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

Abstract

The present application provides a kind of deep coal rock gas reservoir gas content determination method, device and readable storage medium, belong to oil and gas exploration technical field.The method includes: obtaining the substrate transverse relaxation time spectrum of reservoir rock sample after drying, the transverse relaxation time spectrum before adsorption equilibrium under different pressure points and the transverse relaxation time spectrum after adsorption equilibrium under different pressure points;Based on the substrate transverse relaxation time spectrum, the transverse relaxation time spectrum before adsorption equilibrium under different pressure points and the transverse relaxation time spectrum after adsorption equilibrium under different pressure points, determine the transverse relaxation time correction spectrum after adsorption equilibrium under different pressure points;Actual free gas content under different pressure points and actual adsorbed gas content under different pressure points are obtained;Construct the gas content determination model for outputing the gas content of the deep coal rock gas reservoir to be detected.The present application redefines the T2 cutoff value of adsorbed gas and free gas, accurately calculates the adsorbed gas content and free gas content, and can improve the calculation accuracy of reservoir gas content.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, in particular to a deep coal rock gas reservoir gas content determination method, a deep coal rock gas reservoir gas content determination device and a readable storage medium. BACKGROUND

[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 micro-pore structure, fluid properties and physical parameters. In recent years, nuclear magnetic resonance technology has also been widely used in the study of fluid occurrence phase state of rock samples with adsorption capacity.

[0003] As an important part of unconventional natural gas development, accurately predicting the in-situ gas content and occurrence state of deep coal rock gas reservoir is very important in resource reserve evaluation and exploitation 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, and the identification of adsorbed gas and free gas relies mainly on conventional logging data, which has limited identification accuracy. Therefore, qualitative and quantitative identification of gas based on accurate experimental calibration is particularly important. In the prior art, isothermal adsorption experiments combined with water-saturated nuclear magnetic resonance have been used to infer the content ratio of free gas and adsorbed gas; isothermal adsorption and nuclear magnetic resonance synchronous dynamic combined measurement experimental devices have been used to conduct isothermal adsorption and nuclear magnetic resonance synchronous dynamic combined measurement experiments on rock samples in adsorbed gas reservoirs; nuclear magnetic resonance combined with isothermal adsorption has been used to determine the content of free methane gas and adsorbed methane gas in shale; isothermal adsorption and nuclear magnetic resonance combined measurement experiments on coal have been used to calculate the free adsorbed gas. However, in the above isothermal adsorption and nuclear magnetic resonance combined measurement experiments applied to qualitative and quantitative identification of gas occurrence phase in rock samples, it is generally assumed that the first peak reflects the adsorbed gas signal and the second peak reflects the free gas signal. However, in actual samples, adsorbed gas and free gas coexist in nanometer pores, so using this method to determine the proportion of free adsorbed gas has certain errors, resulting in inaccurate results. SUMMARY

[0004] The purpose of the embodiments of the present application is to provide a deep coal rock gas reservoir gas content determination method, device and readable storage medium to at least solve the problem of coexistence of adsorbed gas and free gas in nanometer pores, resulting in certain errors in determining the proportion of free adsorbed gas using this method, and inaccurate results.

[0005] To achieve the above purpose, the first aspect of the present application provides a deep coal rock gas reservoir gas content determination method, which comprises:

[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] determine the free gas signal at different pressure points based on the transverse relaxation time spectrum of the base, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the free gas signal at different pressure points;

[0008] determine the adsorbed gas signal at different pressure points based on the transverse relaxation time spectrum of the base, the transverse relaxation time spectrum before adsorption equilibrium at different pressure points, and the free gas signal at different pressure points;

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

[0010] obtain the actual free gas amount at different pressure points based on the free gas signal at different pressure points and the corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0011] obtain the actual adsorbed gas amount at different pressure points based on the transverse relaxation time spectrum of the base, the free gas signal at different pressure points, and the corrected transverse relaxation time spectrum after adsorption equilibrium at different pressure points;

[0012] construct a gas content determination model based on the actual free gas amount at different pressure points and the actual adsorbed gas amount at different pressure points;

[0013] obtain the rock mass and the pressure of the deep coal rock gas reservoir to be detected after drying;

[0014] input the rock mass and the pressure of the deep coal rock gas reservoir to be detected as the input of the gas content determination model, and obtain the gas content of the deep coal rock gas reservoir to be detected.

