A method and system for quantitatively evaluating the degree of wellbore cleaning

Abstract

The application discloses a method and system for quantitatively evaluating the wellbore cleaning degree, comprising: processing and measuring the vibration screen flowback situation of a drilling well to obtain a real cuttings mass; calculating the theoretical cuttings flowback amount of the drilling well based on the hole diameter expansion rate of a work area where the drilling well is located; obtaining a current cuttings flowback ratio according to the real cuttings mass and the theoretical cuttings flowback amount; and predicting and evaluating the wellbore cleaning degree of the current drilling operation according to the current cuttings flowback ratio and by using a preset wellbore cleaning evaluation standard. The application can provide early warning for drilling risks such as downhole sand sticking and provide accurate reference data for wellbore cleaning treatment before casing running.

Description

Technical Field

[0001] This invention relates to the field of oil drilling engineering technology, and in particular to a method and system for quantitatively evaluating the cleanliness of a wellbore. Background Technology

[0002] As exploration and development progress, drilling engineering is moving towards ultra-deep wells and extended reach horizontal wells. With increasing well depth, the wellbore size decreases, making wellbore cleaning increasingly critical, especially for extended reach horizontal wells. Failure to accurately assess the cleanliness of the wellbore in a timely manner significantly increases the risk of stuck pipe and may even lead to incomplete casing installation due to cuttings beds, resulting in wasted drilling footage and substantial economic losses.

[0003] Currently, the commonly used method for evaluating wellbore cleanliness in the field is to observe the sand return from the vibrating screen or to judge the degree of wellbore cleanliness based on theoretical calculations of the circulation time. However, this method can only qualitatively evaluate the degree of wellbore cleanliness, not quantitatively, thus failing to provide accurate data for downhole stuck pipe risk warning and wellbore treatment before casing installation. Although existing technologies have proposed using Coriolis mass flow meters to monitor annular wellbore cleanliness, this requires modification of the on-site slurry return pipeline and the addition of auxiliary measuring instruments. It cannot provide early warning of sand settling and stuck pipe risk levels, and this method has not yet been applied in actual field practice. Summary of the Invention

[0004] The purpose of this invention is to provide a solution for quantitatively evaluating wellbore cleanliness at drilling sites.

[0005] To address the aforementioned technical problems, this invention provides a method for quantitatively evaluating wellbore cleanliness, comprising: processing and measuring the backflow of cuttings from a vibrating screen during drilling to obtain the actual cuttings mass; calculating the theoretical cuttings return volume based on the wellbore enlargement rate of the drilling area; obtaining the current cuttings return ratio based on the actual cuttings mass and the theoretical cuttings return volume; and predicting and evaluating the wellbore cleanliness of the current drilling operation using a preset wellbore cleanliness evaluation standard based on the current cuttings return ratio. The wellbore cleanliness evaluation standard is determined based on the historical cuttings return ratio variation characteristics with well depth of wells already drilled in the current drilling area.

[0006] Preferably, the step of processing and measuring the return flow of the vibratory screen during drilling to obtain the true cuttings mass includes: collecting the cuttings mixture returned from the vibratory screen and calculating the volume-to-mass ratio of the mixture to the cuttings at different return time intervals; obtaining the cuttings mass increment at the corresponding time interval from the volume increment of the mixture at different return time intervals based on the volume-to-mass ratio; and calculating the current true cuttings mass based on the cuttings mass increment at different return time intervals.

[0007] Preferably, the step of collecting the rock fragment mixture returned from the vibrating screen and calculating the volume-to-mass ratio of the mixture to the rock fragments at different return time intervals includes: using the rock fragment mixture collected at each return time interval to calculate the volume of the mixture at different return time intervals; sequentially washing, extracting, and drying the rock fragment mixture collected at each return time interval, and measuring the mass and density of the dried rock fragments; and calculating the ratio of the mixture volume to the mass of the dried rock fragments at each return time interval.

[0008] Preferably, the step of calculating the theoretical cuttings return amount of the drilling operation based on the wellbore enlargement rate of the drilling area includes: calculating the actual wellbore diameter of the drilling operation based on the current wellbore enlargement rate of the drilling area; and obtaining the theoretical cuttings return amount based on the actual wellbore diameter, the current drilling footage, and the cuttings density.

