2005 Vol. 23, No. 1
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Display Method:
From Shallow-water Shelf to Deep-water Slope——the study on deep-water fan systems in South China Sea
2005, 23(1): 1-11.
Abstract:
Oil and gas are strategic resources. China became oil input country since 1993. In order to ensure the energy security, one of the best energy policies is to find out several giant oil-gas fields in the coastal ocean regions and to establish new petroleum strategic base. The deep-water fan system in South China Sea could become the break through area. The deep-water fan systems play a dominant role for the international oil production and reserve increasing in the last 20 years, more than 60 countries doing well for the research of deep-water fan system. This subject attracts the international academic attention and considered as"one of the principal scientific technical and environmental challenges for the new century"and"deep-water turbidite and related reservoirswill be at the forefront of oil and gas exploration and production for at least the next 25 years. "(D. A. V. Stow, et al. 2000). Deep-water fan system which being discovered recentlywith the characteristics in South China Sea of huge scale,densely distribution, typical architecture and great exp loration future. The deep study for the deep-water fan systems is becoming the major subject for oil and gas industry and scientific academy. This article gives a definition for deep-water fan system, and points out the discovery of large-scale deep-water fan systems in the South China Sea has significant economic potentials and academic values.
Oil and gas are strategic resources. China became oil input country since 1993. In order to ensure the energy security, one of the best energy policies is to find out several giant oil-gas fields in the coastal ocean regions and to establish new petroleum strategic base. The deep-water fan system in South China Sea could become the break through area. The deep-water fan systems play a dominant role for the international oil production and reserve increasing in the last 20 years, more than 60 countries doing well for the research of deep-water fan system. This subject attracts the international academic attention and considered as"one of the principal scientific technical and environmental challenges for the new century"and"deep-water turbidite and related reservoirswill be at the forefront of oil and gas exploration and production for at least the next 25 years. "(D. A. V. Stow, et al. 2000). Deep-water fan system which being discovered recentlywith the characteristics in South China Sea of huge scale,densely distribution, typical architecture and great exp loration future. The deep study for the deep-water fan systems is becoming the major subject for oil and gas industry and scientific academy. This article gives a definition for deep-water fan system, and points out the discovery of large-scale deep-water fan systems in the South China Sea has significant economic potentials and academic values.
2005, 23(1): 21-28.
Abstract:
Some conglomerate bodies that have heavy thickness, extreme coarse grains size and fast facies change occur in the slope zone of the First Member of Tenger Formation in Wuliyasitai Sag, Erlian Basin. However, There is stillmuch controversy about the exact origin of the conglomerate bodies and bewilderment about its size, space distribution, reservoir characteristics and formationalmodel in subtle oil pools. Based on analysis of its tectonic setting and depositional conditions in detail, accorded to the result of cores observation, combination characteristics of borehole lithology and log and seismic facies analysis, etc., and combined with analytic data of petrology and mineralogy and physical property, etc., it is studied in detail that the origin, sedimentary facies zones distribution characteristics,depositionalmodel, reservoir property and formational conditions in subtle oil pools of conglomerate bodies involved in this area. The result indicates that the conglomerate bodies that surrounded by dark graymudstone of deeper lacustrine facies are the deposits of sublacustrine fan facieswith feeder channel. The sedimentary structures that formed by sediment gravity flow, such as massive bedding, normal graded bedding, superposition graded bedding and partial reverse graded bedding are main and recognized. Massive and fine upwards rhythmic layering similar to "AAA" sedimentary sequence are dominant and rep resent for the sedimentation of gravity flow channels. In the seismic profiles,their seismic facieswith clearmoundy and channel filling configuration are typical. The subfacies zones of sublacustrine fan facies develop perfectly and can be classified to inner fan, middle fan and outer fan subfacies. In general, the inner fan subfacies has characteristics of a single channel that described as main channel. The lithofacies of the main channel in the inner fan subfacies are composed ofmassive muddy conglomerate facies and superposition graded bedding conglomerate facies, which deposited alternately by high-density debris flows and grain flows. The middle fan subfacies show the depositional characters of braid channel and its lithofacies,which grain flows and high-density turbidity current are the main transportingways, consist ofmassive sandstone facies, conglomerate facies with pebble and glutenite facies with boulder. The outer fan subfacies are composed of thin turbidite bedswhich can be described by typical Bouma sequence. The sublacustrine fan facies of above have more than two depositional stages. The source area with the characteristics of multip le2source or linear source and extreme coarse grains size results in poor stability, small size and strong tendency to migration of the feeder channel and two or more conglomerate bodies of sublacustrine fan fancies may be formed along the slope zone. Vertically and laterally,these conglomerate bodies overlap each other and distribute in a large area. In the early period of Tenger, the lacustrine basin expands rapidly with deep subsidence in Wuliyasitai Sag. The environment of deep water that fits the sublacustrine fan facies is dominant. Meanwhile, because the tectonic activity of the northwestern margin fault enhances sharply, the southeastern slope zone begins to up lift and forms gradually the slope geomorphy with big gradient and high angle. At the same time, some tectonic break-slope zones occur on the slope with the differential activity of some secondary consequent faults such as Tai 21 eastern fault, etc. The steep grade of the slope, especially tectonic break2slope zones control formation and development of sublacustrine fan. In the base of tectonic break-2slope zones, a great deal of clastic fragment transported by floodwater gravity flows passes the feeder channel and downloads in turn to form the sublacustrine fan with feeder channel. The conglomerate bodies of sublacustrine fan facies have favorable association of source rocks, reservoirs and seal beds and perfect formational conditions in subtle oil pools. The braid channelmicrofacies areas in the middle fan subfaciesmay be the most favorable reservoir zones and have been found thick oil beds in some wells of Tai 43, Tai 47, etc. The effect of producing test in these wells is very good. Although the reservoir property of the main channelmicrofacies areas in the inner fan subfacies is poorer than that of the braid channelmicrofacies areas in the middle fan subfacies, they are still favorable reservoir zones and have obtained commercial oil stream in Tai 21 well, etc. In recent years, the conglomerate bodies of sublacustrine fan facies in the slope zone have been achieved great breakthrough of exp loration in the subtle oil pools.
