Circulation sub with integrated flapper check valve

1 . A circulation sub, comprising:

a cylindrical body defining an internal flowpath extending longitudinally therethrough and being couplable within a drillstring;

a projectile seat piston included within the cylindrical body and longitudinally translatable within the circulation sub;

one or more bypass ports defined radially through the cylindrical body to facilitate fluid communication between the internal flowpath and an external environment of the circulation sub, wherein the projectile seat piston is longitudinally translatable to selectively occlude or expose the one or more bypass ports; and

a flapper check valve pivotably mounted within the cylindrical body and operable to fully seal the internal flowpath and prevent flow therethrough at a longitudinal location between the one or more bypass ports and an uphole end of the cylindrical body in response to a backflow into the circulation sub.

2 . The circulation sub of claim 1 , wherein the projectile seat piston is mated to a compression spring operable to compress when an activation projectile is seated against a projectile seat at an uphole end of the projectile seat piston.

3 . The circulation sub of claim 1 , wherein the projectile seat piston includes an extended lip protruding from an uphole end of a projectile seat, the extended lip being operable to occlude the one or more bypass ports prior to longitudinal translation of the projectile seat piston.

4 . The circulation sub of claim 1 , further comprising a torsion spring mated to the flapper and operable to urge the flapper towards a valve seal of the flapper check valve.

5 . The circulation sub of claim 4 , wherein the torsion spring is further mated to a bumper receivable against a valve body of the flapper check valve to control a speed of the flapper during motion to prevent fluid hammer within the flapper check valve.

6 . The circulation sub of claim 4 , further comprising a flapper bumper installed on the flapper to act as a stopper for the flapper in a closed configuration and to dampen impacts on the flapper.

7 . The circulation sub of claim 1 , further comprising a cage extending axially downward from a valve body of the flapper check valve, the cage including a shock absorber operable to limit travel speed of an activation projectile to prevent damage to the circulation sub.

8 . The circulation sub of claim 1 , further comprising a valve seal included at a downhole end of a valve body of the flapper check valve and engageable with a flapper of the flapper check valve to generate a fluid seal.

9 . A method of controlling flow through a circulation sub, the method comprising:

flowing a fluid through a circulation sub arranged within a drillstring, the circulation sub including:

a cylindrical body defining an uphole end and a downhole end;

a projectile seat piston arranged within the cylindrical body;

one or more bypass ports defined in the cylindrical body;

a valve seal arranged between the one or more bypass ports and the uphole end of the cylindrical body; and

a flapper pivotably mounted within the cylindrical body and engageable with the valve seal;

releasing an activation projectile through the drillstring and into the circulation sub;

receiving the activation projectile at a projectile seat of the projectile seat piston and thereby generating a seal that prevents flow through the projectile seat piston;

longitudinally translating the projectile seat piston within the cylindrical body and thereby exposing the one or more bypass ports to enable fluid communication between an internal flowpath of the circulation sub and an external environment; and

seating the flapper against the valve seal in response to a backflow entering the circulation sub through the one or more bypass ports to thereby prevent backflow into the drillstring uphole of the circulation sub.

10 . The method of claim 9 , wherein longitudinally translating the projectile seat piston within the cylindrical body comprises increasing a pressure of a fluid flow within the internal flowpath against the activation projectile seated on the projectile seat, and thereby longitudinally translating the projectile seat piston towards the downhole end of the cylindrical body.

11 . The method of claim 10 , wherein receiving the activation projectile at the projectile seat piston is preceded by biasing the projectile seat piston towards the uphole end of the cylindrical body with a compression spring until acted upon by the pressure of the fluid flow.

12 . The method of claim 9 , further comprising limiting a travel speed of the flapper via a bumper mated to a torsion spring biasing the flapper towards the valve seal.

13 . The method of claim 12 , further comprising dampening impacts on the flapper via a flapper bumper installed on the flapper.

14 . The method of claim 13 , further comprising limiting a travel speed of the activation projectile via a shock absorber mounted to a cage of the flapper check valve to prevent damage to the circulation sub.

15 . The method of claim 9 , further comprising releasing a blocking fluid through the bypass ports and into the external environment around the circulation sub, the blocking fluid including lost circulation materials operable to seal any lost circulation zones.

16 . The method of claim 9 , further comprising:

releasing further projectiles through the drillstring and into the circulation sub; and

clearing the activation projectile from the projectile seat via the further projectiles and longitudinally translating the projectile seat piston within the cylindrical body to re-isolate the bypass ports.

17 . A system comprising:

a drillstring disposed within a wellbore; and

a circulation sub, including:

a cylindrical body defining an internal flowpath extending longitudinally therethrough and coupled within the drillstring;

a projectile seat piston included within the cylindrical body and longitudinally translatable within the circulation sub;

one or more bypass ports defined radially through the cylindrical body to facilitate fluid communication between the internal flowpath and an external environment around the drillstring, wherein the projectile seat piston is longitudinally translatable to selectively occlude or expose the one or more bypass ports; and

a flapper check valve pivotably mounted within the cylindrical body and operable to fully seal the internal flowpath and prevent flow therethrough at a longitudinal location between the one or more bypass ports and an uphole end of the cylindrical body in response to a backflow into the circulation sub and through the drillstring.

18 . The system of claim 17 , further comprising a compression spring mated to the projectile seat piston and an activation projectile releasable into the drillstring, wherein the activation projectile is seatable on the projectile seat to enable compression of the compression spring via fluid flow into the internal flowpath.

19 . The system of claim 18 , further comprising a cage extending axially downward from a valve body of the flapper check valve, the cage including a shock absorber operable to limit travel speed of the activation projectile to prevent damage to the circulation sub.

20 . The system of claim 17 , wherein the projectile seat piston includes an extended lip protruding from an uphole end of a projectile seat, the extended lip being operable to occlude the one or more bypass ports prior to longitudinal translation of the projectile seat piston.