Reservoir porosity determination method, system, storage medium and electronic device

Abstract

The invention discloses a reservoir porosity determination method, system, storage medium and electronic device, which relate to the technical field of oil and gas exploration, and the method comprises: analyzing a nuclear magnetic resonance T2 spectrum to obtain a T2 spectrum with hydrocarbon signals removed; determining the original water saturation corresponding to the relaxation time of the spectrum peak; obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with hydrocarbon signals removed and the original water saturation; determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation, and drawing a nuclear magnetic resonance spectrum of 100% water saturation based on the relaxation time of the maximum water saturation and the nuclear magnetic resonance amplitude of the maximum water saturation; and calculating the porosity of the target reservoir using the nuclear magnetic resonance spectrum of 100% water saturation. The invention has the beneficial effects of: constructing a nuclear magnetic resonance spectrum of 100% water saturation based on fluid replacement, having a strong theoretical basis, a simple invention process, easy operation and good practical application effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploration, and in particular relates to a reservoir porosity determination method, system, storage medium and electronic equipment. Background Art

[0002] The T2 distribution of NMR is a comprehensive response of pore structure and oil and gas information, and has great advantages in porosity, permeability, pore structure and fluid identification. However, compared with the water-saturated T2 spectrum, the T2 spectrum of NMR logging measured by downhole instruments or the T2 spectrum obtained by laboratory logging has new peaks or shifts due to the influence of oil and gas or drilling mud filtrate, especially in formations with relatively simple pore structures and prone to invasion. The new peak corresponds to the volume relaxation of the hydrocarbon signal, and the presence of water film causes the displacement of the peak. Whether it is the appearance of a new T2 peak or the displacement of the T2 peak, it will affect the calculation accuracy of reservoir parameters such as porosity, permeability, bound fluid volume, and movable fluid volume calculated by NMR T2 spectrum.

[0003] Due to the changes in the downhole invasion zone, the above situation mainly exists in NMR cable logging, but has little effect on NMR logging while drilling, which causes the measurement difference between NMR cable logging and NMR while drilling. Therefore, it is necessary to correct the hydrocarbon signal. Previous research results mainly focused on characterizing the pore structure based on the NMR T2 spectrum of 100% water content, while few people have studied the influence of non-wetting phase hydrocarbons on the NMR T2 spectrum.

[0004] Although some scholars have analyzed the effect of pore hydrocarbon content on the nuclear magnetic resonance T2 spectrum and used the "three-pore component percentage method" to evaluate the pore structure, they did not provide a specific hydrocarbon content correction method. Summary of the invention

[0005] The present invention is based on the above technical problems and proposes a reservoir porosity determination method, system, storage medium and electronic device.

[0006] In a first aspect, an embodiment of the present invention provides a method for determining reservoir porosity, comprising:

[0007] Acquire the nuclear magnetic resonance T2 spectrum of the target reservoir;

[0008] According to the nuclear magnetic resonance T2 spectrum, obtaining the amplitude of the echo signal after removing the hydrocarbon signal;

[0009] Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a T2 spectrum after the hydrocarbon signal is removed is obtained;

[0010] Determining the original water saturation corresponding to the relaxation time of the spectrum peak based on the relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum;

[0011] Obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation;

[0012] According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is determined,

[0013] Based on the relaxation time corresponding to the maximum water saturation and the NMR amplitude of the maximum water saturation, the NMR spectrum of 100% water saturation is plotted;

[0014] The porosity of the target reservoir is calculated using the nuclear magnetic resonance spectrum at 100% water saturation.

[0015] Optionally, obtaining the amplitude of the echo signal after removing the hydrocarbon signal according to the nuclear magnetic resonance T2 spectrum includes:

[0016] According to the nuclear magnetic resonance T2 spectrum, a total echo signal amplitude corresponding to the nuclear magnetic resonance T2 spectrum and an echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum are obtained;

[0017] The amplitude of the total echo signal is subtracted from the amplitude of the echo signal corresponding to the hydrocarbon-containing component to obtain the amplitude of the echo signal after the hydrocarbon signal is removed.

[0018] Optionally, obtaining the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum according to the nuclear magnetic resonance T2 spectrum includes:

[0019] According to the nuclear magnetic resonance T2 spectrum, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum is calculated using a first preset calculation formula; wherein the first preset calculation formula is:

[0020]

[0021] Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

[0022] Optionally, obtaining the T2 spectrum after removing the hydrocarbon signal based on the amplitude of the echo signal after removing the hydrocarbon signal comprises:

[0023] Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is:

[0024]

[0025] Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed;

[0026] Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T 2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signal, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

[0027] Optionally, the determining the original water saturation corresponding to the relaxation time of the spectrum peak based on the size relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum comprises: determining the original water saturation corresponding to the relaxation time of the spectrum peak from a ball-and-tube model based on the size relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum; wherein the ball-and-tube model is:

[0028]

[0029] in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where:

[0030]

[0031] in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

[0032] Optionally, determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation includes:

[0033] According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is calculated using a second preset calculation formula; wherein the second preset calculation formula is:

[0034]

[0035] in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

[0036] Optionally, obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation comprises:

[0037] Based on the T2 spectrum with the hydrocarbon signal removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is:

[0038]

[0039] Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is:

[0040]

[0041] in, is the element in the i-th row and j-th column of the water saturation matrix, T 2i is the transverse relaxation time of the i-th relaxation component.