Some conglomerate bodies that have heavy thickness, extreme coarse grains size and fast facies change occur in the slope zone of the First Member of Tenger Formation in Wuliyasitai Sag, Erlian Basin. However, There is stillmuch controversy about the exact origin of the conglomerate bodies and bewilderment about its size, space distribution, reservoir characteristics and formationalmodel in subtle oil pools. Based on analysis of its tectonic setting and depositional conditions in detail, accorded to the result of cores observation, combination characteristics of borehole lithology and log and seismic facies analysis, etc., and combined with analytic data of petrology and mineralogy and physical property, etc., it is studied in detail that the origin, sedimentary facies zones distribution characteristics,depositionalmodel, reservoir property and formational conditions in subtle oil pools of conglomerate bodies involved in this area. The result indicates that the conglomerate bodies that surrounded by dark graymudstone of deeper lacustrine facies are the deposits of sublacustrine fan facieswith feeder channel. The sedimentary structures that formed by sediment gravity flow, such as massive bedding, normal graded bedding, superposition graded bedding and partial reverse graded bedding are main and recognized. Massive and fine upwards rhythmic layering similar to "AAA" sedimentary sequence are dominant and rep resent for the sedimentation of gravity flow channels. In the seismic profiles,their seismic facieswith clearmoundy and channel filling configuration are typical. The subfacies zones of sublacustrine fan facies develop perfectly and can be classified to inner fan, middle fan and outer fan subfacies. In general, the inner fan subfacies has characteristics of a single channel that described as main channel. The lithofacies of the main channel in the inner fan subfacies are composed ofmassive muddy conglomerate facies and superposition graded bedding conglomerate facies, which deposited alternately by high-density debris flows and grain flows. The middle fan subfacies show the depositional characters of braid channel and its lithofacies,which grain flows and high-density turbidity current are the main transportingways, consist ofmassive sandstone facies, conglomerate facies with pebble and glutenite facies with boulder. The outer fan subfacies are composed of thin turbidite bedswhich can be described by typical Bouma sequence. The sublacustrine fan facies of above have more than two depositional stages. The source area with the characteristics of multip le2source or linear source and extreme coarse grains size results in poor stability, small size and strong tendency to migration of the feeder channel and two or more conglomerate bodies of sublacustrine fan fancies may be formed along the slope zone. Vertically and laterally,these conglomerate bodies overlap each other and distribute in a large area. In the early period of Tenger, the lacustrine basin expands rapidly with deep subsidence in Wuliyasitai Sag. The environment of deep water that fits the sublacustrine fan facies is dominant. Meanwhile, because the tectonic activity of the northwestern margin fault enhances sharply, the southeastern slope zone begins to up lift and forms gradually the slope geomorphy with big gradient and high angle. At the same time, some tectonic break-slope zones occur on the slope with the differential activity of some secondary consequent faults such as Tai 21 eastern fault, etc. The steep grade of the slope, especially tectonic break2slope zones control formation and development of sublacustrine fan. In the base of tectonic break-2slope zones, a great deal of clastic fragment transported by floodwater gravity flows passes the feeder channel and downloads in turn to form the sublacustrine fan with feeder channel. The conglomerate bodies of sublacustrine fan facies have favorable association of source rocks, reservoirs and seal beds and perfect formational conditions in subtle oil pools. The braid channelmicrofacies areas in the middle fan subfaciesmay be the most favorable reservoir zones and have been found thick oil beds in some wells of Tai 43, Tai 47, etc. The effect of producing test in these wells is very good. Although the reservoir property of the main channelmicrofacies areas in the inner fan subfacies is poorer than that of the braid channelmicrofacies areas in the middle fan subfacies, they are still favorable reservoir zones and have obtained commercial oil stream in Tai 21 well, etc. In recent years, the conglomerate bodies of sublacustrine fan facies in the slope zone have been achieved great breakthrough of exp loration in the subtle oil pools.
2005, 23(1): 34-40.
Abstract:
The Lashizhong Formation of the middle Ordovician in Zhuozishang area, Inner Mongolia is a set of turbidite measures, which is composed of lots of turbidite beds with clear Bouma sequence. However, the eminent differences exist between Lashizhong formation and those formed in the unstable and substable continental shelf margin to the deep-sea basin, such as in their total sequence thickness and internal features. This is the reason thatwe call the turbidite of the Lashizhong Formation as the special'turbidite measure. In this paper, the comparison study is performed according to the two turbidite measures, and, furthermore, elucidate the basin characteristics based on the depositional facies, combination, paleocurrent direction and trace fossil, etc., and reached the conclusion that the Lashizhong turbidite is formed in the stable deep-sea basin, which is located between the stable massifs with simple landscape and gentle slope, and the water depth is 200m under the wave base with ample oxygen.
The Lashizhong Formation of the middle Ordovician in Zhuozishang area, Inner Mongolia is a set of turbidite measures, which is composed of lots of turbidite beds with clear Bouma sequence. However, the eminent differences exist between Lashizhong formation and those formed in the unstable and substable continental shelf margin to the deep-sea basin, such as in their total sequence thickness and internal features. This is the reason thatwe call the turbidite of the Lashizhong Formation as the special'turbidite measure. In this paper, the comparison study is performed according to the two turbidite measures, and, furthermore, elucidate the basin characteristics based on the depositional facies, combination, paleocurrent direction and trace fossil, etc., and reached the conclusion that the Lashizhong turbidite is formed in the stable deep-sea basin, which is located between the stable massifs with simple landscape and gentle slope, and the water depth is 200m under the wave base with ample oxygen.
2005, 23(1): 49-59.
Abstract:
Microspar structures represented by complex ptygmatically folded, dotted lags, blobs or vertical and horizontal ribbons and ve ins are common in Pro terozo ic carbona tesw orldw ide. Microspar structures be ing filled by fine,equant sparry calcite (ordolomite) crystals display sharpen lateral boundaries with hosting rocks composed dominantly of limemud or fine-grained carbonatesw ith quartz silt& clay occasionally and tempestites-carbonaceous tubidite rhythmites with m icrospar veins and microspar-intrac last lags in the middle and upper. Microspar structure lim estones are mainly deposited on a remarkab ly ramp carbonate platform, and common with tidal and storm current plane and graded beddings, rhythm ites with scalloped erosional surfaces and depositional filled structures in m icrosparbearing carbonates. Occurence of microspar structure are identically constra ined with in shallow subt idal and peritidal (in term of ramp,.i e., deep inner ramp to shallow m id-ramp), and storm-base in the ramp is the distal sea-floor lim it of m icrospar fo rmation. Vert ical successions o fm icrospar-bearing carbonate are stacked by high-frequency shallow subt idal and peritidal cyclic depositional micro-sequences, which show ing a cycle of thinning, shallowing and depositional dynamic decreasing-upward, and with a peritidal cap of red iron and organic carbonaceous lam inite attrited to sabuha-like m icro facies on the top of individual cycles.
