Coal Mine Hydraulic Fracturing Underground Drainage Research and Engineering Application

2017 ◽  
Vol 863 ◽  
pp. 334-341
Author(s):  
Jun Hui Fu ◽  
Guang Cai Wen ◽  
Fu Jin Lin ◽  
Hai Tao Sun ◽  
Ri Fu Li ◽  
...  
Keyword(s):  
Stress State ◽  
Hydraulic Fracturing ◽  
Coal Mine ◽  
Engineering Application ◽  
Fracture Morphology ◽  
Plane Stress State ◽  
Theoretical Formula ◽  
Test Results ◽  
Breakdown Pressure ◽  
Elastic Mechanics

Using elastic mechanics and fracture mechanics, analyzing the coal seam hydraulic fracturing breakdown pressure, given its theoretical formula. According to hydraulic fracturing stress status, given the form of two typical hydraulic fracture morphology. Analyzing hydraulic fracturing highly elliptical shape. The displacement field in plane stress state is given, and the theoretical formula of fracturing radius of hydraulic fracturing is deduced. The fracturing technology of underground fracturing is presented, and the fracturing location and fracturing parameters are determined. In Sihe Coal Mine conducted fracturing test, the test results showed that: the average of drainage volume of fracturing hole improved 4.4 times compared with non-pressed-hole. The extraction compliance time is reduced by 38%. Roadway tunneling speed was improved by 15%. It can solve the problem of gas overrun in roadway excavation well, and has a good application and popularization value.

scholarly journals Effect of Brittle Mineral Size on Hydraulic Fracture Propagation in Shale Gas Reservoir

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Wei Gao ◽  
Javed Iqbal ◽  
Dan Xu ◽  
Haoyue Sui ◽  
Ruilin Hu
Keyword(s):  
Hydraulic Fracturing ◽  
Ordos Basin ◽  
Maximum Size ◽  
Fracture Morphology ◽  
Size Distributions ◽  
Test Results ◽  
Gas Reservoir ◽  
Fracture Pressure ◽  
Hydraulic Fracture Propagation ◽  
Shale Reservoirs

The properties of brittle minerals have great effect on the morphology of postfracturing network in shale reservoirs in the southeastern Ordos Basin, China. In order to study the effect of brittle mineral size distributions on the fracture parameters, the concrete cubes of 300 mm × 300 mm × 300 mm in size with four distinct brittle mineral sizes of 2.36 mm, 0.425 mm, 0.15 mm, and 0.075 mm were investigated under large-sized triaxial hydraulic fracturing test. The effect mechanism of aggregate on the fracture properties of shale was studied using ultrasonic technique, photosensitive electron microscope, and numerical simulation. The test results obtained for each specimen (both disturbed and undisturbed conditions) indicate that brittle mineral size has significant effect on the fracture extension. The tensile strength, fracture toughness, and fracture pressure were found to decrease with a decrease in maximum brittle mineral size when the maximum brittle mineral size is smaller than 0.425 mm. In addition to this, the degree of attenuation difference also follows the similar trend. Observed fracture morphology reveals that with an increase in maximum size of brittle mineral specimen, the tortuous and complicated cracking path generation increases. These findings would be very helpful in order to better understand the behavior of shale under hydraulic fracturing test.

scholarly journals Numerical Investigation of the Impacts of Borehole Breakouts on Breakdown Pressure

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 888 ◽  
Author(s):  
Hua Zhang ◽  
Shunde Yin ◽  
Bernt Aadnoy
Keyword(s):  
Hydraulic Fracturing ◽  
Shear Failure ◽  
In Situ Stress ◽  
Test Results ◽  
Breakdown Pressure ◽  
Borehole Breakout ◽  
Borehole Breakouts ◽  
The Difference ◽  
Mud Pressure

Borehole breakouts appear in drilling and production operations when rock subjected to in situ stress experiences shear failure. However, if a borehole breakout occurs, the boundary of the borehole is no longer circular and the stress distribution around it is different. So, the interpretation of the hydraulic fracturing test results based on the Kirsch solution may not be valid. Therefore, it is important to investigate the factors that may affect the correct interpretation of the breakdown pressure in a hydraulic fracturing test for a borehole that had breakouts. In this paper, two steps are taken to implement this investigation. First, sets of finite element modeling provide sets of data on borehole breakout measures. Second, for a given measure of borehole breakouts, according to the linear relation between the mud pressure and the stress on the borehole wall, the breakdown pressure considering the borehole breakouts is acquired by applying different mud pressure in the model. Results show the difference between the breakdown pressure of a circular borehole and that of borehole that had breakouts could be as large as 82% in some situations.

