新疆油田百72井火山地层层序、时代及其与后山层型剖面对比

Volcanic Stratigraphic Sequence,Age and Comparison with Mountain Layer Type Profile of Bai 72 Well in Xinjiang Oilfield

井中地层层序的建立和时代确定,是岩石地层单位划分与对比的关键证据,对油气藏的勘探开发具有重要意义。针对新疆百口泉油田百72井主要地层缺乏时代依据,前人所划佳木河组与山区原佳木河组层型(建组)剖面岩石组合不可对比这一关键问题,笔者重新进行了岩心编录和配套样品分析测试,获得了高精度锆石U-Pb测年成果,并结合测井资料,确立百72井1182~2937 m井段层序、时代。研究结果表明:该井段下部以火山熔岩为主、上部以火山碎屑岩为主,间夹多层火山喷发间隙期的陆源碎屑沉积薄层。以陆源碎屑沉积薄层为分段标志,该井段可划分为6个岩性段。在第三岩段杏仁状玄武岩、第五岩段安山质角砾熔岩中分别获得(304.3±3.9)Ma、(306.6±5.1)Ma的LA-ICP-MS锆石U-Pb年龄,指示地层时代为晚石炭世。该岩石组合、层序及时代与百72井之北山区哈拉阿拉特组建组剖面总体可对比,故将前人对其划分二叠纪佳木河组修订为晚石炭世哈拉阿拉特组,这一成果为井中(“盆”)-北缘山区(“山”)地层对比提供了一个范例。

Establishment of stratigraphic sequence and determination of age in the well is the key evidence for the delineation and comparison of rock stratigraphic units.This is of great significance to the exploration and development of oil and gas reservoirs.In response to the key problem that the main stratigraphy of the Baik-ouquan oilfield Bai 72 well,in Xinjiang,lacks a chronological basis and the rock assemblage of the formerly delineated Jiamuhe Formation and the original Jiamuhe Formation in the mountainous area is not comparable,we have reconducted core compilation and supporting sample analysis and testing,established the stratigraphic sequence in the well,obtained high−precision zircon U−Pb dating results,and combined with the logging data to establish the sequence and age of the 1182~2937 m well section of the Bai 72 well.The results show that:The well section is dominated by volcanic lava in the lower part and volcanic clastic rocks in the upper part,interspersed with multiple layers of land−derived clastic sedimentary thin layers during the interval of volcanic eruption.The well section can be divided into six lithologic sections using the thin layers of terrestrial clastic sediments as segmentation markers.The LA−ICP−MS zircon U−Pb age of(304.3±3.9)Ma and(306.6±5.1)Ma were obtained in the almond shaped basalt of the third rock section and the ambersite breccia lava of the fifth rock section,respectively,indicating that the stratigraphic age was Late Carboniferous.The rock assemblage,stratigraphy and age are generally comparable with the Hala’alate Formation section in the northern mountainous region of the Bai 72 well,so it is revised that the Permian Jiamuhe Formation belonged to the Late Carboniferous Hala’alate Formation,providing good example of a stratigraphic comparison between the well("basin")−northern margin mountainous in the Baikouquan oilfield.