[0042] In a second aspect, an embodiment of the present invention provides a reservoir porosity determination system, comprising:

[0043] An acquisition module, used for acquiring a nuclear magnetic resonance T2 spectrum of a target reservoir;

[0044] A hydrocarbon signal-removed echo signal amplitude calculation module, used to obtain the hydrocarbon signal-removed echo signal amplitude according to the nuclear magnetic resonance T2 spectrum;

[0045] A T2 spectrum calculation module for removing hydrocarbon signals, used to obtain a T2 spectrum for removing hydrocarbon signals based on the amplitude of the echo signal for removing hydrocarbon signals;

[0046] An original water saturation determination module is used to determine the original water saturation corresponding to different relaxation times based on the size relationship between the relaxation time of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum; wherein different size relationships correspond to different original water saturations;

[0047] A nuclear magnetic resonance amplitude determination module, used to obtain the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation;

[0048] a relaxation time determination module, for determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation,

[0049] A drawing module, for drawing a nuclear magnetic resonance spectrum of 100% water saturation based on a relaxation time corresponding to the maximum water saturation and a nuclear magnetic resonance amplitude of the maximum water saturation;

[0050] The porosity analysis module is used to calculate the porosity of the target reservoir using the nuclear magnetic resonance spectrum of 100% water saturation.

[0051] Optionally, the echo signal amplitude calculation module for removing hydrocarbon signals includes:

[0052] An echo calculation unit, used for obtaining, according to the nuclear magnetic resonance T2 spectrum, a total echo signal amplitude corresponding to the nuclear magnetic resonance T2 spectrum and an echo signal amplitude corresponding to a hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum;

[0053] The subtraction unit is used to subtract the amplitude of the total echo signal from the amplitude of the echo signal corresponding to the hydrocarbon-containing component to obtain the amplitude of the echo signal after the hydrocarbon signal is removed.

[0054] Optionally, the echo calculation unit is specifically used for:

[0055] According to the nuclear magnetic resonance T2 spectrum, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum is calculated using a first preset calculation formula; wherein the first preset calculation formula is:

[0056]

[0057] Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

[0058] Optionally, the T2 spectrum calculation module for removing hydrocarbon signals is specifically used for:

[0059] Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is:

[0060]

[0061] Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed;

[0062] Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T 2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signal, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

[0063] Optionally, the original water saturation determination module is specifically used to:

[0064] Based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined from the ball-and-tube model; wherein the ball-and-tube model is:

[0065]

[0066] in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where:

[0067]

[0068] in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

[0069] Optionally, the relaxation time determination module is specifically used for:

[0070] According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is calculated using a second preset calculation formula; wherein the second preset calculation formula is:

[0071]

[0072] in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

[0073] Optionally, the nuclear magnetic resonance amplitude determination module is specifically used for:

[0074] Based on the T2 spectrum with the hydrocarbon signal removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is:

[0075]

[0076] Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is:

[0077]

[0078] in, is the element in the i-th row and j-th column of the water saturation matrix, T 2i is the transverse relaxation time of the i-th relaxation component.

[0079] In a third aspect, an embodiment of the present invention provides a storage medium having program code stored thereon, and when the program code is executed by a processor, a reservoir porosity determination method as described in any one of the above embodiments is implemented.

[0080] In a fourth aspect, an embodiment of the present invention provides an electronic device, comprising a memory and a processor, wherein the memory stores a program code that can be executed on the processor, and when the program code is executed by the processor, a reservoir porosity determination method as described in any one of the above embodiments is implemented.

[0081] In a reservoir porosity determination method provided in an embodiment of the present invention, by analyzing the nuclear magnetic resonance T2 spectrum, the T2 spectrum with hydrocarbon signals removed and the relaxation time at different hydrocarbon saturations are calculated respectively, thereby realizing fluid replacement, converting the nuclear magnetic resonance T2 spectrum of the target reservoir into a nuclear magnetic resonance spectrum with 100% water saturation, and then using the nuclear magnetic resonance spectrum with 100% water saturation to calculate the porosity of the target reservoir. The theoretical basis is strong, the invention process is simple, easy to operate, and the practical application effect is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The scope of the present disclosure may be better understood by reading the following detailed description of exemplary embodiments in conjunction with the accompanying drawings. The drawings included are:

[0083] Figure 1 A schematic flow chart of a reservoir porosity determination method proposed in Embodiment 1 of the present invention is shown;

[0084] Figure 2 A schematic flow chart of a reservoir porosity determination method proposed in Embodiment 2 of the present invention is shown;

[0085] Figure 3 The T2 spectra obtained by cable measurement and while drilling measurement are shown;

[0086] Figure 4 A schematic diagram showing measurement while drilling, hydrocarbon signals, and echo trains after the hydrocarbon signals are removed;

[0087] Figure 5 A schematic diagram of the NMR spectrum at 100% water saturation is shown. DETAILED DESCRIPTION

[0088] In order to make the objectives, technical solutions and advantages of the present invention clearer, the implementation method of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0089] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0090] Embodiment 1

[0091] According to an embodiment of the present invention, a method for determining reservoir porosity is provided. Figure 1 FIG. 1 is a flow chart of a reservoir porosity determination method proposed in the first embodiment of the present invention. Figure 1As shown, the reservoir porosity determination method may include: steps 110 to 180.

