RU2121561C1 - Sand-carrier fluid for hydraulic fracturing of formation - Google Patents

Abstract

FIELD: oil-and-gas producing industry; may be used in change of filtering characteristics of formation and performance of hydraulic fracturing. SUBSTANCE: added to 311.5-371 ml (31.15-37.1 mas.%) of water is 30-40 g (3-4 mas. %) of clay; and added to next 311.5-371 ml (31.15-376.1 mas.%) of water is 8-12 g (0.8-1.2 mas.%) of carboxymethyl cellulose. Mixture is set stand for a day for swelling and mixed. Added to formed mixture is 20-25 ml (2.0-2.5 mas.%) of nonionic surfactant and 221-331 ml (20-30 mas.%) of used oil product based on petroleum oils (ρ = 0.905 g/cu.cm). Mixture is foamed. EFFECT: higher sand retentivity of fluid, i.e. stabilization in time of ability of produced system to retain sand of coarse fraction due to improved structural and mechanical properties of formed foam. 2 dwg

Description

 The invention relates to the oil and gas industry and may find application when changing the filtration characteristics of the layers during hydraulic fracturing.

Known liquid sand carrier for hydraulic fracturing of the following composition, wt.%:
Alcoholic yeast bard - 24.51-27.10
Surfactant ML - 80 based on sulfonate and sulfonol - 0.03-0.11
Potassium Chloride - 3.98-4.21
Mineralized Water - Else
(ed. St. N 1765365, class E 21 B 33/138, 1992).

The disadvantage of this composition is the reduced sand-holding ability, since it does not contain a complexing agent, and the system represented by such a composition is thickened with a high viscosity, and not structured. The stability of the composition is 0.450 - 0.075 g / cm ³ , which leads to insufficient sand-holding ability. Moreover, the composition affects the permeability of the formation, and the recovery coefficient of permeability is 80.0-93.5%.

As a prototype taken fluid - sand carrier for hydraulic fracturing of the following composition, wt.%:
Radiated by γ-radiation polyacrylamide (RPAA) - 0.3 - 0.5
Alkali metal dichromate - 0.05 - 0.30
Condensed sulphite-alcohol stillage - 0.1 - 0.5
Water - Else
(RF patent N 2057781, class C 09 K 7/00, E 21 B 43/26, 1996).

 The disadvantage of this composition is the reduced sand-holding ability, which is due to the insufficiently strong forming structure. RPAA has a mesh structure and, when mixed with water, absorbs it for 1-2 hours (“sponge” effect), and the water is in a free state without the formation of any chemical bonds. Over time, on the order of more than 2 hours, a composition syneresis occurs, i.e. spontaneous decrease in the volume of the gel with the simultaneous release of the dispersion medium contained in the loops of the gel. Therefore, most of the sand precipitates, while the rest, very small, is retained due to the content in the system of chromium salt and KSSB involved in the formation of cross-links ("crosslinking") of the functional groups of the RPA that have remained untouched after γ-irradiation. Therefore, the viscoelastic composition is not able to hold the sand in suspension for more than 2 hours. In addition, the known composition has high adhesion to the rock and is poorly removed from the formation, significantly reducing the permeability of the latter. Subsequent restoration of the permeability of the formation is carried out by acid treatment, causing the destruction of the composition. In general, the introduction of additional operations - γ-irradiation of PAA, acid treatment - complicates the technology, as additional equipment and reagents are required, as well as polluting the environment.

The technical result that can be obtained by carrying out the invention is as follows: sand-holding ability is increased, i.e. the ability of the resulting system to retain sand of a larger fraction stabilizes over time by improving the structural and mechanical properties of the resulting foam. The technical result is achieved using a composition including a water-soluble polymer, a surfactant, a thickener and water, which additionally contains spent petroleum products based on petroleum oils, and as a water-soluble polymer, carboxymethyl cellulose, a non-ionic surfactant as a surfactant, clay as a thickener, and the following the ratio of components, wt.%:
Clay - 3 - 4
Waste oil products based on petroleum oils - 20 - 30
Carboxymethyl cellulose (CMC) - 0.8 - 1.2
Nonionic surfactant - 2.0 - 2.5
Water - Else
They use used petroleum products based on petroleum oils according to GOST 21046 - 86. They belong to the IMO group and have the following composition: used motor oils (for aviation piston, carburetor and diesel engines), compressor, vacuum and industrial oils, as well as the following physicochemical parameters :
Viscosity at 20 ^o C, s - Over 40
Kinetic viscosity at 50 ^o C, mm ² / s - Over 35
Flash point determined in an open crucible, ^o C - Not lower than 100
Mass fraction of mechanical impurities,% - Not more than 1
Mass fraction of water,% - Not more than 2
Mass fraction of fractions boiling up to 340 ^o C - Not more than 10
The pour point of fractions boiling up to 340 ^o C,% - Not higher than 10
Density at 20 ^o C kg / m ³ - Not more than 905
Contaminant Content - No
CMC is used according to TU 6-55-39-90, 6-55-40-90.

