A method and device for locating lost circulation zones in wells

Abstract

This invention discloses a method and apparatus for locating lost circulation zones in downhole drilling, belonging to the technical fields of oil and gas drilling and completion, and natural gas hydrate drilling and production. The method involves deploying a downhole micro-measuring chip into the drilling fluid circulation system. After the chip exits the wellbore from the annulus, the pressure measurements recorded inside the chip are read to obtain an annulus pressure profile. By shifting and subtracting the pressure profile, a shifted pressure difference profile is obtained. If a pressure difference abrupt change occurs in the shifted pressure difference profile, the depth of the lost circulation zone can be obtained by reading the corresponding well depth at that abrupt change. Further shifting and subtracting the shifted pressure difference profile and setting a threshold further clarifies the trend of pressure difference changes, making it easier to locate the lost circulation zone. This method achieves the location of lost circulation zones in drilling and overcomes the shortcomings of traditional methods, such as low accuracy and slow speed.

Description

Technical Field

[0001] This invention relates to the fields of oil and gas drilling and completion technology and natural gas hydrate drilling and production technology, and to a method and device for locating lost circulation zones in wells. Specifically, it relates to a method and device for locating lost circulation zones in wells based on a downhole micro-measuring chip. Background Technology

[0002] The development of deep and ultra-deep oil and gas resources is of great significance to my country's energy security. Their main characteristics include deep burial and complex formation pressure systems, leading to frequent downhole losses during drilling. Accurate location of the downhole lost zone is a crucial step in sealing it. While scholars both domestically and internationally have conducted a series of studies on lost zone location, rapid location has not been achieved, resulting in increased incident response time and drilling costs.

[0003] Currently, existing technologies mainly categorize downhole lost circulation zone location methods into two main types: leak detector location and monitoring while drilling. Leak detector location typically requires being lowered into the annulus until the lost circulation zone is located, and then retrieved to the surface. This process is time-consuming, and drilling fluid cannot be circulated during leak detection, increasing well control risks. Monitoring while drilling to obtain the location of the lost circulation zone usually requires inversion using a hydraulic model. However, due to the complex flow of drilling fluid in the annulus, current hydraulic models are not very accurate and it is difficult to accurately determine the lost circulation zone location. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for locating lost circulation zones in downhole drilling. This method enables rapid, continuous, and low-cost location of lost circulation zones after detection during oil and gas drilling and completion, and natural gas hydrate drilling and production. It effectively overcomes the limitations of existing technologies and is crucial for ensuring construction safety, improving operational efficiency, and reducing production costs.

[0005] To address the aforementioned technical problems, in one aspect, embodiments of the present invention provide a method for locating downhole lost circulation zones, comprising the following steps:

[0006] Step 1: Measure the annular pressure profile:

[0007] Once a leak is confirmed downhole, a downhole micro-measuring chip is deployed into the wellbore, maintaining a constant flow rate until the chip circulates out of the wellhead. By combining this with magnetic positioning, the pressure measurements at different locations in the annulus are obtained.

[0008]

[0009] In the formula, the annulus is divided into n measuring points from the bottom to the wellhead. S1 is the depth of the bottom measuring point (m); p1 is the pressure at the bottom measuring point (MPa); S2 is the depth of the second measuring point in the annulus (m); p2 is the pressure at the second measuring point in the annulus (MPa); S3 is the depth of the third measuring point in the annulus (m); p3 is the pressure at the third measuring point in the annulus (MPa); S i Let p be the well depth at the i-th measuring point in the annulus, in meters. i The pressure at the i-th measuring point in the annulus is expressed in MPa and S. n The depth of the measuring point at the annular exit is in meters (m); p n The pressure at the annulus outlet measuring point is in MPa.

[0010] Step 2, Pressure Profile Shift Subtraction:

[0011] The measured pressure profiles were resampled to form two pressure profiles.

[0012]

[0013] In the formula, j≥1, and 10(j-1)+1≤n; k≥1, and 10(k-1)+10≤n. Subtracting the two pressure profiles yields the difference in the shifted pressure profile.

