Abstract: A dynamically controllable variable displacement axial piston pump is described. In an embodiment, the pump comprises a rotating cylinder with hydraulic pistons that contact the face of a swash plate. The angle of the swash plate can be controlled to thereby control the movement of the pistons, the displacement of the pump, and the power generated by the pump. The dynamically controllable variable displacement axial piston pump may be used in combination with a rotary steerable apparatus, including such an apparatus as described herein that uses hydraulic pistons to actuate the deflection of the bit, or in combination with other downhole tools and devices. When used down hole in a drill string with a drilling mud powered turbine, the dynamically controllable variable displacement pump limits and regulates the power provided to the tool over a wide range of drilling mud weights and flow rates.

Abstract: The rotary steerable drilling tool and system described herein combines both point-the-bit and push-the-bit techniques to actively change the direction of the borehole trajectory. In this system, the deflection of the drill bit is limited to a single degree of freedom relative to a coordinate system that is fixed to and rotates with the rotary steerable drilling tool, resulting in a simplified attachment of the bit assembly and bias unit mechanics. Further, steering of the well is accomplished by dynamically controlling the spatial phase and amplitude of the coherent symmetrical bidirectional reciprocating deflections of the drill bit relative to a fixed terrestrial datum as the tool is rotating, simultaneously pointing and pushing the bit.

Abstract: The rotary steerable drilling tool and system described herein combines both point-the-bit and push-the-bit techniques to actively change the direction of the borehole trajectory. In this system, the deflection of the drill bit is limited to a single degree of freedom relative to a coordinate system that is fixed to and rotates with the rotary steerable drilling tool, resulting in a simplified attachment of the bit assembly and bias unit mechanics. Further, steering of the well is accomplished by dynamically controlling the spatial phase and amplitude of the coherent symmetrical bidirectional reciprocating deflections of the drill bit relative to a fixed terrestrial datum as the tool is rotating, simultaneously pointing and pushing the bit. The amplitude and force of the bit deflections can be variably controlled during steering operations to dynamically adjust the instantaneous build rate as needed. When steering is not active, the bit can be mechanically locked into the neutral position.

Abstract: A drill string caliper includes a mandrel configured to be coupled within a drill string. At least one laterally extensible arm is coupled to an exterior of the mandrel. A biasing device is configured to urge the at least one arm into contact with a wall of a wellbore. A sensor is configured to generate an output signal corresponding to a lateral extent of the at least one arm.

Abstract: A method for acquiring a sample of a virgin fluid from a subsurface formation penetrated by a wellbore surrounded by a layer of contaminated fluid is disclosed. The method includes abutting a first packer against a wall of the wellbore, and extending at least a portion of a second packer beyond the first packer, wherein the second packer is at least partially disposed in the first packer. An inlet to a first flowline is at least partially defined by the first packer, and an inlet to a second flowline is defined by the second packer. The method further includes drawing one of virgin fluid, contaminated fluid and combinations thereof into the first flowline; and drawing virgin fluid into the second flowline.

Abstract: A drill string caliper includes a mandrel configured to be coupled within a drill string. At least one laterally extensible arm is coupled to an exterior of the mandrel. A biasing device is configured to urge the at least one arm into contact with a wall of a wellbore. A sensor is configured to generate an output signal corresponding to a lateral extent of the at least one arm.

Abstract: A drill string caliper includes a mandrel configured to be coupled within a drill string. At least one laterally extensible arm is coupled to an exterior of the mandrel. A biasing device is configured to urge the at least one arm into contact with a wall of a wellbore. A sensor is configured to generate an output signal corresponding to a lateral extent of the at least one arm.

Abstract: Example methods and apparatus to perform pressure testing of geological formations are disclosed. A disclosed example method comprises positioning a testing tool in a wellbore formed in the geological formation, sealing a sample interval around the testing tool, sealing a first guard interval around the testing tool and adjacent to the sample interval, reducing a first pressure in the sample interval, reducing a second pressure in the first guard interval, maintaining a volume of a first chamber fluidly coupled to the sample interval during a time interval, and measuring a plurality of pressure data for a fluid captured in the first chamber during the time interval.

Abstract: Apparatus and methods to control fluid flow in a downhole tool are disclosed. A disclosed example system includes a hydraulically actuatable device having a cavity for receiving pressurized hydraulic fluid stored by a reservoir, a first and a second hydraulic pump, a motor and means for selectively flowing hydraulic fluid from the outlet of at least one of the first and second pumps to the at least one cavity. The first and second hydraulic pumps include an inlet fluidly coupled to the reservoir and an outlet fluidly coupled to the cavity, and the motor is operatively coupled to at least one of the pumps.

Abstract: A formation fluid sampling tool is provided with a drill which drills into the formation in a manner perpendicular or oblique to the borehole wall. The tool comprises a mechanism for enhancing the mobility of the reservoir fluid, such as a heating element on the drill, hot fluid which is generated in the tool and injected into the drilled hole, or a solvent which is stored in the tool and injected by the tool into the drilled hole.

Abstract: A drill string caliper includes a mandrel configured to be coupled within a drill string. At least one laterally extensible arm is coupled to an exterior of the mandrel. A biasing device is configured to urge the at least one arm into contact with a wall of a wellbore. A sensor is configured to generate an output signal corresponding to a lateral extent of the at least one arm.

