CN102650208B - Nuclear magnetic resonance logger probe while drilling and nuclear magnetic resonance logger while drilling - Google Patents

Abstract

The invention provides a probe of a nuclear magnetic resonance logging tool while drilling and a nuclear magnetic resonance logging tool while drilling. The NMR logging while drilling instrument includes: a probe skeleton, a mud pipe is pierced through the center of the probe skeleton; a ring-shaped first main magnet and a second main magnet are sleeved in the probe skeleton and on the mud pipe, Both the first main magnet and the second main magnet are axially magnetized, and one end with the same polarity of the first main magnet and the second main magnet is arranged oppositely; An antenna forming a pulsed magnetic field; between the first main magnet and the second main magnet, and coaxially sleeved on the mud pipe, at least one pair of ring-shaped focusing magnets constitute two of the said pair of focusing magnets. A focusing magnet is symmetrical about the middle section of the antenna, and the focusing magnet is radially magnetized. The probe of the nuclear magnetic resonance logging tool while drilling of the present invention can increase the vertical extension length of the sensitive area, improve the signal-to-noise ratio of the measurement and the accuracy of the measurement result.

Description

While drilling nuclear magnetic resonance logging tool probe and while drilling nuclear magnetic resonance logging tool

technical field

The invention relates to nuclear magnetic resonance logging technology, in particular to a probe of a nuclear magnetic resonance logging tool while drilling and a nuclear magnetic resonance logging tool while drilling.

Background technique

The logging-while-drilling nuclear magnetic resonance tool uses the principle of nuclear magnetic resonance to measure the formation conditions around the oil well, so as to detect the information related to the oil and gas characteristics in the formation. It mainly forms a magnetic field through the probe and collects the resonance signal, and then according to the resonance signal. The fluid in the pores can be analyzed to directly measure the density of hydrogen nuclei in the reservoir fluid, and the nuclear magnetic data obtained by using nuclear magnetic resonance signals can be directly converted into apparent water-bearing porosity, and the existence and content of different fluids in the reservoir can also be determined and fluid properties.

Among them, the probe is the key component to excite the nuclear magnetic resonance phenomenon and receive the nuclear magnetic resonance signal under the oil and gas well. The structural design of the probe determines the key performance such as the measurement method of the logging tool, the resonance area where the nuclear magnetic resonance is generated, and the signal strength of the nuclear magnetic resonance. The probe mainly includes a magnet and an antenna. The magnet is used to generate a static magnetic field in the formation around the wellbore to excite the hydrogen atoms in the liquid oil, gas and water in the formation; the antenna is used to transmit radio frequency pulses to the formation to form a pulsed magnetic field. The pulsed magnetic field excites hydrogen atoms in the formation that have been polarized by the static magnetic field to generate nuclear magnetic resonance phenomena, and is also used to receive and collect nuclear magnetic resonance signals generated by hydrogen atoms in the formation.

Fig. 1 is the structure schematic diagram of the probe of the nuclear magnetic resonance logging instrument while drilling in the prior art, as shown in Fig. 1, this probe mainly comprises: two main magnets 11 that are arranged up and down oppositely, are arranged between two main magnets 11 The antenna 12, and the probe frame for accommodating and fixing the main magnet 11 and the antenna 12; wherein, the main magnet 11 is in the shape of a ring, and the same poles of the two main magnets 11 face each other. Under this structure, the direction of the static magnetic field _B0 formed by the main magnet 11 and the direction of the pulsed magnetic field _B1 formed by the radio frequency pulse emitted by the antenna are perpendicular to each other on the cross section of the middle position of the probe ( _B0 is perpendicular to _B1 of the nuclear magnetic resonance One of the necessary excitation conditions), that is, a ring-shaped sensitive region M that can generate nuclear magnetic resonance is formed at the position corresponding to the formation.

The static magnetic field strength of this probe in the prior art is low, and the resonance frequency of nuclear magnetic resonance is also low, resulting in insufficient signal strength. In addition, due to the arrangement of the main magnet and the antenna, the sensitive area M is vertically The height is small, generally: 20-25.5mm, and the acquisition of each group of signals needs to go through a measurement period of 3-5 seconds during the measurement process, and at the same time the probe is continuously drilling, so that in this measurement period, The location of the sensitive area M is switched too frequently, resulting in a low signal-to-noise ratio of the measurement results (research shows that the signal-to-noise ratio is proportional to the height of the sensitive area), which affects the measurement accuracy.

