A method for identifying oil and gas layers in gas logging

Abstract

The present invention relates to the technical field of oilfield exploration, and particularly to a method for identifying oil and gas layers by gas logging. The method comprises the following steps: collecting gas logging data, well logging data and oil test data of wells drilled in multiple working areas, extracting gas logging anomaly value calculation parameters corresponding to anomaly display segments according to a gas logging anomaly statistical table in the gas logging data, drawing a scatter plot according to the parameters to obtain a gas logging interpretation chart, and when determining the oil layer position of a new well, bringing T3, T4, and T5 values into the gas logging interpretation chart, and finding which interpretation area the numerical points of the abnormal segment fall into is the interpretation result of the abnormal segment. When analyzing and determining a new well, the present invention can quickly identify which interpretation area the numerical points of the abnormal segment fall into according to the gas logging interpretation chart, thereby improving the application scope of gas logging and the efficiency and accuracy of oil and gas layer identification, and meeting the requirements of oil and gas exploration.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field exploration, and in particular to a method for identifying oil and gas layers in gas logging. Background Art

[0002] Gas logging is a method of directly measuring the combustible gas content in drilling fluid. Gas logging is performed during drilling. Using this data, you can detect and catalog the composition and content of gases carried by drilling fluid returning from the bottom of the well, as measured by a degasser placed before the shaker. This allows you to identify oil and gas formations. Gas logging is a method used during drilling. Gas logging data can be used to promptly identify oil and gas indications and predict blowouts, making it widely used in oil and gas wells.

[0003] During the oil production process, a certain amount of associated gas is generated. The lighter the oil and the higher the maturity, the more associated gas there is. Under formation conditions, associated gas exists in the reservoir in two forms: dissolved and free. When the oil and gas reservoir is drilled through by the drill bit, the fluid it contains is carried to the surface by the drilling fluid. During the return process, as the pressure and temperature decrease, the natural gas expands rapidly and is released. The natural gas in the drilling fluid is removed by the degasser and measured by the gas meter. The measured gas parameters mainly include total hydrocarbons, CH4, C2H6, C3H8, iC4H 10 、nC4H 10 、iC5H 12 、nC5H 12 , H2, CO2, etc.

[0004] Commonly used oil and gas reservoir identification charts in existing technologies include the Pixler chart, the triangle chart, and the 3H chart. These three charts are primarily based on a combination of gas logging components (C1-C5) and fail to consider the total hydrocarbon value (TG). Research has shown that these charts are less effective in complex oil and gas reservoirs (such as low-permeability reservoirs), and their accuracy in oil and gas reservoir identification cannot meet current oil and gas exploration requirements.

[0005] Therefore, how to propose a new solution for identifying oil and gas layers by gas logging, which can establish a new type of oil and gas layer identification chart for gas logging, achieve good application results in some complex oil and gas layers (such as low permeability oil and gas layers), and make the oil and gas layer identification accuracy meet the needs of existing oil and gas layer exploration is a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0006] In view of this, the present invention provides a method for identifying oil and gas layers by gas logging. By analyzing gas logging data and test data, a gas logging interpretation map is established, which improves the application scope of gas logging and the efficiency and accuracy of oil and gas layer identification, and meets the requirements of oil and gas exploration.

[0007] To solve the above technical problems, the present invention provides a method for identifying oil and gas layers in gas logging, comprising the following steps:

[0008] S1. Collect gas logging data, well logging data and oil testing data of completed wells in multiple work areas;

[0009] S2. Extracting the gas measurement abnormality value corresponding to the abnormal display segment according to the gas measurement abnormality statistical table in the gas measurement data in step S1;

[0010] S3. Calculate the following parameters based on the abnormal gas measurement value in step S2:

[0011] TG=C1+C2+C3+iC4+nC4+iC5+nC5

[0012] Heavy hydrocarbons = C2+C3+iC4+nC4+iC5+nC5

[0013] WH=Heavy hydrocarbons / total hydrocarbons

[0014] BH=(C1+C2) / (C3+iC4+nC4+iC5+nC5)

[0015] T3=C3 / C1

[0016] T4,5=(iC4+nC4+iC5+nC5) / C1;

[0017] Among them, TG is total hydrocarbon, WH is moisture ratio, BH (equilibrium ratio), T3 is the change trend of component value C3 relative to C1, and T4,5 is the change trend of the two components of heavy components C4 and C5 relative to C1;

[0018] S4. Draw a scatter plot based on the parameters obtained in step S3, with T3 as the horizontal coordinate and T4,5 as the vertical coordinate, to obtain a gas logging interpretation chart;

[0019] S5, extracting the gas logging abnormal value corresponding to the abnormal display section of the new well, and calculating T3, T4,5 values based on the gas logging abnormal value;

[0020] S6. Substitute the T3 and T4,5 values in step S5 into the gas logging interpretation chart in step S4 to see which interpretation area the numerical point of the abnormal segment falls into, which is the interpretation result of the abnormal segment.

