Cementing fluids and their applications

Abstract

This invention relates to the field of oil and gas well development technology, and discloses a cementing fluid and its application. The cementing fluid comprises the following components: modified metakaolin, activator, fluid loss reducer, and latex. The cementing fluid provided by this invention possesses low fluid loss and gas channeling prevention properties. While leveraging the advantages of geopolymer properties, it overcomes the problem of poor slurry working performance. The cementing fluid provided by this invention contains a fluid loss reducer and latex, significantly reducing fluid loss and improving gas channeling prevention. Under conditions ranging from room temperature to 120°C, the fluid loss is ≤15mL in 30 minutes, the SPN value is less than 4.5, and after 7 days of curing at room temperature, the 24-hour compressive strength reaches 14-20MPa.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well development technology, specifically to a cementing fluid and its application. Background Technology

[0002] Geopolymers, due to their environmental friendliness and superior properties compared to conventional silicate cement (OPC)-based materials, have been a prominent research topic for new materials researchers since their introduction by French scientist Davidovits in 1985. They are widely considered a substitute for silicate cement. Geopolymers are a three-dimensional network structure of silicate-alumina cementitious materials composed of [SiO4]4- and [AlO4]5- structural units, formed by alkali-active aluminosilicate materials such as metakaolinite under the action of an alkali activator. Compared to other commonly used hydraulic materials, geopolymer materials have significant advantages. Their preparation process can reduce energy consumption by more than 70% and carbon emissions by more than 80% compared to traditional cement, with no sulfur or nitrogen oxide emissions. Geopolymers are also known as "green cement." The three-dimensional network structure of geopolymer raw materials endows them with a series of superior properties: high-temperature stability, mechanical properties, corrosion resistance, and durability, making them a highly promising non-traditional cementitious material.

[0003] While geopolymers have been extensively studied in the construction industry and their superior performance has been demonstrated, their application in cementing is still in its early stages. Because the cementing and construction industries have different performance requirements, the application of geopolymers in cementing requires the development of a series of performance regulation technologies, especially in areas such as gas channeling prevention and fluid loss reduction, which need further optimization to suit specific working conditions.

[0004] Water loss in cement slurry is crucial for the safety and quality of cementing operations. Low water loss effectively reduces contamination of the producing formation, protects effective seepage channels around the well, and its good sealing properties effectively prevent gas channeling, increase production capacity, and ensure stable production of oil and gas wells in the later stages. However, there are currently no reports on technologies for controlling water loss and preventing gas channeling in geopolymer systems. Clearly, this lack of technology has become a key constraint on the application of geopolymer materials in cementing engineering. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor water loss reduction and gas channeling prevention capabilities of existing cementing fluids, and to provide a cementing fluid and its application that significantly reduces water loss and improves gas channeling prevention capabilities.

[0006] To achieve the above objectives, the first aspect of the present invention provides a cementing fluid comprising the following components: modified metakaolin, activator, fluid loss reducer, and latex.

[0007] A second aspect of the present invention provides an application of the cementing fluid provided by the present invention in cementing.

[0008] The beneficial effects that can be obtained by the present invention through the above technical solution include:

[0009] The cementing fluid provided by this invention comprises a fluid loss reducer, latex, activator, and modified metakaolin material. The fluid loss reducer regulates the system's viscosity and fluid loss. The latex and fluid loss reducer work synergistically to further reduce the system's fluid loss and provide anti-channeling, anti-corrosion, and improved mechanical properties of the cement stone. Additionally, the latex improves the brittleness and interfacial bonding of the geopolymer, reducing the formation of microcracks in the geopolymer. The geopolymer material, as the main body of the system, ensures mechanical properties, corrosion resistance, and durability. The latex, fluid loss reducer, activator, and modified metakaolin material work together to give the cementing fluid excellent fluid loss and anti-gas channeling properties. This cementing fluid exhibits a fluid loss of ≤15mL in 30 minutes at temperatures ranging from room temperature to 120℃, and an SPN value of less than 4.5. Furthermore, after hardening, this cementing fluid has strong toughness; after 7 days of curing at room temperature, its 24-hour compressive strength can reach 14-20MPa. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] The first aspect of the present invention provides a cementing fluid, wherein the cementing fluid comprises the following components: modified metakaolin, activator, fluid loss reducing agent and latex.

