SY/T 6490-2000 Laboratory measurement specification for nuclear magnetic resonance parameters of rock samples
Some standard content:
ICS75.020
Registration number: 8165-2001
Petroleum and natural gas industry standard of the People's Republic of ChinaSY/T 6490-2000
Specification for core NMR parameter's measurement in laboratory2000-12-12 Issued
State Administration of Petroleum and Chemical Industry
2001-06-01 Implementation
SY/T 6490—2000
Reference standard
Method principle·
Main measuring instruments
Preparation of main reagents
Preparation of rock samples
Measurement of rock sample nuclear magnetic resonance parameters
8 Processing of results
9 Allowable error of measurement results
Appendix A (suggestive appendix)
Appendix B (suggestive appendix)
T, calculation of characteristic parameters
Calculation of rock sample physical parameters based on rock sample nuclear magnetic resonance test resultsSY/T 6490—2000
In order to better utilize nuclear magnetic resonance measurement instruments to solve geological problems, laboratory experiments must provide basic parameters or basis. For this reason, China has successively introduced or made some laboratory measurement devices for rock sample nuclear magnetic resonance parameters. In order to standardize the measurement operation and ensure the best quality and comparability with the past, this standard is specially formulated.
This standard specifies the method, steps, processing of measurement results and allowable errors for measuring rock sample parameters by nuclear magnetic resonance method in the factory laboratory. The measuring instruments used in the inspection laboratory are different, and corresponding implementation rules can be formulated for specific experimental instruments. Appendix A and Appendix B of this standard are both suggestive appendices. This standard is proposed by China National Petroleum Corporation. This standard is under the jurisdiction of the Petroleum Well Logging Professional Standardization Promotion Committee. The drafting unit of this standard is: Jianghan Measurement and Measurement Research Institute of Petroleum Exploration and Development Science Research Institute. Drafters of this standard: Peng Shilin, Li Changwen, Du Huanhong, Liu Chonghan Scope
Petroleum and Natural Gas Industry Standard of the People's Republic of China Specification for Core NMR Parameters Measurement in Laboratory SY/T 6490-2000
Specification for core NMR parameter's measurement in laboratory This standard specifies the methods and requirements for measuring core NMR parameters in laboratory. This standard is applicable to the measurement of low-field NMR parameters of laboratory rock samples: 2 Referenced standards
The following standards contain provisions that constitute the provisions of this standard by reference in non-standards. When this standard is published, the versions shown are valid. All standards will be revised. All parties using this standard should explore the possibility of using the latest versions of the following standards: SY/I5336-1996 Conventional core analysis method 3 Principle of the method
The nuclear magnetic moment of the hydrogen nuclear spin system in the formation in the low energy state absorbs the energy provided by the radio frequency pulse and migrates to the high energy state, producing the nuclear magnetic resonance phenomenon. During the action of the radio frequency pulse, the macroscopic magnetization loss deviates from the direction of the static magnetic field; after the action of the radio frequency pulse ends, the nuclear spin recovers from the non-equilibrium state of the high energy level to the equilibrium state of the low energy level, and the magnetization vector recovers to the direction of the static magnetic field through free precession, which can be decomposed into longitudinal and transverse components. The longitudinal component recovers to the initial macroscopic magnetization intensity M, which is called the longitudinal relaxation process. The relaxation rate is expressed by 1/T, and T is called the longitudinal relaxation time; the transverse component recovers to the initial state of zero value, which is called the transverse relaxation process. The relaxation rate is expressed by 1/T, and T2 is called the transverse relaxation time. The rock sample nuclear magnetic resonance experimental measurement is to measure the nuclear magnetic relaxation parameters of the rock sample using the nuclear magnetic resonance experimental instrument. According to the measured TI and T2 values, the parameters such as porosity, permeability, producible fluid type, free fluid index, and bound water saturation that are less affected by lithology can be calculated. 4 Main measuring instruments
4.1 Rock sample nuclear magnetic resonance measuring instrument (see Figure 1)
Control module
Pulse sequence
Signal output
Main control computer
Intensity control block
Figure Schematic diagram of rock sample nuclear magnetic resonance experimental measurement Approved by State Bureau of Petroleum and Chemical Industry 2(H)0-12-12 Implementation on June 1, 2001
SY/T6490—2000
a) Permanent magnet and probe module: magnetic field strength 0.0470T or 0.0235T, magnetic field average gradient not less than 100ppm. The probe inner diameter is 40mm or 60mm, and the length is 60mm. Other sizes of probes are optional; b) Logic control module: including frequency synthesizer, pulse generator, RF transmitter, RF receiver, preamplifier, etc.; c) Temperature control module: control the temperature of the magnet and the measuring probe to be constant (the conventional measurement temperature is 30℃), and the temperature error does not exceed 0.1℃;
d) Main control computer: Pentium or above microcomputer, Windows95 or above or WindowsNT system platform; e) Measurement acquisition software, data processing software. 4.2 Related equipment
a) 1 dehydration device, the dehydration pressure must reach 687×103Pa; b) 1 electronic balance, the uncertainty must reach at least 0.01g c) 1 temperature control oven;
d) 1 constant temperature box.
