Method and device for determining gas content of deep coal rock gas reservoir and readable storage medium

Abstract

The invention provides a method and device for determining the gas content of a deep coal rock gas reservoir and a readable storage medium, and belongs to the technical field of oil-gas exploration. The method comprises the following steps: acquiring a substrate transverse relaxation time spectrum of a dried reservoir rock sample, transverse relaxation time spectrums before adsorption equilibrium at different pressure points and transverse relaxation time spectrums after adsorption equilibrium at different pressure points; based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrums before adsorption equilibrium at different pressure points and the transverse relaxation time spectrums after adsorption equilibrium at different pressure points, transverse relaxation time correction spectrums after adsorption equilibrium at different pressure points are determined; obtaining actual free gas volumes under different pressure points and actual adsorption gas volumes under different pressure points; and constructing a gas content determination model for outputting the gas content of the deep coal and rock gas reservoir to be detected. By redefining the T2 cut-off values of the adsorption gas and the free gas, the adsorption gas amount and the free gas amount are accurately calculated, and the calculation precision of the gas content of the reservoir can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and in particular to a method for determining the gas content of a deep coal-rock gas reservoir, a device for determining the gas content of a deep coal-rock gas reservoir, and a readable storage medium. Background Art

[0002] Nuclear magnetic resonance technology has been widely used in various fields of geophysical and geological research, and has become one of the important methods for characterizing reservoir microscopic pore structure, fluid properties and physical parameters. In recent years, nuclear magnetic resonance technology has also begun to be widely used in the study of fluid phase state in rock samples with adsorption capacity.

[0003] As an important part of unconventional natural gas development, deep coal-rock gas reservoirs are very important for accurately predicting their in-situ gas content and occurrence state in resource reserve assessment and mining strategy optimization. However, there is currently a lack of accurate means to distinguish between adsorbed gas and free gas in deep coal-rock gas reservoirs. The identification of adsorbed gas and free gas mostly relies on conventional logging data, and the identification accuracy is limited. Therefore, the qualitative and quantitative identification of gas based on precise experimental calibration is particularly important. In the existing technology, isothermal adsorption experiments combined with saturated nuclear magnetic resonance have been used to infer the proportion of free gas and adsorbed gas content; isothermal adsorption and nuclear magnetic resonance synchronous dynamic joint measurement experimental equipment has been developed, and isothermal adsorption and nuclear magnetic resonance synchronous dynamic joint measurement experiments have been conducted on adsorbed gas reservoir rock samples; nuclear magnetic resonance combined with isothermal adsorption has been used to determine the content of free methane gas and adsorbed methane gas in shale; and isothermal adsorption nuclear magnetic resonance joint measurement experiments of coal have been used to calculate its free adsorbed gas. However, the above isothermal adsorption nuclear magnetic resonance joint measurement experiments are mostly used in the qualitative and quantitative identification of gas phases in rock samples, and most of them assume that the first peak reflects the adsorbed gas signal and the second peak is the free gas signal. However, in actual samples, adsorbed gas and free gas coexist in the nanopores. Therefore, using this method to determine the proportion of free adsorbed gas has a certain error, resulting in inaccurate results. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a method, device and readable storage medium for determining the gas content of deep coal-rock gas reservoirs, so as to at least solve the coexistence of adsorbed gas and free gas in the above-mentioned nanopores. Therefore, using this method to determine the proportion of free adsorbed gas has a certain error, resulting in inaccurate results.

[0005] In order to achieve the above object, the present invention provides a method for determining the gas content of a deep coal-rock gas reservoir in a first aspect, the method comprising:

[0006] Obtaining the base transverse relaxation time spectrum of the dried reservoir rock sample, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0007] Based on the transverse relaxation time spectra before and after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined;

[0008] Based on the transverse relaxation time spectrum of the substrate, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points, the adsorbed gas signal at different pressure points is determined;

[0009] Based on the transverse relaxation time spectrum of the substrate, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points, determining the corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0010] Based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual free gas volume at different pressure points is obtained;

[0011] Based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual adsorbed gas amount at different pressure points is obtained;

[0012] Based on the actual free gas volume at different pressure points and the actual adsorbed gas volume at different pressure points, a gas content determination model is constructed;

[0013] Obtain the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be tested after drying;

[0014] The rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected are used as inputs of a gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

[0015] Optionally, based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined, including:

[0016] For each pressure point:

[0017] The difference between the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point and the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the n-1th pressure point is taken as the increase in the first peak free gas area at the nth pressure point;

[0018] The sum of the increase in the first peak free gas area from the 1st pressure point to the nth pressure point is taken as the free gas signal at the nth pressure point.

