| Qaidam basin is the largest plateau in northern qinghai-tibet plateau basin, the northwest is high and the southeast is low, which is surrounded by the peripheral three big mountains (kun lun, qilian and altun mountains), it constitutes mountain basin which seems like diamond. After the long geologic evolution process, the sedimentary center changes constantly, the reservoir type is variety, it’s powerful for the later structure reform movement, then it forms many kinds of source rocks and reservoir-cap combinations. At present it’s in the west area mainly identifiesfor the the main reservoir of qaidam basin found oil and exploited field, the West Qaidam basin starts on the east of Altun mountain from west and on the east of obo beam GanSen a line from east, which is in the west of Qaidam basin, is about30000km2.By the50years exploration, the West Qaidam basin has been found many sets of tertiary oil and gas sediment group, the resources evaluation indicates that the West Qaidam basin has the rich oil and gas resources, which has ability to form a big oil field. The next section within garichaigou (E31) and the oil sands mountain group (N21) is the tertiary hydrocarbon source rock layer and the main sedimentary reservoir, it is helpful for the large XianHua media on the salt water lake sand body formed in the influence of the distribution of wood west exploration by the sedimentary simulation experiment, and which is important for the West Qaidam basin development.Based on the analysis of the data of qaidam basin, XianHua tertiary the ancient geography, the ancient salinity, ancient climate and the ancient water depth of the western qaidam basin have been recoveried, and on the basis of the core observation, tectonic activities strength, climatic conditions and water medium and the ancient salinity conditions of the original of the the formation of tertiary different period have been made clearly. Based above more detai led in the work, large salty water medium lake basin deposition simulation experiment plan has been formulated detailed for the the west of the Qaidam basin of tertiary (E31, N2-1)deposition, and the sedimentary simulation experiment research has been done, which provides technical theory guidance for the west of the Qaidam basin region of oil and gas exploration of qaidam basin.According to the geographical region, the cistern sedimentary simulation experiment designs the far source braided delta depositional system under the drought condition. And the four experiments simulation has been completed, which each small layer has two recession sedimentation sequence, settlement of the floor to simulate the tectonic movement is made in the process of sand body sedimentation, which simulates the influence of the tectonic movement to sand body formation and distribution.The results of the research show that:(1) From the experimental process and the results, some results has been indicated, such as that the lake of braided delta plain and in front of the lake in the XianHua spectrometry are more development under the upper west margin wood within ganchaigou (E31) under section and the oil sands of the (N2’) deposition, sedimentary microfacies are diversity, which gives priority to tap water and sand dam (inclined column sand dam and longitudinal sand dam) micro phase, accounts for more than80%, former delta and phase development is limited. In the front of delta and former delta conversion, condition of the water move is complex, particle separation is better, handling distance is short, sedimentary speed is fast.(2)As the different level different, types of river are leaded to develp in plenty of material sources of supply and flow. Through the experimental observation, low water level, the braided fluvial river delta is form a body overlapping offsets mainly into the lake. High water level, the braided fluvial river delta has much channel sand dam development characteristics. (3) In the water of the XianHua lake basin, the lake density is more than the density of water injection, river clastic particle carry into the lake, which hardly spreads, it with their own inertia is plane jets shape, sand body sedimentation handling is much farther, sedimentary range is much wider. The ratio between long and wide is more than1for the west of Qaidam basin under the tertiary west margin within ganchaigou (E3’) under section and the oil sands of the (N2’) sand, and the ratio between wide and thich is maor than30, the results show that the sand body is a shape-bird foot shape exhibition cloth.(4) By the experiments, some results have been found, that the lake delta sediments XianHua coarse distribution range is wide, and handling of distance is long, which have close relationship with the water salinity, the water flow intensity, the lake and flow.(5) By implementing end section analysis, XianHua lake delta bedding types are abundant has been found, which give priority to parallel bedding and cross bedding. And there are some discoveries in profile, the development of the dam in the oil sands mountain group (N21) is more obvious than ganchaigou (E31) obvious.(6) By the experiment, the result has been found, that the difference between the water quality and flow condition has great influence to the front delta, in XianHua lake basin, the front is more development, in the flood period, development underwater distributary channel sand. In moderate and dry water period, estuary sand dam is development. In the same experimental conditions, fresh water environment in the delta front isn’t too development.(7)There is a great distinction between the grain size and thickness in key beam and the provenance alar provenance in braided delta, which the distribution of the coarse particle is wider in the provenance of braided river delta, and is also development in front of the braided fluvial river delta. The sand body thickness is thinner than it in the provenance of alar in braided delta. The results are great effected by dynamic conditions. |
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