Through casing element content calculation method for complex reservoir

Abstract

The invention discloses a through-casing element content calculation method for a complex reservoir, which belongs to the technical field of nuclear logging, and specifically comprises the following steps: carrying out through-casing measurement on a stratum to be measured to obtain a real energy spectrum, and carrying out spectrum unfolding and weighted least square methods to obtain the initial yield of each element contained in the energy spectrum; the method comprises the following steps: acquiring constraints of through-casing measurement on each element contained in an energy spectrum, including yield correction, dry weight correction, element reaction cross section influence correction and through-casing / cement sheath correction in sequence, calculating to obtain a yield limit value of each element, and further calculating to obtain a final yield of each element through a weighted least square method with constraints; the accuracy of gamma-ray energy spectrum analysis is improved through multiple times of correction, and the method is particularly suitable for complex lithology identification of buried hill reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear well logging, and in particular relates to a method for calculating through-casing element content in complex reservoirs. Background Art

[0002] In recent years, the global oil demand has grown rapidly, and traditional oil reservoirs can no longer meet the growing demand. Therefore, concealed oil reservoirs such as buried hill oil reservoirs have become one of the important directions of oil and gas exploration. As an important concealed oil and gas resource, buried hill oil reservoirs are crucial to my country's energy security and economic development.

[0003] Buried hill oil reservoirs are affected by complex geological structures, and their reservoirs are mainly composed of fractures, dissolution pores and microstructural fractures. These characteristics determine the distribution, permeability and oil saturation of the reservoir, and directly affect the reserves and development effects of oil and gas. Lithology identification plays a key role in understanding and evaluating buried hill oil reservoirs. By accurately identifying lithology, the physical and chemical properties of the reservoir can be determined, which helps to analyze the genesis and evolution history of the reservoir, and provides important geological basis and technical support for subsequent oil and gas exploration and development.

[0004] At present, the main methods of lithology identification include core observation, standard mineral calculation, gravity and magnetic technology, seismic technology and remote sensing technology. However, in complex lithology such as bedrock buried hill reservoirs, pulsed neutron-based element logging technology shows obvious advantages. First, a large amount of geological information, including lithology type, element composition, etc., can be obtained in real time to provide data support for subsequent work; secondly, it has a high vertical resolution and can identify small changes and different strata, which helps to reveal complex reservoir structures; in addition, it is not affected by porosity and is applicable to various rock types, especially for bedrock buried hill reservoirs, where its value is particularly significant.

[0005] The inversion process of pulsed neutron logging is divided into two parts: element content inversion and mineral content inversion. Element content inversion uses weighted least squares method to process inelastic gamma spectrum and captured gamma spectrum data to obtain the inelastic gamma spectrum yield and captured gamma spectrum yield of the element; mineral content inversion converts the inelastic gamma spectrum yield and captured gamma spectrum yield of the element into inelastic dry weight and captured dry weight through various models, and finally obtains the mineral dry weight.

[0006] In the actual spectrum interpretation process, when the types of elements in the formation to be interpreted are relatively complex, the use of weighted least squares method to interpret the gamma spectrum often produces unrealistic solutions. The main minerals contained in the buried hill reservoir can be divided into three categories: quartz, feldspar and dark minerals. The main component of quartz is SiO2, the composition of feldspar is a mixture of KAlSi3O8, NaAlSi3O8 and CaAl2Si2O8 in a certain proportion, and the dark minerals are mostly Fe and Mg minerals. Therefore, in the complex lithology identification of the buried hill reservoir, when using gamma spectrum data for element analysis, the conventional inversion algorithm may fall into a local optimal situation, which will cause the calculated element content to deviate from the actual value. This deviation will affect the accuracy of mineral identification, and then affect reservoir evaluation and development decisions.

[0007] Therefore, designing an element measurement algorithm for complex reservoirs through casing has positive significance for solving the lithology identification of buried hill reservoirs. Summary of the invention

[0008] In order to solve the problem that the element content deviates from the actual value in the process of complex lithology identification of buried hill reservoirs due to the conventional inversion algorithm falling into the local optimum, the present invention provides a method for calculating the through-casing element content of complex reservoirs, which helps to improve the accuracy of gamma spectroscopy analysis and is particularly suitable for the complex lithology identification of buried hill reservoirs.