Contents of the invention

Aiming at the above-mentioned defects in the prior art, the present invention provides a probe of a nuclear magnetic resonance logging tool while drilling and a nuclear magnetic resonance logging tool while drilling for detecting formation rock and fluid information, which improves the sensitive area that can generate nuclear magnetic resonance The height, improve the signal-to-noise ratio, thereby improving the purpose of measurement accuracy.

The present invention provides a probe of a nuclear magnetic resonance logging tool while drilling, comprising: a columnar probe frame, the central axis of the probe frame is pierced with a mud pipe for the circulation of drilling fluid; The coaxial sleeve on the mud pipe is provided with a ring-shaped first main magnet and a second main magnet, and the first main magnet and the second main magnet are both axially magnetized, and the first main magnet and the second main magnet are One end with the same polarity of the second main magnet is oppositely arranged; on the peripheral side wall of the probe frame and corresponding to the middle position of the first main magnet and the second main magnet, an antenna for forming a pulsed magnetic field is fixedly embedded ; Between the first main magnet and the second main magnet, and on the mud pipe, at least one pair of ring-shaped focusing magnets are coaxially sleeved, forming two of each pair of focusing magnets The focusing magnet is symmetrical with respect to the middle section of the antenna, the focusing magnet is radially magnetized, and the focusing magnet is relatively fixed to the probe frame.

The present invention also provides a logging-while-drilling nuclear magnetic resonance tool, comprising: a downhole drilling tool and an uphole signal processing device, wherein the probe of the nuclear magnetic resonance logging-while-drilling tool as described above is fixedly arranged in the drill collar of the downhole drilling tool.

The probe static magnetic field distribution of the NMR logging tool while drilling provided by the present invention can significantly increase the vertical extension length of the sensitive area capable of generating nuclear magnetic resonance, and when the drill bit is drilling, the rotation of the probe will not affect the measurement At the same time; it can also reduce the number of position switching in the sensitive area during the measurement period of collecting each group of signals, and improve the signal-to-noise ratio of the measurement and the accuracy of the measurement results.

Description of drawings

Fig. 1 is the structural representation of the probe of the NMR logging tool while drilling in the prior art;

Fig. 2 is the structural representation of the probe embodiment of the nuclear magnetic resonance logging instrument while drilling of the present invention;

Fig. 3 is a schematic structural view of an embodiment of the first main magnet or the second main magnet in Fig. 1;

Fig. 4 is a structural schematic diagram of another embodiment of the first main magnet or the second main magnet in Fig. 1;

Fig. 5 is a structural schematic diagram of another embodiment of the first main magnet or the second main magnet in Fig. 1;

Fig. 6 is a schematic structural view of an embodiment of the focusing magnet in Fig. 1;

Fig. 7 is the schematic diagram of the magnetic field strength distribution that the probe of the present invention forms;

FIG. 8 is a schematic structural diagram of the antenna in FIG. 1 .

Detailed ways

The while-drilling nuclear magnetic resonance logging tool can be used in vertical wells, inclined wells, and even horizontal wells. Therefore, the drilling direction of the while-drilling nuclear magnetic resonance logging tool is the extension direction of the central axis of the probe frame, that is, "axial". But it is not necessarily vertical; but for the convenience of description, in the embodiments, it will be described by taking a vertical well as an example, that is to say, "axial" in the following embodiments refers to the vertical direction. However, the content of this embodiment does not limit the present invention.

This embodiment provides a probe of a nuclear magnetic resonance logging tool while drilling, as shown in Figure 2, comprising: a vertically extending, columnar probe frame 10, the central axis of the probe frame 10 is pierced with a hole for the circulation of drilling fluid Mud pipe 101; in the probe frame 10 and coaxially sleeved on the mud pipe 101, a ring-shaped first main magnet 21 and a second main magnet 22 of the same size are arranged, and the first main magnet 21 and the second main magnet The magnets 22 are all axially magnetized, and one end of the first main magnet 21 and the second main magnet 22 with the same polarity are oppositely arranged; on the peripheral side wall of the probe frame 10, and corresponding to the first main magnet 21 and the second main magnet The middle position of the two main magnets 22 is fixedly embedded with an antenna 24 for forming a pulsed magnetic field; between the first main magnet 21 and the second main magnet 22, and coaxially sleeved on the mud pipe 101, at least a pair of circular The ring-shaped focusing magnet 23 constitutes two focusing magnets 23 in each pair of focusing magnets, which are symmetrical to the middle section of the antenna 24 .

