Volcanic rock horizontal well fracturing dessert selection method and fracturing method

Abstract

The invention relates to the field of oil and gas field development, and discloses a volcanic rock horizontal well fracturing dessert selection method and a volcanic rock horizontal well fracturing method.The volcanic rock horizontal well fracturing dessert selection method comprises the steps that a directional drilling well section and a composite drilling well section of a target horizontal well are obtained; the mechanical specific energy of the directional drilling well section is corrected according to the mechanical specific energy of the composite drilling well section, and the corrected mechanical specific energy of the directional drilling well section is obtained; based on the corrected mechanical specific energy of the directional drilling well section and the mechanical specific energy of the composite drilling well section, first corrected mechanical specific energy of the target horizontal well is obtained; and selecting the fractured dessert based on the first mechanical specific energy. Due to the fact that the mechanical specific energy of the directional drilling well section can be corrected, the influence of the drilling mode on the mechanical specific energy can be eliminated. Furthermore, the first mechanical specific energy, obtained after correction, of the target horizontal well can truly reflect the compressibility of the reservoir, so that the accuracy of fracturing dessert selection can be improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development, specifically to a method for selecting sweet spots in horizontal well fracturing of volcanic rock and a method for fracturing horizontal wells of volcanic rock. Background Technology

[0002] In the development of volcanic gas reservoirs, horizontal wells are often enhanced through staged fracturing. Due to the strong lateral and vertical heterogeneity of volcanic reservoirs, the gas content and compressibility of horizontal wells vary greatly. Therefore, the selection of the sweet spot location during staged fracturing is crucial to the success rate of fracturing operations and the post-fracturing production enhancement effect.

[0003] Currently, horizontal wells typically use logging interpretation data to calculate rock mechanics parameters and assess compressibility. However, for unlogged horizontal wells in volcanic gas reservoirs, it is impossible to calculate the relevant horizontal stresses for compressibility evaluation. Furthermore, due to lithological influences, the radioactive elements identified by the GR curve cannot effectively identify volcanic rock lithology. Therefore, the single-factor compressibility assessment method using GR curves for sandstone and shale reservoirs is not applicable to volcanic reservoirs.

[0004] Therefore, mechanical specific energy can generally be used to determine the compressibility of volcanic reservoirs, and then the fracturing sweet spot can be selected based on the reservoir's compressibility. Currently, the calculation of mechanical specific energy mainly considers drilling pressure, rotary table speed, mechanical drilling speed, and drill bit sliding friction coefficient, while ignoring other influencing factors such as drilling method. This leads to inaccurate calculation results for mechanical specific energy, which cannot accurately reflect the compressibility of the reservoir. On the one hand, this results in inaccurate selection of fracturing sweet spots, and on the other hand, it makes it impossible to select fracturing techniques in a targeted manner, ultimately seriously affecting the post-fracturing productivity of horizontal wells. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that the calculation results of mechanical specific energy in the prior art cannot accurately reflect the compressibility of the reservoir, thus leading to inaccurate selection of the fracturing sweet spot. This invention provides a method for selecting the fracturing sweet spot in volcanic rock horizontal wells and a fracturing method for volcanic rock horizontal wells.

[0006] To achieve the above objectives, the present invention provides a method for selecting sweet spots in horizontal well fracturing of volcanic rock, comprising:

[0007] Obtain the directional drilling section and composite drilling section of the target horizontal well;

[0008] The mechanical specific energy of the directional drilling section is corrected based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section.

[0009] Based on the corrected mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section, the corrected first mechanical specific energy of the target horizontal well is obtained;

[0010] The fracturing sweet spot is selected based on the first mechanical specific energy.

[0011] In this embodiment of the application, the step of correcting the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section includes:

[0012] A scatter plot is drawn with the mechanical specific energy of each point in the directional drilling section as the abscissa and the mechanical specific energy of each point in the composite drilling section as the ordinate.

[0013] By fitting the scatter plot, the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is obtained;

[0014] Based on the aforementioned relationship, the corrected mechanical specific energy of the directional drilling section is obtained.

[0015] In this embodiment of the application, the fitting includes linear fitting, and the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is as follows:

[0016] E c =aE d +b;

[0017] Among them, E d E represents the mechanical specific energy of the directional drilling section. c Let a and b be the mechanical specific energy of the composite drilling section, obtained by linear fitting.

[0018] In this embodiment of the application, after obtaining the first mechanical specific energy after correction of the target horizontal well, the method further includes:

[0019] In the drilling route of the target horizontal well, the target drilling stage corresponding to each drill bit is determined, and the initial drilling stage, the middle drilling stage and the final drilling stage of each target drilling stage are determined;

[0020] For any target drilling stage, the first mechanical specific energy of the initial drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the initial drilling stage; the first mechanical specific energy of the final drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the final drilling stage.

[0021] Based on the corrected mechanical specific energy in the early stage of drilling, the first mechanical specific energy in the middle stage of drilling, and the corrected mechanical specific energy in the late stage of drilling, the corrected second mechanical specific energy of the target drilling stage is obtained.

[0022] Based on the corrected second mechanical specific energy of each target drilling stage, the corrected second mechanical specific energy of the target horizontal well is obtained;

[0023] The sweet spot for fracturing is selected based on the second mechanical specific energy after correction of the target horizontal well.

[0024] In this embodiment of the application, the step of correcting the first mechanical specific energy at the initial stage of drilling based on the first mechanical specific energy at the middle stage of drilling to obtain the corrected mechanical specific energy at the initial stage of drilling includes:

[0025] Using the first mechanical specific energy at each point in the initial stage of drilling as the abscissa and the first mechanical specific energy at each point in the middle stage of drilling as the ordinate, a scatter plot corresponding to the initial stage of drilling and the middle stage of drilling is drawn.

