A method and device for correcting nuclear magnetic resonance T2 spectrum of tight reservoirs

Abstract

The embodiment of the present application provides a method and device for correcting the T2 spectrum of a tight reservoir nuclear magnetic resonance, which is applied to the technical field of oil and gas exploration and development. The internal magnetic field gradient of a rock sample is obtained; the standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under short echo interval conditions and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions are measured, and the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct an interval porosity-amplitude relationship model; based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model and the preset T2 cutoff value, the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum. In this way, the influence of the internal magnetic field gradient and the influence of the loss of short relaxation signals under long echo intervals can be reduced at the same time, so as to accurately evaluate reservoir parameters and pore structure.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas exploration and development, and in particular to a method and device for correcting nuclear magnetic resonance T2 spectra of tight reservoirs. Background Art

[0002] In the relevant field, tight reservoirs are a relative concept, without fixed standards or boundaries. They generally refer to reservoirs with matrix permeability less than 0.1 mD, short oil and gas migration distances, and requiring large-scale reservoir fracturing for production. With the continuous development of exploration technology in the petroleum industry, tight reservoirs are receiving increasing attention and have become a key target for oil and gas exploration.

[0003] Nuclear magnetic resonance (NMR) logging primarily detects fluid signals within reservoir pores and is widely used to evaluate reservoir petrophysical parameters and pore structure. However, the presence of paramagnetic minerals such as iron and manganese in reservoirs increases the magnetic field gradient within the rock pores and enhances the diffusion and relaxation of pore fluids. This reduces the reliability of petrophysical parameter evaluation based on T2 spectroscopy. Currently, research on NMR porosity correction for tight reservoirs primarily focuses on eliminating the effects of internal magnetic field gradients on T2 spectral morphology, without considering the loss of short relaxation signals during measurements with long echo intervals. However, research on NMR T2 spectral morphology correction for tight reservoirs is limited. The minimum echo interval for some NMR logging tools is 0.6 ms, at which some short relaxation signals are lost, rendering the measured T2 spectra inaccurate for reservoir evaluation. Currently used NMR porosity correction methods for tight reservoirs fail to simultaneously mitigate the effects of internal magnetic field gradients and the loss of short relaxation signals at long echo intervals, hindering accurate evaluation of reservoir parameters and pore structure. Summary of the Invention

[0004] In view of this, the present application provides a method and device for correcting the T2 spectrum of dense reservoir nuclear magnetic resonance, which can simultaneously reduce the influence of internal magnetic field gradients and the influence of short relaxation signal loss under long echo intervals, so as to accurately evaluate reservoir parameters and pore structure.

[0005] To solve the above problems, the technical solutions provided by this application are as follows:

[0006] In a first aspect, an embodiment of the present application provides a method for correcting a T2 spectrum of a tight reservoir nuclear magnetic resonance spectrum, the correction method comprising:

[0007] Obtaining the internal magnetic field gradient of rock samples;

[0008] Measuring a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model;

[0009] The tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0010] In one possible implementation, the correcting the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model, and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum includes:

[0011] Dividing the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value;

[0012] Correcting the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectral length relaxation portion;

[0013] Correcting the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum;

[0014] The corrected short relaxation portion of the T2 spectrum and the corrected long relaxation portion of the T2 spectrum are combined to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0015] In one possible implementation, the correcting the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain the corrected T2 spectral length relaxation portion includes:

[0016] calculating a diffusion relaxation rate based on the internal magnetic field gradient;

[0017] Obtaining the transverse relaxation rate of the rock sample through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition;

[0018] removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate without the influence of the internal magnetic field gradient;

[0019] forward modeling the target transverse relaxation rate to obtain echo data;

[0020] The corrected T2 spectrum length relaxation portion is obtained by inverting the echo data.

[0021] In one possible implementation, the correcting the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain the corrected short relaxation portion of the T2 spectrum includes:

[0022] Based on the preset interval porosity-amplitude relationship model, the amplitude corresponding to the short echo interval condition at each relaxation component of the nuclear magnetic resonance T2 spectrum of the tight reservoir to be corrected is obtained, and the amplitude is used to represent the signal intensity;

[0023] Determining the calibration relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval by using a pre-acquired signal intensity cross-plot;

[0024] Based on the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the correction relationship scale short echo interval condition, the short relaxation part of the T2 spectrum to be corrected is corrected to obtain the corrected short relaxation part of the T2 spectrum.

