A method for controlling the opening of the density instrument legs in pump-out logging mode

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By comprehensively detecting magnetic marker signals, mud resistivity, downhole pressure, and coupling signals, the opening and closing states of the density instrument are controlled in real time, solving the problem that the density instrument cannot accurately adhere to the well wall, thus improving measurement accuracy and construction safety.

CN117307133BActive Publication Date: 2026-07-31HANG ZHOU RUI LI SHENG DIAN JI SHU GONG SI

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Patent Information

Authority / Receiving Office: CN · China
Patent Type: Patents(China)
Current Assignee / Owner: HANG ZHOU RUI LI SHENG DIAN JI SHU GONG SI
Filing Date: 2023-10-23
Publication Date: 2026-07-31

AI Technical Summary

Technical Problem

Existing technology in pump-out logging mode cannot accurately adhere to the wellbore wall, resulting in large measurement errors and potential safety hazards.

Method used

By comprehensively detecting various conditions such as magnetic marker signals, mud resistivity, downhole pressure, coupling signals, and timing control, the status of the density instrument is monitored in real time to ensure that it accurately opens and closes its legs at specific locations, including setting timing parameters and mud pump pressure coding control.

Benefits of technology

It improves the accuracy and safety of density instrument measurements, reduces measurement errors, and enhances construction safety in storage logging mode.

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Abstract

This invention provides a method for controlling the leg opening of a density instrument in pump-out logging mode. The downhole instrument, including the density instrument, is housed within a protective sleeve containing a magnetic marker attached to the drill string. If a magnetic marker signal is detected, it indicates that the density instrument has been pumped out of the protective sleeve. If a set value has been reached, it indicates that the density instrument has been pumped into position, and a leg opening command is issued and recorded. Logging begins. After a power-on timer expires, it is determined whether the downhole instrument is powered on. If it is powered on, the command is recorded and no further action is taken; otherwise, the power-on command is recorded and the downhole instrument is powered on. This invention not only allows for timed control but also comprehensively determines whether the instrument is in position and meets the leg opening conditions through other methods. Integrating these conditions allows for a more accurate determination of whether the instrument meets the leg opening conditions, improving the security of stored logging and the measurement performance of the density instrument.

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Description

Technical Field

[0001] This invention relates to the field of well logging technology, and mainly to a method for controlling the opening of the legs of a density instrument in pump-out well logging mode. Background Technology

[0002] Chinese patent CN207229095U discloses a radioactive source installation device for a neutron density instrument during drilling. This device enables safe and quick installation of the radioactive source, ensuring that the source is always on the source container, installation device, or instrument. Further technological advancements, such as storage logging, have addressed radioactivity safety concerns by using density instruments to adhere the source to the wellbore using methods like eccentric bows or gravity. However, these methods are not very effective and can lead to measurement errors. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for controlling the opening of the density instrument in pump-out logging mode.

[0004] The objective of this invention is achieved through the following technical solution: A method for controlling the leg opening of a density instrument in pump-out logging mode, comprising the following steps:

[0005] 1. After the density instrument is checked and found to be normal on the ground, estimate the time it will take for the density instrument to reach the target layer from the wellhead and the logging completion time, download the service table and set the timing parameters through the logging software;

[0006] 2. The downhole instrument containing the density instrument is installed inside a protective sleeve. The protective sleeve contains magnetic markers and is installed on the drill string. It is lowered to the target formation along with the drill string, and the density instrument is pumped out of the protective sleeve.

[0007] 3. Determine whether a magnetic marker signal is detected. If a magnetic marker signal is detected, it means that the density instrument has been pumped out of the protective sleeve. Determine whether the downhole instrument is powered. If it is powered, record the command. If not, delay for N minutes, then power on the downhole instrument and record the power-on command.

[0008] 4. Determine whether the resistivity of the mud has reached the set value. If it has reached the set value, it means that the density instrument has been pumped out to the correct position. Issue the command to open the legs of the density instrument and record the command.

