钻井岩心重定向的古地磁方法及其可靠性

Paleomagnetic method of reorienting cores and its reliability

在统计意义上,岩心的黏滞剩磁分量方向在地理坐标系中与现代地磁场方向近似相同。依据此原则,提出了一种钻井岩心古地磁重定向的新方法。以四川江油地区的118块定向岩心为例,对该方法的可靠性进行了研究,结果表明利用该方法进行岩心重定向是可行的,适合于各种类型井的取心,而且计算过程不受地层产状的约束。定向结果的可靠性依赖于其统计性,即必须保证测试的样品足够,一块岩心至少测试3块样品。该方法特别适合于那些当初未考虑定向问题而现在又迫切需要重定向的钻井取心。

Based on the principle that the rock Viscous Remanent Magnetization （VRM） is statistically identical to the direction of modern magnetic field, a new paleomagnetic method is developed to reorient cores. The issue of reliability is discussed while the method is applied to reorienting 118 field oriented outcrop cores from Jiangyou. The results show that the method is feasible, suitable for all types of cores, and independent of stratum occurrence. Its reliability depends on the amount of tested core samples, usually three samples are the minimum for one core. The method is especially suitable for the cores that were unoriented in the process of drilling, but need to be oriented at present.