Specifically, a through hole may be provided at the central axis of the cylindrical probe frame 10, and a circular tubular mud pipe 101 extending up and down may be fixedly embedded in the through hole. Optionally, the through hole may also be The hole can be directly used as the mud pipe 101; the first main magnet 21, the second main magnet 22 and the focusing magnet 23 can be fixedly sleeved around the mud pipe 101. At this time, the probe frame 10 is used to house the first main magnet 21 , The accommodating cavity of the second main magnet 22 and the focusing magnet 23 can be greater than the volume of the above-mentioned parts; but when the mud pipe 101 is a through hole on the probe frame 10, the first main magnet 21, the second main magnet 22 can be and focusing magnets 23 are respectively fixedly embedded in specific positions. At this time, the accommodating cavity for accommodating these parts should match the volume of each part, so as to ensure that the first main magnet 21, the second The relative positions of the two main magnets 22 and the focusing magnet 23 are fixed.

The antenna 24 surrounds the focusing magnets, and the two focusing magnets 23 in each pair of focusing magnets, as well as the first main magnet and the second main magnet are symmetrical about the horizontal mid-section of the antenna 24 . The first main magnet 21 and the second main magnet 22 are axially magnetized, that is, the two ends of the first main magnet 21 and the second main magnet 22 are N poles and S poles respectively; the focusing magnet 23 is radially magnetized , that is, the inner annulus of the focusing magnet 23 can be N pole or S pole, and the outer annulus can be S pole or N pole; and when the N pole of the first main magnet 21 and the N pole of the second main magnet 22 are arranged oppositely , the inner annulus of the focusing magnet 23 is an S pole, and the outer annulus is an N pole; when the S pole of the first main magnet 21 and the S pole of the second main magnet 22 are arranged oppositely, when the S When the pole and the S pole of the second main magnet 22 are arranged oppositely, the inner annulus of the focusing magnet 23 is an N pole, and the outer annulus is an S pole; the static magnetic field intensity formed by the first main magnet 21 and the second main magnet 22 can be the same .

Preferably, the focusing magnets can be many pairs, such as two pairs, and the distance between a pair of focusing magnets 23 close to the horizontal middle section of the antenna 24 can be 2-5mm; The vertical height of the focus magnet 23 of two main magnetic poles 22 can be 1/4～1/2 of a pair of focus magnet 23 near the horizontal middle section of antenna 24; And the diameter of focus magnet 23 also can be less than or equal to the first main magnet The diameter of the magnet 21 or the second main magnet 22 is to further facilitate the arrangement of the antenna 24 .

The arrangement of the first main magnet 21 and the second main magnet 22 focusing magnet 23 in the MWD NMR logging tool probe of the present embodiment, the magnetic induction intensity distribution of the static magnetic field generated is as shown in Figure 7, the outer surface Y of the probe A gap is formed with the well wall J of the vertical well, and the central axis N of the probe Y represents the extension direction of the mud pipe 101 at the same time. It can be seen from Figure 7 that, corresponding to the vertical middle of the probe, the magnetic induction intensity extends vertically and is evenly distributed, so that the vertical extension length of the sensitive area M that can form nuclear magnetic resonance is significantly increased (as shown in Figure 2) , specifically, the length of the sensitive region M of the present embodiment along the drilling direction can reach 100-150 mm, which is about 5 times the length of the sensitive region in the prior art; in addition, the arrangement of multiple pairs of focusing magnets 23 can also improve the The intensity of the static magnetic field is increased, thereby increasing the intensity of the acquired nuclear magnetic resonance signal.

In addition, since at least one pair of focusing magnets 23 is disposed between the first main magnet 21 and the second main magnet 22, the strength of the formed static magnetic field is also increased. Since, the resonant frequency can be determined by:

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}$

Among them, γ is the gyromagnetic ratio, for the hydrogen nucleus f ₀ is the resonant frequency that produces nuclear magnetic resonance; B ₀ is the strength of the static magnetic field.

