Formation pressure calculation method and device for shale gas wells

Abstract

The present invention provides a method for calculating formation pressure for shale gas wells, which includes: Step 1: Establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of drilled wells in the same area; Step 2: Sort out the elemental logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well to obtain a difference value; Step 3: Substitute the difference value into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time. The present invention uses the elemental logging data widely used in shale gas wells. By selecting elements that are sensitive to both rock pore volume parameters and rock pore fluid volume parameters, a relationship model with formation pressure is established, achieving the purpose of calculating shale gas formation pressure in real time, continuously, and accurately through elemental logging data, and overcoming the theoretical inadaptability, parameter inadaptability, and method inadaptability of calculating formation pressure through the dc index currently.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum engineering, and in particular, to a method and device for calculating formation pressure for shale gas wells. Background Art

[0002] Generally speaking, the main principle adopted for calculating formation pressure while drilling is the undercompaction theory, the main parameters are the dc exponent or Sigma exponent, and the main methods are the Eaton method or the ratio method.

[0003] In the prior art, the Eaton method is widely applied in the Gulf region of the United States and is developed on the basis of the theories of Hubbert and Willis. It adheres to a view that underground rock formations are full of bedding planes, joints and fractures, and the fluid pressure in the wellbore only invades along these fracture surfaces and makes them open. Therefore, the fluid pressure that makes the fractures open only needs to overcome the in-situ stress perpendicular to the fracture surface.

[0004] The Eaton method is only applicable to continuously sedimentary basins with relatively new strata deposition and little influence of tectonic movements such as the Gulf of Mexico. However, for regions with older strata ages and great influence of tectonic movements, its prediction effect is poor.

[0005] In the prior art, the ratio method assumes that the ratio between the actual value and the normal trend line value of the curve at the same depth point in the undercompacted interval is proportional to the formation pressure. Its calculation formula is as follows:

[0006] Pa = Pn * Datn / Dato

[0007] In the formula: Pa = formation pressure gradient at the actual depth point;

[0008] Pn = pressure gradient on the normal trend line at the same depth;

[0009] Datn = data value on the normal trend line;

[0010] Dato = actual value of the data curve.

[0011] For shale gas formations, the inadaptability of the Eaton method or the ratio method is reflected in three aspects:

[0012] First, the principle is inadaptable. The pressure formation mechanism of shale gas formations is complex. In addition to undercompaction, more important pressure formation mechanisms are hydrocarbon generation and tectonic extrusion.

[0013] Second, the parameters are inadaptable. Shale gas adopts the horizontal well drilling technology, and the engineering parameters are greatly affected.

[0014] Third, the method is inadaptable. It is difficult to accurately determine the "compaction" trend line of horizontal wells.

[0015] Therefore, on-site mud logging basically does not provide pressure data for shale gas formations. In the prior art, the maximum pressure coefficient calculated by the dc index for a certain shale gas horizontal well is 1.39, while the formation pressure coefficient from a fracturing test for gas testing is 1.91, with a large error.

[0016] Therefore, the present invention provides a method and device for calculating formation pressure of a shale gas well. Summary of the Invention

[0017] To solve the above problems, the present invention provides a method for calculating formation pressure of a shale gas well, the method comprising the following steps:

[0018] Step 1: Establish a formation pressure calculation model for a shale gas well based on sensitive elements according to the drilling data of wells already drilled in the same area;

[0019] Step 2: Organize the elemental logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well to obtain a difference value;

[0020] Step 3: Substitute the difference value into the formation pressure calculation model to calculate in real time the formation pressure or pressure coefficient of the target well.

[0021] According to an embodiment of the present invention, the specific steps in Step 1 include: collecting elemental logging data, gas logging data, engineering parameter logging data, logging data, and fracturing test for gas testing data of wells already drilled.

[0022] According to an embodiment of the present invention, the specific steps in Step 1 include:

[0023] Analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of wells already drilled;

[0024] For each element in the rock sample, sort them in descending order of correlation, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements.

[0025] According to an embodiment of the present invention, the rock pore volume parameters include: porosity, density, dc index.

[0026] According to an embodiment of the present invention, the rock pore fluid volume parameters include: total hydrocarbon, gas content, gas saturation.

