A torque decomposition analysis method for assisting in the assessment of downhole conditions in oil and gas wells

Abstract

This invention discloses a torque decomposition analysis method for assisting in the assessment of downhole conditions in oil and gas wells. For a torque decomposition diagram within a Cartesian coordinate system where torque data is relatively uniformly distributed by depth and exhibits certain clustering or dispersion patterns, the downhole condition can be assessed by observing and comparing the similarities, differences, and interrelationships of drilling torque, idle torque, bit torque, and starting torque at different depths or depth intervals, or by combining this method with other information. In the torque decomposition diagram, if the drilling torque distribution exhibits sudden increases or decreases in a central region, fluctuations, or changes in distribution patterns with well depth, the source of the change in drilling torque pattern can be determined based on the corresponding changes in the idle torque and bit torque at the corresponding depths. Generally, the distribution pattern of the data itself causing the change tends to align with the trend of the drilling torque distribution pattern.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas well drilling engineering technology, and in particular relates to a torque decomposition analysis method for assisting in judging the downhole conditions of oil and gas wells. Background Technology

[0002] Torque is one of the common parameters in oil and gas well drilling engineering. Recording and observing changes in torque is one of the common ways to judge downhole conditions in drilling engineering.

[0003] Currently, the methods for recording and analyzing torque in the industry are limited, with qualitative analysis being stronger than quantitative analysis and a lack of systematic approach. When it is difficult to directly measure drill bit torque, empirical formulas or coefficients are usually used to indirectly approximate the drill bit torque, resulting in low accuracy. Summary of the Invention

[0004] The problem this invention aims to solve is to provide a torque decomposition analysis method for assisting in the assessment of downhole conditions in oil and gas wells. This method categorizes collected torque data into drilling torque, idle torque, and starting torque, and directly calculates the drill bit torque. It plots all torque values ​​on the same graph for more intuitive comparison. The invention also proposes a safe starting torque range and a method for early warning of drill string sticking risk. Furthermore, it proposes drawing control lines for torque distribution ranges and quantitatively analyzing torque distribution by measuring the torque fluctuation radius, thus providing auxiliary information for assessing downhole conditions.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a torque decomposition analysis method for assisting in judging the downhole conditions of oil and gas wells, comprising the following steps:

[0006] S1: Collect data on the variation of drilling torque with well depth obtained from on-site measurements;

[0007] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements;

[0008] S3: Collect data on the variation of starting torque with well depth obtained from on-site measurements;

[0009] S4: Calculated data on the variation of drill bit torque with well depth;

[0010] S5: Plot the drilling torque, idling torque, starting torque and drill bit torque data on a rectangular coordinate system to obtain a torque decomposition diagram;

[0011] S6: By comparing the differences in the drilling torque, idling torque, drill bit torque, and starting torque corresponding to different depths or depth ranges in the torque decomposition diagram, the downhole condition of the oil and gas well can be determined.

[0012] Furthermore, in S3, the starting torque is the highest peak value of the instantaneous torque at the start of the rotational speed after each drill rod is connected or disconnected, and the highest peak value of the torque is taken within 15 seconds after the rotational speed is turned on and stabilized.

[0013] Furthermore, in S4, the drill bit torque at a certain depth is equal to the drilling torque at the same depth minus the idling torque at that depth.

[0014] Furthermore, step S6 includes the following steps:

[0015] S61: Draw control lines in the torque decomposition diagram to determine the torque magnitude and torque fluctuation range;

[0016] S62: Draw the torque fluctuation radius within the torque fluctuation range to measure the torque distribution range;

[0017] S63: Draw the control line of the idling torque distribution range and measure the fluctuation radius to determine the wellbore cleanliness;

[0018] S64: Draw the control line for the drill bit torque distribution range to determine the degree of contact between the drill bit and the formation;

[0019] S65: Draw the control line of the drill bit torque distribution range and measure the fluctuation radius to determine the mechanical vibration when the drill bit drills into the formation;

[0020] S66: Determine the risk of the downhole drill string sticking based on the relationship between the starting torque and the safe range of the starting torque.

[0021] Furthermore, in S61, the control lines include a drilling torque control line, an idle torque control line, and a drill bit torque control line. Each set of control lines includes a center line and two boundary lines. The two boundary lines are located on two symmetrical sides of the center line, and the two boundary lines are parallel to the center line. The distance from the center line to the two boundary lines is equal.

[0022] Furthermore, S62 includes the following steps:

[0023] S621: Draw a straight line H that is not parallel to the center line within the torque fluctuation range;

[0024] S622: The intersection point of the straight line H and the center line is A, and the intersection points of the straight line H and the two boundary lines are B and C;

[0025] S623: The length of line segment AB or AC is the torque fluctuation radius.

[0026] Furthermore, in S63, when the drill pipe and downhole tool structure used in depth A is inconsistent with that used in depth B, the difference in structural length between the two is less than or equal to 10% of the length of the drill pipe and downhole tool structure used in depth A, and is also less than 10% of the length of the drill pipe and downhole tool structure used in depth B; the difference in rotation speed, displacement, and retrieval speed parameters used during idling and reaming of the drill string in depth A and depth B does not exceed 25%; and the difference in wellbore trajectory dogleg degree between depth A and depth B does not exceed 5° / 30m, if the idling torque centerline position of depth A is biased towards higher torque than that of depth B, or the idling torque fluctuation radius of depth A is larger than that of depth B, it indicates that the wellbore cleanliness of depth A is worse than that of depth B.

[0027] Furthermore, in S64, if the drill bit torque centerline position in depth A is biased towards higher torque than that in depth B, it indicates that the drill bit in depth A has a deeper contact with the formation than that in depth B.

[0028] Furthermore, in S65, if the drill bit torque fluctuation radius is larger in depth A than in depth B, it indicates that the mechanical vibration occurring at the drill bit is greater when drilling into the formation in section A than when drilling into the formation in section B.

[0029] Furthermore, S66 includes the following steps:

[0030] S661: The combined range of the idling torque fluctuation range and the drilling torque fluctuation range is called the starting torque safe range. The starting torque should normally be distributed within this starting torque safe range. If the starting torque is greater than this range, it can be considered that there is a risk of the downhole drill string sticking.

