Method for evaluating hobbing cutter replacement opportunity of drilling method shaft sinking

Abstract

The invention provides a drilling method shaft sinking hob replacement opportunity evaluation method, which comprises the following steps: step 1, calculating rock abrasiveness based on a field geological exploration result, step 2, analyzing geometrical parameters of slag outlet rock slag particles, step 3, grading hob abrasion degrees and establishing abrasion indexes, and step 4, evaluating the hob replacement opportunity. And step 5, establishing a relationship among the rock abrasiveness, the geometric parameters of the rock slag particles and the hob abrasion index by using a fitting method, and evaluating whether the hob is changed or not by combining a threshold value set for the hob abrasion index. And a beneficial reference can be provided for on-site drill lifting and tool changing decisions.

Description

Technical Field

[0001] The invention relates to the field of drilling, and in particular to a method for evaluating the timing of replacing a roller cutter in a well drilling method. Background Art

[0002] Coal is mostly located in the Cretaceous-Jurassic weakly cemented strata, and artificial freezing is often used to construct deep and large vertical shafts. Compared with the freezing method, drilling has the advantages of high mechanization, good construction environment, and excellent well quality. However, when drilling into the Jurassic strata, engineering problems such as severe tool wear and low drilling efficiency occurred. Therefore, conducting research on the causes of tool wear in drilling from the perspective of slag particle distribution characteristics and mineral composition is one of the important technical approaches to solve the problem of efficient rock breaking in drilling.

[0003] The drilling method is a vertical shaft construction process that uses mechanical rock breaking, gas lifting, mud and slag removal. Its mechanical rock breaking conditions are quite different from those of TBM tunnel construction. At present, research on rock breaking tool wear is mainly focused on TBM tunnel construction, and there are few methods to quantify tool wear based on the particle size characteristics and mineral composition of rock slag.

[0004] Milling cutters are commonly used as the main rock-breaking tools in drilling wells. Their working environment is full of mud, pressure, repeated impact loads, etc., especially for the Jurassic and Cretaceous strata in the west. Some rock strata have high mud content and complex strata changes. It takes a lot of time and economic costs to lift the drill and change the cutter, which has a great impact on the construction period and progress. There are many factors that affect the wear of the drilling cutter, such as rock strength, tool material, mud properties, drilling parameters, etc., but the current drilling method drilling drill lifting and tool changing process is still in the experience stage, with strong subjectivity, and lacks certain data support to guide the timing of lifting the drill and changing the cutter on site. Generally, on-site workers will choose to lift the drill and change the cutter when they observe that the drilling speed is significantly reduced or the drilling pressure and torque are abnormal. However, this may be caused by the change of strata, which lacks scientificity to a certain extent, and is easy to lead to early or delayed tool change, which seriously affects the efficiency of drilling well construction. Rock slag, as an important feedback parameter on site, can feedback the drilling status during rock-machine interaction, while rock abrasion performance, as an important geological parameter, has been obtained through geological drilling before drilling. Using these two aspects of data as basic data combined with on-site wear status investigation can solve the scientific problem of blindness in the timing of lifting the drill and changing the cutter at the site of well drilling by on-site drilling method, so as to accurately predict the wear of the roller cutter in similar formations or similar working methods. Summary of the invention

[0005] The purpose of the present invention is to provide a method for evaluating the timing of replacing a roller cutter during well drilling, which can provide a useful reference for on-site decision-making on lifting a drill and replacing a cutter.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for evaluating the timing of replacing a roller cutter during well drilling comprises the following steps:

[0008] Step 1: calculate the rock abrasiveness based on the results of on-site geological exploration; step 2: analyze the geometric parameters of the slag particles at the slag outlet; step 3: classify the degree of cutter wear and establish a wear index; step 4: quantify the correlation between the slag parameters and the cutter wear index; step 5: use the fitting method to establish the relationship between the rock abrasiveness, the geometric parameters of the slag particles and the cutter wear index, and evaluate whether to change the cutter based on the threshold set for the cutter wear index.

