Oil-based drilling fluid with double-wall wall repair fluid, its preparation method and application

Abstract

This invention relates to the field of drilling engineering technology and provides a wall repair fluid for oil-based drilling fluids, comprising: 20-80 parts by weight of cementitious binder; 40-100 parts by weight of mineral admixture; 5-30 parts by weight of activator; 10-50 parts by weight of oil corrosion resistant agent; 0-100 parts by weight of density regulator; 0-5 parts by weight of flow modifier; 0.1-20 parts by weight of retarder; 0.1-20 parts by weight of fluid loss reducing agent; and 100 parts by weight of water. The repair fluid of this invention is suitable for temperatures (40-180℃) and densities (1.2-2.1 g / cm³). 3 This invention provides a method for preparing and applying a repair fluid. The repair fluid exhibits good compatibility with the oil phase, high safety, and strong resistance to mixing with oil-based drilling fluids. After solidification, it forms a high-strength, oil-corrosion-resistant, and long-term stable interlayer wall, ensuring that the interlayer wall will not break or collapse again, thus guaranteeing the smooth progress of drilling and well completion operations. The invention also provides a method for preparing and applying the repair fluid.

Description

Technical Field

[0001] This invention belongs to the field of drilling engineering technology, and particularly relates to an oil-based drilling fluid for repairing the wall of the well, its preparation method and application. Background Technology

[0002] As exploration and development deepen, shale gas and tight sandstone gas in new formations and blocks are gradually becoming hotspots. Due to the scarcity of original geological data and the limited number of adjacent wells, the "straight pilot hole + horizontal well" construction mode is generally adopted. That is, the vertical well section is drilled first to find the producing layer, and more formations can be evaluated at the same time. Then, cement plugs are backfilled according to the design requirements, and then side-drilling is carried out to improve the reservoir encounter rate in the horizontal section, so as to achieve the development goal of low cost and high return.

[0003] Currently, horizontal drilling in shale formations primarily uses oil-based drilling fluids. However, the consolidation effect of cement slurry mixed with oil-based drilling fluid is poor, and the strength of the backfilled cement plug is low. This results in insufficient support for the drill string during sidetracking, leading to excessively long sidetracking sections and long, thin sidetracking walls (i.e., the intersection of the horizontal and vertical wellbore, also known as the sidetracking window). Furthermore, the strength of the cement plug is further reduced under long-term corrosion from the oil-based drilling fluid, making it easy to run the drill string into the pilot hole. Frequent drill string movement and reaming attempts to enter the horizontal wellbore cause the sidetracking wall to collapse, resulting in the drill string losing the support of the sidetracking wall and being unable to enter the horizontal wellbore normally. This forces the abandonment of the horizontal section, resulting in huge time and economic losses.

[0004] To address the aforementioned issues, those skilled in the art generally employ two solutions: well-filling sidetracking to locate horizontal wellbores and repairing the wellbore wall with consolidation materials. Well-filling sidetracking to locate horizontal wellbores: Due to problems with wellbore trajectory control, the "zero length" limitation of inclination survey instruments, data accuracy, three-dimensional trajectory, and collision prevention in platform wells, sidetracking technology for locating horizontal wellbores is still immature, and there are few reported successful cases in China, especially in horizontal well sections with depths of 2000–4000m where current technology is insufficient. The solidification material on site is generally cement slurry, which mainly uses the principle of cement cementing to achieve the purpose of repairing the wall of the cavity and to provide a certain support force for the drill bit to enter the horizontal wellbore normally. However, the following problems exist: (1) poor solidification effect of cement mixed with oil-based drilling fluid: cement slurry and oil-based drilling fluid have poor compatibility. The oil phase, which does not have the solidification property, plays a role in wrapping, isolating and lubricating between cement particles, which hinders the full hydration of cement, resulting in a significant decrease in solidification strength, or even difficulty in solidification; (2) poor oil corrosion resistance and insufficient long-term stability of the cavity wall formed after cement slurry solidification: cement solidified body (hereinafter referred to as cement stone) (2) Under the long-term penetration, corrosion and scouring of oil-based drilling fluid, the oil phase gradually penetrates into the structure of cement stone, destroying the bonding force between cement stones, thus reducing its strength, or even causing it to become loose and structurally damaged; (3) Low displacement efficiency and excessive mixing of slurry in large-diameter irregular wellbores: a. Damage to the interlayer wall causes horizontal and vertical wellbores to connect, forming an irregular large-bore wellbore. The annular return velocity is low in large-diameter wellbores, resulting in poor displacement efficiency and a large amount of residual oil-based drilling fluid, cement stone and loose mud cake. After the cement slurry is mixed with excessive oil-based drilling fluid, it loses its consolidation ability; b. The adjustable range of cement slurry density is 1.8~1.9g / cm³. 3 The density of oil-based drilling fluids generally ranges from 1.2 to 2.1 g / cm³, depending on the formation pressure. 3 Between the two, there is a density difference, and the displacement and gravity replacement during the setting process further aggravates the amount of mixed slurry.

[0005] Chinese patent CN113845890A discloses a wellbore repair agent suitable for fractured formations. It uses a wellbore repair agent with strong adhesion, high elasticity and toughness, and high temperature resistance. The components include ultrafine cement, elastic epoxy resin, epoxy resin emulsifier, latent curing agent, nanomaterials, etc. It is mainly used for wellbore repair in high-temperature deep wells with fractured dolomite and carbonate rock formations. However, its applicable temperature is 140-170℃, and it is not suitable for medium and shallow wells with mudstone, sandstone, and shale formations (40-140℃). Moreover, the consolidation strength of the wellbore repair agent after being mixed with oil-based drilling fluid is difficult to achieve the effect of repairing the wall of the well.

