Autogenic processes are widely found in various sedimentary systems and they play an important role in the depositional evolution and corresponding sedimentary architecture.However,autogenic processes are often affect...Autogenic processes are widely found in various sedimentary systems and they play an important role in the depositional evolution and corresponding sedimentary architecture.However,autogenic processes are often affected by changing allogenic factors and are difficult to be identified and analyzed from modern and ancient records.Through the flume tank experiment under constant boundary conditions,the depositional process,evolution principles,and the sedimentary architecture of a river-dominated delta was presented,and a corresponding sedimentary architecture model was constructed.The evolution of river-dominated delta controlled only by autogenic process is obviously periodic,and each autogenic cycle can be divided into an initial progradational stage,a middle retrogratational stage,and a late aggradational–progradational stage.In the initial progradational stage,one feeder channel incised into the delta plain,mouth bar(s)was formed in front of the channel mouth,and small-scale crevasse splays were formed on the delta plain.In the middle retrogradational stage,the feeder channel was blocked by the mouth bar(s)which grew out of water at the end of the initial stage,and a set of large-scale distributary splay complexes were formed on the delta plain.These distributary splay complexes were retrogradationally overlapped due to the continuous migration of the bifurcation point of the feeder channel.In the late aggradational–progradational stage,the feeder channel branched into several radial distributary channels,overlapped distributary channels were formed on the delta plain,and terminal lobe complexes were formed at the end of distributary channels.The three sedimentary layers formed in the three stages constituted an autogenic succession.The experimental delta consisted of six autogenic depositional successions.Dynamic allocation of accommodation space and the following adaptive sediments filling were the two main driving factors of the autogenic evolution of deltas.展开更多
River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects del...River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects deltaic sand distributions and evolutions.However,it's unclear how it influences riverdominated delta growth.This paper integrates Delft3 D simulations and modern analogs to analyze the effects of water discharge,considering growth time,sediment supply,and coupled effects of sediment properties.High water discharges lead to the formation of lobate deltas,and the water discharge of 1,000 m~3/s is a referenced threshold value.Fine-grained,highly-cohesive sediments increase the threshold values of water discharge at which the deltas become lobate from digitate,and vice versa.For the same simulation time,high water discharges favor more rugose shorelines,more distributary channels(especially secondary distributaries),and longer and wider deltas with more land areas.However,for the same sediment supply,high water discharges have few effects on shoreline roughness and the number of distributary channels.展开更多
Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie ...Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie Formation(Es3)on the gentle southern slope of the Gubei Sag,Bohai Bay Basin and draw some conclusions that,for complex sand bodies,with the increase in water level the distributary channels bifurcate frequently,from a simple branching shape to a network shape along with the increase in the development of crevasse splays,mouth bars and sheet sands.For single sand bodies,with an increase in water level in the slope zone of the lake basin close to the source area,the superimposition style transitioned from vertical cutting-stacking and lateral isolation to vertical stitching,isolation and lateral stitching.However,in the central zone of the lake basin far from the source area,the superimposition style transitioned from vertical stitching and lateral stitching to vertical isolation and lateral isolation.When water level stays stable,the greater the distance from the source area the greater the disaggregation ratio of a single sand body.At the same distance from the source area,higher water level tends to result in greater disaggregation ratio of a single sand body.展开更多
In offshore fields with limited well data,intricate geological configurations,and high reservoir heterogeneity,the accurate prediction of sand body distribution and characterization of sedimentary architecture pose si...In offshore fields with limited well data,intricate geological configurations,and high reservoir heterogeneity,the accurate prediction of sand body distribution and characterization of sedimentary architecture pose significant challenges due to inherent geological uncertainties and data limitations.This study employs a comprehensive approach integrating three key methods to enhance prediction accuracy:(i)fusion of spectral-decomposed seismic attributes,(ii)seismic attribute fusion of target and neighboring zones,and(iii)colored seismic inversion.The first method leverages seismic information across various frequencies,yielding reliable results for sand bodies of different thicknesses.The second method mitigates the impact of seismic responses from adjacent zones on sand body predictions,making it particularly suitable for target intervals where neighboring zones significantly influence the seismic response.The third one,colored seismic inversion enhances the prediction of vertical distribution and the stacking relationships of sand bodies.These methods have been applied in an oilfield in the Pearl River Mouth Basin,southern China.Consequently,the sedimentary architecture of a braided river delta reservoir is successfully characterized,leading to the identification of four distributary channels within a depositional Zone 1 of the Zhujiang Formation.Additionally,a comprehensive workflow integrating well logs,seismic data,and depositional models significantly improves predictions of sand body distribution and sedimentary architecture in complex geological settings,providing critical geological insights for optimizing subsequent oilfield development strategies.展开更多