[0015] Optionally, determining the free gas signal at different pressure points based on 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 includes:

[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-1)th pressure point is taken as the first peak free gas area increase at the nth pressure point;

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

[0019] Optionally, determining the free gas signal at different pressure points based on 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 includes:

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

[0021]

[0022] Where 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 ith pressure point; FTSAi 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, comprising:

[0024] For each pressure point:

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

[0026] Optionally, 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, the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points is determined, comprising:

[0027] For each pressure point:

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

[0029] Calculating the sum of the first peak areas of the transverse relaxation time spectrum after adsorption equilibrium at the 1st 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 spectrum after adsorption equilibrium;

[0030] Determining the intersection point of the first curve and the second curve at the nth pressure point as the transverse relaxation time;

[0031] Taking the transverse relaxation time 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 second 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 corrected spectrum after adsorption equilibrium at different pressure points, the actual free gas amount at different pressure points is obtained, including:

[0033] GasA n = k * (FTSf n + STS' n ) ;

[0034] Wherein, GasA n is the actual free gas amount 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 adsorption equilibrium at the nth pressure point.

[0035] Optionally, based on the substrate transverse relaxation time spectrum, the free gas signal at different pressure points and the transverse relaxation time corrected 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] Wherein, GasF n is the actual adsorbed gas amount at the nth pressure point; k is the conversion coefficient; FTSA' n is the first peak area of the transverse relaxation time corrected spectrum after adsorption equilibrium at the nth pressure point; FTSD is the total area of the substrate 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] Wherein, F gas is the actual free gas content of the reservoir rock to be detected; A gas is the actual adsorbed gas content of the reservoir rock to be detected; a, c, d are all fitting coefficients; m is the formation pressure of the reservoir rock to be detected; m is the mass of the reservoir rock to be detected after drying.

[0042] The second aspect of the present application provides a deep coal rock gas reservoir gas content determination device, the device comprises:

[0043] a time spectrum acquisition module configured to acquire 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;

[0044] a free gas signal determination module configured to determine a free gas signal at different pressure points based on 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;

[0045] an adsorbed gas signal determination module configured to determine an adsorbed gas signal at different pressure points based on the base 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 configured to determine a transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points based on the base 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] a real free gas amount determination module configured to obtain a real free gas amount 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] a real adsorbed gas amount determination module configured to obtain a real adsorbed gas amount at different pressure points based on the base 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 establishment module configured to establish a gas content determination model based on the real adsorbed gas amount at different pressure points and the real free gas amount at different pressure points;

[0050] a data acquisition module configured to acquire rock quality and reservoir pressure of a deep coal rock gas reservoir to be detected after drying;

[0051] a reservoir gas content determination module configured to input the rock quality and reservoir pressure of the deep coal rock gas reservoir to be detected after drying into the gas content determination model to obtain a gas content of the deep coal rock gas reservoir to be detected.

[0052] In another aspect, the present application provides a readable storage medium having instructions stored thereon, the instructions being used to cause a machine to perform the deep coal rock gas reservoir gas content determination method.

[0053] The technical scheme separates the first peak gas signal of different occurrence states through twice measurement of the transverse relaxation time measurement before and after the adsorption equilibrium of the methane gas filled under different pressure points, redefines the T2 cutoff value of the adsorbed gas and the free gas, accurately calculates the free gas amount and the adsorbed gas amount, improves the calculation precision of the gas content of the deep coal rock reservoir, improves the precision of the quantitative and qualitative definition of the gas occurrence mode of the reservoir, and provides technical support for the fine evaluation of the oilfield reservoir and the reserve declaration.

