Acoustic Curve Correction Method under the Condition of Complex Borehole Diameter Enlargement

Abstract

The present invention provides a method for correcting acoustic wave curves under the condition of complex borehole diameter enlargement, including: Step 1, analyzing the relationship among formation intervals, lithology and borehole diameter enlargement; Step 2, analyzing the relationship between acoustic wave curves and borehole diameter enlargement, and finding wells and formation intervals with small borehole diameter enlargement as correction references; Step 3, confirming the range of abnormal influence of borehole diameter enlargement on acoustic waves and the correction amount of acoustic wave curves; Step 4, correcting the acoustic wave abnormal area, and comprehensively judging the rationality of the correction by using three methods, namely, the correlation between synthetic seismogram and seismic data, the correlation between seismic trace gather and forward modeling trace gather, and the consistency of calibration of multi-well standard reflection layers. The method for correcting acoustic wave curves under the condition of complex borehole diameter enlargement has strong operability, clear and reliable verification means, improves the reliability of acoustic wave curve correction under the condition of complex borehole diameter enlargement, and ensures the solid foundation for seismic reservoir prediction and seismic reservoir description research.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field exploration and rock physics analysis, and particularly to a method for correcting acoustic curves under the condition of complex borehole diameter enlargement. Background Art

[0002] Acoustic logging data plays an irreplaceable role in oil and gas exploration. Accurate acoustic logging data is quite important in many aspects such as time-depth conversion, synthetic seismogram production, seismic data inversion, reservoir modeling, etc. However, due to the phenomenon of borehole diameter enlargement, the acoustic logging curve will be distorted and cannot reflect the true formation information.

[0003] Generally, borehole diameter enlargement is mainly caused by the softening and collapse of the formation after being soaked by mud in the shale section, or may also be caused by the caving of the wellbore wall during the friction between the brittle formation and the drill bit. Generally, borehole diameter enlargement occurs in some wells in the work area, or in a certain specific lithologic section or well section. At this time, the influencing factors for acoustic curve acquisition are few, and the correction work is relatively simple.

[0004] In some work areas, however, borehole diameter enlargement is more complex. For example, in the Tugulu Group, Xishanyao Formation, Sangonghe Formation, and Badaowan Formation in the central block of the Junggar Basin in Xinjiang, due to reasons such as water sensitivity and poor formation stability, there is an enlargement phenomenon coexisting from severe enlargement to general enlargement in long well sections, multiple layers, and multiple lithologies (sandstone, shale, muddy sandstone, sandy shale) of all wells in the entire work area. Coupled with the use of compensated acoustic logging during the logging process, the measured values in some enlarged sections are not affected by the enlargement, while some are affected, but the degree of influence becomes smaller. This makes the relationship between borehole diameter enlargement and the measured acoustic curve more complex, and a more targeted method for correcting acoustic curves is required.

[0005] Generally speaking, the existing methods for correcting acoustic curves can be divided into three categories:

[0006] The first category is the correction method based on the principle of acoustic logging. For example, Liu Haojie et al. proposed an acoustic time difference correction and compensation method for correcting by using the difference between the average borehole diameter of the contribution section of the measurement point and the borehole diameter of the measurement point according to the regular anomaly phenomenon that the acoustic measurement time difference changes with the displacement of the transmitting acoustic logging tool in the enlarged borehole section; Sui Zhiqiang deduced the calculation formula for acoustic time difference compensation by using the principle of the minimum Fermat time according to the variation law of acoustic wave propagation with borehole diameter and lithology.

[0007] The second category is the acoustic wave curve reconstruction and correction method. This method is the most widely used and can generally be divided into three methods: 1) Using the calibration of the logging curve at the same depth as the expansion section, the rock physics of the formation is established; 2) Using the curve with a long detection distance and less susceptible to expansion to establish the underground volume model of the formation; 3) Using the formation volume model and rock physics laws, the corresponding logging curve is forward modeled. For example, Chen Ganghua et al., based on the phenomenon that the acoustic wave delay increases after mudstone is soaked in mud, proposed an acoustic wave delay reconstruction method based on resistivity curves, under the condition that the surrounding rock satisfies the Faust formula; Liu Aijiang et al. established a regional rock physics model and then forward modeled the acoustic wave curve and density curve to achieve curve correction. Some curve correction methods using AI technology can also be included in this category.

