专利摘要:
Systems and methods with multiplexed microvolt sensor are provided. An exemplary system may include a pulse light source, a first waveguide optical segment operably coupled to the pulse light source, an optical circulator (104) containing a first port, a second port, and a third port, the first port operably coupled to the first optical waveguide segment (151), a second optical waveguide segment (152) operatively coupled to the second port of the optical circulator (104), and a detector element array (110). Each of the sensing elements may comprise a detector (230) and an electro-optical modulator, the electro-optical modulator (220) being operably coupled to the second optical waveguide segment. The exemplary system may further include a third optical waveguide segment (153) operably coupled to the third port of the optical circulator (104), a compensation interferometer (120; 480) operably coupled to the third guide segment an optical wave (153) and a time division multiplexed demodulator (130) operatively coupled to the compensation interferometer (120; 480) and the pulse light source.
公开号:FR3037664A1
申请号:FR1654370
申请日:2016-05-17
公开日:2016-12-23
发明作者:Han-Sun Choi；Tasneem A Mandviwala；David Andrew Barfoot
申请人:Halliburton Energy Services Inc；
IPC主号:

专利说明:

[0001] BACKGROUND MULTIPLEXED MICROVOLT SENSOR SYSTEMS [0001] Underground tanks can change over time due to various conditions including geological problems and treatments performed relative to the tank. These changes can have an impact on the reservoir and the surrounding formation. Hydrocarbon recovery treatments can be improved by injecting water or steam into a tank. In these cases, it may be useful to monitor the injections of water or steam, as well as other fluids in an underground formation, and / or to monitor the progress of these fluids to at least one wellbore. in the tank or away from this or these wells.
[0002] BRIEF DESCRIPTION OF THE DRAWINGS [0002] The following figures are intended to illustrate certain aspects of the present description, and should not be construed as exclusive embodiments. The described subject is able to receive considerable modifications, alterations, combinations and equivalents in form and function, without departing from the scope of this description. Figure 1 is a diagram of an exemplary multiplexed microvolt sensor system according to certain aspects of the present description. FIG. 2 is a diagram of an exemplary detection element of the exemplary multiplexed microvolt sensor system in accordance with certain aspects of the present disclosure. [0005] Fig. 3 is a diagram of an exemplary well system comprising a multiplexed microvolt sensor system according to certain aspects of the present disclosure. FIG. 4 is a diagram of a portion of the exemplary multiplexed microvolt sensor system illustrating an example of propagated light pulses in accordance with certain aspects of the present disclosure. FIG. 5 is a diagram of another example of a multiplexed microvolt sensor system according to certain aspects of the present description. DETAILED DESCRIPTION [0008] The present disclosure generally relates to multiplexed microvolt sensor systems and more particularly to multiplexed microvolt sensor systems using electro-optical modulators and methods of use thereof. [0009] Systems and methods are described herein for measuring an electromagnetic field near a downhole borehole zone (e.g., in the wellbore or attached to a side in the wellbore). outside a formwork or liner). For example, a transmitter may emit an electromagnetic field and this field may be attenuated by the surrounding subterranean formation (e.g., rock, water, hydrocarbons, etc.). The attenuated electric field may be received or detected by a detector in a sensing element. If, for example, water is present, the attenuation of the electric field will change with respect to the possible presence of rock. Thus, by analyzing the attenuation of the electromagnetic field, it can be determined whether fluid (eg, water, steam, CO2, etc.) approaches the wellbore, for example. In this regard, entry of water into a wellbore can result in damage or hydrocarbon production problems from the wellbore. The monitoring of fluids in the underground formation 30 is important because when the hydrocarbons are extracted from a production well, a pressure of the reservoir can begin to decrease. In this regard, a technique for increasing hydrocarbon extraction is to drill a second well strategically placed next to a portion of the reservoir so that a fluid can be inserted (e.g. water, steam, CO2, etc.) thereby pushing the residual hydrocarbons into the reservoir to the production well. However, an operator of the production well must be notified when the fluid used to push the oil is approaching the production well and being close to entering the wellbore. Thus, by sensing and locating the fluid approaching the wellbore, for example, through a fracture network or sub-surface pressure gradient, an operator can implement certain procedures (eg barrier or diversion insertion) with respect to protecting the integrity of the production well. According to embodiments described herein, a detector can detect the electromagnetic field, and a corresponding signal (e.g., a voltage signal) is applied to an optical modulator of the sensing element, to convert the signal. of the electrical detector in the optical field. As such, the detector signal may be optically transmitted at a distance from at least one system (eg, an interrogation system) near a surface of the well, for example. Optical guides (eg, a fiber) can provide at least an advantage when communicating these sensor signals to the surface instead of using a copper cable tool placed in a wellhead at the surface, and extending down to measure an electric field. The use of an optical fiber as transmission medium may for example provide the advantage of low loss and tolerance to, but not limited to, environmental conditions such as elevated temperatures. In addition, another advantage of the multiplexed microvolt sensor systems described herein is that it is not necessary to stop the production of the well to detect whether a water front is approaching or near the borehole ( for example, no disruptive intervention is required to take measurements, as is the case with some copper cable tools that measure electromagnetic fields at the bottom). [0012] In some aspects, a detector or sensor (e.g., an electromagnetic field sensor) may be disposed adjacent a downhole zone. A signal that the detector or sensor records or measures can then be transmitted to the well surface optically. The sensing element may be adapted to modulate an optical signal as a function of an electrical signal applied to an electro-optic modulator (e.g., a lithium niobate electro-optic modulator). By coupling the detector or sensor to the electro-optical modulator, the detected electrical signal to be measured can be converted to an optical signal so that it can be propagated through an optical waveguide. [0013] In some aspects, the multiplexed microvolt sensor system 15 may be used in a production environment (eg, after drilling and while the well is producing hydrocarbons). In some embodiments, many components are in the well and can be permanently installed (or