Drilling lost circulation monitoring method based on downhole pressure data stream
By installing dual measuring subs in the drill string assembly, combining downhole pressure data stream to calculate pressure factor and well leakage index, and using Bayesian detection methods, the problem of low accuracy in existing well leakage monitoring is solved, enabling rapid and reliable identification and location of well leakage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING UNIVERSITY OF SCIENCE AND TECHNOLOGY
- Filing Date
- 2022-10-12
- Publication Date
- 2026-06-23
AI Technical Summary
Existing well leakage monitoring methods have poor accuracy and are difficult to adapt to rapid response to complex downhole conditions, especially when there are multiple leakage points, resulting in low reliability and accuracy of well leakage identification.
The pressure or differential pressure at the well depth is measured using a dual-measuring sub in the drill string assembly. Combined with the basic drilling data, the pressure factor and the actual well leakage index are calculated. The Bayesian online variable point detection method is then used to determine well leakage and infer the leakage parameters.
It improves the accuracy and reliability of well leakage detection, shortens leakage feedback time, facilitates rapid response, and ensures downhole safety.
Smart Images
Figure CN117287188B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of drilling engineering technology, specifically relating to a drilling leakage monitoring method based on downhole pressure data stream. Background Technology
[0002] Loss in wells is a common and complex downhole situation encountered in drilling operations, with most drilling processes experiencing some degree of leakage. Loss in wells causes drilling fluid loss, increases drilling costs, and in severe cases, leads to a drop in well pressure, affecting normal drilling, causing wellbore instability, and inducing formation fluid inrush into the wellbore, resulting in a blowout. Therefore, monitoring and quickly locating loss in wells are crucial for safe operation during drilling.
[0003] Existing methods for detecting well leakage mainly include drilling fluid pool level monitoring, measuring the velocity of moving pressure waves in the drilling fluid using acoustic sensors, and measuring annular drilling fluid flow rate. In recent years, with the development of machine learning and artificial intelligence algorithms, well leakage early warning technologies based on surface logging parameters and employing neural networks, case-based reasoning, support vector machines, random forests, and combinations of various algorithms have emerged. However, due to the extreme complexity of real-world conditions, their application in the field still has certain limitations. Currently, on-site judgment of well leakage mainly relies on changes in the drilling fluid pool level (some companies also consider changes in relative flow rate at the outlet), but this method has poor accuracy, significant drawbacks, and is difficult to adapt to rapid responses in complex downhole conditions.
[0004] Theoretically, annular pressure or annular pressure loss will inevitably change after well leakage, and this can be determined using downhole pressure data. However, since wellbore is typically several kilometers long, there are many factors that interfere with annular pressure. The change in annular pressure loss caused by well leakage is relatively small compared to the pressure drop due to the gravity of the drilling fluid, and it is easily overshadowed by annular pressure fluctuations. In other words, both the leakage rate and the location of the leakage will affect the downhole pressure. It is impossible to determine the leakage rate and location simultaneously using only one downhole pressure reading, especially when there are more than one leakage point in the well. In such cases, the reliability of the above method will be greatly reduced. Summary of the Invention
[0005] In view of this, the present invention provides a drilling leakage monitoring method based on downhole pressure data stream to solve the problems of untimely monitoring of leakage status and low reliability and accuracy of leakage identification in the prior art.
[0006] The technical solution is as follows:
[0007] A drilling leakage monitoring method based on downhole pressure data stream, the key of which includes the following steps:
[0008] S1, Two measuring subs are installed in the drill string assembly. The measuring subs are used to measure the pressure or differential pressure at the corresponding well depth, and one of the measuring subs is located near the lower end of the drill string.
[0009] S2, record basic drilling data for later use. The basic data includes at least the wellbore structure, drill string assembly, drilled wellbore trajectory, and drilling fluid density and rheological properties.