[0006] Chinese patent CN103387825A discloses a curing liquid for branch well wall and its preparation method. The curing liquid includes modified epoxy furan, organic amine curing agent, diluent and other components. It mainly solves the problem of improving the rock strength and stability of the branch well wall in loose sandstone strata by using chemical curing technology in advance when the wall is not damaged. However, it is not suitable for repair work after the wall is damaged. Summary of the Invention

[0007] In view of this, the present invention provides a wall repair fluid for oil-based drilling fluids, its preparation method and application. The repair fluid has strong resistance to oil mixing and a wide range of applicable densities and temperatures, and can be applied to wall repair operations in oil-based drilling fluid wells in different blocks and formations. The wall repair method improves the displacement efficiency in large-diameter irregular wellbores without increasing costs by improving the drill string structure and optimizing the construction process. It has high reproducibility, strong operability and significant application effect. The wall formed by the method provided by the present invention has high strength, strong resistance to oil erosion and high long-term stability, and will not break or collapse again, ensuring the smooth progress of drilling and completion operations.

[0008] This invention provides a wall repair fluid for oil-based drilling fluids, comprising:

[0009]

[0010] The activator is selected from one or more of sodium carbonate, calcium chloride, calcium oxide and sodium sulfate;

[0011] The oil-resistant corrosion resistant agent is selected from one or more of modified pumice powder, microsilica powder, and inorganic salt water purification agents.

[0012] Preferably, the oil-resistant corrosion resistant agent is selected from modified pumice powder, microsilica powder and inorganic salt water purification agent; the mass ratio of the modified pumice powder, microsilica powder and inorganic salt water purification agent is (50-100):(20-45):(10-25).

[0013] Preferably, the modified pumice powder has a mass percentage of oil-resistant corrosion resistant agent greater than or equal to 55%.

[0014] Preferably, the modified pumice powder is calcined pumice powder modified with a silane coupling agent.

[0015] Preferably, the modified pumice powder is prepared according to the following method:

[0016] A1) Pumice powder is mixed with an alkaline substance and activated by calcination to obtain calcined pumice powder;

[0017] A2) Under stirring conditions, the silane coupling agent solution is sprayed onto calcined pumice powder by ambient temperature atomization, and after drying, modified pumice powder is obtained.

[0018] Preferably, the mass ratio of pumice powder to alkaline substance is 1:(0.015~0.035); the calcination activation temperature is 300~550℃; and the calcination activation time is 3~5h.

[0019] The silane coupling agent solution is a solution of silane coupling agent and ethanol; the mass ratio of silane coupling agent to ethanol is (0.4-0.6):1; the mass of the silane coupling agent solution is 0.5%-1.5% of the mass of calcined pumice powder.

[0020] Preferably, the inorganic salt water purification agent is selected from ferric chloride and potassium aluminum sulfate dodecahydrate; the mass ratio of ferric chloride to potassium aluminum sulfate dodecahydrate is (10-20):(0-1).

[0021] Preferably, the cement-based binder is selected from one or more of aluminate cement, ordinary cement, ultrafine cement, and oil well grade G cement;

[0022] The mineral admixture is selected from one or more of the following: ultrafine blast furnace slag, tuff powder, zeolite powder, fly ash, and sintered shale powder.

[0023] The density regulator is selected from weighting agents or weight-reducing agents; the weighting agent is selected from one or more of barite, hematite, and ilmenite; the weight-reducing agent is selected from one or more of perlite microspheres, hollow glass microspheres, and urea-formaldehyde resin microspheres.

[0024] The flow pattern regulator is selected from one or more of sulfonated aldehyde-ketone condensates, hydroxycarboxylic acid compounds, and hydroxypolysaccharide compounds;

[0025] The retarder is selected from one or more of the following: lignin sulfonate retarder, hydroxycarboxylate retarder, cellulose derivative retarder, AMPS polymer retarder, and inorganic-organic polymer oil well cement retarder.

[0026] The water loss reducing agent is selected from one or more of the following: hydroxycarboxylic acid water loss reducing agents, inorganic compound water loss reducing agents, cellulose derivative water loss reducing agents, AMPS multi-component copolymer water loss reducing agents, and inorganic non-metallic-organic polymer water loss reducing agents.

[0027] The present invention also provides a method for preparing the above-mentioned oil-based drilling fluid for wall repair, comprising the following steps:

[0028] S1) Mix water, flow conditioner, retarder and water loss reducer evenly to obtain slurry water;

[0029] S2) Mix the slurry water, cement-based binder, mineral admixture, activator, oil corrosion resistant agent and density regulator evenly to obtain oil-based drilling fluid for wall repair.

[0030] This invention also provides a method for repairing a sandwich wall, comprising the following steps:

[0031] B1) Clean the well walls and wellbore;

[0032] B2) Pump oil-based drilling fluid into the well using wall repair fluid, and then replace the repair fluid with drilling fluid. After the repair fluid exits the drill string, adjust the position of the drill string so that the bottom jet tool reaches the damaged wall, and move the drill string up and down to dynamically pump the repair fluid until the drill string is balanced inside and outside.

[0033] B3) Pull the drill string up to above the level of the repair fluid;

[0034] B4) Circulate and drain the mixed slurry;

[0035] B5) When it condenses.

[0036] This invention provides a wall repair fluid for oil-based drilling fluids, comprising: 20-80 parts by weight of cementitious binder; 40-100 parts by weight of mineral admixture; 5-30 parts by weight of activator; 10-50 parts by weight of oil corrosion resistant agent; 0-100 parts by weight of density regulator; 0-5 parts by weight of flow modifier; 0.1-20 parts by weight of retarder; 0.1-20 parts by weight of fluid loss reducing agent; and 100 parts by weight of water. The oil corrosion resistant agent comprises modified pumice powder, microsilica powder, and inorganic salt water purifier. The mass ratio of the modified pumice powder, microsilica powder, and inorganic salt water purifier is (50-100):(20-45):(10-25), and the modified pumice powder constitutes at least 55% of the oil corrosion resistant agent by mass. Compared with existing technologies, the oil-based drilling fluid for wellbore wall repair, its preparation method, and application provided by this invention can effectively solve the problems of non-consolidation of cement slurry mixed with oil-based drilling fluid and low displacement efficiency in large-diameter irregular wellbores. It provides a reliable technical solution for repairing wellbore walls in large-diameter wells using oil-based drilling fluid. The synergistic effect of multiple components in the oil-resistant corrosion agent not only enhances the consolidation ability of the repair fluid in an oil-based drilling fluid environment but also improves its resistance to oil corrosion, enabling the wellbore wall to provide stable support to the drilling tools for a long period, ensuring smooth subsequent construction operations. Furthermore, the solidified repair fluid forms a... With high structural strength and long-lasting resistance to oil corrosion, this repair fluid avoids the problem of significant strength reduction or even damage caused by prolonged scouring and corrosion from oil-based drilling fluids. Furthermore, it exhibits good stability, is suitable for both low-temperature and medium-to-high-temperature formations, has a wide adjustable density range, and is highly safe. It can be applied to oil-based drilling fluid wells in different blocks and formations, solving the complex problem of drill bits being unable to enter the horizontal wellbore after the interlayer wall is damaged, resulting in abandoned drilling footage. At the same time, its strong resistance to oil corrosion ensures that the interlayer wall will not be damaged or collapsed again, preventing serious accidents such as stuck drill bits or casing failure, thus ensuring the smooth progress of drilling and completion operations.

