A method for calculating carbon dioxide content parameters based on alkane carbon isotopes

Abstract

The present invention discloses a method for calculating carbon dioxide content parameters based on alkane carbon isotopes, which belongs to the technical field of oil and gas exploration, and comprises the following steps: S1: obtaining carbon dioxide content parameters of multiple layers and methane and ethane carbon isotope data of corresponding layers through oil test data of multiple layers of oil and gas fields; S2: constructing a carbon dioxide content parameter calculation model; S3: correcting carbon dioxide content parameters; S4: outputting results. The present invention provides a fast, reliable, high-precision and low-cost carbon dioxide content parameter calculation method based on wellbore gas methane and ethane carbon isotope data, which is more suitable for application in oil and gas reservoir reserve evaluation and development work.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and in particular to a method for calculating carbon dioxide content parameters based on alkane carbon isotopes. Background Art

[0002] In the context of carbon neutrality, in order to achieve green development of oil and gas reservoirs and reduce carbon dioxide emissions, oilfield technicians need to accurately evaluate the carbon dioxide content in oil and gas reservoirs through various geological data during the calculation of oil and gas reservoir reserves and the evaluation of development plans, so as to accurately estimate the oil and gas reservoir reserve parameters and formulate the optimal oil and gas field development implementation plan to avoid the exploitation of high carbon dioxide oil and gas reservoirs. However, the key to these tasks lies in determining the carbon dioxide content parameters of oil and gas reservoirs under formation environmental conditions.

[0003] At present, there are several ways to determine the carbon dioxide content parameters of oil and gas reservoirs:

[0004] Cable formation pump sampling method: The pressure sampling instrument is lowered to the target layer via a cable, and the formation fluid is sampled in situ by a probe to determine the carbon dioxide content.

[0005] Drill pipe formation testing method: establish seepage channels of oil and gas reservoirs by perforating the target layer, obtain production data of oil and gas reservoirs in the target layer, and take samples to confirm the carbon dioxide content in the oil and gas reservoirs.

[0006] Empirical chart method: Based on regional reservoir logging and production data, an empirical chart of the carbon dioxide content in the oil and gas reservoir and related information such as logging is made to estimate the carbon dioxide content.

[0007] Well logging model calculation method: Based on the rock volume model, a set of well logging response equations is established through neutron, density, resistivity and other logging data. Through optimization and other algorithms, parameters such as formation mineral composition and pore fluid composition are solved to obtain the carbon dioxide content in the oil and gas reservoir.

[0008] In the above centralized methods, cable formation pump sampling is time-efficient, but oil and gas reservoirs are easily affected by mud invasion and the pump sampling fluid has a small range, making the sample representativeness poor. Drill pipe formation testing is expensive and has a long operation cycle, which cannot meet the multi-point sampling needs of oil and gas reservoirs. Well logging information is affected by factors such as formation pressure, hydrogen index, mud content, and wellbore conditions. The empirical chart is highly subjective, and the accuracy of the well logging model in calculating carbon dioxide content is low. Summary of the invention

[0009] The object of the present invention is to provide a method for calculating carbon dioxide content parameters based on alkane carbon isotopes, so as to reduce the calculation cost of carbon dioxide content parameters and improve the calculation accuracy.

[0010] The technical solution of the present invention to solve the above technical problems is as follows:

[0011] A method for calculating carbon dioxide content parameters based on alkane carbon isotopes comprises the following steps:

[0012] S1: Obtain the carbon dioxide content parameters of multiple layers and the carbon isotope data of methane and ethane in the corresponding layers through the oil test data of multiple layers of the oil and gas field;

[0013] S2: Construct a carbon dioxide content parameter calculation model;

[0014] S3: Correction of carbon dioxide content parameters;

[0015] S4: Result output.

[0016] Furthermore, in the above step S1, the carbon dioxide content parameters in the borehole gas of multiple layers and the methane and ethane carbon isotope data of the corresponding layers are collected and recorded during the drilling process, and the interval between adjacent layers is at least 1m.

[0017] Furthermore, the above methane and ethane carbon isotope data take the maximum value of the corresponding layer.

[0018] Furthermore, the above step S2 includes the following steps:

[0019] S21: Combine the carbon isotope data of methane and ethane to construct a composite factor;

[0020] S22: Least square method was used to establish a multivariate regression model between carbon dioxide content parameters and methane and ethane carbon isotope data;

[0021] S23: Use power function fitting analysis to obtain the calculation relationship between the carbon dioxide content parameter and the composite factor.

[0022] Furthermore, in the above step S21, the compound factor is:

[0023] Yz=(13C2H6-13CH4) / (13C2H6+13CH4);

[0024] Where: Yz is the composite factor, dimensionless; 13CH4 is the methane carbon isotope data; 13C2H6 is the ethane carbon isotope data.

[0025] Furthermore, in the above step S22, the model correlation coefficient R of the multivariate regression model is dynamically adjusted so that the model correlation coefficient R is not less than 0.998.

