A method and calculation device for underground T2 spectrum temperature correction

Abstract

The embodiment of the present invention relates to the technical field of downhole temperature correction, and discloses a downhole T2 spectrum temperature correction method and calculation device. The embodiment of the present invention obtains a second T2 spectrum by fitting a first T2 spectrum of a target layer according to a Gaussian distribution model, performs temperature correction of the transverse relaxation time on the characteristic points of the second T2 spectrum according to a first temperature correction formula to obtain a third T2 spectrum, then corrects the first nuclear magnetic total porosity of the target layer according to the second temperature correction formula to obtain a second nuclear magnetic total porosity at ground temperature, normalizes the third T2 spectrum to obtain a fourth T2 spectrum, and finally performs temperature correction of the porosity component of the fourth T2 spectrum according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum, thereby achieving temperature correction of nuclear magnetic data measured in a downhole high-temperature environment, thereby making the nuclear magnetic data measured in a downhole high-temperature environment suitable for an evaluation model established at normal ground temperature.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of downhole temperature correction, and in particular to a downhole T2 spectrum temperature correction method and computing device. Background Art

[0002] Currently, NMR logging is widely used for quantitative calculation of conventional reservoir petrophysical parameters such as porosity, permeability, and saturation, fluid type identification, and crude oil viscosity assessment. Most NMR logging evaluation models utilize downhole coring to the surface. Using other rock physics techniques, they accurately measure parameters such as permeability, pore size distribution, and saturation using NMR logging. The NMR T2 distribution is then measured. This distribution is then combined with the actual rock physics parameters of the core using existing theoretical models to develop interpretation models for evaluating reservoir rock physics using NMR logging data. NMR is also becoming an essential technology for the exploration and development of complex and unconventional oil and gas reservoirs, and for improving oil recovery in mature oil fields.

[0003] However, as deep and ultra-deep oil and gas reservoirs become a primary target for exploration and development, the impact of downhole high-temperature environments on the NMR relaxation of rock pore fluids cannot be ignored. Even when using instruments with the same frequency to measure T2 spectra downhole and on the surface, there are differences. Substituting NMR data measured in high-temperature downhole environments into evaluation models established at surface temperatures can result in significant errors. Therefore, how to adapt NMR data measured in high-temperature downhole environments to evaluation models established at surface temperatures is a challenge that needs to be addressed. Summary of the Invention

[0004] In view of the above problems, an embodiment of the present invention provides an underground T2 spectrum temperature correction method and a calculation device, which are used to solve the above problems existing in the prior art.

[0005] According to one aspect of an embodiment of the present invention, a method for downhole T2 spectrum temperature correction is provided, wherein the method comprises:

[0006] Acquiring target layer information, the target layer information including a temperature, a first T2 spectrum, and a fluid component of the target layer;

[0007] Fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain a second T2 spectrum;

[0008] performing temperature correction on peak points of all peaks of the second T2 spectrum according to a first temperature correction formula to generate a third T2 spectrum, wherein the first temperature correction formula includes the temperature and a first constant coefficient related to the fluid component;

[0009] Accumulating porosity components of the first T2 spectrum to obtain a first nuclear magnetic total porosity;

[0010] performing temperature correction on the first nuclear magnetic total porosity according to a second temperature correction formula to obtain a second nuclear magnetic total porosity, wherein the second temperature correction formula includes the temperature and a second constant coefficient related to the fluid component;

[0011] Calculating the porosity component of each peak of the third T2 spectrum according to the Gaussian distribution model;

[0012] performing normalization processing on the third T2 spectrum to obtain a fourth T2 spectrum;

[0013] The fourth T2 spectrum is calculated according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum.

[0014] In some embodiments, fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain the second T2 spectrum includes:

[0015] Determine all the 2，i-1 ) <f(T 2，i ) and f(T 2，i+1 )<f(T 2，i ) of f(T 2，i ) is the first peak of the first T2 spectrum, f(T 2，i ) is the i-th T2 distribution point T of the first T2 spectrum 2，i The corresponding porosity component, f(T 2，i+1 ) is the i+1th T2 distribution point T of the first T2 spectrum 2，i+1 The corresponding porosity component, f(T 2，i-1 ) is the i-1th T2 distribution point T of the first T2 spectrum 2，i-1 The corresponding porosity component;

[0016] Determine a first distribution point value corresponding to the first peak value according to the first peak value;

[0017] Obtain the values ​​satisfying f(T 2，i ) and f(T 2，i-1 ) is less than the first threshold T 2，i With T 2，i-1 ;

[0018] Calculate all T 2，i With the smallest T 2，i-1 The mean of is taken as the second distribution value of the first T2 spectrum;

[0019] Determining a second peak value corresponding to the second distribution point value;

[0020] The second T2 spectrum is obtained by fitting all the first peak values, second peak values, first distribution point values ​​and second distribution point values ​​obtained according to the Gaussian distribution model.

