An interface enhancer for improving the cementing quality of the second interface in high carbon dioxide-containing oil and gas reservoirs and its application

Abstract

The present invention discloses an interface enhancer for improving the cementing quality of the second interface in high-carbon dioxide oil and gas reservoirs and its application. The mass fraction composition of the interface enhancer is as follows: 35 to 50 parts of a curing enhancer, 7 to 15 parts of a curing reactant, 30 to 45 parts of a curing adjuvant, 7 to 13 parts of an anti-pollution agent, and 1 to 5 parts of a high-efficiency dispersant; the curing enhancer is at least one of aluminum silicate fiber, calcium silicate fiber, glass fiber, calcium carbonate whisker, and magnesium carbonate whisker; the length of the curing enhancer is not more than 8 mm. Through comprehensive actions such as curing, plugging, toughening, and repairing, the interface enhancer of the present invention can significantly reduce filtrate loss, improve the density of the filter cake and the curing ability, effectively improve the cementing ability of the cement sheath interface in well cementing, and ensure the integrity of the wellbore seal.

Description

Technical Field

[0001] The present invention relates to an interface enhancer for improving the cementing quality of the second interface in high CO₂-containing oil and gas reservoirs and its application, belonging to the field of additives for preflush fluids in oil well cementing engineering. Background Art

[0002] The world's major oil and gas resources come from marine oil and gas reservoirs, which are characterized by deep burial, high pressure, and high content of acidic gases such as CO₂. In the environment of high CO₂ gas fields, due to the corrosion of CO₂, the sealing of the second interface of the cement sheath will fail, forming a channel for downhole fluid flow, threatening production safety. The second interface of cementing is the weakest and most critical part during the construction of oil and gas wells. Therefore, ensuring the sealing quality of the second interface of cementing is a key technology for facilitating later stratified production and management and preventing safety problems such as annular gas channeling, oil leakage, and gas leakage. Since the drilling fluid is easily contaminated by contacting the cement slurry, the residual drilling fluid filter cake and the cement slurry form a cementing strength at the second interface approaching 0, which seriously affects the cementing quality and the subsequent production operation. At the same time, under the long-term scouring and corrosion of formation CO₂ fluid, the micro-annuli and micro-cracks at the second interface of cementing will gradually expand, resulting in the failure of the sealing performance of the sealing system, and further leading to serious consequences such as interlayer flow and annulus pressure.

[0003] Therefore, both domestic and foreign countries attach great importance to the development of interface enhancers for improving the cementing quality of the second interface. For example, Chinese invention patent 202210042635.2 discloses an erosion-resistant interface enhancer for cementing in coalbed methane wells, its preparation method and application. This interface enhancer is composed of a compound solution prepared with 0.1% surfactant CAEO-15 and 0.3% silane coupling agent as solutes and fresh water and absolute ethanol as solvents, which has an improvement effect on the cementing strength and airtightness of the second interface in coal seams. However, this interface enhancer cannot solidify the drilling fluid filter cake, and the mechanical strength of the filter cake is relatively low, and the cementing at the second interface is easily damaged under stress. Chinese invention patent 201810900364.3 discloses a second interface enhancer for oil wells and its preparation method, and the reaction solution therein is prepared by reacting polyacrylate emulsion, ethylene-vinyl acetate copolymer emulsion, Tween-20, styrene-butadiene copolymer, α-olefin sulfonate, silicone resin polyether emulsion MPS, hydroxyethyl cellulose, and glutaraldehyde at 40-50°C. This reaction solution is a polymer emulsion, which is highly sensitive and has a great influence on the rheology of the cement slurry, and is not conducive to on-site construction application. In addition, the existing technology rarely considers the corrosion of the second interface of cementing by carbon dioxide and the repair of micro-cracks at the second interface in high CO₂-containing gas reservoirs, so the present invention is proposed. Summary of the Invention

[0004] The object of the present invention is to provide an interface enhancer for cementing high-carbon dioxide oil and gas wells. Through comprehensive actions such as curing, toughening, and strengthening the cementing surface, the interface enhancer can significantly reduce filtrate loss, improve the density and curing ability of the filter cake, effectively improve the interface cementing ability of the cement sheath, repair the micro-cracks at the second interface of cementing, and ensure the sealing integrity of the wellbore.