[0027] According to an embodiment of the present invention, the specific steps in Step 1 include the following: Based on the drilling data of the drilled wells, with the formation pressure or pressure coefficient as the ordinate and the combined form of sensitive elements as the abscissa, establish an equation for obtaining the formation pressure or pressure coefficient as the formation pressure calculation model.

[0028] According to an embodiment of the present invention, the specific steps in Step 2 include the following: With the well depth as the horizontal axis and the combined form of sensitive elements as the vertical axis, determine the envelope line and baseline of the sensitive elements, wherein the baseline of the sensitive elements is parallel to the horizontal axis.

[0029] According to an embodiment of the present invention, in Step 2, the difference is calculated through the following formula:

[0030] Δ(M1 / M2) = (M1 / M2) 包络线 - (M1 / M2) 基线

[0031] where Δ(M1 / M2) represents the difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the envelope line of the sensitive element curve, and (M1 / M2) 基线 represents the baseline of the sensitive element curve.

[0032] According to an embodiment of the present invention, in Step 3, the formation pressure or pressure coefficient of the target well is calculated through the following formula:

[0033] P = a × Δ(M1 / M2) + b

[0034] where P represents the formation pressure or pressure coefficient of the target well, a represents the first coefficient, and b represents the second coefficient.

[0035] According to another aspect of the present invention, there is also provided a formation pressure calculation device for shale gas wells, and the device includes:

[0036] A formation pressure modeling module, which is used to establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of drilled wells in the same area;

[0037] A difference calculation module, which is used to sort out the element logging data of the target well, calculate the difference between the envelope line and the baseline of the sensitive elements of the target well, and obtain the difference;

[0038] A formation pressure calculation module, which is used to substitute the difference into the formation pressure calculation model and calculate the formation pressure or pressure coefficient of the target well in real time.

[0039] According to an embodiment of the present invention, the formation pressure modeling module includes: a data collection unit, which is used to collect element logging data, gas logging data, engineering parameter logging data, logging data, and fracturing test gas data of the drilled wells.

[0040] According to an embodiment of the present invention, the formation pressure modeling module includes:

[0041] a correlation unit, which is used to analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of the drilled wells;

[0042] a sensitive element selection unit, which is used to sort each element in the rock sample according to the correlation from high to low, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements.

[0043] According to an embodiment of the present invention, the formation pressure modeling module includes: a model establishment unit, which is used to establish an equation for calculating the formation pressure or pressure coefficient as the formation pressure calculation model based on the drilling data of the drilled wells, with the formation pressure or pressure coefficient as the ordinate and the combination of sensitive elements as the abscissa.

[0044] According to an embodiment of the present invention, the difference calculation module includes: a sensitive element curve unit, which is used to determine the sensitive element envelope line and the sensitive element baseline with the well depth as the horizontal axis and the combination of sensitive elements as the vertical axis, wherein the sensitive element baseline is parallel to the horizontal axis.

[0045] According to an embodiment of the present invention, the difference calculation module includes a first calculation unit, which calculates the difference through the following formula:

[0046] Δ(M1 / M2) = (M1 / M2) 包络线 - (M1 / M2) 基线

[0047] where Δ(M1 / M2) represents the difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the sensitive element curve envelope line, and (M1 / M2) 基线 represents the sensitive element curve baseline.

[0048] The method and device for calculating formation pressure for shale gas wells provided by the present invention adopt element logging data widely used in shale gas wells, select elements that are sensitive to rock pore volume parameters and rock pore fluid volume parameters, establish a relationship model with formation pressure, and achieve the purpose of calculating shale gas formation pressure in real time, continuously and accurately through element logging data, overcome the theoretical inadaptability, parameter inadaptability and method inadaptability of current formation pressure calculation through DC index, formation elements contain rich geological information, and element logging is a relatively mature technology with few factors affected by drilling conditions, so the present invention is simple to operate, low cost, accurate in calculation and has a wider range of applications.

