DE2944607A1 - ROCK DRILLING MACHINE DRIVED BY RADIOACTIVE RADIATION, ESPECIALLY FOR COAL MINING - Google Patents

Description

10674 / MÜ / Elf

CONOCO INC., Ponca City. Oklahoma 74601 (V.St.A.)

Rock drilling machine guided by radioactive radiation, especially for coal mining

The invention relates to the directional guidance of drilling machines and in particular the use of such directional drilling machines for horizontal drilling in coal seams.

Horizontal drilling rock drilling machines have so far been based on various Wise led. It is known to use calculation methods in which the borehole is essentially parallel to an existing hole of known location and direction, as described, for example, in US Pat. No. 3,853,185. Such a parallel guide to a pilot borehole uses radioactive radiation energy to a predetermined distance to hold the existing horizontal borehole, which can be found in the statements of US Pat. No. 3,907,045. It is also known to use radiation measurement methods in the drill hole guidance, in which a radiation source and a detector on the Drilling device itself are attached so that the impingement the radiation on the seam boundaries provides the guidance data,

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with the help of which the direction of the drill is set. Reference is made to US Pat. No. 3,823,787.

The invention is based on the object of designing the guide for a drill so that the naturally occurring Radiation within the seam in which the well is to be driven is used. In other words, it has been found that from the clay slate deposits that normally border coal seams, a natural gamma radiation goes out, and this natural gamma radiation is used by the invention to determine the direction of the drill during the To steer drilling advance through the coal seam. At the beginning of the drilling process, the drill can initially stand a few feet penetrate into the coal seam until external radiation can no longer exert any influence, after which an initial count is then calculated is set for the respective seam and its surroundings, from where the control process of the drilling machine is set is then continued. If this initial count for the particular coal seam and the desired distance from the seam interface with the surrounding rock are determined, then the drill can be operated either remotely or automatically, with the count remaining approximately the same and the drilling machine advances the borehole in a parallel course to the reference interface.

Generally speaking, the invention is based on the object of a method and a device for guiding a drilling machine to create in the horizontal coal seam, which are characterized by high reliability during the work process.

The invention is also intended to create a control method for the drilling that does not previously exist Drilling and no energy source except for the naturally occurring gamma radiation from the vicinity of the coal seam needed. The invention is also intended to provide a drilling

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Machine controls can be created that are easy to calibrate and use to control a selected coal seam is. After all, the control system for the drilling machine should be very precisely based on the pending seam front surface in the Longwall can be controlled either manually or automatically in order to enable mine gas monitoring and / or clearing machine guidance through underground coal seams. The invention is now based on the drawing some embodiments explained in more detail. Show it:

FIG. 1 shows a schematic view of the drilling process in an underground seam;

FIG. 2 shows a drilling machine with which the drilling process is carried out;

FIG. 3 shows a schematic representation of part of the drilling machine from FIG. 2 when using a single radiation detector;

FIG. 4 shows a schematic representation of part of the drilling machine from FIG. 2 when two or more radiation detectors are used;

Figure 5 is a graph of gamma radiation counts in slate and in the coal seam as measured in a selected coal seam;

Figure 6 is a diagram showing the missing pulses per minute of the strength of the between the adjacent clay slate and the measuring point facing lying coal seams;

FIG. 7 shows a circuit diagram of the control of the drilling machine according to FIG. 2; and

FIG. 8 shows an overall circuit diagram of the control circuit of the drilling machine according to Figure 2.

In the case of coal mining, it is necessary at regular intervals

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borrowed to drive a small borehole in the coal seam, which is mainly used to determine the methane gas present in the coal before it is broken down and, if necessary, to let it off. After this Such exploratory bores are made, it is then possible to advance the mining machines by taking advantage of them To conduct exploratory drilling automatically. See U.S. Patent 3,922,015 in this regard. Such exploratory drilling are up to 300 m, and if the deposit allows, even further in the essentially horizontal ones Coal seam driven.

