Given the field in cylindrical coordinates then the work needed to move a point charge Q from any radial distance r to a point at twice that radial distance is-
-KQ ln2
-Kr ln 2
-2K ln Q
-KQ ln r
Since the field has only a radial component
dW =-QE⋅dl
=-QErdr = -KQ/r dr
For the limits of integration use r1 and 2r1