[0009] In order to achieve the above purpose, the technical method adopted by the present invention is as follows:

[0010] A method for calculating the through-casing element content of a complex reservoir comprises the following steps:

[0011] Step 1: Cement rings and casings are sequentially set in the well of the formation to be measured to reinforce the well, and a formation element logging instrument is used to measure the formation through the casing to obtain a true energy spectrum. After the standard spectrum of the casing elements is analyzed, the initial yield of each element contained in the energy spectrum is obtained by the weighted least square method;

[0012] Step 2: Obtain the constraints of the through-casing measurement on the elements contained in the energy spectrum, including:

[0013] Step 2.1: Use the yield correction method to correct the yield of each element, specifically:

[0014] Step 2.1.1, assuming that the mineral M in the formation to be tested contains element E and element E1, a formation element logging numerical simulation calculation model with mineral M as the formation is established through Monte Carlo simulation. After the standard spectrum of casing elements is analyzed, the first analytical yield of element E is obtained, and then the initial yield is obtained by fitting. and the first output correction value COR1 M,E wherein the first yield correction value COR1 M,Eis the yield correction value of mineral M for element E, specifically the difference between the actual yield of element E and the first analytical yield;

[0015] For all minerals containing element E in the measured stratum, the first yield correction value COR1 corresponding to each mineral M,E The sum is the total first yield correction value COR1 of element E E ;

[0016] Step 2.1.2: According to the chemical formula of all minerals containing element E in the stratum to be tested, take the maximum dry weight of element E in different minerals as the first limit value WF1 of the dry weight of element E E , and then determine the first limit value Y1 of the yield of element E E ;

[0017] Step 2.1.3: Based on the total first output correction value COR1 E , the first limit value Y1 for the yield of element E E After correction, the second limit value Y2 of the yield of element E is obtained. E ;

[0018] Step 2.1.4, based on steps 2.1.1 to 2.1.3, obtaining the second limit value of the yield of each element included in the energy spectrum;

[0019] Step 2.2: Use the dry weight correction method to correct the yield of each element, specifically:

[0020] Step 2.2.1: Assuming that the mineral N in the stratum to be tested contains element E and element E2, obtain the second limit value of the yield of element E2 according to step 2.1.4. Then the second limit value of dry weight of element E2 is obtained Through Monte Carlo simulation, a numerical simulation calculation model for formation element logging with mineral N as the formation was established. After the standard spectrum of casing elements was analyzed, the second analytical yield of element E was obtained, and then the second limit value of dry weight was obtained by fitting. and the second yield correction value COR2 N,E wherein the second yield correction value COR2 N,E is the yield correction value of mineral N to element E, specifically the difference between the actual yield of element E and the second analytical yield;

[0021] For all minerals containing element E in the measured stratum, the second yield correction value COR2 corresponding to each mineral N,E The sum is the total second yield correction value COR2 of element E E ;

[0022] Step 2.2.2: Based on the total second output correction value COR2 E, the second limit value Y2 for the yield of element E E After correction, the third limit value Y3 of the yield of element E is obtained. E ;

[0023] Step 2.2.3, based on step 2.2.1 to step 2.2.2, obtaining the third limit value of the yield of each element included in the energy spectrum;

[0024] Step 2.3: Use the influence of element reaction cross section to correct the yield of each element, specifically:

[0025] Step 2.3.1: Assume that the stratum to be tested contains element E and L elements that affect the dry weight of element E due to the reaction cross section. According to step 2.2.3, the third limit value of the yield of the L elements is obtained. The third limit value of the yield of the lth, l=1, 2, ..., Lth element is Y3 l ,l=1,2,…,L;

[0026] Step 2.3.2, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E and the first element as the formation, after the casing element standard spectrum is analyzed, the first analytical dry weight of element E corresponding to the first element is obtained, and then the third limit value of the yield is fitted to be Y3 l Corrected value with first dry weight The relationship between them is:

[0027]

[0028] Where, CCS E,l is the influence factor of the reaction cross section of the lth element on the dry weight of element E; is the reaction cross section correction value of the lth element to the dry weight of element E, specifically the difference between the true dry weight of element E and the first analytical dry weight of element E corresponding to the lth element;

[0029] Sum the first dry weight correction values ​​of L elements to obtain the dry weight correction value

[0030]

[0031] Step 2.3.3: According to the third limit value Y3 of output E , obtain the third limit value WF3 of the dry weight of element E E ;

