Method for evaluating remaining gas content of shale gas horizontal well

Abstract

The present application relates to the technical field of oil and gas development, and particularly relates to a method for evaluating residual gas content of shale gas horizontal well. SRV t r The present application uses obtained formation lithology density DEN, transformed volume V SRV , total gas content G t , and limit recovery rate η r to establish a calculation model of theoretical recoverable reserves V RT of each fracturing section of the shale gas horizontal well, and then combines with obtained gas production contribution rate η gp and produced gas volume V gp to establish a calculation model of residual gas content of each fracturing section and single well, to determine the residual gas content of the shale gas horizontal well, and to evaluate according to the calculation results of residual gas content of each fracturing section of the well to be interpreted and residual gas content of single well to be interpreted. The present application can be applied to residual gas content evaluation of single well, and also can be applied to residual gas evaluation of each fracturing section.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and in particular to a method for evaluating the residual gas content in shale gas horizontal wells. Background Technology

[0002] China possesses abundant shale gas resources, ranking first globally in overall reserves. Over the past decade of exploration and development, China has become the third largest shale gas producer after the United States and Canada. However, with continued shale gas development, most older wells are facing significant pressure decay, resulting in shale gas production falling below the critical fluid carrying capacity, thus increasing the difficulty of production. Repeated fracturing is an effective way to solve this problem, and determining the residual gas content of individual wells and each fracturing stage is the basis for selecting shale gas wells for repeated fracturing.

[0003] Currently, both domestically and internationally, the Real-Time Analysis (RTA) method is mainly used for semi-quantitative evaluation of the remaining gas content in shale gas, lacking quantitative evaluation methods. The RTA method requires recording daily production data from a single well, including casing pressure, transmission pressure, oil pressure, daily water production, and daily gas production, for a continuous period of two years. This high data requirement limits the applicability of this method.

[0004] Chinese patent CN104914030B discloses a full-process airtight gas content measuring instrument and a method for measuring residual gas in rock samples. This method mainly involves an instrument for measuring residual gas in rock samples, which includes a sample fragmentation system, a heating system, and a gas collection and metering system. It primarily measures the residual gas content in rock samples. However, this method can only measure residual gas in small amounts of rock samples. Since a shale gas horizontal well is at least 1500m long, the residual gas content of a small amount of rock sample cannot reflect the residual gas content distribution characteristics of a horizontal well. Therefore, this method is not suitable for residual gas evaluation in shale gas development.

[0005] Chinese patent CN115544756A discloses a method for characterizing residual gas distribution based on post-fracturing fracture network iterative fitting technology. This method uses unstable production analysis to analyze production dynamics based on acquired geological, logging, fracturing, and historical production data, and then uses post-fracturing fracture network fitting technology to characterize the residual gas distribution of the block. The core technology of this method is to use unstable production analysis to predict production dynamics, analyze the technically recoverable reserves, and then determine the residual gas content. The main problem facing this technology is that with the recent shift of older shale gas wells to pressurized extraction, the abandonment pressure of shale gas wells has gradually decreased. As the abandonment pressure decreases, the technically recoverable reserves also increase. The method disclosed in this patent fails to consider the impact of pressurized extraction on technically recoverable reserves, resulting in inaccurate residual gas evaluation results, which can only serve as a reference for on-site evaluation.

[0006] Chinese patent CN116398091A discloses a method for developing shale gas adjustment wells based on remaining reserve abundance. This method includes: acquiring data such as the wellhead location, core elevation, well trajectory, fracturing data, artificial fracture model, production time, daily gas production, daily water production, and measured flowing pressure of existing wells in the well area; conducting numerical simulations of the gas wells in the well area and performing historical fitting; and obtaining a model of remaining reserve abundance calculated using numerical simulation software. This method provides a macroscopic prediction of the remaining gas abundance of horizontal wells and cannot accurately evaluate the remaining gas content in each fracturing stage of the horizontal well. This means that this method cannot serve as a reference for selecting wells for repeated fracturing of existing shale gas wells. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned technical situation by providing a method for evaluating the residual gas content of shale gas horizontal wells. This method considers the impact of pressurized extraction modes on residual gas content, has a wide range of applications, and is applicable not only to the evaluation of residual gas content in single wells but also to the evaluation of residual gas content in each fracturing stage. The calculation results can provide a reference for selecting wells for repeated fracturing.