[0012] According to the present invention, preferably, the cementing fluid comprises the following components in parts by weight: 80-100 parts modified metakaolin, 3-8 parts activator, 3-8 parts fluid loss reducer, and 5-25 parts latex.

[0013] More preferably, the cementing fluid contains the following components in parts by weight: 95-100 parts modified metakaolin, 5-6 parts activator, 7-8 parts fluid loss reducer, and 8-15 parts latex.

[0014] In some embodiments provided by this invention, the fluid loss reducing agent can regulate the viscosity and fluid loss of the system. The latex and the fluid loss reducing agent work together to form a thin film between cement particles, blocking the pores of the filter cake, reducing fluid loss, and playing a role in preventing channeling, preventing corrosion, and improving the mechanical properties of cement stone, thus achieving a good synergistic effect. In addition, the latex can also improve the brittleness and interfacial bonding properties of the geopolymer, reducing the generation of microcracks in the geopolymer. The geopolymer material, as the main body of the system, ensures mechanical properties, corrosion resistance, and durability. By limiting the weight proportions of each component within this range, the cementing fluid has excellent fluid loss and gas channeling prevention properties.

[0015] According to the present invention, preferably, the activator is an aqueous solution containing at least one selected from sodium hydroxide, sodium silicate, sodium metasilicate, calcium sulfate, sodium carbonate, and triethanolamine; more preferably, it is an aqueous solution containing sodium hydroxide and / or sodium silicate.

[0016] According to a specific embodiment of the present invention, preferably, the activator is an aqueous solution containing sodium hydroxide and sodium silicate, wherein, based on the total volume of the activator, the concentration of sodium hydroxide in the activator is 2-6 mol / L and the concentration of sodium silicate is 1-6 mol / L.

[0017] According to the present invention, preferably, the modified metakaolinite contains crystalline characteristic peaks and amorphous characteristic peaks in the XRD spectrum of 2θ in the range of 15-30°, and the modified metakaolinite with this characteristic has hydration reaction activity.

[0018] According to the present invention, preferably, the method for preparing the modified metakaolin includes: calcining the metakaolin at 600°C to 850°C for 1-2 hours.

[0019] Preferably, the preparation method of the modified metakaolin includes: calcining metakaolin in air at 600°C to 850°C for 1-2 hours using a high-temperature tube furnace, followed by cooling. This invention uses a high-temperature tube furnace to calcine and activate metakaolin to form modified metakaolin, i.e., a graded-cured metakaolin geopolymer material.

[0020] According to the present invention, preferably, the water loss reducing agent is selected from at least one of modified cellulose, nonionic polymer water loss reducing agent and anionic polymer water loss reducing agent;

[0021] Preferably, the water loss reducing agent is a modified cellulose and / or a nonionic polymer water loss reducing agent.

[0022] According to a specific embodiment of the present invention, preferably, the water loss reducing agent is a modified cellulose and a nonionic polymer water loss reducing agent, wherein the weight ratio of the modified cellulose and the nonionic polymer water loss reducing agent is (5-7):1, more preferably (6.5-7):1.

[0023] According to a specific embodiment of the present invention, preferably, the modified cellulose is selected from at least one of carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and carboxymethyl hydroxyethyl cellulose (CMHEC); preferably, it is carboxymethyl hydroxyethyl cellulose.

[0024] According to a specific embodiment of the present invention, preferably, the nonionic polymer dehydration agent is PVA (polyvinyl alcohol) with a weight-average molecular weight of 170,000-220,000 g / mol.

[0025] According to the present invention, preferably, the latex is selected from at least one of carboxylated styrene-butadiene latex, acrylic latex, styrene-acrylic latex, and polyvinyl alcohol latex.

[0026] According to a specific embodiment of the present invention, preferably, the latex is a carboxylated styrene-butadiene latex.

[0027] Preferably, the density of the latex is 0.9-1 g / cm³. 3 Its viscosity is approximately 10-20 mPa·s (25℃).

[0028] A second aspect of the present invention provides an application of the cementing fluid provided by the present invention in cementing.