[0026] Fit the scatter plots corresponding to the initial drilling stage and the middle drilling stage to obtain the first relationship between the first mechanical specific energy in the initial drilling stage and the first mechanical specific energy in the middle drilling stage.

[0027] Based on the first relationship, the corrected mechanical specific energy in the initial stage of drilling is obtained;

[0028] The step of correcting the first mechanical specific energy at the end of drilling based on the first mechanical specific energy during the middle stage of drilling to obtain the corrected mechanical specific energy at the end of drilling includes:

[0029] Using the first mechanical specific energy of each point in the final stage of drilling as the abscissa and the first mechanical specific energy of each point in the middle stage of drilling as the ordinate, a scatter plot corresponding to the final stage of drilling and the middle stage of drilling is drawn.

[0030] Fit the scatter plots corresponding to the end of drilling and the middle of drilling to obtain a second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy at the middle of drilling;

[0031] Based on the second relationship, the corrected mechanical specific energy at the end of the drilling process is obtained.

[0032] In this embodiment of the application, the fitting includes linear fitting;

[0033] The first relationship between the first mechanical specific energy in the initial stage of drilling and the first mechanical specific energy in the middle stage of drilling is:

[0034] E m2 =λ1Em1 +β1;

[0035] Among them, E m1 E represents the first mechanical specific energy during the initial stage of drilling. m2 λ1 and β1 are obtained by linear fitting, representing the first mechanical specific energy during the drilling phase.

[0036] The second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy in the middle of drilling is:

[0037] E m2 =λ2E m3 +β2;

[0038] Among them, E m3 λ2 and β2 are the first mechanical specific energy at the end of the drilling process, obtained by linear fitting.

[0039] In this embodiment of the application, after obtaining the second mechanical specific energy after correction of the target horizontal well, the method further includes:

[0040] Plot the second mechanical specific energy curve and the gas logging curve of the target horizontal well;

[0041] The fracturing sweet spot is selected based on the second mechanical energy curve and the gas measurement curve.

[0042] A second aspect of this application provides a method for fracturing a horizontal well in volcanic rock, the fracturing method being used to fracture a target horizontal well based on a fracturing sweet spot selected in the fracturing sweet spot selection method for horizontal wells in volcanic rock provided in the first aspect of this application, the target horizontal well including a first fracturing section, the method comprising:

[0043] Determine the average second mechanical specific energy of the first fracturing section;

[0044] The reservoir type corresponding to the first fracturing section is determined based on the average second mechanical specific energy.

[0045] According to the reservoir type, the first fracturing section is fracturing.

[0046] In this embodiment of the application, before determining the reservoir type corresponding to the first fracturing section based on the average second mechanical specific energy, the method further includes:

[0047] Determine the second mechanical specific energy and brittleness index of the measured horizontal well;

[0048] Establish the correspondence between the second mechanical specific energy and the brittleness index;

[0049] Determining the reservoir type corresponding to the first fracturing stage based on the average second mechanical specific energy includes:

[0050] Based on the average second mechanical specific energy and the corresponding relationship, the brittleness index corresponding to the average second mechanical specific energy is determined, and the reservoir type corresponding to the first fracturing section is determined based on the brittleness index.

[0051] In this embodiment of the application, before determining the reservoir type corresponding to the first fracturing section based on the average second mechanical energy, the method further includes: obtaining the lithology of the well that has been logged and the lithology of the target horizontal well;

[0052] Establishing the correspondence between the second mechanical specific energy and the brittleness index includes:

[0053] For each lithology, a correspondence between the second mechanical specific energy and the brittleness index is established;

[0054] The step of determining the brittleness index corresponding to the average second mechanical specific energy based on the average second mechanical specific energy and the corresponding relationship includes:

[0055] From the various correspondences, a target correspondence corresponding to the lithology of the target horizontal well is determined, and based on the average second mechanical specific energy and the target correspondence, a brittleness index corresponding to the average second mechanical specific energy is determined.

[0056] The above technical solution includes: obtaining the directional drilling section and the composite drilling section of the target horizontal well; correcting the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section; obtaining the corrected first mechanical specific energy of the target horizontal well based on the corrected mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section; and selecting the fracturing sweet spot based on the first mechanical specific energy. Since the mechanical specific energy of the composite drilling section, which more accurately reflects the reservoir's compressibility, can be used to correct the mechanical specific energy of the directional drilling section, the influence of the drilling method on the mechanical specific energy can be eliminated. Furthermore, the corrected first mechanical specific energy of the target horizontal well can accurately reflect the reservoir's compressibility, thereby improving the accuracy of fracturing sweet spot selection.

[0057] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0058] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings:

[0059] Figure 1 The illustration shows a flowchart of a method for selecting sweet spots in fracturing horizontal wells of volcanic rock according to an embodiment of this application;

[0060] Figure 2 The illustration shows a flowchart of another method for selecting sweet spots in horizontal well fracturing of volcanic rock according to an embodiment of this application;

[0061] Figure 3 The diagram schematically illustrates a scatter plot corresponding to a directional drilling section and a composite drilling section according to embodiments of this application.

