2014 Vol. 39, No. 10
Display Method:
PDF 350KB
2014, 39(10): 1283-1294.
doi: 10.3799/dqkx.2014.121
Abstract:
Nankai trough is one of seismogenic zones known for massive earthquakes in the world. Gravity flow deposits in slope basin of Nankai trough accretionary prism record the active history of magesplay faults and the recurrences of great earthquakes. Based on the data of integrated ocean drilling program (IODP), this study explores the characteristics of gravity flow deposits in slope basin and illustrates their implications to the activities of magesplay faults and great earthquakes. The results show that the slope basin was filled successively with wedge-shaped mass transport deposits (MTDs), canyon system and superficial MTDs. Wedge-shaped MTDs developed in the initial stage of magesplay fault activity, which is wedge-shaped and mainly composed of muddy breccia, indicating continuous and strong activities of the magesplay faults at the initial stage. Canyon system consists of several kinds of canyons including slope canyons, great MTDs canyon and axial canyon, which are controlled by steepening slope, increasing regional interstitial fluid pressure and anisotropic uplifting. Superficial MTDs consist of stacking multi-stage low amplitude MTDs and represent as plenty of scars, which formed in a relatively short time, but extensively. It may be caused by the seafloor shaking during a great earthquake. These characteristics of gravity flow deposits record the history of magesplay fault activities and recurrences of great earthquakes as follows: 1.95-1.55 Ma, magesplay fault reactivated sharply at the initial stage which triggered slumps in the upper wall of magesplay fault; 1.55-1.07 Ma, coupling and activities of magesplay fault in the west domain caused strata compressed, deformed and energy assembled in the prism as well as in the magesplay fault; 1.07 Ma to now, energy in the mageplay fault was released discontinuously that resulted in multi great earthquakes.
Nankai trough is one of seismogenic zones known for massive earthquakes in the world. Gravity flow deposits in slope basin of Nankai trough accretionary prism record the active history of magesplay faults and the recurrences of great earthquakes. Based on the data of integrated ocean drilling program (IODP), this study explores the characteristics of gravity flow deposits in slope basin and illustrates their implications to the activities of magesplay faults and great earthquakes. The results show that the slope basin was filled successively with wedge-shaped mass transport deposits (MTDs), canyon system and superficial MTDs. Wedge-shaped MTDs developed in the initial stage of magesplay fault activity, which is wedge-shaped and mainly composed of muddy breccia, indicating continuous and strong activities of the magesplay faults at the initial stage. Canyon system consists of several kinds of canyons including slope canyons, great MTDs canyon and axial canyon, which are controlled by steepening slope, increasing regional interstitial fluid pressure and anisotropic uplifting. Superficial MTDs consist of stacking multi-stage low amplitude MTDs and represent as plenty of scars, which formed in a relatively short time, but extensively. It may be caused by the seafloor shaking during a great earthquake. These characteristics of gravity flow deposits record the history of magesplay fault activities and recurrences of great earthquakes as follows: 1.95-1.55 Ma, magesplay fault reactivated sharply at the initial stage which triggered slumps in the upper wall of magesplay fault; 1.55-1.07 Ma, coupling and activities of magesplay fault in the west domain caused strata compressed, deformed and energy assembled in the prism as well as in the magesplay fault; 1.07 Ma to now, energy in the mageplay fault was released discontinuously that resulted in multi great earthquakes.
2014, 39(10): 1295-1306.
doi: 10.3799/dqkx.2014.122
Abstract:
Haicheng earthquake occurred in the north segment of Jinzhou fracture belt which is the most important active tectonic structure controlling earthquakes in Liaodong Peninsula. In this study, data was collected from 27 in-situ stress and 5 directional testing sensors installed at varying intervals along the total depth of single 600 m borehole located inside a granite rich region in the north segment of Jinzhou fracture belt at the east part of Xiongyue city. Combined with in-situ stress data of SV > SH > Sh, core sampling of the structural features of shallow earth crust rock formations reveals that the vertical principal stress plays a leading role in normal fault activity. Moreover, measured maximum in-situ principal stress trends towards the northeast-east direction and reflects present tensile properties, with dextral activity, of the Jinzhou segment. The results confirm the previous relevant studies, enriching the dynamics data and facilitating the understanding of the active features of the north segment of the Jinzhou fracture belt.
Haicheng earthquake occurred in the north segment of Jinzhou fracture belt which is the most important active tectonic structure controlling earthquakes in Liaodong Peninsula. In this study, data was collected from 27 in-situ stress and 5 directional testing sensors installed at varying intervals along the total depth of single 600 m borehole located inside a granite rich region in the north segment of Jinzhou fracture belt at the east part of Xiongyue city. Combined with in-situ stress data of SV > SH > Sh, core sampling of the structural features of shallow earth crust rock formations reveals that the vertical principal stress plays a leading role in normal fault activity. Moreover, measured maximum in-situ principal stress trends towards the northeast-east direction and reflects present tensile properties, with dextral activity, of the Jinzhou segment. The results confirm the previous relevant studies, enriching the dynamics data and facilitating the understanding of the active features of the north segment of the Jinzhou fracture belt.
2014, 39(10): 1307-1321.
doi: 10.3799/dqkx.2014.123
Abstract:
Based on the satellite-derived gravity data processed by applying various image enhancement methods (including filter, gradient and continuation) and processing of the standardized seismic profiles, plus the establishment of 8 major seismic cross sections, the tectonic features and dynamic evolution of the bay of Bengal basin are explored in this study. Free-air gravity anomalies and their results of enhanced processing indicate that there are NW-trending fracture zones in the west, EW-trending faults in the 90°E ridge, and NE-trending linear structures in the east of the basin, which suggest the influence of sea floor spreading, ridge emplacement and Indian Ocean crust subduction. According to the standardized seismic reflection profiling results, gravity anomalies and stratum thickness, the basin is divided into the following five tectonic units: west depression, 85°E ridge, central depression, 90°E ridge and Rakhine depression. Prior to the collision, the sedimentary framework was controlled by multiple isolated rises developed in 85°E ridge, which was the response of episodic eruption processes of the hotspot. Whereas, the post collisional sediments known as the Bengal fan sediments were not prominently affected by the ridge and the sediments kept on migrating southward during the Eocene to Miocene. The subduction of the 90°E ridge promoted the westward growth of Andaman accretionary in the south (7°-14°N) and controlled the evolution of Rakhine depression, Indo-Burmese wedge and the depocenter of the bay of Bengal basin in the north (14°-20°N). It is found that the protooceanic basin stage (Late Cretaceous to Early Oligocene) and the remnant ocean basin stage (Late Oligocene to present) are two main episodes in the bay of Bengal basin.
