Thin-layer shale microstructure description method

Abstract

The invention belongs to the technical field of oil and gas field exploration and development, and particularly relates to a thin-layer shale microstructure description method. The method comprises the specific steps that marker beds are divided in a horizontal well shale target window, the marker beds are judged in real time through while-drilling natural gamma and rock debris characteristics, on the basis of the change of the thickness of strata between the marker beds, the dip angle and tendency of the strata are calculated according to the intersection relation between the marker beds and well trajectories, and then micro-structure description is conducted on a target area. The method has the advantages of being lower in cost, sufficient in data source and high in accuracy, thin-layer shale microstructure depiction can be achieved, powerful basis can be provided for well trajectory adjustment in the drilling process of the horizontal well, and basis can be provided for optimization of well trajectories of adjacent horizontal wells to be drilled in a well factory mode.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field exploration and development, and in particular relates to a method for characterizing thin-layer shale microstructures. Background Art

[0002] With the gradual consumption of conventional oil and gas resources and the increasing difficulty of mining, as well as the rising demand for energy for economic and social development, the contradiction between oil and gas supply and demand has become increasingly prominent. Unconventional oil and gas resources, including coalbed methane, tight sandstone oil and gas, and shale oil and gas, have attracted more and more attention and have become an important support for the rapid increase in global oil and gas reserves. China's shale oil and gas resources have rich potential. At present, marine shale has built several marine shale gas fields with a scale of hundreds of billions of cubic meters and achieved large-scale commercial development. Compared with marine shale, the widely existing continental shale has the characteristics of thin thickness, frequent sedimentary phase changes, and strong heterogeneity. With the breakthroughs in the continental mud shale oil and gas formations in the Songliao Basin, Bohai Bay Basin, Ordos Basin, Junggar Basin and Sichuan Basin, the Jurassic System in the Sichuan Basin has become a hot research area for the exploration and development of continental shale oil and gas, which has also promoted the development of continental thin-layer shale oil and gas resources.

[0003] Although shale formations with Ro above 0.7 generally contain oil and gas, the efficient development of shale oil and gas can only be achieved by implementing horizontal well drilling and large-scale fracturing in the layers with good oil or gas content. In order to achieve the effective and orderly development of continental thin-layer shale oil and gas, shale oil and gas horizontal wells should preferably select shale formation target windows, and the well trajectory should be as parallel to the target layer as possible and travel in the target layer. It is necessary to provide drilling engineers with accurate well trajectory adjustment plans in a timely manner, and the microstructural characterization of the thin shale target layer is particularly important. Therefore, the detailed characterization of the microstructure of thin shale also needs to be put on the agenda to lay the foundation for the exploration and development of continental shale oil and gas.

[0004] Microstructure refers to the local small structure with fine undulations of the stratum itself in the context of the overall oil field. The width is usually between 200 and 400 meters, and the amplitude does not exceed 20 meters. During the horizontal well drilling process, it is usually necessary to set up a logging while drilling series to determine the formation inclination and the position of the drill bit. The research and use of logging while drilling is still in its infancy in my country. Due to the high price and high cost of using logging while drilling instruments and interpretation software, my country currently mainly uses logging while drilling instruments with natural gamma and resistivity parameters. The characterization of microstructures in the existing technology mainly includes the following two categories: ① Using seismic data: Using seismic data, combined with stratigraphic division, interpret the microstructure of the layer, or on the basis of structural analysis and stratigraphic division, improve the accuracy of the velocity field and ensure the accuracy of microstructure mapping. However, due to the low vertical resolution of seismic data, microstructures with an amplitude of less than 10m in thin shale cannot be accurately identified through seismic data; ② Use the relationship between the well trajectory and the layer of horizontal wells (high-angle wells) to identify microstructures or use a series of logging technologies such as while-drilling imaging logging to obtain the formation dip and inclination. However, in the existing microstructure characterization methods that use the intersection relationship between the layer and the well trajectory, the calculation of the formation dip is mostly based on the equal thickness of the formation, or ignores the intersection of the marker layer inside the target window and the well trajectory. There are problems of large errors and high costs in the process of obtaining the change of formation dip. Therefore, it is urgent to establish a set of cost-effective microstructure characterization technologies suitable for thin shale oil and gas layers to lay a solid foundation for the exploration and development of continental shale oil and gas. Summary of the invention

[0005] The purpose of the present invention is to provide a thin shale microstructure characterization method to solve the problem of inaccurate characterization of thin shale microstructure using seismic data in the prior art and the problem of high cost of characterization of thin shale microstructure using while drilling imaging logging.