[0029] It can be injected into the annulus of oil and gas wells as a cementing fluid to seal the annular space between the casing and the well wall, thereby isolating the oil, gas and water layers and making the casing a channel for oil and gas to enter the well.

[0030] The activator components and mass ratios used in Examples 1-5 and Comparative Examples 1-3 are as follows: Based on the total volume of the activator, the concentration of sodium hydroxide in the activator is 4 mol / L; the concentration of sodium silicate is 3 mol / L.

[0031] The modified metakaolin used in Examples 1-6 and Comparative Examples 1-3 was prepared by calcining metakaolin in air at 650°C for 1.5 hours in a high-temperature tube furnace, followed by cooling to obtain modified metakaolin.

[0032] Example 1

[0033] Weigh out 3 parts by weight of water-loss reducing agent (2.5 parts CMHEC, 0.5 parts PVA with a weight-average molecular weight of 170,000 g / mol) and 10 parts by weight of latex (density 0.9 g / cm³). 3 A cementing fluid is prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) and 6 parts of activator, and then mixing it with 100 parts of modified metakaolin.

[0034] Example 2

[0035] Weigh out 4 parts of water loss reducing agent (3.5 parts of CMHEC, 0.5 parts of PVA with a weight-average molecular weight of 170,000 g / mol) and 5 parts of latex (density 0.9 g / cm³). 3 A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) with 6 parts of activator and then mixing it with 100 parts of modified metakaolin.

[0036] Example 3

[0037] Weigh out 8 parts of water loss reducing agent (7 parts of CMHEC, 1 part of PVA with a weight-average molecular weight of 170,000 g / mol) and 15 parts of latex (density 0.9 g / cm³). 3 A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) with 6 parts of activator and then mixing it with 100 parts of modified metakaolin.

[0038] Example 4

[0039] The preparation method of Example 3 is the same, except that the weight ratios of the water-reducing agent and the latex are different, as detailed below:

[0040] Weigh out 3 parts of the water loss reducing agent (13 parts of CMHEC and 2 parts of PVA with a weight-average molecular weight of 170,000 g / mol) and 15 parts of latex (density 0.9 g / cm³). 3 A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) with 6 parts of activator and then mixing it with 100 parts of modified metakaolin.

[0041] Example 5

[0042] The preparation method is the same as in Example 3, except that the ratio of CMHEC to PVA in the water loss reducing agent is different, as detailed below:

[0043] Weigh 8 parts of water loss reducing agent (4 parts of CMHEC and 4 parts of PVA with a weight-average molecular weight of 170,000 g / mol) and 15 parts of latex (density 0.9 g / cm³). 3 A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) with 6 parts of activator and then mixing it with 100 parts of modified metakaolin.

[0044] Example 6

[0045] The preparation method is the same as in Example 3, except that the ratio of sodium hydroxide to sodium silicate in the activator is different, as detailed below:

[0046] Weigh out 8 parts of water loss reducing agent (7 parts of CMHEC, 1 part of PVA with a weight-average molecular weight of 170,000 g / mol) and 15 parts of latex (density 0.9 g / cm³). 3A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex with a viscosity of 15 mPa·s at 25℃ and 6 parts of activator (based on the total volume of the activator, the concentration of sodium hydroxide in the activator is 1 mol / L; the concentration of sodium silicate is 6 mol / L) with 100 parts of modified metakaolin.

[0047] Comparative Example 1

[0048] The cementing fluid is prepared by weighing 100 parts of modified metakaolin and mixing it evenly with 6 parts of activator.

[0049] Comparative Example 2

[0050] Weigh 0 parts of water-reducing agent and 10 parts of latex (density 0.9 g / cm³). 3 A cementing fluid was prepared by uniformly mixing 6 parts of carboxylated styrene-butadiene latex (viscosity of 15 mPa·s at 25℃) with 6 parts of activator and then mixing it with 100 parts of modified metakaolin.

[0051] Comparative Example 3

[0052] Weigh 3 parts of fluid loss reducer (2.5 parts of CMHEC, 0.5 parts of PVA with a weight average molecular weight of 170,000 g / mol), 0 parts of latex, and 6 parts of activator, mix them evenly, and then mix them with 100 parts of modified metakaolin to prepare a cementing fluid.

