Method for determining wear of rock-cutting tools

Abstract

FIELD: oil and gas production.SUBSTANCE: invention relates to the field of measuring parameters and monitoring during the drilling of oil and gas wells, and can be primarily used in diagnosing the wear of rock-cutting tools, in particular PDC bits and drilling shoes for drilling on a casing string, for the purpose of its effective development, as well as in the development of automated control systems for the drilling process. The method for determining the wear of a rock-cutting tool that is part of the technical system "top drive / rotor - tool - bottom hole assembly - pump" includes measuring the fluctuations in the pressure of the working fluid and the fluctuations in the axial load on the tool, selecting the current performance criteria and determining the performance of the rock-cutting tool. The Gini coefficient GP of the drilling fluid pressure fluctuations, the Gini coefficient GNND of the axial load on the bit fluctuations, the Gini coefficient GM of the torque fluctuations and the mechanical rate of penetration indicators at any moment of drilling are determined. The spread of Gini coefficients is taken as criteria for determining interlayers or wear of the rock-cutting tool with a decrease in the mechanical penetration rate, whereby in interlayers the value of the Gini coefficient for the parameters GP, GNND, GM decreases and the spread of values becomes minimal, and with wear of the rock-cutting tool the value of the Gini coefficient for the parameters GP, GNND, GM increases and the spread of values becomes maximal.EFFECT: increase in the accuracy of assessing the condition of a rock-cutting tool during drilling due to the precise and timely determination of interlayers of hard rock or the onset of wear of the rock-cutting tool.1 cl, 10 dwg, 1 tbl

Description

[0001] The invention relates to the field of measuring parameters and monitoring in the process of drilling oil and gas wells, and can be primarily used in diagnosing the wear of rock-cutting tools, in particular PDC bits and drilling shoes for drilling on a casing string, with the aim of its effective development, as well as in the development of automated control systems for the drilling process.

[0002] During the drilling process of wells using PDC bits and drilling shoes for drilling on a casing string, there is a difficulty in correctly and timely determining the meeting of layers of hard rock or the beginning of wear of the rock-cutting tool when the mechanical rate of penetration (ROP) decreases.

[0003] A method for determining the operability of a rock-cutting tool during the drilling of oil and gas wells is known from the prior art [USSR Patent No. 1800011, IPC E21B 45 / 00, published 03 / 07 / 1993], which is based on determining the operability of the tool, while it includes recording fluctuations in the pressure of the working fluid in the injection line, and calculating the value of the operability diagnostic criterion, namely, the correlation dimension (at the beginning and during drilling), after which the operability criterion and its reference value are determined for each specific drilling interval.

[0004] The disadvantage of this method is the complex procedure for determining and calculating the performance criterion, insufficient reliability of the assessment of the performance state of the rock-cutting tool during operation, allowing for the possibility of an emergency state of the entire technical system (TS).

[0005] A prior art method for determining the performance of a rock-cutting tool for its efficient operation is known, which can be used in the development of automated drilling process control systems [Patent No. 2739875, IPC E21B 45 / 00, published December 29, 2020]. The method is based on the timely diagnosis of the degree of wear of the rock-cutting tool by processing time-domain data of the working fluid pressure and axial load using the Hurst exponent H.

[0006] The disadvantage of this method is the complex procedure for determining the performance criterion using the Hurst exponent H, since the transition of a complex vehicle to a chaotic change in operating mode does not always serve as an indication of the existence of an equipment defect, which can lead to an emergency condition of the entire vehicle.

[0007] The closest to the proposed invention in terms of the set of essential features is the method for determining the operability of a rock-cutting tool [RU Patent No. 2182659, IPC E21B 45 / 00, published on March 19, 2001], which is based on determining the operability of a tool that is part of the “tool - bottom hole assembly (BHA) - pump” TS, wherein the method includes measuring fluctuations in the pressure of the working fluid and fluctuations in the axial load on the tool, further determining the Gini performance criterion adopted as the reference values ​​​​and the tool performance by comparing the current values ​​​​of the Gini criterion with their reference values, wherein the reference values ​​​​of the criteria are determined in the process of drilling the first well on the well cluster with the tool being maximally worn out.

[0008] Determining the Gini coefficient is based on constructing a Lorenz curve or distribution line for the controlled values ​​of process parameters. This is done by plotting the number of measured values ​​of random variables (process parameters measured during drilling) along the coordinate axis as a percentage, versus the number of these values ​​at the beginning and end of each drilling interval along the abscissa axis as a percentage, for various states of the analyzed control objects.

