Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Patent
1991-04-26
1993-02-16
Novosad, Stephen J.
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
175 94, 175 99, 175 38, 175230, 1753253, 175 76, E21B 418, E21B 420, E21B 708, E21B 4400
Patent
active
051862646
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device provided in a rotary drilling system which connects it to a surface facility a drilling tool to guide the latter in a well and exert a hydraulic force thereon in order to move it along the well.
Wells of the petroleum type are usually drilled by means of a drill bit located at the bottom end of a string of hollow pipes (drilling system). The operator uses a brake to place the system partially on the bottom of the hole such that the lower part of the drill string is compressed, and he simultaneously rotates the drill string by means of a rotary table.
An improvement on this method appeared with the use of downhole rotating motors which limit power losses caused by friction of the pipes against the well walls, and which allow better control of any deviations by allowing bent connectors to be installed in the non-rotating part of the string.
However, although rotation of the drill bit is improved in this way, bottom compression of the lower part of the string, called "tool weight", is not always well controlled from the surface.
The appearance on the market of downhole sensors (such as strain gauges, accelerometers, recorders, etc.) revealed extremely vigorous dynamic behavior at the bottom of the system: tool bouncing, temporary jamming, etc. These operating modes usually waste mechanical power and cause excess equipment wear as well as, sometimes, breakage of the drill string or bit, requiring costly retrieval operations.
Some types of equipment such as lengthwise-vibration dampers and stabilizers have been developed in the attempt to control these dynamic phenomena. In practice, stabilizers considerably increase friction and widen the hole, which fairly soon offsets the centering function sought after.
Since vibration modes are variable and poorly known, dampers are often ineffective.
These drilling drawbacks are particularly harmful in very deep and/or sharply sloping wells. Control of tool weight then fails altogether, and the torque required at the surface approaches and sometimes exceeds the capacity of the equipment. Moreover, maintenance of the desired path, achieved by modifying the weight applied and the position and diameter of the stabilizers, becomes extremely difficult and often demands lengthy, expensive corrective maneuvers.
Devices are known for applying a lengthwise force to a drilling tool and increasing its penetration capability into formations during drilling. Such devices are described for example in U.S. Pat. Nos. 3,138,214, 3,225,843, etc. They are particularly useful in slanting holes where the gravitational force component actually applied to the tool is inadequate to make it progress. Devices of this type have a body attached to the system and a sleeve provided around the body and designed to move lengthwise thereto. This sleeve is provided with anchoring pistons that are radially displaceable from a retracted position to an extended position in which they become anchored in the well wall and immobilize the sleeve in the well. The power necessary to extend the pistons is generally obtained from the circulation of drilling mud. The device also has several hydraulic jacks to move the body lengthwise relative to the sleeve when it is in the anchoring position. The power necessary for this translational movement is obtained directly by circulation of mud in the drilling system or by a pump driven by rotation of the body relative to the sleeve and designed to raise the pressure of the mud injected into the jack.
Devices of this type do drive the drilling tool forward, but they are controlled from the surface by operators who, according to information from downhole instruments, anchor the sleeve, slide the body relative to the anchored sleeve, release the sleeve, and return the device to its original position before sliding, then start a new anchoring-extension cycle.
The device according to the invention avoids the above-mentioned disadvantages by automating the operating cycles involving immobilization of the outer sleeve and movement of the d
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Institut Francais du Pe'trole
Novosad Stephen J.
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