基于磁方位校正的地质模型精度分析

ANALYSIS OF ACCURACY OF GEOLOGICAL MODEL SET UP ON BASIS OF MAGNETIC AZIMUTH CORRECTION

在常规地质建模过程中往往忽视了对斜井的磁方位校正环节,在一定程度上影响了模型的精度,文章首先介绍磁方位角的测算原理和校正方法,通过建立构造和偏移量模型,重点讨论磁方位校正过程中地层倾角和定向井水平位移对模型精度的影响,最后通过实例数据表明,当地层倾角超过5°时,对于水平位移400 m的定向井,如果不考虑磁方位角校正,其垂向构造误差会达5 m以上,井轨迹在XY方向上的偏差达50 m之多。因此按照文章设计并完钻的P142-S43井构造误差控制在1.5‰,取得了很好的效果,对地质模型精度的提高有一定的指导意义。

The correction of magnetic azimuth of slanted holes is often ignored in the process of geological modeling,which has impact on the accuracy of geological models to some extent. In this paper the measurement principle and magnetic azimuth correction/calibration methods are introduced,and discussion is focused on the effects of formation dip and horizontal displacement of directional wells on model 's accuracy during magnetic azimuth correction. The field data showed that when formation dip exceeded 5°,in directional wells with 400 meters of horizontal displacement,there resulted in more than 5 meters of structural error in vertical direction,up to 50 meters of deviation in the X-Y directions when the magnetic azimuth correction not taken into consideration. Well P142-S43 planned according to the study result in this paper was drilled to total depth,structural error controlled within 1. 5%. It will be a guide for improving the accuracy of geological models.