First Onsite Automatic Geomagnetic Observatory Improves Well-Bore Positioning

Abstract

Improvements in measurement while drilling (MWD) and service reliability over the past 25 years has made MWD tools the most cost-effective method for calculating wellbore survey position while drilling. However, with more complex well trajectories required to reach more challenging targets, reducing lateral uncertainty has also become a new challenge. It is accepted that no geomagnetic model can properly account for the geomagnetic spatial and temporal local complexity for calculating MWD geomagnetic reference values. It is also well known that measuring local geomagnetic reference requires frequent absolute measurements in order to perform QA/QC, and that those absolute measurements could only be done manually so far, and consequently very few magnetic observatories are in operation. Therefore, solutions have been engineered to enhance the geomagnetic reference model with In-Field Referencing (commonly termed as IFR). Then, its combination with Multi-Station Analysis (MSA) correction algorithms has become a common method for addressing and reducing most of the correctable MWD azimuth, survey position error and lateral uncertainty. Enhanced wellbore positioning could be a real game changer to achieve in-fill wells with high collision avoidance constraints, to develop projects that require high precision to hit the reservoir targets, or those located in specifically difficult areas, from a geomagnetic perspective, such as high latitudes and zones with crustal anomalies. This paper presents the results of the new temporal magnetic field method "IFR4D" that was successfully used to drill two onshore wells in Argentina. The wells targeted the Vaca Muerta shale play, and demonstrated the ability to improve the wells absolute positioning while reducing the lateral aspect of "ellipse of uncertainty" by a combination of: A unique autonomous, remote real-time observatory developed to monitor and allow corrections for the local geomagnetic vector with frequent absolute control of the local and temporal geomagnetic vector field (Dip, Declination and Field Intensity), andA dedicated MSA algorithm defined to use local and temporal In-Field Referencing (IFR2) data at the position and time for each MWD survey station. Once installed on location, the autonomous observatory measured all geomagnetic properties (Dip, Declination and Field Intensity) with no personnel onsite for more than one year, delivering a new level of geomagnetic accuracy to use as the standard reference for the life-time of the field. The data from the observatory was then used remotely while drilling to correct and optimize wellbore position and reduce the lateral aspects of the "ellipse of uncertainty" (EOU).