Patent Publication Number: US-9423503-B2

Title: Borepath analyzer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of provisional patent application Ser. No. 61/731,277, filed on Nov. 29, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates generally to the field of locating underground objects, and in particular to locating and tracking a beacon within the field of operation of a horizontal drilling machine. 
     SUMMARY 
     The present invention is directed to a method for tracking a beacon. The method comprises the steps of placing a tracker at a first location, measuring an amount of interference present at each of a plurality of different frequencies at the first location, and determining a preferred frequency based on the amount of interference. The method further comprises the steps of programming the beacon to emit a beacon signal at the preferred frequency, placing the beacon below ground, and determining a location of the beacon relative to the tracker by detecting the beacon signal at the preferred frequency. 
     The present invention is also directed to a method for analyzing a plurality of different frequencies present along a borepath. The method comprises the steps of measuring an amount of interference at each of the plurality of different frequencies at a first location using a tracker, measuring the amount of interference present at each of the plurality of different frequencies at a second location using the tracker, averaging the amount of interference present at each of the plurality of different frequencies at the first location and at the second location in order to determine a preferred frequency to tune the tracker to during a horizontal drilling operation, and tuning the tracker to the preferred frequency during the horizontal drilling operation. 
     The present invention is also directed to a tracker for locating a beacon. The tracker comprises a first antenna to detect a beacon signal at a plurality of different frequencies, and a processor configured to determine a preferred frequency based on a summary of interference present at each of the plurality of different frequencies. The processor is also configured to tune the antenna to the preferred frequency. The beacon emits the beacon signal at the preferred frequency, and the processor is adapted to process the beacon signal emitted at the preferred frequency detected by the first antenna and determine a location of the beacon relative to the tracker. 
     The present invention is further directed to a horizontal boring system. The system comprises a rotary drilling machine, a drill string, a downhole tool, and a tracker. The drill string has a first end and a second end, the first end is operatively connectable to the rotary machine to drive rotation of the drill string. The second end of the drill string is connected to the downhole tool. The downhole tool comprises a beacon that emits a beacon signal at a plurality of different frequencies. The tracker is used for location of the beacon. The tracker comprises a first antenna to detect the beacon signal, and a processor configured to determine a preferred frequency for the beacon signal based on a summary of interference present at each of the plurality of different frequencies. The processor is adapted to process the beacon signal detected by the first antenna and determine a location of the beacon relative to the tracker. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a horizontal directional drilling system for drilling a horizontal borehole and a tracking system built in accordance with the present invention. 
         FIG. 2  is a perspective view of a tracker constructed in accordance with the present invention. 
         FIG. 3  is a perspective view of the tracker exemplifying a plot formed on a visual display on the tracker in accordance with the present invention. 
         FIG. 4  is a flowchart depicting a method to analyze a desired borepath in accordance with the present invention. 
     
    
    
     DESCRIPTION 
     The horizontal directional drilling industry traditionally uses walkover tracking techniques to follow the progress of a bore, to find the surface location immediately above the drill bit, and to determine the depth of the drill bit from that surface location. The primary tracking tools are a subsurface transmitter, also called a beacon, and a hand-carried surface receiver assembly. The beacon, located in or very near a downhole boring tool, generally emits a beacon signal at a specific frequency. The beacon signal can be used for both location and communication with the above ground receiver assembly. However, there may be instances where interference from outside sources emitting signals interrupts this communication. 
     Turning now to the figures, and first to  FIG. 1 , a horizontal directional drilling system for use with the present invention is shown.  FIG. 1  illustrates a boring machine  12  sitting on the ground surface  14 .  FIG. 1  also illustrates a desired borepath  16 . A drill string  18  is shown connected to a downhole tool  20  at a first end  22  and the boring machine  12  at a second end  24 . The downhole tool  20  comprises a drill bit  26  and a beacon  28 . In operation, the drill bit  26  will bore underground and advance the downhole tool  20  and drill string  18  forward along the desired borepath  16 . The boring machine  12  will add a plurality of pipe sections to the drill string  18  as the downhole tool  20  advances farther along the desired borepath  16 . 
     Continuing with  FIG. 1 , an operator  30  holding a tracker  32  is also shown. During boring operations, the beacon  28  contained within the downhole tool  20  will emit a beacon signal (not shown) at a designated frequency. The tracker  32  is adapted to receive the beacon signal and determine the location of the downhole tool  20  underground relative to the tracker. Based on the determined location of the downhole tool  20  underground, the operator  30  can determine whether or not the downhole tool is boring along the desired borepath  16  or if steering corrections need to be made. 