[0009] Further, in the above-mentioned method for evaluating the timing of replacing the cutter during drilling, in step 1, the rock abrasiveness is calculated by the following method:

[0010] Calculate the equivalent quartz content EQC by thin section analysis:

[0011]

[0012] In formula (1): V i is the mass percentage of the i-th mineral in the rock, %; R i is the ratio of the Rockwell hardness of the i-th mineral to quartz; m is the type of mineral,

[0013] Combined with the uniaxial compressive strength of rock, the rock abrasiveness index RAI is obtained as follows:

[0014] RAI=EQC·UCS (2)

[0015] In formula (2): UCS is the uniaxial compressive strength of rock, MPa.

[0016] Furthermore, in the above-mentioned method for assessing the timing of replacing the roller cutter during well drilling, the step 2 specifically includes:

[0017] The slag particles are wrapped with a gradually shrinking ellipse until the ellipse is circumscribed with the slag particles to obtain a fitting ellipse. The major axis and minor axis of the fitting ellipse are measured to be L1 and L2 respectively, and the slag ellipticity parameter E is obtained accordingly. p As shown in formula (3),

[0018]

[0019] The fitting method is used to construct a circle with the same area S as the identified particle to obtain the particle equivalent circle. The equivalent circle diameter R is calculated using formula (4). Therefore, the particle area S and the equivalent circle diameter R can be used to evaluate the particle size.

[0020]

[0021] Roundness Ci The definition is shown in formula (5), C i The closer the value is to 1, the closer the particle is to a round shape. i The closer the value is to 0, the more slender the particle is. In formula (5), C is the particle circumference.

[0022]

[0023] In order to characterize the distribution law of rock slag particle size, the particle equivalent circle diameter is used as the screening object, and a quasi-exponential function with the natural constant e as the base is constructed as the distribution function to describe the rock slag particle size distribution. The function expression is:

[0024]

[0025] In formula (6): is the cumulative pass rate, %; is the particle equivalent circle diameter, cm; P1 is the maximum value of the cumulative passing rate, D t is the minimum particle size. In the same set of slag identification data, both are fixed values. To obtain a better fitting effect, both are set as one of the fitting parameters. Define k / B t is the uniformity coefficient UC of the slag particles. The smaller the UC value, the more uniform the slag size distribution.

[0026] Furthermore, in the above-mentioned method for evaluating the timing of replacing the roller cutter during well drilling, in step 3, the degree of wear of the roller cutter is divided into five levels, namely slight wear w1, general wear w2, moderate wear w3, severe wear w4, and complete failure w5.

[0027] Furthermore, in the above-mentioned method for evaluating the timing of replacing the roller cutter in the drilling method, in step 3, the roller cutter surface wear-resistant welding layer is not completely worn out, and the wear oblique length is 0 to 5 mm. Through on-site inspection of the cutter shaft state, it is defined as slight wear w1, and it can continue to be used.

[0028] The wear-resistant welding layer on the hob surface is worn out by the inclined friction wear. According to the wear oblique length of 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w2, w3, and w4 respectively.

[0029] Irregular wear and flat friction wear form wear steps on the top of the teeth. According to the wear oblique length, which is in the range of 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w2, w3, and w4 respectively.

[0030] According to the wear oblique length of the edge cutter and the cutter seat in the four intervals of 0-5mm, 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w1, w2, w3, and w4 respectively.

[0031] Tooth breakage and shelling are structural damages of the cutter and are defined as complete failure, and the degree of wear is defined as w5.

[0032] Furthermore, in the above-mentioned method for evaluating the timing of replacing the roller cutter during drilling, in step 3, the average wear index of the single cutter is As shown in formula (7),

[0033]

[0034] Where: n is the number of hobs installed on the cutter head,

[0035] The standard deviation of the average wear index of a single blade is used as the wear uniformity index σ w , the expression is shown in formula (8),

[0036]

[0037] Average wear index of single blade Wear uniformity index σ w As the basis for predicting hob wear.

[0038] Further, in the above-mentioned method for evaluating the timing of replacing the roller cutter during drilling, in step 4, the Pearson coefficient is used to quantify the correlation between the rock slag parameters and the roller cutter wear index. The Pearson coefficient calculation formula is as follows:

[0039]

[0040] In formula (9): r is the Pearson coefficient; X i , Y i are the values ​​of the two variables respectively; are the means of the two variables,

[0041] The correlation between the rock chip geometric parameters and the relevant indicators of hob wear is as follows: rock chip particle size distribution > roundness parameter > uniformity coefficient > ellipticity parameter.

