库车坳陷新近系库车组冲积扇沉积特征及相模式

通过野外露头考察和测井分析,并结合地震和三维电法资料,对库车坳陷新近系库车组冲积扇的沉积特征和分布规律进行研究,建立了冲积扇沉积模式。库车坳陷新近系库车组冲积扇岩性主要为黄色、黄红色砾岩、砂砾岩及含砾砂岩。砾石层中可见底冲刷-充填构造、交错层理和平行层理。测井曲线整体表现出GR低和电阻率高的特征,曲线呈箱形、漏斗形和钟形;地震相以杂乱反射和前积特征为主。为了提高了研究的精度,在钻井分布稀少和地震相特征不明显的地区,将三维电法资料用于冲积扇分布的研究。通过综合研究,认为冲积扇在西部的Bz1井地区和Db1井地区规模最大,在东部地区发育规模小。构造运动是冲积扇发育的主要控制因素,库车期构造运动活动强烈,南天山快速隆升,为冲积扇提供大量的物源,Bz1井地区持续隆升,遭受剥蚀,物源充足,冲积扇规模不断增大;Db1井地区由于受构造断裂的影响,局部隆升,为冲积扇提供了局部物源。通过分析,认为库车坳陷新近系库车组冲积扇主要有长期稳定的继承性单物源冲积扇模式和受局部构造控制的多物源冲积扇模式。

Sedimentary Characteristics and Model of the Alluvial Fan in Kuche Formation of Neogene in Kuqa Depression

According to outcrop investigation and well-logging identification,the sedimentary characteristics and distribution law of the alluvial fan in Kuche Formation of Neogene in Kuqa Depression were systematically studied with seismic and 3D electric method data,and the sedimentary models of the alluvial fan were obtained.The alluvial fan is dominated by the yellow or yellow-red conglomerates and coarse-grained sandstones,and there exist flush-filling structures,cross beddings and parallel beddings in conglomerates.The well-logging curves of the alluvial fan are in the characteristics of low GR and high resistance,and manifest themselves as box-like,infundibuliform and campaniform shapes.The seismic facies are dominated by clutter and foreset facies.In the areas lacking wells,the data of 3D electric method were also used to improve the research precision.The results of comprehensive research reveal that the scales of alluvial fans in the western region nearby well Bz1 and well Db1 are larger than those in the eastern region,and the tectonic movement is the main controlling factor;it experienced strong tectonic movements during the depositional period of Kuqa Depression,and the uplift caused lakes to shrink quickly to the south,and mountain blocks rose and suffered from erosion,providing sediment sources for alluvial fans;the scale and distribution of alluvial fans in the area nearby well Bz1 were expanding continuously;due to tectonic uplift,the alluvial fan in the area nearby well Db1 has the feature of multiple provenances.It is considered that there are two models of alluvial fans in Kuqa Depression,i.e.a model of single provenance of conglomerate,which reveals a long-term,stable and successional depositional process,and a model of multiple provenances of conglomerate,which is controlled by local structures.