Device and method for testing the adhesion strength between drilling fluid mud cake and well wall

Abstract

The present invention provides a device for testing the adhesion strength between drilling fluid mud cake and well wall, wherein the power device comprises a power part and a clamping part; the mold comprises an upper mold clamping end and a lower mold clamping end; and further comprises two mud cake contact plates, namely an upper mold mud cake contact plate and a lower mold mud cake contact plate. The mud cake obtained through the filtration loss experiment is transferred from the filter paper to the two mud cake contact plates to simulate the adhesion between the drilling fluid mud cake and the well wall. The power device provides a constant stretching rate, and the two mud cake contact plates will move relative to each other under the action of the stretching force. When the stretching force is greater than the adhesion force, the upper and lower mud cake contact plates of the mold will separate from each other, that is, the stretching force is equal to the adhesion force. The present invention has a reliable principle, a simple structure, and strong operability.

Description

Technical Field

[0001] The technical field of the testing method and device of the present invention, in particular, relates to a testing device and method for testing the adhesion strength between a drilling fluid mud cake and a well wall. Background Art

[0002] In today's society, huge energy demand has urged the energy mining industry to develop rapidly. In traditional fossil energy mining, drilling fluid is an indispensable part, and drilling fluid is the blood of the entire mining process. Nowadays, the functional requirements for drilling fluid are getting higher and higher, so the performance research and development of drilling fluid is very in-depth, which requires testing of various physical and chemical properties of drilling fluid. In addition to the conventional filtration loss test of drilling fluid, it is also necessary to test the performance that the drilling fluid mud cake needs to meet. The drilling fluid mud cake is formed on the permeation surface when the drilling fluid is filtered into the formation at a certain temperature and a certain pressure difference. In engineering, it is hoped that the filter cake formed is thin and tough, and has a certain strength itself, but there is little attention to the adhesion strength between the drilling fluid mud cake and the well wall.

[0003] The adhesion strength here refers to the adhesion strength between the mud cake formed by the drilling fluid and the well wall. The mutual attraction between the contact parts of two different substances is called adhesion. This attraction is a manifestation of the mutual attraction between the molecules of the two substances. It is only when the distance between the molecules of the two substances is very small (less than 10 -8 Because from a microscopic point of view, the surface of a solid is often uneven, so the effect of adhesion cannot be shown when two solids come into contact. Since liquids and solids can be in close contact, the effect of adhesion can be shown between liquids and solids. The phenomenon of liquid infiltrating solids is the result of the adhesion in the liquid adhesion layer in contact with the solid. When the adhesion is greater than the cohesive force of the liquid, the liquid will infiltrate the solid.

[0004] During the drilling process, when the drill bit drills through the permeable formation, the liquid column pressure of the drilling fluid is generally always greater than the formation pore pressure. Under the action of the pressure difference, the liquid of the drilling fluid will penetrate into the formation. This characteristic is often called the filtration of the drilling fluid. While the liquid is filtering, the solid particles in the drilling fluid will adhere and deposit on the well wall to form a layer of mud cake. The mud cake can be used as a coating on the surface of the well wall on a macro scale. The stronger the adhesion strength of the mud cake on the well wall, the more obvious the anti-collapse effect, and the more beneficial it is to stabilize the well wall.

[0005] If the adhesion strength between the drilling fluid cake and the well wall is large enough, and a great force is required to separate the drilling fluid cake and the well wall from each other, then the drilling fluid can not only reduce the amount of drilling fluid loss, but also stabilize the well wall, effectively preventing the well wall from collapsing and preventing rock cuttings from falling off.

[0006] However, at present, there are relatively few test methods for mud cake adhesion strength. The more commonly used mud cake performance test methods include mud cake needle penetrometers, but mud cake needle penetrometers mostly test the bonding strength and hardness between the internal molecules of the mud cake itself, and cannot accurately test the adhesion strength between the drilling fluid mud cake and other interfaces, let alone the interaction between the mud cake and the well wall. Compared with the mud cake needle penetrometer, the atomic force microscope can reflect the adhesion strength to a certain extent through the interaction between the tiny probe on the probe and the tiny molecules on the surface of the test sample, but the atomic force microscope has no way to reflect the adhesion between the drilling fluid mud cake and the well wall, and the test price of the atomic force microscope is also very expensive, the test amount is also very small, and the process is relatively cumbersome. For the drilling fluid industry test, the test results are not of practical value. Professor Guo Xiaoyang's team at Southwest Petroleum University invented a scraper experimental device to test the strength of the mud cake. The strength of the mud cake is reflected by the interaction between the scraper and the mud cake. This strength is transmitted to the display through the sensor on the scraper, and finally converted into the strength of the mud cake through the formula. This test method has high accuracy; however, its essence is still to reflect the internal bonding strength of the mud cake.