[0042] Among them, the proportion of large slag particles POP, roundness box width BW and single knife average wear index The correlation is high, the uniformity coefficient UC and the wear uniformity index σ w The highest correlation is

[0043] Therefore, for the slag geometric parameters, the proportion of large slag particles POP, roundness box width BW and uniformity coefficient UC are selected as the three fitting independent variables of the wear prediction model.

[0044] Further, in the above-mentioned method for evaluating the timing of replacing the roller cutter during drilling, in step 4,

[0045] The correlation between rock abrasiveness related indicators and hob wear related indicators is: RAI>UCS>quartz content>EQC>feldspar content,

[0046] For rock abrasiveness related indicators, RAI is selected as a fitting independent variable of the wear prediction model.

[0047] The box width BW of the slag roundness distribution, the proportion of large particles POP, the uniformity coefficient UC, and the rock abrasiveness index RAI were selected as independent variables, and the single-knife average wear index Wear uniformity index σ w As the dependent variable, multivariate nonlinear regression was performed.

[0048] Further, in the above-mentioned method for evaluating the timing of replacing the roller cutter during drilling, in step 5,

[0049] The regression results of different rock layers are shown below:

[0050] Sandy rock formation:

[0051]

[0052] Mudstone formation:

[0053]

[0054] In formulas (10)-(13): α and β are the average wear index of a single blade. Wear uniformity index σ w The fit index, R 2 Indicates the fitness of the function, R 2 The larger the value, the higher the fitting accuracy.

[0055] Further, in the above-mentioned method for evaluating the timing of replacing the roller cutter during drilling, in step 5,

[0056] Combined with the on-site tool change records, when the average wear index of a single tool Or wear uniformity index σ w When ≥1, the tool needs to be changed;

[0057] When the average wear index of a single blade And the wear uniformity index σ w When <1, no tool change is required.

[0058] It can be seen from the analysis that the present invention discloses a method for evaluating the timing of replacing the roller cutter during well drilling, wherein the rock abrasiveness is calculated based on the results of on-site geological exploration; during drilling, the rock slag is salvaged and processed, and the rock slag geometric parameters are obtained in combination with an image recognition method; the parameters are substituted into equations (12) to (15) to obtain the single-cutter average wear index and the wear uniformity index, and whether the roller cutter should be replaced is determined based on the aforementioned evaluation criteria. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them:

[0060] Figure 1 Schematic diagram of the shape parameters of slag particles at the slag outlet.

[0061] Figure 2 Schematic diagram of the roundness and ellipticity distribution of rock debris in extremely weakly cemented sandy formations.

[0062] Figure 3 Schematic diagram of the distribution of roundness and ellipticity of rock debris in mud-cemented mud strata.

[0063] Figure 4 Schematic diagram of the distribution of roundness and ellipticity of rock debris in the interbedded strata of calcareous cemented mud and sand.

[0064] Figure 5 Schematic diagram of the roundness and ellipticity distribution of rock debris in calcareous and ferruginous cemented sandy strata.

[0065] Figure 6 Schematic diagram of the cumulative distribution of slag particle size in extremely weakly cemented sandy formations.

[0066] Figure 7 Schematic diagram of the cumulative distribution of slag particle size in mud-cemented mud strata.

[0067] Figure 8 Schematic diagram of the cumulative distribution of rock slag particle size in calcareous cemented mud and sand interlayers.

[0068] Fig. 9 Schematic diagram of the cumulative distribution of slag particle size in calcareous and ferruginous cemented sandy strata.

[0069] Fig.10 Schematic diagram of cutter head wear in extremely weakly cemented sandy formations.

[0070] Fig.11 Schematic diagram of cutter head wear in muddy cemented mud formation.

[0071] Fig.12Schematic diagram of cutter head wear in calcareous cemented mud and sand interbedded strata.

[0072] Fig.13 Schematic diagram of cutter head wear in calcareous and ferruginous cemented sandy formations.

[0073] Fig.14 This is a schematic diagram of the cutter disc and hob layout.

[0074] Fig.15 It is the heat map of the correlation between the parameters related to the slag geometry parameters and the indicators related to the disc cutter wear.

[0075] Fig.16 It is a heat map of the correlation between rock slag abrasiveness related parameters and disc cutter wear related indicators.

