CN115725286A - Solid-phase-free well killing fluid and preparation method thereof - Google Patents
Solid-phase-free well killing fluid and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a solid-free killing fluid and a preparation method thereof, which aim to solve the problem that the conventional killing fluid technology has low flowback efficiency in low-energy and low-permeability oil-gas reservoirs. The solidfree well killing fluid comprises the following components, by mass, 56-94.55 parts of water; 2-5 parts of potassium citrate; 0 to 28 parts of sodium chloride; 1-5 parts of monopotassium phosphate; 0.2-0.5 parts of penetrating agent; 0.5-2.0 parts of imidazoline derivative; 0.1 to 0.5 portion of sodium hexametaphosphate; 0.1 to 0.5 portion of sodium carboxymethyl starch; 0.05 to 0.5 portion of polyphosphonic acid; 0.5-2.0 parts of drag reducer. The non-solid phase well killing fluid provided by the invention has the conventional protective effects of balancing the formation pressure, preventing water sensitivity, preventing water lock, preventing solid phase invasion and the like of the common well killing fluid, can erode, remove blockage, reduce a hydrated and expanded clay layer, enlarge the pore throat, improve the permeability of a near-well reservoir and improve the oil layer protection effect.
Description
Technical Field
The invention relates to oil field chemistry and workover operation engineering, in particular to a solid-free well killing fluid and a preparation method thereof.
Background
In recent years, oil and gas development in China always faces huge pressure of stable production of petroleum, and old oil fields enter the later development stage, follow-up energy supplement is insufficient, and energy deficit is large; most of the unused reserves are hypotonic and compact oil and gas reservoirs, and even if production increasing measures are taken after the oil and gas reservoirs are developed, the yield is reduced quickly after production is put into operation due to the complex geology and small broken blocks of the original reservoirs. The productivity of the oil field is seriously damaged after the oil field operation, and the damage is related to the pore throat reduction, liquid phase trap and water lock damage caused by the invasion of the well killing fluid and other comprehensive damages such as water sensitivity, mechanical impurity blockage, chemical incompatibility and the like. Kill fluids are used to balance formation pressure in oilfield workover operations. After operation, when stratum energy is insufficient, the well killing fluid is difficult to be discharged out of a stratum pore channel, and along with the fact that the well killing fluid stays in a reservoir, invades or fills pores, the effective communication space of the reservoir is inevitably reduced, the oil saturation is relatively reduced, and the oil flow resistance is increased; even the water lock is blocked in the throat, which causes serious water lock damage. Moreover, the well killing fluid itself often reacts with the cementing material in the pore space to induce multiple damages such as water sensitivity and the like; it may also be incompatible with formation water, resulting in chemical plugging, solid phase plugging, etc. Either physical plugging or chemical reactions can severely affect the formation's permeability, the ultimate consequence of which is a reduction in well productivity. Investigations have found that over 90% of the wells are depleted after maintenance operations, typically with a loss of about 10% to 50% of the capacity, and in extreme cases may be completely shut down.
Aiming at the difficult problem of flowback in low-energy and low-permeability oil-gas reservoirs, the researches on leakage prevention and waterproof lock technologies are developed in most oil fields in China, and the oil fields are mainly divided into temporary plugging leakage prevention workover fluid and waterproof lock workover fluid.
(1) The temporary blocking leakage-proof workover fluid comprises a leakage-proof workover fluid system mainly based on a shielding temporary blocking technology and a low-density foam fluid. The shielding temporary blocking and leakage preventing workover fluid is mainly prepared by adding temporary blocking agents with different particle sizes into a system so as to achieve the purpose of shielding and temporarily blocking a stratum. However, the temporary plugging agent particles are more regular and are difficult to match with the heterogeneity of the stratum, so that efficient plugging is difficult, plugging removal is problematic for oil layers with high water content, and the risk of blocking downhole tools by solid-phase particles exists for electric pump wells, so that the technology has certain limitation. In addition, although the low-density micro-bubble fluid used for low-pressure workover at present solves the problem of partial leakage, the foam stability under deep conditions is poor, the pressure resistance is weak, and for some aerated foam fluids, the problems of high preparation cost, inconvenient field use and the like exist.
