Hydrothermal synthetic materials suitable for cementing in ultra-high temperature formations

Abstract

The present invention belongs to the field of oil and gas extraction technology, and specifically relates to a hydrothermal synthetic material suitable for ultra-high temperature formation cementing. The raw material composition, by weight, is as follows: 12.5 to 23 parts of retarder, 180 to 377 parts of solid reactant, 7 to 14 parts of stabilizer, 5 to 8 parts of fluid loss additive, 1 to 3 parts of dispersant, and 0.5 to 1 part of defoamer; the raw material composition, by weight, of the solid reactant is as follows: 68 to 159 parts of calcium hydroxide, 100 parts of silica sand, 11 to 29 parts of microsilica, 0 to 54 parts of coarse α-alumina, 0 to 30 parts of fine α-alumina, and 0 to 7 parts of nano-activated alumina. The present invention obtains a hydrothermal synthetic formula suitable for use in field operations at ultra-high temperatures of 240°C through the optimization of materials and admixtures and the verification of a large number of experiments.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas extraction, and particularly relates to a hydrothermal synthetic material suitable for ultra-high temperature formation cementing. Background Art

[0002] With the dwindling availability of readily recoverable shallow oil and gas resources, the focus of oil and gas exploration and development is gradually shifting to deep and ultra-deep formations. Currently, ultra-deep wells in China exceed 8,000 meters in depth, with bottomhole temperatures and pressures reaching 240°C and exceeding 100 MPa. These extreme downhole environments pose significant challenges to cementing fluids and their associated admixtures. Conventional cement slurry systems, exposed to high temperatures and pressures over time, experience severe strength degradation, pore coarsening, and increased brittleness, making it difficult to guarantee post-cementing quality. Therefore, the research on novel, high-temperature-resistant cementing fluids is becoming increasingly important.

[0003] my country's deep and ultra-deep oil and gas resources amount to 67.1 billion tons of oil equivalent, accounting for 34% of the country's total. Deep and ultra-deep formations have become the primary battlefield for major oil and gas discoveries in the country. Taking the Tarim Basin as an example, oil and natural gas resources buried between 6,000 and 10,000 meters alone account for 83.2% and 63.9% of the total, respectively. Ultra-deep oil and gas resources account for approximately 19% of the global total. In the Shunbei oil and gas field in the Tarim Basin, 41 oil and gas wells have been drilled to vertical depths exceeding 8,000 meters, and four billion-ton oil and gas zones have been identified. Between 2005 and 2013, the number of deep wells completed by CNPC, exceeding 4,000 meters, increased from 189 to 832. Annual drilling of deep and ultra-deep wells has increased rapidly, from 322 and 95 in 2016 to 1,038 and 204 in 2020, respectively. Furthermore, heavy oil and geothermal resources are becoming increasingly important energy development areas. At present, the world's heavy oil reserves exceed 3×10 11 Tons of oil can produce approximately 13 trillion barrels of oil. Currently, sanded Portland cement is a common cement slurry system used for cementing operations in ultra-high-temperature environments, such as deep and ultra-deep wells and heavy oil production wells. This system exhibits certain early-stage high-temperature resistance and is low-cost and easy to operate on-site. However, in long-term ultra-high-temperature environments, sanded Portland cement systems still experience severe high-temperature degradation. To better address the cementing issues in ultra-high-temperature formations, it is necessary to develop a hydrothermal synthesis system suitable for ultra-high-temperature environments. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a hydrothermal synthetic material suitable for cementing in ultra-high temperature formations.

[0005] The formula is as follows: in parts by weight, the raw materials are: 12.5-23 parts of retarder, 180-377 parts of solid reactant, 7-14 parts of stabilizer, 5-8 parts of fluid loss additive, 1-3 parts of dispersant, and 0.5-1 part of defoamer;

[0006] The raw material composition of the solid reactant is as follows: 68-159 parts of calcium hydroxide, 100 parts of silica sand, 11-29 parts of microsilicon, 0-54 parts of coarse α-alumina, 0-30 parts of fine α-alumina, and 0-7 parts of nano-activated alumina.

