2014 Vol. 39, No. 5
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2014, 39(5): 499-508.
doi: 10.3799/dqkx.2014.048
Abstract:
This paper reports LA-ICP-MS zircon U-Pb dating results from the Chenming and Baoquan formations in the eastern Heilongjiang Province in order to constrain their forming age and provenances. Most of detrital zircons are euhedral-subhedral in shape and display striped absorption or oscillatory zoning in CL images, implying their magmatic origin. The others show dark accretionary rim formed by metamorphism. The dating results on magmatic zircons indicate that 59 detrital zircons from feldspathic quartz sandstones in the upper part of the Chenming Formation yielded age populations of 561 Ma, 621 Ma, 683 Ma, 752 Ma, 803 Ma, 822 Ma, 851 Ma, 900 Ma, 922 Ma, 954 Ma, 1 781 Ma, 1 865 Ma and 1 933 Ma. Based on detrital zircon dating results, we conclude that the sedimentary processes of the Chenming Formation could take place after 561 Ma. In the study area, the Baoquan Formation overlain the Chenming Formation with the unconformity relationship, 60 detrital zircons from argillic slates in the lower part of the Baoquan Formation yielded age populations of 425 Ma, 450 Ma, 485 Ma, 900 Ma and 1 750 Ma. According to the above dating results and the field geological relationship, combined with the age populations of the detrial zircons from the Late Paleozoic strata, we consider that the Chenming Formation in the eastern Heilongjiang Province formed between 561 Ma to 510 Ma. The Early Paleozoic strata are firstly discovered with the exact geochronological evidence in the eastern Heilongjiang Province. The above detrital zircon ages indicate that the provenances of the Chenming Formation could mainly come from the Neoproterozoic and Paleoproterozoic igneous rocks around the study area, implying that the minor Precambrian basement relic might be occurred in the eastern margin of the Songnen-Zhangguangcailing Massif in the Early Paleozoic.
This paper reports LA-ICP-MS zircon U-Pb dating results from the Chenming and Baoquan formations in the eastern Heilongjiang Province in order to constrain their forming age and provenances. Most of detrital zircons are euhedral-subhedral in shape and display striped absorption or oscillatory zoning in CL images, implying their magmatic origin. The others show dark accretionary rim formed by metamorphism. The dating results on magmatic zircons indicate that 59 detrital zircons from feldspathic quartz sandstones in the upper part of the Chenming Formation yielded age populations of 561 Ma, 621 Ma, 683 Ma, 752 Ma, 803 Ma, 822 Ma, 851 Ma, 900 Ma, 922 Ma, 954 Ma, 1 781 Ma, 1 865 Ma and 1 933 Ma. Based on detrital zircon dating results, we conclude that the sedimentary processes of the Chenming Formation could take place after 561 Ma. In the study area, the Baoquan Formation overlain the Chenming Formation with the unconformity relationship, 60 detrital zircons from argillic slates in the lower part of the Baoquan Formation yielded age populations of 425 Ma, 450 Ma, 485 Ma, 900 Ma and 1 750 Ma. According to the above dating results and the field geological relationship, combined with the age populations of the detrial zircons from the Late Paleozoic strata, we consider that the Chenming Formation in the eastern Heilongjiang Province formed between 561 Ma to 510 Ma. The Early Paleozoic strata are firstly discovered with the exact geochronological evidence in the eastern Heilongjiang Province. The above detrital zircon ages indicate that the provenances of the Chenming Formation could mainly come from the Neoproterozoic and Paleoproterozoic igneous rocks around the study area, implying that the minor Precambrian basement relic might be occurred in the eastern margin of the Songnen-Zhangguangcailing Massif in the Early Paleozoic.
2014, 39(5): 509-524.