The control method according to the invention makes use of the naturally present radioactivity or its gamma radiation, which usually emanates from the mineral deposits surrounding the coal deposits. Alumina deposits are practically always present, mostly as hanging walls above, sometimes also below coal seams, and these alumina deposits contain gamma-emitting material. In almost all cases the material emitting radiation is uranium, thorium and potassium-40, substances that are found in practically all alumina deposits that have formed at the interface of coal seams. The American Petroleum Institute has defined a standard unit of radioactivity for location purposes as found in "Average Midwestern Alumina" and has defined the average alumina layer as 6 to 7 ppm uranium (in terms of U ₃ Og) 12 ppm Contains thorium and 2% potassium. Of the naturally occurring potassium, 0.0118% is radioactive potassium-4O. This given distribution thus forms the naturally occurring gamma emitter which is used in the invention.

Gamma radiation has three effects by which it affects its surroundings. These are the Compton scattering, the photoelectric one Effect and pair creation. One of the main properties of gamma radiation is that it is exponential

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is absorbed. This means that regardless of the initial intensity of the radiation, the same phenomena for deceleration a given proportion of the radiation when using the same layer thickness of a radiation-absorbing material are valid. This relationship is mathematically analogous to the laws of radioactive decay.

The level of gamma radiation at any point within the coal seam can thus be the sum of the radiation emitted by comes from different, interacting radiation sources. All layers in the vicinity provide their share, and all components follow the experimentally determined expression:

-αχ
^C s ^{= C} f ^e

Here, C denotes the radiation intensity in a medium penetrated by the radiation at the measuring location; C _{f is} the radiation intensity from the same radiation sources at the interface of a mineral layer with the coal deposit; e is the base of the natural logarithm; α is a material constant of the material penetrated by the radiation (eg coal); χ the distance between the measuring location and the alumina / carbon interface.

It is one of the essential features of the invention that the present method is based on the knowledge that the leadership is performed depending on an initial calibration process that takes into account local conditions and is included in its reference value contains all the sources in the vicinity that have an effect with their radiation. Hence they are Meter reference values after the initial measurement at the various Coal seams differ, as there is different radiation due to the different types of clay and deposits of the hanging or the lying as well as due to

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the different radiation absorption coefficients of the individual coal seams. In addition, alumina strips embedded in the coal seam itself can cause changes in the reference level. In any case, however, the generally existing uniformity in the respective arrangement of the alumina layer and Coal seam a reliable setting of the counter reference value, so that with it the drilling machine in a preselected certain Distance from the interface can be performed.

Figure 1 shows schematically the mining strut 10 and the pending of a coal seam 14 of unlimited seam extension and different seam thicknesses, above which coal seam 14 is located an alumina hanging 16, which forms an interface 18 with the coal seam, while through interface 22 from the coal seam 14 the alumina layer 20 is separated.

A probe hole drilling machine, which will be described later, can from a work location 24 in the direction of substantially of the arrow 26 so that it moves along the borehole 28 and the adjoining exploratory borehole 30 is controlled. One of the number of usable drilling machines is shown in FIGS. 2, 7 and 8 and is described below briefly explained.

The drilling machine, designated as a whole by 32 in FIG. 2, contains control instruments which are connected to the work site via lines 34 stay in contact. The drilling machine 32 has a rear borehole unit 36 which is rigidly connected to a drill shaft 38 a holding unit 40 is connected, which in turn is connected via the drill shaft 38 to a drill assembly 42, on the The front end of the drill head 46 sits on the output shaft 44. The drill 32 is a self-advancing drilling unit, which can be controlled in its direction with the help of appropriate instruments. The drilling unit 42 sets composed of a rotation control unit 48, a drilling

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motor 50 and a deflection control unit 52, while the whole group of control instruments in the instrument section labeled 54 can sit. The drill 32 is connected to the work site via hydraulic hoses 56 and 58 and an electric one Cable 60 connected via the hydraulic hose 56 is the Drive pressure for the drill motor 50 is supplied while the hydraulic hose 58, which in reality consists of three individual hoses exists, provides for the control of the holding unit and the deflection unit.