[0008] This invention includes the following steps:

[0009] 1) Obtain the average value of the formation lithology density (DEN) of each fractured section of the horizontal well to be interpreted within the work area;

[0010] 2) Obtain the stimulation volume V of each fractured section of the horizontal well to be interpreted within the work area. SRV ;

[0011] 3) Obtain the total gas content G of each fractured section of the horizontal well to be interpreted within the work area. t ;

[0012] 4) Obtain the ultimate recovery rate η under the pressure boosting production mode of the horizontal wells to be interpreted within the work area. r ;

[0013] 5) Combine the formation lithology density (DEN) of each fractured section obtained in step 1) and the stimulation volume (V) of each fractured section obtained in step 2). SRV Step 3) Obtain the total gas content G of each fracturing section t Step 4) Obtain the ultimate recovery rate η r Used to calculate the theoretical recoverable reserves V of each fracturing section. RT The specific formula is as follows:

[0014] (1)V RT =η r ·V SRV ·G t ·DEN

[0015] Where: theoretical recoverable reserves V RTDimensionless 4 m 3 Fracturing section modification volume V SRV Dimensionless 4 m 3 The lithological density of the strata is measured in g / cm³. 3 Ultimate recovery rate η r Dimensionless, expressed as a decimal;

[0016] 6) Obtain the gas production contribution rate η of each fractured section of the horizontal well to be interpreted within the work area. gp ;

[0017] 7) Obtain the gas production V of the single horizontal well to be interpreted within the work area. gp ;

[0018] 8) The theoretical recoverable reserves V calculated in step 5) RT Step 6) Gas production contribution rate η gp Step 7) Obtain the amount of gas produced, V gp Used to calculate the residual gas content V in each fractured section of the horizontal well to be explained. Rg The specific formula is as follows:

[0019] (2)V Rg =V RT -η gp ·V gp

[0020] Where: V represents the residual gas content in each fracturing section. Rg Dimensionless 4 m 3 Gas production contribution rate η gp Dimensionless, expressed as a decimal, amount of gas produced V gp Dimensionless 4 m 3 ;

[0021] 9) The residual gas content V in each fracturing section calculated according to step 8). Rg Calculate the residual gas content V in a single well Rgw The specific formula is as follows:

[0022]

[0023] Where: V represents the residual gas content of a single well. Rgw Dimensionless 4 m 3 i represents the segment number of each fracturing section in a single well;

[0024] 10) Output and evaluate the calculation results.

[0025] Preferably, in step 1), the average value of the formation lithology density (DEN) of each fractured section of the horizontal well to be interpreted in the work area is obtained based on density logging data.

[0026] Preferably, the stimulation volume V of each fractured section of the horizontal well to be interpreted within the work area is obtained based on the fracturing microseismic monitoring data. SRV .

[0027] In step 3), the free gas content G of each fractured section of the horizontal well to be interpreted within the work area is obtained. f The average value and adsorbed gas content G a The average value is used to calculate the total gas content G in each fracturing section. t The specific formula is as follows:

[0028] (4)G t =G f +G a

[0029] Where: G is the total gas content of each fracturing section. t Dimensionless m 3 / t, free gas content G in each fracturing section f Dimensionless m 3 / t, adsorbed gas content G in each fracturing section a Dimensionless m 3 / t;

[0030] Preferably, in step 4), the ultimate recovery rate η of the horizontal well under the pressure-boosted production mode to be interpreted within the work area is determined. r The specific steps are as follows:

[0031] ① Obtain the average free gas content (G) of a single horizontal well within the work area. wf Average adsorbed gas content (G) per well wa Calculate the average total gas content G of a single well. wt The specific formula is as follows:

[0032] (5)G wt =G wf +G wa

[0033] Where: G is the average total gas content of a single well. wt Dimensionless m 3 / t, average free gas content per well (G) wf Dimensionless m 3 / t, average adsorbed gas content per well (G) wa Dimensionless m 3 / t;

[0034] ②The isothermal saturated adsorbed gas volume V was obtained from isothermal adsorption experiments on core samples from the work area. L Lange pressure P LThe average adsorbed gas content G of a single well obtained in step ① wa Combined, the critical adsorption pressure P of shale in a single well was calculated. c The specific formula is as follows:

[0035] (6)P c =G wa ·P L / (V L -G wa )

[0036] Where: Critical desorption pressure P c The dimensionless isothermal saturated adsorption gas volume V is measured in MPa. L Dimensionless m 3 / t, Langevin pressure P L The dimension is MPa;

[0037] ③ Obtain the abandoned pressure P corresponding to the horizontal well pressurization production mode within the work area. a The Langevin pressure P obtained in step ② L and critical adsorption pressure P c Combined, calculate the adsorbed gas recovery rate E of the horizontal well under the pressure boosting production mode. Ra The specific formula is as follows:

[0038] (7)E Ra =1-P a ·(P L +P c ) / P c / (P L +P a )

[0039] Where: Adsorbed gas recovery rate E Ra Dimensionless, expressed as a decimal, waste pressure P a The dimension is MPa;

