Seismic exploration excitation well sealing method and application thereof in seismic exploration

Abstract

The invention provides a well sealing method of a seismic exploration excitation well and application of the well sealing method in seismic exploration. The preparation method comprises the steps that an explosive column with first water-absorbent resin fixed to the top is placed at the bottom of the seismic exploration excitation well; backfilling the seismic exploration excitation well with a mixture of drilling cuttings and second water-absorbent resin; the seismic exploration excitation well is backfilled with a mixture of soft soil and fine sand to the position 25-35 cm away from a well opening, and an anti-floating clip is arranged at the position; and the seismic exploration excitation well is backfilled with a mixture of soft soil and fine sand till the mixture is flush with a well opening, and well sealing is completed. On the basis, the well shut-in effect is excellent, and the seismic data acquisition construction has better efficiency, safety and environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the technical field of seismic exploration, and in particular to a method for sealing an excitation well in seismic exploration and its application in seismic exploration. Background Art

[0002] In seismic exploration, explosives are needed to generate seismic waves. To ensure the excitation effect and construction safety, the explosives are placed in wells for excitation. After workers place the explosives in the well, drilling cuttings or crushed stones are usually used to seal the wellbore to prevent blowout during the excitation of the explosives. Well sealing is an important process in seismic data acquisition construction, directly affecting the quality of seismic wave excitation and the safety of seismic acquisition construction. In southern regions and areas with a relatively shallow water table, a large amount of water will also seep into the excitation wells, greatly reducing the well sealing effect. When the explosives are excited, a large amount of drilling cuttings will be ejected from the wellhead, losing the excitation energy and posing a safety hazard at the same time. Therefore, it is necessary to design a new well sealing method to improve the quality and safety of seismic data acquisition construction. Summary of the Invention

[0003] To solve the above problems, according to one aspect of the present invention, a method for sealing an excitation well in seismic exploration is provided, which includes the following steps:

[0004] Step S1: Place an explosive column with a first water-absorbing resin fixed at the top at the bottom of the excitation well for seismic exploration;

[0005] Step S2: Backfill a mixture of drilling cuttings and a second water-absorbing resin into the excitation well for seismic exploration;

[0006] Step S3: Backfill a mixture of soft soil and fine sand into the excitation well for seismic exploration to a depth of 25 - 35 cm from the wellhead, and set an anti-floating clamp at this position;

[0007] Step S4: Backfill a mixture of soft soil and fine sand into the excitation well for seismic exploration until it is flush with the wellhead to complete the well sealing. At this time, the well sealing structure of the excitation well is as Figure 1 shown.

[0008] First, the invention places an explosive column with a first water-absorbing resin fixed on top at the bottom of a seismic exploration excitation well. In this way, on the one hand, the first water-absorbing resin can achieve the purpose of water absorption when contacting water, and on the other hand, it will expand rapidly, thereby improving the well sealing effect, and further greatly reducing the risk of a large amount of drilling cuttings spraying out of the wellhead during explosive excitation, resulting in energy loss and potential safety hazards caused by a blowout in the excitation well. Secondly, the invention continues to backfill the seismic exploration excitation well with a mixture of drilling cuttings and a second water-absorbing resin. The second water-absorbing resin material will expand rapidly when contacting water, increasing the friction between the mixture and the well wall, thereby achieving the compaction purpose and further greatly improving the well sealing effect. Furthermore, the invention continues to backfill the seismic exploration excitation well with a mixture of soft soil and fine sand to a distance of 25 - 35 cm from the wellhead, and installs an anti-floating clamp here, which can further enhance the well sealing effect. Finally, backfill the seismic exploration excitation well with a mixture of soft soil and fine sand until it is flush with the wellhead, and the well sealing is completed.

[0009] It should be noted that the invention does not impose special restrictions on the relevant parameters of the above-mentioned soft soil and fine sand, and the materials can be obtained locally. In the mixture of soft soil and fine sand, the more the proportion of fine sand, the better. This can be implemented by those skilled in the art themselves, and will not be elaborated here.

[0010] Further, the expansion coefficients of the first water-absorbing resin and the second water-absorbing resin are independently 180 - 220 times. Such materials can further improve the well sealing effect.

[0011] Further, the first water-absorbing resin and the second water-absorbing resin are in powder form, and the particle sizes are independently 30 - 60 mesh. Such powdered water-absorbing resin materials will become jelly-like after water absorption and expansion, which can further improve the well sealing effect.

[0012] Considering the high efficiency, safety, and environmental protection of seismic data acquisition construction, it is preferred that the first water-absorbing resin and the second water-absorbing resin are independently synthetic resin-based superabsorbent resins. Further, the number-average molecular weight of the synthetic resin-based superabsorbent resin is 72 - 228. Further, the synthetic resin-based superabsorbent resin is starch-grafted sodium polyacrylate, and preferably the grafting rate of the synthetic resin-based superabsorbent resin (the grafting rate refers to the amount of polyacrylic acid grafted onto 1 g of starch) is 550 - 650 g. In some alternative embodiments, the synthetic resin-based superabsorbent resin can be a commercially available product with the model KL-SAP produced by Hubei Yuanfeng Chemical Co., Ltd.

