SYSTEMS AND ASSEMBLIES FOR ENHANCED OIL RECOVERY USING ULTRASONIC-TRANSIENT ELECTROMAGNETIC SETUP

TECHNICAL FIELD

The disclosed embodiments relate generally to recovery of oil, natural gas, and other underground gaseous and liquid minerals, including but not limited to systems and methods for enhanced oil recovery using an Ultrasonic-Transient Electromagnetic (U-TEM) setup.

BACKGROUND

Crude oil development and production in oil reservoirs can include up to three distinct phases: primary, secondary, and tertiary (or enhanced) recovery. During primary recovery, the natural pressure of the reservoir or gravity drive oil into the wellbore, combined with artificial lift techniques (such as pumps) which bring the oil to the surface. Typically, only about 10 percent of a reservoir's original oil in place is produced during primary recovery. Secondary recovery techniques extend a field's productive life by injecting water or gas to displace oil and drive it to a production wellbore, resulting in the recovery of 20 to 40 percent of the original oil in place.

The entire oil and gas recovery process often include a series of processes including drilling, well completion, fracturing, acidification, water injection, well workover, etc. The physical and chemical effects from these processes result in expansion of clay in oil and gas reservoirs, particle migration, scaling, and organic matter precipitation, which result in clogging that limits the recovery rates of the oil and gas reservoirs. This has become a key issue to hydrocarbon recovery. Causes of such clogging include, e.g., reservoir sensitivity, particle migration, organic deposition, inorganic salt precipitation, emulsification clogging, bacterial clogging, and etc.

Existing clogging removal technologies include (1) acidizing by injecting hydrochloric acid (e.g., for carbonate rock reservoir) or a mixture of hydrochloric acid and hydrofluoric acid near the wellbore of sandstone reservoir to dissolve inorganic particles and rock-forming minerals therein and (2) fracturing by forming local high pressure close to the wellbore that, when exceeding the fracture pressure of the rock in the oil layer near the bottom of the well, forces the oil layer to open and form cracks, which are further extended to the expected distance. Due to the formation of these fractures, the permeability near the wellbore zone can be improved, and increased oil recovery can be achieved through the improved seepage capacity.

To further improve the oil recovery rate, tertiary, or enhanced oil recovery (EOR), techniques are being explored by varying the properties of the oil itself, such as reducing oil viscosity, reducing the surface tension, and increasing the permeability of the oil, which could lead to an oil recovery rate of 30% to 60% or more.

However, these EOR techniques have disadvantages:

- 1) due to the heterogeneity of the reservoir, fracturing and acidizing often cannot uniformly unclog reservoirs with large interlayer and intralayer differences, limiting their application in sensitive formations;
- 2) external fluid in the well and its incompatibility with the formation produce new suspended solids and microorganisms, causing secondary contaminations to the formation;
- 3) external low-temperature fluid causes wax and asphalt in the crude oil to precipitate, causing great damages to oil reservoirs with high concentration of wax content and asphalt that blocks circulation channels;
- 4) disposal of flowbacks is not only expensive and difficult but also causes environmental contamination;
- 5) the setups for fracturing are complicated and expensive because the process consumes a large amount of water and emits a large amount of carbon dioxide;
- 6) repeated fracturing and acidizing cause great damages to the formation skeleton, and becomes less and less effective over time; and
- 7) fracturing and acidizing cause great damages to the casing and reduce the life cycle of the well.

SUMMARY

Accordingly, there is a need for more effective and more environmentally friendly EOR techniques during the oil recovery process.

Ultrasonic EOR is a type of physical EOR techniques and it is more effective for formation with certain levels of porosity and permeability. Electromagnetic EOR is another type of physical EOR techniques and it is more effective when the reservoir contains water and charged particles. In practice, given the differences in the pore-throat structure of the formation and the fluid properties, as well as complicated causes of formation clogging and reduction of seepage capacity, including clay swelling and particle migration, fouling, organic matter precipitation, and other factors, ultrasonic EOR or electromagnetic EOR alone is not suitable for diversified geological conditions and different types of oil contamination. For example, due to the complexity of oil deposits and reservoirs, there exist various oil contamination factors, such as high salt water, high viscosity, high temperature, etc., which all affect the effectiveness of a single EOR technique.

Accordingly, although ultrasonic stimulation and electrical stimulation separately can improve reservoir permeability and oil recovery to a certain extent, the effectiveness of a single EOR technique is limited to a certain extent due to the variation of formation properties and contamination factors. In this application, a new stimulation and clog removal technique is proposed, which enhances oil recovery by combining ultrasonic and electromagnetic waves together.

In accordance with some embodiments, an ultrasonic-transient electromagnetic (U-TEM) assembly is provided. The U-TEM assembly includes: a pressure balancer; a bridle having a first end connected to a cable and a second end connected to an adapter; an ultrasonic generator; and an electromagnetic generator. The ultrasonic generator and the electromagnetic generator are located between the bridle and the pressure balancer and coupled to the bridle via the adapter near the second end. The U-TEM assembly is configured to generate ultrasonic waves via the ultrasonic generator and transient electromagnetic waves via the electromagnetic generator concurrently in response to a control signal from the adapter.