[0009] A disadvantage of this method is that the described method for determining tool performance using the Gini coefficient does not reliably identify the specific portion of the Lorenz curve where a random concentration of inequality in the values ​​determining the tool's performance occurred, i.e., at what point in time equipment wear begins, potentially leading to an emergency. The wear assessment in this method is based on two parameters—axial load and drilling fluid pressure fluctuations—which does not always accurately indicate equipment wear, as the Gini coefficient can increase or decrease during drilling due to geological conditions (wellbore contamination, mud loss, or interbedded rock of varying hardness).This method also does not allow for timely and accurate determination during the drilling process of whether a layer of hard rock has been encountered or whether the wear process of the rock-cutting tool has begun, especially for PDC bits and drilling shoes on casing.

[0010] The technical problem of the invention is the development of a method for determining the wear of a rock-cutting tool with the achievement of the following technical result: increasing the accuracy of assessing the technical condition of a rock-cutting tool during drilling due to the accurate and timely determination of interlayers of hard rock or the onset of wear of the rock-cutting tool.

[0011] The specified technical result is achieved by the fact that in the method for determining the wear of a rock-cutting tool, which is part of the TS "upper power drive / rotor - tool - BHA - pump", including measurements of pressure fluctuations of the working fluid, fluctuations of the axial load on the tool, fluctuations of the torque on the upper power drive / rotor and indicators of the mechanical rate of penetration (ROP), the selection of current performance criteria and determination of the performance of the rock-cutting tool, the Gini coefficient G is determined P fluctuations in drilling fluid pressure, Gini coefficient G ННД axial load on bit fluctuations, Gini coefficient G М fluctuations in torque and ROP indicators at any moment of drilling, the criteria for determining interlayers or wear of the rock-cutting tool with a decrease in ROP are the spread of the Gini indices, and for interlayers the value of the Gini coefficient for the parameters G Р, G ННД , G М decreases and the spread of values ​​becomes minimal (the density increases), and with wear of the rock-cutting tool, the value of the Gini coefficient for the parameters G Р , G ННД , G М increases and the spread of values ​​becomes maximum (density decreases).

[0012] Fig. 1 shows the Lorenz curve, Fig. 2 shows the block diagram for implementing the proposed method for determining the performance of a rock-cutting tool when drilling wells; Figs. 3-6 present the results of calculating the Gini coefficient for the interlayer; Figs. 7-10 present the results of calculating the Gini coefficient for the wear of the rock-cutting tool.

[0013] Determining the Gini coefficient is based on constructing the Lorenz curve (Fig. 1), or distribution line. This is done by plotting the number of random variable values ​​P (process parameters measured during drilling) as a function of the ordinate axis in % versus the number of these values ​​N at the beginning and end of each drilling operation, and the abscissa axis in % for various states of the analyzed control objects. To determine the Gini coefficient (G), divide the area S1 between the segment OE and the Lorenz curve by the area S2 of the triangle OFE (Fig. 1).

[0014]

[0015] where - area of ​​triangle OFE.

[0016] This value is constant based on the definition of the Gini coefficient according to the Lorenz curve.

[0017]

[0018]

[0019] The greater the deviation of the Lorenz curve from the OE line, the larger the area S1 will be, and therefore the more the Gini coefficient will approach unity.

[0020] Calculating the Gini coefficient G and comparing the dispersion of Gini coefficient G indicators P by fluctuations in the pressure of the washing liquid, G ННД by fluctuations in axial load on the bit, G M Monitoring fluctuations in torque and ROP indicators at any time during well drilling will enable prompt decisions to be made on managing the drilling process, in particular determining the technical condition and, accordingly, the performance of the rock-cutting tool.

[0021] In Fig. 2 the following are designated: rock-cutting tool 1, weight sensor 2, pressure sensor 3, torque sensor 4, winch speed sensor 5, analog-to-digital converter 6, control and processing unit 7, indication unit 8.