[0014]

[0015] In the formula, S1 is the depth of the bottom hole measuring point, m; p1 is the pressure at the bottom hole measuring point, MPa; S 10 The depth of the well at the 10th measuring point in the annulus, in meters (m); p 10 The pressure at the 10th measuring point in the annulus is measured in MPa and S. 11 The depth of the well at the 11th measuring point in the annulus, in meters (m); p 11 The pressure at the 11th measuring point in the annulus is measured in MPa and S. 20 The depth of the well at the 20th measuring point in the annulus is m; p 20 The pressure at the 20th measuring point in the annulus is measured in MPa and S. 21 The well depth at the 21st measuring point in the annulus is m; p 21 The pressure at the 21st measuring point in the annulus is measured in MPa and S. 30 The depth of the well at the 30th measuring point in the annulus is m; p 30 The pressure at the 30th measuring point in the annulus is measured in MPa and S. 10(j-1)+1 The well depth at the 10(j-1)+1th measuring point in the annulus is in meters (m); p 10(j-1)+1 The pressure at the 10(j-1)+1th measuring point in the annulus, in MPa; S 10(k-1)+10 The depth of the well at the 10(k-1)+10th measuring point in the annulus is in meters (m); p 10(k-1)+10 The pressure at the 10(k-1)+10th measuring point in the annulus, in MPa;

[0016] Step 3: Perform the shift subtraction operation again on the shift pressure difference profile.

[0017] Perform another shift subtraction operation on the above-mentioned shifted pressure profile difference to obtain the discriminant pressure difference profile;

[0018]

[0019] Step 4: Set a discrimination threshold. When the value of the discrimination pressure difference exceeds the discrimination threshold, it can be determined that leakage has occurred at the depth of the well corresponding to the discrimination pressure difference.

[0020] Furthermore, in step 1, the downhole micro-measuring chip is a micro-measuring device that integrates temperature measurement, pressure measurement, and magnetic positioning.

[0021] Furthermore, the miniature measuring body is spherical with a diameter of 1 cm and can withstand the harsh environment of 150°C high temperature and 200MPa high pressure downhole.

[0022] Furthermore, the downhole micro-measuring chip is deployed from the drill pipe into the wellbore. The chip flows with the drilling fluid and records the pressure value along the path. Combined with magnetic positioning technology for depth positioning, the pressure value at different locations in the annulus can be obtained.

[0023] On the other hand, embodiments of the present invention also provide a downhole lost circulation zone location device, comprising:

[0024] The annular pressure profile measurement module is used to determine that a downhole leakage has occurred. After that, a downhole micro-measurement chip is deployed into the wellbore and a constant discharge rate is maintained until the downhole micro-measurement chip is circulated out of the wellhead. By combining magnetic positioning method for depth positioning, the pressure measurement values ​​corresponding to different locations in the annulus are obtained.

[0025] The shifted pressure profile difference calculation module is used to resample the measured pressure profile to form two pressure profiles, and perform a subtraction operation on the two pressure profiles to obtain the shifted pressure profile difference.

[0026] The shift subtraction calculation module is used to perform another shift subtraction operation on the shift pressure profile difference obtained by the shift pressure profile difference calculation module to obtain the discrimination pressure difference profile.

[0027] The discrimination threshold setting module is used to set the discrimination threshold. When the value of the discrimination pressure difference exceeds the discrimination threshold, it can be determined that leakage has occurred at the depth of the well corresponding to the discrimination pressure difference.

[0028] On the other hand, embodiments of the present invention also provide a downhole lost-hole location system, including one or more processors; a memory for storing one or more programs; the processors are configured to execute program instructions stored in the memory, and the program instructions execute the downhole lost-hole location method described above when they are executed.

[0029] On the other hand, embodiments of the present invention also provide a computer-readable storage medium storing a computer program, wherein the computer program, when executed by one or more processors, implements the above-described method for locating downhole lost-hole layers.

[0030] The above-described technical solutions of the embodiments of the present invention have the following beneficial technical effects:

[0031] (1) Ingenious, simple, low cost and easy to use: The WeChat measurement chip on which it is based is easy to use and recycle, without complicated installation and disassembly operations, and is simple and convenient to use.