doi: 10.3799/dqkx.2014.049
Abstract:
Risong rocks and Jiawei acid rock veins are located at Bangong Lake ophiolite mélange belt, western Tibetan Plateau. The lithology is tonalite, corcovadite and granodiorite, displaying a transition from medium-K calc-alkaline series to high-K calc-alkaline series. Rocks show geochemical characteristics of adakites, having high content of SiO2 (63.05%~70.72%), Al2O3(≥15%), Sr (380.4×10-6-625.0×10-6), Sr/Y ratio(> 35) and low content of MgO (0.97%-2.33%) < 3%, HREE, Y(5.64×10-6-13.80×10-6) and Yb(0.46×10-6-1.25×10-6). The differentiation is obvious between HREE and LREE (17.09 < (La/Yb)N < 48.51). Risong granodiorite is dated to 82.0±1.1 Ma by zircon U-Pb dating method; east-west trend granodiorite and south-north trend corcovadite are dated to 90.7±1.2 Ma, 82.9±1.2 Ma respectively. Risong and Jiawei adakitic rocks are enriched in K and depleted in Na, and have low Cr, Ni, Sr/Y and high Th, Th/La, Th/U, Rb/Sr and Mg#(43.09-54.35). These characteristics indicate that they were formed by partial melting of thickened lower crust which was caused by basaltic magma underplating. 91-82 Ma adakites were formed in the early stage after the collision as the product of both interplates thermal upwelling extension and crust-mantle interaction after the closure of Meso-Tethys. Outcropping of adakites in this period can mark the transition from the plate tectonic system to intraplate tectonic system.
Risong rocks and Jiawei acid rock veins are located at Bangong Lake ophiolite mélange belt, western Tibetan Plateau. The lithology is tonalite, corcovadite and granodiorite, displaying a transition from medium-K calc-alkaline series to high-K calc-alkaline series. Rocks show geochemical characteristics of adakites, having high content of SiO2 (63.05%~70.72%), Al2O3(≥15%), Sr (380.4×10-6-625.0×10-6), Sr/Y ratio(> 35) and low content of MgO (0.97%-2.33%) < 3%, HREE, Y(5.64×10-6-13.80×10-6) and Yb(0.46×10-6-1.25×10-6). The differentiation is obvious between HREE and LREE (17.09 < (La/Yb)N < 48.51). Risong granodiorite is dated to 82.0±1.1 Ma by zircon U-Pb dating method; east-west trend granodiorite and south-north trend corcovadite are dated to 90.7±1.2 Ma, 82.9±1.2 Ma respectively. Risong and Jiawei adakitic rocks are enriched in K and depleted in Na, and have low Cr, Ni, Sr/Y and high Th, Th/La, Th/U, Rb/Sr and Mg#(43.09-54.35). These characteristics indicate that they were formed by partial melting of thickened lower crust which was caused by basaltic magma underplating. 91-82 Ma adakites were formed in the early stage after the collision as the product of both interplates thermal upwelling extension and crust-mantle interaction after the closure of Meso-Tethys. Outcropping of adakites in this period can mark the transition from the plate tectonic system to intraplate tectonic system.
2014, 39(5): 525-536.
doi: 10.3799/dqkx.2014.050
Abstract:
This paper presents a calibration strategy for LA-ICP-MS accurate analysis of major and trace elements of hydrous silicate minerals, which is internal standard-independent and applies multiple reference materials for external calibration. The total content of the volatile components in the hydrous silicate minerals was firstly calculated based on the mineral constant stoichiometry. Then, major and trace elements were quantified by calibrating against multiple reference materials (e.g., MPI-DING and USGS glasses) combined with normalization of all metal oxides to the sum of 100% minus the total volatile components. Analyses of amphibole, tremolite, tourmaline as well as epidote by LA-ICP-MS using the calibration strategy match the results of electron microprobe analyses within 5% uncertainty for the major elements which are homogeneous in samples. The results are consistent with the analysis of solution-ICP-MS combined with microsampling (diameter=300 μm) within generally 10% uncertainty for trace elements, except for those elements distributed heterogeneously in the samples. The results show that major and trace elements of hydrous silicate minerals can be accurately analyzed by LA-ICP-MS without applying internal standardization when using MPI-DING and USGS reference glasses as multiple reference materials for calibration.
This paper presents a calibration strategy for LA-ICP-MS accurate analysis of major and trace elements of hydrous silicate minerals, which is internal standard-independent and applies multiple reference materials for external calibration. The total content of the volatile components in the hydrous silicate minerals was firstly calculated based on the mineral constant stoichiometry. Then, major and trace elements were quantified by calibrating against multiple reference materials (e.g., MPI-DING and USGS glasses) combined with normalization of all metal oxides to the sum of 100% minus the total volatile components. Analyses of amphibole, tremolite, tourmaline as well as epidote by LA-ICP-MS using the calibration strategy match the results of electron microprobe analyses within 5% uncertainty for the major elements which are homogeneous in samples. The results are consistent with the analysis of solution-ICP-MS combined with microsampling (diameter=300 μm) within generally 10% uncertainty for trace elements, except for those elements distributed heterogeneously in the samples. The results show that major and trace elements of hydrous silicate minerals can be accurately analyzed by LA-ICP-MS without applying internal standardization when using MPI-DING and USGS reference glasses as multiple reference materials for calibration.