River-dominated lacustrine deltas typically consist of multiple lobes due to autogenic lobe switching that occurs over short time scales.However,the switching patterns of multiple lobes in these deltas remain poorly u...River-dominated lacustrine deltas typically consist of multiple lobes due to autogenic lobe switching that occurs over short time scales.However,the switching patterns of multiple lobes in these deltas remain poorly understood,and the architectural features attributed to lobe switching are also lacking.By integrating Delft3D simulations,flume experiments,and modern deposit analysis,we proposed that autogenic lobe switching follows a cyclic pattern.Autocyclicity begins with the formation of an offshore lobe and concludes after a series of longshore lobe growth events,marked by longshore avulsions occurring along the sides of offshore distributary channels.Longshore avulsions follow a sequence that usually occurs earlier distally than proximally and subsequently occurs on one longshore side and then on the other side.Each lobe begins with rapid growth,which gradually slows and then stops once a channel avulsion is influenced by the backwater effect that triggers lobe switching.Three signals indicate lobe switching:a decrease in progradation rate,foreset slope steepening coupled with topset slope gentling,and the deposition of mud-dominated sediments.The number of autocyclic events never exceeds seven.The first two autocyclicities contribute to more than 55%of delta length and 70%of delta area.The lobes are separated by 1-6 stages of mud-dominated accretion beds that exhibit a downstream-inclined shape and convexup or lateral overlapping pattern.This study conducts a coupled growth-geometric assessment to establish an architectural pattern for river-dominated lacustrine deltas.This architectural pattern offers valuable insights into predicting sandy lobe distribution in river-dominated lacustrine delta reservoirs,and the architecture of muddy accretion beds aids in predicting the rule of oil-water movement and distribution of remaining oil.展开更多
Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed ...Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation.The results show that due to the great sea level rise,the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta,and eventually to tide-dominated delta.Vertically,during the early stage of sedimentation of Oficina Formation,the distributary channels of the delta were dominated by braided river channels.While in the later stage,as the tidal effect was gradually intensified,the channel changed from braided channel to meandering channel.On plane,as a result of differential transgression,sedimentary framework and distribution of sand bodies vary across the study area.Compared with the eastern part,the western part has more braided channels,larger channel bars,less developments of distributary bay and higher ratio of sand to mud.Whereas the braided channels in the south are larger than those in the north.It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area.Factors like the structural and paleogeomorphological change,sea level variation,supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies.It is predicted that the major sandbody is more developed in the central south,which can guide the subsequent horizontal well development.展开更多
基金supported by a National Natural Science Foundation of China(No.41802123)China Postdoctoral Science Foundation funded project(No.2018M630843)Open Fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education(No.K2017-31)
文摘Autogenic processes are widely found in various sedimentary systems and they play an important role in the depositional evolution and corresponding sedimentary architecture.However,autogenic processes are often affected by changing allogenic factors and are difficult to be identified and analyzed from modern and ancient records.Through the flume tank experiment under constant boundary conditions,the depositional process,evolution principles,and the sedimentary architecture of a river-dominated delta was presented,and a corresponding sedimentary architecture model was constructed.The evolution of river-dominated delta controlled only by autogenic process is obviously periodic,and each autogenic cycle can be divided into an initial progradational stage,a middle retrogratational stage,and a late aggradational–progradational stage.In the initial progradational stage,one feeder channel incised into the delta plain,mouth bar(s)was formed in front of the channel mouth,and small-scale crevasse splays were formed on the delta plain.In the middle retrogradational stage,the feeder channel was blocked by the mouth bar(s)which grew out of water at the end of the initial stage,and a set of large-scale distributary splay complexes were formed on the delta plain.These distributary splay complexes were retrogradationally overlapped due to the continuous migration of the bifurcation point of the feeder channel.In the late aggradational–progradational stage,the feeder channel branched into several radial distributary channels,overlapped distributary channels were formed on the delta plain,and terminal lobe complexes were formed at the end of distributary channels.The three sedimentary layers formed in the three stages constituted an autogenic succession.The experimental delta consisted of six autogenic depositional successions.Dynamic allocation of accommodation space and the following adaptive sediments filling were the two main driving factors of the autogenic evolution of deltas.