[0010] S3, during the drilling process, the actual well leakage index at the pressure factor δ anomaly point is calculated using real-time drilling parameters. It compares the actual well leakage index with a manually set critical value to determine whether well leakage has occurred. If the actual well leakage index is greater than the critical value, well leakage is determined to have occurred. Well leakage parameters are inferred based on the pressure factor change status, where the pressure factor δ is the ratio of the real-time pressure loss coefficient at time t to the baseline pressure loss coefficient.
[0011] The above scheme mainly achieves fixed-point pressure measurement through dual measurement subs. It fully utilizes the qualitative relationship between leakage parameters and annular pressure loss by combining data, and converts annular pressure loss into a pressure factor in the form of pressure loss coefficient to highlight the impact of leakage on annular pressure loss. By comparing the actual well leakage index with the given well leakage index, a more accurate well leakage situation can be obtained. Relatively speaking, its judgment reliability and accuracy are higher, which helps to shorten the leakage feedback waiting time, facilitates subsequent rapid response, and ensures downhole safety.
[0012] As a preferred option: the actual well leakage index mentioned in step S3 The calculation process includes the following steps:
[0013] S3.1, Calculate the drilling fluid gravity correction factor;
[0014] S3.2, Calculate the theoretical value of real-time annular pressure loss between the two measured short sections;
[0015] S3.3, Calculate the real-time annular pressure loss between the two measurement sections;
[0016] S3.4 Calculate the real-time pressure loss coefficient, which is the ratio of the actual value of the annular pressure loss to the theoretical value of the annular pressure loss;
[0017] S3.5, Calculate the real-time pressure factor δ;
[0018] S3.6, Calculate the baseline pressure loss coefficient and the average pressure factor, wherein the baseline pressure loss coefficient is the average value of the pressure loss coefficients corresponding to multiple detection points within the sliding detection window;
[0019] S3.7, use the Bayesian online change point detection method to detect whether the pressure factor calculated in S3.5 changes abruptly. If an anomaly is detected, calculate the actual well leakage index at this time.
[0020]
[0021] Where α is the weighting coefficient, which is arbitrarily assigned a value of 0.1-0.2; and Let A and B represent the pressure factors at time t, between A and B, and at points A and B, respectively. Point A is the measurement position of the lower measuring section, and point B is the measurement position of the upper measuring section.
[0022] By adopting the above scheme, after correcting the drilling fluid gravity, the subsequent annular pressure loss is calculated. The annular pressure loss is then converted into a more accurate pressure loss coefficient, which is then used to calculate the pressure factor and the actual well leakage index. This helps to improve the accuracy and reliability of the calculation results.
[0023] As a preferred option, the method also includes step S4, which determines the well leakage location and leakage rate based on the annular pressure loss between the two measuring sections at the multi-measuring point locations.
[0024] The actual well leakage index calculated according to S3.7 If well leakage is determined to have occurred, step S4 is performed as follows: assuming there is one and only one leakage point downhole, and based on... and The changes can be used to preliminarily infer well leakage parameters, such as and All decreased, while If it remains unchanged, the leak point is above point B; for example... and If both decrease, the leakage point is below point B. Simultaneously establish the relationship formula between leakage velocity and leakage location, and use this formula to draw a well leakage parameter analysis chart:
[0025]
[0026] in, Q represents the actual annular pressure loss between points A and B, f(Q) represents the functional relationship between the annular pressure loss and displacement between A and B, and m represents other influencing factors besides Q; L Indicates leakage discharge, L L L represents the distance between the leak point and point A. If the leak point is below point A, then L... L =0,k A ′ B This is the baseline pressure loss coefficient between A and B.
[0027] Using the above method, if it is determined that there is indeed a leak and there is only one leak, and if the location of the leak and the leak rate can be obtained through other means, then the value of the other leak parameter can be quickly obtained.
[0028] Preferably, step S3 is calculated by a monitoring system, which has an execution device connected to it. If well leakage is detected, a warning signal is issued through the execution device connected to the monitoring system. This approach facilitates further reduction of well leakage feedback time, enabling rapid and effective on-site measures to ensure downhole safety.
