CN102518434A - Micro-detection probe for nuclear magnetic resonance analysis of fluid - Google Patents

Abstract

The invention provides a micro-detection probe for nuclear magnetic resonance fluid analysis, comprising: an annular permanent magnet, and a high magnetic permeability shell sleeved on the outer wall of the annular permanent magnet; the middle part of the annular permanent magnet is provided with a strip-shaped micro-coil structure , and the strip-shaped micro-coil structure is covered with a gradient coil; the strip-shaped micro-coil structure includes an upper shielded copper layer, an upper substrate, a stripline copper layer, a lower substrate and a lower shielded copper layer; the upper substrate Fluid channels are respectively set on the upper and lower substrates; the stripline copper layer is sandwiched between the upper substrate and the lower substrate, and is used to form a radio frequency magnetic field in the fluid channel under the action of an applied current; the upper The shielding copper layer is arranged on the upper substrate, on the surface opposite to the stripline copper layer; the lower shielding copper layer is arranged on the lower substrate, on the surface opposite to the stripline copper layer . The strip coil micro-detection probe provided by the invention has small volume and uniform magnetic field strength.

Description

NMR fluid analysis micro-detection probe

technical field

The invention relates to formation fluid parameter detection technology, in particular to a nuclear magnetic resonance fluid analysis micro-detection probe.

Background technique

During the development of oilfield operations, it is necessary to use a modular formation tester to take liquid from the formation to conduct real-time evaluation and analysis of formation fluid pollution and fluid characteristics, and provide important reference data for oil production. Among them, the downhole optical fluid analysis module and the downhole nuclear magnetic resonance fluid analysis module are two common bottom fluid parameter detection devices. The NMR fluid analysis module uses the NMR principle to measure the fluid parameter T ₁ to evaluate the formation fluid pollution, and to measure the parameters T ₂ and D to obtain fluid viscosity, gas-oil ratio and other parameters.

The nuclear magnetic resonance fluid analysis module provides the required magnetic field for the test through the detection probe, so as to test the fluid parameters T ₁ , T ₂ and D by using the nuclear magnetic resonance phenomenon. With the development of hardware technology and micro-electro-mechanical systems (Micro-Electro-Mechanical Systems, MEMS) technology, a micro-detection probe for nuclear magnetic resonance fluid analysis is proposed, which can use a micro-coil probe combined with a small low-cost spectrometer, especially for Combined with mature microfluidic technologies such as capillary electrophoresis or liquid separation to form an on-chip micro-total analysis system to measure fluid parameters. The micro-detection probe in the form of a micro-coil has the characteristics of low power consumption, small size and high detection sensitivity. It can be applied in the petroleum field, and is especially suitable for the measurement requirements of low power consumption while drilling.

The NMR fluid analysis micro-detection probe is based on the principle of NMR spectroscopy. It uses the NMR phenomenon and its chemical shift to study the existence or molecular structure of compounds. Because the ambient temperature of the oil well varies greatly with the depth of the formation, the downhole NMR The uniformity of the static magnetic field cannot meet the requirements of nuclear magnetic resonance spectroscopy. Therefore, the micro-detection probe can provide the required magnetic field for fluid detection to measure fluid parameters T ₁ , T ₂ and D. At present, planar helical microcoils and toroidal tube coils are usually used in micro-detection probes for NMR fluid analysis, which use the structure of planar helical microcoils and toroidal tube coils to provide microchannels and magnetic fields for the fluid passing through the microchannels. The required magnetic field is measured, but the uniformity of the RF magnetic field formed by it is poor.

Contents of the invention

The invention provides a nuclear magnetic resonance fluid analysis micro-detection probe, which can effectively overcome the problems existing in the prior art.

The present invention provides a nuclear magnetic resonance fluid analysis micro-detection probe, comprising: an annular permanent magnet, and a high magnetic permeability shell sleeved on the outer wall of the annular permanent magnet;

The middle part of the annular permanent magnet is provided with a strip-shaped micro-coil structure, and a gradient coil is sleeved on the strip-shaped micro-coil structure;

The strip-shaped microcoil structure includes an upper shielding copper layer, an upper substrate, a stripline copper layer, a lower substrate and a lower shielding copper layer;

The upper substrate and the lower substrate are respectively provided with fluid channels;

The stripline copper layer is interposed between the upper substrate and the lower substrate, and is used to form a radio frequency magnetic field in the fluid channel under the action of an applied current;

The upper shielding copper layer is disposed on the upper substrate, on the surface opposite to the stripline copper layer;

The lower shielding copper layer is disposed on the lower substrate, on the surface opposite to the stripline copper layer.