4.3 Working environment
The room temperature is between 15~25℃, and the humidity is between 50% and 70%. 5 Preparation of main reagents
5.1 Main reagents
a) Sodium chloride (analytical grade);
b) Sodium bicarbonate (analytical grade);
c) Calcium chloride (analytical grade);
d) Manganese chloride (analytical grade);
e) Copper sulfate (analytical grade);
f) Transformer oil;
g) Anhydrous kerosene;
h) Heavy water.
5.2 Preparation of saturated solutionwww.bzxz.net
5.2.1 According to the requirements of the required solution mineralization and type, calculate the mass of solute required to prepare each 2000mL solution. 5.2.2 Dry the solute at 100~120℃ to constant weight, and put it in a desiccator to cool to room temperature. 5.2.3 Weigh the required solute with an electronic balance. 5.2.4 Pour the weighed solute into a 2000mL volumetric flask, then add distilled water to the volumetric flask to the 2000mL mark, and gently shake the volumetric flask until the solute is completely dissolved to obtain a saturated solution. 6 Preparation of rock samples
6.1 Preparation of dry rock samples
6.1.1 Drill a rock sample with a diameter of 38.1
and a length of 25
50mm from the core.
6.1.2 Wash the remaining oil and salt in the rock sample according to the solution extraction method specified in SY/T5336. 6.1.3 After the treated rock sample is air-dried, it is dried in an oven to constant weight (for general rock samples, the temperature is controlled at 100-105°C; for rock samples containing more clay and gypsum, it is placed in an oven with a certain vacuum and humidity, the temperature is generally 62-93°C, and the humidity is generally selected to be 45%), and then placed in a dryer to cool to room temperature. 6.1.4 For loose rock samples, after the above drying, use a heat-shrinkable plastic tube with a suitable diameter and a length 10mm longer than the rock sample to cover the rock sample and dry it at a temperature of 75°C±2°C for 0.5h, and then place it in a dryer to cool to room temperature. 6.2 Preparation of saturated rock samples
The preparation of saturated rock samples shall comply with the method specified in SY/T5336. 2
6.3 Preparation of dehydrated rock samples
SY/T6490—2000
Under the conditions of temperature of 15-25℃ and humidity of 50%-70%, the rock samples are dehydrated by centrifugation or displacement device to prepare dehydrated rock samples with different saturations.
7 Measurement of nuclear magnetic resonance parameters of rock samples
7.1 Preparation before measurement
7.1.1 Turn on the power of the instrument, set the magnet control temperature to 30℃, and keep the probe and magnet at a constant temperature. 7.1.2 Preheat the instrument for more than 16 hours.
7.1.3 Turn on the computer and enter the measurement control software 7.2 Selection and determination principles of measurement parameters
Measurement parameters include system parameters and acquisition parameters.
7.2.1 System parameters are determined by instrument characteristics, corresponding pulse sequences and environment, and can be set manually or by tool software provided by the system. The system parameters mainly include:
a) NMR frequency offset value: the offset value shall not exceed 2% of the rated frequency; b) 90° pulse width: the amplitude of the measured signal shall be maximized; c) 180° pulse width: the amplitude of the measured signal shall be maximized; d) Instrument receiving gain: the gain shall be as large as possible under the condition that the signal is not distorted; e) Other specific parameters required by the instrument.
7.2.2 The acquisition parameters are determined by the instrument characteristics and the research purpose, mainly including: a) echo interval;
b) waiting time;
c) number of collected echoes;
d) number of acquisition scans.
