Patent Abstract:
The present invention relates to a method and apparatus for obtaining measurements of induced resistivity of objects from spaces such as within a down-hole hydrocarbon production well. The invention also relates to measuring the location or direction of objects based upon measured responses from objects engaged or impinges by one or more transmitted signals having different phase and directional orientation. The invention relates to generating at least one signal or wave and transmitting it through a plurality of different materials that may have varying properties of density, magnetic permeability and dielectric that may each emit a separate signal with altered phase and directional orientation. When used with electromagnetic signals, the resistivity of an object or media can provide useful information regarding the composition and the location of object or media. Such embodiments of the present invention utilize the principles of Magnetic Antenna™ and Magnetic Lensing™ to obtain information regarding the location and properties of the target object.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation in part of U.S. Application No. Ser. 09/734,528, filed Dec. 11, 2000, which claims the benefit of U.S. Provisional Application No. 60/170,173, filed Dec. 10, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Use  
           [0003]    The present invention relates to a method and apparatus for obtaining measurements of induced resistivity of objects from confined spaces such as within a down-hole hydrocarbon production well. It is well known that measuring the resistivity of an object or media can provide useful information regarding the composition and the location of object or media. The present invention utilizes the principles of Magnetic Antenna™ and Magnetic Lensing™ to obtain information regarding the location and properties of the target object. The present invention also relates to a method transmitting magnetic, electric, or acoustic energy through varying media to obtain phase differences in the energy that can be directionally oriented.  
           [0004]    2. Description of Related Art  
           [0005]    In many applications of Inductive Resistivity Measurements (IRM), limitations of space or topography prevent the use of multiple antennas arrays. This lack of multiple antennas arrays causes the loss of directional information from received EM waves. An example of space limitations is in the down-hole environment of oil wells. IRM is used in this application for reservoir mapping or the detection of interfaces among oil, water and gas in a geologic formation. The accurate knowledge of the direction of the reflected EM wave is very important in these uses of IRM. Directionality determination must be made in both the vertical and azmuthal senses. Therefore there is a need for a device to encode the radiated EM signals in a way that yields directionality in space limited environments.  
           [0006]    One requirement when obtaining useful or reliable Inductive Resistivity Measurements (IRM) is the ability to determinate the direction, if not the location, of the target object in which resistivity has been induced and now subject to measurement. This directionality makes it possible to determine the location of various objects in which the resistivity has been induced. A customary method of locating the source, or at least ascertaining the direction of the induced signal, is to utilize multiple antennas or signal receiving devises. Measuring the signal from multiple locations provides multiple references points for determining the location based upon conventional coordinate systems or other known methods. Determining the location or the direction of an object in which resistivity signals are induced has provided significant challenges. Prior to the present invention, the utility of IRM in such applications has been severely limited.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention utilizes Magnetic Antenna and Magnetic Lensing techniques to overcome the limitations that heretofore have prevented multiple measurement to be taken from separate locations. Simply stated, the method and apparatus of the present invention discloses creating phase changes in a pulsed or oscillating magnetic flux transmitted from a magnetic flux transmitter. The phase changes are created in a controlled manner by utilization of the magnetic phase coded permeability lensing effect. As the transmitted oscillating magnetic flux passes through differing sections of a magnetic antenna, the phase of the original oscillating flux is modified into multiple phases. These multiple phases are also oriented in different directions. Accordingly, a flux from a single source and having a single phase, is altered into multiple and easily distinguishable flux signals. Further, since the multiple flux signals can each be oriented in different directions by the magnetic lens effect, it is possible to utilize the different induced phases from one or more magnetic flux transmitter to induce responsive oscillating flux signals within the target object from one or more of known locations relative to one or more signal receiving devices. These results in multiple Induced Resistivity Measurements that can provide the location or, at a minimum, the direction of the target object from the separate signal receiving devise.  
           [0008]    Further, the invention can be used to create phase changes in other energy signals, such as acoustic signals and the electric component of an electromagnetic wave.  
           [0009]    Accordingly, it is an object of the present invention to provide a method and apparatus for transmitting an electromagnetic signal through materials having varying magnetic permeability, electrical conductivity, density or geometry to obtain phase changes in the signals that may be directionally oriented.  
           [0010]    It is another object of the present invention to utilize one or more receiving devices to determine the location, as well as direction, of one or more electrically conductive objects within a geologic formation or other media surrounding the invention.  
           [0011]    It is an object of the present invention to provide a method and apparatus for creating multiple and distinguishable signals from a single source and utilizing at least one such signal for locating objects.  
           [0012]    It is another object of the invention to transmit electrical signals through materials having varying dielectric properties to obtain phase changes in the signal that may be directionally oriented.  