[0009] Preferably, a real-time cuttings return ratio curve is plotted based on the dynamic cuttings return ratio data within a specified time period before the current return interval; the current cuttings return ratio is compared with the wellbore cleanliness evaluation standard and the real-time return ratio curve to predict and evaluate the current wellbore cleanliness.

[0010] Preferably, the step of predicting and evaluating the wellbore cleanliness of the current drilling operation based on the current cuttings return ratio and using a preset wellbore cleanliness evaluation standard includes: comparing the current cuttings return ratio with the real-time return ratio curve and a reference curve characterizing the wellbore cleanliness evaluation standard, and predicting whether the current wellbore cleanliness is good or whether there is a risk of sand settling and stuck pipe in the well based on the comparison results. The reference curve is formed based on the fitting results of the correlation between the historical cuttings return ratio data and the well depth data of the wells already drilled in the current work area.

[0011] Preferably, the step of predicting and evaluating the wellbore cleanliness of the current drilling operation based on the current cuttings return ratio and using a preset wellbore cleanliness evaluation standard includes: comparing the current cuttings return ratio with the real-time return ratio curve and the return ratio risk level map characterizing the wellbore cleanliness evaluation standard to determine the safety level of the current drilling operation. The risk level area in the return ratio risk level map includes a normal drilling area, a warning area, and a danger area. The return ratio risk level map is set based on the numerical range of historical cuttings return ratio data of the wells already drilled in the current work area.

[0012] Preferably, the method further includes: determining the target well depth of the casing to be run; obtaining the safe cuttings return ratio at the target well depth of the casing to be run based on the cuttings return ratio of the casing in the adjacent well at the completed well depth; and comparing the real-time return ratio data of the current well at the target well depth with the safe cuttings return ratio to evaluate the casing's successful run.

[0013] On the other hand, embodiments of the present invention also provide a system for quantitatively evaluating the cleanliness of a wellbore, comprising: an actual cuttings feature generation module configured to process and measure the return flow of the vibrating screen during drilling to obtain the actual cuttings mass; a theoretical cuttings feature generation module configured to calculate the theoretical cuttings return volume of the drilling operation based on the wellbore enlargement rate of the drilling area; an evaluation parameter generation module configured to obtain the current cuttings return ratio based on the actual cuttings mass and the theoretical cuttings return volume; and a wellbore cleanliness evaluation module configured to predict and evaluate the cleanliness of the wellbore during the current drilling operation based on the current cuttings return ratio and using a preset wellbore cleanliness evaluation standard, wherein the wellbore cleanliness evaluation standard is determined based on the historical cuttings return ratio variation characteristics with well depth of the wells already drilled in the current drilling area.

[0014] Preferably, the actual rock cuttings feature generation module includes: a volume-to-mass ratio calculation submodule, configured to collect the rock cuttings mixture returned from the vibrating screen and calculate the volume-to-mass ratio of the mixture to the rock cuttings at different return time intervals; a unit-time mass increment calculation submodule, configured to obtain the rock cuttings mass increment at the corresponding time interval based on the volume-to-mass ratio and the volume increment of the mixture at different return time intervals; and a true mass calculation submodule, configured to calculate the current true rock cuttings mass based on the rock cuttings mass increment at different return time intervals.

[0015] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0016] This invention proposes a method and system for quantitatively evaluating the cleanliness of wellbore. The method and system include the following steps: sampling, cleaning, drying, and measuring the mixture returned from a vibrating screen; establishing the relationship between the volume of the returned mixture and the actual mass of cuttings in the mixture; calculating the actual mass of returned cuttings based on the volume of the returned mixture; calculating the theoretical cuttings production using the regional wellbore enlargement rate; obtaining the mass ratio of returned cuttings to theoretical cuttings, i.e., the cuttings return ratio; and quantitatively evaluating the cleanliness of the wellbore using the concept of the cuttings return ratio. This invention can provide early warning for drilling risks such as sand accumulation and stuck pipe, provide accurate reference data for wellbore treatment before casing installation, ensure smooth casing installation, and avoid inadequate casing installation due to insufficient wellbore cleaning, or excessive wellbore treatment that wastes production operation time.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a step diagram of a method for quantitatively evaluating the cleanliness of a wellbore, according to an embodiment of this application.

