RU2373251C2 - Composition for isolation of absorption zones - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: in composition for isolation of absorption zones, consisting of two reagents, one of which is a bentonite-chalk solution containing bentonite mud powder, technical chalk, sodium chloride and water, and the other one is an aluminium salt solution, bentonite-chalk solution additionally contains sodium silicate, with the following ratio of components, wt %: bentonite mud powder 8.88-9.08, technical chalk 29.66-30.27, sodium chloride 10.81-10.90, sodium silicate 0.18-0.54, water - the rest, and other reagent as aluminium salt contains aluminium polyoxychloride, with the following ratio of components, wt %: aluminium polyoxychloride 54.52-54.56, water - the rest, ratio of bentonite-chalk solution and aluminium salt solution makes 4.0-6.6: 1 accordingly.

EFFECT: wider assortment of isolating compositions used for elimination of zones with intense - catastrophe absorptions and higher plastic strength of plug.

3 ex, 1 tbl

Description

The invention relates to the oil and gas industry, and in particular to compositions for isolating absorption zones in fractured cavernous reservoirs under conditions of intense (catastrophic) absorption.

Known composition for blocking the absorbing formations, consisting of two reagents, as the first of which use a bentonite-chalk solution containing, wt.%:

Bentonite Clay Powder 20.0-25.0 Ground chalk 7.0-8.0 Sulfanol 0.10-0.15 Carboxymethyl cellulose 1.0-1.5 Water rest,

and as the second reagent use inhibited hydrochloric acid containing, wt.%:

Hydrochloric acid 23.0-24.0 KI-1 inhibitor 1.0-1.5 Water rest

[USSR author's certificate No. 1802084, 5 IPC Е21В 33/138, з. No. 4890276, priority 10.23.1990, publ. 03/15/1993 in bull. No. 10].

A disadvantage of the known composition is the low insulation efficiency due to insufficient plastic strength of the formed blocking swab. When the reagents are sequentially injected, their mixing in the formation is insufficient due to the fact that the bentonite-chalk solution is pushed into the pores, and mixing with hydrochloric acid is limited only by the zone of their contact. Due to the limited contact of the reagents, it is not possible to obtain a durable clogging swab. In the interaction of hydrochloric acid and bentonite-chalk solution, calcium chloride is formed, which is in dissolved form, which limits the clogging ability of the gel formed and does not allow reliable isolation of the intensive absorption zone.

The closest in technical essence and the set of essential features is the composition for isolating the absorption zones, consisting of two reagents, the first of which use a bentonite-chalk solution containing bentonite clay powder, technical chalk, sodium chloride and water, and the second one uses a solution aluminum sulfate, and the specified mixture has the following ratio of components, wt.%:

Bentonite Clay Powder 13.3-14.6 Chalk technical 11.0-12.2 Sodium chloride 12.6-13.8 Aluminum sulphate 3.9-5.7 Water rest

with a ratio of the first and second reagents 3-5: 1, respectively [RF Patent No. 2277574, 8MPK S09K 8/467, s. No. 2004131406, priority October 27, 2004, publ. 06/10/2006 in bull. No. 16].

The disadvantage of this composition is that the resulting swab has a relatively low plastic strength, which is in the range of 2.15-2.68 kPa.

The objective of the proposed technical solution is to expand the range of insulating compositions used to eliminate zones of intense (catastrophic) absorption, and increase the plastic strength of the tampon.

The task in the inventive composition for the isolation of absorption zones, consisting of two reagents, one of which is used bentonite-chalk solution containing bentonite clay powder, technical chalk, sodium chloride and water, and the other is used an aqueous solution of aluminum salt, is solved by that the bentonite-chalk solution additionally contains sodium silicate in the following ratio of components, wt.%:

Bentonite Clay Powder 8.88-9.08 Chalk technical 29.66-30.27 Sodium chloride 10.81-10.90 Sodium silicate 0.18-0.54 Water rest

and the other reagent as an aluminum salt contains aluminum polyoxychloride in the following ratio of components, wt.%:

Aluminum polyoxychloride 54.52-54.56 Water rest

moreover, the ratio of the bentonite-chalk solution to the aluminum salt solution is 4.0-6.6: 1, respectively.