基金financially supported by the National Natural Science Foundation of China(No.41772101)China Scholarship Council。
文摘River-dominated deltas are commonly developed at modern bays and lakes and ancient petroliferous basins.Water discharge is an important variable at pay zone scales in river-dominated delta reservoirs,which affects deltaic sand distributions and evolutions.However,it's unclear how it influences riverdominated delta growth.This paper integrates Delft3 D simulations and modern analogs to analyze the effects of water discharge,considering growth time,sediment supply,and coupled effects of sediment properties.High water discharges lead to the formation of lobate deltas,and the water discharge of 1,000 m~3/s is a referenced threshold value.Fine-grained,highly-cohesive sediments increase the threshold values of water discharge at which the deltas become lobate from digitate,and vice versa.For the same simulation time,high water discharges favor more rugose shorelines,more distributary channels(especially secondary distributaries),and longer and wider deltas with more land areas.However,for the same sediment supply,high water discharges have few effects on shoreline roughness and the number of distributary channels.
基金supported by Research Foundation of China University of Petroleum-Beijing at Karamay(No.XQZX20210004)。
文摘Changes in water level are one of the important factors controlling the constructive characteristics of deltas.The paper studies the influence of water level changes on sand bodies in the third member of the Shahejie Formation(Es3)on the gentle southern slope of the Gubei Sag,Bohai Bay Basin and draw some conclusions that,for complex sand bodies,with the increase in water level the distributary channels bifurcate frequently,from a simple branching shape to a network shape along with the increase in the development of crevasse splays,mouth bars and sheet sands.For single sand bodies,with an increase in water level in the slope zone of the lake basin close to the source area,the superimposition style transitioned from vertical cutting-stacking and lateral isolation to vertical stitching,isolation and lateral stitching.However,in the central zone of the lake basin far from the source area,the superimposition style transitioned from vertical stitching and lateral stitching to vertical isolation and lateral isolation.When water level stays stable,the greater the distance from the source area the greater the disaggregation ratio of a single sand body.At the same distance from the source area,higher water level tends to result in greater disaggregation ratio of a single sand body.