[0049] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 A flow chart of a method for calculating formation pressure for a shale gas well according to an embodiment of the present invention is shown;

[0052] Figure 2 Shows a total hydrocarbon, dc index and S / Al comparison diagram according to an embodiment of the present invention;

[0053] Figure 3 A curve diagram of a formation pressure calculation model according to an embodiment of the present invention is shown;

[0054] Figure 4 A (S / Al) curve analysis diagram of a certain area X page Y-1HF well according to an embodiment of the present invention is shown; and

[0055] Figure 5 A structural block diagram of a formation pressure calculation device for shale gas wells according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0057] The present invention can overcome the inadaptability of calculating the formation pressure of shale gas horizontal wells by the dc exponent. By selecting elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter, the pressure coefficient can be directly calculated.

[0058] Since the formation elements contain rich geological information, and elemental logging is a relatively mature and widely used shale gas evaluation technology, the method provided by the present invention is simple to operate, low in cost, accurate in calculation, and has a wider application range.

[0059] Figure 1 Shows a flow chart of a method for calculating formation pressure for a shale gas well according to an embodiment of the present invention.

[0060] As Figure 1 , in step S101, a formation pressure calculation model for shale gas wells based on sensitive elements is established according to the drilling data of the drilled wells in the same area.

[0061] Specifically, in step S101, collect the elemental logging data, gas logging data, engineering parameter logging data, logging data, and fracturing test gas data of the drilled wells.

[0062] In one embodiment, in step S101, the sensitive elements are selected by the following method:

[0063] First, analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of the drilled wells.

[0064] Then, for each element in the rock sample, sort them in descending order of correlation, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements.

[0065] Specifically, the rock pore volume parameters include: porosity, density, dc exponent.

[0066] Specifically, the rock pore fluid volume parameters include: total hydrocarbon, gas content, gas saturation.

[0067] Generally speaking, the causes of formation pressure mainly fall into two categories: one is the change in rock pore volume; the other is the change in rock pore fluid volume.

[0068] In one embodiment, as can be seen from Table 1, the elements that are jointly sensitive to the dc exponent, porosity, density, and total hydrocarbon are S, Al, and K. Since both Al and K reflect the content of clay minerals and have a good correlation, the Al element with a higher correlation with the clay mineral content and the S element that reflects the organic matter content are selected as the sensitive elements for formation pressure, and the combination of sensitive elements is represented by the (S / Al) ratio.

[0069] Table 1 Formation Sensitive Element Table

[0070]

[0071] In one embodiment, after selecting S and Al as the sensitive elements, the total hydrocarbon, dc index, and (S / Al) ratio were compared. Figure 2 For the pilot hole profile, it can be seen that during drilling, the drilling time and dc index are greatly affected by drilling coring, and it is difficult to calculate the formation pressure through the dc index; the total hydrocarbon is also affected by engineering parameters such as drilling time and it is difficult to reflect the true gas content of the formation, while the (S / Al) ratio is in good agreement with the fluid abundance of nuclear magnetic resonance logging in terms of the changing trend.

[0072] It can be known that the present invention can overcome the inadaptability of calculating the formation pressure of shale gas horizontal wells by the dc index. By selecting elements that are sensitive to both the rock pore volume parameters and the rock pore fluid volume parameters, the pressure coefficient can be directly calculated. Compared with the prior art, it has a higher accuracy.

[0073] In one embodiment, in step S101, based on the drilling data of the drilled wells, with the formation pressure or pressure coefficient as the ordinate and the combined form of sensitive elements as the abscissa, an equation for obtaining the formation pressure or pressure coefficient is established as the formation pressure calculation model.

[0074] Figure 3 shows the change curve of the difference in the increase of the pressure coefficient and the (S / Al) ratio. In order to establish the formation pressure calculation model, based on the drilling data of the drilled wells, with the pressure coefficient as the ordinate and the combined form of sensitive elements (here the sensitive elements are S and Al) as the abscissa, the fitting function Y = 0.0084*X + 1.7601 is obtained as the formation pressure calculation model.

[0075] Figure 3 shows the correlation analysis between the formation pressure coefficient of a well during fracturing gas testing and the (S / Al) amplitude difference of logging elements. The correlation coefficient reaches 0.93, and the absolute error of the pressure coefficient does not exceed 0.032, having a relatively high accuracy.