The difference of the proposed composition is that the bentonite-chalk solution additionally contains sodium silicate, and the other reagent as aluminum salt contains aluminum polyoxychloride (POHA), as well as a new ratio of components.

Sodium silicate is produced by industry according to TU 5743-002-31178039-2001 in the form of a dry concentrate and is a powdered substance with a silicate module of 1.8-3.2, highly soluble in water, which is used as a binder for various purposes.

It is known that sodium silicate is widely used in compositions for isolating water inflows in a well (RF Patents No. 2064571, 2067157, 2081297).

Aluminum polyoxychloride is produced by the industry according to TU 6-09-05-1456-96 under the name "Aqua-Aurat ™ -30" and is a powdery substance, completely soluble in water, with mass fractions of aluminum oxide 30 ± 3% and chlorine 38 ± 3 %, and is intended for the treatment of drinking and wastewater in industry, agriculture and domestic purposes; for water treatment of thermal power plants and boiler rooms; as well as for sizing paper in the paper industry.

It is known to use aluminum polyoxychloride as a crosslinker in a method for developing an inhomogeneous oil formation, including injecting into the formation an aqueous dispersion of colloidal particles of polyacrylamide, or polysaccharide, or cellulose ether 0.005-0.5 wt.%, Containing 0.0015- aluminum polyoxychloride as aluminum chloride 0.1 wt.%. The injection of the specified composition due to changes in the filtration and oil-displacing parameters of an inhomogeneous formation increases the coverage of the formation by exposure and increases the oil recovery coefficient. [RF patent No. 2298088, 8 IPC Е21В 43/22, С09К 8/88, з. No. 20055130438, priority 30.09.2005, publ. 04/27/2007 in bull. No. 12].

It is also known the use of aluminum polyoxychloride as an additive in a lightweight grouting mortar, including water, clinker, gypsum, tripoli, baked dust from electrostatic precipitators [Patent No. 2230883, 7 IPC ЕВВ 33/138, з. No. 2002109342, priority 04/10/2002, publ. 06/20/2004 in the bul. No. 17].

From the well-known sources of scientific, technical and patent information, the joint use of sodium silicate in a bentonite-chalk solution and a solution of aluminum polyoxychloride to isolate zones of intense absorption has not been identified.

In the claimed composition, sodium silicate reacts with rock-forming minerals when it enters the pores of a rock, and as a result of a chemical reaction, an insoluble precipitate of calcium silicate (CaSiO ₃ ) is formed.

Na ₂ SiO ₃ + Ca (OH) ₂ → CaSiO ₃ ↓ + 2NaOH

Aluminum polyoxychloride is involved in the crosslinking of the components of the bentonite-chalk solution and reaction products, giving the resulting swab increased strength and stability due to additional bonds with the formation of an elastic and branched network.

As a result of chemical reactions of aluminum polyoxychloride with the components of a bentonite-chalk solution, insoluble gelling precipitates of aluminum hydroxide (Al (OH) ₃ ) and calcium chloride (CaCl ₂ ) are formed with the release of carbon dioxide (CO ₂ ), which provides more intensive mixing of the composition and helps to accelerate reactions.

{[Al (OH) _a Cl _b · nH ₂ O] _m } _x + CaCO ₃ + H ₂ O → Al (OH) ₃ ↓ + CaCl ₂ + CO ₂ ↑

The aluminum hydroxide formed during the reaction reacts with alkali to form sodium aluminate (NaAlO ₂ ), followed by the formation of a crystalline precipitate of hydroargillite (Al ₂ O ₃ · 3H2O)

Al (OH) ₃ + NaOH → NaAlO ₂ + 2H ₂ O

NaAlO ₂ + H ₂ O → NaOH + HAlO ₂ ,

where HAlO ₂ - aluminum hydroxide, which in an alkaline medium during hydrolysis forms hydroargillite

2HAlO ₂ + 2H ₂ O → Al ₂ O ₃ · 3H ₂ O

In addition, unreacted sodium silicate forms aluminum hydroxide (Al (OH) ₃ ), silica sol (H ₂ SiO ₃ ), and crystalline substance sodium chloride (NaCl) upon contact with aluminum polyoxychloride.