[0008] The third type is the acoustic curve correction method based on seismic and wellbore constraints. Wang Xia et al. calculated the corrected acoustic moveout using seismic data, two-way travel times between identical standard layers in the original acoustic moveout synthetic record, and wellbore expansion parameters.

[0009] Some of the three methods mentioned above are highly specialized and require stringent conditions, making them difficult for practical operators to implement. Some require reference to other curves, whose reliability cannot be guaranteed under complex wellbore expansion conditions. Still others assume a linear relationship between wellbore expansion and correction, making their practical application under these conditions questionable. To address these complex wellbore expansion scenarios, we developed an acoustic curve correction method that addresses these technical challenges.

[0010] In the Chinese patent application with application number CN201610621073.1, a method and device for correcting well logging curves are involved, wherein the method includes: obtaining preset well logging curve data of a preset well logging; performing depth correction on the current curve data to be corrected in the preset well logging curve data; establishing an intersection diagram and determining the target data points to be corrected from the intersection diagram, and performing diameter expansion correction on the determined target data points; replacing the target data points before correction with the diameter expansion corrected data points to obtain the current curve data after diameter expansion correction; establishing an intersection diagram based on the standard well logging curve data of the preset standard well and the preset well logging curve data after diameter expansion correction, and performing inter-well consistency correction based on the established intersection diagram to obtain the corrected preset well logging curve data. The well logging curve correction method and device provided by the embodiment of this application can improve the accuracy of well logging correction.

[0011] In the Chinese patent application with the application number CN201810984266.2, a method for correcting acoustic wave curves based on seismic and caliper constraints is involved. The method for correcting acoustic wave curves based on seismic and caliper constraints includes: Step 1, perform synthetic seismic record calibration, determine two seismic reflection axes a and b that include the wellbore collapse section, and calculate the two-way seismic travel time Δt1 between the seismic reflection axes a and b; Step 2, calculate the two-way travel time Δt2 between the corresponding reflection axes on the synthetic seismic record for the seismic reflection axes a and b; Step 3, calculate the sum Σac and ΣAC of the values in the depth sections corresponding to the seismic reflection axes a and b for the original acoustic wave curve and the corrected acoustic wave curve respectively; Step 4, calculate the correction coefficient K and perform the correction of the acoustic wave travel time curve. The method for correcting acoustic wave curves based on seismic and caliper constraints can accurately correct the acoustic wave curves in the wellbore collapse section, and the operation is relatively simple and easy to implement.

[0012] In the Chinese patent application with the application number CN202010453865.9, a method for correcting acoustic wave curves in seismic processing is involved, which relates to the technical field of geophysical exploration and development, and includes the acquisition and calculation of logging curves; well-seismic comparison to determine the decomposition level of the logging curve and complete the decomposition of the logging curve; analysis of the statistical characteristics of the multi-well decomposed curves, selection of the decomposed curves to determine the standardization parameters, and perform the standardization correction of the logging curve; establish a suitable rock physics model, calculate the rock physics model line, and calculate the acoustic wave curve based on the rock physics model; determine the abnormal layer section of the acoustic wave curve; obtain GR, RD, DEPTH of the normal layer section of the acoustic wave value and the acoustic wave curve calculated by the rock physics model, establish an acoustic wave curve correction model, and complete the correction of the acoustic wave curve for the abnormal layer section of the acoustic wave. The application of the invention can effectively realize the correction of the acoustic wave curve in seismic processing, reduce the influence of non-geological factors such as wellbore collapse and mud invasion, greatly improve the quality of the acoustic wave curve, and improve the reliability of well-seismic calibration.