Microspar structures represented by complex ptygmatically folded, dotted lags, blobs or vertical and horizontal ribbons and ve ins are common in Pro terozo ic carbona tesw orldw ide. Microspar structures be ing filled by fine,equant sparry calcite (ordolomite) crystals display sharpen lateral boundaries with hosting rocks composed dominantly of limemud or fine-grained carbonatesw ith quartz silt& clay occasionally and tempestites-carbonaceous tubidite rhythmites with m icrospar veins and microspar-intrac last lags in the middle and upper. Microspar structure lim estones are mainly deposited on a remarkab ly ramp carbonate platform, and common with tidal and storm current plane and graded beddings, rhythm ites with scalloped erosional surfaces and depositional filled structures in m icrosparbearing carbonates. Occurence of microspar structure are identically constra ined with in shallow subt idal and peritidal (in term of ramp,.i e., deep inner ramp to shallow m id-ramp), and storm-base in the ramp is the distal sea-floor lim it of m icrospar fo rmation. Vert ical successions o fm icrospar-bearing carbonate are stacked by high-frequency shallow subt idal and peritidal cyclic depositional micro-sequences, which show ing a cycle of thinning, shallowing and depositional dynamic decreasing-upward, and with a peritidal cap of red iron and organic carbonaceous lam inite attrited to sabuha-like m icro facies on the top of individual cycles.
2005, 23(1): 67-72.
Abstract:
Based on volcanic sedimentation petrography facies and their identification on seismic, the relationship between volcanic petrography sedimentation facies and oil-gas reservoirs has been discussed, then proposed the prospec- tive areas. In Yin'gen basin the types of volcanic sedimentation petrography facies include exp losion facies, outflow facies, volcanic-neck facies and volcanic sedimentary facies, especially the outflow facies. According to the geophysical characteristics of volcanic sedimentation petrography facies ( high seismic velocity, high density, high suscep tibil- ity, high resistance and high absorp tion coefficient to seismic wave), four volcanic sedimentation petrography facies and four intruded petrography facies are established. Deep-faults control the distribution of igneous rocks and igneous traps. The prospective zones of igneous reservoir are near fault belts.
Based on volcanic sedimentation petrography facies and their identification on seismic, the relationship between volcanic petrography sedimentation facies and oil-gas reservoirs has been discussed, then proposed the prospec- tive areas. In Yin'gen basin the types of volcanic sedimentation petrography facies include exp losion facies, outflow facies, volcanic-neck facies and volcanic sedimentary facies, especially the outflow facies. According to the geophysical characteristics of volcanic sedimentation petrography facies ( high seismic velocity, high density, high suscep tibil- ity, high resistance and high absorp tion coefficient to seismic wave), four volcanic sedimentation petrography facies and four intruded petrography facies are established. Deep-faults control the distribution of igneous rocks and igneous traps. The prospective zones of igneous reservoir are near fault belts.
2005, 23(1): 84-90.
Abstract:
The lacustrine regression caused by the falling of the relative lake-level in rift basin is called Forced Lacustrine Regression ( FLR). Given the sediments supply in FLR period, the lacustrine regression action will be strengthened and, correspondingly, a set of foreset sandbodies with evidently oblique progradational configuration will be formed. The foreset sandbody usually absents the top set beds and shows an oblique progradational reflection configuration on the seismic profile. The top boundary of the foreset sandbody is corresponding to sequence boundary, and often develop sincise valleys. Three forming mechanisms that give rise to the FLR can be concluded as climate change,structural up lift and basement differential subsidence in gentle slope caused by ep isodic movements of boundary faults.They can also lead to the falling of the relative lake-level in rift basin. The foreset sandbody formed in FLR period will be the favorable exploration target as a subtle reservoir due to its good forming conditions for reservoirs.
The lacustrine regression caused by the falling of the relative lake-level in rift basin is called Forced Lacustrine Regression ( FLR). Given the sediments supply in FLR period, the lacustrine regression action will be strengthened and, correspondingly, a set of foreset sandbodies with evidently oblique progradational configuration will be formed. The foreset sandbody usually absents the top set beds and shows an oblique progradational reflection configuration on the seismic profile. The top boundary of the foreset sandbody is corresponding to sequence boundary, and often develop sincise valleys. Three forming mechanisms that give rise to the FLR can be concluded as climate change,structural up lift and basement differential subsidence in gentle slope caused by ep isodic movements of boundary faults.They can also lead to the falling of the relative lake-level in rift basin. The foreset sandbody formed in FLR period will be the favorable exploration target as a subtle reservoir due to its good forming conditions for reservoirs.
2005, 23(1): 99-107.
Abstract:
The Middle to Upper Triassic Tanzhuang Form ation, being well cropped out near Jiyuan City, Henan Province,represents a part of the infill of the earlyMesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition with in prevailing shallow lake conditions. S ix sedim entary facies clustered into two facies assemb lages were recognized in the lacustrine section. Facies assemb lage 1 consists of the stacked coarsening-upward sequences composed, from base to top, of organic-rich shale ( facies E, typeⅠ), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemb lages 1 record progradat ion o f smallmouth-bar de ltas with in a perennial open lacustr ine system under temperate and humid cond itions. Facies assemb lage 2 lacks a clear vertical prograd ition pattern and consists of in terbedded f ine-grained carbonates and siltstones ( facies C ); de formed and wave-rewo rked sandstones ( fac ies D ) ; organic-rich shales ( facies E, type Ⅱ ) and clayey mudstones ( facies F). The assemb lage also represents a perennia,l hydro log ica lly open, shallow lacustrine system, but characterized by strong seasona l climatic control. The Skolithos linearismonospecific assemb lagema in ly occurred abundantly in faciesC suggests the substrates contro lled by seasona l climate. Water strat ification probably occurred in severa l periods of the lake history. Pangaean megamonsoonal influence is env isaged to expla in the strong seasonality imprint evidenced tow ard the upper part of the Tanzhuang lacustrine co lumn.
