SU953999A3 - Method and apparatus for nuclear magnetic logging - Google Patents

Description

The invention relates to geophysical prospecting and can be used in nuclear magnetic logging in the exploration of oil wells. A nuclear magnetic logging device is known, comprising a surface unit consisting of an alternator, an amplifier and a recorder, and a downhole probe consisting of a receiving coil, a preamplifier connected through a switch to the coil pins, a rectifier connected to the gene The ac unit is acted by the surface unit and through a switch with the ends of the plug; the electrical connection of the downhole probe with the surface unit is made via a wireline cable. The alternating current of the alternating current generator of the surface block is fed through a logging cable to a rectifier, from the output of which goes through a switch to a polarizing receiving coil and polarizes the protons in water, oil and gas surrounding the well. After a polarizing tick has been applied for a time sufficient to create a polarization of protons (5O ms), the polarization current is turned off and the protrists begin to compress in the earth's magnetic field, inducing an emf in the polarizing receiving coil. This signal (at a frequency of about 2 kHz) is amplified by a preamplifier, fed through a logging cable to an amplifier and resistor. The magnitude of the amplitude of the induced signal, the rate of its attenuation judge the type of mineral resources and the potential of l deposits. The disadvantages of this device are the short polarization time, the need for frequent repetition of the polarization cycle in reception, the large power required for the polarization of protons, and the short signal reception time (100 ms). The closest to the invention in its technical essence is the method and device of the nuclear map logging, in which the signals from the alternating go signal are supplied to the load, which is a transformer with an iron core, and each sequence: gi starts and ends at zero amplitude, memorization of the polarity of the last half-period of the previous signal, launching the pic signal in the sequence of polarity n the first- half cycle of opposite polarity to the last previous signal poluperio- od 2.

A disadvantage of the known device is the relatively long time during which the load transformer closes and opens due to the long time of the transition process of the load transformer.

The aim of the invention is to increase speed and reliability.

The goal is achieved in that, according to the method of nuclear magnetic logging, which involves applying a sequence of alternating current signals from an alternating current power source to a load, each signal in the sequence starting and ending with a zero amplitude, remembering the polarity of the last half-period of the previous signal, triggering the subsequent signal in the sequence with the polarity of the first continuous period of the opposite polarity of the last half-period of the previous signal, each signal is The sequence contains an odd number of half-cycles of alternating current. The time period during which the sequence of alternating current signals is applied to the load is short compared with the duration of the transient process required to reach steady-state in the load,

In addition, in the device for carrying out the method comprising a surface unit consisting of an alternating current power source, a first transformer, an alternating current signal supply circuit from an alternating current power source to the first transformer, a downhole ssh having a polarizing receiving coil, a second Transform the Agora, the primary winding of which is connected to the secondary winding of the darksky transformer of the surface unit, the rectifier connected to the secondary winding of the second transformer, ne eklyuchatel for connecting floor rizuyusche-up spool to vyhopu vtr DC converter, and a memory circuit, drive circuit and disconnecting AC signal sequence diagram; Memories, start-up and disconnection circuits for alternating current signals are located in the surface block.

 On 4ig. 1 shows the block.: Hema. device magnetic magnetic logging; in fig. 2 is a valuable electrical schematic drawing illustrating a switch when a signal has zero amplitude between an AC power source and a transformer load of a nuclear magnetic logging device; FIG. 3 - alternating current signals supplied through a switch to the transformer load of the local device; in fig. 4 - Hysteresis loops of an iron-core transformer (B – H diagrams) illustrating an increase in current emissions in an iron-core transformer driven by alternating current during duty cycles that have a duration shorter than the transient time; in fig. 5 - iron core transformer hysteresis loops (B – H diagrams) illustrating the transition from the state with the initial magnetization To a stationary state after being excited by an alternating current signal; in fig. 6 is a sequence of AC signals used in the proposed method and device; in fig. 7 is a schematic drawing of a device with a switch and a diagram thereof. management; in fig. 8 is an electronic control circuit of the device switch; in fig. 9-15 are the voltage plots at the inputs and outputs of the microcircuits used in the electronic control circuit of the device switch.

An apparatus for carrying out the method comprises a surface unit 1 consisting of an alternating current power source 2, a first transformer 3, a circuit 4 supplying a sequence of alternating current signals from an alternating current power source to the first transformer, a downhole probe 5 having a receive receiving coil 6, the second transformer 7, the rectifier 8, the switch 9 and the amplifier 1O. Besides . this, the surface unit comprises a synchronization circuit 11, a receiver 12 and a recording device 13, and the surface unit is connected to the probe by a logging cable 14.