[0009] 5. Start logging while continuously monitoring the timed power-on period. Once the timed power-on period has elapsed, determine if the downhole instruments are powered on. If they are powered on, record the command and do not perform any other operations. If not, record the power-on command and power on the downhole instruments.

[0010] 6. After logging is completed, the drill string is pulled up. At this time, the downhole instrument is in the storage logging mode. At the same time, it detects five parameters: coupling signal, mud pressure code, resistivity zeroing, timed leg retraction, and downhole pressure. Once any parameter is valid, it will determine whether the downhole instrument is powered off and whether the density instrument has retracted its legs. If the power is off and the legs are retracted, the command status is recorded. If the power is not off and the legs are not retracted, the density instrument is controlled to retract its legs after a delay of N minutes and then the power is cut off, ending the logging. The downhole instrument continues to be pulled up.

[0011] A further technical solution involves two types of timing parameters: a) setting the power-on leg opening and retraction power-off times on the ground; b) setting the power-on leg opening trigger time and the power-off delay time after leg retraction. Both methods can coexist and be selected simultaneously or separately when used.

[0012] A further advanced technical solution involves, under special circumstances, issuing mud pressure codes from the surface. Upon receiving the response command, the downhole main control instrument powers up the downhole instruments and controls the density instrument to open its legs.

[0013] In a further technical solution, the magnetic marker is set on the inner wall of the protective sleeve. When the magnetic signal changes drastically when the magnetic signal passes through the protective sleeve, the circuit will detect the signal strength and the trend of change, which will serve as the basis for whether the density instrument 1 pumps out.

[0014] A further technical solution involves mud pressure coding and wellbore pressure detection: Well logging and leg opening / retraction are controlled by issuing mud pressure commands. These commands are implemented through mud pump on / off cycles, with the following steps: The mud pump is turned on and off for 1 minute, repeated 10 times, as the battery on command; the mud pump is turned on and off for 2 minutes, repeated 5 times, as the leg opening command; the mud pump is turned on and off for 3 minutes, repeated 3 times, as the leg retraction command. Wellbore pressure and mud pressure changes are detected by a pressure sensor, and corresponding actions are taken when a corresponding code is detected. Two setpoints, a low limit and a high limit, are established. Before logging begins, the well pressure is monitored in real-time to ensure it is above the high limit. If it is, the density instrument is approaching the measurement section, a prerequisite for leg opening. After logging begins, the wellbore pressure is monitored in real-time. When the wellbore pressure is below the low limit, the density instrument has left the measurement section, another condition for leg retraction.

[0015] A further technical solution involves zero-resistivity control: two setpoints are established for the open-leg resistivity and the closed-leg resistivity. Before logging begins, the resistivity measurement value is monitored in real time to see if it is higher than the open-leg setpoint. If it is higher, it indicates that the density instrument has been pumped out of the protective sleeve, which is a prerequisite for opening the density leg. After logging begins, the resistivity value is monitored in real time. When the resistivity value is lower than the closed-leg resistivity setpoint, it indicates that the density instrument has entered the protective sleeve, which is one of the conditions for retracting the leg.

[0016] A further technical solution involves coupling signal detection: when the density instrument is raised to the sleeve opening of the protective sleeve, the coupling signal detection instrument will detect a significant change in the coupling signal. A start value is set, and when the coupling signal strength is greater than this start value, it indicates that the density instrument has entered the sleeve, which serves as the basis for retracting the legs.

[0017] The beneficial effects of this invention are as follows: This invention not only allows for timed control, but also enables comprehensive judgment of whether the instrument is in position and whether the conditions for opening the valve are met through other methods. These conditions include changes in the magnetic signal detected when the instrument passes a magnetic marker at a specific location, changes in the surface mud pump pressure to induce mud pressure fluctuations, the fact that resistivity values of resistivity instruments return to zero after entering the protective casing, casing coupling signals, downhole pressure, etc. By combining these conditions, it is possible to more accurately determine whether the instrument meets the conditions for opening the valve, thereby improving the safety of stored logging and the measurement performance of density instruments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the present invention.

