The present invention relates to the oil industry, in particular, to induction heaters used in production wells of paraffinic, viscous and other oils for removal of paraffin deposits.
There is known an induction heater (patent RF 2086759, 1995), including a casing, housing and three separate induction coils (one for each phase) with three radiators. The cavity between the housing and the casing is filled with dielectric oil.
The disadvantage of that heater is the use of an expensive 3-core logging cable, an inefficient method of using eddy currents when converting electrical energy into heat and, accordingly, increased electricity consumption.
A close related art of the above device is an induction heater (patent RF 2284407, IPC E21V36/04, 37/00, 2006), containing a casing, a carrier element located coaxially with a casing with a series of induction coils placed on it, equipped with ferrite magnetic wires. In addition, the carrier element is made in the form of a conductive non-magnetic rod, the lower part of which is closed by the output coil of the last winding of the lower coil of the induction heater. The upper part of the carrier element is closed through the connector to the armor shell of the logging cable, the first winding of the upper coil is connected through the connector to the central core of the cable (CCC). The upper part of the casing is made of non-magnetic and non-conductive material, the lower part of the casing is made of magnetic and electrically conductive material, while the coil windings are wound on ferrite magnetic cores with different diameters, and the windings of the upper coil are wound on a ferrite magnetic core with a large diameter, and the windings of the lower coil are wound on a ferrite magnetic core with a smaller diameter.
An essential disadvantage of the aforementioned prior art heater is large power losses, when working at great borehole depths. For example, for borehole depth from 5000 meters or more, as well as at a low output frequency (about 1 kHz), the efficiency of the heater is significantly reduced. The use of ferromagnetic materials for manufacturing the induction coil limits the amount of current in the oscillating LC-circuit due to a low value of the saturation magnetization of ferrites.
There is known a more efficient device, which is a downhole induction heater disclosed in U.S. Pat. No. 9,839,075 issued Dec. 5, 2017, being the closest related art. It eliminates almost all the shortcomings of induction heaters described above. It also provides for protection against a negative impact of the skin effect, which reduces the conductivity of electrical connections during running of high frequency currents.
However, that device also has some structural disadvantages, and insufficient protection from the skin effect in certain parts of the high-frequency electrical connections. These disadvantages reduce the efficiency of induction heating and increases unproductive energy losses in the downhole induction heater described in U.S. Pat. No. 9,839,075.
The present invention allows solving a problem of reducing unproductive losses of electric power, conditioned by negative impact of the skin effect, and increasing the efficiency of induction heating.
The object of the invention is achieved through unique engineering solutions used in the development of structural components of the inventive induction heater in conjunction with employment of modern electronic/control components.
According to the present invention, there is proposed an induction heater being a major component of an equipment complex for removal of paraffin deposits in borehole columns of production oil wells, while the borehole column is filled with borehole liquid under pressure developed therein at significant depths of several kilometers of oil wells. The induction heater is immersed into the borehole column and electrically powered substantially from a standard power supply source.
The induction heater includes an inductor joined essentially with a control module enclosing electronic components. The inductor includes a non-metallic protective cover enclosing particularly an induction coil that heats up a heating rod with a tip, which tip melts the paraffin deposits located immediately below the tip. The non-metallic protective cover also provides for free propagation of HF-magnetic field created by the induction coil, while the HF-magnetic field additionally heats up the column's walls melting paraffin thereon. An internal cavity is formed particularly by certain surfaces of the protective cover, the tip, the induction coil, etc. (see explanation below). The internal cavity communicates with an elastic compensator via a hollow channel. The internal cavity is filled with a liquid filler with suitable electric insulation properties and allowing the inductor to withstand high pressure of the borehole liquid developed inside the borehole column. A surplus of the liquid filler formed in the internal cavity due to volumetric temperature expansion flows into the compensator via the hollow channel. Certain embodiments of the proposed invention envisage regulating the heater's temperature, the rate of downward passage of sections of the borehole column, and operating the inductor at a resonance frequency. Preferred materials and configurations of certain components of the invention are also disclosed herein.
While the invention may be susceptible to embodiment in different forms, there are described in detail herein below, specific embodiments of the present invention, with the understanding that the instant disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as described herein.
According to a preferred embodiment of the present invention, an equipment complex for removal (melting) of paraffin deposits in production oil wells (specifically, in borehole columns) includes an induction heater.
