CN-121993251-A - Analysis and evaluation method for hydraulic fracturing effect of coal seam working face length Kong Duowei

CN121993251ACN 121993251 ACN121993251 ACN 121993251ACN-121993251-A

Abstract

The invention relates to the field of safety, and discloses a method for analyzing and evaluating hydraulic fracturing effect of a long and short Kong Duowei coal seam working face, which comprises the steps of firstly constructing a space detection matrix consisting of long drilling holes and short drilling holes, and acquiring a background fracture image and an initial water outlet state before fracturing by using a panoramic peeping system; the method comprises the steps of carrying out hydraulic fracturing, synchronously collecting pressure flow time sequence data of a fractured hole and water outlet response time of an adjacent hole, scanning again after fracturing to obtain a fracture image, constructing a multisource database containing space-time information, calculating apparent crack expansion speed and determining dominant directions based on time difference of pressure dip points and water outlet response time and combining space distances, finally selecting dominant direction drilling holes to compare fracture forms, calculating fracture network development indexes by combining image analysis items and hydraulic response items, and evaluating fracturing grades. The invention realizes quantitative characterization of the crack propagation dynamic characteristics, solves the subjectivity problem of a single evaluation means, and improves the scientificity of the evaluation result.

Inventors

LIU JUN
WANG KAI
XIAO CHAO
WANG BIN
XIE XIAOHU
LIU YONGQIANG
ZHANG JIAN
LIU HUINI
GUO LONG
YANG GUIBAO

Assignees

陕西旬邑青岗坪矿业有限公司
天地科技股份有限公司
中煤科工开采研究院有限公司
中煤科工(西安)开采工程技术有限公司

Dates

Publication Date: 20260508
Application Date: 20251224

Claims (10)