[0029] As a preferred approach: when plotting the well leakage parameter analysis chart, multiple leakage velocity reference lines are drawn based on the drilling baseline parameters previously recorded for the block. Using this method, given a clear location of the leakage point, the leakage velocity can be quickly determined by comparing the intersection of the leakage point indicator line and the current pressure loss reduction value with the reference lines.
[0030] Preferably, the distance between the two measuring sections is 30m-60m, and the drill string between the two measuring sections is of the same size. A larger distance can amplify the influence of annular pressure loss and ensure the accuracy of equipment measurement records, but it will increase the blind zone for determining leak points. Therefore, considering both factors, the above-mentioned distance is preferred. Based on the measurement accuracy of existing measuring sections, this distance range has good measurement results and facilitates the rapid determination of leak points. At the same time, using a drill string of the same size between the two sections helps to further ensure the accuracy of the calculation results and reduce the calculation difficulty.
[0031] Preferably, the measuring sub is a PWD sub or other similar downhole pressure measuring sub. This approach facilitates acquisition and implementation, meets the data measurement, recording, and transmission requirements, and eliminates the need for additional measuring tools.
[0032] Compared with the prior art, the beneficial effects of the present invention are:
[0033] The well leakage monitoring method based on downhole pressure data stream provided by this invention has good well leakage identification accuracy, facilitates real-time monitoring and feedback of well leakage conditions, and can quickly and roughly determine the well leakage location and leakage amount, etc. It has good accuracy and reliability, facilitates rapid construction response, and helps to ensure downhole safety. Attached Figure Description
[0034] Figure 1 This is a schematic diagram of the process logic for monitoring well leakage using the actual well leakage index in this invention.
[0035] Figure 2 Schematic diagram of a well leakage monitoring system with dual measurement sub sections;
[0036] Figure 3A schematic diagram illustrating the implementation of well leakage monitoring during drilling using this invention (comprehensive relationship diagram of pressure factor, well leakage index, time, and drill bit position);
[0037] Figure 4 This is a diagram showing the analysis of well leakage parameters during drilling using this invention. Detailed Implementation
[0038] The present invention will now be described in further detail with reference to the accompanying drawings.
[0039] refer to Figures 1 to 4 The drilling leakage monitoring method based on downhole pressure data stream shown mainly includes the following steps: S1, installing two measuring subs (commonly referred to as pressure measuring subs or differential pressure measuring subs) in the drill string assembly. The measuring subs are used to measure the pressure or differential pressure at the corresponding well depth, and the lower measuring sub is located near the lower end of the drill string, with its measuring position as shown in the figure. Figure 1 Point A is shown, and the measurement part of the upper measuring sub is point B. In the specific implementation of this application, the PWD sub is preferred as the measuring sub, and the distance between the two measuring subs is 30m-60m. The two measuring subs are drilled with the same size tool.
[0040] S2, record basic data such as well structure, drill string assembly, drilled well trajectory, drilling fluid density, and rheological performance parameters for future use;
[0041] S3, determine whether well leakage has occurred based on ground pressure or drilling fluid level in the tank;
[0042] Alternatively, real-time drilling parameters can be used to calculate the actual well leakage index at the anomaly point of the pressure factor δ. The well leakage index is compared with a manually set critical value to determine whether well leakage has occurred. If the actual well leakage index is greater than the critical value, well leakage is determined to have occurred. Well leakage parameters are inferred based on the change in pressure factor, where the pressure factor δ is the ratio of the real-time pressure loss coefficient at time t to the baseline pressure loss coefficient.
[0043] First refer to Figure 2 Assume a well with a depth of H has the structure shown in the figure, and the distance between the two measurement points A and B is L. AB Point C is represented as the hypothetical leakage point.