[0040] ④ Obtain the original formation pressure P of the horizontal well to be interpreted within the work area. i Original formation pressure P i Gas deviation coefficient Z of free gas under certain conditions if The corresponding abandonment pressure P in the pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a Calculate the free gas recovery rate E of the horizontal well under the pressurized production mode. Rf The specific formula is as follows:

[0041] (8)E Rf =1-P a ·Z if / Z a / P i

[0042] Where: Free gas recovery rate E Rf Dimensionless, expressed as a decimal, original formation pressure P i Dimension: MPa, original formation pressure P i Gas deviation coefficient Z of free gas under certain conditions if Dimensionless, the waste pressure P corresponding to the pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a Dimensionless;

[0043] ⑤ The average free gas content G of a single well obtained in step ① wf Average adsorbed gas content (G) per well wa Average total gas content per well (G) wt The adsorbed gas recovery rate E calculated in step ③ Ra Step ④ calculates the free gas recovery rate E. Rf Combined, calculate the ultimate recovery rate η under the single-well pressurized production mode. r The specific formula is as follows:

[0044] (9)η r =(G wa ·E Ra +G wf ·E Rf ) / G wt

[0045] Where: η is the ultimate recovery rate under single-well pressurized production mode. r Dimensionless, expressed as a decimal.

[0046] Preferably, in step 6), the gas production contribution rate η of each fractured section of the horizontal well to be interpreted is obtained based on the gas production profile logging data. gp .

[0047] Preferably, in step 7), the gas production V of the single horizontal well to be interpreted is obtained based on production dynamic data. gp .

[0048] Preferably, according to step 8), the calculation results of the residual gas content in each fracturing section of the well to be interpreted are output, and the output results are evaluated according to four categories: A, B, C, and D.

[0049] Single-stage residual gas content V Rg The section that accounts for more than 75% of the theoretical recoverable reserves is classified as Category A, which has great potential for repeated fracturing.

[0050] Single-stage residual gas content V Rg The section that accounts for 60% to 75% of the theoretically recoverable reserves is classified as Category B, which has the potential for repeated fracturing.

[0051] Single-stage residual gas content V Rg The section that accounts for 40% to 60% of the theoretically recoverable reserves is classified as Category C, which has poor potential for repeated fracturing.

[0052] Single-stage residual gas content V Rg Those accounting for less than 40% of the theoretical recoverable reserves in this section are classified as Category D, which means they do not have the potential for repeated fracturing.

[0053] Preferably, according to step 9), the calculation results of the residual gas content of the single well to be interpreted are output, and the output results are evaluated according to three categories: I, II, and III.

[0054] Residual gas content V in a single well Rgw More than 60% of the well’s theoretical recoverable reserves are classified as Category I, which is rich in residual gas.

[0055] Residual gas content V in a single well Rgw 40% to 60% of the well’s theoretical recoverable reserves are classified as Class II, which is a medium-sized residual gas.

[0056] Residual gas content V in a single well Rgw If less than 40% of the well's theoretical recoverable reserves are classified as Class III, Class III is characterized by poor residual gas.

[0057] This invention utilizes the obtained stratigraphic lithology density (DEN) and alteration volume (V) SRV Total gas content G t Ultimate recovery rate η r Establish the theoretical recoverable reserves V of each fractured section of a shale gas horizontal well. RT The calculation model is then compared with the obtained gas production contribution rate η. gp Gas production volume V gp This invention combines various methods to establish a calculation model for the residual gas content of each fracturing section and individual wells, determining the residual gas content of shale gas horizontal wells. The results are then evaluated based on the calculated residual gas content of each fracturing section and the individual well in the shale gas well to be interpreted, providing a design basis for selecting wells for repeated fracturing of shale gas horizontal wells. This method is simple, easy to operate, and highly accurate, overcoming the problem of inaccurate calculation results caused by traditional methods that do not consider the impact of pressurization production modes on residual gas content. It also overcomes the limitation of previous methods that could only calculate the residual gas content of individual wells and could not calculate the residual gas content of each fracturing section.

[0058] This invention has been applied to 12 wells in multiple shale gas blocks such as Jiaoshiba and Pingqiao in the Sichuan Basin. The evaluation of the residual gas content in a single well and the residual gas content in each fracturing stage provides a design basis for selecting wells for repeated fracturing. Wells with repeated fracturing potential selected by this method have good repeated fracturing effects, which improves the single-well recovery rate of shale gas horizontal wells. Attached Figure Description

[0059] Figure 1This is a flowchart illustrating the workflow of the present invention.

[0060] Figure 2 The ultimate recovery rate η of this invention r Calculation flowchart;

[0061] Figure 3 A bar chart showing the theoretical recoverable reserves and remaining gas volume of each fractured section of well S9-2HF in the F shale gas field.

