A drilling fluid treating agent with interface enhancement and mud cake lubrication functions, and a preparation method and application thereof

Abstract

The present application belongs to the technical field of drilling fluid treating agent, discloses a drilling fluid treating agent with interface enhancement and mud cake lubrication functions, and a preparation method and application thereof, which is composed of fly ash, sodium silicate nine hydrates, modified sodium lignosulfonate and polypropylene fiber, and the mass percentage content of each component is as follows: fly ash 75%-99%, sodium silicate nine hydrates 0.5%-15%, modified sodium lignosulfonate 0.5%-10%, and polypropylene fiber 0.2%-10%. When the amount added in the drilling fluid is 0.5%-1.5%, the cementing strength of the two interfaces can be increased by 30-50 times, the mud cake lubricity can be increased by 90%-97%, and the effects of interface enhancement and reduction of well wall friction are remarkable. When the drilling fluid is drilled to the middle and late horizontal section of the horizontal well, the drilling fluid is added in a certain proportion, which is simple to operate and easy to apply on site.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid treatment agent technology, and relates to a drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions, its preparation method and application. Background Technology

[0002] As conventional oil and gas resource development enters its mid-to-late stages, the development of unconventional tight reservoirs has gradually become a focus. For these reservoirs, horizontal well fracturing is the most common method of extraction. Due to the characteristics of the horizontal well structure, the tubing string makes extensive contact with the lower wellbore under gravity, increasing displacement resistance in the lower annulus. The residual drilling fluid that cannot be effectively displaced leads to a thicker mud cake on the wellbore. This causes increased friction, torque, and drill string wear in the horizontal section, increasing the risk of stuck pipe and severely impacting drilling safety and extension limits. Furthermore, the thick mud cake on the wellbore has poor compatibility with cement slurry; their affinity is purely physical, preventing proper bonding with the cement sheath. This results in decreased interfacial bonding strength, reduced cementing quality, and ultimately, annular seal failure, flow channeling, and dangerous accidents. It also affects the effectiveness of subsequent fracturing. In summary, tubing string friction and low interfacial bonding strength are the main factors restricting the development of horizontal well technology.

[0003] Currently, oilfield operations typically address horizontal well tubing friction by adding lubricants to the drilling fluid. Commonly used lubricants include asphalt and oil-based liquid lubricants. In the initial stages of horizontal well drilling, these lubricants are highly effective, often reducing the viscosity coefficient of the mud cake to below 0.2. However, as drilling progresses into the later stages, the increased solid content in the drilling fluid diminishes the effectiveness of asphalt and oil-based liquid lubricants. Furthermore, excessive oil-based liquid lubricants can weaken the mud cake on the wellbore, increasing the risk of stuck pipe. To address the issue of poor interfacial bonding strength, high-efficiency drilling fluid flushing is typically used to improve cleaning efficiency, reduce drilling fluid residue on the wellbore, and decrease mud cake thickness; or the density difference between the drilling fluid and cement slurry can be increased to improve displacement efficiency. However, these methods cannot completely remove the drilling fluid mud cake from the wellbore and completely replace the cement slurry. The immiscibility of these two components results in poor affinity between the wellbore and the cement sheath, inevitably leading to a decrease in interfacial bonding strength.

[0004] In summary, oilfields typically improve the lubricity of drilling mud cake by first adding asphalt or oil-based liquid lubricants to the drilling fluid, and then improving the interfacial bonding strength by cleaning the mud cake on the well wall during flushing. The two processes are sequential and not carried out simultaneously. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a water-based drilling fluid treatment agent that combines interface enhancement and mud cake lubrication functions. This treatment agent is simple to use; it can be directly added to the drilling fluid to increase the cementing interface strength and simultaneously improve the lubricity of the mud cake. It also achieves good solidification and bonding between the mud cake and cement slurry on the wellbore and reduces wellbore friction, thereby improving interface bonding strength and increasing drilling speed.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] This water-based drilling fluid treatment agent, which combines interface enhancement and mud cake lubrication functions, is a solid micro powder composed of fly ash, sodium silicate nonahydrate, modified sodium lignosulfonate, and polypropylene fiber. The mass percentage content of each component is as follows: fly ash 75%-99%, sodium silicate nonahydrate 0.5%-15%, modified sodium lignosulfonate 0.5%-10%, and polypropylene fiber 0.2%-10%.