[0076] Such as Figure 1 , in step S102, the element logging data of the target well is sorted out, and the difference between the sensitive element envelope line and the sensitive element baseline of the target well is calculated to obtain the difference.

[0077] In one embodiment, in step S102, with the well depth as the horizontal axis and the combined form of sensitive elements as the vertical axis, the sensitive element envelope line and the sensitive element baseline are determined, wherein the sensitive element baseline is parallel to the horizontal axis.

[0078] In one embodiment, in step S102, the difference is calculated by the following formula:

[0079] Δ(M1 / M2) = (M1 / M2) 包络线 - (M1 / M2) 基线

[0080] where Δ(M1 / M2) represents the difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the envelope curve of the sensitive element curve, and (M1 / M2) 基线 represents the baseline of the sensitive element curve.

[0081] As Figure 1 , in step S103, the difference is substituted into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time.

[0082] In one embodiment, in step S103, the formation pressure or pressure coefficient of the target well is calculated by the following formula:

[0083] P = a × Δ(M1 / M2) + b

[0084] where P represents the formation pressure or pressure coefficient of the target well, a represents the first coefficient, and b represents the second coefficient.

[0085] Figure 4 shows the (S / Al) curve analysis diagram of Well Y-1HF on Page X in a certain area according to an embodiment of the present invention. In one embodiment, Well Y-1HF on Page X is selected as the target well. S is selected as the first sensitive element, and Al is selected as the second sensitive element.

[0086] (1) Establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of the drilled wells in the same area as the target well:

[0087] (a) Collect the element logging data, gas logging data, engineering parameter logging data, logging data, and fracturing test gas data of the drilled wells.

[0088] (b) Analyze the correlation between each element of the rock sample and the rock pore volume parameters (such as porosity, density, dc index) and the rock pore fluid volume parameters (such as total hydrocarbon, gas content, gas saturation), and sort the elements according to the correlation coefficient from high to low, and select two elements (such as S, Al) or multiple elements (as shown in Table 1) that are jointly sensitive to these parameters.

[0089] (c) For the drilled wells in the same area, establish an equation for obtaining the formation pressure or pressure coefficient (pressure gradient) with the formation pressure or pressure coefficient (pressure gradient) of the fracturing test gas as the ordinate and Δ(S / Al) as the abscissa (such asFigure 3 ) The formation pressure calculation model is as follows:

[0090] P = 0.0084 * Δ(S / Al) + 1.7601

[0091] Where, P represents the pressure coefficient, the first coefficient takes the value of 0.0084, and the second coefficient takes the value of 1.7601.

[0092] (2) Organize the elemental logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well to obtain the difference:

[0093] (d) With the well depth as the abscissa and the (S / Al) ratio as the ordinate, determine the baseline and envelope line of the (S / Al) ratio. The determination positions of the two are the same, such as both taking the low point or the midpoint position, and the baseline is parallel to the horizontal axis.

[0094] The kerogen contains S element, the Al element represents the clay mineral content, the (S / Al) ratio represents the organic matter content in the clay minerals, and has a good consistency with the pore fluid saturation (such as Figure 2 ). The peak of the (S / Al) ratio is caused by the S element in pyrite, so the values of the baseline and envelope line should be taken.

[0095] (e) According to the formation pressure depth provided by the fracturing and gas testing, read the difference between the (S / Al) ratio envelope line (or average line, smooth line) and the baseline at the corresponding depth:

[0096] Δ(S / Al) = (S / Al) 包络线 - (S / Al) 基线

[0097] Where, Δ(S / Al) represents the difference, (S / Al) 包络线 represents the sensitive element curve envelope line, (S / Al) 基线 represents the sensitive element curve baseline, S represents the first sensitive element, and Al represents the second sensitive element.

[0098] (3) Substitute the difference into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time:

[0099] (f) Calculate the formation pressure or pressure coefficient of the target well through the following formula:

[0100] P = 0.0084 * Δ(S / Al) + 1.7601

[0101] Where, P represents the formation pressure or pressure coefficient of the target well, the first coefficient takes the value of 0.0084, and the second coefficient takes the value of 1.7601.

