very important significance to effective development of volcanic reservoir in practice.展开更多
In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are pr...In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth-order sequence in the terrestrial lacustrine basin into two system tracts： the wet （rising） half-cycle and the dry （falling） half- cycle, establishing a new-style fourth-order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate-genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.展开更多
Isotopic ages of synsedimentary clay minerals were directly determined with the ultrasonicscattering-settlement separation-K-Ar dilution technique. The apparent age of black mudstoneis 123 Ma for the Quantou Formation...Isotopic ages of synsedimentary clay minerals were directly determined with the ultrasonicscattering-settlement separation-K-Ar dilution technique. The apparent age of black mudstoneis 123 Ma for the Quantou Formation, 111.9-89.0 Ma for the Qingshankou Formation and77.6-76.8 Ma for the upper part of the Nenjiang Formation. The Rb-Sr isochrone age of themuddy limestone-mudstone sequence of the lower part of the Nenjiang Formation is 81 Ma andthat of the muddy evaporite of the middle part of the Quantou Formation is 122.2 Ma. On thebasis of the above isotopic ages, the authors propose a modified scheme of stratigraphic classifi-cation of the Cretaceous of the Songliao basin.展开更多
The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi...The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi area. Negative δ13C excursion above the Yurtus Fm/ Qigeblaq Fm boundary was determined in this study. The pronounced negative carbon isotope excursion occurs in the phosphatic chert layers at the bottom of the Cambrian Yurtus Fm, below which the first appearance of the Asteridium- Heh＇osphaeridium-Comasphaeridium （AHC） acritarch assemblage zone. The δ13C curve of the lower part of the Yurtus Fm in the Aksu-Wushi area was found to be correlated with the early Cambrian δ13C curves of the Zhujiaqing Fm （Daibu Member）, the lower part of the Yanjiahe Fm on the Yangtze Platform in China, the lower Tal Fm in India, the Sukharikha Fm in Siberia, and the upper part of the Tsagaan Oloom Fm in Mongolia through biostigraphy. The lower part of the Yurtus Fm in the Tarim Basin is at the Nemakit-Daldynian stage, and the Precambrian/Cambrian boundary of the Aksu-Wushi area may be located in the phosphatic chert unit which just below the first appearance AHC acritarch assemblage zone. The negative δ13C excursion （N1） across the Precambrian/Cambrian boundary in the studied section may have resulted from oceanic overturning and sea level rise.展开更多
基金Supported by the National Science and Technology Major Project(2017ZX05001)CNPC Technology Project(2023YQX20111).
文摘To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.
基金the Science and Technology Innovation Project of the Laoshan Laboratory (No. LSKJ202203402)the Major Research Project on the Tethys Geodynamic System from the National Science Foundation of China (No. 92055204)。
文摘Fluvial systems play a crucial role in coastal and riverine ecosystems, making it essential to understand their responses to sea level changes for preserving biodiversity and managing natural resources. The evolution of the modern Indus River Delta offers a rare opportunity to study the interplay between sea level fluctuations, tectonism, sediment supply, and the corresponding fluvial responses. This study employs the ‘SedSim' stratigraphic forward model to simulate the delta's evolution from 200 kyr to the next5 kyr, drawing on data from field observations, Landsat imagery, digital elevation models, and previous studies. The model consists of 205 layers, each representing a 1-kyr time step, covering the last two glacial-interglacial cycles. Between 200 kyr and 130 kyr, during a lowstand period, sedimentation on the delta plain continued due to partial flow from the Indus River. During the last interglacial(130–60 kyr), rising sea levels led to peak sediment deposition, characteristic of a highstand phase. From 60 kyr to 18 kyr, sea levels dropped to their lowest during the Last Glacial Maximum(LGM), resulting in extensive erosion and minimal deposition on the delta plain. From 18 kyr to the present, rapidly rising sea levels, coupled with intensified monsoon activity, increased sedimentation rates and triggered avulsion and aggradation processes. The model accurately predicted depositional thickness across the delta plain, indicating a maximum of ca. 200 m at the shoreline platform, ca. 175 m in the northeastern delta, and ca. 100 m in the central delta. The study underscores the delta's vulnerability to future sea level rise, which–at a projected rate of 1 m/kyr–could significantly influence the densely populated, low-lying delta plain. These findings offer valuable insights into the geomorphic evolution of the Indus Delta and emphasize the socioeconomic implications of sea level change, underscoring the importance of proactive management and adaptation strategies.
