Abstract:
An objective of this invention is to provide an apparatus and method to more accurately determine the parameters of a storage cavern before and during use, including fluid filled storage caverns. Another object of this invention is to provide a granular inspection of the storage cavern. Another object of this invention is to provide precision positioning information of sample points.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application takes priority to U.S. patent application Ser. No. #14,924,567, filed on Oct. 27, 2015, which takes priority to US provisional application #62/122,911 filed on Nov. 3, 2014, Each of the above named applications are incorporated herein, in its entirety, by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0003]    Not Applicable 
       BACKGROUND 
       [0004]    Underground storage caverns have been used for storage since the beginning of time. As early as 1940 underground storage caverns have been used to store natural gas, compressed air, hydrogen, and liquid hydrocarbons (including crude oil), amongst others. In many applications salt caverns have been man-made to hold hydrocarbons. The parameters of a storage caverns must be determined prior to use and during its lifetime since storage caverns decay and/or change shape over time. 
         [0005]    Cavern survey logging refers to measurements of storage caverns using acoustic techniques to evaluate the storage cavern size, shape, volume, integrity and other parameters. The survey report is usually presented with the basic measurements and an estimate of cavern parameter change since the previous survey. Survey logging of fluid-filled storage caverns is time-consuming and subject to error from missing storage cavern anomalies and features difficult to characterize. 
         [0006]    Current techniques used to measure cavern parameters are lacking. Referring to  FIGS. 1 a  and 1 b   , in a prior art acoustic technique of measuring storage caverns, a single beam transducer is swept horizontally over 360 degrees at various depths or depth stations. The limited number and type of data points gathered in this technique leave significant information about the storage cavern unknown. Small target detection is difficult, if not impossible, to obtain even with readings at a plurality of depth stations. Prior art techniques are also time consuming and costly.  FIG. 2  is a representation of the data obtained from a prior art cavern measuring system. Consequently, there is a need for the reliable, accurate measurement apparatus and method to determine whether and to what extent a storage cavern has undergone a change of shape, remains serviceable or requires remedial action. 
       SUMMARY OF THE INVENTION 
       [0007]    An objective of this invention is to provide an apparatus and method to more accurately determine the parameters of a storage cavern before and during use, including fluid filled storage caverns. Another object of this invention is to provide a granular inspection of the storage cavern. Another object of this invention is to provide precision positioning information of sample points. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Other features and advantages of the present invention will become apparent in the following detailed descriptions of the preferred embodiment with reference to the accompanying drawings, of which: 
           [0009]      FIG. 1A  is a plan view of a prior art cavern logging survey; 
           [0010]      FIG. 1B  is a cross-section view of a prior art cavern logging survey; 
           [0011]      FIG. 2  is a representation of a prior art cavern logging survey; 
           [0012]      FIG. 3  is a schematic of an embodiment of the cavern survey system; 
           [0013]      FIG. 4  is a perspective view of an embodiment of the cavern probe; 
           [0014]      FIG. 5  is a schematic view of an exemplary multi-beam array; 
           [0015]      FIG. 6A  is a cross sectional view of an exemplary cavern logging survey; 
           [0016]      FIG. 6B  is a cross sectional view of an exemplary cavern logging survey; 
           [0017]      FIG. 7  is a representation of an exemplary cavern logging survey; 
           [0018]      FIG. 8  is a representation of an exemplary cavern logging survey. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, the use of similar or the same symbols in different drawings typically indicates similar or identical items, unless context dictates otherwise. 
         [0020]    The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. 
         [0021]    One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting. 
         [0022]    The present application may use formal outline headings for clarity of presentation. However, it is to be understood that the outline headings are for presentation purposes, and that different types of subject matter may be discussed throughout the application (e.g., device(s)/structure(s) may be described under process(es)/operations heading(s) and/or process(es)/operations may be discussed under structure(s)/process(es) headings; and/or descriptions of single topics may span two or more topic headings). Hence, the use of the formal outline headings is not intended to be in any way limiting. 
         [0023]    Provided herein are embodiments for a cavern surveyor system  100  and methods for use. Referring to  FIG. 8 , the cavern survey system  100  increases the chances of detecting small/irregular anomalies. Additionally, data maybe collected at fewer depth stations. 
         [0024]    Referring to  FIGS. 3 and 4 , the cavern surveyor system  100  is comprised of at least one cavern probe  110  and a telemetry system  200 . The cavern probe  110  is comprised of at least one probe transducer  130  and a pan and tilt assembly  120  that receives and transmits data from the telemetry system  200 . 
         [0025]    Referring to  FIG. 5 , preferably, the probe transducer  130  is comprised of a plurality of transducers where the transducers are aligned for directional signal transmission for beamforming or spatial filtering of signals. Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in a phased array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. Beamforming can be used for radio or sound waves. Preferably, the beam profile has less than 2 dB drop between transducers allowing a very high density of sample points. 