[0025] In one possible implementation, the interval porosity-amplitude relationship model is established as follows:

[0026] Normalizing the peak values ​​of the standard tight reservoir nuclear magnetic resonance T2 spectrum and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected;

[0027] A multi-parameter optimization method is used to establish the interval porosity-amplitude relationship model between the interval porosity of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected of the rock sample under long echo interval conditions after peak normalization and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0028] In one possible implementation, obtaining the internal magnetic field gradient of the rock sample includes:

[0029] Measuring the T2-G spectrum of the rock sample under standard conditions, wherein the standard conditions are a measurement environment of normal temperature, normal pressure, and no noise;

[0030] The internal magnetic field gradient of the rock sample is extracted from the T2-G spectrum.

[0031] In a second aspect, an embodiment of the present application provides a tight reservoir nuclear magnetic resonance T2 spectrum correction device, the correction device comprising:

[0032] an acquisition module for acquiring the internal magnetic field gradient of a rock sample;

[0033] a measurement module, configured to measure a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model;

[0034] The correction module is used to correct the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0035] In one possible implementation, the correction module includes a division submodule, a first syndrome submodule, a second syndrome submodule, and a combination submodule:

[0036] The division submodule is configured to divide the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value;

[0037] The first correction submodule is configured to correct the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectral length relaxation portion;

[0038] The second correction submodule is configured to correct the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum;

[0039] The combining submodule is used to combine the corrected short relaxation part of the T2 spectrum and the corrected long relaxation part of the T2 spectrum to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0040] In one possible implementation, the first syndrome module is specifically configured to:

[0041] The method comprises the following steps: calculating the diffusion relaxation rate based on the internal magnetic field gradient; obtaining the transverse relaxation rate of the rock sample through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate without the influence of the internal magnetic field gradient; forward modeling the target transverse relaxation rate to obtain echo data; and inverting the echo data to obtain the long relaxation portion of the corrected T2 spectrum.

[0042] In one possible implementation, the second syndrome submodule is specifically configured to:

[0043] Based on the preset interval porosity-amplitude relationship model, the amplitude corresponding to the short echo interval condition at each relaxation component of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is obtained, and the amplitude is used to characterize the signal intensity; the correction relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval is determined through the pre-acquired signal intensity intersection diagram; based on the correction relationship, the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the short echo interval condition is calibrated to complete the correction of the short relaxation part of the T2 spectrum to be corrected, and obtain the corrected short relaxation part of the T2 spectrum.

[0044] In a possible implementation, the correction device further includes a relationship model building module.

[0045] The relationship model establishment module is specifically used to:

[0046] The peak values ​​of the standard tight reservoir nuclear magnetic resonance T2 spectrum and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected are normalized; and a multi-parameter optimization method is used to establish the interval porosity-amplitude relationship model between the interval porosity of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions of the peak-normalized rock sample and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0047] In one possible implementation, the acquisition module is specifically configured to:

[0048] The T2-G spectrum of the rock sample is measured under standard conditions, where the standard conditions are a noise-free measurement environment at normal temperature and pressure; and the internal magnetic field gradient of the rock sample is extracted from the T2-G spectrum.

[0049] In a third aspect, the present application provides a business service device, the device comprising: a processor, a memory, and a system bus;

[0050] The processor and the memory are connected via the system bus;

[0051] The memory is used to store one or more programs, and the one or more programs include instructions. When the instructions are executed by the processor, the processor executes the tight reservoir nuclear magnetic resonance T2 spectrum correction method described in the first aspect.

[0052] In a fourth aspect, the present application provides a computer-readable storage medium storing instructions. When the instructions are executed on a device, the device executes the method for correcting the dense reservoir nuclear magnetic resonance T2 spectrum described in the first aspect.

[0053] It can be seen that this application has the following beneficial effects:

[0054] The present application embodiment provides a method for correcting a tight reservoir nuclear magnetic resonance T2 spectrum, which first obtains the internal magnetic field gradient of a rock sample; secondly, measures a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under short echo interval conditions and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; then, based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum. In this way, after obtaining the internal magnetic field gradient of the rock sample, correction is performed based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, which can simultaneously reduce the influence of the internal magnetic field gradient and the influence of the loss of short relaxation signals under long echo intervals, so as to accurately evaluate reservoir parameters and pore structure.

