RU2546684C1 - Preparation method of composition for isolation of behind-casing flows in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in a preparation method of compositions for the isolation of behind-the-casing flows in a well that includes mixing of microcement and additives, oil well portland cement with the specific surface of 800 or 900 m²/kg is used as the microcement and a water-soluble acrylamide polymer, copolymer of vinyl amide and n-vinyl lactam, olefin sulphonate and polyethylene glycol at the water-cement ratio of 0.75-1.2 are used as the additives for the preparation of the composition; a microcement grouting fluid is prepared preliminarily with a solution of the above listed additives in water at simultaneous stirring, then the microcement is added to the produced fluid with the following ratio of ingredients, in weight parts: oil well portland cement with the specific surface of 800 or 900 m²/kg - 100, water-soluble acrylamide polymer - 0.01-0.02, copolymer of vinyl amide and n-vinyl lactam - 1.0-2.5, olefin sulphonate - 0.01-1.0, polyethylene glycol - 0.05-0.15, and water 75-120.

EFFECT: improved workability and efficiency in the isolation of behind-the-casing flows in the well due to the increased strength and expanded time range for hardening of the microcement-based composition.

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Description

 The invention relates to the oil and gas industry, in particular to compositions for the elimination of annular flows in the well.

A known method of preparing an insulating composition (patent RU No. 2501935, IPC ЕВВ 29/10, publ. 12/20/2013, Bull. No. 35), in which microcement is mixed with fresh water with a density of 1000 kg / m in a mass ratio of 2: 3, respectively.

The disadvantage of this method is the rapid curing of the composition, which can cause technological difficulties in the preparation of the insulating composition and insulation work.

Closest to the claimed is a method of preparing a composition based on microcement using additives - plasticizer Glenium-51 (Storchak V.A., Melekhin A.A. Development of grouting mixtures based on microcements // Construction of oil and gas wells on land and at sea . - 2011. - No. 8. - S. 51-53).

The disadvantage of this method of preparing the composition is the short curing time of the composition is 2.5 hours, which can lead to its premature curing, which creates a risk of accident during repair and insulation work in the well.

An object of the invention is to increase the manufacturability and efficiency of elimination of annular crossflows in the well by increasing the strength and expanding the curing time range of the composition based on microcement.

The technical problem is solved by the method of preparation of the composition for the elimination of annular flows in the well, including the mixing of microcement and additives.

New is that cement slab Portland cement with a specific surface of 800 or 900 m ² / kg is used as microcement, water-soluble acrylamide polymer, a copolymer of vinylamide and n-vinyl lactam, olefin sulfonate and polyethylene glycol at a water-cement ratio of 0.75 are used as additives -1.2, the microcement mixing liquid is previously prepared by dissolving the above additives in water with stirring, then microcement is added to the resulting mixing liquid in the following ratio and ingredients, wt. hours:

cement Portland cement with specific 800 or 900 m ² / kg one hundred water soluble acrylamide polymer 0.01-0.02 copolymer of vinylamide and n-vinyl lactam 1.0-2.5 olefinsulfonate 0.01-1.0 polyethylene glycol 0.05-0.15 water 75-120

Below are the reagents used in the claimed method:

- as microcement use Portland cement grouting in accordance with GOST 1581-96, additionally finely ground, with a specific surface of 800 or 900 m ² / kg;

- a water-soluble polymer of acrylamide (C ₃ H ₅ NO)) n of a molecular weight of 5.5 · 10 ⁵ with a bulk density of 910 kg / m ³ , resistant to high temperature (21-121 ° C), finely dispersed powder, is used as an anti-precipitation reagent -Brown. It allows to obtain a homogeneous structure of the composition and prevents the deposition of microcement by increasing the viscosity and imparting sedimentation stability to the solution;

- a copolymer of vinylamide and n-vinyl lactam, an instant white powder, is used as a fluid loss reducer. The solids content is 90-99%. The activity index of hydrogen ions of a 1% aqueous solution of pH 6.5. Increases compressive strength of cement stone;

- olefin sulfonate is used as a plasticizer - a condensation product of sulfonate and an aromatic hydrocarbon, a finely divided brown powder. Bulk density - 1360 kg / m ³ . It is added to the composition in order to improve its rheological characteristics;

- polyethylene glycol, a colorless liquid with a slight odor, without alcohol, is used as an antifoam. The content of hydroxide ion is 28 mg / g. Viscosity at 20 ° C - in the range of 450-550 mm ² / s. Density - 1000 kg / m ³ . Prevents the formation of bubbles, destroys and removes the formed air bubbles.

It is known that cementing Portland cement with a specific surface area of 800 or 900 m ² / kg reacts with water more quickly than cementing. To use the composition based on cement Portland cement in repair and insulation works, it is necessary to increase the setting time, which may adversely affect the strength characteristics of cured cement stone.

The essence of the proposed technical solution consists in the fact that according to the proposed method, a composition is prepared for eliminating annular cross-flows in the well, which includes additives that can increase its setting time, as well as regulate such qualities of Portland cement grout as water loss, flowability, density and curing time at maintaining the strength characteristics of cured cement stone. The composition of the proposed method is prepared directly at the well, is easily pumped into the zone of violation, has sufficient curing time for pumping and the necessary properties of the cured stone. Due to the small size of cement particles, the composition penetrates into the microcracks of rocks and low-permeability formations.