[0008] In the above scheme, the particle size of fly ash is 100-500 mesh, preferably 120-400 mesh.

[0009] In the above scheme, the modified sodium lignin sulfonate has a pH of 7-9.

[0010] In the above scheme, the length of polypropylene fiber is 1.5-200nm, preferably 60-150nm.

[0011] The water-based drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions described above is a mixture of fly ash, sodium silicate nonahydrate, modified sodium lignosulfonate, and polypropylene fiber. During preparation, the four materials are stirred and mixed evenly in a mixer according to their respective content ratio requirements. The resulting treatment agent is then added directly to the drilling fluid according to the required dosage. There is no specific order in the mixing and preparation process.

[0012] The advantages of this invention compared to existing technologies are:

[0013] (1) The water-based drilling fluid treatment agent provided by the present invention, which has both interface enhancement and mud cake lubrication functions, can increase the bonding strength of the cementing interface by 30-50 times and improve the mud cake lubrication by 90%-97% when added to the drilling fluid at a dosage of 0.5%-1.5%. The interface enhancement and well wall friction reduction effects are significant.

[0014] (2) The water-based drilling fluid treatment agent provided by the present invention, which has both interface enhancement and mud cake lubrication functions, is added to the drilling fluid in a certain proportion during the middle and late stages of drilling to the horizontal section of a horizontal well. It is simple to operate and easy to apply in the field.

[0015] (3) The water-based drilling fluid treatment agent provided by this invention, which has both interface enhancement and mud cake lubrication functions, costs RMB 800-4000 per ton. Based on an addition of 0.5%-1.5%, the cost of adding it to each cubic meter of drilling fluid is approximately RMB 10-70, which is relatively low. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the embodiments. The examples described below are merely preferred embodiments of the present invention. It should be noted that the following description is only for explaining the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention. Unless otherwise specified, the materials and reagents used in the following embodiments are obtained commercially.

[0017] Example 1:

[0018] This water-based drilling fluid treatment agent, which combines interface enhancement and mud cake lubrication functions, is composed of fly ash, sodium silicate nonahydrate, modified sodium lignosulfonate, and polypropylene fiber. The mass percentage content of each component is as follows: fly ash 97%, sodium silicate nonahydrate 1%, modified sodium lignosulfonate 1%, and polypropylene fiber 1%. After the above solid powders are thoroughly mixed, they are added to the drilling fluid at a dosage of 0.8% (mass ratio). After thorough mixing, a high-temperature and high-pressure filtration test (3.5 MPa, 95℃) is conducted to prepare mud cake. The filtration loss, viscosity, and lubricity of the mud cake are measured. An interface bonding simulation experiment is also conducted to measure the interface bonding strength. The results are shown in Tables 1, 2, and 3.

[0019] Table 1 Evaluation of the interfacial bonding performance of the drilling fluid treatment agent of the present invention

[0020]

[0021] Table 2 Evaluation of mud cake lubrication performance of the drilling fluid treatment agent of the present invention

[0022]

[0023] Table 3. Effects of the drilling fluid treatment agent of the present invention on drilling fluid performance.

[0024]

[0025] Example 2:

[0026] This water-based drilling fluid treatment agent, which combines interface enhancement and mud cake lubrication functions, is composed of fly ash, fast-dissolving sodium silicate, modified sodium lignosulfonate, and polypropylene fiber. The mass percentage content of each component is as follows: fly ash 97%, sodium silicate nonahydrate 0.5%, modified sodium lignosulfonate 1%, and polypropylene fiber 1.5%. After the above solid micro powders are thoroughly mixed, they are added to the drilling fluid at a dosage of 1.0% (mass ratio). After thorough mixing, a high-temperature and high-pressure filtration test (3.5 MPa, 95℃) is conducted to prepare mud cake. The filtration loss, viscosity, and lubricity of the mud cake are measured. An interface bonding simulation experiment is also conducted to measure the interface bonding strength. The results are shown in Tables 4, 5, and 6.

[0027] Table 4 Evaluation of the interfacial bonding performance of the drilling fluid treatment agent of the present invention

[0028]

[0029] Table 5 Evaluation of mud cake lubrication performance of the drilling fluid treatment agent of the present invention

[0030]

[0031] Table 6. Effects of the drilling fluid treatment agent of the present invention on drilling fluid performance.

