MXPA05012517A - Probe for measuring the electromagnetic properties of a down-hole material - Google Patents

Abstract

A probe 1 for measuring the electromagnetic properties of a down-hole material MC, GF, DM of a well-bore WB comprises a metallic pad 2 in contact with the down-hole material. The pad 2 further comprises an open-ended coaxial wire 4 coupled to an electronic circuit 3 . The open-ended coaxial wire 4 comprises an inner conductor 4 A sunk in an insulator 4 B and is positioned sensibly perpendicularly to the well-bore wall. The electronic circuit 3 is able to send a high-frequency input signal into the open-ended coaxial wire 4 and to determine a reflection coefficient based on a high-frequency output signal reflected by the open-ended coaxial wire 4.

Description

PROBE TO MEASURE THE ELECTROMAGNETIC PROPERTIES OF A MATERIAL IN THE DRILL FUND FIELD OF THE INVENTION The invention relates to a probe for measuring the electromagnetic properties of a material. The invention finds an application in the oilfield industry, in particular for measuring the dielectric properties, particularly the permittivity and conductivity of a material at the bottom of the drilling, in particular a geological formation, a drilling mud or a drilling cake. sludge The invention also relates to a method for measuring the electromagnetic properties of a material at the bottom of the microwave frequency bore.

BACKGROUND IN THE INVENTION It is usual in the oilfield industry to make several measurements during a hole-hole drilling operation. Such measurements are known as measurements while drilling (M D) or record while drilling (LWD). These measurements refer to the properties of the well hole and the properties of the geological formation that is traversed during the excavation of the hole, or a little later. The measurements are made by means of tools integrated in a hole bottom assembly, in particular within a bit set. The tool while measuring-while-drilling typically provides pressure, temperature and trajectory of the well hole in three-dimensional space. The tool to record while drilling typically provides ecological training parameters (resistivity, porosity, sound velocity, gamma rays ...). These measurements are made while the wellbore extends. Measurements that are made at the bottom of the hole can be stored in a memory and then transmitted to the surface (for example, data transmission through pressure pulses, subsequent recovery via wireline, or recovery when the tool is extracted from the hole).

It is also usual in the oil field industry to make several measurements after the well hole drilling operation has been carried out. Such measurements are known as wireline records. Wireline registration uses an electrical cable to lower tools into the wellbore and transmit measured data at the bottom of the borehole to the equipment on the surface. The measurements refer to properties of the well hole (pressure, temperature, drilling fluid ...) and the properties of the geological formation around the well hole (resistivity, porosity, sound velocity, gamma rays ...) against the depth or the time or both.

While several properties of the wellbore can be measurements, there is currently a need to measure the dielectric properties, namely permittivity and conductivity of the bottom material of the borehole, in particular the geological formation or the drilling mud or mud cake in the close vicinity of the well hole wall.

BRIEF DESCRIPTION OF THE INVENTION It is a goal of the invention to propose a probe for measuring the electromagnetic properties of a material from the bottom of the borehole at microwave frequencies, in the close vicinity of the borehole wall and a corresponding measurement method.

According to the invention, a probe for measuring the electromagnetic properties of a bottom material of a well hole bore comprises a metal cushion in contact with the bottom material of the bore. The cushion further comprises an open-ended coaxial wire coupled to an electronic circuit, said open-ended coaxial wire comprising an internal conductor sunk in an isolator and being placed substantially perpendicular to a wall of the wellbore, the electronic circuit being capable of of sending a high frequency input signal into the open end coaxial wire and determining a reflection coefficient based on a high frequency output signal reflected by the open end coaxial wire.

The bottom material of the drilling can be a tota of mud, a drilling mud or a geological formation.

Advantageously, the open-end coaxial wire and the electronic circuit are coupled to a self-calibration array by means of a first switch.

The auto calibration arrangement comprises a second coaxial wire substantially identical to the open end coaxial wire, the second coaxial wire being connected by a second switch to a first termination having a first impedance, a second termination having a second impedance and a second impedance. third termination that has a third impedance. For example, the first termination is a short termination, the second termination is an open termination and the third termination has a determined impedance.