[0013] In a preferred embodiment, the first water-absorbing resin material is loaded into a water-soluble bag, and the water-soluble bag is fixed to the detonating cord of the explosive column (for example, the water-soluble bag can be tied to the detonating cord of the explosive column) to obtain an explosive column with the first water-absorbing resin fixed at the top. The water-soluble bag can delay the swelling rate of the water-absorbing resin. If the water-absorbing resin swells rapidly, it will separate the water and drilling cuttings, not only failing to achieve the above beneficial effects but also weakening the water absorption effect.

[0014] Furthermore, to prevent the drawback of the detonating cord being disconnected due to the swelling of the water-absorbing resin, it is preferred to leave a length of L of the detonating cord between the water-soluble bag and the explosive column; the value of L is greater than or equal to the depth of the water in the seismic exploration excitation well and less than the depth of the water in the seismic exploration excitation well plus 0.5 m.

[0015] In a preferred embodiment, the volume dosage of the first water-absorbing resin is denoted as v, with the unit of m 3 ; v is calculated by the following formula: In the formula, h w represents the depth of the water in the seismic exploration excitation well, with the unit of m; h e is the excitation depth (i.e., the depth of the seismic exploration excitation well - the length of the explosive column), with the unit of m; R is the swelling coefficient of the water-absorbing resin; r is the radius of the wellhead, with the unit of m. The dosage of the second water-absorbing resin is denoted as m x , with the unit of g; m x is calculated by the following formula: In the formula, h w represents the depth of the water in the seismic exploration excitation well, with the unit of m. The dosage of the drilling cuttings is denoted as m y , with the unit of g; m y is calculated by the following formula: m y = 500m x , in the formula, m x represents the dosage of the second water-absorbing resin, with the unit of g.

[0016] According to another aspect of the present invention, there is provided an application of the well sealing method for the seismic exploration excitation well as described above in medium-deep (deeper than 3500 m) seismic exploration.

[0017] Based on the various reasons mentioned above, the present invention effectively improves the well sealing effect of the seismic exploration excitation well, reduces the risk of well blowout of the excitation well, and thus greatly improves the quality and safety of seismic data acquisition construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Shows a schematic diagram of the well structure after sealing the well using the well sealing method for the seismic exploration excitation well in an embodiment of the present invention.

[0019] Figure 2Shows the original single-shot seismic record charts collected after well sealing and excitation using the methods of Example 1 and Comparative Example 1 respectively. Detailed implementation manners

[0020] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention will now be described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0021] Example 1

[0022] In this example, the depth of the excitation well is 12 m, the water depth in the wellbore is 6 m, and the length of the explosive column is 2 m.

[0023] The specific process of sealing the excitation well is as follows:

[0024] 1) Load the first water-absorbing resin (a superabsorbent resin with the model KL-SAP produced by Hubei Yuanfeng Chemical Co., Ltd., grafting rate of 600, expansion coefficient of 200 times, particle size of 45, and number-average molecular weight of 150) into a water-soluble bag, and record the volume usage of the first water-absorbing resin as v, which is calculated by the following formula: In the formula, h w is 6 m; h e is 10 m; R is 200 m; r is 0.05 m; in this example, v is 0.000218287 m 3 , that is, 218.287 cm 3 , in actual construction, the data is rounded, and 218 cm is taken. 3 .

[0025] 2) Tie the water-soluble bag to the shot line and lower it into the wellbore together with the explosive column at one time, leaving a 6 m long shot line between the water-soluble bag and the explosive column.

[0026] 3) Make a mixture of drilling cuttings and the second water-absorbing resin (KL-SAP superabsorbent resin produced by Hubei Yuanfeng Chemical Co., Ltd., grafting rate of 600, expansion coefficient of 200 times, particle size of 45, and number-average molecular weight of 150), backfill the mixture of drilling cuttings and water-absorbing resin, and the backfill depth is 0.6 m. Record the usage of the second water-absorbing resin as m x , which is calculated by the following formula: In the formula, h w is 6 m; in this example, m x is 52.424 g, in actual construction, the data is rounded, and 52 g is taken. Record the usage of the drilling cuttings as m y , which is calculated by the following formula: m y = 500 m x , in the formula, m x takes 52.424 g, in this example, m yIt is 26.212kg, which is rounded up to 26kg in actual construction.

[0027] 4) Backfill soft soil and fine sand to 30 cm from the wellhead and place anti-floating clips there.

[0028] 5) Backfill the wellhead with soft soil and fine sand to complete the well sealing.

[0029] In this embodiment, the water-absorbing material can reach the maximum water absorption capacity within 10 to 20 minutes, and the sealing work of a well can be completed within 20 to 30 minutes, with high sealing efficiency.

[0030] Comparative Example 1

[0031] In this example, the excitation well depth is 12m, the water depth in the wellbore is 6m, and the length of the explosive column is 2m.