[0020] Figure 2 This is a schematic diagram illustrating the principle of drawing a reference curve in a method for quantitatively evaluating the cleanliness of a wellbore, as described in an embodiment of this application.

[0021] Figure 3 This is a schematic diagram illustrating the principle of drawing a return ratio risk level map in a method for quantitatively evaluating the cleanliness of a wellbore, as described in an embodiment of this application.

[0022] Figure 4 This is a block diagram of a system for quantitatively evaluating the cleanliness of a wellbore, according to an embodiment of this application. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0024] Furthermore, the steps illustrated in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in a different order than that shown here.

[0025] As exploration and development progress, drilling engineering is moving towards ultra-deep wells and extended reach horizontal wells. With increasing well depth, the wellbore size decreases, making wellbore cleaning increasingly critical, especially for extended reach horizontal wells. Failure to accurately assess the cleanliness of the wellbore in a timely manner significantly increases the risk of stuck pipe and may even lead to incomplete casing installation due to cuttings beds, resulting in wasted drilling footage and substantial economic losses.

[0026] Currently, the commonly used method for evaluating wellbore cleanliness in the field is to observe the sand return from the vibrating screen or to judge the degree of wellbore cleanliness based on theoretical calculations of the circulation time. However, this method can only qualitatively evaluate the degree of wellbore cleanliness, not quantitatively, thus failing to provide accurate data for downhole stuck pipe risk warning and wellbore treatment before casing installation. Although existing technologies have proposed using Coriolis mass flow meters to monitor annular wellbore cleanliness, this requires modification of the on-site slurry return pipeline and the addition of auxiliary measuring instruments. It cannot provide early warning of sand settling and stuck pipe risk levels, and this method has not yet been applied in actual field practice.

[0027] To address the aforementioned technical problems, this application proposes a method and system for quantitatively evaluating wellbore cleanliness. This method and system establishes a relationship between the volume of the mixture returned from the vibrating screen and the actual mass of rock cuttings in the mixture by processing and measuring samples of the mixture. Based on the volume of the returned mixture, the actual mass of rock cuttings is calculated. The theoretical rock cuttings generation is calculated using the regional wellbore enlargement rate, obtaining the mass ratio of returned rock cuttings to theoretical rock cuttings, i.e., the rock cuttings return ratio. The concept of the rock cuttings return ratio is used to quantitatively evaluate wellbore cleanliness. Based on regional data statistical analysis, a warning value for sand accumulation and stuck pipe risk and a safe value for wellbore treatment before casing installation are set. Thus, this invention not only provides early warning for downhole sand accumulation and stuck pipe risk but also provides accurate reference data for wellbore treatment before casing installation, ensuring smooth casing installation.

[0028] Figure 1 This is a step diagram illustrating a method for quantitatively evaluating wellbore cleanliness according to an embodiment of this application. Refer to the following... Figure 1 The specific process of the method for quantitatively evaluating the cleanliness of wellbore (hereinafter referred to as the "quantitative evaluation method") described in the embodiments of the present invention will be explained.

[0029] Step S110 processes and measures the flowback from the vibrating screen during drilling to obtain the true cuttings mass. Step S110 includes the following steps: First, a mixture of cuttings (sample) flowed back from the vibrating screen is collected, and the volume-to-mass ratio of the mixture to the cuttings is calculated at different flowback time intervals; then, based on the volume-to-mass ratio of the mixture to the cuttings at different flowback time intervals, the increase in the mass of the cuttings at the corresponding time interval is obtained from the increase in the volume of the mixture at different flowback time intervals; finally, based on the increase in the mass of the cuttings at different flowback time intervals, the true cuttings mass at the current flowback time interval is calculated.

[0030] In calculating the volume-to-mass ratio of returned rock fragments at the current return time interval, the first step is to use the rock fragment mixture collected at each return time interval to calculate the volume of the mixture at different return time intervals. The second step is to sequentially wash, extract, and dry the rock fragment mixture collected at each return time interval, and measure the mass and density of the dried rock fragments. The third step is to calculate the ratio of the mixture volume to the mass of the dried rock fragments at each return time interval.