[0062] Figure 4 The schematic diagram illustrates a process flow diagram of another method for selecting sweet spots in fracturing horizontal wells of volcanic rock according to an embodiment of this application;

[0063] Figure 5 The schematic diagram illustrates a process flow diagram of another method for selecting sweet spots in fracturing horizontal wells of volcanic rock according to an embodiment of this application;

[0064] Figure 6 The illustration shows a schematic diagram of a gas measurement curve and a second mechanical energy specific curve according to an embodiment of this application;

[0065] Figure 7 The diagram illustrates a horizontal well fracturing method for volcanic rock according to an embodiment of this application. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0067] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0068] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0069] Example 1

[0070] As described in the background section, current calculations of mechanical specific energy primarily consider drilling pressure, rotary table speed, mechanical drilling speed, and drill bit sliding friction coefficient, neglecting other influencing factors. For example, the drilling method also affects mechanical specific energy. In actual drilling, not only do "difficult-to-drill" lithologies lead to high mechanical specific energy, but directional drilling, due to its inherent characteristics, consumes more mechanical energy than composite drilling methods, thus also resulting in high mechanical specific energy. Therefore, when a high mechanical specific energy occurs, it is impossible to determine whether it is due to "difficult-to-drill" lithologies or the directional drilling method. Consequently, the calculated mechanical specific energy cannot accurately reflect the compressibility of the reservoir, easily leading to inaccurate selection of fracturing sweet spots and ultimately fracturing operation failure.

[0071] To address this, one embodiment of this application provides a method for selecting the sweet spot in fracturing of horizontal wells in volcanic rock. This method can be applied to horizontal wells in volcanic rock where logging has not yet been conducted. Figure 1 As shown, the method may include the following steps:

[0072] Step 101: Obtain the directional drilling section and composite drilling section of the target horizontal well.

[0073] The directional drilling section refers to a section where directional drilling is used. The composite drilling section refers to a section where composite drilling is used.

[0074] In the embodiments of this application, it may involve obtaining all directional drilling sections in the target horizontal well, and obtaining all composite drilling sections in the target horizontal well.

[0075] Step 102: Correct the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section.

[0076] The uncorrected mechanical specific energy of the directional drilling section can be calculated first using the following formula (1), and the uncorrected mechanical specific energy of the composite drilling section can be calculated using the following formula (2):

[0077]

[0078] Among them, E d E represents the mechanical specific energy of the directional drilling section, expressed in Pa. c 1. Mechanical specific energy of the composite drilling section, in Pa; 2. Drilling pressure, in N; 3. Drill bit diameter, in m; 4. RPM rotary table speed, in r / min; 5. ROP mechanical drilling speed, in m / min; 6. μ drill bit sliding friction coefficient, where the sliding friction coefficient of roller cone drill bits is 0.25 and that of PDC drill bits is 0.5.

[0079] In the embodiments of this application, the modified directional drilling section and the composite drilling section used to modify the directional drilling section can be located in the same lithological reservoir.

[0080] In practical applications, when drilling from a first position to a second position, where the distance between the first and second positions is short, and this short drilling segment occurs within the same lithological reservoir, the reservoir's compressibility is essentially stable, resulting in minimal change in the actual mechanical specific energy during this drilling segment. Therefore, a drilling segment comprising both directional and composite drilling sections can be selected as the aforementioned short drilling segment, and the directional and composite drilling sections can be located within the same lithological reservoir. Consequently, the mechanical specific energy of the composite drilling segment, which more accurately reflects the reservoir's compressibility, can be used to correct the mechanical specific energy of the directional drilling segment. The specific distance of the short drilling segment can be set according to actual conditions, for example, it could be 5m, 10m, 15m, etc.

[0081] In horizontal wells, the distribution of directional drilling sections and composite drilling sections can be as follows: any two adjacent directional drilling sections form a composite drilling section, and any two composite drilling sections form a directional drilling section. To further accurately correct the mechanical specific energy of the directional drilling section, the composite drilling section used for correction can be adjacent to the directional drilling section. This further shortens the distance between the corrected directional drilling section and the composite drilling section used for correction, making the reservoir compressibility of the composite drilling section and the directional drilling section more similar. Therefore, the correction of the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section will be more accurate.

[0082] In practice, any directional drilling segment may be corrected by one or more adjacent composite drilling segments. For example, any directional drilling segment may be corrected by the preceding adjacent composite drilling segment, or by the following adjacent composite drilling segment, or by both the preceding and following adjacent composite drilling segments.

[0083] Step 103: Based on the corrected mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section, obtain the corrected first mechanical specific energy of the target horizontal well.

[0084] In the embodiments of this application, all directional drilling sections in the target horizontal well can be modified.

[0085] Therefore, the corrected first mechanical specific energy of the target horizontal well can be specifically: the mechanical specific energy of the directional drilling section in the target horizontal well is replaced with the corrected mechanical specific energy, while the mechanical specific energy of the composite drilling section in the target horizontal well remains unchanged.

[0086] Step 104: Select the fracturing sweet spot based on the first mechanical specific energy.

[0087] The corrected mechanical specific energy of the target horizontal well more accurately reflects reservoir compressibility than the uncorrected mechanical specific energy. Consequently, selecting the sweet spot for fracturing based on the first mechanical specific energy is also more accurate.

[0088] It is understood that the method for selecting fracturing sweet spots in volcanic rock horizontal wells provided in this application involves obtaining the directional drilling section and the composite drilling section of the target horizontal well; correcting the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section; obtaining the corrected first mechanical specific energy of the target horizontal well based on the corrected mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section; and selecting fracturing sweet spots based on the first mechanical specific energy. Since the mechanical specific energy of the composite drilling section, which more accurately reflects the compressibility of the reservoir, can be used to correct the mechanical specific energy of the directional drilling section, the influence of the drilling method on the mechanical specific energy can be eliminated. Furthermore, the corrected first mechanical specific energy of the target horizontal well can accurately reflect the compressibility of the reservoir, thereby improving the accuracy of fracturing sweet spot selection.