[0019] Figure 2 This is a schematic diagram of the process after the measurement segment of the present invention is completed.

[0020] Figure 3 This is a schematic diagram of the protective sleeve.

[0021] Figure 4 This is a schematic diagram of the sensor response curve.

[0022] Figure 5 This is a schematic diagram of mud coding.

[0023] Explanation of the attached labels: Density instrument 1, Protective cover 2, Magnetic marker 3. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of the present invention, the preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings and specific examples.

[0025] like Figure 1-2 As shown, a method for controlling the leg opening of a density instrument in pump-out logging mode is applied to an MLIS cable-guided direct-read storage multi-mode full-penetration logging system. This method integrates six judgment conditions and monitors the status of each condition in real time, accurately determining the downhole instrument status and controlling the leg opening and retraction status of the density instrument in real time. This solves the measurement distortion caused by the density instrument's inability to adhere to the wellbore, and improves the operational safety of the density instrument in storage logging mode. The specific steps are as follows:

[0026] 1. After the density instrument 1 is checked and found to be normal on the ground, estimate the time it will take for the density instrument 1 to reach the target layer from the wellhead and the logging completion time, download the service table and set the timing parameters through the logging software;

[0027] 2. The downhole instrument containing density instrument 1 is installed inside protective sleeve 2. Protective sleeve 2 contains magnetic marker 3 and is installed on the drill string. It is lowered to the target layer together with the drill string. Density instrument 1 is pumped out of protective sleeve 2.

[0028] Magnetic signal detection: In storage logging mode, there is a special protective sleeve with magnetic markers located at the lower end of the protective sleeve. The magnetic markers are on the inner wall of the protective sleeve (see appendix). Figure 3 It is less affected by external magnetic interference. When the storage and control gamma stub passes through the protective sleeve, the circuit will detect a drastic change in the magnetic signal and record the signal strength and trend of change as a basis for whether the downhole instrument (instrument string) is pumped out.

[0029] The DRV5055Q1 is a proportional linear Hall effect sensor that detects position based on changes in magnetic flux density generated by a magnet (see appendix). Figure 4 The horizontal axis represents direction, and the vertical axis represents signal amplitude. It features high temperature and high sensitivity characteristics, with the Hall effect device eccentrically mounted and reliable magnetic marker detection. Power-on and leg opening are initiated after a 1-minute delay upon receiving the signal.

[0030] 3. Determine whether a magnetic marker signal is detected. If a magnetic marker signal is detected, it means that density instrument 1 has pumped out protective sleeve 2. Determine whether the downhole instrument is powered. If it is powered, record the command. If not, delay for 1 minute, then power on the downhole instrument and record the power-on command.

[0031] 4. Determine whether the resistivity of the mud has reached the set value. If it has reached the set value, it means that the density instrument 1 has been pumped out. Issue the density instrument leg opening command and record the command.

[0032] 5. In special circumstances, when the surface issues a mud pressure code, the downhole main control instrument receives the response command, powers on the downhole instruments, and controls the density instrument to open its legs.

[0033] 6. Start logging while continuously monitoring the timed power-on period. Once the timed power-on period has elapsed, determine if the downhole instruments are powered on. If they are powered on, record the command and do not perform any other operations. If not, record the power-on command and power on the downhole instruments.

[0034] 7. After logging is completed, the drill string is pulled up. At this time, the downhole instrument is in the storage logging mode. At the same time, it detects five parameters: coupling signal, mud pressure code, resistivity zeroing, timed leg retraction, and downhole pressure. Once any parameter is valid, it will determine whether the downhole instrument is powered off and whether the density instrument has retracted its legs. If the power is off and the legs are retracted, the command status is recorded. If the power is not off and the legs are not retracted, the density instrument is controlled to retract its legs after a 1-minute delay and then the power is cut off, ending the logging. The downhole instrument continues to be pulled up.

