2001 Vol. 19, No. 4
column
Display Method:
2001, 19(4): 481-487.
Abstract:
The evoIution of strontium isotopic composition of originaI seawater is a function of geoIogicaI time, and mainIy controIIed by the gIobaI sea-IeveI changes. The evoIutionaI curves of the strontium isotopic composition of Carboniferous and Permian marine carbonate rocks, Upper Yangtze PIatform is guite consistent with trend of the sea-IeveI changes. This variation curve of the strontium isotope shows the foIIowing facts： 1）The gIobaI sea-IeveI rise is corresponding to the faIIing of strontium isotope. The point of the minimum vaIue of 87 Sr /86 Sr in the earIy Carboniferous is just the position of maximum fIooding surface for the period of earIy Carboniferous, of which the numeric age is 342 Ma. This key point is just Iocated at the boundary of Tournaisian and Visean, for the Huishui section in Guizhou of Province, which is Iocated at the boundary between Jiusi and Shangsi formation. 2）The Iate Carboniferous is a period of gIobaI sea-IeveI faIIing. 3）The Permian, from the beginning to the end, is a period of gIobaI sea-IeveI rise. During the Iate Permian, we can see that the sea IeveI was rising unceasingIy and the marine water became deepIy in short time. 4）The Iate Permian is provided with the strontium isotopic minimum of marine carbonate rocks throughout the Late PaIaeozoic, representing the gIobaI marine fIooding event. The numeric age of the fIooding is 250 Ma, which nears to the Permian-Triassic boundary. 5）The mass extinction at the boundary of Permian-Triassic is probabIy due to the gIobaI marine fIooding event of Iate Permian.
The evoIution of strontium isotopic composition of originaI seawater is a function of geoIogicaI time, and mainIy controIIed by the gIobaI sea-IeveI changes. The evoIutionaI curves of the strontium isotopic composition of Carboniferous and Permian marine carbonate rocks, Upper Yangtze PIatform is guite consistent with trend of the sea-IeveI changes. This variation curve of the strontium isotope shows the foIIowing facts： 1）The gIobaI sea-IeveI rise is corresponding to the faIIing of strontium isotope. The point of the minimum vaIue of 87 Sr /86 Sr in the earIy Carboniferous is just the position of maximum fIooding surface for the period of earIy Carboniferous, of which the numeric age is 342 Ma. This key point is just Iocated at the boundary of Tournaisian and Visean, for the Huishui section in Guizhou of Province, which is Iocated at the boundary between Jiusi and Shangsi formation. 2）The Iate Carboniferous is a period of gIobaI sea-IeveI faIIing. 3）The Permian, from the beginning to the end, is a period of gIobaI sea-IeveI rise. During the Iate Permian, we can see that the sea IeveI was rising unceasingIy and the marine water became deepIy in short time. 4）The Iate Permian is provided with the strontium isotopic minimum of marine carbonate rocks throughout the Late PaIaeozoic, representing the gIobaI marine fIooding event. The numeric age of the fIooding is 250 Ma, which nears to the Permian-Triassic boundary. 5）The mass extinction at the boundary of Permian-Triassic is probabIy due to the gIobaI marine fIooding event of Iate Permian.
2001, 19(4): 493-500.
Abstract:
There are Iots of different viewpoints about the upIift of the Tibetan PIateau in the worId. The paper provides the proofs for recovering the history of the pIateau upIift by studying Cenozoic stratigraphy of Guide Basin in the northeast Tibetan PIateau. Cenozoic stratigraphy was deposited in Guide Basin wideIy and seven sedimentary facies associations are recognized . They are interpreted as the deposits of deep graveIIy braided, deIta, debris-fIow-dominated braided, shaIIow and haIf-deep Iake, fan deIta, graveIIy braided and piedmont proIuviaI systems, respectiveIy. The reIationship between the sedimentation of Guide basin and the upIift of the Tibetan PIateau reveaIs that the PIateau has experienced six phases in Cenozoic era：preIiminary upIift phase（Late OIigocene）, reIativeIy stabIe and denudation pIanation phase（EarIy-Miocene）, IittIe- scaIe upIift phase（Late EarIy-Miocene）, stabIe and denudation pIanation phase（MiddIe MiddIe-Miocene to Late MiddIe- Miocene）, sustain and stepwise upIift phase（8.2 ~ 3.6 Ma）, rapid and intense upIift phase（3.6 ~ 0 Ma）. The upIift in 3.6 Ma is an important stage of Cenozoic tectonic movements, before then the absoiute eievation of Guide Basin was beiow 1 000 m and since then tectonic movement became more active to form more compiex topography. So the upiift of Tibetan Piateau is a process of muitipie phases, uneguai speed, and irreguiar movement.
There are Iots of different viewpoints about the upIift of the Tibetan PIateau in the worId. The paper provides the proofs for recovering the history of the pIateau upIift by studying Cenozoic stratigraphy of Guide Basin in the northeast Tibetan PIateau. Cenozoic stratigraphy was deposited in Guide Basin wideIy and seven sedimentary facies associations are recognized . They are interpreted as the deposits of deep graveIIy braided, deIta, debris-fIow-dominated braided, shaIIow and haIf-deep Iake, fan deIta, graveIIy braided and piedmont proIuviaI systems, respectiveIy. The reIationship between the sedimentation of Guide basin and the upIift of the Tibetan PIateau reveaIs that the PIateau has experienced six phases in Cenozoic era：preIiminary upIift phase（Late OIigocene）, reIativeIy stabIe and denudation pIanation phase（EarIy-Miocene）, IittIe- scaIe upIift phase（Late EarIy-Miocene）, stabIe and denudation pIanation phase（MiddIe MiddIe-Miocene to Late MiddIe- Miocene）, sustain and stepwise upIift phase（8.2 ~ 3.6 Ma）, rapid and intense upIift phase（3.6 ~ 0 Ma）. The upIift in 3.6 Ma is an important stage of Cenozoic tectonic movements, before then the absoiute eievation of Guide Basin was beiow 1 000 m and since then tectonic movement became more active to form more compiex topography. So the upiift of Tibetan Piateau is a process of muitipie phases, uneguai speed, and irreguiar movement.
2001, 19(4): 506-511.
Abstract:
Changtu sag is Iocated in the northeast of Yan-Liao orogen as an important part of SongIiao Basin. It is fiIIed with voIcanic and sedimentary rocks, which can be grouped into three superseguences：SS!（corresponding to the rifting stage）, SS "（fauIt-rifting stage）and SS#（depressionaI stage）. During the earIy rifting, the sag was fiIIed with a huge of overfIowing and expIoding voIcanics. In the earIier fauIt-rifting stage, there deveIoped the Iowstand systems tract in Iower Jiufotang Formation that totaIIy refIects sedimentary characteristics of a thinner mudstone fIow and the expansion systems tract at the top of Jiufotang Formation that corresponded to a deep-water environment, incIuding fan-deIta and haIf-deep-Iake and deep- Iake. During the Iater fauIt-rifting stage, the depth of water became shaIIower with the predominant sedimentary facies of aIIuviaI apron, fan-deIta, swamp and offshore and shaIIow Iake and so on. The Jiufotang Formation was mainIy composed of muIti-compositionaI congIomerates and sandstones, of which the detritaI composition was dominated by voIcanic cIastics, suggesting their derivation from the earIier erupted voIcanic seguences which was rapidIy unroofed during the upIifting of the orogen. The Shahai Formation was mainIy composed of congIomerates, sandstones, interbeddings between sandstones and mudstone. DetritaI anaIysis shows that at the upper Shahai Fm., there occurred some proportion of metamorphic and granitic components, indicating the increase in the amount of upIifting and unroofing of the entire orogen whiIst the Iowering of upIifting rate. As the sedimentation continued, the centre of sediment and depression moved northwards, refIecting that Yan-Iiao orogen was continuousIy upIifted and separated during Iate Cretaceous. The emergence of the three Iowstand system tracts and three rifting activities demanded that the orogen had undergone at Ieast three rapid upIifting episodes during Cretaceous.
Changtu sag is Iocated in the northeast of Yan-Liao orogen as an important part of SongIiao Basin. It is fiIIed with voIcanic and sedimentary rocks, which can be grouped into three superseguences：SS!（corresponding to the rifting stage）, SS "（fauIt-rifting stage）and SS#（depressionaI stage）. During the earIy rifting, the sag was fiIIed with a huge of overfIowing and expIoding voIcanics. In the earIier fauIt-rifting stage, there deveIoped the Iowstand systems tract in Iower Jiufotang Formation that totaIIy refIects sedimentary characteristics of a thinner mudstone fIow and the expansion systems tract at the top of Jiufotang Formation that corresponded to a deep-water environment, incIuding fan-deIta and haIf-deep-Iake and deep- Iake. During the Iater fauIt-rifting stage, the depth of water became shaIIower with the predominant sedimentary facies of aIIuviaI apron, fan-deIta, swamp and offshore and shaIIow Iake and so on. The Jiufotang Formation was mainIy composed of muIti-compositionaI congIomerates and sandstones, of which the detritaI composition was dominated by voIcanic cIastics, suggesting their derivation from the earIier erupted voIcanic seguences which was rapidIy unroofed during the upIifting of the orogen. The Shahai Formation was mainIy composed of congIomerates, sandstones, interbeddings between sandstones and mudstone. DetritaI anaIysis shows that at the upper Shahai Fm., there occurred some proportion of metamorphic and granitic components, indicating the increase in the amount of upIifting and unroofing of the entire orogen whiIst the Iowering of upIifting rate. As the sedimentation continued, the centre of sediment and depression moved northwards, refIecting that Yan-Iiao orogen was continuousIy upIifted and separated during Iate Cretaceous. The emergence of the three Iowstand system tracts and three rifting activities demanded that the orogen had undergone at Ieast three rapid upIifting episodes during Cretaceous.
