The disclosure relates to a seal assembly for a ram of a blowout preventer for sealing a wellbore penetrating a subterranean formation. The wellbore has a tubular to pass fluid therefrom. The rams are positionable about the tubular. The seal assembly includes a compound seal carried by the ram. The compound seal includes a face seal having a sealing surface sealingly engageable about the tubular and a support seal positionable adjacent to the face seal a distance from the sealing surface. The sealing surface extends along a front face thereof engageable with at least one of the tubular and the face seal of another ram. The support seal is non-engageable with the tubular during sealing and is more deformable than the face seal whereby the compound seal is supported during sealing.