[0076] Fig.17 Comparison chart of the wear prediction model calculation value and the measured value of the cutter wear degree in the extremely weakly cemented sand formation

[0077] Fig.18 Comparison chart of the wear prediction model calculation value in muddy cemented mud formation and the measured value of the cutter wear degree in the field investigation

[0078] Fig.19 Comparison chart of the wear prediction model calculation value and the measured value of the cutter wear degree in the calcareous cemented mud and sand interlayer strata in the field investigation

[0079] Fig. 20 Comparison chart of the wear prediction model calculation value and the actual measured value of the cutter wear degree in the field investigation in calcareous and ferrous cemented sandy formations

[0080] Fig.21 Schematic diagram of a method for evaluating the timing of replacing a roller cutter during well drilling according to an embodiment of the present invention. DETAILED DESCRIPTION

[0081] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present invention and does not limit the present invention. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as a part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present invention encompasses such modifications and variations within the scope of the appended claims and their equivalents.

[0082] One or more examples of the present invention are shown in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the present invention.

[0083] like Figures 1 to 21 As shown, according to an embodiment of the present invention, a method for evaluating the timing of replacing a roller cutter during drilling is provided, comprising the following steps:

[0084] Step 1: Calculate rock abrasiveness based on on-site geological survey results

[0085] The rock abrasiveness is calculated by the following method:

[0086] (1) Calculate the equivalent quartz content EQC by thin section analysis:

[0087]

[0088] In formula (1): V i is the mass percentage of the i-th mineral in the rock, %; R i is the ratio of the Rockwell hardness of the i-th mineral to quartz; m is the mineral type.

[0089] (2) Combined with the uniaxial compressive strength of rock, the rock abrasiveness index RAI is obtained as:

[0090] RAI=EQC·UCS (2)

[0091] In formula (2): UCS is the uniaxial compressive strength of rock, MPa.

[0092] For the drilling well drilling project, field and indoor tests such as drilling, coring, thin section identification, and uniaxial compressive strength were carried out on the above 11 drilling sections, and the abrasiveness index of rocks in different formations was obtained as shown in Table 1. According to Table 1, the main rock names of the rock formations are obtained, and the different drilling sections can be divided into four types of formations, namely, very weakly cemented sandy formations, mud-cemented mud formations, calcareous cemented mud\sand interlayer formations, and iron-cemented sandy formations, including 11 drilling sections.

[0093] Extremely weakly cemented sandy strata and ferruginous cemented sandy strata are collectively referred to as sandy strata.

[0094] Muddy cemented mud strata and calcareous cemented mud and sand interlayer strata are collectively referred to as muddy strata.

[0095] Table 1 Rock abrasiveness related indicators

[0096]

[0097] Step 2: Analyze the geometric parameters of the slag particles at the slag outlet

[0098] Before lifting the drill and changing the cutter, the slag is fished out with a scoop net at the slag outlet, and then the rock particles are obtained through drying, cleaning, and re-drying, and the graphic source files are photographed and saved. The image processing software uses the image recognition method to identify the shape parameters of the particles such as area, major and minor axes, and roundness, and the geometric morphology of the slag and the distribution law of the particles are counted.

[0099] Schematic diagram of the shape parameters of the slag particles at the slag outlet Figure 1 shown.

[0100] Since the particle size of slag particles is distributed between 0.01 and 10 cm, an ordinary camera can meet the identification requirements.

[0101] (1) The slag particles are wrapped by a gradually shrinking ellipse until the ellipse is circumscribed with the slag particles, and the Figure 2 The fitting ellipse shown in the figure has its major and minor axes L1 and L2, respectively, and the slag ellipticity parameter E is obtained accordingly. p As shown in formula (3).

[0102]

[0103] (2) A fitting method is used to construct a circle with the same area S as the identified particle to obtain the particle equivalent circle, which is then calculated using formula (4) to obtain the equivalent circle diameter R. Therefore, the particle area S and the equivalent circle diameter R can be used to evaluate the particle size.

[0104]

[0105] (3) Roundness C i The definition is shown in formula (5), C i The closer the value is to 1, the closer the particle is to a round shape. i The closer the value is to 0, the more slender the particle is. In formula (5), C is the circumference of the particle.

[0106]

[0107] According to the above method, the statistical characteristics of slag particles are analyzed from the perspective of their shape and size distribution. Among them, roundness and ellipticity are used to describe the shape of slag particles, and particles are screened by area and cumulative statistics are used to describe the particle size distribution.