[0102] Such as Figure 4, for the fracturing and gas testing of Well X Page Y-1HF, based on the formation pressure of adjacent wells, the pressure at the vertical depth of 3735.91 m in the pay zone of this well is calculated to be 75.58 Mpa, and the pressure coefficient is 2.02. According to the measured well deviation data, the measured depth at a vertical depth of 3735.91 m is 4900 m (as Figure 4 ), the weighted average value of (S / Al) at this depth is about 32%, while the baseline value of (S / Al) is about 3%. Therefore, the amplitude difference of (S / Al) is 29%. Substituting it into the formula of the formation pressure calculation model, the calculated pressure coefficient is 2.00, which is consistent with the pressure coefficient inferred from the fracturing and gas testing, and the absolute error is 0.02.

[0103] Figure 5 Fig. shows a structural block diagram of a formation pressure calculation device for a shale gas well according to an embodiment of the present invention.

[0104] As Figure 5 , the formation pressure calculation device 500 includes: a formation pressure modeling module 501, a difference calculation module 502, and a formation pressure calculation module 503. The formation pressure modeling module 501 includes: a data collection unit 5011, a correlation unit 5012, a sensitive element selection unit 5013, and a model establishment unit 5014. The difference calculation module 502 includes: a sensitive element curve unit 5021 and a first calculation unit 5022. The formation pressure calculation module 503 includes a second calculation unit 5031.

[0105] Specifically, the formation pressure modeling module 501 is used to establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of the drilled wells in the same area.

[0106] In one embodiment, the data collection unit 5011 is used to collect the element logging data, gas logging data, engineering parameter logging data, logging data, and fracturing and gas testing data of the drilled wells.

[0107] In one embodiment, the correlation unit 5012 is used to analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of the drilled wells.

[0108] In one embodiment, the sensitive element selection unit 5013 is used to sort each element in the rock sample according to the correlation from high to low, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements.

[0109] In one embodiment, the model establishment unit 5014 is used to establish an equation for obtaining the formation pressure or pressure coefficient as the formation pressure calculation model based on the drilling data of the drilled wells, with the formation pressure or pressure coefficient as the ordinate and the combined form of sensitive elements as the abscissa.

[0110] Specifically, the difference calculation module 502 is used to sort out the element logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well, and obtain the difference.

[0111] In one embodiment, the sensitive element curve unit 5021 is used to determine the sensitive element envelope line and the sensitive element baseline with the well depth as the horizontal axis and the combined form of sensitive elements as the vertical axis, wherein the sensitive element baseline is parallel to the horizontal axis.

[0112] In one embodiment, the first calculation unit 5022 calculates the difference through the following formula:

[0113] Δ(M1 / M2) = (M1 / M2) 包络线 -(M1 / M2) 基线

[0114] where Δ(M1 / M2) represents the difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the sensitive element curve envelope line, and (M1 / M2) 基线 represents the sensitive element curve baseline.

[0115] Specifically, the formation pressure calculation module 503 is used to substitute the difference into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time.

[0116] In one embodiment, the second calculation unit 5031 calculates the formation pressure or pressure coefficient of the target well through the following formula:

[0117] P = a × Δ(M1 / M2) + b

[0118] where P represents the formation pressure or pressure coefficient of the target well, a represents the first coefficient, and b represents the second coefficient.

[0119] In summary, the formation pressure calculation method and device for shale gas wells provided by the present invention adopt the element logging data widely used in shale gas wells, establish a relationship model with the formation pressure by selecting elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter, and achieve the purpose of calculating the shale gas formation pressure in real time, continuously, and accurately through the element logging data, overcoming the theoretical inadaptability, parameter inadaptability, and method inadaptability of calculating the formation pressure through the dc index at present. The formation elements contain rich geological information, and element logging is a technology that is less affected by drilling conditions and is relatively mature. Therefore, the present invention is simple to operate, low in cost, accurate in calculation, and has a wider application range.

[0120] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and do not imply limitation.

[0121] As used herein, the phrase "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "one embodiment" or "an embodiment" throughout the specification are not necessarily all referring to the same embodiment.