semipermanently). The multiplexed microvolt sensor system can, for example, be permanently installed in a production well, and can be designed to provide continuous readings or measurements. Accordingly, in a time-division format, the multiplexed microvolt sensor system can determine whether the fluid (eg, a water front) is present and how fast it approaches the wellbore. An optical waveguide (eg, provided by fiber optic cable) can extend from the well surface to a production area within the wellbore. In some embodiments, a fiber cable may contain at least one fiber strand 30 to provide the optical waveguide that extends the full length of the cable. In some implementations, the fiber cable will be pinched or otherwise attached to the outside of the formwork and may be cemented into the wellbore. The arrangement of the optical waveguide and detection elements attached thereto outside the well formwork further provides an advantage in that the metal formwork will not attenuate the electromagnetic signal emitted by the well. transmitter and received by the detector, for example. As can be seen from the examples provided herein, multiplexed microvolt sensor systems can provide continuous measurement and without disruption of AC voltages near a multiple downhole zone, so that detection approaching fluids (eg, a water front) can be determined, however, some electro-optic modulators inherently exhibit a high loss that can prevent a serial connection for multiplexing, and the signal strength can For example, multiplexed microvolt sensor systems using electro-optical modulators (eg, custom phase modulators with lithium niobate) are known to vary due to the polarization shift across a single-mode fiber. As a very sensitive detection component, to solve these problems, FIG. 1 illustrates an example of a multipovt microvolt sensor system. The system 100 may include a pulse light source 102 (eg, a high power, low coherence pulse light source), a sensing element array 110, a compensation interferometer 120 and a time division multiplexed demodulator 130. The system 100 may also include an optical waveguide comprising various segments operatively coupled to an optical circulator 104 having a first port 1, a second port 2, and a third port 3. In the system 100, for example, a first segment Optical waveguide 151 may be operatively coupled to pulse light source 102 and first port 1 of optical circulator 104. A second optical waveguide segment 152 may be operatively coupled to second port 2 of optical circulator 104 and operably coupled to each sensing element 110 of the detector element array 110. The second optical waveguide segment 152 and the sensing element array 110 may extend from a surface of a well and extend down to one side of the corresponding wellbore, for example. A third optical waveguide segment 153 may be operatively coupled to the third port 3 of the optical circulator 104 and to the compensation interferometer 120. It should be noted that the number of optical waveguide segments that can be used is not limited to three, as previously indicated, and the number of optical waveguide segments can be increased or decreased depending on the power supplied to the pulse light source 102. If for example the power increases then the number of optical waveguide segments can be limited to one or two. Similarly, if the power decreases, more than three optical waveguide segments can be used in the system 100. Each sensing element 110 except the last sensing element 110 (e.g., sensor N 1) can be operably coupled to the second optical waveguide segment 152 through a directional coupler 112. The directional coupler 112 can divide a portion of the light pulse towards a sensing element 110 and allow the remainder to pass to the next sensor by the second optical waveguide 152. The directional coupler 112 may for example provide a 10% limiter in some implementations. The last sensing element 110 (e.g., the N-sensor) in the sensing element array 100 may be operatively coupled to the second optical waveguide 152 by a direct connection with an end of the second optical waveguide 152. [0019] FIG. 2 illustrates an exemplary detection element 110 according to at least one of the embodiments. The sensing element 110 may comprise an electro-optical modulator 220 and a detector 230. In some embodiments, the electro-optical modulator 220 may include a sensing interferometer, which may be a niobate-type Michelson interferometer. of lithium. The sensing element 110 may include an input / output waveguide channel 223 which may have a proximal end relative to the pulse light source 102 (see Fig. 1) and a distal end may connect at a proximal end of a first waveguide channel arm 221 and at a proximal end of a second waveguide channel arm 222.
[0003] The proximal end of the input / output waveguide channel 223 may be operatively coupled to an optical waveguide channel 252 extending from the directional coupler 112 (see Fig. 1) for coupling to the second Optical waveguide segment 152. [0020] A first reflector element 225 may be disposed at a distal end of the first waveguide channel arm 221 and a second reflector element 225 may be disposed at a distal end of the second arm In some embodiments, the first and second reflector members 225 may be gold-plated mirrors for improving signal resistance. According to some embodiments, the second waveguide channel arm 222 may be longer than the first waveguide channel arm 221. For example, a distance including the second waveguide channel arm 222 may be longer than the first waveguide channel 221 may be between 0.1 and 5.0 mm in some implementations. The detector 230 may be designed to detect an electromagnetic field and may for example be a coil of electrically conductive material. In some implementations, the coil may be formed of ferromagnetic material. However, the detector 230 may be any other electromagnetic field measuring device according to other implementations. The detector 230 can receive a sinusoidal signal from the electromagnetic field and transmit the sinusoidal signal to the electrodes of the electro-optical modulator 220. The electro-optical modulator 220 may for example contain a first electrode 231, a second electrode 232, and a second electrode 232. third electrode 233. The first waveguide channel arm 221 may be disposed between the first electrode 231 and the second electrode 232. The second waveguide channel arm 222 may be disposed between the first electrode 232 and the third electrode 233. In addition, in some embodiments, the first electrode 231 and the third electrode 233 may be electrically coupled to a first end of the detector 230, and the second electrode 232 may be electrically coupled to a second end of the detector 230. However, other arrangements of the electrodes and waveguide channel arms of the mo Electro-optic diverter 220 may be used by a specialist benefiting from the advantages of the present disclosure. Referring back to FIG. 1, it can be seen that the compensating interferometer 120 may comprise a directional 2x2 coupler 122 to obtain a compensation path difference that may be approximately equal to a path difference. in the electro-optical modulator 220 (e.g., the detection interferometer) corresponding to the first waveguide channel arm 221 and the second waveguide channel