[0021] In some embodiments, fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain the second T2 spectrum further includes:

[0022] Determining whether a difference between the distribution point values ​​corresponding to the peak values ​​between any two peaks of the second T2 spectrum is less than a second threshold;

[0023] If so, the two peaks are fitted to a Gaussian distribution.

[0024] In some embodiments, the first temperature correction formula is T is the temperature of the target layer, T2 is the transverse relaxation time at the peak when the target layer is at temperature T, T ref is the ground temperature, T 2，ref To correct T2 to the ground temperature T ref The transverse relaxation time at , R is a constant, and ΔE is the first constant coefficient.

[0025] In some embodiments, the method further comprises:

[0026] Obtaining the oil saturation of the target layer;

[0027] determining whether the target layer is an oil layer according to the oil saturation;

[0028] If the target layer is not an oil layer, temperature correction is performed on the second T2 spectrum of the target layer according to the first temperature correction formula.

[0029] In some embodiments, performing temperature correction on the first nuclear magnetic total porosity according to a second temperature correction formula to obtain a second nuclear magnetic total porosity includes:

[0030] The second temperature correction formula is: T is the temperature of the target layer, T ref is the ground temperature, φ is the first nuclear magnetic total porosity when the target layer is at temperature T, φ ref To correct φ to the ground temperature T ref The second nuclear magnetic total porosity at , α is the second constant coefficient.

[0031] In some embodiments, the Gaussian distribution model is i is a natural number, T 2，i is the i-th T2 distribution point of the first T2 spectrum and the third T2 spectrum, f(log 10 (T 2，i )) is T 2，iThe amplitude component at , Amp is the amplitude of the Gaussian distribution obtained by fitting, μ is the mean of the Gaussian distribution, σ 2 is the variance of the Gaussian distribution.

[0032] In some embodiments, normalizing the third T2 spectrum to obtain a fourth T2 spectrum includes:

[0033] According to the normalization formula Calculate the amplitude component of the fourth T2 spectrum, T 2，i is the i-th T2 point of the third T2 spectrum, f cor_T2 (T 2，i ) is the fourth T2 spectrum at T 2，i The amplitude component at , k is the number of peaks in the third T2 spectrum, f cor_T2，k (T 2，i ) is the kth peak of the third T2 spectrum at T 2，i The amplitude component at .

[0034] In some embodiments, calculating the fourth T2 spectrum according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum includes:

[0035] According to the formula Calculate the total nuclear magnetic porosity component of the fifth T2 spectrum to generate the fifth T2 spectrum, where φ is the first total nuclear magnetic porosity when the target layer is at temperature T, and φ ref To correct φ to the ground temperature T ref The second NMR total porosity, f cor (T 2，i ) is the fifth T2 spectrum at T 2，i The porosity component at cor_T2 (T 2，i ) is the fourth T2 spectrum at T 2，i The porosity component at , n is the total number of T2 points in the fourth T2 spectrum.

[0036] According to a second aspect of an embodiment of the present invention, the present invention provides a computing device, characterized in that it includes: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus;

[0037] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform the operation of the downhole T2 spectrum temperature correction method as described in any of the above embodiments.

[0038] In an embodiment of the present invention, a second T2 spectrum is obtained by fitting the first T2 spectrum of the target layer according to a Gaussian distribution model, and a temperature correction of the transverse relaxation time is performed on the characteristic points of the second T2 spectrum according to a first temperature correction formula to obtain a third T2 spectrum. Then, the first nuclear magnetic total porosity of the target layer is corrected according to the second temperature correction formula to obtain a second nuclear magnetic total porosity at ground temperature. At this time, the third T2 spectrum is normalized to obtain a fourth T2 spectrum. Finally, the fourth T2 spectrum is temperature-corrected for the porosity component according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum, thereby realizing temperature correction of the nuclear magnetic data measured in a high-temperature downhole environment, so that the nuclear magnetic data measured in a high-temperature downhole environment are suitable for an evaluation model established at normal ground temperature.

[0039] The above description is only an overview of the technical solutions of the embodiments of the present invention. In order to more clearly understand the technical means of the embodiments of the present invention, they can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiments of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are only used to illustrate the embodiments and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the drawings. In the drawings:

[0041] Figure 1 A schematic diagram showing a flow chart of a downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0042] Figure 2 A first T2 spectrum schematic diagram of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0043] Figure 3 A second T2 spectrum schematic diagram of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0044] Figure 4 A third T2 spectrum schematic diagram of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0045] Figure 5 A fourth T2 spectrum schematic diagram of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0046] Figure 6 FIG2 shows a fifth T2 spectrum schematic diagram of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention;

[0047] Figure 7 A schematic diagram of a first T2 spectrum fitting process of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0048] Figure 8 A schematic diagram showing another first T2 spectrum of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0049] Figure 9 A schematic diagram showing another method for fitting a first T2 spectrum to a second T2 spectrum in a downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0050] Figure 10 A comparison diagram showing the nuclear magnetic porosity and core porosity after temperature correction of the target layer using the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown;

[0051] Figure 11 The figure shows a schematic structural diagram of a downhole T2 spectrum temperature correction device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0053] As deep and ultra-deep oil and gas reservoirs become a primary target for exploration and development, the impact of downhole high-temperature environments on the nuclear magnetic resonance relaxation of rock pore fluids cannot be ignored. Even when using instruments with the same frequency to measure T2 spectra downhole and on the surface, there are differences. Substituting NMR data measured in high-temperature downhole environments into evaluation models established at surface temperatures can result in significant errors. Therefore, how to adapt NMR data measured in high-temperature downhole environments to evaluation models established at surface temperatures is a challenge that needs to be addressed.

