Logging curve environment correction method

Abstract

The invention relates to the technical field of oil-gas exploration, in particular to a logging curve environment correction method which comprises the following steps: collecting drilling data, logging data, logging data and logging interpretation data of a target well in a research area; determining a collapsed well section of the target well according to the CALI well logging and the corresponding drill bit diameter; a curve with a good sand shale recognition effect is adopted as a lithologic logging interpretation sensitive parameter curve, and the interval transit time curve of the well section adjacent to the collapsed well section and the lithologic logging interpretation sensitive parameter curve are intersected to obtain a fitted interval transit time curve; and replacing the well logging curve of the collapsed section with the fitted interval transit time curve and the fitted density curve so as to obtain a corrected well logging curve. According to the method, high-quality basic data are provided for seismic data interpretation and inversion prediction, the method can be widely applied to exploration and development of unconventional oil and gas such as shale oil and tight oil, a basis is provided for segmentation and clustering of the horizontal well and selection of fracturing construction parameters, and cost is saved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and is a method for correcting a well logging curve environment. Background Art

[0002] In order to further determine the distribution characteristics of sand bodies in the Beisantai area, it is necessary to conduct rock physical analysis and reservoir inversion prediction in the area. However, during the drilling process, due to a series of reasons such as the vibration of the drill bit, the change of drilling speed, the inconsistency of the looseness of the formation itself, and the long mud soaking time, the formation collapsed and the wellbore radius expanded. Although modern density logging, sonic logging and other instruments can compensate for the abnormalities of the wellbore, they are only limited to a certain range. Large wellbore collapse will still have an unignorable impact on the measurement results, resulting in errors in the results of logging interpretation, layer calibration, seismic inversion, etc. Therefore, reducing or even eliminating the errors caused by wellbore collapse, that is, logging curve environmental correction has become an urgent task. Summary of the invention

[0003] The present invention provides a method for environmental correction of logging curves, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that wellbore collapse in the existing drilling process has a significant impact on the logging results, resulting in errors in the results of logging interpretation, layer calibration, seismic inversion, etc.

[0004] The technical solution of the present invention is achieved by the following measures: A method for environmental correction of a well logging curve is performed according to the following steps:

[0005] S1, collect drilling data, logging data, logging data and logging interpretation data of target wells in the study area;

[0006] S2, determining the collapsed section of the target well according to CALI logging and the corresponding drill bit diameter;

[0007] S3, using the curve with good identification effect on sandstone and mudstone as the sensitive parameter curve of lithology logging interpretation, intersecting the acoustic time difference curve of the adjacent well section of the collapsed well section with the sensitive parameter curve of lithology logging interpretation to obtain the fitted acoustic time difference curve, and fitting and correcting the density curve according to the fitted acoustic time difference curve to obtain the fitted density curve;

[0008] S4, replacing the well logging curve of the collapsed section with the fitted acoustic time difference curve and the fitted density curve, thereby obtaining a corrected well logging curve.

[0009] The following are further optimizations and / or improvements to the above technical solutions:

[0010] In the above step S2, the difference Δd between the CALI logging value and the corresponding drill bit diameter is calculated according to the following formula. When Δd is greater than a, the well section is a collapsed well section.

[0011] Δd=CALI[]-d Formula 1

[0012] Where Δd is the difference between the CALI logging value and the corresponding drill bit diameter; CALI[] is the wellbore caliper logging value, in units of in; and d is the drill bit diameter, in units of in.

[0013] In the above step S3, the lithology logging interpretation sensitive parameter curve is a deep resistivity curve.

[0014] In the above step S3, the acoustic time difference curve of the adjacent well section of the collapsed well section is intersected with the deep resistivity curve to obtain a fitted acoustic time difference curve. The fitting formula of the acoustic time difference curve and the deep resistivity curve of the non-collapsed section is:

[0015]

[0016] Where y is the fitted acoustic time difference curve, us / ft; x is the deep resistivity logging curve, Ω·m; A1, A2, and x0 are constants.

[0017] In the above step S3, the adjacent well sections of the collapsed well section are upper and lower well sections that have the same lithology and physical properties as the collapsed well section and contain fluid.

[0018] In the above step S3, the fitted density curve is obtained by fitting and correcting the fitted acoustic wave curve according to the Gardner empirical formula.

[0019] The present invention provides a method for environmental correction of well logging curves, solves the problem of synthetic seismic records and wellside seismic calibration, provides high-quality basic data for seismic data interpretation and inversion prediction, can be widely used in the exploration and development of unconventional oil and gas such as shale oil and tight oil, provides a basis for the selection of horizontal well segmentation and clustering and fracturing construction parameters, and saves costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attached Figure 1 This is the well logging curve diagram of Well B216 in Example 7 of the present invention.