Based on the satellite-derived gravity data processed by applying various image enhancement methods (including filter, gradient and continuation) and processing of the standardized seismic profiles, plus the establishment of 8 major seismic cross sections, the tectonic features and dynamic evolution of the bay of Bengal basin are explored in this study. Free-air gravity anomalies and their results of enhanced processing indicate that there are NW-trending fracture zones in the west, EW-trending faults in the 90°E ridge, and NE-trending linear structures in the east of the basin, which suggest the influence of sea floor spreading, ridge emplacement and Indian Ocean crust subduction. According to the standardized seismic reflection profiling results, gravity anomalies and stratum thickness, the basin is divided into the following five tectonic units: west depression, 85°E ridge, central depression, 90°E ridge and Rakhine depression. Prior to the collision, the sedimentary framework was controlled by multiple isolated rises developed in 85°E ridge, which was the response of episodic eruption processes of the hotspot. Whereas, the post collisional sediments known as the Bengal fan sediments were not prominently affected by the ridge and the sediments kept on migrating southward during the Eocene to Miocene. The subduction of the 90°E ridge promoted the westward growth of Andaman accretionary in the south (7°-14°N) and controlled the evolution of Rakhine depression, Indo-Burmese wedge and the depocenter of the bay of Bengal basin in the north (14°-20°N). It is found that the protooceanic basin stage (Late Cretaceous to Early Oligocene) and the remnant ocean basin stage (Late Oligocene to present) are two main episodes in the bay of Bengal basin.
2014, 39(10): 1322-1332.
doi: 10.3799/dqkx.2014.124
Abstract:
Dayishan ore field located in the north rim of the middle section of the Nanling metallogenic belt in South China fold zone, and at the intersection of Yangmingshan-Dayishan-Shangpu EW basement fault, Youxian-Ningyuan NE basement fault and Chenzhou-Shaoyang NW concealed deep fault, has been controlled by the Dayishan intrusive rock. The greisens-vein type tin deposit is one of the typical mineralization types in this ore field. The Rb-Sr geochronology of fluid inclusions in quartz of the ore veins is presented and its geological significance of the Baishaziling greisens-vein type tin deposit is discussed in this paper. The Rb-Sr isotopic dating of fluid inclusions of quartz is 160±1 Ma, which indicates that the tin deposit was likely formed in the peaks (160-150 Ma) of Mesozoic mineralization period of Nanling region, and the mineralization was closely related to the magmatic intrusion of the Middle Jurassic monzogranite of Dayishan intrusive rock, as a result of the post-magmatic hydrothermal mineralization. The initial 87Sr/86Sr value of the fluid inclusions is 0.706 79±0.003 66, which may indicate a mantle-derived fluid contribution to the ore-forming fluids.
Dayishan ore field located in the north rim of the middle section of the Nanling metallogenic belt in South China fold zone, and at the intersection of Yangmingshan-Dayishan-Shangpu EW basement fault, Youxian-Ningyuan NE basement fault and Chenzhou-Shaoyang NW concealed deep fault, has been controlled by the Dayishan intrusive rock. The greisens-vein type tin deposit is one of the typical mineralization types in this ore field. The Rb-Sr geochronology of fluid inclusions in quartz of the ore veins is presented and its geological significance of the Baishaziling greisens-vein type tin deposit is discussed in this paper. The Rb-Sr isotopic dating of fluid inclusions of quartz is 160±1 Ma, which indicates that the tin deposit was likely formed in the peaks (160-150 Ma) of Mesozoic mineralization period of Nanling region, and the mineralization was closely related to the magmatic intrusion of the Middle Jurassic monzogranite of Dayishan intrusive rock, as a result of the post-magmatic hydrothermal mineralization. The initial 87Sr/86Sr value of the fluid inclusions is 0.706 79±0.003 66, which may indicate a mantle-derived fluid contribution to the ore-forming fluids.
2014, 39(10): 1333-1342.
doi: 10.3799/dqkx.2014.125
Abstract:
Confined water in deep sandy gravel layer is newly-discovered large-scale pore brines in Heibei concave in the western Qaidam basin, which poses as an alternative area for potash development due to the following features: medium to strong water yield property, closeness to the surface with water level ranging from 8 to 24 m, high degree of mineralization, high KCl content fit for commercial development, and small salt buildup when mined. The statistical results show that concentration changes of TDS, Cl-, Na+, Cs+, B2O3, Ca2+, Mg2+, Sr+, NO3-, and Rb+ in the brine are small with even distribution. On the contrary, concentration changes of SO42- are big with uneven distribution; concentration changes of Br-, I-, Li+, K+ and uniform degree fall in the range in-between those of the two above-mentioned groups of elements; Na+, Cl-, Ca2+ and Sr2+, TDS show normal negatively skewed peak distribution, K+, SO42-, Li+ show non-normal positively skewed peak distribution. In component clustering analysis diagram, K+, SO42-, Li+ fall into a sub-class, whereas Cl-, TDS and Na+ fall into another sub-class The ion content change curve shows that content of Na+ and Cl- share the same change trend with that of mineralization degree and B2O3 in the pore brine from east to west. Compositions of K+, SO42-, Mg2+ are consistent, with the same change trend with that of Li+. Ratio of CNa/CCl in pore brine is 0.85-0.96, and bromine chloride coefficient is 0.01-0.34, similar to those of salt karst filter brine. It finds two laws of salting, namely, magnesium sulfate and chloride in the metastable phase diagram (25 ℃) of the quaternary system of Na+, K+, Mg2+//Cl--H2O and quinary system of Na+, K+, Mg2+//Cl-, SO42--H2O, which might have formed due to interaction of intercrystalline brine in the sedimentary formation and pore water in the sandy gravel.