[0092] In step 110, a nuclear magnetic resonance T2 spectrum of the target reservoir is acquired.

[0093] Here, the nuclear magnetic resonance T2 spectrum of the target reservoir can be obtained by nuclear magnetic logging. The T2 spectrum is the time constant that describes the recovery process of the transverse component of the nuclear magnetization intensity, so it is called the transverse relaxation time. Due to the complexity of the rock pore structure and the diversity of pore fluids and their occurrence states, the relaxation process will be the result of the contribution of multiple components with different relaxation times. It can be expressed by a multi-exponential function: when the formation is saturated with water and the echo interval is relatively small, the T2 spectrum has a good correspondence with the distribution of rock pore size.

[0094] In step 120, the amplitude of the echo signal after removing the hydrocarbon signal is obtained according to the nuclear magnetic resonance T2 spectrum.

[0095] Here, by analyzing the nuclear magnetic resonance T2 spectrum, the echo signal amplitude of the echo signal that does not contain the hydrocarbon signal can be extracted from the nuclear magnetic resonance T2 spectrum.

[0096] In step 130 , a T2 spectrum of the hydrocarbon-removed signal is obtained based on the amplitude of the echo signal of the hydrocarbon-removed signal.

[0097] Here, by inverting the amplitude of the echo signal from which the hydrocarbon signal has been removed, the T2 spectrum from which the hydrocarbon signal has been removed can be obtained.

[0098] In step 140, based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined.

[0099] Here, the original water saturation corresponding to the relaxation time of the spectrum peak is determined by comparing the size relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum.

[0100] The cutoff value can be obtained by collecting typical core samples of the target reservoir for nuclear magnetic resonance experiments. The nuclear magnetic resonance T2 experiment is carried out in accordance with the standard process of "Laboratory Measurement Specifications for Nuclear Magnetic Resonance Parameters of Rock Samples SY / T 6490-2007". If there is no core condition for nuclear magnetic resonance testing, the cutoff value T 2C Take the empirical value. In carbonate rocks, the cutoff value T 2C The value is 100ms; in clastic rocks, the cutoff value T 2C The value is 33ms.

[0101] In step 150, the nuclear magnetic resonance amplitude of the maximum water saturation is obtained according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation.

[0102] Here, it is actually to convert the T2 spectrum of the original water saturation without hydrocarbon signals into the NMR amplitude of the maximum water saturation.

[0103] In step 160, the relaxation time corresponding to the maximum water saturation is determined according to the original water saturation and the relaxation time corresponding to the original water saturation.

[0104] Here, step 160 actually calculates the relaxation time at the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation.

[0105] In step 170 , a nuclear magnetic resonance spectrum of 100% water saturation is plotted based on the relaxation time corresponding to the maximum water saturation and the nuclear magnetic resonance amplitude of the maximum water saturation.

[0106] Here, the specific process of drawing the nuclear magnetic resonance spectrum of 100% water saturation is to draw the nuclear magnetic resonance spectrum of 100% water saturation with the relaxation time corresponding to the maximum water saturation as the horizontal axis of the nuclear magnetic resonance spectrum of 100% water saturation, and with the nuclear magnetic resonance amplitude of the maximum water saturation as the vertical axis of the nuclear magnetic resonance spectrum of 100% water saturation.

[0107] In step 180, the porosity of the target reservoir is calculated using the nuclear magnetic resonance spectrum at 100% water saturation.

[0108] Here, after obtaining the nuclear magnetic resonance spectrum of 100% water saturation, the nuclear magnetic porosity can be calculated based on the nuclear magnetic resonance spectrum of 100% water saturation.

[0109] In this embodiment, by analyzing the nuclear magnetic resonance T2 spectrum, the T2 spectrum with hydrocarbon signals removed and the relaxation time at different hydrocarbon saturations are calculated, thereby realizing fluid replacement, converting the nuclear magnetic resonance T2 spectrum of the target reservoir into a nuclear magnetic resonance spectrum with 100% water saturation, and then using the nuclear magnetic resonance spectrum with 100% water saturation to calculate the porosity of the target reservoir. The invention has a strong theoretical basis, a simple process, is easy to operate, and has good practical application effects.

[0110] Embodiment 2

[0111] Based on the above embodiments, embodiment 2 of the present invention may also provide a method for determining reservoir porosity. Figure 2 FIG. 4 is a flow chart of a reservoir porosity determination method proposed in the second embodiment of the present invention. Figure 2 As shown, the reservoir porosity determination method may include: steps 210 to 280.

