RU2348672C1 - Kill fluid for gas and gas condensate wells, method of its obtainment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: fluid is intended fir killing productive clay sandstones with gas saturation and acidic character of residual pore waters. Method of obtaining kill fluid for gas and gas condensate wells involves component dissolution in water medium and sequential mixing. Chrysotile asbestos is matured for 6-8 hours in water solution of aluminium sulfate, ground in dispersion device, obtained aluminised asbestos suspension is processed by calcium salt of nitryltrimethylphosphonic acid obtained by dissolving potassium hydroxide, nitryltrimethylphosphonic acid and calcium chloride in water. Obtained aluminophosphonic suspension is mixed with solution obtained by dissolving carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC) and potassium chloride in water, then potassium carbonate is added to the obtained composition at the following component ratio, wt %: CMC 1.4-1.6, HEC 0.4 -0.5, potassium chloride 6.8 -7.1, chrysotile asbestos 0.45-0.55, aluminium sulfate 0.45-0.55, potassium hydroxide 0.9 -1.1, nitryltrimethylphosphonic acid 0.9 -1.1, calcium chloride 0.9 -1.1, potassium carbonate 0.40-0.50, the rest is water. Kill fluid for gas and gas condensate wells is obtained by the claimed method.

EFFECT: enhanced sedimentation resistance.

2 cl, 2 ex, 4 tbl

Description

The invention relates to the oil and gas industry and, in particular, to process fluids for damping productive deposits represented by clay sandstones.

Known liquid for killing wells, including the surfactant ML-80, sulfite-alcohol yeast vinasse (BDSB), hydroxyethyl cellulose, produced water and clay swelling inhibitor - potassium chloride [RU. Patent No. 2183735. C1. IPC S09K 7/00; ЕВВ 43/12. Publ. 06/06/20. Well killing fluid].

The disadvantage of silencing liquid is the high consumption rate according to the PRSP and the impossibility of applying this technical solution in the winter in conditions of negative atmospheric temperatures, as well as in areas with no year-round transport connection, since the PRSP contains up to 50% of water and its delivery to the drilling site at minus temperature is problematic, but in the warm season it is not economically justified.

A closer technical solution chosen for the prototype is a liquid containing as a thickener the polymer complex "Praestol 2530 + sulfacell + aluminum sulfate", and as a filler - aluminosilicate microspheres AFM [RU. Patent No. 2187529. C1. IPC S09K 7/00; ЕВВ 43/12. Publ. 08/08/20. Fluid for killing oil, gas and gas condensate wells.].

The disadvantage of this killing fluid is the absence of clay swelling inhibitor in its composition and, therefore, its unsuitability for killing productive clay sandstones.

A known method of producing fluid for killing wells, which includes dissolving the components in an aqueous medium and their subsequent mixing [RU. Patent No. 2082878. C1. IPC S09K 7/06; ЕВВ 43/22. Publ. 1997.06.27. A method of obtaining a fluid killing oil wells.].

The disadvantage of this method is that it does not provide for the mechanochemical treatment of the reagents before mixing them, and therefore the filler reagents have large particles, and the kill fluid that they comprise is a sedimentation-unstable system.

The task of the invention is to develop a method for producing a sedimentation-resistant fluid for killing gas and gas condensate wells, which has a minimal negative effect on the filtration-capacitive properties of the rocks of the near-wellbore zone of the reservoir, represented by clay sandstones with an acidic nature of residual water saturation.

The technical solution of the problem lies in the fact that for killing gas and gas condensate wells, an aluminum phosphonic liquid is proposed, which contains two cellulose ethers as a thickener: carboxymethyl cellulose and hydroxyethyl cellulose, and as a complexing filler, it contains chrysotile asbestos, which is dispersed in aluminum sulfate conditional viscosity (HC ₅₀₀ ) 150-200 s, then hydrophobized with calcium salt of nitrilotrimethylphosphonic acid, and additionally contains potassium hydroxide, carbonate and chloride in the following ratio of components, wt.%: carboxymethyl cellulose 1.4-1.6; hydroxyethyl cellulose 0.4-0.5; potassium chloride 6.8-7.1; asbestos 0.45-0.55; aluminum sulfate 0.45-0.55; potassium hydroxide 0.9-1.1; nitrilotrimethylphosphonic acid 0.9-1.1; calcium chloride 0.9-1.1; potassium carbonate 0.40-0.50; water is the rest.

The task posed when creating a method for producing fluid for killing gas and gas condensate wells is to solve the problem of sedimentation stability of a multicomponent system with fiber-powder mineral filler.