arm 222. For example, a first channel may be provided. compensation waveguide 124 by a certain length of fiber. The first compensation waveguide path 124 may include a reflector 128 (e.g., a faraday mirror (FRM)). A second compensation waveguide path 126 may comprise a phase modulator. The phase modulator may include a loop of the fiber providing the waveguide path that may be wrapped around a piezoelectric disk according to some embodiments. The second compensation waveguide path 126 may also include a reflector 128 (e.g., a FRM mirror). In this regard, to adjust with the optical path difference (OPD) of the adjustment fiber length providing the first compensation waveguide path 124 in the compensation interferometer 120 with the difference between the channel arm lengths 5 of the first waveguide channel arm 221 and the second waveguide channel arm 222 in the electro-optical modulator 220, an apparatus for modulating the optical paths can be used . Since it may be necessary for the interferometer 120 to be precise in some implementations for example, the splicing of the fiber strands to be exactly accurate for the difference between the first compensation waveguide path 124 and the second Compensation waveguide path 126 adjusts with the mismatch of the corresponding channel between the first waveguide channel arm 221 and the second waveguide channel arm 222 may be difficult. Thus, a device (not shown) can be used to modulate the optical paths to several millimeters with just a voltage applied to finely adjust the length of the first compensation waveguide path 124, for example. Thus, the fibers in the optical path difference adjusting fiber strand can be cut within one centimeter of the adjustment distance, and the apparatus for modulating the optical path of the first path compensation waveguide 124 may be used to better adjust the difference between the first waveguide channel arm 221 and the second waveguide channel arm 222 to be less than 1 mm. In some implementations, the device for obtaining the almost exact track adjustment defect may comprise another (second) piezoelectric tube wound with a fiber inserted at least in part in the first waveguide pathway of the In this regard, the optical path difference adjusting fiber may cause a calibration step to finely adjust the channel misalignment distance in the compensation interferometer 120 to be about the same as the first waveguide channel arm 221 and the second waveguide channel arm 222 of the electro-optical modulator 220. The time division multiplexed demodulator 130 may be operably coupled to the compensation interferometer 120 and the pulse light source 102. For example, the time division multiplexed demodulator 130 may produce control pulses (e.g. a pulse control 134) for the pulse light source 102. The time division multiplexed demodulator 130 may also transmit a phase output control signal (PGC) 132 for compensator interferometer compensator modulation 120 (e.g., by controlling a phase modulator of the second compensating waveguide path 126). In some embodiments, the pulse light source 102 may be a high power, low coherence pulse light source. In this context, high power may be power supplies producing at least 100 mW, and a low coherence source may be a light source capable of emitting broadband optical radiation depending on superluminescence. These may for example comprise light emitting diodes (LEDs), superluminescent diodes (SLD), sources of amplified spontaneous emission (ASE) or another light source likely to have a coherence length of a few tens of micrometers. At least one of these light sources may use a semiconductor optical amplifier as a switch. In addition, in some embodiments, a pulsed light source 102 may contain a bias element, for example a Lyot depolarizer or polarization switch, to avoid attenuation of the signals due to shifting. polarization. It may be noted that the state of polarization (SOP) in a single-mode fiber can shift randomly as a beam propagates across the length of the fiber. If the input beam can be linearly polarized and its axis can be orthogonal to the lithium niobate waveguide axis, a total attenuation of the signals can take place. In some embodiments, a Lyot depolarizer may be used at the source side (eg, coupled or integrated with an output of the pulse light source 102) to light emitted a depolarized light. If the depolarized state of the beam can be preserved at the input of the electro-optical modulator 220 containing the Michelson-lithium niobate-type detection interferometer, a total attenuation can be avoided as half of the optical power can still be in other embodiments, the source bias switching between the orthogonal linear polarizations is possible. In some embodiments using source bias switching, non-attenuation of at least one of the two SOPs may occur, but the system signal bandwidth may be halved, and may require customization of the SOP. at least one semiconductor optoelectronic device (e.g., superluminescent diodes) with a corkscrew polarization maintaining fiber (PMF), for example. It should be understood that in some embodiments, a combination of surface equipment of the system 100 (e.g., a pulse light source 102, the compensation interferometer 120, and / or the multiplexed demodulator time division 130) can be part of an interrogation system. In this regard, the interrogation can take place by emitting light pulses in the optical waveguide and to the detection element array 110, and collecting the time-separated, reflected optical reflected return signals. The reflected time-separated optical return signals can then be processed to precisely measure the optical phase variations associated with the electro-optical modulator 220, which correspond to a variation in the voltage of the electromagnetic field detected by the detector 230, for example . [0030] FIG. 3 is an example of a well system 300 comprising the multiplexed microvolt sensor system 100. In this context, a well may be, relative to the well system 300, but not limited thereto, an oil or gas well. In some implementations, the well system 300 may include drilling equipment, a semi-submersible platform or fixed platforms, for example. According to some embodiments, the multiplexed microvolt sensor system 100 may further include a transmitter 140 which may be used to emit electromagnetic energy involving an electromagnetic field including electric and magnetic field components. In this regard, electromagnetic fields 145 may be induced in the subterranean formation 305. It should be understood, however, that this aspect of the description is not limited to a particular mode of induction of electromagnetic fields in the subterranean formation 305. [0032 The sensing element array 110 may be operably coupled to a portion of the optical waveguide extending down the wellbore 310 (eg, the second optical waveguide segment 152 connected to the with Figure 1). The detection element array 110 may for example be disposed near an outer portion of a form 304 of the wellbore 310. For example, a portion of the fiber cable for providing the optical waveguide together with at least a portion of the sensing elements 110 may be pinched or otherwise attached to an outer surface of the formwork 304. In addition or otherwise, a portion of the fiber cable