[0112] In step 210, a nuclear magnetic resonance T2 spectrum of the target reservoir is acquired.

[0113] Here, the nuclear magnetic resonance T2 spectrum of the target reservoir can be obtained by nuclear magnetic logging. The T2 spectrum is the time constant that describes the recovery process of the transverse component of the nuclear magnetization intensity, so it is called the transverse relaxation time. Due to the complexity of the rock pore structure and the diversity of pore fluids and their occurrence states, the relaxation process will be the result of the contribution of multiple components with different relaxation times. It can be expressed by a multi-exponential function: when the formation is saturated with water and the echo interval is relatively small, the T2 spectrum has a good correspondence with the distribution of rock pore size.

[0114] In step 220, the amplitude of the echo signal after removing the hydrocarbon signal is obtained according to the nuclear magnetic resonance T2 spectrum.

[0115] Here, by analyzing the nuclear magnetic resonance T2 spectrum, the echo signal amplitude of the echo signal that does not contain the hydrocarbon signal can be extracted from the nuclear magnetic resonance T2 spectrum.

[0116] In an optional embodiment, in step 220 , the amplitude of the echo signal after removing the hydrocarbon signal is obtained according to the nuclear magnetic resonance T2 spectrum, including: steps 221 to 222 .

[0117] Step 221, obtaining a total echo signal amplitude corresponding to the nuclear magnetic resonance T2 spectrum and an echo signal amplitude corresponding to a hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum according to the nuclear magnetic resonance T2 spectrum;

[0118] Step 222: Subtract the amplitude of the total echo signal from the amplitude of the echo signal corresponding to the hydrocarbon-containing component to obtain the amplitude of the echo signal after the hydrocarbon signal is removed.

[0119] Wherein, in step 221, obtaining the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum according to the nuclear magnetic resonance T2 spectrum includes:

[0120] According to the nuclear magnetic resonance T2 spectrum, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum is calculated using a first preset calculation formula; wherein the first preset calculation formula is:

[0121]

[0122] Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

[0123] After the amplitude of the echo signal corresponding to the hydrocarbon-containing component is obtained, the amplitude of the echo signal after the hydrocarbon signal is removed is obtained by subtracting the amplitude of the total echo signal from the amplitude of the echo signal corresponding to the hydrocarbon-containing component.

[0124] In step 230 , a T2 spectrum of the hydrocarbon-removed signal is obtained based on the amplitude of the echo signal of the hydrocarbon-removed signal.

[0125] Here, by inverting the amplitude of the echo signal from which the hydrocarbon signal has been removed, the T2 spectrum from which the hydrocarbon signal has been removed can be obtained.

[0126] In an optional embodiment, in step 230, obtaining the T2 spectrum of the hydrocarbon signal removed based on the amplitude of the echo signal of the hydrocarbon signal removed includes:

[0127] Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is:

[0128]

[0129] Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed;

[0130] Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T 2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signal, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

[0131] Among them, T 2HC It can be determined by conducting nuclear magnetic resonance experiments. If experimental conditions are not available, take the lowest value of the trough between the water peak and the hydrocarbon peak in the T2 spectrum. Figure 3 The T2 spectra obtained by cable measurement and while drilling measurement are shown in FIG. Figure 3 As shown in the figure, the lowest value of the valley between the water peak and the hydrocarbon peak in the T2 spectrum is taken as T 2HC .

[0132] Figure 4 The schematic diagram of the measurement while drilling, the hydrocarbon signal and the echo string after the hydrocarbon signal is removed is shown in FIG. Figure 4 As shown, the echo signal amplitude corresponding to the hydrocarbon-containing component and the echo signal amplitude after removing the hydrocarbon signal can be obtained through the above steps.

[0133] In step 240, based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined.

[0134] Here, the original water saturation corresponding to the relaxation time of the spectrum peak is determined by comparing the size relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum.

[0135] The cutoff value can be obtained by collecting typical core samples of the target reservoir for nuclear magnetic resonance experiments. The nuclear magnetic resonance T2 experiment is carried out in accordance with the standard process of "Laboratory Measurement Specifications for Nuclear Magnetic Resonance Parameters of Rock Samples SY / T 6490-2007". If there is no core condition for nuclear magnetic resonance testing, the cutoff value T 2C Take the empirical value. In carbonate rocks, the cutoff value T 2C The value is 100ms; in clastic rocks, the cutoff value T 2C The value is 33ms.

[0136] In an optional embodiment, in step 240, based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, determining the original water saturation corresponding to the relaxation time of the peak includes:

[0137] Based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined from the ball-and-tube model; wherein the ball-and-tube model is:

[0138]

[0139] in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where:

[0140]

[0141] in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

[0142] In step 250, the nuclear magnetic resonance amplitude of the maximum water saturation is obtained according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation.

[0143] Here, it is actually to convert the T2 spectrum of the original water saturation without hydrocarbon signals into the NMR amplitude of the maximum water saturation.

