CN103953337B - Nuclear magnetic resonance logging instrument probe - Google Patents

Abstract

The invention discloses a nuclear magnetic resonance logging instrument probe which is fixed on a nuclear magnetic resonance logging instrument and comprises a permanent magnet and an antenna; the permanent magnet is in a chord-tangent columnar structure, the antennas are symmetrically arranged on two sides of a non-circular arc part of the permanent magnet, and magnetic sheets for prolonging magnetic poles are fixed on the circular arc edge of the permanent magnet. The invention can carry out multidimensional well logging around the borehole, and effectively increases the detection depth of the stratum corresponding to the arc edge.

Description

A nuclear magnetic resonance logging instrument probe

technical field

The invention belongs to the field of petroleum logging devices, and mainly relates to a logging instrument probe, in particular to a nuclear magnetic resonance logging instrument probe.

Background technique

NMR logging uses the nuclear magnetic resonance signals generated by excited hydrogen nuclei in liquids (petroleum, water) and gas (natural gas) rich in hydrogen atoms in the pores of the formation. Through logging interpretation, it can be used to quantitatively determine the effective porosity, free Parameters such as fluid porosity, irreducible water porosity, pore size distribution, permeability, viscosity and wetness of crude oil.

The current NMR logging probe design is mainly based on the "Inside-out" idea, Schlumberger's CMR wall-mounted solution, Numar's MAIL series probe material improvement and probe structure optimization, as well as MRX and MREx series eccentric probes . The difference is that: "Inside-out" uses at least two parts of permanent magnets, and carries out axial reverse magnetization on the two permanent magnets respectively. The magnet is used to generate the static magnetic field B ₀ of nuclear magnetic resonance, and the antenna used to generate the radio frequency magnetic field B ₁ is placed between the two cylindrical permanent magnets. The antenna includes a coil and a magnetic core. The coil is generally an improvement of the solenoid structure, and the magnetic core As the soft magnetic material, soft ferrite or magnetic steel is mostly used, so that a static magnetic field B ₀ and a radio frequency magnetic field B ₁ are strictly orthogonal to each other around the wellbore, and B ₀ has a uniform size and a near-circular detection area. In formations of different depths, the size of _B0 is different, that is, a gradient magnetic field is formed, and ring-shaped detection areas of formations at different depths can be obtained by changing the radio frequency signal. Due to the limited length of the instrument, the detection area of this scheme is smaller and the logging speed is slower. The CMR wall-mounted probe adopts three rectangular permanent magnets for radial magnetization, and the three permanent magnets are placed in parallel with the same poles, and the antenna is only placed on one side of the permanent magnet poles, so the radio frequency magnetic field is only generated on the side near the antenna in the formation, forming Near-cylindrical detection area. The CMR probe only generates a uniform static magnetic field in a small area in one direction, the detection area is small, and only single-frequency measurement can be performed. MAIL series probes adopt cylindrical permanent magnet radial magnetization to place the antenna on the outer surface of the cylinder, and achieve strict orthogonality between B ₀ and B ₁ in the radial section. There is no magnetic core in the antenna of the MRIL probe, the stability of the radio frequency magnetic field is not good, and the radio frequency power is high.

Contents of the invention

Purpose of the invention:

The invention relates to a nuclear magnetic resonance logging tool probe, which aims to generate a gradient field in the downhole through the structure design of the probe magnet and the placement of the radio frequency coil, so as to obtain detection areas with different distances.

Technical solutions:

A nuclear magnetic resonance logging instrument probe, fixed on the nuclear magnetic resonance logging instrument, is characterized in that: it includes a permanent magnet and an antenna; the permanent magnet is a string-cut columnar structure, and the antenna is symmetrically arranged on both sides of the non-arc part of the permanent magnet , a magnetic piece for extending the magnetic pole is fixed on the arc edge of the permanent magnet.

The permanent magnet is made of 10-20 pieces of string-cut column-shaped magnetic columns bonded, the total length after bonding is 200cm, the magnetic columns are made of sintered NdFeB or SmCo materials, and the cross-section of the magnetic columns is round The middle part of the two symmetrical chords, the cross-section forms a symmetrical arc; a cylindrical shell-shaped magnetic piece with the same height is placed outside the arc of the magnetic column, and it is placed close to the arc of the permanent magnet magnetic column. The thickness is 10mm, and the whole magnetic sheet is bonded by 10-20 magnetic sheets, and the number is consistent with the number of magnetic columns.