{[Al (OH) _a Cl _b · nH ₂ O] _m } _x + Na ₂ SiO ₃ + H ₂ O → Al (OH) ₃ ↓ + H ₂ SiO ₃ ↓ + NaCl ↓

As a result of chemical reactions, the formation of an almost anhydrous tampon with a higher plastic strength (17.5-45.0 kPa), which is able to reliably plug the near-well space in the absorption zone, occurs rapidly.

It was experimentally established that the joint use in the inventive composition for isolating the absorption zones of a bentonite-chalk solution containing sodium silicate and an aqueous solution of aluminum polyoxychloride at a ratio of 4.0-6.6: 1, respectively, provides a new technical result, which consists in increasing the plastic tampon strength, which increases the efficiency of isolation of absorption zones.

Thus, the introduction of a composition for isolation of an additional component into one reagent, replacement of one component by another in the second reagent, and a new ratio of reagents allowed us to obtain a new technical result consisting in increasing the plastic strength of the resulting tampon, which increases the efficiency of isolation of absorption zones, which allows us to conclude on the conformity of the claimed technical solution to the criterion of "inventive step".

To assess the effectiveness of the proposed technical solution, laboratory studies were conducted.

As components of one (I) reagent used:

- bentonite clay powder according to TU 2-043-953-87;

- technical chalk in accordance with GOST 12085-88;

- sodium chloride according to GOST 13830-91E;

- dry concentrate of sodium silicate according to TU 5743-001-31178039-2001;

- technical water.

To prepare another (II) reagent used:

- aluminum polyoxychloride according to TU 6-09-05-1456-96;

- technical water.

Reagents were prepared as follows.

A sodium chloride solution with a density of 1180 kg / m ^{3 was} previously prepared, for which 283 g of sodium chloride was dissolved in 1000 ml of water.

To prepare the bentonite-chalk solution (reagent I), 1 liter of the prepared sodium chloride solution was taken, 100 g of bentonite clay powder was added to it and stirred for 1 hour. Then, 500 g of powdered chalk and 20 g of dry sodium silicate concentrate were added with stirring and mixed for 4 hours. After that, we measured the parameters of the initial bentonite-chalk solution, which were: density -1410 kg / m ³ , cone spreadability - 18 cm, water loss 56 cm ³ in 30 minutes.

To prepare 1 l of a solution of aluminum salt (II reagent), 614 ml of water was taken, in which 736 g of POHA were dissolved, then the density was measured, which amounted to 1350 kg / m.

Example 1. To study the characteristics of the resulting tampon, 200 cm ^{3 of the} initial bentonite-chalk solution was taken and, with stirring, 20 cm ³ of the PHA solution was added. The content of the components in the first reagent was: bentonite clay powder 9.10 wt.%, Chalk 30.36 wt.%, Sodium chloride 10.90 wt.%, Sodium silicate 0.16 wt.% And water 49.48 wt. %; the content of the components in the second reagent was: POHA 54.35 wt.% and water 45.65 wt.%, and their volume ratio was 10: 1, respectively. As a result of the chemical reaction, after 20 s, insoluble gelling precipitation occurred and a durable tampon formed. Then, on the plastometer according to the method of academician P.A. Rebinder, the plastic strength of the resulting swab was measured, which amounted to 10.5 kPa (experiment 1).

Similarly, studies of the compositions were conducted with various combinations of components, and the results are shown in the table.

Also conducted laboratory studies of the composition of the prototype. To do this, 300 g of bentonite clay powder was introduced into a 1 liter of sodium chloride solution and stirred for 1 h, then 250 g of powdered chalk was added with stirring and stirred for another 4 hours.

