Method and device for correcting nuclear magnetic resonance T2 spectrum of tight reservoir

Abstract

The embodiment of the invention provides a tight reservoir nuclear magnetic resonance T2 spectrum correction method and device, and is applied to the technical field of oil-gas exploration and development. Acquiring an internal magnetic field gradient of the rock sample; measuring a standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under a short echo interval condition and a to-be-corrected tight reservoir nuclear magnetic resonance T2 spectrum under a long echo interval condition, wherein the standard tight reservoir nuclear magnetic resonance T2 spectrum is used for constructing an interval porosity-amplitude relation model; and correcting the to-be-corrected tight reservoir nuclear magnetic resonance T2 spectrum based on the internal magnetic field gradient, a preset interval porosity-amplitude relation model and a preset T2 cut-off value 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 short relaxation signal loss under the long echo interval can be reduced at the same time, so that reservoir parameters and pore structures can be accurately evaluated.

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 a tight reservoir nuclear magnetic resonance T2 spectrum. Background Art

[0002] In the relevant field, tight reservoir is a relative concept, without fixed standards and boundaries. It usually refers to a reservoir with a matrix permeability of less than 0.1mD, a short oil and gas migration distance, and requires large-scale reservoir fracturing to be exploited. With the continuous development of exploration technology in the field of oil industry, tight reservoirs have received more and more attention and have become the key target of oil and gas exploration.

[0003] Nuclear magnetic resonance logging mainly detects fluid signals in reservoir pores and is widely used in the evaluation of reservoir rock physical parameters and pore structure. However, when the reservoir contains paramagnetic minerals such as iron and manganese, the magnetic field gradient inside the rock pores will increase and the diffusion relaxation of pore fluid will be enhanced. At this time, the reliability of rock physical parameter evaluation based on T2 spectrum is reduced. At present, the research on tight reservoir NMR porosity correction is mainly focused on eliminating the influence of internal magnetic field gradient on T2 spectrum morphology, and does not consider the phenomenon of short relaxation signal loss during long echo interval measurement. However, there are few studies on the correction of tight reservoir NMR T2 spectrum morphology. The shortest echo interval of some NMR logging instruments is 0.6ms. At this time, some short relaxation signals will be lost, resulting in the measured T2 spectrum cannot be accurately used for reservoir evaluation. The tight reservoir NMR porosity correction method currently used cannot simultaneously reduce the influence of internal magnetic field gradient and the influence of short relaxation signal loss under long echo interval, and cannot accurately evaluate 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 gradient and the influence of short relaxation signal loss under long echo interval, 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 tight reservoir nuclear magnetic resonance T2 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 a possible implementation, 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:

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

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

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

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

[0015] In a possible implementation, the 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:

[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] Using the target transverse relaxation rate to forward model and obtain echo data;

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

[0021] In a possible implementation, the correcting the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain the corrected short relaxation part 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 characterize the signal strength;

[0023] 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 the 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 condition of the correction relationship scale short echo interval, 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 in the following manner:

[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 under long echo interval conditions of the rock sample after peak normalization and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0028] In a 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, used 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 a possible implementation, the correction module includes a division submodule, a first correction submodule, a second correction submodule and a combination submodule:

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

[0037] The first correction submodule is used to correct the relaxation part of the T2 spectrum length to be corrected based on the internal magnetic field gradient to obtain a corrected relaxation part of the T2 spectrum length;

[0038] The second correction submodule is used to correct the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation part 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 dense reservoir nuclear magnetic resonance T2 spectrum.

[0040] In a possible implementation, the first correction submodule is specifically configured to:

[0041] The diffusion relaxation rate is calculated based on the internal magnetic field gradient; the transverse relaxation rate of the rock sample is obtained through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; the diffusion relaxation rate is removed from the transverse relaxation rate to obtain a target transverse relaxation rate that is not affected by the internal magnetic field gradient; the echo data is forward modeled using the target transverse relaxation rate; and the long relaxation part of the corrected T2 spectrum is inverted using the echo data.

[0042] In a possible implementation manner, the second correction submodule is specifically used 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 by 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, and the correction of the short relaxation part of the T2 spectrum to be corrected is completed, and the corrected short relaxation part of the T2 spectrum is obtained.