[0089] In one embodiment, step 102 corrects the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section, to obtain the corrected mechanical specific energy of the directional drilling section, such as... Figure 2 As shown, it may include:

[0090] Step 1021: Using the mechanical specific energy of each point in the directional drilling section as the abscissa and the mechanical specific energy of each point in the composite drilling section as the ordinate, draw a scatter plot.

[0091] The number of points selected from the directional drilling section corresponds to the number of points selected from the composite drilling section. Specifically, one point can correspond to one meter, and one point can correspond to one mechanical energy value. In practical applications, the points selected in both the directional drilling section and the composite drilling section are points after the drill bit has advanced two meters, thereby improving the accuracy of corrections.

[0092] For example, there are two directional drilling sections: 3348m-3360m and 3962m-3968m. The directional drilling section 3341m-3347m, preceding the directional drilling section 3348m-3360m, and the directional drilling section 3361m-3366m, following the directional drilling section 3348m-3360m, are selected for modification of the directional drilling section 3348m-3360m. Similarly, the directional drilling section 3958m-3961m, preceding the directional drilling section 3962m-3968m, and the directional drilling section 3969m-3971m, following the directional drilling section 3962m-3968m, are selected for modification of the directional drilling section 3962m-3968m.

[0093] The correspondence between the points in the directional drilling section and the points in the composite drilling section is shown in Table 1:

[0094] Table 1. Correspondence between points in directional drilling sections and points in composite drilling sections

[0095]

[0096] A scatter plot was drawn using the mechanical specific energy at each point in the directional drilling section as the x-axis and the mechanical specific energy at each point in the composite drilling section as the y-axis. The scatter plot obtained from the data in Table 1 above can be shown as follows: Figure 3 As shown.

[0097] Step 1022: Fit the scatter plot to obtain the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section.

[0098] In this embodiment, the fitting includes linear fitting. Furthermore, after fitting the scatter plot, the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is as follows:

[0099] E c =aE d +b (3);

[0100] Among them, E d For the mechanical specific energy of the directional drilling section, E c The mechanical specific energy of the composite drilling section, a and b, can be obtained by linear fitting.

[0101] Taking the scatter plot obtained from the data in Table 1 above as an example, after fitting the scatter plot, the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is: E c =0.7926E d -56924.

[0102] Step 1023: Based on the aforementioned relationship, obtain the corrected mechanical specific energy of the directional drilling section.

[0103] The relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is given by E. c =aE d For example, +b can be used to represent aE. d +b represents the corrected mechanical specific energy of the directional drilling section.

[0104] Furthermore, for the target horizontal well, during its directional drilling section, the corrected first mechanical specific energy E of the target horizontal well... m =aE d +b, in its composite drilling section, the first mechanical specific energy E after correction of the target horizontal well. m =E c .

[0105] Example 2

[0106] In practical applications, not only the drilling method but also the drilling depth affects the mechanical specific energy. In the initial stage of drilling, the longer engagement time between the drill bit and the rock leads to a higher mechanical specific energy; similarly, in the later stages of drilling, severe drill bit wear also results in a higher mechanical specific energy. Therefore, when a high mechanical specific energy occurs, it is impossible to determine whether it is due to the "difficulty in drilling" of the rock or the drilling depth. Therefore, in one embodiment, after obtaining the corrected first mechanical specific energy of the target horizontal well in step 103, as... Figure 4 As shown in the embodiments of this application, the method for selecting the sweet spot in volcanic rock horizontal well fracturing also includes:

[0107] Step 105: Determine the target drilling stage corresponding to each drill bit in the drilling route of the target horizontal well, and determine the initial drilling stage, middle drilling stage and final drilling stage of each target drilling stage.

[0108] Generally, multiple drill bits can be used sequentially when drilling a target horizontal well. For any given drill bit, the stage it drills is the target drilling stage. In other words, a target horizontal well includes multiple target drilling stages, and each target drilling stage has an initial drilling stage, a middle drilling stage, and a final drilling stage.

[0109] In practice, based on the drilling data of various drill bits in various lithological reservoirs, we can first obtain the average drilling depth of various drill bits in different lithological reservoirs, as well as the proportions of each average drilling depth in the early stage, middle stage, and late stage of drilling.

[0110] Then, based on the drill bit and lithology used in the target horizontal well, the proportions for the initial drilling stage, the middle drilling stage, and the final drilling stage corresponding to that drill bit and lithology are determined. Furthermore, each target drilling stage in the target horizontal well is divided into the initial drilling stage, the middle drilling stage, and the final drilling stage.

[0111] Statistics show that for most drill bits, the engagement time between the drill bit and the rock is relatively long in the first two meters of drilling, while the wear and tear is most significant in the latter 40% of the drilling process. Therefore, in practical implementation, for any target drilling stage, the stage with a drilling depth h ≤ 2m can be considered the initial drilling stage, and the stage with a drilling depth 2m < h ≤ 0.6h can be considered the initial drilling stage. m The stage is considered the middle stage of drilling, with a drilling depth h > 0.6h. m The stage is considered the final stage of drilling. Among them, h m The route length corresponding to the target drilling stage.

[0112] Step 106: For any target drilling stage, the first mechanical specific energy of the initial drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the initial drilling stage; the first mechanical specific energy of the final drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the final drilling stage.

[0113] Specifically, for any target drilling stage, the first mechanical specific energy at the beginning of the target drilling stage is corrected based on the first mechanical specific energy at the middle stage of the target drilling stage to obtain the corrected mechanical specific energy at the beginning of the target drilling stage; and the first mechanical specific energy at the end of the target drilling stage is corrected based on the first mechanical specific energy at the middle stage of the target drilling stage to obtain the corrected mechanical specific energy at the end of the target drilling stage.

