RU2344153C1 - Drilling agent - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to the field of oil and gas industry, namely, to drilling agents for opening of producing reservoir bed. Drilling agent contains following, wt %: biopolymer xanthan of brands "Saraksan-T" or "Saraksan" 0.2-0.7; α-glucan 0.2-0.8; salt or mixture of salts of univalent metals 1-55; defoaming agent of brand "Sofeksil-9056-20x" 0.01-0.2; bactericide of brand biocide SMB 0.1-0.5; water - the rest. As α-glucan, modified starch or dextran is used. As salts of univalent metals, chlorides or nitrates, or nitrites, or thiosulfates, or carbonates, or acetates, or bromides, or sodium or potassium formates, or their mixtures are used.

EFFECT: preparation of drilling agent with adjusted density without solid phase for high quality opening of producing reservoir bed with the purpose of its initial permeability preservation.

4 cl, 4 tbl, 4 ex

Description

The invention relates to the field of the oil and gas industry, namely to drilling fluids for opening a productive reservoir.

The closest analogue to the claimed one is a drilling fluid containing a solid phase and capable of creating a thixotropic structure with a low filtration rate. The drilling fluid includes a xanthan biopolymer, salts or a mixture of salts of monovalent or divalent metals (sodium chloride, potassium chloride, calcium chloride), α-glucan (starch modified by hydroxyl groups), solid phase (Palex bentonite, calcium carbonate, magnesia, barite) and water (see US patent No. 4422947, IPC C09K 007/02, publ. 12/27/83).

The known technical solution has the disadvantage that a solid phase is introduced into the drilling fluid to create the required density (Palex bentonite, calcium carbonate, magnesia, barite), and therefore it is not possible to control the density to create a drilling fluid without a solid phase, which is not allows you to qualitatively open reservoir layers. When creating this technical solution, the technical problem of creating a drilling fluid with adjustable density without a solid phase was solved for high-quality opening of the reservoir, in order to maintain its initial permeability.

This technical problem is solved by the fact that the drilling fluid consists of a xanthan biopolymer of the Saraksan or Saraksan-T grades, a salt or a mixture of monovalent metal salts, α-glucan (modified starch or dextran), water, Sofexil-9056- defoamer 20x ", a bactericide of the brand Biocide-SMB, in the following ratio of components in the mixture, wt.%:

specified biopolymer 0.2-0.7 α-glucan 0.2-0.8 salt or mixture of monovalent salts of metals 1-55 specified antifoam 0.01-0.2 specified bactericide 0.1-0.5 water rest

Chlorides, or nitrates, or nitrites, or thiosulfates, or carbonates, or acetates, or bromides, or sodium or potassium formates, or mixtures thereof, can be used as monovalent metal salts. As α-glucan, modified starch or dextran is used. The solution has a density of from 1005 to 1700 kg / m ³ .

Xanthan biopolymer is a heteropolysaccharide synthesized by the bacteria Xanthomonas campestris. Xanthan biopolymer of the Saraksan or Saraksan-T grades (see RF patent No. 2252033, IPC 7 A61K 47/36, С12Р 19/06, published on 05/20/05) is allowed in oil production processes.

α-Glucan is a polysaccharide built only from D-glucose monosaccharide residues. Α-glucans include, for example, dextran or starch (unmodified and modified) (see General Organic Chemistry. Volume 2. Edited by N.K. Kochetkov, M .: Chemistry, 1986, p.213). Hydroxyl-modified starch, constructed from D-glucopyranose residues joined by α-1,4-glycosidic bonds, is a polysaccharide reagent for drilling fluids (see TU 6-55-221-147797). Dextran is a polysaccharide consisting of D-glucopyranose residues joined by α-1,6- and α-1,3-glycosidic bonds.

The silicone defoamer of the Sofexil 9056-20x brand is an aqueous emulsion of modified polydimethylsiloxane (TU 2251-009-4294526-00).

Biocide SMB refers to bactericides. The bactericide of the brand Biocide SMB is an organic substance of low molecular weight, which inhibits the vital activity of bacteria and allows you to save the rheological and filtration parameters of the drilling fluid based on biopolymer and α-glucan. In the present invention, Biocide-SMB is used, which is a liquid mixture of the active substances of chloro-methyl-isothiazolinone and methyl-isothiazolinone, which has a wide spectrum of action against bacteria, fungi and yeast, chemically and thermally stable in the pH range from 2 to 9 and temperature exposure up to 65 ° C (TU 9392-049-42942526-2005). SMB biocide provides a longer lifespan of polymer components when the temperature rises above 25 ° C (above this temperature, especially at 30-40 ° C, bacteria are active against polymer reagents, which is accompanied by the decomposition of biopolymer additives) and the time the well remains for longer 2 weeks (up to two weeks, mineral salts dissolved in water act as a preservative agent). The concentration of the bactericide in the solution depends on the density of the solution and the temperature of the reservoir. The higher the density of the solution, the lower the concentration of the bactericide, with increasing temperature of the reservoir, the concentration of the bactericide increases. Typically, the concentration of the bactericide is in the range of 0.1-0.5 wt.%.

