An acceleration correction method and correction device for an array lateral instrument

Abstract

The present invention provides an acceleration correction method and correction device for an array lateral instrument, the method comprising: performing spectrum analysis on an acceleration curve to obtain a fundamental frequency f, integrating acceleration a to obtain velocity, integrating velocity to obtain depth displacement S, using the maximum value △S of depth correction as a criterion for determining whether the acceleration curve needs to be corrected; using a baseline fitting algorithm for the acceleration curve to dynamically select an axial acceleration value queue; and dynamically adjusting the integral interval of the displacement. The present invention obtains a correction criterion by analyzing the spectrum of the acceleration curve; and proposes improvement measures for the old method of using kinematic equations, Kalman filtering, and piecewise integration, determining the fundamental frequency of acceleration change by spectrum analysis, and dynamically adjusting the base value of the axial acceleration and the integral interval, so that the prediction is closer to the actual situation.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum well logging, and in particular to an acceleration correction method and a correction device for an array lateral instrument. Background Art

[0002] With the advancement of logging technology, the application of imaging instruments has greatly improved the measurement resolution, from the early 1 or 2 feet to 1 or 2 inches or even 0.1 inches. Since the depth data of the imaging instrument is obtained through the movement of the measuring cable at the wellhead, there are some differences from the actual movement of the imaging instrument. In previous applications with low resolution, these differences are smaller than the resolution and therefore cannot be displayed. However, in the images of imaging instruments with greatly improved resolution, if motion correction is not performed, distortion is obvious; the existing imaging logging acceleration correction software uses the precise sampling data provided by the imaging instrument, attached with the least squares method and Kalman filtering method, and recursively infers the true movement trajectory of the instrument through the acceleration data to correct the depth error caused by non-uniform motion.

[0003] The array laterograph is a new type of resistivity logging tool. Its resolution (5 cm) is much higher than that of the earlier laterograph tools (0.3 m), so obvious distortion can be seen in the measurement results. After using the correction algorithm developed from the imaging tool, the effect is not ideal due to the different application conditions of the imaging tool and the laterograph, and needs to be improved.

[0004] The sampling data of the imaging instrument is dense, reaching 0.1 inches, and can correct errors of several centimeters. However, the sampling rate of the array lateral direction meter is about 1 cm, which is suitable for its resolution. The acceleration data granularity is insufficient, and the correction algorithm developed by the imaging instrument is not suitable, and parameter adjustment is difficult.

[0005] In addition, the segmented integration of the correction algorithm developed by the imaging instrument is to eliminate the cumulative error of displacement obtained from acceleration, but its parameters (gravity influence, integration interval) are not easy to grasp, and cumulative errors will still occur. The original method of calculating the axial component of gravity through the inclination of the logging instrument has the following problems: first, the nonlinearity of the error caused by the operation and filtering method; second, it is obtained through three-axis acceleration measurement, which is questionable in terms of logical loop.

[0006] Furthermore, the correction algorithm developed by the imaging instrument is not ideal for assisting in correcting the flat-head phenomenon, and often results in over-correction and overall depth compression. Summary of the invention

[0007] In view of this, the purpose of the present invention is to perform acceleration correction on the acceleration curve of the array lateral instrument to eliminate the curve anomalies caused by the difference between the true depth and the measured depth caused by the non-uniform motion of the downhole instrument: such as flat head, tension and compression.

[0008] The logging instrument is lowered into the well by a cable, forming a vibration system similar to a spring oscillator. Even if the well conditions are good, vibrations may occur, which are superimposed on its uniform motion, causing a deviation between the actual depth of the instrument and the measured depth.

[0009] Early instruments did not require acceleration correction, and the acceleration curves were still well reflected, indicating that acceleration correction is not required under all conditions.

[0010] The present invention proposes a criterion to determine whether the measurement results need to be corrected for acceleration. Then, improvement measures are proposed for the old method of using kinematic equations, Kalman filtering, and piecewise integration. The logging instrument is affected by gravity, cable tension, well wall friction, and fluid resistance underground. The motion state is relatively complex and can be roughly regarded as uniform motion superimposed on complex vibrations. Any complex vibration can be decomposed into simple harmonic vibrations. In general, the fundamental frequency vibration has the greatest impact. The fundamental frequency of the acceleration change is determined by spectral analysis, and the base value of the axial acceleration and the integration interval are dynamically adjusted to make the prediction closer to the actual situation. The final correction result is combined with manual judgment to correct the overall deviation and local anomalies.

