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Method for calculating fracture toughness of shale based on scratch experiment

A fracture toughness and scratch test technology, applied in the direction of strength characteristics, test sample preparation, sampling, etc., can solve the problems of heavy workload and achieve the effects of weakening the discrete type, comprehensive experimental support, and low difficulty in sample preparation

Inactive Publication Date: 2017-08-18
SOUTHWEST PETROLEUM UNIV
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Problems solved by technology

Based on the existing shale fracture toughness experimental testing method, obtaining the fracture toughness experimental parameters that meet the needs of engineering design in the entire horizontal section, and that are continuous and representative requires a huge amount of experimental analysis.

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  • Method for calculating fracture toughness of shale based on scratch experiment
  • Method for calculating fracture toughness of shale based on scratch experiment
  • Method for calculating fracture toughness of shale based on scratch experiment

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Embodiment Construction

[0020] The content, features and effects of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The specific steps of the method for calculating shale fracture toughness in the scratch test are as follows:

[0021] Step 1. Select a certain underground shale core, use a rock cutter to cut a columnar core with a diameter of 106mm and a length of 250mm, and then fully dry the core at 60°C for use after completion;

[0022] Step 2. Fix the prepared core on the TerraTek MP scratch tester, and place the core strictly horizontally along the long axis; the scratch test uses a parallelepiped alloy steel tool, and adjust the angle between the tool and the vertical to 15° , The tool width (W) is 5mm; adjust the up and down position of the tool to ensure that the groove depth of the tool on the upper end of the core is about 0.2mm; turn on the feed button and perform a scratch test along the long axis of the core cylinder. Th...

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Abstract

The invention discloses a method for calculating fracture toughness of shale based on scratch experiment. The method is characterized by monitoring loads in horizontal and vertical directions of a cutter in a scratch experiment process and the depth of a scratch groove on the surface of a rock core, substituting the loads and the depth of the scratch groove on the surface of the rock core into a shale fracture toughness calculation model, and calculating the fracture toughness of the shale. Compared with the existing rock fracture toughness experiment test method, the method has the following advantages: (1) the rock core is low in sample preparation difficulty, and the test analysis process is fast and concise; (2) only the shallow surface of the rock core is broken in the test process; the subsequent application is not influenced, and the consumption of the rock core is low; and (3) the tested rock core is large in size and characterization dimension, randomness and discreteness of test results can be greatly reduced, and a fracture toughness curve profile continuous in the long axis direction of the rock core can be obtained. The fracture toughness testing method can provide more effective experiment support for shale gas well fracturing process design and is a worthily-popularized experiment test method of fracture toughness of the shale.

Description

Technical field [0001] The invention relates to the field of experimental evaluation of reservoir rock mechanics parameters during shale gas development, and in particular to a method for calculating shale fracture toughness based on a scratch experiment. Background technique [0002] Shale gas reservoirs generally adopt horizontal wells and staged hydraulic fracturing. One of the key rock mechanics parameters required in the hydraulic fracturing design process is the fracture toughness of shale. The fracture toughness of shale is usually obtained by indoor experimental tests. At present, the commonly used experimental test methods mainly include the central crack disc method, the three-point bending method and the four-point bending method. The test standards of these three methods are relatively mature, but they also have shortcomings, mainly including the following three aspects: (1) The size of the specimen is small, and artificial cracks need to be prefabricated on the speci...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/40G01N1/28G01N1/44
CPCG01N3/40G01N1/286G01N1/44G01N2203/0067G01N2203/0076
Inventor 李相臣杨斌康毅力何志君游利军白佳佳闫霄鹏程秋洋
Owner SOUTHWEST PETROLEUM UNIV
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