MXPA97000829A - Electrical system of heating of cavidad descend - Google Patents

Abstract

The present invention a heating electrical system, of cavity descending, comprising a longitudinal container having at least one opening at one end and, connection means at the opposite end to connect the container to the external pipe, the pipe being connected to a source of gas located on the surface, the container comprising: a heating chamber having at least one heating element that is capable of heating, in use, the gas that is continuously passing through it; a sinuous path inside the heating chamber before being released out of the heater through at least one opening of the container, the heater being characterized in that the container further comprises: a wiring chamber, adjacent to the connecting means, within which the connecting wires of a power supply located on the surface are e electrically connected to at least one heating element, and a cooling chamber located between the heating chamber and the wiring chamber, the gas being circulated inside said cooling chamber before passing through the heating chamber to limit the temperature in the wiring and cooling chambers

Description

ELECTRICAL HEATING SYSTEM. OF CAVITY FALLING FIELD OF THE INVENTION The present invention is compromised with a reusable cavity heater for the formation of thermal treatment in the field of porous underground formations containing oil, gas and water.

BACKGROUND OF THE INVENTION It is not uncommon in the oil production industry to find liquid hydrocarbons that do not flow at a sufficient speed to be of commercial interest. This is generally caused by a high viscosity of the oil at the formation temperature. In order to reduce the viscosity of said oil, a well-known technique is to raise the temperature of the formation. The reduction of oil viscosity has two important effects. First, this allows oil to flow more easily into the formation and reduces the pumping power required to bring it to the surface. Secondly, the reduction of oil viscosity also increases the relative mobility of oil and reduces the relative mobility of water. In this way, the last effect reduces the production of water. Another important application during the thermal treatment is the prevention or removal of waxes or asphaltenes formed within the well borehole or in the region near the well borehole. Other benefits that result from thermal treatments include clay dehydration, thermal fracturing at high temperatures, prevention of thermal fracturing in aquifers at low temperatures and consolidation of sand in unconsolidated formations. In situations of flooding with water, the injection wells release or release their injection capacity due to several problems including the swelling of the clay, and therefore the heat treatment can improve the injection capacity. In the case of the descending cavity electric heater, some of the current ones may be set aside to prevent corrosion of the piping, shell, pumping rods and other components of the descending cavity, and to prevent the formation of corrosion products. White et al., In "Petrol, Technol., 1965, 1007, discloses the use of a downdraft electric heater to ignite the fuel at the site.The heater is removed and air is supplied to maintain a combustion front. Process management improves oil production to four times the pre-combustion rate, while reducing the water cut to 8% .Continuous oil produces twice the normal speed for several months after treatment. No. 5,070,533, discloses a descending cavity heater design using the pipe or shell as electrodes.An electrode is aligned with the production zone.The opposite electrode is located outside the production zone and, preferably at least three times the diameter of the cavity, away from the first electrode In order to pass from one electrode to another, the current must pass through the production zone. by any of a conductive formation or by water in the formation. The high resistance to current flow results in localized heating, and the system is preferably operated only while the well is producing. A major problem with this procedure is the potential for accelerated corrosion on the inner side of the anode. U.S. Pat. No. teaches the combination of a descending cavity heater with a water pump. If the heater is operated, then the pressurized water is directed through the heater and into the formation where it will penetrate the rock formation and thermally stimulate the well. If the heater is not activated, then the pressurized water is returned to the turbine and aids in pumping the descending cavity of production fluids. The use of pressurized water also prevents the heater from overheating and burns the elements. The method is said to prevent heat losses along the steam pumping pipe from the surface. The United States Patent 4, 591,748 is committed to the heating technique based on the supply of electric power at a thermal harmonic frequency of the formation. The three-phase AC power is converted to direct current, and then a single phase of alternating current is separated to the harmonic frequency. The heating of harmonic frequency also happens to the normal ohmic heating. The harmonic frequency of the rock or fluid is determined in the laboratory before application in the well. This frequency can be adjusted during the heating of the well as the harmonic frequency can oscillate with the pressure and temperature. U.S. Patent 5,020,596 discloses a descending cavity heating process that floods the reservoir with water, from an injection well at a desirable pressure. A radiant heater, with a descending cavity, burned fuel is ignited in the injection well and heats the formation and water. The heat radiates along the total length of the heater to maintain the narrow isothermal standards to each