2014, 39(5): 537-545.
doi: 10.3799/dqkx.2014.051
Abstract:
Sandstone types, detrital components and cements, pore types and reservoir quality characteristics, differential diagenetic evolution processes resulted from sandstone types and their petrologic components, impact of the diagengetic evolution on pore structures, reservoir quality and gas yield of the He 8 tight gas-bearing sandstone reservoir, Middle Permian, Upper Paleozoic from the northern Ordos basin are studied, based upon observation of cores, identification and quantitative study of conventional, fluorescent and casting thin sections by vacuum impregnated with epoxy resin under microscope, image measurement of sandstone grain size, pores and pore throats, measurement of porosity and permeability, capillary pressure and homogenization temperature of fluid inclusions, combined with LA-ICP-MS detrital zircon in situ U-Pb dating provenance tracing. The results show that sandstone types and their petrologic components, primary reservoir capacity are controlled by provenance and parent rocks. Different sandstone types experienced differential diagenetic evolution processes and in turn resulted in differentiation in pores and pore throats development, thus reservoir quality and gas yield. Quartzarenite and sublitharenite have experienced relatively more complex multi-diagenetic processes, with inter-crystal micro-pores and micro-dissolution pores developed in kaolinite cements and inter-granular dissolution pores, turning quartzarenite into an excellent gas-bearing reservoir. A great quantity chlorite thin film formation on detrital grains have resulted in significant primary inter-granular pores preserved, together with a large number of inter-crystal pores in clay minerals and in interstitial tuff materials, turning sublitharenite into the second best gas-bearing reservoir. Diagenetic evolution of litharenite with high content of plastic fragments and calcareous cemented sandstone is relatively simple. Litharenite with high content of plastic fragments has experienced intensive compaction in early diagenetic phase, leading to rapid reduction of pores, of which the majority became reservoir with low porosity and low permeability and few turned into tight reservoir at that time; however, part of the primary pores in part litharenite are preserved, which could have formed gas-bearing reservoir if pore network formed by later dissolution event occurred in sandstones. Carbon cements are the major cement which led the calcareous cemented sandstone to be reservoir with low porosity and permeability to tight reservoirs, thus non-reservoir for natural gas. The results are of significance both in theory and practice, for the understanding of diagenetic-hydrocarbon filling and densification process and mechanism, and for tracing "sweet spots" in natural gas-bearing reservoir as well.
Sandstone types, detrital components and cements, pore types and reservoir quality characteristics, differential diagenetic evolution processes resulted from sandstone types and their petrologic components, impact of the diagengetic evolution on pore structures, reservoir quality and gas yield of the He 8 tight gas-bearing sandstone reservoir, Middle Permian, Upper Paleozoic from the northern Ordos basin are studied, based upon observation of cores, identification and quantitative study of conventional, fluorescent and casting thin sections by vacuum impregnated with epoxy resin under microscope, image measurement of sandstone grain size, pores and pore throats, measurement of porosity and permeability, capillary pressure and homogenization temperature of fluid inclusions, combined with LA-ICP-MS detrital zircon in situ U-Pb dating provenance tracing. The results show that sandstone types and their petrologic components, primary reservoir capacity are controlled by provenance and parent rocks. Different sandstone types experienced differential diagenetic evolution processes and in turn resulted in differentiation in pores and pore throats development, thus reservoir quality and gas yield. Quartzarenite and sublitharenite have experienced relatively more complex multi-diagenetic processes, with inter-crystal micro-pores and micro-dissolution pores developed in kaolinite cements and inter-granular dissolution pores, turning quartzarenite into an excellent gas-bearing reservoir. A great quantity chlorite thin film formation on detrital grains have resulted in significant primary inter-granular pores preserved, together with a large number of inter-crystal pores in clay minerals and in interstitial tuff materials, turning sublitharenite into the second best gas-bearing reservoir. Diagenetic evolution of litharenite with high content of plastic fragments and calcareous cemented sandstone is relatively simple. Litharenite with high content of plastic fragments has experienced intensive compaction in early diagenetic phase, leading to rapid reduction of pores, of which the majority became reservoir with low porosity and low permeability and few turned into tight reservoir at that time; however, part of the primary pores in part litharenite are preserved, which could have formed gas-bearing reservoir if pore network formed by later dissolution event occurred in sandstones. Carbon cements are the major cement which led the calcareous cemented sandstone to be reservoir with low porosity and permeability to tight reservoirs, thus non-reservoir for natural gas. The results are of significance both in theory and practice, for the understanding of diagenetic-hydrocarbon filling and densification process and mechanism, and for tracing "sweet spots" in natural gas-bearing reservoir as well.
