THE RELATIONS BETWEEN DEEPDYNAMIC PROCESS AND THEFORMATION OF OIL-GAS POOLS INTHE SONGLIAO BASIN, CHINALi Zhi’an(Changsha Institute of Geotectonics, Academia Sinica, Changsha, 410013, Hunan, China)Songliao basin, cru...THE RELATIONS BETWEEN DEEPDYNAMIC PROCESS AND THEFORMATION OF OIL-GAS POOLS INTHE SONGLIAO BASIN, CHINALi Zhi’an(Changsha Institute of Geotectonics, Academia Sinica, Changsha, 410013, Hunan, China)Songliao basin, crust structure, deep dynamics, the formation of oil-gas poolsThis essay deals in detail with the inhomogeneity of the crust structure and the variation of the Moho, the process of deep dynamics and also relations of deep dynamic process to the formation of oil-gas pools in Songliao Basin.展开更多
The lower Cambrian Niutitang Formation hydrocarbon source rocks at the Dingshan- Lintanchang structure in the southeast Sichuan Basin were of medium-good quality with two excellent hydrocarbon-generating centers devel...The lower Cambrian Niutitang Formation hydrocarbon source rocks at the Dingshan- Lintanchang structure in the southeast Sichuan Basin were of medium-good quality with two excellent hydrocarbon-generating centers developed in the periphery areas, with a possibility of forming a medium to large-sized oil-gas field. Good reservoir rocks were the upper Sinian (Dengying Formation) dolomites. The mudstone in the lower Cambrian Niutitang Formation with a good sealing capacity was the cap rock. The widely occurring bitumen in the Dengying Formation indicates that a paleo oil pool was once formed in the study area. The first stage of paleo oil pool formation was maturation of the lower Cambrian source rocks during the late Ordovician. Hydrocarbon generation from the lower Cambrian source rocks stopped due to the Devonian-Carboniferous uplifting. The lower Cambrian source rocks then restarted generation of large quantities of hydrocarbons after deposition of the middle Permian sediments. This was the second stage of the paleo oil pool formation. The oil in the paleo oil pool began to crack during the late Triassic and a paleo gas pool was formed. This paleo gas pool was destroyed during the Yanshan-Himalayan folding, uplifting and denudation. Bitumen can be widely seen in the Dengying Formation in wells and outcrops in the Sichuan Basin and its periphery areas. This provides strong evidence that the Dengying Formation in the Sichuan Basin and its periphery areas was once an ultra-large structural-lithologic oil-gas field, which was damaged during the Yanshan-Himalayan period.展开更多
Large-scale oil exploration has been done and large quantities of oil-gas fields have been found in the northern shelf basin of the South China Sea for more than 20 years. The tectonic oil-gas pools are the main type....Large-scale oil exploration has been done and large quantities of oil-gas fields have been found in the northern shelf basin of the South China Sea for more than 20 years. The tectonic oil-gas pools are the main type. With the exploration to be deepened, looking for atectonic oil-gas pools is listed in China's exploration strategy. There are advantages for the forming of atectonic oil-gas pools in the northern shelf basin of the South China Sea. Because the level of water has been frequently changing within all historical periods, lithozones are changed alternately in both vertical and lateral directions and formed lithologic deposition especially at low water level stages, such as the low-lying fans of basin-floor fans and slope fans. Due to frequent tectonic movement within all historical periods, many structural surfaces and structural unconformities were formed. At the same time, they also formed many kinds of structural unconformity oil-gas pools. According to our exploration and research, the promising areas of atectonic reservoirs within marine basins include: (1) the basin-floor fan of the deep water district, such as the central depression of the Southeast Qiong basin and Baiyun sag in the Zhujiangkou basin; (2) the frontal area of the large ancient delta, such as the Lingao structural belt in the Yingge Sea basin and Huizhou sag in the Zhujiangkou basin; (3) the unconformity pinchout belt or denudation belt in the slope area and the uplift area, for instance, the Yingdong slope belt in the Yingge Sea basin and Yacheng 13-1 structural belt in the southeast Qiong basin. All this proves that the prospects for atectonic oil-gas pools in the northern shelf basin of the South China Sea are very broad.展开更多
