The Neogene Shawan Formation in the Chepaizi Uplift of the Junggar Basin(NW China)has obtained high oil flow,demonstrating a good potential for oil and gas exploration.The multi-source hydrocarbon generation backgroun...The Neogene Shawan Formation in the Chepaizi Uplift of the Junggar Basin(NW China)has obtained high oil flow,demonstrating a good potential for oil and gas exploration.The multi-source hydrocarbon generation background and strong tectonic activity have led to the simultaneous production of heavy oil and light oil from multi-layer in the area,which makes it very difficult to identify oil origins,presently,the hot debate on the oil origins needs to be clarified.In this paper,due to the selective consumption of different types of compounds in crude oils by severe and intense biodegradation,the commonly used oilsource correlation tools are ineffective or may produce misleading results,this study adopted a biomarker recovery method based on the principle of mass conservation that uses the sum of the mass of the residual biomarkers and their corresponding biodegradation products to obtain the mass of the original biomarkers,improving the reliability of oil origins determination.Based on the nature and occurrence of crude oils,the investigated oils are subdivided into three types,Group A,Group B and Group C.Group A,light oils occurred mainly in lower structure Neogene Shawan Formation in the western Chepaizi Uplift,while Group B,heavy oils occurred mainly in higher structure Neogene Shawan Formation in the western Chepaizi Uplift.The two types of crude oils may come from the mixed source of Jurassic Badaowan Formation source rocks(J_(1)b)and Paleogene Anjihaihe Formation source rocks(E_(2-3)a)in the Sikeshu Sag,and Jurassic Badaowan Formation source rocks(J_(1)b)are the main source of crude oils.Group C,heavy oils occurred mainly in Neogene Shawan Formation in the eastern Chepaizi Uplift,showing good correlation with the Permian(P_(1)f and P_(2)w)source rocks in the Shawan Sag.At the same time,by combining stable carbon isotope and parameters related to triaromatic steroids,the accuracy of the oilsource correlation results by biomarker recovery method was further verified.展开更多
The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed inve...The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed investigations of soft-sediment deformation(SSD) structures are valuable for understanding the trigger mechanisms, deformation processes, and the magnitudes of earthquakes that generate such structures, and help us to understand tectonic activity in the region. To assess tectonic activity during the late Quaternary, we studied a well-exposed sequence of Shawan lacustrine sediments, 7.0 m thick, near Lake Diexi in the upper reaches of the Minjiang River. Deformation is recorded by both ductile structures(load casts, flame structures,pseudonodules, ball-and-pillow structures, and liquefied convolute structures) and brittle structures(liquefied breccia, and microfaults). Taking into account the geodynamic setting of the area and its known tectonic activity, these SSD structures can be interpreted in terms of seismic shocks. The types and forms of the structures,the maximum liquefaction distances, and the thicknesses of the horizons with SSD structures in the Shawan section indicate that they record six strong earthquakes of magnitude 6-7 and one with magnitude >7. A recent study showed that the Songpinggou fault is the seismogenic structure of the 1933 Ms7.5 Diexi earthquake. The Shawan section is located close to the junction of the Songpinggou and Minjiang faults, and records seven earthquakes with magnitudes of ?7. We infer,therefore, that the SSD structures in the Shawan section document deglacial activity along the Songpinggou fault.展开更多