2014, 39(5): 546-556.
doi: 10.3799/dqkx.2014.052
Abstract:
The main prerequisite for the development of middle-deep lacustrine source rocks has been deduced on the basis of the comprehensive analysis of lake forming conditions, core analysis, oil-source correlation and seismic reflection characteristics in the Enping depression, the Pearl River Mouth Basin. Compared with the seismic facies of source rocks of Paleogene Wenchang Formation in the proven hydrocarbon-rich sag (Panyu 4 and Lufeng 13 sags of Huizhou depression), the distribution and model of middle-deep lacustrine source rocks had been reconstructed in the Enping depression. In the study area the source rocks which are characterized by continuous seismic reflections with low frequency and high amplitude are occurred in every third-order sequence. In the Enping 17 sag they are mainly distributed in the central and west parts, while vertically the scope in the Upper Wenchang Formation was smaller than that of Lower Wenchang Formation and the sedimentation center is to the side of Fault 1 that controlled depression. In the Enping 18 sag the source rocks are mainly located in the central part close to Fault 2 that controlled sag, while vertically the scope in the the Upper Wenchang Formation is bigger than that in the Lower Wenchang Formation and the sedimentation center almost remained unchanged. The source rocks that has sheet-like seismic reflections with weak amplitude to blank are primarily distributed in the third-order sequences SQ3-SQ5. In the Enping 17 sag they are restricted in a small negative tectonic unit located south of the internal low uplift. In the Enping 18 sag they are distributed in the deep sag. Based on the distribution of middle-deep lacustrine source rocks, three developmental models are established namely: (1) the widespread source rocks in the transgressive system tracts and highstand system tracts; (2) source rocks developed in the lowstand system tracts, for example in SQ5 in the Wenchang Formation; (3) source rocks developed south of the internal low uplift, restricted in a small negative tectonic unit.
The main prerequisite for the development of middle-deep lacustrine source rocks has been deduced on the basis of the comprehensive analysis of lake forming conditions, core analysis, oil-source correlation and seismic reflection characteristics in the Enping depression, the Pearl River Mouth Basin. Compared with the seismic facies of source rocks of Paleogene Wenchang Formation in the proven hydrocarbon-rich sag (Panyu 4 and Lufeng 13 sags of Huizhou depression), the distribution and model of middle-deep lacustrine source rocks had been reconstructed in the Enping depression. In the study area the source rocks which are characterized by continuous seismic reflections with low frequency and high amplitude are occurred in every third-order sequence. In the Enping 17 sag they are mainly distributed in the central and west parts, while vertically the scope in the Upper Wenchang Formation was smaller than that of Lower Wenchang Formation and the sedimentation center is to the side of Fault 1 that controlled depression. In the Enping 18 sag the source rocks are mainly located in the central part close to Fault 2 that controlled sag, while vertically the scope in the the Upper Wenchang Formation is bigger than that in the Lower Wenchang Formation and the sedimentation center almost remained unchanged. The source rocks that has sheet-like seismic reflections with weak amplitude to blank are primarily distributed in the third-order sequences SQ3-SQ5. In the Enping 17 sag they are restricted in a small negative tectonic unit located south of the internal low uplift. In the Enping 18 sag they are distributed in the deep sag. Based on the distribution of middle-deep lacustrine source rocks, three developmental models are established namely: (1) the widespread source rocks in the transgressive system tracts and highstand system tracts; (2) source rocks developed in the lowstand system tracts, for example in SQ5 in the Wenchang Formation; (3) source rocks developed south of the internal low uplift, restricted in a small negative tectonic unit.
