GRAVITY ACCELERATION MEASUREMENT APPARATUS AND EXTRACTION METHOD IN A ROTATING STATE

Abstract

An apparatus for measuring gravity acceleration of a drilling tool comprises sensors and a measurement circuit. The sensor comprises a three-axis gravity accelerometer, a reference measurement sensor and a temperature sensor. The three-axis gravity accelerometer measures acceleration component signals in three mutually orthogonal directions, and the reference measurement sensor generates a signal that varies with rotation and is not affected by vibration or shock to serve as a reference signal. The temperature sensor measures the temperature in the apparatus to compensate the temperature effect of the gravity accelerometers. The measurement circuit acquires output signals of the sensors and performs cross-correlation processing on the accelerometer components using the reference signal to extract gravity acceleration signals so as to eliminate centrifugal acceleration, vibration, shock and other interferences generated by rotation. The non-interference gravity acceleration signals is used for calculating an inclination angle and a toolface angle of a drilling tool in the rotating state.

Claims

1-8. (canceled)

9. A gravity acceleration measurement apparatus in a rotating state, comprising sensors and a measurement circuit, wherein the sensors are mounted on a drilling tool and rotate with the drilling tool, the sensors comprise a three-axis gravity accelerometer, a reference measurement sensor and a temperature sensor; the three-axis gravity accelerometer measures acceleration component signals in three mutually orthogonal directions; the reference measurement sensor generates a signal that varies with rotation and is not affected by vibration or shock to serve as a reference signal; the temperature sensor measures temperature in the apparatus and the temperature is used for compensating the temperature effect of the gravity accelerometers and eliminating the temperature influence in downhole environment on the gravity accelerometers; and the measurement circuit acquires output signals of the three-axis gravity accelerometer, the reference measurement sensor and the temperature sensor; respectively performs cross-correlation processing on the acceleration component signals subjected to the temperature compensation by using the reference signal, and eliminates centrifugal acceleration, vibration, shock and other interferences generated by rotation to obtain a non-interference gravity acceleration.

10. The gravity acceleration measurement apparatus claim 9, wherein the three-axis gravity accelerometer is three gravity accelerometers that are installed orthogonally to each other, one gravity accelerometer is installed along the axial direction of the drilling tool, the other two gravity accelerometers are installed along the radial direction of the drilling tool, and installation directions of three gravity accelerometers satisfy a right-handed coordinate system; the three-axis gravity accelerometer is connected with a lowpass filter, the lowpass filter performs analog filtering function for the output signals of the three-axis gravity accelerometer to remove higher frequency component of vibration and shock interference than rotating frequency, the filtered signals are acquired by the measurement circuit, and the cut-off frequency of the lowpass filter is related to the frequency bandwidth of the three-axis gravity accelerometer and the rotating speeds of drilling tool.

11. The gravity acceleration measurement apparatus of claim 9, wherein during the installation, an included angle between a sensitive axis of the reference measurement sensor and a rotating axis of the drilling tool is determined by the reference measurement sensor type, so that when the drilling tool rotates, the reference measurement sensor can generate periodic changes in the direction of the sensitive axis.

12. The gravity acceleration measurement apparatus of claim 10, wherein the measurement circuit further comprises an analog-to-digital converter, a memory, a microcontroller and a data interface; the analog-to-digital converter is connected with the three-axis gravity accelerometer, the reference measurement sensor, the temperature sensor and the microcontroller, and the microcontroller is connected with the memory and the data interface; the lowpass filter is connected between the analog-to-digital converter and the three-axis gravity accelerometer; the analog-to-digital converter converts the filtered analog signals of the three-axis gravity accelerometer into digital signals in a format receivable by the microcontroller; the memory is an EEPROM or a FLASH, and the memory stores temperature calibration coefficients, scale factors, offset parameters and correction coefficients for installation error of the three-axis gravity accelerometer; the microcontroller performs calculation according to an algorithm to obtain the non-interference gravity acceleration; and the data interface is used for inputting and outputting data.