[0031] S662: Determine whether the starting torque is within the safe range of starting torque. If not, there is a risk of sticking in the downhole drill string of the oil and gas well.

[0032] S663: The card-sticking risk is divided into three levels from low to high: Level 1 card-sticking risk, Level 2 card-sticking risk, and Level 3 card-sticking risk.

[0033] S664: When the starting torque exceeds the safe range of the starting torque, the downhole drill string of the oil and gas well has a first-level risk of sticking; if the starting torque of the next drill string returns to the safe range of the starting torque, the first-level risk of sticking is eliminated; if the starting torque of the next drill string exceeds the safe range of the starting torque again, the downhole drill string of the oil and gas well has a second-level risk of sticking, and S665 is executed.

[0034] S665: If the starting torque of two consecutive drill strings is greater than the safe range of the starting torque, the downhole drill string of the oil and gas well has a level 2 risk of sticking; if the starting torque of the next drill string returns to the safe range of the starting torque, the risk is reduced to level 1, and S664 is executed; if the starting torque of the next drill string is greater than the safe range of the starting torque again, the downhole drill string of the oil and gas well has a level 3 risk of sticking, and S666 is executed.

[0035] S666: If the starting torque of three consecutive columns is greater than the safe range of the starting torque, the downhole drill string of the oil and gas well has a level three risk of stuck. If drilling operations are resumed after measures are taken to prevent the drill string from getting stuck, and it is necessary to continue to use the starting torque to assist in judging the risk of stuck drill string, the risk level will be recalculated cumulatively.

[0036] The advantages and positive effects of this invention are:

[0037] This invention plots four types of torque—drilling torque, idling torque, drill bit torque, and start-up torque—on the same rectangular coordinate system. It also uses methods such as plotting control lines and fluctuation radii of torque distribution intervals to describe the trend changes in torque distribution, providing auxiliary basis for judging changes in downhole conditions and improving the efficiency and accuracy of operational decision-making. Attached Figure Description

[0038] Figure 1 This is an overall flowchart of an embodiment of the present invention.

[0039] Figure 2 This is a torque decomposition diagram of the X-A5 oil and gas well in a specific embodiment of the present invention, during drilling operations using a 311.15mm drill bit. It illustrates, in conjunction with the specific embodiment, the use of torque decomposition analysis to assist in determining that there are no abnormalities in the downhole conditions.

[0040] Figure 3 This is a torque decomposition diagram of an oil and gas well, code-named X-A18, during drilling operations using a 311.15mm drill bit, specifically according to Embodiment 2 of the present invention. It illustrates, in conjunction with Embodiment 2, the use of torque decomposition analysis to assist in judging the risk of downhole drill string sticking.

[0041] Figure 4 This is a torque decomposition diagram of the X-A2 oil and gas well in the third specific embodiment of the present invention, during drilling operations using a 311.15mm drill bit. Figure 5 Is Figure 4 Based on this, a schematic diagram of the control lines for the distribution range of drill bit torque is drawn. Figure 6 Is Figure 5 Based on this, a schematic diagram of the drill bit torque fluctuation radius is drawn. Figure 4 , Figure 5 , Figure 6The following is a schematic illustration of the use of torque decomposition analysis to assist in the judgment of abnormal conditions in the well, with reference to specific embodiment three.

[0042] Figure 7 This is a torque decomposition diagram of the X-A17 oil and gas well in the fourth specific embodiment of the present invention, during drilling operations using a 311.15mm drill bit. Figure 8 Is Figure 7 Based on this, a schematic diagram of the idling torque distribution range control line and torque fluctuation radius is drawn. Figure 7 , Figure 8 The following is a schematic illustration of the use of torque decomposition analysis to assist in the judgment of abnormal conditions in the well, with reference to specific embodiment four.

[0043] Figure 9 This is a torque decomposition diagram of the S-H4d oil and gas well, a specific embodiment of the present invention, during drilling operations using a 215.9mm drill bit. Figure 10 Is Figure 9 Based on this, a schematic diagram of the drill bit torque variation is further shown. Figure 9 , Figure 10 The fifth specific embodiment illustrates the use of torque decomposition analysis to assist in the judgment of downhole anomalies.

[0044] Figure 11 This is a torque decomposition diagram of the X-A11 oil and gas well, a specific embodiment of the present invention, during drilling operations using a 215.9mm drill bit. Figure 12 It uses the drill bit torque data obtained from torque decomposition of well X-A11 to calculate the drill bit mechanical specific energy value and plot the drill bit mechanical specific energy curve. Figure 11 , Figure 12 The following is a schematic illustration of how torque decomposition analysis can be used to assist in determining the rock-breaking efficiency of downhole drill bits, with reference to Specific Implementation Example 6. Detailed Implementation

[0045] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0047] like Figure 1 As shown, a torque decomposition analysis method for assisting in determining the downhole condition of oil and gas wells includes the following steps:

[0048] S1: Collect data on the variation of drilling torque with well depth obtained from on-site measurements. This refers to the data on the variation of surface torque with well depth measured under conditions of applied drill pressure and throttle rotation. Drilling torque refers to the surface torque measured when the drill bit is in full contact with and interacting with the formation under conditions of applied drill pressure (i.e., drill pressure greater than 0) and throttle rotation, which is referred to in drilling engineering as the drill bit penetrating the formation.

[0049] S2: Collect data on the variation of idling torque with well depth obtained from field measurements, specifically the data on the variation of surface torque with well depth when the drill pressure is 0, the operating speed is 0, and the drill string is descending. Idle torque refers to the surface torque measured when the drill pressure is 0 and the operating speed is 0. A key characteristic of idling torque is that the drill bit does not interact with the formation; in drilling engineering terms, this means the drill bit has not penetrated the formation. Idle torque is generally divided into upward idling torque (where the drill string rotates upwards along the wellbore), downward idling torque (where the drill string rotates downwards along the wellbore), and stationary idling torque (where the drill string rotates but does not move axially relative to the wellbore). The idling torque referred to in this embodiment is downward idling torque.