The invention also relates to a recording tool comprising a probe for measuring the electromagnetic properties of a bottom material of the borehole of a wellbore according to the invention, the probe pad being coupled to the tool by means of of at least one arm, said recording tool receiving a signal representative of the electromagnetic properties of the bottom material of the drilling measurements by the probe.

Finally, the invention relates to a method for measuring the electromagnetic properties of a bottom material from the drilling of a well hole. The method comprises the steps of: placing an open-end coaxial wire in contact with the bottom material of the perforation. send a high frequency input signal on the open end coaxial wire in contact with the bottom material of the hole. Measure a high frequency output signal reflected by the open end coaxial wire, measure a reflection coefficient based on the high frequency output signal. Calculate a dielectric value related to the bottom material of the borehole based on the reflection coefficient, and repeat the previous steps at various points along the hole bore wall.

Optionally, the method further consists in repeating the step of sending the input signal, the steps of measuring the output signal and the reflection coefficient and the step of calculating the dielectric value at least for an input signal of another high frequency at a sensibly identical point along the wall of the well hole.

The method may further comprise a calibration step of an electronic circuit coupled to the open end coaxial wire, which is performed in a certain time interval. Advantageously, the calibration step consists in successively connecting the electronic circuit to at least three different impedances and measuring the reflected high frequency output signal.

With the measuring probe, the tool and the method of the invention, the permittivity and the conductivity of the bottom material of the drilling, ie the geological formation, the drilling mud or the mud cake, are measured with great accuracy (for example an accuracy better than 1% can be obtained).

In addition, the measurement of the permittivity and the conductivity of the drilling mud allow obtaining information about the properties of the invasion liquids. Finally, the measurement of the permittivity and the conductivity of the bottom material of the drilling can be carried out at different frequencies, allowing to obtain petrophysical information about the material of the bottom of the hole (eg, information pertaining to the particle shape). , humidness, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated by way of example and is not limited to the appended figures, in which like references indicate similar elements: Figure 1 schematically illustrates a typical terrestrial location of a hydrocarbon well; Figures 2.A and 2.B schematically show a top view and a cross-sectional view in a cushion comprising a probe according to the invention; Figure 3 illustrates schematically in greater detail the electronic circuit of the probe of Figures 2 and 2.B; and Figure 4 illustrates schematically an auto-calibration array adapted for the probe according to the invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 schematically shows a typical terrestrial location of a hydrocarbon well and the SE surface equipment on a GF hydrocarbon geological formation after the drilling operation has been performed. In this step, the well B is a drilling generally filled with various fluid mixtures (eg, drilling mud DM or the like). The surface equipment SE comprises an oil rig OR and a surface unit SU for deploying a logging tool TL in the wellbore WB.

The registration tool comprises a centralizer comprising a plurality of mechanical arms connected to the recording tool and with a lower nose. The mechanical arm can be deployed radially so as to be in contact with the wall of the well , ensuring a correct placement of the tool into the well (eg, along the central axis of the well ) . The registration tool comprises several sensors or probes that provide type of measurement data related to the geological formation of GF hydrocarbon or to the wellbore WB. The registration tool TL is coupled to the SU surface unit (for example a vehicle comprising a deployment system and a collection of measurement data and a computer and analysis programs.

The recording tool TL comprises, among other sensors and probes, a probe 1 for measuring the electromagnetic properties (dielectric properties) of the bottom material of the bore, particularly the permittivity and conductivity of the GF formation, of the drilling mud DM or of the drilling mud. the cake of mud MC. The terminology "geological formation" corresponds to an area invaded by drilling mud, particularly a volume or a flush zone near the wall of the well in which some of the movable liquids (eg, drilling mud) MD) have been displaced by mud filtering in the permeable geological formation. The term "mud cake" corresponds to the surface layer of solid mud particles that result from the drilling mud produced during the drilling and flattening operation against the wall of the wellbore due to the high pressure.

Figures 2 and 2.B show respectively a cross section top view and a side cross section of the probe 1 of the invention.

