Introduction To Non-magnetic Drill Collars

Introduction To Non-magnetic Drill Collars

Non-magnetic drill collarsDrill Collar are made of a low-carbon high-chromium manganese alloy steel. They are refined after strict chemical composition ratio and forged to achieve their mechanical properties. They have good low magnetic permeability, high-strength mechanical properties, excellent intergranular corrosion cracking resistance and excellent wear resistance. When the magnetic field strength is 1×105/4π A/m, the relative magnetic permeability μr of non-magnetic drill collars is ≤1.010. The magnetic induction gradient of non-magnetic drill collars along the inner hole at any distance of 100mm is ≤0.05μT.

Since all magnetic measuring instruments sense the geomagnetic field of the wellbore when measuring the direction of the wellbore, the measuring instrument must be a non-magnetic environment. However, during the drilling process, the drill tool often has magnetism and magnetic field, which affects the magnetic measuring instrument and cannot obtain the correct wellbore trajectory measurement information data. The use of non-magnetic drill collars can implement a non-magnetic environment and has the characteristics of drill collars in drilling. A considerable number of non-magnetic drill collar products have been included in the API standard in 1990.

The interfering magnetic field lines above and below the non-magnetic drill collar have no effect on the measuring instrument. Therefore, the non-magnetic drill collar creates a non-magnetic environment for the magnetic measuring instrument, ensuring that the data measured by the magnetic measuring instrument is the real earth magnetic field information.