Abstract: A wellbore magnetic tool apparatus is used for generating a magnetic field emanating from a tubing string. The apparatus has a tubular body for connection in series with the tubing string. Magnetic elements are mounted within one or more cavities in the tubular body such that the field directions of all magnetic elements are aligned in a common direction extending along a diametrical axis of the tubular body. The cavities are open to an interior of the body so that the magnetic elements are inserted into the cavities through an inner longitudinal passage of the tubular body. One or more covers close the cavities relative to the longitudinal passage in the tubular body. Magnet receiving cavities open to the interior enable a proportionally larger cavity with greater density of magnets without weakening of the structure of the body.