The pH of the drilling fluid, depending on the type and concentration of salts, ranges from 7 to 11.

Monovalent metal salts in various proportions provide the density of the drilling fluid from 1005 to 1700 kg / m ³ , increase the thickening ability of xanthan, minimize the external effect on the rheological properties of the drilling fluid, and at a high content in the solution (saline solutions) have preservative properties at temperatures up to 30 ° C (above 30 ° C, a bactericide should be added), due to which the drilling fluid remains highly effective for a long time. Xanthan biopolymer of the Saraksan or Saraksan-T grades provides high rheological properties due to its ability to dissolve with the formation of a minimum amount of microgels. α-Glucan provides low water loss and resistance to a high concentration of calcium ions contained in the formation water, while the drilling fluid is compatible with the formation water of calcium chloride type. The amount of defoamer brand "Sofexil-905b-20x" (0.2 wt.%) Is sufficient to prevent the formation of foam of a solution with high density at an angular speed of up to 600 rpm With a decrease in the density of the solution, the amount of antifoam decreases to 0.01 wt.%.

The amount of bactericide decreases with increasing density of the solution, since salts of monovalent metals are also a biocide with an increase in their concentration in the solution.

Preparation of biopolymer solution is carried out using standard equipment.

The drilling fluid preparation unit should include a mixing tank with hydraulic and mechanical stirrers for preparing a working drilling fluid.

The preparation of the solution according to the invention is illustrated by examples.

Example 1

Preparation of 1 m ^{3 of} drilling fluid ρ = 1100 kg / m ³ based on potassium nitrate KNO ₃ with a concentration of xaraxan biopolymer of the brand Saraksan or Saraksan-T 0.5 wt.%, Modified starch 0.5 wt.%, Antifoam brand Sofexil-9056-20x 0.022 wt.%, bactericide brand Biocide SMB 0.2 wt.%.

To prepare 1 m ^{3 of the} solution, 0.93 m ^{3 of} water is taken. With stirring, 170.5 kg of potassium nitrate KNO ₃ is added, the stirring temperature is not lower than 20 ° C (since the dissolution of the salt is endothermic, it absorbs heat). With vigorous stirring and a temperature of at least 20 ° C (if the temperature is lower, the polymers will not dissolve well and insoluble lumps of polymers may form) 5.55 kg of Saraksan or Saraksan-T biopolymer (xanthan gum) is not slowly introduced less than 15 minutes. If less than 15 minutes, the formation of polymer lumps will occur, which in the future will not be able to completely dissolve in an aqueous solution of salts. Due to the possibility of foam formation after the introduction of the biopolymer, it is necessary to introduce 0.22 l of defoamer of the Sofexil-9056-20x brand.

After the introduction of the Sofexil-9056-20x defoamer, 5.55 kg of α-glucan, which is used as modified starch, is slowly introduced with vigorous stirring for at least 15 minutes and the resulting solution is stirred until the reagents are completely dissolved and the desired rheological properties are obtained system. To preserve fluid for a period of more than 2 weeks, 2 kg of Biocide-SMB bactericide is introduced at a reservoir temperature of 25 ° C.

Example 2

The preparation of 1 m ^{3 of} drilling fluid ρ = 1250 kg / m ³ based on potassium chloride KCl and potassium nitrate KNO ₃ with a concentration of xanthan biopolymer brand "Saraksan" or "Saraksan-T" 0.3 wt.%, Dextran 0.25 wt. %, defoamer brand Sofexil-9056-20x 0.15 wt.%, bactericide brand Biocide SMB 0.1 wt.%.

To prepare 1 m ^{3 of the} solution, 0.85 m ^{3 of} water is taken. With stirring, 271 kg of potassium chloride KCl and 97.1 kg of potassium nitrate KNO _{3 are} added, the mixing temperature is at least 20 ° C (not all the salt can dissolve when the temperature is lowered). With vigorous stirring and a temperature of at least 20 ° C (if the temperature is lower, the polymers will not dissolve well and insoluble lumps of polymers may form) 3.8 kg of Saraksan or Saraksan-T biopolymer (xanthan gum) are not slowly introduced less than 15 minutes. If less than 15 minutes, the formation of polymer lumps will occur, which in the future will not be able to completely dissolve in an aqueous solution of salts. Due to the possibility of foam formation after the introduction of the biopolymer, it is necessary to introduce 1.5 l of defoamer of the Sofexil-9056-20x brand.

