Clay soil ball, preparation method and application thereof, and prediction method of water stop time

Abstract

The invention discloses a clay soil ball and a preparation method and application thereof and a prediction method of water stop time, and relates to the technical field of waterstop, the preparation method of the clay soil ball comprises the following steps: S1, cutting waste clay into blocks, and putting the blocks into a drying oven for drying; s2, the dried blocky clay is smashed and ground into clay powder; s3, taking out part of the clay powder in the step S2, adding polyacrylamide, and uniformly stirring to form improved clay powder; and S4, adding water into the improved clay powder, continuously stirring, then preparing into balls, and drying to obtain the clay balls. The invention further discloses the clay soil ball prepared through the preparation method, application of the clay soil ball and a method for predicting the water stop time of the clay soil ball. The technical problem that in the prior art, the clay ball water stopping time cannot be controlled is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of water stopping, and in particular to a clay ball and a preparation method and application thereof, as well as a method for predicting water stopping time. Background Art

[0002] Clay balls are a widely used water-stopping material, mostly used in drilling and well completion processes. The principle is that the clay balls will hydrate when they reach the predetermined water-blocking layer, the surface of the clay balls will peel off and then the balls will break, and the broken clay particles will gradually form a whole through sedimentation and compression, thus achieving a water-stopping effect. However, due to the influence of the processing technology, the quality of clay balls is rough, and there are often problems such as slow sinking speed of clay balls and too fast hydration speed, resulting in "bridging" accidents of clay balls, resulting in poor water-stopping effects.

[0003] Therefore, how to improve the properties of clay balls and enhance the water-stopping effect of clay balls under complex geological conditions is a key technical problem that needs to be urgently solved in drilling and well construction. Summary of the invention

[0004] The purpose of the present invention is to provide a clay ball and a preparation method, application and water-stopping time prediction method thereof, so as to solve the technical problem that the water-stopping time of the clay ball in the prior art cannot be controlled.

[0005] The present application discloses a method for preparing a clay ball, comprising the following steps: S1: Cut the waste clay into blocks and put them into an oven for drying; S2: breaking the dried clay block into pieces and grinding them into clay powder; S3: taking out part of the clay powder from step S2, adding polyacrylamide and stirring evenly to form modified clay powder; S4: adding water to the modified clay powder, continuing to stir, then forming into balls, and drying to obtain clay balls.

[0006] The present application can improve the water-stopping time of the clay ball by adding polyacrylamide, thereby improving the water-stopping effect.

[0007] Based on the above technical solution, the embodiment of the present application can also be improved as follows: Furthermore, in step S3, the polyacrylamide is anionic, and the molecular weight of the polyacrylamide is 8-10 million.

[0008] The present application also discloses a clay ball, which is prepared by the above-mentioned preparation method.

[0009] Based on the above technical solution, the embodiment of the present application can also be improved as follows: Furthermore, the mass content of polyacrylamide in the clay ball is 1%-5%, and the diameter of the clay ball is 8-12 mm. The beneficial effect of adopting this step is that the clay ball of a specific size can be more convenient for subsequent customers to use.

[0010] The present application also discloses an application of a clay ball, and the clay ball is used to stop water in a drilling waterproof layer.

[0011] The present application also discloses a method for predicting the water stop time of a clay ball, comprising the following steps: S1: selecting clay balls with different mass contents and obtaining the hydration time T1 of the clay balls; S2: Establishing a mechanical model for calculating the falling time of a clay ball in water, and calculating the maximum speed Vmax of the clay ball in water; S3: Establishing a finite element analysis model for the falling clay ball, and further verifying and calibrating the Vmax in step S1 to obtain Vmax'; S4: The preset drilling depth is H, and the estimated time for the clay ball to fall is T2=H / Vmax'; S5: The water stop time is obtained as T3, T3=T1+T2.

[0012] Based on the above technical solution, the embodiment of the present application can also be improved as follows: Furthermore, the mechanical model in step S2 shows that Vmax 2 =(mg-ρV 球 g) / 0.5CDρA; Wherein, m is the mass of the clay ball, in kg; ρ is the liquid density, in kg / m 3 ; V 球 is the volume of the clay ball, in m 3 ; g is the acceleration due to gravity, in m / s2; CD is the drag coefficient, which is generally taken as 0.26 for clay balls; A is the projection area of ​​the sphere in the direction of motion, that is, A=πD2 / 4, in m2; Vmax is the maximum movement speed of the clay ball, in m / s.