[0035] As another implementation method, timed control: Before each logging operation, the construction process and well condition information are understood, and the time for the instrument to reach the target layer from the wellhead and the logging completion time are estimated. Timing parameters are set through the logging software. There are two types of timing parameters: a) Setting the power-on and leg-opening times separately on the surface; b) Triggering the leg-opening and leg-retraction power-off times after power-on (the power-off delay time after leg retraction can be set). Both methods can coexist and can be selected simultaneously or separately during use.

[0036] As another implementation method, mud command coding and well pressure detection:

[0037] Well logging and leg opening / retraction are controlled by issuing commands based on mud pressure. These commands can be implemented by changing the on / off state of the mud pump. The specific arrangements are as follows (see appendix). Figure 5 ).

[0038] The mud pump can be turned on and off for 1 minute, repeated 10 times, as a command to turn on the system power battery; the mud pump can be turned on and off for 2 minutes, repeated 5 times, as a command to open the legs; the mud pump can be turned on and off for 3 minutes, repeated 3 times, as a command to retract the legs.

[0039] The pressure sensor installed on the control sub (which controls density instruments and other instruments) can detect well pressure and mud pressure changes, and take corresponding actions when a specific code is detected. The well pressure sensor has a measurement range of 0–140 MPa, and according to the technical specifications provided by the imported sensor, its accuracy is 0.75 MPa (±5%) and its resolution is 0.1 MPa.

[0040] Upon receiving a signal, power on and open the legs after a 1-minute delay, and record the received signal. You can choose whether to trigger the leg retraction and power-off time (the power-off delay time after leg retraction can be set).

[0041] Two settings are set: a low limit and a high limit for well pressure. Before logging begins, the main control unit monitors the well pressure in real time to see if it is higher than the high limit setting. If it is higher than the high limit setting, it means that the instrument is close to the measurement section, which can be used as a prerequisite for density leg opening. After logging begins, the main control unit monitors the well pressure in real time. When the well pressure is lower than the low limit setting, it means that the instrument has left the measurement section, which can be used as one of the conditions for leg retraction.

[0042] As another implementation method, resistivity value is zeroed out:

[0043] Resistivity logging instruments (such as lateral and induction instruments) will show zero resistivity values when inside the casing (protective sleeve) (this zeroing threshold can be adjusted based on the mud mix ratio and the resistivity values of the formation and water layers), but the resistivity values will increase significantly once they reach the open hole. This characteristic can be used as a basis for opening and closing the legs.

[0044] Two set values are set for the resistivity of the open leg and the resistivity of the closed leg. Before logging begins, the main control unit monitors the resistivity measurement value in real time to see if it is higher than the open leg set value. If it is higher than the open leg set value, it means that the instrument has pumped out the protective casing, which can be used as a prerequisite for density open leg. After logging begins, the main control unit monitors the resistivity value in real time. When the resistivity value is lower than the closed leg resistivity set value, it means that the instrument has entered the casing, which is one of the conditions for retracting the leg.

[0045] Once the main controller detects that the condition is met, it will perform the corresponding operation after a 1-minute delay and record the received signal.

[0046] As another implementation method, coupling signal detection: When the instrument is raised to the sleeve opening, the coupling signal detection instrument will detect a significant change in the coupling signal. A start value is set, and when the coupling signal strength is greater than this value, it indicates that the instrument has entered the sleeve, which serves as the basis for retracting the legs. After receiving the signal, the leg retraction is delayed by 1 minute before powering off (the power-off delay time can be set after leg retraction), and the received signal is recorded.

[0047] It is understood that, for those skilled in the art, any equivalent substitutions or modifications to the technical solutions and inventive concepts of this invention should fall within the scope of protection of the appended claims.

