RU2737605C1 - Hydraulic fracturing composition - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil industry, in particular, to compositions for hydraulic fracturing of formation - HF. Composition for hydraulic fracturing of formation, which includes low-viscosity carrier liquid, dispersed in low-viscosity liquid proppant and fiber dispersed in low-viscosity carrying liquid - polylactic acid, low-viscosity carrying liquid contains an aqueous solution of a mixture of xanthan and a water-swellable polymer - a copolymer of acrylamide with potassium acrylate with a cation exchange capacity of 4.6 meq/g. Content of components is as follows, wt%: xanthan 0.2-0.6, with acrylamide with potassium acrylate 0.001-0.2, fresh water - rest. Proppant composition contains aluminosilicate proppant, polylactic acid - polylactic acid with fiber density of 100-300 g/dm³ and fiber length of 3-6 mm. Weight ratio of aqueous solution of mixture of xanthan and copolymer of acrylamide with potassium acrylate, polylactic acid and aluminosilicate proppant is 1:(0.001-0.006):(0.05-0.8).

EFFECT: high efficiency of action of composition by increasing retention capacity due to components of composition, providing creation of structured polymer system, as well as by increasing permeability recovery coefficient.

1 cl, 2 tbl

Description

The proposal relates to the oil industry, in particular to formulations for hydraulic fracturing (hydraulic fracturing).

Known composition of fluid for hydraulic fracturing (patent RU No. 2132458, IPC E21B 43/26, publ. 06/27/1999, bul. No. 18), including polysaccharide - 5.0-10.0 wt. %, structurant - 0.7-1.5 wt. %, sodium hydroxide - 0.5-1.0 wt. %, surfactant (surfactant) - 0.05-0.075 wt. % and water - the rest. The liquid contains starch as a polysaccharide, and a mixture of sodium tetraborate and a peroxide compound, for example, sodium peroxoborate or urea monoperoxyhydrate, in a ratio of 1-5: 1 as a structurant.

The disadvantage of the known composition is insufficient efficiency due to the poor solubility of the starch reagent in cold water, as a result of which there is clogging and a decrease in the phase permeability of the formed fracture during hydraulic fracturing.

Known liquid gelling agent for polysaccharide fracturing fluid (patent RU No. 2381252, IPC С09K 8/68, publ. 02/10/2010, bull. No. 4), including a liquid gelling agent - 0.8-1.2 wt. %, Surfactant - destruction regulator - 0.05-0.25 wt. %, borate crosslinker BS-1 - 0.2-0.4 wt. %, destructor XB - 0.0025-0.1 wt. %, water - the rest.

The disadvantage of the known composition (gelling agent) is the insufficient efficiency of hydraulic fracturing at facilities confined to low-permeability reservoirs due to the high viscosity of the composition.

The known composition of a water-based hydraulic fracturing fluid (patent RU No. 2424271, IPC С09K 8/68, publ. 20.07.2011, bull. No. 20), including potassium chloride - 6.00-7.00 wt. %, sulfacel - 1.30-2.00 wt. %, aluminum sulfate - 0.15-0.80 wt. %, borax - 0.7-0.9 wt. %, disolvan - 0.03-0.05 wt. %, fractionated powdered material based on marble chips IKARB-75M - 2-3 wt. % and produced water - the rest.

The disadvantage of the known composition is insufficient efficiency due to clogging and a decrease in the phase permeability of the formed crack during hydraulic fracturing with solid dispersed particles of marble chips.

The known composition of the fluid-sand carrier for hydraulic fracturing (patent RU No. 2483094, IPC С09K 8/80, Е21В 43/267, publ. 05/27/2013, bull. No. 15), including bentonite mud powder PBMA - 3.00-5 , 00 wt. %, carboxymethyl cellulose - 0.60-1.50 wt. %, organosilicon liquid GKZH-10 - 0.50-1.00 wt. %, celloton-F - 1.00-1.10 wt. %, aluminum sulfate - 0.15-0.80 wt. % and water - the rest.

The disadvantage of the known composition is insufficient efficiency due to clogging and a decrease in the phase permeability of the formed fracture during hydraulic fracturing with solid dispersed particles of clay powder and celloton, and clogging is complicated by the fact that bentonite clay powder has the ability to swell limitedly in fresh water.

The closest in technical essence is the composition for well treatment (patent RU No. 2657065, IPC C09K 8/80, C09K 8/88, C09K 8/92, E21B 43/267 publ. 08.06.2018, bul. No. 16), comprising a low-viscosity carrier liquid, a proppant dispersed in a low-viscosity carrier fluid of 0.06-1 kg / l and a fiber dispersed in a low-viscosity carrier liquid — polylactic acid 1.2-12 g / l.