[0053] Test case

[0054] Test method: The performance parameters of the geopolymer cementing fluid system were tested on the samples in accordance with the method of GB / T 19139-2012.

[0055] Activation experiments were conducted on the cementing fluids obtained in Examples 1-6 and Comparative Examples 1-3, with a water-cement ratio of 50% and strength testing under ambient temperature curing conditions for 7 days. The testing methods followed GB / T 19139-2012, and the test data are shown in Table 1 below.

[0056] Table 1 Performance of Geopolymer Cementing Fluid Systems

[0057]

[0058] As shown in Table 1, the geopolymer cementing fluids of Examples 1-6 can achieve control over fluid loss performance and gas channeling prevention performance by combining fluid loss control agents and latex. Compared with the geopolymer cementing fluids of Comparative Examples 1-3, the addition of fluid loss control agents and latex significantly reduced the fluid loss and SPN value of the systems in Examples 1-6. The hydration and hardening process of cement slurry is a process of transformation from liquid to solid, during which a gelling period occurs. The risk of gas channeling is highest when the liquid loses its pressure transmission capacity but has not yet established solid strength. T30Bc is the time required for the cementing fluid to reach a consistency of 30Bc after stirring, which is the time required for the cementing fluid to transform from a liquid to a gelling state. T100Bc is the limit pumpable time required for the cementing fluid to reach a consistency of 100Bc after stirring. Beyond this time, the cement slurry loses its gelling properties, no longer transmits pressure, begins to solidify, and cementing operations can no longer continue. The shorter the time difference between T100Bc and T30Bc, the lower the likelihood of gas channeling and the stronger the system's resistance to gas channeling. The weight ratio of the water loss reducing agent to latex in Example 4 differs from that in Example 3. Compared to Example 3, the water loss and SPN value are slightly increased, and the time difference between T100Bc and T30Bc is longer. The ratio of CMHEC to PVA in the water loss reducing agent in Example 5 differs from that in Example 3. Compared to Example 3, the water loss and SPN value are slightly increased, and the time difference between T100Bc and T30Bc is longer, indicating slightly poorer resistance to gas channeling. Lower water loss means less water loss to the formation, resulting in a lower SPN value, which characterizes the slurry's resistance to gas channeling. This indicates better resistance to gas channeling. Appropriate T100Bc and T30Bc times provide sufficient time for safe construction without the risk of gas channeling due to excessively long hardening times. By controlling the ratio of modified cellulose and nonionic polymer in the water loss control agent, as well as the weight ratio of the water loss control agent to the latex, within a certain range, the water loss control agent and the latex can achieve a good synergistic effect, resulting in better gas channeling prevention performance of the system. Experience shows that when the SPN value of the slurry is below 4.5, the slurry exhibits excellent gas channeling prevention performance.

[0059] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cementing fluid, characterized in that, The cementing fluid comprises the following components: modified metakaolin, activator, fluid loss additive and latex; The cementing fluid comprises the following components in parts by weight: modified metakaolin 80-100 parts, activator 3-8 parts, fluid loss additive 3-8 parts and latex 5-25 parts; The preparation method of the modified metakaolin comprises: calcining metakaolin at 600-850℃ for 1-2h; The activator comprises an aqueous solution of sodium hydroxide and sodium silicate; The concentration of sodium hydroxide in the activator is 2-6mol / L and the concentration of sodium silicate is 1-6mol / L, based on the total volume of the activator; The fluid loss additive is modified cellulose and non-ionic polymer fluid loss additive, wherein the weight ratio of the modified cellulose to the non-ionic polymer fluid loss additive is (5-7):1; The cellulose is carboxymethyl hydroxyethyl cellulose; The non-ionic polymer fluid loss additive is polyvinyl alcohol; The latex is selected from at least one of carboxyl styrene butadiene latex, styrene-acrylate latex and polyvinyl alcohol latex.

2. The cementing fluid of claim 1, wherein, The latex is carboxyl styrene butadiene latex.

3. Use of the cementing fluid of claim 1 or 2 in cementing.

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