Magnetic Mud Shielding Effects on Measurement-While-Drilling Azimuth Survey Acceptance Tolerance at Low Latitudes: A Case Study, Malaysia

Synthetic oil base drilling muds are re-cycled for cost efficiency and to minimize environmental effects. Invariably, very fine micro-sized magnetic or paramagnetic material from drill-string and casing wear accumulates in the drilling mud over time and cause significant shielding effect on the downhole cross-axial magnetometer sensors. This case study explores various mitigating methods to acquire Measurement-While-Drilling (MWD) surveys within acceptance tolerances and where possible, to define minimum wellbore uncertainties levels depending on the wellbore trajectory relative to earth's magnetics especially at lower latitudes.