Abstract: A method for increasing an amplitude of reciprocal axial extensions and contractions of a shock tool configured to induce axial oscillations in a drillstring during drilling operations includes (a) selecting the shock tool. The shock tool has a central axis and an axial length. The shock tool includes an outer housing, a mandrel telescopically disposed within the outer housing, and a first annular piston fixably coupled to the mandrel. The shock tool has a first amplitude of reciprocal axial extension and contraction at a pressure differential between a first fluid pressure in the outer housing and a second fluid pressure outside the outer housing. In addition, the method includes (b) fixably coupling a second annular piston to the mandrel of the shock tool and increasing the axial length of the shock tool after (a). The second annular piston is axially spaced from the first annular piston.

Abstract: A method for increasing an amplitude of reciprocal axial extensions and contractions of a shock tool configured to induce axial oscillations in a drillstring during drilling operations includes (a) selecting the shock tool. The shock tool has a central axis and an axial length. The shock tool includes an outer housing, a mandrel telescopically disposed within the outer housing, and a first annular piston fixably coupled to the mandrel. The shock tool has a first amplitude of reciprocal axial extension and contraction at a pressure differential between a first fluid pressure in the outer housing and a second fluid pressure outside the outer housing. In addition, the method includes (b) fixably coupling a second annular piston to the mandrel of the shock tool and increasing the axial length of the shock tool after (a). The second annular piston is axially spaced from the first annular piston.

Abstract: A shock tool for reciprocating a drillstring includes an outer housing. The outer housing has a central axis, a first end, a second end opposite the first end, and a passage extending axially from the first end to the second end. In addition, the shock tool includes a mandrel assembly coaxially disposed in the passage of the outer housing and configured to move axially relative to the outer housing. The mandrel assembly has a first end axially spaced from the outer housing, a second end disposed in the outer housing, and a passage extending axially from the first end of the mandrel assembly to the second end of the mandrel assembly. The mandrel assembly includes a mandrel and a first annular piston fixably coupled to the mandrel. The first annular piston is disposed at the second end of the mandrel assembly and sealingly engages the outer housing.

Abstract: A system for generating pressure pulses in drilling fluid includes a concentric drive power section. The power section includes a stator and a rotor rotatably disposed in the stator. The rotor is coaxially aligned with the stator. The system also includes a valve. The valve includes a first valve member coupled to the stator and a second valve member coupled to the rotor. The second valve member is configured to rotate with the rotor relative to the first valve member and the stator. The rotation of the second valve member relative to the first valve member is configured to generate pressure pulses in drilling fluid flowing through the concentric drive power section.

Abstract: A shock tool for reciprocating a drillstring includes an outer housing and a mandrel assembly coaxially disposed in the outer housing. The outer housing has a radially inner surface including a plurality of circumferentially-spaced splines. The mandrel assembly includes a mandrel having a radially outer surface including a plurality of circumferentially-spaced splines and a plurality of circumferentially-spaced troughs. Each spline of the outer housing is disposed in one trough of the mandrel. Each spline of the mandrel includes a top surface, a first lateral side surface extending radially from the top surface, a second lateral side surface oriented parallel to the first lateral side surface, and a bevel extending from the top surface to the second lateral side surface. Each spline of the mandrel also includes a pocket in the second lateral side surface extending radially from a bottom surface of a trough to the bevel.

Abstract: A system for generating pressure pulses in drilling fluid includes a concentric drive power section. The power section includes a stator and a rotor rotatably disposed in the stator. The rotor is coaxially aligned with the stator. The system also includes a valve. The valve includes a first valve member coupled to the stator and a second valve member coupled to the rotor. The second valve member is configured to rotate with the rotor relative to the first valve member and the stator. The rotation of the second valve member relative to the first valve member is configured to generate pressure pulses in drilling fluid flowing through the concentric drive power section.

Abstract: A shock tool for reciprocating a drillstring includes an outer housing and a mandrel assembly coaxially disposed in the outer housing. The outer housing has a radially inner surface including a plurality of circumferentially-spaced splines. The mandrel assembly includes a mandrel having a radially outer surface including a plurality of circumferentially-spaced splines and a plurality of circumferentially-spaced troughs. Each spline of the outer housing is disposed in one trough of the mandrel. Each spline of the mandrel includes a top surface, a first lateral side surface extending radially from the top surface, a second lateral side surface oriented parallel to the first lateral side surface, and a bevel extending from the top surface to the second lateral side surface. Each spline of the mandrel also includes a pocket in the second lateral side surface extending radially from a bottom surface of a trough to the bevel.

Abstract: A shock tool for reciprocating a drillstring includes an outer housing. The outer housing has a central axis, a first end, a second end opposite the first end, and a passage extending axially from the first end to the second end. In addition, the shock tool includes a mandrel assembly coaxially disposed in the passage of the outer housing and configured to move axially relative to the outer housing. The mandrel assembly has a first end axially spaced from the outer housing, a second end disposed in the outer housing, and a passage extending axially from the first end of the mandrel assembly to the second end of the mandrel assembly. The mandrel assembly includes a mandrel and a first annular piston fixably coupled to the mandrel. The first annular piston is disposed at the second end of the mandrel assembly and sealingly engages the outer housing.