for providing the optical waveguide together with at least one Part 30 of the sensing elements 110 may be cemented 302 in the wellbore 310 near the outer surface of the formwork 304. Similarly, if a liner is used to extend the borehole well 310 support, the Detection element array 110 may be disposed near an outer portion of the liner (eg, attached or attached thereto). In some embodiments, the time division multiplexing scheme may be used to communicate with each sensing element 110 in the array. For example, a light pulse may be emitted along the optical waveguide (e.g., the second segment of the optical waveguide 152), and over time each sensing element 110 reflects its corresponding signal with The distance to each detection element 110 related to the delay before a response of the reflection is received. As such, in some embodiments, the segment of the optical waveguide may provide a single optical path. For example, a single fiber strand or a single optical path may be used for the optical transmission of the downwardly propagating light pulses and backward propagating and temporally separated reflective return optical signals on at least a portion of the light guide. an optical wave extending between the first sensing element 110 and the last sensing element 110. Thus, using the low coherence interferometry schemes described herein, multiple sensing elements 110 (e.g., 10 to 20 detection elements 110) may be usable on a single fiber strand or on a single optical path. In some embodiments, however, at least one additional sensor may be added using wavelength division multiplexing techniques. For example, wavelength division multiplexing may be employed by different wavelengths of light (eg, using multiple lasers and downhole optical filters). In some implementations, the array of detector elements 110 operatively coupled to the downhole optical waveguide extends a distance greater than 1500 m. In addition, a distance between each sensing element 110 in the sensing element array 110 may be between 10 and 50 m. In some aspects, forward light propagation in a standard fiber may be such that a light pulse will propagate about 1 meter in 5 nanoseconds. In some implementations, for example, each light pulse emitted from the pulse light source 102 may be a 100 ns pulse (e.g., a pulse width of about 20 meters). In some embodiments, the pulse width of the light pulse to be transmitted to the downwardly extending optical waveguide of the wellbore 310 may be designed so that the light pulse can not reach and bouncing two consecutive detecting elements 110 at a time. If each detection element 110 present in the matrix reaches 100 m of separation for example, then the pulse width of the light pulse can exceed 20 m, but be less than 100 m according to some embodiments. An advantage of sending a larger impulse is that the optical energy can be reflected, resulting in a more sensitive measurement. According to some embodiments, after emitting a first light pulse, a second light pulse may not be emitted until the return / reflected optical signals are received from the first light pulse. In some embodiments, however, in which faster measurements are desired, a second light pulse may be emitted so that the second light pulse 25 arrives next to the first sensing element 110 when the optical feedback signals are received. reflected from the first light pulse arrive at the first sensing element 110. In this regard, the length of fiber to reach the first sensing element 110 (e.g., the fiber length from the optical circulator to the first detection element 110) may not need to be considered to determine a gap between successive light pulses in some embodiments. Only the time required for a light pulse to propagate from the first sensing element 110 to the last sensing element 110, and the return / reflected optical signals from the last sensing element to the first sensing element 110 may be necessary to determine an appropriate interval between successive light pulses, in some embodiments. For example, if the distance between the first detection element 110 and the last detection element 110 can reach 1 km, the interval between successive light pulses can be at least 10 low (eg, 5 ns x 1000 m from the first sensing element 110 to the last sensing element 110 and 5 ns x 1,000 m from the last sensing element 110 to the first sensing element 110), according to some embodiments. In this regard, each detection element 110 may be determined by identifying the delay associated with each optical return / reflected signal of a portion of the input light pulse returning to a photodetector in the multiplexed demodulator. In this regard, the time division multiplexed demodulator 130 may receive each reflected / reflected optical signal at its location in the sensing element array 110. However, it will be appreciated that the well system 300 does not is not limited to any interval distance or to a number of detection elements 110 in the matrix. FIG. 4 illustrates a portion of the multiplexed microvolt sensor system 100 appearing in FIGS. 1 and 2, and further shows possible ways of propagating light pulses or light beams in accordance with certain aspects of the description. In some aspects, the system 100 may employ time-division multiplexed and low coherence interferometry techniques. As indicated herein for example, each detector member 110 of the sensor element array may comprise an electro-optical modulator 220 which may include a lithium niobate Michelson type interferometer. An optical path difference of the first waveguide channel arm 221 and the second waveguide channel arm 222 may range from several hundred micrometers to a few millimeters. The path lengths of each of the two channel arms 221, 222 may be a few centimeters.
[0004] In some implementations, the longer the two channel arms 221, 222, the more sensitive the electro-optical modulator 220 is. The compensation interferometer 120 may have an optical path difference which may correspond to that of the electrooptic modulator 220. In some aspects, the coherence length of the pulse light source 102 (e.g., the superluminescent diode) may be shorter than a path difference of a sensing interferometer portion of the electro-optic modulator 220. However, the coherence length of the pulsed light source 102 may be greater than a difference mismatch 15 of the compensation interferometer paths 120 and that the path difference of the detection interferometer. This relation with respect to the coherence length can be expressed as follows: 1ALs ALc A (ALs) <<ALs [0041] where the represents the coherence length of the pulsed light source 102, ALS represents the difference path of the detection interferometer of the electro-optical modulator 220, and ALc represents the path difference of the compensation interferometer 120. For a time-division multiplexed diagram with N 25 detection elements, the matrix of detectors 110 may be constituted by N-1 directional couplers with N-1 limiters (DC) 112 of different ratios of limiters. If the coupler losses are neglected, DC1 112 may have 1 / N limiter power and (N-1) / N transmission power, DC2 112 may have 1 / (N-1) limiter power, etc. The last DC (N-1) 112 may have 1/2 limiter power and 1/2 transmit power to balance the return pulse train, for example.
