SU551586A1 - A device for recording pressure pulses - Google Patents

Description

one

The invention relates to the field of geophysical methods of exploration and can be used when conducting borehole seismic surveys.

A device for recording pressure pulses in a well should have a high sensitivity over the entire seismic frequency range. The sensitivity of the instrument should not depend on the depth of the instrument.

Membrane-type transducers, which represent an elastic disk (membrane) with a bending piezoelectric element fixed on it, are most sensitive. The membrane is one of the walls of the receiving chamber, filled with a compressible liquid or gas. Such a sensor does not withstand large one-sided (external) pressure when the device is lowered to a great depth, and therefore external pressure must be compensated from the inside.

For this circuit, a compensation chamber is used, which is connected to the external environment through an elastic diaphragm, and to the receiving chamber - a channel. Both chambers are filled with compressible, for example, silicone fluid or gas. The rate of flow of liquid from the compensation chamber to the receiving chamber and, consequently, the speed of compensation of external pressure on the membrane depends on the channel cross section, its length and the viscosity of the liquid. In order to increase the sensitivity of the device, it is desirable that pressure changes due to seismic pulses are not compensated The channel must perform the function of a low-frequency filter: c. Amplify the slowly varying pressure when the device is lowered into the well and eliminate the effect of pressure on the seismic pulse friction side of the diaphragm.

In a known device for compensating hydrostatic pressure, compressed air is used. The design of the compensator contains a special reservoir of rubber filled with air and connected to the internal cavity of the sensor through a small hole, a system of pistons and springs, which serve to regulate the air pressure in the internal cavity by varying its burning effect when the external pressure changes. However, such a device, due to the high compressibility of air, despite its cumbersome nature and complexity, still does not ensure the operation of the hydrophone in the required depth range used in deep-sea exploration.

In a device for recording pressure pulses in downhole studies, a long capillary tube is used as a hydraulic throttle. It also connects the compensation chamber to the internal cavity of the receiving chamber and serves to flow the filling bone with slow pressure changes. This device ensures the operation of a receiver with significant changes in hydrostatic pressure, but when registering a low frequency band (in the seismic range), the capillary tube must be very short and long, which causes discomfort during fabrication. and exploitation. A device is known for recording pulses with a pressure of 1 5 for example; for well drilling seismic studies containing an inverter. for example membrane type, receiving and compensating chambers, connected channels ;. In this device, a wide channel is housed a soleoid, and the channel and the additional chamber are filled with a magnetic dip and separated from the receiving chamber filled with a nonmagnetic liquid::.:; Cf:: Ez by an elastic partition. When about :: the magnetic field of the magnetic field (the solanoad winding is de-energized), the magnetic fluid has a low viscosity and freely transfers the pressure change from the outside to the inside of the receiving chamber. After installing the device at the desired depth, a magnetic field is created around the channel by applying current to the coil of the saltoid. If there is a magnetic field, the liquid increases its viscosity, the channel acquires the properties of a low-pass filter in a single-sided oscillation mode BiijTpb: ,; era. According to the workers and the measurements of the co-current, the viscosity of the magnet is de-energized; it decreases: once again, the free and fast transfer of pressure from the compensation chamber to the receiving chamber is possible. However, the presence of an elastic partition separating the channel from the receiving chamber, the solenoid d placed around the channel complicates the design: 5s1 increases the size and decreases the reliability of the device, and the objective is to simplify the KOHCTpj-rciu: pressure.

This is achieved by placing a plunger with a diameter in the channel that provides an annular gap with the properties of a capillary, and on the side of the receiving chamber the plunger is spring-loaded with an elastic element.

The drawing shows a device for registering pressure pulses; general form.

Claims (1)

The device consists of a well 3 filled with drilling mud 2, a housing 3 with holes 4, which is lowered on a logging cable 1. Inside the housing 3 there is a transducer, which is an elastic membrane 5 with a bending piezo element 6 fixed on it. The membrane 5 blocks the receiving chamber 7, connected by channel 8 with compensation chamber 9. Both chambers and their connecting channel are filled with compressible, for example, silicone fluid. The compensation chamber is separated from the liquid 2 filling the well with a rubber diaphragm 10. A plunger 11 with a diameter smaller than the channel diameter by a certain value is located in the connecting channel so that the annular gap has the properties of a capillary. The connecting channel on the side of the compensation chamber 9 has protrusions 12 that prevent the output of the plug 11 into the compensation cameo. From the receiving chamber side, the plunger 11 is compressed by a spring 13, the other end of which rests on the grate 14, which overlaps the channel. The device works as follows. In the normal state, the plunger 11 is pressed to the protrusions 12. When the device is lowered to the bottom of the well, the hydrostatic pressure increases, which affects both the rubber diaphragm 10 and the membrane 5. The compressible fluid inside the device through the annular gap between the plunger 11 and the wall of the channel 8 begins flow into the receiving chamber 7. Thus, the external pressure on the membrane is compensated 5. If the hydrostatic pressure returns, it melts so quickly that, due to the limited capacity of the annular gap (gap), Itza between the pressures in the compensating and receiving chambers is achieved a certain amount plunger 11 is biased toward the acceptance chamber 7. As a result of this pressure equalization takes place on the membrane 5 is prevented and the destruction of the latter. In addition, the mobility of the plunger 11, the surface of which is one of the walls of the thin slit, prevents obliteration (blockage of the slit). After that, as the device is lowered and set to the desired depth, elastic oscillations are excited in the medium, which in the form of pressure pulses affect the membrane 5 of the sensing element 6 and the rubber diaphragm 10. The alternating rapid pressure fluctuations that occur in the compensation chamber 9 are incapable transfer the liquid from the compensation chamber to the receiving chamber and vice versa. The amplitude of pressure fluctuations is insufficient for displacement of the plunger 11; The force of the spring 13 to the protrusions 1. Thus, the useful pressure wave acts on the membrane 5 from the outer side and, as a result of the deformation, the transducer produces electric oscillations. At the end of the measurement, the device is picked up and installed at the next measurement point. The distance between the observation points is 10–50 m, the ascent rate does not exceed 1-2 km / h. The change in hydrostatic pressure is reliably reliably compensated through the annular gap. Frequent stops for measurements help to better balance the pressures inside the receiving chamber and the external space. Even in the case of an excessively rapid rise of the instrument (which in itself is a violation of the technical standards for logging), due to its stops for receiving useful waves, there will not be a large pressure difference inside and outside the receiving chamber capable of disabling the membrane and the instrument. In this way, the proposed device, in comparison with the known, allows to simplify the design by eliminating the solenoid and magnetic fluid and to increase the reliability of the compensation of hydrostatic pressure. Apparatus for recording pressure pulses, for example, in borehole seismic surveys, comprising a transducer, for example, of a membrane type, receiving and compensating chambers connected by a channel, characterized in that, in order to simplify the design and increase the reliability of the device, a plunger is located in the channel with a diameter that provides an annular gap with the properties of a capillary, and on the side of the receiving chamber the plunger is spring-loaded with an elastic element. ten 9 12