13. The gravity acceleration measurement apparatus of claim 12, wherein the microcontroller is designed with a digital filter for further filtering out an interference component of a Z-axis gravity accelerometer caused by vibration and shock.

14. The gravity acceleration measurement apparatus of claim 9, wherein the three-axis gravity accelerometer is a quartz flexible accelerometer or a MEMS accelerometer; and the reference measurement sensor is any one or two or more of a magnetometer, a gyroscope and a photoelectric encoder; the reference measurement sensor is the magnetometer used for measuring a magnetic field component variety generated by the rotation to serve as the reference signal; or the reference measurement sensor is the gyroscope used for generating an angular velocity variety generated by the rotation and performing integration to obtain an angular displacement as the reference signal; or the reference measurement sensor is the photoelectric encoder used for measuring an angle variety generated by the rotation to serve as the reference signal.

15. The gravity acceleration measurement apparatus of claim 10, wherein the three-axis gravity accelerometer is a quartz flexible accelerometer or a MEMS accelerometer; and the reference measurement sensor is any one or two or more of a magnetometer, a gyroscope and a photoelectric encoder; the reference measurement sensor is the magnetometer used for measuring a magnetic field component variety generated by the rotation to serve as the reference signal; or the reference measurement sensor is the gyroscope used for generating an angular velocity variety generated by the rotation and performing integration to obtain an angular displacement as the reference signal; or the reference measurement sensor is the photoelectric encoder used for measuring an angle variety generated by the rotation to serve as the reference signal.

16. The gravity acceleration measurement apparatus of claim 11, wherein the three-axis gravity accelerometer is a quartz flexible accelerometer or a MEMS accelerometer; and the reference measurement sensor is any one or two or more of a magnetometer, a gyroscope and a photoelectric encoder; the reference measurement sensor is the magnetometer used for measuring a magnetic field component variety generated by the rotation to serve as the reference signal; or the reference measurement sensor is the gyroscope used for generating an angular velocity variety generated by the rotation and performing integration to obtain an angular displacement as the reference signal; or the reference measurement sensor is the photoelectric encoder used for measuring an angle variety generated by the rotation to serve as the reference signal.

17. The gravity acceleration measurement apparatus of claim 12, wherein the three-axis gravity accelerometer is a quartz flexible accelerometer or a MEMS accelerometer; and the reference measurement sensor is any one or two or more of a magnetometer, a gyroscope and a photoelectric encoder; the reference measurement sensor is the magnetometer used for measuring a magnetic field component variety generated by the rotation to serve as the reference signal; or the reference measurement sensor is the gyroscope used for generating an angular velocity variety generated by the rotation and performing integration to obtain an angular displacement as the reference signal; or the reference measurement sensor is the photoelectric encoder used for measuring an angle variety generated by the rotation to serve as the reference signal.

18. The gravity acceleration measurement apparatus of claim 13, wherein the three-axis gravity accelerometer is a quartz flexible accelerometer or a MEMS accelerometer; and the reference measurement sensor is any one or two or more of a magnetometer, a gyroscope and a photoelectric encoder; the reference measurement sensor is the magnetometer used for measuring a magnetic field component variety generated by the rotation to serve as the reference signal; or the reference measurement sensor is the gyroscope used for generating an angular velocity variety generated by the rotation and performing integration to obtain an angular displacement as the reference signal; or the reference measurement sensor is the photoelectric encoder used for measuring an angle variety generated by the rotation to serve as the reference signal.

