Plasma-pulse treatment technology for the advance degassing of coal seams
Plasma Pulse Treatment or PPT is a stimulation technique used to enhance the secondary
permeability of the target formation by creation of new micro fractures and opening of existing ones. Deployed by standard wireline equipment, the Plasma Pulse Streamer applies repeated plasma pulses to the target zone of the formation.
Vertical PPT instrument: An icon of Innovation
Key Feautures
Generates non-linear controlled and directed vibrations/pulses.
Elastic vibrations generate plasma waves.
Elastic vibrations persist post treatment.
Operation duration < 24 hours.
How does it work?
- The generator placed in the target zone creates dense plasma. Pressure pulses open existing and create new microfractures, which enhances the permeability of the formation.
- The generator is capable of producing upto 2000 pluses in one run, causing significant impact on the mechanical integrity of the formation zone, thus creating microcracks.
- The electrodes places in the tool ionizes the wire, which acts as a source of plasma that creates a powerful impulse.
- The pulse characteristic can be optimized in accordance with the requirement and maximizing the impact on the formation.
Advance degassing of coal seams
Coal resources are well known for the Methane adsorption and entrapment properties. It is popularly known as Coal Bed Methane (CBM). CBM is formed during the process of coalification (transformation of plant material into coal).
CBM can pose a challenge in 2 scenarios:
- Posing a hazardous threat for miners working in coal extraction — Mining Industry.
- Difficulty in exaction of this Methane for commercial production — Natural Gas Production Industry.
Where does PPT come into play?
The electrodes are connected by conductor
Plasma is formed
A shock wave is generated and transmitted through the coal seam
The shock wave leads to volumetric elastic oscillations and mud is released into the wellbore
High voltage current is fed to the metal electrodes which causes the evaporation of this conductor
This leads to generation of huge amounts of energy in a short period of time
A quasi-neutral plasma is formed, characterized by temperatures as high as 4*104 K and pressures of 4*1010 Pa
This pressure is transmitted through the coal seam in the form of a shock wave, causing the environment to compress and stretch
A secondary permeability (microcracks) is formed in the coal seam, which binds with natural fracture system
Degassing process
- Drilling vertical wells from the surface.
- Conducting logging in an open hole to clarify the depth and thickness of the coal seam.
- Conducting PPT in the interval of coal seam and, if necessary, in the enclosing rocks.
- Degassing: dispatching the downhole pumping equipment, extraction of liquid, bringing wells to a stable flow rate of methane and 24-hour monitoring.
- Wells are used for degassing in the dome of the collapse. By the beginning of the start of lava, the downhole pumping equipment is removed from the wells and the mining machinery is activated.
Stages of Work for the implementation of the project of advance degassing
Project development
Construction of access roads, laying of power lines and arrangement of well pads
Selection and purchase of equipment
Drilling of wells (using dome degassing wells with re-drilling of coal seam intervals)
Characteristics of PPT equipment
Design Characteristics
- Length of tool 9 ft
- Outer Diameter 4,02 in
- Weight 200 lb
- Maximum operational temperature +100 Cº
Mechanical Characteristics
- Maximal pressure, in/out 25 MPa
- Weight in air 1 800 kg/km
- Breaking Force, not less than 120 kN
Power Characteristics
The power source consumes only 500 watts
at 110/220 volts. The energy stored
in batteries is released in 55 microseconds.
Monitoring options
- Round-the-clock monitoring is carried out with the help of an Automated Process Control System (APCS).
- Remote monitoring is possible as demonstrated in fig 4 and 5.
Fig 4: The shared screen of all wells
Fig 5: The following well parameters are recorded: fluid level in the well, bottomhole pressure, annular pressure, gas flow rate, gas temperature, water flow rate, pump rotation speed, engine current, cumulative production
Restrictions on the use of PPT equipment
- Internal diameter of the production string, not less than 114 mm.
- Reservoir pressure, not more than 40 MPa.
A journey through time
1928
If there is a solid and liquid medium in which compressive
and tensile stresses are created, then any solid medium
can be destroyed. This effect was discovered by P. A. Rebinder
in 1928.
1972
This effect is an adsorption decrease in strength - a change in the mechanical properties of solids due to physicochemical processes that cause a decrease in the surface (interfacial) energy of the body, which can lead to deformation.