Claims

1. A method for controlling the leg opening of a density instrument in pump-out logging mode, characterized in that: The steps include the following: (1) After the density instrument (1) is checked and found to be normal on the ground, estimate the time it takes for the density instrument (1) to reach the target layer from the wellhead and the logging completion time. Download the service table and set the timing parameters through the logging software. This density instrument is a neutron density instrument while drilling. (2) The downhole instrument containing the density instrument (1) is set inside the protective sleeve (2). The protective sleeve (2) contains magnetic markers (3) and is set on the drill string. It is lowered to the target layer along with the drill string. The density instrument (1) is pumped out of the protective sleeve (2). (3) Determine whether a magnetic marker signal is detected. If a magnetic marker signal is detected, it means that the density instrument (1) has pumped out the protective sleeve (2). Determine whether the downhole instrument has been powered. If it has been powered, record the instruction. If not, delay for N minutes, then power the downhole instrument and record the power-on instruction. (4) Determine whether the resistivity of the mud has reached the set value. If it has reached the set value, it means that the density instrument (1) has been pumped out. Issue the density instrument leg opening command and record the command at the same time. (5) Start logging and continuously check if the timed power-on time has arrived. After the power-on time has arrived, determine whether the downhole instrument has been powered on. If it has been powered on, record the command and do not perform any other operations. If not, record the power-on command and power on the downhole instrument. (6) When the logging is completed and the drill string is pulled up, the downhole instrument is in the storage logging mode. At the same time, it detects five parameters: coupling signal, mud pressure code, resistivity zeroing, timed leg retraction, and well pressure. If any parameter is valid, it will determine whether the downhole instrument is powered off and whether the density instrument has retracted its legs. If the power is off and the legs are retracted, the command status is recorded. If the power is off and the legs are retracted, the density instrument is controlled to retract its legs and then the power is off after a delay of N minutes, the logging ends, and the downhole instrument continues to be pulled up. Mud pressure coding and well pressure detection: Well logging and leg opening / retraction are controlled by issuing mud pressure commands. These commands are implemented through mud pump on / off cycles, with the following steps: The mud pump is turned on and off for 1 minute, repeated 10 times, as the battery on command; the mud pump is turned on and off for 2 minutes, repeated 5 times, as the leg opening command; the mud pump is turned on and off for 3 minutes, repeated 3 times, as the leg retraction command. Well pressure and mud pressure changes are detected by pressure sensors, and corresponding actions are taken when a corresponding code is detected. Two setpoints, a low limit and a high limit, are established. Before logging begins, the well pressure is checked in real-time to see if it exceeds the high limit. If it does, it indicates that the density instrument is approaching the measurement section, a prerequisite for leg opening. After logging begins, the well pressure is checked in real-time. When the well pressure is lower than the low limit, it indicates that the density instrument has left the measurement section, one of the conditions for leg retraction. Resistivity value zeroing control: Two set values are set for the open leg resistivity and the closed leg resistivity. Before logging begins, the resistivity measurement value is monitored in real time to see if it is higher than the open leg set value. If it is higher than the open leg set value, it means that the density instrument has been pumped out of the protective sleeve, which is a prerequisite for the density instrument to open its legs. After logging begins, the resistivity value is monitored in real time. When the resistivity value is lower than the closed leg resistivity set value, it means that the density instrument has entered the protective sleeve, which is one of the conditions for retracting the legs.

2. The method for controlling the opening of the density instrument leg in pump-out logging mode according to claim 1, characterized in that: There are two types of timing parameters: a) the ground sets the power-on leg opening time and the leg retraction power-off time respectively; b) the power-on leg opening trigger time and the power-off delay time after leg retraction. Both methods exist simultaneously and can be selected together or separately when using them.

3. The method for controlling the opening of the density instrument leg in pump-out logging mode according to claim 1, characterized in that: The magnetic marker (3) is set on the inner wall of the protective sleeve (2). When the magnetic signal changes drastically when the magnetic signal passes through the protective sleeve (2), the circuit will detect the signal strength and the trend of change, which will serve as the basis for whether the density instrument (1) pumps out.

4. The method for controlling the opening of the density instrument leg in pump-out logging mode according to claim 1, characterized in that: Coupling signal detection: When the density instrument is raised to the sleeve opening of the protective sleeve, the coupling signal detection instrument will detect a significant change in the coupling signal. A start value is set. When the coupling signal strength is greater than this start value, it indicates that the density instrument has entered the sleeve, which serves as the basis for retracting the legs.