[0044] According to fluid mechanics principles, the drilling fluid pressure and pressure difference measured at points A and B by the two PWDs, respectively, have the following relationship with the drilling fluid loss:
[0045] P B =P gB +ΔP fB (1)
[0046] PA =P B +P gAB +ΔP fAB (2)
[0047] When leak point C is above point B
[0048] ΔP AB =P A -P B =P gAB +ΔP fAB (3)
[0049] When leak point C is below point A
[0050] ΔP AB =P A -P B =P gAB +ΔP fAB (4)
[0051] When leak point C is between points A and B
[0052] ΔP AB =P A -P B =P gAB +ΔP fAC +ΔP fCB (5)
[0053] In the formula, P gB P represents the annular drilling fluid static pressure above point B. gAB ΔP represents the annular drilling fluid static pressure between points A and B. AB ΔP represents the annular pressure difference between points A and B. fB ΔP represents the annular drilling fluid flow pressure loss above point B (hereinafter referred to as annular pressure loss). fAB ΔP represents the pressure loss of the drilling fluid flow in the annulus between points A and B. AC ΔP represents the annular pressure difference between points A and C. CB This represents the annular pressure difference between points CB.
[0054] Table 1 shows the pressure variation characteristics of the well with and without leakage during a certain period of the drilling process, assuming all other engineering parameters remain constant. The table also presents the surface parameter changes when leakage occurs, which can help in identifying leakage. Furthermore, by calculating the pressure reduction, the leakage rate (loss amount) and location can be determined.
[0055] Table 1. Characteristics of changes in related parameters during well leakage.
[0056]
[0057] When other engineering parameters also change, such as changes in inlet flow rate, the pressure and pressure difference at points A and B will change regardless of whether leakage occurs. In this case, the pressure and pressure difference at points A and B without leakage can be calculated using a real-time corrected annular pressure calculation theoretical model. This calculation is then compared with the measured pressure and pressure difference data at points A and B to determine whether the pressure fluctuation is caused by normal parameter changes or by well leakage.
[0058] Theoretically, it's feasible to determine well leakage by observing changes in bottom hole pressure. However, since annular pressure loss is much smaller than drilling fluid hydrostatic pressure, the reduction in annular pressure loss caused by well leakage has a very small impact on bottom hole pressure. Furthermore, due to the influence of temperature and pressure within the well, the actual drilling fluid density and performance parameters vary along the entire wellbore. Errors in wellbore trajectory, irregular well diameter, and cuttings accumulation in any section can all cause changes in bottom hole pressure, making single-point pressure readings unsuitable as the primary basis for well leakage detection.
[0059] In this application, two measuring subs are used, and the distance between the two measuring subs is relatively short. The parameters such as the annulus size, drilling fluid density, performance, and wellbore trajectory between the two subs will not vary much in space. The theoretical pressure and pressure difference values are relatively easy to calculate, and their relationship with the measured values is relatively stable over a certain period of time. Therefore, using the pressure measured by the two measuring subs as a basis for leak detection has good reliability and accuracy.
[0060] When performing well leakage detection using dual pressure, a crucial step is the actual well leakage index in step S3. The calculation process for is as follows:
[0061] S3.1, Calculate the drilling fluid gravity correction factor f g (Dimensionless value), specifically, the drill string assembly is lowered to the bottom of the well, the pump is kept off, and after the annulus stabilizes, the pressure data measured by n sets of dual PWD subs (referred to as dual PWD pressure data) is recorded, and the drilling fluid gravity correction coefficient is calculated according to the following formula (6). The dual PWD pressure data can be sent to the surface for calculation and detection in real time in an alternating manner, or it can be stored in the tool first and then exported for reading and calculation after the drill string is pulled out.
[0062]
[0063] In the formula, and These are measured pressure data from the PWD sub section when the drilling fluid is at rest. ρ represents the density of the drilling fluid in the annulus, g represents the acceleration due to gravity, and H represents the pressure of the drilling fluid. B H represents the vertical depth at point B. A This represents the vertical depth at point A.