(2) Waterproof lock workover fluid: including surfactants and lower alcohol anti-latch workover fluids.
The surfactant changes the wettability of the rock surface by reducing the interfacial tension of the liquid phase, and increases the wetting angle between the liquid phase and the rock surface, so that the capillary resistance is reduced, and the aim of preventing water locking is fulfilled. However, as oil field development progresses, the defects of the surfactant are gradually revealed, for example, the surfactant has low cloud point and low temperature resistance, cannot meet the requirement of waterproof lock for well workover in the middle and deep layers, and the fluorocarbon surfactant with high temperature resistance is difficult to popularize and apply due to high cost. On the other hand, due to the adsorption performance of the surfactant and the compatibility problem of the viscosifying fluid loss agent in the workover fluid, the effective concentration is decreased gradually in the using process, so that the waterproof lock effect is weakened or the waterproof lock effect is not effective.
Lower alcohol waterproof lock workover fluid: the water-proof lock is mainly characterized in that alcohol can be utilized to a certain extent to reduce liquid phase meter/interfacial tension through synergistic effect with other surface activities, can be mutually soluble and volatile with water, and can bring out the retained water of the stratum during volatilization to achieve the effect of a water-proof lock. But the action principle determines that the efficiency is short, the treatment is only temporarily released, and measures need to be taken again if external filtrate invades again.
Other systems include the use of surfactants in combination with lower alcohols, but have the potential for salting-out or failure due to insufficient salt resistance.
Disclosure of Invention
The invention aims to solve the technical problem of providing the solid-free well killing fluid and the preparation method thereof, which are used for balancing the formation pressure, inhibiting the expansion of the rock clay of the formation, delaying the scaling reaction in the pores of the rock and improving the permeability of the formation near the well in the well repairing operation of an oil-water well.
In order to solve the technical problems, the invention adopts the technical scheme that: a solid-free well killing fluid comprises, by mass, 56-94.55 parts of water, 2-5 parts of potassium citrate, 0-28 parts of sodium chloride, 1-5 parts of monopotassium phosphate, 0.2-0.5 part of a penetrating agent, 0.5-2.0 parts of an imidazoline derivative, 0.1-0.5 part of sodium hexametaphosphate, 0.1-0.5 part of sodium carboxymethyl starch, 0.05-0.5 part of polyphosphonic acid and 0.5-2.0 parts of a drag reducer.
The purity of the potassium citrate, the sodium chloride, the monopotassium phosphate, the imidazoline derivatives and the sodium hexametaphosphate is more than 98 percent.
The penetrating agent is polyether polyol with industrial grade, and the content is more than 98%.
The sodium carboxymethyl starch is of industrial grade, has a molecular weight of 800-1000, and has a content of more than 98%.
The polyphosphonic acid is industrial grade, and the content is more than 10%.
The drag reducer is polyoxyethylene polyoxypropylene block copolymer, industrial grade, and the content of the drag reducer is more than 95%.
The density of the solid-free well killing fluid is 1.01-1.19g/cm 3 The pH value is between 6 and 7, the corrosion rate is more than or equal to 20 percent, the interfacial tension is less than or equal to 1.0mN/m, and the corrosion rate at 90 ℃ is less than or equal to 0.076mm/a.
A method for preparing solid-free well killing fluid comprises measuring water 56-94.55 parts as base fluid; slowly adding 0.1-0.5 part of sodium carboxymethyl starch, and stirring for at least 30 minutes; adding 2-5 parts of potassium citrate and 0-28 parts of sodium chloride, and stirring for at least 10 minutes; then adding 0.2 to 0.5 portion of penetrating agent, 0.5 to 2.0 portions of drag reducer, 1 to 5 portions of monopotassium phosphate, 0.5 to 2.0 portions of imidazoline derivative, 0.1 to 0.5 portion of sodium hexametaphosphate and 0.05 to 0.5 portion of polyphosphonic acid, stirring for at least 15 minutes, and obtaining the product.