The inductor 4 (in detail shown in
The control module 2 (in detail is shown in
A functional diagram of the equipment complex for removal of paraffin deposits in borehole columns of production oil wells is shown in
A fragment of circuitry of the induction heater is shown in
Specifically, the internal cavity 37 is formed essentially by the following elements: the tip 6 (its upper surface), the protective cover 20 (its inner sidewalls), the inductor cap 16 (its inner sidewalls and top surface), the hollow channel 18 (its inner surface), and the compensator 19 (its inner surface). Mechanical hardness and solidity of the inductor 4 are provided particularly by a threading connection of the heating rod 5 with the connector assembly 11; whereas the connector assembly 11 is attached by a threading connection to the lower part of inner sidewalls of the passage bushing 12 (preferably by three screws), while the upper part of inner sidewalls of the passage bushing 12 is attached by a threading connection to the inductor cap 16 (preferably by three screws).
Factually, the inventive design of the internal cavity 37 along with the compensator 19 provides, on one hand, for mechanical protection of the inductor's components against aggressive factors of environment (i.e. allows the protective cover 20 withstanding high external pressure of the borehole liquid by providing an equal pressure of the liquid filler inside the internal cavity 37). On the other hand, the inventive design allows making the protective cover 20 of a non-metal material (preferably suitable polymer, see above) providing for practically free propagation of the HF magnetic field of the inductor 4 that additionally enables heating up the internal walls 34 of the borehole column melting paraffin deposits adhered thereto. Additionally it provides for an efficient cooling arrangement using vertical convectional flows of the filler liquid inside the internal cavity 37 during its heating by the heating rod 5 and the tip 6. All these major advantages of the present invention significantly enhance operation of the inductor 4, as well as of the downhole induction heater in whole (also see explanation below).
The windows 39 are necessary to pass high hydro-static pressure of the borehole liquid, developed inside the borehole column with walls 34, to the outer surface of the compensator 19, since the protective cover 20 (preferably made of polymer material—see above) cannot withstand that hydro-static pressure. On the other hand, it necessitates developing at least an equal pressure on the inner surface of the compensator 19. This condition requires that the compensator 19 be communicated with the internal cavity 37 (see explanation above, and
During operation of the inductor 4 (see explanation below), the liquid filler is heated up (increasing the inner pressure inside the compensator 19) and expands (due to volumetric temperature expansion) into the inner space of the compensator 19, thereby equalizing the outer hydro-static pressure of borehole liquid by the inner pressure inside the compensator 19.
The induction coil extension 44 connects the induction coil 8 with the inductor contact group 17 and subsequently with the control module contact group 23 (see
The brackets 45 fix the induction coil extension 44 to the walls of the passage bushing 12. The brackets 45 are preferably made of a suitable polymer material.
According to preferred embodiments of the invention, operation of the induction heater as part of the aforesaid equipment complex is carried out as follows. The microprocessor, being part of the CPU 27 (see above) includes long-term memory, which stores a pre-installed computer program. When electric power is supplied from the ground station 32 to the induction heater, the computer program starts executing. The computer program instructs to measure the temperature in the central area of the tip 6 and the temperature of the cooler of transistors of the high-frequency inverter 25, which measurements represent telemetry information. The CPU 27 processes the telemetry information, sends it to the telemetry unit 42 that encodes it, preferably with Manchester II code, thereby obtaining telemetry information, and transmits the telemetry information via the power cable 33 (see
The other microprocessor with Manchester II code (being part of the ground operating means) of the ground station 32 decodes the telemetry information and outputs information to the LED display. The temperature values allow the operator, using the ground operating means, for assessing operability of the induction heater and adjusting the speed of passage of the borehole column's sections downward the oil well containing paraffin deposits (see also
If the temperature of tip 6 drops below 95° C., the rate of paraffin deposits penetration should be reduced, if the temperature exceeds 110° C., the ground operating means automatically reduce the supply voltage of the induction heater by 5% every 2 minutes to establish the temperature of the tip 6 in the range of 95-110° C.
An important task in designing the induction heater is to ensure operation of the series LC-circuit, formed by the induction coil 8 and the capacitor battery 13, at its resonant frequency. In this mode, the series LC-circuit has a close to zero reactance and, therefore, a close to zero of inefficient reactive power. At that, the efficiency of induction heating reaches its maximum value.