In the Northern Jiangsu basin there are high pure CO2 gas pools, low condensed oil-containing CO2 gas pools, high condensed oil-containing CO2 gas pools and He-containing natural gas pools, with the δ13Cco2 (PDB) val...In the Northern Jiangsu basin there are high pure CO2 gas pools, low condensed oil-containing CO2 gas pools, high condensed oil-containing CO2 gas pools and He-containing natural gas pools, with the δ13Cco2 (PDB) values ranging from ?2.87%o to ?6.50%o, 3He/4He 3.71 × 10?6 to 6.42 × 10?6, R/Ra 2.64 to 4.5, 40Ar/36Ar 705 to 734, belonging to typical mantle source inorganic gas pools which are related to young magmatic activity. The gas layers occur in two major reservoir-caprock systems, the terrestrial Meso-Cenozoic clastic rock system and the marine Meso-Palaeozoic carbonate rock-clastic rock system. Controlled by the difference in the scale of traps in the two reservoir-caprock systems, large and medium-scale inorganic gas pools are formed in the marine Meso-Palaeozoic Group and only small ones are formed in the terrestrial Meso-Cenozoic strata. Inorganic gas pools in this basin are distributed along the two deep lithospheric faults on the west and south boundaries of the basin. Gas pools are developed at the intersected part of the ENE-trending faults that control the half graben and the E-W tenso-shear faults, mainly distributed near the Es1, Ny1 and Ny2-Q basalt eruption centres.展开更多
Prolonged extensional regime in peninsular India resulted in formation of rift and grabens,elongated basins and Gondwana sedimentation along them.Downward progression of rift related faults caused decompression
Conditions for the Formation of oil and gas pools in Tertiary volcanics in the western part of the Huimin sag, Shandong and then (?)stribution have been studied based on the geological, seismic and well-logging inform...Conditions for the Formation of oil and gas pools in Tertiary volcanics in the western part of the Huimin sag, Shandong and then (?)stribution have been studied based on the geological, seismic and well-logging information. In this paper, the types and lithofacies of the volcanic rocks in the western part of the Huimin sag are described; the relationship between rocks and electrical properties, the seismic reflection structures, the development and distribution of the volcanic rocks are expounded; and the fourfold role of the volcanic activities in the formation of the oil and gas pools is also dealt with. It is considered by the authors that the volcanic activities were not destructive to the formation of oil and gas pools but a factor favourable to the accumulation of organic matters and their conversion to hydrocarbon. The volcanic rocks might have served as reservoir rocks and cap rocks, or as a synsedimentary anticline. The prerequisites and important factors for the formation of oil and gas pools and their distribution are pointed out in the paper.展开更多
There are three formation stages of Silurian hydrocarbon pools in the Tarim Basin. The widely distributed asphaltic sandstones in the Tazhong (central Tarim) and Tabei (northern Tarim) areas are the results of des...There are three formation stages of Silurian hydrocarbon pools in the Tarim Basin. The widely distributed asphaltic sandstones in the Tazhong (central Tarim) and Tabei (northern Tarim) areas are the results of destruction of hydrocarbon pools formed in the first-stage, and the asphaltic sandstones around the Awati Sag were formed in the second-stage. The hydrocarbon migration characteristics reflected by the residual dry asphalts could represent the migration characteristics of hydrocarbons in the Silurian paleo-pools, while the present movable oil in the Silurian reservoirs is related to the iater-stage (the third-stage) hydrocarbon accumulation.展开更多
The Lower Triassic Jialingjiang Formation reservoirs are distributed widely in the East Sichuan Basin, which are composed mainly of fractured reservoirs. However, natural gas with high concentration of H2S, ranging fr...The Lower Triassic Jialingjiang Formation reservoirs are distributed widely in the East Sichuan Basin, which are composed mainly of fractured reservoirs. However, natural gas with high concentration of H2S, ranging from 4% to 7%, was discovered in the Wolonghe Gas pool consisting primarily of porous reservoirs, while the other over 20 fractured gas reservoirs have comparatively low, tiny and even no H2S within natural gases. Researches have proved the H2S of the above reservoirs are all from the TSR origin. Most of the Jialingjiang Formation natural gases are mainly generated from Lower Permian carbonate rocks, the Wolonghe gas pool's natural gases are from the Upper Permian Longtan Formation, and the natural gases of the Huangcaoxia and Fuchengzhai gas pools are all from Lower Silurian mudstone. The formation of H2S is controlled by the characteristics and temperature of reservoirs, and is not necessarily related with gas sources. The Jialingjiang Formation in East Sichuan is buried deeply and its reservoir temperature has ever attained the condition of the TSR reaction. Due to poor reservoir potential, most of the gas pools do not have enough room for hydrocarbon reaction except for the Wolonghe gas pool, and thus natural gases with high H2S concentration are difficult to be generated abundantly. The south part of East Sichuan did not generate natural gases with high H2S concentration because the reservoir was buried relatively shallow, and did not suffer high temperature. Hence, while predicting the distribution of H2S, the characteristics and temperature of reservoirs are the necessary factors to be considerd besides the existence of anhydrite.展开更多