[0026] Furthermore, in the above step S23, the calculation relationship between the carbon dioxide content parameter and the composite factor is:

[0027] V CO2 =a*Yz+b;

[0028] Where: V CO2 is the carbon dioxide content parameter; a and b are both coefficients and are dimensionless.

[0029] Furthermore, the above step S3 includes the following steps:

[0030] S31: Obtain the carbon isotope data of methane and ethane in the corresponding layers from the oil test data of other layers in the same oil and gas field;

[0031] S32: composite factor obtained based on carbon isotope data of methane and ethane in other horizons;

[0032] S33: Calculate the corrected carbon dioxide content parameters of other layers through the calculation relationship between the carbon dioxide content parameter and the composite factor.

[0033] The present invention has the following beneficial effects:

[0034] The present invention provides a fast and reliable method for calculating carbon dioxide content parameters based on the carbon isotope data of methane and ethane measured in borehole gas. It does not require the collection of additional geological basic data and does not incur data collection operation fees. The calculation of carbon dioxide content parameters can be achieved by simply processing and mining the existing geological data. Compared with other existing methods, the calculation results are highly accurate and low in cost, and are more suitable for application in oil and gas reservoir reserve evaluation and development work. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the method for calculating carbon dioxide content parameters based on alkane carbon isotopes in Example 1;

[0036] Figure 2 Schematic diagram of the carbon dioxide content parameter correction model of Example 2. DETAILED DESCRIPTION

[0037] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0038] Embodiment 1:

[0039] Please refer to Figure 1 This embodiment provides a method for calculating carbon dioxide content parameters based on alkane carbon isotopes, comprising the following steps:

[0040] S1: Obtain the carbon dioxide content parameters of multiple layers and the carbon isotope data of methane and ethane in the corresponding layers through the oil test data of multiple layers of the oil and gas field;

[0041] S2: Construct a carbon dioxide content parameter calculation model;

[0042] S3: Correction of carbon dioxide content parameters;

[0043] S4: Output the calculation results of carbon dioxide content parameters and store them for users to use in reservoir reserve evaluation and development implementation plan formulation.

[0044] In step S2 of this embodiment, during the drilling process, the carbon dioxide content parameters in the borehole gas of at least 6 layers and the methane and ethane carbon isotope data of the corresponding layers are collected and recorded, and the depth interval between adjacent layers is at least 1m, and the depth intervals of all adjacent layers are kept consistent. Among them, the carbon dioxide content parameters are obtained by a chromatographic analyzer, and the methane and ethane carbon isotope data are obtained by an alkane carbon isotope detector.

[0045] In order to avoid interference from data from upper and lower non-oil and gas strata, the carbon isotope data of methane and ethane take the maximum value of the corresponding stratum.

[0046] In this embodiment, step S2 includes the following steps:

[0047] S21: Combine the carbon isotope data of methane and ethane to construct a composite factor:

[0048] Yz=(13C2H6-13CH4) / (13C2H6+13CH4);

[0049] Where: Yz is the composite factor, dimensionless; 13CH4 is the methane carbon isotope data; 13C2H6 is the ethane carbon isotope data.

[0050] S22: Use the least squares method to establish a multivariate regression model of carbon dioxide content parameters and methane and ethane carbon isotope data, and dynamically adjust the model correlation coefficient R of the multivariate regression model so that the model correlation coefficient R is not less than 0.99.

[0051] S23: Use power function fitting analysis to obtain the calculation relationship between the carbon dioxide content parameter and the composite factor:

[0052] V CO2 =a*Yz+b;

[0053] Where: V CO2 is the carbon dioxide content parameter; a and b are both coefficients and are dimensionless.

[0054] Thus, a carbon dioxide content parameter correction model is obtained.

[0055] In this embodiment, step S3 includes the following steps:

[0056] S31: Obtain the carbon isotope data of methane and ethane in the corresponding layers from the oil test data of other layers in the same oil and gas field;

[0057] S32: composite factor obtained based on carbon isotope data of methane and ethane in other horizons;

[0058] S33: Calculate the corrected carbon dioxide content parameters of other layers through the calculation relationship between the carbon dioxide content parameter and the composite factor.

[0059] This embodiment provides a fast and reliable method for calculating the carbon dioxide content parameters based on the carbon isotope data of methane and ethane measured in the borehole gas. The accuracy of the calculation results of this embodiment depends on the abundance of the oil test production data in the oil and gas field area. The large amount of oil test data can improve the accuracy of the coefficients a and b values ​​of the carbon dioxide content parameter calculation model. Compared with other existing methods, the calculation results of this method are more accurate. The calculation method of this embodiment does not require the collection of additional geological basic data, and no data collection operation fees are incurred. It only needs to process and mine the existing geological data to realize the calculation of the carbon dioxide content parameters. Compared with other existing methods, the cost is lower. Therefore, the calculation method of this embodiment is more suitable for the application of oil and gas reservoir reserve evaluation and development work.

[0060] Embodiment 2:

[0061] This embodiment provides a specific example to illustrate the entire calibration method, which is not intended to limit the protection scope of the present invention.