[0055] The embodiment of the present application also provides a device corresponding to the above method, which has the same beneficial effects as the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic flow chart of a method for correcting T2 spectrum of a tight reservoir nuclear magnetic resonance provided in an embodiment of the present application;

[0057] Figure 2 A schematic diagram of a two-dimensional nuclear magnetic resonance T2-G spectrum of volcanic rock provided in an embodiment of the present application;

[0058] Figure 3 A schematic diagram of the T2 spectrum of a volcanic rock sample at different echo intervals provided in an embodiment of the present application;

[0059] FIG4( a ) is a T2 spectrum simulation diagram without an internal gradient magnetic field under different echo interval conditions provided by an embodiment of the present application;

[0060] FIG4( b ) is a T2 spectrum simulation diagram of an internal gradient magnetic field under different echo interval conditions provided by an embodiment of the present application;

[0061] Figure 5 A signal strength cross-plot provided in an embodiment of the present application;

[0062] Figure 6 A schematic diagram of the corrected T2 spectrum of a non-modeled volcanic rock sample provided in an embodiment of the present application;

[0063] Figure 7 A schematic structural diagram of a tight reservoir nuclear magnetic resonance T2 spectrum correction device provided in an embodiment of the present application;

[0064] Figure 8A schematic structural diagram of a tight reservoir nuclear magnetic resonance T2 spectrum correction device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0066] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further limitations, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0067] Nuclear magnetic resonance logging primarily detects fluid signals within reservoir pores and is widely used to evaluate reservoir rock physical parameters and pore structure. However, the presence of paramagnetic minerals such as iron and manganese in reservoirs can lead to increased magnetic field gradients within the rock pores and enhanced pore fluid diffusion relaxation. Currently, research focuses on NMR porosity correction for tight reservoirs.

[0068] However, tight reservoir NMR porosity correction methods focus solely on eliminating the effects of internal magnetic field gradients on T2 spectral morphology, failing to account for the loss of short relaxation signals during measurements with long echo intervals. This reduces the reliability of petrophysical parameter assessment based on T2 spectra. In particular, given the 0.6ms minimum echo interval for NMR logging tools, some short relaxation signals are lost, rendering the resulting T2 spectra inaccurate for reservoir evaluation. Consequently, currently used tight reservoir NMR porosity correction methods fail to simultaneously mitigate the effects of internal magnetic field gradients and the loss of short relaxation signals at long echo intervals, hindering accurate assessment of reservoir parameters and pore structure.

[0069] NMR logging tools include MRIL-P and CMR. MRIL-P is the most widely used, with a minimum echo interval of 0.6 ms, while CMR tools can have a minimum echo interval of 0.2 ms. Short relaxation signals are those corresponding to low T2 on a one-dimensional NMR spectrum.

[0070] The present application provides a method and apparatus for correcting a tight reservoir nuclear magnetic resonance T2 spectrum. The method comprises the following steps: first, obtaining an internal magnetic field gradient of a rock sample; second, measuring a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under short echo interval conditions and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions; wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; and then, based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, correcting the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum. In this way, after obtaining the internal magnetic field gradient of the rock sample, correction is performed based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, thereby not only reducing the influence of the internal gradient magnetic field on the nuclear magnetic resonance T2 spectrum, but also compensating for the short relaxation signal lost under the long echo interval. That is, it can simultaneously reduce the influence of internal magnetic field gradients and the influence of short relaxation signal loss under long echo intervals, so as to accurately evaluate reservoir parameters and pore structure.

[0071] To facilitate understanding of the technical solution provided in the embodiments of the present application, a method and apparatus for correcting the T2 spectrum of a tight reservoir nuclear magnetic resonance provided in the embodiments of the present application will be described below with reference to the accompanying drawings.

[0072] See also Figure 1 , Figure 1 A schematic flow chart of a method for correcting a tight reservoir nuclear magnetic resonance T2 spectrum provided in an embodiment of the present application, the method specifically comprising S101-S103.

[0073] S101: Obtain the internal magnetic field gradient of the rock sample.

[0074] Under standard conditions, T2-G two-dimensional nuclear magnetic resonance experiments are conducted to obtain the internal magnetic field gradient corresponding to pore fluids of different pore sizes in rock samples under water-saturated conditions. In two-dimensional nuclear magnetic resonance logging, T2 and G are used as two independent variables to construct a two-dimensional distribution map of rock pore fluids, see Figure 2 As shown, Figure 2 A schematic diagram of a 2D NMR T2-G spectrum of volcanic rock provided in an embodiment of the present application. The 2D NMR T2-G spectrum of volcanic rock is obtained by jointly inverting multiple sets of T2 spectra at different echo intervals. The internal magnetic field gradient of the rock sample can be extracted from the diagram.

[0075] The standard conditions are laboratory conditions, specifically, a noise-free measurement environment at normal temperature and pressure. It should be noted that in actual operation, the noise level under laboratory conditions is relatively low. For ease of calculation, this weak noise level can be ignored during the experiment.

[0076] In one possible implementation, obtaining the internal magnetic field gradient of a rock sample includes: measuring the T2-G spectrum of the rock sample under standard conditions, and extracting the internal magnetic field gradient of the rock sample from the T2-G spectrum.

[0077] Representative rock samples are selected to ensure that their physical and chemical properties reflect the characteristics of the target formation. Rock samples may also undergo necessary pre-treatment such as cleaning and drying to remove surface impurities and interfering factors.