Based on the theory of formation dynamics of oil/gas pools, the Dongying sag can be divided into three dynamic systems regarding the accumulation of oil and gas: the superpressure closed system, the semi-closed syste...Based on the theory of formation dynamics of oil/gas pools, the Dongying sag can be divided into three dynamic systems regarding the accumulation of oil and gas: the superpressure closed system, the semi-closed system and the normal pressure open system. Based on the analysis of genesis of superpressure in the superpressure closed system and the rule of hydrocarbon expulsion, it is found that hydrocarbon generation is related to superpressure, which is the main driving factor of hydrocarbon migration. Micro fractures formed by superpressure are the main channels for hydrocarbon migration. There are three dynamic patterns for hydrocarbon expulsion: free water drainage, hydrocarbon accumulation and drainage through micro fissures. In the superpressure closed system, the oil-driving-water process and oil/gas accumulation were completed in lithologic traps by way of such two dynamic patterns as episodic evolution of superpressure systems and episodic pressure release of faults. The oil-bearing capacity of lithologic traps is intimately related to reservoir-forming dynamic force. Quantitative evaluation of dynamic conditions for pool formation can effectively predict the oil-bearing capability of traps.展开更多
The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the f...The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution: being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.展开更多
A large number of crude oil and rock samples from various oil pools of the Central Uplift in Dongying Depression were investigated to reveal the origin and accumulation of hydrocarbons. The results showed that the com...A large number of crude oil and rock samples from various oil pools of the Central Uplift in Dongying Depression were investigated to reveal the origin and accumulation of hydrocarbons. The results showed that the composition and areal distribution of hydrocarbons vary with the location of the oil pools. An increasing trend of gammacerane/C30-hopane and steranes/hopanes but a decreasing trend of prystane/phytane (Pr/Ph) and 18(H)-/17(H)- trisnorhopane (Ts/Tm) ratios were observed from southwest to northeast. This indicates a variation of source rocks and hydrocarbon properties. An increasing trend of water salinity with much more input of algae-rich microorganisms in the deposition environment of the source rock was observed from southwest to northeast. However, the thermal maturity of the source rocks showed a decreasing trend in the same direction. Oil-to-oil and oil-to-source rock correlations showed that most oils were sourced from Es3 and Es4 members with a burial depth of more than 3,000-3,150 m and 2,700 m respectively. The oils in the Shinan and Ying 11 sand bodies, which were generally mixed with the Es4 sourced oils, came mostly from Es3 mudstones. It is quite significant that the Es4 derived oils migrated vertically for hundreds of meters and accumulated in an overlying lithologic pool of the Es3^m, i.e., Ying 11 synclinal lithologic pool, which suggests that the mechanisms of migration and accumulation for subtle oil pools in the Dongying Depression are more complex than that of the previously expected.展开更多
Because of the difference ofoil and gas accumulation condition between the hanging wall and the footwall of a fault, there is a peculiar accumulation mechanism that oil and gas mainly exists in the hanging wall of the...Because of the difference ofoil and gas accumulation condition between the hanging wall and the footwall of a fault, there is a peculiar accumulation mechanism that oil and gas mainly exists in the hanging wall of the basement fault, but in the footwall of the shallow detachment fault in the Nanbaxian pool. The oil and gas of the Nanbaxian pool came from the mature Jurassic hydrocarbon source rock of the Yibei depression located at the south of the Nanbaxian pool. Firstly, the oil and gas accumulated in the traps of the hanging wall of the basement fault by way of the unconformity and the basement faults, and turned into some primary deep pools; and then, the shallow detachment fault that formed in the later tectonic movement broke into the deep primary pools, which caused the oil and gas migration upwards along the basement faults and the shallow detachment faults and the evolvement into some secondary oil and gas pools later. The history of the Nanbaxian oil and gas accumulation can be summarized successively as the syndepositional upheaval controlled by faults; single hydrocarbon source rock; unconformities and faults as migration channels; buoyancy, overpressure and tectonic stress as dynamic forces; multistage migration and accumulation of oil and gas; and finally an overlapped double-floor pattern of oil and gas accumulation. The most important explorative targets in the north of the Qaidam Basin are traps connected with the primary pools in the footwall by shallow detachment faults.展开更多
