Braided fluvial delta facies and sedimentary evolution of the Member 1 of Qingshuihe Formation of Lower Cretaceous in Shinan 31 wellblock, Junggar Basin
Rao Zheng1, Yao Pengxiang1, Zhang Chunguang1, Liu Jing1, An Zhiyuan2, Gao Zhenzhong2
1 Shixi Field Operational District,PetroChina Xinjiang Oilfield Company,Karamay 834000,Xinjiang 2 School of Geoscience,Yangtze University,Jingzhou 434023,Hubei
Abstract：Different viewpoints have been proposed about the delta sedimentary facies developed in the Member 1 of Qingshuihe Formation of Lower Cretaceous in Shinan 31 wellblock in central Junggar Basin. The authors considered it was the product of tractive current with strong hydrodynamic conditions according to the stratification character, the composition texture, the texture maturity, the developing characteristic of the pore of the conglomerates and the texture, structure, granularity and distribution characteristics of the sandstones. Its sedimentary environment belonged to the braided fluvial delta. Through the detailed observation and description of cores, combining with the logging facies analyses, on the basis of single well facies analyses of the 211 wells in the Shinan 31 wellblock, according to the across-well analyses and the synthetic analyses of sedimentary facies, it is concluded that all kinds of subfacies of the braided fluvial delta facies were developed in the study area. The sedimentary microfacies including the braided channel, fluvial flood deposit, subaquaeous distributary channel, mouth bar, front delta mud etc.， were identified. During the earlier sedimentary period of the Member 1 of Qingshuihe Formation(K1q21), the study area was dominated by lacustrine facies and braided fluvial delta was only developed in the southeast of the study area. Then the two deltas in two directions developed towards the same direction(K1q1-3-41,K1q1-3-31). Then, the delta plain disappeared in the southeast and only delta front was developed(K1q1-3-21). During the sedimentary period of K1q1-3-11, it was dominated by fine-grained sediments and the sedimentary setting was similar as the former period. During the sedimentary period of K1q1-21, the braided fluvial delta plain and delta front were developed in the north, while in the southeast, only delta front was developed. In the late period of the Member 1 of Qingshuihe Formation(K1q1-11), due to the sudden rise of the lake level, the study area was dominated by front delta facies and was composed of front delta muds with the development of strip-belt-shaped front delta ditch sandstones.
Rao Zheng,Yao Pengxiang,Zhang Chunguang et al. Braided fluvial delta facies and sedimentary evolution of the Member 1 of Qingshuihe Formation of Lower Cretaceous in Shinan 31 wellblock, Junggar Basin[J]. JOPC, 2008, 10(1): 43-52.
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