CN108802836B

CN108802836B - Nuclear magnetic resonance device and logging instrument thereof

Info

Publication number: CN108802836B
Application number: CN201810525584.2A
Authority: CN
Inventors: 蒋新立; 王飞龙; 贾光亮; 温伟; 杨春文; 吴天乾; 马辉; 郑道明
Original assignee: Sinopec Oilfield Service Corp; Sinopec North China Petroleum Engineering Corp
Current assignee: Sinopec Oilfield Service Corp; Sinopec North China Petroleum Engineering Corp
Priority date: 2018-05-28
Filing date: 2018-05-28
Publication date: 2020-03-24
Anticipated expiration: 2038-05-28
Also published as: CN108802836A

Abstract

The invention relates to the field of petroleum gas exploration, in particular to a nuclear magnetic resonance device and a logging instrument thereof. The invention increases the magnetic field intensity by improving the frequency of the radio frequency oscillator in the nuclear magnetic resonance device, and simultaneously ensures that the intensity of the external magnetic field is equal to that of the static magnetic field generated by the magnet and the direction is vertical. The scheme enables the inspection result of the drilling fluid to be detected to be more accurate, and provides important basis for oil gas discovery and reservoir fluid evaluation.

Description

Nuclear magnetic resonance device and logging instrument thereof

Technical Field

The invention relates to the field of petroleum gas exploration, in particular to a nuclear magnetic resonance device and a logging instrument thereof.

Background

Since the middle of the last 90 th century, nuclear magnetic resonance analysis technology is gradually introduced into comprehensive logging while drilling in the petroleum industry at home and abroad, nuclear magnetic resonance analysis of rock samples has been popularized in the petroleum gas industry in China for many years, and with the development of drilling technology, the rock debris breaking degree is getting larger and larger, and the finely-divided rock debris cannot meet the analysis condition of nuclear magnetic resonance. Meanwhile, under the combined influence of pressure difference and diffusion, most of fluid in the fine debris enters the drilling fluid, and oil-gas information in the drilling fluid becomes an important basis for oil-gas discovery and reservoir fluid evaluation. However, the conventional nuclear magnetic resonance logging instrument has low magnetic field frequency (5MHz) and weak excitation capability, cannot effectively excite trace crude oil in the drilling fluid, and cannot meet the requirements of oil-gas information detection and reservoir fluid property evaluation in the drilling fluid.

The existing nuclear magnetic resonance logging instrument has the defects that ① magnetic field frequency is low (5MHz), excitation capacity is weak, the lower limit of detection is high, oil and gas information cannot be detected from conventional oil reservoir (crack-free) drilling fluid, ② temperature control system error is large (+/-0.1), temperature change causes magnetic field frequency fluctuation, detection error is large, ③ nuclear magnetic resonance spectrogram repeated detection is large in shape change when oil and gas information is weak, repeatability detection requirements cannot be met, ④ spectrogram is unstable, crude oil content can be obtained only by using spectrogram signal integration, and crude oil property cannot be identified by using spectrogram shape.

Disclosure of Invention

The invention aims to provide a nuclear magnetic resonance device and a logging instrument thereof, which are used for solving the problem that the drilling fluid cannot be accurately detected due to lower magnetic field frequency in the existing nuclear magnetic resonance technology.

To achieve the above object, an aspect of the present invention includes a nuclear magnetic resonance apparatus including a magnet for generating a static magnetic field, and a radio frequency oscillator with an oscillation coil, a radio frequency receiver with a reception coil, and a recorder, and further including an auxiliary magnetic field generator with an auxiliary coil, the oscillation coil, the reception coil, and the auxiliary coil being arranged perpendicular to each other, the frequency of the radio frequency oscillator being 15 to 25 MHz.

Further, the external magnetic field generated by the radio frequency oscillator through the oscillating coil is the same as the static magnetic field in magnetic field intensity, and the directions of the external magnetic field and the static magnetic field are perpendicular to each other.

The invention also provides a drilling fluid detection logging instrument based on high-frequency nuclear magnetic resonance, which comprises a nuclear magnetic resonance device, an auxiliary magnetic field generator with an auxiliary coil, a radio frequency oscillator with an oscillating coil, a radio frequency receiver with a receiving coil, a test container and a recorder, wherein the nuclear magnetic resonance device comprises a magnet for generating a static magnetic field, the auxiliary magnetic field generator with the auxiliary coil, the oscillating coil, the receiving coil and the auxiliary coil are arranged vertically, and the frequency of the radio frequency oscillator is 15-25 MHz.

