Patent ID: 8167031

Claim:
A blowout preventer (“BOP”) for an oil or gas well, comprising: a BOP body having a through-bore defining a centerline and adapted to allow a tubular member to be disposed therethrough, the body having at least a first guideway defining a guideway centerline formed at an angle to the through-bore centerline; a first ram slidably coupled to the BOP body along the first guideway for travel along the first guideway; a first shear blade coupled to the first ram toward the through-bore to shear a tubular member disposed therein, the first shear blade being disposed laterally across the first ram and having a first shear blade profile with a first portion on one side of the guideway centerline and a second portion on an opposite side of the guideway centerline from the first portion, the first portion and the second portion of the first shear blade profile being asymmetric from each other relative to the guideway centerline; a second ram slidably coupled to the BOP body along a second guideway aligned with the first guideway; and a second shear blade coupled to the second ram and distal from the first shear blade relative to the through-bore, the second shear blade being disposed laterally across the second ram and having a second shear blade profile with a first portion on one side of the guideway centerline and a second portion on an opposite side of the guideway centerline, the first portion and the second portion of the second shear blade profile being asymmetric from each other relative to the guideway centerline; wherein the first shear blade profile is configured to move the tubular member positioned on a first side laterally of the guideway centerline toward the guideway centerline; and wherein the second shear blade profile is configured to move the tubular member positioned on a second side laterally of the guideway centerline toward the guideway centerline; wherein the first shear blade profile defines a first centering profile adapted to push the tubular member toward the centerline of the through-bore; and wherein the second shear blade profile defines a second centering profile adapted to push a tubular member toward the centerline of the through-bore; wherein the first centering profile comprises a first curved profile; wherein the first shear blade profile comprises a first stress concentrator; wherein the first stress concentrator is laterally offset from the guideway centerline; and wherein the first stress concentrator is on the opposite side laterally of the guideway centerline from a majority of the curved profile.