Confined water in deep sandy gravel layer is newly-discovered large-scale pore brines in Heibei concave in the western Qaidam basin, which poses as an alternative area for potash development due to the following features: medium to strong water yield property, closeness to the surface with water level ranging from 8 to 24 m, high degree of mineralization, high KCl content fit for commercial development, and small salt buildup when mined. The statistical results show that concentration changes of TDS, Cl-, Na+, Cs+, B2O3, Ca2+, Mg2+, Sr+, NO3-, and Rb+ in the brine are small with even distribution. On the contrary, concentration changes of SO42- are big with uneven distribution; concentration changes of Br-, I-, Li+, K+ and uniform degree fall in the range in-between those of the two above-mentioned groups of elements; Na+, Cl-, Ca2+ and Sr2+, TDS show normal negatively skewed peak distribution, K+, SO42-, Li+ show non-normal positively skewed peak distribution. In component clustering analysis diagram, K+, SO42-, Li+ fall into a sub-class, whereas Cl-, TDS and Na+ fall into another sub-class The ion content change curve shows that content of Na+ and Cl- share the same change trend with that of mineralization degree and B2O3 in the pore brine from east to west. Compositions of K+, SO42-, Mg2+ are consistent, with the same change trend with that of Li+. Ratio of CNa/CCl in pore brine is 0.85-0.96, and bromine chloride coefficient is 0.01-0.34, similar to those of salt karst filter brine. It finds two laws of salting, namely, magnesium sulfate and chloride in the metastable phase diagram (25 ℃) of the quaternary system of Na+, K+, Mg2+//Cl--H2O and quinary system of Na+, K+, Mg2+//Cl-, SO42--H2O, which might have formed due to interaction of intercrystalline brine in the sedimentary formation and pore water in the sandy gravel.
2014, 39(10): 1343-1354.
doi: 10.3799/dqkx.2014.126
Abstract:
The Late-Middle Permian (about 260 Ma) Emeishan large igneous province in SW China contains two ore-forming magma series, i.e., small ultramafic subvolcanic sills that host magmatic Cu-Ni-PGE sulfide ores and large mafic layered intrusions that host giant Fe-Ti-V oxide deposits. The differences between these two types of ore-forming magma series in the factors controlling mineralization, the nature of magma and magmatic processes, etc., are systematically summarized and analyzed. And the comparisons between Cu-Ni-PGE sulfide-bearing intrusions and Fe-Ti-V oxide-bearing intrusions confirm that Cu-Ni-PGE sulfide mineralization or Fe-Ti-V oxide mineralization depend on the degrees of fractionation crystallization, partial melting, crustal contamination and volatiles (e.g. S and P). The combination of other deposits in the Emeishan large igneous province suggests that the high Ti affinity and low Ti affinity of the Emeishan basalts are not the key factors controlling Cu-Ni-PGE sulfide or Fe-Ti-V oxide mineralization, which are associated with individual factors respectively.
The Late-Middle Permian (about 260 Ma) Emeishan large igneous province in SW China contains two ore-forming magma series, i.e., small ultramafic subvolcanic sills that host magmatic Cu-Ni-PGE sulfide ores and large mafic layered intrusions that host giant Fe-Ti-V oxide deposits. The differences between these two types of ore-forming magma series in the factors controlling mineralization, the nature of magma and magmatic processes, etc., are systematically summarized and analyzed. And the comparisons between Cu-Ni-PGE sulfide-bearing intrusions and Fe-Ti-V oxide-bearing intrusions confirm that Cu-Ni-PGE sulfide mineralization or Fe-Ti-V oxide mineralization depend on the degrees of fractionation crystallization, partial melting, crustal contamination and volatiles (e.g. S and P). The combination of other deposits in the Emeishan large igneous province suggests that the high Ti affinity and low Ti affinity of the Emeishan basalts are not the key factors controlling Cu-Ni-PGE sulfide or Fe-Ti-V oxide mineralization, which are associated with individual factors respectively.
2014, 39(10): 1355-1363.
doi: 10.3799/dqkx.2014.127
Abstract:
A large amount of primary single-phase aqueous fluid inclusions and secondary petroleum inclusions are discovered in the halite in the first member of Palaeogene Shahejie Formation in Shulu depression, which facilitates the determination of the origin of evaporite and the migration and preservation conditions of oil and gas. In this paper, the formation time and the trapping paleopressure of fluid inclusions and the burial history of oil and gas are analyzed by linking the homogenization temperature of both the primary single-phase aqueous fluid inclusions and secondary petroleum inclusions with the petrography of halite. As the results, the homogenization temperature of the aqueous inclusion, which is symbiosis with the petroleum inclusions, ranges from 66.5 to 91.5 ℃ and 103.7 to 108.9 ℃, respectively. The trapping time of the former is about 10.56 to 10.11 Ma and the trapping time of the latter is about 1.10 Ma. It is concluded that the time of oil and gas fluid entering into the salt rock is about the middle-late Guantao Formation and Pleistocene, which is also evidenced by the investigation of the oil and gas generation history. The paleopressure coefficient of the middle part of the salt rock modeled by fluid inclusions is up to 1.64, suggesting that there existed a hyperpressure system under the salt rock which probably facilitated the migration and preservation of oil and gas.
A large amount of primary single-phase aqueous fluid inclusions and secondary petroleum inclusions are discovered in the halite in the first member of Palaeogene Shahejie Formation in Shulu depression, which facilitates the determination of the origin of evaporite and the migration and preservation conditions of oil and gas. In this paper, the formation time and the trapping paleopressure of fluid inclusions and the burial history of oil and gas are analyzed by linking the homogenization temperature of both the primary single-phase aqueous fluid inclusions and secondary petroleum inclusions with the petrography of halite. As the results, the homogenization temperature of the aqueous inclusion, which is symbiosis with the petroleum inclusions, ranges from 66.5 to 91.5 ℃ and 103.7 to 108.9 ℃, respectively. The trapping time of the former is about 10.56 to 10.11 Ma and the trapping time of the latter is about 1.10 Ma. It is concluded that the time of oil and gas fluid entering into the salt rock is about the middle-late Guantao Formation and Pleistocene, which is also evidenced by the investigation of the oil and gas generation history. The paleopressure coefficient of the middle part of the salt rock modeled by fluid inclusions is up to 1.64, suggesting that there existed a hyperpressure system under the salt rock which probably facilitated the migration and preservation of oil and gas.
