AU2014101269A4 - An improved drill hole survey probe - Google Patents

Abstract

Subsequent to extensive investigations the inventors have found that drill hole survey probes suffer loss of calibration as a result of lateral shock, rather than axial shock as would be conventionally expected. A drill hole probe 2 according to a preferred embodiment of the invention includes a shock absorbent housing in the form of a casing 4 that is comprised of an upper portion 6 and a lower portion 8. Each of the upper and lower portions 6 and 8 are made of a resilient and deformable synthetic substance, most preferably polyurethane. The upper and lower portions 6 and 8 are formed with internal recesses that correspond to the shape of a circuit board 10 which is received between the upper and lower portions of the shock absorbent case 4. A ribbon cable 12 extends from the circuit board to thereby connect the board to an external computational device for downloading data that is logged by the board. The probe housing, formed as it is of resilient material protects the probe sensors and electronics from lateral shock and thereby addresses the problem of calibration loss. uH V) LU co U)U

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION Innovation Patent AN IMPROVED DRILL HOLE SURVEY PROBE The following statement is a description of the invention: 1 AN IMPROVED DRILL HOLE SURVEY PROBE TECHNICAL FIELD 5 The present invention relates to survey probes for surveying drill holes, such as drill holes that are used in gas, oil, or other, energy extraction industries. BACKGROUND 10 Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge. Drill holes for the coal seam gas or mining industries may be very long and it 15 can be difficult for a surface drilling team to ensure that the drill hole is proceeding in the correct direction towards a subterranean target. To assist the drilling team a drill hole survey probe may be used to gather survey data to help the drilling team in tracking the path of the drill hole. Physically a drill hole survey probe typically comprises a long, metal, cylindrical housing in 20 which there is located a printed circuit board loaded with attitude detectors, accelerometers and other sensors that are coupled to logging electronic circuitry which is also located on the board within the housing. One such probe is offered by GlobalTech Pty Ltd of Canning Vale, 6155 W.A. Australia under the brandname Pathfinder. 25 In use the probe is attached to the end of a retrieval line and then dropped down the drill hole. As the probe descends down the drill hole its sensors detect data such as change in the attitude and position of the probe and surrounding gravitational and magnetic fields. The data is logged in an 30 electronic memory of the probe. Subsequently the probe is retrieved and the data is downloaded to a suitably programmed computer for analysis. Based on the retrieved data the surface drilling team is able to make drilling adjustments in order to correctly direct the drill hole.

2 It will be realized that as the retrieval wire is unwound the probe descends down the drill hole. Finally the probe approaches the bottom of the drill hole and ultimately it impacts on the drill hole floor. 5 A problem that occurs during the performance of the above described drill hole survey procedure is that it has been found that the survey probe loses its calibration so that the sensor data that is recorded becomes inaccurate. The problem of calibration loss has been addressed in the past by cushioning 10 the circuit board and the sensors that are mounted thereto from axial shock associated with the impact of the sensor on the floor of the drill hole. Cushioning has been provided by using a soft landing "sub" in the form of polyurethane shock absorbing components mounted toward the bottom end of the circuit board. Nevertheless, it has been found that the problem of 15 calibration loss has continued. It is an object of the present invention to provide an improved drill hole probe which addresses the previously described problem of calibration loss. 20 SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided an elongate drill hole survey probe including: a printed circuit board bearing one or more survey sensors and 25 associated electronics; and an elastomeric material disposed along opposed sides of the printed circuit board to thereby cushion said board from lateral shock. Preferably the elastomeric material comprises a first portion and a second 30 portion located on opposite sides of the printed circuit board. In a preferred embodiment of the invention the first portion and the second portion are respectively adhered to the opposite sides of the printed circuit board.