In the Baikouquan Formation of the Shawan Depression,there exist thin,high-quality conglomerate reservoirs with low porosity and low permeability.Only the underwater gray-green conglomerate with medium porosity is con...In the Baikouquan Formation of the Shawan Depression,there exist thin,high-quality conglomerate reservoirs with low porosity and low permeability.Only the underwater gray-green conglomerate with medium porosity is considered a high-quality reservoir.Due to the overlapping wave impedance between these thin highquality reservoirs and tight layers,traditional post-stack inversion and pre-stack simultaneous inversion methods are ineffective in predicting such thin reservoirs.Pre-stack geostatistical inversion,which combines the advantages of simultaneous inversion and geostatistical inversion,has proven to be effective in this context.This study integrates core,logging,and test data to construct petrophysical charts using P-impedance and V_(p)/V_(s) ratios,idengtify key reservoir parameters,and apply pre-stack geostatistical inversion to predict thin high-quality conglomerate reservoirs.The results show that pre-stack geostatistical inversion can accurately identify thin high-quality reservoirs,providing a reliable basis for further exploration and development.展开更多
Well che89,located in the Chepaizi area in the northwest margin of Junggar basin,acquires high production industrial oil flow,which is an important breakthrough in the exploration of the south foreland slope area of J...Well che89,located in the Chepaizi area in the northwest margin of Junggar basin,acquires high production industrial oil flow,which is an important breakthrough in the exploration of the south foreland slope area of Junggar basin.The Chepaizi area is near two hydrocarbon generation depressions of Sikeshu and Shawan,which have sets of hydrocarbon source rock of Carboniferous to Jurassic as well as Upper Tertiary.Geological and geochemical parameters are proper for the accumulation of mixed source crude oil.Carbon isotope,group composition and biomarkers of crude oil in Upper Tertiary of well Che89 show that the features of crude oil in Upper Tertiary Shawan Formation are between that of Permian and Jurassic,some of them are similar to these two,and some are of difference,they should be the mixed source of Permian and Jurassic.Geochemical analysis and geological study show that sand extract of Lower Tertiary Wulunguhe Formation has the same source as the crude oil and sand extract of Upper Tertiary Shawan Formation,but they are not charged in the same period.Oil/gas of Wulunguhe Formation is charged before Upper Tertiary sedimentation,and suffered serious biodegradation and oxidation and rinsing,which provide a proof in another aspect that the crude oil of Upper Tertiary Shawan Formation of well Che89 is not from hydrocarbon source rock of Lower Tertiary.展开更多
基金co-funded by the National Natural Science Foundation of China(42372160,42072172)。
文摘The Neogene Shawan Formation in the Chepaizi Uplift of the Junggar Basin(NW China)has obtained high oil flow,demonstrating a good potential for oil and gas exploration.The multi-source hydrocarbon generation background and strong tectonic activity have led to the simultaneous production of heavy oil and light oil from multi-layer in the area,which makes it very difficult to identify oil origins,presently,the hot debate on the oil origins needs to be clarified.In this paper,due to the selective consumption of different types of compounds in crude oils by severe and intense biodegradation,the commonly used oilsource correlation tools are ineffective or may produce misleading results,this study adopted a biomarker recovery method based on the principle of mass conservation that uses the sum of the mass of the residual biomarkers and their corresponding biodegradation products to obtain the mass of the original biomarkers,improving the reliability of oil origins determination.Based on the nature and occurrence of crude oils,the investigated oils are subdivided into three types,Group A,Group B and Group C.Group A,light oils occurred mainly in lower structure Neogene Shawan Formation in the western Chepaizi Uplift,while Group B,heavy oils occurred mainly in higher structure Neogene Shawan Formation in the western Chepaizi Uplift.The two types of crude oils may come from the mixed source of Jurassic Badaowan Formation source rocks(J_(1)b)and Paleogene Anjihaihe Formation source rocks(E_(2-3)a)in the Sikeshu Sag,and Jurassic Badaowan Formation source rocks(J_(1)b)are the main source of crude oils.Group C,heavy oils occurred mainly in Neogene Shawan Formation in the eastern Chepaizi Uplift,showing good correlation with the Permian(P_(1)f and P_(2)w)source rocks in the Shawan Sag.At the same time,by combining stable carbon isotope and parameters related to triaromatic steroids,the accuracy of the oilsource correlation results by biomarker recovery method was further verified.
