GB1599067A - Ultrasonic testing - Google Patents
Ultrasonic testing Download PDFInfo
- Publication number
- GB1599067A GB1599067A GB720978A GB720978A GB1599067A GB 1599067 A GB1599067 A GB 1599067A GB 720978 A GB720978 A GB 720978A GB 720978 A GB720978 A GB 720978A GB 1599067 A GB1599067 A GB 1599067A
- Authority
- GB
- United Kingdom
- Prior art keywords
- transmitter
- amplitude
- pulse
- distance
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
- G01V1/40—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging
- G01V1/44—Seismology; Seismic or acoustic prospecting or detecting specially adapted for well-logging using generators and receivers in the same well
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/02—Analysing fluids
- G01N29/032—Analysing fluids by measuring attenuation of acoustic waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/015—Attenuation, scattering
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/024—Mixtures
- G01N2291/02441—Liquids in porous solids
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02818—Density, viscosity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0421—Longitudinal waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/04—Wave modes and trajectories
- G01N2291/042—Wave modes
- G01N2291/0428—Mode conversion
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/10—Number of transducers
- G01N2291/103—Number of transducers one emitter, two or more receivers
Description
(54) IMPROVEMENTS IN OR RELATING TO ULTRASONIC TESTING
(71) I, SECRETARY OF STATE FOR ENERGY, London, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed. to be particularly described in and by the following statement:
This invention relates to ultrasonic testing, and is more especially, but not exclusively, concerned with methods by which information can be obtained about rock surrounding a borehole, including the viscosity of any liquid in the pores of the rock.
It has been usual in ultrasonic testing. as applied to the rock surrounding a borehole, to rely on reflection of ultrasonic vibrations from discontinuities in the rock. Such methods have limitations in that receipt of information is dependent on the existence and location of such discontinuities; whereas the information might have more desirably been obtained from a different location. The present invention provides a method which allows the usefulness of ultrasonic testing from boreholes to be improved in scope.
According to one aspect of the invention a method of ultrasonic testing of porous material containing liquid comprises the steps of
(i) transmitting from a transmitter a pulse of a first amplitude of ultrasonic vibrations
into said material
(ii) receiving at a receiver a signal consisting of back scattered ultrasonic vibrations from
said pulse
(iii) from a sample of the back scattered signal calculating a first attenuation coefficient
at a first distance from the transmitter at which the viscosity of liquid in said porous
material is known
(iv) repeating steps (i), (ii) and (iii) with a transmitted pulse of a second, different,
amplitude to calculate a second attenuation coefficient (vtransmitting pulses of said first and second amplitudes, and receiving corresponding
back scattered signals from a second different distance from the transmitter
(vi) using the known first and second attenuation coefficients and the known viscosity of
liquid at the first distance calculating the viscosity of liquid at said second distance, in said
porous material, from the transmitter.
Desirably a received signal, derived from a given transmitted pulse, is sampled over a short period, in integrated over said period, and the result used to calculate the attenuation coefficient for the corresponding distance from the transmitter.
Preferably the calculation step or steps include calculating the logarithm of the amplitude of the received back scattered signal; and preferably further calculating the derivative of the logarithm of the amplitude of the received back scattered signal with respect to the distance from the transmitter from which signals are back scattered.
In particular the method according to the invention is applicable to rock having pores containing petroleum.
The invention will be further explained and described by way of example.
The invention may be applied more especially to determine the viscosity of liquid, eg petroleum. which may lie in porous rock in the vicinity of a borehole.
Consider a pulse of ultrasonic vibrations through a medium comprising porous rock, the pores of which contain a liquid of viscosity TI The pulse leaves the transmitter with an amplitude Ao, and after travelling a distance i the amplitude has fallen to A. In the case (taken for simplicity) of a plane wave the amplitude A is given by the equation
A = Aol -α# .... (1) where a is the attenuation coefficient.Differentiating shows that the attenuation coefficient is numerically equal to d log A
dr
The attenuation coefficient may be obtained in one way by calculating electronically the logarithm of the amplitude of the back scattered signal (log A), displaying it along, say, the Y - axis of an oscilloscope screen, displaying the distance r from the transmitter along the X - axis, and measuring the slope of the curve so displayed.
The attenuation coefficient can be considered as the sum of two parts, that is a = X + YA ........ (2)
The part X is independent of amplitude of the pulse, whereas the part YA is amplitude dependent. It can be written in the form KTI (o A, where K is a structural factor related to the nature of the rock in which the borehole is situated, TI is the viscosity of any liquid contained in pores in the rock, and co = 2 Tr f, where f is the frequency of ultrasonic vbrations used in testing. Usually the part X of the expression is considerably larger numerically than the part YA.The attenuation coefficient may be expressed as a = X + K TI lo A ........ (3) In order to operate the method of the invention a suitable ultrasonic transmitter and receiver are arranged in the borehole at a required depth, connected back electrically to power supplies, control and measuring equipment at the ground surface.