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

[0045] The relationship model building module is specifically used for:

[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 rock sample after peak normalization and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0047] In a possible implementation, the acquisition module is specifically used to:

[0048] The T2-G spectrum of the rock sample is measured under standard conditions, wherein 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 method for correcting the dense reservoir nuclear magnetic resonance T2 spectrum described in the first aspect.

[0052] In a fourth aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores instructions, and 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 above.

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

[0054] The embodiment of the present application provides a method for correcting a tight reservoir nuclear magnetic resonance T2 spectrum, firstly obtaining the internal magnetic field gradient of a rock sample; secondly measuring the standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under the condition of short echo interval and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the condition of long echo interval, 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 the 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 the long echo interval, so as to accurately evaluate the 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 diagram of a flow chart of a method for correcting a tight reservoir nuclear magnetic resonance T2 spectrum 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 a 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 in 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 in 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 a corrected T2 spectrum of a non-modeling volcanic rock sample provided in an embodiment of the present application;

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

[0064] Figure 8A schematic diagram of the structure 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 the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work 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 "comprise", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including 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 equipment. In the absence of further restrictions, the elements defined by the statement "comprising a ..." do not exclude the presence of other identical elements in the process, method, article or equipment including the elements.

[0067] Nuclear magnetic resonance logging mainly detects fluid signals in reservoir pores and is widely used in the evaluation of reservoir rock physical parameters and pore structure. However, when the reservoir contains paramagnetic minerals such as iron and manganese, the magnetic field gradient inside the rock pores becomes larger and the diffusion relaxation of pore fluids is enhanced. At present, the research on nuclear magnetic resonance porosity correction of tight reservoirs is the main focus.

[0068] However, the tight reservoir NMR porosity correction method only focuses on eliminating the influence of the internal magnetic field gradient on the T2 spectrum morphology, and does not consider the phenomenon of short relaxation signal loss during long echo interval measurement. At this time, the reliability of rock physical parameter evaluation based on T2 spectrum is reduced. In particular, the shortest echo interval of the NMR logging instrument is 0.6ms, and some short relaxation signals will be lost, and the measured T2 spectrum cannot be accurately used for reservoir evaluation. In other words, the tight reservoir NMR porosity correction method currently used cannot simultaneously reduce the influence of the internal magnetic field gradient and the influence of the loss of short relaxation signals under long echo intervals, and thus cannot accurately evaluate reservoir parameters and pore structure.

[0069] Among them, the types of nuclear magnetic resonance logging tools include MRIL-P and CMR. MRIL-P is the most widely used, with the shortest echo interval of 0.6ms, and the shortest echo interval of CMR can reach 0.2ms. The short relaxation signal is the signal corresponding to the case of small T2 on the one-dimensional nuclear magnetic resonance spectrum.

[0070] The embodiment of the present application provides a method and device for correcting a tight reservoir nuclear magnetic resonance T2 spectrum, the correction method first obtains the internal magnetic field gradient of a rock sample; secondly, measures 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, 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 the 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 not only reduce the influence of the internal gradient magnetic field on the nuclear magnetic resonance T2 spectrum, but also compensate for the short relaxation signal lost under the long echo interval. That is, it 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.

[0071] In order to facilitate understanding of the technical solution provided in the embodiment of the present application, a method and device for correcting the T2 spectrum of nuclear magnetic resonance of a tight reservoir provided in the embodiment of the present application are described below in conjunction with 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, the T2-G two-dimensional nuclear magnetic resonance experiment is used 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 two-dimensional nuclear magnetic resonance T2-G spectrum of volcanic rock provided in an embodiment of the present application. The two-dimensional nuclear magnetic resonance T2-G spectrum of volcanic rock is obtained by joint inversion of multiple groups of T2 spectra at different echo intervals, from which the internal magnetic field gradient of the rock sample can be extracted.

[0075] The standard conditions are laboratory conditions, specifically, the measurement environment is at normal temperature and pressure without noise. It should be noted that in actual operation, the noise is relatively weak under laboratory conditions. For the convenience of calculation, the weak noise 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] The rock samples are selected to be representative to ensure that their physical and chemical properties can reflect the characteristics of the target formation. The rock samples can also be pre-treated by necessary cleaning, drying, etc. to remove surface impurities and interfering factors.