[0078] A modified Carr-Purcell-Meiboom-Gill (CPMG) sequence can be used for T2-G experimental measurement, but this embodiment of the present application is not limited thereto. Other suitable sequences can also be used for T2-G experimental measurement, or the T2-G spectrum can be directly measured using an instrument. In the embodiment of the present application, the T2-G spectrum is obtained by joint inversion of multiple sets of T2 spectra at different echo intervals.

[0079] During the measurement process, echo signals under different conditions are recorded to generate a T2-G spectrum. To improve data quality, the acquired echo signals are preprocessed through filtering and denoising. A T2-G spectrum is constructed based on the preprocessed echo signals. This T2-G spectrum is used to provide feedback on the relationship between the fluid relaxation time (T2) and the internal magnetic field gradient (G) in the rock sample.

[0080] After obtaining the T2-G spectrum, the internal magnetic field gradient can be extracted from it. The extraction process can include: by observing the signal distribution characteristics in the T2-G spectrum, signal regions related to the internal magnetic field gradient can be identified. Within the signal region, the signal can be enhanced or weakened within a specific G value range to extract the specific numerical information of the internal magnetic field gradient. The extraction process requires the use of professional software or code programming, but this is not limited to this, and the extraction method can be selected according to actual needs.

[0081] S102: measuring a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition.

[0082] Among them, the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model.

[0083] There is only one T2 spectrum in the core. Considering the phenomenon that short relaxation signals are lost when measuring with long echo intervals, the T2 spectrum can be divided into two parts and the two parts can be corrected separately.

[0084] See also Figure 3 , Figure 3This is a schematic diagram of the T2 spectrum of a volcanic rock sample at different echo intervals provided in an embodiment of the present application. The T2 spectrum of the rock sample at different echo intervals under water-saturated conditions was obtained through a one-dimensional nuclear magnetic resonance experiment under laboratory conditions.

[0085] Figure 3 The T2 spectra of rock samples under four echo spacing conditions are shown in the figure, including the echo spacing T E =0.1ms, T E =0.2ms, T E =0.3ms, T E =0.6ms.

[0086] A T2 spectrum containing three peaks is constructed using a numerical simulation method, see Figure 4(a) and Figure 4(b). Figure 4(a) is a T2 spectrum simulation diagram without an internal gradient magnetic field under different echo interval conditions provided by an embodiment of the present application; Figure 4(b) is a T2 spectrum simulation diagram with an internal gradient magnetic field under different echo interval conditions provided by an embodiment of the present application. Figure 4(a) can be used to compare the differences in T2 spectrum morphology under different echo interval conditions for the same formation model when there is no internal gradient magnetic field; Figure 4(b) can be used to compare the differences in T2 spectrum morphology under different echo interval conditions for the same formation model when there is an internal gradient magnetic field. By comparing Figures 4(a) and 4(b), the influence of the internal gradient magnetic field on the T2 spectrum morphology under the same echo interval conditions can be determined.

[0087] By comparison, it was found that when T E = 0.1ms, the difference with the formation nuclear magnetic porosity is small, and the influence of the internal magnetic field gradient is also small. At this time, it can be approximately regarded as the true T2 spectrum of the formation. At present, the shortest echo interval of some nuclear magnetic resonance logging instruments is 0.6ms, so the long echo interval T E = 0.6ms T2 spectrum corrected to short echo interval T E = T2 spectrum under the condition of 0.1ms.

[0088] S103: Correcting the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model, and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0089] An interval porosity-amplitude relationship model is pre-constructed. In one possible implementation method, the peak values ​​of the standard tight reservoir nuclear magnetic resonance T2 spectrum and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected are normalized. A multi-parameter optimization method is used to establish an interval porosity-amplitude relationship model between the interval porosity of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions after peak normalization of the rock sample.

[0090] The interval porosity-amplitude relationship model is shown in formula (1). When the T2 spectrum is subsequently corrected, formula (1), i.e., the interval porosity-amplitude relationship model, can be used to obtain the corresponding amplitude (Ampi) at each relaxation component of the short echo interval T2 spectrum.

[0091] Amp i =k i,1 φ1+k i,2 φ2+k i,3 φ3+b i ,i=1,2,3,…m (1)

[0092] Where m is the preset number of T2 spectrum amplitude points that need to be corrected, which is usually 2 to the power of n and can be determined according to actual needs and experimental time; Ampi is the corresponding amplitude at the i-th relaxation component of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions; φ1, φ2 and φ3 are the interval porosity of the T2 spectrum under long echo interval conditions, which can be obtained from the T2 spectrum of the rock sample; k i,1 、k i,2 and k i,3 It represents the proportionality coefficient, and its specific value can be calibrated through nuclear magnetic resonance experiments on multiple rock samples.