Pulses of ultrasonic vibration are transmitted into the rock successively with different amplitudes to give corresponding attenuation coefficients al and a2 calculated for a region close to the borehole. This is a region of rock which will have been fully penetrated by the drilling fluid, for which the viscosity will be known with reasonable accuracy. Substituting corresponding values in equation (3) gives α 1 = X + K#1 # Al ........ (4) α 2 = X + K#1 # A2 ........ (5)
whence K = αl - α2 .... (6) #1 # (A1 - A2) where #1 is the known viscosity of the drilling fluid.
The structural factor K obtained from equation (6) is assumed not to change substantially between the region close to the borehole, where the rock is permeated with drilling fluid, and a locality more remote from the borehole where the rock may be expected to contain oil. Pulses of differing amplitude are again transmitted into the rock and the corresponding attenuation coefficients calculated, but from back scattered signals from the more remote locality. Then, with the assumption that the structural factor K has remained constant, the viscosity Tl2 at the remote locality can be calculated.
A convenient manner of obtaining the attenuation coefficient in any instance is to apply a strobe arrangement (in the control and measuring equipment) to the received back scattered signal, so that the signal is sampled over a short period, is integrated over said period, and the result used for calculating the attenuation coefficient for the corresponding distance from the transmitter from which the back scattered signal was received. The time delay for the received signal is measured in relation to the transmitted pulse which gave rise to it; as accurate a figure as may be available for the velocity of sound in the rock is then used to convert the time delay to a measure of the distance.
In obtaining values of attenuation coefficient it has been found advantageous to make a plurality of measurements, say 50, relating to any required distance from the borehole, and taking the average of those measurements.
The structural factor K depends, amongst other things, on the acoustical impedance of the rock and the permeability of any pores in the rock to fluid flow. Hence determination of K can provide information regarding the permeability of the rock.
In the method of the invention as exemplified above, the same transducer may be used as transmitter and as receiver for the ultrasonic vibrations; but this is not an essential feature.
The value of K may be obtained by using an acoustic logging tool having three transducers in line, ie along the borehole, using one for transmitting and the other two, at different distances from the first, for receiving. Alternatively two transmitters and one receiver can be employed. The attenuation coefficient for the rock adjacent to the borehole can be evaluated by comparing the amplitude of the signal received after traversing two different distances in the rock, and then a value for K can be obtained using a transmitted signal of a different amplitude, and the principle exemplified in equations (3) to (6).
Ultrasonic frequencies are particularly useful in this invention. However, the principle of the method of the invention is also applicable at lower sound frequencies, as far down as the audio range.
The method according to the invention has been exemplified with reference to the investigation of petroleum bearing rock; but it is in principle applicable to other mixed substances not chemically combined. It may be applied in general to fluid soaked porous solids, saturated sediments and even to gas/liquid mists.
The method of the invention can be employed in a borehole which has already been provided with a metal liner pipe. Moreover, the method can be applied repeatedly, even after production has been begun, in order to check on depletion of an oil well.
Suitable borehole logging tools will be described briefly, with reference to the accompanying drawings in which
Fig 1 illustrates a horizontal logging tool.
Fig 2 is a response curve for the tool of Fig 1.
Fig 3 illustrates a vertical logging tool.
Fig 4 is a response curve for the tool of Fig 3.
The horizontal logging tool (Fig 1) transmits ultrasound at right angles to the borehole wall at a frequency decided approximately by the order of magnitude of the pore size, and receives a signal due to an effect known as back scattering. The waves are pulsed, and the return from one of the resulting bursts of ultrasound is shown in Fig 2. Statistical averaging gives a smooth curve. Using a reasonably accurate estimate for velocity of the ultrasound, the time axis of Fig 2 can be converted to represent the depth from which any section of the return signal originated. Thus variations of the structural factor K along a radius out from the borehole may be determined.
Fig 3 illustrates a vertical logging tool. Pulses are transmitted at an angle to the horizontal so that they are refracted at the borehole wall and subsequently travel parallel to the walls, as in Fig 3. Such an arrangement is already usual in tools determining the velocity of ultrasound.
Fig 4 shows how signals corresponding to two different amplitudes are received by R1 and
R2 (receiving transducers), and fed to a common display and/or data record. On-the-spot trials reveal the best permutation of different transmitted amplitudes, numbers of receiving transducers and their spacing, required to give optimum results in determining K.