The problem is solved in that chrysotile asbestos is kept for 6-8 hours in an aqueous solution of aluminum sulfate, crushed in a dispersing device, the resulting suspension of aluminized asbestos is treated with a solution of calcium salt of nitrilotrimethylphosphonic acid obtained by dissolving potassium hydroxide, nitrilotrimethylphosphonic acid, calcium chloride aluminophosphonic suspension is mixed with a solution obtained by dissolving in water carboxymethyl cellulose, hydroxyethyl cellulose and potassium chloride, ATEM the resulting composition is administered potassium carbonate at the following component ratio, wt.%:

Carboxymethyl cellulose 1.4-1.6 Hydroxyethyl cellulose 0.4-0.5 Potassium chloride 6.8-7.1 Chrysotile Asbestos 0.45-0.55 Aluminum sulphate 0.45-0.55 Potassium hydroxide 0.9-1.1 Nitrilotrimethylphosphonic acid 0.9-1.1 Calcium chloride 0.9-1.1 Potassium carbonate 0.4-0.5 Water rest.

The fluid for killing gas and gas condensate wells is characterized in that it is obtained by the above method.

For the preparation of aluminophosphonic fluids, drilling reagents manufactured by the domestic industry are used:

- carboxymethyl cellulose (CMC) according to TU 2231-057-07508003-2002;

- hydroxyethyl cellulose (Sulfacell) according to TU 2231-013-32957739-01;

- asbestos grade A-6K-5; grade P-6-30;

- aluminum sulfate according to GOST 3758-75;

- nitrilotrimethylphosphonic acid (NTP) according to TU 6-09-5283-86;

- calcium chloride according to GOST 450-77;

- potassium chloride according to GOST 4568-95;

- potassium hydroxide according to GOST 24363-80;

- potassium carbonate (potash) according to GOST 3450-89.

Purpose of reagents in aluminophosphonic liquid: CMC and Sulfacell - thickeners; asbestos - fibrous colmatant; aluminum sulfate - asbestos dispersion activator and complexing agent; NTF - complexing agent and clay swelling inhibitor; calcium chloride - asbestos surface modifier and source of calcium ions for the synthesis of chalk; potassium hydroxide - an accelerator of the dissolution of NTF and a source of potassium ions to inhibit clay swelling; potassium chloride - mineralizer, mud density regulator and clay swelling inhibitor; potassium carbonate - a source of carbonate anions for the synthesis of chalk and a source of potassium ions for inhibiting clay swelling.

The purpose of the kill fluid is to push its hydrocarbon products deep into the formation with the formation of a polymer screen on the well wall reinforced with acid-soluble fillers of fibrous (asbestos) and spherical (chalk) shape.

Example 1. Laboratory method for producing aluminophosphonic liquid

Stages and chemistry of the process of producing aluminophosphonic fluid for killing gas and gas condensate wells

- preparation of a solution of CMC, Sulfacell and potassium chloride;

- dissolution in water of aluminum sulfate:

nAl ₂ (SO ₄ ) ₃ + nH ₂ O → 2nAl ⁺³ + 3nSO ₄ ^-2 + nH ⁺ + nOH ^- ;

- processing of asbestos with a solution of aluminum sulfate:

nMg ₆ Si ₄ O ₁₀ (OH) ₈ + 2nAl ⁺³ → n [Al ₂ Mg ₄ Si ₄ ) O ₁₀ (OH) ₈ ] ⁺² + 2nMg ⁺² ;

- dispersion of asbestos treated with a solution of aluminum sulfate;

- obtaining the calcium salt of nitrilotrimethylphosphonic acid:

N≡ [CH ₂ -P (O) (OH) ₂ ] ₃ + 6KOH → N≡ [CH ₂ -P (O) (OK) ₂ ] ₃ + 3CaCl ₂ → N≡ [CH ₂ -P (O) ( O ₂ Ca)] ₃ + 6KCl;

- processing dispersed asbestos with a solution of calcium salt NTF:

nN≡ [CH ₂ -P (O) (O ₂ Ca)] ₃ + n [Al ₂ Mg ₄ Si ₄ ) O ₁₀ (OH) ₈ ] ⁺² → n [(CaO ₂ ) (O) -P-CH ₂ ] = N-CH ₂ -P (O) = O ₂ = [Al ₂ Mg ₄ Si ₄ ) O ₁₀ (OH) ₈ ] + nCa ²⁺ ;

- mixing asbestos-phosphonic suspension with polymer-salt solution;

- processing aluminophosphonic liquid potassium carbonate:

nCa ²⁺ + nК ₂ СО ₃ → nCaCO ₃ ↓ + 2nК ⁺ .