[0006] In order to solve the above technical problems, the present invention provides a method for characterizing the microstructure of thin shale. According to the geological characteristics of the target layer core obtained from the drilled well, marker layers are divided within the target layer; the marker layers encountered by the well trajectory are identified, and the vertical thickness and equal thickness of the strata between different marker layers are characterized. In combination with the intersection relationship between the well trajectory and the strata between the marker layers, the stratum dip and the azimuth of the stratum dip are calculated each time the well trajectory crosses the same marker layer or two adjacent marker layers, so as to characterize the microstructure of the target area.

[0007] The beneficial effects are as follows: the problem of inaccurate characterization of thin-layer shale microstructure using seismic data in the prior art and the problem of high cost of characterization of thin-layer shale microstructure using while-drilling imaging logging are solved. The present invention divides marker layers inside the horizontal well shale target window, and on the basis of the change in formation thickness between the marker layers, calculates the formation dip and inclination according to the intersection relationship between the marker layers and the well trajectory, and then characterizes the microstructure of the target area. The present invention has the characteristics of lower cost, sufficient data source and high accuracy. It can not only realize the microstructure characterization of thin-layer shale, but also provide a strong basis for adjusting the well trajectory during the drilling of the horizontal well. In addition, it can also provide a basis for optimizing the well trajectory of adjacent horizontal wells to be drilled in the well factory mode.

[0008] Furthermore, the intersection relationship between the marker layer and the well trajectory includes: both the formation and the well trajectory are downwardly inclined and the well trajectory is downwardly inclined relative to the formation, both the formation and the well trajectory are downwardly inclined and the well trajectory is upwardly inclined relative to the formation, the formation is downwardly inclined and the well trajectory is upwardly inclined, the formation and the well inclination angle are upwardly inclined and the well trajectory is upwardly inclined relative to the formation, the formation and the well inclination angle are upwardly inclined and the well trajectory is downwardly inclined relative to the formation, the formation is upwardly inclined and the well trajectory is downwardly inclined, and the formation and the well trajectory are nearly parallel.

[0009] Furthermore, when both the formation and the well trajectory are down-dipping and the well trajectory is down-dipping relative to the formation, the calculation formulas for the formation inclination angles of the well trajectory encountering the first marker layer and the second marker layer are:

[0010]

[0011]

[0012] When both the formation and the well trajectory are down-dipping and the well trajectory is up-dipping relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are:

[0013]

[0014]

[0015] When the formation dips downward and the well trajectory dips upward, the calculation formulas for the formation dip angles of the first marker layer and the second marker layer encountered by the well trajectory are:

[0016]

[0017]

[0018] When both the formation and the well inclination angle are up-dip and the well trajectory is up-dip relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are:

[0019]

[0020]

[0021] When both the formation and the well inclination angle are up-dip and the well trajectory is down-dip relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are:

[0022]

[0023]

[0024] When the formation is up-dip and the well trajectory is down-dip, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are:

[0025]

[0026]

[0027] When the formation is nearly parallel to the well trajectory, the calculation formula for the formation dip is:

[0028]

[0029] Where a is the horizontal projection displacement length of the two marker layers encountered; b is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the second marker layer is encountered; c is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the first marker layer is encountered; α is the well inclination angle when the marker layer is encountered; θ 1 is the formation dip angle of the first marker layer encountered; θ 2 is the stratigraphic dip angle of the second marker layer encountered during drilling; (X, Y, Z) and (X', Y', Z') are the geodetic coordinates of the same marker layer or two different marker layers encountered successively during drilling.

[0030] The beneficial effects are: accurately calculating the positional relationship between the well trajectory and each marker layer in the target layer to characterize the microstructure of the target area, and providing a strong basis for adjusting the well trajectory during the drilling of horizontal wells. In addition, it can also provide a basis for optimizing the well trajectory of adjacent horizontal wells to be drilled in the well factory for well factory mode.

[0031] Furthermore, the azimuth angle calculation formula of the calculated formation dip is as follows:

[0032]

[0033] Among them, δ is the azimuth of the formation dip; (X, Y, Z) and (X', Y', Z') are the geodetic coordinates of the two landmark layers encountered successively.