[0054] The inventors have noticed that the accuracy of reservoir interpretation and evaluation can be improved by performing temperature correction on the nuclear magnetic resonance T2 spectrum measured in a high-temperature downhole environment and substituting the temperature-corrected T2 spectrum into an evaluation model established at normal ground temperature. Currently, in terms of temperature correction of the transverse relaxation time of the T2 spectrum, the existing technology mainly focuses on a certain characteristic value of the T2 spectrum, such as the geometric mean, the peak value of the spectrum peak, etc., to establish a temperature correction model for a single T2 value to perform temperature correction on the characteristic T2 value, and it is impossible to perform temperature correction on the entire T2 spectrum. The existing technology also uses principal component analysis technology to decompose and reconstruct the T2 spectrum to obtain a T2 spectrum at normal ground temperature. However, this method cannot accurately identify each peak, resulting in its inability to be applied to T2 spectra with multiple peaks. The morphology of the T2 spectrum with multiple peaks obtained after correction by this method changes. In actual application, due to the diversity of reservoir fluid components, the T2 spectrum in most cases has multiple peaks, and this method does not meet actual needs.

[0055] After in-depth research, the inventors designed a method for downhole T2 spectrum temperature correction. By fitting the first T2 spectrum of the target layer according to the Gaussian distribution model, the first T2 spectrum after fitting is temperature-corrected by the transverse relaxation time and porosity components using the first temperature correction formula and the second temperature correction formula to obtain the fifth T2 spectrum, thereby realizing temperature correction of the first T2 spectrum of the target layer.

[0056] Figure 1 The flowchart of the downhole T2 spectrum temperature correction method provided by an embodiment of the present invention is shown. The method is executed by a computing device, which may be a computing device including one or more processors. The processor may be a central processing unit (CPU), or an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiment of the present invention, which is not limited here. The one or more processors included in the computing device may be processors of the same type, such as one or more CPUs; or may be processors of different types, such as one or more CPUs and one or more ASICs, which is not limited here. Figure 1 As shown, the method includes the following steps:

[0057] Step 110: Acquire target layer information, which includes the temperature, first T2 spectrum, and fluid composition of the target layer.

[0058] The target layer is the proven layer in the well selected to complete a certain exploration task. Nuclear magnetic resonance logging obtains the temperature, first T2 spectrum and fluid composition of the target layer by performing nuclear magnetic resonance on the target layer. The first T2 spectrum obtained is as follows: Figure 2 As shown in Figure 2, the horizontal axis is the transverse relaxation time (also called the distribution point value), and the vertical axis is the porosity, where the peak value of each peak is the porosity.

[0059] The fluid component is the fluid composition of the target layer. The fluid component includes various waters such as clay water, capillary bound water, movable water, etc., as well as various oils. The target layer can be determined to be a water layer or an oil layer based on the fluid component.

[0060] Step 120: Fit the peak of the first T2 spectrum according to a Gaussian distribution model to obtain a second T2 spectrum.

[0061] Since the first temperature correction formula can only perform temperature correction on the characteristic T2 value of the first T2 spectrum, it is necessary to fit the first T2 spectrum through a Gaussian distribution model to obtain multiple Gaussian distribution curves with characteristic T2 values. Only then can the first temperature correction formula perform temperature correction on the Gaussian distribution curves with characteristic T2 values.

[0062] Obtain the peak values ​​and distribution points of all peaks of the first T2 spectrum to determine the peak point of the first T2 spectrum, for example, obtain Figure 2 In some embodiments, by comparing f(T 2，i ) and the corresponding f(T 2，i+1 ) or f(T 2，i-1 ) to determine the peak point of the first T2 spectrum. f(T 2，i ) is the i-th T2 distribution point T of the T2 spectrum 2，i The corresponding porosity component, f(T 2，i+1 ) is the i+1th T2 distribution point T of the T2 spectrum 2，i+1 The corresponding porosity component, f(T 2，i-1 ) is the i-1th T2 distribution point T of the T2 spectrum 2，i-1 The corresponding porosity component.

[0063] The peak points of the first T2 spectrum are fitted according to the Gaussian distribution model to obtain new peaks, and the new peaks all conform to the Gaussian distribution. All the obtained new peaks are aggregated to generate the second T2 spectrum. Figure 2 and Figure 3 As shown, the first T2 spectrum T 2，i11 The value of T2 spectrum 2，i21 The same value, the T of the first T2 spectrum 2，i12 The value of T2 spectrum 2，i22 The same value, the first T2 spectrum f(T 2，i11 ) value and the second T2 spectrum f(T 2，i21 ) value, the first T2 spectrum f(T 2，i12 ) value and the second T2 spectrum f(T 2，i22 ) value is the same, that is, the peak point of the first T2 spectrum is also the peak point of the new peak.