[0037] Experimental results show that the oil-based drilling fluid wall repair fluid provided by this invention has a wide range of applications, applicable temperatures of 40–180℃, and densities of 1.2–2.1 g / cm³. 3 The thickening time is adjustable from 180 to 550 minutes, making it suitable for repairing wall gaps in wells with varying formation lithology and pressure coefficients. It exhibits good compatibility with oil-based drilling fluids, without significant exothermic reactions or flashover, ensuring high construction safety. The wall gap formed when mixed with oil-based drilling fluid (<35%) exhibits high strength, meeting the requirements for most oil-based drilling fluid well wall gap repair operations. Furthermore, this repair fluid demonstrates excellent consolidation and oil corrosion resistance, with a solidified compressive strength greater than 10 MPa, and a compressive strength exceeding 5.5 MPa when mixed with 35% oil-based drilling fluid. The compressive strength after 30 days of oil immersion is [not specified]. With an increase of 10% and an oil phase immersion depth of less than 10%, this technology solves the problems of non-consolidation and poor oil corrosion resistance of the original technology's oil-based drilling fluid, effectively improving the long-term stability of the wellbore after repair with oil-based drilling fluid. Furthermore, the application method of this repair fluid, without increasing costs, can effectively clean the residual cement stone, loose mud cake, and oil-based drilling fluid in the large-diameter wellbore after the wellbore is damaged by improving the drill string structure and optimizing the construction process. This significantly improves the displacement efficiency, reduces the degree of mixing between the repair fluid and the oil-based drilling fluid, and has high field reproducibility, strong operability, and significant application effects. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides a wall repair fluid for oil-based drilling fluids, comprising:

[0040]

[0041] The activator is one or more of sodium carbonate, calcium chloride, calcium oxide and sodium sulfate;

[0042] The oil-resistant corrosion resistant agent is one or more of the following: modified pumice powder, microsilica powder, and inorganic salt water purification agent.

[0043] The repair fluid provided by this invention has good compatibility with the oil phase and high safety. The wall formed by the oil-based drilling fluid (<35%) has high strength and strong resistance to oil corrosion, and will not break or collapse again, thus ensuring the smooth progress of drilling and well completion operations.

[0044] The cement-based consolidating agent is preferably present in 30-80 parts by weight in the oil-based drilling fluid for wall repair, more preferably in 40-80 parts by weight. In the embodiments provided by the present invention, the cement-based consolidating agent is specifically present in 50 parts by weight, 40 parts by weight, 60 parts by weight, or 80 parts by weight. The cement-based consolidating agent is preferably one or more of aluminate cement, ordinary cement, ultrafine cement, and oil well grade G cement, more preferably ultrafine cement and / or oil well grade G cement.

[0045] The mineral admixture is preferably present in 55-100 parts by weight in the oil-based drilling fluid for wall repair. In the embodiments provided by the present invention, the mineral admixture is specifically present in 60 parts by weight, 80 parts by weight, 90 parts by weight, 100 parts by weight, or 50 parts by weight. The mineral admixture is preferably one or more of ultrafine blast furnace slag, tuff powder, zeolite powder, fly ash, and sintered shale powder. The particle size D of the ultrafine blast furnace slag is... 90 Preferably, the particle size is less than or equal to 100 μm; more preferably, less than or equal to 50 μm; even more preferably, less than or equal to 30 μm; and most preferably, less than or equal to 10 μm. The particle size D of the tuff powder, zeolite powder, fly ash, calcined shale powder, and pumice powder is... 90 Each of the following is preferred to be less than or equal to 150 μm, more preferably less than or equal to 100 μm, even more preferably less than or equal to 70 μm, and most preferably less than or equal to 50 μm.

[0046] The activator in the oil-based drilling fluid wall repair fluid is preferably 10-30 parts by weight, more preferably 10-25 parts by weight; in the embodiments provided by the present invention, the activator in the oil-based drilling fluid wall repair fluid is specifically 10 parts by weight, 15 parts by weight, 20 parts by weight or 25 parts by weight; the activator is preferably one or more of sodium carbonate, calcium chloride, calcium oxide and sodium sulfate, more preferably one or more of sodium carbonate, sodium sulfate and calcium oxide.