[0064] After the calculation is completed, the pump is started to carry out normal drilling (in practice, it can also be during normal circulation, such as circulating and lowering from top to bottom), and real-time data such as well depth, drill bit position, well trajectory, drilling fluid arrangement and downhole pressure are received and recorded.
[0065] S3.2 Calculate the theoretical value of real-time annular pressure loss between the two measuring sections. This calculation is mainly based on basic data and real-time data, and the calculation method is as follows:
[0066] P gAB =f g ρgH AB (7)
[0067]
[0068] P gB =f g ρgH B (9)
[0069]
[0070] P gA =P gB +P gAB (11)
[0071] ΔP fA =ΔP fB +ΔP fAB (12)
[0072] In the formula, P gAB P gB P gA ΔP represents the annular drilling fluid static pressure between points A and B, above point B, and above point A, respectively. fAB ΔP fB ΔP fA These represent the annular drilling fluid flow pressure loss between points A and B, above point B, and above point A, respectively; ρ represents the annular drilling fluid density; g represents the acceleration due to gravity; and H represents the pressure loss due to gravity. B H represents the vertical depth at point B. AB L represents the vertical distance between A and B. AB L represents the distance between A and B. B This indicates the depth of the well at point B (which varies with well depth), L C L represents the length of the bottom drill assembly. Ci D represents the length of the i-th drill string in the bottom sprue assembly (bottom sprue assembly is a drilling-specific concept, generally referring to a string of non-drill pipe drill strings that performs a certain function about 200 meters above the drill bit), D w D represents the wellbore inner diameter. AB D represents the outer diameter of the drill string between A and B. PD represents the outer diameter of the upper drill pipe. ci Let f represent the outer diameter of the i-th drill string in the bottom drill assembly, Q represent the drilling fluid displacement, and f represent the drilling fluid displacement. AB f p f ci represents the annular flow friction coefficient between AB, at the upper drill pipe, and at the i-th type of drill string in the bottom drill string assembly, respectively.
[0073] S3.3, calculate the actual real-time annular pressure loss between the two measuring sections, assuming... and Given the measured pressure data for the PWD short section, the measured pressure loss is:
[0074]
[0075]
[0076]
[0077] S3.4, calculate the real-time pressure loss coefficient. The pressure loss coefficient k is the ratio of the calculated value of the actual measured annular pressure loss to the theoretical value of the annular pressure loss. The subscript j refers to AB, A, and B, which represent the annular pressure loss coefficient between the two measurement sections, and the annular pressure loss coefficient above points A and B, respectively. Then:
[0078]
[0079] S3.5 Calculate the real-time pressure factor δ. Define the pressure factor δ as the ratio of the pressure loss coefficient k at time t to the baseline pressure loss coefficient (normal drilling pressure loss coefficient) k'. Theoretically, during a period of normal drilling (without well leakage), the pressure factor δ should remain within a small range of fluctuation around 1. When the pressure factor drops abnormally, it indicates that well leakage may occur.
[0080]
[0081] S3.6 Calculate the baseline pressure loss coefficient k′. The baseline pressure loss coefficient is the average value of the pressure loss coefficients k corresponding to multiple detection points within the sliding detection window. Set the length of the sliding detection window to x (x can be a number, such as 10-30, or a duration, such as 10-30 seconds). Calculate the pressure loss coefficients at each time point within the window in chronological order. and its average value Set this average value as the baseline pressure loss coefficient k′ j The meaning of j is the same as above. It should be noted that the data in the first window of the test must be normal drilling or circulation data without well leakage.
[0082]
[0083] After the baseline pressure loss coefficient k′ is calculated, the pressure factor at each time point is calculated according to formula (17). and its average value
[0084]
[0085] S3.7, use the Bayesian online change point detection method to detect whether the pressure factor calculated in formula (17) at this point changes abruptly. If all x points are normal, update the benchmark pressure loss coefficient k′ according to formula (17) in S3.6. If an abnormal change is detected, calculate the actual well leakage index at this time according to formula (19).