2001, 19(4): 517-523.
Abstract:
The depositionai features of Cretaceous braided deita in Kuga depression can be conciuded as that（1）the sediments are very coarse, and the median-grained sandstone and fine-grained sandstone are the main rock types with a proportion from 60% to 80% of the totai sandstones. The maximum can be up to 95%;（2）most of these sandstones are composed of feidspathic, iithic feidspathic and iithic sandstone with 30% ~ 50% of guartz and rich in iithociast;（3）sedimentary structures are mainiy massive bedding, iarge trough cross bedding and obiigue bedding with few paraiiei bedding, wave bedding and horizotai bedding;（4）main sedimentary period of the braided channei is fiood stage, so the sedimentation is characterized by rapid migration of channeis with different stages to form thick and continuous sandstone iayers by iots of super imposed sandbodies, which are separated by some thin intercaiated peiitic beds. Based on the data obtained from thin sections, cathodoiuminescence and SEM of outcrop and core sampies, the diagenes can be determined as compaction, cementation, dissoiution, repiacement, pressure dissoiution and recrystaiiization.According to authigenic minerai, ciay minerai, 5% in mix-iayered I /S, inciusion temperature and diagenetic types, the diagenetic stage of the Cretaceous in the study area have reached a period of the iate diagenetic stage. Features of ciay minerais show speciai types and assembiages formed under aikiine diagenetic environment. There are abundant pore types in Cretaceous sandstones, which inciude intergranuiar pore, intragranuiar pore, grain-dissoived pore, matrix-dissoived pore, intercrystai pore, primary intergranuiar pore and structurai fractures.
The depositionai features of Cretaceous braided deita in Kuga depression can be conciuded as that（1）the sediments are very coarse, and the median-grained sandstone and fine-grained sandstone are the main rock types with a proportion from 60% to 80% of the totai sandstones. The maximum can be up to 95%;（2）most of these sandstones are composed of feidspathic, iithic feidspathic and iithic sandstone with 30% ~ 50% of guartz and rich in iithociast;（3）sedimentary structures are mainiy massive bedding, iarge trough cross bedding and obiigue bedding with few paraiiei bedding, wave bedding and horizotai bedding;（4）main sedimentary period of the braided channei is fiood stage, so the sedimentation is characterized by rapid migration of channeis with different stages to form thick and continuous sandstone iayers by iots of super imposed sandbodies, which are separated by some thin intercaiated peiitic beds. Based on the data obtained from thin sections, cathodoiuminescence and SEM of outcrop and core sampies, the diagenes can be determined as compaction, cementation, dissoiution, repiacement, pressure dissoiution and recrystaiiization.According to authigenic minerai, ciay minerai, 5% in mix-iayered I /S, inciusion temperature and diagenetic types, the diagenetic stage of the Cretaceous in the study area have reached a period of the iate diagenetic stage. Features of ciay minerais show speciai types and assembiages formed under aikiine diagenetic environment. There are abundant pore types in Cretaceous sandstones, which inciude intergranuiar pore, intragranuiar pore, grain-dissoived pore, matrix-dissoived pore, intercrystai pore, primary intergranuiar pore and structurai fractures.
2001, 19(4): 530-535.
Abstract:
In the Dagang region, the Ordovician is 600 ~ 800 m thick and mainIy consists of Iimestones and doIostones. Karst reservoirs are deveIoped. The main controIs on karst reservoirs are ：IithoIogy, depositionaI environments, hydroIogy, an- cient Iandform, fractures and weathering time and so on. The IithoIogy composed of doIostones and gypsum is favorabIe for the deveIopment of karst reservoirs. TidaI fIat environments are favorabIe facies to deveIop karst reservoirs. Karst reservoirs are mainIy deveIoped 20 to 200 m beneath the unconformity. Beofore the Carboniferous, the Iand surface of the study area incIined from southwest to northeast, and the ground water fIew from southwest to northeast. Karst reservoir beIt formed in this time aIso trends southwest-northeast. The karst sIope and karst depression with no standing water are favorabIe for the karst reservoir deveIopment, especiaIIy the karst sIope. Karst reservoirs tend to deveIop in the pIace where fractures and fauIts are abundant, and the trend of fractures and fauIts controIs the trend of karst reservoir beIts The Ionger the weathering time, the better the karst wiIIbe deveIoped.
In the Dagang region, the Ordovician is 600 ~ 800 m thick and mainIy consists of Iimestones and doIostones. Karst reservoirs are deveIoped. The main controIs on karst reservoirs are ：IithoIogy, depositionaI environments, hydroIogy, an- cient Iandform, fractures and weathering time and so on. The IithoIogy composed of doIostones and gypsum is favorabIe for the deveIopment of karst reservoirs. TidaI fIat environments are favorabIe facies to deveIop karst reservoirs. Karst reservoirs are mainIy deveIoped 20 to 200 m beneath the unconformity. Beofore the Carboniferous, the Iand surface of the study area incIined from southwest to northeast, and the ground water fIew from southwest to northeast. Karst reservoir beIt formed in this time aIso trends southwest-northeast. The karst sIope and karst depression with no standing water are favorabIe for the karst reservoir deveIopment, especiaIIy the karst sIope. Karst reservoirs tend to deveIop in the pIace where fractures and fauIts are abundant, and the trend of fractures and fauIts controIs the trend of karst reservoir beIts The Ionger the weathering time, the better the karst wiIIbe deveIoped.
2001, 19(4): 541-547.
Abstract:
The reservoir guaiity of the Upper Triassic Chang 2 fiuviai-deitaic sandstones of the Yanchang Oii Fieid in Ordos basin is strongiy infiuenced by the buriai history and facies-reiated diagenetic events. The mechanicai compaction in the eariy diagenetic phase, which resuited in 17.8% porosity ioss, is the main factor causing the ioss of porosity for the sandstones. The diagenetic aiteration of biotite during eariy diagenetic phase accounts for a part of primary porosity ioss in the sandstones. The porosity ioss caused by cementation is 7.1%. In the cements, carbonate and guartz overgrowths are the main cements that reduced the reservoir guaiity of the sandstones. Thin chiorite fiim around detritai guartz grains prevented part of guartz overgrowth and carbonate cement precipitation, which resuited in a part of primary pore preservation and hence caused a better reservoir guaiity. The acidic iiguid reiated to decomposition of organic mater during hydrocarbon enrichment in the iate diagenesis, and meteoric-waters during epidiagenesis, have resuited in dissoiution of detritai feidspars and carbonate cements, and in the formation of kaoiinite, contributing a better retention of reservoir guaiity for the sandstones.
The reservoir guaiity of the Upper Triassic Chang 2 fiuviai-deitaic sandstones of the Yanchang Oii Fieid in Ordos basin is strongiy infiuenced by the buriai history and facies-reiated diagenetic events. The mechanicai compaction in the eariy diagenetic phase, which resuited in 17.8% porosity ioss, is the main factor causing the ioss of porosity for the sandstones. The diagenetic aiteration of biotite during eariy diagenetic phase accounts for a part of primary porosity ioss in the sandstones. The porosity ioss caused by cementation is 7.1%. In the cements, carbonate and guartz overgrowths are the main cements that reduced the reservoir guaiity of the sandstones. Thin chiorite fiim around detritai guartz grains prevented part of guartz overgrowth and carbonate cement precipitation, which resuited in a part of primary pore preservation and hence caused a better reservoir guaiity. The acidic iiguid reiated to decomposition of organic mater during hydrocarbon enrichment in the iate diagenesis, and meteoric-waters during epidiagenesis, have resuited in dissoiution of detritai feidspars and carbonate cements, and in the formation of kaoiinite, contributing a better retention of reservoir guaiity for the sandstones.
2001, 19(4): 563-568.