[0013] Furthermore, the clay ball falling finite element analysis model in step S3 is established by COMSOL simulation coupling software.

[0014] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: 1. This application is an improved clay ball, which will not collapse quickly when placed in water like ordinary clay balls, and water stopping can be controlled during construction; 2. The improved clay ball of this application meets the permeability coefficient requirements, and the "clay water stop layer" formed after the clay ball collapses meets the water stop requirements; 3. This application verifies the falling motion state of the clay ball through numerical simulation calculations, which can better control the water-stopping time.

[0015] 4. This application can achieve precise control of water-stopping time through the concentration of polyacrylamide, making engineering construction easy to control automatically. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is a flow chart of a method for preparing a clay ball according to a specific embodiment of the present invention; DETAILED DESCRIPTION The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention. It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0018] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0019] Embodiment 1: The present application discloses a clay ball and a preparation method thereof, and also discloses the application of the clay ball and the estimation of the water-stopping time of the clay ball, so as to facilitate precise control in subsequent use and facilitate users to select the water-stopping time and ensure the water-stopping effect.

[0020] The present application discloses a method for preparing a clay ball, comprising the following steps: S1: Cut the waste clay into blocks and put them into an oven for drying; S2: breaking the dried clay block into pieces and grinding them into clay powder; S3: taking out part of the clay powder from step S2, adding polyacrylamide and stirring evenly to form modified clay powder; S4: adding water to the modified clay powder, continuing to stir, then forming into balls, and drying to obtain clay balls.

[0021] Specifically, the drying temperature of step S1 is 300° C., and the drying time is 20 h, 21 h, 22 h, 23 h, or 24 h, and it is only necessary to ensure that the clay balls are dried. Similarly, the drying temperature in step S4 is similar, and it is only necessary to ensure drying.

[0022] Wherein, the polyacrylamide is anionic, and the molecular weight of the polyacrylamide is 8-10 million, preferably, the molecular weight is 8 million, 9 million or 10 million.

[0023] Embodiment 2: The present application discloses a clay ball, which is prepared by the method of Example 1, wherein the mass content of polyacrylamide in the clay ball is 1%, and the diameter of the clay ball is 8 mm, 10 mm or 12 mm.

[0024] Embodiment 3: The present application discloses a clay ball, which is prepared by the method of Example 1, wherein the mass content of polyacrylamide in the clay ball is 3%, and the diameter of the clay ball is 8 mm, 10 mm or 12 mm.

[0025] Embodiment 4: The present application discloses a clay ball, which is prepared by the method of Example 1, wherein the mass content of polyacrylamide in the clay ball is 5%, and the diameter of the clay ball is 8 mm, 10 mm or 12 mm.

[0026] Embodiment 5: The present application discloses the application of the clay balls in Examples 2-4, and the clay balls are used to stop water in the drilling watertight layer.

[0027] Embodiment 6: The present application embodiment discloses a method for predicting the water stop time of a clay ball, which is based on the clay ball in Embodiments 2-4 and comprises the following steps: S1: selecting clay balls with different mass contents and obtaining the hydration time T1 of the clay balls; S2: Establishing a mechanical model for calculating the falling time of a clay ball in water, and calculating the maximum speed Vmax of the clay ball in water; S3: Establishing a finite element analysis model for the falling clay ball, and further verifying and calibrating the Vmax in step S1 to obtain Vmax'; S4: The preset drilling depth is H, and the estimated time for the clay ball to fall is T2=H / Vmax'; S5: The water stop time is obtained as T3, T3=T1+T2.

[0028] The mechanical model in step S2 shows that Vmax 2 =(mg-ρV 球 g) / 0.5CDρA; Wherein, m is the mass of the clay ball, in kg; ρ is the liquid density, in kg / m 3 ; V 球 is the volume of the clay ball, in m 3 ; g is the acceleration due to gravity, in m / s2; CD is the drag coefficient, which is generally taken as 0.26 for clay balls; A is the projection area of ​​the sphere in the direction of motion, that is, A=πD2 / 4, in m2; Vmax is the maximum movement speed of the clay ball, in m / s.