When carrying out the method, the decision on the location of the borehole in the respective coal seam requires the general knowledge of the position of the seam as well as its orientation. Then the drill 32 is in the direction of the Arrow 26 and propelled into the exploratory bore 28 over a distance of a few feet, which is sufficient to external Eliminate the effects of gamma radiation, which can occur on the front side 12 of the pending, to exclude. Of this Point at, the gamma radiation count can be read from work location 24, and in conjunction with knowledge of the For the geometry of the coal seam 14, the drill 32 can then be calibrated to an initial value so that a reference gamma ray count is present in relation to the distance from a boundary surface 18 or 22 selected as a reference surface. Occasionally Both interfaces can also contribute to the gamma radiation count, and the calibration can then be based on this joint Effect can be adjusted.

After this initial calibration, the drill 32 can from Work location 24 from as it penetrates into the coal seam 14 over several hundred feet along the borehole guide indicated by dashed lines 30 can be monitored and controlled. In this way, under the guidance of the gamma radiation measurement with control commands, either by an operator based on the readings

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the radiation or emitted by an automatic control device comparing the incoming radiation level readings to predetermined setpoints, wherein then the necessary corrections are made in the direction of advance. Relatively simple programming of a microprocessor-controlled Apparatus enables automatic control in which the incoming radiation level values are constant are compared with predetermined limit values so that when exceeded The direction of the drill 32 is then corrected accordingly to these limits.

It is also provided that the radiation measurement from one direction or from multiple directions with respect to the drill 32. FIG. 3 shows the instrument section 54 of the drilling section 42 with a detector 62 which is directed upwards. Any gamma ray detector can be used be used. Suitable because of the very difficult environmental conditions The detection system does not use sodium iodide scintillation. A BICRON detector is preferably used, as follows is explained in more detail. The detector 62 only needs to be in a suitable position in the instrument section 54 with the correct one Alignment be mounted and is mounted beneath a radiolucent window 64. Behind the actual Detector 62 is a screen of suitable material, and the detected radiation pulses are over lines passed to the control circuit 68. A voltage analogous to the count of a counter is transmitted via a line 70 in the cable 6O headed to work location 24.

A modified embodiment with two or more detectors pointing in opposite directions, in directions offset by 90 ° or in an otherwise provided arrangement is shown in FIG. The instrument section 54 includes here

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the two radiation detectors 72 and 74, which are diametrically aligned opposite to each other and receive the radiation through radiation-permeable windows 76, 78. They deliver the individual pulses via lines 80 and 82 to the control circuit 84, which then reports its counting status via a line 86 to the work location. A detector according to Figure 4 with two detectors looking in opposite directions is particularly suitable for coal seams that are not very thick, the pulse counting in relation to the clay layer in the hanging or lying down can be carried out and that side takes the lead whose fault condition the lower one is.

FIGS. 5 and 6 give a picture of the implementation and the high reliability of the gamma radiation counting for guiding the drilling machine. FIG. 5 shows the diagram of a gamma radiation count in a borehole that has been drilled for the purpose of radiation testing. This diagram shows the radiation characteristics in the transition area from alumina to coal seam. For this purpose, a straight hole was drilled at a dip angle of 17 1/2 degrees with the first 21 1/2 feet running through clay, then the boundary layer with the coal, and then the hole extending over 9 feet into the Coal seam continues. With the aid of a sodium iodide scintillation detector , gamma radiation counting data were periodically ascertained at various points in the borehole. The radiation intensity within the borehole section lying in the alumina is constant between about 7000 and 8300 counts per minute. In the section behind the interface, the radiation then decreases sharply with increasing drilling distance. Line 90 shows that the gamma radiation counts are very well on a straight line connecting the measurement points between 22 and 29 feet.