Abstract:
According to the comprehensive anaiysis of the data of weii iogging, core, seismic and change of heavy-minera, under the guide of the thought and methodoiogy of high-resoiution seguence stratigraphy, and identification of seguence boundary generated by base-ievei cycie, the seguence stratigraphic framework in Weizhou Formation has been estabiished, and 3 super seguence, 9 seguence have been recognized. Seguence characteristics and sedimentary system formation have been investigated. Spatiaiiy, based on the study of depositionai environment in the unit of chronoiogicai seguence, the system tracts and depositionai system were traced. Temporaiiy, the authors have studied the basin evoiution with every seguence and fauiting action on depositionai fiiiing. The deveiopment of basin-fiii supper seguences in Weizhou Formation is controiied by middie term base-ievei cycie change. Because piace difference of seguence stratigraphic unit in middie term base-ievei cycie, stratigraphic thickness, ciassification and distribution of sedimentary system make obvious difference. Lowstand system trac（t LST）deveioped, there had mostiy deveioped braided river deita, aiiuviai fan, siop fan, muitipie fan, fan deitas and near shore subfan sediments in middie term base-ievei cycie faii-rise eariy stage. Water transgressive system trac（t TST）dformed, there mostiy deveioped fine-grain iake faces sediments in middie term base-ievei cycie rise stage. Highstand system trac（t HST）formed, there mostiy deveioped shaiiow iacustrine, fiuviai-deita and fan deitas sedimentary system in middie term base-ievei cycie iate stage. It couid be conciuded that, in Weizhou Formation, most oii- bearing formations are controiied by seguence 2 and seguence 3 of supper seguence 1, and reservoirs are mostiy sandbody in LST and TST. The seai and structure jointiy made the composite traps. The important commerciai accumuiation of oii and gas were formed in North sag of Beibuwan basin.
According to the comprehensive anaiysis of the data of weii iogging, core, seismic and change of heavy-minera, under the guide of the thought and methodoiogy of high-resoiution seguence stratigraphy, and identification of seguence boundary generated by base-ievei cycie, the seguence stratigraphic framework in Weizhou Formation has been estabiished, and 3 super seguence, 9 seguence have been recognized. Seguence characteristics and sedimentary system formation have been investigated. Spatiaiiy, based on the study of depositionai environment in the unit of chronoiogicai seguence, the system tracts and depositionai system were traced. Temporaiiy, the authors have studied the basin evoiution with every seguence and fauiting action on depositionai fiiiing. The deveiopment of basin-fiii supper seguences in Weizhou Formation is controiied by middie term base-ievei cycie change. Because piace difference of seguence stratigraphic unit in middie term base-ievei cycie, stratigraphic thickness, ciassification and distribution of sedimentary system make obvious difference. Lowstand system trac（t LST）deveioped, there had mostiy deveioped braided river deita, aiiuviai fan, siop fan, muitipie fan, fan deitas and near shore subfan sediments in middie term base-ievei cycie faii-rise eariy stage. Water transgressive system trac（t TST）dformed, there mostiy deveioped fine-grain iake faces sediments in middie term base-ievei cycie rise stage. Highstand system trac（t HST）formed, there mostiy deveioped shaiiow iacustrine, fiuviai-deita and fan deitas sedimentary system in middie term base-ievei cycie iate stage. It couid be conciuded that, in Weizhou Formation, most oii- bearing formations are controiied by seguence 2 and seguence 3 of supper seguence 1, and reservoirs are mostiy sandbody in LST and TST. The seai and structure jointiy made the composite traps. The important commerciai accumuiation of oii and gas were formed in North sag of Beibuwan basin.
2001, 19(4): 575-580.
Abstract:
This paper is concerned about the study of seguence stratigraphy of Jurasssic in East Fukang Slope, Junggar Basin. East Fukang Slope is located in Northeast Junggar basin, a dipping southwest sloping zone. The area is about 5 000 km2. Because Jurassic was rarely deformed by the tectonic movement, there are few structural traps with obvious structural closure in this area. Therefore, it is necessary to seek lithological or stratigraphic traps guided by seguence stratigraphic theory. Jurassic in East Fukang Slope consists of Lower Jurassic, including Badaowan Formation（J1 b）and Sangonghe Formation （J1 s）, Middle Jurassic, Xishanyao Formation（J2 x）and Toutunhe Formation（J2t）, and Upper Jurassic, Oigu Formation （J3 q）and Kalazha Formation（J3 k）. Combining with core data, well logging data, seismic data and analysis data in lab, Jurassic could be divided into six seguences, that is：Seguence I（SI）（J1 b1）, SI（I J1 b2）, SII（I J1 s—J2 x1）, SIV（J2 x2）, SV（J2 t）and SV（I J3 g—J3 k）from bottom to top. Moreover, according to synthetic seismic data, the divisions of core and well logging seguence are identical with seismic seguence. The distinguished marks of seguence boundary include：surface of unconformity, the mutation surfaces of fossil, lithology, well logging curve and sedimentary facies, basal conglomerate and surface of scour, coal formation , etc. The definition of the first flooding surface（FFS）and the maximum surface（MFS）is the significant step for the division of systems tract. In the period of Jurassic, due to the steep slope from Baijiahai uplift to Changji sag and the gentle slope from Cainan region to Kelameili Mountain, a slope break formed in the southeast of Baijiahai uplift. Therefore, the FFS can be determined, resulting in the definition of lowstand systems tract（LST）, transgrassive systems tract（TST）and highstand system trac（t HST）. In the study area, identified marks of systems tract boundary include the followings：the first steady and continuous seismic axis across the slope break can indicate the FFS;coal formation or danby？can indicate FFS or MFS;the change of lapping style of subseguences and the change of the colour of sedimentary rocks are available as well. LST is mainly composed of prograding subseguence, TST of aggradating and retrograding subseguences, and HST of aggradating and prograding subseguences. Combining with the paleo - topography feature, the distribution of significant coal formation and the position of FFS and MFS, the seguence stratigraphic model or frame has been established in East Fukang Slope. This model shows that the seguence stratigraphic style of Jurassic apparently was influenced by cycle of relative change of lake level, resulting in the onlaps on the steep side of lake basin regularly moving. The principal factors of seguence stratigraphic style of Jurassic include tectonic subsidence, the supplying rate of sediment, climate and the change of base level. Tectonization was the direct one, by which the unconformity boundary, the most apparent identified mark, was formed. Tectonic subsidence controlled the generation and consumption of accommodation. The changes of sediment supplying rate and subsidence rate could influence the lapping styles of subseguence sets and systems tract. In addition, the change of base level was one of the most significant factors which resulted in the change of accommodation and relative lake level.
This paper is concerned about the study of seguence stratigraphy of Jurasssic in East Fukang Slope, Junggar Basin. East Fukang Slope is located in Northeast Junggar basin, a dipping southwest sloping zone. The area is about 5 000 km2. Because Jurassic was rarely deformed by the tectonic movement, there are few structural traps with obvious structural closure in this area. Therefore, it is necessary to seek lithological or stratigraphic traps guided by seguence stratigraphic theory. Jurassic in East Fukang Slope consists of Lower Jurassic, including Badaowan Formation（J1 b）and Sangonghe Formation （J1 s）, Middle Jurassic, Xishanyao Formation（J2 x）and Toutunhe Formation（J2t）, and Upper Jurassic, Oigu Formation （J3 q）and Kalazha Formation（J3 k）. Combining with core data, well logging data, seismic data and analysis data in lab, Jurassic could be divided into six seguences, that is：Seguence I（SI）（J1 b1）, SI（I J1 b2）, SII（I J1 s—J2 x1）, SIV（J2 x2）, SV（J2 t）and SV（I J3 g—J3 k）from bottom to top. Moreover, according to synthetic seismic data, the divisions of core and well logging seguence are identical with seismic seguence. The distinguished marks of seguence boundary include：surface of unconformity, the mutation surfaces of fossil, lithology, well logging curve and sedimentary facies, basal conglomerate and surface of scour, coal formation , etc. The definition of the first flooding surface（FFS）and the maximum surface（MFS）is the significant step for the division of systems tract. In the period of Jurassic, due to the steep slope from Baijiahai uplift to Changji sag and the gentle slope from Cainan region to Kelameili Mountain, a slope break formed in the southeast of Baijiahai uplift. Therefore, the FFS can be determined, resulting in the definition of lowstand systems tract（LST）, transgrassive systems tract（TST）and highstand system trac（t HST）. In the study area, identified marks of systems tract boundary include the followings：the first steady and continuous seismic axis across the slope break can indicate the FFS;coal formation or danby？can indicate FFS or MFS;the change of lapping style of subseguences and the change of the colour of sedimentary rocks are available as well. LST is mainly composed of prograding subseguence, TST of aggradating and retrograding subseguences, and HST of aggradating and prograding subseguences. Combining with the paleo - topography feature, the distribution of significant coal formation and the position of FFS and MFS, the seguence stratigraphic model or frame has been established in East Fukang Slope. This model shows that the seguence stratigraphic style of Jurassic apparently was influenced by cycle of relative change of lake level, resulting in the onlaps on the steep side of lake basin regularly moving. The principal factors of seguence stratigraphic style of Jurassic include tectonic subsidence, the supplying rate of sediment, climate and the change of base level. Tectonization was the direct one, by which the unconformity boundary, the most apparent identified mark, was formed. Tectonic subsidence controlled the generation and consumption of accommodation. The changes of sediment supplying rate and subsidence rate could influence the lapping styles of subseguence sets and systems tract. In addition, the change of base level was one of the most significant factors which resulted in the change of accommodation and relative lake level.
2001, 19(4): 586-591.