[0013] The above prior arts are all quite different from the present invention and fail to solve the technical problems we want to solve. Therefore, we have invented a new method for correcting acoustic wave curves in the case of complex wellbore diameter expansion. Summary of the Invention

[0014] The object of the present invention is to provide a method for correcting acoustic wave curves in the case of complex wellbore diameter expansion, which can improve the calibration accuracy of standard horizons and target oil and gas layers and the reliability of rock physics analysis.

[0015] The object of the present invention can be achieved by the following technical measures: A method for correcting acoustic wave curves in the case of complex wellbore diameter expansion, which includes:

[0016] Step 1, analyze the relationship between the layer section, lithology and wellbore diameter expansion;

[0017] Step 2: Analyze the relationship between the acoustic wave curve and the borehole diameter enlargement, and find the wells and intervals with small borehole diameter enlargement as the calibration reference.

[0018] Step 3: Confirm the influence range of borehole diameter enlargement on acoustic wave anomalies and the calibration amount of the acoustic wave curve.

[0019] Step 4: Calibrate the acoustic wave anomaly area, and comprehensively judge the rationality of the calibration by using three methods: the correlation between the synthetic seismogram and seismic data, the correlation between the seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflection layer calibration.

[0020] The object of the present invention can also be achieved by the following technical measures:

[0021] In Step 1, superimpose and display the borehole diameter curve, bit diameter, and lithology data or GR curve of each single-well target interval, and analyze the relationship between the interval, lithology, and borehole diameter enlargement.

[0022] In Step 1, from single well to multi-well, use the borehole diameter curve, bit diameter, and lithology data or GR curve of the target interval to superimpose and display, and analyze whether the borehole diameter enlargement is caused by bit replacement, a certain lithology reason, or engineering reasons such as drilling speed according to the interval.

[0023] In Step 2, superimpose and display the borehole diameter curve of each single-well target interval and the acoustic wave curve or the converted interval velocity curve, analyze the relationship between the acoustic wave curve or interval velocity curve and the borehole diameter enlargement, and find the wells and intervals with small borehole diameter enlargement as the calibration reference.

[0024] In Step 3, conduct three-parameter cross display of the borehole diameter curve, acoustic wave curve or interval velocity curve, and lithology data or GR curve of the target interval to confirm the influence range of borehole diameter enlargement on acoustic wave or interval velocity anomalies and the calibration amount of the acoustic wave or interval velocity curve.

[0025] In Step 3, conduct three-parameter cross analysis of the borehole diameter curve, acoustic wave curve or interval velocity curve, and lithology data or GR curve of the target interval to determine the influence range of acoustic wave or interval velocity anomalies affected by borehole diameter enlargement.

[0026] In Step 3, while analyzing the abnormal range, confirm the calibration amount of the acoustic wave or interval velocity curve according to the reference well or interval by lithology.

[0027] In Step 4, conduct lithology-based calibration on the acoustic wave or interval velocity abnormal intervals according to the calibration amount of the acoustic wave curve or interval velocity, and comprehensively judge the rationality of the calibration by using three methods: the correlation or correlation coefficient between the single-well synthetic seismogram and seismic data, the correlation between the single-well seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflection layer calibration.

[0028] In step 4, if there are still abnormal velocities in some layers after correction, it is necessary to repeat steps 3 and this step until both comprehensive judgment results are relatively ideal.

[0029] The acoustic wave curve correction method under the condition of complex well diameter expansion in the present invention first determines the complexity of the expansion by analyzing the relationship between the well diameter expansion and the drill bit diameter, layer section, and lithology, and then analyzes the relationship between the measured acoustic wave curve (layer velocity curve) and the layer section, lithology, and expansion amount, and determines the correction amount of the acoustic wave curve (layer velocity curve) for correction. Finally, the rationality of the correction is comprehensively judged by using three methods: the correlation between the synthetic record and the seismic data, the correlation between the seismic track gather and the forward track gather, and the consistency of the calibration of the standard reflection layer of multiple wells. This acoustic wave curve correction method under the condition of complex well diameter expansion takes into account sufficient correction conditions, strong operability, and clear and reliable verification means, which improves the reliability of the acoustic wave curve correction under the condition of complex well diameter expansion, and further improves the calibration accuracy of the standard layer and the target oil and gas layer and the reliability of the rock physical analysis, ensuring a solid foundation for seismic reservoir prediction and seismic oil reservoir description research. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a specific embodiment of the method for correcting the acoustic wave curve under the condition of complex well diameter expansion of the present invention;

