Exploration and Development of Coal and CBM Resources

Relying on the core technologies of fine geological exploration and coalbed methane resource development, and taking advantage of the synergistic advantages of geology, drilling, geophysical exploration, and other disciplines, we research the geological conditions for coalbed methane mining, design, construction, and general contracting of coalbed methane extraction projects in coal mining areas. Provide customers with a "one-stop" overall solution for coalbed methane development (surface gas extraction). We have mastered the intelligent and refined drainage and extraction technology of coalbed methane suitable for different geoogical conditions and achieved the goal of “long-term, continuous, and stable” coalbed methane well drainage and extraction. Continue to promote scientific and technological progress in efficient coalbed methane extraction in China's coal mining areas.

Extraction Site

Investigation of Hidden Disaster-Causing Factors in Coal Mines

1. Advanced regional prevention and control technology for dynamic disasters caused by strong mine pressure (burst pressure) in coal mines

In response to the problem of preventing and controlling dynamic disasters caused by strong mine pressure in thick hard roofs and overlying coal pillars, Xi'an Institute pioneered the development of a complete technical equipment system for open-hole segmented hydraulic fracturing of directional long boreholes in underground coal mines, forming a technology system for advanced regional transformation of coal and rock formations. It has opened up a new direction for the active prevention and control of dynamic disasters caused by strong mine pressure on the roof of the industry (impact rock pressure) and successfully achieved advanced, regional, active, precise, and effective prevention and control of strong mine pressure dynamic disasters on thick hard roofs and overlying coal pillars underground in coal mines. It has been extended to eight service directions including mine earthquakes, rock bursts, weakening of coal seam gangue layers, improvement of lump coal rate, and gas penetration enhancement and drainage.

Complete Technical System for Open-Hole Staged Fracturing of Directional Long Boreholes in Underground Coal Mines

1.1 Prevention and control model of dynamic disasters caused by strong mine pressure based on long underground borehole open hole staged fracturing

Based on the innovative results of underground long borehole open-hole segmented fracturing technology and equipment, a single thick layer, composite hard roof, and overlying coal pillars were created to prevent and control regional disasters caused by strong mine pressure. By building a collaborative support system of "fracturing collapse filling + coal pillars + load-bearing rock strata", the fracture disturbance of the thick hard roof is controlled, and the deformation and fracture of the high-level rock strata are suppressed; the composite hard roof is fractured in stages with high and low dislocations to achieve staggered timing of the composite hard roof, short distance, no superimposed fracture; methods such as transforming coal pillars and carrier migration space, weakening key rock strata, uniformly distributed concentrated stress and transfer stress transfer paths, suppressing coal pillars, etc., to achieve strong ore deposits with thick hard roofs and overlying coal pillars Safe and effective control of pressure hazardous areas.

Pressure Relief Prevention and Control Model in the Area of Strong Mine Pressure Dynamic Disaster with a Single Thick Layer of Hard Roof

Composite Thick Layer Hard Roof Pressure Relief Prevention and Control Model for Strong Mine Pressure Dynamic Disaster Areas

Pressure Relief and Prevention Model in Areas with Strong Mine Pressure and Dynamic Disaster Caused by Overlying Coal Pillars

1.2 Application cases

Shendong Burtai Coal Mine: Shendong Burtai Coal Mine adopts the underground directional long borehole segmented fracturing technology model to relieve pressure in a single thick layer of hard roof area. A total of 6 working faces with an area exceeding 10,000m have been treated, creating a single hole of 800m divided into 18 segments industry implementation records.

China Coal Northwest Energy Nalinhe No.2 Mine: This is a typical roof impact mine. It adopts the composite hard roof regional pressure relief technology model and created a record of 600m divided into 10 sections with a vertical height of 73m and an accuracy of ±0.2m. Proactive and effective regional management of rockburst disasters, an increase of 2 in a single day, and efficient mining in safe, cost-effective, protected, and treated areas.

Shendong Mining Area: 8 mines in the Shendong Mining Area, including Yujialiang, Shigetai, Liuta, Daliuta, and Shangwan, have adopted the regional pressure relief technology model of overlying legacy coal pillars, and have treated nearly 100 legacy coal pillars in 30 working faces. Pillars create effective prevention and control of highly dangerous areas at extremely close range (<10m) overlying coal pillars.