文摘The challenge of this work is to provide new data on the lithostratigraphy and tectono-stratigraphic evolution of two units belonging to the ophiolitic Ligurian-Piedmont zone of the Western Alps,i.e.the Albergian unit and the Lago Nero unit,exposed in the upper Susa and Chisone valleys(Northwestern Italy).
基金funded by the Major Science and Technology Project of China National Petroleum Corporation(No.2023ZZ22YJ01).
文摘Stratigraphic correlations are essential for the fine-scale characterization of reservoirs.However,conventional data-driven methods that rely solely on log data struggle to construct isochronous stratigraphic frameworks for complex sedimentary environments and multi-source geological settings.In response,this study proposed an intelligent,automatic,log-seismic integrated stratigraphic correlation method that incorporates wavelet frequency-division transform(WFT)and dynamic time warping(DTW)(also referred to as the WFT-DTW method).This approach integrates seismic data as constraints into stratigraphic correlations,enabling accurate tracking of the seismic marker horizons through WFT.Under the constraints of framework construction,a DTW algorithm was introduced to correlate sublayer boundaries automatically.The effectiveness of the proposed method was verified through a stratigraphic correlation experiment on the SA0 Formation of the Xingshugang block in the Lasaxing oilfield,the Songliao Basin,China.In this block,the target layer exhibits sublayer thicknesses ranging from 5 m to 8 m,an average sandstone thickness of 2.1 m,and pronounced heterogeneity.The verification using 1760 layers in 160 post-test wells indicates that the WFT-DTW method intelligently compared sublayers in zones with underdeveloped faults and distinct marker horizons.As a result,the posterior correlation of 1682 layers was performed,with a coincidence rate of up to 95.6%.The proposed method can complement manual correlation efforts while also providing valuable technical support for the lithologic and sand body characterization of reservoirs.
基金the financial support from the National Key R&D Program of China(Grant No.2021YFC3001003)Science and Technology Development Fund,Macao SAR(File No.0056/2023/RIB2)Guangdong Provincial Department of Science and Technology(Grant No.2022A0505030019).
文摘Challenges in stratigraphic modeling arise from underground uncertainty.While borehole exploration is reliable,it remains sparse due to economic and site constraints.Electrical resistivity tomography(ERT)as a cost-effective geophysical technique can acquire high-density data;however,uncertainty and nonuniqueness inherent in ERT impede its usage for stratigraphy identification.This paper integrates ERT and onsite observations for the first time to propose a novel method for characterizing stratigraphic profiles.The method consists of two steps:(1)ERT for prior knowledge:ERT data are processed by soft clustering using the Gaussian mixture model,followed by probability smoothing to quantify its depthdependent uncertainty;and(2)Observations for calibration:a spatial sequential Bayesian updating(SSBU)algorithm is developed to update the prior knowledge based on likelihoods derived from onsite observations,namely topsoil and boreholes.The effectiveness of the proposed method is validated through its application to a real slope site in Foshan,China.Comparative analysis with advanced borehole-driven methods highlights the superiority of incorporating ERT data in stratigraphic modeling,in terms of prediction accuracy at borehole locations and sensitivity to borehole data.Informed by ERT,reduced sensitivity to boreholes provides a fundamental solution to the longstanding challenge of sparse measurements.The paper further discusses the impact of ERT uncertainty on the proposed model using time-lapse measurements,the impact of model resolution,and applicability in engineering projects.This study,as a breakthrough in stratigraphic modeling,bridges gaps in combining geophysical and geotechnical data to address measurement sparsity and paves the way for more economical geotechnical exploration.