Furthermore, the test container is a constant temperature closed box, a cavity which is used for placing a to-be-tested utensil and is provided with an opening at the upper end is arranged in the constant temperature closed box, and a heat insulation layer is arranged around the cavity.

Further, the cross section of the cavity is circular.

The invention has the beneficial effects that: by improving the frequency of a radio frequency oscillator in the nuclear magnetic resonance device, the magnetic field intensity is increased, so that the inspection result of the drilling fluid to be detected is more accurate, and an important basis is provided for oil gas discovery and reservoir fluid evaluation.

Drawings

FIG. 1 is a block diagram of an embodiment of the present invention;

FIG. 2 is a graph of the results of an oil detection experiment using the logging tool of the present invention;

FIG. 3 is a graph showing the results of an oil detection experiment using a conventional logging tool.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

The invention aims to solve the problem that the drilling fluid cannot be accurately detected due to lower magnetic field frequency in a nuclear magnetic resonance device, and the frequency of a radio frequency oscillator is improved, so that the magnetic field intensity is increased, and the drilling fluid can be accurately detected.

The following is a description of a specific embodiment of the present invention.

The structure shown in fig. 1 comprises a radio frequency oscillator 1, an auxiliary magnetic field generator 2,

auxiliary coils

3 and 4, an oscillating coil 5, a receiving coil 6, a radio frequency receiver 7, a recorder 8, a first magnet 9 and a second magnet 10. The constant-temperature closed cavity is also included, as shown in an area indicated by a dotted line frame in figure 1, a concave cylinder is arranged in the middle of the top of the constant-temperature closed cavity, the bottom surface of the cylinder is positioned slightly below the middle of the two electromagnets, and the bottom surface is sealed to ensure constant temperature in the closed cavity; the top surface opening, the top surface position is unanimous with airtight cavity top surface, can put into the thick test tube of 1 inch in the cylinder.

The first magnet, the second magnet, the oscillating coil, the auxiliary coil and the receiving coil are arranged in the constant-temperature closed cavity. After the power is supplied for 0.5 hour, the temperature in the constant-temperature closed cavity is constant, the temperature fluctuation is less than 0.01 ℃, and the magnetic field intensity change caused by the temperature change is less than 0.05 percent. The constant temperature makes the magnetic field change very little, thus makes the analysis result more accurate.

The magnetic field intensity in the analysis chamber (recessed cylinder) between first magnet and the second magnet is stable, and the analysis chamber is located the middle part of two magnets, and 1 inch thick test tube can be put into to the cavity, and the cavity height is greater than 1 inch.

A radio frequency oscillator (with the frequency selectable range of 15-25MHz) generates a magnetic field which is the same as the magnetic field intensity of the magnet and is vertical to the magnetic field intensity through an oscillating coil; the auxiliary magnetic field generator can adjust the intensity of an external magnetic field in a small range through the auxiliary coil, and the magnetic field intensity generated by the radio frequency oscillator is completely the same as that generated by the magnet. The auxiliary magnetic field generator has various options, such as another radio frequency oscillator, and the specific structure of the nuclear magnetic resonance device is not unique and can be other similar structures in the prior art.

The radio frequency receiver and the recorder receive resonance signals through the receiving coil, and the resonance signals are recorded after being amplified, wherein the abscissa of the radio frequency receiver and the ordinate of the radio frequency receiver is the intensity of the magnetic field, and the ordinate of the radio frequency receiver is the intensity of a resonance peak. The oscillating coil, the auxiliary coil and the receiving coil outside the pipe to be tested are mutually vertical and do not interfere with each other.

This embodiment is through integrated electromagnetic force system, has promoted the nuclear magnetic resonance frequency to about 20MHz, guarantees simultaneously that external magnetic field intensity and magnet magnetic field intensity are the same, can realize more stable wave spectrum demonstration.

By adding the constant-temperature closed cavity, the temperature deviation of the magnetic field working environment of nuclear magnetic resonance is not more than 0.01 ℃, and the precision of the magnetic field working environment is improved by 10 times compared with the precision of a 5M nuclear magnetic resonance logging-while-drilling device at 0.1 ℃.

The nuclear magnetic resonance test is carried out on the drilling fluid to be tested, oil-water signals can be clearly distinguished by inverting a T2 wave spectrum, the oil content in the sample can be accurately calculated according to the ratio of the relaxation time integral area and the total relaxation time integral area of oil and water signals in different oil-water samples, and the problems of weak oil-gas display caused by tiny rock debris and oil-gas discovery and evaluation under the condition of weak fluorescence and weak gas measurement of a light oil reservoir are solved.