[0108] The statistical characteristics of 11 groups of slag particle shapes are obtained by taking roundness as the horizontal axis and ellipticity as the vertical axis. Figure 2-Figure 5 The box width in the box plot is the difference between the upper and lower quartiles, the blue dot in the box is the mean, the blue line is the median, and the red dots outside the upper and lower limits are abnormal deviations.

[0109] according to Figure 1 , with area as the screening target, 0~0.01cm 2 Small particles, 0.01~1cm 2 Medium particles, 1 to 10 cm 2 The cumulative distribution of the slag particle size is shown in Table 2. Figure 6-Figure 9 shown.

[0110] Table 2 Cumulative distribution of slag particle size / %

[0111]

[0112] In order to characterize the distribution law of slag particle size, the particle equivalent circle diameter was used as the screening object, and the cumulative characteristic identification curve was fitted with the distribution function. 2 Detect whether a certain distribution model is satisfied. To this end, a quasi-exponential function with the natural constant e as the base is constructed as a distribution function to describe the distribution of slag particle size. The function expression is:

[0113]

[0114] In formula (6): is the cumulative pass rate, %; is the particle equivalent circle diameter, cm; P1 is the maximum value of the cumulative passing rate, D t is the minimum particle size. In the same set of slag identification data, both are fixed values. To obtain a better fitting effect, both are set as one of the fitting parameters. Define k / B t is the uniformity coefficient (UC) of slag particles. The smaller its value is, the more uniform the slag size distribution is.

[0115] The main fitting parameters of slag accumulation are shown in Table 3.

[0116] Table 3 Main fitting parameters of slag accumulation

[0117]

[0118] Step 3: Classify the degree of hob wear and establish wear indicators

[0119] Combined with the hob wear failure mode, the hob wear degree is divided into 5 levels, namely slight wear w1, general wear w2, moderate wear w3, severe wear w4, and complete failure w5.

[0120] The wear-resistant welding layer on the surface of the hob is not completely worn out due to rolling wear, and the oblique wear length is 0 to 5 mm. Through on-site inspection of the cutter shaft status, it is defined as slight wear w1 and can continue to be used.

[0121] The oblique friction wear in which the wear-resistant welding layer on the surface of the hob is almost worn out is defined as w2, w3, and w4 according to the wear oblique length in the three intervals of 5mm-10mm, 10mm-15mm, and 15mm-20mm respectively.

[0122] Irregular wear and plane friction wear form wear steps on the top of the teeth. According to the wear oblique lengths in the ranges of 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w2, w3, and w4 respectively.

[0123] According to the four intervals of the oblique length of the edge cutter and the cutter seat wear, which are 0-5mm, 5mm-10mm, 10mm-15mm, and 15mm-20mm respectively, the wear degrees are defined as w1, w2, w3, and w4 respectively.

[0124] Tooth breakage and shelling are structural damages of the cutter and are defined as complete failure, and the degree of wear is defined as w5.

[0125] According to the wear characteristics of the above hob, the hob wear degree evaluation matrix is ​​shown in Table 4.

[0126] Table 4 Field cutter wear evaluation matrix

[0127]

[0128]

[0129] In order to visualize the relationship between the wear of the hob and the position of the cutterhead, a heat map of the wear of the hob was drawn based on Table 4 and combined with the field survey. Figure 10-13 shown.

[0130] Average wear index of single blade As shown in formula (7).

[0131]

[0132] Where: n is the number of hobs installed on the cutter disc, pieces.

[0133] The deep wear area of ​​the well drilling cutter disc is easily concentrated in the b, c, and d cutter rings, while the center cutter and the surrounding area are mostly shallow wear areas. In extremely weakly cemented sandy formations and mud cemented mud formations, the cutter disc wear is basically distributed in a central symmetric manner. In calcareous cemented mud and sand interlayer formations and calcareous and iron cemented sand formations, the cutter disc is non-centrally symmetric and eccentrically worn.

[0134] Explanation of b, c, d cutter rings: the edge cutter is a cutter ring, k is the center cutter, b~j are positive cutters, and each cutter ring from the edge cutter to the center cutter is installed with 6, 3, 3, 2, 2, 2, 2, 2, 2, 1, 1 cutters. The installation radius of the cutters in the same cutter ring is the same, and the rock breaking range of the cutters in adjacent cutter rings has a certain degree of repeatability. Fig.14 shown.