A GCM study is performed of the effects on Asian summer monsoon initiation of the Qinghai-Xizang Plateauand western Pacific warm pool. results show that the Plateau, being a prominent sensible heat source, acts as a b...A GCM study is performed of the effects on Asian summer monsoon initiation of the Qinghai-Xizang Plateauand western Pacific warm pool. results show that the Plateau, being a prominent sensible heat source, acts as a basicfactor for the formation of the monsoon circulation, the northward transported low-latitude and low-level warm,moist flow in relation to the sensible heating experiences dynamic lifting on the south and east sides of the highland,releasing vast quantities of latent heat through condensation, whereby the monsoon circulation pattern is furthermodulated; the temperature contrast between the Pacific warm pool and the Australian / marine continents serves asanother basic factor for the northern SW summer monsoon genesis over the South-China Sea-the western Pacific,which, however, falls into a category of winter monsoon on a physical basis.展开更多
This article reports the main formation models and distribution of the oil and gas pools in Tarim basin, China, including (1) occurrence of the found oil and gas pools, (2) main formation models of oil and gas poo...This article reports the main formation models and distribution of the oil and gas pools in Tarim basin, China, including (1) occurrence of the found oil and gas pools, (2) main formation models of oil and gas pools, and (3) distribution law of oil/gas pools. Petroleum is distributed widely in the strata of Tarim basin from the Sinian at the bottom to the Neogene at the top. However, the found oil and gas fields are mainly distributed in Shaya (沙雅) uplift, Tazhong (塔中) uplift, and Kuche (库车) depression. This article presents 4 main formation models, namely, early formation and long-term preservation, early formation and late reformation, middle-late multiphase-multisource formation, late single-stage formation. Tarim basin is very rich in petroleum resources. Long-term inherited intrabasinal paleohighs and slope zones are the most favorable areas for accumulation of hydrocarbons, but the types of oil and gas pools are different from area to area. The control of unconformities and faults on hydrocarbon accumulating is prominent in Tarim basin. Preservation conditions are of utmost importance. Formation of some oil and gas pools is the result of reforming and re-accumulating of early accumulated hydrocarbons.展开更多
文摘THE RELATIONS BETWEEN DEEPDYNAMIC PROCESS AND THEFORMATION OF OIL-GAS POOLS INTHE SONGLIAO BASIN, CHINALi Zhi’an(Changsha Institute of Geotectonics, Academia Sinica, Changsha, 410013, Hunan, China)Songliao basin, crust structure, deep dynamics, the formation of oil-gas poolsThis essay deals in detail with the inhomogeneity of the crust structure and the variation of the Moho, the process of deep dynamics and also relations of deep dynamic process to the formation of oil-gas pools in Songliao Basin.
基金supported by the National Basic Research Program of China (No. 2005CB422106)
文摘The lower Cambrian Niutitang Formation hydrocarbon source rocks at the Dingshan- Lintanchang structure in the southeast Sichuan Basin were of medium-good quality with two excellent hydrocarbon-generating centers developed in the periphery areas, with a possibility of forming a medium to large-sized oil-gas field. Good reservoir rocks were the upper Sinian (Dengying Formation) dolomites. The mudstone in the lower Cambrian Niutitang Formation with a good sealing capacity was the cap rock. The widely occurring bitumen in the Dengying Formation indicates that a paleo oil pool was once formed in the study area. The first stage of paleo oil pool formation was maturation of the lower Cambrian source rocks during the late Ordovician. Hydrocarbon generation from the lower Cambrian source rocks stopped due to the Devonian-Carboniferous uplifting. The lower Cambrian source rocks then restarted generation of large quantities of hydrocarbons after deposition of the middle Permian sediments. This was the second stage of the paleo oil pool formation. The oil in the paleo oil pool began to crack during the late Triassic and a paleo gas pool was formed. This paleo gas pool was destroyed during the Yanshan-Himalayan folding, uplifting and denudation. Bitumen can be widely seen in the Dengying Formation in wells and outcrops in the Sichuan Basin and its periphery areas. This provides strong evidence that the Dengying Formation in the Sichuan Basin and its periphery areas was once an ultra-large structural-lithologic oil-gas field, which was damaged during the Yanshan-Himalayan period.
