RU2112134C1 - Gear breaking hydrate and paraffin plugs - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: gear is meant for intensified breakage of hydrate and paraffin plugs in complex holes. Electric heater which working conductors are connected to electrode is lowered into hole on multiconductor cable. Thermal action on matter of plug is conducted simultaneously with application of low-frequency vibration generated by additional gear included in mix of electric heater ( electromagnetic vibrator ). Gear makes it possible to operate both under mode of heating with all six working conductors connected to single-phase source of electric energy and under mode of ohmic resistance of cable when working conductors are connected in pairs in three groups and are linked to three-phase source of energy. EFFECT: improved breaking efficiency of gear. 1 cl, 4 dwg

Description

 The invention relates to the oil industry, in particular to devices for the elimination of hydrated or paraffin plugs in production casing of production wells.

 Known borehole thermoacoustic device [1] containing an acoustic emitter and an associated heater with a terminal chamber. The source of ultrasonic vibrations is made of a permendur-type alloy and creates ultrasonic vibrations in the frequency range from 5 to 30 kHz, which propagate in the radial direction, and the oscillation intensity reaches 5 - 10 W / cm, and a ground-based ultrasonic generator is required for the deep emitter to work, it energy is transmitted via cable to the radiating sections, due to their radial change, acoustic vibrations are created, the direction of which is regulated by reflectors. The combined action of thermal and acoustic fields leads to a multiple increase in the effective thermal diffusivity of the formation in the zone of its processing. Despite the obvious advantages of the combined effects of thermal and acoustic fields on the treated object, it is impossible not to note the narrowly directed applicability of the device only when it affects the bottom-hole formation zone (BHP). Since it is realistic to have a heater with a length of 10-15 m to obtain a sufficient power level (at least 8-10 kW), this requires the use of lubricators of an appropriate length. The high frequency of the ultrasonic emitter and the radial direction of vibration exclude the possibility of its use for the destruction of hydrate and paraffin plugs in the tubing and especially in the annulus.

 A known method of eliminating hydrated and paraffin plugs in wells and a device for its implementation, taken as a prototype [2], the technology of which provides for the shorting of free cable cores from the heater and connecting them to a power source.

 Such a solution to the problem, including the use of free cores in order to obtain additional thermal energy and its removal into the molten substance of the cork to maintain the temperature in this zone above the crystallization temperature, is acceptable.

 Actually, the cable’s operation in the ohmic resistance mode with the heater running does not always give the expected result, since the process of tube destruction due to its unpredictability most often does not fit into the optimal time frame. This leads to overheating of the cable located on the winch drum to such an extent that the protective sheath of its cores does not stand up (it starts to evaporate).

 The purpose of the invention is the intensification of the destruction of hydrate and paraffin plugs both in the tubing and in the annulus of the wells by melting them with an electric heater.

 To implement the technical solution, a hydrate plug destruction device is used, containing a power source and a multicore cable connected with it with an electric heater, the cable being connected to the electric heater by one part of the cores, the other part of the cores is shorted and connected to the power source with the possibility of separate or simultaneous switching on of the electric heater and shorted cores stranded cable. According to the invention, in the device, all operating conductors on the heater side are connected to its electrode, and on the side of the current source in the heater operating mode, all operating conductors are connected to a single-phase current, and in the ohmic resistance mode of the cable, the operating conductors are connected in pairs and are divided into three groups with the possibility of connecting to three-phase current.

 A comparison of the claimed technical solutions with the prototype made it possible to establish their compliance with the criterion of "novelty."

 From the study of other well-known analogues in the art, where such technical features as the closure of all working cable conductors (star connection) to the heater electrode and the connection on the other hand to either a single-phase or three-phase current source, as well as the connection of a free core additional devices in the heater were not identified, therefore, they provide the claimed solution with the criterion of "inventive step".

 The technical result of the claimed device is to accelerate the destruction of hydrate and paraffin plugs in the tubing and in the annulus of the wells in the presence of mechanical impurities and inclusions.

 To implement the technical solution, it is necessary to carry out the corresponding refinement of the known device [2], in particular, to connect closed conductors from the side of the heater with its electrode, and use the seventh free core to connect additional devices, the use of which as part of the heater greatly enhances the destruction of hydrated and paraffin plugs, in particular a low frequency electromagnetic vibrator, as reflected in FIG. fourteen.