The invention has the beneficial effects that:
(1) The effective space of the pore is enlarged by the actions of corrosion, blockage removal and scale inhibition by chelation. The method utilizes hydrogen ions slowly released by monopotassium phosphate and polyphosphonic acid in the system to slowly erode inherent calcium and argillaceous components in rock pores and dissolve calcium carbonate scales in external solid phases under a weakly acidic condition, so that effective space is developed/enlarged in the pores; the added sodium hexametaphosphate can also complex calcium and magnesium ions, enhance the adhesion and increase the viscosity, not only enhances the shrinkage and expansion effect by the anti-expansion agent in a synergistic system, but also prevents regenerated scale and external scale from occupying limited space of pores and relatively expanding the pore volume. Meanwhile, the added imidazoline derivative corrosion inhibitor and sodium hexametaphosphate are matched with polyphosphonic acid, so that a film forming and passivating effect is achieved, a protective layer is formed on the surface of the pipe column, the electrochemical reaction of an acidic medium on steel is inhibited, and the corrosion of the pipe column and equipment is effectively prevented.
(2) The effective porosity is enhanced and maintained by the dilatant and setting action. The added potassium citrate and sodium carboxymethyl starch have synergistic effect, so that not only can the acidity of the system be controlled and the system be kept to have stable corrosion performance, but also the inherent clay layers in reservoir rock can be compressed, the clay layer spacing is reduced, and the effective space of pores is expanded; in addition, the macromolecular polar groups in the system are adsorbed on the surface of clay, the electrostatic repulsion of the clay layer is reduced, the water between double diffused layers is effectively removed, the interlayer spacing is compressed, glucose groups in the sodium carboxymethyl starch are influenced by phosphate, form a net shape through weak crosslinking, and are fixed on the surface of the clay, so that the clay and water molecules can be blocked, the resistance of the water molecules to permeate into the clay layer again is increased, the re-formation of a double diffused layer is prevented, the clay state after shrinkage and expansion is solidified, the water is stably preserved, and the re-occurrence of reversible water absorption expansion reaction is finally prevented.
(3) The added drag reducer reduces flow consumption, reduces blockage, improves the flowability of crude oil and reduces seepage resistance by improving the shearing force of molecular layers in the crude oil in the pore channel.
(4) The added penetrant polyether polyol has fixed hydrophilic and oleophilic groups, and alcohol groups of the penetrant polyether polyol are mutually dissolved and dissolved with oil and water, so that organic components adhered to the surface of the rock can be effectively invaded, the formation of large water-in-oil liquid blocks is prevented, oil blocks adhered to the surface of the rock are dispersed and cleaned, the penetrant polyether polyol plays a role in penetration and dispersion, and the purpose of stripping crude oil is achieved; the surface of the rock is fully exposed after the oil cake is cleaned, the effective contact area of the surfactant and the rock is obviously increased, and the hydrophilic and oleophilic groups in the penetrant can be directionally arranged on the surface of the solution, so that the surface interfacial tension is obviously reduced; the cleaning of the oil block can further improve the corrosion, shrinkage and expansion and flowback efficiency of the system to the rock, and has good synergistic characteristics. The assistant belongs to a nonionic surfactant, has better salt resistance than a conventional anionic surfactant such as sodium dodecyl sulfate, can keep better performance under the condition of containing high salt in a system, and simultaneously, plays roles of emulsification, defoaming and dispersion of the drag reducer in cooperation with the drag reducer, reduces the size of liquid globules, reduces the deformation resistance of the liquid globules in a throat, prevents a Jamin effect, reduces water lock damage and improves the seepage capability of a reservoir. The example shows that the interfacial tension of the solid-free well killing fluid to kerosene is 0.18-0.65mN/m, the interfacial tension is greatly reduced, and the oil washing efficiency can reach more than 60% -75%.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by a person skilled in the art without making any inventive step are within the scope of protection of the present invention.
