Downhole surveying and core sample orientation systems, devices and methods

Abstract

A method and system for obtaining orientation of a core sample core drilled from underlying rock. A core orientation recording device (116) records its orientation at random and/or non-predetermined time intervals from a reference time during a drilling operation. The time intervals are generated to be within a range of minimum and maximum time intervals. After a time interval elapsed from the reference time plus a wait time of at least the minimum random or non-predetermined time interval, the core sample is separated from the underlying rock and brought to the surface and its original orientation is determined from orientation data recorded closest in time to the elapsed time plus the minimum time interval. A remote communicator (160) having the elapsed time interrogates the core orientation recordal device (116) to identify the required orientation data and requires the core orientation recordal device to identify a correct orientation of the core sample.

Claims

1. A method of obtaining an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method comprising: drilling a core sample from a body of material with a core drill having an inner tube; recording measurements indicative of the orientation of the inner tube at random or non-predetermined time intervals, the measurements are time stamped and referable to an initial reference time; recording a time beyond the reference time when the drilling has stopped and before the core sample is separated from the body of material; separating the core sample from the body of material and retrieving the inner tube with the core sample held therein to the surface; and relating the recorded time beyond the reference time to one or more of the measurements recorded at a said random or non-predetermined time interval to obtain an indication of the orientation of the inner tube and consequently the core contained therein at the time beyond the reference time.

2. The method of claim 1, further comprising a random number generator used to generate the random or non-predetermined time intervals.

3. The method of claim 1, the random or non-predetermined time intervals within a known range between a minimum and a maximum time interval.

4. The method of claim 1, wherein recording a time beyond the reference time when the drilling has stopped is an elapsed time from the reference time plus a wait time of at least a minimum allowed random or non-predetermined time interval.

5. A method of providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted, the method comprising: drilling a core sample from a body of material with a core drill having an inner tube; recording measurements of the orientation of the inner tube at random and non-predetermined time intervals during said drilling; the measurements are time stamped and are referable to an initial reference time; providing a specific time beyond the reference time representative of when the drilling has stopped and before the core sample is separated from the body of material; identifying a said measurement recorded at a said random or non-predetermined time interval indicative of the orientation of the inner tube and consequently the core contained therein at the specific time.

6. The method of claim 5, further comprising a random number generator used to generate the random or non-predetermined time intervals.

7. The method of claim 5, the random or non-predetermined time intervals within a known range between a minimum and a maximum time interval.

8. The method of claim 5, wherein recording a time beyond the reference time when the drilling has stopped is an elapsed time from the reference time plus a wait time of at least a minimum allowed random or non-predetermined time interval.

9. A method of providing an indication of the orientation of a core sample relative to a body of subsurface material from which the core sample has been extracted, the method comprising: drilling a core sample from a body of material with a core drill having an inner tube; recording orientation of the inner tube at random or non-predetermined time intervals subsequent to a reference time; removing the inner tube, with the core sample held therein in fixed relation to it, from the body of subsurface material; and identifying the orientation of the inner tube and core sample based on the orientation recorded at at least one of the random or predetermined time intervals based on time elapsed subsequent to the reference time.

10. A core orientation system for use with a core drill having an inner tube to receive a core sample drilled from a body of subsurface material, the system including signal producing means to produce at least one signal relating to a physical orientation of the inner tube, and time measurement means to provide a time measurement indicative of when the core sample is detached from the body of material from which it is taken and held in fixed relation to the inner tube, the time measurement based on elapsing of random and/or non-predetermined time intervals subsequent to a reference time; and input means for inputting the time measurement into the system; at least one processor for processing the at least one signal to provide data indicative of an orientation of the inner tube; and at least one processing means for processing the provided data and the inputted time measurement to produce an indication of the orientation of the core sample relative to the subsurface material from which it has been detached; and display means for the indication of the orientation of the core sample relative to the subsurface material from which it has been detached.

11. The system of claim 10, wherein the random or non-predetermined time intervals are created by a random number generator.

12. The system of claim 10, wherein the random or non-predetermined time intervals are generated to be within a range between a minimum and a maximum time interval.

13. A core orientation system for providing an indication of the orientation of a core sample relative to a body of material from which the core sample has been extracted using a core drill, the core drill having an inner tube, the system including: means for recording the orientation of the inner tube at random and/or non-predetermined time intervals during drilling by the core drill, the time intervals being referable to an initial reference time, and for inputting a specific time beyond the reference time representative of when the core sample was separated from the body of material; and means for relating the inputted specific time to the recorded random or non-predetermined time intervals to obtain an indication of the orientation of the inner tube and consequently the core contained therein at the specific time.