To prepare 1 l of a solution of aluminum sulfate in 565 g of water, 735 g of crystalline hydrate of aluminum sulfate was introduced, heated to a temperature of 90 ° C, completely dissolved and then cooled to room temperature, after which the density was measured, which amounted to 1290 kg / m.

Example 2. They took 200 cm ^{3 of a} bentonite-chalk solution and, while stirring, added 60 cm ^{3 of a} solution of aluminum sulfate. The content of the components in the first reagent was 15.44% by weight of bentonite clay powder, 12.94% of the chalk, 14.53% of sodium chloride and 57.09% of water, and the aluminum sulfate content of the second component 43.48 wt.% And water 56.52 wt.%, And their volume ratio was 3.3: 1, respectively. As a result of the chemical reaction, after 20 s, insoluble precipitation occurred and a strong tampon formed. Then, the plastic strength was measured on the plastometer, which amounted to 2.68 kPa (experiment 10).

Example 3. They took 200 cm ^{3 of} the same bentonite-chalk solution and added 57 cm ³ of the PHA solution. Moreover, the content of components in the first reagent was 16.01 wt.% Bentonite clay powder, 13.42% by weight of chalk, 15.07% by weight of sodium chloride and 55.50% by weight of water; the content of the components in the second reagent was POHA 54 , 56 wt.% And water 45.44 wt.%, And their volume ratio was 3.5: 1, respectively. As a result of a chemical reaction, after 9 seconds, insoluble gelling precipitation occurred and a durable tampon formed. Then, the plastic strength was measured on the plastometer, which amounted to 10.7 kPa (experiment 11).

In this composition, the plastic strength is significantly higher than that of the composition of the prototype (experiment 10), but it is still significantly lower than that of the claimed composition shown in the table (experiment 7), with the addition of the same amount of POHA.

Analysis of the table data showed that the highest plastic density of the tampon is 17.5-45.0 kPa.

The authors experimentally found that the optimal content of the components in the bentonite-chalk solution is their ratio, wt.%:

Bentonite Clay Powder 8.88-9.08 Chalk technical 29.66-30.27 Sodium chloride 10.81-10.90 Sodium silicate 0.18-0.54 Water rest

and in a solution of aluminum salt is the optimal content of components, wt.%:

Aluminum polyoxychloride 54.52-54.56 Water rest

It was found that the optimal content in the claimed composition of bentonite clay powder is in the range of 8.88-9.08 wt.%. When the clay powder content is more than 9.08 wt.%, The viscosity of the bentonite-chalk solution increases, which complicates its pumpability and the plastic strength of the tampon decreases (experiment 1). When the clay powder content is less than 8.88 wt.% In the first reagent, the solid phase becomes insufficiently solid for the formation of the tampon (experiment 9).

The optimal content of technical chalk is 29.66-30.27 wt.%. When the chalk content is more than 30.27 wt.%, The pumpability of the solution worsens and the plastic strength of the tampon decreases (experiment 2). When the chalk content is less than 29.66 wt.% In the reagent I, the carbonate component becomes insufficient for the formation of insoluble gel-forming precipitates from which the swab is formed (experiment 9).

The optimal content of sodium chloride is 10.81-10.90 wt.%. A sodium chloride content of more than 10.90 wt.% Leads to a decrease in the plastic strength of the tampon and an increase in the viscosity of the solution (experiment 2). A content of sodium chloride of less than 10.81 wt.% Leads to an increase in the viscosity of the solution to non-pumpable (experiment 9).

The optimal content of sodium silicate is 0.18-0.54 wt.%. The content of sodium silicate less than 0.18 wt.% Leads to a decrease in the plastic strength of the tampon (experiment 1). The content of sodium silicate of more than 0.54 wt.% Leads to an increase in the viscosity of the solution to non-pumpable (experiment 8).