The solid-free well killing fluid comprises, by mass, 56-94.55 parts of water, 2-5 parts of potassium citrate, 0-28 parts of sodium chloride, 1-5 parts of monopotassium phosphate, 0.2-0.5 part of a penetrating agent, 0.5-2.0 parts of an imidazoline derivative, 0.1-0.5 part of sodium hexametaphosphate, 0.1-0.5 part of sodium carboxymethyl starch, 0.05-0.5 part of polyphosphonic acid and 0.5-2.0 parts of a drag reducer.
The purity of the potassium citrate, the sodium chloride, the monopotassium phosphate, the imidazoline derivatives and the sodium hexametaphosphate is more than 98 percent.
The penetrating agent is polyether polyol with industrial grade content of more than 98%.
The sodium carboxymethyl starch is of industrial grade, has a molecular weight of 800-1000, and has a content of more than 98%.
The polyphosphonic acid is industrial grade, and the content is more than 10%.
The drag reducer is polyoxyethylene polyoxypropylene block copolymer, industrial grade, and the content of the drag reducer is more than 95%.
The density of the solid-free well killing fluid is 1.01-1.19g/cm 3 The pH value is between 6 and 7, the corrosion rate is more than or equal to 20 percent, the interfacial tension is less than or equal to 1.0mN/m, and the corrosion rate at 90 ℃ is less than or equal to 0.076mm/a. The system can dissolve mud, calcium components and invaded solid phase components in rock pores, enlarge effective seepage areas among the pores, enhance demulsification and drag reduction performance, improve the flowback capability of the well killing fluid to the maximum extent and reduce the damage of the reservoir permeability caused by fluid retention; meanwhile, the special identification, release and selective passivation corrosion inhibition technology is adopted, and the damage of the shaft pipe column caused by corrosion can be effectively prevented.
A method for preparing solid-free well killing fluid comprises measuring water 56-94.55 parts as base fluid; slowly adding 0.1-0.5 part of sodium carboxymethyl starch, and stirring for at least 30 minutes; adding 2-5 parts of potassium citrate and 0-28 parts of sodium chloride, and stirring for at least 10 minutes; then adding 0.2 to 0.5 portion of penetrating agent, 0.5 to 2.0 portions of drag reducer, 1 to 5 portions of monopotassium phosphate, 0.5 to 2.0 portions of imidazoline derivative, 0.1 to 0.5 portion of sodium hexametaphosphate and 0.05 to 0.5 portion of polyphosphonic acid, stirring for at least 15 minutes and obtaining the product.
The technical principle of the solid-free well killing fluid is as follows:
(1) Triple mechanism for improving reservoir seepage capability according to interaction among multiple additives
The first mechanism is as follows: the effective pore volume of reservoir rock is enlarged through the actions of corrosion, shrinkage expansion, solidification and scale inhibition to improve the seepage capability. The pores are first enlarged by erosion. The hydrogen ions released slowly by potassium dihydrogen phosphate and polyphosphonic acid in the system are utilized to slowly erode inherent calcium and mud components in the pores of the rock and dissolve calcium carbonate scale in external solid phase under the weak acid condition, thereby developing/increasing effective space in the pores.
And secondly, increase and maintain effective porosity through shrinkage-expansion solidification. By utilizing the synergistic effect of the polyphosphonic acid and the added potassium citrate and sodium carboxymethyl starch, the system acidity can be controlled, the system has stable corrosion performance, and the inherent clay layer in the reservoir rock can be compressed, so that the volume of the clay layer is reduced, and the effective pore volume is enlarged. The specific mechanism is as follows: after a long-term development process, a clay layer in the rock absorbs water under the action of intermolecular attraction, electrostatic repulsion and osmotic pressure to form a thick hydration film, and the distance between the clay layers is expanded to form a diffusion double electric layer; the potassium citrate in the system increases the salt content, reduces the concentration difference between a clay layer and a solution, reduces the osmotic pressure, inhibits the osmotic hydration effect and reduces the clay layer spacing; in addition, the macromolecular polar groups in the system are adsorbed on the surface of clay, the electrostatic repulsion of the clay layer is reduced, the water between double diffused layers is effectively removed, the interlayer spacing is compressed, glucose groups in the sodium carboxymethyl starch are influenced by phosphate, form a net shape through weak crosslinking, and are fixed on the surface of the clay, so that the clay and water molecules can be blocked, the resistance of the water molecules to permeate into the clay layer again is increased, the re-formation of a double diffused layer is prevented, the clay state after shrinkage and expansion is solidified, the water is stably preserved, and the re-occurrence of reversible water absorption expansion reaction is finally prevented.
