Method, system, equipment and medium for evaluating gas-bearing property of water-flooded area

Abstract

The invention discloses a method, a system, equipment and a medium for evaluating the gas-bearing property of a water-flooded area, and the method comprises the steps: confirming three pieces of quantitatively measured skeleton information and fluid medium information in a time domain through different minerals and fluid components, and calculating a fast neutron scattering cross section according to pulse neutron logging data; carrying out qualitative identification on the gas reservoir by combining the fast neutron scattering cross section and the stratum hydrogen-containing index; according to the fast neutron scattering cross section, the thermal neutron capture cross section, the hydrogen content index and the respective volume content, a linear equation set is established, and the simultaneous equation set is solved to obtain the content of different fluid components in the stratum. The gas reservoir evaluation method solves the problem that a conventional gas reservoir evaluation method is seriously influenced by detection depth, borehole environment, invasion, low contrast ratio and pore fluid properties, and does not depend on conventional logging curves and electrical characteristics.

Description

Technical Field

[0001] The present invention belongs to the field of well logging technology, and in particular relates to a method, system, equipment and medium for evaluating gas content in a flooded area. Background Art

[0002] For gas zone identification and evaluation, the neutron-density intersection method is the primary method used in conventional well logging data. However, due to the shallow depths of both neutron and density logs, they are significantly affected by the wellbore environment and invasion, and the low sensitivity of the neutron-density intersection method makes it difficult to distinguish between gas zones and gas-bearing water zones. Special logging methods, such as the P-wave velocity ratio and the elastic modulus difference ratio, can be used to identify gas zones. These methods primarily focus on qualitative identification of gas zones and are difficult to perform effective quantitative calculations. For low-contrast oil and gas zones, deep lateral or deep induction resistivity logging is commonly used in China to distinguish between oil and gas zones and water zones. Water saturation is then quantitatively interpreted based on parameters such as formation resistivity, porosity, and pore structure. Therefore, when the resistivity of oil and gas zones is the same as or lower than that of water layers, i.e., when the contrast is low, relying solely on deep lateral or deep induction resistivity logging to distinguish between oil and water zones and to calculate water saturation based on formation resistivity is unsatisfactory.

[0003] Patent publication number CN111638559B, titled "A Method for Characterizing Fast Neutron Scattering Cross Sections Based on Pulsed Neutron Logging," includes the following steps: Determining the fast neutron scattering cross section by modifying the formula for the inelastic gamma field distribution, and determining that factors influencing the fast neutron scattering cross section characterization include formation density and detector source distance; Establishing a formation density characterization method based on selected pulsed neutron logging instrument parameters to derive a mathematical expression for characterizing the fast neutron scattering cross section using inelastic gamma flux and the ratio of inelastic to captured gamma flux; Establishing a three-dimensional MCNP numerical calculation model to simulate and generate a multi-detector gamma flux information database; Using the least squares method, performing a three-variable linear regression analysis of the fast neutron scattering cross section, gamma flux, and flux ratio information for different formation conditions to derive the mathematical form of the fast neutron scattering cross section calibration formula, ultimately forming a method for characterizing the fast neutron scattering cross section. While this patent application can determine the fast neutron scattering cross section, it cannot be used to evaluate gas-bearing formations. Summary of the Invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a method, system, equipment and medium for evaluating the gas content of water-flooded areas, by using pulsed neutron logging to evaluate the gas content of water-flooded areas, so as to better improve the accuracy of gas content evaluation in water-flooded layer areas.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for evaluating gas content in a flooded area comprises the following steps:

[0007] S1: Confirm the skeleton information and fluid medium information of three quantitative measurements in the time domain through different mineral and fluid components. The three quantitative skeleton information measurements include thermal neutron capture cross section, formation hydrogen index and fast neutron scattering cross section;

[0008] S2: Calculate the fast neutron scattering cross section based on pulsed neutron logging data;

[0009] S3: Qualitative identification of gas layers using the fast neutron scattering cross section and formation hydrogen index;

[0010] S4: Based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index and their respective volume contents, a system of linear equations is established and the contents of different fluid components in the formation are obtained by solving the system of simultaneous equations.

[0011] Optionally, before step S1, inelastic scattering gamma spectra and thermal neutron capture gamma spectra data of three pulsed neutron logging detectors at the deep, far and near depths are collected, and the dry weight of formation elements, dry weight of minerals and volume content are calculated through spectrum stripping and oxygen closure model.

