Self-adaptive correction method for density curve of threaded borehole interval

Abstract

The invention discloses a density curve self-adaptive correction method for a threaded borehole interval, and relates to the technical field of petroleum and natural gas development, and the density curve self-adaptive correction method comprises the following steps: S1, selecting a hole diameter curve and a density curve of the threaded borehole interval, and respectively calculating a difference value of an upper envelope line and a lower envelope line; s2, determining a conversion coefficient R; s3, the fluctuation value of the well diameter fluctuation quantity CAL caused by the threaded well hole is determined; and S4, the well diameter fluctuation quantity is converted into the density fluctuation quantity through the conversion coefficient R, the density fluctuation quantity is overlaid on the actually-measured density curve, and a self-adaptive density correction curve is obtained. The invention provides a thread borehole interval density curve self-adaptive correction method based on a hole diameter curve. The method has the advantages that the density curve is corrected by introducing the hole diameter curve, thin-layer information is well reserved while the influence of the threaded hole on the density curve is eliminated, the accuracy and reliability of logging data are improved, and a more reliable logging basis is provided for oil exploration and development.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas development, and in particular to a density curve adaptive correction method for a threaded wellbore layer. Background Art

[0002] In oil exploration and development, a threaded borehole is a type of borehole morphology formed by the complex interaction between the formation and the drilling tool, and its axis is distributed in a spiral shape in space. The threaded borehole has a significant impact on various logging curves, such as the density curve. The existence of the threaded borehole will change the medium distribution around the wellbore, thereby affecting the accuracy of the measurement results. Specifically, local density anomalies may form at the threaded borehole, making the measured density curve inconsistent with the actual formation density, which brings difficulties to the interpretation and evaluation of the formation.

[0003] In view of the significant impact of threaded boreholes on logging data and the oil industry, it is particularly important to take effective correction measures. Modern logging technology provides a variety of threaded borehole correction methods, such as frequency domain filtering, envelope method, etc. These methods can eliminate the periodic fluctuations of logging curves caused by threaded boreholes, but they will eliminate thin-layer logging information at the same scale, which is not conducive to thin-layer identification.

[0004] Therefore, it is urgent to study an adaptive correction method for density curves suitable for threaded wellbore sections. Summary of the invention

[0005] In order to solve the above technical problems, the present invention discloses a method for adaptively correcting the density curve of a threaded wellbore layer segment. The method introduces a wellbore curve, which not only eliminates the influence of the threaded wellbore on the logging data, but also effectively retains the thin layer logging information, thereby improving the accuracy and reliability of the logging data and providing a more reliable logging basis for oil exploration and development.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for adaptively correcting density curves of threaded wellbore intervals comprises the following steps:

[0008] S1. Select the caliper curve and density curve of the threaded wellbore layer section, and calculate the difference between the upper and lower envelopes respectively;

[0009] S2. Determine the conversion coefficient R;

[0010] S3. Determine the wellbore diameter fluctuation CAL caused by the threaded wellbore 波动值 ;

[0011] S4. The wellbore fluctuation is converted into density fluctuation using the conversion coefficient R, and superimposed on the measured density curve to obtain an adaptive density correction curve.

[0012] Optionally, in step S1, the threaded wellbore layer section refers to a layer section in which both the wellbore curve and the density curve have obvious periodic fluctuations, and the periodic fluctuations of the wellbore curve correspond one-to-one to the periodic fluctuations of the density curve, wherein the fluctuations of the density curve include not only the periodic fluctuations caused by the threaded wellbore, but also the fluctuations caused by thin layers.

[0013] The periodic fluctuation of the density curve is caused by the periodic fluctuation of the caliper curve, so the caliper curve can be used for correction.

[0014] Optionally, in step S1, the difference CAL between the upper and lower envelopes of the caliper curve max-min The value obtained by subtracting the upper and lower envelopes of the caliper curve, and the difference DEN between the upper and lower envelopes of the density curve max-min It is the value obtained by subtracting the upper envelope and the lower envelope of the density curve.

[0015] Optionally, in step S2, the conversion coefficient R is obtained by comparing the difference between the upper and lower envelopes of the density curve with the difference between the upper and lower envelopes of the caliper curve, and the formula is as follows:

[0016] R=DEN max-min / CAL max-min

[0017] In the formula, the conversion coefficient R refers to the density change caused by a unit change in well diameter.

[0018] Optionally, in step S3, a lower envelope is taken from the caliper curve, and the caliper fluctuation CAL is obtained by subtracting the caliper curve from the lower envelope. 波动值 .

[0019] Optionally, in step S4, the result of the adaptive density correction curve is as follows:

[0020] DEN 自适应 =DEN 实测 +R·CAL 波动值

[0021] In the formula, DEN 实测 This is the result of the density curve after adaptive correction.

[0022] The beneficial effect of the present invention is that the present invention provides a method for adaptively correcting the density curve of a threaded wellbore layer based on a caliper curve. The advantage of this method is that by introducing the caliper curve to correct the density curve, the influence of the threaded wellbore on the density curve is eliminated while also well preserving the thin layer information. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the curve characteristics and envelope of the threaded wellbore layer section of the present invention;

[0024] Figure 2 It is a schematic diagram of the fluctuation amount of the well diameter curve and the density curve of the present invention;

[0025] Figure 3 This is the result after adaptive correction of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] A method for adaptively correcting density curves of threaded wellbore intervals comprises the following steps:

[0028] S1. Select the borehole diameter curve and density curve of the threaded wellbore layer, such as Figure 1 As shown in the red curves of Tracks 1 and 2, the difference between the upper and lower envelopes is calculated respectively;

[0029] The threaded wellbore layer section refers to a layer section in which both the wellbore curve and the density curve have obvious periodic fluctuations, and the periodic fluctuations of the wellbore curve correspond one-to-one to the periodic fluctuations of the density curve, wherein the fluctuations of the density curve include not only the periodic fluctuations caused by the threaded wellbore, but also the fluctuations caused by the thin layer.