[0144] In an optional embodiment, in step 250, determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation includes:

[0145] According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is calculated using a second preset calculation formula; wherein the second preset calculation formula is:

[0146]

[0147] in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

[0148] In step 260, the relaxation time corresponding to the maximum water saturation is determined according to the original water saturation and the relaxation time corresponding to the original water saturation.

[0149] Here, step 260 actually calculates the relaxation time at the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation.

[0150] In an optional embodiment, in step 260, the NMR amplitude of the maximum water saturation is obtained according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation, including:

[0151] Based on the T2 spectrum with the hydrocarbon signal removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is:

[0152]

[0153] Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is:

[0154]

[0155] in, is the element in the i-th row and j-th column of the water saturation matrix, T 2iis the transverse relaxation time of the i-th relaxation component.

[0156] Here, when the water saturation is different, the relaxation time of the rock is also different. Therefore, according to the original water saturation and its corresponding relaxation time, the relaxation time at 100% water saturation can be calculated according to the ratio.

[0157] In step 270 , a nuclear magnetic resonance spectrum of 100% water saturation is plotted based on the relaxation time corresponding to the maximum water saturation and the nuclear magnetic resonance amplitude of the maximum water saturation.

[0158] Here, the specific process of drawing the nuclear magnetic resonance spectrum of 100% water saturation is to draw the nuclear magnetic resonance spectrum of 100% water saturation with the relaxation time corresponding to the maximum water saturation as the horizontal axis of the nuclear magnetic resonance spectrum of 100% water saturation, and with the nuclear magnetic resonance amplitude of the maximum water saturation as the vertical axis of the nuclear magnetic resonance spectrum of 100% water saturation.

[0159] Figure 5 A schematic diagram of the NMR spectrum at 100% water saturation is shown, Figure 5 As shown, it can be seen that the NMR spectrum at 100% water saturation is consistent with the NMR spectrum obtained from LWD measurement and the NMR spectrum obtained from cable measurement.

[0160] In step 280, the porosity of the target reservoir is calculated using the nuclear magnetic resonance spectrum at 100% water saturation.

[0161] Here, after obtaining the nuclear magnetic resonance spectrum of 100% water saturation, the nuclear magnetic porosity can be calculated based on the nuclear magnetic resonance spectrum of 100% water saturation.

[0162] In this embodiment, by analyzing the nuclear magnetic resonance T2 spectrum, the T2 spectrum with hydrocarbon signals removed and the relaxation time at different hydrocarbon saturations are calculated, thereby realizing fluid replacement, converting the nuclear magnetic resonance T2 spectrum of the target reservoir into a nuclear magnetic resonance spectrum with 100% water saturation, and then using the nuclear magnetic resonance spectrum with 100% water saturation to calculate the porosity of the target reservoir. The invention has a strong theoretical basis, a simple process, is easy to operate, and has good practical application effects.

[0163] Embodiment 3

[0164] Based on the above embodiments, the third embodiment of the present invention can also provide a reservoir porosity determination method. The reservoir porosity determination method can include:

[0165] S1, obtaining the NMR T2 spectrum and cutoff value of the target reservoir;

[0166] Here, we can collect typical core samples of the target reservoir for NMR experiments. The NMR T2 experiment is carried out according to the standard process of "Laboratory Measurement Specifications for NMR Parameters of Rock Samples SY / T 6490-2007". If there is no core condition for NMR testing, the cutoff value T 2C Take the empirical value. In carbonate rocks, the cutoff value T 2C The value is 100ms; in clastic rocks, the cutoff value T 2C The value is 33ms.

[0167] S2, calculating the amplitude of the echo signal after removing the hydrocarbon signal;

[0168] Here, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum can be calculated using a first preset calculation formula; wherein the first preset calculation formula is:

[0169]

[0170] Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

[0171] Among them, T 2HC It can be determined by conducting nuclear magnetic resonance experiments. If experimental conditions are not available, take the lowest value of the trough between the water peak and the hydrocarbon peak in the T2 spectrum. Figure 3 The T2 spectra obtained by cable measurement and while drilling measurement are shown in FIG. Figure 3 As shown in the figure, the lowest value of the valley between the water peak and the hydrocarbon peak in the T2 spectrum is taken as T 2HC .

[0172] Then, the total echo signal amplitude is subtracted from the echo signal amplitude corresponding to the hydrocarbon-containing component to obtain the echo signal amplitude M after the hydrocarbon signal is removed. hcd .

