Method for correcting sonic transit time in horizontal wells

Abstract

This invention discloses a method for correcting the acoustic transit time of horizontal wells. The method involves obtaining the acoustic transit time Δt of the horizontal well to be corrected and the angle x between the wellbore and the formation bedding plane at the depth point corresponding to Δt. Based on the acquired angle x, a correction coefficient y is calculated for the depth point corresponding to angle x. Finally, the corrected acoustic transit time Δtc for that depth point is calculated based on the acoustic transit time Δt and the calculated correction coefficient y. This invention solves the problem of rapidly determining the correction of acoustic transit time in horizontal wells in the field. The method is simple, easy to implement, widely applicable, and low-cost, providing a new technology for shale oil and gas exploration and development.

Description

Technical Field

[0001] This invention belongs to the field of shale oil and gas exploration and development technology, and specifically relates to a method for correcting the acoustic transit time of horizontal wells. Background Technology

[0002] Acoustic transit time (ACT) is an important method for evaluating reservoir properties. Understanding the variation patterns of ACT measured in horizontal wells and using this transit time to determine reservoir porosity is crucial for improving the accuracy of horizontal well interpretation and reservoir evaluation. However, current acoustic logging instruments are designed for vertical well environments. In horizontal wells, the ACT response characteristics differ significantly from those in vertical wells. Differences in wellbore conditions and formation models are two key factors contributing to the difference in ACT response between horizontal and vertical wells. Therefore, it is essential to study ACT correction methods for horizontal wells to ensure that the formation parameters calculated in horizontal well environments better reflect actual conditions.

[0003] Currently, publicly available methods for correcting sonic transit time in horizontal well logging mainly analyze the geometric relationship between the wellbore trajectory and the formation interface, as well as formation anisotropy. These methods typically include rock physics experimental analysis, the sonic transit time difference translation method between vertical and horizontal wells, and numerical simulation. While existing correction methods have achieved certain geological effects, they suffer from technical drawbacks such as high cost and complex correction processes due to the need for extensive rock anisotropy core experimental data. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned technical problems and provide a simple, easy-to-implement, low-cost, and fast method for determining the acoustic time difference of horizontal wells.

[0005] To achieve the above objectives, this invention provides a method for correcting the acoustic transit time in horizontal wells, the specific steps of which are as follows:

[0006] 1) Obtain the acoustic transit time Δt of the horizontal well to be corrected and the angle x between the horizontal wellbore and the formation plane at the depth point corresponding to the acoustic transit time Δt;

[0007] The unit of measurement for acoustic time difference Δt is μs / m, and the unit of measurement for included angle x is °;

[0008] 2) Calculate the correction coefficient y of the depth point corresponding to the included angle x collected in step 1);

[0009] 3) Calculate the corrected horizontal well acoustic time difference Δtc corresponding to the depth point based on the acoustic time difference Δt in step 1) and the calculated correction coefficient y of the corresponding depth point.

[0010] Furthermore, in step 1), the acoustic time difference Δt and the included angle x are sampled at sampling points according to the actual well logging data, with sampling points ranging from 0.1 to 0.5 m.

[0011] Furthermore, in step 1), the depth correspondence error between the acoustic time difference Δt and the included angle x does not exceed 0.3m.

[0012] Furthermore, in step 2), the calculation process of the correction coefficient y is as follows:

[0013] Based on the included angle x collected in step 1), the correction coefficient y of the corresponding depth point is calculated using the linear model y = ax + b, where a and b are coefficients.

[0014] Furthermore, in step 3), the calculation process for the corrected horizontal well acoustic transit time Δtc is as follows:

[0015] Based on the acoustic transit time Δt collected in step 1) and the calculated correction coefficient y for the corresponding depth point, the corrected horizontal well acoustic transit time Δtc for that depth point is calculated using the formula Δtc=Δt+y.