 Neonol according to TU 38.507-63-300-93, syntanol DS - 10 according to TU 6-14-577-77 and OP according to GOST 8433-81 are used as nonionic surfactants.

 The action of these surfactants in the composition is almost equivalent.

 Clay (clay powders) is used according to TU-39-043-74, RD-39-2829-82. When water, used petroleum oil, clay, CMC, a nonionic surfactant are mixed, an oil-in-water emulsion is formed.

 When air passes through such a system, foaming occurs. The orientation of the molecules is as follows: on the film of the liquid that surrounds the air bubble, a nonionic surfactant molecule is adsorbed, the hydrophilic part of which is represented by ethylene oxide and faces water. Its solubility is determined by the oxygen-containing group, which forms hydrogen bonds with water molecules (Fig. 1). The hydrophobic part of the molecules of a nonionic surfactant, which is the remainder of an amine or phenol, or alkyl phenol, or other hydrocarbon radicals, faces the air part of the bubble.

 Stabilizer and weak surfactant - CMC additionally regulates the properties of the foam. The CMC molecules with their nonpolar ends are introduced between nonpolar molecules of oil and a nonionic surfactant and face the air part of the bubble. The polar parts of the CMC molecule are facing water, and the interaction with water molecules occurs due to hydrogen bonds (Fig. 2).

 It is difficult to explain the processes of interaction in the nonpolar parts of the molecules of a nonionic surfactant, CMC, and oil. To date, the relationship between the nature of the solvent and its ability to dissolve high molecular weight substances has not yet been precisely established. Usually limited to a rule of thumb - like dissolves in like. In other words, non-polar compounds dissolve in non-polar solvents, and polar compounds in polar ones. Therefore, speaking about the interaction of the nonpolar parts of oil molecules, CMC and surfactants, it is worthwhile only to assume that the molecules of some hydrocarbon radicals have valence vacancies (incomplete orbitals), while others have vice versa - donor valence electrons. Therefore, the adhesion of molecules of various hydrocarbons (the claimed component - petroleum oil is a mixture of high molecular weight hydrocarbons of various classes) with the formation of transverse chemical bonds, the so-called bridges, provides the system with a spatial structure in the form of grids, threads, etc. This contributes to the creation of highly viscous adsorption layers with a gel-like structure. The resulting absorption layers at the gas-liquid interface create conditions under which double electric or solvate layers arise from the dispersion medium. It can be assumed that the non-polar parts of the molecules (oil, CMC) involved in the formation of the film, "building up" the non-polar branches of the blowing agent molecules, push its polar groups into the depths of the water, which are actively hydrated and increase the hydration layers.

 Clay particles, which act as a thickener, adhere to the interface, and most of them are in that surface part of the liquid that moistens them better, i.e. water.

 As a result of this, the strength of the hydrated layer increases several times, and the films acquire additional structural and mechanical properties.

 Ultimately, the formed layers on the interfacial film, on the one hand, slow down the flow of liquid in the film, on the other hand, give the foam film high structural viscosity and mechanical strength. These indicators provide a high sand-holding ability of the composition.

 The compositions of the sand carriers for hydraulic fracturing based on the physicochemical mixture of CMC, clay, nonionic surfactant and waste oil products containing petroleum oils that have the claimed technical result are not identified by available sources of fame. It is known to use non-ionic surfactants in hydraulic fracturing fluids (ed. St. N 403844, class E 21 B 43/27, 1973; aut. St. N 420761, class E 21 B 43/27, 1974), and also carboxyalkyl starch (ed. St. N 683640, class E 21 B 43/26, 1979). The present invention has an inventive step.

 In more detail, the essence of the claimed composition for hydraulic fracturing is described by the following examples.

Example 1. In 371 ml (37.1 wt.%) Of water, 30 g (3 wt.%) Of clay are closed, in the next 371 ml (37.1 wt.%) Of water - 8 g (0.8 wt.%) CMC. The prepared solutions are left to swell for a day, after which the solutions are mixed and 20 ml (2.0 wt.%) Of OP-10 nonionic surfactant and 221 ml or 200 g or 20 wt.% (Ρ = 0.905 g / cm ³ ) of spent petroleum products based on petroleum oils. Foam the composition after stirring.