[0062] This embodiment provides a method for calculating carbon dioxide content parameters based on alkane carbon isotopes, comprising the following steps:

[0063] S1: Obtain the carbon dioxide content parameters of multiple layers and the carbon isotope data of methane and ethane in the corresponding layers through the oil test data of multiple layers of the oil and gas field;

[0064] S2: Construct a carbon dioxide content parameter calculation model;

[0065] S3: Correction of carbon dioxide content parameters;

[0066] S4: Output the calculation results of carbon dioxide content parameters and store them for users to use in reservoir reserve evaluation and development implementation plan formulation.

[0067] In step S2 of this embodiment, during the drilling process, the carbon dioxide content parameters in the wellbore gas of 6 layers are collected and recorded, as well as the methane and ethane carbon isotope data of the corresponding layers detected by the alkane carbon isotope detector. The depth interval between adjacent layers is 1m, and the depth intervals of all adjacent layers are kept consistent.

[0068] In order to avoid interference from data from upper and lower non-oil and gas strata, the carbon isotope data of methane and ethane take the maximum value of the corresponding stratum.

[0069] In this embodiment, step S2 includes the following steps:

[0070] S21: Combine the carbon isotope data of methane and ethane to construct a composite factor:

[0071] Yz=(13C2H6-13CH4) / (13C2H6+13CH4);

[0072] Where: Yz is the composite factor, dimensionless; 13CH4 is the methane carbon isotope data; 13C2H6 is the ethane carbon isotope data.

[0073] The corresponding carbon dioxide content parameters, methane and ethane carbon isotope data and composite factors of the six groups are shown in Table 1:

[0074] Table 16: Carbon dioxide content parameters, methane and ethane carbon isotope data and composite factors corresponding to the group

[0075]

[0076] S22: The least squares method is used to establish a multiple regression model of carbon dioxide content parameters and methane and ethane carbon isotope data, and the model correlation coefficient R of the multiple regression model is dynamically adjusted to make the model correlation coefficient R 0.99368.

[0077] S23: Please refer to Figure 2 , the calculation relationship between the carbon dioxide content parameter and the composite factor is obtained by using power function fitting analysis:

[0078] V CO2 =-751.08*Yz-40.485;

[0079] Where: V CO2 is the carbon dioxide content parameter.

[0080] Thus, a carbon dioxide content parameter correction model is obtained.

[0081] In this embodiment, step S3 includes the following steps:

[0082] S31: Obtain the carbon isotope data of methane and ethane in the corresponding layers from the oil test data of other layers in the same oil and gas field;

[0083] S32: composite factor obtained based on carbon isotope data of methane and ethane in other horizons;

[0084] S33: Calculate the corrected carbon dioxide content parameters of other layers through the calculation relationship between the carbon dioxide content parameter and the composite factor.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating carbon dioxide content parameters based on alkane carbon isotopes, characterized in that: The following steps are involved: S1: Obtain the carbon dioxide content parameters of multiple layers and the carbon isotope data of methane and ethane in the corresponding layers through the oil test data of multiple layers of the oil and gas field; S2: Construct a carbon dioxide content parameter calculation model; S3: Correction of carbon dioxide content parameters; S4: Result output; Step S2 includes the following steps: S21: Combine the carbon isotope data of methane and ethane to construct a composite factor; S22: Least square method was used to establish a multivariate regression model between carbon dioxide content parameters and methane and ethane carbon isotope data; S23: using a one-variable linear function fitting analysis to obtain a calculation relationship between the carbon dioxide content parameter and the composite factor; In step S21, the compound factor is: Yz=(13C2H6-13CH4) / (13C2H6+13CH4); Among them: Yz is the composite factor, dimensionless; 13CH4 is the methane carbon isotope data; 13C2H6 is the ethane carbon isotope data; In step S22, the model correlation coefficient R of the multivariate regression model is dynamically adjusted so that the model correlation coefficient R is not less than 0.998; In step S23, the calculation relationship between the carbon dioxide content parameter and the composite factor is: V CO2 =a*Yz+b; Where: V CO2 is the carbon dioxide content parameter; a and b are both coefficients, dimensionless; Step S3 includes the following steps: S31: Obtain the carbon isotope data of methane and ethane in the corresponding layers from the oil test data of other layers in the same oil and gas field; S32: composite factor obtained based on carbon isotope data of methane and ethane in other horizons; S33: Calculate the corrected carbon dioxide content parameters of other layers through the calculation relationship between the carbon dioxide content parameter and the composite factor.

2. The method for calculating carbon dioxide content parameters based on alkane carbon isotopes according to claim 1, characterized in that: In step S1, during the drilling process, the carbon dioxide content parameters in the borehole gas of multiple layers and the methane and ethane carbon isotope data of the corresponding layers are collected and recorded, and the interval between adjacent layers is at least 1m.

3. The method for calculating carbon dioxide content parameters based on alkane carbon isotopes according to claim 2, characterized in that: The carbon isotope data of methane and ethane take the maximum value of the corresponding layer.

Images