[0019] Optionally, based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined, including:

[0020] The free gas signal is calculated using the following formula:

[0021]

[0022] Among them, FTSf n is the free gas signal at the nth pressure point; FTSI i is the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the i-th pressure point; FTSA i-1 is the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the i-1th pressure point.

[0023] Optionally, based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points, the adsorbed gas signal at different pressure points is determined, including:

[0024] For each pressure point:

[0025] The first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point minus the first peak area of ​​the substrate transverse relaxation time spectrum and the free gas signal at the nth pressure point is taken as the adsorbed gas signal at the nth pressure point.

[0026] Optionally, based on the transverse relaxation time spectrum of the substrate, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points, determining the corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points includes:

[0027] For each pressure point:

[0028] Calculating the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum at the nth pressure point, and constructing a first curve at the nth pressure point based on the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum;

[0029] Calculating the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium from the first pressure point to the nth pressure point, and constructing a second curve at the nth pressure point based on the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium;

[0030] Determine the transverse relaxation time corresponding to the intersection of the first curve and the second curve at the nth pressure point;

[0031] The transverse relaxation time is used as the transverse relaxation time cutoff value of the adsorption peak and the free peak of the transverse relaxation time spectrum after adsorption equilibrium at the nth pressure point to obtain the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; the transverse relaxation time cutoff value is used to divide the first peak area and the secondary peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium.

[0032] Optionally, based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual free gas volume at different pressure points is obtained, including:

[0033] GasA n = k*(FTSf n +STS′ n );

[0034] Among them, GasA n is the actual free gas volume at the nth pressure point; k is the conversion coefficient; FTSf n is the free gas signal at the nth pressure point; STS′ n is the secondary peak area of ​​the transverse relaxation time corrected spectrum after the nth adsorption equilibrium.

[0035] Optionally, based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual adsorbed gas amount at different pressure points is obtained, including:

[0036] GasF n = k*(FTSA′ n -FTSD-FTSf n );

[0037] Among them, GasF n is the actual adsorbed gas volume at the nth pressure point; k is the conversion coefficient; FTSA′ n is the first peak area of ​​the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; FTSD is the total area of ​​the base transverse relaxation time spectrum; FTSf n is the free gas signal at the nth pressure point.

[0038] Optionally, the expression of the gas content determination model is:

[0039] F gas =(a*P) / m;

[0040] A gas =[c*ln(P)+d] / m;

[0041] Among them, F gas A is the actual free gas content of the reservoir rock to be tested; gas is the actual adsorbed gas content of the reservoir rock to be tested; a, c, d are all fitting coefficients; m is the formation pressure of the reservoir rock to be tested; m is the mass of the reservoir rock to be tested after drying.

[0042] A second aspect of the present invention provides a device for determining the gas content of a deep coal-rock gas reservoir, the device comprising:

[0043] A time spectrum acquisition module is used to acquire the base transverse relaxation time spectrum of the dried reservoir rock sample, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0044] A free gas signal determination module, used to determine the free gas signals at different pressure points based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points;

[0045] An adsorbed gas signal determination module, used to determine the adsorbed gas signal at different pressure points based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the free gas signal at different pressure points;

[0046] A time spectrum correction module, used to determine a corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points based on the substrate transverse relaxation time spectrum, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0047] An actual free gas volume determination module is used to obtain the actual free gas volume at different pressure points based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points;

[0048] The actual adsorbed gas volume determination module is used to obtain the actual adsorbed gas volume at different pressure points based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points;

[0049] A gas content determination model building module is used to build a gas content determination model based on the actual adsorbed gas content and the actual free gas content at different pressure points;

[0050] A data acquisition module, used to obtain the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected after drying;

[0051] The reservoir gas content determination module is used to use the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected as inputs of the gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

[0052] On the other hand, the present invention provides a readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for determining the gas content of a deep coal-rock gas reservoir.