[0064] The Gaussian distribution model is where f(log 10 (T 2，i )) is the T of the first T2 spectrum 2，i The porosity component at ; Amp is the amplitude of the Gaussian distribution obtained by fitting; μ is the mean of the Gaussian distribution, 10 μ That is, the T2 of the peak point of the first T2 spectrum; σ 2 is the variance of the Gaussian distribution, reflecting the width of the T2 spectrum peak. Substitute the peak point of the first T2 spectrum and the fitted μ and σ into the above Gaussian distribution model to calculate the porosity component f (log 10 (T 2，i )). With the T2 distribution point value as the horizontal coordinate, the f(log 10 (T 2，i)) is the vertical coordinate reconstruction to obtain a new peak, namely the peak of the second T2 spectrum. The reconstructed new peak shape basically coincides with the peak shape of the first T2 spectrum.

[0065] Step 130: Perform temperature correction on the peak points of all peaks of the second T2 spectrum according to a first temperature correction formula to generate a third T2 spectrum. The first temperature correction formula includes temperature and a first constant coefficient related to the fluid component.

[0066] In this step, temperature correction of the transverse relaxation time is performed on the peak points of all peaks in the second T2 spectrum. T is the temperature of the target layer, T2 is the transverse relaxation time at the peak when the target layer is at temperature T, T ref is the ground temperature, T 2，ref To correct T2 to the ground temperature T ref where ΔE is the transverse relaxation time at ΔE, R is a constant, for example, 8.314 J / (mol·K), and ΔE is a first constant coefficient, for example, a parameter that determines the correction trend and degree related to the pore surface chemical properties and fluid composition, ΔE is approximately -2 Kcal / mol for the long relaxation component and approximately -1 Kcal / mol for the short relaxation component.

[0067] The first temperature correction formula only corrects the characteristic point, i.e., the peak point of the second T2 spectrum. Specifically, it only corrects the transverse relaxation time corresponding to the peak point of the second T2 spectrum. The transverse relaxation time corresponding to the peak point is changed according to the first temperature correction formula. Since the parameters of the Gaussian distribution model remain unchanged, it is equivalent to only shifting all the peaks of the second T2 spectrum on the horizontal axis to obtain the third T2 spectrum. Figure 3 and Figure 4 As shown, the second T2 spectrum T 2，i21 The value and the T of the third T2 spectrum 2，i31 The values ​​are different, the T of the second T2 spectrum 2，i22 The value and the T of the third T2 spectrum 2，i32 The values ​​are different, the second T2 spectrum f(T 2，i21 ) value and the third T2 spectrum f(T 2，i31 ) value, the second T2 spectrum f(T 2，i22 ) value and the third T2 spectrum f(T 2，i32 ) values ​​are the same, that is, the peak of the generated third T2 spectrum changes only on the abscissa relative to the peak of the second T2 spectrum. Thus, the temperature correction of the transverse relaxation time of the first T2 spectrum is completed.

[0068] Step 140: Accumulate the porosity components of the first T2 spectrum to obtain a first nuclear magnetic total porosity.

[0069] After completing the temperature correction for the transverse relaxation time of the first T2 spectrum, the porosity component of the first T2 spectrum needs to be corrected. The first NMR total porosity of the first T2 spectrum at the target layer temperature is calculated by integration. This is then used to correct the first NMR total porosity to obtain the second NMR total porosity at the ground temperature.

[0070] Step 150: Perform temperature correction on the first nuclear magnetic total porosity according to a second temperature correction formula to obtain a second nuclear magnetic total porosity. The second temperature correction formula includes temperature and a second constant coefficient related to the fluid component.

[0071] The second temperature correction formula is: T is the temperature of the target layer, T ref is the ground temperature, φ is the first nuclear magnetic total porosity when the target layer is at temperature T, φ ref To correct φ to the ground temperature T ref The second NMR total porosity at , where α is a second constant coefficient determined based on the fluid composition, for example, α is 0.9 for oil and 0.3 for water. Substituting the first NMR total porosity into the second temperature correction formula yields the second NMR total porosity.

[0072] In some embodiments, since the fluid components of the target layer include oil and water, the system will obtain the oil saturation of the target layer and correct the first nuclear magnetic total porosity according to the oil saturation. The second temperature formula is adaptively converted into

[0073] Among them S W is the oil saturation.

[0074] Step 160: Calculate the porosity component of each peak of the third T2 spectrum according to the Gaussian distribution model.

[0075] The porosity component of each peak in the third T2 spectrum is calculated based on the parameters related to the Gaussian distribution model used in the previous step 120 fitting, and the porosity component of each peak in T 2，i The porosity component at , i.e., the value of the ordinate, is calculated using a common method used by those skilled in the art and will not be elaborated on here.