Pulse voltage with the frequency F0 is amplified by power with the high-frequency inverter 25 and the high-frequency transformer 14, and is then supplied to the series LC-circuit.
In the circuit, forced harmonic oscillations arise and electric current flows therethrough. Voltage from the input of the series LC-circuit and a resistor (not shown) from the secondary side of the current transformer 15 proportional to the electric current flowing through the series LC-circuit are fed to the phase detector (preferably, the Texas Instruments chip CD4046BE) of the PLL 26.
The phase detector converts a phase angle of incoming signals into voltage. The sign of the voltage depends on whether the voltage at the input of the series LC-circuit is behind or ahead of the current flowing therethrough. The voltage of the phase detector adjusts the frequency of the VCO so that the angle of phase shift between the current and voltage signals is close to zero, and thus the operating condition of the series LC-circuit at the resonant frequency is satisfied.
The impedance of a series LC-circuit is calculated by the following formula:
wherein: R is the active resistance of the series LC-circuit,
ω×L is the inductive resistance,
is the capacitive resistance,
ω is the natural or cyclic frequency of the voltage applied to the series LC-circuit.
In turn, ω=2×π×f, where f is the frequency of the voltage applied to the series LC-circuit. It can be seen from the formula that when the inductive and capacitive resistance of the components of the series LC-circuit are equal, its impedance is equal to the active resistance of the inductor, that is, the series LC-circuit does not consume reactive power. The phase angle between current and voltage is zero. This is the condition for appearance of resonance of voltages in the series LC-circuit.
If all electrical connections in the circuit are made with a multicore conductor, then the active resistance of the circuit will be very small and amount to several thousandths of Ohm. Then even a small voltage of 1V applied to the series LC-circuit can generate currents of several hundred amperes. The energy of the magnetic field stored in the inductor is directly proportional to the square of the current flowing through the inductance. From the energy point of view, it is advantageous to increase not the coil inductance in the series LC-circuit, but the current flowing through it. Therefore, it is so important to ensure operation of the series LC-circuit at a resonant frequency.
The calculated resonant frequency of the series LC-circuit in the absence of ferromagnetic materials surrounding the inductor 4, such as the borehole column, is to be in the range of 90-100 kHz. During operation, it can vary depending on the size of the borehole column and the type of metal which they are made of, and because of heating the elements of the series LC-circuit during operation.
Usage of the proposed method of frequency tuning provides almost instantaneous, during microseconds, frequency correction and fine tuning to resonance. It should be noted that switching of high-power MOSFET transistors of the high-frequency inverter 25, when operating at a resonant frequency, occurs at a time when the current of the series LC-circuit is close to zero. This mode of operation significantly reduces heating of the MOSFET transistors to minimum values. This is an important feature, since it is not possible to apply active cooling of the powerful MOSFET transistors in the induction heater.
Other advantages (besides those mentioned herein above) of design of the inventive induction heater include:
However, the sections Bpa-Cpa, Cpa-Dpa, Dpa-Epa, and Epa-Fpa have no protection from the skin effect, as they are made of cast copper and brass pipes (section Bpa-Cpa and Cpa-Dpa), brass coupling 4pa (section Dpa-Epa) and semi-cylindrical brass container 1pa (section Epa-Fpa). The thickness of the conductivity layer for the frequency of the inductor disclosed in U.S. Pat. No. 9,839,075 does not exceed 0.2 mm from the outer and inner sides of the conductive surfaces.
An important characteristic of a resonant oscillatory circuit is quality factor. The quality factor determines how many times the energy stored in the oscillation circuit is greater than the energy loss for heating conductors in a single oscillation period and is calculated by the following formula:
where Q is the quality factor, R is the resistance of the resonant circuit, L is the inductance, and C is the capacitance of the capacitor battery.
In the proposed design of the inventive induction heater, a harness composed preferably of 350 enameled copper wires 0.4 mm in diameter is used to make the induction coil 8 and all electrical connections of the series LC-circuit.
With an active resistance value of 0.7*10−3 Ohms, an inductance of 1.2 pH and a capacitor battery's capacitance of 2.4 pF, the Q value will be 1020. As a result, the proposed design of the inventive induction heater has a significantly higher protection against negative impact of the skin effect and, consequently, greater efficiency of induction heating.
