| CPC E21B 41/02 (2013.01) [E21B 34/063 (2013.01); E21B 37/00 (2013.01)] | 18 Claims |

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1. A method comprising:
(a) for a first period of time, shielding an internal fluid flow bore through which a wellbore fluid flows from a magnetic field produced by magnets coupled to a cylindrical wall defining the internal fluid flow bore, and
(b) after the first period of time, un-shielding the magnetic field produced by the magnets, whereby the magnetic field extends into the internal fluid flow bore through which the wellbore fluid flows.
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