1
Roger Fincher, Larry Watkins, Friedhelm Makohl, Detlef Hahn: Method and apparatus for drilling boreholes in earth formations (drilling liner systems). Baker Hughes Incorporated, Madan Mossman & Sriram P C, March 6, 2001: US06196336 (187 worldwide citation)

A drilling liner having a core bit at its bottom end is carried along with a pilot bit on an inner bottom hole assembly driven by a downhole mud motor. In one embodiment, the motor is powered by mud carried by an inner string. Alternatively, the inner string may be omitted and the flow of mud throug ...


2
Detlef Hahn, Friedhelm Makohl: Apparatus and method for simultaneous drilling and casing wellbores. Baker Hughes Incorporated, Madan Mossman & Sriram P C, July 16, 2002: US06419033 (169 worldwide citation)

The present invention provides apparatus and method for drilling a wellbore wherein a pilot wellbore section is drilled with a bit which section is enlarged by a trailing underreamer to the desired size. One or more steering sections between the underreamer and the drill bit are utilized for maintai ...


3
Detlef Hahn, Volker Peters, Cedric Rouatbi: Oscillating shear valve for mud pulse telemetry. Baker Hughes Incorporated, Madan Mossman & Sriram P C, September 30, 2003: US06626253 (56 worldwide citation)

An anti-plugging oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through ...


4
Detlef Hahn, Volker Peters, Cedric Rouatbi: Hydraulically balanced reciprocating pulser valve for mud pulse telemetry. Baker Hughes Incorporated, Madan Mossman & Sriram P C, May 24, 2005: US06898150 (50 worldwide citation)

A reciprocating pulser system for generating pressure fluctuations in a flowing drilling fluid comprising a reciprocating poppet and a stationary valve assembly with axial flow passages. The poppet reciprocates in close proximity to the valve assembly, at least partially blocking the flow through th ...


5
Detlef Hahn, Volker Peters, Cedric Rouatbi, Eckard Scholz: Reciprocating pulser for mud pulse telemetry. Baker Hughes Incorporated, Madan Mossman and Sriram, August 26, 2008: US07417920 (30 worldwide citation)

A method of transmitting pressure pulses from a downhole location through a flowing fluid in a wellbore comprises using a linear actuator to controllably move a reciprocating member axially back and forth between a first position and a second position to at least partially obstruct flow of the flowi ...


6
Detlef Hahn, Volker Peters, Cedric Rouatbi, Heiko Eggers: Oscillating shear valve for mud pulse telemetry and associated methods of use. Baker Hughes Incorporated, Madan Mossman & Sriram P C, December 13, 2005: US06975244 (25 worldwide citation)

An oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through the stator an ...


7
Detlef Hahn, Volker Peters, Cedric Rouatbi, Heiko Eggers: Downlink pulser for mud pulse telemetry. Baker Hughes Incorporated, Madan Mossman & Sriram P C, July 31, 2007: US07250873 (19 worldwide citation)

A mud pulse telemetry system comprises a surface located fluid supply line having a drilling fluid flowing therein. A non-venting pulser is disposed in the drilling fluid in the supply line, and the non-venting pulser is adapted to generate pressure fluctuations in the flowing drilling fluid. A down ...


8
Detlef Hahn, Volker Peters, Cedric Rouatbi, Heiko Eggers: Oscillating shear valve for mud pulse telemetry. Baker Hughes Incorporated, Madan Mossman & Sriram P C, October 9, 2007: US07280432 (18 worldwide citation)

An oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through the stator an ...


9
Detlef Hahn, Volker Peters, Cedric Rouatbi, Heiko Eggers: Oscillating shear valve for mud pulse telemetry. Baker Hughes Incorporated, Cantor Colburn, October 5, 2010: US07808859 (17 worldwide citation)

An oscillating shear valve system for generating pressure fluctuations in a flowing drilling fluid comprising a stationary stator and an oscillating rotor, both with axial flow passages. The rotor oscillates in close proximity to the stator, at least partially blocking the flow through the stator an ...


10
Sven Krueger, Gerald Heisig, Detlef Hahn, Volker Krueger, Peter Aronstam, Harald Grimmer, Roger Fincher, Larry Watkins: Active bottomhole pressure control with liner drilling and completion systems. Baker Hughes Incorporated, Mossman Kumar & Tyler PC, September 6, 2011: US08011450 (12 worldwide citation)

One exemplary APD Device is used with a liner drilling assembly to control wellbore pressure. The APD Device reduces a dynamic pressure loss associated with the drilling fluid returning via a wellbore annulus. Another exemplary APD Device is used to control pressure in a wellbore when deploying well ...