[0086]
[0087] Where α is the weighting coefficient, which is arbitrarily assigned a value of 0.1-0.2; and Let represent the pressure factors between A and B, and at point A and point B, respectively, at time t.
[0088] The specific process for detecting whether the stress factor has abruptly changed is as follows:
[0089] S3.7.1 Given initial values for hyperparameters It can take values between 0 and 1.
[0090]
[0091]
[0092]
[0093] P(r0=0)=1
[0094] S3.7.2 Calculate the predicted probability of the current point.
[0095]
[0096] In the formula, x t represent That is, to represent respectively and
[0097] S3.7.3 Calculate the prior probability that the current point is normal.
[0098]
[0099] In the formula, H is the danger function, which is usually taken as a relatively small constant, such as 0.002.
[0100] S3.7.4 Calculate the prior probability of an anomaly at the current point.
[0101]
[0102] S3.7.5 Calculate the posterior probability of the current point being normal or abnormal.
[0103]
[0104] S3.7.6 Determine if there is an anomaly.
[0105] if If the current point is an anomaly, then it is an anomaly; otherwise, it is a normal point.
[0106] S3.7.7 Update hyperparameter values, receive new data, repeat steps (3.7.2)-(3.7.7) to continuously detect.
[0107]
[0108]
[0109]
[0110]
[0111]
[0112] To further improve the real-time monitoring effect, in this detection method, steps S3 and S4 are both calculated by the monitoring system. The monitoring system includes a processor with the above calculation process programmed in it. The processor has a data receiving end, a data calculation module, a comparison module, and an execution module. It is also connected to a data input panel or input terminal. During real-time monitoring, real-time data such as well depth and pressure can be received by the receiving end through the corresponding sensor line. Other basic drilling data can be directly input through the panel. The manually set well leakage index threshold value can be set according to the block conditions, usually between 0.05 and 0.1.
[0113] During drilling, the monitoring system uses real-time ground data, measurement sub data, and other input basic data to calculate pressure factors and actual well leakage indices. These are then compared with a manually set well leakage index threshold by a comparison module. If well leakage is detected, the system sends a warning signal, such as an audible or visual alarm, to the connected execution device via the execution module. During the monitoring and calculation process, the calculated pressure factor, well leakage index, time, and drill bit position are graphically displayed. Figure 3As shown (which can be accomplished by a graphics conversion module connected to the data output terminal of the monitoring system processor), the specific well depth (drill bit position) can be quickly determined from the graphics, along with the moment when the pressure factor t became abnormal, and a direct assessment of whether well leakage has occurred. The general workflow of the monitoring system is as follows: Figure 1 As shown.
[0114] After determining that well leakage has occurred, step S4 can be further carried out to infer the location and rate of leakage by measuring the annular pressure loss between two measuring sections at multiple measuring points.
[0115] The actual well leakage index is calculated according to formula (19) given in S3.7. If a well leak has been determined to have occurred, step S4 can be performed as follows: Assume there is only one leak in the well (typically, there is only one leak point; if multiple leak points exist, this detection method will have a relatively larger error and is not suitable). Based on... and The changes can be used to preliminarily infer well leakage parameters, such as and All decreased, while If it remains unchanged, the leak point is above point B; for example... and If both decrease, the leak point is below point B. Simultaneously establish a formula relating leakage velocity (leakage discharge rate) and leakage location. Knowing one of these parameters allows you to determine the other, and the formula can be used to plot a well leakage parameter analysis chart.
[0116]
[0117] in, Q represents the actual annular pressure loss between points A and B, f(Q) represents the functional relationship between the annular pressure loss and displacement between A and B, and m represents other influencing factors besides Q; L Indicates leakage discharge, L L L represents the distance between the leak point and point A. If the leak point is below point A, then L... L =0, k′ AB This is the baseline pressure loss coefficient between A and B.
