Low friction cementing system for secondary completion narrow annulus

Abstract

The application relates to a low-friction cement slurry system for secondary completion narrow annulus, which comprises the following components and mass fractions: 100 parts of oil well cement, 30 parts of superfine gelatinable material, 50-80 parts of fresh water, 4-6 parts of powder lightening agent, 1-3 parts of reinforcing agent, 0.3-0.8 parts of dispersing agent, 1.5-3 parts of fluid loss reducer, 0.5-1 part of liquid lightening agent, 6-13 parts of latex, 0-0.5 part of retarder and 0.1-0.3 part of defoaming agent. The low-friction cement slurry system for secondary completion narrow annulus has the characteristics of good rheological property, strong sedimentation stability and low elastic modulus, can significantly reduce the circulating pressure consumption of the cement slurry in the secondary completion narrow annulus cementing construction process, has good cement stone mechanical property, and guarantees the long-term sealing integrity of the cement ring under the repeated fracturing condition of the shale gas well.

Description

Technical Field

[0001] This invention relates to the field of cementing technology in unconventional oil and gas drilling and completion engineering, and more specifically, to a low-friction cement slurry system for narrow annulus in secondary well completion. Background Technology

[0002] Secondary well completion technology, as a means of exploiting remaining reserves in a single well, only requires casing installation, cementing, and fracturing testing within the original wellbore. This significantly reduces construction time and costs. As early as 2017, this technology was applied in over 100 shale gas wells in North America. Cementing in secondary well completion technology differs from conventional formation cementing, primarily in that the annulus size is reduced by 61% compared to conventional formation cementing. Additionally, the original wellbore contains pre-existing perforations and fracturing fractures. The rheological properties of conventional cement slurry can lead to high circulating pressure loss and high construction pump pressure, increasing the risk of leakage and severely limiting the application of conventional cement slurry systems in secondary well completion technology.

[0003] Currently, there is considerable research on narrow annular cementing technology, but less research on low-friction cement slurries for narrow annular wells. Some of these studies primarily focus on low-friction cement slurry systems for ultra-long horizontal well sections, where the annular size is larger than that of secondary completion cementing. Currently, cement slurries for secondary completion cementing in Fuling shale gas wells in China mainly rely on foreign oilfield service companies. Conventional cement slurry systems have poor performance adaptability and pose a risk of cementing loss. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a low-friction cement slurry system for narrow annulus in secondary well completion, which can significantly reduce the pressure loss of cement slurry circulation and the pump pressure during cementing construction, while having good mechanical properties, realizing the localization of cement slurry system for narrow annulus in secondary well completion, and ensuring the long-term sealing integrity of cement annulus under shale gas fracturing conditions.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: Construct a low-friction cement slurry system for narrow annulus in secondary well completion, comprising the following components and their mass fractions: 100 parts oil well cement, 30 parts ultrafine cementitious material, 50-80 parts fresh water, 4-6 parts powder weight-reducing agent, 1-3 parts reinforcing agent, 0.3-0.8 parts dispersant, 1.5-3 parts fluid loss reducing agent, 0.5-1 part liquid weight-reducing agent, 6-13 parts latex, 0-0.5 parts retarder, and 0.1-0.3 parts defoamer.

[0006] According to the above scheme, the ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10μm.

[0007] According to the above scheme, the liquid weight-reducing agent is an alkaline silica sol.

[0008] According to the above scheme, the powder lightening agent is 3M hollow glass microspheres with a density of 0.6 g / cm³.3 Particle size 15-135μm.

[0009] According to the above scheme, the reinforcing agent is silicon dioxide with a particle size of 380-600μm.

[0010] According to the above scheme, the dispersant is one or a mixture of two of polycarboxylic acid polymers or naphthalene sulfonate in any proportion.

[0011] According to the above scheme, the water loss reducing agent is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer.

[0012] According to the above scheme, the latex is styrene-butadiene latex with a solid content of 48%.

[0013] According to the above scheme, the retarder is a mixture of gluconate and boric acid.

[0014] According to the above scheme, the defoamer is a dimethyl silicone oil defoamer.

[0015] The mechanism of this invention is as follows:

[0016] In low-friction cement slurry systems used in narrow annulus well completions, ultrafine cementitious materials and reinforcing agents can effectively fill the spaces between G-grade cement particles, altering the particle packing state of single G-grade cement. Their synergistic effect with dispersants reduces friction between G-grade cement particles, thus improving the rheological properties of the cement slurry. The addition of powder-based weight-reducing agents significantly lowers the liquid-to-solid ratio of the cement slurry. Liquid weight-reducing agents fully fill the gaps between G-grade cement and ultrafine cementitious material particles, significantly improving the settling stability of the cement slurry. Water loss control agents regulate water loss in the cement slurry system. Latex effectively reduces the elastic modulus of cement paste, improving its mechanical properties. Retarder effectively controls the thickening time of the cement slurry. Latex materials generate a large number of air bubbles during cement slurry mixing; defoamers effectively remove these bubbles, preventing them from affecting the density and strength of the cement slurry.