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

[0055] The accompanying drawings are included to provide a further understanding of the embodiments of the present application, and constitute a part of the specification, and are used to explain the embodiments of the present application together with the following detailed description, but do not constitute a limitation of the embodiments of the present application. In the drawings:

[0056] Figure 1 is a flowchart of the method for determining the gas content of the deep coal rock gas reservoir provided by the present application;

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

[0058] Figure 3 is a nuclear magnetic T2 spectrum diagram of the immediate measurement after the gas filling to each pressure provided by the present application;

[0059] Figure 4 is a nuclear magnetic T2 spectrum diagram of the measurement after the adsorption equilibrium of each pressure point provided by the present application;

[0060] Figure 5 is a T2 spectrum area envelope diagram of the immediate measurement under a certain pressure point and the adsorption equilibrium T2 spectrum under the last pressure point provided by the present application;

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

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

[0063] Figure 8 is an adsorbed free peak T2 cutoff value and pressure relationship diagram provided by the present application;

[0064] Figure 9 is an adsorbed gas content and pressure relationship diagram provided by the present application;

[0065] Figure 10 is a free gas content and pressure relationship diagram provided by the present application;

[0066] Figure 11is a calculation result graph of the A well method provided by the present application;

[0067] Figure 12 is a structure schematic diagram of the deep coal rock gas reservoir gas content determination device provided by the present application.

[0068] Reference signs

[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 amount determination module; 60-actual adsorbed gas amount determination module;

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

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

[0074] The specific embodiments of the present application will be described in detail below in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0075] Figure 1 is a flow chart of the deep coal rock gas reservoir gas content determination method provided by the present application; Figure 2 is a nuclear magnetic T2 spectrum graph of the nuclear magnetic measurement of the reservoir rock sample after drying provided by the present application; Figure 3 is a nuclear magnetic T2 spectrum graph of the immediate measurement after charging to each pressure provided by the present application; Figure 4 is a nuclear magnetic T2 spectrum graph measured after the adsorption equilibrium of each pressure point provided by the present application; Figure 5 is an area envelope graph of the immediate measurement at a certain pressure point and the adsorption equilibrium T2 spectrum at the last pressure point provided by the present application; Figure 6 is a first peak signal separation graph provided by the present application; Figure 7 is a free adsorption signal T2 cutoff value division graph provided by the present application; Figure 8 is a graph of the relationship between the adsorption free peak T2 cutoff value and the pressure provided by the present application; Figure 9 is a graph of the relationship between the adsorbed gas content and the pressure provided by the present application; Figure 10 is a graph of the relationship between the free gas content and the pressure provided by the present application; Figure 11 is a calculation result graph of the A well method provided by the present application; Figure 12 is a structure schematic diagram of the deep coal rock gas reservoir gas content determination device provided by the present application.

[0076] As Figure 1As shown, the embodiment of the present application provides a method for determining the gas content of a deep coal rock gas reservoir, which comprises:

[0077] Step one, 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;

[0078] Specifically, in this embodiment, a reservoir rock sample is selected, which is a reservoir rock sample capable of adsorbing methane gas and having actual exploitation value, to ensure that the plug sample is cut regularly, is complete in shape, and is free of damage, cracking, etc. The reservoir rock sample is subjected to drying treatment, and the temperature during the drying treatment is determined according to the reservoir condition of the rock sample, and needs to be controlled to remove the free water and adsorbed water of the rock sample to ensure that no water molecules occupy the adsorption sites, while ensuring that the structural water such as cheese in the rock sample does not denature and separate. The dried rock sample is placed into a special clamp, and the base transverse relaxation time (T2) is measured to obtain the base transverse relaxation time spectrum of the reservoir rock sample, as shown in FIG. 2. Figure 2 As shown, the abscissa is time, and the ordinate is amplitude.

[0079] In addition, the transverse relaxation time (T2) is measured immediately after the methane is filled at each designed pressure point, and the external pressure gauge is verified. The filling pressure is balanced and the gas source is disconnected, and the real-time transverse relaxation time (T2) measurement is completed within two minutes. During this process, the pressure gauge does not change, so the adsorption gas signal increment generated during this time can be ignored. The transverse relaxation time spectrum before adsorption equilibrium at different pressure points is obtained, as shown in FIG. 3. Figure 3 As shown, the abscissa is time, and the ordinate is amplitude. The transverse relaxation time (T2) is measured again after adsorption equilibrium to obtain the transverse relaxation time spectrum after adsorption equilibrium at different pressure points, as shown in FIG. 4. Figure 4 As shown, the abscissa is time, and the ordinate is amplitude. Specifically, the test can be performed in the order of increasing pressure to simulate the actual reservoir condition.