[0034] The beneficial effects are: accurately calculating the drilling direction in the target layer where the well trajectory is located to characterize the microstructure of the target area, and providing a strong basis for adjusting the well trajectory during the drilling of the horizontal well. In addition, it can also provide a basis for optimizing the well trajectory of adjacent horizontal wells to be drilled in the well factory for well factory mode.

[0035] Furthermore, the means for identifying the marker layer encountered by the well trajectory is: judging the marker layer encountered by the well trajectory according to the lithological characteristics of the cuttings logging and the normalized natural gamma value of each marker layer.

[0036] The beneficial effects are: using natural gamma while drilling and rock cuttings characteristics to instantly determine the marker layer, so as to characterize the microstructure of the target area at a lower cost, with more sufficient data sources and higher accuracy.

[0037] Furthermore, the specific steps of normalizing the natural gamma value include: selecting the natural gamma of the stable section of the standard well in the target area as the standard value, and normalizing the natural gamma of the actual wells drilled in the target area based on the standard well. The normalization formula is as follows:

[0038]

[0039] Among them, GR sta is the normalized natural gamma value; is the natural gamma mean value of the stable section of the selected standard well; is the mean value of the natural gamma of the standard segment corresponding to the standardization; GR is the measured natural gamma value.

[0040] Furthermore, the interpolation method is used to characterize the vertical thickness and equal thickness between different marker layers.

[0041] Its beneficial effect is to provide data basis for calculating the formation dip of the marker layer.

[0042] Furthermore, the lithological characteristics of cuttings logging are determined by dripping hydrochloric acid on the cuttings.

[0043] The beneficial effect is that it is helpful to quickly determine the lithology of the cuttings so as to determine the marker layer encountered in the actual drilling.

[0044] Furthermore, the geological characteristics of the target layer core obtained include: lithology, mineral composition, paleontology and sedimentary cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flowchart of the thin-layer shale microstructure characterization based on natural gamma and rock cuttings logging of the present invention;

[0046] Figure 2-1 It is a schematic diagram of the present invention in which both the formation and the well trajectory are down-dipping and the well trajectory is down-dipping relative to the formation;

[0047] Figure 2-2 It is a schematic diagram of the present invention in which both the formation and the well trajectory are down-dipping and the well trajectory is up-dipping relative to the formation;

[0048] Figure 2-3 It is a schematic diagram of the present invention in which the formation is down-dip and the well trajectory is up-dip;

[0049] Figure 2-4 It is a schematic diagram of the present invention in which both the formation and the well inclination angle are up-dip and the well trajectory is up-dip relative to the formation;

[0050] Figure 2-5 It is a schematic diagram of the present invention in which the formation and well inclination angles are both up-dipping and the well trajectory is down-dipping relative to the formation;

[0051] Figure 2-6 It is a schematic diagram of the formation up-dip and the well trajectory down-dip of the present invention;

[0052] Figure 2-7 It is a schematic diagram of the parallel formation and well trajectory of the present invention;

[0053] Figure 3 It is the target area actual drilling marker layer of the present invention;

[0054] Figure 4 It is the vertical thickness diagram between two adjacent marking layers of the present invention;

[0055] Figure 5 It is a cross-sectional view of the microstructure of the target layer in the XXY1-1HF well area according to the present invention. DETAILED DESCRIPTION

[0056] The basic concept of the present invention is to divide the marker layer inside the horizontal well shale target window, use the natural gamma while drilling and the characteristics of the rock cuttings to instantly determine the marker layer, and calculate the formation dip and inclination based on the intersection relationship between the marker layer and the well trajectory on the basis of the change of the formation thickness between the marker layers, so as to further characterize the microstructure of the target area. Based on this concept, a thin-layer shale microstructure characterization method of the present invention can be realized.

[0057] The present invention will be described in detail below with reference to the accompanying drawings and method embodiments.

[0058] Method Example:

[0059] A thin-layer shale microstructure characterization method of the present invention has a flow chart as shown in FIG. Figure 1 As shown, the specific implementation steps include:

[0060] Step 1: Use the core geological characteristics of the target layer system obtained from previous actual drilling in the target area to divide the target layer and the stable marker layers above and below the target layer, and clarify the lithology, electrical properties and sedimentary characteristics of each marker layer; the core geological characteristics include: lithology, mineral composition, paleontology and sedimentary cycles and electrical characteristics such as natural gamma.

