METHOD FOR ENHANCING OIL RECOVERY

Abstract

The method describes a way of improved oil recovery by the action of the electric field of the DC current and the electromagnetic field on the oil deposit (6) that is on the oil, the mentioned method comprises the following steps: a) Selection of the submerged rock clusters formations that contain the oil; b) Selection of one or more boreholes wells where the method will be applied; c) Extracting oil from at least one well borehole; Considering that the afore mentioned steps of the method further comprise of the following steps: A. Connected steel (17) and/or the upstream production tubing (16) of the boreholes wells with the DC electricity source 1 where the steel casings (17) and/or the upstream production tubing (16) assume the roles of the electrodes (7, 8); B. Connecting an electrical current source (1) with an electromagnetic field source (2); C. decreasing the affinity of the reservoir rock to capillary attract the oil, and simultaneously increasing the affinity of the reservoir rock to capillary attract water, reducing viscosity of the oil by applying the electric and magnetic fields, and increasing the electro osmotic flow of oil and layered water from the anode direction to the cathode direction.

Claims

1. A method for improved oil recovery by the action of an electric field of a direct current and a pulsating electromagnetic field on an oil layer (6) within reservoir rock beneath a ground surface, wherein the method comprises the following steps: a) Selection of submerged reservoir rock formation clusters that contain oil within the oil layer; b) Selection of one or more boreholes where the method will be applied; c) Extracting oil from at least one borehole of the one or more boreholes; the method further comprises the following steps: A. connecting steel casing (17) and/or upstream production tubing (16) of the selected borehole with a source of the direct current (1), whereby the steel casing (17) and/or upstream production tubing (16) of the the selected borehole serve as anode and cathode electrodes (7, 8); B. connecting of the source of the direct current (1) with a source of the pulsating magnetic field (2); C. applying the electric field of the direct current and the pulsating electromagnetic field (3), thereby decreasing the oil capillary attraction affinity of the reservoir rock, and simultaneously increasing the water capillary attraction affinity of the reservoir rock to capillary attract water, together with reducing viscosity of the oil and increasing the electro osmotic flow of oil and layered water from the anode electrode to the cathode electrode; wherein the source of the pulsating magnetic field (2) is at least one coil or dipole antenna situated on the ground surface between the electrodes (7, 8) and where the source (2) emits the pulsating electromagnetic field (3) into the oil layer (6) through ground (5).

2. The method, according to claim 1, wherein a direction of polarization of the electric field, induced either by the source of the direct current (1) or the source of the pulsating magnetic field (2), is aligned with the direction of the natural polarization of the oil layer (6).

3. The method according to claim 2, wherein the direction of polarization of the electric field, induced either by the source of the direct current (1) or the source of the pulsating magnetic field (2), does not deviate from the natural polarization direction of the oil layer by more than 45 degrees.

4. The method according to claim 1, wherein the connected casings (17) and the connected tubing (16) are electrically insulated from a surface collecting system (11) by inserting tubes of non-volatile electrically insulating material (12) between the connected tubing (16) and the surface collecting system (11).

5. The method according to claim 1, wherein one selected borehole with one basic channel and one or more side channels (23) is used as the anode electrode and the cathode electrode such that the plus pole is connected to the casing (17) and the minus pole to the tubing (16).

6. The method according to claim 5, wherein a portion of the selected borehole casing in the basic channel is replaced by electrically non-conducting material (22) placed proximate to outlet of a side channel (23).

7. The method according to claim 6, wherein electrical insulation between the connected tubing (16) and the connected casing (17) of the borehole is ensured by the connection of a tubing holder made of non-conductive material (20) and by installation of annular distancers (21) onto intermediate the connected tubing (16) and the connected casing (17).

8. The method according to claim 6, wherein a flow of deposit fluids in the annular space of the selected borehole is prevented by the insertion of a packer (24) over connected casing perforations (18) while a flow of the deposit fluids in the side channel space (23) is prevented by the insertion of a cap over the connected casing perforations (18).

9. The method according to claim 1, wherein the energy supplied by the source of the direct current (1) is in the range of 0.5 to 3 kWh.

10. The method according to claim 1, wherein the energy supplied by the source of the pulsating magnetic field (2) is in the range of 0.5 to 3 kWh.

11. The method according to claim 1, wherein the combined sources of the direct current (1) and pulsating magnetic field (2) do not consume more than 3 kW.