In the above nuclear magnetic resonance fluid analysis micro-detection probe, the stripline copper layer includes an effective stripline copper layer and an edge copper layer;

The width of the middle portion of the effective stripline copper layer is smaller than the width of the end portion, and a groove is formed inwardly from both sides in the middle portion of the effective stripline copper layer;

The edge copper layer is disposed in the groove, and there is a gap between the edge copper layer and the effective stripline copper layer.

In the above micro-detection probe for nuclear magnetic resonance fluid analysis, the shapes of the groove and the edge copper layer are both trapezoidal.

In the above nuclear magnetic resonance fluid analysis micro-detection probe, the upper shielding copper layer, the stripline copper layer and the lower shielding layer are made by MEMS technology.

In the above nuclear magnetic resonance fluid analysis micro-detection probe, the fluid channel is an elliptical fluid channel.

In the above nuclear magnetic resonance fluid analysis micro-detection probe, the upper substrate and the lower substrate are boric acid glass substrates.

In the above nuclear magnetic resonance fluid analysis micro-detection probe, the two ends of the fluid channel are respectively connected with capillaries for introducing external fluid into the fluid channel.

In the above micro-detection probe for nuclear magnetic resonance fluid analysis, the capillary is made of polyetheretherketone resin.

The micro-detection probe of the NMR fluid analyzer provided by the present invention uses the upper shielded copper layer, the stripline copper layer and the lower shielded copper layer to form a stripline microcoil structure, which can be two coils formed on the upper substrate and the lower substrate. The fluid channel provides the required magnetic field, which makes the volume of the probe smaller than that of the existing toroidal coil structure in the case of detecting the same volume of samples; at the same time, the magnetic field formed by the strip line microcoil structure is more uniform, and the ring The static magnetic field B ₀ generated by the permanent magnet has little interference, which makes the detection of fluid parameters more accurate. The micro-detection probe provided by the invention has small volume and low power consumption, and can be combined with a formation testing instrument to measure fluid parameters, thereby effectively reducing the size of the entire formation testing instrument.

Description of drawings

Fig. 1 is the structural schematic diagram when the nuclear magnetic resonance fluid analysis micro-detection probe provided by the embodiment of the present invention is combined with the formation testing instrument;

Fig. 2 is the structural representation of the nuclear magnetic resonance fluid analysis micro-detection probe provided by the embodiment of the present invention;

3A is a schematic perspective view of the strip microcoil in an embodiment of the present invention;

3B is a schematic diagram of the assembly structure of the strip microcoil in the embodiment of the present invention;

4 is a schematic structural view of a stripline copper layer in an embodiment of the present invention;

5 is a schematic diagram of the cross-sectional structure of FIG. 3A and a magnetic field generated when a current is applied to the stripline copper layer;

6 is a schematic diagram of the variation curve of the radio frequency magnetic field amplitude along the direction of the fluid channel according to the embodiment of the present invention;

7 is a schematic structural diagram of a gradient coil in an embodiment of the present invention;

Fig. 8 is a schematic diagram of a pulse sequence when using the NMR fluid analysis micro-detection probe provided by an embodiment of the present invention to measure fluid parameters.