The optimal content of aluminum polyoxychloride (POHA) is 54.52-54.56 wt.%. A decrease in the content of POHA less than 54.52 wt.% Leads to a decrease in the plastic strength of the tampon (experiment 2). An increase in the content of POHA over 54.56 wt.% Leads to the production of a fragile tampon (experiment 9).

The optimal volume ratio of I and II reagents is 4.0-6.6: 1, respectively. With an increase in the ratio of more than 6.6: 1, the viscosity of the first reagent increases to non-pumpable, the time for a chemical reaction increases, and the plastic strength decreases, which is insufficient to create an insulating screen in the catastrophic absorption zone (experiment 2). When the ratio decreases to less than 4.0: 1, the first reagent thickens to non-pumpable, the plastic strength of the tampon increases slightly, and it becomes brittle, which can lead to its destruction in the well when stress is created (experiment 8).

For the implementation of the inventive composition in the field, preliminary studies are conducted. Based on the research results, the necessary calculations are made.

The required volume of the resulting tampon, taking into account its plastic strength, is calculated individually in each case, depending on the characteristics of the absorbing formations (reservoir pressure, injectivity, open porosity of rocks, etc.).

The estimated volume of the bentonite-chalk solution is prepared in advance. To do this, pour industrial water into a separate container, add sodium chloride and mix for 1 hour. Then add bentonite clay powder and mix for 4 hours, then add technical chalk and dry sodium silicate concentrate and mix for another 1 hour, resulting in an initial bentonite-chalk solution with the given parameters.

An aluminum polyoxychloride solution is also prepared in advance. For this, the required amount of industrial water is loaded into a separate container in which aluminum polyoxychloride is dissolved.

The use of the composition is carried out in the following way.

The calculated volume of the bentonite-chalk solution, which is placed in the wellbore above the absorption zone, is pumped into the pipe space. Then, buffer liquid, POHA solution, buffer liquid, cement mortar, squeezing liquid are pumped into the absorption zone through the tube space. Upon reaching the POHA solution of the roof of the absorption zone, squeezing fluid is simultaneously pumped through the pipe and annular spaces. Simultaneous pumping of the squeezing fluid is performed until the POHA solution exits the open end of the drill pipes. Further, with vigorous stirring and in the process of chemical interaction almost instantly (4-14 s), the reaction products are formed in the form of a durable swab that clogs the absorption zone. Then, a cement mortar is placed in the wellbore in the interval of the absorption zone, which interacts with the remaining unreacted POHA solution, forming a cement stone. After which the well is left waiting for the cement to harden.

The advantages of the claimed composition for the isolation of absorption zones:

- improving the reliability of blocking the bottom-hole zone due to the formation of a tampon with high plastic strength of 17.5-45.0 kPa;

- reduction of the curing time of the composition.

Field tests of the inventive composition were conducted to isolate the absorption zones in 2007 at wells No. 9044 of the Orenburg oil and gas condensate field and No. 3 of the Tsarichanskoye field during the elimination of catastrophic absorption, where repeated attempts to eliminate absorption by installing cement bridges with fillers and accelerators for setting cement slurry positive no results. When applying the inventive composition, the absorption was eliminated in one operation.

The use of the inventive composition allows you to expand the range of reagents used to isolate zones of catastrophic absorption.

Claims (1)

Composition for isolating absorption zones, consisting of two reagents, one of which is a bentonite-chalk solution containing bentonite clay powder, industrial chalk, sodium chloride and water, and the other is an aqueous solution of aluminum salt, characterized in that the bentonite the chalk solution additionally contains sodium silicate, in the following ratio of components, wt.%:
Bentonite Clay Powder 8.88-9.08 Chalk technical 29.66-30.27 Sodium chloride 10.81-10.90 Sodium silicate 0.18-0.54 Water Rest
and another reagent as an aluminum salt contains aluminum polyoxychloride, in the following ratio, wt.%:
Aluminum polyoxychloride 54.52-54.56 Water Rest
moreover, the ratio of the bentonite-chalk solution to the aluminum salt solution is 4.0-6.6: 1, respectively.