It is envisaged that the vertical logging tool will determine K wholly in the zone surrounding the borehole, which has been saturated with drilling fluid.
Because of the angle of incidence of the transmitted ultrasound at the borehole wall, a phenomenon known as mode conversion occurs. When sound travels through a solid, its vibrations may be parallel to the direction of travel (longitudinal waves) or at right angles to it (transverse waves). When longitudinal waves are transmitted, a proportion of their energy converts to transverse waves at the wall, both types of wave travel through the rock, and both types convert back to longitudinal waves upon re-entering the liquid filled borehole. Travelling at approximately half the speed of longitudinal waves, transverse waves produce delayed arrivals omitted from Fig 4 for simplicity. Propagating vertically, but vibrating in the horizontal plane, the coefficient K will be affected by horizontal permeability.It is envisaged that it will in fact be these waves which are manipulated to give
K, more especially since it is horizontal permeability that is important in the recovery of down-hole fluids.
A further device is an angle of dip logging tool. Tests with cylindrical plugs of sandstone, taken from core samples, revealed that the level of attenuation is very sensitive to the angle of the bedding planes. Being built up of consolidated layers of sediment, subtle changes in the nature of the particles and the bonding material over geological periods, give rise to these planes.
Careful microscopic analysis has been unable to detect such bedding, but this is in keeping with the ability of ultrasonic waves to detect physical characteristics to which more conventional techniques are insensitive. Thus a further device can be designed to measure the angle of dip of the bedding planes within the rock structure, based upon the same fundamental theory as the other tools.
A further technique usable in borehole logging is spectral analysis. A spectrum of ultrasonic frequencies is transmitted, and the difference between it and the spectrum received having passed through material surrounding the borehole, is analysed and related to various known factors in order to obtain further information.
WHAT I CLAIM IS:
1. A method of ultrasonic testing of porous material, containing liquid, which comprises the steps of
(i) transmitting from a transmitter a pulse of a first amplitude of ultrasonic vibrations
into said material
(ii) receiving at a receiver a signal consisting of back scattered ultrasonic vibrations from
said pulse
(iii) from a sample of the back scattered signal calculating a first attenuation coefficient
at a first distance from the transmitter, at which the viscosity of liquid in said porous
material is known
(iv) repeating steps (i), (ii) and (iii) with a transmitted pulse of a second, different,
amplitude to calculate a second attenuation coefficient
(v) transmitting pulses of first and second amplitudes and receiving corresponding back
scattered signals from a second distance from the transmitter
(vi) using the known first and second attenuation coefficients and the known viscosity of
liquid at the first distance calculating the viscosity of liquid at said second distance, in said
porous material, from the transmitter.
2. A method according to claim 1 in which a received signal derived from a given transmitted pulse is sampled over a short period, is integrated over said period, and the result used to calculate the attenuation coefficient for the corresponding distance from the transmitter.
3. A method of ultrasonic testing of material according to any one of the preceding claims in which the calculation step or steps include calculating the logarithm of the amplitude of the received back scattered signal.
4. A method according to claim 3 in which the calculation step or steps further include calculating the derivative of the logarithm of the amplitude of the received back scattered signal with respect to the distance from the transmitter from which signals are back scattered.
5. A method of ultrasonic testing according to any one of the preceding claims applied to material which is rock and liquid which is petroleum.
6. A method of ultrasonic testing of porous material which comprises the steps of (i) transmitting from a transmitter a pulse of a first amplitude of ultra sonic vibrations
into said material (ii) receiving from said pulse a transmitted first signal at a first receiver and a
transmitted second signal at a second receiver, said receivers being at different distances
from the transmitter
(iii) calculating from said signals a first attenuation coefficient
(iv) repeating steps (i). (ii) and (iii) at a second, different, pulse amplitude
(v) calculating from the resulting signals a second attenuation coefficient
(vi) using said attenuation coefficients at different amplitudes, and the known viscosity
of any liquid in the paths between transmitter and receivers, to calculate a structural
factor related to the permeability of the pores in the material.
**WARNING** end of DESC field may overlap start of CLMS **.
Claims (6)
1. A method of ultrasonic testing of porous material, containing liquid, which comprises the steps of
(i) transmitting from a transmitter a pulse of a first amplitude of ultrasonic vibrations
into said material
(ii) receiving at a receiver a signal consisting of back scattered ultrasonic vibrations from
said pulse
(iii) from a sample of the back scattered signal calculating a first attenuation coefficient
at a first distance from the transmitter, at which the viscosity of liquid in said porous
material is known
(iv) repeating steps (i), (ii) and (iii) with a transmitted pulse of a second, different,
amplitude to calculate a second attenuation coefficient
(v) transmitting pulses of first and second amplitudes and receiving corresponding back
scattered signals from a second distance from the transmitter
(vi) using the known first and second attenuation coefficients and the known viscosity of
liquid at the first distance calculating the viscosity of liquid at said second distance, in said
porous material, from the transmitter.