[0031] Specifically, a suitable sample of the rock fragment mixture discharged from the vibrating screen is taken, and the volume v of the current rock fragment mixture is accurately measured. Then, the obtained rock fragment mixture is cleaned with a cleaning solution, and the real rock fragments are screened out. The rock fragments are then dried using a dryer. Finally, the mass m and density ρ of the dried rock fragments are measured using a solid density meter. 固 Next, the volumetric mass ratio of the current rock cuttings mixture to the dried rock cuttings is calculated using the following expression:

[0032]

[0033] Where λ represents the volumetric mass ratio of the rock cuttings, v represents the volume of the rock cuttings mixture collected at each sampling time, and m represents the mass of the rock cuttings after sampling, washing, and drying. This completes the calculation of the volumetric mass ratio corresponding to one backflow time interval. Then, after each time interval Δt (within each backflow time interval), rock cuttings mixtures are sampled, and the above operation process is repeated to obtain the volumetric mass ratio of the rock cuttings corresponding to different backflow time intervals.

[0034] After calculating the volume-to-mass ratio of the mixture to the rock cuttings at different backflow intervals, this embodiment of the invention will calculate the mass increment of the rock cuttings at different backflow intervals based on the volume-to-mass ratio data of the mixture to the rock cuttings at these different backflow intervals, combined with the volume increment data of the mixture at different backflow intervals.

[0035] Specifically, each time a rock cuttings mixture is sampled, the liquid level (increment) in the rock cuttings container needs to be recorded. The liquid level can be recorded using a steel ruler or an infrared rangefinder. Then, the volume increment of the rock cuttings mixture corresponding to each sampling is calculated based on the cross-sectional area of ​​the rock cuttings container. Finally, the mass of the actual rock cuttings returned within the interval Δt is calculated based on the volume-to-mass ratio λ of the rock cuttings corresponding to each return time interval. The following expressions are used to calculate the volume increment of the sampled rock cuttings mixture and the mass increment of the actual rock cuttings (the returned mass of the actual rock cuttings) per unit return time interval:

[0036] △v=s×△h (2)

[0037]

[0038] Where △v represents the volume increment of the sampled rock cuttings mixture, s represents the cross-sectional area of ​​the rock cuttings container, △h represents the increase in liquid level in the rock cuttings container per unit backflow time interval, and △m represents the mass increment of the actual rock cuttings per unit backflow time interval.

[0039] Finally, based on the actual cuttings increment at different return intervals, the mass of actual cuttings returned within each interval is accumulated to obtain the total mass of actual cuttings returned so far in the current drilling operation. The total mass of actual cuttings returned is calculated using the following expression:

[0040]

[0041] Where, m 总 Δm represents the total mass of actual rock cuttings returned so far, n represents the total number of all unit return time intervals experienced so far, i represents the sequence number of the return time interval, and Δm represents the total mass of actual rock cuttings returned so far. i This represents the actual mass increment of rock cuttings corresponding to the i-th backflow time interval.

[0042] After obtaining the total mass of the actual rock cuttings returned so far, proceed to step S120 to calculate the theoretical value of the total mass of rock cuttings returned so far in this drilling operation.

[0043] like Figure 1 As shown, step S120 calculates the theoretical cuttings return volume of the drilling based on the wellbore enlargement rate of the drilling area.

[0044] In step S120, the actual well diameter of the well being drilled is first calculated based on the well diameter enlargement rate of the reservoir area where the current well is being drilled. Then, the theoretical cuttings return volume is calculated based on the actual well diameter, the footage of the current drilling operation, and the cuttings density.

[0045] Specifically, first, determine the average wellbore enlargement rate of each adjacent well within the reservoir area where the current well is being drilled. Then, based on the average wellbore enlargement rate of the adjacent wells in the area, calculate the actual wellbore diameter of the current well using the following expression:

[0046] D=α×d (5)

[0047] Where D represents the actual wellbore diameter during drilling, α represents the average wellbore enlargement rate, and d represents the drill bit diameter during the current drilling operation. Then, based on the actual wellbore diameter, the footage reached in this drilling operation, and the measured cuttings density, the total mass of theoretically generated cuttings is calculated using the following expression.

[0048]

[0049] Where, m 理论 ρ represents the theoretical cuttings return rate, L represents the footage reached in this drilling operation, and ρ represents the cuts returned. 固 This indicates the density of the (dried) rock fragments measured using a solid density meter at each sampling time.