The Middle to Upper Triassic Tanzhuang Form ation, being well cropped out near Jiyuan City, Henan Province,represents a part of the infill of the earlyMesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition with in prevailing shallow lake conditions. S ix sedim entary facies clustered into two facies assemb lages were recognized in the lacustrine section. Facies assemb lage 1 consists of the stacked coarsening-upward sequences composed, from base to top, of organic-rich shale ( facies E, typeⅠ), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemb lages 1 record progradat ion o f smallmouth-bar de ltas with in a perennial open lacustr ine system under temperate and humid cond itions. Facies assemb lage 2 lacks a clear vertical prograd ition pattern and consists of in terbedded f ine-grained carbonates and siltstones ( facies C ); de formed and wave-rewo rked sandstones ( fac ies D ) ; organic-rich shales ( facies E, type Ⅱ ) and clayey mudstones ( facies F). The assemb lage also represents a perennia,l hydro log ica lly open, shallow lacustrine system, but characterized by strong seasona l climatic control. The Skolithos linearismonospecific assemb lagema in ly occurred abundantly in faciesC suggests the substrates contro lled by seasona l climate. Water strat ification probably occurred in severa l periods of the lake history. Pangaean megamonsoonal influence is env isaged to expla in the strong seasonality imprint evidenced tow ard the upper part of the Tanzhuang lacustrine co lumn.
2005, 23(1): 113-121.
Abstract:
As one of important rock types in marine sequence stratigraphy analysis, carbonate rock and its sequence stratigraphic model have been established. Althrough carbonate rocks inMeso-cenozoic lacustrine sediments in China is not very abundant as that in marine environment, they are still an important constitutes in lacustrine depositional profile. However, papers published in recent years related to lacustrine sequence stratigraphy are very small dealtwith lacustrine carbonate rocks due to the weak research on them. In this paper, based on the establishment of sequence stratigraphic framework of Subei basin, we have also studied the role of lacustrine carbonate rocks in our research. It is proposed that the distribution of carbonate nodules and lump s is a mark for recongnizing sequence boundary and systems tracts; and the depositional shifting of grain carbonate rocks can also serve as an importantmark for different systems tracts. and the p rofile change of carbonate rocks is also indicator for identifying parasequence and parasequence sets. In addition, the stably distributed dark fine carbonate rock and muddy shale interbedding is a mark of condensed section. This paper aims at appealing attention to the special role of carbonate rocks in establishing sequence stratigraphy in lacustrine sediments among the researchers.
As one of important rock types in marine sequence stratigraphy analysis, carbonate rock and its sequence stratigraphic model have been established. Althrough carbonate rocks inMeso-cenozoic lacustrine sediments in China is not very abundant as that in marine environment, they are still an important constitutes in lacustrine depositional profile. However, papers published in recent years related to lacustrine sequence stratigraphy are very small dealtwith lacustrine carbonate rocks due to the weak research on them. In this paper, based on the establishment of sequence stratigraphic framework of Subei basin, we have also studied the role of lacustrine carbonate rocks in our research. It is proposed that the distribution of carbonate nodules and lump s is a mark for recongnizing sequence boundary and systems tracts; and the depositional shifting of grain carbonate rocks can also serve as an importantmark for different systems tracts. and the p rofile change of carbonate rocks is also indicator for identifying parasequence and parasequence sets. In addition, the stably distributed dark fine carbonate rock and muddy shale interbedding is a mark of condensed section. This paper aims at appealing attention to the special role of carbonate rocks in establishing sequence stratigraphy in lacustrine sediments among the researchers.
2005, 23(1): 130-137.
Abstract:
There are many Quaternary laterites around the Dongting Basin. The survey on some typical laterite profiles on the field was carried, and samp ling in the Yueshan laterite p rofile, Yueyang City. Some experiments on the soil samples, such asmagnetic suscep tibilities, clayminerals and size analysises had been done, and the characteristics of the Quaternary laterite profiles in the Dongting Basin were studied, then the Quaternary paleoclimate evolution in the DongtingBasin was discnssed. The Yueshan laterite profile has the distinct stratigraphical facies and the evident profile characteristics, and it has a good stratigraphical correlation with other laterites in the South China. The analyses ofmagnetic suscep tibilities and clay minerals of the Yueshan laterite profile indicate the rules of the Quaternary climate change in the Dongting Basin as follows: the climate of the Dongting Basin in the early stage of the Middle Pleistocene is dry and cold, and the climate of the DongtingBasin in the late stage of theMiddle Pleistocene is humid and hot. The climate in the early stage of the late Pleistocene still keep humid and hot, but the climate begin to turn dry and cold in the late stage of the late Pleistocene. The climate of the DongtingBasin turn humid and hot in the Holocene once more. The size analysis indicates that the sedimentary environment of the Yueshan laterite is flood plain in the basin.
There are many Quaternary laterites around the Dongting Basin. The survey on some typical laterite profiles on the field was carried, and samp ling in the Yueshan laterite p rofile, Yueyang City. Some experiments on the soil samples, such asmagnetic suscep tibilities, clayminerals and size analysises had been done, and the characteristics of the Quaternary laterite profiles in the Dongting Basin were studied, then the Quaternary paleoclimate evolution in the DongtingBasin was discnssed. The Yueshan laterite profile has the distinct stratigraphical facies and the evident profile characteristics, and it has a good stratigraphical correlation with other laterites in the South China. The analyses ofmagnetic suscep tibilities and clay minerals of the Yueshan laterite profile indicate the rules of the Quaternary climate change in the Dongting Basin as follows: the climate of the Dongting Basin in the early stage of the Middle Pleistocene is dry and cold, and the climate of the DongtingBasin in the late stage of theMiddle Pleistocene is humid and hot. The climate in the early stage of the late Pleistocene still keep humid and hot, but the climate begin to turn dry and cold in the late stage of the late Pleistocene. The climate of the DongtingBasin turn humid and hot in the Holocene once more. The size analysis indicates that the sedimentary environment of the Yueshan laterite is flood plain in the basin.
2005, 23(1): 143-149.
Abstract:
Lower-Middle fresh lacustrine shale and coalmeasures with huge thickness have been found in the petroleum system of the northern Qaidam basin. These source rocks are characterized by high abundance of organic matter with mainly type Ⅱ-Ⅲ. The major oil and gas generation stage of the Jurassic source rocks is between theMiddle-Late episodes of the HimalayaMovement ( E3 -2N1 ). At that time, the existingMesozoic paleo-up lifts and the Cenozic folds and faults, which served as oilmigration routes and traps, greatly promoted the oil reservoir formation. In addition, multiple reservoir-cap compositions are confirmed in both the Jurassic and Tertiary strata. The estimated reserves of oil and gas are up to 1 billion ton of oil equivalent in the studied area. However, only about 3% of them have been found so far. Great potential for further hydrocarbon exp loration remains in this area. Three p referential targets for future hydrocarbon exp loration are selected, i. e. Lenghu No. 1 to No. 5 Trap, Nanbaxian2Dahonggou paleo up lift and the front of Saishiteng mountain
Lower-Middle fresh lacustrine shale and coalmeasures with huge thickness have been found in the petroleum system of the northern Qaidam basin. These source rocks are characterized by high abundance of organic matter with mainly type Ⅱ-Ⅲ. The major oil and gas generation stage of the Jurassic source rocks is between theMiddle-Late episodes of the HimalayaMovement ( E3 -2N1 ). At that time, the existingMesozoic paleo-up lifts and the Cenozic folds and faults, which served as oilmigration routes and traps, greatly promoted the oil reservoir formation. In addition, multiple reservoir-cap compositions are confirmed in both the Jurassic and Tertiary strata. The estimated reserves of oil and gas are up to 1 billion ton of oil equivalent in the studied area. However, only about 3% of them have been found so far. Great potential for further hydrocarbon exp loration remains in this area. Three p referential targets for future hydrocarbon exp loration are selected, i. e. Lenghu No. 1 to No. 5 Trap, Nanbaxian2Dahonggou paleo up lift and the front of Saishiteng mountain
2005, 23(1): 156-161.
