Method and apparatus for reducing a skin effect in a downhole environment
A method for reducing a skin effect in a downhole environment is provided, including the step of radiating vibrational waves at a wellbore wall such that the vibrational waves have at least one direction of greatest vibrational energy transfer directed toward the wall, thereby reducing the skin effect. An apparatus for reducing a skin effect in a downhole environment is also provided. The apparatus includes at least one vibrational wave source having at least one direction of greatest vibrational energy transfer, and a means for positioning the vibrational wave source proximate a wellbore wall.
The present invention relates to apparatuses and methods for treating a downhole environment, and more specifically, to apparatuses and methods for reducing a skin effect in a downhole environment.
In any typical hydrocarbon well, damage to the surrounding formation can impede fluid flow and cause production levels to drop. While many damage mechanisms plague wells, one of the most pervasive problems is particles clogging the formation pores that usually allow hydrocarbon flow. These clogging particles can also obstruct fluid pathways in screens; preslotted, predrilled, or cemented and perforated liners; and gravel packs that may line a well. Clogging particles may even restrict fluid flow in open-hole wells. Drilling mud, drilled solid invasion, or even the porous formation medium itself may be sources for these particles. In particular, in situ fines mobilized during production can lodge themselves in the formation pores, preslotted liners, screens and gravel packs, sealing them to fluid flow. Referred to as the “skin effect,” this damage is often unavoidable and can arise at any stage in the life of a typical hydrocarbon well. The hydrocarbon production industry has thus developed well-stimulation techniques to repair affected wells or at least mitigate skin-effect damage.
The two classic stimulation techniques for formation damage, matrix acidizing and hydraulic fracturing, suffer from limitations that often make them impractical. Both techniques require the operator to pump customized fluids into the well, a process that is expensive, invasive and difficult to control. In matrix acidizing, pumps inject thousands of gallons of acid into the well to dissolve away precipitates, fines, or scale on the inside of tubulars, in the pores of a screen or gravel pack, or inside the formation. Any tool, screen, liner or casing that comes into contact with the acid must be protected from its corrosive effects. A corrosion inhibitor must be used to prevent tubulars from corrosion. Also, the acid must be removed from the well. Often, the well must also be flushed with pre- and post-acid solutions. Aside from the difficulties of determining the proper chemical composition for these fluids and pumping them down the well, the environmental costs of matrix acidizing can render the process undesirable. Screens, preslotted liners and gravel packs may also be flushed with a brine solution to remove solid particles. While this brine treatment is cheap and relatively easy to complete, it offers only a temporary and localized respite from the skin effect. Moreover, frequent flushing can damage the formation and further decrease production. In hydraulic fracturing, a customized fluid is ejected at extremely high pressure against the wellbore walls to force the surrounding formation to fracture. The customized gel-based fluid contains a proppant to hold the fractures open to fluid flow. While this procedure is highly effective at overcoming near-borehole skin effects, it requires both specialized equipment and specialized fluids and therefore can be costly. Fracturing can also result in particle deposition in the formation because the gels involved may leave residue in the vicinity of the fractures.
The hydrocarbon production industry developed acoustic stimulation as an alternative to the classic stimulation techniques. In acoustic stimulation used for near-borehole cleaning, high-intensity, high-frequency acoustic waves transfer vibrational energy to the solid particles clogging formation pores. The ensuing vibrations of the solid particles loosen them from the pores. Fluid flow, including production-fluid flow out of the formation or injection-fluid flow into the formation from the well, may cause the particles to migrate out of the pores, clearing the way for greater fluid flow. Acoustic stimulation may also be used to clean preslotted liners, screens and gravel packs. Near-wellbore cleaning by acoustic stimulation has shown great promise in laboratory experiments, and the industry has developed several tools using this technique for use in real-world wells.
Acoustic stimulation tools require a compact source of acoustic waves that may be used downhole. Current tools, however, often radiate acoustic waves over 360 degrees or in an uncontrolled direction in an attempt to reduce the skin effect along the circumference of a wellbore wall at a given depth all at one time. These tools must consume large quantities of energy to radiate waves of sufficient intensity to vibrate the solid particles along the circumference of the wellbore wall. Supplying this energy downhole to create the necessary high-intensity acoustic waves is no easy feat, and thus current tools are poorly suited for removing particles from the formation.