基金supported by National Natural Science Foundation Project of China(Nos.42272186,42302128,42202109,42472179)the Cooperation Project of the PetroChina Corporation(ZLZX2020-02)Young Elite Scientist Sponsorship Program by Bast of China(BYESS2023460)。
文摘In offshore fields with limited well data,intricate geological configurations,and high reservoir heterogeneity,the accurate prediction of sand body distribution and characterization of sedimentary architecture pose significant challenges due to inherent geological uncertainties and data limitations.This study employs a comprehensive approach integrating three key methods to enhance prediction accuracy:(i)fusion of spectral-decomposed seismic attributes,(ii)seismic attribute fusion of target and neighboring zones,and(iii)colored seismic inversion.The first method leverages seismic information across various frequencies,yielding reliable results for sand bodies of different thicknesses.The second method mitigates the impact of seismic responses from adjacent zones on sand body predictions,making it particularly suitable for target intervals where neighboring zones significantly influence the seismic response.The third one,colored seismic inversion enhances the prediction of vertical distribution and the stacking relationships of sand bodies.These methods have been applied in an oilfield in the Pearl River Mouth Basin,southern China.Consequently,the sedimentary architecture of a braided river delta reservoir is successfully characterized,leading to the identification of four distributary channels within a depositional Zone 1 of the Zhujiang Formation.Additionally,a comprehensive workflow integrating well logs,seismic data,and depositional models significantly improves predictions of sand body distribution and sedimentary architecture in complex geological settings,providing critical geological insights for optimizing subsequent oilfield development strategies.
基金supported by the National Natural Science Foundation of China(No.42202178)Science Foundation of China University of Petroleum(Beijing)(No.2462023YJRC034).
文摘River-dominated lacustrine deltas typically consist of multiple lobes due to autogenic lobe switching that occurs over short time scales.However,the switching patterns of multiple lobes in these deltas remain poorly understood,and the architectural features attributed to lobe switching are also lacking.By integrating Delft3D simulations,flume experiments,and modern deposit analysis,we proposed that autogenic lobe switching follows a cyclic pattern.Autocyclicity begins with the formation of an offshore lobe and concludes after a series of longshore lobe growth events,marked by longshore avulsions occurring along the sides of offshore distributary channels.Longshore avulsions follow a sequence that usually occurs earlier distally than proximally and subsequently occurs on one longshore side and then on the other side.Each lobe begins with rapid growth,which gradually slows and then stops once a channel avulsion is influenced by the backwater effect that triggers lobe switching.Three signals indicate lobe switching:a decrease in progradation rate,foreset slope steepening coupled with topset slope gentling,and the deposition of mud-dominated sediments.The number of autocyclic events never exceeds seven.The first two autocyclicities contribute to more than 55%of delta length and 70%of delta area.The lobes are separated by 1-6 stages of mud-dominated accretion beds that exhibit a downstream-inclined shape and convexup or lateral overlapping pattern.This study conducts a coupled growth-geometric assessment to establish an architectural pattern for river-dominated lacustrine deltas.This architectural pattern offers valuable insights into predicting sandy lobe distribution in river-dominated lacustrine delta reservoirs,and the architecture of muddy accretion beds aids in predicting the rule of oil-water movement and distribution of remaining oil.
基金supported by the Important National Science Technology Specific Projects (number 2016ZX05031-001)
文摘Based on the data of core description and sporopollen analysis,the gradual evolution of deltas in vertical direction and transition of channel types in the MPE3 block of the eastern Venezuela Basin have been surveyed by seismic phase and well logging facies interpretation.The results show that due to the great sea level rise,the sedimentary system of the Miocene Oficina Formation in the MPE3 block shifted from the distal-source sandy braided river delta to tide-affected delta,and eventually to tide-dominated delta.Vertically,during the early stage of sedimentation of Oficina Formation,the distributary channels of the delta were dominated by braided river channels.While in the later stage,as the tidal effect was gradually intensified,the channel changed from braided channel to meandering channel.On plane,as a result of differential transgression,sedimentary framework and distribution of sand bodies vary across the study area.Compared with the eastern part,the western part has more braided channels,larger channel bars,less developments of distributary bay and higher ratio of sand to mud.Whereas the braided channels in the south are larger than those in the north.It is the first time we pointed out the impact of marine transgression differences on the sedimentary facies distribution and river type transition in the study area.Factors like the structural and paleogeomorphological change,sea level variation,supply of sediments have strong influence on the evolution of sedimentary system and distribution of sandbodies.It is predicted that the major sandbody is more developed in the central south,which can guide the subsequent horizontal well development.