industry and provide a good extension. The heater consists of three concentric, cylindrical tubes. A burner inside the innermost tube ignites, and burns a source of fuel and air. The openings are dimensioned and positioned to develop the laminar flow of the burner combustion products, such that the heat transfer is effective along its total length. The combustion products are removed from the annular space between the two outer tubes. The heater design minimizes local heat sites and must heat the tank equally. The temperature that can be reached in the tank is dependent on the tank pressure. However, the use of a large radiant heater such as the above, involves significant losses of heat in an effort to achieve equal flow over the total height of the reservoir. U.S. Patent 5,120,935 discloses an electrical heater, packaged bed, of cavity descending, comprising two electrodes, which are displaced from each other. The opening is filled with conductive balls. The resistive heating happens when the current is passed through the heater. The multiple paths of the flow of the current through the heater prevents the failure of the heater, due to the exhaustion of the element. The heater provides a large surface area for heating, while maintaining a low pressure drop between the heater inlet and outlet. The length and diameter can be adjusted to meet well design and heating requirements. The heating of formation is achieved by passing a solvent through the heater, which heats up completely, passes to the formation and transfers the heat to the formation. U.S. Patent 4,694,907 uses a descending cavity electric heater to convert hot water to steam. Instead of producing steam on the surface and pumping it into the descending cavity, it was suggested to heat the water on the surface, pump it into the descending cavity where an electric heater converts hot water into steam. The electric heater is a series of U-tubes disposed circumferentially around the water injection tube. Each U-tube can be controlled individually. The injection tube is closed at the bottom with radially displaced holes. The water flows out of the injection tube and passes to the heater tubes where it vaporizes. Electric power is supplied by means of a Y three-phase system, neutrally grounded, with one end of each heating element that is common and neutral. The system also supplies direct current to the heater. U.S. Patent 5,060,287 is committed to a copper-nickel alloy core cable for descending cavity heating. The cable is able to withstand temperatures at 1000 ° C and use voltages at 1000 volts. The cable is especially useful for heating large intervals. The United States Patent 5, 065,818 discloses a heater using this material which is secured in a deployed hole. The heater can provide heat at approximately 250 watts per foot in length. U.S. Patent 1,681,523 discloses a heater comprising two concentric tubes. The inner tube acts as a conductor and the heating coils are touched at various locations along the total length of the conductor. The other conductor is an insulated wire that runs parallel to the conductive tube all the way to the surface. Both tubes, along with multiple heating elements, are housed in a larger envelope. Air is circulated down through an internal pipe and up through an annular space between the internal and external pipes. On the surface, a pump is used to recirculate the air. In this way, the total length of the pipe is heated, and the circulation of the air distributes the heat. The purpose of such heating is to maintain the entire hot production line to prevent paraffin deposition. Hot air never leaves the system. In addition, the heating temperature and the electrical connections, power and temperature requirements are not taken into consideration. Said heating system is not suitable for the injection of hot fluids in a formation, since for said use, one end of the heater must be open. Also, the multiple connections of the heating elements with the conductors will make the heating system inoperable in the presence of formation fluids, for example, as salt water. It is likely that the temperature applied with this system is not particularly high (the melting point of the paraffin is less than 60 ° C), since the multiple electrical connections will not withstand prolonged exposure to high temperatures.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, there is now provided a downward cavity heating electrical system comprising a longitudinal heater with a container having at least one opening at one end and connection means at the opposite end for connecting the heater to the external pipe, the pipe being connected to a gas source located on the surface, the container comprising: a wiring chamber adjacent to the connection means, to connect the wires of a power source located on the surface, to at least one heating element that converts electrical energy into heat; - a heating chamber comprising at least one heating element for heating a gas passing continuously through the heating chamber; - a cooling chamber sandwiched between the heating chamber and the wiring chamber, where the gas is circulated there before passing through the heating chamber, to prevent an increase in temperature in the wiring chambers and cooling; the gas following a sinuous path in the heating chamber before being released out of the heater through at least one opening of the container.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a first embodiment of the heater used in the heating system of the present invention; Figure 2 illustrates a second embodiment of the heater; Figure 3 is a detailed view of the heating chamber; and Figure 4 is a view along lines 4-4 of Figure 1 or Figure 2; and Figure 5 is a perspective view of the heating system present, in operation in a hole.