文摘Large-scale oil exploration has been done and large quantities of oil-gas fields have been found in the northern shelf basin of the South China Sea for more than 20 years. The tectonic oil-gas pools are the main type. With the exploration to be deepened, looking for atectonic oil-gas pools is listed in China's exploration strategy. There are advantages for the forming of atectonic oil-gas pools in the northern shelf basin of the South China Sea. Because the level of water has been frequently changing within all historical periods, lithozones are changed alternately in both vertical and lateral directions and formed lithologic deposition especially at low water level stages, such as the low-lying fans of basin-floor fans and slope fans. Due to frequent tectonic movement within all historical periods, many structural surfaces and structural unconformities were formed. At the same time, they also formed many kinds of structural unconformity oil-gas pools. According to our exploration and research, the promising areas of atectonic reservoirs within marine basins include: (1) the basin-floor fan of the deep water district, such as the central depression of the Southeast Qiong basin and Baiyun sag in the Zhujiangkou basin; (2) the frontal area of the large ancient delta, such as the Lingao structural belt in the Yingge Sea basin and Huizhou sag in the Zhujiangkou basin; (3) the unconformity pinchout belt or denudation belt in the slope area and the uplift area, for instance, the Yingdong slope belt in the Yingge Sea basin and Yacheng 13-1 structural belt in the southeast Qiong basin. All this proves that the prospects for atectonic oil-gas pools in the northern shelf basin of the South China Sea are very broad.
文摘In the Northern Jiangsu basin there are high pure CO2 gas pools, low condensed oil-containing CO2 gas pools, high condensed oil-containing CO2 gas pools and He-containing natural gas pools, with the δ13Cco2 (PDB) values ranging from ?2.87%o to ?6.50%o, 3He/4He 3.71 × 10?6 to 6.42 × 10?6, R/Ra 2.64 to 4.5, 40Ar/36Ar 705 to 734, belonging to typical mantle source inorganic gas pools which are related to young magmatic activity. The gas layers occur in two major reservoir-caprock systems, the terrestrial Meso-Cenozoic clastic rock system and the marine Meso-Palaeozoic carbonate rock-clastic rock system. Controlled by the difference in the scale of traps in the two reservoir-caprock systems, large and medium-scale inorganic gas pools are formed in the marine Meso-Palaeozoic Group and only small ones are formed in the terrestrial Meso-Cenozoic strata. Inorganic gas pools in this basin are distributed along the two deep lithospheric faults on the west and south boundaries of the basin. Gas pools are developed at the intersected part of the ENE-trending faults that control the half graben and the E-W tenso-shear faults, mainly distributed near the Es1, Ny1 and Ny2-Q basalt eruption centres.
文摘Prolonged extensional regime in peninsular India resulted in formation of rift and grabens,elongated basins and Gondwana sedimentation along them.Downward progression of rift related faults caused decompression
文摘Conditions for the Formation of oil and gas pools in Tertiary volcanics in the western part of the Huimin sag, Shandong and then (?)stribution have been studied based on the geological, seismic and well-logging information. In this paper, the types and lithofacies of the volcanic rocks in the western part of the Huimin sag are described; the relationship between rocks and electrical properties, the seismic reflection structures, the development and distribution of the volcanic rocks are expounded; and the fourfold role of the volcanic activities in the formation of the oil and gas pools is also dealt with. It is considered by the authors that the volcanic activities were not destructive to the formation of oil and gas pools but a factor favourable to the accumulation of organic matters and their conversion to hydrocarbon. The volcanic rocks might have served as reservoir rocks and cap rocks, or as a synsedimentary anticline. The prerequisites and important factors for the formation of oil and gas pools and their distribution are pointed out in the paper.