Abstract:
The Dong fong 1-1 Gas Field of the Y inggehai Basin has great attract iveness because its characterist ics of a shallow burial depth, wide variations of gas composition and occurrence in the diapir fault belt. There have been still problems on gas source and gas-filling model for a long period. In th is paper, the method of hydrocarbon generation kinetics and carbon isotopic fraction kineticsw as applied to some typical source rocks from th is basin, and a geo logical model of gas generation and methane carbon isotopic fraction was suggested. With the comb ination of the geo logical and geochemical background of the Dong fong 1-1 Gas Filed, it was believed that the hydrocarbon gases were mainly from the coal measure source rocks in the Meishan Formation, but non-hydrocarbon gas the calcareous shale in the Shanya Formation. The gas pool is qu ite young, and is related to the diap irism. The hydrocarbon gas was charged after t 1.3Ma, and CO2 gas at about 0.1Ma. Thew ide variat ion compositions of the natura l gas were controlled by episode charges of gases controlled by diapir fault activities.
The Dong fong 1-1 Gas Field of the Y inggehai Basin has great attract iveness because its characterist ics of a shallow burial depth, wide variations of gas composition and occurrence in the diapir fault belt. There have been still problems on gas source and gas-filling model for a long period. In th is paper, the method of hydrocarbon generation kinetics and carbon isotopic fraction kineticsw as applied to some typical source rocks from th is basin, and a geo logical model of gas generation and methane carbon isotopic fraction was suggested. With the comb ination of the geo logical and geochemical background of the Dong fong 1-1 Gas Filed, it was believed that the hydrocarbon gases were mainly from the coal measure source rocks in the Meishan Formation, but non-hydrocarbon gas the calcareous shale in the Shanya Formation. The gas pool is qu ite young, and is related to the diap irism. The hydrocarbon gas was charged after t 1.3Ma, and CO2 gas at about 0.1Ma. Thew ide variat ion compositions of the natura l gas were controlled by episode charges of gases controlled by diapir fault activities.
2005, 23(1): 170-174.
Abstract:
37 samples of hydrocarbon gases in the recent sediment from South China Sea were analyzed for their geochemical composition and 14 samples were analyzed for isotop ic composition of Methane. The re lative average content of methane in the northern continental slope, sou thern con tinental slope and deep-seapla in is 95%, 91% and 94%,respective ly. The content o f heavy hydrocarbon gas is between 0 to 20%, ave rage 9%. The iso topic composition of me thane in con tinental slope area ranged form 30 to 40 and 24 to 36 in deep-sea plain area. Those data show that hydrocarbon gases in the recent sediment from continental slope area maybe come from thermal genetic gases and those from deep sea plain areamay have two resourcesw hich either might be originated from b iogenetic gases or from nonbiogenetic gases via fault.
37 samples of hydrocarbon gases in the recent sediment from South China Sea were analyzed for their geochemical composition and 14 samples were analyzed for isotop ic composition of Methane. The re lative average content of methane in the northern continental slope, sou thern con tinental slope and deep-seapla in is 95%, 91% and 94%,respective ly. The content o f heavy hydrocarbon gas is between 0 to 20%, ave rage 9%. The iso topic composition of me thane in con tinental slope area ranged form 30 to 40 and 24 to 36 in deep-sea plain area. Those data show that hydrocarbon gases in the recent sediment from continental slope area maybe come from thermal genetic gases and those from deep sea plain areamay have two resourcesw hich either might be originated from b iogenetic gases or from nonbiogenetic gases via fault.
2005, 23(1): 12-20.
Abstract:
Basin-prototype belongs to the tectonic propertywhen sedimentation occurs. The method of prototype analysis is just used to distinguish one stage basin types from the other stages. Other than working on the volcanical-fault basins of the first circle produced in the late Jurassic-early period of early Cretaceous, this paper discussed on the prototype and sedimentation of red fault basins along the Ganhang Tectonic Belt of the second circle, they produced after late period of early Cretaceous. There is a series of red fault basins at the center of the Ganhang Tectonic Belt, such as the Fuzhou-Chongren Basin, XinjiangBasin, Jinhua-Quzhou Basin and ZhujiBasin, distributing northeastward and mostly contacting each other in there two ends. Combining with the regional extension background manifested by the basalts at the bottom of red beds, these basins started at the late period of early Cretaceous, and almost every basin disp layed an one-tendency fault basin in geometry, which are all restricted within the normal fault in the north and un- conformable boundary in the south. By the middle2late period of late Cretaceous, all basins turned into dep ressive basins, thus the sediments overlay on the basement of the two sides, and there are some self-generating dolomite, marlite and claystone deposit in the centre. In the evolutional process of the red fault basin, the fluvial sedimentation plays a much important role than any other ways of deposition. The sedimentary facies vary from lake facies to fan facies,delta facies and fluvial facies, etc. This assembly is the basic sedimentation type of an extensional fault basin, and the changing model reflects the evolutional process of the fault basin from initial extension (deep lake) to final wither (ground river).