[0032]

[0033] Comparative Example 1:

[0034] Add 2% saponified oil liquid lubricant to the drilling fluid, stir thoroughly, and then conduct a high-temperature and high-pressure filtration test (3.5 MPa, 95℃). Filter the fluid to prepare mud cake, and measure the lubricity of the mud cake. The results are shown in Table 7.

[0035] Table 7 Comparison of mud cake lubrication performance before and after adding liquid lubricant.

[0036]

[0037] Comparative Example 2:

[0038] 0.8% graphite powder was added to the drilling fluid and stirred thoroughly. A high-temperature and high-pressure filtration test (3.5 MPa, 95℃) was then conducted to prepare mud cakes. The lubricity of the mud cakes was measured, and the results are shown in Table 8.

[0039] Table 8 Comparison of lubrication performance of mud cake before and after adding graphite powder

[0040]

[0041] Comparative Example 3:

[0042] After adding 1% of commercially available interface enhancer to the drilling fluid and stirring thoroughly, an interface bonding simulation experiment was conducted to determine the interface bonding strength. The results are shown in Table 9.

[0043] Table 9 Evaluation of the interfacial bonding performance of commercially available interfacial reinforcing agents

[0044]

[0045] As can be seen from Example 1 and Comparative Example 2, at the same dosage, the drilling fluid treatment agent of the present invention improves the mud cake lubrication performance by approximately three times that of graphite. As can be seen from Examples 1 and 2 and Comparative Example 1, compared to the saponified oil liquid lubricant at a higher dosage (2%), the drilling fluid treatment agent of the present invention improves the mud cake lubrication performance by approximately 4 percentage points at a lower dosage (0.8%-1%), indicating that the drilling fluid treatment agent of the present invention can reach or even exceed the lubrication performance of conventional liquid lubricants at a lower dosage. The above results indicate that the drilling fluid treatment agent of the present invention has the characteristics of low dosage and high mud cake lubrication performance.

[0046] Table 4 in Example 1 and Table 9 in Comparative Example 3 show the interfacial bonding strength measured based on the interfacial bonding experiment. The data analysis shows that, under the same dosage, the interfacial bonding strength of the drilling fluid treatment agent of the present invention is increased by 2.3 times compared with commercially available interfacial reinforcing agents. The drilling fluid treatment agent of the present invention has good interfacial reinforcing performance.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A drilling fluid treatment agent that combines interface enhancement and mud cake lubrication functions is a solid micro powder, characterized in that, It is composed of fly ash, sodium silicate nonahydrate, modified sodium lignosulfonate, and polypropylene fiber. The mass percentage content of each component is as follows: fly ash 97%, sodium silicate nonahydrate 1%, modified sodium lignosulfonate 1%, and polypropylene fiber 1%; or fly ash 97%, sodium silicate nonahydrate 0.5%, modified sodium lignosulfonate 1%, and polypropylene fiber 1.5%; modified sodium lignosulfonate has a pH of 7-9.

2. The drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions as described in claim 1, characterized in that, The particle size of fly ash is 100-500 mesh.

3. The drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions as described in claim 1, characterized in that, The particle size of fly ash is 120-400 mesh.

4. The drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions as described in claim 1, characterized in that, The length of polypropylene fibers ranges from 1.5 to 200 nm.

5. The drilling fluid treatment agent with both interface enhancement and mud cake lubrication functions as described in claim 1, characterized in that, The length of polypropylene fibers is 60-150 nm.

6. A method for preparing a drilling fluid treatment agent that combines interface enhancement and mud cake lubrication functions, characterized in that, According to the formulation of the drilling fluid treatment agent according to any one of claims 1-5, fly ash, sodium silicate nonahydrate, modified sodium lignosulfonate, and polypropylene fiber are stirred and mixed evenly in a mixer according to their respective content ratio requirements, and there is no specific order in the mixing preparation process.

7. The application of a drilling fluid treatment agent that combines interface enhancement and mud cake lubrication functions, characterized in that, In the middle and late stages of drilling a horizontal well to the horizontal section, a drilling fluid treatment agent according to any one of claims 1-5 is added to the drilling fluid. The amount of drilling fluid treatment agent added is 0.5%-1.5% of the drilling fluid by mass percentage.

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