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Figure 6 shows the ratio of Ganuna radiation counts per minute to the coal layer thickness in inches, which lies between the measuring point and the interface with the clay pendent. The result shows that the decrease in gamma radiation counts is very reliable and that the plotted counts in one The area from the boundary layer to 12 inches below it indicates that the carbon layer is at half the amount of radiation reached is 7.3 inches. In other words, in order to absorb half of the incident gamma radiation, this special charcoal requires a layer 7.3 inches thick.

FIG. 7 shows a possible design of the operating control 100 that can be used at the work location 24. The operating control 100 receives its energy supply via a connection 102 and forwards the energy via lines 104 and 106 and a common line 108, in some cases directly to an eight-pole one Plug connection 110, which can be connected to the cable 60 leading to the drill. The voltage of -18 V arrives via line 106 to zero adjustment potentiometers 112 and 114, which are required to adjust the deflection and rotation controls These potentiometers are connected to the +18 V line 104 via series resistors 116 and 118, respectively. The tapping of funds of the potentiometer 112, which is decisive for the inclination via the line 120 to the plug connection 110 and via the cable led to the drill, while the center tap of the for the Rotation decisive potentiometer 114 is connected via a line 122 to the plug connection 110. The indication of measure, inclination and rotation appears on instruments 124, 126 and 128, all of which have a zero adjustment potentiometer on leads 130, 132,134 are connected for control.

The gamma radiation deficit and the values for inclination and rotation of the drilling machine can also be transmitted via an analog-to-digital converter 136 may be fed to a suitable form of digital computer 138 for automatic digital control

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the drill press. Any commercially available microprocessor computer can be used for this purpose, including also the computer model No.2808 from Texas Instruments.

Figure 8 shows the control circuit 140 located in the instrument section 54 of the drilling assembly 42 is located. A detailed description of the structure of the drilling assembly can be found in the US patent application 891 679. The plug connection 110 on the operating control unit 100 is connected to the instrument section via the cable 60 (FIG. 2) 54 is connected via the plug connection 42 of the control circuit 140. The feed lines 104, 106 and 108 go directly to a 12 volt voltage regulator 144, which outputs the voltage required for the regulator, via two lines 146 and 148 a positive 12 volt voltage is fed from the voltage regulator 44 to a high voltage supply source 150, which is connected to a BICRON counter tube 152 delivers a voltage of 1200 V. The BICRON counter tube 152 is a commercially available gamma ray counter tube model 2M2P made by BICRON Corporation. The gamma ray count output on the order of about 2 V can be used on line 154 as an input for a preamplifier / integrated circuit 156 of IC-Type 715393 can be removed. The output from the preamp 156 at point 158 is fed back to the preamplifier input via a resistor and capacitor network 160 as feedback. A diode 162 ensures the suppression of any negative voltage peaks.

The gamma ray count output from terminal 58 is fed to a level limiter circuit 164 in the form of an integrated circuit Dual NOR element of type CM 4001 supplied. The circuit 164 is locked so that it is only exceeded when one Limit value emits an output signal. The output signal appearing at junction 166 is then fed to the input of an integrator 168, which is designed as an operational amplifier in an integrated circuit, for example of the MC1741 type. The integration of the output signal at output terminal 170 of the operator

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tion amplifier is provided by feedback through a capacitor and resistor timing network 172, and the integrated output signal is connected via a line 174 to a resistor network of resistor 176 in series with a calibration potentiometer and fed to an adjoining resistor 180.

The potentiometer 178 forms a gamma count calibration setting, if a signal arrives at one input of a VA converter 182, a DC voltage amplifier, which is sent to its second Input is connected to a DC reference voltage source. The converter 182 is an integrated circuit of the type MC1741 formed, whose output signals are present at connection point 184 and via line 130 to counter value indicator 124 in the actuation control unit 100 (Figure 7) are reported back. The output on line 130 is in the form of a current reading so that the meter 124 is the Displays the instantaneous gamma ray count as detected by the BICRON counter tube 152.

