A monitoring method for the displacement efficiency of cementing annulus in simulated shale gas horizontal wells

Abstract

The invention discloses a monitoring method for simulating the annulus displacement efficiency of shale gas horizontal well cementation. The monitoring method is realized through a low-field nuclear magnetic resonance imager and comprises the steps of 1, placing an annular measurement pipe section into a radio-frequency coil and injecting displacing liquid into a shaft; 2, adjusting the parameters of the low-field nuclear magnetic resonance imager and enabling the measurement pipe section sample to generate nuclear magnetic resonance; 3, sending nuclear magnetic resonance signals of the measurement pipe section sample to a radio frequency unit and converting the signals through a spectrometer system for obtaining spectral lines of the nuclear magnetic resonance signals; 4, obtaining imaging pictures of the measurement pipe section sample in different directions; 5, injecting displacing liquid into an inner pipe of the shaft, repeating the steps 2-4, obtaining T2 spectral lines and imaging pictures of the measurement pipe section sample at different moments, drawing a curve chart of the displacement efficiency and conducting research on the mixing and displacing mechanism of the fluid through the imaging pictures. According to the monitoring method, the flow condition of annulus liquid can be effectively monitored, the mixing and displacing mechanism of the fluid can be researched through the imaging pictures, and the shortcomings of the prior art can be overcome.

Description

technical field [0001] The invention relates to a monitoring method for simulating the displacement efficiency of annulus in shale gas horizontal well cementing. Background technique [0002] The technologies related to shale gas development have been a hot research issue in recent years. One of the new problems brought by shale gas cementing to cementing engineering is the use of oil-based mud, which faces the problem of oil-water incompatibility. To solve this problem, compared with water-based mud cementing, oil-based mud cementing uses a more complex pre-fluid system. There may be oil-based mud and pre-fluid (flushing fluid, spacer fluid) in the annulus from top to bottom. , cement slurry and other liquids, forming a complex slurry column structure system, how to mix oil-based mud and other water-based solutions in the annulus, there is still no clear answer. [0003] The displacement efficiency of cement slurry directly determines the quality of cementing. How to mix a...

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Problems solved by technology

[0004] At present, there are many methods for monitoring the displacement efficiency of the cementing annular space at home and abroad, but they all have obvious shortcomings: the laser velocimetry method can monitor the flow state of the multiphase flow in the annular space and measure the displacement efficiency, but due to the similar fluid used, it cannot It is not convincing to indicate how the fluids are mixed (Xu Bihua et al.. Simulated cementing displacement efficiency measurement method. Patent publication number: CN103556986A); However, it cannot explain how the fluids are mixed during the dynamic flow process, and the influence of different mixing states on the displacement efficiency (Han Hongsheng, Wang Jingsheng. Experimental research on cement slurry replacing mud in eccentric annulus [J].Journal of Northeast Petroleum University, 1989(3)); The temperature method can measure the flow of real cement slurry and drilling fluid, but the temperature sensor needs to be immersed in the annular flow field during measurement, so it will interfere with the flow field. Affects the experimental results, and the heat loss during the flow process is large, and the experimental error is large (Xu Bihua et al. A method for measuring the displacement efficiency of cement slurry using a temperature sensing device. Patent publication number: CN101892831A); the resistivity method can measure the cementing ring Empty displacement efficiency, but there will be interference between the probes, which will affect the measurement of displacement efficiency (Dai Zixin. Analysis and experiment of cementing displacement mechanism [J]. Journal of Southwest Petroleum Institute, 1983 (1): 33-41)

[0005] To sum up, the common problems existing in the existing monitoring methods are that they cannot dynamically characterize the influence of interfluid mixing on displacement efficiency, and they all have their own limitations, making it difficult to provide guidance for engineering applications.

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