The Influence of Strain Conditions in Steel Samples on the Fatigue Crack Growth and Delay after Overload

2014 ◽  
Vol 224 ◽  
pp. 151-156
Author(s):  
Krzysztof Werner
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Stress State ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Strain State ◽  
Plane Stress State ◽  
Test Results ◽  
Single Overload ◽  
Flat Steel

The work presents the results of the analysis of fatigue crack growth in flat steel samples for different strain conditions on crack tip in the sample. Growth of fatigue crack in the samples was studied in conditions of a plane strain state, plane stress state and in the transitory zone between those states. Test results showed a clear influence of these conditions on the fatigue crack growth rate. The paper also includes the test results of effectiveness of retardation of fatigue crack growth after single overload cycles used in different strain conditions.

scholarly journals Experimental Investigation on Hydraulic Fracture Propagation of Carbonate Rocks under Different Fracturing Fluids

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3502 ◽  
Author(s):  
Yintong Guo ◽  
Peng Deng ◽  
Chunhe Yang ◽  
Xin Chang ◽  
Lei Wang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Flow Rate ◽  
Radial Strain ◽  
Fracture Initiation ◽  
Fracture Morphology ◽  
Fracturing Fluid ◽  
Breakdown Pressure ◽  
Pump Flow ◽  
Fracturing Fluids ◽  
Pump Flow Rate

Deep carbonate reservoirs are rich in oil and gas resources. However, due to poor pore connectivity and low permeability, it is necessary to adopt hydraulic fracturing technology for their development. The mechanism of hydraulic fracturing for fracture initiation and propagation in carbonate rocks remains unclear, especially with regard to selection of the type of fracturing fluid and the fracturing parameters. In this article, an experimental study focusing on the mechanisms of hydraulic fracturing fracture initiation and propagation is discussed. Several factors were studied, including the type of injecting fracturing fluids, pump flow rate, fracturing pressure curve characteristics, and fracture morphology. The results showed the following: (1) The viscosity of fracturing fluid had a significant effect on fracturing breakdown pressure. Under the same pump flow rate, the fracturing breakdown pressure of slick water was the lowest. Fracturing fluids with low viscosity could easily activate weakly natural fractures or filled fractures, leading to open microcracks, and could effectively reduce the fracturing breakdown pressure. (2) The fluctuations in fracturing pump pressure corresponded with the acoustic emission hits and changes in radial strain; for every drop of fracturing pressure, acoustic emission hits and changes in radial strain were mutated. (3) Under the same fracturing fluid, the pump flow rate mainly affected fracturing breakdown pressure and had little effect on fracture morphology. (4) The width of the main fracture was affected by the viscosity and pump flow rate. Maximum changes in radial strain at the fracturing breakdown pressure point occurred when the fracturing fluid was guar gum. (5) With gelled acid and cross-linked acid fracturing, the main fractures were observed on the surface. The extension of the fracturing crack was mainly focused near the crack initiation parts. The crack expanded asymmetrically; the wormhole was dissolved to break through to the surface of the specimen. (6) The dissolution of gelled acid solution could increase the width of the fracturing crack and improve the conductivity of carbonate reservoirs.

scholarly journals Directional Hydraulic Fracturing (DHF) of the Roof, as an Element of Rock Burst Prevention in the Light of Underground Observations and Numerical Modelling

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 562
Author(s):  
Marek Jendryś ◽  
Andrzej Hadam ◽  
Mateusz Ćwiękała
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Coal Mining ◽  
Rock Burst ◽  
Coal Mine ◽  
Seismic Activity ◽  
Black Coal ◽  
Directional Hydraulic Fracturing ◽  
Before And After ◽  
The Face

The following article analyzes the effectiveness of directional hydraulic fracturing (DHF) as a method of rock burst prevention, used in black coal mining with a longwall system. In order to define changes in seismic activity due to DHF at the “Rydułtowy” Black Coal Mine (Upper Silesia, Poland), observations were made regarding the seismic activity of the rock mass during coal mining with a longwall system using roof layers collapse. The seismic activity was recorded in the area of the longwall itself, where, on a part of the runway, the rock mass was expanded before the face of the wall by interrupting the continuity of the rock layers using DHF. The following article presents measurements in the form of the number and the shock energy in the area of the observed longwall, which took place before and after the use of DHF. The second part of the article unveils the results of numerical modeling using the discrete element method, allowing to track the formation of goafs for the variant that does not take DHF into consideration, as well as with modeled fractures tracing DHF carried out in accordance with the technology used at “Rydułtowy” coal mine.

scholarly journals Incremental Approach to the Nonlinear Analysis of Reinforcement Concrete with Cracks at Plane Stress State

2015 ◽  
Vol 111 ◽  
pp. 386-389 ◽  
Author(s):  
Nikolay I. Karpenko ◽  
Sergey N. Karpenko ◽  
Aleksey N. Petrov ◽  
Zakhar A. Voronin ◽  
Anna V. Evseeva
Keyword(s):  
Stress State ◽  
Nonlinear Analysis ◽  
Plane Stress ◽  
Plane Stress State ◽  
Incremental Approach
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