19. A gravity acceleration measurement and extraction method, the method employs the apparatus according to claim 9, the method comprising: respectively measuring axial Z-axis and radial X-axis, Y-axis gravity accelerations of a drilling tool by using a three-axis acceleration sensor, and generating a signal that varies with rotation and is not affected by vibration or shock to serve as a reference signal by using a reference measurement sensor; measuring the temperature in the apparatus by using the temperature sensor, and performing temperature compensation on the gravity accelerometers; acquiring the output signals of the three-axis gravity accelerometer, the reference measurement sensor and the temperature sensor by a measurement circuit, performing cross-correlation between the X-axis gravity acceleration, the Y-axis gravity acceleration measured by the three-axis gravity accelerometer and the normalized reference signal to eliminate the X-axis and Y-axis interference components generated by vibration and shock; and meanwhile designing a digital lowpass filter in the microcontroller to further filter the interference component measured by the Z-axis gravity accelerometer, and finally obtaining a three-axis gravity acceleration in the rotating state with the influence of the vibration and shock eliminated.

20. The gravity acceleration measurement and extraction method of claim 19, wherein the method employs the apparatus according to claim 10.

21. The gravity acceleration measurement and extraction method of claim 19, wherein the method employs the apparatus according to claim 11.

22. A gravity acceleration measurement and extraction method, wherein the method employs the apparatus according to claim 12.

23. The gravity acceleration measurement and extraction method of claim 15, wherein the gravity acceleration obtained by the method is used for calculating an inclination angle and a toolface angle in the rotating state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic diagram of installation positions of a three-axis gravity acceleration sensor and a magnetometer in embodiment 1;

[0028] FIG. 2 is a schematic circuit diagram of a gravity acceleration measurement apparatus in a rotating state in embodiment 1;

[0029] FIG. 3 is a schematic diagram of a gravity acceleration measurement method in a rotating state in embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] In order that the objectives, technical solutions and advantages of the present invention are clearer and more apparent, the present invention will be further described below in detail in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are merely used for explaining the present invention rather than limiting the present invention.

[0031] On the contrary, the present invention encompasses any alternatives, modifications, equivalent methods and solutions made within the spirit and scope of the present invention as defined by the claims. Further, in order to make the public better understand the present invention, some specific details are described in detail in the following detailed description of the present invention. It should be understood by those skilled in the art that the present invention may also be fully understood without the description of the details.

Embodiment 1

[0032] A gravity acceleration measurement apparatus in a rotating state includes sensors and a measurement circuit, the sensors include three-axis gravity accelerometer, a reference measurement sensor and a temperature sensor, the three-axis gravity accelerometer is connected with a lowpass filter, an included angle between a sensitive axis of the reference measurement sensor and a rotating axis is determined by the sensor type, so that when a drilling tool rotates, the reference measurement sensor can generate periodic variety in the direction of the sensitive axis. The three-axis gravity accelerometer is installed orthogonally to each other, the Z-axis is arranged along the axial direction of the drilling tool, and X-axis and Y-axis are arranged along the radial direction of the drilling tool. The temperature sensor is installed close to the three-axis gravity accelerometer, a magnetometer is used as the reference measurement sensor, the sensitive axis of the magnetometer is parallel to the X-axis, and the installation mode is as shown in FIG. 1. The measurement circuit includes an analog-to-digital converter, a memory, a microcontroller and a data interface, and the connection mode of the apparatus is as shown in FIG. 2.

[0033] The method for measuring the gravity acceleration in the rotating state by using the above apparatus is as follows: respectively measuring gravity accelerations of the drilling tool in axial direction Z and radial directions X and Y by using the three-axis gravity accelerometer, and generating a signal that varies with rotation and is not affected by vibration or shock to serve as a reference signal by using the reference measurement sensor; measuring the temperature in the apparatus by using the temperature sensor to perform temperature compensation on the gravity accelerometers; acquiring output signals of the sensors by the measurement circuit, performing cross-correlation on the X-axis gravity acceleration and the Y-axis gravity acceleration measured by the three-axis gravity accelerometer with the normalized reference signal to eliminate the interference components of the X-axis gravity acceleration and the Y-axis gravity acceleration generated by vibration and shock; and meanwhile designing the digital lowpass filter by the microcontroller to filter the interference component of the measurement of the Z-axis gravity accelerometer generated by vibration and shock, and finally obtaining a three-axis gravity acceleration in the rotating state with the influence of the vibration and shock eliminated. The non-interference gravity acceleration obtained by the measurement method can be used for calculating an inclination angle and a tool face angle of the drilling tool in the rotating state. The method is shown in FIG. 3