 In FIG. 1 shows a heating device containing a multicore cable 1 in an armored braid and rigidly sealed in the upper part of the housing 2, which performs the role of a single electrode together with the tip 3, and a rubber plate 4 serves to seal the termination of the cable ends. The exposed ends of the working wires are mechanically fixed in the upper part of the second electrode 5 (star connection), which is coaxially fixed by centralizers 6 and 7 inside the housing 2, the container 8 with the catalyst is fixed in the upper part of the electrode 5, and the output the seventh free core is connected to the coil 9 of the electromagnetic vibrator, when turned on, vibrations of the armature 10 to the current source occur with a frequency equal to 50 Hz. To the lower part of the electrode 5, through a threaded connection, a removable electrode 11 is attached, which is electrically connected through an electrolyte medium 12 with a tip 3.

In FIG. 2 shows a circuit diagram of a heater in its initial state, where N is a neutral wire; A, B, C - phase wires of a current source; To ₁ - To ₄ - contacts of the electromagnetic relay; 13 - armored cable braid; 14 - 19 - working cores of the cable; 20 - loose cable core.

 The device operates as follows.

An electric heater, in particular a catalytic one, is lowered into the tubing on a multicore cable 1 (KN7 - 70 - 180), six of which 14 - 19 cores are connected in pairs in three groups for each of the three phases of the current source (Fig. 2) through a switching device with contacts K ₁ - K ₄ at the wellhead and can be switched by the operator to either the heater mode or the ohmic resistance mode of the cable. In the first case (Fig. 3), in which, unlike [2], a significantly higher current of 30 - 35 A can be transmitted without fear of overheating of the insulation of conductors, which significantly increases the power of the heater, thereby increasing its heat transfer to the environment and accelerating the process destruction of the plugs, and also increases the total time spent by the plug material in the molten state.

According to [2], the active power W _{n of the} heater can be found from the expression
W _n = I $\genfrac{}{}{0ex}{}{\text{2}}{\text{to}}$ • R _to
where J _to - the current flowing through the cores of the cable;
R _to - the resistance of one core of the cable.

После прохождения интервала пробки в НКТ и возникновения ситуации, в которой невозможно создать циркуляцию рабочей жидкости (НКТ - затрубное пространство) из-за наличия пробки в затрубном пространстве, известные способы их ликвидации неэффективны в силу их локального действия. Так, например, закачка в НКТ нагретой до 60 - 80^oC технологической жидкости (раствор CaCl₂) не дает должных результатов. Подача тепловой энергии по всему интервалу пробки в затрубном пространстве решает эту проблему за 5 - 7 ч. Работа кабеля 1 в режиме омического сопротивления (фиг. 4) наиболее полно отвечает решению этой весьма сложной производственной задачи. Переключая кабель 1 на этот режим (контакты К₃ реле замкнуты), когда он полностью спущен в НКТ, а нагреватель отключен, за счет сопротивления прохождению трехфазного тока по соединенным попарно и замкнутым на электрод (соединение "звездой") рабочим жилам 14 - 19 происходит генерирование тепла, которое рассеивается с поверхности кабеля по всей его длине.In turn, J _k = U _f / R _k , where U _f is the phase voltage of the current generator. Since in this case all six working cores work as one conductor for a single-phase current, the total resistance R _k will be six times less than when using part of the working cores for power supply (two cores as in the prototype). Thus, the increase in the active power of the heater occurs due to the fact that the energy loss on the cable resistance will be six times less than for a two-wire connection. It follows that the active power of the heater and, accordingly, the thermal energy generated by it increases six times

After passing the plug interval in the tubing and the situation in which it is impossible to create a circulation of the working fluid (tubing - annulus) due to the presence of plugs in the annulus, the known methods for their elimination are ineffective due to their local action. So, for example, injection into a tubing of a process fluid heated to 60 - 80 ^o C (CaCl ₂ solution) does not give the desired results. The supply of thermal energy over the entire interval of the plug in the annulus solves this problem in 5-7 hours. The operation of cable 1 in the ohmic resistance mode (Fig. 4) most fully meets the solution of this very complex production problem. Switching cable 1 to this mode (contacts K _{3 of the} relay are closed) when it is completely lowered into the tubing, and the heater is turned off, due to resistance to the passage of a three-phase current through working wires 14 - 19 connected in pairs and closed to the electrode (star connection) occurs the generation of heat, which is dissipated from the surface of the cable along its entire length.

This mode creates an additional flow of thermal energy, allowing to increase the temperature of the already melted substance of the plug in the tubing by 10 - 15 ^o C and after a few hours of maintaining this state, by increasing the heat transfer through the walls of the tubing, warm the entire interval of the plug in the annulus to such an extent that it begins to collapse, and between the tubing and the annulus there will be a hydrodynamic connection, which serves as a signal for the completion of work.