[0173] S3, calculating the T2 spectrum after removing the hydrocarbon signal;

[0174] Here, based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is:

[0175]

[0176] Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed;

[0177] Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T 2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signal, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

[0178] S4, calculation of relaxation time for different hydrocarbon saturations;

[0179] Here, when the water saturation is different, the relaxation time of the rock is different. Therefore, the relaxation time corresponding to the maximum water saturation can be calculated using the second preset calculation formula according to the original water saturation and the relaxation time corresponding to the original water saturation; wherein the second preset calculation formula is:

[0180]

[0181] in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

[0182] Wherein, based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined from the ball-and-tube model; wherein the ball-and-tube model is:

[0183]

[0184] in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where:

[0185]

[0186] in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

[0187] Here, when the water peak and the hydrocarbon signal peak of the T2 spectrum are greater than T 2C When , the water saturation in the pores can be simplified as

[0188]

[0189] make Substituting into the second preset calculation formula, we get:

[0190]

[0191] Thus, the relaxation time after fluid replacement can be calculated. 2BW is the relaxation time of free water, ms, which can be measured in the laboratory. If there are no experimental conditions, T 2BW The value is between 100ms-400ms

[0192] S5, calculation of the NMR amplitude at maximum water saturation;

[0193] Here, based on the T2 spectrum with hydrocarbon signals removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is:

[0194]

[0195] Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is:

[0196]

[0197] in, is the element in the i-th row and j-th column of the water saturation matrix, T 2i is the transverse relaxation time of the i-th relaxation component.

[0198] S6, plotting the NMR spectrum at 100% water saturation;

[0199] Here, the NMR spectrum of 100% water saturation is plotted with the relaxation time corresponding to the maximum water saturation as the abscissa of the NMR spectrum of 100% water saturation, and the NMR amplitude of the maximum water saturation as the ordinate of the NMR spectrum of 100% water saturation.

[0200] S7, calculating the porosity of the target reservoir based on the nuclear magnetic resonance spectrum at 100% water saturation.

[0201] Embodiment 4

[0202] According to an embodiment of the present invention, a reservoir porosity determination system is also provided, comprising:

[0203] An acquisition module, used for acquiring a nuclear magnetic resonance T2 spectrum of a target reservoir;

[0204] A hydrocarbon signal-removed echo signal amplitude calculation module, used to obtain the hydrocarbon signal-removed echo signal amplitude according to the nuclear magnetic resonance T2 spectrum;

[0205] A T2 spectrum calculation module for removing hydrocarbon signals, used to obtain a T2 spectrum for removing hydrocarbon signals based on the amplitude of the echo signal for removing hydrocarbon signals;

[0206] An original water saturation determination module is used to determine the original water saturation corresponding to different relaxation times based on the size relationship between the relaxation time of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum; wherein different size relationships correspond to different original water saturations;

[0207] A nuclear magnetic resonance amplitude determination module, used to obtain the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation;

[0208] a relaxation time determination module, for determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation,

[0209] A drawing module, for drawing a nuclear magnetic resonance spectrum of 100% water saturation based on a relaxation time corresponding to the maximum water saturation and a nuclear magnetic resonance amplitude of the maximum water saturation;

[0210] The porosity analysis module is used to calculate the porosity of the target reservoir using the nuclear magnetic resonance spectrum of 100% water saturation.

[0211] Here, the nuclear magnetic resonance T2 spectrum of the target reservoir can be obtained by nuclear magnetic logging. The T2 spectrum is the time constant that describes the recovery process of the transverse component of the nuclear magnetization intensity, so it is called the transverse relaxation time. Due to the complexity of the rock pore structure and the diversity of pore fluids and their occurrence states, the relaxation process will be the result of the contribution of multiple components with different relaxation times. It can be expressed by a multi-exponential function: when the formation is saturated with water and the echo interval is relatively small, the T2 spectrum has a good correspondence with the distribution of rock pore size.

[0212] By analyzing the nuclear magnetic resonance T2 spectrum, the T2 spectrum with hydrocarbon signals removed and the relaxation time at different hydrocarbon saturations are calculated, thereby realizing fluid replacement and converting the nuclear magnetic resonance T2 spectrum of the target reservoir into a nuclear magnetic resonance spectrum with 100% water saturation, thereby calculating the porosity of the target reservoir using the nuclear magnetic resonance spectrum with 100% water saturation. The invention has a strong theoretical basis, a simple process, is easy to operate, and has good practical application effects.

[0213] Optionally, the echo signal amplitude calculation module for removing hydrocarbon signals includes:

[0214] An echo calculation unit, used for obtaining, according to the nuclear magnetic resonance T2 spectrum, a total echo signal amplitude corresponding to the nuclear magnetic resonance T2 spectrum and an echo signal amplitude corresponding to a hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum;

[0215] The subtraction unit is used to subtract the amplitude of the total echo signal from the amplitude of the echo signal corresponding to the hydrocarbon-containing component to obtain the amplitude of the echo signal after the hydrocarbon signal is removed.

[0216] Optionally, the echo calculation unit is specifically used for:

[0217] According to the nuclear magnetic resonance T2 spectrum, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum is calculated using a first preset calculation formula; wherein the first preset calculation formula is:

[0218]

[0219] Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

[0220] Optionally, the T2 spectrum calculation module for removing hydrocarbon signals is specifically used for:

[0221] Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is:

[0222]

[0223] Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed;

[0224] Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signal, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

[0225] Optionally, the original water saturation determination module is specifically used to:

[0226] Based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined from the ball-and-tube model; wherein the ball-and-tube model is:

[0227]

[0228] in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where:

[0229]

[0230] in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

[0231] Optionally, the relaxation time determination module is specifically used for:

[0232] According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is calculated using a second preset calculation formula; wherein the second preset calculation formula is:

[0233]

[0234] in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

[0235] Optionally, the nuclear magnetic resonance amplitude determination module is specifically used for:

[0236] Based on the T2 spectrum with the hydrocarbon signal removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is:

[0237]

[0238] Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is:

[0239]

[0240] in, is the element in the i-th row and j-th column of the water saturation matrix, T 2i is the transverse relaxation time of the i-th relaxation component.