[0114] In the embodiments of this application, the above-mentioned modification process can be performed for all target drilling stages.

[0115] It is understandable that during the same drilling stage, the drill bit engages well with the rock in the middle stage, and the wear on the drill bit is not high. Therefore, the first mechanical energy in the middle stage of drilling can more accurately reflect the compressibility of the reservoir. Thus, the first mechanical energy in the middle stage of drilling, which more accurately reflects the compressibility of the reservoir, can be used to correct the first mechanical energy in the early stage and the first mechanical energy in the late stage of drilling.

[0116] In practice, a well section near the initial drilling stage can be selected from the middle stage of drilling, and the first mechanical specific energy of the initial drilling stage can be corrected based on the first mechanical specific energy of that well section. Similarly, a well section near the final drilling stage can be selected from the middle stage of drilling, and the first mechanical specific energy of the final drilling stage can be corrected based on the first mechanical specific energy of that well section. This allows for more accurate corrections at the initial and final drilling stages.

[0117] Step 107: Based on the corrected mechanical specific energy in the initial drilling stage, the first mechanical specific energy in the middle drilling stage, and the corrected mechanical specific energy in the final drilling stage, obtain the corrected second mechanical specific energy for the target drilling stage.

[0118] In the embodiments of this application, the second mechanical specific energy after correction of the target drilling stage can specifically be: the first mechanical specific energy in the initial stage of the target drilling stage is replaced with the corrected mechanical specific energy, the first mechanical specific energy in the middle stage of the target drilling stage remains unchanged, and the first mechanical specific energy in the final stage of the target drilling stage is replaced with the corrected mechanical specific energy.

[0119] Step 108: Based on the corrected second mechanical specific energy of each target drilling stage, obtain the corrected second mechanical specific energy of the target horizontal well.

[0120] Therefore, step 104, which selects the fracturing sweet spot based on the first mechanical energy, may specifically include step 1041, which selects the fracturing sweet spot based on the second mechanical energy after correction of the target horizontal well.

[0121] It is understandable that the second mechanical energy of the target horizontal well, after correction, can more accurately reflect the reservoir's compressibility compared to the first mechanical energy. Furthermore, selecting the sweet spot for fracturing based on the second mechanical energy can further improve accuracy.

[0122] In one embodiment, step 106 corrects the first mechanical specific energy at the initial drilling stage based on the first mechanical specific energy during the middle drilling stage, to obtain the corrected mechanical specific energy at the initial drilling stage, such as... Figure 5 As shown, it may include:

[0123] Step 1061: Using the first mechanical specific energy of each point in the initial stage of drilling as the abscissa and the first mechanical specific energy of each point in the middle stage of drilling as the ordinate, draw a scatter plot corresponding to the initial stage of drilling and the middle stage of drilling.

[0124] The number of points selected during the middle stage of drilling corresponds to the number of points selected during the initial stage. Specifically, one point can be assigned per meter, and each point can be assigned a mechanical energy value.

[0125] For example, if the initial drilling phase is 0m-2m, then 2m to 4m can be selected from the middle drilling phase to correspond to the various points in the initial drilling phase. Specifically, 0m in the initial drilling phase corresponds to 2m in the middle drilling phase, 1m in the initial drilling phase corresponds to 3m in the middle drilling phase, and 2m in the initial drilling phase corresponds to 4m in the middle drilling phase.

[0126] Step 1062: Fit the scatter plots corresponding to the initial drilling stage and the middle drilling stage to obtain the first relationship between the first mechanical specific energy in the initial drilling stage and the first mechanical specific energy in the middle drilling stage.

[0127] In this embodiment, the fitting includes linear fitting. Therefore, after fitting the scatter plot, the first relationship between the first mechanical specific energy in the initial stage of drilling and the first mechanical specific energy in the middle stage of drilling is:

[0128] E m2 =λ1E m1 +β1 (4);

[0129] Among them, E m1 E is the initial mechanical specific energy during the initial stage of drilling. m2 The first mechanical specific energy during the drilling phase, λ1 and β1, can be obtained by linear fitting.

[0130] Step 1063: Based on the first relationship, obtain the corrected mechanical specific energy in the initial stage of drilling.

[0131] Let E be the first relationship between the first mechanical specific energy in the initial stage of drilling and the first mechanical specific energy in the middle stage of drilling. m2 =λ1E m1 Taking +β1 as an example, λ1E m1 +β1 represents the corrected mechanical specific energy during the initial drilling phase.

[0132] In one implementation, step 106 corrects the first mechanical specific energy at the end of drilling based on the first mechanical specific energy during the middle of drilling, to obtain the corrected mechanical specific energy at the end of drilling, such as... Figure 5 As shown, it may include:

[0133] Step 1064: Using the first mechanical specific energy of each point in the final stage of drilling as the abscissa and the first mechanical specific energy of each point in the middle stage of drilling as the ordinate, draw a scatter plot corresponding to the final stage of drilling and the middle stage of drilling.

[0134] The number of points selected during the middle stage of drilling corresponds to the number of points selected at the end stage. Specifically, one point can be assigned per meter, and one point can be assigned a mechanical energy value.

[0135] Step 1065: Fit the scatter plots corresponding to the end of drilling and the middle of drilling to obtain a second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy in the middle of drilling.