[0005] The interface enhancer for improving the cementing quality of the cementing interface provided by the present invention has the following composition in parts by mass:

[0006] 35 - 50 parts of a curing enhancer, 7 - 15 parts of a curing reactant, 30 - 45 parts of a curing adjuvant, 7 - 13 parts of an anti-pollution agent, 1 - 5 parts of a high-efficiency dispersant;

[0007] The composition in parts by mass of the interface enhancer is preferably any one of the following:

[0008] 1) 36 - 43 parts of a curing enhancer, 10 - 15 parts of a curing reactant, 33 - 42 parts of a curing adjuvant, 7 - 11 parts of an anti-pollution agent, 1 - 3 parts of a high-efficiency dispersant;

[0009] 2) 36 parts of a curing enhancer, 15 parts of a curing reactant, 40 parts of a curing adjuvant, 7 parts of an anti-pollution agent, 2 parts of a high-efficiency dispersant;

[0010] 3) 38 parts of a curing enhancer, 10 parts of a curing reactant, 42 parts of a curing adjuvant, 9 parts of an anti-pollution agent, 1 part of a high-efficiency dispersant;

[0011] 4) 43 parts of a curing enhancer, 10 parts of a curing reactant, 33 parts of a curing adjuvant, 11 parts of an anti-pollution agent, 3 parts of a high-efficiency dispersant.

[0012] The curing enhancer is at least one of aluminum silicate fiber, calcium silicate fiber, glass fiber, calcium carbonate whisker, and magnesium carbonate whisker;

[0013] The length of the curing enhancer is not more than 8 mm.

[0014] In the interface enhancer of the present invention, the curing reactant is at least one of nano-SiO2, slag, red mud, silica fume, metakaolin, and fly ash.

[0015] In the interface enhancer of the present invention, the curing adjuvant is at least one of graphene oxide, nano-calcium carbonate, sisal fiber, asbestos fiber, and steel fiber.

[0016] In the interface enhancer of the present invention, the anti-pollution agent is sodium lauroyl glutamate or sodium dodecyl polyoxyethylene ether sulfate.

[0017] In the interface enhancer of the present invention, the high-efficiency dispersant is powdered polystyrene sulfonic acid.

[0018] When preparing the interfacial enhancer of the present invention, it is only necessary to mix each component evenly.

[0019] Based on the above-mentioned interfacial enhancer, the present invention also provides a drilling fluid for oil and gas wells, which is obtained by adding the interfacial enhancer of the present invention to a conventional drilling fluid, and the addition amount of the interfacial enhancer can be 5-15%.

[0020] The interfacial enhancer and drilling fluid provided by the present invention can improve the cementing strength of the second interface of the well cementing in high-carbon dioxide oil and gas reservoirs, improve the cementing ability of the well cementing cement sheath interface, repair the microcracks of the second interface of the well cementing, and ensure the sealing integrity of the wellbore.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The curing enhancer adopted by the present invention can form a network-like skeleton support structure in the drilling fluid filter cake, improve the microstructure between the components of the filter cake, and thus improve the strength of the filter cake. At the same time, the curing enhancer adopted by the present invention can participate in the cement hydration reaction and carbonation reaction, induce the crystallization of calcium silicate hydrate gel and calcium carbonate in the mud cake, and these crystals form a solidified body structure, so that the strength of the filter cake solidified body is improved.