Окончательно активная мощность в этом режиме для трехфазного тока выразится следующим образом:

Из расчета следует, что парное соединение рабочих жил для трехфазного тока увеличивает выход активной мощности и тем самым количество тепла в 3,5 раза больше, чем это достигается в прототипе.Active power W _to , when in the resistance (cable conductors) there is an irreversible conversion of electrical energy into thermal energy, find from the expression
W _to = I $\genfrac{}{}{0ex}{}{\text{2}}{\text{to}}$ • R _to .
In ohmic resistance mode, a three-phase current flows through six connected in pairs, divided into three groups (one group - one phase), so the total cable resistance will be half as much

Finally, the active power in this mode for a three-phase current is expressed as follows:

From the calculation it follows that the paired connection of working cores for three-phase current increases the output of active power and thereby the amount of heat is 3.5 times more than what is achieved in the prototype.

 Due to the symmetry of the voltage load, it is necessary to use an even number of cores, so the seventh core is not used. It is proposed to connect devices to the seventh (free) core, the principle of which is to use any known physical effect that is most suitable for the destruction of hydrate and paraffin plugs in production casing wells, in particular a low-frequency electromagnetic vibrator 9 (Fig. 1).

 The mechanism of its influence on the operation of the heater and the interfacialization of the process of thawing plugs in the conditions of their complication by the presence of mechanical objects (load - rod) or mechanical impurities (sand) is as follows. In the first case, the heater that came into contact with the end face of any long object dropped into the tubing and settled in the cork stops, since the convection heat transfer zone from tip 3 does not exceed 15 - 20 cm and it is necessary to significantly increase the heating time of such intervals. The process generally becomes impossible if the length of the object is more than 40-50 cm. In addition, an increase in the heating time leads to the fact that the higher layers of molten cork material crystallize again and an emergency occurs (cable sticking). In the case of mechanical impurities uniformly scattered throughout the entire volume of the plug, they will settle at the interface (plug - liquid) as the plug breaks. This will happen until their concentration at the interface reaches such a value, after which they will play the role of a heat-reflecting screen, and the heat transfer under the screen will decrease to such an extent that there will be a dynamic equilibrium between the incoming and reflected heat from it. The heater then freezes.

 The inclusion of a low-frequency vibrator in the heater significantly accelerates the destruction of the tube due to the intensification of the effect of heat and mass transfer, which is achieved by increasing the contact surface of the phases and reducing diffusion resistances. For this purpose, additional energy is supplied to the tube substance that interacts in the zone of thermal contact by additional energy by applying low-frequency oscillations to this zone. In systems where the flow is laminar as during the descent of the heater, the heat transfer from the heating surface depends on low-frequency oscillations and can give an increase in the heat transfer coefficient up to 700% [3, p. 213]. This occurs due to the transition from natural (free) convection, when heat transfer by moving some volumes of liquid from the warmer part of the space to the less heated is due to the lower density of the warmer volumes, and their rise in the gravitational field occurs according to Archimedes law to forced convection, when where the flow of the medium is caused by external forces (moving parts of the body).

 In addition, during the decomposition of the electrolyte under the influence of the current passing through it, hydrogen and oxygen atoms are formed, which, reacting with each other, form water molecules. To accelerate this process, catalyst 8 [4] is used, the granules of which are enveloped with a film of water, and its performance decreases, while the concentration of hydrogen and oxygen passes a safe level and explosive ignition of the mixture is possible, which has been repeatedly noted. Vibrational vibrations destroy the boundary film of water, thereby freeing up the effective surface of the catalyst. Thus, in contrast to [4], there is a transition from passive protection of the catalyst (installation in the upper part of the housing) to active protection.

Sources of information:
1. Copyright certificate of the USSR, N 1613588, cl. E 21 B 43/24, 1987.

 2. RF patent, N 2003781, cl. E 21 B 43/24, 1991.

 3. Varsanofiev V.D. and others. Vibration technology in the chemical industry. - M .: Chemistry, 1985.

 4. Copyright certificate of the USSR, N 1539310, cl. E 21 B 43/24, 1987.

Claims (2)

 1. Device for breaking hydrate and paraffin plugs, containing a power source and an associated multi-core cable with an electric heater, the cable being connected to the electric heater by one part of the cores, the other part of the cores is shorted and connected to the power source with the possibility of separate or simultaneous switching on of the electric heater and shorted cores stranded cable, characterized in that all working cores of the cable on the heater side are connected to its electrode, and on the side of the current source, in the heating mode and, all working conductors are connected to a single-phase current, and in the ohmic resistance of the cable conductors are connected working mode paparno and divided into three groups to be connected in three-phase current.  2. The device according to claim 1, characterized in that the free core is used to connect additional devices as part of the heater, in particular a low-frequency electromagnetic vibrator.

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