[0021] Furthermore, the gas test abnormal values include CH4, C2H6, C3H8, iC4H 10 、nC4H 10 、iC5H 12 、nC5H 12 .

[0022] Furthermore, the gas logging interpretation map is a map of the distribution areas of oil layers, poor oil layers, oil-water layers, and oil-water layers / water layers.

[0023] Furthermore, the gas measured in the gas detection anomaly statistical table consists of three parts: broken gas, diffused gas and permeated gas.

[0024] Furthermore, the crushing gas is the natural gas released after the rock is crushed, the diffusion gas is the formation gas diffused into the wellbore under the action of pressure difference, and the permeation gas is the formation gas that penetrates into the wellbore under the action of concentration difference.

[0025] The beneficial effects of the above technical solution of the present invention are as follows:

[0026] The present invention provides a method for identifying oil and gas layers using gas logging. By analyzing gas logging data and test data, a gas logging interpretation chart is established. When analyzing and judging a new well, the gas logging interpretation chart can be used to quickly identify in which interpretation area the numerical points of the abnormal section fall. This improves the application range of gas logging and the efficiency and accuracy of oil and gas layer identification, meeting the requirements of oil and gas exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The histogram of the relationship between T3 (C3 / C1) and oil layer type in the present invention;

[0028] Figure 2 The histogram of the relationship between T4,5 ((C4+C5) / C1) and reservoir type in the present invention;

[0029] Figure 3 This is the gas measurement explanation plate in the present invention. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1-3 , clearly and completely describing the technical solutions of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by ordinary technicians in this field fall within the scope of protection of the present invention.

[0031] Gas logging is a geochemical logging method that identifies the properties of reservoir fluids by measuring the content and composition of hydrocarbon gases in the formation.

[0032] During the oil production process, a certain amount of associated gas is generated. The lighter the oil and the higher the maturity, the more associated gas there is. Under formation conditions, associated gas exists in the reservoir in two forms: dissolved and free. When the oil and gas reservoir is drilled through by the drill bit, the fluid it contains is carried to the surface by the drilling fluid. During the return process, as the pressure and temperature decrease, the natural gas expands rapidly and is released. The natural gas in the drilling fluid is removed by the degasser and measured by the gas meter. The measured gas parameters mainly include total hydrocarbons, CH4, C2H6, C3H8, iC4H 10 、nC4H 10 、iC5H 12 、nC5H 12 , H2, CO2, etc.

[0033] Diffuse gas is generated during near-balanced or underbalanced drilling, or after drilling through high-pressure oil and gas zones. Penetration gas is generated when the formation gas concentration exceeds the gas concentration in the drilling fluid. The presence of diffuse and penetrating gas increases the total hydrocarbon value and results in a high base value. Generally, the density of the drilling fluid is slightly greater than the formation pressure coefficient, so diffuse and penetrating gas are minimal, and gas logging primarily measures fractured gas.

[0034] A method for identifying oil and gas layers by gas logging comprises the following steps:

[0035] S1. Collect gas logging data, well logging data and oil testing data of completed wells in multiple work areas;

[0036] S2. Extracting the gas measurement abnormality value corresponding to the abnormal display segment according to the gas measurement abnormality statistical table in the gas measurement data in step S1;

[0037] S3. Calculate the following parameters based on the abnormal gas measurement value in step S2:

[0038] TG=C1+C2+C3+iC4+nC4+iC5+nC5

[0039] Heavy hydrocarbons = C2+C3+iC4+nC4+iC5+nC5

[0040] WH=Heavy hydrocarbons / total hydrocarbons

[0041] BH=(C1+C2) / (C3+iC4+nC4+iC5+nC5)

[0042] T3=C3 / C1

[0043] T4,5=(iC4+nC4+iC5+nC5) / C1;

[0044] Among them, TG is total hydrocarbon, WH is moisture ratio, BH (equilibrium ratio), T3 is the change trend of component value C3 relative to C1, and T4,5 is the change trend of the two components of heavy components C4 and C5 relative to C1;

[0045] S4. Draw a scatter plot based on the parameters obtained in step S3, with T3 as the horizontal coordinate and T4,5 as the vertical coordinate, to obtain a gas logging interpretation chart;

[0046] S5, extracting the gas logging abnormal value corresponding to the abnormal display section of the new well, and calculating T3, T4,5 values based on the gas logging abnormal value;

[0047] S6. Substitute the T3 and T4,5 values in step S5 into the gas logging interpretation chart in step S4 to see which interpretation area the numerical point of the abnormal segment falls into, which is the interpretation result of the abnormal segment.