The disadvantage of the composition is the low efficiency of the action due to the low retention capacity of the composition and the low coefficient of recovery of the permeability of the low-viscosity carrier fluid with the fibers dispersed in it.

The technical objective of the proposal is to increase the effectiveness of the composition by increasing the retention capacity due to the components of the composition, providing the creation of a structured polymer system, as well as by increasing the coefficient of recovery of permeability.

The technical problem is solved by a composition for hydraulic fracturing, which includes a low-viscosity carrier fluid, proppant dispersed in a low-viscosity carrier fluid, and a fiber - polylactic acid dispersed in a low-viscosity carrier fluid.

The novelty is that, as a low-viscosity carrier liquid, the composition contains an aqueous solution of a mixture of xanthan and a water-swellable polymer - a copolymer of acrylamide with potassium acrylate with a cation exchange capacity of 4.6 meq / g, with the following content of components. % wt .:

Xanthan 0.2-0.6 Copolymer of acrylamide with potassium acrylate 0.001-0.2 Fresh water Rest,

as proppant contains aluminosilicate proppant, as polylactic acid - polylactic acid with a fiber density of 100-300 g / dm ³ and a fiber length of 3-6 mm, while the mass ratio of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate, polylactic acid and aluminosilicate proppant is 1: (0.001 ÷ 0.006) :( 0.05 ÷ 0.8).

To prepare a composition for hydraulic fracturing, use:

- aluminosilicate proppants of medium strength fractions 12/18, 16/30, 16/20, 20/40, manufactured in accordance with GOST R 51761-2013;

- polylactic acid, which is a white fibrous material with a bulk density of 100-300 g / dm ³ and a fiber length of 3-6 mm;

- xanthan, which is a high molecular weight exopolysaccharide of microbial origin with a polysaccharide content of more than 90%;

- copolymer of acrylamide with potassium acrylate is used as a water-swellable polymer (apparent density 85-90%; pH = 8.1 units; cation exchange capacity 4.6 meq / g; maximum absorption in deionized water 400 g / g; water retention at рF1 980 ml / l), for example, the trademark AQUASORB 3005 S or its analogues;

- fresh water.

The content in the composition of these components ensures high success of hydraulic fracturing operations. High hydraulic fracturing success is achieved through the use of an aqueous solution of a mixture of xanthan and acrylamide copolymer with potassium acrylate with dispersed aluminosilicate proppant and polylactic acid fibers. The specified aqueous solution of the mixture is characterized by high pumpability and low friction losses, which reduces the need for pump power (low viscosity of the composition and lower pressure drop). Polylactic acid fibers, aluminosilicate proppant and an aqueous solution of a mixture of xanthan and acrylamide copolymer with potassium acrylate provide improved transfer of aluminosilicate proppant into the formation, and reduce its sedimentation in the wellbore, which minimizes the risks of premature shutdown of the hydraulic fracturing process, reduce the need for volumes of injected water, t .e. use a high proppant loading by using a heavier aluminosilicate proppant. This is explained by the formation of a spatial structure - a network of fibers of polysaccharide molecules and a water-swellable polymer, which collapses with an increase in the shear load, while the viscosity of the composition becomes low, but with a decrease in the shear load, the spatial network is restored, which provides a high retention capacity of the aluminosilicate proppant. The use of the components indicated in the composition provides high values of the permeability recovery factor.

The composition for hydraulic fracturing is prepared in laboratory conditions as follows.

First, an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate is prepared. A calculated amount of xanthan (0.2-0.6 wt%) and a copolymer of acrylamide with potassium acrylate (0.001-0.2 wt%) is introduced into fresh water (99.699-99.2 wt%) and stirred until complete dissolution using a mechanical stirrer at 350 rpm.

After complete dissolution of these components in the prepared aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate, without stopping the stirring, injected fibers of polylactic acid (PLA). The resulting composition is mixed until the PLA fibers are completely dispersed in the specified aqueous solution of the mixture, which is fixed by the absence of lumps and clots. Then, the aluminosilicate proppant is dosed into the resulting composition with stirring on a mechanical mixer, and stirring is continued until the aluminosilicate proppant is completely distributed in the specified composition. In this case, the mass ratio of an aqueous solution of a mixture of xanthan and acrylamide copolymer with potassium acrylate, polylactic acid and aluminosilicate proppant is 1: (0.001 ÷ 0.006) :( 0.05 ÷ 0.8), respectively.

Improving the effectiveness of the proposed composition of hydraulic fracturing is achieved by increasing the retention capacity due to the components of the composition, providing the creation of a structured polymer system, as well as by increasing the coefficient of recovery of permeability.

In laboratory conditions, the retention capacity of the composition and the permeability recovery factor were evaluated.