2014, 39(5): 557-564.
doi: 10.3799/dqkx.2014.053
Abstract:
The Tazhong-16 Carboniferous oil reservoir, located in the central Tazhong area, has the characteristics of low-oil saturation layers preferentially accumulated in the low porosity and permeability sandstone reservoirs and water layers exist in high porosity and permeability reservoirs. Grains containing Oil Inclusion (GOI) method was applied to further understand the mechanisms of the low-oil saturation layers in this field. Most GOI values in both current oil layers and water layers range from 5.6% to 32%, suggesting abundant paleo-oil charge and large amount of oil leak from filled oil layers. The GOI values have positive correlation with high porosity and permeability, indicating oil preferentially charge reservoirs with high porosity and permeability forming oil layers with high-oil saturation. When oil leaks from a trap, the larger pores are drained more easily than the smaller ones, resulting in a decrease of residual oil saturation with increasing porosity and permeability in drained reservoirs. The framework of the Tazhong-16 Carboniferous trap changed during the Late Triassic can be responsible for the large amount of oil leak. Preferential oil charge and preferential leak of the accumulated oil in reservoirs with different porosity and permeability during oil remigration is the mechanism of the formation of water layers with high GOI values and the low-oil saturation layers. Petroleum reservoirs in basins with complex evolution history usually experienced multiple phases of petroleum charge and post-accumulation alteration process. Thus, understanding the origin, charge history and physicochemical alteration processes associated with oil accumulation and preservation become critical for successful petroleum exploration in basins with complex evolution history.
The Tazhong-16 Carboniferous oil reservoir, located in the central Tazhong area, has the characteristics of low-oil saturation layers preferentially accumulated in the low porosity and permeability sandstone reservoirs and water layers exist in high porosity and permeability reservoirs. Grains containing Oil Inclusion (GOI) method was applied to further understand the mechanisms of the low-oil saturation layers in this field. Most GOI values in both current oil layers and water layers range from 5.6% to 32%, suggesting abundant paleo-oil charge and large amount of oil leak from filled oil layers. The GOI values have positive correlation with high porosity and permeability, indicating oil preferentially charge reservoirs with high porosity and permeability forming oil layers with high-oil saturation. When oil leaks from a trap, the larger pores are drained more easily than the smaller ones, resulting in a decrease of residual oil saturation with increasing porosity and permeability in drained reservoirs. The framework of the Tazhong-16 Carboniferous trap changed during the Late Triassic can be responsible for the large amount of oil leak. Preferential oil charge and preferential leak of the accumulated oil in reservoirs with different porosity and permeability during oil remigration is the mechanism of the formation of water layers with high GOI values and the low-oil saturation layers. Petroleum reservoirs in basins with complex evolution history usually experienced multiple phases of petroleum charge and post-accumulation alteration process. Thus, understanding the origin, charge history and physicochemical alteration processes associated with oil accumulation and preservation become critical for successful petroleum exploration in basins with complex evolution history.
2014, 39(5): 565-576.
doi: 10.3799/dqkx.2014.054
Abstract:
Carbonate cement is an important authigenic mineral in sandstone reservoirs of the central uplift belt in the Dongying depression, but no in-depth study has been conducted on its formation mechanisms currently. In this article, carbonate cements of Shahejie Formation of the central uplift belt in the Dongying depression are divided into four periods using petrologic records and their development characteristics are concluded. And then, according to the paragenetic mineral assemblages, carbon and oxygen isotope ratios, chemical elemental composition and other information of carbonate cements, their formation mechanisms were studied. Study results show that carbonates in the study area are mainly affected by the organic acids generated during the process of maturation of organic matter and the dissolution of the carbonate debris during deposition of Es4. In the study area, four periods of carbonate cements developed mostly. The first period of carbonate cements is mainly dolomite. Its formation is related to decomposition effects of methane bacteria on organic matter; the second period of carbonate cements is mainly formed of calcite and there is a layer of chlorite film locating between the second period and the first period of carbonate cements. The formation of cements is related to Ca and HCO3- oversaturation caused by pore fluid condensation; the third period of carbonate cements mainly include calcite, dolomite and ankerite, being characterized by filling dissolution pore of feldspar and primary pore, with their substance derived from the dissolution pore of feldspar and dehydration of mudstone; the fourth period of carbonate cements is characterized by filling the early-stage carbonate-corroded pores. Their substances are derived from the conversion of clay minerals and are usually symbiotic with pyrite particles, and their formation is affected by the hydrocarbon fluid flow.
