Late Cambrian to Early Ordovician sedimentary rocks in the western Tarim Basin, Northwest China, are composed of shallow-marine platform carbonates. The Keping Uplift is located in the northwest region of this basin. ...Late Cambrian to Early Ordovician sedimentary rocks in the western Tarim Basin, Northwest China, are composed of shallow-marine platform carbonates. The Keping Uplift is located in the northwest region of this basin. On the basis of petrographic and geochemical features, four matrix replacement dolomites and one type of cement dolomite are identified. Matrix replacement dolomites include (1) micritic dolomites (MD1); (2) fine-coarse euhedral floating dolomites (MD2); (3) fine-coarse euhedral dolomites (MD3); and (4) medium-very coarse anhedral mosaic dolomites (MD4). Dolomite cement occurs in minor amounts as coarse saddle dolomite cement (CD1) that mostly fills vugs and fractures in the matrix dolomites. These matrix dolomites have δ18O values of ?9.7‰ to ?3.0‰ VPDB (Vienna Pee Dee Belemnite); δ13C values of ?0.8‰ to 3.5‰ VPDB; 87Sr/86Sr ratios of 0.708516 to 0.709643; Sr concentrations of 50 to 257 ppm; Fe contents of 425 to 16878 ppm; and Mn contents of 28 to 144 ppm. Petrographic and geochemical data suggest that the matrix replacement dolomites were likely formed by normal and evaporative seawater in early stages prior to chemical compaction at shallow burial depths. Compared with matrix dolomites, dolomite cement yields lower δ18O values (?12.9‰ to ?9.1‰ VPDB); slightly lower δ13C values (?1.6‰-0.6‰ VPDB); higher 87Sr/86Sr ratios (0.709165-0.709764); and high homogenization temperature (Th) values (98°C-225°C) and salinities (6 wt%-24 wt% NaCl equivalent). Limited data from dolomite cement shows a low Sr concentration (58.6 ppm) and high Fe and Mn contents (1233 and 1250 ppm, respectively). These data imply that the dolomite cement precipitated from higher temperature hydrothermal salinity fluids. These fluids could be related to widespread igneous activities in the Tarim Basin occurring during Permian time when the host dolostones were deeply buried. Faults likely acted as important conduits that channeled dolomitizing fluids from the underlying strata into the basal carbonates, leading to intense dolomitization. Therefore, dolomitization, in the Keping Uplift area is likely related to evaporated seawater via seepage reflux in addition to burial processes and hydrothermal fluids.展开更多
A scientific exploration well(CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy-three core samples and four natural gas samples from the Middle–Late Triassic stra...A scientific exploration well(CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy-three core samples and four natural gas samples from the Middle–Late Triassic strata were analyzed to determine the paleo-depositional setting and the abundance of organic matter(OM) and to evaluate the hydrocarbon-generation process and potential. This information was then used to identify the origin of the natural gas. The OM is characterized by medium n-alkanes(n C15–n C19), low pristane/phytane and terrigenous aquatic ratios(TAR), a carbon preference index(CPI) of ~1, regular steranes with C29 > C27 > C28, gammacerane/C30 hopane ratios of 0.15–0.32, and δDorg of-132‰ to-58‰, suggesting a marine algal/phytoplankton source with terrestrial input deposited in a reducing–transitional saline/marine sedimentary environment. Based on the TOC, HI index, and chloroform bitumen "A" the algalrich dolomites of the Leikoupo Formation are fair–good source rocks;the grey limestones of the Maantang Formation are fair source rocks;and the shales of the Xiaotangzi Formation are moderately good source rocks. In addition, maceral and carbon isotopes indicate that the kerogen of the Leikoupo and Maantang formations is type Ⅱ and that of the Xiaotangzi Formation is type Ⅱ–Ⅲ. The maturity parameters and the hopane and sterane isomerization suggest that the OM was advanced mature and produced wet–dry gases. One-dimensional modeling of the thermal-burial history suggests that hydrocarbon-generation occurred at 220–60 Ma. The gas components and C–H–He–Ar–Ne isotopes indicate that the oilassociated gases were generated in the Leikoupo and Maantang formations, and then, they mixed with gases from the Xiaotangzi Formation, which were probably contributed by the underlying Permian marine source rocks. Therefore, the deeply-buried Middle–Late Triassic marine source rocks in the western Sichuan depression and in similar basins have a great significant hydrocarbon potential.展开更多