           [0013]    It is yet another object of the invention to transmit acoustic signals through materials of varying densities to obtain phase changes in the signal that may be directionally oriented. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention. These drawings, together with the general description of the invention given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention for resistivity measurements within a confined space of a hydrocarbon production well.  
         [0015]    [0015]FIG. 1 illustrates a collar device attached to production tubing or drill pipe comprising distinct sections having differing permeability properties.  
         [0016]    [0016]FIG. 1A illustrates a cross sectional view of the embodiment.  
         [0017]    [0017]FIG. 2 illustrates another embodiment of the invention.  
         [0018]    [0018]FIG. 2A illustrates a cross sectional view of the embodiment of FIG. 2.  
         [0019]    [0019]FIG. 3 illustrates the varying magnetic permeability, dielectric or density of different sections of the invention.  
         [0020]    [0020]FIG. 3A illustrates the relative arc segments of the different sections.  
         [0021]    [0021]FIG. 3B illustrates the differing arcs within which signals from differing segments are emitted  
         [0022]    [0022]FIG. 3C illustrates the directional orientation of differing signal fields emitted from the differing sections of one embodiment of the invention.  
         [0023]    [0023]FIG. 3D illustrates the directional orientation of energy concentrations emitted from another embodiment of the invention.  
         [0024]    [0024]FIG. 4 illustrates an embodiment wherein the generator of the multiple phase oriented signals located separate from the signal receiver on production well tubing.  
         [0025]    [0025]FIG. 5 is a schematic drawing of some of the components utilized in some embodiments of the invention. 
     
    
       [0026]    The above general description and the following detailed description are merely illustrative of the subject invention, and additional modes, advantages and particulars of this invention will be readily suggest to those skilled in the art without departing from the spirit and scope of the invention.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    The invention subject of this application utilizes one or more sources for generating an oscillating or pulsed energy sources such as an ac generated electromagnetic wave. The signal may be transmitted from the signal generator in a distinguishable phase. Subsequent transmission through media having differing properties can cause the signal to attenuate or shift in phase. Differing media will have differing effect on the energy signal. Transmission of light through differing media has well known results in attenuation, direction and phase. Of course the attenuation and phase change can differ with the frequency of the original signal. The differing phase change can be used in the present invention in a controlled manner with one or more generated signals transmitted through multiple media or material of known properties and oriented in a known configuration. The signals emitted from each material will have differing properties, particularly differing phase. Since the each differing material may have distinct orientation to the transmitter and to any signal receiving device(s), it may be possible to ascertain the location of an object responding to the various signals of differing phase. This directionality can be enhanced by controlled selection of material and the strength of signals transmitted into the material. In regard to the transmission of electromagnetic waves through magnetically permeable material, the refraction or change in direction of magnetic flux emitted through the material can be controlled by selectively modifying the relative magnetic permeability of the material. This technique is termed the “Magnetic Lensing”™ effect.  
         [0028]    In the preferred embodiment of the invention subject of this application one or more sources may be utilized for generating magnetic flux. The flux can be generated utilizing a pulsed dc generated magnetic flux or an oscillating magnetic flux. The magnetic flux oscillates or pulses at a controlled frequency and phase.  
         [0029]    This flux is engaged with a magnetic antenna comprised of electrically conductive and magnetically permeable material, e.g., a ferromagnetic metal. It will be appreciated that such material typically acts as a barrier to the transmission of electromagnetic energy or signals. These materials are termed herein as “EM barriers” or “barrier materials.” The present invention teaches use of barrier materials of differing permeability, conductivity and shape to construct a lensed magnetic antenna for emitting oscillating flux of differing phase and for directing or focusing oscillating magnetic flux in a controlled manner. These lensed magnetic antenna components (or “antenna”) can be arranged or configured in multiple designs in accordance with the particular application.  
         [0030]    The antenna components can be configured in a “collar type” antenna shape around a pipe or similar object as illustrated in FIGS. 1, 1A,  2  and  2 A. The lensed magnetic antenna  360  can be made of multiple sections of differing material or like material of differing shape, e.g., thickness. It will be appreciated that the materials of differing thickness or composition will have differing net permeability and conductivity. As a result, the oscillating magnetic flux from the transmitter  300  will be both phase shifted and directed as the portions of flux signal are transmitted through differing segments of the lensed magnetic antenna. As the antenna components are also conductive, the oscillating magnetic flux will also induce eddy currents within the material. These eddy currents will also vary in phase and orientation.  