[0017] The low-friction cement slurry system for narrow annulus in secondary well completion according to the present invention has the following beneficial effects:

[0018] 1. The cement slurry system of the present invention has excellent rheological properties, with a flow index n = 0.80-0.89 and a consistency coefficient k = 0.08-0.20 Pa·s. n The cyclic pressure loss is reduced by 75% compared to conventional cement slurry;

[0019] 2. The cement slurry system of the present invention has the advantages of flexible adjustment of density and thickening time, good settling stability, and a density of 1.60 g / cm³. 3 -1.75g / cm 3 Thickening time: 200-400 min; sedimentation stability: 0.015-0.020 g / cm³3 ;

[0020] 3. The cement slurry system of the present invention has good mechanical properties, with a compressive strength of 13.8-20.6 MPa and an elastic modulus of 3.08-4.19 GPa. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0022] Figure 1 This is a distribution diagram of the particle size test results for the ultrafine gelling material in Example 1. Detailed Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0024] Example 1:

[0025] This invention provides a low-friction cement slurry system for narrow annulus well completion, comprising the following components and their masses: 450g oil well cement, 150g ultrafine cementitious material, 390g fresh water, 24g powder weight-reducing agent, 12g reinforcing agent, 3g dispersant, 12g fluid loss reducing agent, 3g liquid weight-reducing agent, 30g latex, 0g retarder, and 1g defoamer; the ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10μm; the liquid weight-reducing agent is alkaline silica sol; and the powder weight-reducing agent has a density of 0.6g / cm³. 3 The product consists of 3M hollow glass microspheres with a particle size of 15-135 μm; the water loss reducing agent is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer; the latex is styrene-butadiene latex with a solid content of 48%; the retarder is a mixture of gluconate and boric acid; and the defoamer is dimethyl silicone oil defoamer.

[0026] The preparation method of the low-friction cement slurry system for narrow annulus in secondary well completion includes the following steps:

[0027] (1) Under room temperature conditions, add and mix oil well cement, ultrafine cementitious material, powder lightening agent and reinforcing agent in sequence. Each material must be stirred evenly before adding the next material. After mixing evenly, prepare the slurry for later use.

[0028] (2) Add fresh water, water loss reducer, liquid weight reducer, latex, retarder and defoamer to the slurry cup in the following order. Stir well after each addition before adding the next material. After mixing well, the slurry preparation solution is ready for use.

[0029] (3) Under the condition of stirring speed of 3000-4000 RPM, add the slurry ash to the slurry preparation agent water within 10-15s and stir until evenly mixed. Then, increase the stirring speed to 10000-12000 rpm and stir for 30-35s.

[0030] Example 2:

[0031] This invention provides a low-friction cement slurry system for narrow annulus well completion, comprising the following components and their masses: 400g oil well cement, 200g ultrafine cementitious material, 360g fresh water, 24g powder weight-reducing agent, 6g reinforcing agent, 3g dispersant, 12g fluid loss reducing agent, 2g liquid weight-reducing agent, 60g latex, 2.4g retarder, and 1g defoamer; the ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10μm; the liquid weight-reducing agent is alkaline silica sol; and the powder weight-reducing agent has a density of 0.6g / cm³. 3 The product consists of 3M hollow glass microspheres with a particle size of 15-135 μm; the water loss reducing agent is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer; the latex is styrene-butadiene latex with a solid content of 48%; the retarder is a mixture of gluconate and boric acid; and the defoamer is dimethyl silicone oil defoamer.

[0032] The preparation method is the same as in Example 1.

[0033] Example 3:

[0034] This invention provides a low-friction cement slurry system for narrow annulus well completion, comprising the following components and their masses: 450g oil well cement, 150g ultrafine cementitious material, 324g fresh water, 6g powder weight-reducing agent, 6g reinforcing agent, 4.8g dispersant, 12g fluid loss reducing agent, 3g liquid weight-reducing agent, 48g latex, 1.6g retarder, and 1g defoamer; the ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10μm; the liquid weight-reducing agent is alkaline silica sol; and the powder weight-reducing agent has a density of 0.6g / cm³. 3 The product consists of 3M hollow glass microspheres with a particle size of 15-135 μm; the water loss reducing agent is an acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer; the latex is styrene-butadiene latex with a solid content of 48%; the retarder is a mixture of gluconate and boric acid; and the defoamer is dimethyl silicone oil defoamer.