1. The method for analyzing and evaluating the hydraulic fracturing effect of the coal seam working face length Kong Duowei is characterized by comprising the following steps of: S1, constructing a long and short hole space detection matrix and acquiring background data before fracturing, namely constructing a space detection matrix consisting of long drilling holes and short drilling holes by taking a preset fracturing hole as a center, recording three-dimensional space coordinates of each drilling hole, acquiring background fracture images before fracturing and recording initial natural water outlet states of each drilling hole; S2, performing hydraulic fracturing and synchronously collecting multidimensional time sequence information, namely performing hydraulic fracturing on the fracturing holes, collecting pressure and flow time sequence data of the fracturing holes, and synchronously monitoring and recording water outlet response time and water outlet flow data of each drilling hole in the detection matrix; S3, acquiring information after fracturing and constructing a multi-source database, namely acquiring a fracture image after fracturing and constructing the multi-source database containing space information, time sequence information and image information; S4, analyzing a crack expansion path and speed based on time sequence correlation, namely calculating the apparent expansion speed of a crack network based on the time difference between the time stamp of the pressure dip point of the fracturing hole and the water outlet response time of the adjacent drilling hole, combining the linear space distance, and determining the dominant direction of crack expansion; S5, evaluating the fracturing effect based on multi-source information fusion, namely comparing fracture images before and after fracturing in the dominant direction of fracture expansion to identify newly-increased fractures, calculating fracture network development indexes according to data in a multi-source database, and grading the hydraulic fracturing effect according to the fracture network development indexes calculated according to the data.
2. The method for analyzing and evaluating the hydraulic fracturing effect of the long and short hole Kong Duowei on the working surface of the coal seam according to claim 1, wherein in the step S1, the construction of the long and short hole space detection matrix follows the principle of partition grading and multidimensional coverage, and specifically comprises the following steps: Dividing surrounding rock mass into a near field observation area and a far field observation area by taking a fracturing section of a hydraulic fracturing hole as a circle center, wherein the near field observation area is a space range with a radius smaller than one half of a preset theoretical fracturing radius, and the far field observation area is a space range with a radius between one time and one half of the preset theoretical fracturing radius; The short drilling holes are used for enabling the terminal holes to be in the near-field observation area or not enter the far-field observation area, and are respectively arranged along directions parallel to and perpendicular to the maximum horizontal main stress of the coal seam working surface; The long drilled holes are used for penetrating through a far-field observation area and are arranged in a radial or grid mode, and the final hole layer covers the direct top layer and the basic top layer.
3. The method for analyzing and evaluating hydraulic fracturing effect of the working face length Kong Duowei of the coal seam according to claim 1, wherein in the step S1 and the step S3, the step of acquiring the background fracture image and the fractured fracture image is performed by adopting a panoramic drilling peeping system, and the panoramic drilling peeping system comprises a peeping probe, a host, a drilling depth indicator, a connecting rod and a cable wire, and the specific implementation process comprises the following steps: The peeping probe is pushed into the bottom of the drill hole through the connecting rod, in the process of retracting the peeping probe to the direction of the hole opening through the cable wire, the whole circumference continuous shooting is carried out on the hole wall by the peeping probe, meanwhile, the distance data of the current position of the peeping probe relative to the hole opening is recorded by the drill hole depth indicator, the image data and the distance data are synchronously recorded by the host computer, and the corresponding relation between the fracture image and the drill hole depth coordinate is established.
4. The method for analyzing and evaluating hydraulic fracturing effect of a coal seam working face length Kong Duowei according to claim 1, wherein in S2, the water outlet response time of each borehole in the recording and detecting matrix is specifically determined by logic: Monitoring the fluid outflow state of each drilling hole in real time, and comparing the flow data observed in real time with the background flow recorded in the step S1; when the real-time water outlet flow of a certain borehole is monitored to exceed the background flow of the borehole for the first time and the exceeding amplitude reaches a preset response judgment threshold value, judging that a hydraulic response event occurs in the borehole, and locking the absolute time point of the hydraulic response event as the water outlet response time.
5. The method for analyzing and evaluating the hydraulic fracturing effect of the coal seam working face length Kong Duowei according to claim 1, wherein the method for identifying the timestamp of the pressure dip point in S4 is as follows: Calculating the change rate of the pressure value after smoothing the collected pressure time sequence data; And monitoring the pressure value change rate, and recording the moment as a pressure dip point time stamp when the pressure value change rate is changed from a positive value to a negative value and the absolute value of the negative value exceeds a preset dip judgment threshold.
6. The method for analyzing and evaluating hydraulic fracturing effect of a coal seam working face length Kong Duowei according to claim 1, wherein the determining and verifying the dominant direction of crack propagation in S4 includes: sequencing the calculated apparent speed values of the non-zero crack network expansion, and identifying the vector direction with the largest value as the dominant expansion main direction; Searching a long drilling hole and short drilling hole combination pair which are positioned in the same radial interval or adjacent sectors on the space azimuth, and judging that a continuous expansion penetration crack exists if the crack expansion response time of the short drilling hole is earlier than that of the long drilling hole; And performing ground stress field matching verification, namely calculating an included angle between the determined dominant crack expansion direction and the maximum horizontal main stress direction of the area, and judging that the time sequence correlation analysis crack expansion path is a tension main crack guided by ground stress if the included angle is smaller than a preset deflection angle threshold value.
7. The method for analyzing and evaluating hydraulic fracturing effect of a coal seam working surface length Kong Duowei according to claim 1, wherein the step of identifying the newly added fracture in S5 includes: Comparing the fractured fracture image with the pre-fractured background fracture image at the same depth coordinates; Extracting texture characteristics of the newly-appeared cracks after fracturing, and measuring the tendency and inclination angle of the newly-appeared cracks; Judging whether the trend and the inclination angle of the newly-appearing crack have geometric consistency with the crack expansion dominant direction determined in the step S4, and if so, judging that the hydraulic crack is effectively expanded along a time sequence correlation analysis crack expansion path.
8. The method for analyzing and evaluating hydraulic fracturing effect of the coal seam working face length Kong Duowei according to claim 1, wherein the specific process of calculating the fracture network development index in S5 includes: Determining an image analysis item, namely calculating the product of the number of newly increased cracks in unit length after fracturing and the average opening degree increment of the cracks after fracturing for each drilling hole in the detection matrix, accumulating the product results of all the drilling holes in the detection matrix, and dividing the accumulated results by the total length of all the drilling holes in the detection matrix; calculating the ratio of the total number of the drilling holes with water outlet response to the total number of all adjacent drilling holes in the detection matrix; multiplying the image analysis item by a preset image analysis item weight coefficient to obtain a first value, multiplying the hydraulic response item by a preset hydraulic response item weight coefficient to obtain a second value, and adding the first value and the second value to obtain the fracture network development index.
9. The method for analyzing and evaluating the hydraulic fracturing effect of the length Kong Duowei of the working face of the coal seam according to claim 8, wherein the calculating process of the average opening degree increment of the fractured cracks comprises the following steps: extracting crack edge pixels from the fractured crack image; calculating pixel distances among pixels at the edges of the cracks, and converting the pixel distances into actual physical widths according to the pixel and actual size calibration coefficients of the panoramic drilling peeping system; And calculating the difference between the actual physical width after fracturing and the actual physical width before fracturing to obtain the average opening degree increment of the cracks.
10. The method for analyzing and evaluating the hydraulic fracturing effect of the coal seam working face length Kong Duowei according to claim 1, wherein in the step, the specific content for constructing the multi-source database comprises the following steps: performing uniform and regular operation of a time axis, and performing relative treatment on the water outlet response time of all adjacent long drilling holes and short drilling holes by taking the time stamp of the pressure dip point as a reference zero point to obtain crack expansion response lag time; Performing space separation dissociation calculation association operation, and calculating linear Euclidean distance between the coordinates of a source point of a fracturing section of the hydraulic fracturing hole and the coordinates of target points of each long drilling hole and each short drilling hole by using a space analysis geometric algorithm; And constructing a structured data table taking a drilling identification code as a main key, and storing a drilling type identifier, drilling azimuth data, a linear Euclidean distance, a water outlet state identifier and crack propagation response lag time.