Collected from a Late Permian to Early Triassic sedimentary section in the Zhongliang Mountain of Chongqing, Southwest China, sixty marine carbonate samples were measured for the 87Sr/86Sr ratios, and corresponding ev...Collected from a Late Permian to Early Triassic sedimentary section in the Zhongliang Mountain of Chongqing, Southwest China, sixty marine carbonate samples were measured for the 87Sr/86Sr ratios, and corresponding evolution curve was constructed. The concentrations of SiO2, CaO, MgO, Mn and Sr are used to evaluate reservation of strontium isotopic composition for original seawater and the credi-bility of the dissolution method for sample preparation. The results show that most of the samples (except seven samples with the Mn/Sr ratios higher than 2) contain the original geochemistry signa-tures of ancient seawater. Compared to the published 87Sr/86Sr ratios from the Late Permian to Early Triassic, our database reported here is the largest and the curve constructed is the most complete. The strontium isotopic curve from Late Permian to Early Triassic is consistent globally and exhibits a gen-eral trend of steady increase during this period. The minimum of 87Sr/86Sr ratios (0.707011) occurs in the Late Permian (30 m in thickness below the Permian-Triassic boundary), and the maximum (0.708281), near the Early-Middle Triassic boundary. The lack of land plants and the rapid continental weathering result in the increase of 87Sr/86Sr ratios during the interval. The Permian-Triassic boundary in Zhongli-ang Mountain Section has been accepted internationally. The 87Sr/86Sr ratios of six samples near the boundary vary from 0.70714 to 0.70715 with an average of 0.70714, which is consistent with the value of 0.70715 (samples are from articulate brachiopod shells) from Korte et al. published in 2006 (within the error range in experiment). Accordingly, the strontium isotope composition in the Permian-Triassic boundary in this paper is of global significance. It can be confirmed that the 87Sr/86Sr ratios of the sea-water in the Permian-Triassic transition are in the range of 0.70714―0.70715.展开更多
Based on comprehensive studies in petrography,petrofabric analysis and geochemistry,this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkali...Based on comprehensive studies in petrography,petrofabric analysis and geochemistry,this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkaline hot brine under the conditions of the Mesozoic faulted lake basin.The main rock-forming mineral of this dolostone is ferruginous dolomite with a micritic structure.This dolomite mostly exhibits laminae of 0.1–1 mm thick and is often discovered with other minerals,such as albite,analcite,barite and dickite,which have at least two types of interbedded laminae.Petrogeochemistry reveals that this dolostone contains a large number of typomorphic elements of hydrothermal sedimentation,including Sb,Ba,Sr,Mn,and V.In addition,the LREE is in relatively high concentrations and possesses the typical REE distribution pattern with negative Eu anomaly.Oxygen isotope values(δ18OPDB)range from 5.89‰to 14.15‰with an average of 9.69‰.The ratio of87Sr/86Sr is between0.711648 and 0.719546,with an average of 0.714718.These data indicate that the depositional environment is a stable,blocked,anoxic low-lying hot brine pool in the bottom of deep lake controlled by basement faults.The hydrothermal fluid is the alkaline hot brine formed by the combination of the infiltration lake water and mantle-derived magmatic water,consisting of many ions,including Ca2+,Mg2+and Fe2+.Under the driving flow power of magmatic heat,gravity and compaction,the hydrothermal fluid overcame the overburden pressure and hydrostatic pressure of the lake water body,and boiled to explosion,and then the explosion shattered the original laminated micritic ferruginous primary dolostone near the vent and then formed a new type of dolostone called shattered"hydroexplosion breccias".In the low-lying,unperturbed hot brine pool,far from the vent,the laminated micritic ferruginous primary dolostone was quickly crystallized and chemicals precipitated from the hydrotherm.This study of special rocks contributes to research into the causes of the formation of lacustrine carbonate rocks and dolostone.In particular,it provides new examples and research insights for future studies of the lacustrine dolomite from the similar Mesozoic and Cenozoic basins in China.展开更多