[0030] The periodic fluctuation of the density curve is caused by the periodic fluctuation of the caliper curve, so the caliper curve can be used for correction.

[0031] Take the upper and lower envelopes of the wellbore curve, such as Figure 1 The green curve of track 1 is the upper envelope of the wellbore, and the blue curve is the lower envelope of the wellbore. The difference between the upper and lower envelopes of the wellbore curve is CAL. max-min It is the value obtained by subtracting the upper envelope line and the lower envelope line of the wellbore curve.

[0032] Take the upper and lower envelopes of the density curve, such as Figure 1 The green curve of middle track 2 is the upper density envelope, the blue curve is the lower density envelope, and the difference between the upper and lower envelopes of the density curve is DENmax-min It is the value obtained by subtracting the upper envelope and the lower envelope of the density curve.

[0033] S2. Determine the conversion coefficient R;

[0034] like Figure 3 As shown in the red curve of track 3, the conversion coefficient R is obtained by comparing the difference between the upper and lower envelopes of the density curve with the difference between the upper and lower envelopes of the wellbore curve. The formula is as follows:

[0035] R=DEN max-min / CAL max-min

[0036] In the formula, the conversion coefficient R refers to the density change caused by a unit change in well diameter.

[0037] S3, such as Figure 2 As shown in the red curve of track 3, the lower envelope of the wellbore curve is taken, and the wellbore fluctuation CAL is obtained by subtracting the wellbore curve from the lower envelope. 波动值 .

[0038] S4. Use the conversion coefficient R to convert the wellbore fluctuation into density fluctuation, superimpose it on the measured density curve, deduct the density change caused by the wellbore in the density curve, and obtain an adaptive density correction curve. The formula is as follows:

[0039] DEN 自适应 =DEN 实测 +R·CAL 波动值

[0040] In the formula, DEN 实测 This is the result of the density curve after adaptive correction.

[0041] like Figure 3 As shown in the red curve of track 2, it can be seen that the periodic fluctuation of the compensated density curve is significantly eliminated, the curve can better reflect the real density information, and retain the thin layer information of the logging curve. For example, in the threaded wellbore layer section, by comparing the compensated density curve (green line) and the adaptive correction density curve (red line), it can be found that the influence of the threaded wellbore on the density curve is eliminated, which is specifically reflected in Figure 3 Compared with the adaptive correction curve (red curve) and the compensated density curve (green curve) of Zhongdao 2, the adaptive correction curve has no periodic fluctuations. At the same time, this method also retains the thin layer information of the threaded wellbore layer in this example. There is a thin layer in the depth section of 880-881m. The compensated density curve and the adaptive correction density curve both show a high value at the depth of 880-881m, and this high value still exists in the adaptive correction density curve and is not lost with the elimination of the threaded wellbore fluctuations.

[0042] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for adaptively correcting density curves of threaded wellbore intervals, characterized in that: The steps include: S1. Select the caliper curve and density curve of the threaded wellbore layer section, and calculate the difference between the upper and lower envelopes respectively; S2. Determine the conversion coefficient R; S3. Determine the wellbore diameter fluctuation CAL caused by the threaded wellbore 波动值 ; S4. The wellbore fluctuation is converted into density fluctuation using the conversion coefficient R, and superimposed on the measured density curve to obtain an adaptive density correction curve.

2. The method for adaptively correcting density curve of a threaded wellbore layer according to claim 1, characterized in that: In step S1, the threaded wellbore layer section refers to a layer section in which both the wellbore curve and the density curve have obvious periodic fluctuations, and the periodic fluctuations of the wellbore curve correspond one-to-one to the periodic fluctuations of the density curve, wherein the fluctuations of the density curve include not only the periodic fluctuations caused by the threaded wellbore, but also the fluctuations caused by the thin layer.

3. The method for adaptively correcting density curve of a threaded wellbore layer according to claim 2, characterized in that: In step S1, the difference between the upper and lower envelopes of the wellbore curve CAL max-min The value obtained by subtracting the upper and lower envelopes of the caliper curve, and the difference DEN between the upper and lower envelopes of the density curve max-min It is the value obtained by subtracting the upper envelope and the lower envelope of the density curve.

4. A method for adaptively correcting density curves of threaded wellbore sections according to claim 3, characterized in that: In step S2, the conversion coefficient R is obtained by comparing the difference between the upper and lower envelopes of the density curve with the difference between the upper and lower envelopes of the caliper curve. The formula is as follows: R=DEN max-min / CAL max-min In the formula, the conversion coefficient R refers to the density change caused by a unit change in well diameter.

5. A method for adaptively correcting density curves of threaded wellbore sections according to claim 4, characterized in that: In step S3, the lower envelope of the caliper curve is taken, and the caliper fluctuation CAL is obtained by subtracting the caliper curve from the lower envelope. 波动值 .

6. A method for adaptively correcting density curves of threaded wellbore sections according to claim 5, characterized in that: In step S4, the result of the adaptive density correction curve is as follows: THE 自适应 =THE 实测 +R·CAL 波动值 In the formula, DEN 实测 This is the result of the density curve after adaptive correction.

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