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

[0079] During the measurement process, it is necessary to record echo signals under different conditions to generate a T2-G spectrum. In order to improve the quality of the acquired data, the collected echo signals are preprocessed by filtering and denoising, and a T2-G spectrum is constructed based on the preprocessed echo signals. The T2-G spectrum is used to feedback 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 may include: by observing the signal distribution characteristics in the T2-G spectrum, the signal area related to the internal magnetic field gradient can be identified. In the signal area, the expression can be a signal enhancement or weakening within a specific G value range to extract the specific numerical information of the internal magnetic field gradient. The extraction process needs to be implemented with the help of professional software or code programming, which is not limited, 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 NMR 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 of short relaxation signal loss during long echo interval measurement, the T2 spectrum can be divided into two parts and the two parts can be corrected separately.

[0084] See also Figure 3 , Figure 3A schematic diagram of a 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 under water-saturated conditions and different echo intervals is 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 Figure 2, 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 simulation diagram of the T2 spectrum without an internal gradient magnetic field under different echo interval conditions provided in an embodiment of the present application; Figure 4(b) is a simulation diagram of the T2 spectrum with an internal gradient magnetic field under different echo interval conditions provided in 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 of 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 of the same formation model when there is an internal gradient magnetic field. By comparing Figure 4(a) and Figure 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 is 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] Wherein, 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 porosities of the T2 spectrum under long echo intervals, 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 part of the T2 spectrum to be corrected and a short relaxation part of the T2 spectrum to be corrected based on the preset T2 cutoff value; correcting the long relaxation part of the T2 spectrum to be corrected based on the internal magnetic field gradient to obtain a corrected long relaxation part of the T2 spectrum; correcting the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation part of the T2 spectrum; combining the corrected short relaxation part of the T2 spectrum and the corrected long relaxation part of the T2 spectrum to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0094] The T2 cutoff value can be set according to actual conditions, and the embodiments of the present application do not limit this. The properties of different rock samples in different regions are different, so the setting of the T2 cutoff value is not fixed. A T2 time greater than the T2 cutoff value is considered to be a long relaxation, while a T2 time less than the T2 cutoff value is considered to be a short relaxation.

[0095] The T2 spectrum is divided into two parts, long relaxation to be corrected and short relaxation to be corrected, using the T2 cutoff value, and the 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 the preset interval porosity-amplitude relationship model to obtain the corrected short relaxation part of the T2 spectrum.

[0096] Take 10ms as an example for the T2 cutoff value. 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 for correction.

[0097] T E = 0.1 ms, 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 part and the second long relaxation part by the T2 cutoff value; the second short relaxation part is corrected to the same short echo interval as the first short relaxation part, and the corrected T2 spectrum short relaxation part is obtained; the second long relaxation part is corrected to the same short echo interval as the first long relaxation part, and the corrected T2 spectrum long relaxation part is obtained. In this way, the correction of the T2 spectrum under different echo interval conditions is completed.

[0098] After the correction is completed, the corrected T2 spectrum short relaxation part and the corrected T2 spectrum long relaxation part are combined to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum. The corrected tight reservoir nuclear magnetic resonance T2 spectrum can also be compared with the standard tight reservoir nuclear magnetic resonance T2 spectrum to obtain a comparison result, which can be used to evaluate reservoir parameters and pore structure.

[0099] Based on the contents of the above steps S101-S103, it can be known that the internal magnetic field gradient of the rock sample is first obtained; secondly, the standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under the condition of short echo interval and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the condition of long echo interval 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 the 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 not only reduce the influence of the internal gradient magnetic field on the nuclear magnetic resonance T2 spectrum, but also compensate for the short relaxation signal lost under the long echo interval. That is, it 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.

[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 part of the T2 spectrum to be corrected: the echo data is obtained by forward modeling using the target transverse relaxation rate after removing the diffusion relaxation rate, and the corrected relaxation part of the T2 spectrum is obtained by inversion.

[0102] In a possible implementation, the relaxation part of the T2 spectrum to be corrected is corrected based on the internal magnetic field gradient to obtain the corrected relaxation part of the T2 spectrum, specifically including: 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 condition of long echo interval. Removing the diffusion relaxation rate from the transverse relaxation rate to obtain the 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 corrected relaxation part of the T2 spectrum.