The invention uses a high-frequency nuclear magnetic resonance logging device, the nuclear magnetic frequency is improved to about 20MHz, thus the excitation intensity of a magnetic field can be increased, the signal to noise ratio is improved, and simultaneously, the lower limit of the detection of the oil content in the drilling fluid is improved from the previous 5 per thousand to the current 0.5 per thousand Vol (mass ratio). Compared with a conventional nuclear magnetic resonance logging instrument, the high-frequency nuclear magnetic resonance logging device can realize more stable spectrogram display, not only reflects the signal size, but also can analyze the crude oil property by using the spectrogram; the crude oil spectrograms at different positions have different forms, so that the crude oil spectrogram is used for analyzing the crude oil properties and judging the attribution of the crude oil positions.

The logging instrument can realize multiple experiments on the drilling fluid, such as an oil-containing detection experiment and a stability analysis experiment, compared with the prior art, the logging instrument increases the nuclear magnetic frequency and the magnetic field intensity, so that the inspection result of the drilling fluid to be detected is more accurate, and an important basis is provided for oil and gas discovery and reservoir fluid evaluation. The analytical methods and the results of the oil-containing test are given below.

Oil-containing detection experiment, analysis method: the drilling fluid which is not drilled in the drilling process and is displayed by being exposed to oil gas is taken as the drilling fluid for experiments, a proper amount of MnCl 4H2O crystal is added into the drilling fluid, the drilling fluid is shaken and is kept stand for more than 15 minutes, so that manganese ions are uniformly distributed in the drilling fluid. A group of test tubes (15 are selected in the experiment) is added with a proper amount of drilling fluid, and each test tube is added with different amounts of Yanan group of crude oil. And then adding a proper amount of drilling fluid on the crude oil, wherein the total weight of the drilling fluid added twice in each test tube is 10.8 g. And (3) detecting the experimental sample by sample, inverting a signal in a region with the relaxation time of more than 5 milliseconds in a spectrogram to serve as a crude oil signal, and calculating the nuclear magnetic resonance signal intensity of the unit sample and the oil content of the drilling fluid, wherein the nuclear magnetic resonance signal intensity and the oil content of the drilling fluid are shown in table 1.

Table 1 results of oil-containing testing experiments using the logging instrument of the present invention

Sample numbering	Mud weight (g)	Oil weight (g)	Oil content mass fraction (%)	Nuclear magnetic signal	Nuclear magnetic signal of unit sample
						1	10.8	0	0	0	0
2	10.8	0.0054	0.0500	2.6179	0.2423
						3	10.8	0.0095	0.0880	4.7014	0.4349
4	10.8	0.0197	0.1824	9.9082	0.9158
						5	10.8	0.0323	0.2991	17.0126	1.5705
6	10.8	0.0429	0.3972	22.8960	2.1116
						7	10.8	0.0537	0.4972	28.8280	2.6561
8	10.8	0.0757	0.7009	41.3447	3.8016
						9	10.8	0.0866	0.8019	47.4356	4.3572
10	10.8	0.096	0.8889	50.6284	4.6465
						11	10.8	0.1152	1.0667	60.8755	5.5771
12	10.8	0.1258	1.1648	65.8303	6.0252
						13	10.8	0.1344	1.2444	70.1692	6.4173
14	10.8	0.1511	1.3991	79.5683	7.2658
						15	10.8	0.1655	1.5324	88.0782	8.0323

As can be seen from Table 1, when the logging tool of the present invention is used, the mass fraction of oil can be detected when the oil content is small (e.g. 0.0054g), and the detection accuracy is high, while the detection accuracy is still high as the oil content increases. FIG. 2 is a graph of the fit of the test results obtained from Table 1, where the abscissa is the signal intensity per sample and the ordinate is the oil mass fraction, and the fit can be expressed as: and y 0.1867 x.

Table 2 shows the results of the oil content testing experiment performed on the drilling fluid by using the existing logging instrument, and it can be seen from the table that when the oil content is less than 0.37%, the testing result is 0, that is, the oil content in the drilling fluid cannot be detected, and when the oil content is greater than 0.37%, although the oil content can be detected, the error of the testing result is larger, and the testing accuracy is lower as the oil content increases. FIG. 3 is a graph of a fit obtained from Table 2, where the abscissa is the signal intensity per sample and the ordinate is the oil mass fraction, and the fit can be expressed as: y is 0.754x +0.031, and as can be seen from the figure, the data point deviates upward, i.e., the detected value results in a small value.

Comparing table 1 and table 2 and fig. 1 and fig. 2, when the oil-containing detection experiment is performed on the drilling fluid, the logging instrument of the present invention can obtain the detection result not only when the oil content is very small, but also more accurate than the detection result of the prior art.