Abstract:
DetaiIed source rock investigation of "immature oiI"from Bamianhe oiIfieId, Jiyang depression, Eastern China has been carried out not onIy through normaI organic geochemicaI anaIysis, but aIso through absoIute guantitative anaIysis of biomarkers in severaI fractions by co-injection of standard compounds. The oiIs anaIyzed are derived from reducing hypersaIine source depositionaI environment, and have characteristics of oiIs from some other rift basin of eastern China such as Iow Pr /Ph, high abundance of Gammacerane and MTTC. ResuIts indicate that sterane parameters of C29ααα20S/（S + R）of the oiIs in Bamianhe fracture beIt is in the range of 0.3l ~ 0.44 and the oiIs in Tanhai tectonic beIt is Iower than 0.30 showing reIativeIy Iow isomerization. However, other maturity parameters such as n-aIkane carbon number preference index, C3l hopane 22S/（22S + 22R）ratio indices and so on generaIIy show sIight difference between the oiIs, and indicate aII the oiIs have characteristics of mature oiI. OiI-source correIation reveaI that the Iacustrine shaIes of Sahejie Formation distributed above the conventionaI oiI windows, which were considered as effective source intervaIs in a number of Iiterature reports, is not effective petroIeum source beds. The so-caIIed immature oiIs are stiII mostIy from shaIe and mudstone probabIy with buried depth higher than 2700 meter, which is within the conventionaI oiI windows. It is suggested that some Iow maturation characteristics of the oiIs such as reIativeIy Iow C29 steraneααα20S/（S + R）vaIue and the existence of 5β（H）-choIestane are resuIts from the mixing of a IittIe amount immature hydrocarbon or oiIs with Iarge amount of mature oiIs. Then, the genetic mechanism of the so-caIIed immature oiI of Bamianhe oiIfieId stiII obey the degradation theory of kerogen proposed by Tissort.
DetaiIed source rock investigation of "immature oiI"from Bamianhe oiIfieId, Jiyang depression, Eastern China has been carried out not onIy through normaI organic geochemicaI anaIysis, but aIso through absoIute guantitative anaIysis of biomarkers in severaI fractions by co-injection of standard compounds. The oiIs anaIyzed are derived from reducing hypersaIine source depositionaI environment, and have characteristics of oiIs from some other rift basin of eastern China such as Iow Pr /Ph, high abundance of Gammacerane and MTTC. ResuIts indicate that sterane parameters of C29ααα20S/（S + R）of the oiIs in Bamianhe fracture beIt is in the range of 0.3l ~ 0.44 and the oiIs in Tanhai tectonic beIt is Iower than 0.30 showing reIativeIy Iow isomerization. However, other maturity parameters such as n-aIkane carbon number preference index, C3l hopane 22S/（22S + 22R）ratio indices and so on generaIIy show sIight difference between the oiIs, and indicate aII the oiIs have characteristics of mature oiI. OiI-source correIation reveaI that the Iacustrine shaIes of Sahejie Formation distributed above the conventionaI oiI windows, which were considered as effective source intervaIs in a number of Iiterature reports, is not effective petroIeum source beds. The so-caIIed immature oiIs are stiII mostIy from shaIe and mudstone probabIy with buried depth higher than 2700 meter, which is within the conventionaI oiI windows. It is suggested that some Iow maturation characteristics of the oiIs such as reIativeIy Iow C29 steraneααα20S/（S + R）vaIue and the existence of 5β（H）-choIestane are resuIts from the mixing of a IittIe amount immature hydrocarbon or oiIs with Iarge amount of mature oiIs. Then, the genetic mechanism of the so-caIIed immature oiI of Bamianhe oiIfieId stiII obey the degradation theory of kerogen proposed by Tissort.
2001, 19(4): 598-604.
Abstract:
Most of the oiis found in Santanghu basin were regards as immature, mainiy because the vaiues of 20S/（20S + 20R）of C29 sterane are iower than 0.42. Compared with other immature oiis reported in china, they have some speciai characteristics.Through anaiyzes to oii source, these immature oiis mainiy come from Lucaogou Formation of upper Permian which is better source rocks with iow maturity and much abundance of organic matter. Different from other immature source rocks in Santang iake basin, Lucaogou formation abounds with sapropeiic amorphous that content abundant hydrogen. It can be iearned through pyroiysis that the sapropeiic amorphous is the main contributor of hydrocarbon in Lucaogou formation and the Ro of its main hydrocarbon-generating intervai is from 0.35% to 0.6%, which is the main hydrocarbon-generating mechanism of the immature oiis in Santang iake basin. Furthermore, The series of 17α（H）- 25 - norhopane compound was found not oniy in oii, but aiso in Lucaogou formation, which hints that the immature oiis in Santang iake basin may have reiations with the bacteria degradation of terrigenous organic matter.
Most of the oiis found in Santanghu basin were regards as immature, mainiy because the vaiues of 20S/（20S + 20R）of C29 sterane are iower than 0.42. Compared with other immature oiis reported in china, they have some speciai characteristics.Through anaiyzes to oii source, these immature oiis mainiy come from Lucaogou Formation of upper Permian which is better source rocks with iow maturity and much abundance of organic matter. Different from other immature source rocks in Santang iake basin, Lucaogou formation abounds with sapropeiic amorphous that content abundant hydrogen. It can be iearned through pyroiysis that the sapropeiic amorphous is the main contributor of hydrocarbon in Lucaogou formation and the Ro of its main hydrocarbon-generating intervai is from 0.35% to 0.6%, which is the main hydrocarbon-generating mechanism of the immature oiis in Santang iake basin. Furthermore, The series of 17α（H）- 25 - norhopane compound was found not oniy in oii, but aiso in Lucaogou formation, which hints that the immature oiis in Santang iake basin may have reiations with the bacteria degradation of terrigenous organic matter.
2001, 19(4): 611-616.
Abstract:
Linnan Area iocated in western Jiyang Depression, Bohai Guif Basin. Formations reveaied by driiiing inciudes Cambrian, Ordovician, Carboniferous, Permian, Jurassic, Tertiary and Ouaternary. The third member（Es3 ）of Shahe Jie Formation of Tertiary is the most important source rock of Linnan Sag and contributes to aii oiifieids around Linnan Sag. The Es3 has a sedimentary environment of deep to semi-deep iake facies, Kerogen type ! to Ⅱ1 in south and Ⅱ in north Linnan Sag and a high content of organic matter, so it possesses a great potentiai of hydrocarbon generation. The second migration direction and distance of oii are forecasted according to nitrogen-containing compounds and maturation indicators of biomarker in oii sand extracts. The oii in Linnan Sag migrated toward four main directions, i. e. Linpan, Shanghe, Outi and Linnan Oiifieid. The carbazoie content and C29 sterane S（/S + R）decrease and the 1- /4-methyi carbazoie increase with the distance increasing from the center of Linnan Sag to aii oiifieids around it. The anaiysis of hydrocarbon composition inside inciusions shows that oniy one process of migration and accumuiation of oii took piace in Linnan Oiifieid and that this kind of oii beiongs to mature oii formed during iate Miocene Epoch and have a high 4-mythyi sterane content. Two kinds of oii exist in Outi Oiifieid, the first, formed during iate Oiigocene Epoch, has a iow 4-mythyi sterane content and a iow maturation ievei, and migrated to far traps and then escaped. The second is mature oii with a high 4-mythyi sterane and have kept accumuiation state at present. In north area, the oii accumuiation process of Linpan Oiifieid has the same substance with Outi Oiifieid, and Shanghe Oiifieid is simiiar to Linnan Oiifieid.
Linnan Area iocated in western Jiyang Depression, Bohai Guif Basin. Formations reveaied by driiiing inciudes Cambrian, Ordovician, Carboniferous, Permian, Jurassic, Tertiary and Ouaternary. The third member（Es3 ）of Shahe Jie Formation of Tertiary is the most important source rock of Linnan Sag and contributes to aii oiifieids around Linnan Sag. The Es3 has a sedimentary environment of deep to semi-deep iake facies, Kerogen type ! to Ⅱ1 in south and Ⅱ in north Linnan Sag and a high content of organic matter, so it possesses a great potentiai of hydrocarbon generation. The second migration direction and distance of oii are forecasted according to nitrogen-containing compounds and maturation indicators of biomarker in oii sand extracts. The oii in Linnan Sag migrated toward four main directions, i. e. Linpan, Shanghe, Outi and Linnan Oiifieid. The carbazoie content and C29 sterane S（/S + R）decrease and the 1- /4-methyi carbazoie increase with the distance increasing from the center of Linnan Sag to aii oiifieids around it. The anaiysis of hydrocarbon composition inside inciusions shows that oniy one process of migration and accumuiation of oii took piace in Linnan Oiifieid and that this kind of oii beiongs to mature oii formed during iate Miocene Epoch and have a high 4-mythyi sterane content. Two kinds of oii exist in Outi Oiifieid, the first, formed during iate Oiigocene Epoch, has a iow 4-mythyi sterane content and a iow maturation ievei, and migrated to far traps and then escaped. The second is mature oii with a high 4-mythyi sterane and have kept accumuiation state at present. In north area, the oii accumuiation process of Linpan Oiifieid has the same substance with Outi Oiifieid, and Shanghe Oiifieid is simiiar to Linnan Oiifieid.
2001, 19(4): 630-636.
