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Method for measuring wall thickness of downhole casing

A casing wall and thickness measurement technology, which is applied in earthwork drilling, wellbore/well components, sealing/isolation, etc., to eliminate the influence of cement sheath on the counting rate of detectors and improve the accuracy

Inactive Publication Date: 2013-06-26
CHINA NAT PETROLEUM CORP CHUANQING DRILLING ENG CO LTD
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AI Technical Summary

Problems solved by technology

The "Expansion Tube Wall Thickness Calculation Study" described later is only suitable for measuring the wall thickness of the expansion tube

Method used

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  • Method for measuring wall thickness of downhole casing
  • Method for measuring wall thickness of downhole casing
  • Method for measuring wall thickness of downhole casing

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Experimental program
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Embodiment Construction

[0021] A downhole casing wall thickness measurement method, according to the counting rate curve of the far and near detectors, eliminate the influence of formation density and cement sheath density on the casing wall thickness calculation value, and use the regression method to establish a casing wall thickness calculation formula to calculate Casing wall thickness.

[0022] The specific process is as follows:

[0023] ①According to the near detector count rate (TL) and the far detector count rate (PL), the regression method is used to establish the calculation method of casing wall thickness:

[0024] TH=TH ST - K*LN(TL / TL ST )+LN(PL / PL ST )+△TH

[0025] In the above formula, TH is the calculated wall thickness value, TH ST is the standard casing wall thickness, K is the scale coefficient, TL is the near detector count rate value, TL ST is the average counting rate value of the standard well section, PL is the far detector counting rate value, PL ST is t...

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Abstract

The invention discloses a method for measuring the wall thickness of a downhole casing, comprising the following steps of: eliminating the influence of stratum density and cement sheath density on the calculated value of the wall thickness of the downhole casing according to a counting rate curve of a distance detector; and establishing a calculation formula of the wall thickness of the downhole casing to figure out the wall thickness of the downhole casing by utilizing a regression method. The calculation is carried out by adopting the counting rate of the distance detector and the influenceof a stratum and a cement sheath on the counting rate of the distance detector when the stratum density and the cement sheath density are different is eliminated, thereby the calculation accuracy of the wall thickness of the downhole casing is improved.

Description

technical field [0001] The invention relates to a method for measuring casings in oil fields, in particular to a method for measuring the wall thickness of downhole casings, which is suitable for damage evaluation of downhole casings. Background technique [0002] The current gamma density casing wall thickness measurement method only uses the count rate value near the detector for calculation, and does not use the count rate value of the far detector, and does not consider the difference in the density of the formation density and the cement sheath. Due to the influence of Ma photon counting rate, there is a large difference between the calculated casing wall thickness and the actual casing wall thickness, which affects the next construction decision. The main reasons for the above problems are: ① the existing calculation method only uses the near-detector count rate value for calculation; ② does not consider the scattering and absorption of gamma photons by the formation w...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): E21B49/00E21B33/14
Inventor 吉人殷增华刘文龙赵中明
Owner CHINA NAT PETROLEUM CORP CHUANQING DRILLING ENG CO LTD
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