Basin-prototype belongs to the tectonic propertywhen sedimentation occurs. The method of prototype analysis is just used to distinguish one stage basin types from the other stages. Other than working on the volcanical-fault basins of the first circle produced in the late Jurassic-early period of early Cretaceous, this paper discussed on the prototype and sedimentation of red fault basins along the Ganhang Tectonic Belt of the second circle, they produced after late period of early Cretaceous. There is a series of red fault basins at the center of the Ganhang Tectonic Belt, such as the Fuzhou-Chongren Basin, XinjiangBasin, Jinhua-Quzhou Basin and ZhujiBasin, distributing northeastward and mostly contacting each other in there two ends. Combining with the regional extension background manifested by the basalts at the bottom of red beds, these basins started at the late period of early Cretaceous, and almost every basin disp layed an one-tendency fault basin in geometry, which are all restricted within the normal fault in the north and un- conformable boundary in the south. By the middle2late period of late Cretaceous, all basins turned into dep ressive basins, thus the sediments overlay on the basement of the two sides, and there are some self-generating dolomite, marlite and claystone deposit in the centre. In the evolutional process of the red fault basin, the fluvial sedimentation plays a much important role than any other ways of deposition. The sedimentary facies vary from lake facies to fan facies,delta facies and fluvial facies, etc. This assembly is the basic sedimentation type of an extensional fault basin, and the changing model reflects the evolutional process of the fault basin from initial extension (deep lake) to final wither (ground river).
2005, 23(1): 29-33.
Abstract:
The Mantou Format ion in the North China platform, which overlain the Archaean Taishan Group, mainly consists of terrigenous clastic rocks and carbonate interca lations. In the Zhonggong village of the Jinan city, olistotrome with thickness of about 4m occurred in the lower part of the Mantou Formation. Carbonate and fine clastic rocks is its block, and siltstone is its matrix. Deformation styles of the blocks and cross bedding within the blocks demonstrate that there should ex ist an old slope in the North China platform and tectonic uplifting had took place in the Cambrain. They were main factors to induce olistotrome. Identifying and studying the olistostrome with in the Mantou Formation is benefit to study the Paleozoic paleogeography and sedimentary env ironments of the North China platform and the evolution of the buried hills, which can provide some good evidences for the study on the Paleozoic sedimentary basin contained with abundant oil and gas and buried hills, and for prospecting source of oil and gas.
The Mantou Format ion in the North China platform, which overlain the Archaean Taishan Group, mainly consists of terrigenous clastic rocks and carbonate interca lations. In the Zhonggong village of the Jinan city, olistotrome with thickness of about 4m occurred in the lower part of the Mantou Formation. Carbonate and fine clastic rocks is its block, and siltstone is its matrix. Deformation styles of the blocks and cross bedding within the blocks demonstrate that there should ex ist an old slope in the North China platform and tectonic uplifting had took place in the Cambrain. They were main factors to induce olistotrome. Identifying and studying the olistostrome with in the Mantou Formation is benefit to study the Paleozoic paleogeography and sedimentary env ironments of the North China platform and the evolution of the buried hills, which can provide some good evidences for the study on the Paleozoic sedimentary basin contained with abundant oil and gas and buried hills, and for prospecting source of oil and gas.
2005, 23(1): 41-48.
Abstract:
Based on studies of three geological transections (Shadunshang, Yanbei and Dongxia) from 1:50, 000 field mapp ing at Gangkou area, Jianxi, this paper addresses the petrological features and facies distribution of late-Cambrian carbonate rocks of Xiyangshan formation. Three main depositional facies of carbonate-ramp origin are identified, which are circum-platform redepositional clastic apron facies, carbonate turbidite facies and hemi-pelagic muddy facies. The dynamic variations of the depositional processes and the causes of carbonate lens are further analyzed.Carbonate lens observed in Xiyangshan formation are believed to be of multiple causes and may result from the combined action of several different mechanisms. In addition, cyclic carbonate sequences in this area are found to have self-similar and multifractal behaviors.
Based on studies of three geological transections (Shadunshang, Yanbei and Dongxia) from 1:50, 000 field mapp ing at Gangkou area, Jianxi, this paper addresses the petrological features and facies distribution of late-Cambrian carbonate rocks of Xiyangshan formation. Three main depositional facies of carbonate-ramp origin are identified, which are circum-platform redepositional clastic apron facies, carbonate turbidite facies and hemi-pelagic muddy facies. The dynamic variations of the depositional processes and the causes of carbonate lens are further analyzed.Carbonate lens observed in Xiyangshan formation are believed to be of multiple causes and may result from the combined action of several different mechanisms. In addition, cyclic carbonate sequences in this area are found to have self-similar and multifractal behaviors.
2005, 23(1): 60-66.
Abstract:
Pyroclastic base-surge deposits of volcanic cluster in the Longgang region of Jilin Province is one of the few neoteric maar depositswhich are preserved in good condition in China. Based on the lithological characters, lithofacies and sequences, pyroclastic base-surge sequence consists of millimeter-scale to centimeter-scale frequent cyclothem that constitute a regularly vertical stacking pattern, which is made of sub-edge angle and worse graded basaltic sand, lap illus and tuff ash. Mass bedding, dune-like structure, low angle cross-bedding, chute and pool structure, parallel bedding and scouring through are widely developed in base-surge deposits. Pryoclastic granularity, de- posit structures and thickness are developed with a regularly transverse discip linarian from inner to external of maar. The characteristic of pyroclastic ejecta ismore differentwith ignimbrite and alluvial and /or diluvial deposits from vol- canic cone. B its of strombolian-type scoria and Hawaii-type effusive lava may accompany lately after Phreatomagmatic erup tion, they constitute a erup tive activity cycle in its entirely.
Pyroclastic base-surge deposits of volcanic cluster in the Longgang region of Jilin Province is one of the few neoteric maar depositswhich are preserved in good condition in China. Based on the lithological characters, lithofacies and sequences, pyroclastic base-surge sequence consists of millimeter-scale to centimeter-scale frequent cyclothem that constitute a regularly vertical stacking pattern, which is made of sub-edge angle and worse graded basaltic sand, lap illus and tuff ash. Mass bedding, dune-like structure, low angle cross-bedding, chute and pool structure, parallel bedding and scouring through are widely developed in base-surge deposits. Pryoclastic granularity, de- posit structures and thickness are developed with a regularly transverse discip linarian from inner to external of maar. The characteristic of pyroclastic ejecta ismore differentwith ignimbrite and alluvial and /or diluvial deposits from vol- canic cone. B its of strombolian-type scoria and Hawaii-type effusive lava may accompany lately after Phreatomagmatic erup tion, they constitute a erup tive activity cycle in its entirely.
2005, 23(1): 73-83.
Abstract:
During Cretaceous, Ordos Basin had gone two desert sedimentation evolution stages involved from Yijun- Luohe stage to Huanhe stage and from Luohandong stage to J ingchuan stage, controlled by areolation and hydro dyna- mism, under the climate evolution and tectonic lifting and subsidence. Luohe stage and Luohandong stage are two ma- jor sedimentation stages of desert facies, desert facies can be divided five sub-facies such as gobis, wades, dunes, inter-dunes, and desert lakes. Among them, sandstones of dunes are the most important desert sediments of Cretaceous; they have many pores, big thickness, stable distribution, lower salt content, and good capability of water-bearing, water-leading, water penetrating. So, dunes sediments not only have good groundwater occurrence-circulation condi- tions, but also bear groundwater of better quality.