a) In a 1 L glass two-necked round bottom flask equipped with a propeller-type mechanical stirrer with a rotational speed of 2 s ^-1 , 717 ml of water are poured, a stirrer is turned on and 5.3 g of Sulfacell, 15.9 g of CMC and 74.2 g of chloride are sequentially introduced potassium. The contents of the flask are stirred for 4 ... 6 hours until all components are completely dissolved.

b) Pour 100 ml of water into a chemically resistant glass beaker with a capacity of 150 ml, pour 5.3 g of aluminum sulfate (calculated on anhydrous salt), mix until aluminum sulfate dissolves, pour 5.3 g of asbestos. Stirred for 5 ... 10 minutes. An unstable suspension is obtained with a conditional viscosity (HC ₅₀₀ ) of 20-25 seconds, measured using a VBR-1 viscometer. The suspension is left to “soak” for 6 ... 8 hours, after which the alumina-asbestos suspension is dispersed using a laboratory homogenizer (model MPW-302) at a speed of 10 ... 20 s ^-1 for 3 ... 5 minutes to the nominal viscosity (HC ₅₀₀ ) 150-200 sec.

c) In a 250 ml glass two-necked flask equipped with a propeller-type mechanical stirrer with a rotation speed of 2 s ^-1 , 100 ml of water are poured, a stirrer is turned on, and 10.6 g of potassium hydroxide, 10.6 g of nitrilotrimethylphosphonic acid (NTP) are sequentially introduced . Stir until both reagents are completely dissolved, after which 10.6 g of calcium chloride are added (calculated as anhydrous salt). Stirred for 10 ... 15 minutes.

d) The contents of the glass according to item b) is transferred to a flask with a solution of calcium salt of NTF according to item c) and stirred for 30 minutes. Get complexing filler - hydrophobized aluminophosphonic chrysotile asbestos.

e) Hydrophobized aluminophosphonic chrysotile asbestos is added portionwise to a flask with stirring containing an aqueous solution of Sulfetzell, CMC and potassium chloride. Stirred until a homogeneous suspension is obtained, after which 5.3 g of potassium carbonate are added. Aluminophosphonic liquid is stirred for 1 ... 1.5 hours. Then determine its technological indicators. Similarly, aluminophosphonic fluid variants are obtained (Tables 1 and 2).

Example 2. Preparation of aluminophosphonic liquid for killing gas and gas condensate wells (calculation for 4 m ³ )

0.4 m ^{3 of} water is poured into the capacity of the cementing unit and 21 kg of aluminum sulfate are poured (calculated on anhydrous Al ₂ (SO ₄ ) ₃ salt). Stirred on the principle of "capacity-pump-capacity" until complete dissolution of aluminum sulfate. To a solution of aluminum sulfate add 21 kg of asbestos. Mix again. An unstable suspension is obtained with a conditional viscosity (HC ₅₀₀ ) of 20-25 seconds, which is left to “soak” for 6 ... 8 hours.

In the second tank of the unit, a solution of the calcium salt of nitrilotrimethylphosphonic acid (Ca-NTP) is prepared. For this, 0.4 m ^{3 of} water is poured into the capacity of the cementing unit, 40 kg of potassium hydroxide and 40 kg of NTF are also poured there. Stirred for 20 minutes using a pump. Then 40 kg of calcium chloride are poured into the same place (calculation for anhydrous salt). Stirred on the principle of "capacity-pump-capacity" for 0.5 hours.

The contents of both containers of the cementing unit are mixed and the resulting suspension is pumped through the dispersant to obtain a homogeneous mass (3-5 cycles) with a nominal viscosity (HC ₅₀₀ ) of 150-200 sec.

2.87 m ^{3 of} water is poured into the clay mixer, 21 kg of Sulfacell and 62.4 kg of CMC are loaded there. Stirred for 4 hours (until complete dissolution of both polymers). Then 303 kg of potassium chloride are poured into the clay mixer. Stirred for 20 minutes until the salt is completely dissolved (control by density).

Using the pump, the aluminum phosphonic suspension is pumped from the unit tank to the clay mixer and mixed with the polymer-salt solution located there. The total mass is stirred for 2 hours. 21 kg of potassium carbonate (potash) are added. Stirred for 20 minutes. The indicators of the aluminophosphonic liquid are determined.

Table 3 shows the time spent on preparing one portion of the aluminophosphonic liquid with a volume of 4 m ³ .

From the results of Tables 1 and 2, it can be seen that the aluminophosphonic liquid (AFJ: options) has heat resistance that meets the conditions of occurrence of productive formations in the fields of the Siberian platform, is sedimentation stable for a long time (more than 30 days) and has good crust-forming properties.