         [0026]    In one embodiment the probe transducer  130  is a multi-beam array having at least 256 equally spaced transducers, where each transducer is vertically orientated to the others, allowing data collection at 45 degrees, from the vertical plane, and 1 degree, from the horizontal plane. In another embodiment, there are 512 probe transducers  130  resulting in an acoustic pattern of 1°×90°. 
         [0027]    The pan and tilt assembly  120  allows the probe transducer  130  to rotate 360° and tilt. This allows the cavern probe  110  to collect a larger amount of data at fewer depth stations within the cavern. Referring to  FIG. 6 , the pan and tilt assembly  120  may position the cavern probe  110  in the following exemplary configurations in order to inspect a cavern: a 1° wide acoustic beam maybe be panned horizontally thru 360° simultaneously covering ±22.5° vertically from the centerline of a single sweep; tilting the array up from the horizontal centerline by 35° allowing the a 1° wide acoustic beam to be panned thru 360° simultaneously covering +12.5° to +57.5° vertically in a single sweep; titling the array up from the horizontal centerline by +47.5° allowing the 1° wide acoustic beam to be panned thru 360° in a single sweep +47.5° to 92.5° vertically, A similar pattern may be used to inspect lower regions of the cavern and/or the cavern floor.  FIG. 7  represents the data points that may he obtained from the cavern probe  110 . 
         [0028]    The telemetry system  200  is any known automated communications process by which data is received and transmitted. The telemetry system  200  is positioned at a location outside a storage cavern  10 . 
         [0029]    In some embodiments, the cavern probe  110  is further comprised of a velocimeter  140 . The velocimeter  140  is a sonar system that continuously measures the acoustic time of flight to a target at a known distance (e.g. to a cavern wall). If a cavern is contains fluid, for example, the velocimeter  140  measures the varying time of flight through the fluid. The data is used to correct the information received by the probe transducer  130  using any known algorithm. 
         [0030]    In some embodiments, the cavern transducer  130 , pan and tilt assembly  120 , and velocimeter  140  are received in an electronic pressure housing  150  that prevents the cavern transducer  130 , the pan and tilt assembly  120 , and velocimeter  140  from being damaged by hydrostatic pressures and elevated temperatures. In some embodiments, the housing  150  provides safeguard for pressures up to 25,000 psi and temperatures up to 150° C. 
         [0031]    In some embodiments, the electronic pressure housing is a closed, tubular vessel having an endcap  151 ; the endcap  151  seals with an “O-ring” or other similar device. The endcap  151  allows access to the cavern transducer  130 , pan and tilt assembly  120 , and velocimeter  140  for maintenance and replacement. In some embodiments, the housing  150  is further comprised of an entry cone  160  and a cable head connector  190 . 
         [0032]    In some embodiments, the cavern surveyor system  100  is further comprised of an umbilical wireline  170  and a wireline depth encoder  180 . The wireline debt encoder  180  measures the amount of wireline payed out from a fixed point providing an accurate measure of the depth of the cavern probe  110 . The wireline umbilical  170  allows communication between the cavern probe  110  and the telemetry system  200 . 
         [0033]    In some embodiments, the telemetry system is comprised of a computing device  210  that receives and transmits information to a communications interface  220 . The communications interface  220  is comprised of a wireline depth encoder interface  221  and a wireline umbilical interface  222 . The wireline umbilical interface  220  operably mates to the wireline umbilical  170  allowing data to be sent and received from the cavern probe  110  to the telemetry system  200 . The wireline depth encoder interface  221  operably mates with the wireline depth encoder  180  allowing probe depth data to be sent to the computing device  210 . 
         [0034]    In some embodiment, the electronic pressure housing  150  further comprises circuits to effect: data telemetry and tool control communication between the cavern probe ( 110 ) and the computing device ( 210 ) via the communications interface ( 220 ) and wireline umbilical ( 170 ); power delivery through the wireline umbilical ( 170 ) required for the various electronics assemblies contained in the pressure and temperature resistant housing ( 150 ); at least one microprocessor that controls the cavern probe ( 110 ) and data communication of acoustic returns to the computing device ( 210 ); acoustic transmission, acoustic reception and conditioning of signals to/from the probe transducer ( 130 ); velocity of sound measurement of ambient fluid in which the probe transducer ( 130 ) is immersed for the purpose of correcting the acoustic data captured by the probe transducer ( 130 ); at least one gyro ( 155 ) to orient the probe transducer ( 130 ) for the purpose of accurately determining the position(s) from which acoustic data is captured; at least one motor that actively positions the probe transducer ( 130 ); other sensors (temperature, pressure, etc.) that might be of interest.