Carbonate cement is an important authigenic mineral in sandstone reservoirs of the central uplift belt in the Dongying depression, but no in-depth study has been conducted on its formation mechanisms currently. In this article, carbonate cements of Shahejie Formation of the central uplift belt in the Dongying depression are divided into four periods using petrologic records and their development characteristics are concluded. And then, according to the paragenetic mineral assemblages, carbon and oxygen isotope ratios, chemical elemental composition and other information of carbonate cements, their formation mechanisms were studied. Study results show that carbonates in the study area are mainly affected by the organic acids generated during the process of maturation of organic matter and the dissolution of the carbonate debris during deposition of Es4. In the study area, four periods of carbonate cements developed mostly. The first period of carbonate cements is mainly dolomite. Its formation is related to decomposition effects of methane bacteria on organic matter; the second period of carbonate cements is mainly formed of calcite and there is a layer of chlorite film locating between the second period and the first period of carbonate cements. The formation of cements is related to Ca and HCO3- oversaturation caused by pore fluid condensation; the third period of carbonate cements mainly include calcite, dolomite and ankerite, being characterized by filling dissolution pore of feldspar and primary pore, with their substance derived from the dissolution pore of feldspar and dehydration of mudstone; the fourth period of carbonate cements is characterized by filling the early-stage carbonate-corroded pores. Their substances are derived from the conversion of clay minerals and are usually symbiotic with pyrite particles, and their formation is affected by the hydrocarbon fluid flow.
2014, 39(5): 577-586.
doi: 10.3799/dqkx.2014.055
Abstract:
It is important for sequence stratigraphy and oil-gas exploration to explore major internal sequence compositions such as the evolution of erosion and filling patterns. In this paper, incised valley characteristics and evolutionary model are studied using 3D seismic data, drilling data and paleontological data. The results show that there are a series of incised valleys in the study area, which are determined and divided into three different kinds of strike including E-W, S-E and N-S respectively by the seismic profile. The morphology of incised valleys on the seismic profile shows a V-shape, while the internal filling patterns are of progradational configuration, divergent configuration and on-lap configuration. Regional geological data indicate that Chepaizi area started to uplift during the Heisey-Indosinian movement, resulting in the formation of an incised valley by a drop in base level. After the Paleogene, the base level restarted to rise, so the incised valley started to fill, with the filling time related to the position of ancient coastline. The evolutionary model of incised valleys is controlled by tectonics, topography, paleoclimate and source supply.
It is important for sequence stratigraphy and oil-gas exploration to explore major internal sequence compositions such as the evolution of erosion and filling patterns. In this paper, incised valley characteristics and evolutionary model are studied using 3D seismic data, drilling data and paleontological data. The results show that there are a series of incised valleys in the study area, which are determined and divided into three different kinds of strike including E-W, S-E and N-S respectively by the seismic profile. The morphology of incised valleys on the seismic profile shows a V-shape, while the internal filling patterns are of progradational configuration, divergent configuration and on-lap configuration. Regional geological data indicate that Chepaizi area started to uplift during the Heisey-Indosinian movement, resulting in the formation of an incised valley by a drop in base level. After the Paleogene, the base level restarted to rise, so the incised valley started to fill, with the filling time related to the position of ancient coastline. The evolutionary model of incised valleys is controlled by tectonics, topography, paleoclimate and source supply.
2014, 39(5): 587-600.
doi: 10.3799/dqkx.2014.056
Abstract:
This paper systematically elaborates the effects of oil cracking on homogenization temperature and trapping pressure of oil inclusion using crude oil crack kinetic and petroleum inclusion thermodynamics modeling. The results demonstrate that homogenization temperature shows a trend of increase and the trapping pressure shows a trend of decrease at the initial stage of oil cracking (TR < 13%, T < 160 ℃); with the progressing of oil cracking (TR < 24%, T < 190 ℃), homogenization temperature shows a trend of decrease and the trapping pressure shows a trend of increase, however, the homogenization temperature still exceeds the initial homogenization temperature and the trapping pressure is still below the initial trapping pressure at this stage of oil cracking. After that, the homogenization temperature continues to decrease or even turns negative values in some severe oil cracking processes; at the same time, trapping pressure continues to increase or exceed litho static pressure. In addition, oil cracking only results in normal pressure or under pressure during the initial stage of oil cracking (TR < 13%, T < 160 ℃), while oil cracking will lead to overpressure (TR > 40%) or even exceeding litho static pressure (TR > 70%) during the high level of oil cracking. Therefore, deeply buried reservoirs with pressure systems from under pressure to normal pressure should be paid more attention especially when formation temperature ranges from 160 ℃ to 190 ℃, and oil cracking gas exploration should be focused on the reservoirs with overpressure or ultrahigh pressure when formation temperature is over 190 ℃.