[0007] In addition, the module method is also a commonly used method for drilling fluid mud cake adhesion strength testing. Although this method can conveniently reflect the adhesion of mud cake to external iron blocks, it is easily interfered by human factors, and the test results are affected by personal observation.

[0008] How can we simply, intuitively and scientifically reflect the interaction between the drilling fluid cake and the wellbore? This is a question worth pondering. If this problem can be solved, it will not only make an important contribution to the evaluation of wellbore stability, but also have a good reference value in the cementing process. Summary of the invention

[0009] In order to solve the above problems, the present invention provides an experimental method and device which are simple in principle, easy to operate, and can measure the adhesion strength between drilling fluid mud cake and well wall.

[0010] The invention provides a testing device for testing the adhesion strength between a drilling fluid mud cake and a well wall, comprising: a power device, a mold, and a data acquisition device.

[0011] The power device adopts the MZ-4000 electronic universal testing machine, which includes a power part and a clamping part. The power part provides a constant stretching rate and a constant pulling force; the clamping part is composed of two upper and lower clamps, which are used for clamping to ensure stability during the stretching process, and there is a sensor on each of the upper and lower clamps to detect the change of force during the stretching process.

[0012] The above-mentioned mold includes a clamped portion and a contact surface portion;

[0013] The clamped part includes upper and lower clamping ends, which are an upper mold clamping end and a lower mold clamping end respectively;

[0014] The contact surface part includes two mud cake contact plates, namely an upper mold mud cake contact plate and a lower mold mud cake contact plate;

[0015] The lower mold clamping end is connected to the lower mold mud cake contact plate, and the upper mold clamping end is connected to the upper mold mud cake contact plate;

[0016] The clamped part is used to clamp with the chuck part of the universal testing machine, which can ensure the stability of the stretching process, and the distance between the two mud cake contact plate templates can be adjusted by adjusting the clamping part to adapt to mud cakes of any thickness; the mold materials are all from the rocks in the target formation used by the drilling fluid, and are made through on-site sampling, selection, processing and polishing, in order to make the test environment close to the real formation.

[0017] The width of the upper mold mud cake contact plate is slightly narrower than that of the lower mold mud cake contact plate, which allows the two mud cake contact plates to avoid contact and friction with each other during the stretching process. The groove of the lower mold mud cake contact plate can be filled with mud cakes generated by various filtration tests.

[0018] The above-mentioned data acquisition device is a universal tensile testing machine control acquisition system, which is connected to the universal testing machine through a circuit. Through interface control, the position relationship between the upper and lower clamping ends can be adjusted, and the stretching rate during the experiment can also be set.

[0019] The utility model also comprises a display, and the data acquisition device is connected to the display through an electric circuit, and the magnitude of the tensile force in the tensile experiment is displayed on the display through a digital display.

[0020] The method for testing the adhesion strength between the drilling fluid mud cake and the well wall includes the following steps:

[0021] Using the mud cake produced by the filter press experiment, transfer the mud cake to the surface of the mud cake contact plate of the lower mold. After flattening, cover the mud cake contact plate of the upper mold on the mud cake contact plate of the lower mold. Place 3 1kg weights on the mold and let it stand for 5 minutes.