[0136] In this embodiment, the fitting includes linear fitting. Furthermore, after fitting the scatter plot, the second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy in the middle of drilling is:

[0137] E m2 =λ2E m3 +β2 (5);

[0138] Among them, E m3 The first mechanical specific energy at the end of drilling can be obtained by linear fitting, and the specific values ​​of λ2 and β2 can be obtained by linear fitting.

[0139] Step 1066: Based on the second relationship, obtain the corrected mechanical specific energy at the end of the drilling process.

[0140] The second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy in the middle of drilling is E. m2 =λ2E m3 Taking +β2 as an example, λ2E m3 +β2 is the mechanical specific energy corrected at the end of the drilling process.

[0141] Furthermore, for the target drilling stage, in its initial drilling phase, the corrected second mechanical specific energy E p =λ1E m1 +β1; During its mid-drilling phase, the corrected second mechanical specific energy E p =E m2 During the final stages of drilling, the corrected second mechanical specific energy E p =λ2E m3 +β2.

[0142] In steps 1061-1063 and steps 1064-1066 above, steps 1061-1063 and steps 1064-1066 can be implemented separately.

[0143] In practical applications, to further improve the accuracy of fracturing sweet spots, in one embodiment, after obtaining the corrected second mechanical energy of the target horizontal well in step 108, the fracturing sweet spot selection method for volcanic rock horizontal wells provided in this application embodiment further includes: plotting the second mechanical energy curve of the target horizontal well and the gas logging curve of the target horizontal well; then step 1041, which selects fracturing sweet spots based on the corrected second mechanical energy of the target horizontal well, may specifically include: selecting fracturing sweet spots based on the second mechanical energy curve and the gas logging curve.

[0144] In practice, gas logging data can be acquired during the drilling process of the target horizontal well, and a gas logging curve for the target horizontal well can be plotted based on the gas logging data. Then, the second mechanical energy curve and the gas logging curve are adjusted to ensure that their depths correspond.

[0145] In practical applications, based on the gas logging data and the well logging interpretation results of adjacent wells, the median gas logging values ​​corresponding to the gas layer, poor gas layer, gas-bearing layer, and dry layer of the reservoir corresponding to the target horizontal well can be determined. Then, the gas logging curve is shifted and adjusted as a whole according to the median gas logging value corresponding to the dry layer, so that when depth is the horizontal axis and the gas logging value and the second mechanical energy value are the vertical axes, the gas logging curve is located above the second mechanical energy curve.

[0146] like Figure 6 As shown, for a more intuitive demonstration, the portion sandwiched between the gas measurement curve and the second mechanical energy curve can be filled. The larger the filled area, the deeper the corresponding portion is, and the more suitable it is as a fracturing sweet spot.

[0147] Therefore, selecting the fracturing sweet spot based on the second mechanical energy curve and the gas measurement curve may include: taking the depth corresponding to the part with the larger filling area as the fracturing sweet spot.

[0148] Generally speaking, a larger filling area indicates a higher gas content and a lower second mechanical energy value. A higher gas content usually indicates a higher gas concentration, while a lower second mechanical energy value usually indicates better compressibility. Therefore, this area can be selected as a fracturing sweet spot. This, in turn, can improve the success rate of fracturing operations and the oil and gas production rate.

[0149] In practical applications, the number of selected cracked desserts can be multiple.

[0150] Example 3

[0151] Based on the method for selecting the fracturing sweet spot in volcanic rock horizontal wells provided in the above embodiments of this application, this application also provides a method for fracturing volcanic rock horizontal wells. This fracturing method can fracture a target horizontal well based on the fracturing sweet spot selected in the above embodiments of this application. The target horizontal well includes a first fracturing stage, such as... Figure 7 As shown, this fracturing method may include the following steps:

[0152] Step 201: Determine the average second mechanical specific energy of the first fracturing section.

[0153] This can be achieved by averaging the second mechanical specific energy corresponding to each location in the first fracturing section to obtain the average second mechanical specific energy.

[0154] Before determining the first fracturing segment from the target horizontal well, the volcanic rock horizontal well fracturing method provided in this application embodiment may further include: combining the fracturing sweet spot into segments based on the second mechanical specific energy of the fracturing sweet spot; and determining the first fracturing segment based on the segment combination.

[0155] The number of fracturing sweet spots can be multiple, extending from the bottom of the well to the wellhead. These multiple fracturing sweet spots can be, for example, D1, D2, D3...D... n In this embodiment of the application, the compressibility difference coefficient ζ between the fracturing sweet spots can be used as a reference. n Multiple fracturing sweet spots can be combined into clusters to simplify and optimize the fracturing process.

[0156] Specifically, ζ n =(E pDn -E pDn-1 ) / E pDn-1 When the continuous cracking of desserts is ζ n When the stress is relatively small, these consecutive fracturing sweet spots can be clustered together. Then, a first fracturing segment is determined based on the clustered segment combination, in which the stress difference between each fracturing sweet spot is small.

[0157] Additionally, when ζ n When the stress difference is greater than 0.3, it indicates a significant stress difference between the fracturing sweet spots. In this case, a ball-feeding temporary plugging technique can be used to open the two fracturing sweet spots separately. Specifically, during fracturing, the ball-feeding temporary plugging technique can be used to temporarily plug the opening of one fracturing sweet spot, and then the other fracturing sweet spot can be fracturing. When ζ n When the stress difference is ≤0.3, it indicates that the stress difference between the fracturing sweet spots is small. In this case, a large flow rate and limited-flow perforation can be used to open both fracturing sweet spots. Specifically, during fracturing, the number of perforations at one of the fracturing sweet spots can be reduced, and then a large flow rate of fracturing fluid can be introduced to open both fracturing sweet spots.