Authigenic Lepidocrocite and Greigite Particles inAquatic Environments off the Yangtze River Estuary
2014, 39(10): 1364-1370.
doi: 10.3799/dqkx.2014.128
Abstract:
A scanning electron micrometer with energy-dispersive X-ray analytical system is used to investigate the suspended particles collected in 2010 in aquatic environments off the Yangtze River estuary in this study. The results show that iron oxide and iron sulfide co-exist in the same environment. Iron oxide is lepidocrocite, which accumulates in porously irregular aggregates. Iron sulfide is greigite and aggregates into organized framboids. The greigite framboids are enclosed by organic films. Lepidocrocite is in agreement with the environmental conditions. Meanwhile, greigite only exists at a local patch covered with organic films. Both lepidocrocite and greigite particles settle down easily, but their preservation depends on the early diagenesis conditions. It is suggested that at least a minor part of the iron sulfide framboids commonly found in the sedimentary sequences perhaps originates from their upward aquatic environment.
A scanning electron micrometer with energy-dispersive X-ray analytical system is used to investigate the suspended particles collected in 2010 in aquatic environments off the Yangtze River estuary in this study. The results show that iron oxide and iron sulfide co-exist in the same environment. Iron oxide is lepidocrocite, which accumulates in porously irregular aggregates. Iron sulfide is greigite and aggregates into organized framboids. The greigite framboids are enclosed by organic films. Lepidocrocite is in agreement with the environmental conditions. Meanwhile, greigite only exists at a local patch covered with organic films. Both lepidocrocite and greigite particles settle down easily, but their preservation depends on the early diagenesis conditions. It is suggested that at least a minor part of the iron sulfide framboids commonly found in the sedimentary sequences perhaps originates from their upward aquatic environment.
2014, 39(10): 1371-1380.
doi: 10.3799/dqkx.2014.129
Abstract:
The existence of a complete stratigraphic sequence in Paleogene Shahejie Formation in northern Liaoxi depression is confirmed and five sequences are identified in this paper by comprehensive analysis of seismic profiles, well logs and cores data. It is found that there is not any unconformity surface between Member 1 and Member 2 of Shahejie Formation, so they form the highstand system tract and lowstand-transgressive system tract of the sequence respectively. SQs3-1 (the upper submember of Member 3) is nearly denudated in uplift area and widely distributed in the depression zone. All kinds of sedimentary facies have been recognized in the study area, including the fan delta system, braided delta system, nearshore subaqueous fan system and beach-bar system. The sedimentary system distribution is controlled by syndepositional fault, paleo-uplift and depression. The favorable sand bodies in the study area consist of those developed in the lowstand system tract at the edge of the paleouplift, deep water gravity flow sand in the center of the sub-sag and carbonate in the upper part of the paleouplift. With the underlying massive dark mudstone and shale in the third sequence of Shahejie Formation and the overlying pelolithic layer of the first sequence of Shahejie Formation, they can form good reservoir-cap assemblages and form litho-stratigraphic traps in the uplift, sub-sag, fault slope break and the gentle slope belt.
The existence of a complete stratigraphic sequence in Paleogene Shahejie Formation in northern Liaoxi depression is confirmed and five sequences are identified in this paper by comprehensive analysis of seismic profiles, well logs and cores data. It is found that there is not any unconformity surface between Member 1 and Member 2 of Shahejie Formation, so they form the highstand system tract and lowstand-transgressive system tract of the sequence respectively. SQs3-1 (the upper submember of Member 3) is nearly denudated in uplift area and widely distributed in the depression zone. All kinds of sedimentary facies have been recognized in the study area, including the fan delta system, braided delta system, nearshore subaqueous fan system and beach-bar system. The sedimentary system distribution is controlled by syndepositional fault, paleo-uplift and depression. The favorable sand bodies in the study area consist of those developed in the lowstand system tract at the edge of the paleouplift, deep water gravity flow sand in the center of the sub-sag and carbonate in the upper part of the paleouplift. With the underlying massive dark mudstone and shale in the third sequence of Shahejie Formation and the overlying pelolithic layer of the first sequence of Shahejie Formation, they can form good reservoir-cap assemblages and form litho-stratigraphic traps in the uplift, sub-sag, fault slope break and the gentle slope belt.
2014, 39(10): 1381-1390.
doi: 10.3799/dqkx.2014.130
Abstract:
It is necessary to reconstruct its evolution of critical physical conditions while researching the formation mechanism and accumulation process of "Continuous" tight sandstone gas reservoir since it is one of significant unconventional hydrocarbon resources. Taking Yinan 2 "continuous" tight sandstone gas reservoir as the study area, the evolution of critical physical conditions is reconstructed with numerical modeling as well as basin model technology. The earliest formation time of "Continuous" tight sandstone gas reservoir is determined based on the temporal coupling between critical physical conditions and reservoir evolution. The results show that critical physical conditions of "Continuous" tight sandstone gas reservoir are dynamic, changing with the geological settings. As for Yinan 2 "continuous" tight sandstone gas reservoir, the earliest formation time is about 9 Ma, and the corresponding porosity is about 6.95%. The present critical porosity is about 7.26%.Combined with the geological conditions, it is further confirmed that Yinan 2 gas reservoir is a "Continuous" tight sandstone gas reservoir.
It is necessary to reconstruct its evolution of critical physical conditions while researching the formation mechanism and accumulation process of "Continuous" tight sandstone gas reservoir since it is one of significant unconventional hydrocarbon resources. Taking Yinan 2 "continuous" tight sandstone gas reservoir as the study area, the evolution of critical physical conditions is reconstructed with numerical modeling as well as basin model technology. The earliest formation time of "Continuous" tight sandstone gas reservoir is determined based on the temporal coupling between critical physical conditions and reservoir evolution. The results show that critical physical conditions of "Continuous" tight sandstone gas reservoir are dynamic, changing with the geological settings. As for Yinan 2 "continuous" tight sandstone gas reservoir, the earliest formation time is about 9 Ma, and the corresponding porosity is about 6.95%. The present critical porosity is about 7.26%.Combined with the geological conditions, it is further confirmed that Yinan 2 gas reservoir is a "Continuous" tight sandstone gas reservoir.