The Yitong(伊通) basin is a Late Mesozoic and Cenozoic continental sedimentary basin in Northeast China.On the basis of well tests and seismic data,we use the 2D modeling technique to rebuild the pressure evolution ...The Yitong(伊通) basin is a Late Mesozoic and Cenozoic continental sedimentary basin in Northeast China.On the basis of well tests and seismic data,we use the 2D modeling technique to rebuild the pressure evolution and hydrocarbon migration in the Moliqing(莫里青) fault depression of the Yitong basin.Based on the modeling results,four conclusions are drawn as follows.(1) The Eocene Shuangyang(双阳) Formation within the Moliqing fault depression had entirely undergone three epi-sodic cycles of pressure accumulation and release in geological history,and the three tectonic move-ments since the Middle Eocene played important roles in the episodic changes of excess pressure.(2) The present formation pressure distribution is characterized by normal pressure in almost the entire fault depression with some residual overpressure.The differential distribution of pressure results mainly from the difference in rock facies,sedimentation rate,hydrocarbon generation,and fault activi-ties.(3) The hydrocarbon migration is more active during the release of pressure in the Moliqing fault depression,which happened mainly in the Middle-Late Oligocene and provided the driving force for hydrocarbon migration.(4) The hydrocarbon migration was mostly directed to the Shuangyang For-mation within the Jianshan(尖山) uplift and the Kaoshan(靠山) sag.With the superior condition ofhydrocarbon accumulation and the higher de-gree of hydrocarbon concentration,the north-west part of Kaoshan sag is considered a favor-able area for oil and gas exploration in the Moliqing fault depression.展开更多
Detailed characterization of diagenetic fluid behaviour and evolution is commonly hindered by shortage of appropriate and economic methods to carry out in situ analysis in the tiny diagenetic mineral crystals. Using m...Detailed characterization of diagenetic fluid behaviour and evolution is commonly hindered by shortage of appropriate and economic methods to carry out in situ analysis in the tiny diagenetic mineral crystals. Using micromill sampling method, this study presents in situ stable isotopic data for the growth zones of saddle dolomite crystals in the hydrothermally-altered dolostones of Upper Cambrian (Furongian) at Keping, Tarim Basin, NW China. These data show minor and large variations in δ13C ( 0.7‰ to 1.5‰ VPDB) and δ18O ( 8.3‰ to 13.8‰ VPDB), respectively, from the cores to outer rims of the dolomite crystals and suggest that saddle dolomites precipitated from dolomitizing fluids with similar carbon sources but oscillatory temperatures during different formation stages. This scenario is confirmed by microthermometry of fluid inclusions within the growth zones of dolomite crystals. This study indicates that in situ isotope analysis could provide more detailed information related to the source and pathway of dolomitizing fluids, facilitating better characterization of dolomitizing fluids and processes.展开更多
A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous po...A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous point source function is then derived based on the Green function. Various boundary conditions of the reservoirs are considered for this case and the corresponding solutions are obtained through the mirror image reflection and the principle of superimposition. The line source solution is obtained by integration. Subsequently, the horizontal-well bottom hole pressure response function for a non-linear gas flow in the homogeneous gas reservoir is obtained, and the response curve of the dimensionless bottom hole pressure and the derivative for a horizontal well in the homogeneous gas reservoir are obtained. In the end, the sensitivities of the relevant parameters are analyzed, The well test model presented in this paper can be used as the basis of the horizontal well test analysis for tight gas reservoirs.展开更多
