Jettisonable ball seal

A system for isolating a wellbore, comprising:

• a setting tool having an upper end, a lower end, and an outer diameter;
• a seal ball;
• a shear pin selectively connecting the lower end of the setting tool to an upper end of the seal ball, wherein the shear pin is configured to break in response to a predetermined force;
• and
• a seal sub having a ball seat and a seal ball catch feature, wherein at least a portion of the ball seat has an inner diameter that is larger than the outer diameter of the setting tool and that is smaller than an outer diameter of the seal ball;
• wherein as the setting tool passes through the ball seat, the seal ball contacts the ball seat of the seal sub and the seal ball catch feature of the seal sub, and wherein the predetermined force is applied to the setting tool and the shear pin to break the shear pin and leave the seal ball in simultaneous direct physical contact the ball seat of the seal sub and the seal ball catch feature of the seal sub.