[0061] Step 2: Standardize the natural gamma of the actual wells drilled in the target area into a unified natural gamma interval, and clarify the distribution range of the normalized natural gamma value, which specifically includes: selecting the natural gamma of the stable section of the standard well in the target area as the standard value, and standardizing the natural gamma of the actual wells drilled in the target area based on the standard well. The standardization formula is as follows:

[0062]

[0063] Among them, GR sta is the normalized natural gamma value; and They are respectively the mean natural gamma value of the stable section of the selected standard well and the mean natural gamma value of the standard section corresponding to the well to be standardized; GR is the measured natural gamma value, in API units.

[0064] Step three, based on the lithological characteristics of the cuttings logging and the normalized natural gamma in step two, identify the marker layer encountered by the actual horizontal well.

[0065] Step 4: Based on the interpolation method, the marker layer determined in step 1 is characterized, and the vertical thickness and equal thickness map between the bottom surfaces of adjacent marker layers is used to calculate the formation dip.

[0066] Step 5: According to the intersection relationship between the drilling marker layer and the well trajectory, the formation dip angle and the azimuth angle of the formation dip angle where the well trajectory crosses two adjacent marker layers are calculated. The specific calculation is as follows:

[0067] 1) If Figure 2-1 As shown in the figure, when both the formation and the well trajectory are down-dipping and the well trajectory is down-dipping relative to the formation, the calculation formula for the formation dip angle of the first marker layer encountered by drilling is:

[0068]

[0069] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0070]

[0071] 2) If Figure 2-2 As shown in the figure, when both the formation and the well trajectory are down-dipping and the well trajectory is up-dipping relative to the formation, the calculation formula for the formation dip angle of the first marker layer encountered by drilling is:

[0072]

[0073] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0074]

[0075] 3) If Figure 2-3 As shown in Figure 2, when the formation dips downward and the well trajectory dips upward, the calculation formula for the formation dip angle of the first marker layer encountered by drilling is:

[0076]

[0077] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0078]

[0079] 4) If Figure 2-4 As shown in the figure, when both the formation and the well inclination angle are up-dip and the well trajectory is up-dip relative to the formation, the calculation formula for the formation inclination of the first marker layer encountered by drilling is:

[0080]

[0081] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0082]

[0083] 5) If Figure 2-5 As shown in the figure, when both the formation and the well inclination angle are up-dipping and the well trajectory is down-dipping relative to the formation, the calculation formula for the formation inclination angle of the first marker layer encountered by drilling is:

[0084]

[0085] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0086]

[0087] 6) If Figure 2-6 As shown in Figure 1, when the formation is up-dip and the well trajectory is down-dip, the calculation formula for the formation dip angle of the first marker layer encountered by drilling is:

[0088]

[0089] The calculation formula for the formation dip angle when drilling into the second marker layer is:

[0090]

[0091] 7) If Figure 2-7 As shown in the figure, when the well trajectory passes through the same marker layer, it can be considered that the formation is nearly parallel to the well trajectory. At this time, the formation dip calculation formula is:

[0092]

[0093] 8) The azimuth angle calculation formula of the calculated formation dip is as follows:

[0094]

[0095] Wherein, a is the horizontal projection displacement length of the two marker layers encountered by drilling, in m; b is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the second marker layer is encountered, in m; c is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the first marker layer is encountered, in m; α is the well inclination angle when the marker layer is encountered, in °; θ 1 is the formation dip angle of the first marker layer encountered, θ 2 is the stratigraphic dip angle of the second marker layer encountered, in degrees; (X, Y, Z) and (X', Y', Z') are the geodetic coordinates of the two marker layers encountered successively.

[0096] Step six, based on the formation dip and azimuth of the two marker layers calculated in step five, characterize the interlayer microstructure of the marker layers encountered by horizontal wells and high-angle wells in the target area, and combine the marker layer stratification of all actual vertical wells drilled in the target area to perform geostatistical interpolation to characterize the microstructure of the thin shale target layer in the target area.