In accordance with some embodiments, a method for enhancing oil recovery is provided. The method includes: placing an ultrasonic-transient electromagnetic (U-TEM) assembly in a well, the U-TEM assembly including an ultrasonic generator and an electromagnetic generator; adjusting a vertical displacement of the U-TEM assembly such that the U-TEM assembly is located at a first depth within the well corresponding to a first target zone of treatment; and actuating the U-TEM assembly with electric power to transmit ultrasonic waves and transient electromagnetic waves into the first target zone of treatment concurrently, wherein the ultrasonic waves are generated by the ultrasonic generator and the transient electromagnetic waves are generated by the electromagnetic generator.

In accordance with some embodiments, a method for enhancing oil recovery is provided. The method includes: placing an ultrasonic-transient electromagnetic (U-TEM) assembly in a well; adjusting a vertical displacement of the U-TEM such that the U-TEM is located at a first depth within the well corresponding to a first target zone of treatment; actuating the U-TEM assembly to transmit ultrasonic waves and transient electromagnetic waves into the first target zone of treatment concurrently for a predefined time period; applying a first type of chemical treatment to a formation region corresponding to the first target zone of treatment using a pump for reducing oil viscosity; and alternately performing the actuating operation and the applying operation during an oil recovery process.

Thus, devices and systems are disclosed with methods for enhancing oil recovery. Such methods, devices, and systems may complement or replace conventional methods, devices, and systems for enhancing oil recovery.

The features and advantages described in the specification are not necessarily all-inclusive and, in particular, some additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims provided in this disclosure. Moreover, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes and has not necessarily been selected to delineate or circumscribe the subject matter described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present disclosure can be understood in greater detail, a more particular description can be had by reference to the features of various embodiments, some of which are illustrated in the appended drawings. The appended drawings, however, merely illustrate pertinent features of the present disclosure and are therefore not necessarily to be considered limiting, for the description can admit to other effective features as the person of skill in this art will appreciate upon reading this disclosure.

FIG. 1 is a block diagram illustrating an exemplary U-TEM oil recovery system in accordance with some embodiments.

FIG. 2 illustrates an exemplary way to enhance oil recovery in accordance with some embodiments.

FIG. 3 illustrates how ultrasonic waves affect fluid in capillaries, without presence of electromagnetic waves.

FIG. 4 illustrates how ultrasonic waves affect fluid in capillaries, with presence of electromagnetic waves.

FIG. 5 illustrates an exemplary U-TEM assembly in accordance with some embodiments.

FIG. 6 illustrates a cross-section of an exemplary U-TEM assembly in accordance with some embodiments.

FIG. 7 illustrates an exemplary ultrasonic generator in accordance with some embodiments.

FIG. 8 illustrates an exemplary ultrasonic generator in accordance with some embodiments.

FIG. 9 illustrates a cross-section of an exemplary electromagnetic generator in accordance with some embodiments.

FIG. 10A illustrates a cross-section of an exemplary bridle in accordance with some embodiments.

FIG. 10B is an enlarged view of a cross-section of a portion of an exemplary bridle in accordance with some embodiments.

FIG. 11 illustrates the structure of an exemplary oil well in accordance with some embodiments.

FIG. 12 illustrates an exemplary relationship between transmission coefficient and ultrasound frequencies.

FIG. 13 is a flow diagram illustrating an exemplary method of enhancing oil recovery in accordance with some embodiments.

FIGS. 14A-14D are flow diagrams illustrating exemplary methods of enhancing oil recovery in accordance with some embodiments.

FIGS. 15A-15C are flow diagrams illustrating an exemplary method of enhancing oil recovery in accordance with some embodiments.

FIGS. 16A-16C are flow diagrams illustrating exemplary methods of enhancing oil recovery in accordance with some embodiments.

In accordance with common practice, the various features illustrated in the drawings are not necessarily drawn to scale, and like reference numerals can be used to denote like features throughout the specification and figures.

DETAILED DESCRIPTION

As noted above, a single EOR technique, such as ultrasonic EOR alone or electromagnetic EOR alone, cannot account for the interlayer and intralayer formation differences and various types of contaminations from prior oil recovery processes. The present disclosure describes, among other things, an ultrasonic-transient electromagnetic (U-TEM) assembly and applying ultrasonic and electromagnetic waves emitted by the U-TEM assembly to formation for improved EOR. Ultrasonic and electromagnetic waves work together to break down the clogging structure, create microcracks in rocks, reduce fluid viscosity, and reduce surface tension, resulting in a higher oil recovery rate.

Example Systems and Devices

FIG. 1 is a block diagram illustrating an exemplary oil recovery system 100 in accordance with some embodiments. The oil recovery system 100 includes a workover rig 104 and an engineering vehicle 105 on the ground 108. The engineering vehicle 105 includes a control cabinet 106 and has a cable 102 that delivers a piece of underground equipment 103 into a well 101 via the workover rig 104. The underground equipment 103 includes an Ultrasonic-Transient Electromagnetic (U-TEM) assembly, which generates both ultrasonic waves and transient electromagnetic waves into the formation of the underground 107. The ultrasonic waves and transient electromagnetic waves generated by a U-TEM assembly propagate into a target formation and work collectively to achieve the effects of reducing formation clogging and fluid viscosity, so as to improve reservoir permeability and recovery rates.

