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Borehole Stepchange Entry Linkage

IP.com Disclosure Number: IPCOM000246476D
Publication Date: 2016-Jun-09
Document File: 9 page(s) / 998K

Publishing Venue

The IP.com Prior Art Database

Abstract

The entry linkage is a mechanical device that allows a tool with collapsible arms to collapse when entering a sudden change in borehole diameter. Some oilfield tools with collapsible arms are fixed in such a way that one end of an arm is pinned and the other end of the arm is free to slide. Because of this arrangement, when a tool enters a section of a well with a sudden decrease in borehole diameter, the edge of this new borehole section may strike the end of the arm that is free to slide. Because the other end is pinned and assuming that the freely sliding end has a limited range of sliding, the arm may not close or may close violently and cause damage to the tool. The entry linkage is pinned in front of the sliding end of the arm. When the borehole changes diameter, the leading edge of the new borehole section strikes the linkage forcing it to rotate. The linkage is fixed inside a sliding groove in the sliding end of the arm or vice versa. This linkage provides a normal force to the arm and thusly applies enough torque to cause the arm to close.

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Title:  Borehole Stepchange Entry Linkage

Abstract:  The entry linkage is a mechanical device that allows a tool with collapsible arms to collapse when entering a sudden change in borehole diameter. Some oilfield tools with collapsible arms are fixed in such a way that one end of an arm is pinned and the other end of the arm is free to slide. Because of this arrangement, when a tool enters a section of a well with a sudden decrease in borehole diameter, the edge of this new borehole section may strike the end of the arm that is free to slide. Because the other end is pinned and assuming that the freely sliding end has a limited range of sliding, the arm may not close or may close violently and cause damage to the tool. The entry linkage is pinned in front of the sliding end of the arm. When the borehole changes diameter, the leading edge of the new borehole section strikes the linkage forcing it to rotate. The linkage is fixed inside a sliding groove in the sliding end of the arm or vice versa. This linkage provides a normal force to the arm and thusly applies enough torque to cause the arm to close.

Description:  The Borehole Stepchange Linkage (BSL) is a device that provides for controlled collapse of arms on oilfield tools when entering immediate and drastic changes in borehole diameter.   

Figure 1: Entry linkage

 It is not uncommon for oilfield tools with collapsible/extendible arms to enter sections of wells with drastically reduced cross-sections. When entering these small sections, there is a risk that the arms of the tool will not close or that they will close but cause damage to the tool. The risk is highest when the change in borehole diameter is greatest. The risk is present in all sorts of arm designs including those utilizing bow-springs, pinned connections, sliding connections, external springs, piston-actuation, and more. The arms may be coupled together or independent. The risk is present in circular and elliptical cross sections as well as other shapes. The risk is independent upon the number of arms.   

                                                      Figure 2: End of view of a three armed tool

Each arm is composed of three parts shown in Figures 3 and 4:

1)      a rigid section on the uphole end of the tool (A)

2)      a bow-spring (B)

3)      a rigid section on the downhole end of the tool (C)

Part A is pinned and free to rotate in the image plane. Part C is free to rotate and slide parallel to the tool’s axis. Parts A and C are connected to part B and therefore coupled together. Part B behaves as the sole actuator for the arm. The tool travels downhole into a borehole section of reduced area shown as the black lines around the tool in Figure 3. It is desired that the tool close from the position in Figure 3 to the position in Figure 4. 

                                                      Figure 3: Open arm state

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