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

[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, which 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 interval porosity of the T2 spectrum under the condition of long echo interval and the amplitude of the T2 spectrum under the condition of short echo interval is established to correct the short relaxation part of the T2 spectrum.

[0112] In one possible implementation, the short relaxation part of the T2 spectrum to be corrected is corrected based on a preset interval porosity-amplitude relationship model to obtain the corrected short relaxation part 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 part of the T2 spectrum to be corrected, and obtaining the corrected short relaxation part of the T2 spectrum.

[0113] The short relaxation part of the T2 spectrum to be corrected under the condition of long echo interval is corrected to the state under the condition of short echo interval, wherein the construction method of the interval porosity-amplitude relationship model is as mentioned above. Based on the interval porosity-amplitude relationship model, the amplitudes corresponding to the m T2 spectrum amplitude points to be corrected can be determined. The amplitude is the result after peak normalization processing, and the change in amplitude can reflect the change 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 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 ordinate is the short echo interval condition (T E =0.1ms) The signal intensity corresponding to the short relaxation peak of the T2 spectrum. The signal intensity cross-plot is obtained by linear fitting of the experimental data and can be adjusted according to actual needs.

[0115] The correction relationship between the signal intensities corresponding to short relaxation peaks at different echo intervals can be determined through the signal intensity cross plot, 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, using 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 corresponds to the cross-plot, such as Figure 5 As shown, the amplitude of the short relaxation part of the T2 spectrum to be corrected.

[0117] See also Figure 6 , Figure 6 A schematic diagram of the corrected T2 spectrum of a non-modeled volcanic rock sample provided in the embodiment of the present application. The correction curve and the measured curve match well, and the difference between the corrected porosity and the measured porosity is small, which proves the reliability of the correction method provided in the embodiment of the present application.

[0118] The correction method provided in the embodiment of the present application can overcome the shortcomings of the prior art that the research on NMR porosity correction is mainly based on the correction of NMR T2 spectrum, and the NMR T2 spectrum morphology correction is less. It can effectively correct the tight reservoir NMR T2 spectrum, not only reducing the influence of the internal gradient magnetic field on the NMR T2 spectrum, but also effectively compensating for the short relaxation signal lost under the condition of long echo interval. After verification by actual core data, the accuracy of NMR porosity evaluation is improved, and the applicability of NMR logging in tight reservoir evaluation is enhanced.

[0119] The above-mentioned embodiment of the present application provides a method for correcting a T2 spectrum of a dense reservoir nuclear magnetic resonance based on the above-mentioned method. Next, a device for correcting a T2 spectrum of a dense reservoir nuclear magnetic resonance provided in the embodiment of the present application is described, which is used to perform the above-mentioned Figure 1 Next, the function of the tight reservoir nuclear magnetic resonance T2 spectrum correction device is described. The structural schematic 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 acquire the internal magnetic field gradient of the rock sample;

[0122] The measurement module 702 is used to measure the standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under the condition of short echo interval and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the condition of long echo interval, 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 used 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 to obtain a corrected tight reservoir nuclear magnetic resonance T2 spectrum.

[0124] In a 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 used to divide the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation part of the T2 spectrum to be corrected and a short relaxation part of the T2 spectrum to be corrected based on the preset T2 cutoff value;

[0126] The first correction submodule is used to correct the relaxation part of the T2 spectrum length to be corrected based on the internal magnetic field gradient to obtain a corrected relaxation part of the T2 spectrum length;

[0127] The second correction submodule is used to correct the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation part 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 dense reservoir nuclear magnetic resonance T2 spectrum.

[0129] In a possible implementation, the first correction submodule is specifically configured to:

[0130] The diffusion relaxation rate is calculated based on the internal magnetic field gradient; the transverse relaxation rate of the rock sample is obtained through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; the diffusion relaxation rate is removed from the transverse relaxation rate to obtain a target transverse relaxation rate that is not affected by the internal magnetic field gradient; the echo data is forward modeled using the target transverse relaxation rate; and the long relaxation part of the corrected T2 spectrum is inverted using the echo data.

[0131] In a possible implementation manner, the second correction submodule is specifically used 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 by 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, and the correction of the short relaxation part of the T2 spectrum to be corrected is completed, and the corrected short relaxation part of the T2 spectrum is obtained.