[0011] The present invention provides an acceleration correction method for an array lateral instrument, comprising the following steps:

[0012] S1. Perform spectrum analysis on the acceleration curve to obtain the fundamental frequency f, then we have the following formula:

[0013] a=g z +ASIN(2πft);

[0014] Where a is the acceleration, g z is the axial component of gravitational acceleration (the radial component has little effect on depth correction);

[0015] Integrating the acceleration a gives the velocity:

[0016] v = ∫a dt = v 0 +∫ 0 t ASIN(2πft)dt;

[0017] =v 0 -A / (2πf)*COS(2πft);

[0018] Integrating the velocity gives the depth displacement:

[0019] S = ∫vdt

[0020] =S 0 +v 0 t–A / (2πf) 2 *SIN(2πft);

[0021] Where S 0 +v 0 t is the law of variation of apparent depth (i.e., recording depth); the depth correction term caused by oscillation motion is:

[0022] △S=-A / (2πf) 2 *SIN(2πft);

[0023] Maximum value of depth correction △S=A / (2πf) 2 , △S=A / (2πf) 2 As a criterion for whether the acceleration curve needs acceleration correction;

[0024] f = 1 / T, which can be calculated by simply intercepting the period interval length on the acceleration curve and dividing it by the normal speed measurement. Of course, it can also be obtained through the spectrum analysis of this method;

[0025] Assume that the depth resolution of the acceleration curve is X, and the following conditions are met:

[0026] △S>2X, that is, the depth deviation exceeds twice the resolution, then acceleration correction is required;

[0027] Through the analysis of early acceleration curves, it is concluded that the △S caused by instrument vibration is generally in the order of a few tenths of a meter, so the early acceleration curves with a resolution of 1 or 2 feet do not require acceleration correction;

[0028] S2, using the baseline fitting algorithm of the acceleration curve, the axial acceleration value queue in the interval before and after the current acceleration point is used to obtain the base value of the axial acceleration by the minimum variance fitting method. The axial acceleration value queue is dynamically adjusted according to the acceleration cycle and is an integer multiple of the acceleration cycle; the length can flexibly respond to the inclination change rate of the instrument in the deflection section;

[0029] S3, dynamically adjust the integral interval of the displacement. The integral interval of the displacement also changes the fixed interval method and is dynamically selected according to the integer multiples of the motion cycle;

[0030] In simple harmonic vibration, the equilibrium position displacement and acceleration are both zero. Through the spectrum analysis of step S1, combined with the judgment of the baseline zero point of the acceleration curve, the upper and lower limits of the displacement integration interval are determined, and compared with the depth of the original integration interval, the linear error is automatically corrected. In this way, the linear integration error can be eliminated as a whole.

[0031] The final correction result is combined with the auxiliary judgment of the blockage to correct the overall deviation and local anomalies.

[0032] The present invention also provides an acceleration correction device for an array lateral instrument, which uses the acceleration correction method as described above.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention obtains correction criteria through spectrum analysis of the acceleration curve; and proposes improvement measures for the old method using kinematic equations, Kalman filtering and piecewise integration, and determines the fundamental frequency of acceleration change by spectrum analysis, so as to dynamically adjust the base value of axial acceleration and the integration interval, so that the prediction is closer to the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0036] In the attached picture:

[0037] Figure 1 The present invention is a flowchart of an acceleration correction method for an array lateral instrument;

[0038] Figure 2 Flow chart of the correction criteria of an embodiment of the present invention. DETAILED DESCRIPTION

[0039] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0040] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0041] It should be understood that although the terms first, second, and third may be used in the present disclosure to describe various information, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0042] The specific implementation steps of the embodiment of the present invention are described as follows with reference to the accompanying drawings:

[0043] The embodiment of the present invention provides an acceleration correction method for an array lateral instrument, see Figure 1 As shown, the following steps are included:

[0044] S1. See Figure 2 As shown in the figure, the fundamental frequency f is obtained by spectrum analysis of the acceleration curve, and the following formula is obtained:

[0045] a=g z +ASIN(2πft);

[0046] Where a is the acceleration, g z is the axial component of gravitational acceleration (the radial component has little effect on depth correction);

[0047] Integrating the acceleration a gives the velocity:

[0048] v = ∫a dt = v 0 +∫ 0 t ASIN(2πft)dt;

[0049] =v 0 -A / (2πf)*COS(2πft);

[0050] Integrating the velocity gives the depth displacement:

[0051] S = ∫vdt

[0052] =S 0 +v 0 t–A / (2πf) 2 *SIN(2πft);

[0053] Where S 0 +v 0 t is the law of variation of apparent depth (i.e., recording depth); the depth correction term caused by oscillating motion is:

[0054] △S=-A / (2πf) 2 *SIN(2πft);

[0055] Maximum value of depth correction △S=A / (2πf) 2 , △S=A / (2πf) 2 As a criterion for whether the acceleration curve needs acceleration correction;

[0056] f = 1 / T, which can be calculated by simply intercepting the period interval length on the acceleration curve and dividing it by the normal speed measurement. Of course, it can also be obtained through the spectrum analysis of this method;

[0057] Assume that the depth resolution of the acceleration curve is X, and the following conditions are met:

[0058] △S>2X, that is, the depth deviation exceeds twice the resolution, then acceleration correction is required;

[0059] Through the analysis of early acceleration curves, it is concluded that the △S caused by instrument vibration is generally in the order of a few tenths of a meter, so the early acceleration curves with a resolution of 1 or 2 feet do not require acceleration correction;

[0060] S2, using the baseline fitting algorithm of the acceleration curve, the axial acceleration value queue in the interval before and after the current acceleration point is used to obtain the base value of the axial acceleration by the minimum variance fitting method. The axial acceleration value queue is dynamically adjusted according to the acceleration cycle and is an integer multiple of the acceleration cycle; the length can flexibly respond to the inclination change rate of the instrument in the deflection section;

[0061] S3, dynamically adjust the integral interval of the displacement. The integral interval of the displacement also changes the fixed interval method and is dynamically selected according to the integer multiples of the motion cycle;

[0062] In simple harmonic vibration, the equilibrium position displacement and acceleration are both zero. Through the spectrum analysis of step S1, combined with the judgment of the baseline zero point of the acceleration curve, the upper and lower limits of the displacement integration interval are determined, and compared with the depth of the original integration interval, the linear error is automatically corrected. In this way, the linear integration error can be eliminated as a whole.

[0063] The final correction result is combined with the auxiliary judgment of the blockage to correct the overall deviation and local anomalies.

[0064] The embodiment of the present invention further provides an acceleration correction device for an array lateral instrument, which uses the acceleration correction method as described above.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] The present invention obtains correction criteria through spectrum analysis of the acceleration curve; and proposes improvement measures for the old method using kinematic equations, Kalman filtering and piecewise integration, and determines the fundamental frequency of acceleration change by spectrum analysis, so as to dynamically adjust the base value of axial acceleration and the integration interval, so that the prediction is closer to the actual situation.

[0067] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make the same changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, replacement, and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calibrating acceleration of an array lateral instrument, characterized in that: The following steps are involved: S1. Perform spectrum analysis on the acceleration curve to obtain the fundamental frequency f, then we have the following formula: a = g z + ASIN(2πft); Where a is the acceleration, g z is the axial component of gravitational acceleration; Integrating the acceleration a gives the velocity: v = ∫ a dt = v0 + ∫0 t ASIN(2πft)dt; = v0 - A / (2πf) *COS(2πft); Integrating the velocity gives the depth displacement S: S = ∫vdt = S0 + v0t – A / (2πf) 2 *SIN(2πft); Where S0 + v0t is the law of apparent depth change; the depth correction term caused by oscillatory motion is: △S = -A / (2πf) 2 *SIN(2πft) ; The maximum value of depth correction △S=A / (2πf) 2 , △S=A / (2πf) 2 As a criterion for whether the acceleration curve needs acceleration correction; Assume that the depth resolution of the acceleration curve is X, and the following conditions are met: △S > 2X, that is, the depth deviation exceeds twice the resolution, acceleration correction is required; S2, using the baseline fitting algorithm of the acceleration curve to dynamically select the axial acceleration value queue; S3, dynamically adjust the integral interval of displacement; The method of using the baseline fitting algorithm of the acceleration curve in step S2 includes: obtaining the base value of the axial acceleration by a minimum variance fitting method through an axial acceleration value queue in a front and rear interval of the current acceleration point; The method of dynamically selecting the axial acceleration value queue in step S2 includes: dynamically adjusting the axial acceleration value queue according to the acceleration period to be an integer multiple of the acceleration period; The method for dynamically adjusting the integral interval of the displacement through the step S3 includes: determining the upper and lower limits of the integral interval of the displacement in combination with the judgment of the zero crossing point of the baseline of the acceleration curve, and comparing them with the depth of the original integral interval to automatically correct the linear error.

2. The acceleration correction method according to claim 1, characterized in that: The step S3 also includes: auxiliary judgment of the blockage, and correction of the overall deviation and local abnormality.

3. An acceleration correction device for an array lateral instrument, characterized in that: Use the acceleration correction method as claimed in claim 1 or 2.

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