文摘Shaw's method used to correlate 40 sections across the Permo-Triassic boundary in South China is applied in the paper. Two steps are adopted to get an Integral Composite Section (ICS) by synthesizing these data : First , South China is divided into five areas and composite section developed for each area . Then the second step . the Changxing composite section is regarded as a composite standard (CSRS) while the ICS is produced by matching the CSRS with composite sections of the other areas. Three biozones in the Changxingian and two biozones in the Griesbachian can be discerned on the basis of computing Z values in the ICS. These biozones are marked by the Z values which quantitatively represent their time ranges ; therefore , they may increase accuracy of stratigraphic time correlation . The mass extinction at the end of the Permian is an abrupt event that is supported by the relative rate of extinction near the P/T boundary . About 90% of invertebrate species died out by the end of the Permian . The duration of the mass extinction is rather short ,approximately 0.018Ma .
基金Supported by Project of China Geological Survey (No. 1212011120153 - 3)
文摘Late Paleozoic strata in northeastern China are distributed in a zonal pattern around the old-land on the Jiamusi-Mongolia Block. They are composed of active deposits in the regular distributed tectonic lithofacies zones. This indicates that the late Paleozoic strata belong to continental margin deposits. According to the strong conformability of the sedimentary strata in the same continental margin and distinct differences among the three continental margins, three stratigraphical regions of the Jiamusi-Mongolia Stratigraphical Province are recognized along the northern, southern and eastern margins of the Jiamusi-Mongolia Block, named respectively as Xing＇an Stratigraphical Region, Inner Mongolia grass-Songhua River Stratigraphical Region and Baoqing-Hunchun Stra- tigraphical Region. Due to the characteristics of continental margin deposits and active sediments, the strata can be correlated on the level of formation by the methods of analysing the rock association in the same stratigraphic region. Therefore, some revisions of the lithologieal formations of the late Paleozoic strata in northeastern China have been made, and a new chart of lithostratigraphic correlation has been proposed. Furthermore, the present stratigraphic framework is setting on the International Stratigraphic Chart on the level of stage, after comprehen- sive researches to lithostratigraphy, biostratigraphy and chronostratigraphy, especially the conodont biostratigra- phy and isotopic ages of volcanic rocks obtained in recent years.
文摘The sedimentary characteristics and their combination succession of the Permian in the Shandong nd Huainan-Huaibei coalfields are analyzed. The mid-and short-term stratigraphic base-level cycles are identified. High-resolution sequences are divided based on the above results. The study shows that the stratigraphic base-level cyclic method is an efficient way in the determination of the high-resolution sequences, especially in the classification of tbe terrestrial and transitional depositional succession.
文摘The International Commission on Stratigraphy(ICS)has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries.The primary objective of ICS is to define precisely a global standard set of timecorrelative units(Systems,Series,and Stages)for stratigraphic successions worldwide.These units are,in turn,the basis for the Periods,Epochs and Ages of the Geological Time Scale.Setting an international global standard is fundamental for expressing geological knowledge.It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked,equated and collated.This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.
基金This study is sponsored by the "SSLC", a state key project supported by the State Science and Technology Committee of China and the Ministry of Geology and Mineral Resources
文摘Sequence boundary is studied in detail in reference to the Permian Guadalupian Lopingian boundary, based on high resolution correlation of conodont zones. A conceptual synchronous stratigraphic boundary, corresponding to the age of the sequence boundary dated in the conformable portion of the sequence boundary, is defined as the sequence chronostratigraphic boundary (SCB). The sequence boundary is proved to be dual in nature in regards to tin-synchrony and diachroneity of stratigraphic boundaries. The merits of the sequence boundary in stratigraphic subdivision, correlation and classification are elucidated in comparison with the lithostratigraphic boundary, the biostratigraphic boundary and the traditional approach of the global stratotype section and point (GSSP ). By integrating the virtues of the sequence boundary and the GSSP, it is proposed that the GSSP should be established in the conformable portion of the related sequence boundary. The boundary established in light of this approach is defined as the best natural boundary. The analysis of the sequence boundary leads to the conclusion that sequence stratigraphy is a regional and transitional stratigraphic system between local lithostratigraphy and global chronostratigraphy. Therefore, a new tripartite stratigraphic classification scheme is tentatively proposed.