SUMMARYThe present invention relates to apparatuses and methods for treating a downhole environment, and more specifically, to apparatuses and methods for reducing a skin effect in a downhole environment. An example method for reducing a skin effect in a downhole environment may comprise the step of radiating vibrational waves at a wellbore wall such that the vibrational waves have at least one direction of greatest vibrational energy transfer directed toward the wall, thereby reducing the skin effect.
An example apparatus for reducing a skin effect in a downhole environment may comprise at least one vibrational wave source having at least one direction of greatest vibrational energy transfer and a means for positioning the vibrational wave source proximate a wellbore wall. Some example apparatuses for reducing a skin effect in a downhole environment may comprise a vibrational wave source having at least one direction of greatest vibrational energy transfer and at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall. These example apparatuses may also include a decentralizer, wherein the decentralizer positions the vibrational wave source proximate the wellbore wall and a wireline, wherein the wireline may be used to place the vibrational wave source in the well.
Other example apparatuses for reducing a skin effect in a downhole environment may also comprise a vibrational wave source having at least one direction of greatest vibrational energy transfer and at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall. These example apparatuses may include a rotator-resolver, wherein the rotator-resolver orients the vibrational wave source such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall. These example apparatuses may also include at least two articulated joints connecting the vibrational wave source to the rotator-resolver and at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
An example apparatus for reducing a skin effect in a downhole environment may comprise a vibrational wave source having at least one direction of greatest vibrational energy transfer and at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall. These apparatuses may also include a rotator-resolver, wherein the rotator-resolver orients the vibrational wave source such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall. The example apparatuses may include a vibrational wave source pad attached to the rotator-resolver and at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
Another example apparatus for reducing a skin effect in a downhole environment may comprise a plurality of vibrational wave sources wherein each vibrational wave source has at least one direction of greatest vibrational energy transfer. The example apparatuses may also include at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the plurality of vibrational wave sources and a wellbore wall and a rotator-resolver, wherein the rotator-resolver orients the plurality of vibrational wave sources such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall. These apparatuses may also include a vibrational wave source pad attached to the rotator-resolver and at least one retractable arm, wherein the at least one retractable arm positions the plurality of vibrational wave sources proximate the wellbore wall.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the exemplary embodiments, which follows.
BRIEF DESCRIPTION OF DRAWINGSA more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, wherein:
While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTIONThe present invention relates to apparatuses and methods for treating a downhole environment, and more specifically, to apparatuses and methods for reducing a skin effect in a downhole environment. We provide a system for positioning a vibrational wave source downhole to optimally reduce a skin effect. The system may treat a variety of structures and materials located downhole, including, but not limited to, porous materials such as screens, gravel packs, frac packs or geologic formations. Moreover, the system may also treat openhole wells and wells with cemented and perforated casings or slotted liners.
An exemplary apparatus for reducing a skin effect in a downhole environment includes at least one vibrational wave source and a means for positioning the vibrational wave source proximate a wellbore wall. The vibrational wave source has at least one direction of greatest energy transfer.
Oval-mode acoustic wave source 104 includes a housing 101 and a vibratory mechanism, denoted generally by the numeral 102. The vibratory mechanism 102 causes housing 101 to expand and contract at acoustic frequencies. As a result, housing 101 produces acoustic waves that propagate radially outward from an outer surface 103 of housing 101. Housing 101 may be cylindrical, and vibratory mechanism 102 may have four piezoelectric transducers 105, 106, 107, and 108 spaced equally around the circumference of housing 101. When subject to a changing voltage at opposite ends, piezoelectric transducers 105, 106, 107, and 108 may expand and contract, causing vibrations in housing 101 that create the desired vibrational waves. Arrows 109, 109′, 110, 110′, 111, 111′, 112, and 112′ in
Once the first pair of opposing piezoelectric transducers 201 has expanded to its maximum size, and the second pair of opposing piezoelectric transducers 202 has contracted to its minimum size, housing 101 has experienced its maximum overall distortion in this direction. First pair of opposing piezoelectric transducers 201 then begins to contract, and second pair of opposing piezoelectric transducers 202 begins to expand, as shown in
The housing motion repeats with the repeated motion of the first and second pair of opposing piezoelectric transducers, causing the oval-mode vibrations that drive the desired vibrational waves. Returning to