[0080] Step two, determining the free gas signal at different pressure points based on 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;

[0081] In this embodiment, the free gas signal at different pressure points is determined by the following steps, which comprise:

[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-1)th pressure point is taken as the first peak free gas area increment at the nth pressure point;

[0084] The sum of the increase in the first peak free gas area from the first 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, where the maximum value of n is N, and the free gas signals under the 1-n pressure points are obtained and merged 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 at 11.703 MPa and 13.825 MPa.

[0091] Step 3: 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;

[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 the free gas signals under the 1st to nth pressure points, which are combined as the 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 four, determining the transverse relaxation time correction spectrum after adsorption equilibrium at different pressure points 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;

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

[0098] For each pressure point:

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

[0100] calculating the sum of the first peak area of the transverse relaxation time spectrum after adsorption equilibrium at 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 area of the transverse relaxation time spectrum after adsorption equilibrium;

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

[0102] taking the transverse relaxation time 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 is a positive integer, and each point of the pressure points from 1 to N is calculated to obtain the first curve and the second curve at the first to nth pressure points, and the intersection point of the first curve and the second curve corresponding to the transverse relaxation time in the same coordinate system is obtained as the transverse relaxation time cutoff value of the adsorption peak and the free peak of the transverse relaxation time spectrum after adsorption equilibrium, to divide the new first peak area and the secondary peak area, so as to accurately separate the adsorbed gas signal region and the free gas signal region in the T2 spectrum at each pressure point. As shown in the following figure, the newly determined transverse relaxation time cutoff value is more inclined to the first peak of the transverse relaxation time spectrum after adsorption equilibrium. Figure 7

[0104] ​In the prior art, the minimum point between the first peak and the second peak is usually taken as the division to obtain the first peak area and the second peak area. However, the first peak area and the second peak area calculated in this way are not accurate enough. Therefore, in the present embodiment, by redefining the T2 cutoff value of the adsorbed gas and the free gas, the adsorbed gas signal region and the free gas signal region in the T2 spectrum at each pressure point are accurately divided, the free gas amount and the adsorbed gas amount can be accurately calculated, the calculation accuracy of the gas content of the deep coal rock reservoir is improved, the accuracy of quantitatively and qualitatively defining the gas occurrence mode of the reservoir is improved, and technical support is provided for fine evaluation of the oilfield reservoir and declaration of the reserves.

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

[0106] T2cutoff = j*P + s;

[0107] In the formula, T2cutoff is the transverse relaxation time (T2) cutoff value; P is the pressure; j and s are fitting coefficients, which are dimensionless; and the following formula is used to calculate the transverse relaxation time (T2) cutoff value at 13.825 MPa: Figure 8

[0108] Step five, based on the free gas signal at different pressure points and the transverse relaxation time corrected spectrum after adsorption equilibrium at different pressure points, the actual free gas amount at different pressure points is obtained;

[0109] Specifically, in the present embodiment, the following formula can be used to calculate the free gas proportion first:

[0110]

[0111] Then, the free gas proportion is converted into the actual free adsorbed gas amount:

[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] Wherein, GasA n ​is 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 peak area and 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 spectrum corrected for the transverse relaxation time 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 amount:

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

[0121] This results in the following calculation formula:

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

[0129] As shown in Figure 9 and Figure 10 , 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 under different pressure points can be obtained.

[0130] Step eight, obtaining the mass of the rock of the deep coal rock gas reservoir to be detected after drying and the pressure of the deep coal rock gas reservoir;

[0131] Step nine, taking the mass of the rock of the deep coal rock gas reservoir to be detected and the pressure of the deep coal rock gas reservoir as inputs of the gas content determination model, obtaining the gas content of the deep coal rock gas reservoir to be detected.