12. The method according to claim 9, wherein the source of the direct current (1) provides a voltage of 5 mV to 100 mV per meter of distance between the anode and cathode electrodes (7, 8).

13. The method according to claim 2, wherein the casing (17) and the tubing (16) are electrically insulated from a surface collecting system (11) by inserting tubes of non-volatile electrically insulating material (12) between the tubing (16) and the surface collecting system (11).

14. The method according to claim 3, wherein the casing (17) and the tubing (16) are electrically insulated from a surface collecting system (11) by inserting tubes of non-volatile electrically insulating material (12) between the tubing (16) and the surface collecting system (11).

15. The method according to claim 2, wherein one selected borehole with one basic channel and one or more side channels (23) is used as the anode electrode and the cathode electrode such that the plus pole is connected to the casing (17) and the minus pole to the tubing (16).

16. The method according to claim 3, wherein one selected borehole with one basic channel and one or more side channels (23) is use as the anode electrode and the cathode electrode such that the plus pole is connected to the casing (17) and the minus pole to the tubing (16).

17. The method according to claim 9, wherein the combined sources of the direct current (1) and pulsating magnetic field (2) do not consume more than 3 kW.

18. The method according to claim 10, wherein the combined sources of the direct current (1) and pulsating magnetic field (2) do not consume more than 3 kW.

Description

BRIEF DESCRIPTION OF DRAWINGS AND TERMS

[0033] FIG. 1 is a borehole with a source of direct current connected to the electrodes and to the source of the magnetic field

[0034] FIG. 2 shows the installation on the borehole according to the present invention

[0035] FIG. 3 is a view of an execution of the present invention with a single borehole

[0036] The terms on the drawings have the following meaning: [0037] 1—source of DC, [0038] 2—source of pulsating magnetic field, [0039] 3—pulsating electromagnetic field emitted from source 2 through ground 5 into the oil layer 6, [0040] 4—surface of soil (soil), [0041] 5—the soil above the oil bearing reservoir (overburden) [0042] 6—oil bearing layer that can be a sandstone, carbonate, dolomite, shale or other porous rock in which are present oil, water and gas, [0043] 7—anode—a conduit that penetrates into the oil layer. It can be an oil production borehole, water injection well, conserved or neutralized liquidated borehole, or some other conductive material that penetrates into the oil layer, [0044] 8—Cathode—producing borehole [0045] 9—electrical conductors in which the DC source is connected to the anode 7 and the cathode 8, [0046] 10—electric conductors by which the source of the electromagnetic waves 2 is connected to the direct current source 1 to achieve the interference of the signal i.e. electrical impulses that are fed from the source 7 to the layer 6 via the anode 7 and the cathode 8 and the electromagnetic impulses of the source 2 used to affect the oil layer 6, [0047] 11—a metal pipe that goes from the borehole into a collecting reservoir [0048] 12—a tube of electrically non-volatile nonconductive material such as, for example, rubber or plastic, is inserted to provide electrical circuit closure through the oil layer, [0049] 13—electrical contact connection of minus (negative) pole minus half of the direct current source with the borehole serving as the cathode. The contact is connected to a steel pipe connected on one side by the casing 17 and the tubing 16 and, on the other side to the inserted tube of the insulating material 12, [0050] 14—an electric contact plus half connection of plus (positive) pole of the direct current source with the borehole serving as the anode. The contact is connected to a steel pipe connected on one side by the casing 17 and the tubing 16 and, on the other side to the inserted tube of the insulating material 12, [0051] 15—cementation of the borehole. The cement layer between the casing 17 and the soil (sediment layers) through which the borehole passes provides partial electrical isolation between the casing 17 and the ground, enabling most of the electric energy to flow through the electric energy circuit closed through the oil layer between the anode and the cathode, [0052] 16—Tubing, that is the production tube of the borehole. Tubing is made of el. conductive material, [0053] 17—casing i.e. borehole casing. Casing is made of electrically conductive material, [0054] 18—perforations through a part of the casing and the cement which are passing through the oil layer and providing a contact of the oil layer with the borehole. Through these perforations oil, water and gas penetrate into the production borehole, while providing electrical contact with the layer, [0055] 19—the direction of closing of the electric circuit through the oil layer and the direction of action of the electric field, [0056] 20—electrical insulation between tubing and casing, [0057] 21—distancer i.e. a cylindrical device of electrically non-volatile nonconductive material which is mounted around the tubing and prevents the contact of the tubing and casing, thereby and consequently closing the electrical field, [0058] 22—the cut-off portion of the casing which can be subsequently filled with cement prevents the electric current flow through the casing to go deeper than the cut-off portion, [0059] 23—side borehole channel, [0060] 24—packer, [0061] 25—plug in the side borehole.

