Method for testing cementing strength of cement first cementing surface of oil well

Abstract

The invention discloses a method for testing the cementing strength of a cement first cementing surface of an oil well. The method comprises the steps of: (1) making a simulated casing-cement ring combined structure sample; (2) vertically placing the simulated casing-cement ring combined structure sample, and clamping the two ends on a hydraulic tensile testing machine; starting the testing machine, loading the sample slowly and uniformly to obtain a yield load value F; stopping loading immediately after the sample is broken, obtaining the load value at this time which is the maximum load value F<max>; reading the extension length L of a yield stage on a force-extension graph; calculating the cementing strength between a cement stone and the parallel portion of a metal tensile rod, that is, the cementing strength of the cement first cementing surface. The method for testing the cementing strength of the cement first cementing surface of the oil well is reliable in principle, easy and convenient to operate, can simultaneously test the cementing strength and the tensile strength of the cement stone, optimizes the cement slurry formula, obtains a cement slurry system meeting on-site construction requirements, and has broad market application prospect.

Description

technical field [0001] The invention relates to a method for testing the bonding strength of the first bonding surface of oil well cement during the cementing process of oil and gas wells in the field of oil and natural gas exploration and development. Background technique [0002] As exploration and development move towards deep formations, cementing engineering faces more and more severe challenges and difficulties. Conditions such as high temperature, high pressure, high acidity and complex loads have increasingly higher requirements on the integrity of the cement sheath. Cementing engineering is an important link in drilling operations, and it is the key to ensure the normal operation of downhole follow-up operations. The strength of cementing surface of well cementing will directly affect the effective development of oil and gas wells. [0003] For oil and gas wells, the most common failure is the failure of the bonding interface; for brittle materials, the bonding str...

AI Technical Summary

Problems solved by technology

Although scholars at home and abroad have conducted some research on the cementation performance of the joint surface, there is no simple and easy-to-operate method to test the cementation strength of the cemented surface, and there is no uniform standard for the test of the cemented surface cementation strength. The main problems are as follows:

[0005] (1) At present, most of the devices for testing the strength of the cemented surface have problems such as complex structure, large volume, and difficult real-time operation.

For example, "An Experimental Device and Method for Testing the Bonding Strength of the Cement Sheath and the Casing" (CN106593414 A), although the formation pressure can be simulated, the operation process is cumbersome and the device is relatively complicated. For the laboratory, a large number of cement materials need to be tested for bonding. In terms of surface strength, it is not convenient and feasible

[0006] (2) The test of the strength of the cemented surface alone cannot measure other properties of the material at the same time

For example, "A device and method for testing the bond strength of well cement" (CN 105092465 A), the conventional extrusion method is used to measure the bond strength of cement stones. Although the device has been improved, the test method is relatively simple

[0007] (3) Conventional cement stone tensile strength test, in addition to split tensile, there are few other test methods

Because the split tensile method is an indirect test, the tested strength deviates greatly from the true value

And other tensile tests are more complicated and not easy to operate, such as "oil well cement high temperature and high pressure tensile stress-strain system and test method thereof" (CN 102401770 A), utilize the stress-strain system to test the tensile stress of cement stone, there is no experimental Universal operability indoors

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