[0016] Furthermore, the calculation process for coefficients a and b in step 2) is as follows:

[0017] 21) Obtain multiple sets of known horizontal well acoustic transit time Δt0 and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0;

[0018] 22) Based on the multiple sets of known horizontal well acoustic transit time Δt0 in step 21) and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0, the coefficients a and b are calculated using the formula y0=ax0+b.

[0019] Furthermore, in step 21), the depth error corresponding to the acoustic time difference Δt and the included angle x does not exceed 0.3m.

[0020] Further, in step 22), data samples are obtained according to the principle that the relative error of the natural gamma values ​​of corresponding depth points in the same layer and the same layer group is less than 20%, and the coefficients a and b are calculated according to the formula y0=ax0+b based on the data samples.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention solves the problem of quickly determining the correction of acoustic time difference in horizontal wells on site. The method is simple, easy to implement, widely applicable, and low in cost, providing a new technology for shale oil and gas exploration and development. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the horizontal well acoustic time difference correction method of the present invention;

[0023] Figure 2The linear regression analysis diagram is used to obtain the acoustic time difference correction coefficient for the horizontal well in Example 1. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 The method for correcting the acoustic transit time of a horizontal well, as shown, includes the following specific steps:

[0026] 1) Obtain the acoustic transit time Δt of the horizontal well to be corrected and the angle x between the horizontal wellbore and the formation plane at the depth point corresponding to the acoustic transit time Δt;

[0027] The unit of measurement for acoustic time difference Δt is μs / m, and the unit of measurement for included angle x is °;

[0028] The aforementioned acoustic transit time Δt and included angle x are based on actual well logging sampling points, with sampling points ranging from 0.1 to 0.5 m, preferably 0.3 m;

[0029] The depth correspondence error between the acoustic time difference Δt and the included angle x does not exceed 0.3m;

[0030] 2) Calculate the correction coefficient y of the depth point corresponding to the included angle x collected in step 1);

[0031] The calculation process for the correction coefficient y is as follows:

[0032] Based on the included angle x collected in step 1), the correction coefficient y of the corresponding depth point is calculated using the linear model y = ax + b, where a and b are coefficients.

[0033] 3) Calculate the corrected horizontal well acoustic time difference Δtc corresponding to the depth point based on the acoustic time difference Δt in step 1) and the calculated correction coefficient y for the corresponding depth point;

[0034] The calculation process for the corrected horizontal well acoustic transit time Δtc is as follows:

[0035] Based on the acoustic transit time Δt collected in step 1) and the calculated correction coefficient y for the corresponding depth point, the corrected horizontal well acoustic transit time Δtc for that depth point is calculated using the formula Δtc=Δt+y.

[0036] The calculation process of coefficients a and b in step 2) of this invention is as follows:

[0037] 21) Obtain multiple sets of known horizontal well acoustic transit time Δt0 and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0;

[0038] The depth correspondence error between the acoustic time difference Δt and the included angle x does not exceed 0.3m;

[0039] 22) Based on the known horizontal well acoustic transit time Δt0 and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0, data samples are obtained according to the principle that the relative error of the natural gamma value comparison at the corresponding depth point is less than 20% and the corresponding layer position and layer group are corresponding. The coefficients a and b are calculated according to the formula y0=ax0+b based on the data samples.

[0040] This invention statistically analyzes the acoustic transit time data of horizontal wells, normalizes the acoustic transit time of standard layers at each level, establishes the relationship between acoustic transit time and the included angle to obtain correction coefficients, and then corrects the acoustic transit time using these correction coefficients. This eliminates the anisotropic effects in horizontal well acoustic transit time measurements without requiring a large amount of measurement data or complex calculations, thus improving the efficiency and accuracy of the technology.

[0041] The correction relationship established by this invention has strong universality, reduces the difficulty and cost of technical implementation, improves the practicality and adaptability of the technology, and increases the interpretation accuracy of horizontal wells, thus playing an important role in promoting development.