This embodiment of a method according to the present invention may be repeated at a second portion 303 of wellbore wall 302 to expand the width of the cleaned area along the circumference of the well, as shown in
Once vibrational wave source 100 is activated, it will remove the solid particles from second portion 303 just as it did at portion 301. The process may be repeated at any location along the circumference of wellbore wall 302. It is not necessary, however, to clean all of wellbore wall 302 because fluid in the formation can migrate radially, axially and circumferentially to the nearest cleaned portion of wellbore wall 302. Example apparatuses may therefore achieve improved production flow rates using shorter operation times and lower power than tools that clean the entire circumference of wellbore wall 302. Example apparatuses may also allow for cleaning in situations when the power available is insufficient to adequately stimulate the wellbore wall around its full circumference. Because its outer diameter is smaller than the inner diameter of well 300, vibrational wave source 100 can fit through other passages having inner diameters smaller than the inner diameter of well 300, such as through the landing nipple inside production tubing 401 shown in cross-section in
In certain exemplary embodiments, vibrational wave source 100 will produce vibrational waves with frequencies in the range of about 8 kHz to about 40 kHz. In certain preferred embodiments, the vibrational waves will have frequencies ranging from about 10 kHz to about 20 kHz. Bursts of vibrational waves with intervening periods of inactivation are preferred so that fluid flow, such as production-fluid flow from the formation into the well or injection-fluid flow from the well into the formation, can flush away the loosened particles. The activation period for the vibrational wave source should last approximately 2,000 to approximately 20,000 cycles to bring the motion of the solid particles to the full resonance amplitude. Longer activation periods are acceptable, however, and may even be desirable in wells with severe skin-effect damage. The inactivation period between bursts should be selected empirically to optimize cleaning relative to the permeability of the skin effect.
Certain example apparatuses include a means for placing the vibrational wave source in a well. A suitable placement means will be apparent to persons of ordinary skill in the art having the benefit of this disclosure. The placement means may be a prior-art wireline, as shown in
Apparatus 1000 includes a means for positioning vibrational wave source 100 proximate the wellbore wall to focus the vibrational energy at only one portion of the wellbore wall at a time. This position helps apparatus 1000 avoid dispersing vibrational energy over the entire circumference of the wellbore wall. A suitable positioning means will depend on the chosen placement means, as persons of ordinary skill in the art having the benefit of this disclosure will realize. The positioning means may include a decentralizer. In particular, apparatuses may include a decentralizer with at least one bowed spring member that pushes against one side of the wellbore wall to position the vibrational wave source proximate an opposing side of the wellbore wall.
The means for placing the vibrational wave source in a well also may be prior-art coiled tubing, as shown in
In certain example apparatuses 1000, vibrational wave source 100 may be not only positioned proximate the wellbore wall but also oriented to direct the at least one direction of greatest vibrational energy transfer toward the wellbore wall. Certain example apparatuses therefore include a means for orienting the vibrational wave source in the well. In certain example apparatuses 1000, this orienting means will comprise a rotator-resolver that rotates the vibrational wave source to the desired circumferential orientation. To control the circumferential orientation of vibrational wave source 100, the tool body may include conventional equipment sufficient to detect the orientation of vibrational wave source 100 and to instruct the rotator-resolver to readjust that orientation. The tool body may contain controls to adjust the spacing between vibrational wave source 100 and the wellbore wall. A suitable design for the rotator-resolver will be apparent to persons of ordinary skill in the art having the benefit of this disclosure. Further, other means for orienting the vibrational wave source may be apparent to those of ordinary skill in the art having the benefit of this disclosure. These orienting means may be more useful when vibrational wave source 100 stops at a particular location to radiate waves, rather than moving continuously the orienting means. The orienting means, however, may be successfully used in the continuous-operation method if vibrational wave source 100 moves slowly enough.
In certain example apparatuses including a rotator-resolver, the decentralizer may include a member with at least two articulated joints connecting the vibrational wave source to the rotator-resolver and at least one retractable arm. The retractable arm may position the vibrational wave source proximate the wellbore wall.
In example apparatuses including a rotator-resolver, the decentralizer may comprise a vibrational wave source pad and at least one retractable arm.
Certain example apparatuses may further include at least one standoff contactor that maintains a standoff distance between the vibrational wave source and the wellbore wall.
In certain exemplary embodiments, the standoff distance may be varied to optimize reduction of the skin effect. The effectiveness of cleaning can be greatly enhanced if the apparatus is positioned at a standoff distance from the wellbore wall such that the vibrational wave source creates a standing wave pattern between the vibrational wave source and the wellbore wall.