[0076] Step 170: Normalize the third T2 spectrum to obtain a fourth T2 spectrum.

[0077] Since the third T2 spectrum contains multiple temperature-corrected Gaussian distribution curves, it is necessary to merge the multiple temperature-corrected Gaussian distribution curves into one curve for subsequent nuclear magnetic total porosity correction of the fourth T2 spectrum.

[0078] According to the normalization formula Calculate the magnitude component of the fourth T2 spectrum, T 2，iis the ith T2 point of the third T2 spectrum, f cor_T2 (T 2，i ) is the fourth T2 spectrum at T 2，i The amplitude component at , k is the number of peaks in the third T2 spectrum, f cor_T2，k (T 2，i ) is the kth peak of the third T2 spectrum at T 2，i The amplitude component at the third T2 spectrum. 2，i The porosity components of the distribution points are added to obtain the fourth T2 spectrum at T 2，i The porosity components of the points are distributed, and all the obtained porosity components are summarized to generate the fourth T2 spectrum.

[0079] like Figure 4 and Figure 5 As shown, the third T2 spectrum f(T 2，i33 )1 value and the third T2 spectrum f(T 2，i33 )2 values ​​are added to obtain the fourth T2 spectrum f(T 2，i43 ) value, calculate the T of all fourth T2 spectra 2，i The corresponding value is used to generate the fourth T2 spectrum. 2，i31 The value and T of the fourth T2 spectrum 2，i41 The value is the same, the T of the third T2 spectrum 2，32 The value of T2 spectrum 2，42 The value is the same, the third T2 spectrum f(T 2，i31 ) value and the fourth T2 spectrum f(T 2，i41 ) values ​​are different, the third T2 spectrum f(T 2，i32 ) value and the fourth T2 spectrum f(T 2，i42 ) values ​​are different, that is, the peak of the generated fourth T2 spectrum is only accumulated on the vertical axis and thus changes relative to the peak of the third T2 spectrum.

[0080] Step 180: Calculate the fourth T2 spectrum according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum.

[0081] This step corrects the total nuclear magnetic porosity of the fourth T2 spectrum. Specifically, each point T 2，i The corresponding porosity component is corrected according to the second nuclear magnetic total porosity, that is, the total porosity at ground temperature, to obtain the porosity of each distribution point T at ground temperature. 2，i The corresponding porosity component.

[0082] According to the formula Calculate the total nuclear magnetic porosity component of the fifth T2 spectrum to generate the fifth T2 spectrum, φ ref To correct φ to the ground temperature T ref The second nuclear magnetic total porosity at the time of φ is the first nuclear magnetic total porosity when the target layer is at temperature T, fcor (T 2，i ) is the fifth T2 spectrum at T 2，i The porosity component at cor_T2 (T 2，i ) is the fourth T2 spectrum at T 2，i The porosity component at T2 is n, and the total number of T2 points in the fourth T2 spectrum is n. First calculate the fourth T2 spectrum at T 2，i The porosity component of the fourth T2 spectrum accounts for the proportion of the total porosity component, and then the fifth T2 spectrum is obtained by multiplying the second nuclear magnetic total porosity with the proportion. 2，i Finally, all the calculated porosity components of the fifth T2 spectrum are summarized to generate the following Figure 6 The fifth T2 spectrum is shown.

[0083] In an embodiment of the present invention, a second T2 spectrum is obtained by fitting the first T2 spectrum of the target layer according to a Gaussian distribution model, and a temperature correction of the transverse relaxation time is performed on the characteristic points of the second T2 spectrum according to a first temperature correction formula to obtain a third T2 spectrum. Then, the first nuclear magnetic total porosity of the target layer is corrected according to the second temperature correction formula to obtain a second nuclear magnetic total porosity at ground temperature. At this time, the third T2 spectrum is normalized to obtain a fourth T2 spectrum. Finally, the fourth T2 spectrum is temperature-corrected for the porosity component according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum, thereby realizing temperature correction of the nuclear magnetic data measured in a high-temperature downhole environment, so that the nuclear magnetic data measured in a high-temperature downhole environment are suitable for an evaluation model established at normal ground temperature.

[0084] In some embodiments, step 120 includes:

[0085] Step a01: Determine all the 2，i-1 )<f(T 2，i ) and f(T 2，i+1 )<f(T 2，i ) of f(T 2，i ) is the first peak of the first T2 spectrum, f(T 2，i ) is the i-th T2 distribution point T of the first T2 spectrum 2，i The corresponding porosity component, f(T 2，i+1 ) is the i+1th T2 distribution point T of the first T2 spectrum 2，i+1 The corresponding porosity component, f(T 2，i-1 ) is the i-1th T2 distribution point T of the first T2 spectrum 2，i-1 The corresponding porosity component.

[0086] Step a02: Determine a first distribution point value corresponding to the first peak value based on the first peak value.