[0047] The content of the oil-resistant corrosion resistant agent in the oil-based drilling fluid wall repair fluid is preferably 15-46 parts by weight, more preferably 22.6-45.3 parts by weight; in the embodiments provided by the present invention, the content of the oil-resistant corrosion resistant agent in the oil-based drilling fluid wall repair fluid is specifically 5 parts by weight, 15 parts by weight, 22.6 parts by weight, 2.65 parts by weight, or 45.3 parts by weight; the oil-resistant corrosion resistant agent is preferably one or more of modified pumice powder, microsilica powder, and inorganic salt water purification agent, more preferably modified pumice powder, microsilica powder, and inorganic salt water purification agent; further preferably, the modified pumice powder accounts for more than or equal to 55% of the oil-resistant corrosion resistant agent by mass; the mass ratio of the modified pumice powder, microsilica powder, and inorganic salt water purification agent is preferably (50-100). The ratio of modified pumice powder, microsilica powder, and inorganic salt water purification agent is (20-45):(10-25), more preferably (50-90):(20-40):(10-20), and even more preferably (50-75):(20-35):(10-15). In some embodiments provided by the present invention, the mass ratio of the modified pumice powder, microsilica powder, and inorganic salt water purification agent is specifically 75:25:13 or 50:30:10.6. The modified pumice powder is preferably calcined pumice powder modified with a silane coupling agent, more preferably alkaline pumice powder modified with a silane coupling agent. In the present invention, the modified pumice powder is preferably prepared by the following method: A1) mixing pumice powder with an alkaline substance, calcining and activating to obtain calcined pumice powder; A2) coupling silane under stirring conditions. The agent solution is sprayed onto calcined pumice powder at room temperature via atomization. After drying, modified pumice powder is obtained. The particle size of the pumice powder is preferably 800 mesh, more preferably 600 mesh, even more preferably 400 mesh, and most preferably 325 mesh. The alkaline substance can be any alkaline substance well known to those skilled in the art, and there are no special limitations. In this invention, hydroxides and carbonates are preferred. The hydroxide is preferably an alkali metal hydroxide, more preferably sodium hydroxide and / or potassium hydroxide. The carbonate is preferably an alkali metal carbonate and / or an alkaline earth metal carbonate, more preferably one or more of sodium carbonate, potassium carbonate, and calcium carbonate. The mass ratio of the hydroxide to the carbonate is preferably (55-75):(30-50). The mass ratio of the pumice powder to the alkaline substance is... The ratio is 1:(0.015~0.035); the calcination activation temperature is preferably 300~550℃; the calcination activation time is preferably 3~5h; the stirring speed is preferably 800~1500r / min, more preferably 1000~1500r / min, and even more preferably 1200r / min; the silane coupling agent solution is preferably a solution of silane coupling agent and ethanol; the mass ratio of silane coupling agent to ethanol is preferably (0.4~0.6):1; the silane coupling agent can be any silane coupling agent well known to those skilled in the art, and there are no special restrictions. In this invention, the preferred silane coupling agent is KH-502; the mass of the silane coupling agent solution is preferably 0.5%~1% of the mass of the calcined pumice powder.5%; after drying, it is preferably dispersed by high-speed stirring to obtain modified pumice powder; the microsilica powder is preferably silica powder with a purity greater than 98%; the particle size of the microsilica powder is preferably 0.1-0.3μm; the inorganic salt water purification agent is preferably ferric chloride and potassium aluminum sulfate dodecahydrate; the mass ratio of ferric chloride to potassium aluminum sulfate dodecahydrate is preferably (10-20):(0-1), more preferably (10-18):(0.3-1), even more preferably (10-15):(0.5-0.8), and most preferably (10-15):0.6. In this invention, the mechanism of action of the oil corrosion resistant agent is as follows: ① High-temperature calcination causes the organic matter in the micropores and pores of the pumice powder to volatilize, thus unblocking the pores and resulting in a higher specific surface area and adsorption capacity. Treatment with a silane coupling agent solution improves the oleophilicity of the porous structure, enhancing compatibility and dispersibility during the adsorption and absorption of the oil phase. This helps to adsorb the oil phase in the repair solution into the porous microstructure, reducing the possibility of the oil phase encapsulating the solidifying agent particles and hindering the hydration reaction, and significantly improving the reactivity of the solidifying agent after mixing with the oil phase; ② Micron-sized silica powder can effectively fill the micropores between the repair solution particles, improving density; ③ Anhydrous ferric chloride and potassium aluminum sulfate dodecahydrate can consume the negative products generated by the solidification reaction, making the solidified body structure uniform and improving its resistance to oil phase penetration. Through the synergistic effect and mutual cooperation of multiple components of the oil corrosion resistant agent, the oil corrosion resistance and long-term stability of the sandwich wall formed by the solidification of the repair solution are improved.

[0048] The density regulator can be added according to the required density of the oil-based drilling fluid wall repair fluid based on the different blocks, formation lithology, and pressure coefficients. The density regulator is preferably a weighting agent or a weight-reducing agent. The weighting agent is preferably one or more of barite, hematite, and ilmenite; the weight-reducing agent is preferably one or more of perlite microspheres, hollow glass microspheres, and urea-formaldehyde resin microspheres. Adding a density regulator can broaden the adjustable range of the repair fluid density, overcoming the problem of excessive mixing when in contact with drilling fluid due to the narrow adjustable range of cement slurry density.

[0049] The flow pattern modifier is preferably present in 0-3 parts by weight in the oil-based drilling fluid wall repair fluid, more preferably 0-2 parts by weight, and even more preferably 1-2 parts by weight; the flow pattern modifier is preferably one or more of sulfonated aldehyde-ketone condensates, hydroxycarboxylic acid compounds, and hydroxy polysaccharide compounds.

[0050] The retarder content in the oil-based drilling fluid wall repair fluid is preferably 0-15 parts by weight, more preferably 0-10 parts by weight, and even more preferably 1-5 parts by weight. In the embodiments provided by the present invention, the retarder content in the oil-based drilling fluid wall repair fluid is specifically 0 parts by weight, 1 part by weight, 2 parts by weight, 3.5 parts by weight, 4 parts by weight, or 5 parts by weight. The retarder can be any retarder well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably one or more of lignin sulfonate retarder, hydroxycarboxylate retarder, cellulose derivative retarder, AMPS polymer retarder, and inorganic-organic polymer oil well cement retarder, more preferably high-temperature retarder ZYH or high-temperature oil well cement retarder ZRT-1 among AMPS polymer retarders.

[0051] The content of the fluid loss reducing agent in the oil-based drilling fluid wall repair fluid is preferably 0.5 to 20 parts by weight, more preferably 1 to 15 parts by weight, and even more preferably 2 to 11 parts by weight. In the embodiments provided by the present invention, the content of the fluid loss reducing agent in the oil-based drilling fluid wall repair fluid is specifically 2 parts by weight, 4 parts by weight, 4.5 parts by weight, 6 parts by weight, or 11 parts by weight. The fluid loss reducing agent can be any fluid loss reducing agent well known to those skilled in the art and is not particularly limited. In the present invention, it is preferred to be one or more of hydroxycarboxylic acid fluid loss reducing agents, inorganic compound fluid loss reducing agents, cellulose derivative fluid loss reducing agents, AMPS multi-component copolymer fluid loss reducing agents, and inorganic non-metallic-organic polymer fluid loss reducing agents. More preferably, it is the high-temperature fluid loss reducing agent ZYJ in AMPS multi-component copolymers and / or the inorganic non-metallic-organic polymer high-temperature oil well cement fluid loss reducing agent ZFA-1.