[0050] Further, after calculating the theoretical value of the total mass of rock cuttings currently returned, the process proceeds to step S130 to calculate the rock cuttings return ratio parameter used to evaluate the cleanliness of the wellbore in real time.

[0051] Continue to refer to Figure 1 Step S130 obtains the current cuttings return ratio based on the actual cuttings mass calculated in step S110 and the theoretical cuttings return amount calculated in step S120.

[0052] Specifically, based on the total actual mass of rock cuttings calculated in step S110 and the theoretical value of the amount of rock cuttings returned calculated in step S120, the rock cuttings return ratio at the current return time interval is calculated using the following expression:

[0053]

[0054] Where β represents the cuttings return ratio.

[0055] Next, after calculating the current cuttings return ratio, the process proceeds to step S140, where the calculated cuttings return ratio is compared with a threshold to predict the wellbore cleanliness level at the current time interval during the drilling operation.

[0056] like Figure 1 As shown, step S140 uses a preset wellbore cleanliness evaluation standard to predict and evaluate the cleanliness of the wellbore at the current moment during the drilling operation, based on the current cuttings return ratio calculated in step S130. In this embodiment of the invention, the wellbore cleanliness evaluation standard is determined based on the historical cuttings return ratio variation characteristics with well depth of each drilled well in the current drilling area.

[0057] Furthermore, to improve the wellbore cleanliness prediction capability, in step S140 of this embodiment, when evaluating the current wellbore cleanliness, not only is the wellbore cleanliness evaluation standard formed by historical data information referenced, but also the change data of the cuttings return ratio within a specified time period before the current return ratio is evaluated. Specifically, firstly, a real-time return ratio curve is plotted based on the dynamic cuttings return ratio data within a specified time period before the current return interval. Then, the current cuttings return ratio is compared with both the wellbore cleanliness evaluation standard and the real-time return ratio curve, thereby predicting and evaluating the current wellbore cleanliness based on the comparison results.

[0058] In the first embodiment, the wellbore cleanliness evaluation standard can be characterized using a preset reference curve. In this embodiment, a preset reference curve is formed based on the fitting results of the correlation between historical cuttings return ratio data and well depth data for each drilled well (or well section) within the reservoir area to which the current drilling well belongs. Furthermore, the process of drawing the reference curve in this embodiment not only requires statistical analysis of the relationship between cuttings return ratio and well depth for each drilled well section, and drawing the reference curve for the current reservoir area after obtaining a certain data sample, but also requires updating and drawing the real-time reference curve during the real-time drilling operation of the drilling well. This allows for real-time prediction of the wellbore cleanliness level at different flowback time intervals, using the updated reference curve as a benchmark.

[0059] Figure 2 This is a schematic diagram illustrating the principle of drawing a reference curve in a method for quantitatively evaluating the cleanliness of a wellbore, as described in an embodiment of this application. Figure 2 This diagram illustrates the process of plotting a reference curve using historical cuttings return ratio data at different well depths. The historical cuttings return ratio data refers to the cuttings return ratios recorded at different well depths during drilling operations on the drilled section. Figure 2 As shown, in the process of drawing the reference curve, the well depth is used as the horizontal axis and the return ratio is used as the vertical axis.

[0060] During the real-time prediction and evaluation process, the current cuttings return ratio is compared with both the real-time return ratio curve and a preset reference curve. Based on the comparison results, a prediction is made regarding whether the current wellbore cleanliness is good or if there is a risk of sand buildup and stuck pipe. Specifically, if the current cuttings return ratio of the drilling well is higher than the reference curve, it indicates a good wellbore cleanliness; if the current cuttings return ratio is lower than the reference curve, it indicates insufficient wellbore cleanliness. Furthermore, if the current cuttings return ratio is lower than the reference curve, and the difference between the current cuttings return ratio and the aforementioned real-time return ratio curve reaches a preset sudden drop threshold, it indicates an increased risk of stuck pipe or that drilling fluid performance is affected. In this case, an alarm signal is immediately generated to prompt relevant personnel to address the current risk promptly.