[0032] (2) Rapid leakage layer location: The leakage layer location method involved in this invention does not require drilling or lowering the measuring instrument via cable, thus saving a lot of time.

[0033] (3) Wider application scenarios: This invention expands the application scenarios of leakage layer location, and can be used to locate leakage layers in a timely and effective manner in drilling, cementing and hydrate drilling and production, so as to buy more time for leakage plugging operations and ensure the safety and efficiency of drilling and completion operations. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the measurement of microspheres;

[0035] Figure 2 This is a schematic diagram showing the movement of a measuring ball within the wellbore.

[0036] Figure 3 This is a flowchart illustrating the implementation of this invention;

[0037] Figure 4 This is a schematic diagram of an example well;

[0038] Figure 5 It is an annular pressure profile;

[0039] Figure 6 It is a profile of the displacement pressure difference;

[0040] Figure 7 It is used to determine the pressure difference profile. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0042] This invention provides a method for locating lost circulation zones in downhole wells. The method involves deploying a downhole micro-measuring chip into the drilling fluid circulation system. After the chip exits the wellbore from the annulus, the pressure measurements recorded inside the chip are read to obtain an annulus pressure profile. By shifting and subtracting this pressure profile, a shifted pressure difference profile is obtained. If a pressure difference abrupt change occurs in the shifted pressure difference profile, the depth of the lost circulation zone can be obtained by reading the corresponding well depth at that abrupt change. Further shifting and subtracting the shifted pressure difference profile and setting a threshold further clarifies the trend of pressure difference changes, making it easier to locate the lost circulation zone. This method achieves the location of lost circulation zones in drilling and overcomes the shortcomings of traditional methods, such as low accuracy and slow speed.

[0043] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a downhole micro-measuring chip, spherical in shape and 1 cm in diameter. The chip integrates a temperature sensor, a pressure sensor, and a magnetic positioning sensor, and can withstand the harsh temperature and pressure environment of the well. The temperature sensor records the temperature of the chip during its movement, the pressure sensor records the temperature of the chip as it moves through the wellbore, and the magnetic positioning sensor records the magnetic signal indicating the chip's position during its movement. When surface personnel detect a leakage in the well, the micro-measuring chip is deployed into the wellbore through the drill string channel while maintaining a constant pump flow rate until the measuring chip circulates out of the wellbore through the annulus channel.

[0044] Figure 2 This diagram illustrates the movement of a downhole micro-measuring chip within the wellbore. The right side shows a schematic of the drilling rig and wellbore flow channels, while the left side is an enlarged view of the wellbore flow channels. The initial position of the downhole micro-measuring chip is located at position S at the wellhead. n At this location, the downhole micro-measuring chip flows with the drilling fluid in the direction indicated by the arrow through the drill string channel and the drill bit (at point S1) water inlet, enters the annulus channel, and records the pressure measurement values ​​along the way. By combining this with magnetic positioning methods for depth correction, the corresponding pressure measurement values ​​at different locations in the annulus can be obtained. The flow channel inside the drill string wall is the drill string channel, while the flow channel outside the drill string wall forms the annulus channel with the formation and casing wall.

[0045]

[0046] Where: S1 is the bottom depth of the well, m; p1 is the bottom pressure of the well, MPa; S iThe depth of the well at a certain measurement location in the annulus is given in meters (m); p i Pressure at a certain measurement location in the annulus, MPa; S n The depth of the annular exit is m; p i The annular outlet pressure is expressed in MPa. The curve showing the variation of this pressure value with well depth is the annular pressure profile.

[0047] The measured pressure profiles were resampled to form two pressure profiles.

[0048]

[0049] In the formula, j≥1, and 10(j-1)+1≤n; k≥1, and 10(k-1)+10≤n. Subtracting the two pressure profiles yields the difference in the shifted pressure profile.

[0050]

[0051] Perform another shift-subtraction operation on the above-mentioned shifted pressure profile difference to obtain the discriminant pressure difference profile.

[0052]

[0053] A discrimination threshold is set. When the value of the discrimination pressure difference exceeds the discrimination threshold, it can be determined that leakage has occurred at the depth of the well corresponding to the discrimination pressure difference.