[0032] Step 2.3.4: Corrected value based on dry weight The third limit value WF3 for dry weight of element E E After correction, the fourth limit value of dry weight of element E WF4 is obtained. E, and then the fourth limit value Y4 of the yield of element E is obtained E ;

[0033] Step 2.3.5, based on steps 2.3.1 to 2.3.4, obtaining the fourth limit value of the yield of each element included in the energy spectrum;

[0034] Step 2.4, determine whether each element exists in the formation to be tested and the cement sheath at the same time, or exists in the formation to be tested and the casing at the same time. If so, go to step 2.5; otherwise, take the fourth limit value of the yield of the element as its yield constraint, and go to step 3;

[0035] Step 2.5: Correct the yield of each element by casing / cement sheath, specifically:

[0036] Step 2.5.1, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E as the formation, after the casing element standard spectrum is analyzed, the third analytical yield of element E is obtained, and then the thickness of the casing / cement sheath and the third yield correction value COR3 of element E are obtained by fitting. E wherein the third yield correction value COR3 E is the difference between the true yield of element E and the third analytical yield;

[0037] Step 2.5.2: According to the actual thickness of cement sheath and casing set in step 1, obtain the third yield correction value COR3 corresponding to the cement sheath E1 , and the third yield correction value COR3 corresponding to the casing E2 , and sum to get the total third yield correction value COR3 of element E E , and then the fourth limit value Y4 of the yield of element E E After correction, the fifth limit value Y5 of the yield of element E is obtained. E , as the yield constraint of element E;

[0038] Step 2.5.3, based on steps 2.5.1 to 2.5.2, obtain the yield constraint of each element included in the energy spectrum;

[0039] Step 3: Based on the yield constraints of each element, the constrained weighted least squares method is used to obtain the final yield of each element included in the energy spectrum.

[0040] Furthermore, in step 2.1.2, for the mineral M contained in the formation to be tested, the dry weight WF of the element E is calculated according to the chemical formula of the mineral M. E The specific formula is:

[0041]

[0042] Where Matom is the total relative atomic mass of element E in mineral M; M molecule is the relative molecular mass of mineral M.

[0043] Furthermore, in step 2.1.2, the first limit value Y1 of the yield of element E is determined E The specific formula is:

[0044]

[0045] Where S is the relative sensitivity factor of element E obtained by simulation or measurement; XY is the oxide index.

[0046] Furthermore, the second limit value Y2 of the yield of element E in step 2.1.3 E The calculation formula is:

[0047] Y2 E =Y1 E -COR1 E

[0048] Furthermore, the formation element logging instrument is a pulsed neutron instrument, which is green and safe.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The present invention proposes a method for calculating the through-casing element content for complex reservoirs. The yield limit value of each element is calculated through sequential yield correction, dry weight correction, element reaction cross-section influence correction and through-casing / cement ring correction, and then the final yield of each element is calculated through the constrained weighted least squares method. The present invention improves the accuracy of gamma ray spectrum analysis through multiple corrections, and is particularly suitable for complex lithology identification of buried hill reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0052] Figure 1 is a flow chart of the method for calculating the through-casing element content in a complex reservoir proposed in Example 1;

[0053] Figure 2 It is a schematic diagram of a numerical simulation calculation model for logging while drilling formation elements after cement sheath and casing are set in the formation to be measured in Example 1;

[0054] Figure 3 It is a comparison curve between the inverted energy spectrum obtained by the through-casing element content calculation method for complex reservoirs and the initial inverted energy spectrum in Example 1. DETAILED DESCRIPTION

[0055] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0056] Example 1

[0057] This embodiment proposes a method for calculating the through-casing element content for a complex reservoir, wherein the complex reservoir is specifically a buried hill reservoir. The fractured reservoir of the buried hill oil reservoir contains minerals such as quartz, feldspar and dark minerals. The process is as follows: Figure 1 As shown, the following steps are included:

[0058] Step 1: Figure 2 As shown, cement rings and casings are sequentially set in the well of the formation to be measured to reinforce the well. The formation element logging instrument (specifically a pulsed neutron instrument) is used to measure the formation through the casing to obtain the real energy spectrum. After the standard spectrum of the casing elements is analyzed, the initial yield of each element contained in the energy spectrum is obtained by the weighted least squares method. The specific process is as follows:

[0059] The true energy spectrum can be regarded as a linear combination of the standard spectra of the corresponding through-casing elements, and the equation group is expressed as:

[0060]

[0061] Where, d i ,i=1,2,…,n is the normalized count rate of the ith channel in the real energy spectrum; s ij ,i=1,2,…,n,j=1,2,…,m is the normalized count rate of the jth element in the standard spectrum of the element at the ith channel address; y j ,j=1,2,…,m is the relative yield of the jth element;

[0062] The system of equations can be written in matrix form as:

[0063]

[0064] In the formula, ε i ,i=1,2,…,n is the counting error of the ith address;

[0065] Then, the matrix form is recorded as:

[0066] d=s·y+ε

[0067] The initial yield of each element contained in the energy spectrum is obtained by weighted least squares method, that is, the optimal solution of element yield is found by minimizing the error. Since the statistical errors of the counts of each channel address of the real energy spectrum are not equal, the minimization problem of fitting error should be considered as the weighted sum of the square of the error, that is,

[0068] R=ε T Wε=(ds·y) T W(ds·y)

[0069] Where W is the diagonal weight matrix, which can be expressed as:

[0070]

[0071] Step 2: Obtain the constraints of the through-casing measurement on the elements contained in the energy spectrum, including:

[0072] Step 2.1: Use the yield correction method to correct the yield of each element, specifically:

[0073] Step 2.1.1, assuming that the mineral M in the stratum to be tested contains element E and element E1, for example, Mg and Ca exist simultaneously in dolomite, dolomite is the mineral M, Mg is the element E1, and Ca is the element E;

[0074] Through Monte Carlo simulation, a numerical simulation calculation model of formation element logging with mineral M as the formation was established. After the standard spectrum of casing elements was analyzed, the first analytical yield of element E was obtained, and then the initial yield was obtained by fitting. and the first output correction value COR1 M,E The relationship between them is:

[0075]

[0076] Among them, the first output correction value COR1 M,E is the yield correction value of mineral M for element E, specifically the difference between the actual yield of element E and the first analytical yield; a1, b1 and c1 are all COR1 M,E The fitting coefficient of

[0077] For all minerals containing element E in the measured stratum, the first yield correction value COR1 corresponding to each mineral M,E The sum is the total first yield correction value COR1 of element E E ;

[0078] Step 2.1.2: According to the chemical formula of all minerals containing element E in the stratum to be tested, take the maximum dry weight of element E in different minerals as the first limit value WF1 of the dry weight of element E E ;

[0079] Taking mineral M as an example, the dry weight of element E is calculated according to the chemical formula of mineral M. The specific formula is:

[0080]

[0081] Where M atom is the total relative atomic mass of element E in mineral M; M molecule is the relative molecular mass of mineral M;

[0082] For example, the main component of potassium feldspar is KAlSi3O8. If the mineral M is pure potassium feldspar, the dry weight of Si element is 0.2161. After comparison and taking the maximum value, the first limit value of the dry weight of element E in the buried hill reservoir can be obtained;

[0083] Then determine the first limit value Y1 of the yield of element E E , the specific formula is:

[0084]

[0085] Where S is the relative sensitivity factor of element E obtained by simulation or measurement, specifically:

[0086]

[0087] Where N A is Avogadro's constant, σ C is the thermal neutron absorption cross section of element E, M is the gamma ray transmission and detection probability, A is the atomic weight of element E, for example, the relative sensitivity factor of Ca element is 1.847; XY is the oxide index, specifically the conversion relationship between element E and its corresponding oxide, which can be obtained through the chemical formula. For example, the oxide corresponding to Ca is CaO, so its oxide index O XY is 1.399;

[0088] Step 2.1.3: Based on the total first output correction value COR1 E , the first limit value Y1 for the yield of element E E After correction, the second limit value Y2 of the yield of element E is obtained. E ,Right now:

[0089] Y2 E =Y1 E -COR1 E

[0090] Step 2.1.4, based on steps 2.1.1 to 2.1.3, obtaining the second limit value of the yield of each element included in the energy spectrum;

[0091] Step 2.2: Use the dry weight correction method to correct the yield of each element, specifically:

[0092] Step 2.2.1, assuming that the mineral N in the stratum to be tested contains element E and element E2, Al and Ca exist simultaneously in anorthite, anorthite is taken as mineral N, Al as element E2, and Ca as element E;

