Communications – electrical: acoustic wave systems and devices – Seismic prospecting – Well logging
Patent
1992-01-28
1993-10-19
Lobo, Ian J.
Communications, electrical: acoustic wave systems and devices
Seismic prospecting
Well logging
367911, 324366, 181102, G01V 140
Patent
active
052552454
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention has for its object a total field imaging probe enabling logs to be made over the whole periphery of the wall of a hole excavated in the sub-soil.
The technical sector of the invention is the manufacture and exploitation in situ of tools or probes for making measurements of the characteristics of the soil in a bore-hole traversing geological formations and for remotely reading and analyzing these measurements.
One of the principal applications of the invention is the use thereof for effecting imaging logs of wells making it possible to obtain a good coverage of the whole of the excavation, using different conventional individual measuring means, such as acoustic or microresistive measurements.
In fact, different systems and processes are known, of which certain have formed the subject matter of Patent Applications and which relate to the same object and/or the same application as the present invention, but of which the technical solutions retained do not allow good performances and/or are difficult to implement.
In the following description and by way of definition, the generic term "electrical logging" or "log" designates the continuous recording of physical parameters of the formations encountered during excavation, as a function of the depth.
It will firstly be recalled that imaging logging is a novel concept making it possible, from conventional individual measurements, to present along an evolute of the wall of the borehole as a function of the depth, the response of this wall to a physical measurement, such measurement having a vertical and horizontal definition of the order of several tens of centimeters for usual logs.
This representation, on any displayable visual support and, furthermore, oriented in space, therefore constitutes an artificial image of the formations encountered.
Implementation thereof essentially necessitates:
an investigation with the aid of the parameter measured, allowing the maximum coverage of the wall of the well;
means for locating in space;
a processing of each measurement representing the amplitude of this parameter in the form of a colour or a gradual range of greys; for example, the high resistivities in white and the very low in black. The amplitude of a sound wave, emitted by a sensor, after reflection by the wall of the well, may be processed in the same manner.
DESCRIPTION OF RELATED ART
For example, Patent FR 2 532 059 filed on Aug. 19, 1982 by the firm SCHLUMBERGER PROSPECTION ELECTRIQUE, describes a device for the visual presentation of results of measurement, applicable to this type of processing.
It is obvious that, in order to be representative of the formations encountered, these measurements must investigate a maximum percentage of the wall of the well.
To that end, one possibility is to effect an acoustic imaging from a rotating sensor serving as emitter and receiver, and mechanically posing no problems. The density of the data received depends only on controllable parameters:
speed of rotation;
ascensional speed;
number of scans per revolution.
This applies to any other measurement made from a rotating sensor, such as for example the one described in Patent Application FR 2 448 621 filed on Sep. 2, 1979 by the INSTITUT FRANCAIS DU PETROLE and entitled: "Probe with rotating shoe for effecting measurements in a borehole".
On the other hand, any measurement necessitating the contacting of sensors or of shoes on the wall of a well poses mechanical problems recalled hereinafter.
In fact, in order to produce this contact, the probes usually use rigid or semi-rigid shoes constituting one side of a parallelogram, the opposite side being defined at its ends by one or two articulations located on the body of the probe, as described for an acoustic imaging in U.S. patent application Ser. No. 948 206 filed on Dec. 31, 1986 by the firm SHELL INTERNATIONAL RESEARCH.
The coverage of the measurement depends on the size of the shoes, their number and the diameter of the excavation. Furthermore, the descent of tool in th
REFERENCES:
patent: 2930969 (1960-03-01), Baker
patent: 4236113 (1980-11-01), Wiley
patent: 4862090 (1989-08-01), Vannier et al.
patent: 4899320 (1990-02-01), Hearn et al.
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