7.2.3 Principles for selecting acquisition parameters:
a) To guide field logging and meet the needs of geological interpretation; b) To meet the research purpose and meet user needs; c) To obtain sample information to the maximum extent. The measurement acquisition parameters that need to be selected are echo interval, waiting time, number of collected echoes, and number of acquisition scans. For the MARAN-2 instrument, the recommended parameter values are shown in Table 1. Recommended values for measurement acquisition parameters
Standard water sample
Echo interval
Waiting time
Number of collected echoes
Note: For low-porosity and low-permeability rock samples, the number of scans should be appropriately increased to ensure the signal-to-noise ratio of the collected signal. 7.3 Pre-measurement scale
Number of acquisition scans
7.3.1 Select three standard samples of different proportions (high, medium, low) or different volumes: distilled water, heavy water prepared in proportion, anhydrous kerosene, or other standard samples.
7.3.2 Set the measurement parameters, measure the standard sample, compare the measurement results with the standard spectrum, and determine the stability and accuracy of the measuring instrument.
7.4 Rock sample measurement
SY/T 6490—2000
7.4.1 Place the prepared rock sample in a non-magnetic container (such as a glass test tube) that does not contain hydrogen and put it into the measurement cavity. 7.4.2 According to the measurement content, select the corresponding pulse sequence (for MARAV type instruments: for measuring T, use the INVFRC pulse sequence; for measuring T2, use the CPMG pulse sequence; for diffusion measurement, use the LDIFFA pulse sequence). 7.4.3 Set the measurement system parameters and acquisition parameters, and after confirming that the current parameters are correct, start the measurement. 5 Measurement results
After the measurement is completed, save the measurement results. 8 Processing of the measurement results
8.1 After measuring with the INVFRC pulse sequence, the processing program (such as WinDxp used by MARAN type instruments) calculates the distribution of the weft relaxation time T1.
8.2 After measuring with the CPMG pulse sequence, the processing program (such as WinDxp used by MARAV type instruments) calculates the distribution of the transverse relaxation time T2.
8.3 After confirming that the measurement results meet the requirements according to the fitting curve quality control chart, save the relevant data and drawings, and write a measurement report. 8.4 The measurement report shall include the main system parameters, acquisition parameters, original attenuation curve, T1/T2 spectrum and related rock sample physical property parameters obtained by processing, see Appendix A (suggested Appendix) and Appendix B (suggested Appendix). 9 Allowable error of measurement results
9.1 The relative error between the initial amplitude of the attenuation curve of the longitudinal relaxation time T1 and the transverse relaxation time T2 measured by the nuclear magnetic resonance experiment of the standard sample and the standard spectrum shall be less than 3%.
9.2 The rock samples to be measured shall be sampled and repeatedly measured, with a sampling rate of 10% and a minimum number of sampled rock samples of two; the relative error of the initial amplitude of the attenuation curve of the experimentally measured longitudinal relaxation time T1 and transverse relaxation time T2 shall be less than 5%. 4
A1T, Fitting model of spectrum analysis
SY/T 6490—2000
Appendix A
(Suggested Appendix)
T, Calculation of characteristic parameters
Data processing software can be used to perform single exponential, double exponential and multi-exponential fitting on the measured echo. The basic fitting relationship is shown in Formula (AI), Formula (A2) and Formula (A3):
Single exponential:
Double exponential:
Multi-exponential:
A(2)-Ane-t/T
A(t) -- Ae tTa + Ae-+iT
Where: A4()——NMR relaxation amplitude value; An, A.,Al, A,
- are the fitting coefficients of the nuclear magnetic relaxation curve: T2- transverse relaxation time, ms:
T2a, Tab, T2- are the fitting components of the transverse relaxation time Tz, ms. A2T, Determination of the cutoff value
It is generally believed that T: The cutoff value is approximately near the intersection of the two peaks of the T spectrum. The left peak (greater than T, cutoff value) is called the movable peak, and the left peak (less than T, cutoff value) is called the immovable peak. The ratio of the lower envelope area of the movable peak to the immovable peak is the ratio of the movable and immovable fluids. Therefore, after determining the ratio of movable and immovable fluids of each rock sample by centrifugation, the T2 cutoff value T2cutoff
of each rock sample can be determined by comparing the T2 spectrum. Another method to determine the T2u value is: calculate the cumulative porosity based on the T spectrum of the core after centrifugation, and then find a point on the T2 spectrum before centrifugation so that the cumulative porosity on its left is equal to the total cumulative porosity after centrifugation. The T2 value corresponding to this point is the T2 cutoff value T2mtofcA3The average value of T2
The average value of T2 is often used to characterize the T2 distribution, and the average value of Tz is calculated according to formula (A4), formula (A5), and formula (A6): ST
T2Arithmetic mean =
T2Average mean = (T)
T2Average mean estimate
Where: ——NMR cumulative porosity, %; where—corresponds to the most T2; porosity component, %: T2 transverse relaxation time T2 fitting component, ms. .