[0061] In the second embodiment, the wellbore cleanliness evaluation standard can also be characterized using a cuttings return ratio risk level map. In this embodiment, at least two different level thresholds need to be set based on the numerical range of the correlation between historical cuttings return ratio data and well depth data for each drilled well (or well section) within the reservoir area to which the current drilling well belongs, to form at least three risk assessment level regions, thereby establishing a cuttings return ratio risk level map. The risk level regions in the cuttings return ratio risk level map include normal drilling zones, warning zones, and danger zones, see [link to relevant documentation]. Figure 3 ( Figure 3This is a schematic diagram illustrating the principle of drawing a return ratio risk level map in a method for quantitatively evaluating wellbore cleanliness according to an embodiment of this application.

[0062] Specifically, by statistically analyzing historical cuttings return ratios for each drilled well (or well section) within the reservoir area currently being drilled, considering factors such as sand buildup and stuck pipe that affect wellbore cleanliness, and historical cuttings return ratios during safe drilling operations, a first warning curve distinguishing between safe and warning zones, and a second warning curve distinguishing between warning and danger zones, are drawn to gradually improve the cuttings return ratio risk level map. (Refer to...) Figure 3 .like Figure 3 As shown, the horizontal axis represents well depth, and the vertical axis represents the cuttings return ratio.

[0063] During real-time prediction and evaluation, the current cuttings return ratio is compared with the real-time return ratio curve and a pre-drawn return ratio risk level map to determine the safety level of the current drilling operation. Specifically, under normal drilling conditions (high wellbore cleanliness to maintain safe drilling operations), the current cuttings return ratio falls within the safe zone on the risk level map; when the current cuttings return ratio falls within the warning zone, an alarm signal is immediately generated, and on-site attention should be paid to prompt relevant personnel to adjust drilling fluid performance and drilling parameters in a timely manner to improve cuttings carrying capacity; when the current cuttings return ratio falls within the danger zone, a shutdown instruction signal must be generated immediately, and drilling must be stopped for special handling to ensure a clean wellbore.

[0064] Furthermore, the real-time cuttings return ratio data generated by the quantitative evaluation method described in this embodiment of the invention can not only provide early warning for drilling risks such as sand accumulation and stuck pipe in the well, but also provide accurate reference data for wellbore cleaning before casing installation. Specifically, step one is to determine the target well depth to be installed with casing in this well; step two is to obtain the cuttings return ratio data of the adjacent well at the same well depth based on the cuttings return ratio corresponding to the casing at the completed well depth (e.g., through interpolation), and use this return ratio data as the safe cuttings return ratio of this well at the target well depth to be installed with casing; step three is to compare the real-time return ratio data corresponding to the target well depth of this well with the safe cuttings return ratio data of this well determined in step two, and evaluate the casing installation of this well based on the comparison results, providing data basis for wellbore cleaning.

[0065] In this way, based on the cuttings return ratios of neighboring wells in the region before casing running, a clean treatment evaluation basis (safe cuttings return ratio) for safe casing running in this well is drawn. After the well is completed, based on the completed well depth, the safe cuttings return ratios of neighboring wells are used to diagnose whether the current casing running operation can safely reach the target position (for example, if the return ratio data corresponding to the completed well depth is lower than the safe cuttings return ratio threshold, the current wellbore needs to be purged). When the safe running standard can be met, the drilling can be stopped and the casing running operation can be carried out.

[0066] On the other hand, based on the above-mentioned quantitative evaluation method, this embodiment of the invention also provides a system for quantitatively evaluating the cleanliness of wellbore (hereinafter referred to as "quantitative evaluation system"). Figure 4 This is a block diagram of a system for quantitatively evaluating the cleanliness of a wellbore, according to an embodiment of this application.

[0067] like Figure 4 As shown, the quantitative evaluation system of this invention includes: an actual cuttings feature generation module 41, a theoretical cuttings feature generation module 42, an evaluation parameter generation module 43, and a wellbore cleanliness evaluation module 44. The actual cuttings feature generation module 41 is implemented through step S110, configured to process and measure the return flow of the vibrating screen during drilling to obtain the actual cuttings mass. The theoretical cuttings feature generation module 42 is implemented through step S120, configured to calculate the theoretical cuttings return volume of the drilling operation based on the wellbore enlargement rate of the drilling area. The evaluation parameter generation module 43 is implemented through step S130, configured to obtain the current cuttings return ratio based on the actual cuttings mass and the theoretical cuttings return volume. The wellbore cleanliness evaluation module is implemented through step S140, configured to predict and evaluate the wellbore cleanliness of the current drilling operation based on the current cuttings return ratio and a preset wellbore cleanliness evaluation standard. The wellbore cleanliness evaluation standard is determined based on the historical cuttings return ratio of drilled wells in the current work area as a function of well depth.