[0035] The preparation method is the same as in Example 1.

[0036] The cementing slurry system products obtained in Examples 1 to 3 of the present invention were tested for performance according to the test methods of the petroleum industry standard. The test results are shown in Table 1 below.

[0037] Comparative Example 1:

[0038] This invention provides a low-friction cement slurry system for narrow annulus well completion in secondary wells, comprising 600g oil well cement, 390g fresh water, 24g powder weight-reducing agent, 12g reinforcing agent, 3g dispersant, 12g fluid loss reducing agent, 3g liquid weight-reducing agent, 30g latex, 0g retarder, and 1g defoamer. The liquid weight-reducing agent is alkaline silica sol; the powder weight-reducing agent is 3M hollow glass microspheres with a density of 0.6g / cm³ and a particle size of 15-135μm; the fluid loss reducing agent is acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer; the latex is styrene-butadiene latex with a solid content of 48%; the retarder is a mixture of gluconate and boric acid; and the defoamer is dimethyl silicone oil defoamer.

[0039] Comparative Example 2:

[0040] This invention provides a low-friction cement slurry system for narrow annulus well completion in secondary wells, comprising 450g oil well cement, 150g ultrafine cementitious material, 393g fresh water, 24g powder weight-reducing agent, 12g reinforcing agent, 3g dispersant, 12g fluid loss reducing agent, 30g latex, 0g retarder, and 1g defoamer. The ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10μm; the liquid weight-reducing agent is alkaline silica sol; the powder weight-reducing agent is 3M hollow glass microspheres with a density of 0.6g / cm³ and a particle size of 15-135μm; the fluid loss reducing agent is acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer; the latex is styrene-butadiene latex with a solid content of 48%; the retarder is a mixture of gluconate and boric acid; and the defoamer is dimethyl silicone oil defoamer.

[0041] Table 1 Comparison of Product Performance Parameters in Examples

[0042]

[0043] As can be seen from the test data in Table 1 above, the low-friction cement slurry system for narrow annulus completion described in this invention has the characteristics of adjustable density and thickening time, excellent rheological properties, low elastic modulus, and high compressive strength. It can effectively reduce the circulating pressure loss of the cement slurry system and the pump pressure during cementing operations. At the same time, the reduced elastic modulus can ensure the long-term sealing integrity of the cement annulus during repeated fracturing processes. In Comparative Example 1, no ultrafine cementitious material was added, and the consistency coefficient was significantly improved compared with Examples 1, 2, and 3, indicating that ultrafine cementitious material has a significant impact on improving the rheological properties of cement slurry. In Comparative Example 2, no liquid weight-reducing agent was added, and the consistency coefficient was significantly lower than that of Examples 1-3 and Comparative Example 1, but the settling stability was significantly improved. This indicates that, based on the particle size distribution achieved by G-grade cement, ultrafine cementitious material, and reinforcing agent, the addition of liquid weight-reducing agent can significantly improve the settling stability of cement slurry.

[0044] The present invention performs particle size testing on the ultrafine gelatinizable material in Example 1, and the results of the particle size analysis are shown in [the table below]. Figure 1 The particle size distribution diagram shows that the ultrafine cementitious material in Example 1 has a small particle size, which can effectively fill the gaps between oil well cement particles, and ensure the settling stability of the system while improving the rheological properties of the cement slurry system.

[0045] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A low-friction cement slurry system for narrow annulus in secondary well completion, characterized in that, The product comprises the following components, by weight: 100 parts oil well cement, 30 parts ultrafine cementitious material, 50-80 parts fresh water, 4-6 parts powder weight-reducing agent, 1-3 parts reinforcing agent, 0.3-0.8 parts dispersant, 1.5-3 parts water loss reducing agent, 0.5-1 part liquid weight-reducing agent, 6-13 parts latex, 0.2-0.5 parts retarder, and 0.1-0.3 parts defoamer. The ultrafine cementitious material is ultrafine cement with a particle size of 6.5-10 μm. The liquid weight-reducing agent is alkaline silica sol. The powder weight-reducing agent is 3M hollow glass microspheres with a density of 0.6 g / cm³. 3 The particle size is 15-135μm, the reinforcing agent is silica with a particle size of 380-600μm, the dispersant is one or a mixture of two of polycarboxylic acid polymers or naphthalene sulfonate in any proportion, the water loss reducing agent is acrylamide / 2-acrylamide-2-methylpropanesulfonic acid copolymer, the latex is styrene-butadiene latex, the retarder is a mixture of gluconate and boric acid, and the defoamer is dimethyl silicone oil defoamer.

2. The low-friction cement slurry system for narrow annulus in secondary well completion according to claim 1, characterized in that, The solid content of the styrene-butadiene latex is 48%.

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