[0062] Figure 4 This is a bar chart showing the theoretical recoverable reserves and remaining gas volume of each fractured section of the W4HF well in the F shale gas field. Detailed Implementation

[0063] Reference Figure 1 The specific steps of this invention are as follows:

[0064] 1) Obtain the average value of the formation lithology density (DEN) of each fractured section of the horizontal well to be interpreted in the work area based on density logging data;

[0065] 2) Obtain the stimulation volume V of each fractured section of the horizontal well to be interpreted within the work area based on the fracturing microseismic monitoring data. SRV ;

[0066] 3) Obtain the free gas content (G) of each fractured section of the horizontal well to be interpreted within the work area based on well logging interpretation and evaluation data. f Average value, adsorbed gas content G a Average value, calculate the total gas content G of each fracturing section t The specific formula is as follows:

[0067] G t =G f +G a

[0068] 4) Determine the ultimate recovery rate η under the pressure-boosting production mode of the horizontal wells to be interpreted within the work area. r The specific steps are as follows:

[0069] ① Based on well logging interpretation and evaluation data, obtain the average free gas content G of the single horizontal well to be interpreted within the work area. wf Average adsorbed gas content G wa Calculate the average total gas content G of a single well. wt The specific formula is as follows:

[0070] G wt =G wf +G wa

[0071] ② The isothermal saturated adsorbed gas volume V was obtained through isothermal adsorption experiments on core samples within the work area. L Lange pressure P LThe average adsorbed gas content G of a single well obtained in step ① wa Combined, the critical adsorption pressure P of shale in a single well was calculated. c The specific formula is as follows:

[0072] P c =G wa ·P L / (V L -G wa )

[0073] ③ Obtain the abandoned pressure P corresponding to the horizontal well to be interpreted under the pressure boosting production mode based on the mining data within the work area. a The Langevin pressure P obtained in step ② L and critical adsorption pressure P c Combined, calculate the adsorbed gas recovery rate E of the horizontal well under the pressure boosting production mode. Ra The specific formula is as follows:

[0074] E Ra =1-P a ·(P L +P c ) / P c / (P L +P a )

[0075] ④ Obtain the original formation pressure P of the horizontal wells to be interpreted in the work area through well logging interpretation and evaluation data. i The original formation pressure P was obtained through core experimental data. i Gas deviation coefficient Z of free gas under certain conditions if The corresponding abandonment pressure P in the pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a Calculate the free gas recovery rate E of the horizontal well under the pressurized production mode. Rf The specific formula is as follows:

[0076] E Rf =1-P a ·Z if / Z a / P i

[0077] ⑤ The average free gas content G of the single well to be interpreted obtained in step ① wf Average adsorbed gas content (G) per well wa Average total gas content per well (G) wt The adsorbed gas recovery rate E calculated in step ③ Ra Step ④ calculates the free gas recovery rate E. Rf Combined, calculate the ultimate recovery rate η under the single-well pressurized production mode. rThe specific formula is as follows:

[0078] η r =(G wa ·E Ra +G wf ·E Rf ) / G wt

[0079] 5) Combine the formation lithology density (DEN) of each fractured section obtained in step 1) and the stimulation volume (V) of each fractured section obtained in step 2). SRV Step 3) Obtain the total gas content G of each fracturing section t Step 4) Obtain the ultimate recovery rate η r Multiplication is used to calculate the theoretical recoverable reserves V of each fracturing section. RT The specific formula is as follows:

[0080] V RT =η r ·V SRV ·G t ·DEN

[0081] 6) Obtain the gas production contribution rate η of each fractured section of the horizontal well to be interpreted within the work area based on the gas production profile logging data. gp ;

[0082] 7) Obtain the gas production V of the single horizontal well to be interpreted within the work area based on production dynamic data. gp ;

[0083] 8) The theoretical recoverable reserves V calculated in step 5) RT The gas production contribution rate η obtained in steps 6) and 7) gp Gas production volume V gp Combined, calculate the residual gas content V in each fractured section of the horizontal well to be explained. Rg The specific formula is as follows:

[0084] V Rg =V RT -η gp ·V gp

[0085] 9) The residual gas content V of each fracturing section calculated according to step 8) Rg Calculate the residual gas content V in a single well Rgw The specific formula is as follows:

[0086]

[0087] 10) Output and evaluate the calculation results:

[0088] Based on step 9), the calculation results of the residual gas content of the single well to be interpreted are output. The output results are evaluated individually according to three categories: I, II, and III: Single well residual gas content V Rgw More than 60% of the well's theoretical recoverable reserves are classified as Class I (enriched with residual gas), and the residual gas content of a single well is V. Rgw 40% to 60% of the well's theoretical recoverable reserves are classified as Class II (moderate residual gas), with a single well residual gas content V. Rgw If less than 40% of the well's theoretical recoverable reserves are classified as Class III (poor in terms of residual gas),