[0093] In one possible implementation, a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected based on an internal magnetic field gradient, a preset interval porosity-amplitude relationship model, and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum, including: dividing the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value; correcting the long relaxation portion of the T2 spectrum to be corrected based on the internal magnetic field gradient to obtain a corrected long relaxation portion of the T2 spectrum; correcting the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum; and combining the corrected short relaxation portion of the T2 spectrum and the corrected long relaxation portion of the T2 spectrum to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0094] The T2 cutoff value can be set based on actual conditions and is not limited in the present embodiments. Different rock samples from different regions have different properties, so the setting of the T2 cutoff value is not fixed. T2 times greater than the T2 cutoff value are considered long relaxations, while T2 times less than the T2 cutoff value are considered short relaxations.

[0095] The T2 spectrum is divided into two parts, the long relaxation part to be corrected and the short relaxation part to be corrected, using the T2 cutoff value. T2 spectrum correction is performed separately. The long relaxation part of the T2 spectrum to be corrected is corrected based on the internal magnetic field gradient to obtain the corrected long relaxation part of the T2 spectrum. The short relaxation part of the T2 spectrum is corrected based on a preset interval porosity-amplitude relationship model to obtain the corrected short relaxation part of the T2 spectrum.

[0096] Take the T2 cutoff value as 10ms as an example, and use 10ms to set T E =0.1ms T2 spectrum and T E = 0.6ms T2 spectrum is divided into two parts: long relaxation and short relaxation. Different methods are used to analyze T E =0.6ms T2 spectrum was used for correction.

[0097] T E = 0.1ms, the T2 spectrum of the rock sample is divided into the first short relaxation part and the first long relaxation part by the T2 cutoff value; E = 0.6ms, the T2 spectrum of the rock sample is divided into the second short relaxation portion and the second long relaxation portion using the T2 cutoff value. The second short relaxation portion is corrected to the same short echo interval as the first short relaxation portion to obtain the corrected T2 spectrum short relaxation portion; the second long relaxation portion is corrected to the same short echo interval as the first long relaxation portion to obtain the corrected T2 spectrum long relaxation portion. This completes the correction of the T2 spectrum under different echo interval conditions.

[0098] After calibration, the corrected short-relaxation portion of the T2 spectrum is combined with the corrected long-relaxation portion of the T2 spectrum to obtain a corrected tight reservoir NMR T2 spectrum. The corrected tight reservoir NMR T2 spectrum can also be compared with a standard tight reservoir NMR T2 spectrum to obtain a comparison result, which can be used to evaluate reservoir parameters and pore structure.

[0099] Based on the contents of steps S101-S103 above, it can be seen that first, the internal magnetic field gradient of the rock sample is obtained; secondly, a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under short echo interval conditions and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions are measured, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; then, based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum. In this way, after obtaining the internal magnetic field gradient of the rock sample, correction is performed based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, which not only reduces the influence of the internal gradient magnetic field on the nuclear magnetic resonance T2 spectrum, but also compensates for the short relaxation signal lost under long echo intervals. That is, it can simultaneously reduce the influence of internal magnetic field gradients and the influence of short relaxation signal loss under long echo intervals, so as to accurately evaluate reservoir parameters and pore structure.

[0100] In another embodiment of the present application, the correction process of the long relaxation part of the T2 spectrum to be corrected and the correction process of the short relaxation part of the T2 spectrum to be corrected are described respectively.

[0101] For the relaxation portion of the T2 spectrum to be corrected: the target transverse relaxation rate after removing the diffusion relaxation rate is used to forward model the echo data, and the corrected relaxation portion of the T2 spectrum is obtained by inversion.

[0102] In one possible implementation, the T2 spectral length relaxation portion to be corrected is corrected based on the internal magnetic field gradient to obtain the corrected T2 spectral length relaxation portion. Specifically, the method includes: calculating the diffusion relaxation rate based on the internal magnetic field gradient, obtaining the transverse relaxation rate of the rock sample from the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions, removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate unaffected by the internal magnetic field gradient; forward modeling the target transverse relaxation rate to obtain echo data; and inverting the echo data to obtain the corrected T2 spectral length relaxation portion.

[0103] The internal magnetic field gradient of the rock sample is obtained using existing T2-G experimental data, and the diffusion relaxation rate is calculated. The transverse relaxation rate of the rock sample is obtained by using the tight reservoir nuclear magnetic resonance T2 spectrum data of the rock sample to be corrected under long echo interval conditions. The diffusion relaxation rate is removed from the transverse relaxation rate to obtain a transverse relaxation rate without the influence of the internal magnetic field gradient, completing the correction of the internal gradient magnetic field.