The discovery of natural gas reservoirs from the Triassic Feixianguan Formation in the Northeastern Sichuan Basin is an important breakthrough in the field of marine carbonate rocks for Chinese oil and gas exploration...The discovery of natural gas reservoirs from the Triassic Feixianguan Formation in the Northeastern Sichuan Basin is an important breakthrough in the field of marine carbonate rocks for Chinese oil and gas exploration in recent years.Because of the dolomite-hosted reservoirs in the Feixianguan Formation,these dolomites and their formation mechanisms have been a research focus for sedimentary geologists and petroleum geologists.Based on the homogenization temperatures of fluid inclusions,oxygen isotopic composition and their calculated temperatures,and the burial and thermal history of the typical well,it is considered that the majority of dolomites are formed by low-temperature dolomitizing fluids in the Triassic Feixianguan Formation,Northeastern Sichuan Basin.Only a minority of dolomites are formed by high-temperature dolomitizing fluids.The ending depth interval of low-temperature dolomitizing fluids was about 1000-2500 m,of which the correspondingly ending timing interval was approximately from early-middle Middle Triassic to early-middle Late Triassic.The main depth interval of high-temperature dolomitizing fluids was about 3200-4500 m,of which the correspondingly main timing interval was approximately early-middle Middle Jurassic.The low-temperature and high-temperature dolomitizing fluids have different meanings to the formation and evolution of the pore volumes of dolomite reservoirs in the Feixianguan Formation,Northeastern Sichuan Basin.展开更多
基金in part provided by Petro China(Grant No.09HT10500000068)Sinopec(Grant No.G5800-07-ZS-WX032)the State Key Lab of Oil/Gas Reservoir Geology and Exploitation at CDUT(Grant No.PLC200801)to H.Qing
文摘Late Cambrian to Early Ordovician sedimentary rocks in the western Tarim Basin, Northwest China, are composed of shallow-marine platform carbonates. The Keping Uplift is located in the northwest region of this basin. On the basis of petrographic and geochemical features, four matrix replacement dolomites and one type of cement dolomite are identified. Matrix replacement dolomites include (1) micritic dolomites (MD1); (2) fine-coarse euhedral floating dolomites (MD2); (3) fine-coarse euhedral dolomites (MD3); and (4) medium-very coarse anhedral mosaic dolomites (MD4). Dolomite cement occurs in minor amounts as coarse saddle dolomite cement (CD1) that mostly fills vugs and fractures in the matrix dolomites. These matrix dolomites have δ18O values of ?9.7‰ to ?3.0‰ VPDB (Vienna Pee Dee Belemnite); δ13C values of ?0.8‰ to 3.5‰ VPDB; 87Sr/86Sr ratios of 0.708516 to 0.709643; Sr concentrations of 50 to 257 ppm; Fe contents of 425 to 16878 ppm; and Mn contents of 28 to 144 ppm. Petrographic and geochemical data suggest that the matrix replacement dolomites were likely formed by normal and evaporative seawater in early stages prior to chemical compaction at shallow burial depths. Compared with matrix dolomites, dolomite cement yields lower δ18O values (?12.9‰ to ?9.1‰ VPDB); slightly lower δ13C values (?1.6‰-0.6‰ VPDB); higher 87Sr/86Sr ratios (0.709165-0.709764); and high homogenization temperature (Th) values (98°C-225°C) and salinities (6 wt%-24 wt% NaCl equivalent). Limited data from dolomite cement shows a low Sr concentration (58.6 ppm) and high Fe and Mn contents (1233 and 1250 ppm, respectively). These data imply that the dolomite cement precipitated from higher temperature hydrothermal salinity fluids. These fluids could be related to widespread igneous activities in the Tarim Basin occurring during Permian time when the host dolostones were deeply buried. Faults likely acted as important conduits that channeled dolomitizing fluids from the underlying strata into the basal carbonates, leading to intense dolomitization. Therefore, dolomitization, in the Keping Uplift area is likely related to evaporated seawater via seepage reflux in addition to burial processes and hydrothermal fluids.