     Turning now to  FIG. 2 , the tracker  32  is shown in greater detail. The tracker  32  comprises a receiver assembly  34  and a first antenna  36 . The receiver assembly  34  comprises a housing  38 . The tracker  32  may also comprise a second antenna  40  and a third antenna (not shown). The antennas  36  and  40  may be spaced apart on a horizontal frame  42 , as shown in  FIG. 2 , or the antennas may be in a vertical plane with the receiver assembly  34 , as shown in  FIG. 1 . The housing  38  comprises a visual display  44  and a plurality of input devices  46 . A processor  47  may be disposed within the housing  38 . The receiver assembly  34  may also comprise a handle  48 . 
     The antennas  36  and  40  shown in  FIG. 2  are adapted to detect the beacon signal emitted from the beacon  28  ( FIG. 1 ) at the designated frequency. Once the antennas  36  and  40  detect the beacon signal, they send an antenna signal (not shown) to the receiver assembly  34 . The processor  47  of the receiver assembly  34  interprets the antenna signal and identifies the location of the beacon  28  ( FIG. 1 ) underground relative to the receiver assembly. The beacon  28  is capable of emitting the beacon signal at a plurality of different frequencies. Similarly, the antennas  36  and  40  are capable of detecting the beacon signal at the plurality of different frequencies. For example, the beacon  28  may transmit the beacon signal at 1,000 Hz, 2,000 Hz, 3,000 Hz, or 30,000 Hz, depending on which frequency the operator  30  has programmed the beacon to emit. 
     The antennas  36  and  40  are also adapted to detect alternative magnetic field sources being emitted at one of the plurality of different frequencies within range of the tracker  32 . Objects emitting magnetic field sources within range of the tracker  32 , such as power lines, gas lines, railroads, etc., may interrupt the communication between the beacon  28  and the tracker. This interruption is referred to as interference. The amount of interference present at the different frequencies may vary depending on what frequency the alternative magnetic field source is emitting its signal. One frequency may have a much greater amount of interference present while a second frequency may have a much lower amount of interference present. The lower the amount of interference present, the more effectively the tracker  32  can communicate with the beacon  28 . Thus, one frequency may be more effective than other frequencies at certain locations along the desired borepath  16  for the beacon  28  and the tracker  32  to communicate during drilling operations. Based on this, the tracker  32  of the present invention is configured to analyze the amount of interference present at the plurality of different frequencies along the course of the desired borepath  16  prior to starting boring operations and determine the preferred frequency at which the beacon  28  ( FIG. 1 ) should communicate with the tracker  32 . 
     Turning back to  FIG. 1 , to analyze the borepath, the operator  30  must first ensure that there are no beacons  28  on in the area to disrupt the interference analysis. The tracker  32  is then placed in “analyze mode.” This may be initiated by pressing one of the input devices  46  on the tracker  32  ( FIG. 2 ). The operator  30  will start by analyzing a first location (I) along the desired borepath  16 . To do this, the operator  30  holds the tracker  32  over the first location (I) and tells the tracker to analyze the first position (I). This may be initiated by pressing one of the input devices  46  on the tracker  32 . The tracker  32  will then measure a type of interference and an amount of noise at each of the plurality of different frequencies present and selected to be analyzed at the first location (I), such as 1,000 Hz, 2,000 Hz, 3,000 Hz, or 30,000 Hz frequencies. 
     Referring now to  FIG. 3 , once the operator  30  begins analyzing the first location (I) ( FIG. 1 ), a plot  50  may begin on the visual display  44  of the tracker  32  indicating the interference or relative noise floors present at the plurality of different frequencies analyzed. The lower a point on the plot  50  for a specific frequency, the deeper that frequency can be detected without interference. The most effective frequency or frequencies to emit the beacon signal during boring can be determined by the lowest points on the plot  50 . Once the operator  30  is done analyzing the first location (I), the operator may move and perform the same analysis on a second location (II) and a third location (III) ( FIG. 1 ). The operator  30  may analyze as many locations as needed along the desired borepath  16 . The plot  50  will be created at each location analyzed along the borepath  16 . The analysis of the multiple locations will be stored within the processor  47  ( FIG. 2 ) of the tracker  32  along with the GPS coordinates of the multiple locations. The required power level to complete the analysis of the entire desired borepath  16  may not be known by the tracker  32 . Prior to analyzing, the operator  30  may select the appropriate power level for the analysis based on the job requirements. 