Technological and strength characteristics of the prepared composition by the proposed method was investigated in laboratory conditions by standard methods, the research results are presented in the table. A mixing liquid of cement Portland cement was prepared in a 3-liter beaker: in 1600 g of water for the water-cement ratio (W / C) 1, 0.32 g (0.02 wt.) Of a water-soluble acrylamide polymer was dissolved with mechanical stirring for 30 minutes, then 32 g (1.5 parts by weight) of a copolymer of vinylamide and n-vinyl lactam were added and mixed for another 30 minutes until completely dissolved. To the resulting solution, 1.6 g (0.1 parts by weight) of polyethylene glycol and 14.4 g (0.9 parts by weight) of olefin sulfonate were added and stirred for 15 minutes. After the above additives were dissolved, 1600 g (100 parts by weight) of cement Portland cement were added to the mixing liquid and mixed for 30 minutes (experiment No. 1, table). Density, spreadability, water loss, curing time and compressive strength after 7 days were determined, the test results are presented in the table. The compressive strength after 7 days for the composition according to the proposed method is higher: at W / C = 0.75-1.2 is in the range of 10.2-24.04 MPa, while the closest analogue at W / C = 0, 7-1 is in the range of 8-17 MPa (without olefinsulfonate) and 6-12 MPa (with olefinsulfonate). Grouting Portland cement in the claimed method has a specific surface area of 800 or 900 m ² / kg, while the closest analogue is 650 m ² / kg. This indicates a smaller particle size of the cement Portland cement in the claimed method, as well as its better penetrating ability compared to the closest analogue. Due to the very small particles of grouting Portland cement, the composition according to the claimed method penetrates microcracks of hard rocks and fine-grained soils, providing water resistance, strength and durability, which increases its insulating ability and, accordingly, efficiency. The curing time of the obtained composition is two times longer than that of the closest analogue, which increases the manufacturability of the proposed method.

Based on the results obtained, experiments No. 1-2, 5-7 with a W / C in the range of 0.75-1.2, which showed a flowability at which the compositions are well pumped through tubing, are optimal, have an optimal time. curing and good strength characteristics. In experiment No. 3, the spreadability of the composition is more than 250 mm and it shrinks when cured. Experiments No. 4 and No. 8 showed a spreadability that does not allow pumping the compositions along the tubing - 160 and 170 mm, respectively, so these compositions were excluded from the optimal range.

Based on the results, a composition was selected with an optimal range of additive content, in which it has the necessary technological characteristics in the following ratio of ingredients, wt. hours:

cement Portland cement with specific surface of 800 or 900 m ² / kg one hundred water soluble acrylamide polymer 0.01-0.02 copolymer of vinylamide and n-vinyl lactam 1.0-2.5 olefinsulfonate 0.01-1.0 polyethylene glycol 0.05-0.15 water 75-120.

An example of the proposed method (experience No. 1, table). The proposed method was used to eliminate annular flow in the well with a current bottom of 1781.6 m and a perforation interval of 1758.8-1760.8; 1761.8-1762.4; 1768-1769 m. The drilled packer was lowered onto the tubing and planted to a depth of 1766 m. 2.7 tons of cement Portland cement (100 parts by weight) were loaded into the hopper of the UNB-125 × 50 СО aggregate. 2.7 m ³ (100 parts by weight) of water were collected in a mixing tank of UNB-125 × 50 СО. 0.54 kg (0.02 parts by weight) of a water-soluble acrylamide polymer was gradually added to water with constant circulation in water, after it was dissolved in small portions, 40.5 kg (1.5 parts by weight) of a vinyl amide copolymer and n- vinyl lactam, after its dissolution, 24.3 kg (0.9 parts by weight) of olefin sulfonate was gradually added in small portions, stirred for 10 minutes, then 2.7 kg (0.1 parts by weight) of polyethylene glycol was gradually added in small portions and mixed until completely dissolved. Mixing liquid prepared in a UNB-125 × 50 СО mixing tank was gradually fed from the hopper 2.7 tons (100 parts by weight) of cement Portland cement and mixed until the density was equalized. The volume of the resulting composition based on cement Portland cement was 3.50 m ³ with a density of 1600 kg / m ³ . 3.50 m ^{3 of the} obtained composition, 1.0 m ^{3 of} water, 4.1 m ^{3 of} process fluid were pumped into the tubing. Raised the packer landing gear to a depth of 1764 m. With the tool pacing during lifting, a control backwash of the cement Portland cement solution was carried out to 8.0 m ^{3 of} clean water. Raised the packer landing device on 73 mm tubing from the well. They left the well for curing the grouting Portland cement for 48 hours. Then the well was mastered and put into operation. As a result of the work, the water cut of the well decreased by 30%. The remaining examples are carried out similarly and are shown in the table.

Thus, the proposal provides an increase in manufacturability and the elimination of annular crossflows in the well by increasing the strength and expanding the curing time range of the composition based on cement Portland cement.

Claims (1)

A method of preparing a composition for eliminating annular cross-flows in a well, comprising mixing microcement and additives, characterized in that cement slab Portland cement with a specific surface of 800 or 900 m ² / kg is used as microcement, water-soluble acrylamide polymer, vinylamide copolymer are used as additives for preparing the composition and n-vinyl lactam, olefin sulfonate and polyethylene glycol at a water-cement ratio of 0.75-1.2, a microcement mixing liquid is previously prepared by dissolving in water and mixing the above additives and then mixing the resulting liquid is added microcement with the following ratio of ingredients, wt. hours:
cement Portland cement with specific surface of 800 or 900 m ² / kg one hundred water soluble acrylamide polymer 0.01-0.02 copolymer of vinylamide and n-vinyl lactam 1.0-2.5 olefinsulfonate 0.01-1.0 polyethylene glycol 0.05-0.15 water 75-120