Abstract:
Magnetic effects in sediment of Yangtze River estuary tidal flat is studied in laboratory by different drying treatments. Three treatments, including oven-drying, air-drying and lyophilization are applied in the core（total length：21 cm, sampled from high tidal-flat）and tidal flat surface（0 ~ 5 cm）sediment samples（high, middle and low tidal flat）, and then the magnetic properties, water and total organic matter contents has been measured systematically. Results show that oven-drying, air-drying and lyophilization treatment processes de affect the most of magnetic minerals . The SIRM—χ crossplot of the core samples shows linearly significant correlation, the upper part sub-samples of the core have high value of SIRM andχ , the bottom part have low value of SIRM andχ. According to F300mT, "S- 20mT and"S- 100mT, ferrimagnetic minerals dominate the magnetic properties in the Yangtze River estuary tidal flat sediments. The particlesize of whole core become finer from bottom to upper sub-samples. The differences of the three samples treatments are insignificant, according to type of magnetic minerals, consistence of dominated magnetic minerals, concentration of magnetic minerals and particle size, in the whole core sub-samples and its variations. The oven-drying is still effective sample treatment, and the lyophilization is the best sample drying method of the three. Under the general condition, the effect of oven-drying and air-drying samples to magnetic change, compare with lyophilization, is so little that it does not result in magnetic parameters wrong interpretation. However, for clay samples, airdrying samples will cause much difference in the value of magnetic parameters, thus its air-drying water contents after magnetic measurement should be avoided or calibrated. Another result shows that organic matter contents are positively correlated with main magnetic parameters. This study has some limits because of only test for the tidal flat sediment samples, so if do some further deduction on this topic, more studies on various sediments and soiis sampies are necessary.
Magnetic effects in sediment of Yangtze River estuary tidal flat is studied in laboratory by different drying treatments. Three treatments, including oven-drying, air-drying and lyophilization are applied in the core（total length：21 cm, sampled from high tidal-flat）and tidal flat surface（0 ~ 5 cm）sediment samples（high, middle and low tidal flat）, and then the magnetic properties, water and total organic matter contents has been measured systematically. Results show that oven-drying, air-drying and lyophilization treatment processes de affect the most of magnetic minerals . The SIRM—χ crossplot of the core samples shows linearly significant correlation, the upper part sub-samples of the core have high value of SIRM andχ , the bottom part have low value of SIRM andχ. According to F300mT, "S- 20mT and"S- 100mT, ferrimagnetic minerals dominate the magnetic properties in the Yangtze River estuary tidal flat sediments. The particlesize of whole core become finer from bottom to upper sub-samples. The differences of the three samples treatments are insignificant, according to type of magnetic minerals, consistence of dominated magnetic minerals, concentration of magnetic minerals and particle size, in the whole core sub-samples and its variations. The oven-drying is still effective sample treatment, and the lyophilization is the best sample drying method of the three. Under the general condition, the effect of oven-drying and air-drying samples to magnetic change, compare with lyophilization, is so little that it does not result in magnetic parameters wrong interpretation. However, for clay samples, airdrying samples will cause much difference in the value of magnetic parameters, thus its air-drying water contents after magnetic measurement should be avoided or calibrated. Another result shows that organic matter contents are positively correlated with main magnetic parameters. This study has some limits because of only test for the tidal flat sediment samples, so if do some further deduction on this topic, more studies on various sediments and soiis sampies are necessary.
2001, 19(4): 648-651.
Abstract:
The paiaeociimatic and paiaeoenvironmentai information is studied by using the carbon and oxygen isotope profiies from the Late Pieistocene Lamprotula in Linfen and Xiangfe areas, where occur aboundant iameiiibranchs, especiaiiy fossii Lamprotula. The conciusions are as foiiows：1. The cessation of Lamprotula（Cuneolamprotula）bazini（Heude）sheii deposition in faii and summer is rich in16O, withδ 18O vaiue of - 14.5‰, whiie one in winter and spring is rich in18O, with δ 18O vaiue of - 12.2‰, and this fiuctuationof 2.2‰ may indicate a magnitute of change in seasonai temperature of water up to 10℃.2. The paiaeoenviroment of fossii Lamprotula was simiiar to ecoiogy of iiving Lamprotula in iower reaches of the Yangtze river, thus the most suitabie water for the Late Pieistocene Lamprotula was at temperature of 25 ~ 29℃ with a pH vaiue of 7 ~ 8. Therefore, the seasonai temperature of water changes from 20 ~ 24℃ to 30 ~ 34℃. 3. The sheii mean oxygen isotope vaiues of Lamprotula（Cuneolamprotula）bazini（Heude）and Lamprotula（ Lamprotula） zonata（Heude）are - 12.9‰ and - 12.6 ‰, respectiveiy. This sheiiδ18O vaiues can be converted to waterδ18O vaiues by the iinear eguationδ 18Op（ SM0W）= 1.07δ 18O s - 0.58, and, therefore, δ 18O vaiues of water where their iived is about - 14.4‰~ - 14.1‰. These vaiues are approximateiy 4‰ iighter than the meanδ 18O vaiue of the present rainfaii（ - 10‰）. It suggests that the annuai mean precipitation on Xiangfe Lake during the Late Pieistocene exceeded that of the pvesent by 200 ~ 267 mm.
The paiaeociimatic and paiaeoenvironmentai information is studied by using the carbon and oxygen isotope profiies from the Late Pieistocene Lamprotula in Linfen and Xiangfe areas, where occur aboundant iameiiibranchs, especiaiiy fossii Lamprotula. The conciusions are as foiiows：1. The cessation of Lamprotula（Cuneolamprotula）bazini（Heude）sheii deposition in faii and summer is rich in16O, withδ 18O vaiue of - 14.5‰, whiie one in winter and spring is rich in18O, with δ 18O vaiue of - 12.2‰, and this fiuctuationof 2.2‰ may indicate a magnitute of change in seasonai temperature of water up to 10℃.2. The paiaeoenviroment of fossii Lamprotula was simiiar to ecoiogy of iiving Lamprotula in iower reaches of the Yangtze river, thus the most suitabie water for the Late Pieistocene Lamprotula was at temperature of 25 ~ 29℃ with a pH vaiue of 7 ~ 8. Therefore, the seasonai temperature of water changes from 20 ~ 24℃ to 30 ~ 34℃. 3. The sheii mean oxygen isotope vaiues of Lamprotula（Cuneolamprotula）bazini（Heude）and Lamprotula（ Lamprotula） zonata（Heude）are - 12.9‰ and - 12.6 ‰, respectiveiy. This sheiiδ18O vaiues can be converted to waterδ18O vaiues by the iinear eguationδ 18Op（ SM0W）= 1.07δ 18O s - 0.58, and, therefore, δ 18O vaiues of water where their iived is about - 14.4‰~ - 14.1‰. These vaiues are approximateiy 4‰ iighter than the meanδ 18O vaiue of the present rainfaii（ - 10‰）. It suggests that the annuai mean precipitation on Xiangfe Lake during the Late Pieistocene exceeded that of the pvesent by 200 ~ 267 mm.
2001, 19(4): 488-492.
Abstract:
Based on the detaiIed regionaI geoIogicaI setting anaIysis, this paper deaIs with the research of ore-bearing basin, the depositionaI facies and seguence stratigraphic anaIysis have been done for the first time in ShaIagang mining region.And aII kinds of characteristic gravity-fIow sediments, for erampIe, sIide, debris-fIow and turbidity deposits, are significantIy documented . SiIiceous submarine fans made up of different grain sizes and different types of siIiceous rock are aIso discovered for the first time in Gyangze basin. The evoIution stages of depositionaI fiIIing with sIope setting are divided in Gyangze basin
Based on the detaiIed regionaI geoIogicaI setting anaIysis, this paper deaIs with the research of ore-bearing basin, the depositionaI facies and seguence stratigraphic anaIysis have been done for the first time in ShaIagang mining region.And aII kinds of characteristic gravity-fIow sediments, for erampIe, sIide, debris-fIow and turbidity deposits, are significantIy documented . SiIiceous submarine fans made up of different grain sizes and different types of siIiceous rock are aIso discovered for the first time in Gyangze basin. The evoIution stages of depositionaI fiIIing with sIope setting are divided in Gyangze basin
2001, 19(4): 501-505.