[0021] Attached Figure 2 This is a curve diagram for determining the wellbore collapse of Well B216 in Example 7 of the present invention.

[0022] Attached Figure 3 This is the intersection diagram of resistivity and acoustic wave time difference in Example 7 of the present invention.

[0023] Attached Figure 4 This is a comparison chart of the logging curves of Well B216 before and after correction in Example 7 of the present invention.

[0024] Attached Figure 5 This is a calibration comparison diagram before and after correction in Example 7 of the present invention.

[0025] Attached Figure 6 This is a comparison section of the inversion effect before and after the well logging curve correction in Example 7 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0027] The present invention will be further described below in conjunction with embodiments:

[0028] Embodiment 1: The method for environmental correction of the well logging curve is carried out according to the following steps:

[0029] S1, collect drilling data, logging data, logging data and logging interpretation data of target wells in the study area;

[0030] S2, determining the collapsed section of the target well according to CALI logging and the corresponding drill bit diameter;

[0031] S3, the curve with good recognition effect on sandstone and mudstone is used as the sensitive parameter curve of lithology logging interpretation, and the acoustic time difference curve of the adjacent well section of the collapsed well section is intersected with the sensitive parameter curve of lithology logging interpretation to obtain the fitted acoustic time difference curve, and the dense well section is identified according to the fitted acoustic time difference curve.

[0032] The density curve is fitted and corrected to obtain the fitted density curve;

[0033] S4, replacing the well logging curve of the collapsed section with the fitted acoustic time difference curve and the fitted density curve, thereby obtaining a corrected well logging curve.

[0034] Embodiment 2: As an optimization of the above embodiment, in step S2, the difference Δd between the CALI logging value and the corresponding drill bit diameter is calculated according to the following formula. When Δd is greater than a, the well section is a collapsed well section.

[0035] Δd=CALI[]-d Formula 1

[0036] Where Δd is the difference between the CALI logging value and the corresponding drill bit diameter; CALI[] is the wellbore caliper logging value, in units of in; and d is the drill bit diameter, in units of in.

[0037] Embodiment 3: As an optimization of the above embodiment, in step S3, the lithology logging interpretation sensitive parameter curve is a deep resistivity curve.

[0038] Embodiment 4: As an optimization of the above embodiment, in step S3, the acoustic time difference curve of the adjacent well section of the collapsed well section is intersected with the deep resistivity curve to obtain a fitted acoustic time difference curve. The fitting formula of the acoustic time difference curve and the deep resistivity curve of the non-collapsed section is:

[0039]

[0040] Where y is the fitted acoustic time difference curve, us / ft; x is the deep resistivity logging curve, Ω·m; A1, A2, and x0 are constants.

[0041] Embodiment 5: As an optimization of the above embodiment, in step S3, the adjacent well sections of the collapsed well section are upper and lower well sections with consistent lithology and physical properties with the collapsed well section and containing fluid.

[0042] Embodiment 6: As an optimization of the above embodiment, in step S3, the fitted density curve is obtained by fitting and correcting the fitted acoustic wave curve according to the Gardner empirical formula.

[0043] Example 7: The logging curve environmental correction method is actually applied in a block in Beisantai. The specific steps are as follows:

[0044] The first step is to collect drilling data, logging data, logging data and logging interpretation data of the target wells in the study area. Take B216 well as an example (see the logging curve diagram Figure 1 ), by loading the collected data, it can be seen that there are obvious anomalies in the acoustic density curve and density in the abnormal section of the wellbore curve at depths of 2097m to 2115m, 2144m to 2149m, 2152m to 2166m and 2186m to 2192m.

[0045] In the second step, Δd is obtained by calculating the difference between the CALI logging and the drill bit diameter of the corresponding well. When Δd is greater than a, it is determined to be a collapsed well section, such as Figure 2 The collapsed well section marked in gray will cause abnormal acoustic time difference and density logging values.

[0046] The third step is to calculate the fitting curve. The curve correction is performed by collecting and sorting out the relationship between the undistorted curves in the upper and lower well sections with similar lithology, physical properties and fluid content adjacent to the distorted section of the curve. The natural gamma curve in the study block has a poor effect on lithology identification, while the resistivity curve has a good effect on sandstone and mudstone identification. Therefore, the resistivity curve and the acoustic time difference curve are used for intersection fitting, and the acoustic time difference fitting formula is obtained as follows:

[0047]

[0048] Where y is the deep resistivity fitting acoustic wave curve, us / ft; x is the deep resistivity logging, Ω·m.