2014, 39(10): 1391-1397.
doi: 10.3799/dqkx.2014.131
Abstract:
Complicated phase changes occur during the depletion exploitation of gas condensate reservoirs, which causes the precipitation of condensate oil and the mixed flow of gas phase and oil phase. Due to few research reports done so far, a new dimensionless deliverability equation of gas condensate reservoir is established by means of Taylor series expansion and polynomial regression on the basis of the inflow performance equation of gas condensate reservoir in pseudo-steady state in this study. Firstly, the definite integration of pseudo-pressure function in the equation is developed by Taylor series based on the inflow performance equation of gas condensate reservoir in pseudo-steady state; secondly, the coefficients of Taylor series are calculated by steady-state theory and polynomial regression method; finally, the dimensionless deliverability equation of gas condensate reservoir is established by analytic method. Its application shows that the inflow performance curve calculated by the dimensionless deliverability equation coincides with actual data of system well testing, which indicates that this equation can describe the two-phase inflow performance of gas condensate reservoir more accurately. Moreover, the open flow potential obtained by dimensionless deliverability equation is smaller than that by conventional dry gas conversion method; the open flow potential calculated by dimensionless deliverability equation which considers high velocity flow effect is much higher than the one that ignores the high velocity flow effect.
Complicated phase changes occur during the depletion exploitation of gas condensate reservoirs, which causes the precipitation of condensate oil and the mixed flow of gas phase and oil phase. Due to few research reports done so far, a new dimensionless deliverability equation of gas condensate reservoir is established by means of Taylor series expansion and polynomial regression on the basis of the inflow performance equation of gas condensate reservoir in pseudo-steady state in this study. Firstly, the definite integration of pseudo-pressure function in the equation is developed by Taylor series based on the inflow performance equation of gas condensate reservoir in pseudo-steady state; secondly, the coefficients of Taylor series are calculated by steady-state theory and polynomial regression method; finally, the dimensionless deliverability equation of gas condensate reservoir is established by analytic method. Its application shows that the inflow performance curve calculated by the dimensionless deliverability equation coincides with actual data of system well testing, which indicates that this equation can describe the two-phase inflow performance of gas condensate reservoir more accurately. Moreover, the open flow potential obtained by dimensionless deliverability equation is smaller than that by conventional dry gas conversion method; the open flow potential calculated by dimensionless deliverability equation which considers high velocity flow effect is much higher than the one that ignores the high velocity flow effect.
2014, 39(10): 1398-1406.
doi: 10.3799/dqkx.2014.132
Abstract:
This paper explores three issues related with the current coal-seam modeling, namely, integration of multi-source geological data, dynamic modeling and uncertainty assessment for the modeling results by studying 3D coal-seam modeling of five prospect areas from Ailaiwukugou to Taijizhao located in northern Dongsheng coalfield in Inner Mongolia. Firstly, data integration is carried out according to its inherent logic and outer geometrical relationship. The former translates data into sections or profiles, and the latter further converts them into a uniform simple format, which is called uniform discretized samples. Secondly, based on these samples and boundary lines, inverse distance weighting (IDW) method is employed to evaluate the height of both top and base floor of coal layer and then 3D coal models are dynamically built according to these attribute values by triangulated irregular network (TIN). Thirdly, interpolation variance, an alternative uncertainty measurement for IDW estimates, is applied to assess uncertainty of the resulting 3D coal-seam models. Finally, the whole modeling workflow is discussed in detail and implemented based upon a 3D geo-information system named QuantyView. In the application in our study area, the proposed method works well in dynamically modeling the coal layers and their uncertainties in multi-source geological data environment, which shows that it is practical and feasible for 3D modeling in other coalfields.
This paper explores three issues related with the current coal-seam modeling, namely, integration of multi-source geological data, dynamic modeling and uncertainty assessment for the modeling results by studying 3D coal-seam modeling of five prospect areas from Ailaiwukugou to Taijizhao located in northern Dongsheng coalfield in Inner Mongolia. Firstly, data integration is carried out according to its inherent logic and outer geometrical relationship. The former translates data into sections or profiles, and the latter further converts them into a uniform simple format, which is called uniform discretized samples. Secondly, based on these samples and boundary lines, inverse distance weighting (IDW) method is employed to evaluate the height of both top and base floor of coal layer and then 3D coal models are dynamically built according to these attribute values by triangulated irregular network (TIN). Thirdly, interpolation variance, an alternative uncertainty measurement for IDW estimates, is applied to assess uncertainty of the resulting 3D coal-seam models. Finally, the whole modeling workflow is discussed in detail and implemented based upon a 3D geo-information system named QuantyView. In the application in our study area, the proposed method works well in dynamically modeling the coal layers and their uncertainties in multi-source geological data environment, which shows that it is practical and feasible for 3D modeling in other coalfields.
2014, 39(10): 1407-1420.