It can be seen that when the volume of the sensitive area is constant, the resonance frequency is proportional to the strength B ₀ of the static magnetic field. Therefore, the probe of the NMR logging tool provided in this embodiment has a relatively high resonance frequency, and the signal-to-noise ratio of the measurement is generally It is proportional to the 3/2 power of the resonance frequency, and further improves the signal-to-noise ratio of the measurement, which is beneficial to obtain better measurement accuracy.

When performing nuclear magnetic resonance measurements of vertical wells, the probe of the NMR logging tool while drilling in this embodiment can be fixedly installed in the drill collar above the drill bit (the side of the drill bit away from the drilling direction), or fixedly installed in the drill collar. Between the collar and the drill bit as part of the drill collar. Since the sensitive area M formed by the probe provided in this embodiment can form nuclear magnetic resonance is a cylindrical shape coaxial with the central axis of the drill bit, therefore, when the drill bit drills vertically downward, the rotation of the probe with the drill bit will not affect the measurement; At the same time, due to the increase in the length of the sensitive area M in the drilling direction, the position switching times of the sensitive area M are also significantly reduced during the measurement period of collecting each group of signals, that is to say, because the length of the sensitive area M increases by five times, so that the vertical displacement of the drill bit in one measurement cycle will not exceed the sensitive area M, thereby avoiding the prior art, the antenna 24 has completely moved out of the transmitting device during the period of waiting for the echo signal after the antenna transmits the radio frequency signal The position of the sensitive area M at the time of the signal, and at the position of the sensitive area M at this time, because the residence time has not yet reached the polarization time required for the polarization of the formation, the final signal is inaccurate; This embodiment improves the signal-to-noise ratio of the measurement by increasing the length of the sensitive area M in the drilling direction (it has been confirmed that the signal-to-noise ratio is proportional to the length of the sensitive area in the drilling direction in the nuclear magnetic resonance measurement), and improves the final The precision of the measurement results.

Preferably, as shown in Figure 2, the focus magnets 23 can be two pairs, and the four focus magnets that constitute two pairs of focus magnets are arranged at equal intervals in the vertical direction, and the top surface of the focus magnet at the top and the focus magnet at the bottom The bottom surface of the magnet protrudes from both ends of the antenna.

In the above-described embodiment, as shown in FIG. 8 , the antenna 24 is a wire wound into a cylindrical helix, and the central axis of the columnar helix is connected to the first main magnet 21, the second main magnet 22 and the focus. The central axis of the magnet 23 is on the same straight line, so as to adapt to the rotational movement of itself; Connect to an LRC resonant circuit (not shown), so that the resonant frequency of the antenna 24 is the same as the resonant frequency of the hydrogen nuclei in the formation at the sensitive area M by adjusting the capacitance in the LRC resonant circuit, so as to excite the nuclear magnetic resonance phenomenon .

The probe of the NMR logging tool in this embodiment can form the NMR sensitive region M with a radial thickness of 15-20mm, which can effectively eliminate the adverse effects of the radial vibration of the probe caused by the drill bit on the measurement accuracy.

Further, the above-mentioned antenna 24 can be manufactured by using a flexible printed circuit board (Flexible Printed Circuit Board, FPCB) etching technology.

In the above-described embodiment, as shown in FIGS. 2 and 8 , the lead of the cylindrical helix constituting the middle portion of the antenna 24 is larger than the lead of the cylindrical helix constituting the two ends of the antenna 24; that is, in the middle of the antenna 24 Partly, the distance between two adjacent coils is relatively small, and the coils are wound densely. At both ends of the antenna 24 , the distance between two adjacent coils is relatively large, and the coils are wound relatively sparsely. In this embodiment, the optimization of the spacing of multiple coils of the antenna can make the radio frequency magnetic field generated by the antenna have better uniformity in the vertical direction, and will not adversely affect the distribution of the radio frequency magnetic field in the radial direction of the antenna; thus further It is ensured that the static magnetic field jointly formed by the first main magnet 21 , the second main magnet 22 and the focusing magnet 23 matches, so as to fully excite the hydrogen nuclei in the sensitive region M of the formation.