[0050] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. The starting torque is the highest peak value of the instantaneous torque at the start of rotation speed after each drill pipe is connected or disconnected. The highest peak value of torque within 15 seconds after the rotation speed is turned on and stabilized is taken.

[0051] S4: Calculate the data on the change of drill bit torque with well depth. Specifically, subtract the idle torque from the drilling torque at the same depth to calculate the data on the change of drill bit torque with well depth. Drill bit torque refers to the torque transmitted from the surface through the drilling tools to the downhole drill bit and acting on it. The aforementioned drilling tools generally refer to commonly used tools in drilling engineering, such as drill pipe, weighted drill pipe, drill collars, connectors, shock absorbers, downhole measurement and power tools, as well as other downhole tools connected directly or indirectly between the rotary table or top drive and the drill bit. Drill bit torque is generally not directly measured in drilling engineering. When drilling pressure is applied and the rotation speed is turned on, the drill bit torque is greater than 0. When the drilling pressure is 0 or the rotation speed is 0, the drill bit torque is equal to 0. Sometimes, when the drill string rotates and moves upward along the wellbore from the bottom of the well, the drilling pressure is 0, and the drill bit torque is also greater than 0 due to friction between the drill bit and the open hole wall, but this condition is not within the scope of this embodiment.

[0052] S5: Plot a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and bit torque data on the Cartesian coordinate system to obtain a torque decomposition diagram. S6: Compare the differences in drilling torque, idle torque, bit torque, and starting torque at different depths or depth ranges in the torque decomposition diagram to determine the downhole condition of the oil and gas well.

[0053] Specifically, S6 includes the following steps:

[0054] S61: Draw control lines in the torque decomposition diagram to determine the torque magnitude and torque fluctuation range. Specifically, in the torque decomposition diagram, drilling torque, idling torque, and drill bit torque often exhibit a fluctuating distribution. That is, the magnitude of each of these torque values ​​is not fixed within a certain depth range, nor does it have a simple linear or functional relationship with depth, but rather fluctuates within a certain range. This embodiment determines the relative magnitude and fluctuation range of torque by drawing control lines in the torque decomposition diagram. Control lines can be drawn separately for drilling torque, idling torque, and drill bit torque within a certain depth range. The control lines can be straight line segments or segments of curves that conform to a certain functional law; in this embodiment, straight line segments are used.

[0055] Specifically, each set of control lines includes a center line and two boundary lines. The two boundary lines are located on opposite sides of the center line, are parallel to the center line, and are equidistant from the center line.

[0056] The slope and position of the center line and boundary lines are not uniquely determined. The following principles should be followed when drawing the lines: the center line should be along the distribution trend of the most concentrated torque, and the torque points should be evenly distributed on both sides of the center line; the area between the boundary lines should encompass the vast majority of the torque distribution points, which should be determined according to the needs of the project or research. In this embodiment, the boundary lines should encompass more than 90% of the torque distribution points.

[0057] S62: Plot the torque fluctuation radius within the torque fluctuation range to measure the torque distribution range. The torque fluctuation radius is an important indicator for measuring the torque distribution range. Specifically, S62 includes the following steps:

[0058] S621: Draw a straight line H that is not parallel to the center line within the torque fluctuation range.

[0059] S622: The intersection of line H and the center line is A, and the intersection of line H and the two boundary lines is B and C.

[0060] S623: The length of line segment AB or AC is the torque fluctuation radius.

[0061] Specifically, there are generally two ways to draw the straight line H: one is perpendicular to the center line, and the other is parallel to the torque coordinate axis of the rectangular coordinate system in the torque decomposition diagram. Both methods can be used, but it is important to note that when comparing the torque distribution ranges of different regions, the method of drawing the straight line H in different torque distribution intervals should be consistent. That is, the straight line H in each region should be perpendicular to the center line of its respective region, or parallel to the torque coordinate axis. The two methods should not be mixed in the same comparative analysis or series of analyses. This embodiment uses the method of drawing the straight line H parallel to the torque coordinate axis.

[0062] Within a Cartesian coordinate system, torque data exhibits a relatively uniform distribution based on depth, with certain clustering or dispersion patterns. By observing and comparing the similarities, differences, and interrelationships of drilling torque, idle torque, bit torque, and starting torque at different depths or depth ranges, one can determine or combine this data with other information to assist in assessing downhole conditions, including wellbore condition, tubing condition, and bit condition. Typically, this can help determine or assist in assessing wellbore cleanliness, the risk of stuck tubing, bit rock-breaking efficiency, bit wear, downhole power tool condition, formation lithology changes, and formation drillability. This provides more evidence for analyzing the possibility of changes in downhole conditions; however, this analysis is supplementary rather than decisive, and should be combined with other relevant geological and engineering data for comprehensive analysis to draw conclusions.

[0063] In torque decomposition diagrams, the drilling torque distribution with well depth may exhibit sudden increases or decreases in the central region, fluctuations, and changes in distribution pattern. By analyzing the corresponding changes in the idling torque and drill bit torque at the same depth, it can be determined whether the source of the drilling torque pattern change is a change in the idling torque or the drill bit torque. Generally, the change in the distribution pattern of the source data itself is consistent with the trend of the drilling torque distribution pattern.

[0064] S63: Draw the control line of the idling torque distribution range and measure the fluctuation radius to determine the wellbore cleanliness. Specifically, when the drill pipe and downhole tools used in depth sections A and B have basically the same structure, and the length of the drill pipe or downhole tool with inconsistent structure accounts for no more than 10% of the total length of the drill pipe and downhole tools in the well, that is, the structure of the drill pipe and downhole tools at depth A is Wa, and the structure of the drill pipe and downhole tools at depth B is Wb, and the part that differs between Wa and Wb is Wa-b, the length of Wa-b is less than or equal to 10% of the length of Wa, and also less than 10% of the length of Wb; the difference in rotation speed, displacement, and retrieval speed parameters used by the drill string during idle rotation and reaming between depth sections A and B does not exceed 25%; and the difference in wellbore trajectory dogleg degree between depth sections A and B does not exceed 5° / 30m, if the idle torque centerline position of depth section A is biased towards higher torque than that of depth section B, or the idle torque fluctuation radius of depth section A is larger than that of depth section B, it indicates that the wellbore cleanliness of depth section A is worse than that of depth section B.