The probe 1 comprises a metal cushion 2. The cushion 2 can be brought into contact with the bottom material of the perforation (for example the mud cake MC). The cushion is made of a metallic material (for example steel) and has a length of a few centimeters. The cushion is coupled to the TL tool by two arms Al, A2. The TL tool provides energy, control signals and gathers measurements made by the probe 1. The arms Al, A2 allow the deployment of probe 1 inside the well and against the wall of the well WBW. The well wall consists of either the GF formation covered by the MC mud cake (a surface layer of solid mud) or the GF formation itself. Drilling mud DM is present inside the well .

To determine the dielectric properties of the bottom material of the perforation, the cushion 2 comprises an open end coaxial wire 2. The open end coaxial wire 4 is a coaxial wire comprising an internal conductor 4A sunk in an insulator 4B. For example, the open end coaxial wire has a diameter of about 4 millimeters. The open-end coaxial wire 4 is positioned perpendicular to the axis AA 'of the cushion. The open-end coaxial wire 4 is connected to the electronic circuit 3. Preferably, the electronic circuit is closed to the open-end coaxial wire, to avoid any loss of signal and phase shift due to the fact that the signals of the microwave type are involve in the measurement. The measurement of open-end coaxial wire is based on the principle that the reflected signal produced by the coaxial opening of the probe is dependent on the sample material from the bottom of the bore that terminates the probe, namely the mud cake, the mud piercing or the formation. The electrical parameters (complex permittivity) of the bottom material of the perforation can be deduced by measuring the admittance of the aperture (or reflection coefficient).

The open-ended coaxial wire has a limited depth of sensitivity corresponding to approximately the radius of the coaxial probe (e.g., 1 mm for an open-ended coaxial wire having a diameter of approximately 2 mm). This means that the coaxial probe is sensitive to the massive electrical property of the material in the vicinity of the probe. Preferably, the open end coaxial wire is calibrated. Thus, the open-end coaxial is coupled to a self-calibration array. The operation of the electronic circuit and the auto fix arrangement will be explained later with more details.

The open end coaxial wire 4 and the electronic circuit 3 operate as follows. The open end coaxial wire in the metal cushion is in direct contact with the bottom material of the hole (mud cake, mud or formation). A microwave signal is sent to the coaxial wire opening, and the complex reflection coefficient Su is measured by electronic circuit 3. The complex reflection coefficient Su correlates only with the dielectric properties of the bottom material of the borehole that is in contact with the probe. A simple linear inversion process provides the permittivity and conductivity of the bottom material of the borehole. The complex permittivity e of the bottom material of the borehole is e = e'-y'e ", where e" = s / (? E0), s is the conductivity of the bottom material of the borehole and? is the angular frequency of operation.

The frequency of operation? it can be chosen from approximately 100 MHz to approximately 2 GHz, for example 900 MHz.

The open-end coaxial wire can be modeled as two parallel capacitances that have a capacitance of C = CL + eC? where CL corresponds to the edge field inside the coaxial wire and C0 is the edge capacitance due to the field in the air.

A negligible radiation resistance is assumed for the open-end coaxial wire, which is true at 900 MHz for the small opening of the open-end coaxial wire.

The reflection coefficient at the end of the probe is: Sn = (l-yVZ0C) / (l-y? Z0C) where Z0 is the characteristic impedance of the coaxial wire.

In particular, with the ec permittivity of the coaxial line. Finally, the material permitivity of the bottom of the hole is given by: with Q «C0.

The value of CL and C0 are set by the design of the open end coaxial wire and do not depend on the material of the bottom of the hole.

This measurement works over a large range of conductivity (eg, 0 to 1000 mS / m) and permittivity (eg, l to 81). The accuracy of the measurements obtained is typically better than 1%.