In order to prevent swelling, dissolution and softening of layered aluminosilicates cementing the matrix of productive sandstone, inhibitory components were introduced into the composition of the alumophosphonic liquid: K ⁺ , Ca ^{+ 2,} and NTF. To block the input (output for hydrocarbon fluid) transport channels providing a “reservoir-to-well” connection, the aluminophosphonic liquid contains a fibrous phase hydrophobized with the calcium salt of nitrilotrimethylphosphonic acid. Filtration control in the aluminophosphonic liquid layer is carried out due to two water-soluble cellulose ethers (CMC + Sulfacell).

Aluminophosphonic liquid is intended for killing (blocking) productive clay sandstones with gas saturation and acidic character of residual pore water.

The possibility of restoring the permeability of sandstones after completion of the operations using the proposed method is confirmed by filtration experiments performed on a high-pressure installation UIPK-1M.

Conducting a filtration study

The work uses sandstone samples of the Parfenovo horizon of the Kovykta field, prepared in a standard way for filtration studies.

After creating acid residual water saturation with formation water with a density of 1.244 g / cm ³ and a pH of 3.6, having a composition, g / l: Ca ⁺² 106.64; Mg ⁺² 9.35; K ⁺ 7.44; Na ⁺ 0.36; Cl ^- 226.97; Br ^- 4.68, killing fluid is supplied to the end of the sample and pumped through the sample in an amount of 1.5 pore volumes, then blocking fluid is supplied in the same direction and a pressure of 5.0 to 8.4 MPa is created. Filtration is continued until the stabilization of the process of liquid penetration into the core. After this, the permeability (K ₁ ) of the sandstone is determined by the decan, feeding it into the sample from the opposite end. Then, the inlet end face of the sandstone sample is brought into contact with the clay composition, simulating the effect of the clay bath. The exposure time of the clay-acid bath (without pumping it through the sample) is 4 hours.

After the clay bath, the permeability (K ₂ ) of the sandstone is determined by the decan, again feeding it into the sample from the opposite end.

The results of the assessment of the effect of the kill fluid and the clay-acid bath on the sandstone samples of the Parthenov horizon of the Kovykta deposit are given in Table 4.

Table 4 Sample No. (Well No.) Sample exposure time, hour (at pressure, MPa) Filtration properties of a sandstone sample Alumophosphonic liquid AFZh-2 Clay acid bath composition, wt.%: HCl 5; NH ₄ HF ₂ 1.7; water - the rest The initial permeability with residual water saturation, MD The recovery coefficient of the permeability of the sample after exposure to AFJ-2 (K ₁ ), MD The recovery coefficient of the permeability of the sample after exposure to a clay bath (K ₂ ), MD 1270 (3) 7.0 (7.1) 1.8 (8.0) 6.7 (5.0) 4.0 (0.1) 0.15 76 102 5-II (17) 5.0 (5.0) 1.5 (6.0) 8.6 (7.3) 2.0 (8.4) 4.0 (0.1) 27.60 82 94

The data obtained confirm the possibility of implementing the proposed method of plugging formations with a clay-sandstone type reservoir and acidic residual water saturation and show the efficiency of reservoir release with complete restoration of its initial permeability when creating depression and pumping hydrocarbon fluid from the opposite end of a clay sandstone sample.

Claims (2)

1. A method of producing a fluid for killing gas and gas condensate wells, comprising dissolving the components in an aqueous medium and mixing them sequentially, characterized in that chrysotile asbestos is kept for 6-8 hours in an aqueous solution of aluminum sulfate, and the suspension obtained is ground in a dispersing device aluminized asbestos is treated with a solution of the calcium salt of nitrilotrimethylphosphonic acid obtained by dissolving in water potassium hydroxide, nitrilotrimethylphosphonic acid, calcium chloride obtained w alyumofosfonovuyu suspension was mixed with a solution obtained by dissolving in water, carboxymethyl cellulose, hydroxyethyl cellulose, and potassium chloride, then the resulting composition is administered potassium carbonate at the following component ratio, wt.%:
carboxymethyl cellulose 1.4-1.6 hydroxyethyl cellulose 0.4-0.5 potassium chloride 6.8-7.1 chrysotile asbestos 0.45-0.55 aluminum sulfate 0.45-0.55 potassium hydroxide 0.9-1.1 nitrilotrimethylphosphonic acid 0.9-1.1 calcium chloride 0.9-1.1 potassium carbonate 0.40-0.50 water rest 2. Liquid for killing gas and gas condensate wells, characterized in that it is obtained by the method according to claim 1.