[0065] S64: Draw control lines for the drill bit torque distribution range to determine the degree of contact between the drill bit and the formation. If the drill bit torque centerline position in depth A is biased towards higher torque than in depth B, it indicates that the drill bit has a deeper contact with the formation in depth A than in depth B, meaning the drill bit has penetrated deeper into the formation in engineering terms. This deeper contact between the drill bit and the formation mainly stems from three reasons: Reason 1, significant changes in key drilling parameters such as drilling pressure, rotation speed, and mud pump displacement; Reason 2, replacement of the drill bit or drill bit components, downhole tools, etc., between sections A and B; Reason 3, significant differences in formation lithology between sections A and B. Based on the actual situation, if any one of the three reasons occurs, the change in drill bit torque is determined to be mainly caused by that reason; if two or three of the three reasons occur, the change in torque is determined to be caused by two or more main reasons.

[0066] S65: Draw control lines for the drill bit torque distribution range and measure the fluctuation radius to determine the mechanical vibration of the drill bit when drilling into the formation. If the drill bit torque fluctuation radius is larger in depth A than in depth B, it indicates that the mechanical vibration at the drill bit is greater when drilling into formation A than when drilling into formation B. The main reasons can be determined by referring to the three reasons mentioned above.

[0067] If the drill bit torque suddenly decreases at a certain depth and tends to approach zero, accompanied by a sharp decrease in the rate of drilling (RDR) while maintaining constant drilling pressure, rotational speed, and mud pump displacement, the possible causes are mainly threefold: First, the drilled formation has become harder, reducing its drillability. Second, the drill bit's mechanical structure has been severely damaged, or the drill bit is covered in mud. Third, the downhole power tool is damaged and can no longer effectively transmit power to the drill bit. If no power tool is installed downhole, the third cause is not considered.

[0068] Torque decomposition allows for a more accurate analysis of drill bit rock-breaking efficiency based on the theory of drill bit mechanical energy. Mechanical energy refers to a physical concept used in drilling engineering to describe the efficiency of drill bits in breaking rock. While various methods exist for calculating mechanical energy, their core principles are largely the same; specific algorithms are not described here. It's important to note that many mechanical energy algorithms require drill bit torque as a parameter. However, drill bit torque is typically not directly measurable, and the industry commonly uses empirical formulas to estimate it, resulting in lower accuracy. By simultaneously collecting the parameters needed for mechanical energy calculation, drilling torque and idling torque can be acquired and the drill bit torque calculated using the method described in this embodiment. This drill bit torque can be directly used to calculate mechanical energy with higher accuracy.

[0069] S66: Based on the relationship between the starting torque and the safe range of the starting torque, assess the risk of the drill string sticking in the well. Specifically, S66 includes the following steps:

[0070] S661: The combined range of the idling torque fluctuation range and the drilling torque fluctuation range is called the starting torque safe range. The starting torque should normally be distributed within this starting torque safe range. If the starting torque is greater than this range, it can be considered that there is a risk of the downhole drill string sticking.

[0071] S662: Determine whether the starting torque is within the safe range of starting torque. If not, there is a risk of the oil and gas well downhole drill string sticking.

[0072] S663: The risk of card sticking is divided into three levels from low to high: Level 1 card sticking risk, Level 2 card sticking risk, and Level 3 card sticking risk.

[0073] S664: When a starting torque exceeds the safe range of starting torque, there is a level one risk of stuck wire in the oil and gas well downhole drill string; if the starting torque of the next string returns to the safe range of starting torque, the level one risk of stuck wire is eliminated; if the starting torque of the next string exceeds the safe range of starting torque again, there is a level two risk of stuck wire in the oil and gas well downhole drill string, and S665 is executed.

[0074] S665: If the starting torque of two consecutive drill strings is greater than the safe range of starting torque, the downhole drill string of the oil and gas well has a level 2 risk of sticking; if the starting torque of the next drill string returns to the safe range of starting torque, the risk is reduced to level 1 sticking, and S664 is executed; if the starting torque of the next drill string is greater than the safe range of starting torque again, the downhole drill string of the oil and gas well has a level 3 risk of sticking, and S666 is executed.

[0075] S666: If the starting torque of three consecutive columns is greater than the safe range of starting torque, there is a level 3 risk of stuck drill string in the oil and gas well. If drilling operations are resumed after measures are taken to prevent the drill string from getting stuck, and it is necessary to continue to use the starting torque to help determine the risk of stuck drill string, the cumulative risk level will be recalculated. Specific Implementation Example 1

[0077] The technical solution of the present invention will be further described below with reference to specific embodiments, such as... Figure 2 As shown, taking an oil and gas well designated X-A5 as an example, this is a torque breakdown diagram during drilling operations using a 311.15mm drill bit. The horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the diagram are: ○ drilling torque, × drill bit torque, + idle torque, and △ starting torque.

[0078] The specific implementation steps are as follows:

[0079] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0080] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0081] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. After each drill pipe is connected or disconnected, the highest peak value of the instantaneous torque at the starting speed is taken. The highest peak value of torque within 15 seconds after the speed is turned on and stabilized is taken.

[0082] S4: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0083] S5: Plot a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and drill bit torque data from S1 to S4 on a Cartesian coordinate system diagram, see... Figure 2 .

[0084] S6: By Figure 2 It can be seen that the drilling torque has the highest overall trend, while the drill bit torque and idle torque have a lower overall trend than the drilling torque. The drill bit torque distribution does not change significantly with well depth, and the value in the central region remains basically unchanged. The idle torque, drilling torque, and starting torque also show an increasing trend with increasing well depth, and the increase is basically stable. The starting torque is distributed within the merged range of the idle torque fluctuation range and the drilling torque fluctuation range, that is, the starting torque is within the safe range.