[0241] The specific implementation process of each of the above functional modules has been described in detail in the above embodiments, and reference may be made to the above embodiments, and will not be repeated in this embodiment.

[0242] Embodiment 4

[0243] According to an embodiment of the present invention, a storage medium is further provided, on which a program code is stored. When the program code is executed by a processor, the reservoir porosity determination method as described in any one of the above embodiments is implemented.

[0244] When the program code is executed by the processor, the following steps are implemented:

[0245] Step 410, obtaining a nuclear magnetic resonance T2 spectrum of the target reservoir;

[0246] Step 420, obtaining the amplitude of the echo signal after removing the hydrocarbon signal according to the nuclear magnetic resonance T2 spectrum;

[0247] Step 430, obtaining a T2 spectrum of the hydrocarbon signal removed based on the amplitude of the echo signal of the hydrocarbon signal removed;

[0248] Step 440, determining the original water saturation corresponding to the relaxation time of the spectrum peak based on the relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum;

[0249] Step 450, obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation;

[0250] Step 460, determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation,

[0251] Step 470, plotting a nuclear magnetic resonance spectrum of 100% water saturation based on the relaxation time corresponding to the maximum water saturation and the nuclear magnetic resonance amplitude of the maximum water saturation;

[0252] Step 480: Calculate the porosity of the target reservoir using the nuclear magnetic resonance spectrum at 100% water saturation.

[0253] It is worth mentioning that the storage medium can be, for example, flash memory, hard disk, multimedia card, card-type memory (for example, SD or DX memory, etc.), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, disk, optical disk, server, App application store, etc.

[0254] Embodiment 5

[0255] According to an embodiment of the present invention, there is also provided an electronic device, which includes a memory and a processor, wherein the memory stores a program code that can be run on the processor, and when the program code is executed by the processor, the reservoir porosity determination method as described in any one of the above embodiments is implemented.

[0256] The technical scheme of the present invention is described in detail above in conjunction with the accompanying drawings. Considering that in the related art, few people have studied the influence of non-wetting phase hydrocarbons on the nuclear magnetic resonance T2 spectrum. The present invention provides a reservoir porosity determination method, system, storage medium and electronic device. By analyzing the nuclear magnetic resonance T2 spectrum, the T2 spectrum with hydrocarbon signals removed and the relaxation time at different hydrocarbon saturations are calculated respectively, thereby realizing fluid replacement, converting the nuclear magnetic resonance T2 spectrum of the target reservoir into a nuclear magnetic resonance spectrum with 100% water saturation, and using the nuclear magnetic resonance spectrum with 100% water saturation to calculate the porosity of the target reservoir. The theoretical basis is strong, the invention process is simple, easy to operate, and the practical application effect is good.

[0257] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0258] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0259] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0260] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for enabling an electronic device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0261] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for determining reservoir porosity, characterized in that: include: Acquire the nuclear magnetic resonance T2 spectrum of the target reservoir; According to the nuclear magnetic resonance T2 spectrum, obtaining the amplitude of the echo signal after removing the hydrocarbon signal; Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a T2 spectrum after the hydrocarbon signal is removed is obtained; Determining the original water saturation corresponding to the relaxation time of the spectrum peak based on the relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum; Obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation; According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is determined, Based on the relaxation time corresponding to the maximum water saturation and the NMR amplitude of the maximum water saturation, the NMR spectrum of 100% water saturation is plotted; The porosity of the target reservoir is calculated using the nuclear magnetic resonance spectrum at 100% water saturation.

2. The reservoir porosity determination method according to claim 1, characterized in that: The step of obtaining the amplitude of the echo signal after removing the hydrocarbon signal according to the nuclear magnetic resonance T2 spectrum comprises: According to the nuclear magnetic resonance T2 spectrum, a total echo signal amplitude corresponding to the nuclear magnetic resonance T2 spectrum and an echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum are obtained; The amplitude of the total echo signal is subtracted from the amplitude of the echo signal corresponding to the hydrocarbon-containing component to obtain the amplitude of the echo signal after the hydrocarbon signal is removed.

3. The reservoir porosity determination method according to claim 2, characterized in that: Obtaining the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum according to the nuclear magnetic resonance T2 spectrum includes: According to the nuclear magnetic resonance T2 spectrum, the echo signal amplitude corresponding to the hydrocarbon-containing component in the nuclear magnetic resonance T2 spectrum is calculated using a first preset calculation formula; wherein the first preset calculation formula is: Among them, M hc is the echo signal amplitude corresponding to the hydrocarbon-containing component, p(T 2i ) is the i-th component of the NMR T2 spectrum, T 2i is the transverse relaxation time of the i-th relaxation component, T 2HC is the relaxation time corresponding to the hydrocarbon signal, and t is the time.