文摘There are three formation stages of Silurian hydrocarbon pools in the Tarim Basin. The widely distributed asphaltic sandstones in the Tazhong (central Tarim) and Tabei (northern Tarim) areas are the results of destruction of hydrocarbon pools formed in the first-stage, and the asphaltic sandstones around the Awati Sag were formed in the second-stage. The hydrocarbon migration characteristics reflected by the residual dry asphalts could represent the migration characteristics of hydrocarbons in the Silurian paleo-pools, while the present movable oil in the Silurian reservoirs is related to the iater-stage (the third-stage) hydrocarbon accumulation.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 40602016)the National Key Basic Research and Development Planning Project (2006CB202307).
文摘The Lower Triassic Jialingjiang Formation reservoirs are distributed widely in the East Sichuan Basin, which are composed mainly of fractured reservoirs. However, natural gas with high concentration of H2S, ranging from 4% to 7%, was discovered in the Wolonghe Gas pool consisting primarily of porous reservoirs, while the other over 20 fractured gas reservoirs have comparatively low, tiny and even no H2S within natural gases. Researches have proved the H2S of the above reservoirs are all from the TSR origin. Most of the Jialingjiang Formation natural gases are mainly generated from Lower Permian carbonate rocks, the Wolonghe gas pool's natural gases are from the Upper Permian Longtan Formation, and the natural gases of the Huangcaoxia and Fuchengzhai gas pools are all from Lower Silurian mudstone. The formation of H2S is controlled by the characteristics and temperature of reservoirs, and is not necessarily related with gas sources. The Jialingjiang Formation in East Sichuan is buried deeply and its reservoir temperature has ever attained the condition of the TSR reaction. Due to poor reservoir potential, most of the gas pools do not have enough room for hydrocarbon reaction except for the Wolonghe gas pool, and thus natural gases with high H2S concentration are difficult to be generated abundantly. The south part of East Sichuan did not generate natural gases with high H2S concentration because the reservoir was buried relatively shallow, and did not suffer high temperature. Hence, while predicting the distribution of H2S, the characteristics and temperature of reservoirs are the necessary factors to be considerd besides the existence of anhydrite.
文摘Based on the theory of formation dynamics of oil/gas pools, the Dongying sag can be divided into three dynamic systems regarding the accumulation of oil and gas: the superpressure closed system, the semi-closed system and the normal pressure open system. Based on the analysis of genesis of superpressure in the superpressure closed system and the rule of hydrocarbon expulsion, it is found that hydrocarbon generation is related to superpressure, which is the main driving factor of hydrocarbon migration. Micro fractures formed by superpressure are the main channels for hydrocarbon migration. There are three dynamic patterns for hydrocarbon expulsion: free water drainage, hydrocarbon accumulation and drainage through micro fissures. In the superpressure closed system, the oil-driving-water process and oil/gas accumulation were completed in lithologic traps by way of such two dynamic patterns as episodic evolution of superpressure systems and episodic pressure release of faults. The oil-bearing capacity of lithologic traps is intimately related to reservoir-forming dynamic force. Quantitative evaluation of dynamic conditions for pool formation can effectively predict the oil-bearing capability of traps.
文摘The Tazhong reef-fiat oil-gas field is the first large-scale Ordovician organic reef type oil-gas field found in China. Its organic reefs were developed in the early Late Ordovician Lianglitag Formation, and are the first large reefs of the coral-stromatoporoid hermatypic community found in China. The organic reefs and platform-margin grain banks constitute a reef-flat complex, mainly consisting of biolithites and grainstones. The biolithites can be classified into the framestone, baffiestone, bindstone etc. The main body of the complex lies around the wells from Tazhong-24 to Tazhong-82, trending northwest, with the thickness from 100 to 300 m, length about 220 km and width 5-10 km. It is a reef-flat lithologic hydrocarbon reservoir, with a very complex hydrocarbon distribution: being a gas condensate reservoir as a whole with local oil reservoirs. The hydrocarbon distribution is controlled by the reef complex, generally located in the upper 100-200 m part of the complex, and largely in a banded shape along the complex. On the profile, the reservoir shows a stratified feature, with an altitude difference of almost 2200 m from southeast to northwest. The petroleum accumulation is controlled by karst reservoir beds and the northeast strike-slip fault belt. The total geologic reserves had reached 297.667 Mt by 2007.