Figure 3 illustrates schematically the electronic circuit 3 of the probe of Figures 2 and 2.B. The electronic circuit 3 comprises an WIO input / output to connect to the open end coaxial wire, and an output signal SO to provide an output signal comprising the information related to a measurement amplitude and a measurement phase. The usual and known circuits of energization and control are omitted in this figure. The electronic circuit 3 comprises a transmitter circuit 3 'and a receiver circuit 3. "The transmitter and receiver circuits are both coupled to a high frequency source 31. The emitter circuit 3' comprises a low frequency source 32, modulator 33 and a directional coupler 34. The receiver circuit 3"comprises the directional coupler 34, an amplifier 35, a mixer 36, and a digitizing and processing module 37. The high frequency source 31 is coupled to the modulator 33 and the mixer 36, and provides these elements with a high frequency microwave signal 0 (approximately 100 MHz to approximately 2 GHz (for example 900 MHz). The high frequency source 31 serves as a reference for the 3"receiver circuit, in particular the mixer 36. The low frequency source 32 is coupled to the modulator 33 and provides two phase and quadrature signals of low frequency O0 (a few kHz - for example 10 kHz).

These signals are sent to the modulator 33 comprising a modulator In Phase and Quadrature (IQ) that performed a frequency shift. The resulting input signal IS having a frequency? 0 + 0 0 is provided to the directional coupler 34.

The directional coupler 34 provides the input signal IS to the WIO input / output coupled to the open end coaxial wire.

The directional coupler 34 is also coupled to the amplifier 35. The directional coupler 34 provides the OS output signal reflected by the open end coaxial wire through the WIO input / output. The output signal OS having a frequency? 0 + O0 is amplified by the amplifier 35. The resulting amplified output signal having a frequency? 0 + O0 is provided to the mixer 36.

The mixer 36 which also receives the high frequency signal 0 from the high frequency source 31 provides a low frequency signal O0 to the digitizing and processing module 37. The low frequency signal O0 is digitized and processed through of a usual synchronous detection scheme The digitizing and processing module 37 provides a signal to the output signal SO in the form j4cos (τ t + f), where A and f correspond respectively to the amplitude and phase of the coefficient of complex reflection Su- Gain and phase shift due to the chain of high frequency electronics that can affect the measurements, can be canceled with a calibration process (described later).

Then, the permittivity and conductivity of the bottom material of the perforation can be determined as explained above, by means of an appropriate supplementary processing arrangement (not shown) of the electronic circuit, or by an appropriate supplementary processing arrangement (not shown). ) of the TL tool, or by means of the SU surface unit. The permittivity and conductivity measurements of the bottom material of the borehole can be transmitted to the surface unit for further processing by means of a known transmission method.

The electronic circuit 3 can be designed as a small tablet (approximately 10 cm2) integrated in the cushion.

In the above described mode, the high frequency source provides a certain high frequency signal. Alternatively, the high frequency source can generate high frequency signals of different frequencies, so that the frequency of the input signal can be varied. Thus, different measurements can be made at different frequencies. For example, several measurements of the permittivity and the conductivity of the bottom material of the drilling can be performed in a substantially identical position (preferably the same position) in the well hole but at several frequencies, p. ex. , one measurement in 100 MHz, one at 500 MHz and. one to 1 GHz. A scatter curve can be calculated based on these measurements. The dispersion curve analysis can give various information about the petrophysical parameters of the bottom material of the perforation (eg, shape of the formation particle, humidification of the formation particle, etc.).

The accuracy of the probe can be affected by the drift of the temperature of the electronic circuit 3. An accuracy of the electronic circuit 3 of at least 0.05 dB in amplitude and 0.1 degrees in phase can be obtained by means of coupling through a first switch 5 the electronic circuit 3 to an auto-calibration array 6 as shown in Figure 4. The calibration array 6 is used to calibrate the electronic circuit 3 and the open-end coaxial wire 4. At certain time intervals, by example of time in type or systematically before each measurement, electronic circuit 3 initiates an automatic calibration procedure.

The auto-calibration array 6 comprises a second coaxial wire 6A, a second switch 6B and a short termination 6C, an open termination 6D and a termination 6E of 50 Ohm.

The second coaxial wire 6A is identical to the open end coaxial wire 4 and compensates for the length and losses of the probe.