[0093] According to step 2.1.4, the second limit value of the yield of element E2 is obtained Then the second limit value of dry weight of element E2 is obtained Right now:

[0094]

[0095] Through Monte Carlo simulation, a numerical simulation calculation model for formation element logging with mineral N as the formation was established. After the casing element standard spectrum was analyzed, the second analytical yield of element E was obtained, and then the second limit value of dry weight was obtained by fitting. and the second yield correction value COR2 N,E The relationship between them is:

[0096]

[0097] Among them, the second output correction value COR2 N,E is the yield correction value of mineral N to element E, specifically the difference between the actual yield of element E and the second analytical yield; a2, b2, c2 and d2 are all COR2 N,E The fitting coefficient of

[0098] For all minerals containing element E in the measured stratum, the second yield correction value COR2 corresponding to each mineral N,E The sum is the total second yield correction value COR2 of element E E ;

[0099] Step 2.2.2: Based on the total second output correction value COR2 E , the second limit value Y2 for the yield of element E E After correction, the third limit value Y3 of the yield of element E is obtained. E ,Right now:

[0100] Y3 E =Y2 E -COR2 E

[0101] Step 2.2.3, based on step 2.2.1 to step 2.2.2, obtaining the third limit value of the yield of each element included in the energy spectrum;

[0102] Step 2.3: Use the influence of element reaction cross section to correct the yield of each element, specifically:

[0103] Step 2.3.1: Assume that the stratum to be tested contains element E and L elements that affect the dry weight of element E due to the reaction cross section. According to step 2.2.3, the third limit value of the yield of the L elements is obtained. The third limit value of the yield of the lth element, l=1,2 is Y3 l ,l=1,2;

[0104] In this embodiment, Ca is the element E, K and Fe are the elements that affect the dry weight of the element E due to the reaction cross section, that is, the first element is K, and the second element is Fe;

[0105] Step 2.3.2, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E and the first element as the formation, after the casing element standard spectrum is analyzed, the first analytical dry weight of element E corresponding to the first element is obtained, and then the third limit value of the yield is fitted to be Y3 l Corrected value with first dry weight The relationship between them is:

[0106]

[0107] Where, CCS E,l is the influence factor of the reaction cross section of the lth element on the dry weight of element E; is the reaction cross section correction value of the lth element to the dry weight of element E, specifically the difference between the true dry weight of element E and the first analytical dry weight of element E corresponding to the lth element;

[0108] Sum the first dry weight correction values ​​of L elements to obtain the dry weight correction value

[0109]

[0110] In this embodiment, CCS E,1 and CCS E,2 They are 0.574326428 and 0.574326428 respectively;

[0111] Step 2.3.3: According to the third limit value Y3 of output E , obtain the third limit value WF3 of the dry weight of element E E ,Right now:

[0112]

[0113] Step 2.3.4: Corrected value based on dry weight The third limit value WF3 for dry weight of element EE After correction, the fourth limit value of dry weight of element E WF4 is obtained. E ,Right now:

[0114]

[0115] Then we get the fourth limit value Y4 of the yield of element E: E ,Right now:

[0116]

[0117] Step 2.3.5, based on steps 2.3.1 to 2.3.4, obtaining the fourth limit value of the yield of each element included in the energy spectrum;

[0118] Step 2.4, determine whether each element exists in the formation to be tested and the cement sheath at the same time, or exists in the formation to be tested and the casing at the same time. If so, go to step 2.5; otherwise, take the fourth limit value of the yield of the element as its yield constraint, and go to step 3;

[0119] Step 2.5: Correct the yield of each element by casing / cement sheath, specifically:

[0120] Step 2.5.1, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E as the formation, after the casing element standard spectrum is analyzed, the third analytical yield of element E is obtained, and then the thickness of the casing / cement sheath and the third yield correction value COR3 of element E are obtained by fitting. E wherein the third yield correction value COR3 E is the difference between the true yield of element E and the third analytical yield;

[0121] Step 2.5.2: According to the actual thickness of cement sheath and casing set in step 1, obtain the third yield correction value COR3 corresponding to the cement sheath E1 , and the third yield correction value COR3 corresponding to the casing E2 , and sum to get the total third yield correction value COR3 of element E E , and then the fourth limit value Y4 of the yield of element E E After correction, the fifth limit value Y5 of the yield of element E is obtained. E , as the yield constraint of element E, that is:

[0122] Y5 E =Y4 E -COR3 E

[0123] Step 2.5.3, based on steps 2.5.1 to 2.5.2, obtain the yield constraint of each element included in the energy spectrum;

[0124] Step 3: Based on the yield constraints of each element, the constrained weighted least squares method is used to obtain the final yield of each element included in the energy spectrum.