DETAILED DESCRIPTION OF THE INVENTION

[0062] The method is based on the effects caused by the action of a direct electric current flowing to the oil layer through at least two boreholes and passing through the oil layer, i.e. through the porous rock saturated with crude oil, water with dissolved salts and gas, with electromagnetic impulses from the surface source causing the additional polarization of the soil particles of which the oil layer is formed, i.e. causing induced polarization, water, and heavy metal particles, which are an integral part of the reservoir rock material. In a particularly preferred version of the invention, the direction of the natural polarization of the reservoir rocks is also taken into account, and the position of the anode and cathode is selected or the direction of the polarity of the electromagnetic field surface field is directed so that the induced polarization is as much in conformity with the direction of the natural polarization of the deposit.

[0063] In the basic version of the invention, the source of the direct current 1 acts together with the source of the electromagnetic impulses 2 to the oil layer 6. Electro magnetic impulse source is applied to ground surface 5 between two oil boreholes serving as electrodes thus emitting electromagnetic impulses 3. The electromagnetic impulses 3 extend through the soil above the oil layer 4 and act on the oil layer 6 causing induced polarization. The direct current source 1 is connected to the cables 9 by surface mountings or other suitable electrically conductive part of the boreholes about the surface of the earth. As electrodes, that is as anodes 7 and cathode 8, are used the existing boreholes that have the contact with the same oil layer 6 or that have hydraulic communication, but it is not essential that an oil borehole is used as the anode, as it can also be used a water injection well, a preserved borehole or any electrical conductive element, as long as the condition of the simultaneous contact between the borehole and the cathode 8 and anode 7 and the same oil layer 6 is fulfilled. The DC direct electric current source 1 is connected to the source of electromagnetic impulses (2) by conductors.

[0064] In the where when existing boreholes are used as a cathode (8) and anode (7), tubings of electrically non-volatile material (12) are connected to the outlet from the borehole to the collecting tubing system (11) which is connected to the rest of the collecting tubing in any convenient way to ensure leakproofness of all fluids and gases. In this version, as electric conductive element closing the circuit from the source (1) through the oil layer (6) and the electrodes (7) and (8) are used the existing electric conductive elements of the borehole such as casing (17) and/or upstream tubing (16). Electrical insulation and preventing the circuit is closed over the layers (4) above the treated oil layer (6) is achieved by means of a cement layer (15) which is already an integral part of the boreholes. In this embodiment, the DC current from the source (1) flows, i.e., the circuit is closed between the plus and minus poles, respectively between the anode (7) and the cathode (8) using the casing (17) and/or the upstream tubing (16) as electric conduits. The electric circuit is further closed by the perforations of the borehole (18) which enable the hydraulic and electrical connection between the borehole and the oil layer (6). The electric field operates from the anode (8) to the cathode (7). This embodiment is possible in such a way that more than one borehole is connected to the circuit, for example, that an anode is connected to multiple cathodes or multiple anodes to one cathode.

[0065] There are cases when one oil reservoir or layer is drilled from only one production borehole, due to the small volume of the reservoir or due to other reasons, for example when the reservoir is divided into blocks by faults and there is no hydraulic communication between the blocks. Also, in some cases it is economically profitable to treat all existing productive boreholes in a given field by a tertiary oil recovery method as described in this document. Also, it is possible that the elaboration of a certain oil field is planned in such a way as to produce boreholes that each make a separate hydrodynamic unit to be treated, using a method previously described in this document. In such cases, a new borehole must be made or the existing borehole must be adapted and equipped to serve both as an anode and as a cathode.