Detailed ways

Fig. 1 is a schematic structural view of the nuclear magnetic resonance fluid analysis micro-detection probe provided by the embodiment of the present invention when it is combined with a formation tester; Fig. 2 is a structural schematic diagram of the nuclear magnetic resonance fluid analysis micro-detection probe provided by the embodiment of the present invention; Fig. 3A is the present invention The perspective structure diagram of the strip-shaped microcoil in the embodiment of the invention; FIG. 3B is a schematic diagram of the assembly structure of the strip-shaped microcoil in the embodiment of the invention. As shown in Figure 1, the schematic diagram of the formation testing instrument being arranged in the oil well, the formation testing instrument includes a hydraulic module 1, a probe module 2, a micro-detection probe 3, a sampling module 4 at the end of measurement and a pumping module 5, wherein the hydraulic module 1. The formation fluid can be introduced into the instrument through the probe module 2; the micro-detection probe 3, which is the NMR fluid analysis micro-detection probe provided by the embodiment of the present invention, can perform NMR relaxation time and diffusion measurement on the formation fluid; measure The end sampling module 4 can sample the fluid or drain the fluid to the wellbore 6 through the pump out module 5 .

As shown in Figure 2, it is a schematic diagram of the enlarged structure of the micro-detection probe 3 in Figure 1, the micro-detection probe 3 may specifically include: an annular permanent magnet 31, a high magnetic permeability shell 32, a strip-shaped micro-coil structure 33 and a gradient coil 34, Wherein, the high magnetic permeability casing 32 is sleeved on the outer wall of the ring-shaped permanent magnet 1 ; the strip-shaped micro-coil structure 33 is set in the middle of the ring-shaped permanent magnet 31 , and the gradient coil 34 is sleeved on the strip-shaped micro-coil structure 33 . In this embodiment, the annular permanent magnet 31 can form a uniform static magnetic field B ₀ in the central area, and the high magnetic permeability shell 32 can shield the magnetic field from radiating outwards, and also provide a closed magnetic circuit, thereby improving the magnetic field formed in the central area uniformity and stability.

As shown in FIG. 3A and FIG. 3B , the strip microcoil structure 33 includes an upper substrate 331, a lower substrate 332, a stripline copper layer 333, an upper shielding copper layer 334 and a lower shielding copper layer 335, wherein the upper substrate 331 and the lower The substrates 332 are arranged oppositely, the upper substrate 331 and the lower substrate 332 are respectively provided with a fluid channel C, and the fluid channel C runs through the fluid channel of the substrate; the stripline copper layer 333 is sandwiched between the upper substrate 331 and the lower substrate 332, the The stripline copper layer 333 is used to form a radio frequency magnetic field in the fluid channel under the action of an applied current; the upper shielding copper layer 334 is arranged on the surface of the upper substrate 331 opposite to the stripline copper layer 333, as shown in FIG. 3B The upper surface of the upper substrate 331 is shown, and the lower shielding copper layer 335 is disposed on the surface of the lower substrate 332 opposite to the stripline copper layer 333 , that is, the lower surface of the lower substrate 332 as shown in FIG. 3B .

In this embodiment, the upper shielding copper layer 334, the stripline copper layer 333 and the lower shielding copper layer 335 form a strip-shaped microcoil, which provides the required radio frequency magnetic field for the measurement of fluid parameters, which can be formed on glass by MEMS technology. On the substrate, specifically, it can be made on a glass substrate by MEMS processes such as photoresist mask and copper electroplating; the stripline copper layer 333 can apply current to generate the required magnetic field, and at the same time can receive signals, so that Fluid parameters are measured through the stripline copper layer 333 . It can be seen that the current channel in this embodiment is composed of the stripline copper layer 333, the upper shielding copper layer 334 and the lower shielding copper layer 335, wherein the current flows through the stripline copper layer 333, and the upper shielding copper layer 334 The lower shielding copper layer 335 is both a shielding layer and a loop, so that when the current passes through the stripline copper layer 333, the radio frequency magnetic field formed in the fluid channel on the upper substrate 331 and the lower substrate 332 is more uniform, and the area of the uniform magnetic field larger.

Those skilled in the art can understand that, in actual measurement, both the upper shielding copper layer 334 and the lower shielding copper layer 335 are grounded copper layers, and share the ground with the ground end of the stripline copper layer 333, so that the three copper layers can be used , to generate a strip-like microcoil structure to provide the required RF magnetic field for fluid measurement.

In this embodiment, the fluid channel formed on the upper substrate 331 and the lower substrate 332 is an elliptical fluid channel, and the elliptical fluid channel is set so that when the stripline copper layer 333 applies a current, a more fluid channel is formed in the fluid channel. With a uniform magnetic field, the magnetic field experienced by the fluid flowing through the fluid channel is also more uniform, which can effectively improve the accuracy of fluid parameter measurement.