[0118] Well leakage parameter analysis chart is roughly as follows Figure 4 As shown, mainly based on Figure 3As shown, after a sudden change in the pressure factor, a graph is plotted at a specific measurement point (or at a specific location at a specific time), assuming the leakage rate remains constant. The annular pressure drop between the two measurement sections (PWD1 at the bottom and PWD2 at the top) differs depending on the location of the leakage point. For example, if the leakage point is below PWD1, the reduction in annular pressure drop between the two measurement sections has already reached its minimum and will remain constant. When the leakage point is between the two measurement sections, the lower the leakage point, the greater its impact on the reduction in annular pressure drop; conversely, the higher the leakage point, the smaller the impact, until it is above PWD2, at which point the reduction in annular pressure drop between the two measurement sections is zero. Of course, under the same conditions, the greater the leakage rate, the greater the reduction in annular pressure drop between the two measurement sections. Therefore, reference lines for the reduction in annular pressure drop corresponding to different leakage rates can be pre-done on the graph as needed.
[0119] When the leakage rate can be accurately obtained from the monitoring of the surface drilling fluid tank, the actual leakage rate indicator line can be drawn on the graph. The location where the actual leakage rate indicator line intersects with the indicator line of the current pressure drop value of the annular pressure loss between the two measuring subsections is determined as the location of the leak.
[0120] When the location of the leak is known through other means, a vertical line is drawn corresponding to the depth of the leak. The leakage velocity corresponding to the intersection of the line with the current pressure reduction value is the actual leakage velocity. A more accurate value can be obtained by comparing the intersection with the reference line.
[0121] refer to Figures 1 to 4 The drilling leakage monitoring method based on downhole pressure data stream is shown. This method was used to monitor leakage during drilling in a well within a certain block. During drilling, the drill bit diameter was 215.9 mm, PWD1 was 28 m from the drill bit, PWD2 was 86 m from the drill bit, the distance between the two PWDs was 58 m, and there was a 127 mm weighted drill pipe between the two PWDs. The drilling fluid density was 1.25 g / cm³. 3 The displacement is 33L / s. Leakage was observed on the ground at 16:16 in the afternoon, with an average leakage rate of about 11L / s.
[0122] The data before and after the leakage were detected by the well leakage monitoring system as follows: Figure 3 As shown in the figure and display, it can be quickly determined that the well leakage started at 16:11:43 when drilling reached a depth of 2794.78m. This time is significantly earlier than the time when the leakage was observed on the ground. Therefore, it is evident that the monitoring method of this application can detect well leakage earlier than the ground observation method. The well leakage identification accuracy is higher and the reliability is better. This is conducive to quickly taking corresponding plugging or other construction measures on site to ensure downhole safety.
[0123] Based on experience from adjacent wells and a comprehensive assessment of drilling conditions, the leak is preliminarily suspected to be at the bottom of the well. The calculated maximum leakage velocity is 11.6 L / s, and the minimum leakage velocity is 8.9 L / s, with the velocity varying at different times. The well leakage parameter analysis results at a drilling depth of 2795.5m are as follows: Figure 4 As shown, if the leak point is between the lower PWD1 and the drill bit (2767.5-2795.5m), the leakage rate can be calculated to be 11.3L / s (which can also be obtained by drawing a line (not shown) and comparing it with the reference line). This is close to the leakage rate observed on the ground, further confirming the feasibility of this detection method in quantifying the leakage rate.
[0124] All formulas and parameters in this application use internationally accepted units corresponding to the petroleum industry. For example, length is expressed in meters (m), pressure in megapascals (MPa), and density in grams per cubic centimeter (g / cm³). 3 All flow rates (displacement, leakage, etc.) are expressed in liters per second (L / s), time is expressed in seconds (s), and diameter is expressed in millimeters (mm). This is for reference only and will not be elaborated further here.
[0125] This application requires knowledge of either the location or the rate of well leakage when determining the location and rate of leakage, and can only perform calculations for a single leakage point. In the existing technology, there is currently no relatively accurate method to directly obtain the location and / or rate of well leakage. Therefore, it is better to use its detection method directly for real-time monitoring of well leakage during drilling. By judging the well leakage situation through the sudden change pressure factor, its monitoring is more timely and reliable.