[0053] This technical solution conducts two measurements of the transverse relaxation time before and after adsorption equilibrium after filling with methane gas at different pressure points, realizes the separation of gas signals in different occurrence states of the first peak, redefines the T2 cutoff value of adsorbed gas and free gas, accurately calculates the amount of free gas and adsorbed gas, improves the calculation accuracy of the gas content in deep coal reservoirs, and improves the accuracy of quantitative and qualitative definition of reservoir gas occurrence mode, providing technical support for detailed evaluation of oilfield reservoirs and reserve declaration.

[0054] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings:

[0056] Figure 1 It is a flow chart of the method for determining the gas content of deep coal-rock gas reservoir provided by the present invention;

[0057] Figure 2 It is the nuclear magnetic T2 spectrum of the nuclear magnetic measurement of the reservoir rock sample after drying provided by the present invention;

[0058] Figure 3 It is the nuclear magnetic T2 spectrum measured immediately after being inflated to various pressures provided by the present invention;

[0059] Figure 4 The present invention provides a nuclear magnetic T2 spectrum measured after adsorption equilibrium at each pressure point;

[0060] Figure 5 It is the T2 spectrum area envelope diagram of the adsorption equilibrium at a certain pressure point measured instantly and at the previous pressure point provided by the present invention;

[0061] Figure 6 This is a first peak signal separation diagram provided by the present invention;

[0062] Figure 7 It is a T2 cutoff value division diagram of the free adsorption signal provided by the present invention;

[0063] Figure 8 It is a relationship diagram between the adsorption free peak T2 cutoff value and pressure provided by the present invention;

[0064] Fig. 9 is a graph showing the relationship between adsorbed gas content and pressure provided by the present invention;

[0065] Fig.10 It is a graph of the relationship between free gas content and pressure provided by the present invention;

[0066] Fig.11This is a calculation result diagram of the method of Well A provided by the present invention;

[0067] Fig.12 It is a structural schematic diagram of a device for determining gas content in deep coal-rock gas reservoirs provided by the present invention.

[0068] Description of Reference Numerals

[0069] 10-time spectrum acquisition module; 20-free gas signal determination module;

[0070] 30-adsorbed gas signal determination module; 40-time spectrum correction module;

[0071] 50-actual free gas volume determination module; 60-actual adsorbed gas volume determination module;

[0072] 70-gas content determination model building module; 80-data acquisition module;

[0073] 90- Reservoir gas content determination module. DETAILED DESCRIPTION

[0074] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0075] Figure 1 It is a flow chart of the method for determining the gas content of deep coal-rock gas reservoir provided by the present invention; Figure 2 It is the nuclear magnetic T2 spectrum of the nuclear magnetic measurement of the reservoir rock sample after drying provided by the present invention; Figure 3 It is the nuclear magnetic T2 spectrum measured immediately after being inflated to various pressures provided by the present invention; Figure 4 The present invention provides a nuclear magnetic T2 spectrum measured after adsorption equilibrium at each pressure point; Figure 5 It is the T2 spectrum area envelope diagram of the adsorption equilibrium at a certain pressure point measured instantly and at the previous pressure point provided by the present invention; Figure 6 This is a first peak signal separation diagram provided by the present invention; Figure 7 It is a T2 cutoff value division diagram of the free adsorption signal provided by the present invention; Figure 8 It is a relationship diagram between the adsorption free peak T2 cutoff value and pressure provided by the present invention; Fig. 9 is a graph showing the relationship between adsorbed gas content and pressure provided by the present invention; Fig.10 It is a graph of the relationship between free gas content and pressure provided by the present invention; Fig.11 This is a calculation result diagram of the method of Well A provided by the present invention; Fig.12 It is a structural schematic diagram of a device for determining gas content in deep coal-rock gas reservoirs provided by the present invention.