     Referring now to both  FIGS. 1 and 3 , once the operator  30  has finished measuring the interference present along the desired borepath  16  using the tracker  32 , the operator may tell the tracker  32  to summarize the amount of interference present at the different frequencies for the entire borepath. This may be initiated by pressing one of the input devices  46  on the tracker  32 . The summary provides the operator  30  with the average amount of interference for each frequency measured along the entire borepath and provides the operator with the recommended frequency at which to emit the beacon signal from the beacon  28  and to tune the tracker  32  to during horizontal drilling operations. Since the amount of interference may vary at different locations along the borepath  16 , the summary may recommend more than one frequency to use during drilling operations. The operator  30  may determine the preferred frequency or frequencies based on the provided recommendation. However, the preferred frequency may vary from the recommended frequency or frequencies based on the specific needs of the boring operation. After forming the summary of interference, the tracker  32  may also recommend one of a plurality of different digital modulation schemes, such as OOK, FSK, PSK, etc., to operate on based on the amount of interference at each of the plurality of different frequencies. 
     Continuing with  FIG. 1 , the beacon  28  may be programmed to emit only one preferred frequency during the entire boring operation, or if using a multiple frequency beacon, the beacon may be programmed to emit two or more different preferred frequencies while boring. However, the beacon  28  may only emit one of the two or more preferred frequencies at a time. Therefore, the operator  30  may toggle back and forth between the different frequencies depending on which frequency is preferred at certain locations along the borepath  16 . The beacon  28  may be manually set to emit the preferred frequency or frequencies prior to boring operations or it may be set using Bluetooth prior to boring operations if the beacon is capable of Bluetooth communication. Once the beacon  28  is programmed, the beacon, along with the downhole tool  20 , may be placed underground and boring operations may begin. 
     Turning now to  FIG. 4 , a flowchart depicting a method to analyze the desired borepath  16  is shown. To start, the operator  30  will place the tracker  32  in “analyze mode” by pressing one of the input devices  46  on the tracker (step  100 ). The operator  30  will then analyze the first location (I) by holding the tracker  32  over the first location (I) and pressing one of the input devices  46  to initiate the analysis (step  102 ). The tracker  32  will analyze the first location (I) by measuring the amount of interference and noise present at each of the selected frequencies at the first location (I) (step  104 ). Following this analysis, the tracker  32  will create a plot  50  on the visual display  44  identifying the amount of interference present at the selected frequencies at the first location (I) (step  106 ). The tracker  32  will save this data along with the GPS coordinates of the first location (I) (step  108 ). 
     Continuing with  FIG. 4 , the operator  30  will analyze as many additional locations along the desired borepath  16  as necessary by repeating steps  102  through  108  at each additional location (step  110 ). The tracker  32  will then average all of the data collected and create a summary of interference (step  112 ). The tracker  32  will then provide the operator  30  with the recommended frequency or frequencies at which to emit the beacon signal and to tune the tracker to during horizontal drilling operations; the operator  30  will then determine the preferred frequency or frequencies based on the recommended frequency (step  114 ). 
     After the operator  30  determines the preferred frequency or frequencies, the operator will program the beacon  28  to emit the preferred frequency or frequencies (step  116 ). The beacon  28  is then placed underground (step  118 ) and the boring machine  12  may begin boring operations (step  120 ). While boring, the beacon  28  will emit the preferred frequency based on the preferred frequency at the location of the beacon (step  122 ). Once the beacon  28  emits the preferred frequency, the operator  30  may detect the location of the beacon relative to the tracker  32  (step  124 ). After locating the beacon  28 , the operator  30  will ensure that the downhole tool  20  is continuing along the desired borepath  16  and if necessary, the operator  30  will make steering corrections before continuing to bore (step  126 ). The operator  30  may continue detecting the beacon  28  at the preferred frequency until boring of the desired borepath  16  is complete (step  128 ). 
     Prior to completing boring operations, the operator  30  will determine if a second or different frequency is preferred to detect the beacon  28  as the beacon moves to a new location along the desired borepath  16  (step  130 ). If the second frequency is not preferred at the new location, the operator  30  will continue detecting the beacon signal at the original preferred frequency while boring operations continue (steps  126  and  124 ). If the second frequency is preferred, the operator  30  will change the beacon  28  to emit the second preferred frequency. The operator  30  will then detect the beacon  28  relative to the tracker  32  using the second preferred frequency while boring operations continue. The operator  30  will toggle between the different preferred frequencies as needed until boring operations are completed (step  132 ). The operator  30  may perform step  130  as many times as needed along the desired borepath  16 . 
     The present invention provides a tracking system with the ability to analyze the different frequencies the beacon is capable of emitting and determine which frequency has the least amount of interference present at certain locations along the borepath. 
     Various modifications can be made in the design and operation of the present invention without departing from its spirit. Thus, while the principal preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, it should be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.