3 It is preferred that the first and second portions are formed with recesses that complement the opposite sides of the printed circuit board. 5 Preferably the elastomeric material comprises polyurethane. It is preferred that the probe include an alignment shoe at one end thereof to assist in aligning the probe during use. 10 A rigid tube may be located around the first and second portions towards one end of the probe to thereby assist in holding the first and second portions together. A casing for a drill hole survey printed circuit board of a type bearing one or 15 more survey sensors and associated electronics, the casing including: first and second portions of elastomeric material shaped to complement first and second sides of the printed circuit board. Preferably the elastomeric material comprises polyurethane. 20 It is preferred that the casing includes an alignment shoe at one end thereof to assist in aligning the probe during use. A rigid tube may be located around the first and second portions towards one 25 end of the casing to thereby assist in holding the first and second portions together. BRIEF DESCRIPTION OF THE DRAWINGS 30 Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding 4 Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: Figure 1 comprises a graph that illustrates data collected by the inventors while investigating the effect of lateral shock on a drill hole survey 5 probe. Figure 2 is an isometric view of a probe according to a preferred embodiment of the present invention. Figure 3 is a top plan (i.e. zero degree) view of the probe. Figure 4 is a side view (i.e. 90 degree) view of the probe. 10 Figure 5 is a view of the underside of the probe. Figure 6 is a cross section through a lower portion of a housing of the probe. Figure 7 is a top plan view of the lower portion of the housing. Figure 8 is a side view of the lower portion. 15 Figure 9 is a view of the underside of the lower portion. Figure 10 is an end view of a first end of the lower portion. Figure 11 is an end view of a second end of the lower portion. Figure 12 is an isometric view of the lower portion and of a printed circuit board of the probe. 20 Figure 13 is a cross section through an upper portion of a housing of the probe. Figure 14 is a top plan view of the upper portion of the housing. Figure 15 is a side view of the upper portion. Figure 16 is a view of the underside of the upper portion. 25 Figure 17 is an end view of a first end of the upper portion. Figure 18 is an end view of a second end of the upper portion. Figure 19 is an isometric view of a topside of the upper portion. Figure 20 is an isometric view of an underside of the upper portion. 30 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In seeking to overcome the previously discussed loss of calibration of the drill hole probe the inventors have made a number of experiments and investigations.

5 Initially the inventors had expected that increased cushioning of the electronic components from axial shock due to the impact of the probe with the bottom of the drill hole would overcome the problem of loss of calibration. Surprisingly, this turned out not to be the case as will now be discussed. 5 In one experiment conducted by the inventors the axial cushioning, polyurethane, shock absorption components were removed from the probe and replaced with rigid components to determine the axial impact that was believed to cause the circuit board to go out of calibration. The soft landing 10 sub, comprising the polyurethane shock absorption components, was replaced with a machined acetal sub and the probe's compression coupler was replaced with a coupler moulded from hard polyurethane. The probe was then dropped through a vertical length of 040mm PVC pipe onto a concrete floor. The drop height was increased by 100mm increments and the probe 15 was tested for loss of calibration between each drop. In this experiment the total weight of the probe was 4.95kg. The inventors found that the probe remained in calibration up to and including a drop height of 2.0 meters. When dropped from 2.0 meters, the probe hit the 20 floor at a velocity of around 6.3m/s (22.6km/h). Impact at this velocity imparted a kinetic energy of 97 Joules on the probe. Since, surprisingly, the probe remained in calibration despite the substantial axial shock the inventors therefore hypothesized that counter to expectations a significant level of axial impact was not necessarily the cause of the probe's loss of calibration. 25 The inventors then performed a further experiment wherein the axial drop test was replicated using a dummy board bearing impact indicators to help ascertain the amount of shock that the probe's board was subjected to during impact. The dummy board was machined from acetal (Delrin) and made to be 30 a similar weight to that of the probe's board. The impact indicators were located in a position on the dummy board that would be equidistant between the magnetic and gravity sensors on the probe's board.