Abstract:
There are many outcrops of middIe Jurassic Series in the Yungang area of Datong Basin. Some of them are the sections that were cut during road buiIding. Others are the outcrops formed by naturaI erosion. However, the outcrops are the fine windows to study the depositionaI system of the Jurassic stratum. Chen et aI（1962）onIy thought that the Iower Jurassic Series was deposited by the fIuviaI river in pIain and the upper Jurassic Series was deposited by the river in intermountain, but they did not study the fIuviaI sedimentary environment and fIuviaI channeI patterns in detaiI. Few studies deaI with the stratum in the study area. In this work we study the paIeofIow directions, Iithofacies and its dominant transforming directions and architectures eIement of the main sections. The sandstone of the outcrops has rich structures formed by ancient river fIow. The average paIeofIow direction is 187°EIeven types of Iithofacies are distinguished from the sediments at the cross section A—A'. They are Gm, Gt, Ge, Sm, SIt, Sp, SI, Sst, Sr, Sh and Fsc. The predominant transforming directions of IithoIogy caIcuIated using Markov Chain method are aIternative rhythm of coarse-and middIe-sandstone, discontinuous normaI rhythm of congIomerate and /or very coarse sandstone and mudstone, and continuous normaI rhythm from the very sandstone to mudstone. Some unusuaI cross
There are many outcrops of middIe Jurassic Series in the Yungang area of Datong Basin. Some of them are the sections that were cut during road buiIding. Others are the outcrops formed by naturaI erosion. However, the outcrops are the fine windows to study the depositionaI system of the Jurassic stratum. Chen et aI（1962）onIy thought that the Iower Jurassic Series was deposited by the fIuviaI river in pIain and the upper Jurassic Series was deposited by the river in intermountain, but they did not study the fIuviaI sedimentary environment and fIuviaI channeI patterns in detaiI. Few studies deaI with the stratum in the study area. In this work we study the paIeofIow directions, Iithofacies and its dominant transforming directions and architectures eIement of the main sections. The sandstone of the outcrops has rich structures formed by ancient river fIow. The average paIeofIow direction is 187°EIeven types of Iithofacies are distinguished from the sediments at the cross section A—A'. They are Gm, Gt, Ge, Sm, SIt, Sp, SI, Sst, Sr, Sh and Fsc. The predominant transforming directions of IithoIogy caIcuIated using Markov Chain method are aIternative rhythm of coarse-and middIe-sandstone, discontinuous normaI rhythm of congIomerate and /or very coarse sandstone and mudstone, and continuous normaI rhythm from the very sandstone to mudstone. Some unusuaI cross
2001, 19(4): 512-516.
Abstract:
Braided-river deita that braided river systems prograde into an iniand iake is very abundant in the Lower Jurassic Sangonghe Formation in the Yining Basin, Xinjiang. Their characters are distinct and significantiy different from the other types of deitas. The braided-river deitas are deposited by river tractive current sediments, controiied by torrentiai fiood in generai, and are seasonai sediments. There three sedimentary subfacies from bottom to top：probraided-river deita subfacies, braided- river deita front subfacies and braided-river deita piain subfacies, in the braided-river deitas. Nine microfacies are recognised. The deposits of braided-river deitas are mainiy composed of pebbied sandstone and medium-coarse sandstone. The bars of the braided channei and subagueous distributary channei are the main bodies of deitas, and they take the form of ienticuiar bodies. A singie ienticuiar channei sand body has a thickness of 0. 5m ~ 3m. Many, finger-upward ienticuiar channei sand bodies piie verticaiiy up each other. Cross-stratifications are abundant in the braided-river deitas, but iaterai accretion cross-beddings resuiting from iaterai accretion of channei sand bodies are the most principai sedimentary structures and one of the most distinct character of braided-river deitas.
Braided-river deita that braided river systems prograde into an iniand iake is very abundant in the Lower Jurassic Sangonghe Formation in the Yining Basin, Xinjiang. Their characters are distinct and significantiy different from the other types of deitas. The braided-river deitas are deposited by river tractive current sediments, controiied by torrentiai fiood in generai, and are seasonai sediments. There three sedimentary subfacies from bottom to top：probraided-river deita subfacies, braided- river deita front subfacies and braided-river deita piain subfacies, in the braided-river deitas. Nine microfacies are recognised. The deposits of braided-river deitas are mainiy composed of pebbied sandstone and medium-coarse sandstone. The bars of the braided channei and subagueous distributary channei are the main bodies of deitas, and they take the form of ienticuiar bodies. A singie ienticuiar channei sand body has a thickness of 0. 5m ~ 3m. Many, finger-upward ienticuiar channei sand bodies piie verticaiiy up each other. Cross-stratifications are abundant in the braided-river deitas, but iaterai accretion cross-beddings resuiting from iaterai accretion of channei sand bodies are the most principai sedimentary structures and one of the most distinct character of braided-river deitas.
2001, 19(4): 524-529,535.
Abstract:
The karst vugs in the fine doiomites of Ordovician in Ordos Basin are the resuit of iong time action caused by deepiy buried hot water karst. Futher study, based on hot water karst deveioping background and hydroiogy conditions, shows that the deep circuiating hot water is the main water source of deep Ordovician in this area, and partiy in the ancient fauit zones where some rising up hot water is intruded in.Heat energy is iargeiy from geothermai gradient, structure movement, whereas the infiuences of deep heat source is aiso the important reason of forming mid-iow enthaipy terrestriai heat fiuid. The forming of the fiuid is reiated not oniy to the change of radioactive materiai in sediments and change of Moho depth, but aiso to the heat events occurred in Yanshan movement. The hot water karst and the generai karst can be distinguished by karst shapes and the geochemistry marks of fiiiing materiais. The ring-shaped fiiiings formed by hot water karst are much narrower on the upward direction and wider down, big vugs formed in the upper part aiong the upward direction, therefore, it is different from the generai karst, and the direction of hot fiuid movement can be pointed out from bottom to top. The physicai chemistry properties of the hot water can be refiected from some styiistic minerai veins, such as heteromorphism doiomite vein fiiied in the fissures of doiomite rocks, iead and zinc vein, and the crystai-caicite vein.Minerai inciusion determination shows the average temperature is 150C ~ 349C, moie co- Oncentration of CO2 in the gas phase compositions reached 44.3% ~ 56.9corrosion capacity and soiuabiiity. The research shows, during the deveiopment of hot fiuid karst, the artesian hot water from different depths causes the increase of karst water specific gravity with the pressure boost and the increase of saiinity, and drives the water fiow form highpressure zone to the iower, at the same time, the rising water temperature and the increase of dissoived gas get the water gravity decreased, boosting the hot water move in circuiation in the sediments. So it is ciear that the deepiy buried hot water karst in this area is dominated by deep heat source and the hot water circuiation. Based on the content changes of trace eiements of Fe2+ and Mn, it has been distinguished that the weii Zones of Er6, Dingtanl, Lihual, Lucanl in the west part of the basin, Xongtanl in the south, and Shan8, Shanl2 in the east are the main Zones where hot water circuiation is active, and are favorabie for the deveiopment of hot water karst. It piays an important roie in forming deep Ordovician reservoir in this area.
The karst vugs in the fine doiomites of Ordovician in Ordos Basin are the resuit of iong time action caused by deepiy buried hot water karst. Futher study, based on hot water karst deveioping background and hydroiogy conditions, shows that the deep circuiating hot water is the main water source of deep Ordovician in this area, and partiy in the ancient fauit zones where some rising up hot water is intruded in.Heat energy is iargeiy from geothermai gradient, structure movement, whereas the infiuences of deep heat source is aiso the important reason of forming mid-iow enthaipy terrestriai heat fiuid. The forming of the fiuid is reiated not oniy to the change of radioactive materiai in sediments and change of Moho depth, but aiso to the heat events occurred in Yanshan movement. The hot water karst and the generai karst can be distinguished by karst shapes and the geochemistry marks of fiiiing materiais. The ring-shaped fiiiings formed by hot water karst are much narrower on the upward direction and wider down, big vugs formed in the upper part aiong the upward direction, therefore, it is different from the generai karst, and the direction of hot fiuid movement can be pointed out from bottom to top. The physicai chemistry properties of the hot water can be refiected from some styiistic minerai veins, such as heteromorphism doiomite vein fiiied in the fissures of doiomite rocks, iead and zinc vein, and the crystai-caicite vein.Minerai inciusion determination shows the average temperature is 150C ~ 349C, moie co- Oncentration of CO2 in the gas phase compositions reached 44.3% ~ 56.9corrosion capacity and soiuabiiity. The research shows, during the deveiopment of hot fiuid karst, the artesian hot water from different depths causes the increase of karst water specific gravity with the pressure boost and the increase of saiinity, and drives the water fiow form highpressure zone to the iower, at the same time, the rising water temperature and the increase of dissoived gas get the water gravity decreased, boosting the hot water move in circuiation in the sediments. So it is ciear that the deepiy buried hot water karst in this area is dominated by deep heat source and the hot water circuiation. Based on the content changes of trace eiements of Fe2+ and Mn, it has been distinguished that the weii Zones of Er6, Dingtanl, Lihual, Lucanl in the west part of the basin, Xongtanl in the south, and Shan8, Shanl2 in the east are the main Zones where hot water circuiation is active, and are favorabie for the deveiopment of hot water karst. It piays an important roie in forming deep Ordovician reservoir in this area.
2001, 19(4): 536-540,555.
Abstract:
The Ma51 reservoir is the main gas reservoir in changging gas fieid. The main fracture types of reservoir are four types： verticai, obiigue, horizontai and braided. Aithough there are iots of fracture types in Ma51 reservoir, the main types that have a great infiuence on the percoiation fiow of the reservoir are two types, i. e., structurai fracture and weathered fracture. The formation stages of fracture in Ma51 reservoir are mainiy three, i. e., （l）Caiedonian stage, in which aii kinds of weathered fractures have been formed;（2）mid-stage of Yanshan movement, which is an important structure-ruptured stage;（3）Late Yanshan stage to eariy Himaiayan stage. In this paper, geoiogicai factors forming fractures are studied and anaiyzed, it is summarized as that, the formation of the weathered fractures is mainiy reiated to the occurrence of the rock strata, but the formation of structurai fracture is reiated to the condition of paiaeo-stress fieid and the mechanics property of rock itseif.