文摘There are a number of small -scale brown coal basins in the central part of Yunnan. The coal-bearing strata are made up of alluvialfan-lacustrine-swamp genetic Seguences’ On the basis of the detialedgenatic stratigraphic analyses with some basins, three types of chronestratigraphic interfaces and second grade or the geneticstratigraphic units are defined. This paper reveals inherent relationswith regrad to the genetic stratigraphic evolution and coal formation of the small-scale fault basins’
文摘The protection of classical or significant reference stratigraphic sections of the nation’s valuable geoheritage has become a priority by the Chinese government and national stratigraphic commission.The process for the protection and documentation of stratigraphic sections includes:(1)marked tablets showing the standardized bed,member and formation divisions and,where applicable,standardized meter intervals for future investigations;(2)a monument or other on-site interpretive information;and(3)field guides for different audiences summarizing its importance with maps and detailed descriptions.In particular,the ten Global Stratotype Sections and Points(GSSPs)established in southern China are well preserved and managed;and some are now within tourist-friendly educational national geoparks.We suggest that other national stratigraphic commissions might incorporate some of the experiences from China’s current efforts to preserve and standardize important reference sections for Earth history research.
基金supported by the National Science Foundation of China (NSFC) (Nos. 41272122, 41202074 and 41172123)the Major National Science and Technology Programs in the "Twelfth Five-Year" Plan of China (No. 2011ZX05009-002-02)+1 种基金the Open Research Program Foundation of Teaching Laboratory of China University of Geosciencesthe Foundation of Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences) of Ministry of Education (No. TPR-2013-14)
文摘In active rift basins, tectonism is extremely important for sequence stratigraphic patterns, affecting both the sequence architecture and internal makeup. Sequence stratigraphic framework of a Paleogene rift succession in Qiongdongnan Basin, northern South China Sea, was built using seismic profiles, complemented by well logs and cores. One first-order and three second-order sequences were identified on the basis of basin-scale unconformities, and seven third-order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin. Through unconformity analysis and backstripping procedure, the Paleogene synrift tectonic evolution of deep- water area of Qiongdongnan Basin was proved to be episodic, which can be divided into rifting stage-I, rifting stage-II and rifting stage-III. Episodic rifting resulted in the formation of various types of struc- tural slope break belts, which controlled different architectures and internal makeup of sequences. This study enhances the understanding of the control of tectonic evolution on sequence stratigraphic pat- terns and establishes relevant patterns in a typical rift basin, and further proposes the favorable sand- stone reservoirs developing in different sequence stratigraphic patterns, which will be pretty helpful for subtle pool exploration in deepwater area of petroliferous basins.
文摘The onshore oil and gas exploration has stepped into a new stage in China, with equal attention paid to both stratigraphic and subtle reservoirs and structural reservoirs. In the past few years, the increases in oil reserves in most basins were found mainly in the stratigraphic and subtle reservoirs. Latest resource evaluation shows that the onshore stratigraphic and subtle reservoirs in China account for 42% of the total remaining resource, the highest in the four major exploration regions. Therefore, these reservoirs will be the most practical, potential and prevalent fields for long-lasting oil and gas exploration in onshore China. Among PetroChina's annual oil geologic reserves of 4.3 × 108t^4.6× 108t, the stratigraphic and subtle reservoirs account for more than 50%. In such basins as Songliao, Ordos, Bohai Bay, Junggar, Tarim, Sichuan and Erlian basins, stratigraphic and subtle reservoirs with geologic reserves ranging from 5×107t to 3×108t were discovered, including Ansai, Jing'an, Daqingzijing, Liuxi, well-21 area in Shinan, and Hadexun. Stratigraphic and subtle reservoirs in the four types of inland basins differ from each other in the formation conditions and the distribution patterns. While continental basins are controlled by unconformity surface, maximum flooding surface and fracture surface, the Paleozoic marine basins are influenced by paleouplift, unconformity surface, and fluctuation of the sea level. Through exploration practices and research, PetroChina has formed its own technique series focused on 3-D seismics and sequence stratigraphy.