基金the joint support by the National Natural Science Foundation of China(41807298,41672211,41572346)the Special Project of Fundamental Scientific Research of the Institute of Geology,China Earthquake Administration(IGCEA1713)
文摘The eastern margin of the Tibetan Plateau is characterized by frequent earthquakes; however, research of paleo-earthquakes in the area has been limited^ owing to the alpine topography and strong erosion. Detailed investigations of soft-sediment deformation(SSD) structures are valuable for understanding the trigger mechanisms, deformation processes, and the magnitudes of earthquakes that generate such structures, and help us to understand tectonic activity in the region. To assess tectonic activity during the late Quaternary, we studied a well-exposed sequence of Shawan lacustrine sediments, 7.0 m thick, near Lake Diexi in the upper reaches of the Minjiang River. Deformation is recorded by both ductile structures(load casts, flame structures,pseudonodules, ball-and-pillow structures, and liquefied convolute structures) and brittle structures(liquefied breccia, and microfaults). Taking into account the geodynamic setting of the area and its known tectonic activity, these SSD structures can be interpreted in terms of seismic shocks. The types and forms of the structures,the maximum liquefaction distances, and the thicknesses of the horizons with SSD structures in the Shawan section indicate that they record six strong earthquakes of magnitude 6-7 and one with magnitude >7. A recent study showed that the Songpinggou fault is the seismogenic structure of the 1933 Ms7.5 Diexi earthquake. The Shawan section is located close to the junction of the Songpinggou and Minjiang faults, and records seven earthquakes with magnitudes of ?7. We infer,therefore, that the SSD structures in the Shawan section document deglacial activity along the Songpinggou fault.
文摘In the Baikouquan Formation of the Shawan Depression,there exist thin,high-quality conglomerate reservoirs with low porosity and low permeability.Only the underwater gray-green conglomerate with medium porosity is considered a high-quality reservoir.Due to the overlapping wave impedance between these thin highquality reservoirs and tight layers,traditional post-stack inversion and pre-stack simultaneous inversion methods are ineffective in predicting such thin reservoirs.Pre-stack geostatistical inversion,which combines the advantages of simultaneous inversion and geostatistical inversion,has proven to be effective in this context.This study integrates core,logging,and test data to construct petrophysical charts using P-impedance and V_(p)/V_(s) ratios,idengtify key reservoir parameters,and apply pre-stack geostatistical inversion to predict thin high-quality conglomerate reservoirs.The results show that pre-stack geostatistical inversion can accurately identify thin high-quality reservoirs,providing a reliable basis for further exploration and development.
基金Supported by National Natural Science Foundation of China(Grant Nos.40602013 and 40572078)Doctor’s Foundation(Grant No.20060489002)
文摘Well che89,located in the Chepaizi area in the northwest margin of Junggar basin,acquires high production industrial oil flow,which is an important breakthrough in the exploration of the south foreland slope area of Junggar basin.The Chepaizi area is near two hydrocarbon generation depressions of Sikeshu and Shawan,which have sets of hydrocarbon source rock of Carboniferous to Jurassic as well as Upper Tertiary.Geological and geochemical parameters are proper for the accumulation of mixed source crude oil.Carbon isotope,group composition and biomarkers of crude oil in Upper Tertiary of well Che89 show that the features of crude oil in Upper Tertiary Shawan Formation are between that of Permian and Jurassic,some of them are similar to these two,and some are of difference,they should be the mixed source of Permian and Jurassic.Geochemical analysis and geological study show that sand extract of Lower Tertiary Wulunguhe Formation has the same source as the crude oil and sand extract of Upper Tertiary Shawan Formation,but they are not charged in the same period.Oil/gas of Wulunguhe Formation is charged before Upper Tertiary sedimentation,and suffered serious biodegradation and oxidation and rinsing,which provide a proof in another aspect that the crude oil of Upper Tertiary Shawan Formation of well Che89 is not from hydrocarbon source rock of Lower Tertiary.