Abstract: A method for acquiring a sample of a virgin fluid from a subsurface formation penetrated by a wellbore surrounded by a layer of contaminated fluid is disclosed. The method includes abutting a first packer against a wall of the wellbore, and extending at least a portion of a second packer beyond the first packer, wherein the second packer is at least partially disposed in the first packer. An inlet to a first flowline is at least partially defined by the first packer, and an inlet to a second flowline is defined by the second packer. The method further includes drawing one of virgin fluid, contaminated fluid and combinations thereof into the first flowline; and drawing virgin fluid into the second flowline.

Abstract: A method for acquiring a sample of a virgin fluid from a subsurface formation penetrated by a wellbore surrounded by a layer of contaminated fluid is disclosed. The method includes abutting a first packer against a wall of the wellbore, and extending at least a portion of a second packer beyond the first packer, wherein the second packer is at least partially disposed in the first packer. An inlet to a first flowline is at least partially defined by the first packer, and an inlet to a second flowline is defined by the second packer. The method further includes drawing one of virgin fluid, contaminated fluid and combinations thereof into the first flowline; and drawing virgin fluid into the second flowline.

Abstract: Example methods and apparatus to perform pressure testing of geological formations are disclosed. A disclosed example method comprises positioning a testing tool in a wellbore formed in the geological formation, sealing a sample interval around the testing tool, sealing a first guard interval around the testing tool and adjacent to the sample interval, reducing a first pressure in the sample interval, reducing a second pressure in the first guard interval, maintaining a volume of a first chamber fluidly coupled to the sample interval during a time interval, and measuring a plurality of pressure data for a fluid captured in the first chamber during the time interval.

Abstract: A method for acquiring a sample of a virgin fluid from a subsurface formation penetrated by a wellbore surrounded by a layer of contaminated fluid is disclosed. The method includes abutting a first packer against a wall of the wellbore, and extending at least a portion of a second packer beyond the first packer, wherein the second packer is at least partially disposed in the first packer. An inlet to a first flowline is at least partially defined by the first packer, and an inlet to a second flowline is defined by the second packer. The method further includes drawing one of virgin fluid, contaminated fluid and combinations thereof into the first flowline; and drawing virgin fluid into the second flowline.

Abstract: A method for acquiring a sample of a virgin fluid from a subsurface formation penetrated by a wellbore surrounded by a layer of contaminated fluid includes abutting a first packer against a wall of the wellbore, and extending at least a portion of a second packer beyond the first packer, wherein the second packer is at least partially disposed in the first packer. An inlet to a first flowline is at least partially defined by the first packer, and an inlet to a second flowline is defined by the second packer. The method further includes drawing one of virgin fluid, contaminated fluid and combinations thereof into the first flowline; and drawing virgin fluid into the second flowline.

Abstract: Apparatus and methods to control fluid flow in a downhole tool are disclosed. A disclosed example system includes a hydraulically actuatable device having a cavity for receiving pressurized hydraulic fluid stored by a reservoir, a first and a second hydraulic pump, a motor and means for selectively flowing hydraulic fluid from the outlet of at least one of the first and second pumps to the at least one cavity. The first and second hydraulic pumps include an inlet fluidly coupled to the reservoir and an outlet fluidly coupled to the cavity, and the motor is operatively coupled to at least one of the pumps.

Abstract: A probe assembly samples fluid from a wellbore penetrating a subsurface formation having a virgin fluid therein beyond a layer of contaminated fluid surrounding the wellbore. The probe assembly includes a probe body extendable from a downhole tool, and a packer carried by the probe body and having a distal surface adapted for sealingly engaging the wellbore. The packer has an outer and inner periphery, with the inner periphery being defined by a bore through the packer. The packer is further equipped with channel(s) formed in the distal surface and arranged to define an annular cleanup intake intermediate the inner and outer peripheries. The passageway(s) extend(s) through the packer for conducting virgin fluid and/or contaminated fluid between the channel(s). A sampling tube is sealingly disposed in the bore of the packer for conducting virgin fluid to a second inlet in the probe body and the downhole tool.

Abstract: Techniques for reduced contamination formation evaluation are provided. The techniques relate to drawing fluid into a downhole tool positionable in a wellbore penetrating a subterranean formation having a virgin fluid and a contaminated fluid therein. Fluid is drawn into at least two inlets for receiving the fluids from the formation. At least one evaluation flowline is fluidly connected to at least one of the inlets for passage of the virgin fluid into the downhole tool. At least one cleanup flowline is fluidly connected to the inlets for passage of the contaminated fluid into the downhole tool. At least one fluid circuit is fluidly connected to the evaluation flowline and/or cleanup flowlines for selectively drawing fluid therein. At least one fluid connector is provided for selectively establishing a fluid connection between the flowlines. At least one sensor is provided for measuring downhole parameters in one of the flowlines.

Abstract: A hydrostatic transmission system for driving a rotatable member includes a differential having an output coupled with the rotatable member, a first hydrostatic drive having an output coupled to a first input of the differential, and a second hydrostatic drive having an output coupled to a second input of the differential. The output of the first hydrostatic drive is rotatable in a first selected direction and at a first selected speed. The output of the second hydrostatic drive is rotatable in a second selected direction and at a second selected speed. A rotational speed and direction of the output of the differential is related to the algebraic sum of the rotational speeds and directions of the outputs of the hydrostatic drives. In one embodiment, the speeds of the first and second drives are maintained above a minimum stable threshold, while operating the rotatable drive at very low or zero speed, by selecting the first direction to be opposite the second direction.