[0005] The microtensions detected by the detector 230 can be converted into optical phase by the electro-optical modulator 220. The optical signal phase can be converted into voltage readings by the time division multiplexed demodulator 130. [0043] By for example, when a sinusoidal voltage AC can be applied near the waveguide channel arm 221 and the second channel waveguide arm 222 by the first electrode 231, the second electrode 232 and the third electrode 233, the optical path variation for the two channel arms may be complementary (e.g., when the length of either the first waveguide channel arm 221 or the second waveguide channel arm 222 increases, the other decreases due to the opposite voltages applied to the two channel arms by the electrodes connected to the detector 230. According to some aspects of low coherence interferometry of the system 100, the The coherence level, Ic, of the pulsed light source 102 with a bandwidth A A can be expressed as: 22 = kc 02 Where λ represents the central wavelength of the pulsed light source 102, k a coefficient dependent on the pulse light source profile 102 (e.g., a probability density function of the pulse light source 102). According to some implementations, the coherence length of the pulsed light source 102 and the optical path difference (OPD) of the detection and compensation interferometers, a superluminescent diode source of 1550 nm with a bandwidth of 30.degree. Full width half-width (FWHM) bandwidth and approximate Gaussian density function (k = 0.664) may approximate a coherence length of 53.2 μm. Referring to FIG. 4, the two channel arms of the detection interferometer of the sensing element 110 may be identified as channel arm "a" and channel arm "B". The compensation interferometer 120 may be identified as a compensating waveguide path "1" and a compensating waveguide pathway "2". In some aspects, the channel arm "b" and the compensation waveguide track "2" may be longer than the channel arm "a" and the compensation waveguide track "1" , and their differences are both AL (eg, concordant).
[0006] When a light pulse can be reflected or bounced by the two reflector elements 225 of the electro-optical modulator 220 (FIG. 2), two different return beams of different paths are produced. These two return beams can be identified as Ba and Bb and can be propagated to the compensator interferometer 120 through the DC1 120, the optical circulator 104 and the 2x2122 directional coupler. Ba and Bb can both be reflected. again by the two reflectors 128 of the compensation interferometer 120, which thus produces four different beams of different paths. The optical path differences of all possible combinations of return beam pairs among the four different return beams with respect to the source coherence length appear in Table I below: Table I Differences in optical paths between two return beams of the four return beams.
[0007] 25 Two beams on 4 OPD OPD <the (or interference of the beams ) Bai and Bbl AL No Bai and Ba2 AL No Bai and Bb2 2AL No Bbi and Ba2 0 Yes Bbi and Bb2 AL No Ba2 and Bb2 AL No 3037664 19 [0049] Referring to the Table I, only the pair of matching optical path difference beams, Bbl and E382, can interfere, thereby producing the detection optical signals at the time division multiplexed demodulator 130 (or interrogator). The other pairs (or pairs) of return radii may not interfere, as the optical path differences may be longer than the coherence length of the pulsed light source 102 (eg, high power pulse light source). and of low coherence). Some embodiments of the multiplexed microvolt detection system 100 generate optical phase shifts of approximately pi radians in case of voltage variation applied to the modulator of about one volt. As such, a shift of about three radians may correspond to a variation of 1 V in the detector 230. The time division multiplexed demodulator 130 may have a sensitivity of more than 100 prad / m per hertz half power for certain frequencies. Thus, the system 100 can detect small voltages. For example, in the case of a sinusoidal voltage signal AC detected by the sensing element 110, the amplitude of the voltage signal can be detected and determined in the tens of microvolts. In this regard, as described herein, the transmitter 140 may emit an electromagnetic field that has a sinusoidal amplitude such that if the fluid (eg, water, vapor, CO2, etc.) can be At present, the amplitude of the electromagnetic field (e.g., the electromagnetic field 145 (see Fig. 3)) may attenuate differently and can be received and detected by at least one sensing element 110 of the matrix of elements. The voltages produced by the detector 230 may be small. However, with such a low voltage, a typical sensing element 110 may typically not be able to carry this small voltage signal over a long distance. Thus, if this small detected voltage signal is to be electrically connected to the surface (eg, by a copper line at the bottom through a wellhead), the detected voltage signal may not be discernible as lost in the background noise. Thus, it will be appreciated that by modulating the detected voltage signal 5 with the electro-optical modulator 220, the detected voltage signal can be converted into an optical phase variation signal, at which point the signal information will be transmitted. optically by the optical waveguide with little loss (e.g., of the order of 0.2 dB per kilometer for a single-mode fiber). Processes and techniques for detecting a voltage in the range of microvolts in connection with FIG. 4 and with FIGS. 1 to 3 are described. It will be understood, however, that the operations of the method described can be carried out implemented in connection with other processes / processes and aspects of the description presented here. Although certain aspects of the process are described in connection with the exemplary embodiments shown in FIGS. 1 to 4, the method is not limited thereto. An exemplary method may include emitting an electromagnetic field in an underground formation for detection by a sensing element. The sensing element may be coupled to an optical waveguide that extends to the bottom of a wellbore (e.g., wellbore 310 of Figure 3). A light pulse can be transmitted from the optical waveguide to the sensing element. A light source of high power and low pulse coherence having a coherence length which may be shorter than a path difference of a detection element detection interferometer, and which may be longer than a path difference adjustment error of a compensation interferometer (e.g., the compensation interferometer 120 of Figs. 1 and 4) and the path difference of the detection interferometer can be used to transmit the 'light pulse. The method may further comprise receiving two return light pulses from the optical background waveguide from the sensing element. The two return light pulses can be modulated according to the detection of the electromagnetic field by the sensing element. The method may further comprise the direction of the two light pulses back to the compensation interferometer, for example by an optical circulator to the compensation interferometer. The compensation interferometer may include two optical waveguide channels and two mirror sets for reflecting the two return light pulses. Thus, the method may further comprise receiving four compensated light return pulses from the compensation interferometer. The method may further comprise determining a signal of the sensing element based on the four compensated return light pulses. For example, a time division multiplexed demodulator or interrogator may determine the signal of the sensing element from the only pair of return beams with matching optical path differences, as shown here. Figure 