During Cretaceous, Ordos Basin had gone two desert sedimentation evolution stages involved from Yijun- Luohe stage to Huanhe stage and from Luohandong stage to J ingchuan stage, controlled by areolation and hydro dyna- mism, under the climate evolution and tectonic lifting and subsidence. Luohe stage and Luohandong stage are two ma- jor sedimentation stages of desert facies, desert facies can be divided five sub-facies such as gobis, wades, dunes, inter-dunes, and desert lakes. Among them, sandstones of dunes are the most important desert sediments of Cretaceous; they have many pores, big thickness, stable distribution, lower salt content, and good capability of water-bearing, water-leading, water penetrating. So, dunes sediments not only have good groundwater occurrence-circulation condi- tions, but also bear groundwater of better quality.
2005, 23(1): 91-98.
Abstract:
Trace fossils from the tidal flat Tataertage Formation (Silurian) consist of at least 12 ichnogenera and 12 ichnospecies, namely, Skolithos linearis, Skolithos verticalis, Ophiom orpha nodosa, Thalassinoides suevicus, D iplocraterion parallelum, A renicolites isp., M acaronichnus segrega tis, Cy lindrichnus isp., Taen idium satanassi, Palaeophycus tubu laris, Planolites beverlegensis and Cochlichnus anguineus. These trace fossils, which are mainly p reserved in full relief and epirelief, can be known as the domichnia, fodinichnia and pascichnia of invertebrates. According to their palaeoecological and sedimentological features, these trace fossils can be divided into 3 ichnoassemblags, i. e. ①Skolithos-Tha lassinoides assemblage, forming in the sand flat sedimentary environment, mainly consists of a set of Skolithos linea ris, Tha lassinoides suevicus, M acaronichnus segregatis, D iplocraterion pa rallelum, A renicolites isp.,Cy lindrichnus isp. and so on; ②Planolites-Palaeophycus assemblage, which is p redominantly composed of Planolites beverlegensis, Palaeophycus tubu laris, M acaronichnus segregatis, Skolithos vertica lis, Ophiom orpha nodosa, Taenidium satanassi and so forth, is characterized by high diversity and abundance of trace fossils. The ichnoassemblage is associated with the mixed flat between average high tidal and average low tidal base; ③Cochlichnus-Planolites assemblage, including Cochlichnus angu ineus and Planolites beverlegensis, occurs in the mud flat sedimentary environment near average low tidal base.
Trace fossils from the tidal flat Tataertage Formation (Silurian) consist of at least 12 ichnogenera and 12 ichnospecies, namely, Skolithos linearis, Skolithos verticalis, Ophiom orpha nodosa, Thalassinoides suevicus, D iplocraterion parallelum, A renicolites isp., M acaronichnus segrega tis, Cy lindrichnus isp., Taen idium satanassi, Palaeophycus tubu laris, Planolites beverlegensis and Cochlichnus anguineus. These trace fossils, which are mainly p reserved in full relief and epirelief, can be known as the domichnia, fodinichnia and pascichnia of invertebrates. According to their palaeoecological and sedimentological features, these trace fossils can be divided into 3 ichnoassemblags, i. e. ①Skolithos-Tha lassinoides assemblage, forming in the sand flat sedimentary environment, mainly consists of a set of Skolithos linea ris, Tha lassinoides suevicus, M acaronichnus segregatis, D iplocraterion pa rallelum, A renicolites isp.,Cy lindrichnus isp. and so on; ②Planolites-Palaeophycus assemblage, which is p redominantly composed of Planolites beverlegensis, Palaeophycus tubu laris, M acaronichnus segregatis, Skolithos vertica lis, Ophiom orpha nodosa, Taenidium satanassi and so forth, is characterized by high diversity and abundance of trace fossils. The ichnoassemblage is associated with the mixed flat between average high tidal and average low tidal base; ③Cochlichnus-Planolites assemblage, including Cochlichnus angu ineus and Planolites beverlegensis, occurs in the mud flat sedimentary environment near average low tidal base.
2005, 23(1): 108-112.
Abstract:
By ana lyzing the c layminerals of P /T boundary inMeishan Section show that the paragenetic association has no re lationsh ip to crystalization, but con incides with the change of formations and members, wh ich re flect the change of c limate, source and geography. IC has no notab le regu lar variation; otherwise, nomatter the paragentic as2 soc iation or IC have changed evidently, ind icate that pH and temperature have changed acu tely, which may result in themass extinction of the Permianmarine invertebrates at the end of Permian.
By ana lyzing the c layminerals of P /T boundary inMeishan Section show that the paragenetic association has no re lationsh ip to crystalization, but con incides with the change of formations and members, wh ich re flect the change of c limate, source and geography. IC has no notab le regu lar variation; otherwise, nomatter the paragentic as2 soc iation or IC have changed evidently, ind icate that pH and temperature have changed acu tely, which may result in themass extinction of the Permianmarine invertebrates at the end of Permian.
2005, 23(1): 122-129.
Abstract:
Grain-size distribution of 149 sediment samp les of Core DD2 and 3 suspended sediment samp les, pretreated by removing the organic matter and carbonate, are measured by use ofMalvern 2000. The samp ling sites are located in the inner shelf of the East China Sea. Vertical distribution of grain-size parameters of Core DD2 is studied. Standard deviations are calculated for all 149 samp les. Two peaks are observed in plot standard deviation values vs.grain-size classes, at about 19 and 130μm grain size, respectively. They are environmentally sensitive grain-size population. And about 19μm is sensitive to coastal current of the East China Sea, the other is to storm current. Each of these size classes rep resents a population of grainswith the highest variability through time. Vertical contents of sensitive grain-size population are carried out. It shows that the sedimentations of upper Core DD2 was controlled by coastal current and was in relatively stable environment. This result is supported by the comparison analysis between the modern suspended sediments and Core DD2. And lower part was controlled by combination of coastal and storm currents and was in unstable environment.