The slope value of the drilling assembly 32 is determined with the aid of an accelerometer 186, the output signal of which is fed to a VA converter amplifier 188 of the MC1741 type. The converter amplifier receives the reference input signal from the operator control unit 100 via the line 122. The output signal of amplifier 188 returns via line 132 to the inclinometer or display instrument 126 of the control unit. Accelerometer 186 detects static displacement, as does the Columbia Columbia Type SA107 device Research Laboratories does. The accelerometer 186 provides a continuous DC voltage output that corresponds to the set The tilt angle is proportional, with a signal between 0 and 5 V corresponding to the tilt angle range between 0 and 90 °.

The rotation is carried out in a similar way with the help of an accelerator

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inclinometer 190 found, the output signal of a identical circuit with VA converter amplifier 192 is fed. The amplifier 192 is similarly using a Zero balance reference input biased via control line 122 and the output voltage, which represents a measure of the rotation of the drilling unit, is sent on a line 134 to the Rotation indicating instrument 128 is returned in the control unit 100.

The guidance control of the drill 32 is from the place of work The subject of U.S. Patent 3,888,319. The operator can, based on the readings of the count, tilt and rotation, on the appropriate Displays 124, 126 and 128 continuously the drill 32 with respect to the layer of earth above and / or below it.

Initial measurement data for the gamma ray count is obtained at each individual seam location within the first section of the borehole (Figure 1), or other, more direct counting means can be used can be used. After the gamma ray absorption coefficient of the coal seam per unit length has been determined, the calibration potentiometer 178 (FIG. 8) can be set to one desired value can be adjusted, whereupon a long drilling distance can be driven, with the exact gamma counts are displayed in counter value display instrument 126 (and thus the position of the drilling machine in relation to the interface).

The method described above is suitable for the control a drilling machine through a mineral seam, especially for drilling exploratory boreholes through horizontal ones Coal seams that lie above or below layers of alumina. In the method according to the invention, it is those in the alumina layers Existing natural radioactivity is exploited, since layers of alumina can almost always be found in the vicinity of coal deposits this control method can be used for drilling probing

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drilling holes can be used in practically all cases.

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L e r s e i t e

Claims (6)

29U607 10674 / Mü / Elf U.S. Ser.No.972,656 of December 26, 1978 CONOCO INC., Ponca City, OkI. 74601 (V.St.A.) Patent claims: 1.) Method for guiding an earth boring machine in a selected one Earth layer, characterized in that first a bore into the layer up to one A certain depth is introduced and the gamma radiation hitting the drill at this point is determined and a count is determined, and that the drilling continues for a predetermined distance through the layer and the drill thereby is performed in such a way that the counting speed is kept approximately at the same value. 2.) The method according to claim 1, characterized that the initial bore is sufficiently deep that the natural gamma radiation prevailing there without distorting external radiation influences can be determined. 030028/0558 ORIGINAL INSPECTED 29U607 3.) The method according to claim 1, characterized in that the selected layer of earth is a coal seam is in a substantially horizontal position and that the gamma radiation from the alumina deposits adjacent to the coal seam originates. 4.) The method according to claim 3, characterized that the gamma radiation count is determined at the first depth in order to determine the gamma radiation absorption of the Determine coal seams at a certain distance from the adjacent alumina layer, and that then inclination and Rotation of the drilling machine during the further course of drilling can be selected so that the gamma radiation count between predetermined Limit values fluctuates. 5.) The method according to claim 4, characterized that the measured gamma ray count and the predetermined limit values are continuously compared with one another to automatically control the drill. 6.) The method according to claim 1, characterized that the course of the direction of the drill with the help of a received at a remote control location display of the Gamma radiation counts is controlled. 030028/05 5 6