Finally, effective pores are enlarged through the complexation and scale inhibition effects. The added sodium hexametaphosphate can complex calcium and magnesium ions, enhance cohesiveness and increase viscosity, and not only can enhance the shrinking and swelling effect of the anti-swelling agent in a synergistic system, but also can prevent regenerated scale and external scale from occupying limited space of pores and relatively expanding the pore volume; the sodium hexametaphosphate, the polyphosphonic acid and the potassium citrate in a specific proportion can stably adjust the pH value to be relatively stable in construction operation, and the pH value can be maintained between 6 and 7 even if clear water invades the well killing fluid, so that the blockage removal failure is avoided, and bicarbonate ions, carbonate ions and the like in formation water can be prevented from generating scale reaction with calcium ions.
And a second mechanism: and the seepage capability of a reservoir is improved through a lubricating and drag reduction mechanism.
The drag reducer in the system reduces flow consumption, reduces blockage, improves the flowability of crude oil and reduces seepage resistance by improving the shearing force of molecular layers in the crude oil in the pore channel.
And a third mechanism: cleaning oil block, preventing adhesion, treating rock in synergistic mode, enlarging space and improving seepage capacity
The penetrant polyether polyol in the system has fixed hydrophilic and oleophilic groups, and alcohol groups of the penetrant polyether polyol are mutually dissolved and dissolved with oil and water, so that organic components adhered to the surface of the rock can be effectively invaded, including high-condensation and high-viscosity oil blocks or a mixture of the oil blocks and water, the oil blocks adhered to the surface of the rock are prevented from being formed and dispersed and cleaned, the penetrating and dispersing effects are achieved, and the purpose of stripping crude oil is achieved; the surface of the rock is fully exposed after the oil cake is cleaned, the effective contact area of the surfactant and the rock is obviously increased, and the hydrophilic and oleophilic groups in the penetrant can be directionally arranged on the surface of the solution, so that the surface interfacial tension is obviously reduced; the cleaning of the oil block can further improve the corrosion, shrinkage and expansion and flowback efficiency of the system to the rock, and has good synergistic characteristics. The assistant belongs to a nonionic surfactant, has better salt resistance than a conventional anionic surfactant such as sodium dodecyl sulfate, can keep better performance under the condition of containing high salt in a system, and simultaneously, plays roles of emulsification, defoaming and dispersion of the drag reducer in cooperation with the drag reducer, reduces the size of liquid globules, reduces the deformation resistance of the liquid globules in a throat, prevents a Jamin effect, reduces water lock damage and improves the seepage capability of a reservoir. The example shows that the interfacial tension of the solid-free well killing fluid to kerosene is 0.18-0.65mN/m, the interfacial tension is greatly reduced, and the oil washing efficiency can reach more than 60% -75%.
(2) By the mechanisms of film forming passivation and slow corrosion, the corrosion inhibition performance of the system is improved, and the corrosion of the pipe column is effectively prevented.
The imidazoline derivative corrosion inhibitor in the system is matched with polyphosphonic acid, has the function of film forming and passivation, forms a protective layer on the surface of the pipe column, inhibits the electrochemical reaction of an acidic medium on steel, and effectively prevents the pipe column and equipment from being corroded. Moreover, the retarding mechanism and the special proportion of the components enable a well killing fluid system to automatically turn after operation, the back-flowing process and the formation water are quickly fused in a flowing state to react (the formation water is generally sodium bicarbonate water type), the pH value is controlled to be close to 7, and the corrosion inhibition components of the solid-phase-free well killing fluid are prevented from losing protection of a pipe column due to dilution caused by 'inrush' of the formation water in the back-flowing process.