FIG. 2 illustrates an exemplary way to enhance oil recovery in accordance with some embodiments. It is well-known that there exist various reservoir space types of pores, cavities and fractures with complicated combination patterns in the underground, which create different pore-throat structures. The complicated pore-throat structures of hydrocarbon reservoirs have complex porosity-permeability relationship and demonstrate the phenomena of high porosity and low permeability. FIG. 2-1 illustrates such a pore-throat structure. As shown in FIG. 2-1, large pore volumes 202 are connected through at least a pore throat 203, which is formed between matrix 201 and clogged by particles 204. Particles 204 tend to be stuck in the pore throat 203 and are difficult to remove, preventing the fluid from flowing between the large pore volumes 202 on both sides of the pore throat 203.

When ultrasonic waves are applied to porous media saturated with mixed fluids of oil and brine, a large number of new charged particles can be generated in the formation through mechanisms including electrochemical, electromechanical, and/or droplet percussion effects. Specifically, under the electrochemical mechanism, ultrasonic waves can trigger chemical reactions in the fluid. Depending on the reaction process, some positively/negatively charged ions and/or pollutant-carrier particles are generated. For petroleum under high pressure and high temperature, ultrasonic waves excite and accelerate the free radical reactions required for decomposition of the petroleum, resulting in the acidic ionization of the aggregated petroleum components. Under the electromechanical effect mechanism, when ultrasonic waves propagate in the porous media, weak eddies are formed, causing strong mechanical vibrations on the charges on the rock pore walls, thereby resulting in local ionization and generating charged particles. Under the droplet percussion mechanism, when the ultrasonic waves are applied to the mixed fluid containing oil and water, the droplets are directly peeled off or directly destroyed in the “shock” and release a large number of charged ions and/or charged compounds. As shown in FIG. 2-2, ultrasonic waves generate charged particles at least at or near the pore throat 203.

These newly formed charged particles are affected by the electromagnetic waves propagating in the formation. Specifically, an electric field exerts a Coulomb force on a charged particle, in the same or opposite direction as the electric field, and a magnetic field exerts a Lorentz force on the charged particle, which is always perpendicular to the velocity of the particle and the direction of the magnetic field. The magnitude and direction of the force are affected by factors including the strength of the electromagnetic field, the charge-to-mass ratio of the particles, the velocity and direction of the particles, the initial position and momentum, etc. The electromagnetic field triggers the charged particles to produce different accelerations, causing them to loosen, oscillate, migrate, change shapes, turn, etc. in the formation. For example, as shown in FIG. 2-3, electromagnetic waves, which include the electrical field 204 shown in FIG. 2-2, move and redirect charged particles. Gradually, clogged particles that were originally bound in the pore throats of the formation can be freed, as shown in FIG. 2-4, so as to achieve the purpose of unclogging the formation, dredging the seepage channel and increasing the oil recovery rate.

FIGS. 3 and 4 provide another example in which ultrasonic waves and transient electromagnetic waves work collectively to reduce formation clogging and fluid viscosity.

Rocks are a form of porous media, and fluid-saturated rocks in the subsurface is a complex multi-phase and multi-component physical-chemical system. When the matrix is in contact with aqueous solutions, ionization, ion adsorption, and/or ion dissolution in the reservoir pore capillaries happens, causing electrostatic charges accumulating on the solid surface. These charges cause opposite-charged ions to accumulate on the solid surface and repel ions of the same charge away from the solid wall, forming an adsorbing layer with a thickness of about one ion in diameter, the layer often referred to the “Stern layer”. The strong electrostatic force causes the ions in the adsorption layer to be firmly adsorbed on the solid surface. Outside the adsorption layer is a diffusion layer, which contains same-charged ions and opposite-charged ions, both of which are mobile. The adsorption and diffusion layers form the so-called “electric double layer” (EDL). In the EDL, the concentration and electrostatic potential of ions obey the Poisson-Boltzmann distribution law, and the EDL's structure mainly depends on the concentration of ions in the solution, the type of interaction between the ions and the solvent, and the electrochemical properties of the solid.

The EDL plays an important role at the interface between rock (301 and 401) surfaces and fluid in the capillaries (302 and 402). When no external electric field is applied, the flow of the fluid in the capillary of the formation is mostly a laminar flow or streamline flow. For example, the oil-water interface exhibits a parabolic flow pattern. At this time, if ultrasonic waves are applied to the formation rock, and periodic amplitude expansions and contractions of the ultrasonic waves cause the parabolic flow pattern of the oil-water interface in the capillary to change. However, it is difficult to promote the flow because the fluid is bound by the EDL. As shown in FIG. 3, when the ultrasonic waves propagate and the amplitude of the ultrasonic waves increase (e.g., from FIG. 3-1 to FIG. 3-2), the oil-water interface, e.g., the parabolic curve (304), is stretched but the fluid is not flowing due to the EDL. When the ultrasonic waves further propagate and the amplitude of the ultrasonic waves becomes negative (e.g., from FIG. 3-2 to FIG. 3-3), the parabolic curve (304) is compressed, and the fluid remains bounded by the EDL, as shown in FIG. 3-3.

Existence of electric and/or electromagnetic field changes such fluidity properties. When an external electric or electromagnetic field is applied, the free ions in the diffusion layer of the EDL move along the axial direction of the pipeline according to the Coulomb force. Because the fluid is viscous, the movement of the free ions also drives the surrounding fluid microgroups to move together in particular directions, resulting in the flow of fluid in the entire channel. Under such condition, the flow of the fluid in the capillary of the formation is mostly a laminar flow or streamline flow, now showing a plug flow pattern.