[0031] Figure 2 A schematic diagram of layer data, drill bit diameter, wellbore curve, and lithologic superposition analysis in a specific embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the superposition analysis of the wellbore curve and the interval velocity curve in a specific embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the intersection analysis of three parameters: wellbore curve, interval velocity curve, and lithology in a specific embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram showing the comparison of layer velocity data before and after lithology correction in a specific embodiment of the present invention;

[0035] Figure 6 Schematic diagram of correlation analysis and comparison between synthetic records and seismic data before and after correction of the interlayer velocity curve in a specific embodiment of the present invention;

[0036] Figure 7 Schematic diagram of correlation analysis and comparison between seismic traces and forward modeling gathers before and after correction of the layer velocity curve in a specific embodiment of the present invention;

[0037] Figure 8 Schematic diagram showing the consistency comparison of standard reflector calibration in multiple wells before and after correction of the middle layer velocity curve in one embodiment of the present invention. Detailed implementation manners

[0038] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing the specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0040] The acoustic wave curve correction method under the complex wellbore diameter expansion situation of the present invention comprehensively analyzes the relationships among wellbore diameter expansion, stratification data, bit curves, wellbore diameter curves, and lithology data. By the cross-analysis of three parameters, namely the wellbore diameter curve, acoustic wave curve (layer velocity curve), and lithology data (natural gamma ray GR), the correction amount of the acoustic wave curve (layer velocity curve) is determined and corrected and verified; the relationships among wellbore diameter expansion, formation intervals, bits, and lithology are determined; possible reference standard wells or standard formation intervals are determined; by the cross-analysis of three parameters, namely the wellbore diameter curve, acoustic wave curve (layer velocity curve), and lithology data (GR), the abnormal areas where the acoustic wave (layer velocity) is affected by wellbore diameter expansion are determined, and at the same time, the correction amount is determined; the correction amount is used to correct the abnormal areas of the acoustic wave (layer velocity), and the rationality of the correction is comprehensively judged by three methods, namely the correlation between synthetic seismogram and seismic data, the correlation between seismic trace gather and forward modeling trace gather, and the consistency of multi-well standard reflection layer calibration.

[0041] The following are several specific embodiments of applying the present invention.

[0042] Embodiment 1

[0043] In a specific Embodiment 1 of applying the present invention, the acoustic wave curve correction method under the complex wellbore diameter expansion situation of the present invention includes:

[0044] Step 1, the wellbore diameter curves, bit diameters, and lithology data (or GR curves) of the target formation intervals of each single well are superimposed and displayed to analyze the relationships among formation intervals, lithology, and wellbore diameter expansion;

[0045] From single wells to multiple wells, by superimposing and displaying the wellbore diameter curves, bit diameters, and lithology data (or GR curves) of the target formation intervals, analyze whether the diameter expansion in each formation interval is caused by bit replacement, a certain lithology reason, or engineering reasons such as drilling speed.

[0046] Step 2: Superimpose and display the borehole diameter curve and the acoustic wave curve (or the converted interval velocity curve) of each single well target interval, analyze the relationship between the acoustic wave curve (interval velocity curve) and the borehole diameter enlargement, and try to find the wells and intervals with small borehole diameter enlargement as the calibration reference;

[0047] Use the superimposed display of the borehole diameter curve and the acoustic wave curve (or the converted interval velocity curve) of the target interval to qualitatively analyze the relationship between the change amount of the acoustic wave curve (interval velocity curve) and the borehole diameter enlargement amount, and try to find the wells and intervals with little influence of enlargement as the calibration standard.