[0089] Based on step 8), the calculation results of the residual gas content in each fracturing section of the well to be interpreted are output. The output results are evaluated according to four categories: A, B, C, and D: Single-section residual gas content V Rg More than 75% of the theoretically recoverable reserves in this section are classified as Class A (with strong potential for repeated fracturing), and the residual gas content in a single section is V. Rg Class B (with retracement potential), comprising 60%–75% of the theoretically recoverable reserves in this section, has a single-section residual gas content V. Rg 40%–60% of the theoretically recoverable reserves in this section are classified as Class C (poor potential for repeated fracturing), with a single section residual gas content V. Rg Those accounting for less than 40% of the theoretical recoverable reserves in this section are classified as Category D (not possessing the potential for repeated fracturing).

[0090] The present invention will now be described in detail with reference to specific embodiments.

[0091] Example 1: S9-2HF well in the F shale gas field of Sichuan Basin

[0092] 1) The average formation lithology density (DEN) of the six fractured sections of well S9-2HF was obtained based on the density logging data (see Table 1);

[0093] 2) Based on the microseismic monitoring data of the S9-2HF well, the stimulation volume V of the six fracturing sections in the well was obtained. SRV (See Table 1);

[0094] 3) Based on the logging interpretation and evaluation data of well S9-2HF, the free gas content (G) of the six fractured sections of the well was obtained. f Average value, adsorbed gas content G a The average value was used to calculate the total gas content G of the six fracturing sections. t (See Table 1);

[0095] 4) Determine the ultimate recovery rate η of well S9-2HF under boosted production mode. r The specific steps to obtain it are as follows:

[0096] ①The average free gas content G in well S9-2HF was obtained based on the logging interpretation and evaluation data. wf =3.91m3 / t, average adsorbed gas content G wa =2.16m 3 / t, calculate the average total gas content G of this well. wt =6.07m 3 / t;

[0097] ②Based on isothermal adsorption experiments of core samples from the F shale gas field, the isothermal saturated adsorption gas volume V was obtained. L =3.87m 3 / t, Langevin pressure P L =11.07MPa, which is consistent with the average adsorbed gas content G of a single well obtained in step ①. wa Combining these factors, the critical adsorption pressure P of the shale in well S9-2HF was calculated. c =13.98MPa;

[0098] ③ The abandoned pressure P corresponding to the S9-2HF well in the boosted production mode a = 3.00 MPa, compared with the Langevin pressure P obtained in step ② L and critical adsorption pressure P c Combined, the adsorbed gas recovery rate E of well S9-2HF under pressurized production mode was calculated. Ra =0.618;

[0099] ④ Obtain the original formation pressure P of well S9-2HF by interpreting and evaluating well logging data. i =35.22 MPa, the original formation pressure P was obtained from core test data. i Gas deviation coefficient Z of free gas under certain conditions if =1.04, corresponding abandonment pressure P in pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a =0.92, calculate the free gas recovery rate E of well S9-2HF under pressurized production mode. Rf =0.904

[0100] ⑤ The average free gas content G of the single well to be interpreted obtained in step ① wf Average adsorbed gas content (G) per well wa Average total gas content per well (G) wt The adsorbed gas recovery rate E calculated in step ③ Ra Step ④) Calculation of free gas recovery rate E Rf Based on this, the ultimate recovery rate η of well S9-2HF under the booster production mode was calculated. r =0.802;

[0101] 5) Combine the formation lithology density (DEN) of each fractured section obtained in step 1) and the stimulation volume (V) of each fractured section obtained in step 2). SRVStep 3) Obtain the total gas content G of each fracturing section t Step 4) Obtain the ultimate recovery rate η r Multiply by each of the six fracturing sections to calculate the theoretical recoverable reserves V. RT (See Table 1);

[0102] 6) Obtain the gas production contribution rate η of the six fractured sections in well S9-2HF based on the gas production profile logging data. gp (See Table 1);

[0103] 7) Obtain the gas production V of well S9-2HF based on production dynamic data. gp =2850.10×10 4 m 3 ;

[0104] 8) The theoretical recoverable reserves V calculated in step 5) RT The gas production contribution rate η obtained in steps 6) and 7) gp Gas production volume V gp Based on this, the residual gas content V in the six fracturing sections of well S9-2HF was calculated. Rg (See Table 1);

[0105] 9) The residual gas content V of each fracturing section calculated using step 8). Rg To calculate the residual gas content V of a single well Rgw =6865.58×10 4 m 3 ;