[0052] The density of the oil-based drilling fluid wall repair fluid provided by this invention is preferably 1.2–2.1 g / cm³. 3 .

[0053] The oil-based drilling fluid wall repair fluid provided by this invention can be adapted to temperatures of 40–180°C by adjusting the content of each component.

[0054] The oil-based drilling fluid and its application method provided by this invention can effectively solve the problems of non-consolidation of cement slurry mixed with oil-based drilling fluid and low displacement efficiency in large-diameter irregular wells. It provides a reliable technical solution for repairing the wall of large-diameter wells in oil-based drilling fluids. The synergistic effect of multiple components in the oil-resistant corrosion agent not only enhances the consolidation ability of the repair fluid in the oil-based drilling fluid environment but also improves its resistance to oil corrosion, enabling the wall to provide stable support to the drilling tools for a long period, ensuring smooth subsequent construction operations. Furthermore, the solidified body formed by the repair fluid after consolidation has high strength. It has long-lasting resistance to oil corrosion and will not suffer from significant strength reduction or even damage due to prolonged scouring and corrosion by oil-based drilling fluids. Furthermore, this repair fluid has good stability and is suitable for low-temperature and medium-high-temperature formations. It has a wide range of adjustable density and high safety, and can be applied to oil-based drilling fluid wells in different blocks and formations. It solves the complex problem of drill bits being unable to enter the horizontal wellbore after the interlayer wall is damaged, resulting in scrapped footage. At the same time, its strong resistance to oil corrosion ensures that the interlayer wall will not be damaged or collapsed again, causing serious accidents such as stuck drill bits, casing failure, and wellbore scrapping, thus ensuring the smooth progress of drilling and completion operations.

[0055] The present invention also provides a method for preparing the above-mentioned oil-based drilling fluid for wall repair, comprising the following steps: S1) mixing water, flow modifier, retarder and fluid loss reducer evenly to obtain slurry water; S2) mixing the slurry water, cement-based binder, mineral admixture, activator, oil corrosion resistant agent and density modifier evenly to obtain oil-based drilling fluid for wall repair.

[0056] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0057] This invention also provides a method for repairing a wall cavity, comprising the following steps: B1) cleaning the well wall and wellbore; B2) pumping repair fluid into the well, then replacing the repair fluid with drilling fluid; after the repair fluid exits the drill string, adjusting the drill string position so that the bottom jet tool reaches the damaged area of ​​the wall cavity, and moving the drill string up and down to dynamically pump the repair fluid until the drill string is balanced inside and outside; B3) pulling the drill string up to above the repair fluid level; B4) circulating and draining the mixed slurry; B5) waiting for it to set.

[0058] The repair method provided by this invention can effectively clean residual cement stone, loose mud cake, and oil-based drilling fluid in large-diameter wells after the wall of the well is damaged. Without increasing costs, by improving the drill string structure and optimizing the construction process, and relying on the high-speed jetting and scouring effect of the jet tool, the displacement efficiency in large-diameter irregular wells is greatly improved, and the mixing degree of repair fluid and drilling fluid is reduced. It is suitable for wall repair operations in branch wells, sidetracking wells, and pilot horizontal wells, including water-based drilling fluid and oil-based drilling fluid wells. Cement slurry or the repair fluid and preparation method proposed in this invention can be used in water-based drilling fluid wells, but the repair fluid and preparation method proposed in this invention must be used in oil-based drilling fluid wells to achieve good results.

[0059] First, the well wall and wellbore are cleaned. In this invention, the improved drill string structure specifically involves attaching a jetting tool to the bottom of the smooth drill pipe. The optimized construction process specifically involves lowering the smooth drill pipe with the jetting tool attached to the bottom below the damaged part of the clamping wall to clean the well wall and wellbore. The jetting tool is preferably a bypass valve or a rotary jetting auxiliary tool, more preferably a bypass valve. In this invention, it is preferred to lower the smooth drill pipe with the jetting tool attached to the bottom to 5-15m below the damaged part of the clamping wall, more preferably 10m. Cleaning the well wall and wellbore is preferably done by high-volume circulating flushing, more preferably by simultaneously moving the drill string up and down significantly to break up the cement stone and loose mud cake adhering to the well wall and clean the wellbore.

[0060] Then, preferably, the side channel of the bottom jet tool is opened, and the repair fluid is pumped into the well. Drilling fluid is then used to replace the repair fluid. After the repair fluid exits the drill string, the drill string position is adjusted so that the bottom jet tool is at the damaged section of the wall. The drill string is then moved up and down to dynamically pump the repair fluid until the drill string is balanced. In this invention, it is preferable to first adjust the repair fluid formula according to the formation temperature, drilling fluid properties, and wellbore conditions to make its density consistent with the drilling fluid before pumping it into the well. When the repair fluid exits the drill string for 3-5 meters... 3 Then, adjust the position of the drill bit so that the bottom jet tool is at the damaged part of the clamping wall; the preferred range of drill bit movement is 10m above and below the damaged part of the clamping wall.

[0061] After the dynamic pump replaces the repair fluid until the drill string is balanced inside and outside, it is preferable to pull the drill string to a position above the repair fluid level, more preferably to a position 200-400m above the repair fluid level, and even more preferably to a position 300m above the repair fluid level, and then circulate the mixed slurry to drain it.

[0062] Finally, after curing, the repair of the partition wall can be completed; the curing time is preferably 40 to 72 hours.

[0063] To further illustrate the present invention, the following describes in detail, with reference to embodiments, an oil-based drilling fluid for repairing interlayer walls, its preparation method, and its application.