A shown in FIG. 4, with the presence of an electric and/or electromagnetic field, the oil-water interface exhibits a plug-like curve (404). As the ultrasonic waves propagate, the amplitude of the ultrasonic waves increases (see, e.g., from FIG. 4-1 to FIG. 4-2), the plug-like curve (404) is stretched. At the same time, the fluid moves along the axial direction (see, e.g., the distance between the vertical dash line and the vertical dash-dot line in FIG. 4-2). As the ultrasonic waves further propagate and the amplitude of the ultrasonic waves becomes negative (see, e.g., from FIG. 4-2 to FIG. 4-3), the oil-water interface, e.g., the plug-like curve (404), is compressed but notable movement of fluid may not happen, as shown in FIG. 4-3. Accordingly, with the presence of the electric and/or electromagnetic field, when the ultrasonic waves are applied to the formation rocks, and the periodic amplitude expansions and contractions of the ultrasonic waves periodically push the fluid to flow in the capillaries. In sum, the combined effect of the Coulomb force and the pressure exerted by ultrasonic waves, collectively, cause the migration of fluid and adsorbed substances in the capillaries, thereby improving the fluidity of fluid in pores and throats.

FIG. 5 illustrates an exemplary U-TEM assembly in accordance with some embodiments. The U-TEM assembly 500 generates both ultrasonic waves and electromagnetic waves, which improve the fluidity of fluid and thereby enhance oil recovery as detailed above. As shown in FIG. 5, the U-TEM assembly 500 includes a pressure balancer 501, a bridle 505, an ultrasonic generator 502, and an electromagnetic generator 503. The bridle 505 has a first end connected to a cable, e.g., cable 102 in FIG. 1, and a second end connected to an adapter 504. The ultrasonic generator 502 and the electromagnetic generator 503 are located between the bridle 505 and the pressure balancer 501 and are coupled to the bridle 505 via the adapter 504. The U-TEM assembly 500 is configured to generate ultrasonic waves via the ultrasonic generator 502 and transient electromagnetic waves via the electromagnetic generator 503 concurrently in response to a control signal from the adapter. Specifically, the adapter's cable core connects to the bridle's cable core, thereby passing electric power and signals to from the bridle 505 (which are in turn passed from the cable 102) to the ultrasonic generator 502 and the electromagnetic generator 503.

FIG. 6 illustrates a cross-section of an exemplary U-TEM assembly in accordance with some embodiments. As shown, the U-TEM assembly 600 includes an adapter 602 covered by a protective cap 601. The U-TEM assembly 600 includes an inductor coil 603, which is part of an electromagnetic generator. A first end of the electromagnetic generator is connected to the adapter 602, and a second end of the electromagnetic generator is connected to a first end of an ultrasonic generator 606 via a first connector 605. A second end of the ultrasonic generator 606 is connected to a pressure balancer via a second connector 607.

In accordance with some embodiments, the U-TEM assembly 600 includes a case 604, and the ultrasonic generator and the electromagnetic generator are enclosed in the case 604 to protect them from being damaged by the surrounding environment.

The ultrasonic generator and the electromagnetic generator can be electrically connected in different ways. For example, in accordance with some embodiments, the ultrasonic generator and the electromagnetic generator are in serial electrical connection. Alternatively, the ultrasonic generator and the electromagnetic generator are in parallel electrical connection.

There are different ways of connecting the ultrasonic generator and the electromagnetic generator mechanically, independently from how they are electrically connected. For example, in accordance with some embodiments, the ultrasonic generator and the electromagnetic generator are in serial mechanical connection. As illustrated in FIG. 5, the pressure balancer 501 is mechanically connected to a first end of the ultrasonic generator 502. A second end of the ultrasonic generator 502 is mechanically connected to a first end of the electromagnetic generator 503. A second end of the electromagnetic generator 503 is mechanically connected to the bridle 505, directly or via an adapter 504.

In accordance with some other embodiments, the ultrasonic generator and the electromagnetic generator in the U-TEM assembly may be swapped. For example, the pressure balancer is mechanically connected to a first end of the electromagnetic generator, a second end of the electromagnetic generator is mechanically connected to a first end of the ultrasonic generator, and a second end of the ultrasonic generator is mechanically connected to the bridle, directly or via an adapter.

In accordance with some other embodiments, the ultrasonic generator and the electromagnetic generator are in mechanical nesting connection. For example, at least a portion of the ultrasonic generator is located within the electromagnetic generator. Alternatively, at least a portion of the electromagnetic generator is located within the ultrasonic generator.

In accordance with some embodiments, an ultrasonic generator includes a conductive metal tube and one or more transducer components. As shown in FIG. 7, a transducer component 700 includes a piezoelectric ceramic tube 701, a heat resistant insulating skeleton 702 enclosed in the piezoelectric ceramic tube 701, and a plurality of piezoelectric copper sheets 706 located on an external surface of the heat resistant insulating skeleton 702. The plurality of piezoelectric copper sheets 706 are in conduction with a conductive metal tube 703 and the piezoelectric ceramic tube 701. In accordance with some embodiments, the piezoelectric copper sheets 706 may be in an arc shape.

As shown in FIG. 7, the transducer component 700 also includes a plurality of conductive screws 705, which are in one-to-one correspondence with the plurality of piezoelectric copper sheets 706. Each piezoelectric copper sheet 706 is fixed to a mounting groove 704 by its corresponding conductive screw 705. A first end of each conductive screw 705 penetrates the heat resistant insulating skeleton 702 and contacts the conductive metal tube 703, so that each piezoelectric copper sheet 706 is connected to the conductive metal tube 703. A second end of each conductive screw 705 is in contact with an inner surface of the piezoelectric ceramic tube 701, so that each piezoelectric copper sheet 706 is also connected to the piezoelectric ceramic tube 701. In this way, the conductive metal tube 703 and the piezoelectric ceramic tube 701 are connected.