[0032] The specific process of sealing the stimulation well is as follows:

[0033] 1) Lower the explosive column into the wellbore at one time.

[0034] 2) Backfill the drilling cuttings to 30 cm from the wellhead and place anti-floating clips there.

[0035] 5) Backfill the drilling cuttings to the wellhead again to complete the well sealing.

[0036] Well sealing effect:

[0037] (1) Blowout rate: The method in Example 1 and the method in Comparative Example 1 were respectively repeated 38 times (i.e., the total number of wells), and the number of blowout wells (i.e., the number of blowout wells) was recorded. The blowout rate was calculated as the number of blowout wells / total number of wells.

[0038] When the method in comparative example 1 is used to seal the well, the blowout rate is about 80%, while when the method in embodiment 1 is used to seal the well, the blowout rate is about 10%.

[0039] (2) Signal-to-noise ratio: The signal-to-noise ratio is the ratio of the effective signal to the noise in a seismic record. The signal-to-noise ratio of a raw single-shot seismic record is calculated using the spectrum estimation method described in the article "Quantitative Calculation and Method Comparison of Signal-to-Noise Ratio of Seismic Data" by Zhang Junhua et al. (2009) published in Petroleum Geophysical Exploration.

[0040] Figure 2(The horizontal axis represents: trace number / trace; the vertical axis represents: time / ms) shows the original seismic single-shot records (high-pass 50 Hz) collected after well sealing and excitation using the methods of Example 1 and Comparative Example 1 respectively. The single-shot quality of Example 1 is higher than that of Comparative Example 1. Further, the signal-to-noise ratio values at the same position on the original record are calculated by the spectrum estimation method. Among them, the signal-to-noise ratio of Example 1 is 1.1, and the signal-to-noise ratio of Comparative Example 1 is 0.69. Compared with Comparative Example 1, the signal-to-noise ratio of the seismic data obtained in the target layer of the high-frequency component in Example 1 is higher, increasing by nearly 60%, which is more conducive to mid-depth seismic exploration.

Claims

1. A method for sealing an excitation well in seismic exploration, characterized in that, It includes the following steps: Step S1: Place the explosive column with the first water-absorbing resin fixed at the top at the bottom of the seismic exploration excitation well. Step S2: Backfill the seismic exploration excitation well with a mixture of drilling cuttings and the second water-absorbing resin. Step S3: Backfill the seismic exploration excitation well with a mixture of soft soil and fine sand to a distance of 25 - 35 cm from the wellhead, and set an anti-floating clamp here. Step S4: Backfill the seismic exploration excitation well with a mixture of soft soil and fine sand until it is flush with the wellhead to complete well sealing.

2. The well sealing method of the seismic exploration excitation well according to claim 1, characterized in that, The expansion coefficients of the first water-absorbing resin and the second water-absorbing resin are independently 180 - 220 times.

3. The well sealing method for seismic exploration excitation wells according to claim 1 or 2, characterized in that, The first water-absorbing resin and the second water-absorbing resin are in powder form, and the particle sizes are independently 30 - 60 mesh.

4. The well sealing method of the seismic exploration excitation well according to claim 1 or 2, characterized in that, The first water-absorbing resin and the second water-absorbing resin are synthetic resin-based superabsorbent resins. Preferably, the number-average molecular weight of the synthetic resin-based superabsorbent resin is 72 - 228. More preferably, the synthetic resin-based superabsorbent resin is starch-grafted sodium polyacrylate.

5. The well sealing method of the seismic exploration excitation well according to claim 1, characterized in that, Put the first water-absorbing resin into a water-soluble bag, and fix the water-soluble bag on the detonating wire of the explosive column to obtain the explosive column with the first water-absorbing resin fixed at the top.

6. The well sealing method of the seismic exploration excitation well according to claim 5, characterized in that, A detonating wire with a length of L is reserved between the water-soluble bag and the explosive column; the value of L is greater than or equal to the depth of the water in the seismic exploration excitation well and less than the depth of the water in the seismic exploration excitation well plus 0.5 m.

7. The well sealing method of the seismic exploration excitation well according to claim 1, characterized in that, Let the volume dosage of the first water-absorbing resin be denoted as v, with the unit of m 3 ; The v is calculated by the following formula: Where h w represents the depth of water in the seismic exploration excitation well, with the unit of m; h e is the excitation depth, with the unit of m; R is the expansion coefficient of the water-absorbing resin; r is the radius of the wellhead, with the unit of m.

8. The well sealing method of the seismic exploration excitation well according to claim 1, characterized in that, Record the dosage of the second water-absorbing resin as mx, with the unit of g; mx is calculated by the following formula: where h w represents the depth of water in the seismic exploration excitation well, with the unit of m.

9. The well sealing method of the seismic exploration excitation well according to claim 7, characterized in that, Record the dosage of the drilling cuttings as m y , with the unit of g; the m y is calculated by the following formula: m y = 500 m x In the formula, mx represents the dosage of the second water-absorbing resin, with the unit of g.

10. Application of the well sealing method for the seismic exploration excitation well according to any one of claims 1 to 9 in medium-deep seismic exploration.

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