基金the Special Key Discipline-Geological Resources and Geological Engineering Scholarship(No.11000-13Z00703)of Chengdu University of Technology(CDUT)Oil and Gas Plays Accumulation and Enrichment Mechanisms in the Sichuan Basin Research Program for funding this research.
文摘A scientific exploration well(CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy-three core samples and four natural gas samples from the Middle–Late Triassic strata were analyzed to determine the paleo-depositional setting and the abundance of organic matter(OM) and to evaluate the hydrocarbon-generation process and potential. This information was then used to identify the origin of the natural gas. The OM is characterized by medium n-alkanes(n C15–n C19), low pristane/phytane and terrigenous aquatic ratios(TAR), a carbon preference index(CPI) of ~1, regular steranes with C29 > C27 > C28, gammacerane/C30 hopane ratios of 0.15–0.32, and δDorg of-132‰ to-58‰, suggesting a marine algal/phytoplankton source with terrestrial input deposited in a reducing–transitional saline/marine sedimentary environment. Based on the TOC, HI index, and chloroform bitumen "A" the algalrich dolomites of the Leikoupo Formation are fair–good source rocks;the grey limestones of the Maantang Formation are fair source rocks;and the shales of the Xiaotangzi Formation are moderately good source rocks. In addition, maceral and carbon isotopes indicate that the kerogen of the Leikoupo and Maantang formations is type Ⅱ and that of the Xiaotangzi Formation is type Ⅱ–Ⅲ. The maturity parameters and the hopane and sterane isomerization suggest that the OM was advanced mature and produced wet–dry gases. One-dimensional modeling of the thermal-burial history suggests that hydrocarbon-generation occurred at 220–60 Ma. The gas components and C–H–He–Ar–Ne isotopes indicate that the oilassociated gases were generated in the Leikoupo and Maantang formations, and then, they mixed with gases from the Xiaotangzi Formation, which were probably contributed by the underlying Permian marine source rocks. Therefore, the deeply-buried Middle–Late Triassic marine source rocks in the western Sichuan depression and in similar basins have a great significant hydrocarbon potential.
基金the National Natural Science Foundation of China (Grant No. 40472068, 40672072)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050616005)
文摘Collected from a Late Permian to Early Triassic sedimentary section in the Zhongliang Mountain of Chongqing, Southwest China, sixty marine carbonate samples were measured for the 87Sr/86Sr ratios, and corresponding evolution curve was constructed. The concentrations of SiO2, CaO, MgO, Mn and Sr are used to evaluate reservation of strontium isotopic composition for original seawater and the credi-bility of the dissolution method for sample preparation. The results show that most of the samples (except seven samples with the Mn/Sr ratios higher than 2) contain the original geochemistry signa-tures of ancient seawater. Compared to the published 87Sr/86Sr ratios from the Late Permian to Early Triassic, our database reported here is the largest and the curve constructed is the most complete. The strontium isotopic curve from Late Permian to Early Triassic is consistent globally and exhibits a gen-eral trend of steady increase during this period. The minimum of 87Sr/86Sr ratios (0.707011) occurs in the Late Permian (30 m in thickness below the Permian-Triassic boundary), and the maximum (0.708281), near the Early-Middle Triassic boundary. The lack of land plants and the rapid continental weathering result in the increase of 87Sr/86Sr ratios during the interval. The Permian-Triassic boundary in Zhongli-ang Mountain Section has been accepted internationally. The 87Sr/86Sr ratios of six samples near the boundary vary from 0.70714 to 0.70715 with an average of 0.70714, which is consistent with the value of 0.70715 (samples are from articulate brachiopod shells) from Korte et al. published in 2006 (within the error range in experiment). Accordingly, the strontium isotope composition in the Permian-Triassic boundary in this paper is of global significance. It can be confirmed that the 87Sr/86Sr ratios of the sea-water in the Permian-Triassic transition are in the range of 0.70714―0.70715.