[0007] Preferably, the raw material composition is as follows, in parts by weight: 12.5 to 23 parts of retarder, 180 to 376.8 parts of solid reactant, 7.7 to 13.6 parts of stabilizer, 5.6 to 7.7 parts of fluid loss additive, 1.0 to 2.6 parts of dispersant, and 0.6 to 1 part of defoamer;

[0008] The raw material composition of the solid reactant is as follows: 68.6 to 158.4 parts of calcium hydroxide, 100 parts of silica sand, 11.4 to 28.7 parts of microsilicon, 0 to 53.4 parts of coarse α-alumina, 0 to 29.9 parts of fine α-alumina, and 0 to 6.4 parts of nano-activated alumina.

[0009] The retarder is HX-36L or BCR-300L.

[0010] The retarder accounts for 7-8% of the total mass of the solid reactant I.

[0011] The stabilizer is a high-temperature resistant suspension stabilizer HX-16S; the fluid loss additive is a high-temperature resistant fluid loss additive HX-12L; and the dispersant is a dispersant USD-1.

[0012] The underlying mechanism of this invention is that calcium oxide and silicon oxide undergo a hydration reaction at high temperatures to produce a material with a certain strength, which is suitable for cementing operations. However, the calcium oxide in the calcium oxide reacts too vigorously with water, generating a large amount of heat, causing the slurry to thicken rapidly and becoming unsuitable for field operations. Therefore, the inventors conducted experimental research and ultimately used calcium hydroxide.

[0013] The present invention not only utilizes α-alumina to improve the high-temperature stability of the formula, but also allows aluminum compounds to participate in the hydration reaction, and adds more active nano-activated alumina to the formula. Experiments have shown that the combination of the two can greatly improve the performance of the formula.

[0014] In this invention, α-alumina with two different particle sizes, as well as a combination of silica sand and microsilica, utilizes the principle of close packing, whereby fine material fills the gaps between coarse particles, making the material more compact and thus improving the performance of the final formulation. The stabilizer used in this invention is the high-temperature-resistant suspension stabilizer HX-16S, produced by OMEC Petroleum Technology Co., Ltd.; the fluid loss additive is the high-temperature-resistant fluid loss additive HX-12L; the defoamer is the defoamer G603, produced by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.; and the dispersant is the dispersant USD-1, produced by Weihui Chemical Co., Ltd.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Hydrothermal synthesis materials have been the focus of research on ultra-high temperature formations and geothermal well cementing materials in recent years, but current research is basically concentrated on theoretical research. The present invention obtains a hydrothermal synthesis formula that can be applied to field operations through the optimization of materials and admixtures and the verification of a large number of experiments.

[0017] 2. The key difficulty and innovation of the present invention lies in the study of the hydrothermal synthesis formula at an ultra-high temperature of 240°C, a temperature that has not yet been reached in research. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Thickening time (a) and thickening time summary diagram (b) of each formula with different retarder types and dosages;

[0019] Figure 2 The compressive strength and Young's modulus of each formula (a) and water permeability data (b);

[0020] Figure 3 This is a comparison chart of the compressive strength data of the preferred high-temperature resistant formula. DETAILED DESCRIPTION

[0021] 1. Raw materials and experimental methods

[0022] 1.1 Raw materials

[0023] Calcium hydroxide was produced by Sinopharm Chemical Reagent Co., Ltd.; silica sand was produced by Henan Tongbai Processing Plant; microsilica was produced by Kuche Tabei Mud Material Co., Ltd.; coarse and fine α-alumina was produced by Guangdong Senxin Industry and Trade Co., Ltd.; and nano-activated alumina was produced by Hubei Huifu Nanomaterials Co., Ltd. The density of each dry powder material was measured using a Quantachrome UltraPYC1200e fully automatic true density analyzer from the United States, and the particle size distribution was measured using a Malvern Mastersizer 2000 laser particle size analyzer from the United Kingdom, as shown in Table 1.

[0024] Table 1 Experimental material properties

[0025]

[0026] The admixtures used in the experiment mainly include: tartaric acid produced by Sinopharm Chemical Reagent Co., Ltd.; high-temperature resistant retarder HX-36L, high-temperature resistant suspension stabilizer HX-16S, and high-temperature resistant fluid loss additive HX-12L produced by OMEC Petroleum Technology Co., Ltd.; high-temperature retarder BCR-300L and defoamer G603 produced by Tianjin PetroChina Boxing Engineering Technology Co., Ltd.; and dispersant USD-1 produced by Weihui Chemical Co., Ltd.