[0054] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0055] Figure 3 This is a flowchart illustrating an embodiment of the present invention. Figure 4 This is a vertical well in an onshore oil field. The surface temperature is 20℃, the drilling fluid temperature pumped in from the surface is 40℃, the drill pipe outer diameter is 127mm, the drill pipe inner diameter is 108mm, the wellbore diameter is 215.9mm, and the drilling fluid density is 1.38g / cm³. When the open-hole section reached 1000m, the drilling engineer noticed a significant drop in the mud pit level, thus determining that a loss had occurred downhole. The engineer pumped a downhole micro-measuring chip into the wellbore and measured the following... Figure 5 The annular pressure profile shown is not clearly defined, making it impossible to identify the leakage layer.

[0056] Applying the above-mentioned method for locating leak layers, a shift-and-subtraction operation is performed on the annular pressure profile to obtain the following result: Figure 6 The diagram shows a displacement pressure difference profile. It is clear from this profile that at a well depth of 4000m, there is a significant abrupt increase in the displacement pressure difference, indicating leakage at that depth. The leakage layer is located at 4000m.

[0057] To further facilitate the location of the leakage layer, a shift and subtraction operation was performed on the pressure difference profile to obtain the following result: Figure 7 The pressure difference profile shown is used to determine the leakage layer at 4000m. By setting the discrimination threshold to 0.001MPa, the leakage layer can be easily determined.

[0058] Drilling engineers successfully sealed the leak by performing plugging technology at depths of 3950m to 4050m.

[0059] This method can locate lost-stretching zones without the need to trip the drilling string or install leak detection devices in the drill string assembly, saving a lot of time. It is simple to operate and does not affect drilling operations.

[0060] The proposed method for locating lost-hole formations based on downhole micro-measuring chips enables rapid, continuous, and low-cost location of lost-hole formations during oil and gas drilling and completion, as well as natural gas hydrate drilling and production. This helps field operators accurately pinpoint the location of lost-hole formations, facilitating rapid and efficient plugging and effectively addressing the challenges of complex formation engineering. Furthermore, this method only requires pumping the micro-measuring chip into the wellbore along with the drilling fluid after a loss occurs. After retrieval at the annulus outlet, the measurement data is read to determine the location of the lost-hole formation, eliminating the need for tripping the drill string or running in other tools, thus saving significant time in locating the lost-hole formation.

[0061] It is expected that field trials and widespread application will be conducted in oilfields in Xinjiang, Sichuan-Chongqing, and other regions within the next 3-5 years, covering drilling and completion processes as well as offshore natural gas hydration drilling and production. Currently, high-temperature, high-pressure deep wells are more than 20% more complex than conventional shallow wells, resulting in more than three times the non-productive time and costs, and a significant increase in the frequency of leakage, greatly extending non-productive time. Applying the tools and supporting technologies described in this invention will reduce the total time spent handling leakage by approximately 50% within the next 3-5 years, resulting in direct economic benefits of approximately 5 million yuan.