[0076] like Figure 1As shown, an embodiment of the present invention provides a method for determining the gas content of a deep coal-rock gas reservoir, the method comprising:

[0077] Step 1, obtaining a base transverse relaxation time spectrum of the dried reservoir rock sample, a transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and a transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0078] Specifically, in this embodiment, a reservoir rock sample is selected, and the reservoir rock sample is a deep coal rock that can absorb methane gas and has actual mining value. It is ensured that the plunger sample is cut regularly, the shape is complete, and there is no bump, damage, cracking, etc.; the reservoir rock sample is dried, and the temperature during the drying treatment is determined according to the reservoir conditions of the rock sample. It needs to be controlled to ensure that free water and adsorbed water in the rock sample are removed to ensure that no water molecules occupy the adsorption site, and at the same time ensure that the structural water kerogen in the rock sample does not denature and detach. The dried rock sample is placed in a special clamp, and the transverse relaxation time (T2) of the substrate is measured to obtain the substrate transverse relaxation time spectrum of the reservoir rock sample, such as Figure 2 As shown, the horizontal axis is time and the vertical axis is amplitude.

[0079] In addition, the transverse relaxation time (T2) was measured immediately after methane was filled at each designed pressure node. It was verified by an external pressure gauge that the instant transverse relaxation time (T2) measurement was completed within two minutes from the balance of the filling pressure and disconnection of the gas source. During this process, the pressure gauge did not change. Therefore, the increase in the adsorbed gas signal generated by adsorption during this time can be ignored. The transverse relaxation time spectrum before adsorption equilibrium at different pressure points was obtained, as shown in Figure 2. Figure 3 As shown, the horizontal axis is time and the vertical axis is amplitude. After adsorption equilibrium, the transverse relaxation time (T2) is measured again to obtain the transverse relaxation time spectrum after adsorption equilibrium at each pressure point, as shown in Figure 4 As shown, the horizontal axis is time and the vertical axis is amplitude. Specifically, the test can be carried out in a sequence from small to large pressure to simulate the real reservoir situation.

[0080] Step 2: determining the free gas signal at different pressure points based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points;

[0081] In this embodiment, the following steps are taken to determine the free gas signal at different pressure points, including:

[0082] For each pressure point:

[0083] The difference between the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point and the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the n-1th pressure point is taken as the increase in the first peak free gas area at the nth pressure point;

[0084] The sum of the increase in the first peak free gas area from the 1st pressure point to the nth pressure point is taken as the free gas signal at the nth pressure point.

[0085] Specifically, the value of n here is a positive integer, and calculation is performed on each of the 1-N pressure points, wherein the maximum value of n is N, and the free gas signals under the 1-n pressure points are obtained and combined as the free gas signals under different pressure points.

[0086] In another embodiment, the free gas signal at different pressure points may be determined in the following manner, including:

[0087] The free gas signal is calculated using the following formula:

[0088]

[0089] Among them, FTSf n is the free gas signal at the nth pressure point; FTSI i is the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the i-th pressure point; FTSA i-1 is the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the i-1th pressure point.

[0090] like Figure 5 As shown, the free gas signals are at 11.703 MPa and 13.825 MPa.

[0091] Step 3, determining the adsorbed gas signal at different pressure points based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points;

[0092] In this embodiment, for each pressure point:

[0093] The first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point minus the first peak area of ​​the substrate transverse relaxation time spectrum and the free gas signal at the nth pressure point is taken as the adsorbed gas signal at the nth pressure point.

[0094] Specifically, the value of n here is a positive integer, and calculation is performed on each pressure point from 1 to N to obtain free gas signals under the 1st to nth pressure points, which are combined as adsorbed gas signals under different pressure points.

[0095] like Figure 6 As shown, the first peak signal separation diagram is obtained, and the composition of the first peak area can be clearly obtained in the diagram.

[0096] Step 4: determining a corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points based on the substrate transverse relaxation time spectrum, the adsorbed gas signal at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0097] In this embodiment, the following steps are used to determine the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, including:

[0098] For each pressure point:

[0099] Calculating the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum at the nth pressure point, and constructing a first curve at the nth pressure point based on the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum;

[0100] Calculating the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium from the first pressure point to the nth pressure point, and constructing a second curve at the nth pressure point based on the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium;

[0101] Determine the transverse relaxation time corresponding to the intersection of the first curve and the second curve at the nth pressure point;

[0102] The transverse relaxation time is used as the transverse relaxation time cutoff value of the adsorption peak and the free peak of the transverse relaxation time spectrum after adsorption equilibrium at the nth pressure point to obtain the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; the transverse relaxation time cutoff value is used to divide the first peak area and the secondary peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium.