[0087] Steps a01 to a02 are used to determine all peak points in the first T2 spectrum. Figure 7 As shown, the f(T 2，i ) satisfies f(T 2，i-1 ) <f(T 2，i ) and f(T 2，i+1 )<f(T 2，i ), f(T 2，i-1 ) and f(T 2，i+1 ) is the distribution point T 2，i The porosity components corresponding to the two adjacent points determine point P1 as the first peak point of the first T2 spectrum, f(T 2，i ) is the first peak value T2, and f(T 2，i ) The first point value corresponding to 2，i .

[0088] Step a03: Obtain the values ​​satisfying f(T 2，i ) and f(T 2，i-1 ) is less than the first threshold T 2，i With T 2，i-1 .

[0089] Step a04: Calculate all T 2，i With the smallest T 2，i-1 The mean of is taken as the second distribution value of the first T2 spectrum.

[0090] Step a05: Determine a second peak value corresponding to the second distribution point value.

[0091] In the first T2 spectrum, since the relaxation times of some fluid components in the target layer are close to those of other fluid components, there may be Figure 7 The platform formed by the lines P3, P2 and P4 shown in the figure, at this time, f(T 2，i-1 )-f(T 2，i ) is less than a certain set value, it is considered that the T2 value of the fluid component is at T 2，i Nearby, take all such T 2，i The mean of the values ​​of f(T is considered to be the relaxation time at the peak of the fluid component. Steps a03 to a05 are used to determine the relaxation time at the peak of the fluid component that is close to the relaxation time of the fluid component in the first T2 spectrum. When the presence of f(T 2，i ) and f(T 2，i-1 ) is less than the first threshold T 2，i With T 2，i-1 , will continue to detect and deploy T 2，i Adjacent points T 2，i-1 The corresponding f(T 2，i-1 ) and f(T 2，i-2 ) or the distribution point T 2，i+1 The corresponding f(T 2，i+1) and f(T 2，i ) is less than a first threshold. In some embodiments, the first threshold is set to 0.1. 2，i-1 The corresponding f(T 2，i-1 ) and f(T 2，i-2 ) or the distribution point T 2，i+1 The corresponding f(T 2，i+1 ) and f(T 2，i ) is greater than or equal to the first threshold, then the calculated value that satisfies f(T 2，i ) and f(T 2，i-1 ) is less than the first threshold value of all T 2，i Distribution value and minimum T 2，i-1 The mean of the distribution point values ​​is calculated as the second distribution point value of the platform, and the second peak corresponding to the second distribution point value is found in the first T2 spectrum. For example, Figure 7 In the above example, we can determine f(T 2，a ) and f(T 2，a-1 ) and f(T 2，a+1 ) and f(T 2，a ) is less than the first threshold, where T 2，a-1 To obtain the minimum T 2，i-1 Distribution value, T 2，a+1 and T 2，a To obtain T 2，i Distribution value, calculate T 2，a-1 、T 2，a+1 and T 2，a The mean value is T 2，a , the distribution point value T 2，a As the second distribution point value, with T 2，a The corresponding f(T 2，a The second distribution point value and the second peak value are used for subsequent fitting according to the Gaussian distribution model to obtain a corresponding Gaussian distribution curve, thereby generating a second T2 spectrum.

[0092] Step a06: fitting all the first peak values, second peak values, first distribution point values ​​and second distribution point values ​​obtained according to the Gaussian distribution model to obtain a second T2 spectrum.

[0093] like Figure 7 and Figure 2 As shown, the point corresponding to the first peak value and the first distribution value is point P1, and the point corresponding to the second peak value and the second distribution value is point P2. Points P1 and P2 are used as peak points of the Gaussian distribution, and fitting is performed according to the Gaussian distribution model to obtain a second T2 spectrum composed of multiple Gaussian distribution curves.

[0094] Through steps a01 to a06, all peaks of the first T2 spectrum are determined, and then the peaks of the first T2 spectrum are fitted according to the Gaussian distribution model, so that the shape of the finally generated second T2 spectrum is not much different from the shape of the first T2 spectrum. In addition, the platform of the first T2 spectrum is also processed accordingly, and the characteristic T2 value of the first T2 spectrum is not missed, thereby improving the accuracy of subsequent temperature correction of the first T2 spectrum.

[0095] In some embodiments, step 120 further includes:

[0096] Step b01: Determine whether the difference between the distribution point values ​​corresponding to the peak values ​​between any two peaks of the second T2 spectrum is less than a second threshold.

[0097] Step b02: If yes, fit the two peaks into a Gaussian distribution.

[0098] The first T2 spectrum may contain Figure 8 The peak distribution value of the two adjacent peaks is T 2，b and T 2，b-1 Since the distribution points of the two peak-to-peak values ​​are close, for the convenience of calculation, they are regarded as one peak and Gaussian fitting is performed on them, and the following is obtained: Figure 9 The second T2 spectrum shown in FIG2 is a peak. This approach allows only one Gaussian distribution to be calculated subsequently, improving the efficiency of the downhole T2 spectrum temperature correction method. In some embodiments, the second threshold is 5, and two peaks with a difference in distribution value less than 5 are considered to be a single peak.