[0049] The fourth step is to replace the well logging curve of the collapsed section with the fitted acoustic time difference curve in combination with the determined collapsed section, so as to obtain a reasonable acoustic wave curve. The density curve is fitted and corrected according to the Gardner empirical formula using the corrected acoustic wave curve.

[0050] Comparison of synthetic records before and after correction (see Figure 5 ) It can be clearly seen that the corrected curve eliminates the influence of the real upper and lower surrounding rock impedance information on the target sand body. Figure 6 Comparison of the inversion effects before and after the logging curve correction shows that the use of the corrected curve for sand body inversion can better characterize the target sand body.

[0051] The present invention comprehensively considers the influence of geological parameters and engineering parameters on production capacity, optimizes key parameters, establishes a production capacity potential index, and also considers the influence of closure stress on fracturing construction parameters and the influence of different proppant types to form a normalized method. In the application of a block in Beisantai, the horizontal well production capacity prediction model established based on the logging curve environmental correction method of the present invention has a good linear relationship with the actual production, the prediction error is small, and the arithmetic mean relative error of the cumulative production calculated for 180 days is 9.6%.

[0052] In summary, the present invention provides a method for environmental correction of well logging curves, solves the problem of synthetic seismic records and wellside seismic calibration, and provides high-quality basic data for seismic data interpretation and inversion prediction. It comprehensively considers the influence of geological parameters and engineering parameters on production capacity, as well as the influence of closure stress on fracturing construction parameters, and forms a normalized method, which can be widely used in the exploration and development of unconventional oil and gas such as shale oil and tight oil, and provides a basis for the selection of horizontal well segmentation and clustering and fracturing construction parameters, thereby saving costs.

[0053] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for environmental correction of well logging curves, characterized in that Follow these steps: S1, collect drilling data, logging data, logging data and logging interpretation data of target wells in the study area; S2, determining the collapsed section of the target well according to CALI logging and the corresponding drill bit diameter; S3, using the curve with good identification effect on sandstone and mudstone as the sensitive parameter curve of lithology logging interpretation, intersecting the acoustic time difference curve of the adjacent well section of the collapsed well section with the sensitive parameter curve of lithology logging interpretation to obtain the fitted acoustic time difference curve, and fitting and correcting the density curve according to the fitted acoustic time difference curve to obtain the fitted density curve; S4, replacing the well logging curve of the collapsed section with the fitted acoustic time difference curve and the fitted density curve, thereby obtaining a corrected well logging curve.

2. The method for environmental correction of well logging curves according to claim 1, characterized in that In step S2, the difference Δd between the CALI logging value and the corresponding drill bit diameter is calculated according to the following formula. When Δd is greater than a, the well section is a collapsed well section. Δd=CALI[]-d Formula 1 Where Δd is the difference between the CALI logging value and the corresponding drill bit diameter; CALI[] is the wellbore caliper logging value, in units of in; and d is the drill bit diameter, in units of in.

3. The method for environmental correction of well logging curves according to claim 1 or 2, characterized in that In step S3, the lithology logging interpretation sensitive parameter curve is a deep resistivity curve.

4. The method for environmental correction of well logging curves according to claim 3, characterized in that In step S3, the acoustic time difference curve of the adjacent well section of the collapsed well section is intersected with the deep resistivity curve to obtain a fitted acoustic time difference curve. The fitting formula of the acoustic time difference curve and the deep resistivity curve of the non-collapsed section is: Where y is the fitted acoustic time difference curve, us / ft; x is the deep resistivity logging curve, Ω·m; A1, A2, and x0 are constants.

5. The method for environmental correction of well logging curves according to claim 1, 2 or 4, characterized in that In step S3, the adjacent well sections of the collapsed well section are upper and lower well sections that have the same lithology and physical properties as the collapsed well section and contain fluid.

6. The method for environmental correction of well logging curves according to claim 3, characterized in that In step S3, the adjacent well sections of the collapsed well section are upper and lower well sections that have the same lithology and physical properties as the collapsed well section and contain fluid.

7. The method for environmental correction of well logging curves according to claim 1, 2 or 4, characterized in that In step S3, the fitted density curve is obtained by fitting and correcting the fitted acoustic wave curve according to the Gardner empirical formula.

8. The method for environmental correction of well logging curves according to claim 3, characterized in that In step S3, the fitted density curve is obtained by fitting and correcting the fitted acoustic wave curve according to the Gardner empirical formula.

9. The method for environmental correction of well logging curves according to claim 5, characterized in that In step S3, the fitted density curve is obtained by fitting and correcting the fitted acoustic wave curve according to the Gardner empirical formula.

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