[0103] Specifically, the value of n here is a positive integer, and each point of the pressure points from 1 to N is traversed for calculation to obtain the first curve and the second curve under the 1st to nth pressure points, and the transverse relaxation time corresponding to the intersection of the first curve and the second curve is obtained in the same coordinate system, which is used as the transverse relaxation time cutoff value of the adsorption peak and the free peak of the transverse relaxation time spectrum after adsorption equilibrium, and the new first peak area and secondary peak area are divided, which can accurately separate the adsorbed gas signal area and the free gas signal area in the T2 spectrum under each pressure point. Figure 7 As shown in Figure 3, the newly determined transverse relaxation time cutoff value is more biased towards the first peak of the transverse relaxation time spectrum after adsorption equilibrium.

[0104] In the prior art, the lowest point between the first peak and the secondary peak is usually taken as the dividing point to obtain the first peak area and the secondary peak area. However, the calculated first peak area and the secondary peak area using this method are not accurate enough. Therefore, in this embodiment, by redefining the T2 cutoff value of adsorbed gas and free gas, the adsorbed gas signal area and the free gas signal area in the T2 spectrum at each pressure point are accurately divided, the free gas volume and the adsorbed gas volume can be accurately calculated, the calculation accuracy of the gas content in deep coal reservoirs can be improved, and the accuracy of quantitatively and qualitatively defining the gas occurrence mode of the reservoir can be improved, providing technical support for the detailed evaluation of oilfield reservoirs and reserve declaration.

[0105] In another embodiment, by fitting and analyzing the transverse relaxation time cutoff values ​​at different pressure points, it can be obtained that the relationship between the transverse relaxation time (T2) cutoff value and the pressure at each pressure point is a linear relationship, such as the following formula:

[0106] T2cutoff=j*P+s;

[0107] Where T2cutoff is the transverse relaxation time (T2) cutoff value; P is the pressure; j and s are the fitting coefficients, dimensionless, such as Figure 8 As shown, the change law of the transverse relaxation time (T2) cutoff value under 13.825MPa.

[0108] Step 5: based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual free gas volume at different pressure points is obtained;

[0109] Specifically, in this embodiment, the free gas ratio can be calculated using the following formula:

[0110]

[0111] Then, convert the free gas percentage into the actual free adsorbed gas volume:

[0112] GasA n =k*RFp n *(FTSA′ n -FTSD+STS′ n );

[0113] Thus, the following calculation formula is obtained:

[0114] GasA n = k*(FTSf n +STS′ n );

[0115] Among them, GasA nis the actual free gas volume at the nth pressure point; k is the conversion coefficient, and k = h*Vm / 1000, k is the conversion coefficient between the peak area and the methane gas volume, dimensionless; h is a constant, obtained by fitting the NMR signal with the amount of methane substance; FTSA′ n is the first peak area of ​​the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; FTSD is the total area of ​​the base transverse relaxation time spectrum; FTSf n is the free gas signal at the nth pressure point; STS′ n is the secondary peak area of ​​the transverse relaxation time corrected spectrum after the nth adsorption equilibrium.

[0116] Step 6: Based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual adsorbed gas amount at different pressure points is obtained;

[0117] Specifically, in this embodiment, the free gas ratio can be calculated using the following formula:

[0118]

[0119] Then, convert the free gas percentage into the actual free adsorbed gas volume:

[0120] GasF n = k * RAp n *(FTSA′ n -FTSD+STS′ n );

[0121] Thus, the following calculation formula is obtained:

[0122] GasF n = k*(FTSA′ n -FTSD-FTSf n );

[0123] Among them, GasF n is the actual adsorbed gas volume at the nth pressure point; k is the conversion coefficient, k is the conversion coefficient, and k = h*Vm / 1000, k is the conversion coefficient between the peak area and the methane gas volume, dimensionless; h is a constant, obtained by fitting the NMR signal with the amount of methane substance; FTSA′ n is the first peak area of ​​the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; FTSD is the total area of ​​the base transverse relaxation time spectrum; FTSf n is the free gas signal at the nth pressure point.