[0012] Optionally, in step S3, the fast neutron scattering cross-section value is first calculated according to the GRAT_REF gas ratio mode specified by the laboratory; the calculated fast neutron scattering cross-section value is read in the standard layer section identified on the logging curve; the fast neutron scattering cross-section is calculated using the GRAT_MODE gas ratio mode or the GRAT_BSL gas ratio mode; the GRAT_MODE gas ratio mode uses the statistical mean of the GRAT gas ratio as the input of the GRAT_BSL gas ratio mode, and the GRAT_BSL gas ratio mode uses manual input as the input value of GRAT_BSL.

[0013] Alternatively, the formula for calculating the fast neutron scattering cross section value using the laboratory-specified GRAT_REF gas ratio mode is:

[0014]

[0015] Where FNXS is the fast neutron scattering cross section; Gain is the calibration factor; a1, a2, and a3 are laboratory theoretical values.

[0016] Optionally, the calculation formula for GRAT_MODE gas ratio mode or GRAT_BSL gas ratio mode is:

[0017]

[0018] The calculation formula for log(GRAT_Lime) is:

[0019]

[0020] Where gain is the calibration coefficient; a1, a2, and a3 are laboratory theoretical values; and GRAT_Lime is the gas ratio value of limestone.

[0021] Optionally, the calculated fast neutron scattering cross section value is read in a standard mudstone section or a water-bearing limestone section identified on the well logging curve.

[0022] Optionally, the fast neutron scattering cross section of the water-bearing limestone has a value of 7.5.

[0023] A flooded area gas content evaluation system, comprising:

[0024] An information collection module is used to confirm three quantitative measurements of skeleton information and fluid medium information in the time domain through different mineral and fluid components. The three quantitative measurements of skeleton information include thermal neutron capture cross section, formation hydrogen index, and fast neutron scattering cross section;

[0025] A first calculation module is used to calculate the fast neutron scattering cross section based on the pulsed neutron logging data;

[0026] Identification module, used to qualitatively identify gas layers by combining fast neutron scattering cross section and formation hydrogen index;

[0027] The second calculation module is used to establish a linear equation system based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index and their respective volume contents, and solve the simultaneous equation system to obtain the contents of different fluid components in the formation.

[0028] An electronic device comprises a memory, a processor and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for evaluating gas content in flooded areas are implemented.

[0029] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for evaluating gas content in flooded areas.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This method utilizes pulsed neutron logging, which relies on the sensitivity of fast neutron scattering cross sections to gas-bearing reservoirs, to evaluate the gas content of reservoirs in flooded areas. This method addresses the significant impact of previous gas reservoir evaluation methods on detection depth, wellbore environment, invasion, low contrast, and pore fluid properties. It provides a novel approach that independently evaluates reservoir gas content from a new perspective, using formation attributes, rather than relying on conventional logging curves or electrical characteristics. Formation testing has demonstrated a high rate of agreement in reservoir gas content evaluation using the fast neutron scattering cross section of pulsed neutron logging.

[0032] The present invention addresses the problem that conventional logging cannot effectively evaluate the gas content in the flooded areas of the condensate reservoirs in the Tarim region, and introduces pulsed neutron logging measurements. Pulsed neutron logging is based on the interaction between neutrons and the fluids contained in minerals and pore spaces, and measures parameters that are sensitive to different formation properties. The latest one introduced is the measurement of fast neutron scattering cross section. The fast neutron scattering cross section reflects the ability of the formation to attenuate high-energy neutrons. Generally, solids and liquids have similar fast neutron scattering cross section values, while gases have significantly lower fast neutron scattering cross section values. This feature reflects that the fast neutron scattering cross section is not very sensitive to changes in liquid-filled porosity, but is very sensitive to changes in gas-filled porosity. Based on the sensitivity of the fast neutron scattering cross section value to gas, gas layers can be qualitatively identified. The fast neutron scattering cross section has a formation volume attribute, which follows the linear volume mixing law. In addition to the rock skeleton, the formation generally has pore space that can be filled with various fluids (oil, water or gas). The total fast neutron scattering cross section of the formation is the volume-weighted sum of the fast neutron scattering cross sections of all these components. Pulsed neutron logging provides independent measurements of the thermal neutron capture cross section (SIGMA) and neutron porosity. SIGMA primarily reflects the neutron capture ability of formation elements, primarily hydrogen in formation water. Neutron porosity primarily reflects the neutron deceleration ability of formation elements, primarily hydrogen atoms, in the formation. Combining the fast neutron scattering cross section, SIGMA, and neutron porosity, through a series of linear equations, can be used to calculate complex multiphase fluid saturation, thereby quantitatively evaluating gas-bearing reservoirs. This is unaffected by various factors, including electrical properties, wellbore conditions, completion status, and invasion. In addition, pulsed neutron logging independently measures inelastic scattering and thermal neutron capture spectra. By decomposing the spectra and applying oxygen closure models, dry weight formation element and mineral content, as well as volume profiles, can be derived, providing more reliable information for gas-bearing reservoir evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0034] In the attached figure:

[0035] Figure 1 Flow chart of the steps of the present invention;

[0036] Figure 2 The characteristic layer selection diagram of the logging response characteristic value of pulse neutron logging results in different media;

[0037] Figure 3 is a cross-plot of the energy of the neutron flux in the formation changing with time;

[0038] Figure 4 Define a schematic for the time gate;

[0039] Figure 5 This is the crossplot of the relationship between GRAT and the fast neutron scattering cross section FNXS;

[0040] Figure 6 It is pulsed neutron logging gamma spectroscopy formation element and mineral profile;

[0041] Figure 7 Calculate formation fast neutron scattering cross section FNXS for GRAT_MODE gas ratio mode and GRAT_BSL gas ratio mode;

[0042] Figure 8 Crossplots of fast neutron scattering cross section FNXS, hydrogen index TPHI and neutron capture cross section SIGMA for gas layer identification;

[0043] Figure 9 This is the gas content evaluation result of pulse neutron logging in Well A. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] It should be noted that in the claims, any reference signs placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claim. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The present application may be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0048] The present invention will be described in detail below with reference to the accompanying drawings.

[0049] like Figure 1 As shown, a method for evaluating gas content in flooded areas according to the present invention specifically comprises the following steps:

[0050] 1) Analyze and process the inelastic scattering gamma spectra and thermal neutron capture gamma spectra of the three detectors of pulsed neutron logging, deep, far and near, and calculate the dry weight of formation elements, mineral dry weight and volume content through stripping spectrum and oxygen closure model, in preparation for the subsequent use of mineral volume content. Figure 3 The figure shows the changing trend of neutrons of different energies in the formation over time after the neutron generator emits neutron pulses into the formation.

[0051] 2) Three quantitative measurements of skeleton information, fluid medium information, and fluid information are confirmed within a unit time domain through different mineral and fluid components. The three quantitative measurements of skeleton information include neutron capture cross section, formation hydrogen index, and fast neutron scattering cross section. At the same time, characteristic layer segments are found through the response of conventional curves to help calibrate the measurement values ​​to an accurate numerical range.

[0052] from Figure 2 As can be seen in Figure 2, the neutron capture cross section is sensitive to highly salinized formation water, while the formation hydrogen index (TPHI) is sensitive to fluids. Both are sensitive to pore fluids and, to some extent, indicate the presence of a reservoir.

[0053] The fast neutron scattering cross section is sensitive to natural gas. Therefore, the fast neutron scattering cross section (FNXS) is a key factor in evaluating gas-bearing reservoirs, and accurate calculation of the FNXS of reservoirs is a prerequisite for accurate evaluation of gas-bearing reservoirs.

[0054] 3) Calculate the fast neutron scattering cross section based on pulsed neutron logging (PNX) data.

[0055] First, select the GRAT_REF gas ratio mode to calculate the fast neutron scattering cross section value. The fast neutron scattering cross section is a theoretical value calculated based on the wellbore size, casing information, etc., as shown in formula (1):

[0056]

[0057] The fast neutron scattering cross section can reflect the probability of elastic scattering between fast neutrons and formation element atoms in a unit volume of formation.

[0058] Where GRAT_REF is the apparent limestone GRAT gas ratio for the laboratory-specified casing and borehole size; GRAT gas ratio is the gamma-ray count rate corrected for the thermal neutron capture GR background and normalized by the neutron count rate (NMTCR).

[0059] Gain is the calibration coefficient; a1, a2, and a3 are laboratory theoretical values; GRAT_REF is the apparent limestone GRAT gas ratio (Gas Ratio) for the laboratory-specified casing and wellbore.