[0085] Figure 2 The image shown is a common decomposition diagram of normal torque. Figure 2 There are no abnormal signs shown. Specific Implementation Example 2

[0087] like Figure 3 As shown, taking an oil and gas well designated X-A18 as an example, this is a torque decomposition diagram during drilling operations using a 311.15mm drill bit. The horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the diagram are: ○ drilling torque, × drill bit torque, + idle torque, and △ starting torque, mainly illustrating the method for identifying abnormal starting torque.

[0088] The specific implementation steps are as follows:

[0089] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0090] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0091] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. After each drill pipe is connected or disconnected, the highest peak value of the instantaneous torque at the starting speed is taken. The highest peak value of torque within 15 seconds after the speed is turned on and stabilized is taken.

[0092] S4: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0093] S5: Draw a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and drill bit torque data described in S1 to S4 on a Cartesian coordinate system diagram, see [link / details]. Figure 3 .

[0094] S6: As Figure 3 As shown, the starting torque at 2978m is greater than the safe starting torque range obtained by combining the idling torque fluctuation range and the drilling torque fluctuation range for the first time. This is judged as a level 1 risk of drill string sticking, and the monitoring of drill string sticking risk should be strengthened.

[0095] Once the starting torque recovers within the safe range after 2978m, the risk of primary sticking is eliminated.

[0096] The starting torque at 3094m is greater than the safe starting torque range, which is judged as a level 1 risk of drill string sticking. Monitoring of drill string sticking risk should be strengthened.

[0097] If the starting torque of the next drill string after 3094m is still greater than the safe range, the risk of drill string sticking is upgraded to level two. While strengthening the monitoring of drill string sticking risk, emergency preparation measures should be made for sticking.

[0098] After two consecutive drill string starting torques at 3094m and 3180m exceeded the safe range, monitoring showed that the starting torque for the next drill string returned to within the safe range, and the drill string sticking risk was classified as Level 1. Furthermore, continued monitoring showed that the starting torque for the next drill string remained within the safe range, thus eliminating the drill string sticking risk.

[0099] If the starting torque of the drill string is found to be greater than the safe range at 3526m, 3555m, and 3584m, the risk of drill string sticking is raised to level three. Drilling should be stopped immediately and measures should be taken to prevent drill string sticking. Specific Implementation Example 3

[0101] The technical solution of the present invention will be further described below with reference to specific embodiments, such as... Figure 4As shown, taking an oil and gas well designated X-A2 as an example, this is a torque decomposition diagram during drilling operations using a 311.15mm drill bit. The horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the diagram are: ○ drilling torque, × drill bit torque, + idle torque, and △ starting torque.

[0102] The specific implementation steps are as follows:

[0103] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0104] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0105] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. After each drill pipe is connected or disconnected, the highest peak value of the instantaneous torque at the starting speed is taken. The highest peak value of torque within 15 seconds after the speed is turned on and stabilized is taken.

[0106] S4: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0107] S5: Draw a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and drill bit torque data described in S1 to S4 on a Cartesian coordinate system diagram, see [link / details]. Figure 4 .

[0108] S6: As Figure 4 As shown, the overall trend of idling torque increases with increasing well depth, the data distribution is relatively uniform and the degree of aggregation is good, and there are no abnormalities; the starting torque distribution is within the safe range and there are no abnormalities; the drilling torque data distribution pattern is similar to that of the drill bit torque, both of which show an increase in the central region value around 1730m, and the torque data distribution is more dispersed than before around 2220m, that is, the torque fluctuation range is larger.

[0109] To study and further illustrate the trend of drill bit torque variation in well X-A2, the drilling torque, idling torque, and starting torque in the torque decomposition diagram were hidden, retaining only the drill bit torque. A drill bit torque control line was then plotted in the diagram, as shown below. Figure 5 As shown.

[0110] Figure 5The two horizontal dotted lines shown divide the entire torque distribution into three regions. Within each region, control lines for the torque distribution interval are drawn: one solid line segment represents the center line of the torque distribution interval, and two dashed lines represent the boundary lines. The depth limits for dividing the regions are not precise. The main basis for defining the regions is a significant change in torque, including two types of significant changes: first, a significant change in the continuity of torque values ​​in the central region where the torque distribution is relatively dense along the well depth; and second, a significant change in the range of torque distribution.

[0111] Figure 6 The image shown is hidden. Figure 5 The diagram of the drill bit torque point only retains the illustrations of the partition line segments, the center line of the torque distribution interval, and the boundary line. The purpose of this diagram is only to more clearly illustrate the characteristics and functions of each line segment and to avoid the overlap between the line segment endpoint markings and the drill bit torque point, which would lead to unclear distinction.

[0112] The dashed lines MM′ and NN′ divide the drill bit torque distribution map into three zones: A, B, and C. The zones are defined by the significant changes in the magnitude of the drill bit torque center region along well depth in zones A and B, and the significant changes in the range of the drill bit torque distribution area in zones B and C. In zone A, the dashed line segment AbAb′ represents the left boundary line of the drill bit torque, the dashed line segment AcAc′ represents the right boundary line, and AaAa′ represents the center line of the drill bit torque distribution interval. The two boundary lines are parallel to the center line, and the distance from the center line to the two boundary lines is equidistant. The slope and position of the center line and boundary lines are not uniquely determined. The following principles are followed when drawing the lines: the center line should follow the distribution trend of the most concentrated torque, and the torque points should be evenly distributed on both sides of the center line; the area between the boundary lines should encompass the vast majority of the torque distribution points, specifically determined according to the needs of the project or research. This method recommends that the area between the boundary lines encompass more than 90% of the torque distribution points.

[0113] The boundary lines of region B are BbBb′ and BcBc′, and the center line is BaBa′; the boundary lines of region C are CbCb′ and CcCc′, and the center line is CaCa′.

