Abstract: A drilling system and method for drilling a well bore in to an earth formation is provided with drilling means for drilling a well bore and pumping means for pumping drilling fluid into the wellbore during drilling. Also provided is a drilling outlet system for retrieving drilling fluid from the well bore. The drilling fluid outlet system has choke means for choking the return flow of retrieved drilling fluid, and alternating means for alternating the flow direction through the choking means.

Abstract: A system comprising a drilling vessel, a riser connected to the drilling vessel, a drillstring within the riser, the drillstring extending into a borehole, a drill bit connectable to the drillstring, a pump system comprising an inlet in the riser and an outlet to the drilling vessel, and a pump controller adapted to control a pressure within the riser and the borehole by raising or lowering a fluid level within the riser.

Abstract: A drilling system for drilling a bore hole into an earth formation, the bore hole having an inside wall. A drill string reaches into the bore hole from a surface, leaving a drilling fluid return passage between the drill string and the bore hole inside wall. A bottom hole assembly is supported by the drill string, and a drilling fluid discharge conduit is provided in fluid communication with the drilling fluid return passage. A drilling fluid is pumped through the drill string into the bore hole and to the drilling fluid discharge conduit via the drilling fluid return passage. Means are provided for obtaining information on the existing down hole pressure of the drilling fluid in the vicinity of the bottom hole assembly and back pressure means for controlling the drilling fluid back pressure.

Abstract: Drilling system and method for drilling a bore hole into an earth formation, the bore hole having an inside wall. A drill string reaches into the bore hole and leaves a drilling fluid return passage between the drill string and the bore hole inside wall. A drilling fluid discharge conduit is in fluid communication with the drilling fluid return passage, and pump means are provided for pumping a drilling fluid through the drill string into the bore hole and to the drilling fluid discharge conduit via the drilling fluid return passage. The drilling fluid back pressure is controlled utilizing back pressure control means for controlling back pressure means. The system further provides fluid injection means comprising an injection fluid supply passage fluidly connecting an injection fluid supply with the drilling fluid return passage and further comprising an injection fluid pressure sensor arranged to provide a pressure signal in accordance with an injection fluid pressure in the injection fluid supply passage.

Abstract: The invention relates to a drilling system and method for drilling a well bore into an earth formation, comprising: drilling means for drilling a well bore; pumping means for pumping drilling fluid into the well bore during drilling; and a drilling fluid outlet system for retrieving drilling fluid from the well bore, said drilling fluid outlet system comprising choke means for choking the return flow of retrieved drilling fluid, and alternating means for alternating the flow direction through the choking means.

Abstract: A hydraulic motor for use in subterranean drilling operations in which a drive fluid within a first reservoir is forced through the motor by a high pressure working fluid, such as drilling mud, the drive fluid entering a second reservoir upon exiting the motor. Upon a change in valving, the drive fluid in the second reservoir is forced through the motor by the high pressure working and back into the first reservoir.