2. Enhanced drainage technology of hydraulic fracturing gas in underground coal mines

In response to different geological conditions and coal body structures, we have adapted the hydraulic fracturing technology of underground directional long boreholes in coal mines to the enhanced extraction of anti-permeability gas from coal seams. For soft and low permeability coal seams, medium to low permeability coal seams with moderate hardness, and medium to hard low permeability coal seams, the "coal seam roof and floor comb-shaped hole integral/segmented fracturing technology, and floor cross-layer directional long drilling integral Fracturing technology and bedding directional long borehole integral/staged hydraulic fracturing technology" are used to implement fracturing to increase penetration and enhance drainage. At the same time, it can be used in combination with equipment such as special sand fracturing and directional injection for underground coal mines to improve the effect of fracturing and improve gas control efficiency.

Schematic Diagram of Integral/Staged Fracturing Technology for Comb-Shaped Holes in the Floor of Crushed Soft Coal Seam

Schematic Diagram of Overall Fracturing Technology for Directional Long Drilling through the Coal Seam Floor

Schematic Diagram of Overall/Segmented Hydraulic Fracturing Technology for Directional Long Borehole Drilling in Medium-Hard Coal Seams

2.1 Technical advantages

1) Rapid setting in open hole drilling, multi-stage fracturing stage by stage, increasing the strength of single-stage fracturing and improving the overall fracturing effect.

2) The depth of fracturing drilling is more than 500m, and more than 10 stages of fracturing are performed in a single hole.

3) Sand fracturing can be implemented to fill and support the fracturing cracks and improve the conductivity of the cracks.

4) Transform the coal and rock mass structure, increase the gas permeability of the coal seam, and improve the coal seam gas drainage effect.

5) Improve coverage and borehole gas extraction efficiency to achieve advanced and precise regional prevention and control.

2.2 Scope of application

1) Efficient gas drainage in the top/floor segmented hydraulic fracturing area of long boreholes in crushed soft coal seams

2) Directional deep-hole staged hydraulic fracturing of medium-hard coal seams to increase permeability and high-efficiency drainage in coal seam areas

3) Hydraulic fracturing of directional long boreholes in the airborne working face to enhance the penetration of coal seams and enhance gas drainage

4 ) Large-area/panel-type advanced gas drainage of coal seams based on “fracturing + pre-drainage”

5) High gas pressure crushes soft and strong outburst coal seams and uses long directional boreholes for remote area drainage and pressure relief

2.3 Application effects

The directional long borehole staged hydraulic fracturing coal seam anti-reflection technology has been applied and promoted in typical coal mining areas such as Yangquan, Hancheng, Huangling, Binchang, Jiaozuo, Xinjiang, and Guizhou. Taking the hydraulic fracturing drilling of Xinjing Company in the Yangquan Mining Area as an example, the hydraulic fracturing of coal seam drilling has an influence length of more than 300m and a maximum influence radius of 58m. Within 3 months after fracturing, the average gas drainage concentration of the drilling hole is 72.27%. The average amount of pure gas extracted in a single day is 2475m3/d, a good record. The application of this technology has effectively improved the efficiency of mine gas extraction and expanded the coal seam gas control area.

Actual Trajectory Map of Downhole Bedding Long Borehole

Bedding Directional Drilling Hydraulic Fracturing Drainage Renderings

3. Gas content testing technology for long-distance closed coring of underground coal seams in coal mines

The gas content is the sum of lost gas volume, desorbed gas volume, and residual gas volume. Disadvantages of the conventional testing method: the gas loss is calculated based on the on-site desorption rate, while long borehole coring results in inaccurate estimation of gas loss due to the presence of coal cores and long exposure time. The advantages of long-distance sealed coring gas content testing technology for underground coal seams: ensuring that the coal core is sealed during the entire process of drilling, retraction, and natural desorption, reducing gas loss estimation steps, and greatly improving the accuracy of gas content testing.

3.1 Long-distance sealed coring device and process flow

Device Actual Picture

3.2 Technical advantages

1) Real-time measurement and control of directional hole drilling trajectories and long-distance drilling technology are used to achieve long-distance and precise fixed-point coring downhole.

2) Realize that the coal core is sealed during the entire process of drilling, retraction, and natural desorption, improving the gas content testing accuracy by more than 20% and making the test results closer to reality.

3) Suitable for coal seams or rock formations with various geological conditions

3.3 Application cases

Jincheng Sihe Mine: Long-distance sealed coring gas content tests were conducted in multiple coal lane strips of the mine, and sealed coal seam coring samples were collected at 56 measuring points. The maximum core hole depth reached 516m, and the average sample collection rate reached more than 90%, the gas content measured value is about 1.23~1.88 times that of the conventional coring method, which provides reliable data support for understanding the occurrence of coal seam gas and evaluating the regional gas drainage effect.