Implementation of such design of the induction heater is possible only if all elements of the inductor 4 are located in a cavity (the internal cavity 37 described above) filled with a special liquid filler. This makes it possible to protect the inductor's elements from high hydraulic pressure of the borehole fluid and mechanical damage. As noted above, silicon-organic fluid is preferably used as the filler, which has suitable electrical insulating properties.
As a result of heating the inductor's components during operation, vertically oriented convection flows of the filler are formed in the cavity of the inductor 4. They eliminate the sharp temperature gradients in the cavity of the inductor 4 and provide heat exchange with the environment through the walls of the protective casing 20. Any surplus of the filler, formed during operation of the induction heater, due to volumetric temperature expansion is neutralized (absorbed) by the compensator 19.
Thus, the VOC signal of the PLL 26 (see
Schematically, the paraffin removal process is shown in
Number | Name | Date | Kind |
---|---|---|---|
2757739 | Douglas | Aug 1956 | A |
4319632 | Marr, Jr. | Mar 1982 | A |
4453319 | Morris | Jun 1984 | A |
4538682 | McManus | Sep 1985 | A |
7096953 | de Rouffignac | Aug 2006 | B2 |
7121342 | Vinegar | Oct 2006 | B2 |
7172038 | Terry | Feb 2007 | B2 |
7363979 | Hill | Apr 2008 | B2 |
7370704 | Harris | May 2008 | B2 |
7405358 | Emerson | Jul 2008 | B2 |
7461691 | Vinegar | Dec 2008 | B2 |
7543643 | Hill | Jun 2009 | B2 |
7563983 | Bryant | Jul 2009 | B2 |
7730936 | Hernandez-Solis | Jun 2010 | B2 |
7798220 | Vinegar | Sep 2010 | B2 |
8146669 | Mason | Apr 2012 | B2 |
8225866 | de Rouffignac | Jul 2012 | B2 |
8257112 | Tilley | Sep 2012 | B2 |
8327932 | Karanikas | Dec 2012 | B2 |
8485256 | Bass | Jul 2013 | B2 |
8857051 | Burns | Oct 2014 | B2 |
8943686 | Hartford | Feb 2015 | B2 |
9048653 | D'Angelo, III | Jun 2015 | B2 |
9080409 | Craney | Jul 2015 | B2 |
9466896 | Harmason | Oct 2016 | B2 |
9839075 | Sokryukin | Dec 2017 | B1 |
10645762 | Elserman | May 2020 | B2 |
20020028070 | Holen | Mar 2002 | A1 |
20030098149 | Wellington | May 2003 | A1 |
20030146002 | Vinegar | Aug 2003 | A1 |
20030196789 | Wellington | Oct 2003 | A1 |
20040104045 | Larovere | Jun 2004 | A1 |
20040149443 | La Rovere | Aug 2004 | A1 |
20060289536 | Vinegar | Dec 2006 | A1 |
20070127897 | John | Jun 2007 | A1 |
20090071646 | Pankratz | Mar 2009 | A1 |
20090260824 | Burns | Oct 2009 | A1 |
20100089584 | Burns | Apr 2010 | A1 |
20100258265 | Karanikas | Oct 2010 | A1 |
20110134958 | Arora | Jun 2011 | A1 |
20110247805 | De St. Remey | Oct 2011 | A1 |
20110247816 | Carter, Jr. | Oct 2011 | A1 |
20110248018 | Bass | Oct 2011 | A1 |
20120039358 | Bosselmann | Feb 2012 | A1 |
20120084978 | Hartford | Apr 2012 | A1 |
20120085564 | D'Angelo, III | Apr 2012 | A1 |
20120255772 | D'Angelo, III | Oct 2012 | A1 |
20130167872 | Weston | Jul 2013 | A1 |
20140246193 | Wollen | Sep 2014 | A1 |
20150292299 | Blendinger | Oct 2015 | A1 |
20160265325 | Sharma | Sep 2016 | A1 |
20170094726 | Elserman | Mar 2017 | A1 |
20170361501 | van der Zalm | Dec 2017 | A1 |
20200061760 | Haimer | Feb 2020 | A1 |
Number | Date | Country | |
---|---|---|---|
20200157918 A1 | May 2020 | US |