         [0031]    [0031]FIG. 1 illustrates separate antenna segments  370  through  383  configured into a single collar shaped lensed magnetic antenna  360 . Separate portions of the oscillating flux emitted from transmitter  300  are transmitted outward through separate antenna segments in the manner indicated by vector  889 . The power supply, amplifiers, signal generator, or receiver comprising apparatus of the invention  500  are not shown. Means to partially saturate the permeable segments comprising the lensed magnetic antenna  360  are also not shown. It may be anticipated that the means to couple with the antenna may be required to reduce the permeability of at least some of the segments in order that the oscillating magnetic flux can couple and penetrate into the surface of the antenna  360 . This may require placement of one or more saturation coils, not shown, within the space  952  proximate to the transmitter  300 .  
         [0032]    Although it is anticipated that the invention may be used in conjunction with an outer well casing (not shown) comprised of an EM barrier material and in which the production tubing  100  and antenna  360  are positioned, embodiments of the invention may include use of non-permeable casing material. In this or other embodiments, it may be deemed advantageous to place the saturation coil (not shown) or other components of the invention inside the annulus  116  of the production tube  100 .  
         [0033]    [0033]FIG. 1A shows the arrangement of the oscillating magnetic flux transmitter  300  with the individual antenna segments, e.g.,  374 ,  377 , etc. It will be noted that each antenna segment is immediately adjacent to the transmitter  300 . It will be appreciated that a small gap or spacing (not shown) of a known thickness may be maintained between the transmitter  300  and the lensed magnetic antenna  360 .  
         [0034]    [0034]FIG. 1A shows oscillating magnetic flux of a single phase transmitted from the transmitter  300 . Since the flux is transmitted through segments of the antenna  360  having differing permeability or thickness, the oscillating magnetic flux within each segment will experience differing phase shifts. This results in phase angles θ 1  and θ 2 . Alternatively, these antenna segments could be of uniform thickness but using different materials with different permeability values. The segments of differing material could be configured in a predetermined phase-coded pattern. This phase coded configuration could be related to a particular directional orientation. This directional orientation of phase shift could be used to mark or encode magnetic flux induced in a conductive target object. The properties of the received signals from the differing phased magnetic flux induced in the target object could provide information related to the location or direction of the object. Since targets also can change the phase of an EM wave, the spatial relationship of the phase-coded configuration would be important in determining the returning wave direction.  
         [0035]    Further, the differing permeability of antenna segments will result in differing relative permeability, i.e., differing degrees of reduced permeability and degrees of magnetic saturation. Therefore, the magnetic flux may be directionally oriented as it is emitted from the surface of the individual segment. This is illustrated in FIG. 1A by the vector lines  289  and  292  not being normal to the outer surface of the respective segment.  
         [0036]    It will be appreciated that a phase code configuration be utilized that will be distinctive from possible induced phase changes within the targets.  
         [0037]    It will, of course, be beneficial to have knowledge of the expected target object. For example, an advancing waterfront contact target would be changing the EM phase in a different way than stationary targets.  
         [0038]    In one embodiment of the invention, the varying permeability creating the selected lensing of the transmitted magnetic flux may be comprised of alternating sections of the coating over the lensed magnetic antenna  360 . Each segment will have selected permeability variations of one (e.g., stainless steel) and ten (a semi-saturated ferromagnetic material). The resulting signals into the media would be coded at the separation angle of the lens segments and shown in FIGS. 3B, 3C and  3 D.  
         [0039]    [0039]FIG. 2 illustrates a differing configuration wherein the transmitter  300  is not adjacent to each separate lens segment of the antenna collar  360 . In contrast to FIG. 1 and  1 A, an oscillating magnetic flux signal from the transmitter  300  may pass through several differing segments of the antenna, e.g.,  373  and  374  prior to being emitted from the antenna segment  375  in the altered phase and direction. This is shown in FIG. 2A by the path of signal vectors  281 ,  283 ,  284 , and  287 . It will be appreciated that FIGS. 1, 1A,  2  and  2 A do not show the means of the apparatus  500  for receiving a separate oscillating flux signal that may be generated from eddy currents induced within target objects from oscillating magnetic flux emitted from various segments, e.g.  373 ,  374  and  375 , of the antenna collar  360 .  
         [0040]    [0040]FIG. 3 illustrates the antenna segments  370  through  374  have differing magnetic permeability, shown as μ 0 -μ 4  respectively.  
         [0041]    [0041]FIG. 3A illustrates the arc of out surface of each antenna segment. It will be appreciated that each arc, e.g., θ 1  θ 2  and θ 3 , are co-terminus and that there is no overlap.  