[0027] 1.2 Experimental methods

[0028] (1) Slurry thickening test method

[0029] To ensure that the experimental materials react at a high temperature of 240°C, the thickening time of each formulation needed to be adjusted. The thickening experiments were conducted using a BSRD-8042DG cement slurry high-temperature and high-pressure thickener manufactured by Liaoning Bestread Petroleum Equipment Manufacturing Co., Ltd. (the instrument requires 90 minutes to reach the specified temperature and pressure).

[0030] (2) Sample preparation

[0031] First, the solid and liquid materials were weighed separately. Nano-activated alumina was added to the liquid material and dispersed for ten minutes using an ultrasonic disperser. Then, the solid material was added. Cement slurry was prepared according to API10B-2 standard and poured into a cylindrical steel mold with an inner diameter of 25mm and a height of 70mm. The mold was then placed in a high-temperature and high-pressure curing kettle and cured for 2 days and 30 days (240℃ / 50MPa). After removing the cement stone samples that had been cured at high temperature and high pressure, they were cut at both ends using a core cutter and the end faces were polished to reduce the impact of uneven end faces on subsequent tests. The final sample height was approximately 50mm. The samples used for compressive strength and water permeability were immersed in water before the experiment to ensure they were always saturated.

[0032] (3) Slurry mechanical properties test method

[0033] The compressive strength test was conducted using a UTM5105X microcomputer-controlled universal testing machine from Shenzhen Sansi Zongheng Co., Ltd. The machine was equipped with a video extensometer (MercuryRT series), which can simultaneously measure the horizontal and vertical deformation of the sample to calculate the Young's modulus.

[0034] (4) Water permeability test method

[0035] The water permeability test method is as follows: place the cement stone sample in a core holder, connect the inlet end to a constant pressure and constant speed pump, connect the outlet end to a small glass bottle and place it on a high-precision balance, and cover the liquid surface in the small glass bottle with a layer of silicone oil to reduce water evaporation; under a certain confining pressure and driving pressure, according to the change of the balance reading over time, the volume flow rate of water is calculated by selecting the stable straight line segment (the test results show that the calculated flow rate is very consistent with the inlet flow rate measured by the constant pressure and constant speed pump). Finally, the water permeability can be calculated according to formula (1).

[0036]

[0037] Where: L is the sample length, cm; A is the sample cross-sectional area, cm 2 ;K W is the water permeability, μm 2 ; Q is the water permeability flow rate cm 3 / s, ΔP is the water permeability pressure difference, 0.1MPa; μ W is the gas viscosity, mPa·s;

[0038] 2. Optimization of high temperature resistant retarder

[0039] In order to compare the retarding effects of different retarders more scientifically, the amount of retarder used in this part of the experiment refers to the percentage of the total mass of the solid reactants.

[0040] The experimental formulations are shown in Table 2. The Ca / Al / Si molar ratio for Formulation A1 is 1:2:1, the Ca / Si molar ratio for Formulation A2 is 1:2, and the Ca / Si molar ratio for Formulation A3 is 1:1. The water-to-solid ratio for all three formulations is 0.5. The experiment first optimized the types and dosages of three retarders: tartaric acid, HX-36L, and BCR-300L, based on Formulation A1. The preferred type of retarder was selected, specifically those suitable for hydrothermal synthesis systems. The optimized retarders were then used to test dosages suitable for Formulations A2 and A3.

[0041] Table 2 Experimental formula (based on the amount of silica sand, the amount of each material is converted)

[0042]

[0043] In the early stages of the experiment, it was found that adding a small amount of tartaric acid to formula A1 would destroy the sedimentation stability of the slurry. When the addition amount was 1%, the slurry showed super-retarded setting and did not solidify after 10 hours. Therefore, tartaric acid was eliminated in the early stages of the experiment. Figure 1 As shown (H=HX-36L, B=BCR-300L in the figure).

[0044] Depend on Figure 1 It can be seen that at the same dosage, HX-36L has a better high-temperature retarding effect than BCR-300L. Further research shows that HX-36L is a tetrapolymer retarder, while BCR-300L is a ternary copolymer retarder. Generally speaking, the comprehensive performance of tetrapolymer retarders is better than that of ternary copolymer retarders, including rheological properties, high temperature resistance and salt resistance. Therefore, HX-36L has a better high-temperature retarding effect, and the fluidity of the slurry is better after adding HX-36L (21-27Bc). Therefore, HX-36L is the most suitable retarder for the hydrothermal synthesis system among the three retarders. The dosage of formulas A2 and A3 was further optimized using HX-36L, and the optimal dosage of HX-36L in formulas A1, A2 and A3 was finally obtained to be 7-8% (the percentage of retarder to the total mass of solid reactants) respectively.