[0048] Among them, the gas test abnormal values include CH4, C2H6, C3H8, iC4H 10 、nC4H 10 、iC5H 12 、nC5H 12 The gas measured in the gas logging anomaly statistics table consists of three parts: broken gas, diffused gas and permeable gas. The broken gas is the natural gas released after the rock is broken, the diffused gas is the formation gas diffused into the wellbore under the action of pressure difference, and the permeable gas is the formation gas that penetrates into the wellbore under the action of concentration difference. The gas logging interpretation map is a map of the distribution areas of oil layers, differential oil layers, oil-water layers, and oil-water layers / water layers.

[0049] The gas logging interpretation procedure includes stratification, value selection, calculation, drawing and interpretation, as follows:

[0050] (1) Layering principle:

[0051] The well section where the total hydrocarbon is twice the base value is an abnormal well section; the top and bottom depths of the abnormal well section are determined based on the principle of drilling from high to low and total hydrocarbon from low to high, and referring to lithology, electrical properties, etc.

[0052] (2) Value selection principles:

[0053] The lowest and highest values of the abnormal well section are selected for total hydrocarbons. The high and low range values within the abnormal well section are selected starting from one meter of top depth during drilling. The while-drilling and total stripping data with the highest total hydrocarbon amount and the most complete components are selected.

[0054] (3) Parameter calculation:

[0055] Calculate the relative percentage of each component, dilution coefficient, drilling fluid gas content, formation gas content, etc.

[0056] (4) Drawing submission:

[0057] According to the calculated parameters, the plot is made on the drawing board to determine the location of the value point.

[0058] (5) Comprehensive explanation:

[0059] On the basis of gas logging data, combined with lithologic data, electrical data, geochemical data, and adjacent well data, a comprehensive judgment of fluid properties is made.

[0060] The total hydrocarbon curve is the only continuous curve among all wellbore measurement methods that can detect formation hydrocarbon gas in real time. Its height and curve shape directly reflect the vertical changes of oil and gas. Therefore, the peak shape of the total hydrocarbon curve can also be used to make a preliminary judgment on the reservoir fluid properties. Through the analysis of a large amount of data, the following seven types have been extracted: full shape, underfull shape, single peak, wavy shape, finger shape, inverted triangle, and regular triangle, as shown in Table 1-1:

[0061] Table 1-1 Correspondence between the total hydrocarbon curve shape and oil layer type

[0062]

[0063]

[0064] Experimental Example 1

[0065] 1. Data Table

[0066] The following 26 wells (see Table 4-1) were selected as the subject of this gas logging research project. Based on the oil test results, the gas logging component values and gas logging parameter values for oil layers, poor oil layers, oil-water layers, oil-water layers, and water layers are tabulated below (see Tables 4-2 to 4-6).

[0067] Table 4-1 Logging, oil testing and gas logging interpretation of 26 wells

[0068]

[0069] Continued Table 4-1-1

[0070]

[0071] Table 4-2 Oil layer data

[0072]

[0073] Continued Table 4-2-1 Oil Reservoir Data

[0074] 32 0.8814 0.2660 0.4210 0.1811 0.3908 0.2131 0.2279 2.5813 33 0.9069 0.2450 0.4015 0.1811 0.3728 0.2026 0.2144 2.5243 34 0.9814 0.2380 0.3950 0.1811 0.3668 0.1991 0.2079 2.5693 35 1.2194 0.2466 0.4120 0.1270 0.2925 0.1094 0.1132 2.5201 36 0.9595 0.2122 0.3806 0.1171 0.2741 0.1053 0.1105 2.1593 37 1.2981 0.2518 0.4049 0.1193 0.2783 0.1059 0.1107 2.5690 38 0.5223 0.1289 0.2664 0.0734 0.1770 0.0730 0.0803 1.3213 39 0.3511 0.0925 0.2017 0.0567 0.1380 0.0595 0.0663 0.9658 40 0.4704 0.1103 0.2264 0.0615 0.1501 0.0638 0.0714 1.1539 41 1.2620 0.2728 0.4430 0.1316 0.3028 0.1251 0.1327 2.6700

[0075] Continued Table 4-2-2

[0076]

[0077] Continued Table 4-2-3

[0078]

[0079] Table 4-3 Poor oil layer data

[0080]

[0081] Continued Table 4-3-1

[0082]

[0083] Table 4-4 Oil and water in the same layer data

[0084]

[0085] Continued Table 4-4-1

[0086]

[0087] Table 4-5 Data of oil-bearing water layers

[0088]

[0089] Continued Table 4-5-1

[0090]

