Measuring and Analyzing the Magnetic Content of Drilling Fluid

Magnetic contamination of drilling fluid can impact the accuracy of a directional survey by shielding the magnetic field. Additionally, this contamination, such as swarf or finer magnetic particles, can agglomerate on the downhole tool or BOP and cause tool failure in the worst-case scenario. Thus, it is necessary to measure the magnetic content of drilling fluid. However, there is no recommended practice in API or ISO for this purpose. A simple experimental setup and measurement system was developed that can be easily deployed in the rig site to measure the magnetic contamination of drilling fluid. 47 drilling fluid samples were collected from a multilateral production well drilled with a semi-submersible drilling rig located in one of the North Sea's fields. The magnetic content of these samples was measured using the established method, and the microstructure of the collected content was analyzed using a scanning electron microscope (SEM) and x-ray diffraction analysis (XRD). Ditch magnets are commonly installed in the flowline on the rig to remove the swarf and finer magnetic particles, if the design is optimized. Ditch magnet measurement data of the well that the drilling fluid samples were collected from is presented. Operational details and common factors that might increase the production of the magnetic content were also investigated. By comparing the measured magnetic contamination of the drilling fluid samples and ditch magnet measurement data, it was possible to evaluate the efficiency of the ditch magnet system.