6 Three sets of impact indicators were used, with shock thresholds of 25G, 50G and 1 OG respectively. The inventors found that the results of the experiment were as follows: 5 The 25G indicators activated at a drop of 200mm. The 50G indicators activated at a drop of 400mm. The 1OOG indicators activated at a drop of 800mm. 10 From these results the inventors concluded that the board was able to withstand shock in excess of 1OOG in an axial impact and still remain in calibration. Therefore, the inventors hypothesized that contrary to conventional wisdom the loss of calibration must be due to some other factor and not to axial shock. 15 In seeking to find a cause for the probe losing calibration the inventors eventually conducted a further test in which the probe was subjected to lateral, not axial, impacts. It will be realized that since in normal use the probe is not subjected to significant lateral shock that this experiment was not 20 expected to yield helpful results. The lateral shock test was performed in the following manner. The probe was secured horizontally and a 1 kg weight dropped through a vertical length of 040mm PVC pipe from increasing height onto the side of the probe. It was 25 assumed that an impact near the sensors would be most likely to cause a failure, so the probe was positioned so that the weight would impact between the magnetic and gravity sensors. A 3.3mm thick steel tube was placed over the probe at the point of impact to protect the brass pressure barrel from damage. The soft polyurethane compression coupler inside the probe was 30 replaced with a rigid connector moulded from 80 Shore D polyurethane. At each drop height the probe was rotated so that the effect of impact either directly onto the face of the sensors (00) or onto the edge of the board (900) could be individually assessed.

7 A first probe was tested and remained in calibration until dropped from 1.25 metres with impact at 00. From this height, the weight would be hitting the steel tube protecting the 5 probe at a velocity of 5.0m/s (17.8km/h) and would have a kinetic energy of 12.3 Joules. Testing then continued using a second probe with 900 (i.e. edge on to the PCB) impacts only. Following a drop from 1.4 metres a loss of calibration was 10 detected. From this height, the weight would be hitting the steel tube protecting the probe at a slightly higher velocity of 5.2m/s (1 8.2km/h), delivering a kinetic energy of 13.7 Joules. 15 From the above results the inventors hypothesized that the sudden loss of calibration that has been witnessed in the field is much more likely to be as a result of lateral impacts rather than axial impacts. Possible lateral impacts in the field could be from the probes being dropped on their sides, being 20 bumped during handling, or during transit. The test also demonstrated that the probe was actually more vulnerable to an impact directed face on toward the sensors than an impact on the edge of the board. 25 The inventors then replicated the lateral drop test using a dummy board mounted with impact indicators to help ascertain the amount of shock that the probe's board is subjected to during lateral impacts. The dummy board was machined from acetal (Delrin) and made to be a similar weight to that of the 30 probe's board. The impact indicators were located in a position on the dummy board that would be equidistant between the magnetic and gravity sensors on the probe's board.