The auto calibration operates as follows. First, the electronic circuit 3 is coupled to the auto calibration arrangement 6 by means of the switch 5 via the WIO input / output. Subsequently, the electronic circuit 3 sends and receives a signal through the second coaxial wire 6A and the short termination 6C, then the open termination 6D and finally the termination 6E of 50 Ohm by the successive action of the second switch 6B. For each termination measurement, a reflection coefficient is determined and a new calibration curve is calculated with these measurements.

This calibration is particularly well suited for a tool that operates at the bottom of the hole. This automatic calibration prevents calibration in the laboratory and automatically corrects the drift in the electronics and the open end coaxial wire.

The three terminations are not necessarily the short termination, the open termination and the 50 Ohm termination. Alternatively, the three terminations may be different to only cover the impedance range of the open-end coaxial wire.

The above description focused on the particular application of the invention to a wireline registration tool. However, it will be apparent to a person skilled in the art that the probe of the invention can easily be adapted to the recording application while drilling (see background of the invention).

The drawings and their previous description illustrate more than limit the invention.

No reference sign in a claim should not be construed as limiting the claim. The word "comprises" does not exclude the presence of other elements than those listed in a claim. The words "one / one" or "an" preceding an element do not exclude the presence of a plurality of such element.

Claims (10)

1. - A probe for measuring the electromagnetic properties of a material from the bottom of the borehole (MC, GF, DM) of a well hole (WB), the probe comprising a metal cushion in contact with the bottom material of the borehole, characterized because the cushion additionally comprises an open-ended coaxial wire coupled to an electronic circuit (3), said open-ended coaxial wire comprising an internal conductor sunk in an isolator and being placed substantially perpendicularly to a wall of a well hole, the electronic circuit being capable of sending a high frequency input signal in the open end coaxial wire and of determining a reflection coefficient based on a high frequency output signal reflected by the open end coaxial wire.

2. - The probe according to claim 1, characterized in that the bottom material of the perforation is a mud cake (MC) or a geological formation (GF) or a drilling mud (DM).

3. - The probe according to claim 1 or 2, characterized in that the open-end coaxial wire and the electronic circuit are coupled to a self-calibration array by means of a first switch.

4. - The probe in accordance with the claim 3, characterized in that the auto-calibration array comprises a second coaxial wire substantially identical to the open-ended coaxial wire, the second coaxial wire being connected by a second switch to a first termination having a first impedance, a second termination having a second impedance and a third termination that has a third impedance.

5. - The probe in accordance with the claim 4, characterized in that the first termination is a short termination, the second termination is an open termination and the third termination has a determined impedance.

6. - A recording tool (TL) comprising: a probe for measuring the electromagnetic properties of a bottomhole material (MC, GF, DM) of a well hole (WB) according to any one of the preceding claims , the probe cushion being coupled to the tool (TL) by at least one arm, said recording tool (TL) receiving a signal representative of the electromagnetic properties of the bottom material of the perforation (MC, GF, DM) measured by the probe.

1. - A method for measuring the electromagnetic properties of a bottomhole material (MC, GF, DM) of a well hole (WB), characterized in that it comprises the steps of: - placing an open-end coaxial wire in contact with the bottom material of the perforation, - send a high frequency input signal in the open end coaxial wire in contact with the bottom material of the perforation, - measure a high frequency output signal reflected by the coaxial wire of open end, -measuring a reflection coefficient (Su) based on the high frequency output signal, -calculating a dielectric value (e, s) related to the bottom material of the borehole (MC, GF, DM), and -repeating the previous steps at different points along the wall of the well hole.

8. - The method according to claim 7, characterized in that a further calibration step of an electronic circuit coupled to the open-end coaxial wire is performed in a certain time interval.

9. - The method according to claim 8, characterized in that the calibration step consists of successively connecting the electronic circuit to at least three different impedances and measuring the reflected high-frequency output signal.

10. - The method according to claim 7, characterized in that the method further consists in repeating the step of sending the input signal, the measurement steps of the output signal and the reflection coefficient and the step of calculating the value of the dielectric at least for an input signal of another high frequency at a substantially identical point along the wall of the wellbore.