庐枞盆地科学钻探地球物理测井及深部铀异常的发现

Geophysical logging in scientific drilling borehole and find of deep Uranium anomaly in Luzong basin

庐枞盆地砖桥科学钻探ZK01孔为深部探测技术与实验研究专项在庐枞盆地施工的钻探验证孔,全井段实施了连续取心和地球物理测井工作.测井工作分三次完成,测井总深度1994.02m.测井项目包括视电阻率、极化率、磁化率、纵波速度、超声成像、自然伽马、密度、井斜、井径、井温、泥浆电阻率、井中三分量磁测等10多种方法,获得了钻孔剖面原位物性参数、钻孔几何形态及井壁超声图像.通过对地球物理测井和钻孔岩心编录等资料的研究,完成了岩性的人工识别与支持向量机判别,建立了钻孔测井解释岩性剖面;通过对矿化地层的测井响应分析,将电阻率和磁化率作为粗安岩矿化的识别标识;根据超声成像测井资料推断本地区深部地层最大水平主应力方向为南北走向.在ZK01孔1500~1900m发现放射性异常,对铀当量大于万分之一的21处异常进行了定量解释,铀矿化段累积厚度93.02m,为庐枞地区深部找铀矿提供了重大线索.

The geophysical logging of scientific drilling borehole ZK01 in Luzong district is a part of the project ＂Detection Technology and Experiment for Deeper Formations（SinoProbe）＂,which relies on the subject ＂Drilling verification of important anomalies and study of metal vertical distribution rule＂of the project SinoProbe-03 ＂Study of three-dimensional detection and experiment for deeper mineral resources＂.The purposes of geophysical logging include delimiting and verifying geological section,identifying target stratum and studying the wall rock alteration related to the formation of mineral deposit as well as finding mineral deposit,and providingphysical properties for in-situ determination of rock and ore.Micrologger II portable logging system of Robertson Geologging,UK is the main data acquisition equipment for the geophysical logging.The logging work of borehole ZK01 was carried out in three times from September 28,2011 to April 1,2012 with a total logging depth of1994.02 m.Over ten methods were used in the logging project,including apparent resistivity,polarizability,magnetic susceptibility,acoustic compressed velocity,ultrasonic imaging,gamma-ray,density,borehole deviation,caliper,fluid temperature,mud resistivity,and borehole three-component magnetic,etc,and the in-situ physical properties of borehole section together with borehole geometry and ultrasonic images of borehole wall were obtained.Through the study of geophysical logging and borehole logging data,artificial lithology identification and support vector machine discrimination are achieved to help establish the lithological section of the logging borehole;through logging response analysis of the mineralized stratums,and treating resistivity and magnetic susceptibility as the identification of mineralized trachyandensite,pyritized trachyandensite is found to concentrate from 610 mto 1440 m and kaolinized trachyandensite is found to be distributed above 1200 m.According to the ultrasonic logging data,the maximum horizontal principal stress of deeper formation around ZK01 is in the direction of north-south.Radioactive anomalies are found from 1500 mto 1900 min borehole ZK01.Quantitative interpretation is carried out towards 21 anomalies whose uranium equivalent is over 1/10000 with a total thickness of 93.02 m.The mineralization grade of uranium and thorium in such area is lower but may form a certain scale or even richer reserve,which,therefore,is still worth attention for future use.