This paper systematically elaborates the effects of oil cracking on homogenization temperature and trapping pressure of oil inclusion using crude oil crack kinetic and petroleum inclusion thermodynamics modeling. The results demonstrate that homogenization temperature shows a trend of increase and the trapping pressure shows a trend of decrease at the initial stage of oil cracking (TR < 13%, T < 160 ℃); with the progressing of oil cracking (TR < 24%, T < 190 ℃), homogenization temperature shows a trend of decrease and the trapping pressure shows a trend of increase, however, the homogenization temperature still exceeds the initial homogenization temperature and the trapping pressure is still below the initial trapping pressure at this stage of oil cracking. After that, the homogenization temperature continues to decrease or even turns negative values in some severe oil cracking processes; at the same time, trapping pressure continues to increase or exceed litho static pressure. In addition, oil cracking only results in normal pressure or under pressure during the initial stage of oil cracking (TR < 13%, T < 160 ℃), while oil cracking will lead to overpressure (TR > 40%) or even exceeding litho static pressure (TR > 70%) during the high level of oil cracking. Therefore, deeply buried reservoirs with pressure systems from under pressure to normal pressure should be paid more attention especially when formation temperature ranges from 160 ℃ to 190 ℃, and oil cracking gas exploration should be focused on the reservoirs with overpressure or ultrahigh pressure when formation temperature is over 190 ℃.
2014, 39(5): 601-610.
doi: 10.3799/dqkx.2014.057
Abstract:
The main exploration targets of petroleum prospecting in Subei Basin shift gradually from structural reservoirs to subtle reservoirs nowadays. As potential gas and oil-bearing reservoirs, gravity flow sediment prospecting becomes more important for subtle reservoirs exploration. Based on the core observation, well logging, seismic profile characters, gravity flow deposits developed in E2d of Huangjue-Majiazui district in Gaoyou sag and their genies are studied. It is found that nearshore subaqueous alluvial fans and slump-turbidities developed in E2d1 in study area, while fan deltas and slump-turbidities developed in E2d2. The development of sandbodies is considered to be closely coordinated with the special structural pattern, special and active tectonic backgrounds. Discovery of slump-turbidities provides theoretical framework for oil and gas exploration.
The main exploration targets of petroleum prospecting in Subei Basin shift gradually from structural reservoirs to subtle reservoirs nowadays. As potential gas and oil-bearing reservoirs, gravity flow sediment prospecting becomes more important for subtle reservoirs exploration. Based on the core observation, well logging, seismic profile characters, gravity flow deposits developed in E2d of Huangjue-Majiazui district in Gaoyou sag and their genies are studied. It is found that nearshore subaqueous alluvial fans and slump-turbidities developed in E2d1 in study area, while fan deltas and slump-turbidities developed in E2d2. The development of sandbodies is considered to be closely coordinated with the special structural pattern, special and active tectonic backgrounds. Discovery of slump-turbidities provides theoretical framework for oil and gas exploration.
2014, 39(5): 611-619.
doi: 10.3799/dqkx.2014.058
Abstract:
In order to accurately simulate land subsidence caused by seepage field as a result of groundwater exploitation and stress field, two models are established in this study: one is groundwater seepage and land subsidence coupling numerical simulation model of the three-dimensional seepage of groundwater and one-dimensional vertical consolidation in light of Terzaghi effective stress principle; and the other is three-dimensional coupling model of groundwater seepage and land subsidence based on the Biot's consolidation theory combined with the nonlinear rheological theory of soil, extending the constitutive relation in Biot's consolidation theory to viscoelastic plasticity, taking into consideration of the dynamic change relationship of mechanical parameters and hydraulic parameters. The comparison and analysis show that the changing tendency of land subsidence calculated by groundwater seepage and land subsidence coupling numerical simulation model of the three-dimensional seepage of groundwater and one-dimensional vertical consolidation is the same as that of water level variation. When the water level falls back to the initial water level, total subsidence is 0. Land subsidence calculated by Biot's three-dimensional full coupling model falls behind of water level change. When the water level falls back to the initial water level, soil does not rebound to initial 0 subsidence state. There exists permanent remain of subsidence. In aspect of parameter change, porosity, hydraulic conductivity and Poisson's ratio have the tendency of decreasing first and then increasing. Modulus of elasticity has the tendency of decreasing first and then increasing. But these parameter values tend to be stable, corresponding to land subsidence variation.