doi: 10.3799/dqkx.2014.133
Abstract:
To further explore the hydrocarbon accumulation mechanism in Liaodong bay depression, its typical accumulation models are summarized and grouped, and the main controlling factors of each model are studied in this paper based on the analyses of hydrocarbon accumulation conditions and characteristics using seismic, drilling, geochemical and oil testing data. The research results show that Liaodong bay depression has superior hydrocarbon accumulation conditions including three sets of source rocks (Es3, Es1 and Ed3), three reservoir-cap assemblages (upper, middle and lower), multi-type of conducting medium, and the oil and gas reservoirs which have been found are mainly tectonic reservoirs. The distribution rule of reservoirs is rich in Pre-E, Ed2 and vertical Es1+2 formation and abundant in the transverse fault zones. The hydrocarbon accumulation models of Liaodong bay depression can be grouped into 5 major types and 15 sub-types, including one-direction single-source single-migration path Pre-E reservoir, one-direction single-migration path Palaeocene reservoir, complex-migration path Palaeocene reservoir, one-direction deep-source complex-migration path Neogene reservoir and self-source-reservoir-capping reservoir. The Pre-E reservoir is mainly distributed in the northern and central sections of Liaoxi low uplift and the main controlling factors are hydrodynamic and physical property of Pre-E formation. Single-migration path Palaeocene reservoirs are mainly distributed in the sag zones and steep slope zones of Liaoxi and Liaozhong sag, and the main controlling factors are fault and maturity of the source rock. Complex-migration path Palaeocene reservoirs are mainly distributed in the northern and central sections of Liaoxi low uplift and the gentle slope zone of Liaozhong southern sag, and the main controlling factors are hydrodynamic and migration path. Neogene reservoirs are mainly distributed in the fault zones of southern part of Liaodong bay depression, and the hydrocarbon accumulation of this type is mainly controlled by cap rock and the faulting of Neogene. Self-source-reservoir-capping reservoirs are mainly formed in the inner part of the source rock, and mainly influenced by the physical property of the reservoir.
To further explore the hydrocarbon accumulation mechanism in Liaodong bay depression, its typical accumulation models are summarized and grouped, and the main controlling factors of each model are studied in this paper based on the analyses of hydrocarbon accumulation conditions and characteristics using seismic, drilling, geochemical and oil testing data. The research results show that Liaodong bay depression has superior hydrocarbon accumulation conditions including three sets of source rocks (Es3, Es1 and Ed3), three reservoir-cap assemblages (upper, middle and lower), multi-type of conducting medium, and the oil and gas reservoirs which have been found are mainly tectonic reservoirs. The distribution rule of reservoirs is rich in Pre-E, Ed2 and vertical Es1+2 formation and abundant in the transverse fault zones. The hydrocarbon accumulation models of Liaodong bay depression can be grouped into 5 major types and 15 sub-types, including one-direction single-source single-migration path Pre-E reservoir, one-direction single-migration path Palaeocene reservoir, complex-migration path Palaeocene reservoir, one-direction deep-source complex-migration path Neogene reservoir and self-source-reservoir-capping reservoir. The Pre-E reservoir is mainly distributed in the northern and central sections of Liaoxi low uplift and the main controlling factors are hydrodynamic and physical property of Pre-E formation. Single-migration path Palaeocene reservoirs are mainly distributed in the sag zones and steep slope zones of Liaoxi and Liaozhong sag, and the main controlling factors are fault and maturity of the source rock. Complex-migration path Palaeocene reservoirs are mainly distributed in the northern and central sections of Liaoxi low uplift and the gentle slope zone of Liaozhong southern sag, and the main controlling factors are hydrodynamic and migration path. Neogene reservoirs are mainly distributed in the fault zones of southern part of Liaodong bay depression, and the hydrocarbon accumulation of this type is mainly controlled by cap rock and the faulting of Neogene. Self-source-reservoir-capping reservoirs are mainly formed in the inner part of the source rock, and mainly influenced by the physical property of the reservoir.
2014, 39(10): 1421-1430.
doi: 10.3799/dqkx.2014.134
Abstract:
A new oil field with a reserve of more than 100 million tons has been found in the Penglai 9-1 buried hill, consisting of Paleoproterozoic metamorphic rocks and Yanshan granites. The granites surrounded by Paleoproterozoic metamorphic rocks are distributed in central valley floor of the buried hill. The oil pool mainly accumulates in the reservoirs of granite weathered crust located in the valley floor of the buried hill. The granites can be classified into granodirorite and adamellite. Paleoproterozoic metamorphic rocks mainly consist of phyllite, schist, metasandstone, quartzite and mylonite. Although both metamorphic rocks and granites have experienced similar weathering and deformation, differences in mineral constitution, mechanical property and weathering ways between metamorphic rocks and granites result in alternative development of high quality reservoirs in the granites. The reservoirs in metamorphic rocks belong to porosity types and development of secondary porosity is quite limited, no effective reservoirs may be formed in the metamorphic rocks. The reservoirs in granites are characterized by development of porosity and fissure, high quality reservoirs mainly develop in the sandy, pebbly weathering zone and fissured zone, in which the reservoirs in fissured zone are the thickest. Except for intensity of hypergenic karstification and tectonic deformation, lithologic constitution and lithofacies of the granites play a controlling role in development of high quality reservoirs in granite weathered crust. The factors such as weathered intensity, deformation, lithologic constitution and lithofacies, etc. contribute to vertical zonation characteristics of weathered crust reservoir at the granite buried hill, the reservoir types changed from porosity to fissure from the top of the weathered crust to the bottom. The various secondary porosity and fissure are the most important reservoir spaces in buried hill granite reservoirs.
A new oil field with a reserve of more than 100 million tons has been found in the Penglai 9-1 buried hill, consisting of Paleoproterozoic metamorphic rocks and Yanshan granites. The granites surrounded by Paleoproterozoic metamorphic rocks are distributed in central valley floor of the buried hill. The oil pool mainly accumulates in the reservoirs of granite weathered crust located in the valley floor of the buried hill. The granites can be classified into granodirorite and adamellite. Paleoproterozoic metamorphic rocks mainly consist of phyllite, schist, metasandstone, quartzite and mylonite. Although both metamorphic rocks and granites have experienced similar weathering and deformation, differences in mineral constitution, mechanical property and weathering ways between metamorphic rocks and granites result in alternative development of high quality reservoirs in the granites. The reservoirs in metamorphic rocks belong to porosity types and development of secondary porosity is quite limited, no effective reservoirs may be formed in the metamorphic rocks. The reservoirs in granites are characterized by development of porosity and fissure, high quality reservoirs mainly develop in the sandy, pebbly weathering zone and fissured zone, in which the reservoirs in fissured zone are the thickest. Except for intensity of hypergenic karstification and tectonic deformation, lithologic constitution and lithofacies of the granites play a controlling role in development of high quality reservoirs in granite weathered crust. The factors such as weathered intensity, deformation, lithologic constitution and lithofacies, etc. contribute to vertical zonation characteristics of weathered crust reservoir at the granite buried hill, the reservoir types changed from porosity to fissure from the top of the weathered crust to the bottom. The various secondary porosity and fissure are the most important reservoir spaces in buried hill granite reservoirs.