[0023] 2) The curing reactant adopted by the present invention can interact with the cement slurry and the drilling fluid filter cake, consume calcium hydroxide at the interface between the cement slurry and the filter cake, and form calcium silicate hydrate gel, so that the cement sheath is tightly cemented with the solidified filter cake and the cement sheath is tightly cemented with the rock formation.

[0024] 3) On the one hand, the curing assistant adopted by the present invention can induce the crystallization of calcium silicate hydrate and calcium carbonate, change the arrangement mode of calcium silicate hydrate and calcium carbonate crystals, make the crystal microstructure show a dense arrangement, and quickly improve the mechanical strength of the solidified body. On the other hand, the curing assistant adopted by the present invention can quickly block the formation leakage channels, prevent filtrate leakage and filter cake damage.

[0025] 4) The anti-pollution agent adopted by the present invention can improve the hydrophilicity of the drilling fluid filter cake, remove the virtual filter cake in the drilling fluid filter cake, compress the thickness of the drilling fluid filter cake, and improve the strength of the drilling fluid filter cake.

[0026] 5) The high-efficiency dispersant adopted by the present invention can achieve uniform dispersion distribution of the curing reactant and curing assistant adopted by the present invention in the drilling fluid filter cake through the electrostatic repulsion of strong sulfonic acid anions. Description of the Drawings

[0027] Figure 1 It is a microscopic morphology diagram of the drilling fluid solidified body for well cementing of high-carbon dioxide oil and gas wells prepared by adding the interfacial enhancer in Example 1 of the present invention. Detailed Embodiments

[0028] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0029] Unless otherwise specified, the materials, reagents, etc. used in the following examples are all commercially available.

[0030] Example 1: Preparation of an interface enhancer for cementing high - carbon - dioxide oil and gas wells

[0031] It is composed of the following materials by weight: 38 parts of aluminum silicate fiber with a length of 6 mm, 10 parts of nano - SiO₂, 42 parts of sisal fiber with a length of 4 mm, 9 parts of sodium lauroyl glutamate, and 1 part of powdered polystyrene sulfonic acid.

[0032] Example 2: Preparation of an interface enhancer for cementing high - carbon - dioxide oil and gas wells

[0033] It is composed of the following materials by weight: 36 parts of glass fiber with a length of 4 mm, 15 parts of red mud, 25 parts of sisal fiber with a length of 3 mm, 10 parts of nano - calcium carbonate, 5 parts of graphene oxide, 7 parts of sodium lauroyl glutamate, and 2 parts of powdered polystyrene sulfonic acid.

[0034] Example 3: Preparation of an interface enhancer for cementing high - carbon - dioxide oil and gas wells

[0035] It is composed of the following materials by weight: 43 parts of calcium carbonate whisker with a length of 5 mm, 7 parts of red mud, 3 parts of nano - SiO₂, 23 parts of asbestos fiber with a length of 7 mm, 6 parts of nano - calcium carbonate, 4 parts of graphene oxide, 11 parts of sodium dodecyl polyoxyethylene ether sulfate, and 3 parts of powdered polystyrene sulfonic acid.

[0036] Comparative Example 1

[0037] It is composed of the following materials by weight: 76 parts of glass fiber with a length of 4 mm, 7 parts of red mud, 3 parts of nano - SiO₂, 11 parts of sodium dodecyl polyoxyethylene ether sulfate, and 3 parts of powdered polystyrene sulfonic acid.

[0038] Test Example

[0039] Set up blank - group drilling fluid, Example 1 drilling fluid, Example 2 drilling fluid, and Example 3 drilling fluid. The components of each drilling fluid are as follows:

[0040] Blank - group drilling fluid formula: 1000 parts by weight of water + 40 parts by weight of bentonite + 15 parts by weight of sulfonated asphalt + 20 parts by weight of carboxymethyl cellulose + 20 parts by weight of vinyltrimethoxysilane + 10 parts by weight of hydrolyzed polyacrylonitrile ammonium salt + 1 part by weight of soda ash.