Measuring Point Layout and Coal Core Photos of the Long-Distance Sealed Coring Section

Qidong Coal Mine: The main coal seam of the mine is a typical soft and low-permeability coal seam. In this mine, multiple bottom and roof comb-shaped long drilled coal seam sealed coring original gas content tests were carried out. The maximum core hole depth reached 483m, and the gas content was tested. The content measurement results provide accurate data support for mines to understand the distribution patterns of coal seam gas in mining areas and comprehensive regional gas control.

Measuring Point Layout for Long-Distance Closed Coring Section of Comb-Shaped Borehole in Broken Soft Coal Seam

4. Complete set of technology and equipment for segmented hydraulic fracturing of directional long boreholes in coal mines

We have independently developed segmented hydraulic fracturing technology and equipment for underground directional long boreholes in coal mines. It has developed hydraulic sandblasting continuous prefabricated guided fracture technology, open hole or in-casing segmented hydraulic fracturing technology, and fracturing tool jamming technology. technology and fracturing effect testing and other key technologies, and have been successfully used in the fields of coal seam hard roof and strong mine pressure dynamic disaster prevention and coal seam enhanced gas drainage, which has greatly promoted the prevention and control of long-distance and large-scale advanced dynamic disasters and gas enhancement in coal mines. Advances in extraction technology.

4.1 Directional long borehole segmented hydraulic fracturing hard roof dynamic disaster prevention technology

As resources in the central and eastern regions become increasingly depleted, coal resource mining gradually moves to the west. As mining depth increases, the frequency and intensity of severe mine pressure disasters caused by hard roofs gradually increase. In response to this type of disaster, we have used the open-hole segmented hydraulic fracturing technology of underground long directional boreholes in coal mines for regional prevention and control, which can weaken the hard roof of the coal seam in advance before the mining of the working face, effectively reducing the area of the suspended roof and reducing the steps to press. distance, precise prevention, and control from the source of power.

Schematic Diagram of Staged Fracturing Process Technology

4.2 Technical advantages

1) The governance level control is precise, the coverage area is wide, and the segmentation and zoning governance effect is better

2) Mining can be carried out in advance of the working face without affecting each other.

3) The fracturing pump unit can achieve large displacement, high pressure, and remote intelligent control 2km away; the open hole sealing capacity of the in-hole fracturing device is more than 70MPa, and the fracturing effect is guaranteed

4) The treatment process does not produce waste water and waste gas and is safe, environmentally friendly, and pollution-free.

5) It is not affected by factors such as terrain, surface construction, green compensation, and road construction, and can be implemented at any time as needed, reducing prevention and control costs.

4.3 Scope of application

1) Management of coal seam hard roof and strong mine pressure disasters

2) Treatment of severe mine pressure disaster caused by coal pillars left in the overlying goaf area

3) Premature weakening of abnormal geological bodies

4) Advanced weakening transformation of thick hard coal seams

5) Active prevention and control in areas with advanced ground pressure (mine earthquake) disasters

4.4 Technology applications

This technological achievement has been promoted and applied in 35 large-scale fully mechanized mining working faces in 16 mines of Shendong Company, China Coal Northwest Energy, Shandong Yankuang Company, Xinjiang Company, and Binchang Company. The business involves strong mine pressure, impact Fields such as ground pressure, mine earthquakes, and high-stress concentration in overlying coal pillars. Taking Burtai Coal Mine as an example, compared with the unfractured area and adjacent untreated areas, the fracturing treatment area of the working face has a pressure step distance, dynamic load coefficient, and maximum pressure that are 20.00% to 69.70% lower than those of the unfracturing area. 5.79% to 7.90% and 13.44% to 18.64%; the stress reduction of the coal wall along the trough is 22.22% to 32.05%, and the effect is significant.

Underground Hard Roof Strong Mine Pressure Disaster Control Project Site

Fracturing treatment face support resistance cloud chart

Comparison Chart of Coal Wall Stress Monitoring along the Trough

5. Coalbed methane resource extraction potential evaluation and design technology

Based on the self-generation and self-storage characteristics of coalbed methane and comprehensive research on coalbed methane geological big data in typical coal-bearing areas at home and abroad, a complete set of technical systems covering coalbed methane geological research + resource calculation + production capacity prediction + development potential evaluation + development engineering design has been formed. It can accurately predict the extraction potential of coalbed methane resource blocks and coal mine gas, and provide reliable technical means for strategic decision-making on coalbed methane resource development and coal mine gas control design.