[0048] Step 3: Conduct three-parameter crossplot display of the borehole diameter curve, the acoustic wave curve (or interval velocity curve), and the lithology data (GR curve) of the target interval to confirm the abnormal range of the influence of borehole diameter enlargement on the acoustic wave (interval velocity) and the correction amount of the acoustic wave (interval velocity) curve;

[0049] Conduct three-parameter crossplot analysis of the borehole diameter curve, the acoustic wave curve (or interval velocity curve), and the lithology data (GR curve) of the target interval to determine the abnormal range of the acoustic wave (interval velocity) affected by borehole diameter enlargement. Using this analysis method, it is possible to effectively determine the intervals of the compensated acoustic wave logging curve affected by borehole diameter enlargement and the intervals not affected by borehole diameter enlargement. While analyzing the abnormal range, confirm the correction amount of the acoustic wave (interval velocity) curve according to the reference well or interval by lithology.

[0050] Step 4: Correct the abnormal area of the acoustic wave (interval velocity), and comprehensively judge the rationality of the correction by using three methods: the correlation between the synthetic seismogram and the seismic data, the correlation between the seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflector calibration. If necessary, repeat the work of Steps 3 and 4 until the correlation reaches a reasonable range.

[0051] Correct the abnormal intervals of the acoustic wave (interval velocity) by lithology according to the correction amount of the acoustic wave curve (interval velocity), and comprehensively judge the rationality of the correction by using three methods: the correlation (correlation coefficient) between the single-well synthetic seismogram and the seismic data, the correlation between the single-well seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflector calibration. If there are still some intervals with abnormal velocities after correction, it is necessary to repeat Steps 3 and this step until the two comprehensive judgment results are both satisfactory.

[0052] Embodiment 2

[0053] In a specific Embodiment 1 of applying the present invention, Figure 1 This is a flow chart of the acoustic wave curve correction method for complex borehole diameter enlargement in a specific embodiment of the present invention. The method specifically includes the following steps:

[0054] In step 101, the zoned data of the target intervals of each well, the bit curve, the borehole diameter curve, and the lithology data are superimposed and comprehensively analyzed to determine the relationship between borehole diameter enlargement, the bit, and the lithology. The process proceeds to step 102.

[0055] In step 102, the borehole diameter curve and the acoustic wave curve (interval velocity curve) of the target intervals of each well are superimposed and comprehensively analyzed to determine a reference standard well or standard interval. The process proceeds to step 103.

[0056] In step 103, a three-parameter crossplot analysis of the borehole diameter curve, the acoustic wave curve (interval velocity curve), and the lithology data (GR) is performed to determine the abnormal zones where the acoustic wave (interval velocity) is affected by borehole diameter enlargement, and at the same time, the correction amount is determined. The process proceeds to step 104.

[0057] In step 104, the abnormal zones of the acoustic wave (interval velocity) are corrected, and at the same time, three methods, namely the correlation between the seismic data and the synthetic seismogram, the correlation between the seismic trace gather and the forward modeling trace gather, and the consistency of calibration of the multi-well standard reflection layers, are used to comprehensively judge the reliability of the correction results.

[0058] Embodiment 3

[0059] In a specific Embodiment 3 of applying the present invention, Figure 2 This is a schematic diagram of the superimposed analysis of the zoned data, bit diameter, borehole diameter curve, and lithology in a specific embodiment of the present invention. The analysis shows that this well has the following characteristics: Below 3770 meters, the overall borehole diameter enlargement is serious. Near 3900 meters, there is an obvious mutation in the bit diameter, and the corresponding borehole diameter curve also has a mutation. The maximum borehole diameter enlargement in the Ktg interval is in the section from 3770 to 3900 meters. The main lithologies, including sandstone, mudstone, argillaceous sandstone, and calcareous sandstone intervals, all have borehole diameter enlargement, and the enlargement degree of a single lithology is inconsistent. There is no obvious pattern in the borehole diameter enlargement of thick layers, thin layers, and thin interbeds. Only some thick sandstone intervals and argillaceous sandstone intervals have relatively small borehole diameter enlargement, but the relationship is not obvious either.

