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Method for predicting and evaluating mud shale hydrofracturing crack net expansion rule

A mud shale and shale technology, applied in the field of shale gas development engineering, can solve problems such as no clear characterization, difficult quantitative characterization of fractures, and complex fracture network system

Inactive Publication Date: 2018-09-21
ZHONGYUAN ENGINEERING COLLEGE
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Problems solved by technology

[0004] In order to solve the problems existing in the background technology, the present invention proposes a method for predicting and evaluating the expansion law of hydraulic fracturing of mud shale, which solves the problem that the crack network system formed after hydraulic fracturing of mud shale is complicated, It is difficult to quantitatively characterize fractures, and there is no clear characterization in actual fracturing design

Method used

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  • Method for predicting and evaluating mud shale hydrofracturing crack net expansion rule
  • Method for predicting and evaluating mud shale hydrofracturing crack net expansion rule

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Embodiment 1

[0037] Embodiment 1: a kind of method of prediction and evaluation shale hydraulic fracturing fracture network expansion law, comprises the following steps:

[0038] S1: Fracturing of shale; first process the shale into a cubic sample, apply a confining pressure less than the tensile strength of the shale, and then use a high-pressure pulse water jet generator to perform multi-stage and stage-by-stage fracturing of the shale according to engineering requirements Or repeat fracturing, and finally, carefully observe and mark the fracture network that appears on the shale surface;

[0039] S2: Extraction of modal fracture network; use a high-definition digital camera to collect shale fracture network, and use PS technology to convert the captured high-definition fracture network image into a two-dimensional grayscale modal fracture network with white background color and black fracture network image;

[0040] S3: Cracked network modulus conversion; convert the two-dimensional gr...

Embodiment 2

[0043] Embodiment 2: a kind of method for predicting and evaluating the expansion law of hydraulic fracturing of mud shale, comprises the following steps:

[0044] S1: Shale fracturing; process the shale into a 30cm×30cm×30cm sample, apply a confining pressure less than the tensile strength of the shale, and then use a high-pressure pulse water jet generator to perform multi-fractionation of the shale according to engineering requirements Stage fracturing or refracturing, and finally, carefully observe and mark the fracture network that appears on the shale surface;

[0045] S2: Extraction of modal fracture network; collect the shale fracture network with a high-definition digital camera, and adjust the image size to 2 n ×2 n , the image of the pixel of n=0, 1, 2..., convert the high-definition cracked net image of shooting into the two-dimensional grayscale modality cracked net image that the background color is white and the cracked net is black with PS technology;

[0046...

Embodiment 3

[0069] Embodiment 3: Another calculation method of the fractal dimension in the step S4.4: use square grids of different lengths to cover the cracks, and when the length ε of the square grids changes, the number of grids covering the cracks N( ε) will inevitably change accordingly. According to the fractal theory, there is a formula: N(ε)∝ε -D , when the square grid length is ε 1 , ε 2 , ε 3 ,...,ε k , the number of square grids covering the crack is correspondingly N(ε 1 ), N(ε 2 ), N(ε 3 ),……, N(ε k ), N(ε)∝ε -D Take the double logarithm on both sides of , and get: lgN(ε)=-D*lgε+A, where A is an undetermined constant; D is the fractal dimension of the crack to be tested, also called the box dimension; the grid length is taken as horizontal The coordinates and the number of grids are plotted as the ordinate, and the D value is equal to the absolute value of the slope value of the fitting line of the coordinate graph. Other method steps are the same as in Example 2.

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Abstract

The invention provides a method for predicting and evaluating a mud shale hydrofracturing crack net expansion rule, and solves the problems that a crack net system formed after hydraulic power fracturing of mud shale is complex, quantitative representation for cracks is difficult, and no definite representation exist in the actual fracturing design. The research method comprises the steps that firstly, hydrofracturing is carried on analog engineering, then a modal crack net is extracted, then modal crack net digitalization is carried out, lastly, statistical analysis and research of a digitalcrack net are carried out, the crack net area, crack length, width, fractal dimension and other parameters are analyzed concretely, counting and representing are carried out on the crack net to obtainthe damage degree of shale, the complex degree and extension form of the crack net are represented, the comprehension of the shale damage degree and crack net extension form can obtain the crack netexpansion rule and evaluate a hydrofracturing effect, wherein the more seriously the rock is destroyed, the more complex the crack net is generated, and the better the shale hydrofracturing effect is.

Description

technical field [0001] The invention relates to the engineering problem of shale gas development, in particular to a method for predicting and evaluating the expansion law of hydraulic fracturing of mud shale. Background technique [0002] With the rapid development of the global economy, energy has increasingly become a key factor restricting the economic development of a country, and it is the energy guarantee for the development of the national economy. As an unconventional energy source, shale gas has the characteristics of low carbon, low pollution and large reserves, and has a good development prospect. my country's shale gas has deep burial and complex causes, and mostly exists in the shale in the form of adsorption, free, and dissolution. Because the reservoir has low porosity and extremely low matrix permeability, it is necessary to carry out reservoir reconstruction. Clear water fracturing is the most important reservoir stimulation method for developing shale gas ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50
CPCG06F30/20G06F2119/06
Inventor 胡江春王红芳孙发用崔力孙光林张孟辉李渊吉梦洁李鹏飞鲁家濠
Owner ZHONGYUAN ENGINEERING COLLEGE
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