[0034] The gravity acceleration measurement and extraction method in the rotating state is specifically as follows:

[0035] (1) Acceleration Signal Measurement

[0036] The gravity acceleration measurement apparatus is installed on the drilling tool and rotates around the Z-axis together with the drilling tool while drilling, the rotating angular frequency of the drilling tool is set as =2f, the sampling frequency of the analog-to-digital converter is set as

[00001]$f_s=\frac{1}{T_s},$

then the output signal of the acceleration sensor installed along the X-axis direction is:

g.sub.x(k)=A.sub.x cos(kT.sub.s+)+n.sub.1(k)=g.sub.x(k)+n.sub.x(k)(1)

represents an initial phase of the output signal of the acceleration sensor in the X-axis direction, g.sub.x(k) represents an X-axis gravity acceleration signal without noise, and n.sub.x(k) represents various noise signals including random noise generated by the circuit, centrifugal acceleration generated by the rotation, vibration and shock interferences of the drilling tool, and the like.

[0037] The output signal of the acceleration sensor in the Y-axis direction has a 90-degree phase difference from the output signal of the acceleration sensor in the X-axis direction. Therefore, the initial phase of the output signal of the acceleration sensor in the Y axis direction is (-90) degrees, then:

[00002]$\begin{array}{cc}{\stackrel{\_}{g}}_y\left(k\right)=A_y.Math.\cos \left(k{T}_s+-\frac{}{2}\right)+n_y\left(k\right)=A_y.Math.\sin \left(k{T}_s+\right)+n_y\left(k\right)& \left(2\right)\\ .Math.{\stackrel{\_}{g}}_y\left(k\right)=g_y\left(k\right)+n_y\left(k\right)& \left(3\right)\end{array}$

[0038] g.sub.x(k) represents a Y axis gravity acceleration signal without noise, n.sub.y(k) represents various noise signals including the random noise generated by the circuit, the centrifugal acceleration generated by the rotation, the vibration and shock interferences of the drilling tool, and the like.

[0039] The digital acceleration signal acquired and generated by analog-to-digital converter requires temperature compensation, sensor scale factor and offset correction, installation error correction, etc.

[0040] (2) Magnetic Reference Signal Measurement

[0041] A magnetometer is installed in the measurement apparatus to serve as the reference measurement sensor, as the signals measured on the horizontal plane (X and Y directions) by the magnetometer are better, the sensitive axis of the magnetometer is installed parallel to the X-axis, the output thereof is used as the reference signal, and the normalized magnetometer signal is expressed as:

r.sub.x(k)=cos(kT.sub.g)+n.sub.2(k)=r.sub.x(k)+n.sub.r(k)(4)

[0042] (3) Gravity Acceleration Extraction Method Through Correlation Detection

[0043] The signals measured by the X-axis and Y-axis accelerometers are processed based correlation detection with the reference signal measured by the magnetometer respectively, and cross-correlation operation is performed on the formula (1) and the formula (4) to obtain a cross-correlation result of the X axis acceleration and the reference signal measured by the magnetometer.

