Device and method for evaluating influences of sudden change of working fluid temperature on mechanical integrity of pit shaft

Abstract

The invention discloses a device and a method for evaluating the influences of the sudden change of the working fluid temperature on the mechanical integrity of a pit shaft. The device comprises a test main body and a working platform, the working plate comprises a computer, the computer is provided with a pressure temperature control terminal, the test main body comprises a support and a kettle body, a simulated surrounding rock-cement ring-cannula assembly is arranged in the kettle body, and the kettle body is provided with a gas feeding and discharging pipeline. The method comprises the following steps: filling an annular space with cement, waiting for setting the cement to form a ring in order to form the simulated surrounding rock-cement ring-cannula assembly, changing the experiment temperature and the experiment pressure according to different downhole conditions, measuring the radial displacement of a cannula by a foil gauge, measuring the circumferential displacement of the simulated surrounding rocks by a circumferential displacement meter, and using a high pressure gas on the end surface of the cement ring to evaluate the failure or not of the sealing of the cement ring. The device and the method have the advantages of reliable principle, simplicity in operation, real simulation of the circulation of a drilling fluid, increase of the influences of the instantaneous reduction of the temperature, caused by the injection of a large amount of a low temperature fluid to the pit shaft during working, on the cannula cement ring, and provision of theoretic basis for the researches of the mechanical integrity of the pit shaft.

Description

technical field [0001] The invention relates to an evaluation device and method based on the impact of sudden temperature changes of the wellbore working fluid on the mechanical integrity of the wellbore in the field of petroleum engineering cementing. Background technique [0002] Oil and gas well cementing operation refers to the process in which cement slurry is injected into the annular space between the downhole casing and the formation, condenses and solidifies within the design time, and forms a cement sheath with a certain strength. In the downhole environment, the cement sheath not only has to bear the erosion of formation fluid, but also needs to ensure the mechanical integrity of the cement sheath under the load caused by different working conditions, and ensure the isolation between layers. [0003] With the current drilling deeper and deeper, the service environment of the cement sheath in the downhole is getting worse, and the formation conditions of high tempe...

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Problems solved by technology

[0005] There are many deficiencies in the above-mentioned testing devices and methods, the most notable being the reduction of wellbore temperature changes. Although the current simulation devices are all aimed at achieving downhole temperature and pressure conditions, and the pressure and temperature can be changed by operation during the experiment and the cement can be detected. The ring casing is damaged, but the current device is to cool the entire kettle body to achieve the purpose of changing the temperature. In actual operation, when the working fluid in the wellbore is switched, the low-temperature fluid is pumped in quickly, and the temperature in the wellbore will drop instantaneously. This instantaneous cooling process will cause at least 20% of the temperature in the wellbore to drop, while the formation temperature will not change, so there will be an instantaneous temperature difference between the cement sheath and the casing, which is not involved in the current research and development of the device

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