[0060] like Figure 4 The following figure shows the definition of the timing gate GRAT used in inelastic gas measurements. The count rate is calculated in Gate A, which includes the excitation period, and Gate B, which is the early capture gate after each excitation. The captured gamma-ray background in the excitation count rate in Gate A can be predicted and is proportional to the capture count rate in Gate B. Figure 5 It is shown that under the same borehole conditions and various formation conditions, the measured GRAT has a good correspondence with the fast neutron scattering cross section, so the fast neutron scattering cross section of the formation can be obtained using the measured GRAT.

[0061] The calculated fast neutron scattering cross section value is read in the standard mudstone section or water-bearing limestone section identified on the logging curve. The fast neutron scattering cross section of water-bearing limestone is 7.5. If the fast neutron scattering cross section calculated in the calibrated well section is approximately equal to 7.5, the calculated value matches the theoretical value and is an appropriate fast neutron scattering cross section value.

[0062] If the difference is obvious, the GRAT_MODE gas ratio mode or the GRAT_BSL gas ratio mode is selected to calculate the fast neutron scattering cross section. The two gas ratio modes use the same formula to calculate the fast neutron scattering cross section.

[0063] As shown in the following formula (2), the GRAT_MODE gas ratio mode uses the statistical mean of GRAT as the input of GRAT_BSL, while the GRAT_BSL gas ratio mode uses an adjustable human input as the input value of GRAT_BSL for calculation.

[0064] First, the GRAT_MODE gas ratio mode is used to calculate the fast neutron scattering cross section. By checking the fast neutron scattering cross section values ​​in mudstone or water-bearing limestone, the input value of GRAT_BSL is adjusted according to the GRAT statistical mean provided by the GRAT_MODE gas ratio mode. The calculated fast neutron scattering cross section value in the mudstone and water-bearing limestone sections is approximately equal to 7.5. In this way, the fast neutron scattering cross section calculated for the entire well section is more appropriate.

[0065]

[0066] The calculation of log(GRAT_Lime) is shown in formula (3):

[0067]

[0068] GRAT_BSL is a method that uses artificially input GRAT values ​​to calculate the fast neutron scattering cross section.

[0069] GRAT_Lime is the gas ratio (GRAT) value of limestone.

[0070] 4) Based on the fact that the fast neutron scattering cross section value is sensitive to the gas content, and the hydrogen index is sensitive to the water (hydrogen index) content, the fast neutron scattering cross section and the hydrogen index are combined to qualitatively identify the gas layer.

[0071] 5) The fast neutron scattering cross section (FNSC) is a volumetric formation property that follows a linear volume mixing law. The FNSCs with different subscripts represent the FNSCs of different components, and V is the volume fraction of each component. A formation is typically modeled as a volume containing the rock matrix and pore space, which can be filled with various fluids (oil, water, or gas). The FNSC is the volume-weighted sum of the FNSCs of all these components, similar to other formation properties. Similarly, the thermal neutron capture cross section and hydrogen index from pulsed neutron logging also share this property.

[0072] Based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index, and the volume content of each mineral component in the formation (including clay, quartz, feldspar) and the volume content of different fluid types (oil, gas, water), a series of linear equations are established, see equation group (4). Solving the simultaneous equations can obtain the content of different components in the formation, and thus the porosity and gas saturation of the reservoir can be obtained, so as to evaluate the gas content of the reservoir.

[0073]

[0074] Where: V is the volume content of formation minerals, quartz is quartz, water is water, gas is gas, illite is illite, and SIGMA is the neutron capture cross section.

[0075] A flooded area gas content evaluation system of the present invention comprises:

[0076] An information collection module is used to confirm three quantitatively measured skeleton information and fluid medium information in the time domain through different mineral and fluid components. The three quantitatively measured skeleton information includes neutron capture cross section, formation hydrogen index and fast neutron scattering cross section;

[0077] A first calculation module is used to calculate the fast neutron scattering cross section based on the pulsed neutron logging data;

[0078] Identification module, used to qualitatively identify gas layers by combining fast neutron scattering cross section and formation hydrogen index;

[0079] The second calculation module is used to establish a linear equation system based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index and their respective volume contents, and solve the simultaneous equation system to obtain the contents of different fluid components in the formation.