The product of the invention has the erosion deblocking function which is obviously different from the conventional acidification deblocking/potential acid deblocking agent: firstly, the application purposes are different, the former is the well killing fluid, the well killing fluid is weakly acidic, and the corrosion resistance meets the well killing fluid standard; the latter is a working solution for production increasing measures, is strong acid, has a pH value generally lower than 4, and is easy to corrode a pipe column; therefore, the construction process is different, the former is conventional well repairing operation, and the latter needs special acidification process and matched special acidification pipe column; correspondingly, the two performances are different, the former can not only dissolve, remove blockage, shrink and resist scale, but also wash oil and assist in discharging, so as to prevent organic scale blockage; the latter is easy to be acid-sensitive and form acid sludge after being dissolved.
Compared with the traditional potassium chloride anti-swelling inhibition mechanism, the potassium citrate has the inhibition performance, and the potassium citrate not only can prevent the clay from further permeating, hydrating and swelling by utilizing the special stabilization effect of potassium ions on the crystal lattices of the clay, but also can remove the adsorbed water among the crystal lattices by the synergistic action with a high molecular group, thereby achieving the purposes of shrinking and swelling; meanwhile, the macromolecular bridges are adsorbed on the lattice surface to isolate and block, so that the clay layer is solidified, the shrinkage-expansion effect can be stably maintained, and the defects of single action mechanism, reversible reaction and unstable performance of the traditional anti-expansion agent such as potassium chloride and ammonium chloride are overcome.
The product of the invention has the cleaning and discharge-assisting performance, and has the same point with the conventional alcohol treating agent, namely, the product has the wetting and stripping effect on organic scale; the difference is that the action mechanism is further, other treating agents aim at organic scale, and the final treatment target is formation rock on the premise of cleaning the organic scale. After the rock surface adhesive layer is stripped, the nonionic groups in the cleaning agent and the drag reducer are combined to inhibit clay expansion and reduce interfacial tension.
The density of the product system of the invention is 1.01 to 1.19 (g/cm) 3 ) The pH value is between 6 and 7, the corrosion rate is more than or equal to 20 percent, the interfacial tension is less than or equal to 1.0mN/m, and the corrosion rate (90 ℃) is less than or equal to 0.076mm/a.
The main properties are shown in Table 1.
TABLE 1 Performance of the no-solid killing fluid
EXAMPLE 1 preparation of 100 parts of a solid free kill fluid
Adding 91.8 parts of clear water into a stirring tank, slowly adding 0.3 part of sodium carboxymethyl starch in turn under the stirring condition, stirring for 30 minutes, stirring for 10 minutes for 2 parts of potassium citrate, uniformly dissolving, then adding 0.3 part of penetrating agent and 0.5 part of drag reducer, uniformly stirring, and finally adding 4 parts of monopotassium phosphate, 0.5 part of imidazoline derivative and 0.2 part of sodium hexametaphosphate; 0.4 part of polyphosphonic acid, and stirring for 15 minutes to obtain a finished product.
TABLE 2 Corrosion Rate test data for steel sheets of different materials
Note: experiment temperature: 90 ℃; experimental time =72 hours;
EXAMPLE 2 preparation of 20 tons of solid free kill fluid
Adding 18.2 tons of clear water into a stirring tank, slowly adding 60kg of sodium carboxymethyl starch under stirring for 30 minutes, stirring 1 ton of potassium citrate for 10 minutes, uniformly dissolving, then adding 100kg of penetrating agent and 200kg of drag reducer, uniformly stirring, finally adding 240kg of monopotassium phosphate, 150kg of imidazoline derivative, 50kg of sodium hexametaphosphate and 50kg of polyphosphonic acid, and uniformly stirring for 15 minutes to obtain a finished product.
TABLE 3 Corrosion Rate test data for steel sheets at 90 deg.C
EXAMPLE 3 preparation of 30 tons of solid free kill fluid
Adding 24.8 tons of clear water into a stirring tank, sequentially and slowly adding 100kg of sodium carboxymethyl starch and stirring for 30 minutes under the stirring condition, stirring for 20 minutes, uniformly dissolving 1.2 tons of potassium citrate and 3 tons of sodium chloride, then adding 120kg of penetrating agent and 240kg of drag reducer and stirring uniformly, finally adding 240kg of monopotassium phosphate, 120kg of imidazoline derivative, 60kg of sodium hexametaphosphate and 90kg of polyphosphonic acid and stirring for 15 minutes to obtain the finished product.
