A method of sealing annular space between an upright outer tube and an upright inner tube extending within the outer tube along an axial direction thereof involves pouring a liquid seal material into the annular space onto a support member fitted within the annular space between the outer tube and the inner tube in a manner substantially closing around the inner tube. The liquid seal material is poured in an amount sufficient to fill radial space between the inner tube and the outer tube fully around the inner tube, the liquid seal material is then cured to form an annular seal between the inner tube and the outer tube. The method is useful in sealing of the annular spacing between the surface and production casing of a gas well and installing a venting system to facilitate controlled venting of the annular space.