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Preparation method of sample for testing shear strength parameters of well cementation second interface

A technology of interfacial shear strength and parameter testing, applied in the field of oil and gas well engineering, can solve problems such as poor accuracy, unevenness, and large dispersion of test results, and achieve the effect of convenient sample preparation and strong practicability

Active Publication Date: 2021-08-27
INST OF ROCK AND SOIL MECHANICS - CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] 1. Since the hole is drilled in the center of the cylindrical core, it is not convenient to finely describe the complex morphology of the wellbore rock, and the real openhole wall is uneven and uneven;
[0008] 2. Using the method of punching shear or compressive shear, what is essentially obtained is a shear strength under an equivalent 0 normal stress, and it is impossible to obtain shear strength parameters with wider application by applying different normal stresses, namely Cohesion and Angle of Internal Friction
[0009] 3. In the process of compression shearing or punching shearing, it is very easy to cause unbalanced force on the entire annular shearing surface due to eccentricity, and the test results are more discrete and less accurate

Method used

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  • Preparation method of sample for testing shear strength parameters of well cementation second interface
  • Preparation method of sample for testing shear strength parameters of well cementation second interface
  • Preparation method of sample for testing shear strength parameters of well cementation second interface

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preparation example Construction

[0030] see figure 1 , the sample preparation method for testing the shear strength parameters of the second cementing interface provided by the embodiment of the present invention includes:

[0031] Prepare rock samples with concave-convex undulating surfaces; the selected rock samples can be downhole cores or surface outcrops; the surface of rock samples used to prepare the second cementing interface can be manually split or finely carved by numerical control The uneven and undulating surface is made by the method, which is used to simulate the different rough states of the well wall after drilling.

[0032] Drilling fluid mud is deposited on the rough surface of the rock sample; the entire rough surface of the rock sample is completely immersed in the drilling mud, and drilling fluid mud cakes with different deposition thicknesses can be formed on the rock surface by controlling the immersion time as required.

[0033] The rough surface of the rock sample is flushed with fl...

Embodiment

[0038] In this example, a sample containing the cemented second interface will be prepared for the direct shear test, specifically simulating the cemented second interface formed between the sandstone formation and the cement sheath. The sandstone sample is the surface outcrop corresponding to the tight sandstone gas reservoir, and the drilling mud, spacer fluid, and cement slurry are all formulated on site. Firstly, a sandstone-cement composite cube sample with an overall size of 100mm×100mm×100mm was prepared, and then a Brazilian disc sample with a diameter of 50mm and a height of 100mm was cut and prepared with the sandstone-cement stone interface as the center. The specific production process is as follows:

[0039] (1) Prepare a sandstone sample with a concave-convex undulating surface.

[0040] A large piece of sandstone outcrop was selected, cut and polished, and made into a rectangular block with a size of 100mm×100mm×52mm. A precision CNC engraving machine was used ...

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Abstract

The invention discloses a preparation method of a sample for testing shear strength parameters of a well cementation second interface, which is applied to the technical field of oil and gas well engineering and aims to solve the problems that the discreteness of a test result is relatively large and shear strength parameters such as cohesion and an internal friction angle cannot be calculated in the prior art. The method comprises the steps that firstly, a rock sample containing a concave-convex fluctuating surface is prepared on an initial selected rock sample according to different rough states of a well wall after well drilling; then drilling fluid slurry is deposited on the rough surface of the rock sample, fluid flushing is conducted on the rough surface of the rock sample, well cementation cement slurry continues to be poured on the rough surface of the rock sample, and then a rock-set cement combination containing an interface is formed through overall maintenance; and after demolding, cutting is carried out to obtain a sample containing an interface and used for testing shear strength parameters. By adopting the method disclosed by the invention, a plurality of same test samples can be prepared at the same time, so that interfacial shear strength parameters can be determined by different normal stress direct shear tests.

Description

technical field [0001] The invention belongs to the technical field of oil and gas well engineering, in particular to a sample preparation technology for testing the shear strength parameters of the second cementing interface. Background technique [0002] Drilling is a very important link and means in oil and gas exploration and development. During the drilling process of a well, when the drill bit drills to a certain depth, the drill bit needs to be pulled out from the well, and a hollow steel pipe string called casing is lowered into the well, and then inserted into the annular space between the wellbore and the casing. Inject cement slurry (a mixture of dry cement, water and admixture) into the space and allow it to solidify; then use a drill bit with a smaller diameter to continue drilling. Depending on the complexity of the formation to be drilled, a well must go through this process once to several times before reaching the target oil and gas layer. [0003] The pur...

Claims

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Application Information

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IPC IPC(8): G01N1/28G01N1/32G01N1/34G01N1/36
CPCG01N1/286G01N1/32G01N1/34G01N1/36G01N2001/2873G01N2001/366G01N2203/0298
Inventor 郭印同曾义金王磊常鑫杨春和杨广国刘奎杨涵志郭武豪毕振辉赵国凯
Owner INST OF ROCK AND SOIL MECHANICS - CHINESE ACAD OF SCI