[0029] The clay ball falling finite element analysis model in step S3 is established by COMSOL simulation coupling software.

[0030] Further explanation of step S2 is provided, and force analysis is performed on the clay ball: The clay ball is subject to a downward effective weight F', an upward drag force f and an upward additional mass force Fa. According to Newton's second law of motion, we can get: ma=F'-f-Fa (1) Where: m is the mass of the clay ball; a is the acceleration of the clay ball.

[0031] The effective weight of a clay ball can be expressed as: F' = mg - ρV ball g (2) Where: ρ is the liquid density; Vball is the volume of the clay ball; g is the gravitational acceleration.

[0032] The resistance of the clay ball can be expressed as: f = 0.5CDρAv2 (3) Where: CD is the drag coefficient, which is generally taken as 0.26 for a clay ball; A is the projection area of ​​the sphere in the direction of motion, that is, A=πD2 / 4; v is the velocity of the clay ball.

[0033] The additional mass force of the clay ball can be expressed as: Fa = CmρVballa (4) Where: Cm is the additional mass coefficient, which is generally taken as 0.5 for clay balls.

[0034] Substituting equations (2), (3) and (4) into equation (1), we can obtain: (m+CmρVball)a=mg-ρVballg-0.5CDρAv2(5) When the clay ball is dropped from the wellhead, the initial acceleration is the acceleration of gravity. As the clay ball falls, the speed of the clay ball continues to increase, and the resistance it encounters also increases. During this process, the clay ball is performing an accelerated motion with decreasing acceleration. When the resistance it encounters is equal to its effective weight, the acceleration of the clay ball is 0, and the additional mass force is also 0. At this point, the speed of the clay ball reaches its maximum. After that, the clay ball will maintain its maximum speed and perform uniform linear motion in the water. The maximum speed is called the limit speed Vmax: Vmax 2 =(mg-ρV 球 g) / 0.5CDρA(6) The clay ball has a mass of 1.1 g and a diameter of 10 mm. The simulated liquid is water, that is, ρ = 1000 kg / m3. Substituting the data into equation (6), we get vm = 0.75 m / s.

[0035] According to the relationship between the calculated limiting speed of the ball in water and the required limiting depth, it can be found that the limiting depth required for the limiting speed Vmax=0.75m / s is 0.68m. Compared with the drilling depth of 100m, it can be considered that the clay ball moves at a uniform speed, and a preliminary estimate of the falling time can be made.

[0036] The hydration time described in step S1 of the present application is obtained through experiments, as follows: Experiments were performed on gradients of different amounts of polyacrylamide: Experimental conditions: ambient temperature 25±0.5℃, humidity 20±2%; Experimental samples: Sample 1: Clay ball with a diameter of 8 mm and a polyacrylamide content of 0%; Sample 2: Clay ball with a diameter of 8 mm and a polyacrylamide content of 1%; Sample 3: Clay ball with a diameter of 8 mm and a polyacrylamide content of 3%; Sample 4: Clay ball with a diameter of 8 mm and a polyacrylamide content of 5%; Sample 5: Clay ball with a diameter of 10 mm and a polyacrylamide content of 0%; Sample 6: Clay ball with a diameter of 10 mm and a polyacrylamide content of 1%; Sample 7: Clay ball with a diameter of 10 mm and a polyacrylamide content of 3%; Sample 8: Clay ball with a diameter of 10 mm and a polyacrylamide content of 5%; Sample 9: Clay ball with a diameter of 12 mm and a polyacrylamide content of 0%; Sample 10: Clay ball with a diameter of 12 mm and a polyacrylamide content of 1%; Sample 11: Clay ball with a diameter of 12 mm and a polyacrylamide content of 3%; Sample 12: Clay ball with a diameter of 12 mm and a polyacrylamide content of 5%; Place the above samples in multiple beakers one by one, and record the data of the hydration rate of the clay ball to obtain the following data table: Table 1: Hydration time and hydration rate of samples 1-4