2014, 39(10): 1431-1437.
doi: 10.3799/dqkx.2014.135
Abstract:
The pore characteristics of sliding zone soils, treated with vacuum freeze-drying and drying methods, respectively, are studied using water adsorption and constant-rate mercury injection porosimetry in branch tunnel Ⅰ of Huangtupo landslide located in Three Gorges Reservoir. It is found that the condensation and congestion function of water vapor in the ink bottle pore of dried sample lead to smaller specific surface area and weaker water vapor adsorption ability than those of the freeze-dried sample. The shrinkage functions and weaker adsorption potential in the dried sample make the granular structure closer, which in turn leads to smaller cumulative pore volume and maximum pore volume than those of freeze-dried sample. Considering the water vapor surface tension, the pore surface fractal dimension of freeze-dried sample is greater than that of the dried samples, which indicates that the pore surface of dried samples becomes smoother with a variety of chemical bonds. The mercury intrusion porosimetry results show that the pore diameter and pore volume of freeze-dried sample are greater than those of the dried samples in the range of micropore and mesopore. But in the pore diameter range of 0.133-129.051 μm, the pore volume of freeze-dried sample is greater than that of the dried samples. The particle volume of dried sample with diameter greater than 41.421 μm is bigger than that of the freeze-dried samples.
The pore characteristics of sliding zone soils, treated with vacuum freeze-drying and drying methods, respectively, are studied using water adsorption and constant-rate mercury injection porosimetry in branch tunnel Ⅰ of Huangtupo landslide located in Three Gorges Reservoir. It is found that the condensation and congestion function of water vapor in the ink bottle pore of dried sample lead to smaller specific surface area and weaker water vapor adsorption ability than those of the freeze-dried sample. The shrinkage functions and weaker adsorption potential in the dried sample make the granular structure closer, which in turn leads to smaller cumulative pore volume and maximum pore volume than those of freeze-dried sample. Considering the water vapor surface tension, the pore surface fractal dimension of freeze-dried sample is greater than that of the dried samples, which indicates that the pore surface of dried samples becomes smoother with a variety of chemical bonds. The mercury intrusion porosimetry results show that the pore diameter and pore volume of freeze-dried sample are greater than those of the dried samples in the range of micropore and mesopore. But in the pore diameter range of 0.133-129.051 μm, the pore volume of freeze-dried sample is greater than that of the dried samples. The particle volume of dried sample with diameter greater than 41.421 μm is bigger than that of the freeze-dried samples.
2014, 39(10): 1438-1444.
doi: 10.3799/dqkx.2014.136
Abstract:
As one of the effective non-engineering measurements, zoning of mountain torrent hazards is an important part of flood prevention and disaster mitigation system. A torrent hazard evaluation model is built by using GIS spatial analysis and modeling techniques and fuzzy mathematics method in this paper, in which the evaluation index weight is determined with analytic hierarchy process according to the results of orthogonal analysis. In addition, seven factors are chosen as the new evaluation index system to evaluate the torrent hazards, combined with the definition of mountain torrent hazard and the analysis of factors causing mountain torrent disaster, with the application of orthogonal design method, and the observed influence degree of rainfall and conflux time on mountain torrent. The areas of the upper reach of the Huaihe River were chosen as the case study area of mountain torrent hazards zonation. The results show that areas with the shortest confluence time and the largest hypsographic feature are the most dangerous areas.
As one of the effective non-engineering measurements, zoning of mountain torrent hazards is an important part of flood prevention and disaster mitigation system. A torrent hazard evaluation model is built by using GIS spatial analysis and modeling techniques and fuzzy mathematics method in this paper, in which the evaluation index weight is determined with analytic hierarchy process according to the results of orthogonal analysis. In addition, seven factors are chosen as the new evaluation index system to evaluate the torrent hazards, combined with the definition of mountain torrent hazard and the analysis of factors causing mountain torrent disaster, with the application of orthogonal design method, and the observed influence degree of rainfall and conflux time on mountain torrent. The areas of the upper reach of the Huaihe River were chosen as the case study area of mountain torrent hazards zonation. The results show that areas with the shortest confluence time and the largest hypsographic feature are the most dangerous areas.
2014, 39(10): 1445-1453.
doi: 10.3799/dqkx.2014.137
Abstract:
The Shijiahe culture is a milestone in Chinese civilization development. However, there are still disputes as to the absolute age of the Shijiahe culture and the interaction between climate changes and human activities during this epoch. Sample profile from the Tanjialing site, i.e. a typical site of Shijiahe culture, was analyzed based on AMS 14C dating and geochemical elements, combined with the methods of principle component analysis (PCA) and ratio of elements (C value). The results show that the absolute age of the Shijiahe culture is around 4 800-4 100 cal. a BP based on three AMS 14C dating measured in the America NSF-Arizona AMS Laboratory, consistent with the relative age of Shijiahe culture. Between 4 850 and 4 300 cal. a BP, high value of the second principle component (F2), C value and Mg/Ca ratio indicate that the environment might be relatively warm and wet. Meanwhile, high values of the first and third principle components (F1 and F3) reflect strong human disturbances. For the period from 4 300 to 4 124 cal. a BP, low value of F2, C value and Mg/Ca ratio are indicative of cold and drought conditions. Meanwhile, low values of F1 and F3 might be related to weak human disturbances and the collapse of the Shijiahe culture. This study reveals that the flood events in the climate changes from warm and wet to cold and drought background could be one potential trigger of the collapse of the Shijiahe Culture.