[0064] All reagents used in the following examples are commercially available. Oil well G-grade cement and ultrafine cement were purchased from Sichuan Jiahua Enterprise (Group) Co., Ltd.; fly ash and ultrafine blast furnace slag were purchased from Shandong Kangjing New Material Technology Co., Ltd.; perlite cenospheres, microsilica powder (0.1-0.3μm), and zeolite powder were purchased from Lingshou County Qiangdong Mineral Products Processing Plant; sulfonated aldehyde-ketone condensate USZ was purchased from Weihui Chemical Co., Ltd.; medium-high temperature retarder ZYH, high-temperature oil well cement retarder ZRT-1 and retarder ZYH-1, and modified pumice powder could be provided by the Drilling Engineering Technology Research Institute of Sinopec Zhongyuan Petroleum Engineering Co., Ltd. The medium-high temperature retarder ZYH can be prepared according to the method of Example 1 provided in Chinese Patent CN109503760B. The modified pumice powder is calcined pumice powder modified with a silane coupling agent. The preparation method is as follows: a) Take a certain amount of pumice, crush and grind it, and pass it through a 325-mesh sieve to obtain pumice powder; mix the pumice powder and an alkaline substance (sodium hydroxide: calcium carbonate = 60:40) at a mass ratio of 1:0.025, stir and mix evenly, and activate at 450℃ for 4 hours to obtain calcined pumice powder; b) Add the calcined pumice powder obtained in step a) to a high-speed mixer and stir at 1200 r / min. At the same time, spray the silane coupling agent (KH-502) solution (a solution with a mass ratio of silane coupling agent to ethanol of 0.5:1) evenly onto the powder through a spraying device. The mass ratio of silane coupling agent solution to calcined pumice powder is 1%. Heat and dry to evaporate the solvent. Finally, stir and disperse at high speed and collect the sample to obtain modified pumice powder.

[0065] Example 1

[0066] Step 1) Preparation of slurry water: Mix 100 parts water and 2 parts water loss reducing agent ZYJ evenly by weight to obtain slurry water.

[0067] Step 2) Preparation of repair solution: In the slurry water of step 1), add 50 parts of solidifying agent oil well grade G cement, 60 parts of mineral admixture fly ash, 10 parts of activator calcium oxide, 5 parts of oil corrosion resistant agent microsilica powder, and 20 parts of density regulator perlite beads. Mix evenly, measure the density of the repair solution and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0068] Example 2

[0069] Step 1) Preparation of slurry water: By weight, mix 100 parts water, 1 part retarder ZYH and 4 parts water loss reducer ZYJ evenly to obtain slurry water.

[0070] Step 2) Preparation of repair solution: In the slurry water of step 1), add 50 parts of the binder ultrafine cement, 80 parts of the mineral admixture ultrafine blast furnace slag, 10 parts of the activator sodium sulfate, and 15 parts of the oil corrosion resistant modified pumice powder. Mix them evenly, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0071] Example 3

[0072] Step 1) Preparation of slurry water: Mix 100 parts water, 2 parts retarder ZYH and 4.5 parts water loss reducer ZYJ evenly by weight to obtain slurry water.

[0073] Step 2) Preparation of repair solution: In the slurry water prepared in Step 1), add 40 parts of solidifying agent oil well grade G cement, 70 parts of mineral admixture ultrafine blast furnace slag, 20 parts of mineral admixture fly ash, 15 parts of activator sodium carbonate, 15 parts of oil corrosion resistant modified pumice powder, 5 parts of oil corrosion resistant microsilica powder, 2.5 parts of oil corrosion resistant anhydrous ferric chloride, and 0.1 parts of oil corrosion resistant potassium aluminum sulfate dodecahydrate. Mix well, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0074] Example 4

[0075] Step 1) Preparation of slurry water: By weight, mix 100 parts water, 3.5 parts retarder ZRT-1 and 2 parts water loss reducing agent ZYA-1 evenly to obtain slurry water.

[0076] Step 2) Preparation of repair solution: In the grouting water of step 1), add 60 parts of the consolidating agent ultrafine cement, 90 parts of the mineral admixture zeolite powder, 15 parts of the activator calcium oxide, 2.5 parts of the oil corrosion resistant agent anhydrous ferric chloride, 0.15 parts of the oil corrosion resistant agent potassium aluminum sulfate dodecahydrate, and 10 parts of the density regulator barite. Mix well, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0077] Example 5

[0078] Step 1) Preparation of slurry water: By weight, mix 100 parts water, 4 parts retarder ZRT-1, 6 parts water loss reducer ZFA-1, and 1 part flow modifier sulfonated aldehyde ketone condensate USZ evenly to obtain slurry water.

[0079] Step 2) Preparation of repair solution: Add 40 parts of solidifying agent oil well grade G cement, 100 parts of mineral admixture ultrafine blast furnace slag, 20 parts of activator calcium oxide, and 50 parts of density regulator barite to the slurry water in step 1. Mix well, measure the density of the repair solution and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0080] Example 6

[0081] Step 1) Preparation of slurry water: By weight, mix 100 parts water, 5 parts retarder ZRT-1, 11 parts water loss reducer ZFA-1, and 2 parts flow pattern regulator sulfonated aldehyde ketone condensate USZ, and mix evenly to obtain slurry water.

[0082] Step 2) Preparation of repair solution: In the slurry water prepared in Step 1, add 80 parts of solidifying agent (oil well grade G cement), 20 parts of mineral admixture (fly ash), 30 parts of mineral admixture (zeolite powder), 25 parts of activator (calcium oxide), 25 parts of modified pumice powder, 15 parts of microsilica powder, 5 parts of anhydrous ferric chloride, 0.3 parts of oil corrosion resistant agent (potassium aluminum sulfate dodecahydrate), and 90 parts of density regulator (barite). Mix well, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0083] Comparative Example 1

[0084] To prepare ordinary cement slurry, mix 100g of water with 230g of cement until homogeneous, measure the density, and pour the mixture into a 50.8mm×50.8mm×50.8mm mold to form the slurry.

[0085] Comparative Example 2

[0086] Step 1) Preparation of slurry water: Mix 100 parts water, 2 parts retarder ZYH and 4.5 parts water loss reducer ZYJ evenly by weight to obtain slurry water.