[0066] The possible way in which one borehole can be made or adapted to serve simultaneously both as the anode and as the cathode is shown in FIG. 3. As shown, it is possible to create and equip a new borehole or an already existing borehole. The borehole is made in such a way that one or more borehole channels, which can be under any angle in relation to the ground, is made one or more borehole channels or lateral canals 23. The electrical connection contact minus half pole of the direct current 1 source is connected to the tubing of the base borehole which serves as the cathode. The contact binds to the surface reinforcement or the surface-accessible steel tubing that is on one side connected by 17 and the upstream tubing 16, and on the other to the inserted tubing made of insulating material 12. Prior to connecting the minus pole, the tubing 16 is separated by a special device of electrically non-volatile nonconductive material 20 so as not to be in electrical contact with the casing 17 and also around the tubing 16 are incorporated special devices, the so-called spacers or distancers 21 of non-electrically conductive material in form of a hollow cylinder with an inner diameter sufficient for the tubing to pass through it. 16. Distancers 21, are incorporated in an arbitrary number which has to be sufficient to provide insulation, i.e. to prevent contact between the steel parts of the casing 17 and the tubing 16, thereby closing the electrical circuit between them. The anode or the positive pole bonds in a manner that is electrically coupled with the ascesion pipe or casing 17 and electricity flows through the casing of the core main borehole to the cut-off part of the casing 22 and the also through the length of the whole casing 17 of one or more lateral channels. The current circuit is closed through the oil layer 6 and the direction of the action of the electric field 19 is from positive polarized perforations 18 toward the negative polarized perforations 18. For the purpose of the present invention it is not important whether the perforations of the base and the lateral channels are positive or negative, it is important that they are polarized differently and that the circuit is closed through the oil layer 6 and through the perforation 18. Inside the basic borehole at any point above the perforation 16 and below the cut-out part of the casing 22 the packer 24 is inserted to prevent the fluids to flow into the annular space between the casing 17 and the tubing 16, while inside the lateral side cavity wellbore 23 above the perforations 18 a plug is to be made 25 to prevent the fluids to enter in the side borehole and then in the basic borehole. The cement layer 15 ensures electrical insulation between the borehole casing and the soil layer through which the borehole and lateral duct pass and ensures and this ensures that the electric circuit is closed exclusively through the perforations 18 and the petroleum layer 6. In this version, the surface source of electromagnetic impulses 2 is used in the manner described above.

Field Test

[0067] On the oil field that is on the deposit of very heavy and viscous oil, there are complex geological structures characterized by scattered fractured carbonate reservoir rocks of large permeability but very low porosity of deposits reservoir rocks, also with very high levels of groundwater bottom water (aquifer) pressure, low deposit reservoir temperatures and a very high viscosity of oil within the deposit oil reservoir. Such deposits are classified as marginally profitable and the tests which were performed show surprising efficiency of the process and installation according to the present invention.

[0068] Specification of the oilfield is given in Table 1:

TABLE-US-00001 TABLE 1 oil field parameters lithology Fractured i.e. carbonate rock Porosity 2.5% Permeability 1 Darcy Deposit temperature (° C.) 40 Static deposit pressure (bar) 100

[0069] The test was made in conditions where the boreholes oil wells used as electrodes were set at the distance of 510 m one from the other. The depth of the borehole oil well used, according to the present invention, as a cathode is of 1210 m and the depth of the oil well borehole used according to the present invention as an anode is of 1219 m, both are cemented and tempered cased: cathode up to 1204 m and the remaining 6 m is not tempered cased, making it an “open hole” and the anode up to 1213 m is also cemented and tempered cased while the remaining 7 m is ‘undone’ not cased that is an ‘open hole’. Those un cased or open hole completed 6 m at the cathode borehole that is 7 m in the anode borehole form a connection with the oil layer, i.e. the cementation and closure steel casing ceases on the top of the oil layer.

[0070] By performing surface measuring of the voltage between one of the static electrodes and the other electrode that is moving in five degree steps, the direction of the natural polarization of the field is determined, and the polarization direction of the electromagnetic field from the sources of electromagnetic waves is oriented to coincide with the direction of natural polarization. The boreholes were prepared in such a way that a series of upstream production tubes—tubings were extended up to half a meter from the bottom of the borehole to allow the upstream holes production tubing to enter the open hole section of the borehole. Both boreholes are prepared in this way.

[0071] The production of the borehole oil well planned to serve as a cathode was measured in such a way that the production of the borehole well is directed to a special reservoir, and by measuring the amount of oil and water in the reservoir that is daily emptied, it was established the average oil and water production immediately prior to the application of the invention. The production was measured in the same way after the start of the application of the invention, and oil and water production at the selected dates is shown in Table 2. Dec. 3, 2017 was the date of the begging of measuring and it relates to measurements prior to the initial date of method application and the measurements on dates later than that date refer to the time after the application of the method.