[0022] Adjust the chuck of the power device to ensure that the upper chuck and the lower chuck are on the same vertical line;

[0023] When the mud cake is fully fitted with the two mud cake contact plates, remove the weights, transfer the fitted mold to the power device, clamp the upper mold clamping end with the upper chuck, and clamp the lower mold clamping end with the lower chuck;

[0024] Then set the experimental parameters on the power device, observe the change of the pulling force, observe the mold, and stop the experiment when the two mud cakes contact plates slide against each other. Record the maximum process force F (N) during the tensile test and remove the mold; measure the contact area S (cm 2 ), and the adhesion strength e (kPa) is obtained through formula conversion; the specific formula is as follows:

[0025]

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the mud cake obtained through the filtration test is transferred from the filter paper to the two mud cake contact plates of the mold, and the two mud cake contact plates are tightly fitted together under a certain pressure and a certain time, so as to simulate the adhesion between the drilling fluid mud cake and the well wall. After the two mud cake contact plates are stably bonded, a constant tensile rate is provided by the power device of the universal mechanical testing machine, and this rate generates a constant tensile force, which is transmitted to the mold through the clamp. The two mud cake contact plates will move relative to each other under the action of the tensile force, but a force in the opposite direction will be generated under the adhesion of the mud cake. When the tensile force is greater than the adhesion force, the upper and lower mud cake contact plates of the mold will separate from each other. In this process, there is an extreme case, that is, the tensile force is equal to the adhesion force. The universal mechanical testing machine will record the maximum force, that is, the adhesion force. In addition, the adhesion strength of the mud cake at different temperatures can be tested by heating the mold to simulate the adhesion strength of the mud cake at different formation temperatures. The invention has reliable principles, simple structure, strong operability and wide applicability. The device can provide accurate and convenient means and methods for testing the adhesion strength between the drilling fluid mud cake and the well wall to meet the performance requirements of the drilling fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the mud cake adhesion strength detection device of the present invention;

[0028] Figure 2 It is a schematic diagram of the mold structure of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the schemes in the embodiments of the present invention will be described clearly and completely in combination with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0030] like Figure 1As shown, the present invention is a device for testing the adhesion strength of drilling fluid mud cake / well wall, which is mainly composed of three parts, including a mold 3, a power device 2, and a data acquisition device 1. The mold 3 includes a clamped part and a contact surface part;

[0031] The clamped part includes upper and lower clamping ends, which are upper mold clamping end 3-4 and lower mold clamping end 3-1 respectively;

[0032] The contact surface part includes two mud cake contact plates, namely an upper mold mud cake contact plate 3-3 and a lower mold mud cake contact plate 3-2;

[0033] The lower mold clamping end 3-1 is connected to the lower mold mud cake contact plate 3-2, and the upper mold clamping end 3-4 is connected to the upper mold mud cake contact plate 3-3;

[0034] The mold 3 includes two upper and lower mud cake contact plates, which can slide against each other. Since the upper and lower clamping ends are vertical to each other in space, the distance between the two upper and lower clamping ends can be adjusted. The width of the upper mold mud cake contact plate 3-3 is slightly narrower than the width of the lower mold mud cake contact plate 3-2, which allows the two mud cake contact plates to avoid contact with each other and friction during the stretching process. The groove of the lower mold mud cake contact plate 3-2 can be filled with mud cakes produced by various filtration loss experiments.

[0035] The power device 2 adopts the MZ-4000 electronic universal testing machine, which includes a power part and a clamping part. The power part provides a constant stretching rate and a constant pulling force; the clamping part is an upper clamp and a lower clamp, which are used for clamping to ensure stability during the stretching process, and each of the upper clamp and the lower clamp has a sensor for detecting the change of force during the stretching process.

[0036] It also includes a display. The data acquisition device 1 is connected to the display through a circuit. The tension in the tensile test is displayed on the display through a digital display.

[0037] Through the above device, a constant stretching rate is provided through the power device 2 of the universal mechanical testing machine. This rate generates a constant tensile force, which is transmitted to the mold 3 through the clamp. The two mud cake contact plates will move relative to each other under the action of the tensile force, but a force in the opposite direction, i.e., adhesion force, will be generated under the adhesion of the mud cake. When the tensile force is greater than the adhesion force, the upper and lower mud cake contact plates of the mold 3 will separate from each other. In this process, there is a limit case, i.e., the tensile force is equal to the adhesion force. The universal mechanical testing machine will record the maximum force, i.e., adhesion force. The principle of the present invention is reliable, the operability is strong, and the applicability is wide. The device can provide an accurate and convenient means and method for testing the adhesion strength of drilling fluid mud cake to meet the performance requirements of drilling fluid.