Schematic Diagram of Exploration Equipment

Coalbed Methane Resource Evaluation Results Chart

6. High-efficiency development technology of staged fracturing for horizontal wells on coal seam roofs

A U-shaped horizontal well with a remote end connected to a vertical well is used. The horizontal section of the horizontal well is arranged in the roof rock layer about 2 m away from the coal seam, and casing is installed for cementing. A combination of pumping bridge plug and downward directional perforation is used. The stage fracturing process implements high-intensity fracturing operations with large liquid volume, large displacement, and medium sand ratio; finally, drainage and gas production is carried out in vertical wells.

Coalbed Methane Development Model by Staged Fracturing of Horizontal Wells on Coal Seam Roof

Discharge Curve Chart

7. Coalbed methane parameter testing technology

Coal bed methane testing technology mainly includes coal bed pressure maintaining coring technology, coal bed methane content determination and sample analysis and testing technology, ground drilling coal seam original gas pressure measurement technology, coal bed methane well testing, and in-situ stress testing, which can be used to obtain coal seam information. Gas content, gas components, high-pressure isothermal adsorption parameters, coal quality, mechanical properties, original gas pressure of coal seams in ground drilling, coal seam permeability (k), reservoir pressure (Pi), skin coefficient (S ), investigation radius (Ri), reservoir temperature (T), fracture pressure (Pb), closing pressure (Pc) and other parameters, providing necessary technologies for coal mine construction, gas prevention and control, rock burst control, and surface coalbed methane development support.

Coalbed Methane Pressure Maintaining Coring Device

Coalbed Methane Content Determination and Sample Analysis Equipment

On-Site Construction Drawing of Original Gas Pressure Measurement of Coal Seam through Ground Drilling in Huaibei Mining

Coalbed Methane Well Testing Device

In Situ Stress Testing Device

8. Pressure relief and drainage technology for high-level and large-diameter boreholes in underground roofs

Using underground near-horizontal directional long drilling technology, the drilling trajectory enters the target layer in the middle and lower part of the coal seam roof fissure zone to achieve the purpose of extracting corner gas on the working surface. Directional drilling technology allows high-level drilling groups to cover the upper corners and goaf drainage areas in a targeted manner, avoiding blindness in construction and unnecessary engineering volume, improving drainage efficiency; and effectively reducing project connections and ventilation Auxiliary operations and other tasks can shorten the construction period and reduce construction costs.

Schematic Diagram of Gas Drainage Technology for High-Level Directional Long Boreholes on Coal Seam Roofs

Upper Corner Gas Concentration Under Different Extraction Methods

9. Downhole pneumatic directional drilling and gas drainage technology

A pneumatic screw drilling tool is used as the power drilling tool at the bottom of the hole. The high-pressure nitrogen provided by the nitrogen generator is used to drive the screw drilling tool to drive the drill bit to rotate to break rock and discharge slag. It is equipped with a measurement-while-drilling system to achieve manual control of the drilling trajectory. Pneumatic directional long drilling solves the problem of short drilling length in " extracting first and then digging" soft coal seams and improves the efficiency of coal seam excavation.

Moving Towards a Progressive Gas Control Model of Revealed Coal Tunnels

A Progressive Gas Control Model of the Working Surface Tends

ZDY15000LD Directional Drilling Rig

DMJ-900/20 High Pressure Nitrogen Device

10. Well-ground combined gas drainage technology

As a new model of coal mine gas disaster control, well-surface joint technology uses the technical advantages of surface well fracturing and underground directional long drilling to collaboratively carry out mine gas disaster control; its main technical features: surface pump Injection, downhole fracturing, downhole drainage, well and roadway combination, and rapid outburst elimination.

Regionalized Mine Gas Disaster Control Technology by Joint Well-Site Fracturing

The application model of mine gas disaster control technology in joint coal mines can be mainly divided into the following three models:

Rapid Gas Drainage Mode in the Intensive Staged Fracturing Area through Ultra-Long Directional Drilling for the Excavation Working Face

Progressive Gas Drainage Model in the Directional Long Borehole Factory-Based Staged Fracturing Area for Mining Working Faces

Progressive Gas Drainage Model in the Directional Long Borehole Factory-Based Staged Fracturing Area for Mining Working Faces

11. Coal mine roof gas mining horizontal well

horizontal boreholes on the surface of the stope to the overlying rock fissure zones or coal seams that may be formed by coal seam mining, we can make full use of the pressure relief and permeability-enhancing effect of coal seam mining, so that as much gas as possible can be extracted through the fissure network and wellbore to On the ground, it achieves the purpose of reducing the gas emission in the mining working face, alleviating the excessive gas pressure and developing coal bed methane.

Well-to-Ground Connected Composite Gas Drainage and Extraction