基金supported by National Natural Science Foundation of China(Grant No.41002033)National Science and Technology Major Project(Grant No.2011ZX05030-003-02)Foundation for Fostering Middleaged and Young Key Teachers of Chengdu University of Technology
文摘Based on comprehensive studies in petrography,petrofabric analysis and geochemistry,this paper describes a unique and rare laminated micritic ferruginous primary dolostone crystallized and precipitated from the alkaline hot brine under the conditions of the Mesozoic faulted lake basin.The main rock-forming mineral of this dolostone is ferruginous dolomite with a micritic structure.This dolomite mostly exhibits laminae of 0.1–1 mm thick and is often discovered with other minerals,such as albite,analcite,barite and dickite,which have at least two types of interbedded laminae.Petrogeochemistry reveals that this dolostone contains a large number of typomorphic elements of hydrothermal sedimentation,including Sb,Ba,Sr,Mn,and V.In addition,the LREE is in relatively high concentrations and possesses the typical REE distribution pattern with negative Eu anomaly.Oxygen isotope values(δ18OPDB)range from 5.89‰to 14.15‰with an average of 9.69‰.The ratio of87Sr/86Sr is between0.711648 and 0.719546,with an average of 0.714718.These data indicate that the depositional environment is a stable,blocked,anoxic low-lying hot brine pool in the bottom of deep lake controlled by basement faults.The hydrothermal fluid is the alkaline hot brine formed by the combination of the infiltration lake water and mantle-derived magmatic water,consisting of many ions,including Ca2+,Mg2+and Fe2+.Under the driving flow power of magmatic heat,gravity and compaction,the hydrothermal fluid overcame the overburden pressure and hydrostatic pressure of the lake water body,and boiled to explosion,and then the explosion shattered the original laminated micritic ferruginous primary dolostone near the vent and then formed a new type of dolostone called shattered"hydroexplosion breccias".In the low-lying,unperturbed hot brine pool,far from the vent,the laminated micritic ferruginous primary dolostone was quickly crystallized and chemicals precipitated from the hydrotherm.This study of special rocks contributes to research into the causes of the formation of lacustrine carbonate rocks and dolostone.In particular,it provides new examples and research insights for future studies of the lacustrine dolomite from the similar Mesozoic and Cenozoic basins in China.
基金supported by the National Natural Science Foundation of China (No. 40172051)the Jilin Oil Field Scientific Project of China National Petroleum Corporation (No. 2006026157)the Special Fund for Basic Scientific Research of Central Colleges, China University of Geosciences (Wuhan) (Nos. 2010029056, CUGL10024)
文摘The Yitong(伊通) basin is a Late Mesozoic and Cenozoic continental sedimentary basin in Northeast China.On the basis of well tests and seismic data,we use the 2D modeling technique to rebuild the pressure evolution and hydrocarbon migration in the Moliqing(莫里青) fault depression of the Yitong basin.Based on the modeling results,four conclusions are drawn as follows.(1) The Eocene Shuangyang(双阳) Formation within the Moliqing fault depression had entirely undergone three epi-sodic cycles of pressure accumulation and release in geological history,and the three tectonic move-ments since the Middle Eocene played important roles in the episodic changes of excess pressure.(2) The present formation pressure distribution is characterized by normal pressure in almost the entire fault depression with some residual overpressure.The differential distribution of pressure results mainly from the difference in rock facies,sedimentation rate,hydrocarbon generation,and fault activi-ties.(3) The hydrocarbon migration is more active during the release of pressure in the Moliqing fault depression,which happened mainly in the Middle-Late Oligocene and provided the driving force for hydrocarbon migration.(4) The hydrocarbon migration was mostly directed to the Shuangyang For-mation within the Jianshan(尖山) uplift and the Kaoshan(靠山) sag.With the superior condition ofhydrocarbon accumulation and the higher de-gree of hydrocarbon concentration,the north-west part of Kaoshan sag is considered a favor-able area for oil and gas exploration in the Moliqing fault depression.
