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

Geomagnetic field contains rich information from inner core the earth to the universe, and has complicated time-space features and evolution patterns. The international geomagnetic reference field (IGRF) can satisfactorily reflect time-space distribution and changes of the geomagnetic field, and provide petroleum engineering with a simple and practical technical measure to obtain geomagnetic data. This paper reviewed features and key elements of geomagnetic field, 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 field 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 oilfield or the region, or use the same declination value for certain spatial position over a long time.