[0124] Step 7: Based on the actual adsorbed gas volume and the actual free gas volume at different pressure points, a gas content determination model is constructed;

[0125] In this embodiment, the expression of the gas content determination model is:

[0126] F gas =(a*P) / m;

[0127] A gas =[c*ln(P)+d] / m;

[0128] Among them, F gas A is the actual free gas content of the reservoir rock to be tested; gas is the actual adsorbed gas content of the reservoir rock to be tested; a, c, d are all fitting coefficients; m is the formation pressure of the reservoir rock to be tested; m is the mass of the reservoir rock to be tested after drying.

[0129] like Fig. 9 and Fig.10 As shown, the gas content determination model can be represented by the curve shown in the figure, so that the actual free gas content and the actual adsorbed gas content at different pressure points can be obtained.

[0130] Step 8, obtaining the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be tested after drying;

[0131] Step nine: using the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected as inputs to a gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

[0132] like Fig.11 As shown in the figure, the gas content determination model in this scheme is used for actual application, and the calculation result diagram of Well A in a certain oil field is obtained. In the figure, from left to right, lithology indication data are represented by: depth data; resistivity curve data; CNL, DEN, and DT are three porosity curve data; SW and POR are porosity and saturation data; T2_CUT and CMR are nuclear magnetic logging data; actual free gas volume and adsorbed gas volume calculated by nuclear magnetic method, among which the yellow area in the track is the calculated actual adsorbed gas volume, and the green area is the calculated actual free gas volume; lithology profile data: from left to right in the track, SH represents mudstone, SAND represents sandstone, COAL represents coal seam, SILT represents siltstone, LIME represents limestone, DOLO represents dolomite, and TZNY represents carbonaceous mudstone.

[0133] like Fig.12 As shown, the second aspect of the present invention provides a device for determining the gas content of a deep coal-rock gas reservoir, the device comprising:

[0134] The time spectrum acquisition module 10 is used to acquire the base transverse relaxation time spectrum of the dried reservoir rock sample, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0135] A free gas signal determination module 20, for determining free gas signals at different pressure points based on transverse relaxation time spectra before adsorption equilibrium at different pressure points and transverse relaxation time spectra after adsorption equilibrium at different pressure points;

[0136] The adsorbed gas signal determination module 30 is used to determine the adsorbed gas signal at different pressure points based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points;

[0137] A time spectrum correction module 40 is used to determine a corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points based on the substrate transverse relaxation time spectrum, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0138] The actual free gas volume determination module 50 is used to obtain the actual free gas volume at different pressure points based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points;

[0139] The actual adsorbed gas volume determination module 60 is used to obtain the actual adsorbed gas volume at different pressure points based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points;

[0140] A gas content determination model building module 70 is used to build a gas content determination model based on the actual adsorbed gas content and the actual free gas content at different pressure points;

[0141] The data acquisition module 80 is used to obtain the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected after drying;

[0142] The reservoir gas content determination module 90 is used to use the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected as inputs of the gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

[0143] On the other hand, the present invention provides a readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for determining the gas content of a deep coal-rock gas reservoir.

[0144] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiments can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor (processor) perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0145] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application.

[0146] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0147] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A method for determining the gas content of a deep coal-rock gas reservoir, characterized in that: The method comprises: Obtaining the base transverse relaxation time spectrum of the dried reservoir rock sample, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points; Based on the transverse relaxation time spectra before and after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined; Based on the transverse relaxation time spectrum of the substrate, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points, the adsorbed gas signal at different pressure points is determined; Based on the transverse relaxation time spectrum of the substrate, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points, the corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points is determined; Based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual free gas volume at different pressure points is obtained; Based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual adsorbed gas amount at different pressure points is obtained; Based on the actual free gas volume at different pressure points and the actual adsorbed gas volume at different pressure points, a gas content determination model is constructed; Obtain the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be tested after drying; The rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected are used as inputs of a gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

2. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined, including: For each pressure point: The difference between the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point and the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the n-1th pressure point is taken as the increase in the first peak free gas area at the nth pressure point; The sum of the increase in the first peak free gas area from the 1st pressure point to the nth pressure point is taken as the free gas signal at the nth pressure point.

3. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points, the free gas signals at different pressure points are determined, including: The free gas signal is calculated using the following formula: Among them, FTSf n is the free gas signal at the nth pressure point; FTSI i is the first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the i-th pressure point; FTSA i-1 is the first peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium at the i-1th pressure point.

4. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points and the free gas signal at different pressure points, the adsorbed gas signal at different pressure points is determined, including: For each pressure point: The first peak area of ​​the transverse relaxation time spectrum before adsorption equilibrium at the nth pressure point minus the first peak area of ​​the substrate transverse relaxation time spectrum and the free gas signal at the nth pressure point is taken as the adsorbed gas signal at the nth pressure point.

5. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the substrate transverse relaxation time spectrum, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points, a corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points is determined, including: For each pressure point: Calculating the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum at the nth pressure point, and constructing a first curve at the nth pressure point based on the sum of the first peak areas of the adsorbed gas signal and the substrate transverse relaxation time spectrum; Calculating the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium from the first pressure point to the nth pressure point, and constructing a second curve at the nth pressure point based on the sum of the first peak areas of the transverse relaxation time spectra after adsorption equilibrium; Determine the transverse relaxation time corresponding to the intersection of the first curve and the second curve at the nth pressure point; The transverse relaxation time is used as the transverse relaxation time cutoff value of the adsorption peak and the free peak of the transverse relaxation time spectrum after adsorption equilibrium at the nth pressure point to obtain a transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; The transverse relaxation time cutoff value is used to divide the first peak area and the second peak area of ​​the transverse relaxation time spectrum after adsorption equilibrium.

6. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual free gas volume at different pressure points is obtained, including: GasA n =k*(FTSf n +STS′ n ); Among them, GasA n is the actual free gas volume at the nth pressure point; k is the conversion coefficient; FTSf n is the free gas signal at the nth pressure point; STS′ n is the secondary peak area of ​​the transverse relaxation time corrected spectrum after the nth adsorption equilibrium.

7. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: Based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points, the actual adsorbed gas amount at different pressure points is obtained, including: GasF n =k*(FTSA′ n -FTSD-FTSf n ); Among them, GasF n is the actual adsorbed gas volume at the nth pressure point; k is the conversion coefficient; FTSA n ′ is the first peak area of ​​the transverse relaxation time correction spectrum after adsorption equilibrium at the nth pressure point; FTSD is the total area of ​​the base transverse relaxation time spectrum; FTSf n is the free gas signal at the nth pressure point.

8. The method for determining the gas content of a deep coal-rock gas reservoir according to claim 1, characterized in that: The expression of the gas content determination model is: F gas =(a*P) / m; A gas =[c*ln(P)+d] / m; Among them, F gas A is the actual free gas content of the reservoir rock to be tested; gas is the actual adsorbed gas content of the reservoir rock to be tested; a, c, d are all fitting coefficients; m is the formation pressure of the reservoir rock to be tested; m is the mass of the reservoir rock to be tested after drying.

9. A device for determining the gas content of a deep coal-rock gas reservoir, characterized in that: The device comprises: A time spectrum acquisition module is used to obtain the base transverse relaxation time spectrum of the dried reservoir rock sample, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points; A free gas signal determination module, used to determine the free gas signals at different pressure points based on the transverse relaxation time spectra before adsorption equilibrium at different pressure points and the transverse relaxation time spectra after adsorption equilibrium at different pressure points; An adsorbed gas signal determination module, used to determine the adsorbed gas signal at different pressure points based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the free gas signal at different pressure points; A time spectrum correction module is used to determine the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points based on the substrate transverse relaxation time spectrum, the adsorbed gas signal at different pressure points and the transverse relaxation time spectrum after adsorption equilibrium at different pressure points; An actual free gas volume determination module is used to obtain the actual free gas volume at different pressure points based on the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points; The actual adsorbed gas volume determination module is used to obtain the actual adsorbed gas volume at different pressure points based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points; A gas content determination model building module is used to build a gas content determination model based on the actual free gas content and the actual adsorbed gas content at different pressure points; A data acquisition module, used to obtain the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected after drying; The reservoir gas content determination module is used to take the rock quality and deep coal-rock gas reservoir pressure of the deep coal-rock gas reservoir to be detected as inputs of the gas content determination model to obtain the gas content of the deep coal-rock gas reservoir to be detected.

10. A readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the method for determining the gas content of a deep coal-rock gas reservoir as described in any one of claims 1 to 8.

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