In accordance with some embodiments, a transducer component includes multiple (e.g., three) piezoelectric copper sheets and multiple (e.g., three) conductive screws. The number of piezoelectric copper sheets and conductive screws are not fixed—it could be smaller or bigger than three.

In accordance with some embodiments, an ultrasonic generator includes more than one transducer component, and each transducer component may or may not have the same number of piezoelectric copper sheets and conductive screws.

As shown in FIG. 8, an ultrasonic generator 800 includes multiple transducer components 802 connected in series. In accordance with some embodiments, two adjacent transducer components are separated via a spacer 707 as shown in FIG. 7. Because the vibration frequencies for the transducer components are the same, separating these transducer components, e.g., via spacers, prevents device damage when multiple transducer components are in resonance.

During oil recovery, a cable is placed through the conductive metal tube 703 and is in conduction with the conductive metal tube 703. The cable carries high-frequency and high-power current to the conductive metal tube 703, passing the piezoelectric copper sheets 706, and ultimately reaching the piezoelectric ceramic tube 701. Due to the inverse piezoelectric effect, the voltage applied to the piezoelectric ceramic tube 701 causes the piezoelectric ceramic tube 701 to generate mechanical vibrations, thereby emitting ultrasonic waves.

FIG. 9 illustrates a cross-section of an exemplary electromagnetic generator in accordance with some embodiments. As shown, the electromagnetic generator 900 includes a tube 903 enclosing a shaft 904 located in the middle of the tube 903. A high-power electromagnetic coil 905 is located on at least a portion of the shaft 904. A copper pin rod 901 covered by a protective case 902 is used to supply oscillating current to the electromagnetic generator 900. Specifically, the electromagnetic coil 905 emits the transient electromagnetic waves in response to oscillating current entering into the electromagnetic coil.

During oil recovery, transient electromagnetic field (or transient electromagnetic waves), as compared to a steady-state magnetic field, is generated in response to the alternately powering on and off of a connection circuit. The transient electromagnetic field generates electromagnetic energy with sufficiently high power, which is exerted into the formation through a casing of an oil well, effectively overcoming the shielding effect of the casing.

In accordance with some embodiments, the ultrasonic generator and the electromagnetic generator in a U-TEM assembly are connected to an electric cable via a bridle. In accordance with some embodiments, the electric cable is a single-core electric cable. Thus, the ultrasonic generator generates ultrasonic signals using electric energy provided via the single-core electric cable, and the electromagnetic generator generates transient electromagnetic waves using electric energy provided via the single-core electric cable. Use of a single-core cable allows supply of high voltage and high current that are needed by the U-TEM assembly.

FIG. 10A illustrates a cross-section of an exemplary bridle in accordance with some embodiments. As shown, the bridle 1000 has a tube, which is sealed using silicon and rubber forming a sealed cavity 1008. The tube includes a through hole 1003 for filling silicone grease into the cavity 1008. In accordance with some embodiments, the bridle 1000 has a sealing assembly, including a first soft sealing sleeve 1002 and a second soft sealing sleeve 1004. Both the first and second soft sealing sleeves are made of insulating rubber and each seals an end of the cavity 1008. Both the first and second soft sealing sleeves are in a tapered shape, having a wider end and a narrower end. In accordance with some embodiments, the bridle 1000 also includes a cable inlet segment 1001 and a cable outlet segment 1010. The cable inlet segment 1001 has a first through hole 1011 and the cable outlet segment 1010 has a second through hole. When an electric cable is inserted into the bridle 1000, the cable goes through the first through hole 1011, pressing the narrower end of first soft sealing sleeve 1002 toward the cavity 1008. In accordance with some embodiments, the electric cable includes a layer having a plurality of steel wires. The electric cable then goes through the cavity 1008 filled with silicone grease, exiting a steel ring 5 located in the sealed cavity 1008. In accordance with some embodiments, as shown in FIG. 10A, the steel ring 5 is a tapered steel ring, having a narrower end toward the cavity 1008 and a wider end away from the cavity 1008. As shown in FIG. 10B, the tapered steel ring 1005 has a compression ring 1006, e.g., between the wider end of the tapered steel ring 1005 and the second soft sealing sleeve 1004. After the cable goes through the steel ring 1005, at least one of the plurality of steel wires of the electric cable 1012 is reverse threaded on the tapered steel ring 1005. As shown in FIG. 10A, the cable core 1009 runs through the compression ring 1006, the second soft sealing sleeve 1004, and the cable outlet segment 1010 in sequence. In accordance with some embodiments, the bridle 1000 further includes a lock cap 1007, which is detachably connected to a piece of equipment, including but not limited to an electromagnetic generator, an ultrasonic generator, or both, either directly or via an adapter.

Example EOR Methods Using U-TEM

FIGS. 15A-15C are flow diagrams illustrating an exemplary method 1500 of enhancing oil recovery in accordance with some embodiments. The method 1500 may be performed using a U-TEM assembly described above.