基金supported by the National Natural Science Foundation of China (NSFC) (No. 41472216)the Natural Science Foundation of Shandong Province (No. ZR2016DB29)+3 种基金the Project supported by Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral, Shandong University of Science and Technology (No. DMSM2017015)the Water Conservancy Scientific Research and Technology Promotion Projects of Shandong Province (No. SDSLKY201808)the Natural Science Foundation of Jinan University (No. XBS1647)Petroleum Development Centre of the Shengli Oilfield Company for their support
文摘To improve the success rate of locating hydrocarbon reservoirs in pre-Cenozoic inland compressional basins, taking the Early Yanshanian succession of eastern Yihezhuang salient as an example, this paper studied the sedimentary facies and sequence stratigraphic patterns. First, through seismic profiles, well logs, cores and outcrops, the sequence framework was established and internal sedimentary facies were identified. Further, according to analysis of single-wells and connecting-wells, the vertical evolution and horizontal distribution of sedimentation inside the sequence frameworks were discussed. The following results were acquired:(1) meandering river characterized by dual structures superposing each other was developed, and the dual structures can be further divided into three kinds;(2) the entire Early Yanshanian succession was interpreted as one first-order sequence, composed of three third-order sequences, including SQ-Fz1, SQ-Fz2 and SQ-St from bottom to top. Each third-order sequence can be further divided into three system tracts;(3) in different system tracts, different types of dual structures developed separately, and sedimentary bodies showed different horizontal distribution scales and vertical superposition patterns. Finally, the model of sequence stratigraphic patterns was established. This study enhanced the use of sequence stratigraphy to inland tectonically active basins, and would be helpful to predict reservoirs in pre-Cenozoic residual basins.
基金financially was supported by Colorado School of Minessupported by the Science and Technology Ministry of China (2016ZX05033003)+1 种基金China Academy of Sciences (XDA14010204)Sinopec (G5800-15-ZS-KJB016)
文摘This paper presents a unique and formal method of quantifying the similarity or distance between sedimentary facies successions from measured sections in outcrop or drilled wells and demonstrates its first application in inverse stratigraphic modeling. A sedimentary facies succession is represented with a string of symbols, or facies codes in its natural vertical order, in which each symbol brings with it one attribute such as thickness for the facies. These strings are called attributed strings. A similarity measure is defined between the attributed strings based on a syntactic pattern-recognition technique. A dynamic programming algorithm is used to calculate the similarity. Inverse stratigraphic modeling aims to generate quantitative 3D facies models based on forward stratigraphic modeling that honors observed datasets. One of the key techniques in inverse stratigraphic modeling is how to quantify the similarity or distance between simulated and observed sedimentary facies successions at data locations in order for the forward model to condition the simulation results to the observed dataset such as measured sections or drilled wells. This quantification technique comparing sedimentary successions is demonstrated in the form of a cost function based on the defined distance in our inverse stratigraphic modeling implemented with forward modeling optimization.