5 illustrates another example of multiplexed microvolt sensor system 400. System 400 may be characterized as a coherency domain multiplex scheme. In this regard, a second compensation interferometer having a path mismatch that differs from the first compensation interferometer can be used. In the illustrated system 400 of FIG. 5, identical reference numbers correspond to identical numbers in the system 100 (e.g., the reference element 4xx is the same or is similar to lxx). The system 400 may further include a divider 472 for dividing the return / reflected optical signals to a first compensation interferometer 480 and a second compensation interferometer 490. In addition, a matrix of detection elements 307 is used. 410 of the system 400 comprises a first set of detection elements 410 and a second set of detection elements 410. The first set of detection elements 410 can be controlled consecutively and the second set of detection elements 410 ordered. consecutively thereafter (e.g., a first set of sensing elements 410 being the detector 1, the detector 2, ... and the detector X, and the second set of sensing elements 410 being the detector X + 1, ... the N-1 detector and the N detector). In other implementations, the first set and the second set of sensing elements 410 may alternatively alternate or be interleaved in the array of sensing elements 410. [0059] Still referring to FIG. In Fig. 2, each electro-optical modulator 220 of the first set of sensing elements 410 may comprise a first established detection interferometer, including a first waveguide channel arm 221 and a second waveguide channel arm 222. which may be longer than the first waveguide channel arm 221 by a first established distance (eg 2 mm). Each electro-optical modulator 220 of the second set of detection elements 410 may comprise a second established detection interferometer, including a first waveguide channel 221 and a second waveguide channel 222 which may be longer than the first waveguide channel arm 221 of the second set of detection elements by a second set distance (eg 4 mm) so that the second set distance can be greater than the first distance established. The first compensation interferometer 480 may comprise a directional 2x2 coupler 482 to obtain a compensation path difference that may be approximately equal to a path difference in the electro-optical modulator 220 (e.g., the interferometer). detection device) corresponding to the first waveguide channel arm 221 and the second waveguide channel arm 222 of the first set of detection elements 410. For example, a first waveguide channel may be provided. compensation 484 by a certain length of fiber. The first compensation waveguide path 484 may include a reflector 488 (eg, a Faraday Rotary Mirror (FRM)). A second compensation waveguide path 486 may include a phase modulator. The phase modulator may comprise a loop of the fiber providing the waveguide path that may be wrapped around a piezoelectric disk according to some embodiments. The second compensation waveguide path 486 may also include a reflector 488 (e.g., a FRM mirror). The optical path difference (OPD) of the first compensation interferometer 480 may be adjusted with the difference between the channel arm lengths of the first waveguide channel arm 221 and the second waveguide channel arm. 222 in the electro-optical modulator 220 of the first set of sensing elements 410. The second compensation interferometer 490 may comprise a directional 2x2 coupler 492 to obtain a compensation path difference which may be approximately equal to The difference in paths in the electro-optical modulator 220 (e.g., the detection interferometer) corresponding to the first waveguide channel arm 221 and the second waveguide channel arm 222 of the second set of elements For example, a first compensation waveguide path 494 may also be provided by a certain length of fiber (e.g., whereby the first path gu Compensation wave ide 494 of the second compensation interferometer 490 may be longer than the first compensation waveguide path 484 of the first compensation interferometer 480). The first compensation waveguide path 494 may include a reflector 498 (e.g., a FRM mirror). A second compensation waveguide path 496 may include a phase modulator. The phase modulator may include a loop of the fiber providing the waveguide path which may be surrounded around a piezoelectric disk according to some embodiments. The second compensation waveguide path 496 may also include a reflector 498 (e.g., a FRM mirror). The OPD of the second compensation interferometer 490 can be adjusted with the difference between the channel arm lengths of the first waveguide channel arm 221 and the second waveguide channel arm 222 in the modulator. electro-optic 220 of the second set of sensing elements 410. The time division multiplexed demodulator 430 may be operably coupled to the first compensation interferometer 480 and the second compensation interferometer 490. The division multiplex demodulator time controller 430 may also output a first phase produced support control signal 438 (PGC) for a compensator modulation of the first compensation interferometer 480 and a second control signal 439 of PGC for the compensator modulation of the second interferometer 490. Another aspect of system 400 may be similar to those described with respect to system 100a. Accordingly, coherence domain multiplexing with time-division multiplex demodulation is possible in some embodiments. Thus, an increased number of sensing elements 410 may be deployed on a single fiber strand or on a single optical path. Embodiments described herein include: A. A system which contains a pulsed light source, a first optical waveguide segment operatively coupled to the pulse light source, an optical circulator comprising a first port, a second port and a third port, the first port being operably coupled to the first optical waveguide, a second optical waveguide segment operatively coupled to the second port of the optical circulator, a matrix 3037664 detection elements, each of the detection elements comprising a detector and an electro-optical modulator, the electrooptic modulator being operably coupled to the second optical waveguide segment, a third optical waveguide segment operatively coupled to the third port of the optical circulator, a compensation interferometer operatively coupled to the third optical waveguide segment and a time division multiplexed demodulator operably coupled to the compensation interferometer and the pulse light source. B. A method which comprises emitting an electromagnetic field in a subterranean formation for detection by a sensing element, the sensing element being coupled to an optical waveguide, the transmission of a light pulse by a low coherence high power pulse light source having a coherence length less than a path difference of a sensing element detection interferometer, and longer than a mismatch error the path difference of a compensation interferometer and the path difference of the detection interferometer, the light pulse being transmitted by the optical waveguide, and the reception of two light return pulses through the light guide. optical wave from the sensing element, the two return light pulses being modulated according to the detection of the electromagnetic field by the detection lement. C. A well system which contains an interrogation system designed to produce a light pulse and to receive a plurality of return light pulses, an optical waveguide operatively coupled to the interrogation system, and an array of detection elements operatively coupled to an optical waveguide, the array of sensing elements being disposed proximate an outer portion of at least one of a casing or liner