[0041] Example 1 Drilling Fluid Formula: 1000 parts by weight of water + 40 parts by weight of bentonite + 15 parts by weight of sulfonated asphalt + 20 parts by weight of carboxymethyl cellulose + 20 parts by weight of vinyltrimethoxysilane + 10 parts by weight of hydrolyzed polyacrylonitrile ammonium salt + 1 part by weight of soda ash + 100 parts by weight of the interface enhancer corresponding to Example 1. Among them, the addition amount of the interface enhancer is 0.9% of the drilling fluid.

[0042] Example 2 Drilling Fluid Formula: 1000 parts by weight of water + 40 parts by weight of bentonite + 15 parts by weight of sulfonated asphalt + 20 parts by weight of carboxymethyl cellulose + 20 parts by weight of vinyltrimethoxysilane + 10 parts by weight of hydrolyzed polyacrylonitrile ammonium salt + 1 part by weight of soda ash + 100 parts by weight of the interface enhancer corresponding to Example 2. Among them, the addition amount of the interface enhancer is 0.9% of the drilling fluid.

[0043] Example 3 Drilling Fluid Formula: 1000 parts by weight of water + 40 parts by weight of bentonite + 15 parts by weight of sulfonated asphalt + 20 parts by weight of carboxymethyl cellulose + 20 parts by weight of vinyltrimethoxysilane + 10 parts by weight of hydrolyzed polyacrylonitrile ammonium salt + 1 part by weight of soda ash + 100 parts by weight of the interface enhancer corresponding to Example 3. Among them, the addition amount of the interface enhancer is 0.9% of the drilling fluid.

[0044] Comparative Example 1 Drilling Fluid Formula: 1000 parts by weight of water + 40 parts by weight of bentonite + 15 parts by weight of sulfonated asphalt + 20 parts by weight of carboxymethyl cellulose + 20 parts by weight of vinyltrimethoxysilane + 10 parts by weight of hydrolyzed polyacrylonitrile ammonium salt + 1 part by weight of soda ash + 100 parts by weight of the interface enhancer corresponding to Comparative Example 1. Among them, the addition amount of the interface enhancer is 0.9% of the drilling fluid.

[0045] Prepare the solidified liquid slurries of the blank group drilling fluid, Example 1 drilling fluid, Example 2 drilling fluid, Example 3 drilling fluid, and Comparative Example 1 drilling fluid respectively in accordance with the national standard GB / T19139 - 2012. Pour the slurry into the mold, and after curing in a water bath at 80°C for 3 days, 7 days, and 14 days, measure the compressive strength of the solidified body respectively.

[0046] Pour the blank group drilling fluid, the drilling fluid of Example 1, the drilling fluid of Example 2, and the drilling fluid of Example 3 into the specified scale line position of the autoclave body of the high-temperature and high-pressure fluid loss instrument. Then put the core into the autoclave body to fully contact with the drilling fluid. Set the working pressure of the autoclave body to 3.5 MPa and the working temperature to 80 °C, and keep it for 30 min. After the autoclave body cools down, take out the core with the drilling fluid filter cake attached and place it at the center position of the cementing mold. Inject a certain amount of well cement slurry between the mold and the core. The components of the well cement slurry include 100% G-class oil well cement, 0.5% sulfonated ketone aldehyde condensate, 1% carboxymethyl cellulose, and 44% water. After sealing, put a part of the cementing mold into a curing autoclave with a curing temperature of 80 °C and test the cementing strength of the second cementing interface after curing for 1 day, 3 days, and 7 days. After sealing, put the other part of the cementing mold into a curing autoclave with a curing temperature of 80 °C and a CO2 of 3.0 MPa passed through it and test the cementing strength of the second cementing interface after curing for 1 day, 3 days, and 7 days.

