1、Introduction
Magnetic drill collars are made of low carbon high chromium manganese alloy steel, which is refined by strict chemical composition ratio and forged to achieve its mechanical properties. It has good low permeability, high strength mechanical properties, excellent intergranular corrosion cracking resistance and excellent wear resistance. When the magnetic field intensity is 1x105/4πA/m, the relative permeability urs1.010 of the non-magnetic drill collar is less than 0.05uT when the magnetic field intensity is 1x105/4πa /m.
2、Effect
Because all magnetic measuring instruments, when measuring the direction of the borehole, are induced by the borehole geomagnetic field, the measuring instruments must be in a magnetically free environment. However, in the process of drilling, the drilling tool often has magnetic properties, which will affect the magnetic measuring instrument, and the correct borehole trajectory measurement information data can not be obtained. The use of non-magnetic drill collars can implement the non-magnetic environment, and has the characteristics of drill collars in drilling.
3、Working Principle
Schematic diagram of the action principle of non-magnetic drill collars
① Geomagnetic field line :
② magnetic measuring instrument :
③ Steel drill collars :
④ interfered magnetic field line :
⑤ bit joint; The interference magnetic field lines above and below the magnetic collars have no effect on the position of the measuring instrument.
Therefore, the magnetic collars create a magnetic environment for the magnetic measuring instrument and ensure that the data measured by the magnetic measuring instrument is true geomagnetic field information.
無磁鉆鋌種類
1、無磁鉆鋌一般按API7-1標準生產,長度一般為30FT或31FT,即9150mm或9450mm
2、按形狀可分為無磁鉆鋌,無磁螺旋鉆鋌,無磁承壓鉆桿,無磁短節等