Grain-size distribution of 149 sediment samp les of Core DD2 and 3 suspended sediment samp les, pretreated by removing the organic matter and carbonate, are measured by use ofMalvern 2000. The samp ling sites are located in the inner shelf of the East China Sea. Vertical distribution of grain-size parameters of Core DD2 is studied. Standard deviations are calculated for all 149 samp les. Two peaks are observed in plot standard deviation values vs.grain-size classes, at about 19 and 130μm grain size, respectively. They are environmentally sensitive grain-size population. And about 19μm is sensitive to coastal current of the East China Sea, the other is to storm current. Each of these size classes rep resents a population of grainswith the highest variability through time. Vertical contents of sensitive grain-size population are carried out. It shows that the sedimentations of upper Core DD2 was controlled by coastal current and was in relatively stable environment. This result is supported by the comparison analysis between the modern suspended sediments and Core DD2. And lower part was controlled by combination of coastal and storm currents and was in unstable environment.
2005, 23(1): 138-142.
Abstract:
Based on the environmental magnetic measurement on the core with the length of 140cm collected from Honghu Lake, it has been analyzed the chart that the environmental magnetic parameters vary alone with the depth.The result suggests that the stable single domain and fine viscous ferromagnetic minerals dominate the characteristics of sediments. The magnetic minerals grain size increasingly reduces from the bottom to top. By combination AMS dating and geochemistry analyses, it can be deduced that Honghu Lake experiences swampy and lacustrine sediment from last 1200a. Moreovermagnetic characteristics changing corresponds to palaeoclimatic changes. In cold and dry condition,the magnetic parameters are higher than that in warm and wet condition. They record the course that Honghu Lake extends and shrinks along with climate; at one time reflects the human activities' impact on the lake.
Based on the environmental magnetic measurement on the core with the length of 140cm collected from Honghu Lake, it has been analyzed the chart that the environmental magnetic parameters vary alone with the depth.The result suggests that the stable single domain and fine viscous ferromagnetic minerals dominate the characteristics of sediments. The magnetic minerals grain size increasingly reduces from the bottom to top. By combination AMS dating and geochemistry analyses, it can be deduced that Honghu Lake experiences swampy and lacustrine sediment from last 1200a. Moreovermagnetic characteristics changing corresponds to palaeoclimatic changes. In cold and dry condition,the magnetic parameters are higher than that in warm and wet condition. They record the course that Honghu Lake extends and shrinks along with climate; at one time reflects the human activities' impact on the lake.
2005, 23(1): 150-155.
Abstract:
The crude oils in the western Qaidam Basin are immature-low mature oils from the source rocks deposited under saline lacustrine environment, which are typical genetic kind. Gasikule oilfield is the largest oilfield in western Qaidam Basin. Oil accumulation conditions for E13 oil pool in the oilfield, such as oil generation, migration, accumulation and trap, and so on, were systematically studied and the formation mechanism of the oil was discussed. This provides scientific evidence for the genetic understanding of the studied oil pool and further exploration development in the western Qaidam Basin.
The crude oils in the western Qaidam Basin are immature-low mature oils from the source rocks deposited under saline lacustrine environment, which are typical genetic kind. Gasikule oilfield is the largest oilfield in western Qaidam Basin. Oil accumulation conditions for E13 oil pool in the oilfield, such as oil generation, migration, accumulation and trap, and so on, were systematically studied and the formation mechanism of the oil was discussed. This provides scientific evidence for the genetic understanding of the studied oil pool and further exploration development in the western Qaidam Basin.
2005, 23(1): 162-169.
Abstract:
Through the stepwise separation and extract on free hydrocarbon, sealed hydrocarbon, hydrocarbon in carbonate cement, bounded hydrocarbon and inclusion hydrocarbon within quartz grain on six oil sand samp les from Yanchang Fm. (Triassic), Xifeng oilfield, Ordos basin, all these hydrocarbons have been analyzed by GC-MS. On the basis of diagenetic sequence, in combination with the feature of the analyzed samples, the results show that thismethod is practicable. And the study on linear alkane with different existence states shows the nalkaneswith single peak are dominant in the study area with wide range of carbon number and weaker odd-carbon preference. The parentmaterial types of these hydrocarbons are typeⅠ-Ⅱkerogen deposited in the reducing fresh water lacustrine environment.Obvious differences occur in Pr /Ph ratio and CP I value in these hydrocarbonswith different existence state. Generally, it has a decreasing tendency from free hydrocarbon, sealed hydrocarbon, cement hydrocarbon to inclusion hydrocarbon, togetherwith their group composition features, this phenomena can reflect the oil generation step s and filling periods of oil pool and microscale heterogeneity within oil pools.
Through the stepwise separation and extract on free hydrocarbon, sealed hydrocarbon, hydrocarbon in carbonate cement, bounded hydrocarbon and inclusion hydrocarbon within quartz grain on six oil sand samp les from Yanchang Fm. (Triassic), Xifeng oilfield, Ordos basin, all these hydrocarbons have been analyzed by GC-MS. On the basis of diagenetic sequence, in combination with the feature of the analyzed samples, the results show that thismethod is practicable. And the study on linear alkane with different existence states shows the nalkaneswith single peak are dominant in the study area with wide range of carbon number and weaker odd-carbon preference. The parentmaterial types of these hydrocarbons are typeⅠ-Ⅱkerogen deposited in the reducing fresh water lacustrine environment.Obvious differences occur in Pr /Ph ratio and CP I value in these hydrocarbonswith different existence state. Generally, it has a decreasing tendency from free hydrocarbon, sealed hydrocarbon, cement hydrocarbon to inclusion hydrocarbon, togetherwith their group composition features, this phenomena can reflect the oil generation step s and filling periods of oil pool and microscale heterogeneity within oil pools.
2005, 23(1): 183-186.
Abstract:
The evaluation of pressure effects is obtained by performing the hydrolysis of methyl octadecanonate as a model reaction catalyzed by seven different samp les of immature source rock that had first been extracted with organic solvents. The results show that p ressure plays an important role in the reaction and the pressure effects are not negligible. The pressure effects are different among the seven immature source rock. As a conquence, an enhanced or lowered ratios of hydrolysis takes place as a result of the pressure effects. The reasons that lead to such a result are discussed. It is suggested that the pressure effects observed is a complex of the promotion and restraint caused by pressure.
The evaluation of pressure effects is obtained by performing the hydrolysis of methyl octadecanonate as a model reaction catalyzed by seven different samp les of immature source rock that had first been extracted with organic solvents. The results show that p ressure plays an important role in the reaction and the pressure effects are not negligible. The pressure effects are different among the seven immature source rock. As a conquence, an enhanced or lowered ratios of hydrolysis takes place as a result of the pressure effects. The reasons that lead to such a result are discussed. It is suggested that the pressure effects observed is a complex of the promotion and restraint caused by pressure.