[0104] When there is an internal magnetic field gradient in the core, the transverse relaxation rate is:

[0105]

[0106] in, is the transverse relaxation rate, which can be read from the T2 spectrum of the rock sample; is the volume relaxation rate; is the surface relaxation rate; is the diffusion relaxation rate; ρ2 is the transverse surface relaxation intensity; is the specific surface area of ​​rock pores; D is the diffusion coefficient of the fluid, which varies with different fluids. The diffusion coefficient of water is 2.5×10 -3 cm 3 / s; γ is the gyromagnetic ratio, usually 2.67×10 -4 rad / (s·Gs); T E is the echo interval; G is the internal magnetic field gradient.

[0107] In the above formula (2), the diffusion relaxation caused by the internal magnetic field gradient is the main factor causing the low nuclear magnetic porosity. It can be corrected by eliminating the influence of the internal magnetic field gradient. The corrected transverse relaxation rate is:

[0108]

[0109] in, is the corrected transverse relaxation rate, that is, the target transverse relaxation rate.

[0110] Then, the target transverse relaxation rate is forward modeled to obtain echo data, and the echo data is inverted to obtain the corrected T2 spectrum length relaxation part.

[0111] For the short relaxation part of the T2 spectrum: the interval porosity-amplitude relationship model between the T2 spectrum interval porosity under long echo interval conditions and the T2 spectrum amplitude under short echo interval conditions is established to correct the short relaxation part of the T2 spectrum.

[0112] In one possible implementation, the short relaxation portion of the T2 spectrum to be corrected is corrected based on a preset interval porosity-amplitude relationship model to obtain the corrected short relaxation portion of the T2 spectrum, including: obtaining the amplitude corresponding to the short echo interval condition at each relaxation component of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model, and the amplitude is used to characterize the signal intensity; determining the correction relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval through a pre-acquired signal intensity cross-plot; and calibrating the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the short echo interval condition based on the correction relationship, completing the correction of the short relaxation portion of the T2 spectrum to be corrected, and obtaining the corrected short relaxation portion of the T2 spectrum.

[0113] The short relaxation portion of the T2 spectrum to be corrected under long echo interval conditions is corrected to the state under short echo interval conditions. The method for constructing the interval porosity-amplitude relationship model is described above. Based on the interval porosity-amplitude relationship model, the amplitudes corresponding to the m T2 spectrum amplitude points requiring correction are determined. This amplitude is the result of peak normalization, and changes in the amplitude reflect changes in signal intensity.

[0114] See also Figure 5 , Figure 5 A signal strength cross-plot provided in an embodiment of the present application shows T E =0.1ms and T E =0.6ms when the T2 spectrum short relaxation peak corresponding to the signal intensity cross-plot. The horizontal axis is the long echo interval condition (T E =0.6ms) T2 spectrum short relaxation peak corresponding to the signal intensity, the vertical axis is the short echo interval condition (T E =0.1ms) T2 spectrum short relaxation peak corresponding to the signal intensity, the signal intensity cross-plot is obtained by linear fitting of the experimental data and can be adjusted according to actual needs.

[0115] The signal intensity cross-plot can be used to determine the correction relationship between the signal intensities corresponding to short relaxation peaks at different echo intervals, and the amplitude of the T2 spectrum to be corrected under the condition of short echo interval can be calibrated based on the correction relationship.

[0116] For example, T E =0.1ms and T E =0.6ms T2 spectrum peak normalization, the use of multiple linear regression method for nine rock samples (here is just an example, the number of rock samples is not limited to establish the normalized rock sample T E =0.6ms T2 spectrum interval porosity and T E =0.1ms T2 spectrum amplitude interval porosity - amplitude relationship model, see formula (1). Use the interval porosity - amplitude relationship model to correct the short relaxation part of the T2 spectrum. Establish T E =0.1ms and T E = 0.6ms when the signal intensity of the short relaxation peak of the T2 spectrum corresponding to the cross-plot, such as Figure 5 As shown, the amplitude of the short relaxation part of the T2 spectrum to be corrected is scaled.

[0117] See also Figure 6 , Figure 6 This is a schematic diagram of the corrected T2 spectrum of a non-modeled volcanic rock sample provided in this example. The calibration curve matches the measured curve well, and the difference between the corrected porosity and the measured porosity is small, demonstrating the reliability of the calibration method provided in this example.

[0118] The correction method provided in the embodiments of this application overcomes the shortcomings of the prior art, which primarily focuses on NMR porosity correction and rarely corrects NMR T2 spectral morphology. It can effectively correct the NMR T2 spectrum of tight reservoirs, not only reducing the impact of internal gradient magnetic fields on the NMR T2 spectrum but also effectively compensating for the short relaxation signal lost under long echo intervals. Validated with actual core data, the method improves the accuracy of NMR porosity evaluation and enhances the applicability of NMR logging in tight reservoir evaluation.