14. The system of claim 13, wherein the random or non-predetermined time intervals are created by a random number generator.

15. The system of claim 13, wherein the random or non-predetermined time intervals are generated to be within a range between a minimum and a maximum time interval.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a general arrangement of a drill assembly for obtaining core sample according to an embodiment of the present invention.

(2) FIG. 2 shows features of a known core sample orientation system.

(3) FIGS. 3 and 4 show an outer drilling tube consisting of connectable hollow steel tubes. FIG. 4 shows an extension piece connected inline between two adjacent tubes in order to compensate the length of the outer drilling tube in relation to the additional length gained by the inner tube assembly due to an instrument, such as a core sample orientation data gathering device.

(4) FIG. 5 shows features of an assembly including a downhole instrument, such as a core sample orientation device.

(5) FIG. 6 shows a communication device as utilised according to an embodiment of the present invention.

(6) FIG. 7 shows a flowchart relating to a method and/or system according to at least one embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

(7) With reference to FIG. 1, a drill assembly 10 is provided for drilling into a subsurface body of material 12 which includes a drillstring 14 including a drill bit 16 an out tube 22 formed of linearly connected tube sections 22a, 22b . . . , and an inner tube assembly 18 including an inner tube 24 for receiving the core 26 drilled from the subsurface body.

(8) One or more pressure sensors 28, 30, 32 can be provided to detect pressure, change in pressure and/or pressure differential. These can communicate with the core orientation data recording device 116 and/or an operator at the surface.

(9) Drilling can cease and the core orientation device 116 can record data relating to the orientation of the core, such as gravitational field strength, gravitational field direction, magnetic field strength and/or magnetic field direction.

(10) Digital and/or electro-mechanical sensors, and/or one or more pressure sensors in a core orientation data recording device 116, are used to determine the core orientation just prior to the core break, and to detect the signal of the break of the core from the body of material.

(11) Data recorded or used may optionally include ‘dip’ angle α to increase reliability of core orientation results.

(12) Dip (also referred to as inclination or declination) is the angle of the inner core tube drill assembly with respect to the horizontal plane and can be the angle above or below the horizontal plane depending on drilling direction from above ground level or from underground drilling in any direction. This provides further confirmation that the progressive drilling of a hole follows a maximum progressive dip angle which may incrementally change as drilling progresses, but not to the extent which exceeds the ‘dogleg severity’. The ‘dogleg severity’ is a normalized estimate (e.g. degrees/30 metre) of the overall curvature of an actual drill-hole path between two consecutive directional survey/orientation stations.

(13) At the surface, a remote communication device (remote communicator) 160 is set by an operator to commence a reference/start time (say, ‘t’).

(14) The remote communicator 160 also communicates with the core orientation device 160 and the core orientation device commences a timer/counter, say ‘T’. The core orientation device 160 is then inserted into the drill hole.

(15) In FIG. 2, a known prior art inner tube assembly 110 replaces a standard greater with a two unit system 114, 116 utilising a specialised greater unit 114 and electronics unit 116 particular to the two unit system.

(16) The electronics unit is sealed to the greater unit by o-rings, which have a tendency to fail in use and allow liquid into the electronics unit, risking loss of data and/or display failure.

(17) The electronics unit has an LCD display 118 at one end. This allows for setting up of the system prior to deployment and to indicate visually alignment of the core sample when retrieved to the surface.

(18) The greater unit is connected to a backend assembly 120 and the electronics unit 116 is connected to a sample tube 122 for receiving a core sample 124. The electronics unit is arranged to record orientation data every few seconds during core sampling.

(19) The start time or reference can be synchronised with actual time using a counter or watch, such as a stop watch or other handheld timer.

(20) Referring to FIG. 4, the electronics unit 116 of FIG. 2 includes accelerometers 128, a memory 130, a timer 132 and the aforementioned display 118.

(21) As shown in relation to FIG. 5, a system 140 according to an embodiment of the present invention is provided in relation to an outer drilling tube 134 consisting of connectable hollow steel tubes 134a-n has an extension piece 136 connected inline between two adjacent tubes in order to compensate the length of the outer drilling tube in relation to the additional length gained by the inner tube assembly 140 due to the core sample orientation data gathering device 142.

(22) The core sample orientation data gathering device 142 is a fully sealed cylindrical unit with screw threads at either end. A first end 144 connects to a standard length and size greater unit 146 and a second end 148 connects to a core sample tube 150. The greater unit connects to a standard backend assembly 120.