TABLE 4 Corrosion Rate test data for steel sheets at 90 deg.C
Note: experiment temperature: at 90 ℃; experimental time =72 hours;
the non-solid phase well killing fluid not only has the conventional protective functions of balancing the formation pressure, preventing water sensitivity, preventing water lock, preventing solid phase invasion and the like of the common well killing fluid, but also can erode, remove blockage, reduce a hydrated and expanded clay layer, expand pore throats under the double action, improve the permeability of a near-well reservoir, fundamentally solve the flowback problem and strengthen the protective effect of an 'attack type' oil layer.
In summary, the disclosure of the present invention is not limited to the above-mentioned embodiments, and persons skilled in the art can easily set forth other embodiments within the technical teaching of the present invention, but such embodiments are included in the scope of the present invention.
Claims (8)
1. The solid-free well killing fluid is characterized by comprising, by mass, 56-94.55 parts of water, 2-5 parts of potassium citrate, 0-28 parts of sodium chloride, 1-5 parts of monopotassium phosphate, 0.2-0.5 part of a penetrating agent, 0.5-2.0 parts of an imidazoline derivative, 0.1-0.5 part of sodium hexametaphosphate, 0.1-0.5 part of sodium carboxymethyl starch, 0.05-0.5 part of polyphosphonic acid and 0.5-2.0 parts of a drag reducer.
2. The solidless kill fluid of claim 1 wherein the potassium citrate, sodium chloride, monopotassium phosphate, imidazoline derivative, sodium hexametaphosphate are greater than 98% pure.
3. The solidless well control fluid as recited in claim 1 wherein the penetrating agent is a polyether polyol, technical grade, having a content of greater than 98%.
4. The solidless well killing fluid according to claim 1, wherein the sodium carboxymethyl starch is industrial grade, has a molecular weight of 800-1000, and has a content of more than 98%.
5. The solidless well control fluid of claim 1 wherein the polyphosphonic acid is technical grade and is present in an amount of 10% or more.
6. The solidless kill fluid of claim 1 wherein the drag reducing agent is a polyoxyethylene polyoxypropylene block copolymer, technical grade, having a content of greater than 95%.
7. The solidless well killing fluid as claimed in any one of claims 1-6, wherein the solidless well killing fluid has a density of 1.01-1.19g/cm 3 The pH value is between 6 and 7, the corrosion rate is more than or equal to 20 percent, the interfacial tension is less than or equal to 1.0mN/m, and the corrosion rate at 90 ℃ is less than or equal to 0.076mm/a.
8. A preparation method of a solid-free well killing fluid is characterized in that 56-94.55 parts of measured water is taken as a base fluid; slowly adding 0.1-0.5 part of sodium carboxymethyl starch, and stirring for at least 30 minutes; adding 2-5 parts of potassium citrate and 0-28 parts of sodium chloride, and stirring for at least 10 minutes; then adding 0.2 to 0.5 portion of penetrating agent, 0.5 to 2.0 portions of drag reducer, 1 to 5 portions of monopotassium phosphate, 0.5 to 2.0 portions of imidazoline derivative, 0.1 to 0.5 portion of sodium hexametaphosphate and 0.05 to 0.5 portion of polyphosphonic acid, stirring for at least 15 minutes and obtaining the product.
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| CN106479464A (en) * | 2015-08-31 | 2017-03-08 | 中国石油化工股份有限公司 | A kind of temporarily stifled type high temperature well killing fluid being applied to low-permeability oil deposit and preparation method |
| CN105154037A (en) * | 2015-09-15 | 2015-12-16 | 中国石油天然气股份有限公司 | Solid-phase-free composite synergistic high-density kill fluid and preparation method thereof |
| CN111500266A (en) * | 2019-01-30 | 2020-08-07 | 中国石油化工股份有限公司 | Completion fluid composition and application thereof |
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