基金supported by SINOPEC(G5800-07-ZS-WX032)the National Key Scientific Special Program of China(2008ZX05008-003-002 and 2011ZX05008-003-10)+1 种基金the National Basic Research Program of China(2012CB214802)the State Key Laboratory of Oil/Gas Reservoir Geology and Exploitation at CDUT(PL200801)
文摘Detailed characterization of diagenetic fluid behaviour and evolution is commonly hindered by shortage of appropriate and economic methods to carry out in situ analysis in the tiny diagenetic mineral crystals. Using micromill sampling method, this study presents in situ stable isotopic data for the growth zones of saddle dolomite crystals in the hydrothermally-altered dolostones of Upper Cambrian (Furongian) at Keping, Tarim Basin, NW China. These data show minor and large variations in δ13C ( 0.7‰ to 1.5‰ VPDB) and δ18O ( 8.3‰ to 13.8‰ VPDB), respectively, from the cores to outer rims of the dolomite crystals and suggest that saddle dolomites precipitated from dolomitizing fluids with similar carbon sources but oscillatory temperatures during different formation stages. This scenario is confirmed by microthermometry of fluid inclusions within the growth zones of dolomite crystals. This study indicates that in situ isotope analysis could provide more detailed information related to the source and pathway of dolomitizing fluids, facilitating better characterization of dolomitizing fluids and processes.
基金the National Science Fund for Distinguished Young Scholars of China (Grant No. 51125019)the National Key Basic Research and Development Program of China (973 Program, Grant No. 2011CB201005)the Research Foundation of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University (Grant No. PLN-ZL201201)
文摘A fundamental solution for homogeneous reservoir in infinite space is derived by using the point source function with the consideration of the threshold pressure gradient. The fundamental solution of the continuous point source function is then derived based on the Green function. Various boundary conditions of the reservoirs are considered for this case and the corresponding solutions are obtained through the mirror image reflection and the principle of superimposition. The line source solution is obtained by integration. Subsequently, the horizontal-well bottom hole pressure response function for a non-linear gas flow in the homogeneous gas reservoir is obtained, and the response curve of the dimensionless bottom hole pressure and the derivative for a horizontal well in the homogeneous gas reservoir are obtained. In the end, the sensitivities of the relevant parameters are analyzed, The well test model presented in this paper can be used as the basis of the horizontal well test analysis for tight gas reservoirs.
基金supported by National Natural Science Foundation of China(Grant Nos. 40839908 and 40672072)the Research Fund for the Doctoral Program of Higher Education of China (Grant No.20050616005)
文摘The discovery of natural gas reservoirs from the Triassic Feixianguan Formation in the Northeastern Sichuan Basin is an important breakthrough in the field of marine carbonate rocks for Chinese oil and gas exploration in recent years.Because of the dolomite-hosted reservoirs in the Feixianguan Formation,these dolomites and their formation mechanisms have been a research focus for sedimentary geologists and petroleum geologists.Based on the homogenization temperatures of fluid inclusions,oxygen isotopic composition and their calculated temperatures,and the burial and thermal history of the typical well,it is considered that the majority of dolomites are formed by low-temperature dolomitizing fluids in the Triassic Feixianguan Formation,Northeastern Sichuan Basin.Only a minority of dolomites are formed by high-temperature dolomitizing fluids.The ending depth interval of low-temperature dolomitizing fluids was about 1000-2500 m,of which the correspondingly ending timing interval was approximately from early-middle Middle Triassic to early-middle Late Triassic.The main depth interval of high-temperature dolomitizing fluids was about 3200-4500 m,of which the correspondingly main timing interval was approximately early-middle Middle Jurassic.The low-temperature and high-temperature dolomitizing fluids have different meanings to the formation and evolution of the pore volumes of dolomite reservoirs in the Feixianguan Formation,Northeastern Sichuan Basin.