The cross section of the magnetic column is a circle with a radius of 60-70mm, and the distance between the two symmetrical strings is 90-100mm.

The antenna is set close to the string trimming of the permanent magnet, including the magnetic core and the radio frequency coil. The magnetic core is close to the permanent magnet, and the radio frequency coil is wound on the magnetic core; the magnetic core is made of soft ferrite material and stacked piece by piece .

The magnetic core is placed in the center close to the planes on both sides of the permanent magnet. The magnetic core is composed of 40-50 magnetic core laminations with a cross-sectional size of 60mm×20mm, and its total length is the same as that of the permanent magnet.

Advantages and effects:

This NMR logging tool probe of the present invention has the following advantages and beneficial effects:

(1) Logging in the center mode, using sintered NdFeB or SmCo material with high magnetic energy product as the material of the permanent magnet, and a magnetic piece for extending the magnetic pole effect is fixed on the arc edge of the permanent magnet;

(2) The antenna makes full use of the remaining space of the magnet to generate a radio frequency magnetic field, and the laminated structure of the antenna core is used to reduce the eddy current loss generated by the radio frequency magnetic field;

(3) The probe generates a gradient magnetic field in the formation around the wellbore, realizing multi-dimensional logging at different depths of the formation around the wellbore, and increasing the detection depth of the formation corresponding to the arc edge of the magnet.

Description of drawings:

Fig. 1 is the front view of the probe of the central nuclear magnetic resonance logging tool of the present invention, which is a half-sectional view;

Fig. 2 is a top view of the probe structure of the central nuclear magnetic resonance logging tool of the present invention;

Fig. 3 is a partial view of the antenna magnetic core of the central nuclear magnetic resonance logging tool of the present invention;

Fig. 4 is a radial cross-sectional semi-sectional view of the probe after the antenna structure is improved.

Explanation of reference signs:

1. Magnetic column; 2. Magnetic core; 3. Radio frequency coil; 4. Single magnetic sheet; 5. Magnetic core lamination; 2-1. First magnetic core; 2-2. Second magnetic core; 2-3 , The third magnetic core.

detailed description:

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

The invention relates to a nuclear magnetic resonance logging instrument probe. The permanent magnet adopts sintered NdFeB material or SmCo material. The detection area is pushed far away, that is, the detection depth in this direction is increased, and the centered measurement can be realized. The antenna is placed close to the trimming side of the permanent magnet, its magnetic core is placed close to the permanent magnet, and a saddle-shaped coil is wound on the magnetic core. The magnetic core is made of soft ferrite material and stacked one by one. A fan-shaped shell-shaped magnet is placed on the arc edge of the permanent magnet magnetic pole, and a magnetic steel material or an amorphous magnetic material is used.

The nuclear magnetic resonance logging tool probe of the present invention is fixed on the nuclear magnetic resonance logging tool, and includes a permanent magnet and an antenna; the permanent magnet is a string-cut columnar structure, and the antenna is symmetrically arranged on both sides of the non-arc part of the permanent magnet. A magnetic piece for extending the magnetic pole is fixed on the arc edge of the permanent magnet.

The permanent magnet is made by bonding 10-20 pieces of magnetic columns 1 with string-cut columnar structure. The total length after bonding is 200cm. The magnetic columns 1 are made of sintered NdFeB or samarium cobalt materials. It is the middle part of two symmetrical chords of a circle, and the cross-section forms a symmetrical arc; a cylindrical shell-shaped magnetic sheet unit 4 with the same height as it is placed outside the arc of the magnetic column 1, and placed close to the arc edge of the permanent magnet magnetic column , the thickness of the single magnetic sheet is 10mm, and the whole magnetic sheet is made of 10-20 single magnetic sheets bonded together, and the number is consistent with the number of magnetic columns (that is, the main magnet that generates the static magnetic field consists of 10-20 magnetic columns and The same number of magnetic sheet monomers are stacked and bonded); the magnetic sheet monomers are made of magnetic steel materials or amorphous magnetic materials.

The cross-section of the magnetic column 1 is the middle part of the symmetrical string, the radius of the circle is 60-70 mm, the distance between the two symmetrical strings is 90-100 mm, and the opposite sides of the two arcs are N pole and S pole respectively.

The antenna is set close to the chord trimming of the permanent magnet, including a magnetic core 2 and a radio frequency coil 3, the magnetic core 2 is close to the permanent magnet, and the radio frequency coil 3 is wound on the magnetic core 2 (the radio frequency coil 3 is wound on a winding shell and fixed on the magnetic core 2); the magnetic core 2 is made of soft ferrite material, and is stacked one by one.

