Boring or penetrating the earth – Automatic control – Of boring means including a below-ground drive prime mover
Patent
1992-11-20
1993-12-28
Bui, Thuy M.
Boring or penetrating the earth
Automatic control
Of boring means including a below-ground drive prime mover
E21B 4700
Patent
active
052731227
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an automatic method for monitoring the vibrational state of a drill string.
Research in the oil industry has led to providing drill strings at their top with numerous sensors such as accelerometers and/or strain gauges, making available magnitudes such as torsional, axial or transverse accelerations, axial force, torque and bending moments.
However, the vibrational data coming from these sensors possess an obvious complexity for a non-specialist desiring to make use of them. Traditional spectrum analysers actually in general produce only curves whose analysis is not immediate.
However, the foreman driller needs to know instantaneously the vibrational behaviour of his drill string, and in particular a possible instability of the said behaviour, in order to be able to adjust as fast and as well as possible the various drilling parameters, namely the weight on the bit, the speed of rotation and also the mud flow rate.
These instabilities occur because the drill string consists of a mechanical assembly which has natural modes and which is capable of responding to various mechanical stresses occurring during drilling, such as working of the bit on the rock and interactions between the well and the said drill string, this being the case both axially and laterally or torsionally.
Such instabilities are to be eliminated because they are the origin of extra strain for the material which risks leading to breaking of the drill string; furthermore, they consume a portion of the energy which it would be preferable to transmit directly to the bit, the latter then being converted into energy for cutting the rock, which contributes to a more efficient advance of the drilling.
The object of the present invention is therefore an automatic method for monitoring the vibrational state of a drill string, which makes it possible to use the measurements provided by a set of sensors situated at the top of a drill string, in particular by warning a user in a simple manner of possible instabilities in these measurements.
In order to do this, the invention provides an automatic method of monitoring the vibrational state of a drill string provided with sensors, the said method comprising the following steps: magnitudes measured by the sensors,
Other characteristics and advantages of the present invention will emerge more clearly on reading the following description which is made with reference to the attached drawings in which:
FIG. 1 is a block diagram of the whole of the monitoring system;
FIG. 2 is a logic diagram describing certain steps of the signalling to the user; and
FIGS. 3a, 3b and 3c are explanatory curves of the present invention.
As represented in FIG. 1, the monitoring system comprises a bank of programmable filters 8 as well as RMS converters 10 or anti-aliasing filters 12 making it possible to process the signals coming from the sensors 14 disposed on the drill string 16; the data coming from the converters 10 are grouped at a multiplexer 18 then transmitted to an analog/digital converter 20 and finally to one or more processors 22. The microprocessor or microprocessors 22 are possibly assisted by one or more signal processors 24 and are coupled with an interface 26; the user may transmit data to the processor or processors 22 by means of a keyboard 28 and a communication link 30. It is possible to input to the interface 26 certain information concerning the reference spectra 32 relating to each sensor, the said interface 26 being connected to audio 34 and/or visual 36 signalling means.
In order to detect possible instabilities in the magnitudes measured by the sensors, it is suitable to carry out the following steps:
Obtaining a reference spectrum for each of the sensors:
In order to do this, two methods are possible. The foreman driller determines in the first case a state which he judges adequate for effective drilling, possibly assisted in this by a specialist in vibrations in the field of drilling. Various vibrational measurements provided by the sensors correspond to this state,
REFERENCES:
patent: 3703096 (1972-11-01), Vitter, Jr. et al.
patent: 4150568 (1979-04-01), Berger et al.
patent: 4637479 (1987-01-01), Leising
patent: 4903245 (1990-02-01), Close et al.
patent: 4928521 (1990-05-01), Jardine
patent: 5186579 (1993-02-01), Hanamoto et al.
Bui Thuy M.
Elf Aquitaine Production
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