Claims (2)

The device works in the following way. The or HcrcfHHHKa 2 signal for supplying the alternating gok posgupag through the circuit of 4 alternating and alternating gok signals of the first transformer 3, the output GOK of which through the logging cable 14 goes to the second transformer 7 of the lower probe 5. Extracting current of the second transformer 7 is rectified by an extractor 8 and arrives at the terminals of the hiluminescence receiving coil b through the switch 9 at the times when the protons of the substance surrounding the probe are polarized. The switch 9 connects the leads of the polysuk tse-receiving coil 6 to the input of the amplifier 10 at the moments of measurement of the precession signal. The precession signal from the amplifier output goes through the logging cable 14 to the receiver 12 and is fixed by the recording device 13. The synchronization circuit Li controls the operation of the switch 9. In FIG. 2 shows a schematic connection of an alternating current power source 2 through a circuit 4 for feeding an alternating current signal sequence to a first transformer 3, the output of which is connected to a transformer load, depicted as a resistor 15. load. FIG. 3 shows a sequence of signals arriving at a transformer in a known device (FIG. 2). In this case, the signal begins, as a rule, with. half a half period and ends with a negative bye; and a period and contains an even number of half periods of the signal. In this case, the residual magnetization of the transformer core moves up along the B axis in the hysteresis diagram B – H {4ig. 4), as a result of which there are more and more large emissions of H (or current). The transition from the state with the initial magnetization PQ of the transformer core to the steady state is shown in the hysteresis diagram (Fig. 5). FIG. Figure 7 shows schematically the functional features of the circuit for supplying a sequence of AC signals from an AC power source to the first transformer. The AC power source 2 is connected to the first transformer 3 through a simple switch 16 of the alternating current signal supply circuit 4, which is equipped with a control circuit 17. The electronic control circuit responds to the reference voltage received from the source 18 of the reference voltage, and the previous sequence signals arriving at the transformer 3. The electronic control circuit 17 (FIG. 8) contains comparators 19 and 20, And 21 and 22 comparators, trggs 23, 24 and 25 and the NOT / OR valve circuits. The voltage plots obtained at the outputs of the elements of the control electronic circuit 17 are shown in FIG. 9 - 15. In FIG. 9 shows plots of the reference voltage supplied to the input of the electronic control circuit 17, FIG. U-Eshor voltage at the output of the trigger 25, FIG. 11 and 12-voltage plots at the first and second outputs of the trigger 24, 4ig. 13 shows the output voltages of the valve 26; FIG. 14 shows the voltage levels at the output of the flip-flop 23, and FIG. 15 shows output voltage diagrams of the control circuit 17. The proposed method and device make it possible to increase the speed and reliability of the device operation, which improves the accuracy of measurements when reading minerals, including water, oil, Gas, and reduces costs when searching for them. Claim 1. Method of nuclear magnetic logging, including the supply of alternating current signal sequence from an alternating current power source to a load, each signal in the sequence starting and ending at zero amplitude, remembering the polarity of the last control of the previous sipsal, launching the aftergrowth signal sequences with the polarity of the first output of the opposite polarity of the last half period of the previous signal, characterized in that, in order to increase the performance and reliability, each sequence signal contains an odd number of half-cycles of alternating current. 2. The method according to clause I, which is said to be so that the period of time during which the sequence of alternating current signals is applied to the load is small compared with the duration of the transient process required to reach the load steady state. 3. Device for the implementation of the manual for PP. 1 and 2, containing a surface unit, consisting of a mixing power source, a first transformer, an alternating ga sequence signal supply circuit from an alternating current power source to the first transformer, a borehole unit having a Poliguc-type receiving coil, a second transformer, primary winding which is connected to the secondary winding of the first transformer of the surface unit, a rectifier connected to the secondary winding of the second transformer, a switch for connecting the receiver to the receiver coils to the rectifier output, as well as a memory circuit, a start-up and shut-down sequence of alternating current signals, characterized in that the memory circuit, start-up and shutdown sequences of the e sequence (ac power signals are located in the surface unit. , taken into account that review 1. US Patent 3667О35, CL 324-О.5, published 1972. 2. US patent N 4dl2712, cl. 324-O.5, published. 1977. i V. i: s R N f5 rb I t, i, Reference signal Z3 20 years SI / 7I 4f Phi1.8 Lalladallalld Fi. ten Ф14г. eleven