[0158] Step 202: Determine the reservoir type corresponding to the first fracturing section based on the average second mechanical specific energy.

[0159] In this embodiment of the application, before performing step 202, the volcanic rock horizontal well fracturing method provided in this embodiment of the application may further include: determining the second mechanical specific energy and brittleness index of the measured horizontal well; and establishing the correspondence between the second mechanical specific energy and the brittleness index.

[0160] The wells that have been logged can be wells that have already undergone logging and interpretation. Furthermore, the logged wells must have the same reservoir lithology as the target horizontal well. The brittleness index can be used to characterize the pressure-bearing capacity of the reservoir; generally, the larger the brittleness index, the better the pressure-bearing capacity of the reservoir. The second mechanical specific energy of the logged horizontal well can be obtained based on the methods provided in the above embodiments of this application, and will not be elaborated further here.

[0161] The brittleness index obtained from the well logging can be calculated based on the well logging data. Therefore, the correspondence between the second mechanical specific energy and the brittleness index can be obtained.

[0162] Then, step 202 determines the reservoir type corresponding to the first fracturing section based on the average second mechanical specific energy, which may specifically include: determining the brittleness index corresponding to the average second mechanical specific energy based on the average second mechanical specific energy and the corresponding relationship, and determining the reservoir type corresponding to the first fracturing section based on the brittleness index.

[0163] Typically, reservoir compressibility is classified based on the brittleness index. For volcanic reservoirs, those with a brittleness index exceeding 60% are classified as Class I reservoirs, those with an index between 40% and 60% as Class II reservoirs, and those with an index less than 40% as Class III reservoirs. Therefore, the corresponding reservoir type can be determined based on the brittleness index.

[0164] In practical applications, the correspondence between the second mechanical specific energy and the brittleness index is also related to lithology. Therefore, further, before performing step 202, the volcanic rock horizontal well fracturing method provided in this application embodiment may also include: obtaining the lithology of the logged well and the lithology of the target horizontal well; establishing the correspondence between the second mechanical specific energy and the brittleness index includes: establishing the correspondence between the second mechanical specific energy and the brittleness index for each lithology; then, determining the brittleness index corresponding to the average second mechanical specific energy based on the average second mechanical specific energy and the correspondence may include: determining the target correspondence corresponding to the lithology of the target horizontal well from each of the correspondences, and determining the brittleness index corresponding to the average second mechanical specific energy based on the average second mechanical specific energy and the target correspondence.

[0165] The lithology of the wells already logged can be obtained from the logging data. The lithology of the target horizontal well can be obtained from the gamma-ray per minute (GPM) data of the target horizontal well.

[0166] The above-described correspondence between the second mechanical specific energy and the brittleness index for each lithology can be applied to existing well logs. In practice, logging data from multiple wells with different lithologies can be obtained. Then, for each lithology, a corresponding correspondence between the second mechanical specific energy and the brittleness index can be established.

[0167] Therefore, when determining the brittleness index of a target horizontal well, one can first determine the target correspondence with the lithology of the target horizontal well from the correspondence relationships (the correspondence between the second mechanical energy and the brittleness index). Then, based on the second mechanical energy of the target horizontal well, determine the brittleness index corresponding to that second mechanical energy from the target correspondence relationships.

[0168] Step 203: Fracturing the first fracturing section according to the reservoir type.

[0169] In a specific embodiment, Class I reservoirs can be fracturing with low-viscosity fluids and using high-volume fracturing fluids for complex fracture network fracturing. The low-viscosity fluid can refer to fracturing fluid with a viscosity ≤10 mPas; the high-volume fracturing fluid can refer to a 16m³ / h fracturing fluid. 3 Construction discharge rate of / min or above.

[0170] For Class II reservoirs, a combination of low-viscosity and medium-viscosity fracturing fluids can be selected, along with in-fracture temporary plugging technology, to modify the flow rate and increase the complexity of the artificial fractures. The medium-viscosity fluid refers to fracturing fluid with a viscosity of 10 mPas to 30 mPas.

[0171] For Class III reservoirs, high-viscosity fluids can be selected, and moderate stimulation can be achieved using medium-to-high flow rate fracturing fluids. The high-viscosity fluid can refer to fracturing fluids with a viscosity ≥ 30 mPas; the medium-to-high flow rate can refer to fracturing fluids with a viscosity of 10 mPas. 3 / min-16m 3 Construction discharge rate per minute.

[0172] It is understood that by adopting the volcanic rock horizontal well fracturing method provided in this application embodiment, since the second mechanical energy of the target horizontal well can more accurately reflect the compressibility of the reservoir, the reservoir type of each fracturing section of the target horizontal well can be accurately determined based on the second mechanical energy, thereby accurately selecting the fracturing process and achieving the production enhancement effect.

[0173] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0174] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for selecting sweet spots in horizontal well fracturing of volcanic rock, characterized in that, include: Obtain the directional drilling section and composite drilling section of the target horizontal well; The mechanical specific energy of the directional drilling section is corrected based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section. Based on the corrected mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section, the corrected first mechanical specific energy of the target horizontal well is obtained; The fracturing sweet spot is selected based on the first mechanical specific energy.

2. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 1, characterized in that, The step of correcting the mechanical specific energy of the directional drilling section based on the mechanical specific energy of the composite drilling section to obtain the corrected mechanical specific energy of the directional drilling section includes: A scatter plot is drawn with the mechanical specific energy of each point in the directional drilling section as the abscissa and the mechanical specific energy of each point in the composite drilling section as the ordinate. By fitting the scatter plot, the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is obtained; Based on the aforementioned relationship, the corrected mechanical specific energy of the directional drilling section is obtained.

3. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 2, characterized in that, The fitting includes linear fitting, and the relationship between the mechanical specific energy of the directional drilling section and the mechanical specific energy of the composite drilling section is as follows: AND c =aE d +b; Among them, E d E represents the mechanical specific energy of the directional drilling section. c Let a and b be the mechanical specific energy of the composite drilling section, obtained by linear fitting.

4. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 1, characterized in that, After obtaining the first mechanical specific energy after correction of the target horizontal well, the method further includes: In the drilling route of the target horizontal well, the target drilling stage corresponding to each drill bit is determined, and the initial drilling stage, the middle drilling stage and the final drilling stage of each target drilling stage are determined; For any target drilling stage, the first mechanical specific energy of the initial drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the initial drilling stage; the first mechanical specific energy of the final drilling stage is corrected based on the first mechanical specific energy of the middle drilling stage to obtain the corrected mechanical specific energy of the final drilling stage. Based on the corrected mechanical specific energy in the early stage of drilling, the first mechanical specific energy in the middle stage of drilling, and the corrected mechanical specific energy in the late stage of drilling, the corrected second mechanical specific energy of the target drilling stage is obtained. Based on the corrected second mechanical specific energy of each target drilling stage, the corrected second mechanical specific energy of the target horizontal well is obtained; The sweet spot for fracturing is selected based on the second mechanical specific energy after correction of the target horizontal well.

5. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 4, characterized in that, The step of correcting the first mechanical specific energy at the initial stage of drilling based on the first mechanical specific energy at the middle stage of drilling to obtain the corrected mechanical specific energy at the initial stage of drilling includes: Using the first mechanical specific energy at each point in the initial stage of drilling as the abscissa and the first mechanical specific energy at each point in the middle stage of drilling as the ordinate, a scatter plot corresponding to the initial stage of drilling and the middle stage of drilling is drawn. Fit the scatter plots corresponding to the initial drilling stage and the middle drilling stage to obtain the first relationship between the first mechanical specific energy in the initial drilling stage and the first mechanical specific energy in the middle drilling stage. Based on the first relationship, the corrected mechanical specific energy in the initial stage of drilling is obtained; The step of correcting the first mechanical specific energy at the end of drilling based on the first mechanical specific energy during the middle stage of drilling to obtain the corrected mechanical specific energy at the end of drilling includes: Using the first mechanical specific energy of each point in the final stage of drilling as the abscissa and the first mechanical specific energy of each point in the middle stage of drilling as the ordinate, a scatter plot corresponding to the final stage of drilling and the middle stage of drilling is drawn. Fit the scatter plots corresponding to the end of drilling and the middle of drilling to obtain a second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy at the middle of drilling; Based on the second relationship, the corrected mechanical specific energy at the end of the drilling process is obtained.

6. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 5, characterized in that, The fitting includes linear fitting; The first relationship between the first mechanical specific energy in the initial stage of drilling and the first mechanical specific energy in the middle stage of drilling is: E m2 =λ1E m1 +β1; Among them, E m1 E represents the first mechanical specific energy during the initial stage of drilling. m2 λ1 and β1 are obtained by linear fitting, representing the first mechanical specific energy during the drilling phase. The second relationship between the first mechanical specific energy at the end of drilling and the first mechanical specific energy in the middle of drilling is: E m2 =λ2E m3 +β2; Among them, E m3 λ2 and β2 are the first mechanical specific energy at the end of the drilling process, obtained by linear fitting.

7. The method for selecting sweet spots in horizontal well fracturing of volcanic rock according to claim 4, characterized in that, After obtaining the second mechanical specific energy after correction for the target horizontal well, the method further includes: Plot the second mechanical specific energy curve and the gas logging curve of the target horizontal well; The fracturing sweet spot is selected based on the second mechanical energy curve and the gas measurement curve.

8. A method for fracturing horizontal wells in volcanic rock, characterized in that, The fracturing method is used to fracturing a target horizontal well based on the fracturing sweet spot selected in claim 4, the target horizontal well including a first fracturing section, the method comprising: Determine the average second mechanical specific energy of the first fracturing section; The reservoir type corresponding to the first fracturing section is determined based on the average second mechanical specific energy. According to the reservoir type, the first fracturing section is fracturing.

9. The method for fracturing horizontal wells in volcanic rock according to claim 8, characterized in that, Before determining the reservoir type corresponding to the first fracturing stage based on the average second mechanical specific energy, the method further includes: Determine the second mechanical specific energy and brittleness index of the measured horizontal well; Establish the correspondence between the second mechanical specific energy and the brittleness index; Determining the reservoir type corresponding to the first fracturing stage based on the average second mechanical specific energy includes: Based on the average second mechanical specific energy and the corresponding relationship, the brittleness index corresponding to the average second mechanical specific energy is determined, and the reservoir type corresponding to the first fracturing section is determined based on the brittleness index.

10. The method for fracturing horizontal wells in volcanic rock according to claim 9, characterized in that, Before determining the reservoir type corresponding to the first fracturing section based on the average second mechanical specific energy, the method further includes: obtaining the lithology of the well logging and the lithology of the target horizontal well; Establishing the correspondence between the second mechanical specific energy and the brittleness index includes: For each lithology, a correspondence between the second mechanical specific energy and the brittleness index is established; The step of determining the brittleness index corresponding to the average second mechanical specific energy based on the average second mechanical specific energy and the corresponding relationship includes: From the various correspondences, a target correspondence corresponding to the lithology of the target horizontal well is determined, and based on the average second mechanical specific energy and the target correspondence, a brittleness index corresponding to the average second mechanical specific energy is determined.

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