DETAILED DESCRIPTION OF THE INVENTION The electric cavity heating system of the present invention is particularly suitable for stimulating the production of oil and gas formations, which contain clay materials, and is more suitable for applications such as those described in the co-pending application. serial number 08 / 070,812, filed on June 3, 1993, now the USA 5,361,845. Other uses include steam generation at the site, initiation of combustion at the site, heating near the boreholes for the reduction of the viscosity of heavy oil, stimulation of water injection to the well, emulsion fractures near the well drilling, etc. The present invention will now be described with reference to the accompanying drawings in which the preferred embodiments are illustrated. Observing Figures 1 and 2, there is illustrated a descending cavity heater 10 having a wiring chamber 12, a cooling chamber 14 and a heating chamber 16, contained in a container or collar 18. The chambers are threaded in 13 and 15 through the joint union. The threaded can be replaced with welded or similar. The heater 10 is enclosed at one end with a bushing 20 and is provided with a connector 22, preferably threaded, at the opposite end, for connection to any conventional pipeline means, including chilled pipes, used in the oil and gas industry . The connector 22 has a centered channel 23 extending the entire length thereof, and exiting the tube or pipe 24, preferably made of stainless steel, which is inserted into the heater 10 and extends through the chambers 22 and 16. , the pipe section 24 in the chamber 14 being cut and removed. Another tube or pipe 25 is inserted into the chamber 16 around the pipe 24, thereby defining clearances 26 and 28 between the pipe 24 and the pipe 25 on the one hand, and the pipe 25 and the container 18 on the other hand. A plurality of spacing members 30 and 32 (Figure 4) are installed to hold in place the pipes 24 and 25. A heat source comprising a plurality of bar-like heating elements 34 is placed on the surface of the pipe.

. The heating elements can be fixed, fixed, welded or free. The heating elements 34 are conventional and can be briefly described as follows: each comprises a first section made of two nickel wires extending from the wiring chamber 12 through the cooling chamber 14. The second section is in the heating chamber 16 and comprises two INCONEL wires electrically connected to the nickel wires. Both sections are contained in a housing filled with a dielectric material such as magnesium oxide. The result is that little heat is generated in the cooling chamber 14, due to the nickel wires, while the INCONEL wires, which are resistant, convert the electricity into heat in the heating chamber. Each heating element 34 is inserted into a tube 31 which is connected at 35 with pins 36 to an extension of the heater 38, the latter also being made of dielectric material, so that very little heat, if any, is transferred from the heating chamber 16, or from the heating element 34 to the cooling chamber 14 and the wiring chamber 12. The heater extensions 38 are combined in groups of 3 in the wiring chamber 12 to form 3 wires 40 which are connected to an appropriate power source (Figure 5) on the surface. In Figure 2, the extension of the heater 38 and the tube 31 have been removed, since it has been found that very little heat is produced from the nickel wires, thus returning to the use of the optional heater extension. In both embodiments of Figure 1 and 2, it should be noted that the nickel wires extend a few inches adjacent the wall 46 in the heating chamber 16, to ensure that no heat is possible, if any, penetrate the cooling chamber 14 and in the wiring chamber 12. In a preferred embodiment, a set of connectors is inserted between the wires 40 and the cable connected to the power source. This set of connectors is generally located in the vicinity of the heater 10 in the well borehole. Examples of such connectors are provided in U.S. Patent No. 4,627,490. The heater 10 is preferably equipped with a thermocouple 42 to monitor the temperature at each end of each chamber (6 occurrences). Looking closer to the heating chamber 16 in Figure 3, it will be seen that the pipe 25 has a closed end 44, while the other end is also closed, by the wall 46 adjacent to the cooling chamber 14. The pipe 25 comprises at least one opening 48, generally in the form of a groove. To ensure that the gas is uniformly dispersed, the slots must be distributed at regular intervals at the same end around the pipe 25. The container 18 comprises at least one opening 50. Again, as for pipe 25, it is they prefer the slots, and they must be distributed around the container 18 in the same way as around the pipe 25. Due to the presence of the separators 30 and 32 that keep the pipes in place, it may also be possible to have a pipeline shorter 25 that would not be in contact with wall 46, thereby allowing gas passage. In the same way, the bushing 20 can be removed from the end of the heating chamber 16, or grooves can be made in the bushing 20. In operation, as illustrated in FIG. 5, the heater 10 is lowered into the borehole of the bore. Well 51, provided with a conventional metallic internal envelope 54, in the area of the area of interest, the heating elements 34 are heated, and the gas, preferably nitrogen is injected from the surface, generally a main supply pipe of nitrogen , if the gas is nitrogen, and the pipe 24 through the channel 23. Since the section of the pipe 24 has been removed from the cooling chamber 14, the gas is allowed to flow freely there, and acts as a quencher. As the gas enters the heating chamber 16 through the pipe 24, its temperature begins to increase due to the presence of the heating elements 34 on the surface of the pipe 25. The gas follows a sinuous path indicated by the arrows before being ejected from the heater through the openings 50 at the desired temperature. Said sinuous path provides a suitable residence time for the heat to rise to the desired temperature. The ability to manipulate the gas flow velocity at the surface also allows the flexibility of the gas residence time within the heating chamber. It should also be noted that the nitrogen is also injected into the envelope 54, around the pipe to maintain a positive downward pressure, so that the hot gas is concentrated in the area of interest, thereby reducing heat losses to the upper part of the area (Figure 5). Each heating element has a power of 7.2 kW. In the heater described here, nine heating elements 34 are used, thus allowing a total power of the equipment of 65 kW. Preferably, the heating elements are connected by groups of 3 in parallel connections, so that if one group fails, the heater will still be able to operate with 6 elements. Gases suitable for injection in the above heater include air, oxygen, methane, vapor, inert gases and the like. Inert gases are preferred, with nitrogen being most preferred. The gas flow rate can vary from 5,000 m3 / day to 57,000 or higher, m3 / day (standard conditions of 150C and 1 atmosphere). Accordingly, a power of 65kW and a nitrogen flow rate of approximately 10,000m3 / day would correspond to a high temperature of up to 800oC. A temperature above 600 ° C is generally sufficient for the applications of the present electric heating system. In this way it is possible to control the temperature both by varying the flow velocity of the gas, and by regulating the output power.