(23) FIG. 6 shows an embodiment of the hand held communication device 160 which communicates with the downhole instrument (such as the core sample orientation device) that is retrieved to the surface, receives wirelessly receives data or signals from the core sample orientation data gathering device 142.

(24) The core sample orientation data gathering device 142 includes a transmitter which can use line of sight data transfer through the window, such as by infra red data transfer, or a wireless radio transmission.

(25) The communication device 160 can store the signals or data received from the core sample orientation data gathering device 142. The communication device 160 includes a display 162 and navigation buttons 164, 166, and a data accept/confirmation button 168. Also, the hand held device is protected from impact or heavy use by a shock and water resistant coating or casing 170 incorporating protective corners of a rubberised material.

(26) Setting up of the device is carried out before insertion into the drill hole. Data retrieval is carried out by infra red communication between the core sample orientation data gathering device 142 and a core orientation data receiver or communication device 160.

(27) After recovering the core sample inner tube back at the surface, and before removing the core sample from the tube, the operator removes the ‘back end assembly, and the attached greater unit. The operator then uses the remote communication device 160 to obtain orientation data from the core sample orientation data gathering device using line of sight wireless infra red communication between the remote device and the core sample orientation data gathering device.

(28) However, it will be appreciated that communication of data between the core sample orientation data gathering device 142 and the communication device 160 may be by other wireless means, such as by radio transmission.

(29) The whole inner tube 150, core sample 152 and core sample orientation data gathering device 142 are rotated as necessary to determine a required orientation of the core sample. The indicators on the greater end of the core sample orientation data gathering device 142 indicate to the operator which direction, clockwise or anti-clockwise, to rotate the core sample.

(30) Preferably, one colour of indicator is used to indicate clockwise rotation and another colour to indicate anti-clockwise rotation is required. This is carried out until the core sample is orientated with its lower section at the lower end of the tube. The core sample is then marked for correct orientation and then used for analysis.

(31) FIG. 7 shows a flowchart of operational methodology and/or use of a system according to at least one embodiment of the present invention.

(32) If a core orientation recording device 116 and a remote communicator 160 is in a standby mode 202, the respective device is ‘woken up’ to a start mode 204.

(33) The core orientation recording device 116 commences a random time interval timer at time T.

(34) The timer start at time T can be initiated by the remote communicator 160 also commencing a timer of it's own at time t. Thus, the time t of the remote communicator and time T of the core orientation recording device can be synchronised to start together.

(35) The core orientation recording device generates a random time interval R, 210 and records 212 it's own orientation at the end of R seconds random time interval, where the random time interval is less than a maximum time interval Y and greater than a minimum time interval X i.e. Y>R>X. The orientation measurement is time stamped with accordance to the lapsed time on of the timer T.

(36) Time t and T is progressing 214. When the core sample is ready to be broken from the subsurface material, a ‘mark’ is taken 216.

(37) If the mark is taken (YES decision), the elapsed time M of the time t of the remote communicator 160 is recorded 218. If a mark is not taken (NO decision), the time t continues

(38) A period of time Z is waited 220 to ensure recordal of the next orientation of the core orientation recording device and therefore of the core. Preferably the time period Z is at least as large as the largest random time interval that might be generated i.e. Z> or =Y.

(39) Once the time period M+Z is waited out 222, the core is then broken and the core sample, inner (core) tube and the core orientation recordal device are returned to the surface.

(40) The remote communicator 160 is used to initiate communication 224 with the core orientation recordal device 116.

(41) At the surface, the core orientation recording device 116 communicates 226 with the remote communicator 160. The core orientation recording device stops measuring orientation. The remote communicator transmits lapsed time M+Z to the core orientation recording device.

(42) The remote communication device 160 identifies 230 the recorded orientation data with the largest lapsed time that has/have a time stamp between M and M+Z seconds as the correct measurement to orient the core sample.

(43) At the surface, the core orientation recording device enters an orientation mode 232. The core orientation recording device is rotated to the original orientation when the ‘Mark’ was taken e.g. until a visual indication of correct orientation is given, 234.

(44) If the core orientation recording device is orientated correctly as per original orientation when the MARK was taken, a decision 236 is made, YES/NO? If YES, 238, the remote communication device 160 confirms that the orientation of the core orientation recordal device 116 is correct i.e. a ‘pass’. Identification of the correct core orientation has been found and is noted, and the core orientation recordal device and the remote communicator can go into a standby mode again. If NO, 240, the core orientation recordal device confirms that the orientation is not correct and the process of seeking the correct orientation by rotating the core orientation recordal device continues until a YES is confirmed.