TABLE-US-00002 TABLE 2 oil production and water share in production before and after the application of the method Date of Oil produced Water share in total production measurement (barrel per day) (%) 3 Dec. 2017 2.52 94 15 Jan. 2018 7.56 80 14 Feb. 2018 12.20 72 20 Mar. 2018 14.18 71 16 Apr. 2018 16.35 61 20 May 2018 17.20 52 Jun. 18, 2018 18.91 47 22 Jul. 2018 24.60 39 20 Aug. 2018 29.25 34 19 Sep. 2018 32.15 31

[0072] The fluid level in the annular space was also measured using a sonolog acoustic device. The fluid level was monitored during the first month after the application of the invention to see the electro-osmotic effect. The increase in fluid levels, that is the reduction of the fluid level distance from the top of the boreholes, indicates the presence of the electro osmotic effect. Measurement results on Dec. 3, 2017 refers to the fluid level prior to the beginning of the method, and on the other dates after the beginning of the application of the method. For the entire time of the fluid level measurement in the annular space (annulus between well casing and tubing), the depth pump parameters have not changed, such as length of the piston stroke and the number of strokes per minute.

[0073] The fluid level in the annular space of the borehole oil well before and after the beginning of the application of the invention is shown in Table 3.

TABLE-US-00003 TABLE 3 Liquid level in the annular space of the borehole which was used as the cathode Date of Fluid level in the annular space of the borehole, measurement measured from the mouth up to the fluid level (m) 3 Dec. 2017 310 11 Dec. 2017 240 Dec. 18, 2017 180 26 Dec. 2017 130 3 Jan. 2018 75 10 Jan. 2018 16 20 May 2018 18

[0074] Prior to connecting direct current sources, rubber tubings pipes were inserted into at surface outlets of the both boreholes oil wells, by replacing instead of a shorter short steel tubing part of surface gathering system to provide electrical isolation of the borehole from the surface produced fluids gathering collector system. Thereafter, the DC electricity source was connected via an electric cable mounted on the columns extending between the two boreholes oil wells serving as anode and cathode. Each side of the cable which represented plus pole (one side) and minus pole (other side) was connected with a steel pipe, which is further connected to one side on the casing and the tubing of the boreholes oil wells and, on the other, to the non-conductive pipe. and The insulated ends of the cables were clamped by clamps to the described steel tubing on both oil wells boreholes, and insulated by insulating tape. Subsequently, the DC electricity source was connected to the generating source of electromagnetic waves, which was placed in a perfectly flat position between two oil wells boreholes. Furthermore, the DC electricity source, which as a part includes an alternating current rectifier, was connected to a nearby AC electricity source.

[0075] After launching the invention, in addition to regular monitoring of the amount of oil and water produced, oil samples taken from the borehole oil well serving as a cathode were analyzed and compared with also laboratory-analyzed samples of oil taken from the same oil well prior to the start of the application of the invention.

[0076] The composition of the oil was determined by a column chromatographic method based on the principle of different absorption capabilities of certain types of compounds—SARA analysis.

[0077] The deasphalted sample is to be applied to a glass column filled with n-hexane and an adsorption agent (silica gel and aluminum oxide). The sample dissolved in n-hexane is applied to the column, eluting saturated hydrocarbons. Then benzene is gradually added to elute the aromatic hydrocarbons and a mixture of benzene and methanol which elute resins. Types of compounds are separated based on the growing polarity of the solvent used for elution. After separation and evaporation of the solvent, saturated hydrocarbons, aromates and resins were weighted. The mass of asphaltene is determined from the difference in the total mass and mass of said compounds. The results are given in Table 2 by mass %.

TABLE-US-00004 TABLE 4 The composition of the oil before and after the application of the process according to the invention Saturated Aromatic NSO- Asphal- hydrocarbons hydrocarbons resins tenes (% by (% by (% by (% by Sample type mass) mass) mass) mass) oil before 14.61 45.47 18.93 20.99 treatment oil after 18.05 48.28 14.81 18.86 treatment

[0078] The oil viscosity before and after application of the process according to the present invention was determined by Stabinger: ASTM D7042

TABLE-US-00005 TABLE 5 Viscosity before and after the application of the process according to the invention Viscosity at 50° C. Dynamic Kinematic Sample type mPa s mm2/s oil before treatment 28076.0 27983.0 oil after treatment 2615.0 2646.6

[0079] From Table 4 and 5, it is apparent that the application of the procedures according to the present invention produces oil of better quality and substantially less viscosity, which indicates that heavy oil is converted to a significantly lighter oil which is far more suitable for exploitation.