To create this standing wave pattern, standoff contactor 550 should be sized to keep the vibrational wave source at a distance equal to an integer multiple of λ/2 away from the wellbore wall. While the distance between vibrational wave source 700 and wall 702 may be any integer multiple of λ/2 to produce a standing wave pattern, in practice, lower-order harmonics produce better cleaning results: the acoustic aspect ratio of vibrational waves in lower-order harmonics tends to result in deeper penetration into the formation or intervening structure or material. Moreover, vibrational waves in lower-order harmonics undergo fewer cycles per unit time, thereby decreasing the acoustic attenuation per unit distance of the vibrational waves. Once a standing wave pattern is generated, the intensity of the vibrational waves is enhanced at the wellbore wall: the intensity of the reflected vibrational wave 701 adds to the intensity of the incident vibrational wave 702, resulting in a pressure amplitude that is greater than the pressure caused by the incident wave along a thin pressure zone near the wellbore wall. This pressure zone can be seen in Pattern A. The pressure zone may be further amplified by using a vibrational wave source that can focus generated waves on the wellbore wall. Some example apparatuses may therefore include a vibrational wave source that can focus its waves on the wall of the wellbore, such as a vibrational wave source that includes focused transducers.
The standoff distance can be chosen at the surface based on the anticipated skin effect properties and estimated speed at which the vibrational waves will travel in the wellbore wall. However, the standoff distance required to establish a standing wave pattern may vary with variations in the speed of sound downhole. As persons of ordinary skill in the art are aware, the speed of sound in downhole fluids will vary with the temperature and pressure of the downhole fluids, often increasing with depth in a borehole. Variations in the formation fluid constituents, fluids present in the well or particles present in these fluids can cause the speed of sound downhole to change. In particular, the speed of sound might change as the skin effect is reduced. If the standoff distance can be adjusted downhole, a standing wave can be maintained despite fluctuations in the speed of sound.
The apparatus may further include a means for detecting accretions of particles between the vibrational wave source and the wellbore wall. If this detecting means detects a threshold level of accreted particles, the vibrational wave source may be moved away from the wellbore wall. The vibrational wave source may then radiate vibrational waves to break up the accretions and reposition proximate the wellbore wall to continue the cleaning process. In the example apparatus shown in
The apparatus may also comprise a means for monitoring energy transfer from the vibrational wave source to the wellbore wall. If the amount of energy transferred is insufficient or excessive, the vibrational wave source can be repositioned, or the cleaning process repeated, to optimally reduce the skin effect. The vibrational waves radiated by vibrational wave source 803 may also be altered to optimally reduce the skin effect at that wellbore wall 302 if necessary. In an example apparatus shown in
In an alternate example shown in
Example apparatuses include at least one vibrational wave source. In certain examples, however, the apparatus may include a plurality of vibrational wave sources displaced axially at the same circumferential orientation, displaced radially at the same axial location, or displaced in some combination of the two configurations. The number of vibrational wave sources chosen can depend on the power available to the apparatus as well as its mechanical complexity.
The vibrational wave sources that form the plurality vibrational wave sources of the apparatus may be activated continuously, or in succession, with or without intervening periods of inactivation. For example, the vibrational wave source 1020′ may first radiate vibrational waves at portion 1021 of the wellbore wall for a period of time. Vibrational wave source 1020′ then stops to allow fluid flow to flush away any particles from portion 1021 and from any structures or materials present at portion 1021. Once vibrational wave source 1020′ stops, vibrational wave source 1030′ will radiate vibrational waves for another period of time at portion 1031 of the wellbore wall and then stop to allow fluid flow to flush away any particles from portion 1031 and from any structures or materials present at portion 1031. Once vibrational wave source 1030′ stops, vibrational wave source 1040′ will radiate vibrational waves for another period of time at portion 1041 of the wellbore wall and then stop to allow fluid flow to flush away any particles from portion 1041 and from any structures or materials present at portion 1041. If necessary, vibrational wave source 1020′ may radiate vibrational waves again, and the process may be repeated with vibrational wave sources 1030′ and 1040′. Moreover, vibrational wave sources 1020′, 1030′, and 1040′ may radiate vibrational waves at different frequencies to optimally reduce the skin effect.