         [0042]    [0042]FIG. 3B illustrates an arc of angle θ A  within which a transmitted signal may be emitted from a particular antenna segment. It will be appreciated that the arc may also overlap with the arc of at least the next adjacent antenna segment. This is shown by the overlap of arc θ A4  of possible signal transmission from segment  374  with the possible transmission arc θ A3  from segment  373 . The direction and phase of emitted signals (not shown) provides a marker or coding as to the origin of the oscillating magnetic flux. An electrically conductive object located outside of the antenna collar  360  may be engaged with flux emitted from one or more antenna segments. Eddy currents may be generated within the object through well-understood electromechanical principles. The eddy currents and resulting magnetic flux will have properties characteristic of the phase and direction of the magnetic flux from the applicable antenna segment, e.g.  374 ,  372 . . This will accordingly provide information regarding the location of the object or the media that is responding to the flux transmitted by the lensed magnetic antenna. The specific length and geometry of the arc will be a function of the permeability and conductivity of the antenna section, the degree that the relative permeability of the segment is reduced, the configuration of the lensing segments comprising the magnetic flux antenna, and the properties of eddy currents induced within the antenna segments.  
         [0043]    [0043]FIG. 3C illustrates that the multiple segments, and associated differing permeability and conductivity may achieve the directional lensing of oscillating flux. It will be appreciated that the directional orientation or vector of flux,  286  and  287 , emitted from certain segments,  376  and  377 , will not be normal to the outer surface (“second surface”) of the respective segments of the antenna configuration. This can be contrasted to the vector  285  representing flux emitted from  385 . It will of course be appreciated that this directionality will be impacted or achieved in part by the properties of the eddy currents induced in the separate antenna segments. FIG. 3D also illustrates the directionality achieved in flux vectors  279  and  283  emitted from the differing antenna segments.  
         [0044]    In some embodiments of the invention, it may be desired to place electrical insulating material (not shown) between antenna segments to reduce cross transmission of eddy currents.  
         [0045]    [0045]FIG. 4 illustrates a configuration of the invention wherein a receiver device  580  is placed on the production tubing  100  at a location separate from the magnetic flux antenna  360 . The separation of the transmitter  300  and the receiver  580  may facilitate nulling of the direct transmission of signal. It is envisioned that the device may be used in conjunction with well casing  111  not comprising an EM barrier, e.g., stainless steel, etc.  
         [0046]    The lens segments may vary in thickness, causing like permeable materials to create varying phase shifting in the transmitted oscillating flux through the lens at different points by different amounts. This phase shifting occurs because the permeable material absorbs oscillating flux in proportion to the permeability value of the material and its thickness. In two dimensions, this phenomenon is shown in FIG. 4.  
         [0047]    [0047]FIG. 4A illustrates an alternate configuration wherein the receiver  580  is oriented around the entire outer diameter of the production tubing  100 . It will be appreciated that in other embodiments, the axis of the receiver may be located orthogonal to the axis of the transmitter  300  or antenna collar  360 . Further, multiple receivers may be utilized, each oriented in a specified manner to the antenna or transmitter and thereby providing multiple reference points for determining the location of target objects possessing electrically conductive properties with the area of interest. Examples can include the location of water or the water within a hydrocarbon reservoir. In yet other embodiments, multiple receivers may be configured with opposing or bucked direction of windings.  
         [0048]    The varying conductivity and permeability of the different antenna segments will further impact the characteristics (phase, frequency or amplitude) of the oscillating flux emitted from the differing antenna segments. It will be appreciated that flux engaging the differing segments will induce eddy currents within the segment. As a result of the skin depth phenomena, the largest concentration of eddy currents will be at the surface of the segment most adjacent to the transmitter. However, increased transmission of magnetic flux will reduce the permeability of at least some portions of the segments, particularly in the area most adjacent to the transmitter. As the permeability is reduced the skin depth increases. At a point at which a portion of the segment is sufficiently saturated such that eddy currents are induced at the opposite surface of segments, the skin effect will again cause the eddy currents to extend along this second surface of the antenna segment.  
         [0049]    [0049]FIG. 5 illustrates some of the components utilized in the oscillating magnetic flux embodiment of the invention. Such components include a power supply  560 , a signal generator  563 , transmitter  300 , receiver  580 , amplifier  564 , signal converter  581  and an output display  582 . Also show in a separate saturation flux generator  551  utilized to reduce the permeability of antenna segments.  
         [0050]    Persons skilled in the technology will appreciate it after reading this application that available equipment and techniques for generating other forms of energy signals, such as acoustic signals, may be transmitted through various materials that may alter the phase and directional orientation of the signal. Further, that alteration of the phase and directionality from a single source may provide information concerning the location or direction of objects responding to impingement with one or more such distinguishable signals.

Technology Classification (CPC): 6