The method 1500 includes placing (S1502) an ultrasonic-transient electromagnetic (U-TEM) assembly in a well, the U-TEM assembly including an ultrasonic generator and an electromagnetic generator. In accordance with some embodiments, the ultrasonic generator and the electromagnetic generator are connected (S1504) to an electric cable via a bridle, as described above with respect to FIGS. 5 and 6. The U-TEM assembly further includes (S1506) a case, and the ultrasonic generator and the electromagnetic generator are enclosed in the same case.

The method 1500 further includes adjusting (S1508) a vertical displacement of the U-TEM assembly such that the U-TEM assembly is located at a first depth within the well corresponding to a first target zone of treatment. For example, as shown in FIG. 1, by controlling the length of at least a portion of cable 102, the vertical displacement of the U-TEM assembly in the well 101 can be adjusted. And by placing the U-TEM assembly at different depths within the well 101, the U-TEM system 100 enhances oil recovery for different target zones in the formation.

The method 1500 further includes actuating (S1510) the U-TEM assembly with electric power to transmit ultrasonic waves and transient electromagnetic waves into the first target zone of treatment concurrently. The ultrasonic waves are generated by the ultrasonic generator and the transient electromagnetic waves are generated by the electromagnetic generator. In accordance with some embodiments, the transient electromagnetic waves are generated (S1512) using an electromagnetic coil in the electromagnetic generator, as described above with respect to FIGS. 6 and 9.

In accordance with some embodiments, the electric power includes (S1516) an oscillating current provided to the electromagnetic generator. The oscillating current has an ON state and an OFF state, and the oscillating current switches between the ON state and the OFF state at least twice per second. The number of switching between the ON and OFF states may be adjusted as needed. Due to such ON-AND-OFF switching, the electromagnetic generator generates transient electromagnetic field, as opposed to static electromagnetic field. It should be noted that the frequency for ON-AND-OFF state switching may be adjusted as needed, e.g., at different depths or times.

In accordance with some embodiments, the electric power includes (S1514) intermittent high-frequency oscillating signals provided to the ultrasonic generator as described with respect to FIGS. 7 and 8. Such intermittent high-frequency oscillating signals causes mechanical vibration of the ultrasonic generator's piezoelectric ceramic tube, e.g., 701 in FIG. 7, thereby emitting ultrasonic waves. The frequency of the ultrasonic waves is between 10 KHz and 50 KHz. The frequency of the ultrasonic waves may be adjusted as needed.

In accordance with some embodiments, the method 1500 further includes adjusting (S1518) an output frequency of the ultrasonic generator to be within a first output frequency window, the first output frequency window having a transmittance through the first target zone of treatment substantially higher than a transmittance of a second output frequency window through the same first target zone of treatment.

FIG. 11 illustrates the structure of an exemplary oil well from a top-down view in accordance with some embodiments. As shown, the well includes a layer of cement 1102 covered by a layer of casing 1103. The sound source 1107 may be an ultrasonic generator. Ultrasonic waves generated from the sound source 1107 have to propagate through multiple layers, including at least the silicone oil filled in the equipment 1106, the case of the equipment 1105, liquid in the well 1104, well casing 1103 and a cement layer 1102, before reaching the formation 1101. When passing through these layers, the high-power ultrasound reflects and transmits between the layers. The reflection and transmission coefficients of the ultrasound for each layer are determined by various factors, such as the frequency of the ultrasound waves, the longitudinal wave velocity, the shear wave velocity, the density and thickness of each layer. Ultimately, these factors cause the ultrasonic energy passing through these layers to change with the ultrasound frequency.

FIG. 12 illustrates an exemplary relationship between transmission coefficient and ultrasound frequencies. As shown, as the ultrasound frequency changes, the transmission coefficient periodically reaches its local maxima, e.g., reaching transmission coefficient of 0.95, forming several high-transmission windows. It should be noted that the maximum transmission coefficient for different high-transmission windows may be different. For example, the maximum transmission coefficients of high-transmission windows in lower frequency range may be smaller than those in higher frequency range. Taking the ±1 range around the maximum transmission coefficient as the window size, the window sizes of different high-transmission windows may also be different. For example, the window widths in lower frequency range may be bigger than those in higher frequency range.

Accordingly, by adjusting the ultrasound frequency, ultrasound energy reaching the formation can be maximized. In accordance with some embodiments, the output frequency of the ultrasonic generator is adjusted (S1522) based on at least characteristics of the layer of cement, characteristics of the layer of casing, and formation characteristics of the first target zone of treatment. For example, characteristics of the layer of cement include at least the dimensions, thickness, material and mechanical properties of that layer. Characteristics of the layer of casing include at least the dimensions, thickness, material and mechanical properties of that layer. Formation characteristics of the first target zone of treatment include at least the mechanical properties of the formation in the first target zone of treatment.

The location of a high-transmission window also depends on the dimension of the ultrasound generator. Below is a table illustrating the high-transmission windows for different wellbore dimensions and ultrasound generator dimensions combinations. As shown, different characteristics combination, including but not limited to the wellbore diameter and the ultrasound generator diameter, have different high-transmission windows, and/or different number of effective high-transmission windows.