[0114] The centerline of region B is significantly shifted towards a direction with higher torque values ​​compared to the centerline of region A. This indicates that the drill bit torque is generally higher in the section from approximately 1730m to 2220m than in the section above 1730m, suggesting that the drill bit makes deeper contact with the formation after 1730m, which is considered by engineers to mean that the drill bit penetrates deeper into the formation. To determine the cause of this change, three main factors should be considered: First, a significant change in key drilling parameters such as drill pressure, rotation speed, and mud pump displacement; second, replacement of the drill bit or drill bit components, or downhole tools around 1730m; and third, a significant difference in formation lithology before and after 1730m. Based on the actual situation, if any one of these three factors occurs, the change in drill bit torque is determined to be primarily caused by that factor; if two or three of these factors occur, the change in torque is determined to be caused by two or more major factors.

[0115] exist Figure 6 The radius of the drill bit torque distribution range is plotted and measured. There are two methods for plotting the torque fluctuation radius: one is to draw a perpendicular line to the center line, which intersects the center line of the torque distribution range and each of the two boundary lines at one point. For example... Figure 6 If line segment RbRc in region A is perpendicular to the center line AaAa′ of region A, then the length of line segment RaRb or RaRc is the torque fluctuation radius of region A. Another way to draw the torque fluctuation radius is to draw a straight line parallel to the torque coordinate axis, which intersects the center line of the torque distribution interval and each of the two boundary lines at one point. For example... Figure 6 In region A, line segment ObOc is parallel to the horizontal axis of the graph, i.e., the torque axis. Therefore, the length of line segment OaOb or OaOc represents the torque fluctuation radius in region A. Both methods can be used, but it's crucial that when comparing the torque distribution ranges of different regions, the method for drawing the torque fluctuation radius is consistent. That is, the torque fluctuation radius of each region should be either perpendicular to its centerline or parallel to the coordinate axis. The two methods should not be mixed. This method recommends using the method of drawing the radius parallel to the torque axis.

[0116] exist Figure 6In the drilling data, the torque fluctuation radius OaOb in zone A is roughly the same as that in zone B (PaPb), while the torque fluctuation radius QaQb in zone C is significantly larger than both OaOb and PaPb, indicating that the drill bit in zone C experienced more severe vibrations during rotary drilling. Understanding the magnitude of the torque fluctuation radius and the changes in the torque fluctuation range can be combined with other information to assist engineers and researchers in analyzing the causes of the problem. If drill bit A was used in zone B and drill bit B was used in zone C, drill bit A is more suitable for the given formation and drilling parameters. If group A of engineering parameters was used in zone B and group B of engineering parameters was used in zone C, group A parameters are more conducive to obtaining a more stable torque. If the same engineering parameters were used in zones B and C, and the drill bit was not changed, the formation lithology can be assessed based on logging and geological data. If the formation change is indeed the cause of the significantly increased drill bit torque fluctuation range, suggestions can be made to adjust drilling parameters or replace the drill bit or drilling tools to obtain a more stable drill bit torque.

[0117] Obtaining the radius of torque fluctuation in the drill bit provides more evidence for analyzing the possibility of changes in downhole conditions. However, this analysis is auxiliary rather than decisive. It should be combined with other relevant geological and engineering data for comprehensive analysis to draw conclusions. Specific Implementation Example 4

[0119] The technical solution of the present invention will be further described below with reference to specific embodiments, such as... Figure 7 As shown, taking an oil and gas well designated X-A17 as an example, this is a torque breakdown diagram during drilling operations using a 311.15mm drill bit. The horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the diagram are: ○ drilling torque, × drill bit torque, + idle torque, and △ starting torque. Figure 7 The top left shows the complete torque decomposition diagram; because there are many overlapping torque data points, the torques are displayed separately to facilitate identification of their distribution characteristics. Figure 7 The top right corner displays only the drill bit torque and starting torque; Figure 7 The bottom left shows only the drilling torque; Figure 7 The bottom right corner displays only the idle torque.

[0120] The specific implementation steps are as follows:

[0121] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0122] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0123] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. After each drill pipe is connected or disconnected, the highest peak value of the instantaneous torque at the starting speed is taken. The highest peak value of torque within 15 seconds after the speed is turned on and stabilized is taken.

[0124] S4: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0125] S5: Plot a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and drill bit torque data obtained in steps S1 to S4 on a Cartesian coordinate system diagram, see [link to diagram]. Figure 7 .

[0126] S6: By Figure 7 As can be seen, the starting torque is distributed within the safe range with no obvious abnormalities; the drill bit torque and drilling torque are both normal; the idling torque, starting from around 1800m, shows a significantly more dispersed distribution in the lower part compared to the upper part, with a significantly larger fluctuation range. A straight line MM′ is plotted in the torque decomposition graph to distinguish between two regions with significantly different torque fluctuation ranges, such as... Figure 7 As shown in the bottom right corner.

[0127] To further analyze the changes in the idling torque fluctuation range, control lines for the idling torque distribution intervals were drawn for the two regions divided by MM′, as follows: Figure 8 As shown on the left. To more clearly illustrate the characteristics and functions of each line segment and to avoid confusion caused by overlap between the line segment endpoint markers and the idling torque points, the idling torque data points are hidden, and only the control lines of their distribution range are retained, as shown on the left. Figure 8 right.

[0128] The dashed line MM′ divides the idling torque distribution map into upper and lower sections, based on a significant change in the range of the idling torque distribution area. In the half-section above 1800m, the dashed line segment AbAb′ represents the left boundary line of the idling torque, the dashed line segment AcAc′ represents the right boundary line of the idling torque, and AaAa′ represents the center line of the idling torque distribution interval. The two boundary lines are parallel to the center line, and the distance from the center line to the two boundary lines is equal. The slope and position of the center line and boundary lines are not uniquely determined. The following principles are followed when drawing the lines: the center line should follow the distribution trend of the most concentrated torque, and the torque points should be evenly distributed on both sides of the center line; the area between the boundary lines should encompass the vast majority of the torque distribution points, specifically determined according to the needs of the project or research. This method recommends that the area between the boundary lines encompass more than 90% of the torque distribution points.

[0129] The boundary lines of the half-zone below 1800m are BbBb′ and BcBc′, and the center line is BaBa′.