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

[0134] The relationship model building module is specifically used for:

[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 rock sample after peak normalization and the amplitude of the standard tight reservoir nuclear magnetic resonance T2 spectrum under short echo interval conditions.

[0136] In a possible implementation, the acquisition module is specifically used to:

[0137] The T2-G spectrum of the rock sample is measured under standard conditions, wherein 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 embodiment of the present application provides a tight reservoir nuclear magnetic resonance T2 spectrum correction device, which includes: an acquisition module, a measurement module and a correction module. The acquisition module is used to obtain the internal magnetic field gradient of the rock sample; the measurement module is used to measure the standard tight reservoir nuclear magnetic resonance T2 spectrum of the rock sample under the condition of short echo interval and the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the condition of long echo interval, 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, the preset interval porosity-amplitude relationship model and the preset T2 cutoff value to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum. In this way, after the internal magnetic field gradient of the rock sample is obtained, the 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 the long echo interval, so as to accurately evaluate the reservoir parameters and pore structure.

[0139] Based on the method for correcting the T2 spectrum of a dense reservoir NMR provided in the above method embodiment, the present application embodiment provides a device for correcting the T2 spectrum of a dense 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 dense 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 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 embodiments.

[0143] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and 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, and the relevant parts can be referred 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 may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[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 composition and steps of each example have been generally described in the above description according to function. 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 to be beyond the scope of this application.

[0145] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those 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 will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for correcting T2 spectrum of nuclear magnetic resonance of a tight reservoir, 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, characterized in that: The method of correcting 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 to obtain the 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 part of the T2 spectrum to be corrected and a short relaxation part of the T2 spectrum to be corrected based on the preset T2 cutoff value; Correcting the T2 spectrum length relaxation portion to be corrected based on the internal magnetic field gradient to obtain a corrected T2 spectrum length relaxation portion; Correcting the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation part of the T2 spectrum; The corrected T2 spectrum short relaxation part and the corrected T2 spectrum long relaxation part are combined to obtain the corrected tight reservoir nuclear magnetic resonance T2 spectrum.

3. The calibration method according to claim 2, characterized in that: 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 comprises: 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; Using the target transverse relaxation rate to forward model and obtain echo data; The corrected T2 spectrum length relaxation part is obtained by inverting the echo data.

4. The calibration method according to claim 2, characterized in that: The step of correcting the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain the corrected short relaxation part 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 characterize the signal strength; 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 the pre-acquired signal intensity cross-plot; Based on the amplitude of the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the condition of the correction relationship scale short echo interval, 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, characterized in that: 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 under long echo interval conditions of the rock sample 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, characterized in that: 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 compact reservoir nuclear magnetic resonance T2 spectrum correction device, characterized in that: The correction device comprises: An acquisition module for acquiring the internal magnetic field gradient of a rock sample; A measurement module, used 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 used to divide the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected into a long relaxation part of the T2 spectrum to be corrected and a short relaxation part of the T2 spectrum to be corrected based on the preset T2 cutoff value; The first correction submodule is used to correct the relaxation part of the T2 spectrum length to be corrected based on the internal magnetic field gradient to obtain a corrected relaxation part of the T2 spectrum length; The second correction submodule is used to correct the short relaxation part of the T2 spectrum to be corrected based on the preset interval porosity-amplitude relationship model to obtain a corrected short relaxation part 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 dense reservoir nuclear magnetic resonance T2 spectrum.

9. The calibration device according to claim 8, characterized in that: The first correction submodule is specifically used for: The diffusion relaxation rate is calculated based on the internal magnetic field gradient; the transverse relaxation rate of the rock sample is obtained through the tight reservoir nuclear magnetic resonance T2 spectrum to be corrected under the long echo interval condition; the diffusion relaxation rate is removed from the transverse relaxation rate to obtain a target transverse relaxation rate that is not affected by the internal magnetic field gradient; the echo data is forward modeled using the target transverse relaxation rate; and the long relaxation part of the corrected T2 spectrum is inverted using the echo data.

10. The calibration device according to claim 8, characterized in that: The second correction submodule is specifically used for: 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 by 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, and the correction of the short relaxation part of the T2 spectrum to be corrected is completed, and the corrected short relaxation part of the T2 spectrum is obtained.

Images