[0119] The above embodiment of the present application provides a method for correcting the T2 spectrum of a tight reservoir nuclear magnetic resonance based on the above. Next, a device for correcting the T2 spectrum of a tight reservoir nuclear magnetic resonance provided in the embodiment of the present application is described, which is used to perform the above Figure 1 Next, the function of the tight reservoir nuclear magnetic resonance T2 spectrum correction device is described. The structural diagram of the tight reservoir nuclear magnetic resonance T2 spectrum correction device is shown in FIG. Figure 7 As shown, it includes an acquisition module 701 , a measurement module 702 and a correction module 703 .

[0120] in,

[0121] An acquisition module 701 is used to obtain the internal magnetic field gradient of the rock sample;

[0122] The measurement module 702 is configured to measure a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model;

[0123] The correction module 703 is configured to correct the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model, and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0124] In one possible implementation, the correction module 703 includes a division submodule, a first correction submodule, a second correction submodule, and a combination submodule:

[0125] The division submodule is configured to divide the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value;

[0126] The first correction submodule is configured to correct the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectral length relaxation portion;

[0127] The second correction submodule is configured to correct the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum;

[0128] The combining submodule is used to combine the corrected short relaxation part of the T2 spectrum and the corrected long relaxation part of the T2 spectrum to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0129] In one possible implementation, the first syndrome module is specifically configured to:

[0130] The method comprises the following steps: calculating the diffusion relaxation rate based on the internal magnetic field gradient; obtaining the transverse relaxation rate of the rock sample through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate without the influence of the internal magnetic field gradient; forward modeling the target transverse relaxation rate to obtain echo data; and inverting the echo data to obtain the long relaxation portion of the corrected T2 spectrum.

[0131] In one possible implementation, the second syndrome submodule is specifically configured to:

[0132] Based on the preset interval porosity-amplitude relationship model, the amplitude corresponding to the short echo interval condition at each relaxation component of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is obtained, and the amplitude is used to characterize the signal intensity; the correction relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval is determined through the pre-acquired signal intensity intersection diagram; based on the correction relationship, the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the short echo interval condition is calibrated to complete the correction of the short relaxation part of the T2 spectrum to be corrected, and obtain the corrected short relaxation part of the T2 spectrum.

[0133] In a possible implementation, the correction device further includes a relationship model building module.

[0134] The relationship model establishment module is specifically used to:

[0135] The peak values ​​of the standard tight reservoir nuclear magnetic resonance T2 spectrum and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected are normalized; and a multi-parameter optimization method is used to establish the interval porosity-amplitude relationship model between the interval porosity of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions of the peak-normalized rock sample and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0136] In one possible implementation, the acquisition module is specifically configured to:

[0137] The T2-G spectrum of the rock sample is measured under standard conditions, where the standard conditions are a noise-free measurement environment at normal temperature and pressure; and the internal magnetic field gradient of the rock sample is extracted from the T2-G spectrum.

[0138] The present invention provides a device for correcting a tight reservoir nuclear magnetic resonance T2 spectrum, comprising an acquisition module, a measurement module, and a correction module. The acquisition module is configured to acquire the internal magnetic field gradient of a rock sample; the measurement module is configured to measure a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under short echo interval conditions and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under long echo interval conditions, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; and the correction module is configured to correct the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, thereby obtaining a corrected tight reservoir nuclear magnetic resonance T2 spectrum. Thus, after obtaining the internal magnetic field gradient of the rock sample, correction is performed based on the internal magnetic field gradient, the preset interval porosity-amplitude relationship model, and the preset T2 cutoff value, thereby reducing the influence of the internal magnetic field gradient and the influence of the loss of short relaxation signals under long echo intervals, thereby accurately evaluating reservoir parameters and pore structure.

[0139] Based on the method for correcting the T2 spectrum of a tight reservoir NMR provided in the above method embodiment, the present invention provides a device for correcting the T2 spectrum of a tight reservoir NMR, see Figure 8 , the device includes: a processor, a memory, and a system bus;

[0140] The processor and the memory are connected via the system bus;

[0141] The memory is used to store one or more programs, and the one or more programs include instructions. When the instructions are executed by the processor, the processor executes the method for correcting the tight reservoir nuclear magnetic resonance T2 spectrum described in any one of the above embodiments.

[0142] Based on a method for correcting the T2 spectrum of nuclear magnetic resonance in a tight reservoir provided in the above-mentioned method embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores instructions. When the instructions are executed on a device, the device executes the method for correcting the T2 spectrum of nuclear magnetic resonance in a tight reservoir described in any of the above-mentioned embodiments.