[0091] Table 4-6 Water layer data

[0092]

[0093] Continued Table 4-6-1 Water Layer Data

[0094]

[0095] According to the data analysis in the above table,

[0096] TG=C1+C2+C3+iC4+nC4+iC5+nC5

[0097] Heavy hydrocarbons = C2+C3+iC4+nC4+iC5+nC5

[0098] WH=Heavy hydrocarbons / total hydrocarbons

[0099] BH=(C1+C2) / (C3+iC4+nC4+iC5+nC5)

[0100] T3=C3 / C1

[0101] T4,5=(iC4+nC4+iC5+nC5) / C1;

[0102] It can be seen that the relationship between the five parameters TG (total hydrocarbons), heavy hydrocarbons, WH (humidity ratio), BH (balance ratio), and T3 and the reservoir type is shown in Table 4-7:

[0103] Table 4-7 Relationship between parameter curves and reservoir types

[0104]

[0105] After analyzing the gas logging data of 26 wells, the interval values of 6 gas logging parameters corresponding to different oil layer types were obtained (see Table 4-8 below).

[0106] Table 4-8 Parameter interval values corresponding to different reservoir types

[0107]

[0108] After analyzing the gas logging data of 26 wells, it was found that the two parameters T3 and T4,5 can more accurately determine the reservoir type. The relationship between T3 and T4,5 and the reservoir type is shown in the histogram. Figure 1 、 Figure 2 .

[0109] Based on the gas logging parameter data of 26 wells, a scatter plot was drawn with T3 as the horizontal axis and T4,5 as the vertical axis to divide the oil layer type area, and the gas logging interpretation map was obtained, see Figure 3 .

[0110] Based on the gas logging interpretation chart, when determining the location of oil and gas layers in a new well, it is only necessary to extract the gas logging anomaly value corresponding to the abnormal display segment of the new well, and calculate the T3, T4,5 values based on the gas logging anomaly value. The obtained T3, T4,5 values are then brought into the gas logging interpretation chart. The interpretation result of the abnormal segment is determined by looking at which interpretation area the numerical point of the abnormal segment falls.

[0111] In the present invention, unless otherwise clearly specified and limited, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be internal communication between two elements or an interaction relationship between two elements. Unless otherwise clearly specified and limited, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to specific circumstances.

[0112] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for identifying oil and gas layers by gas logging, characterized in that: The following steps are involved: S1. Collect gas logging data, well logging data and oil testing data of completed wells in multiple work areas; S2. Extracting the gas measurement abnormality value corresponding to the abnormal display segment according to the gas measurement abnormality statistical table in the gas measurement data in step S1; S3. Calculate the following parameters based on the abnormal gas measurement value in step S2: TG=C1+C2+C3+iC4+nC4+iC5+nC5 Heavy hydrocarbons = C2+C3+iC4+nC4+iC5+nC5 WH=Heavy hydrocarbons / total hydrocarbons BH=(C1+C2) / (C3+iC4+nC4+iC5+nC5) T3=C3 / C1 T4,5=(iC4+nC4+iC5+nC5) / C1; Among them, TG is total hydrocarbon, WH is moisture ratio, BH is equilibrium ratio, T3 is the change trend of component value C3 relative to C1, and T4,5 is the change trend of heavy components C4 and C5 relative to C1; S4. Draw a scatter plot based on the parameters obtained in step S3, with T3 as the horizontal coordinate and T4,5 as the vertical coordinate, to obtain a gas logging interpretation chart; S5, extracting the gas logging abnormal value corresponding to the abnormal display section of the new well, and calculating T3, T4,5 values based on the gas logging abnormal value; S6. Substitute the T3 and T4,5 values obtained in step S5 into the gas logging interpretation chart obtained in step S4 to determine the interpretation area where the numerical value of the abnormal segment falls, which is the interpretation result of the abnormal segment. The gas logging interpretation map is a map of the distribution areas of oil layers, poor oil layers, oil-water layers, and oil-water layers / water layers.

2. The method for identifying oil and gas layers by gas logging according to claim 1, wherein: The abnormal gas test values include CH4, C2H6, C3H8, iC4H 10 、nC4H 10 、iC5H 12 、nC5H 12 .

3. The method for identifying oil and gas layers by gas logging according to claim 1, wherein: The gas measured in the gas measurement anomaly statistics table consists of three parts: broken gas, diffused gas and permeated gas.

4. The method for identifying oil and gas layers by gas logging according to claim 3, wherein: The crushing gas is the natural gas released after the rock is crushed, the diffusion gas is the formation gas diffused into the wellbore under the action of pressure difference, and the permeation gas is the formation gas that penetrates into the wellbore under the action of concentration difference.

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