[0037] Table 2: Hydration time and hydration rate of samples 5-8

[0038] Table 3: Hydration time and hydration rate of samples 9-12

[0039] The experimental conclusions are: The hydration rules of the modified clay balls with different polyacrylamide mass ratios are the same. Generally speaking, they hydrate rapidly at the beginning, then gradually slow down until they no longer hydrate and disintegrate. The hydration rate of the clay balls decreases with the increase of the polyacrylamide mass ratio. The maximum hydration rates of the four clay balls with 0, 1%, 3% and 5% polyacrylamide were 75.1%, 69.2%, 50.2% and 30.8% respectively. The maximum hydration rate decreased with the increase of the mass ratio of polyacrylamide.

[0040] The maximum hydration time of four clay balls with 0, 1%, 3% and 5% polyacrylamide added was 15min, 30min, 50min and 60min respectively. The maximum hydration time increased with the increase of polyacrylamide mass ratio; The diameter has little effect on the hydration rate of clay balls.

[0041] The above experiments prove that in the present invention, waste clay is improved by polyacrylamide to form balls. Under the conditions of ambient temperature of 25±0.5°C and humidity of 20±2%, the hydration rate of clay balls decreases with the increase of polyacrylamide mass ratio; the maximum hydration rate decreases with the increase of polyacrylamide mass ratio; and the maximum hydration time increases with the increase of polyacrylamide mass ratio.

[0042] The above experiments were repeated, and it was concluded that the hydration time of clay balls with a polyacrylamide content of 1% was 25-30 minutes; the hydration time of clay balls with a polyacrylamide content of 3% was 50-60 minutes; and the hydration time of clay balls with a polyacrylamide content of 5% was more than 60 minutes.

[0043] In the description of the present invention, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a clay ball, characterized in that: The following steps are involved: S1: Cut the waste clay into blocks and put them into an oven for drying; S2: breaking the dried clay block into pieces and grinding them into clay powder; S3: taking out part of the clay powder from step S2, adding polyacrylamide and stirring evenly to form modified clay powder; S4: adding water to the modified clay powder, continuing to stir, then forming into balls, and drying to obtain clay balls.

2. The preparation method according to claim 1, characterized in that: In the step S3, the polyacrylamide is anionic, and the molecular weight of the polyacrylamide is 8-10 million.

3. A clay ball, characterized in that: Prepared by the preparation method according to claim 1 or 2.

4. The clay ball according to claim 1, characterized in that: The mass content of polyacrylamide in the clay ball is 1%-5%, and the diameter of the clay ball is 8-12 mm.

5. An application of a clay ball, characterized in that: The clay ball described in claim 3 or 4 is used to stop water in the drilling water barrier layer.

6. A method for predicting the water stop time of a clay ball according to claim 3 or 4, characterized in that: The following steps are involved: S1: selecting clay balls with different mass contents and obtaining the hydration time T1 of the clay balls; S2: Establishing a mechanical model for calculating the falling time of a clay ball in water, and calculating the maximum speed Vmax of the clay ball in water; S3: Establishing a finite element analysis model for the falling clay ball, and further verifying and calibrating the Vmax in step S1 to obtain Vmax'; S4: The preset drilling depth is H, and the estimated time for the clay ball to fall is T2=H / Vmax'; S5: The water stop time is obtained as T3, T3=T1+T2.

7. The prediction method according to claim 6, characterized in that: The mechanical model in step S2 shows that Vmax 2 =(mg-ρV 球 g) / 0.5CDρA; Wherein, m is the mass of the clay ball, in kg; ρ is the liquid density, in kg / m 3 ; V 球 is the volume of the clay ball, in m 3 ; g is the acceleration due to gravity, in m / s2; CD is the drag coefficient, which is generally taken as 0.26 for clay balls; A is the projection area of ​​the sphere in the direction of motion, that is, A=πD2 / 4, in m2; Vmax is the maximum movement speed of the clay ball, in m / s.

8. The prediction method according to claim 7, characterized in that: The clay ball falling finite element analysis model in step S3 is established by COMSOL simulation coupling software.

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