[0068] Furthermore, the aforementioned actual rock cuttings feature generation module 41 includes: a volumetric mass ratio calculation submodule 411, a unit time mass increment calculation submodule 412, and a true mass calculation submodule 413. The volumetric mass ratio calculation submodule 411 is configured to collect the rock cuttings mixture returned from the vibrating screen and calculate the volumetric mass ratio of the mixture to the rock cuttings at different return time intervals; the unit time mass increment calculation submodule 412 is configured to obtain the rock cuttings mass increment at the corresponding time interval based on the volumetric mass ratio and the volume increment of the mixture at different return time intervals; the true mass calculation submodule 413 is configured to calculate the current true rock cuttings mass based on the rock cuttings mass increment at different return time intervals.

[0069] Furthermore, the aforementioned theoretical cuttings feature generation module 42 includes: a true wellbore calculation submodule 421 and a theoretical cuttings return calculation submodule 422. The true wellbore calculation submodule 421 is configured to calculate the true wellbore diameter of the well being drilled based on the current wellbore enlargement rate of the drilling area; the theoretical cuttings return calculation submodule 422 is configured to obtain the theoretical cuttings return amount based on the true wellbore diameter, the current drilling footage, and the cuttings density.

[0070] This invention discloses a method and system for quantitatively evaluating the cleanliness of a wellbore. The method and system include the following steps: sampling, cleaning, drying, and measuring the mixture returned from a vibrating screen; establishing the relationship between the volume of the mixture returned from the vibrating screen and the actual mass of rock cuttings in the mixture; calculating the actual mass of rock cuttings returned based on the volume of the mixture; calculating the theoretical amount of rock cuttings generated using the regional wellbore enlargement rate; obtaining the mass ratio of returned rock cuttings to theoretical rock cuttings, i.e., the rock cuttings return ratio; and quantitatively evaluating the cleanliness of the wellbore using the concept of the rock cuttings return ratio. This invention can provide early warning for drilling risks such as sand accumulation and stuck pipe, provide accurate reference data for wellbore treatment before casing installation, ensure smooth casing installation, and avoid inadequate casing installation due to insufficient wellbore cleaning, or excessive wellbore treatment that wastes production operation time.

[0071] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0072] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0073] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0074] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for quantitatively evaluating the cleanliness of a wellbore, characterized in that, include: The backflow of the vibrating screen during drilling is processed and measured to obtain the true quality of cuttings; Based on the wellbore enlargement rate of the drilling area, calculate the theoretical cuttings return rate of the drilling operation. Based on the actual rock cuttings mass and the theoretical rock cuttings return amount, the current rock cuttings return ratio is obtained; Based on the current cuttings return ratio, the wellbore cleanliness of the current drilling operation is predicted and evaluated using a preset wellbore cleanliness evaluation standard. This standard is determined based on the historical cuttings return ratio variation characteristics with well depth in the current work area, and includes: Based on the dynamic cuttings return ratio data within a specified time period prior to the current return interval, a real-time return ratio curve is plotted. Then, the current cuttings return ratio is compared with both the wellbore cleanliness evaluation standard and the real-time return ratio curve to predict and evaluate the current wellbore cleanliness. The current cuttings return ratio is compared with the real-time return ratio curve and a reference curve characterizing the wellbore cleanliness evaluation standard. Based on the comparison results, a prediction is made as to whether the current wellbore cleanliness is good or whether there is a risk of sand accumulation and stuck pipe in the well. The reference curve is formed by fitting the correlation between historical cuttings return ratio data and well depth data of wells drilled in the current work area. The current cuttings return ratio is compared with the real-time return ratio curve and the return ratio risk level map characterizing the wellbore cleanliness evaluation standard to determine the safety level of the current drilling operation. The risk level area in the return ratio risk level map includes the normal drilling area, the warning area, and the danger area. The return ratio risk level map is set according to the numerical range of historical cuttings return ratio data of the wells drilled in the current work area.