[0125] Figure 3 is a comparison curve of the inversion energy spectrum (recorded as after using this method) and the initial inversion energy spectrum (before using this method) obtained by the actual energy spectrum in this embodiment through the through-casing element content calculation method for complex reservoirs, wherein the initial inversion energy spectrum is obtained based on the initial yield of each element obtained in step 1, and the inversion energy spectrum obtained by the through-casing element content calculation method for complex reservoirs is obtained based on the final yield of each element obtained in step 3; according to Figure 3 It can be seen that the inverted energy spectrum after using this method is closer to the real energy spectrum, indicating that the through-casing element content calculation method for complex reservoirs proposed in this embodiment is helpful to improve the accuracy of gamma spectrum analysis, and is particularly suitable for complex lithology identification of buried hill reservoirs.

[0126] The above embodiments are intended to provide a better understanding of the present invention, but are not limited to the optimal implementation mode and do not constitute a limitation on the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall be within the protection scope of the present invention.

Claims

1. A method for calculating the through-casing element content in complex reservoirs, characterized in that: The following steps are involved: Step 1: In the well of the formation to be measured, cement sheath and casing are sequentially set, and the formation element logging instrument is used to measure the formation to be measured through the casing to obtain the real energy spectrum. After the standard spectrum of casing elements is analyzed, the initial yield of each element contained in the energy spectrum is obtained by weighted least square method; Step 2: Obtain the constraints of the through-casing measurement on the elements contained in the energy spectrum, including: Step 2.1, use the yield correction method to correct the yield of each element; Step 2.2, use the dry weight correction method to correct the yield of each element; Step 2.3, using the influence of element reaction cross section, correct the yield of each element; Step 2.4, determine whether each element exists in the formation to be tested and the cement sheath at the same time, or exists in the formation to be tested and the casing at the same time. If so, go to step 2.5; otherwise, take the fourth limit value of the yield of the element as its yield constraint, and go to step 3; Step 2.5, the yield of each element is corrected by casing / cement sheath to obtain the yield constraint of each element included in the energy spectrum; Step 3: Based on the yield constraints of each element, the constrained weighted least squares method is used to obtain the final yield of each element included in the energy spectrum.

2. The method for calculating the through-casing element content in complex reservoirs according to claim 1, characterized in that: The specific process of step 2.1 is: Step 2.1.1: Assuming that the mineral M in the formation to be tested contains element E and element E1, a numerical simulation calculation model for formation element logging with mineral M as the formation is established through Monte Carlo simulation. After the standard spectrum of casing elements is analyzed, the first analytical yield of element E is obtained, and then the initial yield Y is obtained by fitting. E1 and the first output correction value COR1 M,E wherein the first yield correction value COR1 M,E is the yield correction value of mineral M for element E, specifically the difference between the actual yield of element E and the first analytical yield; For all minerals containing element E in the measured stratum, the first yield correction value COR1 corresponding to each mineral M,E The sum is the total first yield correction value COR1 of element E E ; Step 2.1.2: According to the chemical formula of all minerals containing element E in the stratum to be tested, take the maximum dry weight of element E in different minerals as the first limit value WF1 of the dry weight of element E E , and then determine the first limit value Y1 of the yield of element E E ; Step 2.1.3: Based on the total first output correction value COR1 E , the first limit value Y1 for the yield of element E E After correction, the second limit value Y2 of the yield of element E is obtained. E ; Step 2.1.4: Based on steps 2.1.1 to 2.1.3, obtain the second limit value of the yield of each element included in the energy spectrum.

3. The method for calculating the through-casing element content in complex reservoirs according to claim 2 is characterized in that: The specific process of step 2.2 is: Step 2.2.1: Assuming that the mineral N in the stratum to be tested contains element E and element E2, obtain the second limit value of the yield of element E2 according to step 2.1.

