Wells – Processes – With indicating – testing – measuring or locating
Reexamination Certificate
1998-09-11
2001-01-30
Will, Thomas B. (Department: 3673)
Wells
Processes
With indicating, testing, measuring or locating
C166S206000, C175S096000, C175S230000
Reexamination Certificate
active
06179055
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a tool conveyance system, and more particularly, to a method and apparatus for conveying a tool along a non-vertical well.
To economically produce hydrocarbons from a reservoir, it has become increasingly common to drill a borehole, through an earth formation, which deviates from the traditional vertical orientation. The deviation may result from drilling a borehole using either a sharp or gradually increasing angle away from the vertical axis. The deviation may also result from drilling a borehole which extends horizontally from a vertical shaft. Generally the formations surrounding such deviated or horizontal boreholes are logged, and the wells completed, with tools lowered into the wellbore on a wireline or cable. Such tools usually depend upon the force of gravity to convey the tool along the well or borehole. However, when the borehole is drilled at a sufficiently high angle, or the inner surface of the well is particularly rough, the force of gravity is insufficient to overcome the friction of the tool and wireline against the inner surface of the well. Stiff devices, such as drill pipe and coiled tubing, have been used for pushing logging tools along horizontal and highly deviated boreholes. Drill pipe and coiled tubing conveyance are not ideally suited to all conditions, however. For instance, connecting and disconnecting drill pipe can be very labor-intensive and expensive, and coiled tubing conveyance is limited because of helical buckling of the tubing.
Previous attempts to propel tools along a deviated well bore have included providing such tools with driven wheels for tractoring the tools along the well, or with gripping feet hydraulically extended from the outside of the tool. Packaging such systems within the diameter of some well tools can be difficult, however, and may lead to non-optimal solutions. For instance, packaging motors powerful enough to drive wheels extending from the tool often requires the motors to be coupled to their respective wheels through 90 degree gear boxes. The distance to which gripping feet may be extended from the surface of the tool is also typically limited by packaging limitations and the required bore length of an associated actuating cylinder mounted across the tool. Many of the means developed for driving large pipeline inspecting and cleaning machines along pipe bores are not applicable to conveying tools along wellbores, simply due to the size restrictions of the small diameter bores. Many well casings are not more than about four or six inches in diameter.
Furthermore, electrically powered downhole systems should be as efficient as possible to reduce wireline current and the losses associated with transporting such current over extremely long cables. Unfortunately, increasing cable diameter to supply more power, either hydraulic or electric power, also increases the force required to drag the heavier cable along a horizontal well bore.
Thus, a more economical and expedient means of conveying a tool through the horizontal or highly deviated portion of a borehole is desired. Ideally, a conveyance apparatus will be able to readily adapt to a large variety of different inner diameters along the same well. Preferably, a conveyance tool which engages the inside surface of the well would also reliably disengage the well surface upon a loss of power or other foreseen failure, to enable the tool to be safely retrieved.
SUMMARY OF THE INVENTION
The present invention features an improved downhole conveyance system for conveying tools, such as logging tools, along a non-vertical well.
According to one aspect of the invention, an apparatus for conveying a tool along a non-vertical well is provided. The apparatus includes an elongated housing adapted to be attached to a tool to be conveyed, a cam anchor arranged to extend laterally from the housing and pivotably attached to the housing at a linearly displaceable pivot point, and an actuator operatively connected to the housing and constructed to linearly displace the cam anchor pivot point along the housing. The cam anchor has an arcuate cam surface for slidingly engaging an inner surface of the well as the cam anchor pivot point is displaced in a first direction, and for gripping the inner surface of the well as the cam anchor pivot point is displaced in a second direction, to convey the tool along the well.
Preferably, the apparatus has first and second such cam anchors attached to the housing at respective pivot points spaced along the housing, with the arcuate cam surfaces of the cam anchors aligned in a common direction. First and second such actuators are constructed to separately displace the pivot points of the first and second cam anchors, respectively, to convey the tool along the well.
In some presently preferred embodiments, the cam anchor is adapted to pivot about its pivot point to a retracted position, with its arcuate cam surface disengaged from the inner surface of the well. In some cases a spring is arranged to bias the cam anchor toward its retracted position.
In some embodiments, the cam anchor has a pair of oppositely directed anchor members pivotably attached to the housing at a common pivot point and arranged to simultaneously engage opposing portions of the inner surface of the well. Both anchor members are preferably adapted to pivot about their common pivot point to retracted positions with their arcuate cam surfaces disengaged from the inner surface of the well, the apparatus having spring arranged to bias both anchor members toward their retracted positions.
In some cases, the cam anchor has a plurality of projections extending from its arcuate cam surface for gripping the inner surface of the well. These projections are preferably of a hard, durable material, such as carbide.
The inner surface of the well may consist of earth or well casing, for example.
In some embodiments, the conveyed tool contains both a logging sensor responsive to a downhole well characteristic, and electronics adapted to activate the actuator.
Preferably, the apparatus is adapted to automatically retract the cam anchor to its retracted position upon a loss of power. In one presently preferred embodiment, the apparatus includes a retract assembly comprising the cam anchor and a cocking piston. The retract assembly is linearly displaceable along a housing slot by the actuator between forward and rearward positions, with the cocking piston extending from the retract assembly and arranged to engage a surface of the housing at one end of the slot and to be compressed by the housing as the retract assembly is displaced to its forward position, thereby urging the cam anchor toward its extended position.
In some embodiments, the retract assembly includes a retract assembly housing, a retract piston, and an extension spring. The retract piston is disposed within a bore of the retract assembly housing and connected to the pivot point of the cam anchor. The retract piston is in hydraulic communication with the cocking piston and adapted to be displaced within the housing bore to move the pivot point as the cocking piston is compressed. The extension spring is connected to the retract assembly housing and the cam anchor and arranged to urge the cam anchor toward its extended position as the cocking piston is compressed.
In one preferred embodiment, the retract assembly includes a first one-way check valve arranged to enable hydraulic flow from the cocking piston to the retract piston as the cocking piston is compressed, a normally open solenoid valve arranged to enable hydraulic flow from the retract piston to the cocking piston in the absence of electrical voltage at the solenoid, and a spring arranged to bias the retract piston toward a cam-retracting position. Preferably, the apparatus also defines a compensation cavity in hydraulic communication with the retract piston and adapted to receive hydraulic fluid from the retract assembly when the solenoid valve opens and the cocking piston is blocked from fully extending.
Accordi
Post Roger A.
Roy Carl J.
Sallwasser Alan J.
Jeffery Brigitte L.
Lee Jong-Suk
Ryberg John J.
Schlumberger Technology Corporation
Will Thomas B.
LandOfFree
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