Study on hydraulic-controlled blasting technology for pressure relief and permeability improvement in a deep hole

TLDR: In this article, a numerical model of hydraulic-controlled blasting was established, and the spacing distance of the blasting holes and the effective radius of the spraying were numerically simulated using ANSYS/LS-DYNA software.

About: This article is published in Journal of Petroleum Science and Engineering.The article was published on 2017-11-01 and is currently open access. It has received 89 citations till now. The article focuses on the topics: Coal mining & Permeability (earth sciences).

Figures

Fig. 10. Layout of the boreholes. 2 For blasting safety, the permissible emulsion explosive for coal mine is selected based on this 3 test; the charge length is equal to the borehole length through the 2nd coal seam. The method of 4 installing the auxiliary charge in a PVC casing is adopted, and the detonating fuse is installed in the 5 PVC casing. The detonators are connected in parallel, s shown in Fig. 11. The plugging of blasting 6 hole is very important during hydraulic-controlled blasting. Plugging can prevent the blasting 7 products from being ejected from the orifice prematurely and prolong their effective time. Because 8 the quantity of explosive charge for this test is large, the requirement of sealing hole is relatively 9 high. In view of this situation, the sealing method using double materials is adopted in this sealing 10 design, so the mixture of yellow mud and polyurethane in the inner 3 m ~ 6 m at the orifice is used 11 as sealing material, which is shown in Fig. 11. 12

Frequently asked questions

Q1. Why is the tension zone first generated around the blasting hole?

With the increase of the spacing distance between control holes, due 3 to stress resilience, the tension zone is first generated around the blasting hole. 

Q2. What contributions have the authors mentioned in the paper "Study on hydraulic-controlled blasting technology for pressure relief and permeability improvement in a deep hole" ?

Ye et al. this paper used a combination of simulations and field tests to investigate the variation of the coal mass subject to the influence of hydraulic slotting. 

Q3. What are the future works in "Study on hydraulic-controlled blasting technology for pressure relief and permeability improvement in a deep hole" ?

The 205 coal mining face in Yian coal mine was selected to study and numerically 17 simulate the blasting process and obtain the relative parameters of pressure relief and permeability 18 improvement. In future research, it is necessary to consider the particularity and difference of coal seam 19 itself. 20 ( 1 ) Hydraulic-controlled blasting can cause the blasting energy to take on directional 21 propagation, and the density and range of fractures can be greatly improved. 11 ( 6 ) The practice and application showed that hydraulic-controlled blasting can be used as a new 12 method of pressure relief and permeability improvement of the coal seam with high gas content and 13 low permeability. 

Q4. What is the effect of hydraulic fracturing on the coal mass?

Hydraulic fracturing can alter the 9 structure of the coal mass, which can increase fractures in coal mass, improve permeability, and 10 weaken strength. 

Q5. What is the result of hydraulic-controlled blasting in coal seam?

Due to the guidance action of 1 the control hole, the result of hydraulic-controlled blasting is that a cylindrical compression-2 crushing ring around the blasting hole in coal mass is produced, and the fracture network is formed 3 along the connecting line between the blasting hole and control hole. 

Q6. What is the effect of hydraulic slotting on the coal seam?

The findings revealed that hydraulic slotting could substantially increase 23 porosity and the fracture connectivity rate, which significantly improves the coal seam permeability 24 and gas drainage efficiency. 

Q7. What was the purpose of the pre-injection internal blasting in coal seam?

In the former 15 Soviet Union, pre-injection internal blasting in coal seam was performed in an 8-m deep borehole 16 with a 40-mm diameter to prevent coal and gas outbursts in both a thin coal seam and a thick coal 17 seam [Zhang, 2004]. 

Q8. What is the mechanism of pressure relief and permeability improvement in hydraulic-controlled blasting?

62. Mechanisms for pressure relief and permeability improvement in hydraulic-7controlled blasting 8When blasting occurs underwater, it not only generates a shock wave and explosive gases, but 9 it also generates a high pressure gas pulsation. 

Q9. How long is the drainage time after hydraulic-controlled blasting?

For the 1# blasting hole, 17 when hydraulic-controlled blasting is adopted, the drainage time of achieving a drainage volume of 18 650 m3 is approximately 6 days. 

Q10. What is the effect of the shaped charge jet on the coal wall?

Liu and Wojtecki, et al. have preformed tests using a shaped charge jet, the 20 results showed that the shaped charge jet acts on the coal wall of borehole and forms an initial guide 21 fracture, facilitating fracture expansion over a wide range in the coal mass under the action of the 22 air wedge formed by the detonation gas [Liu, et al. 

Q11. how much is the permeability coefficient after hydraulic-controlled blasting?

The average 19P0P1P23.02.5 2.01.51.00.50-5 0 5 10 15 20 25 30Time/hBlasting timeM ANUS CRIP TAC CEPTEDpermeability coefficient after hydraulic-controlled blasting is 1.60 m2/MPa2·d, which is 22.8 times 1 of the value using the common parallel drainage holes. 

Q12. What are the characteristics of hydraulic-controlled blasting?

As a result, hydraulic-controlled 11 blasting has five distinct characteristics [Chen and Lin, 1996]: high energy utilization, wedge effect 12 of high-velocity water, safe sealing effect, good blasting effect, and interference balancing of the 13 shock wave, stress wave and seismic wave. 

Q13. How much is the permeability coefficient after hydraulic-controlled blasting?

the average permeability 4 coefficient after hydraulic-controlled blasting is 3.14 times of that after ordinary controlled blasting.