4. The reservoir porosity determination method according to claim 1, characterized in that: The step of obtaining the T2 spectrum after removing the hydrocarbon signal based on the amplitude of the echo signal after removing the hydrocarbon signal comprises: Based on the amplitude of the echo signal after the hydrocarbon signal is removed, a relationship model between the amplitude of the echo signal after the hydrocarbon signal is removed and the T2 spectrum after the hydrocarbon signal is removed is constructed; wherein the relationship model is: Inverting the relationship model using a regularization algorithm to obtain a T2 spectrum with hydrocarbon signals removed; Among them, M hcd To remove the echo signal amplitude of hydrocarbon signal, p hcd (T 2i ) is the T2 spectrum after removing hydrocarbon signals, T 2HC is the relaxation time of hydrocarbon signals, T 2i is the transverse relaxation time of the i-th relaxation component, and t is time.

5. The reservoir porosity determination method according to claim 1, characterized in that: The determining of the original water saturation corresponding to the relaxation time of the spectrum peak based on the magnitude relationship between the relaxation time of the spectrum peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum comprises: Based on the relationship between the relaxation time of the peak of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum, the original water saturation corresponding to the relaxation time of the peak is determined from the ball-and-tube model; wherein the ball-and-tube model is: in, is the initial water saturation, T 2f is the relaxation time of the peak of the NMR T2 spectrum, T 2c is the cutoff value, where: in, is the water-containing porosity of the target reservoir, is the hydrocarbon-bearing porosity of the target reservoir.

6. The reservoir porosity determination method according to claim 1, characterized in that: The step of determining the relaxation time corresponding to the maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation comprises: According to the original water saturation and the relaxation time corresponding to the original water saturation, the relaxation time corresponding to the maximum water saturation is calculated using a second preset calculation formula; wherein the second preset calculation formula is: in, is the initial water saturation, is the relaxation time corresponding to the original water saturation, is the maximum water saturation, is the relaxation time corresponding to the maximum water saturation, T 2BW is the relaxation time of free water.

7. The reservoir porosity determination method according to claim 1, characterized in that: The method of obtaining the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation comprises: Based on the T2 spectrum with the hydrocarbon signal removed and the original water saturation, the nuclear magnetic resonance amplitude of the maximum water saturation is calculated using a third preset calculation formula; wherein the third preset calculation formula is: Among them, p sw＝100％ is the NMR amplitude at maximum water saturation, and are the hydrogen index of the wetting phase fluid obtained by cable NMR and while drilling NMR, respectively, and p hcd To remove the T2 spectrum of hydrocarbon signals, is a water saturation matrix, and the elements in the water saturation matrix are original water saturations; the elements in the water saturation matrix are determined by a fourth preset calculation formula, wherein the fourth preset calculation formula is: in, is the element in the i-th row and j-th column of the water saturation matrix, T 2i is the transverse relaxation time of the i-th relaxation component.

8. A reservoir porosity determination system, characterized in that: include: An acquisition module, used for acquiring a nuclear magnetic resonance T2 spectrum of a target reservoir; A hydrocarbon signal-removed echo signal amplitude calculation module, used to obtain the hydrocarbon signal-removed echo signal amplitude according to the nuclear magnetic resonance T2 spectrum; A T2 spectrum calculation module for removing hydrocarbon signals, used to obtain a T2 spectrum for removing hydrocarbon signals based on the amplitude of the echo signal for removing hydrocarbon signals; An original water saturation determination module is used to determine the original water saturation corresponding to different relaxation times based on the size relationship between the relaxation time of the nuclear magnetic resonance T2 spectrum and the cutoff value of the nuclear magnetic resonance T2 spectrum; wherein different size relationships correspond to different original water saturations; A nuclear magnetic resonance amplitude determination module, used to obtain the nuclear magnetic resonance amplitude of the maximum water saturation according to the T2 spectrum with the hydrocarbon signal removed and the original water saturation; a relaxation time determination module, configured to determine a relaxation time corresponding to a maximum water saturation according to the original water saturation and the relaxation time corresponding to the original water saturation, A drawing module, for drawing a nuclear magnetic resonance spectrum of 100% water saturation based on the relaxation time corresponding to the maximum water saturation and the nuclear magnetic resonance amplitude of the maximum water saturation; The porosity analysis module is used to calculate the porosity of the target reservoir using the nuclear magnetic resonance spectrum of 100% water saturation.

9. A storage medium having program code stored thereon, characterized in that: When the program code is executed by a processor, the reservoir porosity determination method according to any one of claims 1 to 7 is implemented.

10. An electronic device, characterized in that: The electronic device includes a memory and a processor. The memory stores program codes that can be run on the processor. When the program codes are executed by the processor, the reservoir porosity determination method according to any one of claims 1 to 7 is implemented.

Images