An apparatus and method for pre-installation of a petroleum wellhead on the seabed. The apparatus includes two principal components: a wellhead (1) and a ballast tube (9). The wellhead includes a tube in which are fixed guide fins (3) and structural fins (8). The ballast tube (9) includes a tube with a holding member (12) for its recovery after the wellhead (1) has been fixed on the seabed. The ballast tube (9) is placed inside the wellhead (1) and the assembly is launched towards the seabed, being embedded in it by the inherent weight of the assembly. After the wellhead (1) has been fixed, the ballast tube (9) is raised to the surface.