The Dabie Orogen constitutes the eastern part of the Qinling‐Tongbai‐Hong'an‐Dabie orogenic belt, however, whether it has involved into the early Palaeozoic subduction–related event as well‐recorded in the western part is still in debate. This study provides new petrological, geochronological and geochemical data for the Beilou and Mafan plutons in the Dabie‐Hong'an orogens. The Beilou pluton is dominated by granite, some of which have been strongly deformed to form mylonites. The Beilou pluton was emplaced at ca. 490 and ca. 450 Ma, whereas the Mafan pluton was emplaced at 450–430 Ma. The whole‐rock major‐ and trace‐element analyses results indicate that both plutons are depleted in high‐field‐strength elements and heavy rare earth elements. The Beilou pluton also has positive whole‐rock εNd(t) values and generally positive zircon εHf(t) values, whereas all but one of the Mafan pluton samples yield positive whole‐rock εNd(t) and consistently positive zircon εHf(t) values. All of the samples have low (87Sr/86Sr)i ratios. These data indicate that these plutons are formed from magmas generated by the partial melting of metasomatized mantle wedge material with minor additions of crustal materials, representing arc magmatic rocks associated with subduction. Detailed detrital zircon dating of flysch sequences of the Foziling Group within the Dabie Orogen indicates that the early Palaeozoic magmatic rocks had once been distributed in the whole Orogen, although only the Beilou pluton now is exposed in the western Dabie Orogen.
Abstract. This article in view of the complex roof conditions was carried on study about the new technology of removing gangue and retaining roadway, and tells a method of progressive reinforced concrete wall segment with gangue to keep the roadway, the roadway beside the support system is mainly composed of the lining, waste rock wall and the outer wall, the wall and the outer wall of concrete material width to build the strength of the progressive type filling body, waste rock wall with woven bag with waste rock assembled, paragraphs geological survey on the actual distance should be based on working face. This method relies on the interior of the gangue wall to make the pressure control and allow the roof to sink. In this paper, the finite deformation control of the roof is realized by the gangue wall and the high strength filling body. This method has the characteristics of low entry cost, good forming of roadway, high security and good stability, and can be applied to complex geological conditions such as hard roof.
It's difficult to fully discover all the geological reserves during exploration stage, because the fracture system of complex fault block oilfield is very complicated. As the reserve scale in single block is limited, the decline rate of the oilfield is usually very fast. As a result, finding new replacement reserves inside the oilfield is an important method to ensure stable production of complex fault block oilfields.
Base on the improvement of the Vogel method and material balance method to calculate the reservoir dynamic reserves under the degassing conditions of A14 well area. Using Allan profiling to construct lithologic docking relationship between A14 well area and adjacent fault block. Calculate SGR(Shale Gouge Ratio) for different docking areas. According to the statistics of shale content and porosity in the oilfield area, core experiment results with porosity and displacement pressure, the displacement pressure on both sides of the fault docking area can be used to predict the oil column height of adjacent block.
To ensure the initially high-speed production of A14 well area, it's necessary to reduce the times of shut-in static pressure measurement. The continuous reservoir pressure under the degassing conditions is calculated by the improvement of the Vogel method. Avoid the error of dynamic geological reserve calculation caused by too little reservoir pressure data. Result shows that the geological reserves of A14 well area is much smaller than its dynamic reserves. Study on the sealing property of faults around the A14 well area shows that the fault on the east side of the A14 well area is a non-closed fault, and the adjacent fault block is an oil-bearing fault block. Well A20 confirmed the oil-bearing properties for the fault block on the east side of the A14 well area. The result of pressure testing while drilling also shows that pressure drop in the east block of the A14 well area. All of that verify the reliability of previous research.
Aiming at the development of complex fault block oilfield, a method based on dynamic reserves research result to study the sealing property of peripheral faults to predict the height of oil columns in adjacent blocks is proposed. Achieved the purpose of finding new replacement reserves inside the oilfield. The reliability of the research is verified by the pressure testing while drilling. It provides a valuable experience for the development in similar oilfield.
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