[0097] The specific embodiment of the method for characterizing the microstructure of thin shale using the present invention is as follows:

[0098] A typical semi-deep lake-facies high-clay dark shale is developed in the X-th layer of the XXX formation in the XX area of ​​the XX basin. Two sets of dark black shales are developed from top to bottom, with thicknesses of about 10m and 6m respectively. In 2020, the XXY1 well deployed in the area obtained a high-yield gas flow of 104,000 cubic meters per day. The exploration breakthrough also promoted the development of shale gas in the area. The XXY1-1HF well is the first shale gas horizontal well deployed in the first terrestrial unconventional test well group in the area. The specific steps for characterizing the microstructure of the thin shale target layer of the XXY1-1H well in the Puguang gas field are as follows:

[0099] ① Based on the previous coring, element logging and logging cuttings data, the geological characteristics analysis was carried out, and the small layers of the adjacent wells were finely compared. The three small layers of the Puguang East syncline XXY1-1HF well area were marked as follows: Figure 3 As shown in the figure, 10 geological marker layers were identified from top to bottom, and the lithology, electrical properties and sedimentary characteristics of the marker layers were clarified. Among them, the characteristics of the marker layer of the third sublayer of the first section of the XXY1-1HF well area are shown in Table 1 below:

[0100] Table 1

[0101]

[0102] ② Select Well XXY1 as the standard well in the target area. Its shale section of 3383.45-3393.35m is a stable formation in the area, with an average value of 130.75API. For example, the corresponding depth section of Well Puguang 4 is 3211.88-3222.4m, the average natural GR is 103.11API, and the conversion coefficient is 1.27. Formula (1) is used to standardize the natural gamma of all wells in the target area into a unified natural gamma interval. Figure 3 shown.

[0103] ③ According to the natural gamma of each marker layer after standardization in step 2, as well as the lithology and paleontological characteristics of the cuttings logging, the marker layer encountered in the actual horizontal well is determined: the natural gamma and cuttings undergo obvious changes, and hydrochloric acid is used to determine whether it is a marker layer. Among them, when drilling K3-2, K3-3, K3-4 and K3-5, the cuttings appear as a shell layer. Because they contain shell fossils composed of calcite, they foam violently when hydrochloric acid is dripped. When drilling K3-1, the cuttings appear as black shale with a high natural gamma value, and no foaming occurs when hydrochloric acid is dripped.

[0104] ④ Based on the interpolation method, the vertical thickness and isopach maps between the bottom surfaces of adjacent marker layers are drawn for the marker layers determined in ①: the vertical depths between the marker layers of all vertical wells drilled in the target area are counted, and the vertical thickness and isopach maps between different marker layers are drawn using the interpolation method, such as Figure 4 shown.

[0105] ⑤ According to the intersection relationship between the drilling marker layer and the well trajectory, calculate the formation dip angle and azimuth of the formation dip angle where the well trajectory crosses two adjacent marker layers. Figure 5 As shown in the figure (where T is the top of the marker layer and B is the bottom of the marker layer), taking the first encounter of K3-1T and K3-2T marker layers as an example, the geodetic coordinates and altitudes of the two points are (18767398.48, 3494395.27, -2617.5) and (18767370.19, 3494472.74, -2615), respectively. The intersection relationship between the formation and the well trajectory is that the formation well trajectory is down-dipping and the well trajectory is down-dipping relative to the formation. The well inclination angle α is 1.89°. When encountering the K3-1T and K3-2T marker layers, the vertical thickness c and b of the two marker layers are calculated by interpolation under this coordinate system to be 0.245m and 0.245m respectively, and the well trajectory length a is 10.31m. The formation dips of the two marker layers are calculated to be 3.25° and 3.25° respectively using formula (2) and formula (3), and the azimuth is calculated to be 339.94° using formula (15). Then, the formation dips and azimuths of the formation dips when encountering the remaining marker layers are calculated. The results are shown in Table 2 below:

[0106] Table 2

[0107]

[0108]

[0109] ⑥ Based on the stratigraphic dip and azimuth of the two marker layers calculated above, the interlayer microstructure of the marker layers encountered by horizontal wells and high-angle wells in the target area is characterized, and combined with the marker layer stratification of all actually drilled vertical wells in the target area, geostatistical interpolation is performed to characterize the microstructure of the thin shale target layer in the target area.

[0110] The present invention divides the marker layer inside the horizontal well shale target window, utilizes the natural gamma while drilling and the cuttings characteristics to instantly judge the marker layer, calculates the formation dip and tendency according to the intersection relationship between the marker layer and the well trajectory based on the change of the formation thickness between the marker layers, and then performs microstructural characterization of the target area. The present invention has the characteristics of lower cost, sufficient data source and high accuracy, and can not only realize the microstructural characterization of thin-layer shale, but also provide a strong basis for the adjustment of the well trajectory during the drilling of the horizontal well, and also provide a basis for the optimization of the well trajectory of adjacent horizontal wells to be drilled in the well factory mode.