The antenna is placed in the center close to the magnet, that is, the magnetic core 2 is placed in the center close to the two sides of the permanent magnet. The magnetic core 2 is 200cm long and is formed by stacking 40-50 magnetic core laminations 5 with a cross-sectional size of 60mm×20mm. Its overall length is the same as that of the permanent magnet.

The invention can perform multi-dimensional well logging around the borehole. The detection depth of the formation corresponding to the arc edge is increased.

Example 1:

As shown in Fig. 1, the permanent magnet of the center-type nuclear magnetic resonance logging tool probe is made of 10 magnetic columns with the same cross-sectional size and equal volume, which are radially magnetized along the opposite side of the arc, and the total length is 200 cm. The column is made of sintered NdFeB material. The cross section of the magnetic column is the middle part of two symmetrical chords of a circle, and the section forms a symmetrical arc. The outer surface of the magnetic column forms a symmetrical curved surface and a plane, and the magnetization is carried out along the direction parallel to the plane. The directions of the two curved surfaces of the magnetic column are N pole and S pole respectively, forming a fan-shaped gradient magnetic field around the borehole and increasing The detection depth of the formation corresponding to the arc. The diameter of the magnetic column is 140mm, and the distance between the two strings is 100mm, see Figure 2.

As shown in Figure 1, the antenna of the center-type nuclear magnetic resonance logging tool probe is composed of a magnetic core 2 and a radio frequency coil 3, and the magnetic core is formed by stacking and bonding 40 magnetic core laminations 5, as shown in Figure 3. Its purpose is to reduce the eddy current loss generated by the radio frequency current, and the radio frequency coil is wound on the coil shell.

As shown in Fig. 1, the two ends of the arc-shaped poles of the permanent magnet of the center-type nuclear magnetic resonance logging instrument probe are pasted with magnetic sheets. The magnetic column of the magnet is bonded, and its function is to uniform the magnetic field generated by the permanent magnet in the formation and push the detection area farther away.

Example 2:

It is basically the same as Embodiment 1, except that the antenna is a gradient antenna, the size of the end close to the permanent magnet is larger, and the size of the end far away from the permanent magnet is smaller, as shown in FIG. 4 . The radial dimensions of the magnetic cores used in this embodiment are: the first magnetic core 2-1 is 80mm×8mm, the second magnetic core 2-2 is 70mm×8mm, and the third magnetic core 2-3 is 60mm×5mm. The axial direction is still lamination as shown in Fig. 3 .

Claims (3)

1. a kind of NMR logging instrument probe, is fixed on NMR logging instrument, it is characterised in that：Including permanent magnet and day Line；Permanent magnet is flat-cut column structure, and along two circular arc opposite side radial magnetizings, antenna symmetry is arranged on the non-circular arc portion of permanent magnet Both sides, be fixed with the magnetic sheet for extending magnetic pole in the arc-shaped edges of permanent magnet；Permanent magnet is by 10-20 block flat-cut column structures Magnetic pole（1）Bonding is formed, and the total length after bonding is 200cm, magnetic pole（1）It is made of sintered NdFeB or samarium-cobalt material, magnetic Post（1）Cross section for circle two symmetrical strings center section, section forms symmetrical arc；In magnetic pole（1）The outside of circular arc Lay with it with high cylindrical shell magnetic sheet monomer（4）, it is close to the placement of permanent magnet magnetic pole arc-shaped edges, magnetic sheet monomer thickness is 10mm, overall bonded by 10-20 block magnetic sheets monomer of magnetic sheet is formed, and the quantity of quantity and magnetic pole is consistent；Magnetic pole（1）It is transversal Face is that a radius is 60-70mm circular, and distance is 90-100mm between the string of two symmetrical strings.

2. NMR logging instrument probe according to claim 1, it is characterised in that：Antenna is close to the flat-cut side of permanent magnet Set, including magnetic core（2）And radio-frequency coil（3）, magnetic core（2）It is close to permanent magnet, radio-frequency coil（3）Around the home in magnetic core（2）On；Magnetic Core（2）Using soft magnetic ferrite, and piecewise be stacked form.

3. NMR logging instrument probe according to claim 2, it is characterised in that：Magnetic core（2）It is close to the two of permanent magnet Side plane is placed centrally, magnetic core（2）By the 40-50 block magnetic core laminations that sectional dimension is 60mm × 20mm（5）Stacked to form, its is total Length is identical with permanent magnet.