[0022] The proposed method for determining the performance of a rock-cutting tool in a drilling rig environment is implemented as follows. Rock-cutting tool 1, as part of a BHA, is lowered into the borehole to the desired depth to begin drilling, or the borehole is spudded from the surface. Weight sensor 2 is installed on the fixed end of the wireline to measure fluctuations in the axial load on the bit, pressure sensor 3 is installed on the pump manifold line to measure fluctuations in the working fluid pressure, torque sensor 4 is connected to the top drive or rotor, and winch speed sensor 5 is installed on the winch drum of the drilling rig's hoisting system. During drilling, signals from the axial load on the bit, pressure, torque, and ROP, each via its own communication channel, are sent to analog-to-digital converter 6. Processing and control unit 7 calculates the Gini coefficient G. Р by fluctuations in the pressure of the washing liquid, G ННДby fluctuations in axial load on the bit, G М Torque fluctuations and the ROP indicator are monitored minute-by-minute with a Δt=1 s sampling interval in the background during well drilling, comparing the spread of Gini coefficient values. Indicator unit 8 is designed for visual monitoring and, in the event of a sharp decrease in ROP, signals the following codes regarding the performance of the rock-cutting tool:

[0023] "Interlayer" - the operational state of the rock-destroying tool in the current interval;

[0024] "Wear" - failure of the rock-cutting tool in the current interval.

[0025] Table 1 shows an example of calculating the Gini coefficient for the pressure of the drilling fluid with a discrete interval of Δt=1 s and the following notations are adopted:

[0026] N - the number of drilling fluid pressure fluctuation values ​​obtained during well drilling by reading sixty values ​​at equal intervals (60 seconds);

[0027] N, % - to plot the Lorenz curve, represent “N” as a percentage:

[0028] 100%:60=1.667%;

[0029] Preal - a fragment of a recording of fluctuations in the pressure of the drilling fluid, presented in the form of a statistical series, the numerical values ​​​​are obtained at equal intervals of time;

[0030] Horn - statistical series of the real curve Preal, presented in ascending order;

[0031] P, % - ordered real curve Horn in percent.

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038] According to the above-described method, the Gini coefficients are calculated for the entire drilling interval using the following parameters:

[0039] - load on bit (LOB);

[0040] - torque (M);

[0041] - washing liquid pressure (P).

[0042] Fig. 3-6 shows the results of processing the data on the Gini coefficient for the interlayer in the 234 m interval, where a sharp decrease in the MSP indicator from 55 m / h to 4 m / h is noted, the value of the Gini coefficient for all parameters decreases and at the same time the density of values ​​increases.

[0043] Fig. 7-10 shows the results of processing the data on the Gini coefficient for wear in the range of 800-812 m, where a decrease in the MSP indicator from 30 m / h to 3 m / h is noted, the value of the Gini coefficient for all parameters begins to increase and at the same time the density of values ​​decreases (the spread of values ​​increases).

[0044] Thus, by monitoring the Gini performance diagnostic criteria for interlayers or wear of rock-cutting tools, it is possible to promptly and accurately determine the drilling process in interlayers of hard rock or the onset of wear of rock-cutting tools, thereby preventing non-productive time during well construction.

[0045] Due to the fact that the set of features characterizing the proposed method is unknown in this field of technology, it is possible to conclude that the claimed invention meets the condition of “novelty”.

[0046] The proposed method for determining the wear of rock-cutting tools can be used in the development of automated drilling systems, as well as in other areas where the technical condition of objects is assessed by measuring parameter fluctuations over relatively long time series represented as a stationary random process. This method improves the reliability of assessing the technical condition of rock-cutting tools during operation and allows for the determination of tool wear.

Claims

A method for determining the wear of a rock-cutting tool that is part of the technical system "upper power drive / rotor - tool - bottom hole assembly - pump", including measuring fluctuations in the pressure of the working fluid and fluctuations in the axial load on the tool, selecting current performance criteria and determining the performance of the rock-cutting tool, characterized in that the Gini coefficient G is determined Р fluctuations in drilling fluid pressure, Gini coefficient G ННД axial load on bit fluctuations, Gini coefficient G М fluctuations in torque and mechanical rate of penetration at any moment of drilling, the criteria for determining interlayers or wear of the rock-cutting tool with a decrease in the mechanical rate of penetration are the spread of the Gini indices, and for interlayers the value of the Gini coefficient for the parameters G Р , G ННД , G Мdecreases and the spread of values ​​becomes minimal, and with wear of the rock-cutting tool, the value of the Gini coefficient for the parameters G Р , G ННД , G М increases and the spread of values ​​becomes maximum.

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