[0106] 10) Output and evaluate the calculation results. The residual gas content of well S9-2HF is 6865.58 × 10⁻⁶. 4 m 3 This represents 70.7% of the well's theoretical recoverable reserves, classifying it as Category I, indicating abundant residual gas in the well. The residual gas content in the well's six fracturing sections ranges from 399.58 × 10⁻⁶. 4 m 3 ~1925.67×10 4 m 3 Among them, the residual gas content in sections 5, 2, and 1 was significant, at 1446.20 × 10⁻⁶. 4 m 3 1925.67×10 4 m 3 1801.75×10 4 m 3 The remaining gas content in these three fracturing sections accounts for more than 75% of the theoretical recoverable reserves of that section, classifying it as Category A and possessing significant potential for repeated fracturing. This well underwent repeated fracturing in August 2022, and the tested production after repeated fracturing was 5.12 × 10⁻⁶. 4 m3 / d, with a tested production recovery rate of 62.1%. The repeated fracturing effect is significant, indicating that the evaluation of the remaining gas content in this well is highly consistent with the final production effect of repeated fracturing.

[0107] Table 1. Calculation parameters for residual gas content in six fractured sections of Well S9-2HF in Shale Gas Field 1.

[0108]

[0109] Example 2: Well W4HF in the F Shale Gas Field of Sichuan Basin

[0110] 1) The average formation lithology density (DEN) of the 15 fractured sections of the W4HF well was obtained based on the density logging data (see Table 2).

[0111] 2) Based on the microseismic monitoring data of the W4HF well, the stimulation volume V of the 15 fractured sections in the well was obtained. SRV (See Table 2);

[0112] 3) Based on the logging interpretation and evaluation data of well W4HF, the free gas content (G) of the 15 fractured sections of the well was obtained. f Average value, adsorbed gas content G a The average value was used to calculate the total gas content G of these 15 fracturing sections. t (See Table 2);

[0113] 4) Determine the ultimate recovery rate η of well W4HF under pressurized production mode. r The specific steps to obtain it are as follows:

[0114] ①The average free gas content G in well W4HF was obtained based on the well logging interpretation and evaluation data. wf =1.73m 3 / t, average adsorbed gas content G wa =3.45m 3 / t, calculate the average total gas content G of this well. wt =5.18m 3 / t;

[0115] ② Well W4HF and Well S9-2HF in Example 1 both belong to the F shale gas field. The core isothermal adsorption experimental data from Example 1 can be used, i.e., the temperature saturated adsorption gas volume V. L =3.87m 3 / t, Langevin pressure P L =11.07MPa, which is consistent with the average adsorbed gas content G of a single well obtained in step ①. wa Combining these factors, the critical adsorption pressure P of the shale in well W4HF was calculated. c =8.95MPa;

[0116] ③ The abandonment pressure P corresponding to the W4HF well in the boosted production mode a = 3.00 MPa, compared with the Langevin pressure P obtained in step ② L and critical adsorption pressure P c Combined, the adsorbed gas recovery rate E of well W4HF under pressurized production mode was calculated. Ra =0.523;

[0117] ④ Obtain the original formation pressure P of well W4HF through well logging interpretation and evaluation data. i =34.90 MPa, the original formation pressure P was obtained from core test data. i Gas deviation coefficient Z of free gas under certain conditions if =1.0393, corresponding abandonment pressure P in pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a =0.9114, calculate the free gas recovery rate E of well W4HF under pressurized production mode. Rf =0.902;

[0118] ⑤ The average free gas content G of the single well to be interpreted obtained in step ① wf Average adsorbed gas content (G) per well wa Average total gas content per well (G) wt The adsorbed gas recovery rate E calculated in step ③ Ra Step ④ calculates the free gas recovery rate E. Rf Based on this, the ultimate recovery rate η of well W4HF under the booster production mode was calculated. r =0.775;

[0119] 5) Combine the formation lithology density (DEN) of each fractured section obtained in step 1) and the stimulation volume (V) of each fractured section obtained in step 2). SRV Step 3) Obtain the total gas content G of each fracturing section t Step 4) Obtain the ultimate recovery rate η r Multiply by each component to calculate the theoretical recoverable reserves V of the 15 fracturing sections. RT (See Table 2);

[0120] 6) Obtain the gas production contribution rate η of the 15 fractured sections in well W4HF based on the gas production profile logging data. gp (See Table 2);

[0121] 7) Obtain the gas production volume V of well W4HF based on production dynamic data. gp =7564.01×10 4 m 3 ;

[0122] 8) The theoretical recoverable reserves V calculated in step 5) RTThe gas production contribution rate η obtained in steps 6) and 7) gp Gas production volume V gp Based on this, the residual gas content V in the 15 fracturing sections of well W4HF was calculated. Rg (See Table 2);