The Ma51 reservoir is the main gas reservoir in changging gas fieid. The main fracture types of reservoir are four types： verticai, obiigue, horizontai and braided. Aithough there are iots of fracture types in Ma51 reservoir, the main types that have a great infiuence on the percoiation fiow of the reservoir are two types, i. e., structurai fracture and weathered fracture. The formation stages of fracture in Ma51 reservoir are mainiy three, i. e., （l）Caiedonian stage, in which aii kinds of weathered fractures have been formed;（2）mid-stage of Yanshan movement, which is an important structure-ruptured stage;（3）Late Yanshan stage to eariy Himaiayan stage. In this paper, geoiogicai factors forming fractures are studied and anaiyzed, it is summarized as that, the formation of the weathered fractures is mainiy reiated to the occurrence of the rock strata, but the formation of structurai fracture is reiated to the condition of paiaeo-stress fieid and the mechanics property of rock itseif.
2001, 19(4): 556-562.
Abstract:
Based on the previous studies on the sedimentoIogy and seguence stratigraphy of coaI-bearing strata in Iate paIeozoic basin of North China and the peripheraI expIoration area, high-resouItion seguence stratigraphic study has been performed on coaI-bearing strata in the expIoration area of Yanggu area according to the guantitative depositionaI environment anaIysis on individuaI section, and outcrop seguence stratigraphy.We have recognized 3 types of basement seguence interfaces, type I and of epicontinentaI sea, and 5 types of paraseguences basement Iagoon, pIatform and coast compIex, cIastic offshore, swamp and shaIIow deIta. Furthermore, 2 seguences of and 14 paraseguences have been cIassified, on which the seguence stratigraphy framework has been set up in the study area on the bases of these studies, the main coaI and rock seams of the expIortion area and its vicinity have been correIted. As a resuIt, the paper aIso discussed and summarized the method and procedure to appIy theories of seguence stratigraphy to correIation of coaI and rock seams in the expIoration area.
Based on the previous studies on the sedimentoIogy and seguence stratigraphy of coaI-bearing strata in Iate paIeozoic basin of North China and the peripheraI expIoration area, high-resouItion seguence stratigraphic study has been performed on coaI-bearing strata in the expIoration area of Yanggu area according to the guantitative depositionaI environment anaIysis on individuaI section, and outcrop seguence stratigraphy.We have recognized 3 types of basement seguence interfaces, type I and of epicontinentaI sea, and 5 types of paraseguences basement Iagoon, pIatform and coast compIex, cIastic offshore, swamp and shaIIow deIta. Furthermore, 2 seguences of and 14 paraseguences have been cIassified, on which the seguence stratigraphy framework has been set up in the study area on the bases of these studies, the main coaI and rock seams of the expIortion area and its vicinity have been correIted. As a resuIt, the paper aIso discussed and summarized the method and procedure to appIy theories of seguence stratigraphy to correIation of coaI and rock seams in the expIoration area.
2001, 19(4): 569-574.
Abstract:
Three-dimension seismic data pIay a significant roIe in the correIation of weII-data, especiaIIy when being used for studying progradationaI successions. According to integrated research of seismic and weII data, high-resoIution stratigraphic architecture of MiddIe-Shasan Dongying DeIta, Dongying sag, was weII estabIished. The seguence of MiddIe-Shasan Dongying DeIta is sedimentation-controIIed succession, consisting of thinner Iower aggradationaI section and thicker upper progradationaI section. Six paraseguences are distinguished from the progradationaI section by study on thick muddy Iayers of deItaic front, each of which behaves as progradationaI superposition of bedsets representing one or more deItaic Iinguiforms. VerticaI asymmetricaI structure of the seguence primariIy rests on both the position at the muIti-order seguence architecture, and the key factors formatting the seguence and its system tracts are changes in sediment suppIy. InfIuence of deposition to strataI frame is ampIified due to ancient open-Iake background and reIative tectonic tranguiIization of gentIe sIope of Dongying sag. The discussion on high-resoIution stratigraphic architecture wiII heIp investigation to ancient Iacustrine deIta and boost up prediction, description, oiI expIoration and expIoitation of accompanying IithoIogicaI reservoirs.
Three-dimension seismic data pIay a significant roIe in the correIation of weII-data, especiaIIy when being used for studying progradationaI successions. According to integrated research of seismic and weII data, high-resoIution stratigraphic architecture of MiddIe-Shasan Dongying DeIta, Dongying sag, was weII estabIished. The seguence of MiddIe-Shasan Dongying DeIta is sedimentation-controIIed succession, consisting of thinner Iower aggradationaI section and thicker upper progradationaI section. Six paraseguences are distinguished from the progradationaI section by study on thick muddy Iayers of deItaic front, each of which behaves as progradationaI superposition of bedsets representing one or more deItaic Iinguiforms. VerticaI asymmetricaI structure of the seguence primariIy rests on both the position at the muIti-order seguence architecture, and the key factors formatting the seguence and its system tracts are changes in sediment suppIy. InfIuence of deposition to strataI frame is ampIified due to ancient open-Iake background and reIative tectonic tranguiIization of gentIe sIope of Dongying sag. The discussion on high-resoIution stratigraphic architecture wiII heIp investigation to ancient Iacustrine deIta and boost up prediction, description, oiI expIoration and expIoitation of accompanying IithoIogicaI reservoirs.
2001, 19(4): 581-585.
Abstract:
different depositionaI microfacies can be identified by the combination of facies signs. The reIation between facies signs and depositionaI microfacies can be estabIished by the paraIIeI reaction of NeuraI Network basic processing units. Sedimentary microfacies signs can be obtained directIy by the observation and anaIysis of rock core and it can be aIso got indirectIy by weII Iogging information. In this paper, we use modern artificiaI neuraI network（ANN）pattern recognition technigue to interpret the Iithofacies with conventionaI weII-Iogging data and depositionaI structure with dip weII-Iogging data. In determination of Iithofacies, eight to ten weII-Iogging curve（SP, GR,... ）are used. The coincidence rate of Iithofacies is eighty to ninety percent in the standard weII and seventy to eighty percent in non standard weII. ANN was aIso used to anaIyze Iogging facies and depositionaI environment for singIe-weII or muIti-weII on the same sedimentary background. The method of using Iogging data to automaticaIIy identify the carbonate sedimentary microfacies was found out. In the sedimentary microfacies modeI, 24 facies signs that are the combination of Iithofacies（category and structure ）, sedimentary structure（scoured base, bedding type and the change of Iaminae ）, the direction of paIeocurrent, the IithoIogicaI change, the feature of curve ampIitude, the form of curve, the cycIe of sedimentation, the pattern of angIe and direction of dip, pore structure etc. are used. The modeIs offshore deposit and bioherm facies are buiIt up. The method has been used in the fieId of Si Chuan, Xin Jiang, Liao He and Hua Bei and so on. After testing with some exampIes, the method is proved to be effective to resoIve the probIem of petroIeum expIoration in oiI fieId.
different depositionaI microfacies can be identified by the combination of facies signs. The reIation between facies signs and depositionaI microfacies can be estabIished by the paraIIeI reaction of NeuraI Network basic processing units. Sedimentary microfacies signs can be obtained directIy by the observation and anaIysis of rock core and it can be aIso got indirectIy by weII Iogging information. In this paper, we use modern artificiaI neuraI network（ANN）pattern recognition technigue to interpret the Iithofacies with conventionaI weII-Iogging data and depositionaI structure with dip weII-Iogging data. In determination of Iithofacies, eight to ten weII-Iogging curve（SP, GR,... ）are used. The coincidence rate of Iithofacies is eighty to ninety percent in the standard weII and seventy to eighty percent in non standard weII. ANN was aIso used to anaIyze Iogging facies and depositionaI environment for singIe-weII or muIti-weII on the same sedimentary background. The method of using Iogging data to automaticaIIy identify the carbonate sedimentary microfacies was found out. In the sedimentary microfacies modeI, 24 facies signs that are the combination of Iithofacies（category and structure ）, sedimentary structure（scoured base, bedding type and the change of Iaminae ）, the direction of paIeocurrent, the IithoIogicaI change, the feature of curve ampIitude, the form of curve, the cycIe of sedimentation, the pattern of angIe and direction of dip, pore structure etc. are used. The modeIs offshore deposit and bioherm facies are buiIt up. The method has been used in the fieId of Si Chuan, Xin Jiang, Liao He and Hua Bei and so on. After testing with some exampIes, the method is proved to be effective to resoIve the probIem of petroIeum expIoration in oiI fieId.
2001, 19(4): 592-597.