[0060] Figure 3 This is a schematic diagram of the superimposed analysis of the borehole diameter curve and the interval velocity curve in a specific embodiment of the present invention. The analysis shows that although affected by borehole diameter enlargement, the interval velocity ranges and the characteristics and laws of the formation and interval velocity of each well are basically the same. The well with the smallest borehole diameter enlargement is Well D7, and the interval velocity correction of other wells can refer to the velocity characteristics of this well to a certain extent.

[0061] Figure 4Schematic diagram of the cross - analysis of borehole diameter curve, interval velocity curve, and three lithology parameters in a specific embodiment of the present invention. Analyzing this well, it is considered that: in the target interval of this well, the phenomenon of borehole diameter enlargement is serious, and the borehole diameter spreads widely in the range from 0.315 m to 0.425 m. Among them, the borehole diameter enlargement of some sandstones and argillaceous sandstones is relatively small, and there is an obvious demarcation line at 0.33 m; the interval velocity in the target interval of this well is distributed in the range from 3000 m / s to 5200 m / s, but mainly distributed in the range from 3800 m / s to 4800 m / s. Among them, the center of interval velocity of sandstones and argillaceous sandstones is 4300 m / s, and the lower bound is concentrated at 3900 m / s. The center of interval velocity of mudstones and sandy mudstones is 4400 m / s, and the lower bound is concentrated at 4000 m / s. Although the borehole diameter enlarges in the whole well section, the interval velocities of thick - layer sandstones and argillaceous sandstones with relatively small borehole diameter enlargement are concentrated. It is judged that the compensated logging of this part of the lithology interval is effective. In actual operation, the 0.33 - meter demarcation line of borehole diameter where these sandstones and argillaceous sandstones are concentrated is used as the actual borehole diameter enlargement judgment line (the green line in the figure), and the lower bound of interval velocity of 3900 m / s is used as the abnormal demarcation line of these two lithologies. The borehole diameter of the vast majority of mudstones, argillaceous sandstones, sandy mudstones, and some sandstones enlarges seriously, but there is an obvious center of interval velocity. The interval velocities of the sandstones and argillaceous sandstones among them are in the same range as those of the sandstones and argillaceous sandstones with relatively small borehole diameter enlargement. It is judged that the compensated acoustic logging of the interval corresponding to this center is also effective. Combining the above analysis, it is judged that the lower bound of interval velocity of 4000 m / s of mudstones and sandy mudstones at this center is the abnormal demarcation line of these two lithologies. Through the above analysis, it is determined that the main interval velocity abnormal area is in the lower - right part of the figure. Among them, the center of interval velocity of sandstones and argillaceous sandstones in the abnormal area is 3700 m / s, and the center of interval velocity of mudstones and sandy mudstones in the abnormal area is 3800 m / s. In this way, it is calculated that the interval velocity correction value of sandstones and argillaceous sandstones in the abnormal area is 600 m / s, and the interval velocity correction value of mudstones and sandy mudstones is 600 m / s.

[0062] Figure 5 Schematic diagram of the comparison before and after the interval velocity data is corrected by lithology in a specific embodiment of the present invention. According to Figure 4 the interval velocity abnormal correction amount in, the correction is carried out in two categories: sandstones and argillaceous sandstones, and mudstones and sandy mudstones, and repeated correction is carried out according to the feedback of the next - step work until the next - step work meets the requirements.

[0063] Figure 6 Schematic diagram of the correlation analysis and comparison between the synthetic seismogram and seismic data before and after the interval velocity curve correction in a specific embodiment of the present invention. From the comparison results, it can be seen that after the interval velocity curve is corrected, the energy of the synthetic seismogram and the seismic data is more matched, the consistency of the wave - group relationship is better, the bottom of the Cretaceous shows an obvious downward shift, the position of the oil layer moves from the wave peak to the wave valley, and the overall correlation rises from 40% to 76%.