In order to accurately simulate land subsidence caused by seepage field as a result of groundwater exploitation and stress field, two models are established in this study: one is groundwater seepage and land subsidence coupling numerical simulation model of the three-dimensional seepage of groundwater and one-dimensional vertical consolidation in light of Terzaghi effective stress principle; and the other is three-dimensional coupling model of groundwater seepage and land subsidence based on the Biot's consolidation theory combined with the nonlinear rheological theory of soil, extending the constitutive relation in Biot's consolidation theory to viscoelastic plasticity, taking into consideration of the dynamic change relationship of mechanical parameters and hydraulic parameters. The comparison and analysis show that the changing tendency of land subsidence calculated by groundwater seepage and land subsidence coupling numerical simulation model of the three-dimensional seepage of groundwater and one-dimensional vertical consolidation is the same as that of water level variation. When the water level falls back to the initial water level, total subsidence is 0. Land subsidence calculated by Biot's three-dimensional full coupling model falls behind of water level change. When the water level falls back to the initial water level, soil does not rebound to initial 0 subsidence state. There exists permanent remain of subsidence. In aspect of parameter change, porosity, hydraulic conductivity and Poisson's ratio have the tendency of decreasing first and then increasing. Modulus of elasticity has the tendency of decreasing first and then increasing. But these parameter values tend to be stable, corresponding to land subsidence variation.
2014, 39(5): 620-628.
doi: 10.3799/dqkx.2014.059
Abstract:
In order to understand the deep structural characteristics of Junggar basin, the conductivity structure of the region is analyzed in the paper using MT data obtained at standard points (45°N 88°E) in Junggar Basin based on SinoProbe project. Employing the method of nonlinear conjugate gradient for a 2D inversion of two short profiles in the study area, and analysis of the regional geological data, it is found that the ground has a good electrical layered structure in the middle-east Junggar Basin. A comparative analysis of the electrical layer and the crustal structure is made on the basis of geological data, finding that they show good consistency. Finally, it is concluded that the Moho depth is about 46 km, and the thickness of the lithosphere is about 100 km. The results can better the understanding of deep crustal structure in Middle-East Junggar Basin.
In order to understand the deep structural characteristics of Junggar basin, the conductivity structure of the region is analyzed in the paper using MT data obtained at standard points (45°N 88°E) in Junggar Basin based on SinoProbe project. Employing the method of nonlinear conjugate gradient for a 2D inversion of two short profiles in the study area, and analysis of the regional geological data, it is found that the ground has a good electrical layered structure in the middle-east Junggar Basin. A comparative analysis of the electrical layer and the crustal structure is made on the basis of geological data, finding that they show good consistency. Finally, it is concluded that the Moho depth is about 46 km, and the thickness of the lithosphere is about 100 km. The results can better the understanding of deep crustal structure in Middle-East Junggar Basin.
2014, 39(5): 629-636.
doi: 10.3799/dqkx.2014.060
Abstract:
Audio magnetotelluric sounding is used in this study for geological mapping exploration of three-dimensional nature to determine the underground electrical characteristics and relationship of deep structure of two outcrops of rock mass in Baogutu area of Western Junggar The two-dimensional OCCAM inversion electric structure results in the form of three-dimensional mapping, displaying the underground electrical characteristics from various angles. Two pieces of rock mass in the deep structure are found to be connected by channels. It is concluded that the mechanical energy generated in the cooling process of magma intrusion and porphyry convection led to fissures in the rock mass, which in turn led to structural fissures after the formation of anticline in Carboniferous Siebel Kuras Group, Baogutu Group, and Tailegula Group, because of the movement of cooling thermal and, thus causing, rock combination of cracks, Baogutu rock formed eventually when hydrothemal moved through these channels.
Audio magnetotelluric sounding is used in this study for geological mapping exploration of three-dimensional nature to determine the underground electrical characteristics and relationship of deep structure of two outcrops of rock mass in Baogutu area of Western Junggar The two-dimensional OCCAM inversion electric structure results in the form of three-dimensional mapping, displaying the underground electrical characteristics from various angles. Two pieces of rock mass in the deep structure are found to be connected by channels. It is concluded that the mechanical energy generated in the cooling process of magma intrusion and porphyry convection led to fissures in the rock mass, which in turn led to structural fissures after the formation of anticline in Carboniferous Siebel Kuras Group, Baogutu Group, and Tailegula Group, because of the movement of cooling thermal and, thus causing, rock combination of cracks, Baogutu rock formed eventually when hydrothemal moved through these channels.
