Reaction valve drilling jar system

A drilling system comprising:

• a drill string disposed in a wellbore, said drill string including a drill pipe, a jar coupled to said drill pipe and having a mandrel that is slidingly received within a sleeve, a reaction valve coupled between said drill pipe and said jar, and a bypass valve coupled between said reaction valve and said jar, said reaction valve movable between an open position and a throttled position, and said bypass valve operable to bypass fluid flow downstream from said of said reaction valve from said drill string to a wellbore annulus;
• a drilling rig carrying said drill string and operable to rotate said drill string;
• and
• a control system operatively coupled to said reaction valve so as to selectively position said reaction valve;
• whereby
• throttling a flow of drilling fluid across said reaction valve creates a differential pressure and an axial force that is transferred to said jar so as to urge said mandrel to move with respect to said sleeve.

A jar assembly for connection to a drill pipe, said drill pipe forming a conduit for a flow of drilling fluid, the jar assembly comprising:

• a reaction valve;
• a jar coupled to said reaction valve, said jar having a mandrel that is slidingly received within a sleeve;
• a bypass valve coupled between said reaction valve and said jar, said bypass valve operable to bypass said flow downstream of said reaction valve from said drill string to a wellbore annulus;
• and
• a control system operatively coupled to said reaction valve so as to selectively throttle said flow of drilling fluid across said reaction valve;
• whereby
• throttling said flow of drilling fluid across said reaction valve creates a differential pressure and an axial force that is transferred to said jar so as to urge said mandrel to move with respect to said sleeve.