[0087] Step 2) Preparation of repair solution: In the slurry water in step 1), add 40 parts of solidifying agent oil well grade G cement, 70 parts of mineral admixture ultrafine blast furnace slag, 20 parts of mineral admixture fly ash, 15 parts of activator sodium carbonate, and 15 parts of oil corrosion resistant modified pumice powder. Mix evenly, measure the density of the repair solution and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0088] Comparative Example 3

[0089] Step 1) Preparation of slurry water: Mix 100 parts water, 2 parts retarder ZYH and 4.5 parts water loss reducer ZYJ evenly by weight to obtain slurry water.

[0090] Step 2) Preparation of repair solution: In the slurry water in step 1), add 40 parts of solidifying agent oil well grade G cement, 70 parts of mineral admixture ultrafine blast furnace slag, 20 parts of mineral admixture fly ash, 15 parts of activator sodium carbonate, and 5 parts of oil corrosion resistant microsilica powder. Mix evenly, measure the density of the repair solution and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0091] Comparative Example 4

[0092] Step 1) Preparation of slurry water: Mix 100 parts water, 2 parts retarder ZYH and 4.5 parts water loss reducer ZYJ evenly by weight to obtain slurry water.

[0093] Step 2) Preparation of repair solution: In the slurry water of step 1), add 40 parts of solidifying agent oil well grade G cement, 70 parts of mineral admixture ultrafine blast furnace slag, 20 parts of mineral admixture fly ash, 15 parts of activator sodium carbonate, 2.5 parts of oil corrosion resistant agent anhydrous ferric chloride, and 0.1 parts of oil corrosion resistant agent potassium aluminum sulfate dodecahydrate. Mix evenly, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0094] Comparative Example 5

[0095] Step 1) Preparation of slurry water: Mix 100 parts water, 2 parts retarder ZYH and 4.5 parts water loss reducer ZYJ evenly by weight to obtain slurry water.

[0096] Step 2) Preparation of repair solution: In the slurry water prepared in Step 1), add 40 parts of solidifying agent oil well grade G cement, 70 parts of mineral admixture ultrafine blast furnace slag, 20 parts of mineral admixture fly ash, 15 parts of activator sodium carbonate, 10 parts of oil corrosion resistant modified pumice powder, 10 parts of oil corrosion resistant microsilica powder, 2.5 parts of oil corrosion resistant anhydrous ferric chloride, and 0.1 parts of oil corrosion resistant potassium aluminum sulfate dodecahydrate. Mix well, measure the density of the repair solution, and pour it into a 50.8mm×50.8mm×50.8mm mold to form the solution.

[0097] The repair solution was prepared according to Examples 1-6 and Comparative Examples 1-5. The density and thickening time of the repair solution slurry, as well as the compressive strength of the solidified body (50.8mm×50.8mm×50.8mm mold) at different curing temperatures, were measured. The thickening time and compressive strength were tested according to the national standard GB / T 19139-2003 "Test Methods for Oil Well Cement". The density was measured using methods well-known in the art. The results are shown in Tables 1 and 2.

[0098] (1) Comprehensive performance evaluation

[0099] Table 1. Comprehensive Performance Evaluation of Repair Fluid

[0100]

[0101] As shown in Table 1, the repair solution provided by the present invention has the following significant advantages: (1) Wide applicability: the thickening time is adjustable from 180 to 550 min within a temperature range of 40 to 180℃; the density range is 1.2 to 2.1 g / cm³. 3 (1) It can meet the requirements of wall repair work in different blocks, formation pressure and lithology; (2) High safety: The repair fluid of this invention has strong resistance to oil-based drilling fluid pollution. When mixed with different proportions of oil-based drilling fluid, the thickening time is extended to a certain extent. No exothermic or flash solidification phenomenon occurs, which meets the on-site safety requirements; (3) Strong consolidation and resistance to oil mixing: The compressive strength of the solidified body formed by pure repair fluid is greater than 10 MPa, and the compressive strength of the body mixed with 35% oil-based drilling fluid is greater than 5.5 MPa; Comparative Example 1 is cement slurry, which cannot be consolidated after mixing with oil-based drilling fluid; Comparing Example 3, Example 6 and Example 5 (without addition), it was found that the compressive strength of the oil-based drilling fluid mixed with different proportions after adding oil corrosion resistant agent was significantly increased, indicating that it has the effect of improving the resistance of repair fluid to oil-based drilling fluid mixing.

[0102] (2) Evaluation of resistance to oil mixing

[0103] Table 2 Evaluation of the oil-resistant properties of the repair solution

[0104]

[0105] Table 2 shows that when oil-based drilling fluid is not mixed, the oil corrosion resistant agent has virtually no effect on the thickening time and compressive strength of the repair fluid, and does not affect construction safety or the stability of the repair fluid. However, when mixed with oil-based drilling fluid, the compressive strength of the multi-component oil corrosion resistant agent (Example 3) mixed with 35% oil-based drilling fluid decreased by 17.26%, while the reduction rates of the single-component oil corrosion resistant agent (Comparative Examples 2, 3, and 4) were 36.36%, 59.38%, and 65.19%, respectively. This indicates that the multi-component oil corrosion resistant agent improves the compressive strength of the repair fluid. Oil-based drilling fluids exhibit good consolidation capabilities, with modified pumice powder showing the best effect when added as a single component. As shown in Comparative Example 5, when the proportion of modified pumice powder in the oil-resistant corrosion agent is less than 55%, the compressive strength reduction rate of the 35% oil-based drilling fluid is 39.87%. This further illustrates that the large specific surface area, unique porous structure, and strong surface oleophilicity of modified pumice powder are beneficial for adsorbing oil phase molecules in oil-based drilling fluids. At the same time, its high hydration reactivity plays a major role in improving the resistance to oil mixing, making it an essential material in oil-resistant corrosion agents with a proportion ≥55%.