Although this example method activates vibrational wave sources in succession from left to right in
The multiple vibrational wave sources may assume different configurations to offer wider coverage, if desired. In an alternative example shown in
The apparatus may also include a means for determining how much the skin effect in the downhole environment has been reduced. This determining means may measure a speed of sound or propagation speed for the vibrational waves in a wellbore wall that has already been cleaned. The speed of sound after cleaning can be compared with a measured control speed at which vibrational waves traveled in the same wellbore wall prior to cleaning. The control speed can be determined empirically by measuring the speed of sound for vibrational waves at low acoustic intensities propagating in the wellbore wall. For example, production improvement observed in a test well in a particular reservoir could be correlated with the change in the speed of sound. Empirical data from other cleanings may be useful to supplement this comparison.
Any apparatus for reducing a skin effect in a downhole environment may incorporate a means for determining how much the skin effect has been reduced. For example, the vibrational wave source pads 1201 and 1202 shown in
Therefore, the present invention is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as those that are inherent therein. While the invention has been depicted and described, and is defined by reference to the exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the invention are exemplary only and are not exhaustive of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.
Claims
1. A method of reducing a skin effect in a downhole environment, comprising the step of radiating vibrational waves at a wellbore wall such that the vibrational waves have at least one direction of greatest vibrational energy transfer directed toward the wellbore wall, thereby reducing the skin effect.
2. The method of claim 1 wherein the radiating step comprises the step of positioning at least one vibrational wave source proximate the wellbore wall, wherein the at least one vibrational wave source has at least one direction of greatest energy transfer.
3. The method of claim 2 wherein the radiating step further comprises the steps of:
- radiating vibrational waves from at least one vibrational wave source at the wellbore wall; and
- flushing away any particles from the wellbore wall and from any structures or materials present at the wellbore wall with fluid flow.
4. The method of claim 3 wherein the step of radiating vibrational waves from at least one vibrational wave source and the step of flushing away any particles occur simultaneously.
5. The method of claim 2 wherein the radiating step further comprises the steps of:
- radiating vibrational waves from a plurality of vibrational wave sources at the wellbore wall; and
- flushing away any particles from the wellbore wall and from any structures or materials present at the wellbore wall with fluid flow.
6. The method of claim 5 wherein the step of radiating vibrational waves from a plurality of vibrational wave sources comprises the step of radiating vibrational waves in succession from each vibrational wave source.
7. The method of claim 5 wherein the step of radiating vibrational waves from a plurality of vibrational wave sources comprises the step of radiating vibrational waves simultaneously.
8. The method of claim 5 wherein the step of radiating vibrational waves from a plurality of vibrational wave sources comprises the step of radiating vibrational waves simultaneously and substantially continuously.
9. The method of claim 5 wherein the step of radiating vibrational waves from a plurality of vibrational wave sources comprises the step of radiating vibrational waves having at least two different frequencies from the plurality of vibrational wave sources.
10. The method of claim 5 wherein the step of radiating vibrational waves from a plurality of vibrational wave sources comprises selecting an order of activation and one or more periods of activation time for the plurality of vibrational wave sources to optimize usage of available power.
11. The method of claim 2 wherein the at least one vibrational wave source is an acoustic wave source having at least one direction of greatest energy transfer.
12. The method of claim 11 wherein the acoustic wave source is an oval-mode acoustic wave source having a plurality of directions of greatest energy transfer.
13. The method of claim 2 further comprising the step of placing the at least one vibrational wave source in the well.
14. The method of claim 2 further comprising the step of orienting the at least one vibrational wave source such that at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall.
15. The method of claim 2 further comprising the step of maintaining a standoff distance between the vibrational wave source and the wellbore wall.
16. The method of claim 2 further comprising the step of optimizing reduction of the skin effect by creating a standing wave pattern between the vibrational wave source and the wellbore wall.
17. The method of claim 2 further comprising the steps of:
- detecting accretions of particles between the wellbore wall and the at least one vibrational wave source;
- moving the at least one vibrational wave source away from the wellbore wall when a threshold level of accreted particles between the wellbore wall and the at least one vibrational wave source is detected;
- radiating vibrational waves at the accreted particles; and
- repositioning the at least one vibrational wave source proximate the wellbore wall.
18. The method of claim 2 further comprising the steps of:
- monitoring whether the vibrational wave source transfers sufficient vibrational energy to the wellbore wall to reduce the skin effect; and
- repositioning the vibrational wave source to optimally decrease the skin effect.