2. A method according to claim 1 in which a received signal derived from a given transmitted pulse is sampled over a short period, is integrated over said period, and the result used to calculate the attenuation coefficient for the corresponding distance from the transmitter.
3. A method of ultrasonic testing of material according to any one of the preceding claims in which the calculation step or steps include calculating the logarithm of the amplitude of the received back scattered signal.
4. A method according to claim 3 in which the calculation step or steps further include calculating the derivative of the logarithm of the amplitude of the received back scattered signal with respect to the distance from the transmitter from which signals are back scattered.
5. A method of ultrasonic testing according to any one of the preceding claims applied to material which is rock and liquid which is petroleum.
6. A method of ultrasonic testing of porous material which comprises the steps of (i) transmitting from a transmitter a pulse of a first amplitude of ultra sonic vibrations
into said material (ii) receiving from said pulse a transmitted first signal at a first receiver and a
transmitted second signal at a second receiver, said receivers being at different distances
from the transmitter
(iii) calculating from said signals a first attenuation coefficient
(iv) repeating steps (i). (ii) and (iii) at a second, different, pulse amplitude
(v) calculating from the resulting signals a second attenuation coefficient
(vi) using said attenuation coefficients at different amplitudes, and the known viscosity
of any liquid in the paths between transmitter and receivers, to calculate a structural
factor related to the permeability of the pores in the material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB720978A GB1599067A (en) | 1978-05-30 | 1978-05-30 | Ultrasonic testing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB720978A GB1599067A (en) | 1978-05-30 | 1978-05-30 | Ultrasonic testing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1599067A true GB1599067A (en) | 1981-09-30 |
Family
ID=9828730
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB720978A Expired GB1599067A (en) | 1978-05-30 | 1978-05-30 | Ultrasonic testing |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB1599067A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0231063A2 (en) * | 1986-01-27 | 1987-08-05 | Mobil Oil Corporation | Borehole logging method for determining the damping of acoustic tube waves in subsurface formations along a borehole wall |
| GB2256049A (en) * | 1991-05-22 | 1992-11-25 | Wrc Plc | Measurement of flocculation layer depth and density |
| GB2339908A (en) * | 1996-01-26 | 2000-02-09 | Baker Hughes Inc | Downhole tool |
| GB2324153B (en) * | 1996-01-26 | 2000-05-03 | Baker Hughes Inc | A drilling system with an acoustic measurement-while-drilling system for determining parameters of interest and controlling the drilling direction |
| US6088294A (en) * | 1995-01-12 | 2000-07-11 | Baker Hughes Incorporated | Drilling system with an acoustic measurement-while-driving system for determining parameters of interest and controlling the drilling direction |
-
1978
- 1978-05-30 GB GB720978A patent/GB1599067A/en not_active Expired
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0231063A2 (en) * | 1986-01-27 | 1987-08-05 | Mobil Oil Corporation | Borehole logging method for determining the damping of acoustic tube waves in subsurface formations along a borehole wall |
| EP0231063A3 (en) * | 1986-01-27 | 1988-11-09 | Mobil Oil Corporation | Borehole logging method for determining the damping of acoustic tube waves in subsurface formations along a borehole wall |
| GB2256049A (en) * | 1991-05-22 | 1992-11-25 | Wrc Plc | Measurement of flocculation layer depth and density |
| US6088294A (en) * | 1995-01-12 | 2000-07-11 | Baker Hughes Incorporated | Drilling system with an acoustic measurement-while-driving system for determining parameters of interest and controlling the drilling direction |
| GB2339908A (en) * | 1996-01-26 | 2000-02-09 | Baker Hughes Inc | Downhole tool |
| GB2339908B (en) * | 1996-01-26 | 2000-05-03 | Baker Hughes Inc | A drilling system with an acoustic measurement-while-drilling system for determining parameters of interest and controlling the drilling direction |
| GB2324153B (en) * | 1996-01-26 | 2000-05-03 | Baker Hughes Inc | A drilling system with an acoustic measurement-while-drilling system for determining parameters of interest and controlling the drilling direction |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PS | Patent sealed | ||
| PCNP | Patent ceased through non-payment of renewal fee |