[0135] The replacement of roller cutters during drilling requires multiple processes such as lifting the drill, evaluating wear, disassembling the roller cutters, and drilling. In order to reduce the man-hours of auxiliary drilling, improve drilling efficiency, and reduce costs, the site tends to replace all the roller cutters every time the drill is lifted. To this end, before lifting the drill to change the cutters, the wear uniformity of the roller cutters is evaluated to clarify the timing of lifting the drill and reduce the number of times the drill is lifted. Therefore, the standard deviation of the average wear index of a single cutter is used as the wear uniformity index σw , the expression is shown in formula (8).

[0136]

[0137] According to formula (7) and (8), the average wear index of a single blade can be obtained: Wear uniformity index σ w The calculated values ​​are shown in Table 5. σ w The process quantity that reflects the wear state of the cutter disc when lifting the drill can be used as a basis for predicting the wear of the cutter.

[0138] Table 5 Calculated values ​​of wear index

[0139]

[0140] Step 4: Quantify the correlation between rock slag parameters and disc cutter wear indicators

[0141] The Pearson coefficient is used to quantify the correlation between rock slag parameters and disc cutter wear indicators. The Pearson coefficient calculation formula is as follows:

[0142]

[0143] In formula (9): r is the Pearson coefficient; X i , Y i are the values ​​of the two variables respectively; are the means of the two variables.

[0144] Based on 11 sets of drilling data, a heat map of the correlation between rock chip geometric parameters and cutter wear related indicators is drawn. Fig.15 As shown, area I represents the autocorrelation of the rock chip geometry parameters, while area II represents the correlation between the parameters related to the rock chip geometry parameters and the indicators related to the disc cutter wear.

[0145] Depend on Fig.15 It can be seen that the correlation between the rock chip geometric parameters and the relevant indicators of hob wear is as follows: rock chip particle size distribution > roundness parameter > uniformity coefficient > ellipticity parameter, among which the proportion of large rock chip particles POP, roundness box width BW and the average wear index of a single cutter are The correlation is high, the uniformity coefficient UC and the wear uniformity index σ w Therefore, for the slag geometric parameters, the proportion of large slag particles POP, roundness box width BW and uniformity coefficient UC are selected as the three fitting independent variables of the wear prediction model.

[0146] The rock abrasiveness related indicators are shown in Table 1. Based on the above, the correlation heat map between the rock slag geometric parameters and the disc cutter wear related indicators is drawn as shown in Fig.15As shown in the figure, areas I and III represent the autocorrelation of rock abrasiveness related parameters and cutter wear related indicators, while area II represents the correlation between rock abrasiveness related parameters and cutter wear related indicators.

[0147] Depend on Fig.16 It can be seen that the correlation between rock abrasiveness related indicators and hob wear related indicators is: RAI>UCS>quartz content>EQC>feldspar content. Therefore, for rock abrasiveness related indicators, RAI is selected as a fitting independent variable of the wear prediction model.

[0148] In summary, the box width BW of the slag roundness distribution, the proportion of large particles POP, the uniformity coefficient UC, and the rock abrasiveness index RAI are selected as independent variables, and the single-knife average wear index is used as the Wear uniformity index σ w As the dependent variable, multivariate nonlinear regression was performed.

[0149] Step 5: Use the fitting method to establish the relationship between the rock abrasiveness, the geometric parameters of the rock slag particles and the disc cutter wear index, and evaluate whether to change the cutter based on the threshold set for the disc cutter wear index.

[0150] The regression results of different rock layers are shown below:

[0151] Sandy rock formation:

[0152]

[0153] Mudstone formation:

[0154]

[0155] In formulas (10)-(13): α and β are the average wear index of a single blade. Wear uniformity index σ w The fit index, R 2 Indicates the fitness of the function, R 2 The larger the value, the higher the fitting accuracy.

[0156] When the average wear index of a single cutter is too large, the rock breaking efficiency of the cutter will decrease, thereby reducing the drilling speed. When the wear uniformity of the cutter on the cutterhead is poor, it is easy to cause the eccentric torque of the cutterhead to be too large, causing the drilling pressure and torque to fluctuate, thereby aggravating the wear and failure of the cutter.