The Shijiahe culture is a milestone in Chinese civilization development. However, there are still disputes as to the absolute age of the Shijiahe culture and the interaction between climate changes and human activities during this epoch. Sample profile from the Tanjialing site, i.e. a typical site of Shijiahe culture, was analyzed based on AMS 14C dating and geochemical elements, combined with the methods of principle component analysis (PCA) and ratio of elements (C value). The results show that the absolute age of the Shijiahe culture is around 4 800-4 100 cal. a BP based on three AMS 14C dating measured in the America NSF-Arizona AMS Laboratory, consistent with the relative age of Shijiahe culture. Between 4 850 and 4 300 cal. a BP, high value of the second principle component (F2), C value and Mg/Ca ratio indicate that the environment might be relatively warm and wet. Meanwhile, high values of the first and third principle components (F1 and F3) reflect strong human disturbances. For the period from 4 300 to 4 124 cal. a BP, low value of F2, C value and Mg/Ca ratio are indicative of cold and drought conditions. Meanwhile, low values of F1 and F3 might be related to weak human disturbances and the collapse of the Shijiahe culture. This study reveals that the flood events in the climate changes from warm and wet to cold and drought background could be one potential trigger of the collapse of the Shijiahe Culture.
2014, 39(10): 1454-1464.
doi: 10.3799/dqkx.2014.138
Abstract:
Magnetic susceptibility is one of the most widely used and most easily to be obtained parameters of environmental magnetism. However, the meaning and interpretation of magnetic susceptibility is the most complicate. High, low frequency magnetic susceptibility and non-hysteresis remanence were measured for seventy-nine weathering-pedogenic topsoil samples collected from the east part of China, from north to south, covering the main climatic zones within China. Moreover, relationship between these magnetic parameters and climate indexes such as precipitation and annual average temperature was analyzed. The results indicate that: (1) Significant difference of magnetic properties is existed among weathering-pedogenesis topsoil that derived from different parent rocks. The relationship between all magnetic susceptibility parameters and climate indexes is much different. Difference of geological conditions and parent rocks must be taken full consideration when the relationship between magnetism and climate conditions is discussed in large spatial scale. (2) The non-hysteresis remanence magnetic susceptibility is negatively related to precipitation and annual average temperature for topsoil derived from granite. However, it is positively related to precipitation for topsoil derived from balsalt. The widely recognized relationship between magnetic strength of paleosol and pedogenesis of loess-paleosol sequence from the Chinese Loess Plateau isn't always proper to apply in other climate area. (3) Magnetic particles tend to be finer during weathering and soil-forming process. However, single magnetic parameter can't reflect the climate and environmental change because some ultrafine particles are easy to be carried out in situ due to increasing rainfall intensity. (4) Magnetic susceptibility of non-hysteresis remanence of weathering-pedogenic topsoil can reflect the weathering degree of weathering soil. The magnetic variation mechanism of weathering-pedogenic topsoil, especially magnetic mineral transformation of corresponding soil profile, is still needed further study.
Magnetic susceptibility is one of the most widely used and most easily to be obtained parameters of environmental magnetism. However, the meaning and interpretation of magnetic susceptibility is the most complicate. High, low frequency magnetic susceptibility and non-hysteresis remanence were measured for seventy-nine weathering-pedogenic topsoil samples collected from the east part of China, from north to south, covering the main climatic zones within China. Moreover, relationship between these magnetic parameters and climate indexes such as precipitation and annual average temperature was analyzed. The results indicate that: (1) Significant difference of magnetic properties is existed among weathering-pedogenesis topsoil that derived from different parent rocks. The relationship between all magnetic susceptibility parameters and climate indexes is much different. Difference of geological conditions and parent rocks must be taken full consideration when the relationship between magnetism and climate conditions is discussed in large spatial scale. (2) The non-hysteresis remanence magnetic susceptibility is negatively related to precipitation and annual average temperature for topsoil derived from granite. However, it is positively related to precipitation for topsoil derived from balsalt. The widely recognized relationship between magnetic strength of paleosol and pedogenesis of loess-paleosol sequence from the Chinese Loess Plateau isn't always proper to apply in other climate area. (3) Magnetic particles tend to be finer during weathering and soil-forming process. However, single magnetic parameter can't reflect the climate and environmental change because some ultrafine particles are easy to be carried out in situ due to increasing rainfall intensity. (4) Magnetic susceptibility of non-hysteresis remanence of weathering-pedogenic topsoil can reflect the weathering degree of weathering soil. The magnetic variation mechanism of weathering-pedogenic topsoil, especially magnetic mineral transformation of corresponding soil profile, is still needed further study.
2014, 39(10): 1465-1472.
doi: 10.3799/dqkx.2014.139
Abstract:
An indoor experiment was conducted to investigate the development law of the shrinkage crack network in soil in this study. By application of digital image processing technology and the measurement functions of AutoCAD, geometric characteristics of shrinkage crack network were quantitatively analyzed under different moisture contents. The results show that the crack first was initiated when the moisture content was 43%. The length of crack skeleton and crack perimeter began to stabilize once the moisture content was close to 23%, and so did the crack ratio at the moisture content of 7%. The average width of the crack developed in three stages, namely, fluctuation growth, linear growth and stabilization, which reached a stable value as the moisture content came to 7%. The ratio of the crack fragments and intersections decreased as the moisture contents became lower and remained stable at 1.67 ultimately, which, together with dispersity of the aggregate and frequency distribution of intersection angles, revealed the square network distribution trend of the crack network. The mean tortuosity of the crack was reduced from 1.06 to 1.02 with the moisture content dropped and stabilized at 1.02, which indicates the whole tortuosity of the cracks and the variation law of the crack tortuosity during different periods.
An indoor experiment was conducted to investigate the development law of the shrinkage crack network in soil in this study. By application of digital image processing technology and the measurement functions of AutoCAD, geometric characteristics of shrinkage crack network were quantitatively analyzed under different moisture contents. The results show that the crack first was initiated when the moisture content was 43%. The length of crack skeleton and crack perimeter began to stabilize once the moisture content was close to 23%, and so did the crack ratio at the moisture content of 7%. The average width of the crack developed in three stages, namely, fluctuation growth, linear growth and stabilization, which reached a stable value as the moisture content came to 7%. The ratio of the crack fragments and intersections decreased as the moisture contents became lower and remained stable at 1.67 ultimately, which, together with dispersity of the aggregate and frequency distribution of intersection angles, revealed the square network distribution trend of the crack network. The mean tortuosity of the crack was reduced from 1.06 to 1.02 with the moisture content dropped and stabilized at 1.02, which indicates the whole tortuosity of the cracks and the variation law of the crack tortuosity during different periods.