[0045] 3. Evaluation of high temperature resistance performance of formula

[0046] The optimized amount of high-temperature retarder HX-36L was added to formulas A1, A2 and A3 to form formulas A1', A2' and A3', which were placed in a high-temperature and high-pressure curing kettle for curing for 2 days and 30 days.

[0047] Table 3 Experimental formula (based on the amount of silica sand, the amount of each material is converted)

[0048]

[0049] The compressive strength, Young's modulus and water permeability of the three formulations after different curing times were tested to evaluate the performance changes of the formulations after 30 days of high temperature curing, thereby evaluating the high temperature stability of the hydrothermal synthetic materials. The test results are as follows: Figure 2 shown.

[0050] Depend on Figure 2 It can be seen that:

[0051] (1) The performance of formula A1' is far superior to that of the other two formulas. Since formula A1' contains α-alumina and nano-activated alumina of different particle sizes, while A2' and A3' do not contain alumina, it can be seen that α-alumina and nano-activated alumina can greatly improve the performance of the hydrothermal synthesis system.

[0052] (2) Formulations A2' and A3' have different calcium-silicon ratios and do not contain alumina, but the test results show that the performance of the two is similar, indicating that the molar ratio has no significant effect on the performance of the formulation.

[0053] (3) After 30 days of high-temperature curing, the performance changes of the three formulations were very small, indicating that the hydrothermal synthesis system has excellent high-temperature stability.

[0054] (4) The final optimized hydrothermal synthesis system formula is A1': 77.4 parts of calcium hydroxide + 100 parts of silica sand + 25.6 parts of microsilica + 17.1 parts of coarse α-alumina + 29.9 parts of α-alumina + 6.4 parts of nano-activated alumina + 10.3 parts of stabilizer + 7.7 parts of fluid loss additive + 2.6 parts of dispersant + 0.9 parts of defoamer + 20.5 parts of retarder.

[0055] 4. Optimal high temperature resistant formula

[0056] As shown in Sections 2 and 3, formulation A1' performed the best of the three. Because A1''s Ca / Al / Si molar ratio is 1:2:1, two other formulations were designed to further investigate the properties of this type of formulation. Neither A11' nor A12' contains nano-activated alumina or fine α-alumina. A11' contains even less microsilicon, while A12' has the same microsilicon content as A1'. However, all three formulations maintain a Ca / Al / Si molar ratio of 1:2:1. The specific formulations are shown in Table 4.

[0057] Table 4 High temperature resistant optimal experimental formula

[0058]

[0059] A11' and A12' were cured at 240℃ for 2 days and 30 days, and their compressive strength was measured. Compared with A1', the following results were obtained: Figure 3 shown.

[0060] Depend on Figure 3 As can be seen, all three formulations exhibit strong high-temperature stability, with compressive strength showing little change after 30 days of curing at 240°C. Formulation A11' has a lower microsilica content, resulting in lower compressive strength. Compared to A12', A1' utilizes finer α-alumina and nano-activated alumina, resulting in the highest compressive strength. Overall, however, all three formulations exhibit strong high-temperature stability.

Claims

1. Hydrothermal synthetic material suitable for ultra-high temperature formation cementing, characterized by: In parts by weight, its raw material composition is: 20.5 parts of retarder, 256.4 parts of solid reactants, 10.3 parts of stabilizer, 7.7 parts of fluid loss additive, 2.6 parts of dispersant, 0.9 parts of defoamer; The raw material composition of the solid reactant is, by weight, 77.4 parts of calcium hydroxide, 100 parts of silica sand, 25.6 parts of microsilica, 17.1 parts of coarse α-alumina, 29.9 parts of fine α-alumina, and 6.4 parts of nano-activated alumina; the elemental molar ratio of Ca / Al / Si is 1:2:1; the D50 of the coarse α-alumina is 55.5 μm, the D50 of the fine α-alumina is 9.0 μm, and the D50 of the nano-activated alumina is 0.013 μm; The retarder is HX-36L; the stabilizer is the high-temperature resistant suspension stabilizer HX-16S; the fluid loss additive is the high-temperature resistant fluid loss additive HX-12L; and the dispersant is dispersant USD-1.

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