Before reaching the heating chamber, the injected gas is at room temperature, and it cools the wiring chamber and the cooling chamber, thereby preventing undesirable overheating in these chambers. Preferably, the wiring chamber is also sealed to the fluid to allow application of the heater in any environment in the well bore, such as water, oil, gas, and mixtures thereof. For the material safety problem, the heater must include an automatic shut-off system to cut the power and prevent overheating of the cooling and wiring chambers. The total length of an electric heater according to the present invention and illustrated in Figure 1, is approximately 462 cm. , 3/4 parts of which being the length of the heating chamber, and each of the cooling and wiring chambers representing 1/8 of the length of the heater. As the diameter of the deep boreholes of the well generally do not exceed 12 cm. , the heater diameter should be around 8 to 9 cm. , to facilitate its introduction and placement. The design of the electric heater of the present invention has several advantages: If one of the heating elements fails, the heater can still be operated at low power; therefore, there is no need to remove it from the well bore; It can be used in drilling rough wells, which contain brine, oil and gas. All parts of the present heater are made of stainless steel, except for the heating elements and the heating extensions, which are sealed in 600 sheets of INCONEL. Although the invention has been described in relation to specific embodiments thereof, it will be understood that it will be capable of further modifications and this application is intended to cover any variations, uses or adaptations of the invention following, in general, the principles of the invention and including such deviations from the present disclosure as it becomes within the daily knowledge or practice within the technique to which the invention pertains, and can be applied to the essential characteristics set forth above, and remain within the scope of the claims annexes.

Claims (11)

1. - A downward cavity heating electrical system comprising a longitudinal heater with a container having at least one opening at one end and, connection means at the opposite end for connecting the heater to the external pipe, the pipe being connected to a source of gas located on the surface, the container comprising: a wiring chamber adjacent to the connecting means, for connecting the wires of a power source located on the surface, to at least one heating element that converts electric power in heat; - a heating chamber comprising at least one heating element for heating a gas passing continuously through the heating chamber; - a cooling chamber sandwiched between the heating chamber and the wiring chamber, where the gas is circulated there before passing through the heating chamber, to prevent an increase in temperature in the wiring chambers and cooling; the gas following a sinuous path in the heating chamber before being released out of the heater through at least one opening of the container.

2. - A heating system according to claim 1, further characterized in that the sinuous path is effected by providing a first pipe surrounding a second pipe extending coaxially in the heating chamber, the first and second pipes having at least one opening at opposite ends, at least one opening of the first pipe being at the same end as at least one container opening.

3. The heating system according to claim 1, further characterized in that it comprises means for monitoring the temperature in each chamber of the heater.

4. The heating system according to claim 3, further characterized in that the means for monitoring the temperature are at least one thermocouple.

5. - The heating system according to claim 1, further characterized in that the gas is an inert gas.

6. The heating system according to claim 5, further characterized in that the gas is nitrogen.

7. The heating system according to claim 1, further characterized in that the heating element is a rod-like tube.

8. - The heating system according to claim 2, further characterized in that the heating element is located on the external surface of the first pipe.

9. - The heating system according to claim 2, further characterized in that at least one opening of the first pipe is adjacent to the cooling chamber.

10. The heating system according to claim 1, further characterized in that the wiring chamber is sealed to the fluid.

11. The heating system according to claim 1, further characterized in that the power of the heater is 65 kW.