of a well each of the sensing elements comprising a detector and an electro-optical modulator, the electro-optical modulator being operatively coupled to the optical waveguide, each of the electro-optical modulators comprising a first channel arm wave and a second waveguide channel arm longer than the first waveguide channel arm. Each of Embodiments A, B and C may have at least one of the following additional elements in any combination: Element 1: the pulsed light source is a high power pulsed light source and low coherence. Element 2: The pulsed light source contains a polarization element. Element 3: The second optical waveguide segment is a simple optical path. Element 4: The detector is a coil of electroconductive material. Element 5: Each of the electro-optical modulators with the exception of a last electro-optical modulator in the sensing element array is operably coupled to the second optical waveguide segment by a directional coupler. Element 6: A last electro-optical modulator in the array of sensing elements is operatively coupled to the second optical waveguide by direct connection to one end of the second optical waveguide. Element 7: The electro-optical modulator contains a detection interferometer. Element 8: the detection interferometer is a Michelson type interferometer with lithium niobate. Element 9: The detection interferometer contains a first waveguide channel arm and a second waveguide channel arm longer than the first waveguide channel arm. Element 10: A distance over which the second waveguide channel arm exceeds the first waveguide channel arm is between 0.1 mm and 5.0 mm. Element 11: The first waveguide channel arm has a proximal end relative to the pulsed light source and a distal end with a first reflective element thereon, and the second waveguide channel arm has a proximal end relative to the pulsed light source and a distal end to which is a second reflective element. Element 12: The detection interferometer contains an input / output waveguide channel containing a proximal end relative to the pulsed light source and a distal end that connects to the proximal end of the first channel arm waveguide and the proximal end of the second waveguide channel arm. Element 13: The detection interferometer contains a first electrode, a second electrode, and a third electrode, the first waveguide channel arm being disposed between the first electrode and the second electrode, and the second guide channel arm. wave being disposed between the second electrode and the third electrode. Element 14: The first electrode and the third electrode are electrically coupled to a first end of the detector, and the second electrode is electrically coupled to a second end of the detector. Element 15: The compensation interferometer is designed to provide a compensation path difference approximately equal to a path difference in the detection interferometer corresponding to the first waveguide channel arm and the second channel arm. waveguide. Element 16: further comprising a transmitter configured to emit an electromagnetic field for sensing element array detection. Element 17 further comprising an additional compensating interferometer operably coupled to the third optical waveguide segment and the time division multiplexed demodulator, and the array of sensing elements comprising a first set of sensing elements and a plurality of sensing elements. second set of sensing elements, each electro-optical modulator of the first set of sensing elements including a first waveguide channel arm having a proximal end relative to the pulsed light source and a distal end to which a first reflective element is disposed, and a second waveguide channel arm longer than the first waveguide channel arm of a first established distance, the second waveguide channel arm having one end proximal to the pulsed light source and a distal end to which a second element Reflecting is arranged, and each electro-optical modulator of the second set of sensing elements including a first waveguide channel arm having a proximal end relative to the pulsed light source and a distal end at which a first reflective element is disposed, and a second waveguide channel arm longer than the first waveguide channel arm of the second set of detection elements by a second established distance greater than the first established distance, the second waveguide channel arm having a proximal end relative to the pulsed light source and a distal end to which a second reflecting element is disposed. [0072] Element 18: further comprising the direction of the two light pulses back to the compensation interferometer, the compensation interferometer comprising two optical waveguide channels and two mirror assemblies for reflecting the two light pulses in return, receiving four compensated light pulses compensated from the compensation interferometer, and determining a signal of the sensing element according to the four compensated return light pulses. Element 19: the matrix of detector elements operatively coupled to the optical waveguide extends from a distance greater than 1500 m. Element 20: A distance between each sensing element in the sensing element array may be between 10 and 50 m. By way of non-limiting example, the examples of combinations applicable to A, B and C comprise: Element 7 with element 8; element 7 with element 9; element 9 with element 10; Element 9 with element 11; element 11 with element 12; element 9 with element 13; element 13 with element 14; element 9 with element 15.

权利要求:
Claims (23)
[0001]
REVENDICATIONS1. A system (100; 400) for measuring an electromagnetic field (145) near a downhole well area (310) comprising: a pulse light source (102); a first optical waveguide segment (151) operably coupled to the pulsed light source (102); an optical circulator (104) including a first port, a second port, and a third port, the first port operatively coupled to the first optical waveguide segment (151); a second optical waveguide segment (152) operatively coupled to the second port of the optical circulator (104); an array of detection elements (110; 410), each of the detection elements (110; 410) comprising a detector (230; 430) and an electro-optical modulator (220), the electro-optical modulator (220) being operably coupled to the second optical waveguide segment (152); a third optical waveguide segment (153) operably coupled to the third port of the optical circulator (104); a compensation interferometer (120; 480) operatively coupled to the third optical waveguide segment (153); and a time division multiplexed demodulator (130; 430) operatively coupled to the compensation interferometer (120; 480) and the pulse light source (102).
[0002]
The system (100; 400) of claim 1, wherein the pulsed light source (102) is a high power, low coherence pulsed light source (102). 3037664 30
[0003]
The system (100; 400) of claim 1, wherein the pulsed light source (102) contains a polarization element.
[0004]
The system (100; 400) of claim 1, wherein the second optical waveguide segment (152) is a single optical path.
[0005]
The system (100; 400) of claim 1, wherein the detector (230; 430) is a coil of electroconductive material.
[0006]
The system (100; 400) of claim 1, wherein each of the electro-optic modulators (220) except for a last electro-optic modulator (220) in the sensing element array (110). 410) is operatively coupled to the second optical waveguide segment (152) by a directional coupler (112; 122; 492).
[0007]
The system (100; 400) of claim 1, wherein a last electro-optic modulator (220) in the matrix of the sensing elements (110; 410) is operatively coupled to the second optical waveguide (152). ) by a direct connection to one end of the second optical waveguide.