[0132] As shown in Figure 11 , the gas content determination model in the present scheme is actually used, and the calculation result graph of well A in a certain oilfield is obtained. In the graph, from left to right, the lithology indication data, the depth data, the resistivity curve data, the CNL, DEN, DT, the porosity and saturation data, the T2_CUT, CMR, the actual free gas content and the adsorbed gas content calculated by the nuclear magnetic logging data are represented. Among them, the yellow area in the channel is the calculated actual adsorbed gas content, and the green area is the calculated actual free gas content. The lithology profile data: the data in the channel from left to right, SH represents mudstone, SAND represents sandstone, COAL represents coal seam, SILT represents siltstone, LIME represents limestone, DOLO represents dolomite, and TZN represents carbonaceous mudstone.

[0133] As shown in Figure 12 , the second aspect of the present application provides a deep coal rock gas reservoir gas content determination device, which comprises:

[0134] The time spectrum acquisition module 10 is configured to acquire the base T2 spectrum of the dried reservoir rock sample, the T2 spectrum before adsorption equilibrium at different pressure points, and the T2 spectrum after adsorption equilibrium at different pressure points.

[0135] The free gas signal determination module 20 is configured to determine the free gas signal at different pressure points based on the T2 spectrum before adsorption equilibrium at different pressure points and the T2 spectrum after adsorption equilibrium at different pressure points.

[0136] The adsorbed gas signal determination module 30 is configured to determine the adsorbed gas signal at different pressure points based on the base T2 spectrum, the T2 spectrum before adsorption equilibrium at different pressure points, and the free gas signal at different pressure points.

[0137] The time spectrum correction module 40 is configured to determine the corrected T2 spectrum after adsorption equilibrium at different pressure points based on the base T2 spectrum, the adsorbed gas signal at different pressure points, and the T2 spectrum after adsorption equilibrium at different pressure points.

[0138] The actual free gas amount determination module 50 is configured to obtain the actual free gas amount at different pressure points based on the free gas signal at different pressure points and the corrected T2 spectrum after adsorption equilibrium at different pressure points.

[0139] The actual adsorbed gas amount determination module 60 is configured to obtain the actual adsorbed gas amount at different pressure points based on the base T2 spectrum, the free gas signal at different pressure points, and the corrected T2 spectrum after adsorption equilibrium at different pressure points.

[0140] The gas content determination model establishment module 70 is configured to establish a gas content determination model based on the actual adsorbed gas amount at different pressure points and the actual free gas amount at different pressure points.

[0141] The data acquisition module 80 is configured to acquire the rock quality of the dried deep coal rock gas reservoir to be detected and the deep coal rock gas reservoir pressure.

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

[0143] In another aspect, the present application provides a readable storage medium, which stores instructions for causing a machine to perform the deep coal rock gas reservoir gas content determination method.

[0144] Those skilled in the art can understand that all or part of the steps of the method for implementing the above-mentioned embodiments can be instructed by a program to relevant hardware, the program is stored in a storage medium, and includes a plurality of instructions for enabling a single-chip microcomputer, a chip or a processor to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0145] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or in the form of software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the present application.

[0146] The optional embodiments of the present application are described in detail above in combination with the drawings, but the embodiments of the present application are not limited to the specific details in the above-mentioned embodiments, and within the technical concept range of the embodiments of the present application, the technical solutions of the embodiments of the present application can be subjected to various simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present application. In addition, it should be noted that each specific technical feature described in the above-mentioned specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, various possible combination manners are not described again in the embodiments of the present application.

[0147] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the embodiments of the present application, and it should be considered as the disclosed content of the embodiments of the present application.

Claims

1. A method for determining the gas content of a deep coal-rock gas reservoir, characterized in that: The method comprises: 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; 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 amount 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 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 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, wherein: 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, 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 first 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, wherein: 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, 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, wherein: 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, wherein: 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, 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 n-th pressure point, and constructing a first curve at the n-th 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 amount 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, wherein: 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, wherein: 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 is the actual free gas content of the reservoir rock to be tested; A gas is the actual adsorbed gas content of the reservoir rock to be tested; a, c, and d are all fitting coefficients; m is the formation pressure of the reservoir rock to be tested; and 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 is used to determine 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; An adsorbed gas signal determination module 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; A time spectrum correction module is used to determine the 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; The 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 amount determination module is used to obtain the actual adsorbed gas amount 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 actual adsorbed gas content at different pressure points; A data acquisition module 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; 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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