Boring or penetrating the earth – Automatic control
Reexamination Certificate
2001-06-11
2004-10-26
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Automatic control
C175S045000, C175S073000
Reexamination Certificate
active
06808027
ABSTRACT:
FIELD OF INVENTION
The present invention relates to the field of oil and gas drilling. More specifically the present invention relates to an apparatus and method for selecting or controlling, from the surface, the direction in which a wellbore proceeds.
A drill operator often wishes to deviate a wellbore or control its direction to a given point within a producing formation. This operation is known as directional drilling. One example of this is for a water injection well in an oil field which is generally positioned at the edges of the field and at a low point in that field (or formation).
In addition to controlling the required drilling direction, the formation through which a wellbore is drilled exerts a variable force on the drill string at all times. This along with the particular configuration of the drill can cause the drill bit to wander up, down, right or left. The industrial term given to this effect is “bit-walk” and many methods to control or re-direct “bit-walk” have been tried in the industry. The effect of bit walk in a vertical hole can be controlled, by varying the torque and weight on the bit while drilling a vertical hole. However, in a highly inclined or horizontal well, bit-walk becomes a major problem.
BACKGROUND OF THE INVENTION
At present, in order to deviate a bole left or right, the driller can choose from a series of special downhole tools such as downhole motors, so-called “bent subs” and more recently a steerable motors.
A bent sub is a short tubular that has a slight bend to one side, is attached to the drill string, followed by a survey instrument, of which an MWD tool (Measurement While Drilling which passes wellbore directional information to the surface) is one generic type, followed by a downhole motor attached to the drill bit. The drill is lowered into the wellbore and rotated until the MWD tool indicates that the leading edge of the drill bit is facing in the desired direction. Weight is applied to the bit through drill collars and, by pumping drilling fluid through the drill string, the downhole motor rotates the bit.
U.S. Pat. No. 3,561,549 relates to a device which gives sufficient control to deviate and start an inclined hole from or control bit-walk in a vertical wellbore. The drilling tool has a non-rotating sleeve with a plurality of fins (or wedges) on one side is placed immediately below a downhole motor in turn attached to a bit.
U.S. Pat. No. 4,220,213 relates to a device which comprises a weighted mandrel. The tool is designed to take advantage of gravity because the heavy side of the mandrel will seek the low-side of the hole. The low side of the wellbore being the side furthest away from the vertical.
U.S. Pat. No. 4,638,873 relates to a tool which has a spring-loaded shoe and a weighted heavy side which can accommodate a gauge insert held in place by a retaining bolt.
U.S. Pat. No. 5,220,963 discloses an apparatus having an inner rotating mandrel housed in three non-rotating elements.
Thus, it is known how to correct a bit-walk in a wellbore. However, if changes in the forces that cause occur while drilling, all the prior art tools must be withdrawn in order to correct the direction of the wellbore. The absolute requirement for tool withdrawal means that a round trip must be performed. This results in a compromise of safety and a large expenditure of time and money.
The applicant's own previous patent application WO 96/31679 and U.S. Pat. No. 5,979,570 partially addresses the problem of bit-walk in an inclined wellbore. The device described in this patent application and patent comprises eccentrically bored inner and outer sleeves. The outer sleeve being freely moveable so that it can seek the low side of the wellbore, the weighted side of the inner eccentric sleeve being capable of being positioned either on the right side or the left side of the weighted portion of the outer eccentric sleeve to correct in a binary manner for bit walk.
The applicant has now developed an improved downhole tool which can correct for bit walk in a highly inclined wellbore and which is capable of controlling both the inclination and the Azimuthal plane of the well bore.
SUMMARY OF THE INVENTION
In a first aspect, the present invention provides an apparatus for selectively controlling the direction of a well bore, the apparatus comprising:
a mandrel rotatable about a rotation axis; a direction controller means comprising at last two members spaced apart along said mandrel and configured to apply a force to said mandrel with a component perpendicular to the said rotation axis;
a housing having an eccentric longitudinal bore forming a weighted side and being configured to freely rotate under gravity; and
a driver for selectively varying the angle of the force relative to the weighted side of the housing about said rotation axis, the driver being capable of moving the two parts independently of one another.
The provision of a two part direction controller allows more control over the drilling direction in order to drill in a required direction and to compensate for bit-walk. Further, the provision of a two part direction controller allows a null or a zero force to be applied to the mandrel by precessing the direction controller about the mandrel.
The two parts of the direction controller can be configured in a number of different ways. Preferably, the two parts are located on different sides of the central plane. A particularly preferable arrangement is achieved when both of the two parts are capable of applying a independent force to the mandrel. For example, the two parts may be located on either side of the central plane of the housing. For example, both parts may comprise eccentric sleeves.
In an alternative configuration, only one part is capable of applying a radial force to the mandrel, the other part only being capable of applying a symmetric force about the mandrel. For example, one part may be an eccentric sleeve and the other may be a concentric sleeve. If the arrangement is envisaged where a concentric sleeve is located on one side of the central plane and an eccentric sleeve is located on the other, then it is possible to form a so-called “point the bit” arrangement. The eccentric sleeve may be located either above or below the central plane of the housing. Two eccentric sleeves oriented at 180° to each other about the mandrel can also achieve this effect.
References have been made to the at least one part being eccentrically bored. However, it should be noted that the same effect can be achieved with a sleeve which is spatially symmetric about the rotation axis, but which has a denser material or a weight located at one side of the sleeve.
Further there is no requirement for the direction controller to be a sleeve. A cam or even a linear actuator could be used to the same effect as an eccentric sleeve.
The driver is configured to move the two parts of the direction control means independent of one another. This is applicable regardless of the nature of the direction controller for example if the direction control means comprises a sleeve, cam, linear actuator or another component which can achieve the same result.
Where the direction controller comprises a linear actuator, the actuator may be mounted such that that can move about the circumference of said mandrel to apply a force to the mandrel at the required position. Preferably, a plurality of linear actuators are placed around the circumference of the mandrel. More preferably, at least three actuators are used at equal angles in a plane about said mandrel. The three actuators being capable of applying a force to the mandrel in any direction in a plane about its axis. Therefore, in a second aspect, the present invention provides an apparatus for selectively controlling the direction of a wellbore, the apparatus comprising: a mandrel which is rotatable about a rotation axis;
a direction controller comprising at least one linear actuator configured to apply a force to said mandrel;
a housing having an eccentric longitudinal bore and being configured to freely rotate under gravi
Chance Jack P.
Lasater Jeffrey B.
Marcellus Emerson
McLoughlin Stephen John
Sutherland George B.
Alworth C. W.
Bagnell David
Collins Giovanna
RST (BVI), Inc.
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