Wellbore diameter
Ultrasound generator
Location of high-

(inches)
equipment diameter (mm)
transmission windows (KHz)

5.5
70
23 ± 1

5.5
80
25 ± 1, 19.4 ± 1

5.5
90
22.5 ± 1, 19.3 ± 1

5.5
100
22 ± 1

5.5
110
24 ± 1, 45 ± 1

7
70
17.5 ± 1, 34 ± 1

7
80
17.5 ± 1, 19.5 ± 1, 29.5 ± 1,

44 ± 1

7
90
16.5 ± 1, 19.3 ± 1, 28.6 ± 1

7
100
16.5 ± 1, 31 ± 1

7
110
16.4 ± 1, 33.5 ± 1, 44.5 ± 1

FIG. 13 is a flow diagram illustrating an exemplary method of enhancing oil recovery in accordance with some embodiments. Specifically, FIG. 13 illustrates an exemplary method of optimizing the ultrasound transmission coefficient during oil recovery. As shown, the method 1300 includes obtaining (S1310) the geometry, size, density, compressional wave velocity, shear wave velocity, etc. of tubing, casing, cement, formation, etc. for the well under production. The method 1300 further includes calculating (S1320) of acoustic windows (or high-transmission windows) based on these parameters. The method 1300 further includes selecting (S1330) the location of the acoustic window with the largest transmission coefficient as the site operation frequency and then carrying out (S1340) ultrasonic operation work.

It should be noted that the formation characteristics vary in different zones of treatment, depending on the depth of the zones of treatment in the well. Thus, to maximize the transmission coefficient of the ultrasound waves into the formation, the frequency of the ultrasound waves needs to be adjusted between different formation layers. In addition to adjusting the output frequency of the ultrasonic generator based on at least the formation characteristics of the first target zone of treatment, the method 1500 further includes adjusting (S1524) the vertical displacement of the U-TEM assembly such that the U-TEM assembly is located at a second depth within the well corresponding to a second target zone of treatment, and adjusting (S1526) the output frequency of the ultrasonic generator based on at least formation characteristics of the second target zone of treatment.

Due to the interlayer differences, the ultrasonic operation time for different layers may also vary. In accordance with some embodiments, the method 1500 further includes, while the U-TEM assembly remains (S1528) at the first depth within the well corresponding to a first target zone of treatment, continuing generating (S1530) the ultrasonic waves and the transient electromagnetic waves for a first predefined time period based on at least formation characteristics of the first target zone of treatment. The method 1500 further includes, in response to expiration (S1532) of the first predefined time period, adjusting (S1534) the vertical displacement of the U-TEM assembly such that the U-TEM assembly is located at a third depth within the well corresponding to a third target zone of treatment, and generating (S1536) the ultrasonic waves and the transient electromagnetic waves for a second predefined time period based on at least formation characteristics of the second target zone of treatment. The method 1500 further includes ceasing (S1538) to generate the ultrasonic waves and the transient electromagnetic waves in response to expiration of the second predefined time period. In accordance with some embodiments, the duration of the second predefined time period is different from that of the first predefined time period.

At present, a variety of injection techniques and measures are used in the production process to enhance oil recovery, mainly including: fracturing, acidification, injection of chemicals, microorganisms and nanomaterials, injection of steam, such as CO₂, N₂and other gases, and injection of water. Although methods such as use of polymers can increase oil and gas production capacity to a certain extent, the technical applicability is not universal and there exist many technical defects with respect to these methods. For example, due to the reservoir heterogeneity, large interlayer and intralayer differences make a single technique ineffective; the application of the above-mentioned methods are limited in sensitive formations; external fluids and incompatibility with formations produce new suspended particles and microorganisms, causing secondary contamination to the formation; great damages to reservoirs with high pour point oil, wax, colloid, and asphalt; and external low-temperature fluids cause wax, colloid, and asphalt in crude oil to precipitate, clogging circulation channels; repeated acidizing and fracturing damage the formation skeleton greatly while being less and less effective over time for enhancing oil recovery.

During the development of oil wells and water injection wells, pore clogging is relatively a common problem because some oil reservoirs have relatively large particles (such as oil residue, sediment, etc.), which are easily suspended in the liquid and enter the pores, causing clogging. In addition, changes in formation pressure or high mineral content in the well can also cause insoluble salts to precipitate from the water molecules and form crystals in the pores, thereby causing clogging. For some acid-insoluble clogging particles, it is difficult to remove by acidizing. If they are not removed after repeated acidizing, they may accumulate in and near the wellbore, affecting the diffusion range of acid fluid and the overall acidizing effect. At the same time, in an acidizing process of carbonate rocks and conventional reservoirs, when the acid liquid is injected into the formation by a pump truck, the acid liquid remains in a static state in the formation, making it hard for the acid-soluble substances in the matrix to contact fully with the injected acid liquid and for the injected acid liquid to enter certain micropores. These are all causes for a poor acidification effect and unsatisfactory yield.

Here, a new oil recovery enhancing method is proposed, which aims to overcome the above limitations of using a single oil recovery technique. In accordance with some embodiments, the method employs in-well ultrasonic, electromagnetic and chemical methods to resolve clogging and increase oil production yield. Through the effective combination of physical and chemical methods, it can meet different types of contaminations and reservoir characteristics. This technology has strong applicability and effectiveness and can significantly improve the effect of plug removal and enhance the effect of acidizing operations.

FIGS. 16A-16C are flow diagrams illustrating exemplary methods of enhancing oil recovery in accordance with some embodiments. The method 1600 for enhancing oil recovery includes placing (S1602) an ultrasonic-transient electromagnetic (U-TEM) assembly in a well. As detailed above, for example with respect to FIGS. 5 and 6, the U-TEM assembly includes (S1604) an ultrasonic generator and an electromagnetic generator. In accordance with some embodiments, the ultrasonic generator and the electromagnetic generator are connected (S1606) to an electric cable via a bridle. In accordance with some embodiments, the U-TEM assembly further including (S1608) a case, and the ultrasonic generator and the electromagnetic generator are enclosed in the same case.