19. The method of claim 2 further comprising the steps of:
- monitoring whether the vibrational wave source transfers sufficient vibrational energy to the wellbore wall to reduce the skin effect; and
- altering the vibrational waves radiated by the vibrational wave source to optimally decrease the skin effect.
20. The method of claim 2 further comprising the step of determining how much the skin effect in the downhole environment has been reduced.
21. The method of claim 20 wherein the determining step comprises the steps of:
- measuring a speed of sound for the downhole environment; and
- comparing the measured speed of sound to a control speed of sound for a previously-cleaned wellbore wall.
22. The method of claim 20 wherein the determining step comprises the steps of:
- measuring a speed of sound for the downhole environment; and
- comparing the measured speed of sound to a control speed of sound measured before the vibrational waves were radiated at the wellbore wall.
23. The method of claim 20 wherein the determining step comprises the steps of:
- measuring an acoustic attenuation value for the downhole environment; and
- comparing the acoustic attenuation value to a control acoustic attenuation value for a previously-cleaned wellbore wall.
24. An apparatus for reducing a skin effect in a downhole environment, comprising:
- at least one vibrational wave source having at least one direction of greatest vibrational energy transfer; and
- a means for positioning the vibrational wave source proximate a wellbore wall.
25. The apparatus of claim 24 wherein the vibrational wave source comprises an oval-mode acoustic wave source
26. The apparatus of claim 24 further comprising a tool body, wherein the tool body houses a control for the vibrational wave source.
27. The apparatus of claim 24 further comprising a means for placing the vibrational wave source in a well.
28. The apparatus of claim 27 wherein the means for placing the vibrational wave source in the well comprises a wireline.
29. The apparatus of claim 27 wherein the means for placing the vibrational wave source in the well comprises coiled tubing.
30. The apparatus of claim 27 wherein the means for placing the vibrational wave source in the well comprises a well tractor.
31. The apparatus of claim 24 wherein the means for positioning the vibrational wave source proximate the wellbore wall is a decentralizer.
32. The apparatus of claim 31 wherein the decentralizer comprises a bowed spring member that pushes against a first side of the wellbore wall to position the vibrational wave source proximate a second, opposing side of the wellbore wall.
33. The apparatus of claim 31 further comprising a means for orienting the vibrational wave source such that at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall.
34. The apparatus of claim 33 wherein the means for orienting the vibrational wave source comprises a rotator-resolver, wherein the rotator-resolver orients the vibrational wave source such that the at least one direction of greatest energy transfer is directed toward the wellbore wall.
35. The apparatus of claim 34 wherein the decentralizer comprises:
- at least two articulated joints connecting the vibrational wave source to the rotator-resolver; and
- at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
36. The apparatus of claim 34 wherein the decentralizer comprises:
- a vibrational wave source pad attached to the rotator-resolver; and
- at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
37. The apparatus of claim 24 further comprising at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and the wellbore wall.
38. The apparatus of claim 37 wherein the at least one standoff contactor maintains a standoff distance chosen to enable creation of a standing wave pattern between the vibrational wave source and the wellbore wall.
39. The apparatus of claim 37 wherein the at least one standoff contactor includes contact points that contact the wellbore wall.
40. The apparatus of claim 39 further comprising an actuator that moves the vibrational wave source relative to the contact points to adjust the standoff distance.
41. The apparatus of claim 24 further comprising a means for detecting accretions of particles between the vibrational wave source and the wellbore wall.
42. The apparatus of claim 41 wherein the means for detecting accretions of particles comprises:
- an accelerometer coupled to the vibrational wave source, wherein the accelerometer produces an electrical signal proportional to vibrations experienced by the vibrational wave source; and
- a processing unit that monitors the electrical signal, wherein the processing unit can detect a signature vibration pattern indicating that particles have accreted.
43. The apparatus of claim 24 further comprising a means for monitoring energy transfer from the vibrational wave source to the wellbore wall.
44. The apparatus of claim 43 wherein the means for monitoring energy transfer comprises:
- a hydrophone suitable for use in downhole environments, wherein the hydrophone converts vibrational energy traveling through a fluid present near the wellbore wall into an electrical signal; and
- a processing unit, which monitors the electrical signal.
45. The apparatus of claim 43 wherein the means for monitoring energy transfer comprises:
- an accelerometer connected to the vibrational wave source, wherein the accelerometer produces an electrical signal proportional to vibrations experienced by the vibrational wave source; and
- a processing unit, which monitors the electrical signal.