Z(/T2)
·(A6)
SY/T 6490--2000
Appendix B
(Suggested Appendix)
Calculation of rock sample physical parameters from rock sample NMR experimental results B1 Determination of rock sample NMR porosity
For the T: spectrum measured by the fully saturated rock sample, use a standard calibration sample (such as distilled water) to calibrate and convert the signal intensity into porosity. The conversion formula (BI) is as follows:
-sign+:00%
wherein, where n——-standard sample NMR porosity: M—total amplitude of the T2 spectrum of the standard sample;
total water content of the standard sample: cm;
accumulated number of standard sample during NMR data collection: -receiving gain of the standard sample during NMR data collection: -amplitude of the T2 spectrum of the first T2 component of the standard sample: volume of the standard sample, cm;
accumulated number of times when the NMR data of the standard sample is collected: g—receiving gain when the NMR data of the standard sample is collected. Determination of B2 permeability
The air permeability of the rock sample is statistically analyzed with the NMR core measurement results. Four NMR permeability calculation models are mainly used for analysis and comparison. The method is as follows. ) SDR model, using the nuclear magnetic porosity of water-saturated rock samples, T, the geometric mean value to calculate the nuclear magnetic permeability, the model parameter is Cs, by the statistical analysis of formula (B2) obtained: Ki = Ca (100)
) 4, T
where: Cs - model parameter, obtained by statistical analysis of rock sample experimental measurement data in the corresponding area; K, - - nuclear magnetic permeability, 10°3μrrz; nuclear magnetic porosity, %:
T—T, geometric mean value, ms
..(B2)
b) SLR-res model, using the nuclear magnetic porosity of water-saturated rock samples, T, the geometric mean value to calculate the nuclear magnetic permeability, the model parameters are (z, m, n, also by the statistical analysis of formula (B3) obtained: met
K2= C2(100)
Wherein: Cz, m, n-
Model parameters, obtained by statistical analysis of rock sample experimental measurement data in the corresponding area: K,--Nuclear magnetic permeability, [0\3um.
...(R3)
c)(cates model, the nuclear magnetic permeability is calculated based on the nuclear magnetic porosity of the water-saturated sample and the bound water volume and movable water volume obtained by T, cutoff value method or SI3VI method. The model parameter is Cl, obtained by statistical analysis of formula (R4): R,-
Wherein: mny2
Wherein: Cn1——Model parameters. Obtained by statistical analysis of rock sample experimental measurement data in the corresponding area; 6
K3——Nuclear magnetic permeability, 10 3μm2;
SY/T 64902000
Nuclear magnetic movable fluid porosity, %;
wherein.n-Nuclear magnetic bound porosity, %.
l) Coates extended model, using the nuclear magnetic porosity of water-saturated rock samples and the obtained bound water volume and movable water volume to calculate the nuclear magnetic permeability, the model parameters are C, m," obtained by statistical analysis of formula (B5): K
wherein: C, m, n-model parameters, obtained by statistical analysis of rock sample experimental measurement data in the corresponding area: K,-Nuclear magnetic permeability, 10-3μm2.
Determination of nuclear magnetic bound water saturation
Nuclear magnetic bound water saturation is generally determined by two methods. The first method is that, corresponding to the rock sample nuclear magnetic resonance (HS)
T, spectrum curve, the nuclear magnetic bound water saturation is equal to the ratio of the area under the immovable peak of the small fT2 cutoff value T2stf in the T, spectrum to the area under the entire T, spectrum. The bound water volume is equal to the product of the bound water saturation and the porosity, and the movable water volume is equal to the difference between the pore volume and the bound water volume: In actual data processing, the determination of the T, cutoff value Tacun is the key. The first method uses the SBVI method to calculate the bound water saturation, that is, each term of the relaxation time contains the contribution of bound water, but the relaxation time is different, and the corresponding number of bound water contained in the pore is different. In this way, as long as the proportion of bound water in each relaxation time is determined and the bound water weight coefficient of each T, item is given, the bound water saturation of the rock sample can be calculated according to formula (P6) and formula (B7):
Suir =Zw,r:
W,=100/(aI2i+1)
Where: Sn is the calculated nuclear magnetic bound water saturation; W is the weight coefficient;
Tz,—-the fraction of transverse relaxation time T2, ms; --the weight factor for calculating the weight coefficient.
·(E6)
The key to the SBVI method is the determination of the weight coefficient. The weight coefficient in this appendix is given in the form of a function. α is obtained by statistical methods.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.