[0042] Example 1

[0043] Using 81 samples from the Wangguang area of ​​Jianghan Oilfield, multiple sets of known horizontal well sonic transit time Δt0 and the angle x0 between the wellbore and the formation bedding plane at the corresponding depth points of the known horizontal wells were obtained. Data samples were obtained according to the principle that the relative error of the natural gamma value comparison at the same depth point within the same stratigraphic position and group is less than 20%. Based on the data samples, the coefficients a and b were calculated using the formula y0 = ax0 + b. The model coefficients a = -0.3304 and b = 2.8388 were determined (e.g., ...). Figure 2 As shown), the correlation strength R 2 =0.8288, that is, y = -0.3304x + 2.8388;

[0044] The specific steps for correcting the acoustic transit time in horizontal wells are as follows:

[0045] 1) Obtain the acoustic transit time Δt of the horizontal well to be corrected and the angle x between the horizontal wellbore and the formation plane at the depth point corresponding to the acoustic transit time Δt;

[0046] 2) Based on the included angle x collected in step 1), calculate the correction coefficient y for the corresponding depth point using the linear model y = -0.3304x + 2.8388;

[0047] 3) Based on the acoustic transit time Δt collected in step 1) and the calculated correction coefficient y for the corresponding depth point, the corrected acoustic transit time Δtc for the horizontal well at that depth point is calculated using the formula Δtc=Δt+y.

Claims

1. A method for correcting acoustic traveltime in a horizontal well, characterized by: The specific steps of the correction method are as follows: 1) Obtain the acoustic transit time Δt of the horizontal well to be corrected and the angle x between the horizontal wellbore and the formation plane at the depth point corresponding to the acoustic transit time Δt; The unit of measurement for acoustic time difference Δt is μs / m, and the unit of measurement for included angle x is °; 2) Calculate the correction coefficient y of the depth point corresponding to the included angle x collected in step 1); 3) Calculate the corrected horizontal well acoustic time difference Δtc corresponding to the depth point based on the acoustic time difference Δt in step 1) and the calculated correction coefficient y of the corresponding depth point.

2. The method of claim 1, wherein: In step 1), the acoustic time difference Δt and the included angle x are sampled at sampling points according to the actual well logging data, with sampling points ranging from 0.1 to 0.5 m.

3. The method for correcting the acoustic time difference in a horizontal well according to claim 1, characterized in that: In step 1), the depth error corresponding to the acoustic time difference Δt and the included angle x does not exceed 0.3m.

4. The method for correcting the acoustic time difference in a horizontal well according to claim 1, characterized in that: In step 2), the calculation process for the correction coefficient y is as follows: Based on the included angle x collected in step 1), the correction coefficient y of the corresponding depth point is calculated using the linear model y = ax + b, where a and b are coefficients.

5. The method for correcting the acoustic time difference in a horizontal well according to claim 1, characterized in that: In step 3), the calculation process for the corrected horizontal well acoustic transit time Δtc is as follows: Based on the acoustic transit time Δt collected in step 1) and the calculated correction coefficient y for the corresponding depth point, the corrected horizontal well acoustic transit time Δtc for that depth point is calculated using the formula Δtc=Δt+y.

6. The method for correcting the acoustic time difference in a horizontal well according to claim 1, characterized in that: The calculation process for coefficients a and b in step 2) is as follows: 21) Obtain multiple sets of known horizontal well acoustic transit time Δt0 and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0; 22) Based on the multiple sets of known horizontal well acoustic transit time Δt0 in step 21) and the angle x0 between the wellbore and the formation plane at the depth point corresponding to the known horizontal well acoustic transit time Δt0, the coefficients a and b are calculated using the formula y0=ax0+b.

7. The method for correcting the acoustic time difference in a horizontal well according to claim 6, characterized in that: In step 21), the depth error corresponding to the acoustic time difference Δt and the included angle x does not exceed 0.3m.

8. The method for correcting the acoustic time difference in a horizontal well according to claim 6, characterized in that: In step 22), data samples are obtained according to the principle that the relative error of the natural gamma values ​​of corresponding depth points in the same layer and the same layer group is less than 20%. Based on the data samples, coefficients a and b are calculated using the formula y0 = ax0 + b.

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