8 Three sets of impact indicators were used, with shock thresholds of 25G, 50G and 1 OG respectively. The inventors found that the results of the experiment were as follows: 5 The 25G indicators activated at a drop of 250mm The 50G indicators activated at a drop of 400mm The 1 OG indicators activated at a drop of 1600mm 10 The inventors graphed the activation points of the impact indicators as shown in Figure 1. The shock that causes the board to go out of calibration after lateral impact was roughly interpolated as 86G for 00 (onto the face of the sensors) impact and 92G after the probe had been rotated through 900 (onto the edge of the board) impact. 15 In order to shield the components from lateral shock the existing plastic parts of the probe board were replaced with an acetal case machined to provide rigid support along the entire length of the board. However, testing found that eliminating the flexibility of the board worsened its performance under lateral 20 impact. Consequently the inventors hypothesized that the rigid enclosure may in fact facilitate increased transmission of shock vibration through to the electronics on the board. Finally, soft polyurethane components were made to replace the hard plastic 25 case on the board. The polyurethane case covered most of the board so as to provide full support but without having the board rigidly fixed. After testing the inventors found that the soft polyurethane case enabled the board to withstand much higher impacts without loss of calibration. Referring now to Figures 2 to 5 there is depicted a drill hole probe 2 according 30 to according to a preferred embodiment of the invention. Figures 6 to 20 are various views of different components of the probe 2 as will be discussed. The drill hole probe 2 includes a shock absorbent housing in the form of a casing 4 that is comprised of an upper portion 6 and a lower portion 8. Each 9 of the upper and lower portions 6 and 8 are made of a resilent and deformable synthetic substance, most preferably polyurethane. The upper and lower portions 6 and 8 are formed with internal recesses 9 (Figs 16, 20) and 11 (Figs 7, 12) respectively that correspond to the shape of a circuit board 10 5 (Fig 12) which is received between the upper and lower portions 6, 8 of the shock absorbent case 4. Referring again to Figure 2, a ribbon cable 12 extends from the circuit board 10 to thereby connect the board to an external computational device for 10 downloading data that is logged by the board. During assembly the circuit board 10 is located in the lower portion 8 of the housing and glued thereto with a suitable adhesive, such as "super glue". The same adhesive is then used used to glue the top portion 6 of the housing 4 to 15 the board 10. The reason why the upper and lower portions are each glued to the board rather than gluing the upper and lower portions to each other is that there is very little contact area between the upper and lower portions for the adhesive. A much better bond is achieved by gluing the two portions directly to the circuit board rather than to each other. 20 The drill probe 2 also includes an alignment shoe 14 to assist in aligning the probe in use. The alignment shoe provides a fixed rotational datum for the probe's sensors. 25 A rigid tube in the form of aluminum tube 16 is located about the first and second portions 6, 8 towards one end of the probe to assist in holding the first and second portions together. In use it has been found that the probe of Figure 2 largely addresses the loss 30 of calibration problem that was previously discussed since it isolates the circuit board and the sensors and electronics that are mounted thereon from the effect of lateral shock which the inventors have determined through research and experiment to unexpectedly be the cause of the problem.

10 In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term "comprises" and its variations, such as "comprising" and "comprised of" is used throughout in an inclusive sense and not to the exclusion of any 5 additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within 10 the proper scope of the appended claims appropriately interpreted by those skilled in the art. Throughout the specification and claims (if present), unless the context requires otherwise, the term "substantially" or "about" will be understood to 15 not be limited to the value for the range qualified by the terms. Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment 20 described without departing from the spirit and scope of the invention.

Claims (11)

1. An elongate drill hole survey probe including: a printed circuit board bearing one or more survey sensors and associated electronics; and an elastomeric material disposed along opposed sides of the printed circuit board to thereby cushion said board from lateral shock.

2. A probe according to claim 1, wherein the elastomeric material comprises a first portion and a second portion located on opposite sides of the printed circuit board.

3. A probe according to claim 2, wherein the first portion and the second portion are respectively adhered to the opposite sides of the printed circuit board.

4. A probe according to claim 2 or claim 3, wherein the first and second portions are formed with recesses that complement the opposite sides of the printed circuit board.

5. A probe according to any one of claims 2 to 4, including a rigid tube located around the first and second portions towards one end of the probe to thereby assist in holding the first and second portions together.

6. A probe according to any one of the preceding claims, wherein the elastomeric material comprises polyurethane.

7. A probe according to any one of the preceding claims including an alignment formation at one end thereof to assist in aligning the probe during use. 12

8. A casing corresponding to a drill hole survey printed circuit board of a type bearing one or more survey sensors and associated electronics, the casing including: first and second portions of elastomeric material shaped to complement first and second sides of the printed circuit board.

9. A casing according to claim 8, wherein the elastomeric material comprises polyurethane.

10. A casing according to claim 8 or claim 9, wherein the casing includes an alignment shoe at one end thereof to assist in aligning the probe during use.

11. A casing according to any one of claims 8 to 10, including a rigid tube located around the first and second portions towards one end of the casing to thereby assist in holding the first and second portions together.