Variable blowout preventer apparatus and method

A blowout preventer, comprising:

• a housing comprising a longitudinal passage and a pair of ram passages extending from the longitudinal passage;
• and
• a first ram assembly disposed in a first of the pair of ram passages and comprising a first ram block assembly, wherein the first ram block assembly comprises:
• a ram block body comprising a first endface and a second endface opposite the first endface, wherein the second endface comprises a concave sealing surface;
• and
• a seal assembly coupled to the ram block body and comprising a plug defining a convex sealing surface, wherein the plug is positioned at the second endface of the ram block body.

A method for operating a blowout preventer, comprising:

• (a) actuating the blowout preventer into a first closed position in which a first ram block assembly of a first ram assembly and a second ram block assembly of a second ram assembly seal against a tubular member extending through a longitudinal passage of the blowout preventer;
• (b) actuating the first ram block assembly from a first configuration to a second configuration;
• and
• (c) actuating the blowout preventer into a second closed position with the first ram block assembly sealing against the second ram block assembly.