More specifically, in the above-mentioned embodiment, please refer to FIGS. 2 to 6, the first main magnet is formed by sequentially splicing at least three magnet blocks; and/or the second main magnet 22 is formed by sequentially splicing at least three magnet blocks ; and/or the focusing magnet 23 is spliced sequentially by at least three magnet blocks. That is, each magnet can be an integral structure or a structure spliced by multiple small magnets; for example, the first main magnet 21 or the second main magnet 22 can be stacked and fixed together by a plurality of ring-shaped sub-magnets 212 structure (as shown in Figure 3), or the first main magnet 21 or the second main magnet 22 can also adopt a ring structure (as shown in Figure 4 ) spliced by a plurality of sub-magnets 231 whose horizontal section is trapezoidal, Certainly, the first main magnet 21 or the second main magnet 22 can also adopt an integral structure (as shown in Figure 5); the focusing magnet 23 can adopt the annular structure ( As shown in FIG. 6 ), of course, an integral structure or the structure of the first main magnet 21 or the second main magnet 22 in FIG. 4 may also be adopted.

Another embodiment of the present invention provides a nuclear magnetic resonance logging tool while drilling, including: a downhole drilling tool and an uphole signal processing device. As for the well tool probe, the specific structure and working principle of the LWD NMR logging tool probe are similar to those of the above-mentioned embodiments, and will not be repeated here.

In the NMR logging tool while drilling provided in this embodiment, the probe forms a static magnetic field, which can significantly increase the vertical extension of the sensitive area that can generate NMR. When the drill bit is drilling, the rotation of the probe is guaranteed. While affecting the measurement, it can also reduce the number of position switching in the sensitive area during the measurement cycle of collecting each group of signals, and improve the signal-to-noise ratio of the measurement and the accuracy of the measurement results.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting 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 is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (8)

1. a NMR while drilling instrument probe, comprising: the probe framework of column, and the central axis of described probe framework is equipped with the mud tube for drilling fluid circulation; In described probe framework and on described mud tube, coaxial sleeve is provided with the first circular main magnet and the second main magnet, described first main magnet and the second main magnet are axial charging, and described first main magnet one end identical with described second main magnet polarity is oppositely arranged; It is characterized in that, on the peripheral sidewall of described probe framework and the centre position of corresponding described first main magnet and the second main magnet is fixedly embedded with antenna for the formation of pulsed magnetic field; Between described first main magnet and the second main magnet and on described mud tube, coaxial sleeve is provided with the circular focusing magnet of at least one pair of, form two focusing magnets in described often pair of focusing magnet symmetrical about the middle section of described antenna, described focusing magnet is radial magnetizing, and described focusing magnet is relative with described probe framework is fixedly installed.

2. NMR while drilling instrument probe according to claim 1, it is characterized in that, described focusing magnet is two right, form four focusing magnets of two pairs of focusing magnets vertically to arrange at equal intervals, and the two ends of described antenna are stretched out in the end face being positioned at the focusing magnet of top and the bottom surface distribution of focusing magnet that is positioned at lowermost end.

3. NMR while drilling instrument probe according to claim 2, is characterized in that, described first main magnet is extremely relative with the N of the second main magnet, and the outer shroud side of described focusing magnet is N pole, inner ring side is S pole.

4., according to the arbitrary described NMR while drilling instrument probe of claims 1 to 3, it is characterized in that, described antenna is turned to a wire of cylindrical screw wire.

5. NMR while drilling instrument probe according to claim 4, is characterized in that, described antenna is formed by copper wire winding.

6. NMR while drilling instrument probe according to claim 5, is characterized in that, the helical pitch forming the circular helix of the mid portion of described antenna is greater than the helical pitch of the circular helix forming described antenna ends place.

7. the NMR while drilling instrument probe according to claim 1 or 2 or 3, is characterized in that,

Described first main magnet is spliced successively by least three pieces of magnet block; And/or

Described second main magnet is spliced successively by least three pieces of magnet block; And/or

Described focusing magnet is spliced successively by least three pieces of magnet block.

8. a NMR while drilling instrument, comprising: down-hole equipment and aboveground signal handling equipment, is characterized in that, is fixedly installed just like the NMR while drilling instrument probe described in any one of claim 1-7 in the drill collar of described down-hole equipment.