CN1389743A - Acoustic resonance method of measuring sand flow cavity volume - Google Patents

Abstract

A hollow volume formed by sand inflow from oil well and its measurement method features in that the measurement system comprises sound source and sound wave received, transducer to fully use the resonance phenomenon of liquid at the mouth of the hollow between sound source and the received transducer to determine the hollow volume using the extremely small value of the received signal frequency spectrum. Sound source may be a pulse source similar to electric sparks signal source or moving coil, piezoelectric, magnetostriction and mechanical transducer excited by electric signals. The resonance frequency at the hollow mouth is determined by frequency spectrum analysis either with hardware or software.

Description

A kind of method of measuring sand flow cavity volume with acoustic resonance

The present invention relates to a kind ofly measure the method for sand flow cavity volume with acoustic resonance, it is the method that belong to applied geophysics, petroleum engineering field a kind of measures the empty volume that sand production causes.It mainly is the method that adopted sound wave measuring system to combine with specific hole mathematical model determine the to shake out volume in hole.

At present, in oil formation testing and petroleum production engineering, because aspects such as geologic condition and exploitation construction sand production can occur and form the stratum cavitation.Shake out and may stop up on the one hand oil pipe and also may destroy geologic structure on the other hand and cause the oil well underproduction even stopping production.So the sand control construction is a crucial job.Owing to the volume that does not also have means to the hole that shakes out now both at home and abroad carries out quantitative measurment.Therefore, make the sand control construction have certain blindness, success ratio to have a greatly reduced quality.The object of the present invention is to provide a kind of method of the empty volume that can cause at the measurement sand production of down-hole use, it is to have adopted in pit shaft to be measured sound wave measuring system is set, and the hole that will shake out is specific for certain mathematical model, utilizes the minimal value of received signal frequency spectrum to determine the volume in cavity then.Thereby can improve measuring accuracy widely and improve the efficient of sand control construction.This method mainly is to have adopted the method that combines of sound wave measuring system and specific hole mathematical model, its major technology characteristics are that the measuring system that is adopted is to be made of sound source and sound wave receiving transducer, and be arranged among the pit shaft to be measured, the cavity that shakes out in the pit shaft to be measured is set at specific hole mathematical model, by the resonance effect of mouthful place's liquid of existing cavity between measurement sound source and the receiver, and utilize the minimal value of received signal frequency spectrum to determine empty volume; The mathematical modulo in its hole that shakes out is a heimholtz resonator, and the resonance frequency of its hole mouth is: $f_r=\frac{c}{2\mathrm{\π}}\sqrt{\frac{S}{\mathrm{Vl}}},$ In the formula, S is the sectional area at hole, and l is the length at hole, and V is a cavity volume, and c is the velocity of sound of empty inner fluid; Employed sound source can be an impulse source that is similar to the spark signal source, also can be the signal source that can send the frequency sweep sound wave continuously.

Below in conjunction with embodiment in detail technical characterstic of the present invention is described in detail.