[0047] Figure 1 It is the microscopic morphology diagram of the cured body of the drilling fluid added with the interface enhancer for cementing high-carbon dioxide oil and gas wells prepared in Example 3. It can be seen that the interface enhancer of the present invention can make the drilling fluid filter cake form a network-like skeleton support structure and improve the microstructure between the filter cakes.

[0048] The compressive strength of the cured body of the drilling fluid added with the interface enhancer for cementing high-carbon dioxide oil and gas wells and the cementing strength of the second interface are shown in Table 1, Table 2, and Table 3 respectively.

[0049] Table 1 Compressive strength of the cured body of the drilling fluid added with the interface enhancer for cementing high-carbon dioxide oil and gas wells

[0050]

[0051] The test and evaluation results in Table 1 show that the interface enhancer for cementing high-carbon dioxide oil and gas wells of the present invention can effectively improve the compressive strength of the cured body of the drilling fluid filter cake and improve the interface bearing capacity of the second cementing interface; compared with Comparative Example 1, the curing auxiliary agent in the present invention has a significant effect on improving the interface bearing capacity.

[0052] Table 2 Cementing strength of the second interface of the cementing added with the interface enhancer for cementing high-carbon dioxide oil and gas wells

[0053]

[0054] The test and evaluation results in Table 2 show that the interface enhancer for cementing high-carbon dioxide oil and gas wells of the present invention can effectively improve the cementing strength of the second cementing interface and improve the interface cementing quality of the second cementing interface. Compared with Comparative Example 1, the curing auxiliary agent in the present invention has a more significant improvement on the second cementing interface.

[0055] Table 3 Cementing bond strength of the second interface for cementing in high CO2-containing oil and gas wells with the interfacial enhancer added under CO2 environment

[0056]

[0057] The test and evaluation results in Table 3 show that the interfacial enhancer for cementing in high CO2-containing oil and gas wells of the present invention can resist the erosion of CO2 on the second cementing interface and further improve the cementing bond strength of the second interface. Compared with Comparative Example 1, the curing aid can effectively enhance the CO2 erosion resistance of the interface.

Claims

1. Application of an interface enhancer in improving the bonding strength of the second interface in cementing of high CO₂-containing oil and gas reservoirs; The mass composition of the interface enhancer is as follows: 35 - 50 parts of a curing enhancer, 7 - 15 parts of a curing reactant, 30 - 45 parts of a curing auxiliary, 7 - 13 parts of an anti-pollution agent, 1 - 5 parts of a high-efficiency dispersant; The curing enhancer is at least one of calcium carbonate whiskers and magnesium carbonate whiskers; The length of the curing enhancer is not more than 8 mm; The curing reactant is nano-SiO₂ and red mud; The curing auxiliary is at least one of graphene oxide, nano-calcium carbonate, asbestos fiber, and steel fiber; The anti-pollution agent is sodium lauroyl glutamate or sodium dodecyl polyoxyethylene ether sulfate; The high-efficiency dispersant is powdered polystyrene sulfonic acid.

2. Application of a drilling fluid in improving the bonding strength of the second interface in cementing of high CO₂-containing oil and gas reservoirs; The drilling fluid includes an interface enhancer, and the mass content of the interface enhancer is 5 - 15%; The mass composition of the interface enhancer is as follows: 35 - 50 parts of a curing enhancer, 7 - 15 parts of a curing reactant, 30 - 45 parts of a curing auxiliary, 7 - 13 parts of an anti-pollution agent, 1 - 5 parts of a high-efficiency dispersant; The curing enhancer is at least one of calcium carbonate whiskers and magnesium carbonate whiskers; The length of the curing enhancer is not more than 8 mm; The curing reactant is nano-SiO₂ and red mud; The curing auxiliary is at least one of graphene oxide, nano-calcium carbonate, asbestos fiber, and steel fiber; The anti-pollution agent is sodium lauroyl glutamate or sodium dodecyl polyoxyethylene ether sulfate; The high-efficiency dispersant is powdered polystyrene sulfonic acid.

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