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A method for predicting the strength of hydration-damaged shale

A shale and strength technology, applied in the field of unconventional oil and gas exploration and development, can solve the problems of shale mechanical strength damage, shale softening, aggravating the difficulty of effective support of deep shale, and achieve the goal of improving work efficiency and rapid prediction Effect

Active Publication Date: 2021-01-29
CHINA PETROLEUM & CHEM CORP +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The water entering the formation will damage the mechanical strength of the shale, making the shale soft, resulting in the closure of self-supporting fractures and the embedding of proppant, which further exacerbates the problem that deep shale is difficult to support effectively
[0005] At present, there are few researches on the hydration intensity of deep shale at home and abroad. Therefore, it is urgent to establish a method to predict the hydration damage intensity of shale.

Method used

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  • A method for predicting the strength of hydration-damaged shale
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  • A method for predicting the strength of hydration-damaged shale

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Embodiment 1

[0043] figure 1 A flow chart of a method for predicting the strength of hydration-damaged shale is provided for the embodiment of the present invention, such as figure 1 As shown, the method of the present embodiment includes the following steps:

[0044] S1: Prepare standard rock samples of the target shale block: prepare N standard rock samples of the target shale block, select one of the standard rock samples without soaking treatment, and soak the other N-1 standard rock samples for t 1 , t 2 ···t n-1 Specifically, considering the influence of shale anisotropy on rock strength and deformation, samples should be taken in the same direction when preparing standard rock samples in the target shale block, and water should be avoided during the processing of standard rock samples, and standard rock samples should not be used during testing. Hydration occurs before. Specifically, the soaking device is as shown in the accompanying drawings figure 2 As shown, the soaking dev...

Embodiment 2

[0063] Taking a certain shale block as an example below, the implementation method of the present invention will be further described in detail, as follows:

[0064] According to step S1, prepare 5 standard rock samples of the target shale block, 1 standard rock sample is not soaked in water, and the remaining 4 standard rock samples are soaked in water for 3 days, 5 days, 10 days and 20 days respectively .

[0065] According to step S2, it is obtained that the closure pressure of the block is 70MPa. After drying the soaked standard rock samples, a triaxial mechanical test is carried out under a confining pressure of 70MPa to obtain the rock elastic modulus E of each standard rock sample. n , Poisson's ratio v n , internal friction angle The measurement results are shown in Table 1.

[0066] Table 1 Triaxial mechanical test parameter list

[0067]

[0068] According to step S3, utilize the result of triaxial rock mechanics experiment, obtain Poisson's ratio-immersion t...

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Abstract

The invention discloses a method for predicting the strength of hydration-damaged shale, which comprises the following steps: S1: preparing a standard rock sample of a target shale block, and performing soaking treatment; S2: drying the standard rock sample and performing triaxial mechanics Experiment; S3: Using the results of triaxial mechanics experiments, the Poisson's ratio-immersion time curve and elastic modulus-immersion time curve of the standard rock sample are obtained; S4: According to the Mohr-Coulomb strength theory, the internal friction angle of each standard rock sample is determined , to obtain the relationship between the internal friction angle and immersion time; S5: Using the softening constitutive model of the Weibull distribution under water immersion, the Weibull distribution parameter m after immersion is obtained, and the rock compressive strength F after shale hydration damage is obtained 0 ; S5: Calculate the hydration damage degree of shale. This method can quantitatively express the influence of hydration damage on the mechanical parameters of shale rock under different confining pressure and hydration time conditions, so as to achieve the effect of quantitatively predicting the degree of hydration damage.

Description

technical field [0001] The invention relates to the technical field of unconventional oil and gas exploration and development, in particular to a method for predicting the strength of hydration-damaged shale. Background technique [0002] Shale gas refers to the unconventional natural gas that occurs in organic-rich shale-based reservoir rock series. It is continuously generated biochemical gas, thermogenic gas or a mixture of the two, and can exist in natural gas in a free state. In cracks and pores, it exists on the surface of kerogen and clay particles in an adsorbed state, and a very small amount is stored in kerogen and asphaltene in a dissolved state. The proportion of free gas is generally 20% to 85%. [0003] my country's deep shale gas resources with a burial depth greater than 3500m are abundant, accounting for more than 60% of shale gas resources, and have good development prospects. It is easy to close under the closing pressure, which is an important reason for ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/12G01N1/28G01N1/30
CPCG01N1/28G01N1/30G01N3/12G01N2203/0256
Inventor 郭建春李远照廖如刚赵志红高东伟张驰李婷张晗苏慕博文李鹏毕文韬崔静
Owner CHINA PETROLEUM & CHEM CORP
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