[0099] In some embodiments, the downhole T2 spectrum temperature correction method further includes:

[0100] Step c01: Obtain the oil saturation of the target layer.

[0101] Step c02: Determine whether the target layer is an oil layer based on the oil saturation.

[0102] Step c03: If the target layer is not an oil layer, temperature correction is performed on the second T2 spectrum of the target layer according to the first temperature correction formula.

[0103] As mentioned above, the target layer can be either a water layer or an oil layer. If the target layer is an oil layer, since the crude oil is located in the pores and does not undergo surface relaxation, the crude oil relaxation time is not very useful for evaluating petrophysical parameters such as pore structure and permeability, except for reflecting the crude oil viscosity. In addition, the oil signal easily overlaps with the water signal on the T2 spectrum, making it difficult to distinguish. Therefore, temperature correction of the T2 spectrum is not required for the oil layer, and only temperature correction is performed for the water layer.

[0104] By determining the oil saturation of the target layer, it is determined whether the target layer is an oil layer or a water layer. In some embodiments, a target layer with an oil saturation exceeding 20% ​​is an oil layer. When the target layer is determined to be a water layer, the second T2 spectrum of the target layer is temperature corrected according to the first temperature correction formula. If the target layer is an oil layer, no temperature correction is required. This reduces the calculation of the second T2 spectrum and improves the efficiency of the downhole T2 spectrum temperature correction method.

[0105] In some embodiments, the downhole T2 spectrum temperature correction method can achieve T2 spectrum correction at continuous depths in a single pass. The corrected T2 spectrum is right-shifted and smooth and continuous, with little noticeable change in shape, achieving the desired correction effect and possessing practical significance. Experiments have shown that before temperature correction, the high downhole temperature environment accelerates the surface relaxation of fluid components, resulting in relaxation times significantly shorter than those obtained from surface core testing. However, after temperature correction using the downhole T2 spectrum temperature correction method, the positions and distribution widths of the long and short relaxation peaks in the downhole target layer's T2 spectrum are substantially consistent with those from core testing.

[0106] In some embodiments, as Figure 10 As shown in the figure, after the temperature correction of the oil layer or water layer in a well by the downhole T2 spectrum temperature correction method, the nuclear magnetic porosity and the core porosity have excellent consistency, with an average error within 10%, achieving the correction effect.

[0107] Figure 11 The schematic diagram of the structure of the computing device provided by the embodiment of the present invention is shown. The specific embodiment of the present invention does not limit the specific implementation of the computing device.

[0108] like Figure 11 As shown, the computing device may include: a processor 202 , a communication interface 204 , a memory 206 , and a communication bus 208 .

[0109] Processor 202, communication interface 204, and memory 206 communicate with each other via communication bus 408. Communication interface 204 is used to communicate with other devices, such as client devices or other server network elements. Processor 202 is used to execute program 210, which may specifically perform the steps described in the embodiment of the downhole T2 spectrum temperature correction method.

[0110] Specifically, the program 210 may include program code including computer-executable instructions.

[0111] Processor 202 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention. The one or more processors included in a computing device may be processors of the same type, such as one or more CPUs, or processors of different types, such as one or more CPUs and one or more ASICs.

[0112] The memory 206 is used to store the program 210. The memory 206 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0113] An embodiment of the present invention further provides a computer-readable storage medium, in which at least one executable instruction is stored. When the executable instruction is run, the operation of the downhole T2 spectrum temperature correction method of any of the above embodiments is executed.

[0114] The algorithm or demonstration provided herein are not inherently relevant to any particular computer, virtual system or other equipment. Various general-purpose systems may also be used together with the teachings based on this. According to the above description, it is apparent that the structure required for constructing this type of system. In addition, the embodiment of the present invention is not directed to any specific programming language yet. It should be understood that various programming languages ​​can be utilized to realize the content of the present invention described herein, and the above description of specific languages ​​is for the purpose of disclosing the best mode of the present invention.

[0115] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0116] Similarly, it should be understood that in order to streamline the present invention and facilitate understanding of one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim.