4. Then we get the second limit value of dry weight of element E2: Through Monte Carlo simulation, a numerical simulation calculation model for formation element logging with mineral N as the formation was established. After the standard spectrum of casing elements was analyzed, the second analytical yield of element E was obtained, and then the second limit value of dry weight was obtained by fitting. and the second yield correction value COR2 N,E wherein the second yield correction value COR2 N,E is the yield correction value of mineral N to element E, specifically the difference between the actual yield of element E and the second analytical yield; For all minerals containing element E in the measured stratum, the second yield correction value COR2 corresponding to each mineral N,E The sum is the total second yield correction value COR2 of element E E ; Step 2.2.2: Based on the total second output correction value COR2 E , the second limit value Y2 for the yield of element E E After correction, the third limit value Y3 of the yield of element E is obtained. E ; Step 2.2.3: Based on steps 2.2.1 to 2.2.2, obtain the third limit value of the yield of each element included in the energy spectrum.

4. The method for calculating the through-casing element content in complex reservoirs according to claim 3 is characterized in that: The specific process of step 2.3 is: Step 2.3.1: Assume that the stratum to be tested contains element E and L elements that affect the dry weight of element E due to the reaction cross section. According to step 2.2.3, the third limit value of the yield of the L elements is obtained. The third limit value of the yield of the lth, l=1, 2, ..., Lth element is Y3 l ,l=1,2,…,L; Step 2.3.2, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E and the first element as the formation, after the casing element standard spectrum is analyzed, the first analytical dry weight of element E corresponding to the first element is obtained, and then the third limit value of the yield is fitted to be Y3 l Corrected value with first dry weight The relationship between them is: Where, CCS E,l is the influence factor of the reaction cross section of the lth element on the dry weight of element E; is the reaction cross section correction value of the lth element to the dry weight of element E, specifically the difference between the true dry weight of element E and the first analytical dry weight of element E corresponding to the lth element; Sum the first dry weight correction values ​​of L elements to obtain the dry weight correction value Step 2.3.3: According to the third limit value Y3 of output E , obtain the third limit value WF3 of the dry weight of element E E ; Step 2.3.4: Corrected value based on dry weight The third limit value WF3 for dry weight of element E E After correction, the fourth limit value of dry weight of element E WF4 is obtained. E , and then the fourth limit value Y4 of the yield of element E is obtained E ; Step 2.3.5: Based on steps 2.3.1 to 2.3.4, obtain the fourth limit value of the yield of each element included in the energy spectrum.

5. The method for calculating the through-casing element content in complex reservoirs according to claim 4 is characterized in that: The specific process of step 2.5 is as follows: Step 2.5.1, through Monte Carlo simulation, establish a formation element logging numerical simulation calculation model with element E as the formation, after the casing element standard spectrum is analyzed, the third analytical yield of element E is obtained, and then the thickness of the casing / cement sheath and the third yield correction value COR3 of element E are obtained by fitting. E wherein the third yield correction value COR3 E is the difference between the true yield of element E and the third analytical yield; Step 2.5.2: According to the actual thickness of cement sheath and casing set in step 1, obtain the third yield correction value COR3 corresponding to the cement sheath E1 , and the third yield correction value COR3 corresponding to the casing E2 , and sum to get the total third yield correction value COR3 of element E E , and then the fourth limit value Y4 of the yield of element E E After correction, the fifth limit value Y5 of the yield of element E is obtained. E , as the yield constraint of element E; Step 2.5.3: Based on steps 2.5.1 to 2.5.2, obtain the yield constraints of each element included in the energy spectrum.

6. The method for calculating the through-casing element content in complex reservoirs according to claim 5, characterized in that: Furthermore, in step 2.1.2, for the mineral M contained in the formation to be tested, the dry weight WF of the element E is calculated according to the chemical formula of the mineral M. E The specific formula is: Where M atom is the total relative atomic mass of element E in mineral M; M molecule is the relative molecular mass of mineral M.

7. The method for calculating the through-casing element content in complex reservoirs according to claim 5, characterized in that: Determine the first limit value Y1 of the yield of element E in step 2.1.2 E The specific formula is: Where S is the relative sensitivity factor of element E obtained by simulation or measurement; XY is the oxide index.

8. The method for calculating the through-casing element content in complex reservoirs according to claim 5, characterized in that: The second limit value Y2 of the yield of element E in step 2.1.3 E The calculation formula is: Y2 E =Y1 E -COR1 E 。

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