Universal roller type variable diameter centralizer

Abstract

The invention relates to a universal roller reducing centralizer. The centralizer comprises a body, an upper joint, a reducing mechanism and a universal roller mechanism. The reducing mechanism is located inside the body and the upper joint, a piston and a piston rod of the reducing mechanism are located inside the upper joint, a guide block is pushed by the piston under the effect of a reset spring and a drilling fluid, the universal roller mechanism is placed in grooves evenly distributed in the peripheral direction, outside the body, a core pin can move back and forth under the effect of hydraulic pressure and spring force, a universal roller is mounted on a plunger through an axle, cone steps are formed in the outer surface of the core pin and can drive the plunger to move outwards, and therefore the working outer diameter of the centralizer is changed, when the hydraulic pressure is reduced to the minimum, the outer diameter of the centralizer is the minimum, and it is convenient for a drill string to trip in and trip out. The situations can be achieved that the outer diameter of the centralizer is tightly close to well wall in real time and has the anti-friction effect, and the centering degree of the drill string, the well wall quality and the drilling efficiency are improved.

Description

technical field [0001] The invention relates to a downhole tool used for oil drilling and well cementing, in particular to a universal roller type variable diameter centralizer which utilizes the pressure of drilling fluid to change the diameter to realize drag reduction and centralization. Background technique [0002] In the drilling operations of horizontal wells, directional wells and conventional wells in oil and gas fields, due to the gravity and the complex mutual force between the drill bit and the formation, the drill string is prone to deflection or easy to lie on the well wall, making it difficult to center and seriously affect drilling quality. The diameter of the centralizing block of the conventional drill string centralizer cannot be changed, and the centralization accuracy is not high. It has limited effect on improving the centering degree of the drill string, and it cannot play a centralizing role at all in the loose well section and the well wall expansion...

AI Technical Summary

Problems solved by technology

[0004] In order to solve the problems described in the background technology that the centralization accuracy is not high, the centering effect is limited, the frictional resistance of the borehole wall is large, and the centralization effect cannot be achieved at all in the loose well section and the enlarged well section of the well wall, the present invention provides a universal Roller-type variable-diameter centralizer, by controlling the hydraulic pressure to push the core rod, the core rod relies on the inclined surface to push the plunger to move, thereby driving the universal roller to expand outward to change the working outer diameter of the centralizer, so that the universal roller can be close to the well wall in real time and Has the effect of reducing resistance

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