[0130] exist Figure 8 Plot and measure the radius of the idling torque distribution interval. For example... Figure 8 In the upper right half of the region, the line segment ObOc is parallel to the horizontal axis of the graph, i.e. the torque axis. Therefore, the length of the line segment OaOb or OaOc is the radius of torque fluctuation in the upper half of the region. Figure 8 In the lower right half, line segment PbPc is parallel to the horizontal axis in the graph. The length of line segment PaPb or PaPc is the torque fluctuation radius in the lower half. The length of PaPb is significantly greater than that of OaOb, indicating a larger idling torque fluctuation radius in the lower half.

[0131] Based on the comparison of the idling torque fluctuation radius, it is indicated that the drilling tool experiences greater vibration and frictional resistance when rotating below 1800m in the wellbore compared to when rotating above 1800m. Combined with other well information, no different sizes of drill pipe or downhole tools were used around 1800m depth, and the rotation speed, displacement, and retrieval speed used during idling and reaming did not change significantly at this depth. The dogleg variation of the wellbore trajectory between depths of 1285m and 2432m did not exceed 5° / 30m. Therefore, it is concluded that the wellbore cleanliness deteriorates below 1800m, with a significant increase in cuttings content. This information can assist engineers in making decisions to improve the cuttings-carrying capacity of the drilling fluid and to implement engineering measures to clean the cuttings within the wellbore. Specific Implementation Example 5

[0133] The technical solution of the present invention will be further described below with reference to specific embodiments, such as... Figure 9 As shown, taking an oil and gas well designated S-H4d as an example, during drilling operations using a 215.9mm drill bit, a sharp decrease in mechanical drilling rate occurred when drilling to a depth of approximately 4605m. To analyze this phenomenon, a torque decomposition diagram of well S-H4d during drilling operations using a 215.9mm drill bit is presented as follows. Figure 9 In the graph, the horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the graph are: ○ drilling torque, × drill bit torque, and + idle torque. This embodiment does not cover changes in starting torque; therefore, starting torque is not shown in the torque decomposition graph of this embodiment.

[0134] The specific implementation steps are as follows:

[0135] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0136] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0137] S3: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0138] S4: Plot a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, and drill bit torque data obtained in steps S1 to S3 on a Cartesian coordinate system diagram, see... Figure 9 .

[0139] S6: By Figure 9 As can be seen, at a depth of approximately 4605m, the drill bit torque decreases sharply, with the central torque value suddenly converging near 0. Simultaneously, the central drilling torque value also decreases significantly. However, the idle torque does not decrease significantly, and there is considerable overlap between the drilling torque and idle torque data points after 4605m. This indicates that the decrease in drilling torque is caused by a decrease in drill bit torque.

[0140] Hide Figure 9 Medium drilling torque and idle torque, only the drill bit torque is retained, such as Figure 10 As shown. From Figure 10 The sudden change in drill bit torque before and after the 4605m depth can be observed more clearly in the middle.

[0141] An investigation of drilling parameters during the drilling of this well with a 215.9mm drill bit into the formation from 4416m to 4645m revealed that the drilling pressure, rotational speed, and mud pump displacement did not change significantly around the 4605m depth. Based on the torque decomposition results and comprehensive analysis of the drilling parameters, the sharp decrease in mechanical drilling rate and drill bit torque can be attributed to three main reasons: First, the encountered formation lithology became harder, reducing drillability. Second, the drill bit's mechanical structure suffered severe damage, or the drill bit became mud-covered. Third, the downhole power tools were damaged, preventing effective power transmission to the drill bit.

[0142] The torque decomposition method, combined with the analysis of drilling parameters, provides auxiliary analytical basis for determining the sharp decrease in mechanical drilling rate that occurred when the 215.9mm drill bit in well S-H4d drilled into the formation at a depth of about 4605m. Specific Implementation Example Six

[0144] The technical solution of the present invention will be further described below with reference to specific embodiments, such as... Figure 11As shown, taking an oil and gas well designated X-A11 as an example, this is a torque decomposition diagram during drilling operations using a 215.9mm drill bit. The horizontal axis represents torque in kilonewton-meters (kN·m), and the vertical axis represents well depth in meters (m). The data included in the diagram are: ○ drilling torque, × drill bit torque, + idle torque, and △ starting torque.

[0145] The specific implementation steps are as follows:

[0146] S1: Collect data on the variation of drilling torque with well depth obtained from field measurements, that is, data on the variation of surface torque with well depth measured under the condition of applying drilling pressure (drilling pressure greater than 0) and starting the rotation speed.

[0147] S2: Collect data on the variation of idling torque with well depth obtained from on-site measurements, i.e., data on the variation of surface torque with well depth when drilling pressure is 0, starting rotation speed, and drilling tool descending.

[0148] S3: Collect data on the change of starting torque with well depth obtained from on-site measurements. After each drill pipe is connected or disconnected, the highest peak value of the instantaneous torque at the starting speed is taken. The highest peak value of torque within 15 seconds after the speed is turned on and stabilized is taken.

[0149] S4: Subtract the idle torque from the drilling torque at the same depth to calculate the data on how the drill bit torque changes with well depth.

[0150] S5: Draw a Cartesian coordinate system with torque as the horizontal axis and well depth as the vertical axis. Plot the drilling torque, idle torque, starting torque, and drill bit torque data described in S1 to S4 on a Cartesian coordinate system diagram, see [link / details]. Figure 11 .

[0151] S6: By Figure 11 It is evident that the overall trends of drill bit torque, idle torque, and drilling torque with well depth are relatively stable, without any obvious anomalies. The starting torque is distributed within the merged range of the idle torque fluctuation range and the drilling torque fluctuation range, meaning that the starting torque is within the safe range.

[0152] Mechanical specific energy of a drill bit, abbreviated as MSE, is used to measure the efficiency of a drill bit in breaking rock. The calculation of MSE requires the drill bit torque, the specific formula and calculation method of which are outside the scope of this patent and will not be described here. Drill bit torque data is obtained using a torque decomposition method. This data is then substituted into the MSE calculation formula to obtain the relationship between the mechanical specific energy of the X-11 well (215.9mm drill bit) and the formation depth (4285m to 4674m). A curve is then plotted on a rectangular coordinate system, as shown below. Figure 12 As shown.