[0117] Those skilled in the art will appreciate that the modules in the devices in the embodiments can be adaptively changed and set in one or more devices different from the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and can be divided into multiple sub-modules or sub-units or sub-components. Except that at least some of such features and / or processes or units are mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed so far can be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) can be replaced by an alternative feature that provides the same, equivalent or similar purpose.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A method for temperature correction of downhole T2 spectrum, wherein the peak value of the T2 spectrum is porosity and the distribution value is transverse relaxation time, characterized in that: The method comprises: Acquiring target layer information, the target layer information including a temperature, a first T2 spectrum, and a fluid component of the target layer; Fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain a second T2 spectrum; The peak points of all peaks of the second T2 spectrum are temperature-corrected according to a first temperature correction formula to generate a third T2 spectrum, wherein the first temperature correction formula includes the temperature and a first constant coefficient related to the fluid component; wherein the first temperature correction formula is T is the temperature of the target layer, T2 is the transverse relaxation time at the peak when the target layer is at temperature T, T ref is the ground temperature, T 2,ref To correct T2 to the ground temperature T ref The transverse relaxation time at , R is a constant, ΔE is the first constant coefficient; Accumulating porosity components of the first T2 spectrum to obtain a first nuclear magnetic total porosity; The first nuclear magnetic total porosity is temperature corrected according to a second temperature correction formula to obtain a second nuclear magnetic total porosity, wherein the second temperature correction formula includes the temperature and a second constant coefficient related to the fluid component; wherein the second temperature correction formula is φ is the first nuclear magnetic total porosity of the target layer at temperature T, φ ref To correct φ to the ground temperature T ref The second nuclear magnetic total porosity at , α is the second constant coefficient; Calculating the porosity component of each peak of the third T2 spectrum according to the Gaussian distribution model; performing normalization processing on the third T2 spectrum to obtain a fourth T2 spectrum; The fourth T2 spectrum is calculated according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum.

2. The downhole T2 spectrum temperature correction method according to claim 1, characterized in that: The step of fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain a second T2 spectrum includes: Determine all the 2,i-1 ) <f(T 2,i ) and f(T 2,i+1 ) <f(T 2,i ) of f(T 2,i ) is the first peak of the first T2 spectrum, f(T 2,i ) is the i-th T2 distribution point T of the first T2 spectrum 2,i The corresponding porosity component, f(T 2,i+1 ) is the i+1th T2 distribution point T of the first T2 spectrum 2,i+1 The corresponding porosity component, f(T 2,i-1 ) is the i-1th T2 distribution point T of the first T2 spectrum 2,i-1 The corresponding porosity component; Determine a first distribution point value corresponding to the first peak value according to the first peak value; Obtain the values ​​satisfying f(T 2,i ) and f(T 2,i-1 ) is less than the first threshold T 2,i With T 2,i-1 ; Calculate all T 2,i With the smallest T 2,i-1 The mean of is taken as the second distribution value of the first T2 spectrum; Determining a second peak value corresponding to the second distribution point value; The second T2 spectrum is obtained by fitting all the first peak values, second peak values, first distribution point values ​​and second distribution point values ​​obtained according to the Gaussian distribution model.

3. The underground T2 spectrum temperature correction method according to claim 1, characterized in that: The step of fitting the peak of the first T2 spectrum according to a Gaussian distribution model to obtain a second T2 spectrum further includes: Determining whether a difference between the distribution point values ​​corresponding to the peak values ​​between any two peaks of the second T2 spectrum is less than a second threshold; If so, the two peaks are fitted to a Gaussian distribution.

4. The downhole T2 spectrum temperature correction method according to claim 1, characterized in that: The method further comprises: Obtaining the oil saturation of the target layer; determining whether the target layer is an oil layer according to the oil saturation; If the target layer is not an oil layer, temperature correction is performed on the second T2 spectrum of the target layer according to the first temperature correction formula.

5. The underground T2 spectrum temperature correction method according to claim 1, characterized in that: The Gaussian distribution model is i is a natural number, T 2,i is the i-th T2 distribution point of the first T2 spectrum and the third T2 spectrum, f(log 10 (T 2,i )) is T 2,i The amplitude component at , Amp is the amplitude of the Gaussian distribution obtained by fitting, μ is the mean of the Gaussian distribution, σ 2 is the variance of the Gaussian distribution.

6. The downhole T2 spectrum temperature correction method according to claim 1, characterized in that: Normalizing the third T2 spectrum to obtain a fourth T2 spectrum includes: According to the normalization formula Calculate the amplitude component of the fourth T2 spectrum, T 2,i is the i-th T2 point of the third T2 spectrum, f cor_T2 (T 2,i ) is the fourth T2 spectrum at T 2,i The amplitude component at , k is the number of peaks in the third T2 spectrum, f cor_T2,k (T 2,i ) is the kth peak of the third T2 spectrum at T 2,i The amplitude component at .

7. The downhole T2 spectrum temperature correction method according to claim 1, characterized in that: Calculating the fourth T2 spectrum according to the second nuclear magnetic total porosity to obtain a fifth T2 spectrum includes: According to the formula Calculate the total nuclear magnetic porosity component of the fifth T2 spectrum to generate the fifth T2 spectrum, where φ is the first total nuclear magnetic porosity when the target layer is at temperature T, and φ ref To correct φ to the ground temperature T ref The second NMR total porosity, f cor (T 2,i ) is the fifth T2 spectrum at T 2,i The porosity component at cor_T2 (T 2,i ) is the fourth T2 spectrum at T 2,i The porosity component at , n is the total number of T2 points in the fourth T2 spectrum.

8. A computing device, characterized in that include: A processor, a memory, a communication interface, and a communication bus, wherein the processor, the memory, and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute the downhole T2 spectrum temperature correction method according to any one of claims 1 to 7.

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