[0038] Specific usage:

[0039] Using the mud cakes produced by various filter pressing experiments, the mud cakes are transferred to the surface of the lower mold mud cake contact plate 3-2. After flattening, the upper mold mud cake contact plate 3-3 is gently covered on the lower mold mud cake contact plate 3-2. Then the entire mold 3 is placed flat on the test bench, and then 3 1kg weights are placed on the mold 3 and left to stand for 5 minutes. During this process, the power device 2, i.e., the chuck of the universal mechanical testing machine, is adjusted to ensure that the two chucks are on the same vertical line and that no deviation occurs during the clamping of the mold 3. After the mud cake is fully fitted with the two mud cake contact plates, gently remove the weights, transfer the fitted mold 3 to the universal mechanical testing machine, clamp the upper mold clamping end 3-4 of the upper mold mud cake contact plate 3-3 with the upper chuck, and clamp the lower mold clamping end 3-1 of the lower mold mud cake contact plate 3-2 with the lower chuck; then set the experimental parameters on the universal mechanical testing machine, such as the stretching rate, etc.; after the parameter setting is completed, click to start the experiment, and the change in the tension size can be observed from the display. Observe the mold 3, and stop the experiment when the two mud cake contact plates slide against each other. Record the maximum process force F (N) during the stretching experiment from the display, and remove the mold; measure the contact area S (cm 2 ), and through the formula conversion, the adhesion strength e (kPa) is obtained. The specific formula is as follows:

[0040]

[0041] The following are some experimental test data.

[0042]

[0043] The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for testing the adhesion strength between drilling fluid cake and well wall, characterized in that: A testing device for testing the adhesion strength between a drilling fluid cake and a well wall is used, comprising: a power device (2), a mold (3), and a data acquisition device (1); The power device (2) comprises a power part and a clamping part; the power part provides a constant stretching rate and a constant pulling force; the clamping part comprises an upper clamp and a lower clamp; The data acquisition device (1) is a control acquisition system of the power device (2), which is connected to the power device (2) through a circuit, controls and adjusts the position relationship between the upper chuck and the lower chuck, and sets the stretching rate during the experiment; It also includes a display, and the data acquisition device (1) is connected to the display through an electric circuit, and the magnitude of the tensile force in the tensile test is displayed on the display through a digital display; The mold (3) comprises a clamped portion and a contact surface portion; The clamped part includes upper and lower clamping ends, which are respectively an upper mold clamping end (3-4) and a lower mold clamping end (3-1); The contact surface portion includes two mud cake contact plates, namely an upper mold mud cake contact plate (3-3) and a lower mold mud cake contact plate (3-2); The lower mold clamping end (3-1) is connected to the lower mold mud cake contact plate (3-2), and the upper mold clamping end (3-4) is connected to the upper mold mud cake contact plate (3-3); The width of the upper mold mud cake contact plate (3-3) is narrower than the width of the lower mold mud cake contact plate (3-2); The lower mold mud cake contact plate (3-2) is provided with a groove; The power device (2) adopts an MZ-4000 electronic universal testing machine; The method comprises the following steps: Using the mud cake produced by the filter press experiment, the mud cake is transferred to the surface of the mud cake contact plate (3-2) of the lower mold, and after being flattened, the upper mold mud cake contact plate (3-3) is covered on the lower mold mud cake contact plate (3-2), and a weight is placed on the mold (3) and allowed to stand; Adjust the chuck of the power device (2) to ensure that the upper chuck and the lower chuck are on the same vertical line; After the mud cake is fully fitted with the two mud cake contact plates, the weight is removed, and the fitted mold (3) is transferred to the power device (2), the upper mold clamping end (3-4) is clamped by an upper chuck, and the lower mold clamping end (3-1) is clamped by a lower chuck; Set the experimental parameters on the power device (2), observe the change in the pulling force, observe the mold (3), and stop the experiment when the two mud cake contact plates slide against each other. Record the maximum process force F, N, during the tensile test; remove the mold (3); measure the contact area S, cm, of the mud cake on the two mud cake contact plates 2 ; Through formula conversion, the adhesion strength e, kPa is obtained; the specific formula is as follows: 。

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