文摘A large number of crude oil and rock samples from various oil pools of the Central Uplift in Dongying Depression were investigated to reveal the origin and accumulation of hydrocarbons. The results showed that the composition and areal distribution of hydrocarbons vary with the location of the oil pools. An increasing trend of gammacerane/C30-hopane and steranes/hopanes but a decreasing trend of prystane/phytane (Pr/Ph) and 18(H)-/17(H)- trisnorhopane (Ts/Tm) ratios were observed from southwest to northeast. This indicates a variation of source rocks and hydrocarbon properties. An increasing trend of water salinity with much more input of algae-rich microorganisms in the deposition environment of the source rock was observed from southwest to northeast. However, the thermal maturity of the source rocks showed a decreasing trend in the same direction. Oil-to-oil and oil-to-source rock correlations showed that most oils were sourced from Es3 and Es4 members with a burial depth of more than 3,000-3,150 m and 2,700 m respectively. The oils in the Shinan and Ying 11 sand bodies, which were generally mixed with the Es4 sourced oils, came mostly from Es3 mudstones. It is quite significant that the Es4 derived oils migrated vertically for hundreds of meters and accumulated in an overlying lithologic pool of the Es3^m, i.e., Ying 11 synclinal lithologic pool, which suggests that the mechanisms of migration and accumulation for subtle oil pools in the Dongying Depression are more complex than that of the previously expected.
文摘Because of the difference ofoil and gas accumulation condition between the hanging wall and the footwall of a fault, there is a peculiar accumulation mechanism that oil and gas mainly exists in the hanging wall of the basement fault, but in the footwall of the shallow detachment fault in the Nanbaxian pool. The oil and gas of the Nanbaxian pool came from the mature Jurassic hydrocarbon source rock of the Yibei depression located at the south of the Nanbaxian pool. Firstly, the oil and gas accumulated in the traps of the hanging wall of the basement fault by way of the unconformity and the basement faults, and turned into some primary deep pools; and then, the shallow detachment fault that formed in the later tectonic movement broke into the deep primary pools, which caused the oil and gas migration upwards along the basement faults and the shallow detachment faults and the evolvement into some secondary oil and gas pools later. The history of the Nanbaxian oil and gas accumulation can be summarized successively as the syndepositional upheaval controlled by faults; single hydrocarbon source rock; unconformities and faults as migration channels; buoyancy, overpressure and tectonic stress as dynamic forces; multistage migration and accumulation of oil and gas; and finally an overlapped double-floor pattern of oil and gas accumulation. The most important explorative targets in the north of the Qaidam Basin are traps connected with the primary pools in the footwall by shallow detachment faults.
文摘A GCM study is performed of the effects on Asian summer monsoon initiation of the Qinghai-Xizang Plateauand western Pacific warm pool. results show that the Plateau, being a prominent sensible heat source, acts as a basicfactor for the formation of the monsoon circulation, the northward transported low-latitude and low-level warm,moist flow in relation to the sensible heating experiences dynamic lifting on the south and east sides of the highland,releasing vast quantities of latent heat through condensation, whereby the monsoon circulation pattern is furthermodulated; the temperature contrast between the Pacific warm pool and the Australian / marine continents serves asanother basic factor for the northern SW summer monsoon genesis over the South-China Sea-the western Pacific,which, however, falls into a category of winter monsoon on a physical basis.
基金supported by the National Basic Research Program of China (No. 2005CB422100)
文摘This article reports the main formation models and distribution of the oil and gas pools in Tarim basin, China, including (1) occurrence of the found oil and gas pools, (2) main formation models of oil and gas pools, and (3) distribution law of oil/gas pools. Petroleum is distributed widely in the strata of Tarim basin from the Sinian at the bottom to the Neogene at the top. However, the found oil and gas fields are mainly distributed in Shaya (沙雅) uplift, Tazhong (塔中) uplift, and Kuche (库车) depression. This article presents 4 main formation models, namely, early formation and long-term preservation, early formation and late reformation, middle-late multiphase-multisource formation, late single-stage formation. Tarim basin is very rich in petroleum resources. Long-term inherited intrabasinal paleohighs and slope zones are the most favorable areas for accumulation of hydrocarbons, but the types of oil and gas pools are different from area to area. The control of unconformities and faults on hydrocarbon accumulating is prominent in Tarim basin. Preservation conditions are of utmost importance. Formation of some oil and gas pools is the result of reforming and re-accumulating of early accumulated hydrocarbons.