Claims

1. A method for characterizing thin-layer shale microstructure, characterized in that: Based on the geological characteristics of the target layer core obtained from the drilled well, the marker layer is divided within the target layer; the marker layer encountered by the well trajectory is identified, and the vertical thickness and equal thickness of the strata between different marker layers are characterized. In combination with the intersection relationship between the well trajectory and the strata between the marker layers, the stratum dip and the azimuth of the stratum dip are calculated each time the well trajectory crosses the same marker layer or two adjacent marker layers, so as to characterize the microstructure of the target area.

2. The thin-layer shale microstructure characterization method according to claim 1, characterized in that: The intersection relationship between the marker layer and the well trajectory includes: both the formation and the well trajectory are downwardly inclined and the well trajectory is downwardly inclined relative to the formation, both the formation and the well trajectory are downwardly inclined and the well trajectory is upwardly inclined relative to the formation, the formation is downwardly inclined and the well trajectory is upwardly inclined, the formation and the well inclination angle are upwardly inclined and the well trajectory is upwardly inclined relative to the formation, the formation and the well inclination angle are upwardly inclined and the well trajectory is downwardly inclined relative to the formation, the formation is upwardly inclined and the well trajectory is downwardly inclined, and the formation and the well trajectory are nearly parallel.

3. The thin-layer shale microstructure characterization method according to claim 2, characterized in that: When both the formation and the well trajectory are down-dipping and the well trajectory is down-dipping relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are: When both the formation and the well trajectory are down-dipping and the well trajectory is up-dipping relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are: When the formation dips downward and the well trajectory dips upward, the calculation formulas for the formation dip angles of the first marker layer and the second marker layer encountered by the well trajectory are: When both the formation and the well inclination angle are up-dip and the well trajectory is up-dip relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are: When both the formation and the well inclination angle are up-dip and the well trajectory is down-dip relative to the formation, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are: When the formation is up-dip and the well trajectory is down-dip, the calculation formulas for the formation inclination angles of the first marker layer and the second marker layer encountered by the well trajectory are: When the formation is nearly parallel to the well trajectory, the calculation formula for the formation dip is: Wherein, a is the horizontal projection displacement length of the two marker layers encountered; b is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the second marker layer is encountered; c is the vertical thickness of the two marker layers calculated by the interpolation method at this coordinate when the first marker layer is encountered; α is the well inclination angle when the marker layer is encountered; θ1 is the formation dip angle when the first marker layer is encountered; θ2 is the formation dip angle when the second marker layer is encountered; (X, Y, Z) and (X', Y', Z') are the geodetic coordinates of successively encountering the same marker layer or two different marker layers.

4. The thin-layer shale microstructure characterization method according to claim 1, characterized in that: The azimuth angle calculation formula of the calculated formation dip is as follows: Among them, δ is the azimuth of the formation dip; (X, Y, Z) and (X', Y', Z') are the geodetic coordinates of the two landmark layers encountered successively.

5. The thin-layer shale microstructure characterization method according to claim 1, characterized in that: The means of identifying the marker layer encountered by the well trajectory is: judging the marker layer encountered by the well trajectory based on the lithological characteristics of the cuttings logging and the standardized natural gamma value of each marker layer.

6. The thin-layer shale microstructure characterization method according to claim 5, characterized in that: The specific steps of standardizing the natural gamma value include: selecting the natural gamma of the stable section of the standard well in the target area as the standard value, and standardizing the natural gamma of the actual wells in the target area based on the standard well. The standardization formula is as follows: Among them, GR sta is the normalized natural gamma value; is the natural gamma mean value of the stable section of the selected standard well; is the mean value of the natural gamma of the standard segment corresponding to the standardization; GR is the measured natural gamma value.

7. The thin-layer shale microstructure characterization method according to claim 1, characterized in that: The interpolation method is used to characterize the vertical thickness and equal thickness between different marker layers.

8. The thin-layer shale microstructure characterization method according to claim 5, characterized in that: The lithological characteristics of cuttings logging are determined by dripping hydrochloric acid on the cuttings.

9. The thin-layer shale microstructure characterization method according to claim 1, characterized in that: The geological characteristics of the target layer core obtained include lithology, mineral composition, paleontology and sedimentary cycle.

Images