The method 1600 further includes adjusting (S1610) a vertical displacement of the U-TEM such that the U-TEM is located at a first depth within the well corresponding to a first target zone of treatment, and actuating (S1612) the U-TEM assembly to transmit ultrasonic waves and transient electromagnetic waves into the first target zone of treatment concurrently for a predefined time period. As detailed above, for example with respect to FIGS. 6 and 9, the transient electromagnetic waves are generated (S1614) using an electromagnetic coil in the electromagnetic generator.

The method 1600 further includes applying (S1616) a first type of chemical treatment to a formation region corresponding to the first target zone of treatment using a pump for reducing oil viscosity. In accordance with some embodiments, chemical reagents are injected into the formation, e.g., through an injection pipe having a high-pressure pump, and interact with rocks and/or fluids in the formation. In accordance with some embodiments, the radial distance of the acidizing is several meters from the wellbore central axis. In accordance with some embodiments, applying (S1616) a first type of chemical treatment includes applying (S1618) at least one of acid fluid and surfactant. In accordance with some embodiments, different types of injections may be performed, including but not limited to fracturing, acidification, injection of chemicals, microorganisms and nanomaterials steam, CO₂, N₂, and other gases, as well as water, polymers, etc.

The sequence of injection (including chemical treatment) and U-TEM operation may vary. In accordance with some embodiments, the first type of chemical treatment is applied (S1630) after ceasing to generate the ultrasonic waves and the electromagnetic waves. As shown in FIG. 14A, wellbore pretreatment (S1402) is first performed. In accordance with some embodiments, wellbore pretreatment includes drilling, washing, and/or scraping the target well to prepare for the subsequent operations. Then, ultrasonic, electromagnetic, and/or U-TEM operation is carried out (S1404) in the well, as detailed above. After completion of the ultrasonic, electromagnetic, and/or U-TEM operation, injection operation, such as chemical treatment, is carried out (S1406) in the well. Thereafter, tubing and oil recovery is performed (S1408).

In accordance with some embodiments, the operation of generating the ultrasonic waves and the electromagnetic waves is resumed (S1632) after applying the first type of chemical treatment. As shown in FIG. 14D, the ultrasonic, electromagnetic, and/or U-TEM operation (S1434) is performed after the injection operation, such as chemical treatment (S1432), is conducted for a predetermined duration.

In accordance with some embodiments, the first type of chemical treatment is applied (S1620) before generating the ultrasonic waves and the electromagnetic waves. As shown in FIG. 14B, wellbore pretreatment is again performed (S1410). Then, injection operation, such as chemical treatment, is carried out (S1412) in the well. Ultrasonic, electromagnetic, and/or U-TEM operation is then carried out (S1414) in the well. Thereafter, tubing and oil recovery is performed (S1418).

In accordance with some embodiments, as shown in FIG. 14C, the injection operation, such as chemical treatment (S1424) and the ultrasonic, electromagnetic, and/or U-TEM operation (S1422) may be carried out at the same time. For example, in accordance with some embodiments, the injection operation and the ultrasonic, electromagnetic, and/or U-TEM operation may start at the same time. Alternatively, the ultrasonic, electromagnetic, and/or U-TEM operation may start while the injection operation is still on going.

The method 1600 further includes alternately performing (S1626) the actuating operation (S1612) and the applying operation (S1616) during an oil recovery process. For example, the injection operation may be carried out more than once. As shown in FIG. 14B, after the ultrasonic, electromagnetic, and/or U-TEM operation is carried out (S1414), the U-TEM assembly ceases (S1622) to generate the ultrasonic waves and the electromagnetic waves. Thereafter, another injection operation, such as a second type of chemical treatment, is carried out (S1624) in the well. See also FIG. 14D. In accordance with some embodiments, the second type of chemical treatment is the same (S1628) as the first type of chemical treatment. In accordance with some other embodiments, the second type of chemical treatment is different from the first type of chemical treatment.

During an oil recovery process, the number of injection operations and after the ultrasonic, electromagnetic, and/or U-TEM operations may vary. In addition, the duration for the injection operation, such as chemical treatment, and the ultrasonic, electromagnetic, and/or U-TEM operation may also vary between operations and between different target zones of treatment within an operation.

It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the claims. As used in the description of the embodiments and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, the term “if” can be construed to mean “when” or “upon” or “in response to determining” or “in accordance with a determination” or “in response to detecting” that a stated condition precedent is true, depending on the context. Similarly, the phrase “if it is determined [that a stated condition precedent is true]” or “if [a stated condition precedent is true]” or “when [a stated condition precedent is true]” can be construed to mean “upon determining” or “in response to determining” or “in accordance with a determination” or “upon detecting” or “in response to detecting” that the stated condition precedent is true, depending on the context.

The foregoing description, for purposes of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or limit the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain principles of operation and practical applications, to thereby enable others skilled in the art.

	Number	Date	Country
Parent	PCT/CN2023/124097	Oct 2023	WO
Child	18824790		US

SYSTEMS AND ASSEMBLIES FOR ENHANCED OIL RECOVERY USING ULTRASONIC-TRANSIENT ELECTROMAGNETIC SETUP

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

International Classifications

Abstract

Description

Claims

RELATED APPLICATIONS

Continuations (1)