2. The method according to claim 1, characterized in that, The steps for processing and measuring the backflow of cuttings from the vibratory screen during drilling to obtain the true quality of the cuttings include: Collect the rock debris mixture returned from the vibrating screen and calculate the volume mass ratio of the mixture to the rock debris at different return time intervals; Based on the volume-to-mass ratio, the mass increment of rock fragments at different time intervals is obtained from the volume increment of the mixture at different backflow time intervals; The current actual rock cutting mass is calculated based on the rock cutting mass increment at different return intervals.

3. The method according to claim 2, characterized in that, The steps of collecting the rock cuttings mixture returned from the vibrating screen and calculating the volumetric mass ratio of the mixture to the rock cuttings at different return time intervals include: Calculate the volume of the mixture at different runoff intervals using the rock debris mixture collected at each runoff interval; The rock fragment mixture collected at each return interval was sequentially washed, extracted, and dried, and the mass and density of the dried rock fragments were measured. Calculate the ratio of the volume of the mixture to the mass of the dried rock chips at each backflow interval.

4. The method according to claim 1, characterized in that, The step of calculating the theoretical cuttings return rate of a drilling well based on the wellbore enlargement rate in the drilling area includes: Calculate the actual well diameter of the well being drilled based on the current well diameter enlargement rate of the work area; The theoretical cuttings return rate is obtained based on the actual well diameter, the current drilling footage, and the cuttings density.

5. The method according to any one of claims 1-4, characterized in that, The method further includes: Determine the target well depth for running the casing; Based on the cuttings return ratio of the adjacent well casing at the completed well depth, the safe cuttings return ratio at the target well depth to be run into the casing is obtained; The real-time cuttings return ratio at the target well depth is compared with the safe cuttings return ratio to evaluate the casing insertion.

6. A system for quantitatively evaluating the cleanliness of a wellbore, characterized in that, include: The actual cuttings feature generation module is configured to process and measure the backflow of the vibrating screen during drilling to obtain the actual cuttings quality. The theoretical cuttings feature generation module is configured to calculate the theoretical cuttings return volume of the drilling operation based on the wellbore enlargement rate of the drilling area. The evaluation parameter generation module is configured to obtain the current cuttings return ratio based on the actual cuttings mass and the theoretical cuttings return amount. The wellbore cleaning evaluation module is configured to predict and evaluate the wellbore cleanliness of the current drilling operation based on the current cuttings return ratio and using preset wellbore cleaning evaluation standards. The wellbore cleaning evaluation standards are determined based on the historical characteristics of cuttings return ratios with well depth in the current work area, including: Based on the dynamic cuttings return ratio data within a specified time period prior to the current return interval, a real-time return ratio curve is plotted. Then, the current cuttings return ratio is compared with both the wellbore cleanliness evaluation standard and the real-time return ratio curve to predict and evaluate the current wellbore cleanliness. The current cuttings return ratio is compared with the real-time return ratio curve and a reference curve characterizing the wellbore cleanliness evaluation standard. Based on the comparison results, a prediction is made as to whether the current wellbore cleanliness is good or whether there is a risk of sand accumulation and stuck pipe in the well. The reference curve is formed by fitting the correlation between historical cuttings return ratio data and well depth data of wells drilled in the current work area. The current cuttings return ratio is compared with the real-time return ratio curve and the return ratio risk level map characterizing the wellbore cleanliness evaluation standard to determine the safety level of the current drilling operation. The risk level area in the return ratio risk level map includes the normal drilling area, the warning area, and the danger area. The return ratio risk level map is set according to the numerical range of historical cuttings return ratio data of the wells drilled in the current work area.

7. The system according to claim 6, characterized in that, The actual rock cuttings feature generation module includes: The volumetric mass ratio calculation submodule is configured to collect the rock debris mixture returned from the vibrating screen and calculate the volumetric mass ratio of the mixture to the rock debris at different return time intervals. The submodule for calculating mass increment per unit time is configured to obtain the mass increment of rock cuttings at the corresponding time interval based on the volume mass ratio and the volume increment of the mixture at different backflow time intervals. The true mass calculation submodule is configured to calculate the current true mass of cuttings based on the mass increment of cuttings at different backflow intervals.

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