Description

Analysis and evaluation method for hydraulic fracturing effect of coal seam working face length Kong Duowei Technical Field The invention relates to the field of safety, in particular to a method for analyzing and evaluating hydraulic fracturing effect of a coal seam working face with length Kong Duowei. Background The hydraulic fracturing technology of the roof of the coal seam working face is a key means for improving the stress distribution of surrounding rock, preventing dynamic disasters such as rock burst and the like and improving the air permeability of the coal seam. The scientific detection and evaluation of the fracturing effect after the hydraulic fracturing operation are core basis for verifying the construction effectiveness, guiding the implementation of a subsequent exploitation scheme and optimizing the secondary fracturing design. However, the existing fracturing effect evaluation technology still has limitations in practical engineering application. Firstly, in the aspects of observation arrangement and crack identification, a conventional monitoring means generally adopts a single-hole depth or uniform drilling arrangement mode, and the staged observation of a fracturing near-field initiation region and a far-field extension region is lacking, so that the three-dimensional coverage of the full life cycle space track of the crack is difficult to realize. Meanwhile, the existing method often lacks of fine acquisition of background data before fracturing, so that in the later-stage effect analysis, geological structure cracks of the rock mass and new cracks generated by hydraulic fracturing are difficult to effectively strip, an observation blind area is generated, and the integrity and accuracy of capturing the three-dimensional space form of the cracks are reduced. Secondly, in analysis of fracture propagation characteristics, the prior art focuses on static observation of the final state of fracturing, and lacks deep excavation of time sequence correlation characteristics between pumping pressure fluctuation and hydraulic response of peripheral drilling holes in the fracturing process. The static observation mode cannot reveal the dynamic kinematics rule of the crack expansion in the rock mass, and the expansion speed, the dominant expansion azimuth and the geological resistance distribution condition of the crack are difficult to obtain, so that the adjustment and optimization of the fracturing process parameters lack quantitative dynamic basis. In addition, in terms of the final effect assessment system, the existing methods generally rely only on single water yield data or manually interpreted local image data for qualitative description. Because of the lack of a comprehensive quantization model capable of carrying out weighted fusion on microscopic fracture morphology change and macroscopic hydraulic response characteristics, an evaluation result often has stronger subjectivity and unilateral property, and a scientific, unified and quantifiable fracturing effect grading standard is difficult to form, so that the accuracy of engineering acceptance is influenced. Disclosure of Invention The invention provides a method for analyzing and evaluating hydraulic fracturing effect of a coal seam working face length Kong Duowei, which aims to solve the technical problems that the existing fracturing effect evaluating means is single and the expanding path and dynamic characteristics of a crack in a rock body cannot be quantitatively represented. The technical scheme adopted by the invention is as follows, comprising the following steps: Firstly, constructing a long and short hole space detection matrix, acquiring background data before fracturing, constructing a space detection matrix consisting of long holes and short holes by taking a preset fracturing hole as a center, recording three-dimensional space coordinates of each hole, acquiring a background fracture image before fracturing by using a panoramic drilling peeping system, recording an initial natural water outlet state of each hole, and establishing a physical observation reference and a data comparison reference; secondly, hydraulic fracturing is implemented, multidimensional time sequence information is synchronously collected, pressure and flow time sequence data of the fracturing holes are collected in the process of hydraulic fracturing of the fracturing holes, water outlet response time and water outlet flow data of all drilling holes in a detection matrix are synchronously monitored and recorded, and time sequence alignment of a power source and a response end is realized; Thirdly, acquiring information after fracturing, constructing a multi-source database, acquiring a fracture image after fracturing, constructing the multi-source database containing space information, time sequence information and image information, and providing data support for association analysis; Then analyzing a crack expansion path and speed based on t