油气田钻井岩芯及岩芯裂缝方位确定的古地磁原理与方法

THE PALEOMAGNETIC PRINCIPLE AND METHOD APPLIING TO ORIENTATION OF CORE AND CRACKS IN OIL AND GAS FIELD

岩石在现代地磁场中获得的粘滞剩磁（VRM）可以通过分离剩磁低温分量获得，并且它与现代地磁场方向一致．因此，通过提取岩芯剩磁的低温分量，可以恢复岩芯的现代磁坐标，进而确定岩芯在现代地理坐标中的位置．本文对吐哈油田，长庆油田岩芯及地表露头样品作了系统热退磁分析，讨论了剩磁低温分量与现代地磁场关系，建立了岩芯方位古地磁学定向方法，并将这种方法用于长庆油田钻井岩芯定问及裂缝方位确定．通过对长庆油田40口井的含裂缝岩芯的走向，揭示了油层地下裂缝展布方位．

The rock viscous remanent magnetization (VRM), from modern Earth magneticfield, will be obtained by studing the low-tempreture components of depositionalremanent magnetization (DRM), which is identical with the direction of modern magneticfleld. Based on the principle, corresponding directon of core at the modern geomagneticcoordinates can be defined. This paper present consequence of thermal demagnetization oncore and surface samples in Tuha Oil Field, discuss relation between the low-tempretureparts of DRM and the modern magnetic field, and establish the Paleomagnetic methodappling to core orientation, which is also appling in Changqing Oile Field. The cracksspreading condition in reserves were revealed by the orientation study of cracks of cores inforty drills reveals.