[0123] 9) The residual gas content V of each fracturing section calculated using step 8). Rg To calculate the residual gas content V of a single well Rgw =11863.85×10 4 m 3 ;

[0124] 10) Output and evaluate the calculation results. The residual gas content of well W4HF is 11863.85 × 10⁻⁶. 4 m 3 This represents 61.1% of the well's theoretical recoverable reserves, classifying it as Category I, indicating abundant residual gas in the well. The residual gas content in the well's 15 fracturing sections ranges from 22.11 × 10⁻⁶. 4 m 3 ~2910.04×10 4 m 3 Among them, the residual gas content in segments 14, 10, 6, 5, and 4 was significant, at 2910.04 × 10⁻⁴. 4 m 3 1554.91×10 4 m 3 276.23×10 4 m 3 1104.30×10 4 m 3 378.07×10 4 m 3 The residual gas content in these five fracturing sections reached over 75% of the theoretical recoverable reserves for that section, classifying them as Category A and possessing significant potential for repeated fracturing. This well underwent repeated fracturing in June 2023, and the tested production after repeated fracturing was 18.38 × 10⁻⁶. 4 m 3 / d, with a tested production recovery rate of 88.1%. The repeated fracturing effect is significant, indicating that the evaluation of the remaining gas content in this well is highly consistent with the final production effect of repeated fracturing.

[0125] Table 2 shows the calculation parameters for residual gas content in 15 fractured sections of Well W4HF in the F2F shale gas field.

[0126]

Claims

1. A method for evaluating the residual gas content in a shale gas horizontal well, characterized in that, The following steps are included: 1) Obtain the average value of the formation lithology density (DEN) of each fractured section of the horizontal well to be interpreted within the work area; 2) Obtain the stimulation volume V of each fractured section of the horizontal well to be interpreted within the work area. SRV ; 3) Obtain the total gas content G of each fractured section of the horizontal well to be interpreted within the work area. t ; 4) Obtain the ultimate recovery rate η under the pressure boosting production mode of the horizontal wells to be interpreted within the work area. r ; 5) Combine the formation lithology density (DEN) of each fractured section obtained in step 1) and the stimulation volume (V) of each fractured section obtained in step 2). SRV Step 3) Obtain the total gas content G of each fracturing section t Step 4) Obtain the ultimate recovery rate η r Used to calculate the theoretical recoverable reserves V of each fracturing section. RT The specific formula is as follows: (1)V RT =η r ·V SRV ·G t ·DEN Where: theoretical recoverable reserves V RT Dimensionless 4 m 3 Fracturing section modification volume V SRV Dimensionless 4 m 3 The lithological density of the strata is measured in g / cm³. 3 Ultimate recovery rate η r Dimensionless, expressed as a decimal; 6) Obtain the gas production contribution rate η of each fractured section of the horizontal well to be interpreted within the work area. gp ; 7) Obtain the gas production V of the single horizontal well to be interpreted within the work area. gp ; 8) The theoretical recoverable reserves V calculated in step 5) RT Step 6) Gas production contribution rate η gp Step 7) Obtain the amount of gas produced, V gp Used to calculate the residual gas content V in each fractured section of the horizontal well to be explained. Rg The specific formula is as follows: (2)V Rg =V RT -η gp ·V gp Where: V represents the residual gas content in each fracturing section. Rg Dimensionless 4 m 3 Gas production contribution rate η gp Dimensionless, expressed as a decimal, amount of gas produced V gp Dimensionless 4 m 3 ; 9) The residual gas content V of each fracturing section calculated according to step 8) Rg Calculate the residual gas content V in a single well Rgw The specific formula is as follows: (3) Where: V represents the residual gas content of a single well. Rgw Dimensionless 4 m 3 i represents the segment number of each fracturing section in a single well; 10) Output and evaluate the calculation results.

2. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 1), the average value of the formation lithology density (DEN) of each fractured section of the horizontal well to be interpreted in the work area is obtained based on density logging data.

3. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 2), the stimulation volume V of each fractured section of the horizontal well to be interpreted within the work area is obtained based on the fracturing microseismic monitoring data. SRV .

4. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 3), the free gas content G of each fractured section of the horizontal well to be interpreted within the work area is obtained. f The average value and adsorbed gas content G a The average value is used to calculate the total gas content G in each fracturing section. t The specific formula is as follows: (4)G t =G f +G a Where: G is the total gas content of each fracturing section. t Dimensionless m 3 / t, free gas content G in each fracturing section f Dimensionless m 3 / t, adsorbed gas content G in each fracturing section a Dimensionless m 3 / t.

5. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 4), the ultimate recovery rate η of the horizontal well under the pressure-boosted production mode to be interpreted within the work area is determined. r The specific steps are as follows: ① Obtain the average free gas content (G) of a single horizontal well within the work area. wf Average adsorbed gas content (G) per well wa Calculate the average total gas content G of a single well. wt The specific formula is as follows: (5)G wt =G wf +G wa Where: G is the average total gas content of a single well. wt Dimensionless m 3 / t, average free gas content per well (G) wf Dimensionless m 3 / t, average adsorbed gas content per well (G) wa Dimensionless m 3 / t; ②The isothermal saturated adsorbed gas volume V was obtained from isothermal adsorption experiments on core samples from the work area. L Lange pressure P L The average adsorbed gas content G of a single well obtained in step ① wa Combined, the critical adsorption pressure P of shale in a single well was calculated. c The specific formula is as follows: (6)P c =G wa ·P L / (V L -G wa ) Where: Critical desorption pressure P c The dimensionless isothermal saturated adsorption gas volume V is measured in MPa. L Dimensionless m 3 / t, Langevin pressure P L The dimension is MPa; ③ Obtain the abandoned pressure P corresponding to the horizontal well pressurization production mode within the work area. a The Langevin pressure P obtained in step ② L and critical adsorption pressure P c Combined, calculate the adsorbed gas recovery rate E of the horizontal well under the pressure boosting production mode. Ra The specific formula is as follows: (7)E Ra =1-P a ·(P L +P c ) / P c / (P L +P a ) Where: Adsorbed gas recovery rate E Ra Dimensionless, expressed as a decimal, waste pressure P a The dimension is MPa; ④ Obtain the original formation pressure P of the horizontal well to be interpreted within the work area. i Original formation pressure P i Gas deviation coefficient Z of free gas under certain conditions if The corresponding abandonment pressure P in the pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a Calculate the free gas recovery rate E of the horizontal well under the pressurized production mode. Rf The specific formula is as follows: (8)E Rf =1-P a ·With if / Z a / P i Where: Free gas recovery rate E Rf Dimensionless, expressed as a decimal, original formation pressure P i Dimension: MPa, original formation pressure P i Gas deviation coefficient Z of free gas under certain conditions if Dimensionless, the waste pressure P corresponding to the pressurized mining mode a Gas deviation coefficient Z of free gas under certain conditions a Dimensionless; ⑤ The average free gas content G of a single well obtained in step ① wf Average adsorbed gas content (G) per well wa Average total gas content per well (G) wt The adsorbed gas recovery rate E calculated in step ③ Ra Step ④ calculates the free gas recovery rate E. Rf Combined, calculate the ultimate recovery rate η under the single-well pressurized production mode. r The specific formula is as follows: (9)η r =(G wa ·E Ra +G wf ·E Rf ) / G wt Where: η is the ultimate recovery rate under single-well pressurized production mode. r Dimensionless, expressed as a decimal.

6. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 6), the gas production contribution rate η of each fractured section of the horizontal well to be interpreted is obtained based on the gas production profile logging data. gp .

7. The method for evaluating the residual gas content of shale gas horizontal wells as described in claim 1, characterized in that, In step 7), the gas production V of the single horizontal well to be interpreted within the work area is obtained based on production dynamic data. gp .

8. The method for evaluating the residual gas content of shale gas horizontal wells as described in any one of claims 1-7, characterized in that, Based on step 8), the calculation results of the residual gas content in each fracturing section of the well to be interpreted are output. The output results are evaluated according to four categories: A, B, C, and D. Single-stage residual gas content V Rg The section that accounts for more than 75% of the theoretical recoverable reserves is classified as Category A, which has great potential for repeated fracturing. Single-stage residual gas content V Rg The section that accounts for 60% to 75% of the theoretically recoverable reserves is classified as Category B, which has the potential for repeated fracturing. Single-stage residual gas content V Rg The section that accounts for 40% to 60% of the theoretically recoverable reserves is classified as Category C, which has poor potential for repeated fracturing. Single-stage residual gas content V Rg Those accounting for less than 40% of the theoretical recoverable reserves in this section are classified as Category D, which means they do not have the potential for repeated fracturing.

9. The method for evaluating the residual gas content of shale gas horizontal wells according to any one of claims 1-7, characterized in that, Based on step 9), the calculation results of the residual gas content of the single well to be interpreted are output, and the output results are evaluated according to three categories: I, II, and III. Residual gas content V in a single well Rgw More than 60% of the well’s theoretical recoverable reserves are classified as Category I, which is rich in residual gas. Residual gas content V in a single well Rgw 40% to 60% of the well’s theoretical recoverable reserves are classified as Class II, which is a medium-sized residual gas. Residual gas content V in a single well Rgw If less than 40% of the well's theoretical recoverable reserves are classified as Class III, Class III is characterized by poor residual gas.

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