Method for replacing producing well shaft casing pipe

Abstract

The invention relates to a method for replacing a producing well shaft casing pipe. The method sequentially includes the steps of firstly, using a packer to block the inner cavity of a residual casingpipe; secondly, using a hydraulic inner cutter to cut off the abraded casing pipe on the upper portion of the residual casing pipe; thirdly, pulling out the cut casing pipe; fourthly, mounting a casing pipe mill shoe at the bottom of a drilling tool to mill a fish top outer chamfer at the fish top of the residual casing pipe; fifthly, mounting a float collar and a new casing pipe at the upper endof a cementing tool; sixthly, lowering the drilling tool to allow the fish top to smoothly enter an externally-inserted guide shoe, continuously lowering the drilling tool to allow the fish top to reach a lengthening cylinder, and starting a pump to circulate workover fluid; seventhly, injecting cement slurry after the circulation is normal to allow the cement slurry to enter the annulus throughcement injection holes; eighthly, putting in a rubber plug, and pushing the rubber plug to the top of the float collar to achieve setting; ninthly, lowering the drilling tool again until the fish topouter chamfer and a butt joint connector inner chamber are connected in an embedded manner, and pressing down 500kN to achieve casing pipe butt joint and sealing. The method is simple, practicable, convenient to operate, low in production cost and downhole risks, simple in butt joint and setting operation and high in sealing reliability.

Description

technical field [0001] The invention relates to a method for changing the casing of an oil production wellbore. In the construction of replacing the damaged casing of the wellbore, it is used for the butt cementing of the newly replaced casing string in the wellbore and the original remaining casing in the wellbore, which belongs to the overhaul of the wellbore. technology field. Background technique [0002] Oil and natural gas are exploited through the wellbore formed by drilling. The wellbore casing string in the wellbore is formed by screwing the casing one by one through the thread. With the increase of oil and gas well production time, the downhole environment is getting worse and it is easy Breakage of casing. Usually, the cemented casing outside the casing is not easy to be damaged. The bare pipe section above the cemented section is more likely to be damaged due to double-sided corrosion, and sometimes it can be broken into several pieces. In this case, it is neces...

AI Technical Summary

Problems solved by technology

There are many construction steps and complex procedures for undercutting and casing replacement operations, which require the use of undercut drilling tools, which are not suitable for deep well casing replacement operations

This is because during casing undercutting operations, the undercut drilling tool is usually inserted into the casing for undercutting. Due to the small size and low strength of the inserted undercut drilling tool, the backing-off depth is limited

If conventional reverse thread drilling tools are used for reverse threading, the reverse thread position cannot be accurately determined, and it may be reversed into several pieces

If a large casing is inserted and docked, the sealing reliability of the casing butt joint will be poor

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