The retention capacity of the composition is determined as follows.

50 g of a prepared aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate is poured into a glass with a capacity of 100 cm ³ . In the specified solution, using a mechanical stirrer, the calculated amount of polylactic acid fibers (PLA) is dispersed and the calculated amount of aluminosilicate proppant is poured. The mass ratio of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate, PLA and aluminosilicate proppant is 1: (0.001 ÷ 0.006) :( 0.05 ÷ 0.8). The resulting composition is stirred on an overhead stirrer at a speed of not more than 300 rpm for 1 min until the aluminosilicate proppant is evenly distributed, after which the composition is poured into a graduated cylinder with a capacity of 100 cm ³ .

Turn on the stopwatch and after 20 minutes observe the retention of the specified aqueous solution of the mixture with polylactic acid aluminosilicate proppant in suspension.

The results of studies to determine the retention capacity of the composition are shown in table. one.

The permeability recovery factor is determined using the UIK-4 installation as follows. More than 5 pore volumes of oil are filtered through the prepared porous medium. Then the oil-saturated porous medium is left in a static mode for 24 hours for the adsorption processes to proceed. Then the oil is filtered again until the pressure drop stabilizes and the oil permeability with bound water is determined. At the next stage, one pore volume of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate with dispersed fibers of polylactic acid is injected in the opposite direction at a constant pressure gradient of 31.4 MPa / m. After injection, the model of the porous medium is kept for 18 h in static mode (the temperature and pressure conditions of the experiment are observed, filtration was not carried out). Then, in the original direction, oil filtration is resumed with the same flow rate until the pressure drop is completely stabilized, and the phase permeability for oil is determined. The values of the recovery coefficients for oil permeability are determined as the ratio of the relative phase permeability for oil obtained after filtration of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate with dispersed fibers of polylactic acid to its initial value.

The results of determining the permeability recovery factor are shown in table. 2.

From table. 1 and 2 it can be seen that the retention capacity of the composition and the coefficient of recovery of permeability depend on the quantitative content of the components in the composition. The optimal concentrations of the components are possessed by the compositions (compositions 3-11, tables 1, 2) with a xanthan content of 0.2-0.6 wt. %, copolymer of acrylamide with potassium acrylate 0.001-0.2 wt. %, water - the rest.

When the content in the composition is less than 0.2 wt. % xanthan, copolymer of acrylamide with potassium acrylate less than 0.001 wt. % there is a rapid settling of the aluminosilicate proppant prior to the fracturing process. The holding capacity of the composition is 7-12 minutes (compositions 1, 2, Table 1).

When the content of the xanthan mixture in the aqueous solution is more than 0.6 wt. %, copolymer of acrylamide with potassium acrylate 0.2 wt. % (composition 12 table. 1), and in an aqueous solution of a mixture of xanthan - 0.6 wt. %, copolymer of acrylamide with potassium acrylate more than 0.2 wt. % (composition 13 table. 1) there is a uniform distribution of aluminosilicate proppant in the composition, which provides a high retention capacity of the aluminosilicate proppant in an aqueous solution of a mixture of xanthan and acrylamide copolymer with potassium acrylate with fibers dispersed in it and the successful implementation of the hydraulic fracturing process. However, an increase in the content of components in the composition is inexpedient from an economic point of view, as well as from a technological point of view, due to the high cost of reagents.

From table. 2 it follows that the permeability recovery factor when using the proposed aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate with dispersed fibers of polylactic acid averaged 91.3% (compositions 3-11) and for the prototype - 65.6% (compositions 14, 15).

When the content of the copolymer of acrylamide with potassium acrylate is less than 0.001 wt. % (compositions 1, 2, Table 2), the permeability recovery factor slightly differs from the proposed composition (composition 3, Table 2). However, due to the low retention capacity of the composition (composition 1, 2, Table 1), it is impossible to ensure successful hydraulic fracturing, since the aluminosilicate proppant settles rapidly.

Thus, the above test results of the proposed composition ensure the success of hydraulic fracturing due to high indicators - retention capacity and permeability recovery factor.