In this embodiment, both the upper substrate 331 and the lower substrate 332 are boric acid glass substrates, so that the upper shielding copper layer 334 , the stripline copper layer 333 and the lower shielding copper layer 335 are separated by the boric acid glass substrate.

FIG. 4 is a schematic structural diagram of a copper layer of a strip line in an embodiment of the present invention. In this embodiment, as shown in FIG. 4 , the stripline copper layer 333 includes an effective stripline copper layer 3331 and two edge copper layers 3332, wherein the effective stripline copper layer 3331 has a central width smaller than its end width , so that a groove A recessed from both sides inward is formed in the middle of the effective stripline copper layer 333, the edge copper layer 3332 is arranged in the groove A, and the edge copper layer 3332 and the effective stripline copper layer 3331 There is a gap B between them, so that the edge copper layer 3332 is not connected to the effective stripline copper layer 3331 . By setting the middle part of the effective stripline copper layer 3331 as a groove structure with both sides inwardly recessed, the middle part of the effective stripline copper layer 3331 is narrower, so that when the current passes through, the current at the narrower middle part As the density increases, the magnetic field strength _B1 generated in the fluid channels in the upper substrate 331 and the lower substrate 332 will increase, thereby increasing the magnetic field strength applied to the fluid in the fluid channels.

In this embodiment, the above-mentioned groove A and the edge copper layer 3332 are trapezoidal structures that cooperate with each other, so that a stronger magnetic field intensity can be generated in the middle of the effective stripline copper layer 3331 .

In this embodiment, in order to facilitate the fluid entering the formation testing instrument into the fluid channel, capillary tubes can be connected to the two ends of the fluid channel for introducing external fluid into the fluid channel. Specifically, the capillary tube can be used A capillary made of polyetheretherketone (Poly-Ether-Ether-Ketone, PEEK) resin.

FIG. 5 is a schematic diagram of the cross-sectional structure of FIG. 3A and the magnetic field generated when a current is applied to the stripline copper layer. As shown in Figure 5, the upper shielding copper layer 334 and the lower shielding copper layer 335 are two shielding layers, which can shield the magnetic field; the current density in the middle of the stripline copper layer 333 is relatively large, and the The magnetic field can be confined in the central region of the entire micro-detection probe, wherein the direction of the static magnetic field _B0 generated by the annular permanent magnet 31 in FIG. 2 is shown in _FIG. The direction is shown in FIG. 5 , and it can be seen that the direction of _B1 formed by the two elliptical fluid channels C in the upper substrate 331 and the lower substrate 332 is opposite. In this way, the micro-coil structure formed by the copper layer of the strip line and the ring-shaped permanent magnet can provide the required B ₀ and B ₁ magnetic fields for fluid parameter measurement, which has met the test requirements.

Fig. 6 is a schematic diagram of the variation curve of the amplitude of the radio frequency magnetic field along the direction of the fluid channel according to the embodiment of the present invention. As shown in Figure 6, when the stripline copper layer 333 applies current, a schematic diagram of the change in the amplitude of the radio frequency magnetic field generated along the fluid channel direction of the upper substrate or the lower substrate, wherein the abscissa in Figure 6 is the length of the stripline copper layer, and the vertical The coordinates are the magnetic field strength of the radio frequency magnetic field generated by the stripline copper layer. It can be seen that at the position of the stripline copper layer -4mm to 4mm, the magnetic field intensity generated is about 2.04 Gauss (Gauss). Therefore, the stripline The effective length of the copper layer is 8mm, and the length of the elliptical fluid channel formed on the upper and lower substrates should be at least 8mm.

Fig. 7 is a schematic structural diagram of a gradient coil in an embodiment of the present invention. As shown in Figure 7, the gradient coil 34 can form a magnetic field gradient to complete the measurement of diffusion. Specifically, the gradient coil 34 can include upper and lower coils, and a certain current can be applied to the gradient coil 34 when measuring the fluid diffusion coefficient D , the direction of the current is shown by the arrow in Fig. 7, so that a gradient magnetic field can be formed to measure the fluid parameter D. The magnetic field formed by the gradient coil 34 has a linear gradient in the z direction, and is parallel to the direction of the static magnetic field B ₀ , that is, superimposed on the static magnetic field B ₀ , and the two form a new gradient magnetic field.