[0062] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for locating lost circulation zones in downhole wells, characterized in that, Includes the following steps: Step 1: Measure the annular pressure profile: Once a leak is confirmed downhole, a downhole micro-measuring chip is deployed into the wellbore, maintaining a constant flow rate until the downhole micro-measuring chip circulates out of the wellhead. By combining this with magnetic positioning, the pressure measurement values ​​at different locations in the annulus are obtained. In the formula, the annulus is divided into n measuring points from the bottom to the wellhead; S1 is the depth of the bottom measuring point (m); p1 is the pressure at the bottom measuring point (MPa); S2 is the depth of the second measuring point in the annulus (m); p2 is the pressure at the second measuring point in the annulus (MPa); S3 is the depth of the third measuring point in the annulus (m); p3 is the pressure at the third measuring point in the annulus (MPa); S i Let p be the well depth at the i-th measuring point in the annulus, in meters. i The pressure at the i-th measuring point in the annulus is expressed in MPa. S n The depth of the measuring point at the annular exit is in meters (m); p n The pressure at the annulus outlet measuring point is in MPa. Step 2, Pressure Profile Shift Subtraction: The measured pressure profiles were resampled to form two pressure profiles. In the formula, j≥1, and 10(j-1)+1≤n; k≥1, and 10(k-1)+10≤n; the difference between the two pressure profiles is obtained by subtracting them. In the formula, S1 is the depth of the bottom hole measuring point, m; p1 is the pressure at the bottom hole measuring point, MPa; S 10 The depth of the well at the 10th measuring point in the annulus, in meters (m); p 10 The pressure at the 10th measuring point in the annulus is measured in MPa and S. 11 The depth of the well at the 11th measuring point in the annulus, in meters (m); p 11 The pressure at the 11th measuring point in the annulus is measured in MPa and S. 20 The depth of the well at the 20th measuring point in the annulus is m; p 20 The pressure at the 20th measuring point in the annulus is measured in MPa and S. 21 The well depth at the 21st measuring point in the annulus is m; p 21 The pressure at the 21st measuring point in the annulus is measured in MPa and S. 30 The depth of the well at the 30th measuring point in the annulus is m; p 30 The pressure at the 30th measuring point in the annulus is measured in MPa and S. 10(j-1)+1 The well depth at the 10(j-1)+1th measuring point in the annulus is in meters (m); p 10(j-1)+1 The pressure at the 10(j-1)+1th measuring point in the annulus, in MPa; S 10(k-1)+10 The depth of the well at the 10(k-1)+10th measuring point in the annulus is in meters (m); p 10(k-1)+10 The pressure at the 10(k-1)+10th measuring point in the annulus, in MPa; Step 3: Perform the shift subtraction operation again on the shift pressure difference profile; Perform another shift subtraction operation on the above-mentioned shifted pressure profile difference to obtain the discriminant pressure difference profile; In the formula δ p1 δ is the pressure difference at the first measuring point, in MPa; p11 The pressure difference at the 11th measuring point, in MPa; δ p21 The difference in pressure at the 21st measuring point, in MPa; Step 4: Set a discrimination threshold. When the value of the discrimination pressure difference exceeds the discrimination threshold, it is determined that leakage has occurred at the depth of the well corresponding to the discrimination pressure difference. In step 1, the downhole micro-measuring chip is a micro-measuring device that integrates temperature measurement, pressure measurement, and magnetic positioning. The miniature measuring body is spherical with a diameter of 1 cm and can withstand the harsh environment of 150°C high temperature and 200MPa high pressure in the well.

2. The downhole leakage zone location method according to claim 1, characterized in that, The downhole micro-measuring chip is dropped from the drill pipe into the wellbore. The chip flows with the drilling fluid and records the pressure value along the path. Combined with magnetic positioning technology, depth positioning is performed to obtain the pressure value at different locations in the annulus.

3. A downhole leakage zone location device, characterized in that, For implementing the downhole leakage zone location method according to claim 1 or 2, the downhole leakage zone location device includes: The annular pressure profile measurement module is used to determine that a downhole leakage has occurred. After that, a downhole micro-measurement chip is deployed into the wellbore and a constant discharge rate is maintained until the downhole micro-measurement chip is circulated out of the wellhead. By combining magnetic positioning method for depth positioning, the pressure measurement values ​​corresponding to different locations in the annulus are obtained. The shifted pressure profile difference calculation module is used to resample the measured pressure profile to form two pressure profiles, and perform a subtraction operation on the two pressure profiles to obtain the shifted pressure profile difference. The shift subtraction calculation module is used to perform another shift subtraction operation on the shift pressure profile difference obtained by the shift pressure profile difference calculation module to obtain the discrimination pressure difference profile. The discrimination threshold setting module is used to set the discrimination threshold. When the value of the discrimination pressure difference exceeds the discrimination threshold, it is determined that leakage has occurred at the depth of the well corresponding to the discrimination pressure difference.

4. A downhole lost-flow formation location system, characterized in that, Includes one or more processors; A memory for storing one or more programs; the processor is configured to execute program instructions stored in the memory, which, when executed, perform the downhole lost-hole location method according to any one of claims 1 to 2.

5. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program, when executed by one or more processors, implements the downhole lost-hole location method according to any one of claims 1 to 2.

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