[00003]$\begin{array}{cc}{\stackrel{\_}{R}}_{g_x.Math.r_x}\left(\right)=\frac{1}{N}.Math.\underset{k=0}{\overset{N-1}{.Math.}}.Math..Math.{\stackrel{\_}{g}}_x\left(k+\right){\stackrel{\_}{r}}_x\left(k\right)=R_{g_x.Math.r_x}\left(\right)+R_{g_x.Math.n_r}\left(\right)+R_{r_x.Math.n_x}\left(\right)+R_{n_x.Math.n_r}\left(\right)& \left(5\right)\end{array}$

[0044] In the formula (5), a sinusoidal signal is irrelevant to random noise, therefore R.sub.g.sub.x.sub.n.sub.y() and R.sub.g.sub.x.sub.n.sub.x() and are zero; and because the magnetometer is insensitive to vibrating signals, the coherence between the random noise of the acceleration signal and the random noise of the magnetic reference signal is very weak, and thus R.sub.g.sub.x.sub.n.sub.y()0.

[00004]$\begin{array}{cc}{\stackrel{\_}{R}}_{g_x.Math.r_x}\left(\right)=R_{g_x.Math.r_x}\left(\right)=\frac{A_x}{2}.Math.\cos \left(+\right)& \left(6\right)\end{array}$

[0045] Similarly, the cross-correlation operation is performed on the formula (3) and the formula (4) to obtain a correlation signal of the Y-axis acceleration and the reference signal measured by the magnetometer.

[00005]$\begin{array}{cc}{\stackrel{\_}{R}}_{g_y.Math.r_x}\left(\right)=\frac{1}{N}.Math.\underset{k=0}{\overset{N-1}{.Math.}}.Math..Math.{\stackrel{\_}{g}}_y\left(k+\right){\stackrel{\_}{r}}_x\left(k\right)=R_{g_y.Math.r_x}\left(\right)+R_{g_y.Math.n_r}\left(\right)+R_{r_x.Math.n_2}\left(\right)+R_{n_2.Math.n_g}\left(\right)& \left(7\right)\\ .Math.{\stackrel{\_}{R}}_{g_y.Math.r_x}\left(\right)=R_{g_y.Math.r_x}\left(\right)=\frac{A_y}{2}.Math.\sin \left(+\right)& \left(8\right)\end{array}$

[0046] Comparing the formula (1) with the formula (6), we obtain:

g.sub.x(t)=2R.sub.g.sub.x.sub.r.sub.x(t)=A.sub.x cos(t+)(9)

[0047] The formula (9) is the output signal of the acceleration sensor in the X-axis direction after the noise is removed.

[0048] Comparing the formula (2) with the formula (8), we obtain:

g.sub.y(t)=2R.sub.g.sub.y.sub.r.sub.x(t)=A.sub.y cos(t+)(10)

[0049] The formula (10) is the output signal of the acceleration sensor in the Y-axis direction after the noise is removed. As the Z-axis is the rotating axis, in view of the fact that the acceleration of the Z-axis direction varies only when the inclination angle changes in the actual drilling process, and the inclination angle changes very slowly, and thus the acceleration signal of the Z-axis can be regarded as a direct current signal which changes very slowly, and the digital lowpass filter is designed in the microcontroller to further filter the vibration and shock interferences.

[0050] The gravity acceleration further obtained by the measurement method can be used for calculating the inclination angle and the toolface angle of the drilling tool.

[0051] (4) Method for Calculating the Inclination Angle and the Toolface Angle

[0052] The inclination angle is:

[00006]$\begin{array}{cc}=\arctan \left(\frac{\sqrt{g_x^2+g_y^2}}{g_z}\right)=\arctan \left(2\frac{\sqrt{{\stackrel{\_}{R}}_{g_x.Math.r_x}^2+{\stackrel{\_}{R}}_{g_y.Math.r_x}^2}}{A_z}\right)& \left(11\right)\end{array}$

[0053] The toolface angle is:

[00007]$\begin{array}{cc}=-\arctan \left(\frac{g_y}{g_x}\right)=-\arctan \left(\frac{{\stackrel{\_}{R}}_{g_y.Math.r_x}}{{\stackrel{\_}{R}}_{g_x.Math.r_x}}\right)& \left(12\right)\end{array}$

[0054] g.sub.z represents the Z-axis gravity acceleration signal subjected to digital lowpass filtering.