[0106] (3) Evaluation of oil corrosion resistance and long-term stability

[0107] The 50.8mm×50.8mm×50.8mm modules obtained in Example 3 and Comparative Example 1 were placed in a beaker containing 0# diesel fuel. The mouth of the beaker was sealed with a plastic film. After being immersed in the beaker for 1D, 7D, 15D and 30D at room temperature, the modules were removed and the compressive strength and diesel fuel penetration depth ratio were measured. The results are shown in Table 3.

[0108] Table 3 Evaluation of the oil corrosion resistance and long-term stability of the repair solution

[0109]

[0110] As shown in Table 3, after immersing the cement stone in diesel for 15 days, the diesel penetration depth reached 100%, and the compressive strength decreased by 88.42%. After 30 days, the compressive strength dropped to 0. This indicates that as the immersion corrosion time increases, the oil phase completely penetrates the interior of the cement stone, and the corrosion damages its internal structure, leading to a decrease in compressive strength until complete destruction. In contrast, the solidified body formed by the repair liquid provided by this invention, after immersing in diesel for 30 days, showed a 10% increase in compressive strength, with the diesel penetration depth ratio being only 9.8%. This indicates that the oil-resistant corrosion agent can hinder the penetration of the oil phase, ensuring the long-term reaction of the active ingredients, resulting in a continuous increase in strength and guaranteeing the long-term stability of the sandwich wall.

[0111] The preferred embodiments of the present invention disclosed above are merely for illustrating the present invention, and the present invention is not limited thereto. Those skilled in the art will understand that, within the scope of the present invention's concept, modifications can be made to the technical solutions of the present invention, or some technical features can be combined in any other way. Such modifications or combinations do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the various embodiments of the present invention, and should be considered as the content disclosed in the present invention, all of which fall within the protection scope of the present invention.

Claims

1. A wall repair fluid for oil-based drilling fluids, characterized in that, include: 20-80 parts by weight of cement-based binder; 40-100 parts by weight of mineral admixtures; Activator 5-30 parts by weight; Oil-resistant corrosion agent, 10-50 parts by weight; Density regulator 0~100 parts by weight; Flow pattern regulator 0-5 parts by weight; 0-20 parts by weight of retarder; 0.1-20 parts by weight of water loss reducer; 100 parts by weight of water; The cement-based consolidating agent is selected from one or more of aluminate cement, ordinary cement, ultrafine cement and oil well G-grade cement; The mineral admixture is selected from one or more of the following: ultrafine blast furnace slag, tuff powder, zeolite powder, fly ash, and sintered shale powder. The activator is selected from one or more of sodium carbonate, calcium chloride, calcium oxide and sodium sulfate; The oil-resistant corrosion resistant agent is selected from modified pumice powder, microsilica powder and inorganic salt water purification agent; the mass ratio of the modified pumice powder, microsilica powder and inorganic salt water purification agent is (50~100):(20~45):(10~25); The modified pumice powder is calcined pumice powder modified with a silane coupling agent. The inorganic salt water purification agent is selected from ferric chloride and potassium aluminum sulfate dodecahydrate; the mass ratio of ferric chloride to potassium aluminum sulfate dodecahydrate is (10~20):(0~1).

2. The oil-based drilling fluid for repairing the wall of the wellbore according to claim 1, characterized in that, The modified pumice powder has a mass percentage of oil-resistant corrosion resistant agent greater than or equal to 55%.

3. The oil-based drilling fluid for repairing the wall of the wellbore as described in claim 1, characterized in that, The modified pumice powder is prepared according to the following method: A1) Pumice powder is mixed with an alkaline substance and activated by calcination to obtain calcined pumice powder; A2) Under stirring conditions, the silane coupling agent solution is sprayed onto calcined pumice powder by ambient temperature atomization, and after drying, modified pumice powder is obtained.

4. The oil-based drilling fluid for repairing the wall of the wellbore as described in claim 3, characterized in that, The mass ratio of pumice powder to alkaline substance is 1:(0.015~0.035); the calcination activation temperature is 300~550℃; and the calcination activation time is 3~5 h. The silane coupling agent solution is a solution of silane coupling agent and ethanol; the mass ratio of silane coupling agent to ethanol is (0.4~0.6):1; the mass of the silane coupling agent solution is 0.5%~1.5% of the mass of calcined pumice powder.

5. The oil-based drilling fluid for repairing the wall of the wellbore according to claim 1, characterized in that, The density regulator is selected from weighting agents or weight-reducing agents; the weighting agent is selected from one or more of barite, hematite, and ilmenite; the weight-reducing agent is selected from one or more of perlite microspheres, hollow glass microspheres, and urea-formaldehyde resin microspheres. The flow pattern regulator is selected from one or more of sulfonated aldehyde-ketone condensates, hydroxycarboxylic acid compounds, and hydroxypolysaccharide compounds; The retarder is selected from one or more of the following: lignin sulfonate retarder, hydroxycarboxylate retarder, cellulose derivative retarder, AMPS polymer retarder, and inorganic-organic polymer oil well cement retarder. The water loss reducing agent is selected from one or more of the following: hydroxycarboxylic acid water loss reducing agents, inorganic compound water loss reducing agents, cellulose derivative water loss reducing agents, AMPS multi-component copolymer water loss reducing agents, and inorganic non-metallic-organic polymer water loss reducing agents.

6. A method for preparing the oil-based drilling fluid for wall repair as described in claim 1, characterized in that, Includes the following steps: S1) Mix water, flow conditioner, retarder and water loss reducer evenly to obtain slurry water; S2) Mix the slurry water, cement-based binder, mineral admixture, activator, oil corrosion resistant agent and density regulator evenly to obtain oil-based drilling fluid for wall repair.

7. A method for repairing a sandwich wall, characterized in that, Includes the following steps: B1) Clean the well walls and wellbore; B2) Pump the oil-based drilling fluid of any one of claims 1 to 5 into the well using the wall repair fluid, and then use drilling fluid to replace the repair fluid. After the repair fluid exits the drill string, adjust the position of the drill string so that the bottom jet tool reaches the damaged wall, and move the drill string up and down to dynamically pump the repair fluid until the drill string is balanced inside and outside. B3) Pull the drill string up to above the level of the repair fluid; B4) Circulate and drain the mixed slurry; B5) Waiting for condensation.

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