[0157] Combined with the on-site tool change records, when the "single tool average wear index Or wear uniformity index σ w When the diameter is ≥1”, the cutter disc is no longer suitable for continued drilling and needs to be replaced.

[0158] When the "single blade average wear index And the wear uniformity index σ w When <1”, there is no need to change the tool.

[0159] like Figure 17-Figure 20 The following is a comparison chart of the calculated value of the prediction model and the measured value of the wear degree of the roller cutter in the field survey. Data points falling into area (a) in the figure indicate that the cutter does not need to be changed, and area (b) indicates that the cutter needs to be replaced. For the average wear index of a single cutter, 9 points fall into area (b), 1 point falls into area (a), and only 1 point falls into area (c); while for the wear uniformity index, 6 points are located in area (b), 4 points are located in area (a), and 1 point falls into area (c). Combining the dual indicators to determine whether to change the drill shows that there was only one misjudgment in 11 drilling sections, and the success rate of the dual indicators in predicting whether to lift the drill and change the cutter reached 90.9%.

[0160] Proposed Fig.21 The method for evaluating the timing of replacing the roller cutter during drilling is shown as follows: the rock abrasiveness is calculated based on the results of on-site geological exploration; during drilling, the rock debris is salvaged and processed, and the rock debris geometric parameters are obtained in combination with image recognition methods; the parameters are substituted into equations (12) to (15) to obtain the single-cutter average wear index and wear uniformity index, and whether the roller cutter should be replaced is determined based on the aforementioned evaluation criteria.

[0161] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0162] (1) The wear of the drilling cutter is closely related to the geological conditions of the rock formation. The cutter consumption per unit footage in different formations is as follows: mud-cemented mud formation > calcareous cemented mud and sand interlayer formation ≈ calcareous and ferruginous cemented sand formation > extremely weakly cemented sand formation.

[0163] (2) The geometric morphology of the slag can indirectly reflect the degree of cutter wear per unit footage in different strata. The particle size distribution of the slag in the Cretaceous and Jurassic strata conforms to a quasi-exponential function, with a correlation coefficient R2 of 0.976 to 0.997. The uniformity coefficient can be used to describe the uniformity of the slag and has a high correlation with the cutter wear uniformity index.

[0164] (3) Taking the width of the rock chip roundness distribution box, the proportion of large particles, the uniformity coefficient, and the rock abrasiveness index as the main factors of cutter wear, a cutter wear prediction model suitable for the Cretaceous and Jurassic strata was fitted. Compared with the field measured indicators, the model prediction success rate reached 90.9%.

[0165] (4) The proposed hob wear evaluation method has good operability. Or wear uniformity index (σ w )≥1, the cutterhead is no longer suitable for continued drilling, which can provide a useful reference for on-site drill lifting and cutter replacement decisions.

[0166] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating the timing of replacing a roller cutter during drilling, characterized in that: The steps include: Step 1: Calculate rock abrasiveness based on on-site geological survey results. Step 2: Analyze the geometric parameters of the slag particles at the slag outlet. Step 3: Classify the degree of wear of the hob and establish a wear index. Step 4: quantify the correlation between rock slag parameters and disc cutter wear indicators. Step 5: Use the fitting method to establish the relationship between the rock abrasiveness, the geometric parameters of the rock slag particles and the disc cutter wear index, and evaluate whether to change the cutter based on the threshold set for the disc cutter wear index.

2. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: In step 1, the rock abrasiveness is calculated by the following method: Calculate the equivalent quartz content EQC by thin section analysis: In formula (1): V i is the mass percentage of the i-th mineral in the rock, %; R i is the ratio of the Rockwell hardness of the i-th mineral to quartz; m is the type of mineral, Combined with the uniaxial compressive strength of rock, the rock abrasiveness index RAI is obtained as follows: RAI=EQC·UCS (2) In formula (2): UCS is the uniaxial compressive strength of rock, MPa.

3. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: The step 2 specifically includes: The slag particles are wrapped with a gradually shrinking ellipse until the ellipse is circumscribed with the slag particles to obtain a fitting ellipse. The major axis and minor axis of the fitting ellipse are measured to be L1 and L2 respectively, and the slag ellipticity parameter E is obtained accordingly. p As shown in formula (3), The fitting method is used to construct a circle with the same area S as the identified particle to obtain the particle equivalent circle. The equivalent circle diameter R is calculated using formula (4). Therefore, the particle area S and the equivalent circle diameter R can be used to evaluate the particle size. Roundness C i The definition is shown in formula (5), C i The closer the value is to 1, the closer the particle is to a round shape. i The closer the value is to 0, the more slender the particle is. In formula (5), C is the particle circumference. In order to characterize the distribution law of rock slag particle size, the particle equivalent circle diameter is used as the screening object, and a quasi-exponential function with the natural constant e as the base is constructed as the distribution function to describe the rock slag particle size distribution. The function expression is: In formula (6): is the cumulative pass rate, %; is the particle equivalent circle diameter, cm; P1 is the maximum value of the cumulative passing rate, D t is the minimum particle size. In the same set of slag identification data, both are fixed values. To obtain a better fitting effect, both are set as one of the fitting parameters. Define k / B t is the uniformity coefficient UC of the slag particles. The smaller the UC value, the more uniform the slag size distribution.

4. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: In step 3, the degree of wear of the hob is divided into five levels, namely slight wear w1, general wear w2, moderate wear w3, severe wear w4, and complete failure w5.

5. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 4, characterized in that: In step 3, the wear-resistant welding layer on the surface of the hob is not completely worn out, and the wear oblique length is 0 to 5 mm. Through on-site inspection of the cutter shaft state, it is defined as slight wear w1, and it can continue to be used. The wear-resistant welding layer on the hob surface is worn out by the inclined friction wear. According to the wear oblique length of 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w2, w3, and w4 respectively. Irregular wear and flat friction wear form wear steps on the top of the teeth. According to the wear oblique length, which is in the range of 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w2, w3, and w4 respectively. According to the wear oblique length of the edge cutter and the cutter seat in the four intervals of 0-5mm, 5mm-10mm, 10mm-15mm, and 15mm-20mm, the wear degrees are defined as w1, w2, w3, and w4 respectively. Tooth breakage and shelling are structural damages of the cutter and are defined as complete failure, and the degree of wear is defined as w5.

6. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 5, characterized in that: In step 3, the average wear index of a single blade As shown in formula (7), Where: n is the number of hobs installed on the cutter head, The standard deviation of the average wear index of a single blade is used as the wear uniformity index σ w , the expression is shown in formula (8), Average wear index of single blade Wear uniformity index σ w As the basis for predicting hob wear.

7. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: In step 4, the Pearson coefficient is used to quantify the correlation between the rock slag parameters and the disc cutter wear index. The Pearson coefficient calculation formula is as follows: In formula (9): r is the Pearson coefficient; X i , Y i are the values ​​of the two variables respectively; are the means of the two variables, The correlation between the rock chip geometric parameters and the relevant indicators of hob wear is as follows: rock chip particle size distribution > roundness parameter > uniformity coefficient > ellipticity parameter. Among them, the proportion of large slag particles POP, roundness box width BW and single tool average wear index The correlation is high, the uniformity coefficient UC and the wear uniformity index σ w The highest correlation is Therefore, for the slag geometric parameters, the proportion of large slag particles POP, roundness box width BW and uniformity coefficient UC are selected as the three fitting independent variables of the wear prediction model.

8. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 7, characterized in that: In step 4, The correlation between rock abrasiveness related indicators and hob wear related indicators is: RAI>UCS>quartz content>EQC>feldspar content, For rock abrasiveness related indicators, RAI is selected as a fitting independent variable of the wear prediction model. The box width BW of the slag roundness distribution, the proportion of large particles POP, the uniformity coefficient UC, and the rock abrasiveness index RAI were selected as independent variables, and the single-knife average wear index Wear uniformity index σ w As the dependent variable, multivariate nonlinear regression was performed.

9. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: In step 5, The regression results of different rock layers are shown below: Sandy rock formation: Mudstone formation: In formulas (10)-(13): α and β are the average wear index of a single blade. Wear uniformity index σ w The fit index, R 2 Indicates the fitness of the function, R 2 The larger the value, the higher the fitting accuracy.

10. The method for evaluating the timing of replacing the roller cutter during drilling according to claim 1, characterized in that: In step 5, Combined with the on-site tool change records, when the average wear index of a single tool Or wear uniformity index σ w When ≥1, the tool needs to be changed; When the average wear index of a single blade And the wear uniformity index σ w When <1, no tool change is required.

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