After the introduction of the Sofexil-9056-20x antifoam, 3.15 kg of α-glucan, which is used as dextran, is slowly introduced with vigorous stirring for at least 15 minutes and the resulting solution is stirred until the reagents are completely dissolved. To preserve fluid for a period of more than 1 month, 1 kg of Biocide-SMB brand of bactericide is administered.

Example 3

Preparation of 1 m ^{3 of} drilling fluid ρ = 1300 kg / m ³ based on sodium nitrite NaNO ₂ with a concentration of xaraxan biopolymer of the Saraksan or Saraksan-T brand 0.4 wt.%, Dextran 0.3 wt.%, Antifoam brand "Sofexil-9056-20x" 0.1 wt.%, Bactericide brand Biocide SMB 0.2 wt.%.

To prepare 1 m ^{3 of the} solution, 0.780 m ^{3 of} water is taken. With stirring, 519.6 kg of sodium nitrite NaNO _{2 is} added, the stirring temperature is at least 20 ° C (not all the salt can dissolve when the temperature is lowered). With vigorous stirring and a temperature of at least 2 ° C (if the temperature is lower, the polymers will not dissolve well and insoluble lumps of polymers may form) 5.2 kg of Saraksan or Saraksan-T biopolymer (xanthan gum) are not slowly introduced. less than 15 minutes. If less than 15 minutes, the formation of polymer lumps will occur, which in the future will not be able to completely dissolve in an aqueous solution of salts. Due to the possibility of foam formation after the introduction of the biopolymer, it is necessary to introduce 1 l of defoamer of the Sofexil-9056-20x brand.

After the introduction of the Sofexil-9056-20x defoamer, 3.9 kg of α-glucan, which is used as dextran, is slowly introduced with vigorous stirring for at least 15 minutes and the resulting solution is stirred until the reagents are completely dissolved. To preserve fluid for a period of more than 1 month, 2 kg of Biocide-SMB bactericide is introduced at a reservoir temperature of 25 ° C.

Example 4

Preparation of 1 m ^{3 of} drilling fluid ρ = 1500 kg / m ³ based on potassium formate KNSSOO with a concentration of xaraxan biopolymer of the Saraksan or Saraksan-T brand 0.3 wt.%, Modified starch 0.25 wt.%, Antifoam brand "Sofexil-9056-20x" 0.2 wt.%, Bactericide brand Biocide SMB 0.2 wt.%.

To prepare 1 m ^{3 of the} solution, 0.75 m ^{3 of} water is taken. With stirring, 750 kg of KNSOO potassium formate is added, the stirring temperature is at least 20 ° C (not all the salt can dissolve when the temperature is lowered). With vigorous stirring and a temperature of at least 20 ° C (if the temperature is lower, the polymers will not dissolve well and insoluble lumps of polymers may form) 4.5 kg of Saraksan or Saraksan-T biopolymer (xanthan gum) are not slowly introduced less than 15 minutes. If less than 15 minutes, the formation of polymer lumps will occur, which in the future will not be able to completely dissolve in an aqueous solution of salts. Due to the possibility of foam formation after the introduction of the biopolymer, it is necessary to introduce 2 l of defoamer of the Sofexil-9056-20x brand.

After the introduction of the defoamer of the Sofexil-9056-20x brand, with intensive stirring, 3.7 kg of modified starch are slowly introduced for at least 15 minutes and the resulting solution is stirred until the reagents are completely dissolved. To preserve fluid for a period of more than 1 month, 2 kg of Biocide-SMB bactericide are administered.

The invention is shown in the examples.

The properties of the proposed drilling fluid are presented in tables 1-4. Rheological and mechanical parameters and water loss were determined one day and 30 days after the preparation of the solution. Water loss was determined at a pressure of 0.1013 MPa. Viscosity characteristics were determined using a Fann viscometer. The effective viscosity was determined at 600 rpm. Due to the selected combination of polymers, the solution at high shear rates has a high viscosity, and at high shear rates, the viscosity of the solution approaches the viscosity of water. When the flow stops, a gel-like thixotropic structure is instantly formed, which is determined at a shear rate of 3 rpm on a Fann viscometer.