[0008]
The system (100; 400) of claim 1, the optical modulator comprises a detection interferometer.
[0009]
The system (100; 400) of claim 8, wherein the detection interferometer (110; 410) is a lithium niobate Michelson type interferometer. 30
[0010]
The system (100; 400) according to claim 8, wherein the detection interferometer contains a first waveguide channel arm (221) and a second longer waveguide channel arm (222). as the first waveguide channel arm.
[0011]
The system (100; 400) of claim 10, wherein a distance of which the second waveguide channel arm (222) exceeds the first waveguide channel arm (221) is between 0.1 and 5.0 mm.
[0012]
The system (100; 400) of claim 10, wherein: the first waveguide channel arm (221) has a proximal end relative to the pulsed light source and a distal end at which a first reflective element; and the second waveguide channel arm (222) has a proximal end with respect to the pulsed light source and a distal end with a second reflective element thereon.
[0013]
The system (100; 400) according to claim 12, wherein the detection interferometer contains an input / output waveguide channel (223) containing a proximal end with respect to the pulsed light source and a distal end which connects to the proximal end of the first waveguide channel arm (221) and the proximal end of the second waveguide channel arm. 25
[0014]
The system (100; 400) according to claim 10, wherein the detection interferometer contains a first electrode (231), a second electrode (232) and a third electrode (233), the first guide channel arm wave (221) being disposed between the first electrode (231) and the second electrode (232), and the second waveguide channel (222) being disposed between the second electrode (232) and the third electrode ( 233) 3037664 32
[0015]
The system (100; 400) of claim 14, wherein the first electrode (231) and the third electrode (233) are electrically coupled to a first end of the detector (230), and the second electrode (232) is coupled. electrically at a second end of the detector (230; 430).
[0016]
The system (100; 400) of claim 10, wherein the compensation interferometer (120; 480) is arranged to provide a compensation path difference approximately equal to a difference of paths in the interferometer of FIG. sensing corresponding to the first waveguide channel arm (221) and the second waveguide channel arm (222).
[0017]
The system (100; 400) of claim 1, further comprising: a transmitter configured to emit an electromagnetic field (145) for detection by the array of sensing elements (110; 410).
[0018]
The system (100; 400) of claim 1, further comprising: an additional compensation interferometer (490) operatively coupled to the third optical waveguide segment (153) and the division multiplexed demodulator (130; time, and the array of sensing elements (110; 410) comprising a first set of sensing elements (410) and a second set of sensing elements (410), each electro-optical modulator (220) present in the first set of sensing elements (410) includes a first sensing detection interferometer including a first waveguide channel arm (221) having a proximal end relative to the pulsed light source (102) and a distal end to which there is a first reflective element (488), and a second waveguide channel arm (222) longer than the first waveguide channel arm (221) of a first distance established, the second waveguide channel arm (222) having a proximal end relative to the pulsed light source (102) and a distal end having a second reflective element (488), and each electro modulator method (220) present in the second set of detection elements (410) comprises a second set detection interferometer comprising a first waveguide channel arm (221) having a proximal end relative to the light source at pulses and a distal end to which a first reflective element (488) is located, and a second waveguide channel arm (222) longer than the first waveguide channel arm (221) of the second set of detection elements of a second set distance greater than the first established distance, the second waveguide channel arm (222) having a proximal end relative to the second pulsed light source (102) and a distal end with a second reflective element (488) thereon. 20
[0019]
19. A method of measuring an electromagnetic field (145) near a downhole zone (310) comprising: emitting an electromagnetic field (145) into a subterranean formation (305); ) for detection by a sensing element (110; 410), the sensing element (110; 410) being coupled to an optical waveguide (252); transmitting a light pulse by a low coherence, high power pulsed light source (102) having a shorter coherence length than a path difference of a detection element detecting interferometer ( 110; 410), and longer than a difference adjustment error of 3437 paths of a compensation interferometer (120; 480), and the path difference of the detection interferometer (120; 480), the light pulse being transmitted by the optical waveguide (252); and receiving two return light pulses through the optical waveguide (252) from the sensing element (110; 410), the two return light pulses being modulated according to the detection of the electromagnetic field (145) by the sensing element (110; 410). 10
[0020]
The method of claim 19, further comprising: directing the two light pulses back to the compensation interferometer (120; 480), the compensating interferometer (120; 480) having two waveguiding channels. Optics (494, 496) and two mirror assemblies (488) for reflecting the two return light pulses; receiving four compensated return light pulses from the compensation interferometer (120; 480); and determining a signal (132) of the sensing element (110; 410) based on the four compensated return light pulses.
[0021]
21. A well system (300) comprising: an interrogation system adapted to produce a light pulse and to receive a set of return light pulses; an optical waveguide (252) operatively coupled to the interrogation system; and a detector element array (110; 410) operatively coupled to an optical waveguide (252), the array of sensing elements (110; 410) being disposed proximate an exterior portion of an optical waveguide (252). at least one form (304) or liner of a well. 3037664 (310), each of the sensing elements (110; 410) comprising a detector (230; 430) and an electro-optical modulator (220), the electro-optical modulator (220) being operatively coupled with the guide optical wave modulator (252), each of the electro-optical modulator (220) comprising a first waveguide channel arm (221) and a second waveguide channel arm (222) longer than the first waveguide channel (221); waveguide channel arm (221). 10
[0022]
The well system (300) of claim 21, wherein the array of detector elements (110; 410) operably coupled to the optical waveguide (252) extends over a distance greater than 1500 m. 15
[0023]
The well system (300) of claim 21, wherein a distance between each sensing element (110; 410) in the sensing element array (110; 410) may be between 10 and 50 m. 20

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法律状态:
2018-03-02| ST| Notification of lapse|Effective date: 20180131 |

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PCT/US2015/036121|WO2016204738A1|2015-06-17|2015-06-17|Multiplexed microvolt sensor systems|

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