[0064] Figure 7Schematic diagram for the correlation analysis and comparison of seismic traces and forward modeling gather before and after the correction of the layer velocity curve in a specific embodiment of the present invention. It can be seen from the comparison results that after the correction of the layer velocity curve, the energy and AVO characteristics of each reflection layer, especially the standard reflection layer and the oil layer, in the forward modeling gather are more consistent with the actual gather.

[0065] Figure 8 Schematic diagram for the comparison of the calibration consistency of the multi-well standard reflection layer before and after the correction of the layer velocity curve in a specific embodiment of the present invention. It can be seen from the comparison results that after uniformly calibrating the bottom of the coal seam with the most obvious reflection on the strong wave peak reflection axis, the bottom of the Cretaceous after correcting the layer velocity curve is uniformly calibrated on the medium-strong wave peak, and the calibration results are more consistent and reasonable than before the correction of the layer velocity curve. The top of the oil layer in Well D701 is calibrated at the trough, which is consistent with the reservoir calibration of the adjacent Well D7.

[0066] The present invention relates to a correction method for the abnormal acoustic wave curve caused by the complex enlargement of the borehole diameter, which can accurately correct the acoustic wave curve in the complex borehole wall collapse section, and to a certain extent solve the problem that the inaccurate calibration of the synthetic record is caused by the abnormal acoustic wave time difference curve caused by the borehole wall collapse. Compared with the correction method based on the acoustic logging principle, the curve reconstruction acoustic wave curve correction method, and the acoustic wave curve correction method based on seismic and borehole diameter constraints, this method is more applicable to the complex borehole diameter enlargement situation, with reasonable correction theory and easy to operate.

[0067] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0068] Except for the technical features described in the specification, the rest are the known technologies of those skilled in the art.

Claims

1. A method for correcting acoustic wave curves in the case of complex borehole diameter enlargement, characterized in that The acoustic curve correction method under the condition of complex wellbore diameter enlargement includes: Step 1: Superimpose and display the wellbore diameter curve, bit diameter, and lithology data or GR curve of each single well target interval to analyze the relationship between the interval, lithology, and wellbore diameter enlargement; For multiple wells, conduct cross-analysis using the wellbore diameter curve, bit diameter, and lithology data or GR curve of the target interval; Step 2: Analyze the relationship between the acoustic curve or interval velocity curve and wellbore diameter enlargement, and find wells and intervals with small wellbore diameter enlargement as correction references; Use the wellbore diameter curve of the target interval and the acoustic curve or the converted interval velocity curve for superimposed display, qualitatively analyze the relationship between the change amount of the acoustic curve or interval velocity curve and the wellbore diameter enlargement amount, and find wells and intervals with little influence from enlargement as correction standards; Step 3: Conduct three-parameter cross-display of the wellbore diameter curve, acoustic curve or interval velocity curve, and lithology data or GR curve of the target interval to confirm the abnormal range of the influence of wellbore diameter enlargement on the acoustic wave or interval velocity and the correction amount of the acoustic wave or interval velocity curve; Conduct three-parameter cross-analysis of the wellbore diameter curve, acoustic curve or interval velocity curve, and lithology data or GR curve of the target interval to determine the abnormal range of the acoustic wave or interval velocity affected by wellbore diameter enlargement; while analyzing the abnormal range, confirm the correction amount of the acoustic wave or interval velocity curve by lithology according to the reference well or interval; Step 4: Correct the abnormal area of the acoustic wave or interval velocity, and comprehensively judge the rationality of the correction by using three methods: the correlation between the synthetic seismogram and seismic data, the correlation between the seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflector calibration. If necessary, repeat the work in Steps 3 and 4 until the correlation reaches a reasonable range; Correct the abnormal interval of the acoustic wave or interval velocity by lithology according to the correction amount of the acoustic curve or interval velocity, and comprehensively judge the rationality of the correction by using three methods: the correlation or correlation coefficient between the single-well synthetic seismogram and seismic data, the correlation between the single-well seismic trace gather and the forward modeling trace gather, and the consistency of multi-well standard reflector calibration; if there are still some intervals with abnormal velocities after correction, it is necessary to repeat Steps 3 and this step until the two comprehensive judgment results are both satisfactory.

Images