Table 2 results of oil-containing testing experiments using existing logging instruments

Sample numbering	Mud weight (g)	Crude oil weight (g)	Oil content mass fraction (%)	Nuclear magnetic signal	Nuclear magnetic signal of unit sample
						1	13.4	0	0	0	0
2	13.4	0.01	0.10	0	0
						3	13.4	0.03	0.23	0	0
4	13.4	0.05	0.37	0	0
						5	13.4	0.07	0.49	5.25	0.39
6	13.4	0.08	0.60	11.73	0.87
						7	13.4	0.10	0.72	13.91	1.03
8	13.4	0.11	0.82	16.08	1.19
						9	13.4	0.13	0.93	18.40	1.36
10	13.4	0.14	1.04	20.85	1.54
						11	13.4	0.17	1.24	23.75	1.75
12	13.4	0.25	1.84	34.26	2.51
						13	13.4	0.33	2.42	45.31	3.30
14	13.4	0.44	3.18	59.51	4.30
						15	13.4	0.52	3.76	69.46	4.99
16	13.4	0.70	4.98	92.07	6.53
						17	13.4	0.90	6.28	114.26	7.99

The specific implementation mode related to the invention is given above, and the frequency of the radio frequency oscillator in the nuclear magnetic resonance device is increased, so that the magnetic field intensity is increased, the external magnetic field intensity is equal to the static magnetic field intensity generated by the magnet, the inspection result of the drilling fluid to be tested is more accurate, and important basis is provided for oil gas discovery and reservoir fluid evaluation.

However, the invention is not limited to the described embodiments, and the content of the invention is to increase the frequency of the radio frequency oscillator in the nuclear magnetic resonance apparatus and increase the magnetic field strength, so that the specific equipment or the specific structure of the nuclear magnetic resonance apparatus is not limited to the above embodiments, and may be equivalent to other structures in the prior art, and the technical solution formed in this way is formed by performing fine adjustment on the above embodiments, and still falls into the protection scope of the invention.

Claims

1. A nuclear magnetic resonance apparatus including a magnet for generating a static magnetic field, and a radio frequency oscillator with an oscillation coil, a radio frequency receiver with a reception coil, and a recorder, and further including an auxiliary magnetic field generator with an auxiliary coil, the oscillation coil, the reception coil, and the auxiliary coil being arranged perpendicularly to each other, characterized in that: the frequency of the radio frequency oscillator is 15-25 MHz; still include the test container, the test container is a constant temperature seal box, be equipped with one in the constant temperature seal box and be used for placing the household utensils that await measuring, upper end open-ended cavity, there is a recessed cylinder in the middle of the top of cavity, and the cylinder bottom surface is located slightly lean on the lower position in the middle of two electro-magnets, and the bottom surface is sealed, guarantees that temperature is invariable in the airtight cavity, is the heat preservation around the cavity.

2. A nmr apparatus according to claim 1, wherein: the radio frequency oscillator generates an external magnetic field through the oscillating coil, the magnetic field intensity of the external magnetic field is the same as that of the static magnetic field, and the directions of the external magnetic field and the static magnetic field are perpendicular to each other.

3. A drilling fluid detection logging instrument based on high-frequency nuclear magnetic resonance comprises a nuclear magnetic resonance device, wherein the nuclear magnetic resonance device comprises a magnet used for generating a static magnetic field, a radio-frequency oscillator with an oscillating coil, a radio-frequency receiver with a receiving coil, a testing container and a recorder, and further comprises an auxiliary magnetic field generator with an auxiliary coil, wherein the oscillating coil, the receiving coil and the auxiliary coil are arranged perpendicularly to each other, and the drilling fluid detection logging instrument is characterized in that: the frequency of the radio frequency oscillator is 15-25 MHz; the testing container is a constant-temperature closed box, a cavity which is used for placing a to-be-tested utensil and is provided with an opening at the upper end is arranged in the constant-temperature closed box, a concave cylinder is arranged in the middle of the top of the cavity, the bottom surface of the cylinder is positioned in the middle of the two electromagnets and is slightly close to the lower position, the bottom surface is sealed, the constant temperature in the closed cavity is ensured, and a heat insulation layer is arranged around the cavity.

4. The drilling fluid detection logging instrument based on high-frequency nuclear magnetic resonance as claimed in claim 3, characterized in that: the radio frequency oscillator generates an external magnetic field through the oscillating coil, the magnetic field intensity of the external magnetic field is the same as that of the static magnetic field, and the directions of the external magnetic field and the static magnetic field are perpendicular to each other.

5. The drilling fluid detection logging instrument based on high-frequency nuclear magnetic resonance as claimed in claim 3, characterized in that: the cross section of the cavity is circular.