[0126] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.
Claims
1. A drilling leakage monitoring method based on downhole pressure data stream, characterized in that, Includes the following steps: S1, Two measuring subs are installed in the drill string assembly. The measuring subs are used to measure the pressure or differential pressure at the corresponding well depth. One of the measuring subs is close to the lower end of the drill string. The distance between the two measuring subs is 30m-60m, and the two measuring subs are drill strings of the same size. S2, record basic drilling data for later use. The basic data includes at least the wellbore structure, drill string assembly, drilled wellbore trajectory, and drilling fluid density and rheological properties. S3, during the drilling process, the pressure factor is calculated using real-time drilling parameters. Actual well leakage index at anomaly points The actual well leakage index is compared with a pre-defined well leakage index threshold to determine if well leakage has occurred. If the actual well leakage index exceeds the threshold, well leakage is determined to have occurred, and well leakage parameters are inferred based on changes in the pressure factor. for t The ratio of the real-time pressure loss coefficient to the reference pressure loss coefficient at any given time; the reference pressure loss coefficient is the normal drilling pressure loss coefficient. Step S4: Determine the well leakage location and leakage rate based on the annular pressure loss between the two measuring sections at the multiple measuring points; The actual well leakage index in step S3 The calculation process includes the following steps: S3.1, Calculate the drilling fluid gravity correction factor; S3.2, Calculate the theoretical value of real-time annular pressure loss between the two measured short sections; S3.3, Calculate the real-time annular pressure loss between the two measurement sections; S3.4 Calculate the real-time pressure loss coefficient, which is the ratio of the actual value of the annular pressure loss to the theoretical value of the annular pressure loss; S3.5, Calculate the pressure factor in real time. ; S3.6, Calculate the baseline pressure loss coefficient and the average pressure factor, wherein the baseline pressure loss coefficient is the average value of the pressure loss coefficients corresponding to multiple detection points within the sliding detection window; S3.7, use the Bayesian online change point detection method to detect whether the pressure factor calculated in S3.5 changes abruptly. If an anomaly is detected, calculate the actual well leakage index at this time. , ； in, The weighting coefficient is arbitrarily assigned a value between 0.1 and 0.
2. , and These represent the pressure factors between A and B, and at points A and B, respectively, at time t. Point A is the measurement position of the lower measuring section, and point B is the measurement position of the upper measuring section. The actual well leakage index calculated according to S3.7 If well leakage is determined to have occurred, step S4 is performed as follows: assuming there is one and only one leakage point downhole, and based on... , and The changes can be used to preliminarily infer well leakage parameters, such as and All decreased, while If it remains unchanged, the leak point is above point B; for example... , and If both decrease, the leakage point is below point B. Simultaneously establish the relationship formula between leakage velocity and leakage location, and use this formula to draw a well leakage parameter analysis chart: ； in, This represents the actual annular pressure loss between points A and B. This represents the functional relationship between the annular pressure loss and displacement between A and B. m Indicates except Other influencing factors; Indicates the amount of leakage. This indicates the distance between the leak point and point A. If the leak point is below point A, then... , This is the baseline pressure loss coefficient between A and B.
2. The drilling leakage monitoring method based on downhole pressure data stream according to claim 1, characterized in that: Step S3 is completed by the monitoring system, which has an execution device that is connected to it. If a well leakage is detected, a warning signal is issued through the execution device that is connected to the monitoring system.
3. The drilling leakage monitoring method based on downhole pressure data stream according to claim 1, characterized in that: When drawing the well leakage parameter analysis chart, multiple leakage velocity reference lines are drawn based on the drilling basic parameters previously recorded in the block.
4. The drilling leakage monitoring method based on downhole pressure data stream according to any one of claims 1 to 3, characterized in that: The measurement section is a PWD measurement section.