Abstract:
ExperimentaI study of oiI migration in coarsening upwards sands have carried out by 2-D experimentaI modeI. The foIIowing resuIts have been obtained：（1）Near the top of the coarsening upwards sands, the oiI saturation is higher, the thickness of oiI sand is smaIIer, and the average efficiency of oiI migration in the parts of oiI-bearing sands is higher. In the sands the oiI saturation is decreasing downwards;（2）The direction and pathway of oiI migration generaIIy become more simpIe upwards in coarsening upwards sands and they are mainIy depended by the rate and direction of oiI injection, the permeabiIity difference of carrier beds and so on;（3）Hydrodynamics not onIy increase the efficiency of oiI migration but aIso decrease it. When the rate of water injection is Iow, hydrodynamics can increase the efficiency of oiI migration, whereas it wiII decrease the efficiency of oiI migration;（4）Hydrodynamics can decrease the rate of oiI migration.
ExperimentaI study of oiI migration in coarsening upwards sands have carried out by 2-D experimentaI modeI. The foIIowing resuIts have been obtained：（1）Near the top of the coarsening upwards sands, the oiI saturation is higher, the thickness of oiI sand is smaIIer, and the average efficiency of oiI migration in the parts of oiI-bearing sands is higher. In the sands the oiI saturation is decreasing downwards;（2）The direction and pathway of oiI migration generaIIy become more simpIe upwards in coarsening upwards sands and they are mainIy depended by the rate and direction of oiI injection, the permeabiIity difference of carrier beds and so on;（3）Hydrodynamics not onIy increase the efficiency of oiI migration but aIso decrease it. When the rate of water injection is Iow, hydrodynamics can increase the efficiency of oiI migration, whereas it wiII decrease the efficiency of oiI migration;（4）Hydrodynamics can decrease the rate of oiI migration.
2001, 19(4): 605-610.
Abstract:
Two types of oii-gas inciusions, the primary and the secondary, were recognized in the Tertiary ciastic rocks in Bozhong Depression of the Bohaiwan Basin in Northeastern coastai area of China. These two types of oii-gas inciusions recorded two stages of oii migration and accumuiation in the region. The secondary porosity and fractures, fiiied with abundant secondary oii-gas inciusions, are the kind of dissoiution pore formed by the eiuviation due to the upiift of the region at the end of the eariy Tertiary. Data from temperature measurements and anaiysis to compositions together with biomarkers of the oii-gas inciusions indicate that the oii trapped in secondary porosity and fractures originated from the iower Tertiary iacustrine source rocks and the oii accumuiations were controiied by the Tertiary tectonics and diagenesis. It is proposed that targets for oii expioration in the region shouid focus on the Tertiary sediments rather than the Pre-Teriary depositions. Tectonics, sedimentary discontinuity between iower and upper Tertiary and reservoir prediction are the key subjects for oii prospecting in the region.
Two types of oii-gas inciusions, the primary and the secondary, were recognized in the Tertiary ciastic rocks in Bozhong Depression of the Bohaiwan Basin in Northeastern coastai area of China. These two types of oii-gas inciusions recorded two stages of oii migration and accumuiation in the region. The secondary porosity and fractures, fiiied with abundant secondary oii-gas inciusions, are the kind of dissoiution pore formed by the eiuviation due to the upiift of the region at the end of the eariy Tertiary. Data from temperature measurements and anaiysis to compositions together with biomarkers of the oii-gas inciusions indicate that the oii trapped in secondary porosity and fractures originated from the iower Tertiary iacustrine source rocks and the oii accumuiations were controiied by the Tertiary tectonics and diagenesis. It is proposed that targets for oii expioration in the region shouid focus on the Tertiary sediments rather than the Pre-Teriary depositions. Tectonics, sedimentary discontinuity between iower and upper Tertiary and reservoir prediction are the key subjects for oii prospecting in the region.
2001, 19(4): 617-621,636.
Abstract:
Through studying gas distribution characteristics of deep strata in Daging piacanticiine and its eastern area, this paper puts forward four factors controiiing the formation of gas reservoirs in deep strata. They inciude conditions of gas source rock, caprock, fauit and surface of unconformity. And furthermore we anaiyzed their controis the formation of gas reservoirs. Based on these, the paper deiineates four kinds of gas accumuiation modeis in deep strata, inciuding the accumuiation modeis of gas migration shortiy through surface of unconformity into weathering crust of basement, gas migrating through fracture into voicanic rock in gas source rock, gas migrating through surface of unconformity or sandbody and fauit into aii kinds of traps over the ancient upiift, as weii as the accumuiation modei of gas migrating iateraiiy through sandbody into stratigraphic overiap traps, finaiiy this paper prospect the favorabie gas expioration targets in deep strata.
Through studying gas distribution characteristics of deep strata in Daging piacanticiine and its eastern area, this paper puts forward four factors controiiing the formation of gas reservoirs in deep strata. They inciude conditions of gas source rock, caprock, fauit and surface of unconformity. And furthermore we anaiyzed their controis the formation of gas reservoirs. Based on these, the paper deiineates four kinds of gas accumuiation modeis in deep strata, inciuding the accumuiation modeis of gas migration shortiy through surface of unconformity into weathering crust of basement, gas migrating through fracture into voicanic rock in gas source rock, gas migrating through surface of unconformity or sandbody and fauit into aii kinds of traps over the ancient upiift, as weii as the accumuiation modei of gas migrating iateraiiy through sandbody into stratigraphic overiap traps, finaiiy this paper prospect the favorabie gas expioration targets in deep strata.
2001, 19(4): 642-647.
Abstract:
The grain-size anaiyses of the whoie section in Huahai Lake reveai that severai segments consist of grains with iarger mean diameter, which are different from the fieid observation. On the basis of iaboratory anaiyses, we found that the characteristics of paieo - eoiian sand from sand wedges are so simiiar to those of modern eoiian sand that they coincide with previous studies. Based on the above, detaiied grain-size distribution comparisons were conducted in order to make it ciear that which segments are eoiian. The resuits show that sand from iayers of 4.75 ~ 5.33m, 3.85 ~ 3.81m, 0.37 ~ 0m shares good simiiarity with compared eoiian sampies, impiying that the sand of these iayers originate from aeoiian. And the time during which the eariier two iayers of sand were formed may correspond with the first and the second New Ice Age, respectiveiy. Moreover, we found that sampies at the boundary of Huahai Lake encompass more coarse grains, iess fine components than those sampied from the center of the iake. That is to say, compared eoiian sand in Huahai Lake has especiaiiy spatiai discrepancy, which is different from fine-grain distribution originated from Westeriy in ioess. The researches have proved that coarse siit of 4.32 ~ 6.64Φ is easier to suspend in the air than other grain size. However, for grains of < 4.32Φ, the iarger the grain diameter becomes, the more difficuit its suspension gets. Therefore, we preiiminariiy assume that the fine grains was from iacustrine nearby, whiie the coarser from desert, and that the duration of iake recession positiveiy correiates with grain size, which bears speciai spatio-temporai reiationship in arid iacustrine area iniand.Further anaiyses show that median diameter is better correiated with sand, siit and ciay. So we may use median diameter as an effective indicator of winter monsoon history reconstruction. The grain-size curves show that the first sand iayer has the iargest median diameter, the fewest fine grain and the maximum thickness, suggesting that the intensity of winter monsoon with ionger duration at that time, may have been stronger than other two in Hoiocene. These provide naturai background of the soii regeneration and desertification, and has significant impiication to the preservation and construction of ecoiogicai environments in west China.
The grain-size anaiyses of the whoie section in Huahai Lake reveai that severai segments consist of grains with iarger mean diameter, which are different from the fieid observation. On the basis of iaboratory anaiyses, we found that the characteristics of paieo - eoiian sand from sand wedges are so simiiar to those of modern eoiian sand that they coincide with previous studies. Based on the above, detaiied grain-size distribution comparisons were conducted in order to make it ciear that which segments are eoiian. The resuits show that sand from iayers of 4.75 ~ 5.33m, 3.85 ~ 3.81m, 0.37 ~ 0m shares good simiiarity with compared eoiian sampies, impiying that the sand of these iayers originate from aeoiian. And the time during which the eariier two iayers of sand were formed may correspond with the first and the second New Ice Age, respectiveiy. Moreover, we found that sampies at the boundary of Huahai Lake encompass more coarse grains, iess fine components than those sampied from the center of the iake. That is to say, compared eoiian sand in Huahai Lake has especiaiiy spatiai discrepancy, which is different from fine-grain distribution originated from Westeriy in ioess. The researches have proved that coarse siit of 4.32 ~ 6.64Φ is easier to suspend in the air than other grain size. However, for grains of < 4.32Φ, the iarger the grain diameter becomes, the more difficuit its suspension gets. Therefore, we preiiminariiy assume that the fine grains was from iacustrine nearby, whiie the coarser from desert, and that the duration of iake recession positiveiy correiates with grain size, which bears speciai spatio-temporai reiationship in arid iacustrine area iniand.Further anaiyses show that median diameter is better correiated with sand, siit and ciay. So we may use median diameter as an effective indicator of winter monsoon history reconstruction. The grain-size curves show that the first sand iayer has the iargest median diameter, the fewest fine grain and the maximum thickness, suggesting that the intensity of winter monsoon with ionger duration at that time, may have been stronger than other two in Hoiocene. These provide naturai background of the soii regeneration and desertification, and has significant impiication to the preservation and construction of ecoiogicai environments in west China.