[0122] Although the embodiments disclosed in the present invention are as described above, the content described is only an embodiment for facilitating the understanding of the present invention and is not intended to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains may make any modifications and variations in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for calculating formation pressure of shale gas wells, characterized in that, the method comprises the following steps: Step 1: Establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of drilled wells in the same area; Step 2: Sort out the element logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well, and obtain the difference; Step 3: Substitute the difference into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time; Specifically, Step 1 includes the following steps: Analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of the drilled well; For each element in the rock sample, sort them in descending order of correlation, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements; Based on the drilling data of the drilled well, establish an equation for obtaining formation pressure or pressure coefficient with formation pressure or pressure coefficient as the ordinate and the combined form of sensitive elements as the abscissa as the formation pressure calculation model; In Step 2, the difference is calculated through the following formula: △(M1 / M2) = (M1 / M2) 包络线 -(M1 / M2) 基线 where, △(M1 / M2) represents the said difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the envelope curve of the said sensitive element, and (M1 / M2) 基线 represents the baseline of the curve of the said sensitive element; In Step 3, the formation pressure or pressure coefficient of the target well is calculated through the following formula: P = a×△(M1 / M2)+b wherein, P represents the formation pressure or pressure coefficient of the target well, a represents the first coefficient, and b represents the second coefficient.

2. The method according to claim 1, characterized in that, Specifically, Step 1 includes the following steps: Collect the element logging data, gas logging data, engineering parameter logging data, logging data and fracturing test gas data of the drilled well.

3. The method according to claim 1, characterized in that, The rock pore volume parameters include: porosity, density, dc index.

4. The method according to claim 1, characterized in that, The rock pore fluid volume parameters include: total hydrocarbon, gas content, gas saturation.

5. The method according to claim 1, characterized in that, Specifically, Step 2 includes the following steps: Take the well depth as the horizontal axis and the combined form of sensitive elements as the vertical axis to determine the sensitive element envelope line and the sensitive element baseline, wherein the sensitive element baseline is parallel to the horizontal axis.

6. A formation pressure calculation device for shale gas wells, characterized in that, executes the method according to any one of claims 1-5, and the device includes: A formation pressure modeling module, which is used to establish a formation pressure calculation model for shale gas wells based on sensitive elements according to the drilling data of drilled wells in the same area; A difference calculation module, which is used to sort out the element logging data of the target well, calculate the difference between the sensitive element envelope line and the sensitive element baseline of the target well, and obtain the difference; A formation pressure calculation module, which is used to substitute the difference into the formation pressure calculation model to calculate the formation pressure or pressure coefficient of the target well in real time.

7. The device according to claim 6, characterized in that, The formation pressure modeling module includes: a data collection unit, which is used to collect element logging data, gas logging data, engineering parameter logging data, logging data, and fracturing test gas data of the drilled wells.

8. The device according to claim 6, wherein, the formation pressure modeling module includes: a correlation unit, which is used to analyze the correlation between each element in the rock sample and the rock pore volume parameter and the rock pore fluid volume parameter based on the drilling data of the drilled wells; a sensitive element selection unit, which is used to sort each element in the rock sample according to the correlation from high to low, and select two or more elements that are jointly sensitive to the rock pore volume parameter and the rock pore fluid volume parameter as the sensitive elements.

9. The device according to claim 6, wherein, the formation pressure modeling module includes: a model establishment unit, which is used to establish an equation for calculating the formation pressure or pressure coefficient as the formation pressure calculation model based on the drilling data of the drilled wells, with the formation pressure or pressure coefficient as the ordinate and the combined form of sensitive elements as the abscissa.

10. The device according to claim 6, wherein, the difference calculation module includes: a sensitive element curve unit, which is used to determine the sensitive element envelope line and the sensitive element baseline with the well depth as the horizontal axis and the combined form of sensitive elements as the vertical axis, wherein the sensitive element baseline is parallel to the horizontal axis.

11. The device according to claim 6, wherein, the difference calculation module includes a first calculation unit, which calculates the difference through the following formula: △(M1 / M2) = (M1 / M2) 包络线 -(M1 / M2) 基线 where, △(M1 / M2) represents the said difference, M1 represents the first sensitive element, M2 represents the second sensitive element, and (M1 / M2) 包络线 represents the envelope curve of the said sensitive element, and (M1 / M2) 基线 represents the baseline of the curve of the said sensitive element.

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