In actual design and construction, the deviser is the method for the present invention that realizes like this: measuring system is made of a sound source and an acoustic receiver and corresponding measurement mechanism, and is shown in the pit shaft by accompanying drawing 1 and is provided with.During measurement, measuring system is carried on transferring to the bottom of measuring well section, and measures last carrying in the process.Sound source is propagated to receiving transducer one side in in-hole fluid after sending acoustic signals.If a perf (borehole) is arranged send out receiving between the probe, and the sleeve pipe external cause shakes out and has a cavity of a certain volume, and the fluid of then should cavity mouth (borehole) locating will vibrate.When the resonance frequency of the frequency of sound wave and hole fluid was identical, resonance took place and the strong absorption acoustic wave energy in the fluid at mouthful place, cavity, and then the signal of this frequency content that receives of receiving transducer is a minimal value for other frequency content signal.The acoustic model of the fluid oscillation at place, cavity is set at heimholtz resonator as shown in Figure 2.This model is an open containers of being made up of cavity and short tube, and hypothesis satisfies: the dimension of (1) cavity (hole) volume V is much smaller than wave length of sound.(2) volume of short tube is much smaller than the hole volume.(3) medium compression and when expanding in the hole, the hole wall can not be out of shape.So the fluid in the short tube at hole mouth place is done body vibration just as one " piston ", its resonance frequency is $f_r=\frac{c}{2\mathrm{\π}}\sqrt{\frac{S}{\mathrm{Vl}}}$ In the formula, S is the sectional area of short tube (borehole), and l is the length (can be taken as the thickness of sleeve pipe) of short tube, and V is a cavity volume, and c is the velocity of sound of empty inner fluid.As seen, as long as accurately measure the minimal value of the frequency spectrum of received signal, just can determine the resonant frequency of the fluid oscillation at mouthful place, cavity, and then can calculate the cavity volume that shakes out according to formula (1).If the thickness of getting sleeve pipe is the diameter of 10mm, borehole is that the velocity of sound of liquid in 10mm, the cavity is 1550m/s, when the variation range of empty volume is 0.01m ³～5m ³The time, the scope that requires frequency of sound wave is 10Hz～300Hz.

Measuring system is carried on the bottom of well section to be measured begins, and measures in last each depth point of carrying in the process, and this method has two kinds of metering systems.(1) frequency sweep working method

Press measuring principle shown in the accompanying drawing 1, repeatedly encourage sonic probe to make it to launch the frequency sweep acoustic signals with the frequency sweep electric signal, the scope of frequency of sound wave is 10Hz～300Hz, and the frequency spectrum of the signal that receiving transducer is received is analyzed, minimal value by the received signal frequency spectrum is determined resonance frequency, again by $f_r=\frac{c}{2\mathrm{\π}}\sqrt{\frac{S}{\mathrm{Vl}}}$ The calculating cavity volume that shakes out.This moment, sound source was moving-coil type or piezoelectric type or a magnetostriction type or a mechanical type transducer that is encouraged by electric signal.(2) pulsed mode

By measuring principle shown in Figure 1, employing is similar to the broadband laser pulse focus of sparker source as sound source, and the pulsed sound that it produces is propagated in well, and the time-domain signal that receiving transducer is received carries out spectrum analysis, minimal value by the received signal frequency spectrum is determined resonance frequency, again by $f_r=\frac{c}{2\mathrm{\π}}\sqrt{\frac{S}{\mathrm{Vl}}}$ The calculating cavity volume that shakes out.

The acoustic measurement method of the measurement sand flow cavity volume that the present invention proposes, the shape in measurement result and hole is irrelevant.Therefore, do not require the systematicness of void shape.Its measuring method reliability height, be easy to realize, cost is low, has great promotion and application prospect.

Claims (3)

1. method of measuring sand flow cavity volume with acoustic resonance, it mainly is the method that combines that has adopted sound wave measuring system and specific hole mathematical model, it is characterized in that the measuring system that is adopted is to be made of sound source and sound wave receiving transducer, and be arranged among the pit shaft to be measured, the cavity that shakes out in the pit shaft to be measured is set at specific hole mathematical model, by the resonance effect of mouthful place's liquid of existing cavity between measurement sound source and the receiver, and utilize the minimal value of received signal frequency spectrum to determine empty volume.

2. a kind of method according to claim 1 with acoustic resonance measurement sand flow cavity volume, the mathematical modulo that it is characterized in that the described hole that shakes out is a heimholtz resonator, the resonance frequency of its hole mouth is: $f_r=\frac{c}{2\mathrm{\π}}\sqrt{\frac{S}{\mathrm{Vl}}}$ Wherein, S is the sectional area at hole, and l is the length at hole, and V is a cavity volume, and c is the velocity of sound of empty inner fluid.

3. a kind of method of measuring sand flow cavity volume with acoustic resonance according to claim 1, it is characterized in that described sound source can be an impulse source that is similar to the spark signal source, also can be the signal source that can send the frequency sweep sound wave continuously.