In the case of a solid body, in addition to reducing the surface energy, for the manifestation of the Rehbinder effect, it is also important that the medium has defects in the structure necessary for the initiation of cracks, which then spread under the influence of the treatment.
In the case of a solid body, in addition to reducing the surface energy, for the manifestation of the Rehbinder effect, it is also important that the medium has defects in the structure necessary for the initiation of cracks, which then spread under the influence of the treatment.
1997
When gas bubbles appear, the process of cavitation occurs. The leading role in the formation of bubbles during cavitation is played by gases released inside bubbles. These gases are always contained in the liquid, and with a local decrease in pressure, they begin to vigorously precipitate inside the said bubbles.
2007
The company has developed a source of directional controlled broadband oscillations, which is a metal pipe with a diameter of 102 mm and a length of 2700 mm, with a radiator equipped with high-voltage electrodes, a power battery, pulsed storage capacitors and a device for supplying a calibrated metal conductor into the inter-electrode space, to which, at the operator's command, an electrical impulse of high power is applied, causing the conductor to evaporate, turning into a quasi-neutral plasma (high-pressure neutral gas bubble).
The power source consumes only 500 watts at 110/220 volts. The energy stored in batteries is released in 55 microseconds.
The power source consumes only 500 watts at 110/220 volts. The energy stored in batteries is released in 55 microseconds.
2015
The analysis showed that the coal seam in its acoustic properties is ideally suited for the application of plasma-pulse treatment. Georezonans has refined the technology that was originally used for the improvement of oil production and patented the method of advance degassing.
If coal seams and enclosing rocks proactively create tensile and compressive stresses according to the periodic principle through wells drilled from the surface, prior to coal mining, then the process of self-modulation will begin to increase in the coal seam treatment effect. And a significant amount of gas adsorbed and dissolved in the coal will pass into the free state.
The “natural trigger”, which triggers gas-dynamic phenomena in the coal seam, is the same for all deposits belonging to the natural nonlinear, dissipative, dynamic system that is in a stressful state, despite their diversity. In this case, the driving force is the energy of free gas and the energy of elastic deformation, which take part in unexpected emissions into the working space of the mines.
If coal seams and enclosing rocks proactively create tensile and compressive stresses according to the periodic principle through wells drilled from the surface, prior to coal mining, then the process of self-modulation will begin to increase in the coal seam treatment effect. And a significant amount of gas adsorbed and dissolved in the coal will pass into the free state.
The “natural trigger”, which triggers gas-dynamic phenomena in the coal seam, is the same for all deposits belonging to the natural nonlinear, dissipative, dynamic system that is in a stressful state, despite their diversity. In this case, the driving force is the energy of free gas and the energy of elastic deformation, which take part in unexpected emissions into the working space of the mines.
1928
1972
1997
2007
2015
Developers of technology
- St. Petersburg State Mining Institute named after G.V. Plekhanov (Technical University), (Dr. Sc., Professor A.A.Molchanov).
- Research Institute of Electrophysical Equipment named after D.V. Efremova (NIIEFA JSC), (Dr. Sc., Professor O.P. Pechersky).
- The mathematical model of fluid-poroelastic behavior of the reservoir during PPT was developed by the “Institute of Applied Mathematics. M.V. Keldysh of RAS".
- Microseismic studies in the application of PPT on coal seams were carried out by the JSC “Inverse Problem Technologies” and the Research Institute of Applied Informatics and Mathematical Geophysics of the Baltic Federal University named after Immanuel Kant.
- Bench tests of the effect of PPT on the fluid were carried out jointly with the “Scientific Center for Nonlinear Wave Mechanics and Wave Technologies (RAS)”.
- Bench tests of the effect of PPT on the fluid were carried out jointly with the “Scientific Center for Nonlinear Wave Mechanics and Wave Technologies (RAS)”.
- Three-dimensional geodynamic and hydrodynamic modeling of PPT in coal seams was repeatedly built by specialists from Moscow State University of Lomonosov.
- In the development of methods for influencing the productive layers of hydrocarbons, theoretical studies of the Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, as well as the Institute of Thermophysics named after. S.S. Kutateladze of SB RAS were used.