[0153] The drill bit torque obtained by torque decomposition can more accurately assist in the analysis of drill bit rock breaking efficiency using the drill bit mechanical specific energy theory.

[0154] In summary, this invention plots four types of torque—drilling, idling, drill bit, and start-up—on the same rectangular coordinate system. It also uses the method of plotting control lines and fluctuation radii of torque distribution intervals to describe the trend changes in torque distribution, providing auxiliary basis for judging changes in downhole conditions and improving the efficiency and accuracy of operational decision-making.

[0155] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well, the method comprising: The method comprises the following steps: ​ S1: collecting data of drilling torque varying with well depth obtained from field measurement; S2: collecting data of idle torque varying with well depth obtained from field measurement; S3: collecting data of starting torque varying with well depth obtained from field measurement; S4: calculating data of drill bit torque varying with well depth; S5: plotting the drilling torque, the idle torque, the starting torque and the drill bit torque data in a rectangular coordinate system diagram to obtain a torque decomposition diagram; S6: comparing the difference patterns of the drilling torque, the idle torque, the drill bit torque and the starting torque corresponding to different depths or depth intervals in the torque decomposition diagram to determine the downhole condition of the oil and gas well.

2. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 1, wherein: In the S3, the starting torque is the highest peak value of instantaneous torque after each column of drill pipe is connected or disconnected, and the highest peak value of torque within 15 seconds after the rotation speed is started is taken.

3. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well according to claim 1 or 2, characterized in that: In the S4, the drill bit torque at a certain depth is equal to the drilling torque at the same depth minus the idle torque at the depth.

4. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well according to claim 1 or 2, characterized in that: The S6 comprises the following steps: S61: plotting a control line in the torque decomposition diagram to determine the torque size and the torque fluctuation interval; S62: plotting a torque fluctuation radius in the torque fluctuation interval to measure the torque distribution range; S63: plotting a control line of the idle torque distribution interval and measuring the fluctuation radius to determine the borehole cleaning condition; S64: plotting a control line of the drill bit torque distribution interval to determine the contact degree of the drill bit with the formation; S65: plotting a control line of the drill bit torque distribution interval and measuring the fluctuation radius to determine the mechanical vibration condition of the drill bit when drilling the formation; S66: determining the sticking risk of the downhole drill string according to the relationship between the starting torque and the starting torque safety interval.

5. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 4, wherein: In the S61, the control line comprises a drilling torque control line, an idle torque control line and a drill bit torque control line, each set of the control line comprises a center line and two boundary lines, the two boundary lines are located on the two sides of the center line respectively, the two boundary lines are parallel to each other, and the distance from the center line to the two boundary lines is equal.

6. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 5, wherein: The S62 comprises the following steps: S621: drawing a straight line H in the torque fluctuation interval, which is not parallel to the center line; S622: the intersection of the straight line H and the center line is A, and the intersection of the straight line H and the two boundary lines is B and C; S623: the length of the line segment AB or AC is the torque fluctuation radius.

7. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 4, wherein: In the S63, when the drill pipe and downhole tool structure used in the A depth section is inconsistent with the drill pipe and downhole tool structure used in the B depth section, the difference structure length between the two is less than or equal to 10% of the length of the drill pipe and downhole tool structure used in the A depth section, and less than or equal to 10% of the length of the drill pipe and downhole tool structure used in the B depth section; the difference between the rotation speed, displacement and lowering speed parameters used when the drill string idles and reams in the A depth section and the B depth section is not more than 25%; when the hole trajectory dogleg of the A depth section and the B depth section differs by not more than 5° / 30m, if the idle torque center line position of the A depth section deviates to high torque than that of the B depth section, or the idle torque fluctuation radius of the A depth section is larger than that of the B depth section, it indicates that the hole cleaning condition of the A depth section is worse than that of the B depth section.

8. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 4, wherein: In the S64, if the drill bit torque center line position of the A depth section deviates to high torque than that of the B depth section, it indicates that the A depth section has a deeper contact with the formation than the B depth section.

9. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 4, wherein: In the S65, if the drill bit torque fluctuation radius of the A depth section is larger than that of the B depth section, it indicates that the mechanical vibration occurring at the drill bit when drilling the A section formation is larger than that when drilling the B section formation.

10. The torque-decomposition analysis method for assisting in determining downhole conditions in a hydrocarbon well of claim 4, wherein: The S66 includes the following steps, S661: the combined interval of the idle torque fluctuation interval and the drilling torque fluctuation interval is referred to as the starting torque safety interval, and the starting torque normally should be distributed within the starting torque safety interval, and if the starting torque is greater than the interval, it can be considered that there is a risk of sticking of the downhole drill string; S662: whether the starting torque is within the starting torque safety interval is judged, and if not, there is a risk of sticking of the downhole drill string of the oil and gas well; S663: the sticking risk is divided into first-level sticking risk, second-level sticking risk and third-level sticking risk from low to high; S664: when one of the starting torques is greater than the starting torque safety interval, there is a first-level sticking risk of the downhole drill string of the oil and gas well; if the starting torque of the next column returns to within the starting torque safety interval, the first-level sticking risk is removed; if the starting torque of the next column is greater than the starting torque safety interval again, there is a second-level sticking risk of the downhole drill string of the oil and gas well, and S665 is executed; S665: if the starting torques of two consecutive columns are greater than the starting torque safety interval, there is a second-level sticking risk of the downhole drill string of the oil and gas well; if the starting torque of the next column returns to within the starting torque safety interval, it is reduced to a first-level sticking risk, and S664 is executed; if the starting torque of the next column is greater than the starting torque safety interval again, there is a third-level sticking risk of the downhole drill string of the oil and gas well, and S666 is executed; S666: if the starting torques of three consecutive columns are greater than the starting torque safety interval, there is a third-level sticking risk of the downhole drill string of the oil and gas well; after the drilling operation is resumed after taking measures to prevent the sticking of the drill string, if it is necessary to continue to use the starting torque to assist in judging the sticking risk of the drill string, the risk level is cumulatively recalculated.

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