The present invention relates in general to wellbore drilling operations.
In conventional drilling operations, mud or other drilling fluid is pumped down a hollow bore in the drill string and is ejected from the drill bit to lift the drill cuttings out of the bore-hole.
In an inclined well-bore, at a certain deviation or sail angle, some of the drill cuttings being transported back to the surface by the drilling fluid fall out of the main flow and settle on the lower portion of the bore-hole forming a cuttings bed. These cuttings interfere with the drilling process and with the rotation of the rotating drill-pipe which also lies on the low side of the bore-hole. The cuttings bed may also jam up against the bottomhole assembly of the drillstring, leading to stuck pipe and potentially significant lost time and hole damage.
Therefore, it is a desire to provide an apparatus or method to alleviate the problem associated with cuttings beds.
In view of the foregoing, and other considerations, the present invention relates to detecting cuttings bed in a downhole environment.
Accordingly, systems and methods for detecting a cuttings bed are disclosed. In one example, a system for detecting includes a drill bit and a drillstring. The drillstring includes a cuttings bed detector to detect the cuttings bed. The cuttings bed detector is positioned uphole of the drill bit.
In another example, a system for detecting a cuttings bed includes a section of casing with a cuttings bed detector.
In another example, a system for detecting a cuttings bed includes a section of casing with an ultrasonic source, a drillstring with an ultrasonic receiver, and a cuttings bed detector that includes the ultrasonic source and the ultrasonic receiver.
In another example, a method for detecting a cuttings bed includes the steps of positioning a drill bit downhole, and positioning a cuttings bed detector uphole of the drill bit.
The foregoing has outlined some of the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific example, when read in conjunction with the accompanying drawings, wherein:
Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views.
As used herein, the terms “up” and “down”; “upper” and “lower”; “uphole” and “downhole”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms “up,” “upper,” “uphole,” and other like terms are meant to indicate a position that is closer to the surface along the linear distance of the borehole. It is noted that through the use of directional drilling, a wellbore may not extend straight up and down. Thus, these terms describe relative positions along with the wellbore.
As drillstring 14 advances through borehole 16, the drill bit 28 drills the formations and generated drill cuttings that must be removed. The mud flow through the drill bit serves to cool and lubricate the drill bit, and to remove the drill cutting and carry them to the surface in the mud flow through the annulus between the drill string and the borehole wall. Cuttings may fall out of the mud flow and settle in a location in the borehole 16. Typically, cuttings bed 24 forms at locations such as where the mud flow fluid velocity drops below the level required to carry the cuttings produced by the drill bit, or in places where the fluid velocity is suddenly reduced. For example, cuttings bed 24 may be formed at casing points where the hole size increases, as well as where the flow area in the annulus increases because of a reduction in the diameter of the drill string, such as at the top of the bottomhole assembly 26. In addition, borehole angles close to the angle of repose for cuttings may be more likely to cause the formation of cuttings bed 24 due to avalanching, such as a borehole with an angle of about 60 degrees.
As will be described in more detail later, a cuttings bed detector may be located on the drill string, or it may be located in a casing or other equipment installed in a borehole. In one example, data from detector located in the drill string is transmitted to surface device via a wired drill pipe system. In another example, data from a detector located in the casing may be transmitted to the surface device via a wired casing structure. In some examples data may be collected by a sensor in one of the drill string or the casing, and then transmitted to a receiver in the other for retransmission to the surface. For example, a cuttings bed detector may be located in a casing and it may transmit data to a receiver in a drill string, and the data may be retransmitted to the surface via a wired drill pipe structure. In another example, a sensor may be mounted in a drill string and the data may be transmitted to a receiver located in a casing structure and then retransmitted to the surface through a wired casing structure.
Cuttings bed detectors are any device that may detect the presence of a cuttings bed in the wellbore or that may determine an increased likelihood of a cuttings bed based on measurements. Examples of such devices include shallow nuclear density measurement, ultrasonic measurement, low-frequency pulse echo, acoustic attenuation measurement, pressure transducer array, and mechanical detection. Specific examples of cuttings bed detectors will be described later.
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System 10 also includes cuttings bed remover 40 mounted on drillstring 14. A cuttings bed remover is any device that is able to remove or reduce a cuttings bed. In one example, a drilling team or surface device 32 may control remover 40 via system 34, or other telemetry devices. In another example, cuttings bed detector 30 may communicate directly with remover 40, activating remover 40 upon detecting cuttings bed 24. In this manner, remover 40 may be combined with any of the disclosed cuttings bed detection systems to provide a closed loop control system without the need for telemetry to the surface.
In one example, cuttings bed remover 40 includes retractable impellors 41. Retractable impellors 41 may include vanes that are pushed out from the tool body into the annulus to move the cuttings. Remover 40 may include an electrical actuator that is initially configured so that the differential pressure between the interior and exterior of remover 40 keeps the vanes retracted. Motivating the actuator flips the differential pressure to move the vanes outside of remover 40. In another example of remover 40, drillstring 14 includes fixed impellors 43 distributed along the length of drill string 14 or at changes in the drillstring diameter, e.g., above the collars.
In another example, cuttings bed remover 40 may disperse cuttings bed 24 using fluid jetting. Drillstring 14 may include one or more valves 45. When positioned in the region of cuttings bed 24, valve 45 may be opened to release fluid to disturb the cuttings. Typically, this action would be combined with increasing the total mud flow rate so that the flow through bit 28 remains constant. The fluid flow may be pulsed and oriented, e.g., circumferentially to move cuttings at the bottom side of the hole, or upwards to move the cuttings up the hole. In another example, remover 40 may include a fluid by-pass valve to allow the system pressure drop to be maintained while increasing the carrying capacity of the annular fluid through increased velocity. With increased fluid flow, the valve need not necessarily be positioned proximate to cuttings bed 24.
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In one example of system 10g, casing mounted cutting bed detector 60 detects cuttings bed 24 using ultrasonic measurements. In this example, source 62 includes an ultrasonic source and receiver 64 includes an ultrasonic sensor. In another example, detector 60 detects bed 24 using sonic measurements. In this example, source 62 includes a sonic source and receiver 64 includes a sonic sensor. The sonic source and sonic receiver may be positioned fairly close to each other, e.g., a few inches apart. Detector 60 measures the time of travel between source 62 and receiver 64. A fluid borne wave may be significantly slower with cuttings bed 24 present. In another example, detector 60 utilizes a low frequency pulse echo to detect cuttings bed 24.
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Alternatively, or in addition to wired casing system 34, system 10 may include a wired drill pipe system 72 to transmit or relay data from downhole to further uphole, such as surface device 32. For example, drillstring 14 may include several communicatively connected tubular members 74. In the examples shown in
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From the foregoing detailed description, it should be apparent that a system and method for detecting cuttings beds that is novel has been disclosed. Although specific embodiments have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed examples without departing from the spirit and scope of the invention as defined by the appended claims which follow.