In this embodiment, the NMR fluid analysis micro-detection probe can apply a certain magnetic field to the fluid entering the fluid channel, so as to measure the NMR relaxation time and diffusion of the fluid, so as to obtain the fluid parameters T ₁ , T ₂ and D. Among them, the transverse relaxation time T ₂ is the most commonly used measurement parameter in NMR logging. Through the analysis of T ₂ , geological information such as fluid type and fluid content can be obtained effectively. Specifically, the transverse relaxation time T ₂ The measurement is usually completed with the CPMG pulse sequence a shown in Figure 8, which is based on the spin echo pulse sequence, and the transverse relaxation is determined through the observed decay process of the spin echo sequence; the longitudinal relaxation time T ₁ It is a quantity that characterizes the degree of recovery of the magnetization vector, and is closely related to geological information such as fluid type and fluid content. Its basic measurement method is completed through the saturation recovery pulse sequence b shown in Figure 8; The amount of fluid viscosity, the basic measurement method is through the pulse sequence c shown in Figure 8 to complete. The specific measurement process of the fluid parameters T ₁ , T ₂ and D in this embodiment is similar to the prior art, and will not be described in detail here.

The NMR fluid analysis probe of the embodiment of the present invention can be used in downhole NMR fluid analysis for the detection of the NMR characteristics and composition of the fluid. The NMR fluid analysis can be used in combination with a cable or a formation tester while drilling. Obtain information on formation fluid properties in the context of reservoir conditions, for openhole or perforated cased holes.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (8)

1. a nuclear magnetic resonance fluid is analyzed little detection probe, it is characterized in that, comprising: annular permanent magnet, and be set in the high magnetic conductive shell on the said annular permanent magnet outer wall;

The middle part of said annular permanent magnet is provided with banded little loop construction, and is arranged with gradient coil on the little loop construction of said band shape;

The little loop construction of said band shape comprises shielding copper layer, upper substrate, strip line copper layer, infrabasal plate and shields the copper layer down;

Be respectively arranged with the fluid passage on said upper substrate and the infrabasal plate;

Said strip line copper layer is folded between said upper substrate and the infrabasal plate, is used in said fluid passage, forming RF magnetic field applying under the function of current;

The said shielding copper layer of going up is arranged on the said upper substrate, with said strip line copper layer back to the surface;

Said down shielding copper layer is arranged on the said infrabasal plate, with said strip line copper layer back to the surface.

2. nuclear magnetic resonance fluid according to claim 1 is analyzed little detection probe, it is characterized in that, said strip line copper layer comprises effective strip line copper layer and edge copper layer;

The middle part width of said effective strip line copper layer forms the groove that is caved inward by both sides less than the width of end at the middle part of said effective strip line copper layer;

Said edge copper layer is arranged in the said groove, and has the gap between said edge copper layer and the said effective strip line copper layer.

3. nuclear magnetic resonance fluid according to claim 2 is analyzed little detection probe, it is characterized in that, the shape of said groove and edge copper layer is trapezoidal.

4. analyze little detection probe according to claim 1,2 or 3 described nuclear magnetic resonance fluids, it is characterized in that, said shielding copper layer, strip line copper layer and the following screen layer gone up forms through the MEMS fabrication techniques.

5. analyze little detection probe according to claim 1,2 or 3 described nuclear magnetic resonance fluids, it is characterized in that, said fluid passage is oval fluid passage.

6. nuclear magnetic resonance fluid according to claim 1 is analyzed little detection probe, it is characterized in that, said upper substrate and infrabasal plate are the borate glass substrate.

7. the little detection probe of nuclear magnetic resonance fluid analyzer according to claim 1 is characterized in that the two ends of said fluid passage are connected with capillary tube respectively, is used for external fluid is imported said fluid passage.

8. the little detection probe of nuclear magnetic resonance fluid analyzer according to claim 7 is characterized in that, said capillary tube is made the capillary tube that obtains for adopting polyether-ether-ketone resin.

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