[0143] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or device embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiment. The device and device embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.

[0144] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0145] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for correcting T2 spectrum of dense reservoir nuclear magnetic resonance, characterized in that: The correction method comprises: Obtaining the internal magnetic field gradient of rock samples; Measuring a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; The tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

2. The calibration method according to claim 1, wherein: The step of correcting the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model, and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum includes: Dividing the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value; Correcting the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectral length relaxation portion; Correcting the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum; The corrected short relaxation portion of the T2 spectrum and the corrected long relaxation portion of the T2 spectrum are combined to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

3. The calibration method according to claim 2, wherein: The step of correcting the T2 spectrum length relaxation portion to be corrected based on the internal magnetic field gradient to obtain the corrected T2 spectrum length relaxation portion includes: calculating a diffusion relaxation rate based on the internal magnetic field gradient; Obtaining the transverse relaxation rate of the rock sample through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate without the influence of the internal magnetic field gradient; forward modeling the target transverse relaxation rate to obtain echo data; The corrected T2 spectrum length relaxation portion is obtained by inverting the echo data.

4. The calibration method according to claim 2, wherein: The correcting the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain the corrected short relaxation portion of the T2 spectrum includes: Based on the preset interval porosity-amplitude relationship model, the amplitude corresponding to the short echo interval condition at each relaxation component of the nuclear magnetic resonance T2 spectrum of the tight reservoir to be corrected is obtained, and the amplitude is used to represent the signal intensity; Determining the calibration relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval by using a pre-acquired signal intensity cross-plot; Based on the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the correction relationship scale short echo interval condition, the short relaxation part of the T2 spectrum to be corrected is corrected to obtain the corrected short relaxation part of the T2 spectrum.

5. The calibration method according to claim 4, wherein: The interval porosity-amplitude relationship model is established in the following way: Normalizing the peak values ​​of the standard tight reservoir nuclear magnetic resonance T2 spectrum and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected; A multi-parameter optimization method is used to establish the interval porosity-amplitude relationship model between the interval porosity of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected of the rock sample under long echo interval conditions after peak normalization and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

6. The calibration method according to claim 1, wherein: The step of obtaining the internal magnetic field gradient of the rock sample comprises: Measuring the T2-G spectrum of the rock sample under standard conditions, wherein the standard conditions are a measurement environment of normal temperature, normal pressure, and no noise; The internal magnetic field gradient of the rock sample is extracted from the T2-G spectrum.

7. A device for correcting T2 spectrum of dense reservoir nuclear magnetic resonance, characterized in that: The correction device comprises: an acquisition module for acquiring the internal magnetic field gradient of a rock sample; a measurement module, configured to measure a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used to construct a preset interval porosity-amplitude relationship model; The correction module is used to correct the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected based on the internal magnetic field gradient, a preset interval porosity-amplitude relationship model and a preset T2 cutoff value to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

8. The calibration device according to claim 7, characterized in that: The correction module includes a division submodule, a first correction submodule, a second correction submodule and a combination submodule: The division submodule is configured to divide the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation portion of the T2 spectrum to be corrected and a short relaxation portion of the T2 spectrum to be corrected based on the preset T2 cutoff value; The first correction submodule is configured to correct the T2 spectral length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectral length relaxation portion; The second correction submodule is configured to correct the short relaxation portion of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation portion of the T2 spectrum; The combining submodule is used to combine the corrected short relaxation part of the T2 spectrum and the corrected long relaxation part of the T2 spectrum to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

9. The calibration device according to claim 8, characterized in that: The first correction submodule is specifically configured to: The method comprises the following steps: calculating the diffusion relaxation rate based on the internal magnetic field gradient; obtaining the transverse relaxation rate of the rock sample through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; removing the diffusion relaxation rate from the transverse relaxation rate to obtain a target transverse relaxation rate without the influence of the internal magnetic field gradient; forward modeling the target transverse relaxation rate to obtain echo data; and inverting the echo data to obtain the long relaxation portion of the corrected T2 spectrum.

10. The calibration device according to claim 8, characterized in that: The second correction submodule is specifically configured to: Based on the preset interval porosity-amplitude relationship model, the amplitude corresponding to the short echo interval condition at each relaxation component of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected is obtained, and the amplitude is used to characterize the signal intensity; the correction relationship between the signal intensities corresponding to the short relaxation peak of the short echo interval and the short relaxation peak of the long echo interval is determined through the pre-acquired signal intensity intersection diagram; based on the correction relationship, the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the short echo interval condition is calibrated to complete the correction of the short relaxation part of the T2 spectrum to be corrected, and obtain the corrected short relaxation part of the T2 spectrum.

Images