Example 1: composition: 0.5 wt.% Xanthan (used xanthan grades "Saraksan-T" or "Saraksan", the amount of the latter - in terms of dry product), as α-glucan used modified starch 0.5 wt.% , 0.2 wt.% The biocide-SMB bactericide, 0.02 wt.% Defoamer of the Sofexil-9056-20x brand, potassium nitrate KNO ₃ - 170.5 kg, providing a density of 1100 kg / m ³ .

Indicators of the rheological and mechanical properties of the drilling fluid according to example 1 are presented in table 1.

Table 1 Day η _pl , MPa · s η _eff , MPa · s τ ₀ , dPa CHC _10s , DPa SNA _10min, dPa Water loss, cm ³ one 11.5 24.25 124.44 61 78.08 3 thirty 13 26 132.5 63,44 82.96 2.5

where η _PL - plastic viscosity,

η _eff - effective viscosity, calculated at 600 rpm,

τ ₀ - dynamic shear stress,

CHC _{10 s} - static shear stress after 10 s,

SNS _10min - static shear stress after 10 min.

Example 2: composition: 0.3 wt.% Xanthan gum (used xanthan grades "Saraksan-T" or "Saraksan", the amount of the latter - in terms of dry product), as α-glucan used dextran 0.25 wt.%, 0.1 wt.% Biocide-SMB bactericide, 0.15 wt.% Defoamer brand Sofexil-9056-20x, potassium chloride KCl 271 kg and potassium nitrate KNO ₃ 97.1 kg, providing a density of 1250 kg / m ³ .

Indicators of the rheological and mechanical properties of the drilling fluid according to example 2 are presented in table 2.

table 2 Day η _pl , MPa · s η _eff , MPa · s τ ₀ , dPa CHC _10s , dPa SNA _10min, dPa Water loss, cm ³ one 14.5 32 130,4 58.56 68.33 3 thirty 15,5 35 134.7 63,44 73,2 3

Example 3: composition: 0.4 wt.% Xanthan gum (used xanthan grades "Saraksan-T" or "Saraksan", the amount of the latter - in terms of dry product), as α-glucan used dextran 0.3 wt.%, 0.2 wt.% Bactericide brand Biocide-SMB, 0.1 wt.% Defoamer brand Sofexil-9056-20x, sodium nitrite NaNO ₂ 519.6 kg, providing a density of 1300 kg / m ³ .

Indicators of the rheological and mechanical properties of the drilling fluid according to example 3 are presented in table 3.

Table 3 Day η _pl , MPa · s η _eff , MPa · s τ ₀ , dPa CHC _10s , dPa SNA _10min, dPa Water loss, cm ³ one 16 36 126.54 53.68 65.88 2.5 thirty 17 38 132.4 58.56 70.76 2,3

Example 4: composition: 0.3 wt.% Xanthan (used xanthan grades "Saraksan-T" or "Saraksan", the amount of the latter - in terms of dry product), as α-glucan used modified starch 0.25 wt.% , 0.2 wt.% The biocide-SMB bactericide, 0.2 wt.% Defoamer of the Sofexil-9056-20x brand, KNSOO potassium formate 750 kg, providing a density of 1500 kg / m ³ .

The rheological and mechanical properties of the drilling fluid according to example 4 are presented in table 4.

Table 4 Day η _pl , MPa · s η _eff , MPa · s τ ₀ , dPa CHC _10s , dPa SNA _10min, dPa Water loss, cm ³ one 33 48 124.44 58.56 73,2 2,8 thirty 34 fifty 131.12 63,44 78.08 2.5

Claims (4)

1. A drilling fluid comprising a xanthan biopolymer, α-glucan, a salt or a mixture of monovalent metal salts and water, characterized in that it contains a Saraxan-T or Saraksan brand xanthan biopolymer, Sofexil-9056-20x defoamer , a bactericide of the brand Biocide SMB in the following ratio of components, wt.%:
Specified Biopolymer 0.2-0.7 α-glucan 0.2-0.8 Salt or mixture of salts of monovalent metals 1-55 Specified Antifoam 0.01-0.2 Specified Bactericide 0.1-0.5 Water Rest 2. The drilling fluid according to claim 1, characterized in that the modified starch is used as α-glucan. 3. The drilling fluid according to claim 1, characterized in that dextran is used as α-glucan. 4. The drilling fluid according to claim 1, characterized in that the salts of monovalent metals are chlorides, or nitrates, or nitrites, or thiosulfates, or carbonates, or acetates, or bromides, or sodium or potassium formates, or mixtures thereof.