Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zon...Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zone of this gas field, we focused in our study on the provenance and detailed sedimentary facies of sandstone of the He8 （the eighth part of the Shihezi formation, Permian system） and Shanxil （the first part of the Shanxi formation, Permian system） members, based on core observations, analyses in petrography, granularity and logging. The results show that： 1） the sandstone provenance of Shanxil and He8 in the eastern zone of the Sulige gas field is from the north of the Ordos Basin, characterized by dual directions from the north and northeast. 2） The He8 and Shanxil members were deposited in a fluvial-delta sedimentary system. The He8 was mainly deposited in braided rivers, in- cluding braided channels, channel bars, levee and floodplain sub-environments, whereas the Shanxil Member was deposited in braided rivers and deltas, including braided channels, channel bars, floodplains, tributaries and inter-tributary sub-environments. 3） Sedimentary facies bands migrated in drastic fashion towards the basin from the Shanxil to the He8 Member. Base levels of sedi- mentation generally present a trend of small increases in-amplitude, large decreasing amplitudes and slow and gradual Increases. 4） The continuity of the reservoir sandbodies along the source direction is better than that perpendicular to the direction. Compared with Shanxil, both dimensions and continuity of the sandbodies in He8 are better from which we conclude that it is the most fa- vorable part of the reservoir.展开更多
The sedimentary facies of the subaqueous Changjiang （Yangtze） River delta since the late Pleistocene was studied based on lithology and foraminifera analysis for two boreholes, CJK07 and CJK11, along with 14C dating...The sedimentary facies of the subaqueous Changjiang （Yangtze） River delta since the late Pleistocene was studied based on lithology and foraminifera analysis for two boreholes, CJK07 and CJK11, along with 14C dating. Four sedimentary facies were identified, namely fluvial, tidal flat, offshore, and prodelta facies. The fluvial sedimentary facies is comprised of fluvial channel lag deposits, fluvial point bar deposits, and floodplain deposits, showing a fining-upward sequence in general with no benthic foraminifera. A layer of stiff clay overlies the fluvial deposits in core CJK07, indicating a long-term exposure environment during the Last Glacial Maximum （LGM）. During the postglacial sea-level rise around 13-7.5 cal ka BP, the tidal flat facies was deposited in core CJK11, characterized by abundant silt-clay couplets. Euryhaline species dominate the subtidal fiat foraminiferal assemblages, while almost no foraminifera was found in the intertidal fiat. The offshore environment was the major sedimentary environment when the sea level reached its highest level around 7.5 cal ka BP, with a maximum accumulation rate of 10 mm/a found in core CJK11. Prodelta sediments have been deposited in core CJK11 since -3 cal ka BP, after the formation of the Changjiang River delta. The difference in sedimentary facies between core CJK07 and CJK11 is due to their location： core CJK07 was in an interfluve while core CJK11 was in an incised valley during the LGM. Furthermore, AMS 14C dating of core CJK07 shows poor chronological order, indicating that the sediments were reworked by strong tidal currents and that sediment deposited since -7.7 cal ka BP in core CJK07 was eroded away by modem hydrodynamic forces caused by the southward shift of the Changjiang River delta depocenter.展开更多
基金supported by the National Basic Re-search Program of China (No2003CB214603)
文摘Given sustaining exploration, the eastern zone of the Sulige gas field may soon become a key area of exploitation. In order to explore its genesis, types and distribution of the reservoir sandstones in the eastern zone of this gas field, we focused in our study on the provenance and detailed sedimentary facies of sandstone of the He8 （the eighth part of the Shihezi formation, Permian system） and Shanxil （the first part of the Shanxi formation, Permian system） members, based on core observations, analyses in petrography, granularity and logging. The results show that： 1） the sandstone provenance of Shanxil and He8 in the eastern zone of the Sulige gas field is from the north of the Ordos Basin, characterized by dual directions from the north and northeast. 2） The He8 and Shanxil members were deposited in a fluvial-delta sedimentary system. The He8 was mainly deposited in braided rivers, in- cluding braided channels, channel bars, levee and floodplain sub-environments, whereas the Shanxil Member was deposited in braided rivers and deltas, including braided channels, channel bars, floodplains, tributaries and inter-tributary sub-environments. 3） Sedimentary facies bands migrated in drastic fashion towards the basin from the Shanxil to the He8 Member. Base levels of sedi- mentation generally present a trend of small increases in-amplitude, large decreasing amplitudes and slow and gradual Increases. 4） The continuity of the reservoir sandbodies along the source direction is better than that perpendicular to the direction. Compared with Shanxil, both dimensions and continuity of the sandbodies in He8 are better from which we conclude that it is the most fa- vorable part of the reservoir.
基金Supported by the Marine Public Welfare Research Project(No.200805063)the National Natural Science Foundation of China(Nos.41076023 and 41106065)+1 种基金the Basic Fund Project of National Science and Technology Ministry(No.2008FY220300)the Coastal Investigation and Research Project of China(No.908-02-02-05)
文摘The sedimentary facies of the subaqueous Changjiang （Yangtze） River delta since the late Pleistocene was studied based on lithology and foraminifera analysis for two boreholes, CJK07 and CJK11, along with 14C dating. Four sedimentary facies were identified, namely fluvial, tidal flat, offshore, and prodelta facies. The fluvial sedimentary facies is comprised of fluvial channel lag deposits, fluvial point bar deposits, and floodplain deposits, showing a fining-upward sequence in general with no benthic foraminifera. A layer of stiff clay overlies the fluvial deposits in core CJK07, indicating a long-term exposure environment during the Last Glacial Maximum （LGM）. During the postglacial sea-level rise around 13-7.5 cal ka BP, the tidal flat facies was deposited in core CJK11, characterized by abundant silt-clay couplets. Euryhaline species dominate the subtidal fiat foraminiferal assemblages, while almost no foraminifera was found in the intertidal fiat. The offshore environment was the major sedimentary environment when the sea level reached its highest level around 7.5 cal ka BP, with a maximum accumulation rate of 10 mm/a found in core CJK11. Prodelta sediments have been deposited in core CJK11 since -3 cal ka BP, after the formation of the Changjiang River delta. The difference in sedimentary facies between core CJK07 and CJK11 is due to their location： core CJK07 was in an interfluve while core CJK11 was in an incised valley during the LGM. Furthermore, AMS 14C dating of core CJK07 shows poor chronological order, indicating that the sediments were reworked by strong tidal currents and that sediment deposited since -7.7 cal ka BP in core CJK07 was eroded away by modem hydrodynamic forces caused by the southward shift of the Changjiang River delta depocenter.