[0080] An electronic device of the present invention comprises a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the method for evaluating gas content in flooded areas are implemented.

[0081] A computer-readable storage medium of the present invention stores a computer program, which implements the steps of the method for evaluating gas content in flooded areas when executed by a processor.

[0082] Example

[0083] The following combination Figure 1 The specific embodiments of the present invention are further described.

[0084] In this embodiment, taking development well A in the flooded area of ​​an oil field as an example, a method for evaluating the gas content of a reservoir based on pulsed neutron logging includes the following steps:

[0085] 1) Based on the inelastic scattering and thermal neutron capture gamma-ray spectra of pulsed neutron logging, the element dry weight and mineral volume profile of the formation are obtained through the spectrum and oxygen closure model, see Figure 6 The volume content of the formation mineral components can be obtained from this, which provides the mineral volume content for the simultaneous linear equations.

[0086] 2) The fast neutron scattering cross section is calculated using the GRAT_MODE gas ratio mode, GRAT_BSL is equal to 51.3, and the fast neutron scattering cross section mode calculated by the above formula (2) has a reading of about 8.4 in the mudstone section of the well section 5230-5240m. The fast neutron scattering cross section is then calculated using the GRAT_BSL gas ratio mode, and the input value of GRAT_BSL is adjusted to 46. The FNXS_BSL is obtained after calculation using the above formula (2). The reading of the fast neutron scattering cross section mode in the mudstone section of the well section 5230-5240m is about 7.5. Based on this, it is believed that the fast neutron scattering cross section calculated when GRAT_BSL is equal to 46 is more accurate. Figure 7 .

[0087] 3) The gas layer is identified by intersection of fast neutron scattering cross section, hydrogen index and neutron capture cross section. The intersection diagram is shown in Figure 8 As shown in the intersection diagram, we can see that the intersection of the three can be used to identify the gas layer very well.

[0088] 4) Based on the actual situation of the example well, Equation (4) is updated as shown in Equation (5). Based on the existing mineral volume content, fast neutron scattering cross section, neutron capture cross section and formation hydrogen index, by solving the simultaneous equations, the formation water volume (Vwater) and gas volume (Vgas) can be obtained. The sum of the formation water volume and the gas volume is the formation pore volume, and the quotient of the gas volume and the formation pore volume is the gas saturation. Based on this, the gas content of the reservoir is evaluated. The comprehensive evaluation results are shown in the figure. Figure 8 As shown in the figure. It can be seen from the figure that the intersection of the fast neutron scattering cross section and the formation hydrogen index, as well as the intersection of the fast neutron scattering cross section and the neutron capture cross section can qualitatively indicate the gas layer. Based on the porosity and gas saturation, the gas layer, poor gas layer and dry layer are comprehensively interpreted. In addition, from Figure 9 As can be seen in the figure, conventional electrical properties curves in the interpreted gas-bearing zone show low values, even lower than the resistivity of the mudstone sections above and below. Furthermore, the three-porosity curves are unable to effectively identify gas zones, further demonstrating the superiority of pulsed neutron logging in evaluating gas-bearing properties in the flooded areas of the Tarim Sag.

[0089] SIGMA=V quartz *SIGMA quartz +V water *SIGMAwater +V gas *SIGMA gas +V illite *SIGMA illite +V calcite *SIGMA calcite +V dolomite *SIGMA dolomite +V pyrite *SIGMA pyrite +V anhyrite *SIGMA anhyrite

[0090] TPHI=V quartz *TPHI quartz +V water *TPHI water +V gas *TPHI gas +V illite *TPHI illite +V calcite *TPHI calcite +V dolomite *TPHI dolomite +V pyrite *TPHI pyrite +V anhyrite *TPHI anhyrite

[0091] FNXS=V quartz *FNXS quartz +V water *FNXS water +V gas *FNXS gas +V illite *FNXS illite +V calcite *FNXS calcite +V dolomite *FNXS dolomite +V pyrite *FNXS pyrite +V anhyrite *FNXS anhyrite

[0092] 1=V quartz +V water +V gas +V illite +V calcite +V dolomite +V pyrite +V anhyrite (5)

[0093] Among them: V is the volume content of formation minerals, quartz is quartz, water is water, gas is gas, illite is illite, SIGMA is the neutron capture cross section, anhyrite is gypsum, pyrite is pyrite, dolomite is dolomite, and calcite is calcite.