基金sponsored by the Magnitude Project of Ministry of Science and Technology of China (No. 2008ZX05016-001)the China Postdoctoral Science Foundation (No. 20100480344)Youth Innovation Fund of Research Institute of Petroleum Exploration and Development of PetroChina (No. 2009-B-10-03)
文摘Taking member one of Yingcheng Formation of Cretaceous in Xudong area, Xushen Gas Field of Songliao Basin for an example and aimed at the diachronous problem generally existed in vol- canic reservoir division, firstly advanced the method of two steps and two unites in the researches of volcanic reservoir finely division that guided by the method that sources controlled and founded the stratigraphic trellis. In this process, volcanic edifices and bodies were identified and traced. The results indicated that aimed strata in study areas could be carved up to six layers of YCII1, YCII2, YCII-II, YCIIlI, YCIII2 and YCIIII from the top to the bottom. Analyzing causes and firmly united of well data and seismic data could achieve fine stratigraphic division of volcanic reservoir. Surfaces of layers and volcanic bodies were basically unanimous in side direction. Stratum inclination gradually reduced with the distances increased from craters. The results of volcanic reservoir division had preferable con- sistency with lithologies and volcanic lithofacies and dynamic development data. The researches offered a useful method to stratigraphic division of volcanic reservoir and it had very important significance to effective development of volcanic reservoir in practice.
基金These research results are part of a key international cooperation project carried out during 2003 and 2005 and financially supported by SINOPEC.
文摘In recent years, with the development of terrestrial sequence stratigraphy, more attention has been focused on the study of the terrestrial lacustrine sequence stratigraphic model globally. Different viewpoints are preferred by researchers. Under the guidance of the theory of sequence stratigraphy, the findings of this paper indicate that climate is a major factor controlling the formation of the fourth-order sequence, based upon the study of the sequence stratigraphy in the Green River Formation of the Uinta basin in the USA. It also divides the fourth-order sequence in the terrestrial lacustrine basin into two system tracts： the wet （rising） half-cycle and the dry （falling） half- cycle, establishing a new-style fourth-order sequence stratigraphic model for the terrestrial lacustrine basin, that is, the climate-genetic sequence stratigraphic model. As a result, the theory of sequence stratigraphy is greatly enriched.
基金Note:The study was supported by the China National Natural Science Foundation Grant No 49172107.
文摘Isotopic ages of synsedimentary clay minerals were directly determined with the ultrasonicscattering-settlement separation-K-Ar dilution technique. The apparent age of black mudstoneis 123 Ma for the Quantou Formation, 111.9-89.0 Ma for the Qingshankou Formation and77.6-76.8 Ma for the upper part of the Nenjiang Formation. The Rb-Sr isochrone age of themuddy limestone-mudstone sequence of the lower part of the Nenjiang Formation is 81 Ma andthat of the muddy evaporite of the middle part of the Quantou Formation is 122.2 Ma. On thebasis of the above isotopic ages, the authors propose a modified scheme of stratigraphic classifi-cation of the Cretaceous of the Songliao basin.
基金financially supported by the National Natural Science Foundation of China (Grant No.41203023)National Basic Research Program of China (Grant No.2007CB411301)
文摘The upper Qigeblaq Formation （Fm） dolostones and the Yurtus Fm phosphatic cherts, black shales, limestones, and dolostones are widely distributed in the Precambrian/Cambrian transitional succession of the Aksu-Wushi area. Negative δ13C excursion above the Yurtus Fm/ Qigeblaq Fm boundary was determined in this study. The pronounced negative carbon isotope excursion occurs in the phosphatic chert layers at the bottom of the Cambrian Yurtus Fm, below which the first appearance of the Asteridium- Heh＇osphaeridium-Comasphaeridium （AHC） acritarch assemblage zone. The δ13C curve of the lower part of the Yurtus Fm in the Aksu-Wushi area was found to be correlated with the early Cambrian δ13C curves of the Zhujiaqing Fm （Daibu Member）, the lower part of the Yanjiahe Fm on the Yangtze Platform in China, the lower Tal Fm in India, the Sukharikha Fm in Siberia, and the upper part of the Tsagaan Oloom Fm in Mongolia through biostigraphy. The lower part of the Yurtus Fm in the Tarim Basin is at the Nemakit-Daldynian stage, and the Precambrian/Cambrian boundary of the Aksu-Wushi area may be located in the phosphatic chert unit which just below the first appearance AHC acritarch assemblage zone. The negative δ13C excursion （N1） across the Precambrian/Cambrian boundary in the studied section may have resulted from oceanic overturning and sea level rise.
