国际地磁参考场解算方法及石油工程应用

Algorithm for international geomagnetic reference field and its application in petroleum engineering

地磁场包含了从地球内核到宇宙空间的丰富信息,且具有复杂的时空特性及演化规律。国际地磁参考场能较好地描述地磁场的时空分布及变化特征,为石油工程等领域获取地磁数据提供了简洁实用的技术手段。介绍了地磁场特征、地磁场要素和国际地磁参考场,给出了国际地磁参考场的解算方法和步骤,以及在石油工程领域推广应用国际地磁参考场的方法。应用IGRF-12国际地磁参考场,研究了1920~2020年的100年间塔里木盆地地磁场的时空分布及其演化特征,结果表明：塔里木盆地的最大磁偏角为5.98°,最小磁偏角为0.52°,二者相差5.46°。在石油工程应用中,为保证井眼轨迹监测与控制精度,应随时随地更新地磁数据,不能简单地用同一个磁偏角数值来覆盖整个油田或地区,也不能在某个空间位置上长期使用同一个磁偏角数值。

Geomagnetic feld contains rich information from inner core the earth to the universe, and has complicated time-space features and evolution patterns. The international geomagnetic reference feld （IGRF） can satisfactorily refect time-space distribution and changes of the geomagnetic feld, and provide petroleum engineering with a simple and practical technical measure to obtain geo-magnetic data. This paper reviewed features and key elements of geomagnetic feld, and IGRF. Algorithm and procedures for IGRF have been proposed to promote application of IGRF in petroleum engineering. The IGRF-12 has been used to study time-space distribution and evolution pattern of geomagnetic feld in the Tarim Basin over 100 years from 1920 to 2020. The research results show that the Tarim Basin has a maximum declination of 5.98°, minimum declination of 0.52°, and a difference of 5.46° between the two. In petroleum engineering, geomagnetic data need to be updated timely to ensure accurate monitoring and control over borehole trajectory. It is not proper to use the same declination value to cover the entire oilfeld or the region, or use the same declination value for certain spatial position over a long time.