Table 1. Results of studies to determine the retention capacity of the composition

No-measure of experience An aqueous solution of the mixture, wt. % Weight of an aqueous solution of a mixture of xanthan and acrylamide copolymer with potassium acrylate, g Weight of poly-lactic acid (PLA), g Weight of aluminum-silicate propane, g Mass ratio
an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate:
PMK:
aluminosilicate proppant Keeping ability, min Xan-tan Copolymer acrylamide with potassium acrylate Fresh water one 2 3 4 5 6 7 8 nine one 0.1 0.0009 99.8991 fifty 0.1 2.5 1: 0.001: 0.05 7 2 0.15 0.0005 99.8495 fifty 0.1 fifty 1: 0.001: 0.10 12 3 0.2 0.001 99,799 fifty 0.05 2.5 1: 0.001: 0.8 22 4 0.2 0.05 99.75 fifty 0.15 2.5 1: 0.003: 0.05 25

Continuation of table 1

one 2 3 4 5 6 7 8 nine 5 0.2 0.2 99.6 fifty 0.3 25 1: 0.006: 0.5 29 6 0.3 0.001 99.699 fifty 0.15 25 1: 0.003: 0.5 26 7 0.3 0.05 99.65 fifty 0.15 40 1: 0.003: 0.8 28 8 0.3 0.2 99.5 fifty 0.05 40 1: 0.001: 0.05 26 nine 0.6 0.001 99.399 fifty 0.05 25 1: 0.001: 0.5 31 ten 0.6 0.05 99.35 fifty 0.3 2.5 1: 0.006: 0.05 33 eleven 0.6 0.2 99.2 fifty 0.3 40 1: 0.006: 0.8 35 12 0.8 0.2 99.0 fifty 0.5 25 1: 0.010: 0.5 39 13 0.6 0.25 99.15 fifty 0.5 25 1: 0.010: 0.5 37 Prototype guar PMK water Liquid mass, g Proppant weight, g - 14 0.24 0.48 99.28 fifty - 25 - 17 GOEC PMK water 15 0.05 0.3 99.65 fifty - 25 - 16 Note - GOEC - hydroxyethyl cellulose.
The research of the prototype was carried out by the applicant independently.

Table 2. Results of studies to determine the permeability recovery factor

No-measure of experience An aqueous solution of the mixture,
wt. % Mass of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate, g Mass of poly-lactic acid (PLA), g Mass ratio of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate: PMA Permeability, μm ² Coeffi-
restoration
lazy permeability,
% Xan-tan Sopo-lymer acry-lami-da with potassium acrylate Fresh water Before After one 2 3 4 5 6 7 8 nine ten one 0.1 0.0009 99.8991 fifty 0.1 1: 0.001 4.7 4.6 97.87 2 0.15 0.0005 99.8495 fifty 0.1 1: 0.001 4.5 4,3 95.56 3 0.2 0.001 99,799 fifty 0.05 1: 0.001 4.8 4.6 95.83 4 0.2 0.05 99.75 fifty 0.15 1: 0.003 4.6 4.1 89.13 5 0.2 0.2 99.6 fifty 0.3 1: 0.006 5.1 4.6 90.20 6 0.3 0.001 99.699 fifty 0.15 1: 0.003 4.1 3.9 95.12 7 0.3 0.05 99.65 fifty 0.15 1: 0.003 3.6 3.2 88.89 8 0.3 0.2 99.5 fifty 0.05 1: 0.001 4.4 4.1 93.18 nine 0.6 0.001 99.399 fifty 0.05 1: 0.001 4.0 3.7 92.50 ten 0.6 0.05 99.35 fifty 0.3 1: 0.006 3.7 3.3 89.19 eleven 0.6 0.2 99.2 fifty 0.3 1: 0.006 4.8 4.2 87.50 12 0.8 0.2 99.0 fifty 0.5 1: 0.010 3.9 3.1 79.49 13 0.6 0.25 99.15 fifty 0.5 1: 0.010 4.8 3.3 68.75 Prototype guar PMK water 14 0.24 0.48 99.28 - - - 4.8 3.2 66.67 GOEC PMK water 15 0.05 0.3 99.65 - - - 4.5 2.9 64.44 Note - The research of the prototype was carried out by the applicant independently.

The use of the proposed composition makes it possible to increase efficiency by increasing the retention capacity due to the components of the composition, providing the creation of a structured polymer system, as well as by increasing the permeability recovery factor.

Claims (3)

A composition for hydraulic fracturing, including a low-viscosity carrier fluid, a proppant dispersed in a low-viscosity carrier fluid, and a fiber - polylactic acid dispersed in a low-viscosity carrier fluid, characterized in that the composition contains an aqueous solution of a mixture of xanthan and a water-swellable polymer - a copolymer of acrylamide with potassium acrylate with a cation exchange capacity of 4.6 meq / g, with the following content of components, wt%: Xanthan 0.2-0.6 Copolymer of acrylamide with potassium acrylate 0.001-0.2 Fresh water Rest, as proppant contains aluminosilicate proppant, as polylactic acid - polylactic acid with a fiber density of 100-300 g / dm ³ and a fiber length of 3-6 mm, while the mass ratio of an aqueous solution of a mixture of xanthan and a copolymer of acrylamide with potassium acrylate, polylactic acid and aluminosilicate proppant is 1: (0.001-0.006) :( 0.05-0.8).