[0094] Oil test was conducted in the well section of 4858.0-4917.5m and 5059-5084.5m respectively. In the well section of 4858.0-4917.5m, the working system was 5mm nozzle, and the daily gas production was converted to 85112m3 3 , equivalent to daily oil production of 6.21m 3 The test results indicate a condensate gas layer. 5059-5084.5m well section, fluid drainage to increase production. Daily gas production 3252m 3 , cumulative gas production 5928m 3 The oil test results and the logging interpretation results are highly consistent. This shows that the method of evaluating gas content in flooded areas based on pulsed neutron logging is effective.

[0095] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0096] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0097] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0099] Unless otherwise specified, the working modes or control modes involved in the above embodiments are all conventional working modes or control modes in the art.

[0100] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limiting. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for evaluating gas content in flooded areas, characterized in that: The following steps are involved: S1: Confirm the skeleton information and fluid medium information of three quantitative measurements in the time domain through different mineral and fluid components. The three quantitative skeleton information measurements include thermal neutron capture cross section, formation hydrogen index and fast neutron scattering cross section; S2: Calculate the fast neutron scattering cross section based on pulsed neutron logging data; S3: Qualitative identification of gas layers using the fast neutron scattering cross section and formation hydrogen index; S4: Based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index and their respective volume contents, a system of linear equations is established and the contents of different fluid components in the formation are obtained by solving the system of simultaneous equations.

2. A method for evaluating gas content in flooded areas according to claim 1, characterized in that: Before step S1, inelastic scattering gamma spectra and thermal neutron capture gamma spectra data of three pulsed neutron logging detectors at the deep, far and near depths are collected, and the dry weight of formation elements, dry weight of minerals and volume content are calculated through spectrum stripping and oxygen closure model.

3. The method for evaluating gas content in flooded areas according to claim 1, wherein: In step S3, first, the fast neutron scattering cross section value is calculated according to the GRAT_REF gas ratio mode specified by the laboratory; the calculated fast neutron scattering cross section value is read in the standard layer section identified on the well logging curve; the fast neutron scattering cross section is calculated using the GRAT_MODE gas ratio mode or the GRAT_BSL gas ratio mode; The GRAT_MODE gas ratio mode uses the statistical mean of the GRAT gas ratio as the input of the GRAT_BSL gas ratio mode, and the GRAT_BSL gas ratio mode uses artificial input as the input value of GRAT_BSL.

4. A method for evaluating gas content in flooded areas according to claim 3, characterized in that: The formula for calculating the fast neutron scattering cross section value using the laboratory-specified GRAT_REF gas ratio model is: Where FNXS is the fast neutron scattering cross section; Gain is the calibration factor; a1, a2, and a3 are laboratory theoretical values.

5. The method for evaluating gas content in flooded areas according to claim 3, characterized in that: The calculation formula for GRAT_MODE gas ratio mode or GRAT_BSL gas ratio mode is: The calculation formula for log(GRAT_Lime) is: Where gain is the calibration coefficient; a1, a2, and a3 are laboratory theoretical values; and GRAT_Lime is the gas ratio value of limestone.

6. A method for evaluating gas content in flooded areas according to claim 3, characterized in that: The calculated fast neutron scattering cross section value is read in the standard mudstone section or water-bearing limestone section identified on the well logging curve.

7. A method for evaluating gas content in flooded areas according to claim 6, characterized in that: The fast neutron scattering cross section of water-bearing limestone is 7.

5.

8. A flooded area gas content evaluation system, characterized in that: include: An information collection module is used to confirm three quantitative measurements of skeleton information and fluid medium information in the time domain through different mineral and fluid components. The three quantitative measurements of skeleton information include thermal neutron capture cross section, formation hydrogen index, and fast neutron scattering cross section; A first calculation module is used to calculate the fast neutron scattering cross section based on the pulsed neutron logging data; Identification module, used to qualitatively identify gas layers by combining fast neutron scattering cross section and formation hydrogen index; The second calculation module is used to establish a linear equation system based on the fast neutron scattering cross section, thermal neutron capture cross section, hydrogen index and their respective volume contents, and solve the simultaneous equation system to obtain the contents of different fluid components in the formation.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the method for evaluating gas content in flooded areas according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the method for evaluating gas content in flooded areas according to any one of claims 1 to 7.

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