46. The apparatus of claim 43 wherein the means for monitoring energy transfer from the vibrational wave source to the wellbore wall comprises:
- an accelerometer that produces an electrical signal proportional to vibrations experienced by the wellbore wall, wherein the accelerometer is acoustically isolated from the vibrational wave source; and
- a processing unit that measures the electrical signal.
47. The apparatus of claim 24 wherein the apparatus for reducing a skin effect in a downhole environment comprises a plurality of vibrational wave sources.
48. The apparatus of claim 47 wherein the plurality of vibrational wave sources are displaced axially with an axial gap between each vibrational wave source.
49. The apparatus of claim 47 wherein the plurality of vibrational wave sources are displaced circumferentially with a circumferential gap between each vibrational wave source.
50. The apparatus of claim 24 further comprising a means for determining how much the skin effect in the downhole environment has been reduced.
51. The apparatus of claim 50 wherein the means for determining how much the skin effect in the downhole environment has been reduced comprises:
- an accelerometer contacting the wellbore wall, wherein the accelerometer is acoustically isolated from the vibrational wave source; and
- a processing unit coupled to the accelerometer.
52. An apparatus for reducing a skin effect in a downhole environment, comprising:
- a vibrational wave source having at least one direction of greatest vibrational energy transfer;
- at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall;
- a decentralizer, wherein the decentralizer positions the vibrational wave source proximate a wellbore wall; and
- a wireline, wherein the wireline may be used to place the vibrational wave source in the well.
53. The apparatus of claim 52 further comprising a hydrophone.
54. The apparatus of claim 52 further comprising an accelerometer.
55. An apparatus for reducing a skin effect in a downhole environment, comprising:
- a vibrational wave source having at least one direction of greatest vibrational energy transfer;
- at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall;
- a rotator-resolver, wherein the rotator-resolver orients the vibrational wave source such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall;
- at least two articulated joints connecting the vibrational wave source to the rotator-resolver; and
- at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
56. The apparatus of claim 55 further comprising a hydrophone.
57. The apparatus of claim 55 further comprising an accelerometer.
58. An apparatus for reducing a skin effect in a downhole environment, comprising:
- a vibrational wave source having at least one direction of greatest vibrational energy transfer;
- at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the vibrational wave source and a wellbore wall;
- a rotator-resolver, wherein the rotator-resolver orients the vibrational wave source such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall;
- a vibrational wave source pad attached to the rotator-resolver; and
- at least one retractable arm, wherein the at least one retractable arm positions the vibrational wave source proximate the wellbore wall.
59. The apparatus of claim 58 further comprising a hydrophone.
60. The apparatus of claim 58 further comprising an accelerometer.
61. An apparatus for reducing a skin effect in a downhole environment, comprising:
- a plurality of vibrational wave sources wherein each vibrational wave source has at least one direction of greatest vibrational energy transfer;
- at least one standoff contactor, wherein the at least one standoff contactor maintains a standoff distance between the plurality of vibrational wave sources and a wellbore wall;
- a rotator-resolver, wherein the rotator-resolver orients the plurality of vibrational wave sources such that the at least one direction of greatest vibrational energy transfer is directed toward the wellbore wall;
- a vibrational wave source pad attached to the rotator-resolver; and
- at least one retractable arm, wherein the at least one retractable arm positions the plurality of vibrational wave sources proximate the wellbore wall.
62. The apparatus of claim 61 further comprising a hydrophone.
63. The apparatus of claim 61 further comprising an accelerometer.
Type: Application
Filed: Sep 29, 2004
Publication Date: Nov 8, 2007
Inventors: James Birchak (Spring, TX), Sau-Wai Wong (Houston, TX), James Estep (Houston, TX), William Trainor (Houston, TX), Wei Han (Missouri City, TX), Wes Ritter (Katy, TX), Kwang Yoo (Houston, TX), Lyle Lehman (Katy, TX), James Venditto (Hilliard, OH), Harry Smith (Montgomery, TX), Diederik van Batenburg (Delft), Ali Mese (Houston, TX), Jeroen Groenenboom (Den Haag), Frederick Van der Bas (Vlaardingen), Pedro Zuiderwijk (Delft), Peter van der Sman (Heemstede)
Application Number: 10/953,237
International Classification: E21B 28/00 (20060101); E21B 37/00 (20060101);