The sand-holding ability of the composition (CEM) after 1 h is 0.083 g / cm ³ , after 5 h 0.095 g / cm ³ , the foam ratio is 2.7, the plastic viscosity is 0.09 PA • s, the dynamic shear stress is 3.00 Pa • s, filtratootdacha 4.5 cm ^3/30 min, formation permeability recovery after workup 98.5%.

Example 2. Carry out all operations as described in example 1, and prepare a foaming system of the following composition, wt.% / G:
Clay - 4/40
Waste oil products based on petroleum oils (at ρ = 0.905 g / cm ³ take 331 ml of liquid) - 30/300
Carboxymethyl cellulose - 1.2 / 12
Nonionic surfactant of the brand neonol 1013 - 2.5 / 25
Water - 62.3 / 623
The EMP after 1 h is 0.015 g / cm ³ , after 5 h 0.024 g / cm ³ , the foam ratio is 2.1, the plastic viscosity is 0.13 Pa • s, the dynamic shear stress is 5.0 Pa • s, the filtrate yield is 3.0 cm ^3/30 min, formation permeability recovery after workup 99.0%.

Example 3. Carry out all operations as described in example N1, and prepare a foaming system of the following composition, wt.% / G:
Clay - 3.5 / 35
Waste oil products based on petroleum oils (at ρ = 0.095 g / cm ³ take 276 ml of liquid) - 25/250
Carboxymethyl cellulose - 1.0 / 10
Nonionic surfactant Sintanol DS-10 - 2.3 / 23
Water - 68.2 / 682
After 1 h, the CCP is 0.060 g / cm ³ , after 5 h, 0.083 g / cm ³ , the foam multiplicity is 2.2, the plastic viscosity is 0.15 Pa • s, the dynamic shear stress is 4.2 Pa • s, the filtrate yield is 4.2 cm ^3/30 min, formation permeability recovery after treatment with water to 98.8%.

Example 4. Carry out all operations as described in example 1, and prepare a foaming system of the following composition, wt.% / G:
Clay - 2.9 / 29
Waste oil products based on petroleum oils (at ρ = 0.905 g / cm ³ take 210 ml of liquid) - 19.0 / 190
Carboxymethyl cellulose - 0.7 / 7
Water - 77.4 / 774
The EMP after 1 h is 0.26 g / cm ³ , after 5 h the precipitate is observed, the foam multiplicity is 3.0, the plastic viscosity is 0.07 Pa • s, the dynamic shear stress is 2.80 Pa • s, the filtrate yield is 5.2 cm ³ / 30 min, recovery of permeability 98.0%.

Example 5. Perform all operations as described in example 1, and prepare a foaming system of the following composition, wt.% / G:
Clay - 4.1 / 41
Waste oil products based on petroleum oils (at ρ = 0.905 g / cm ³ take 342.5 liquids) - 31.0 / 310
Carboxymethyl cellulose - 1.3 / 13
Water - 63.6 / 636
The EMP after 1 h is 0.012 g / cm ³ , after 5 h it is 0.036 g / cm ³ , the foam multiplicity is 2.2, the plastic viscosity is 0.15 Pa • s, the dynamic shear stress is 5.0 Pa • s, the filtrate yield is 3.0 cm ^3/30 min, the permeability recovery of 99.1%.

 The content of clay in an amount of less than 3 wt.%, Waste oil products based on petroleum oils in an amount of less than 20 wt.%, Carboxymethyl cellulose in an amount of less than 0.8 wt.%, Non-ionic surfactant in an amount of less than 2.0 wt.% Is not effective , since it significantly reduces the dynamics of sand-holding ability, due to a sharp decrease in the stability of the foam due to changes in rheological properties.

 The content of clay in an amount of more than 4 wt.%, Waste oil products based on petroleum oils in an amount of more than 30 wt.%, Carboxymethyl cellulose in an amount of more than 1.2 wt.%, Nonionic surfactant in an amount of more than 2.5 wt.% Is not economically feasible , since it does not contribute to the improvement of rheological properties.

 The inventive composition has several advantages in relation to the prototype: the dynamics of sand-holding ability for sand of a larger fraction in comparison with the prototype increases to 5 hours (the prototype 2 hours), while maintaining satisfactory rheological characteristics; the composition is easily washed with water and minimizes contamination of the bottomhole zone (permeability recovery coefficient is 98.5-99.0%), while acid treatment is required to restore permeability according to the prototype, which affects the reservoir properties of the formation.

Claims (1)

Sand-carrier fluid for hydraulic fracturing, including a water-soluble polymer, a surfactant, a thickener and water, characterized in that it additionally contains spent petroleum products based on petroleum oils, and carboxymethyl cellulose as a water-soluble polymer, as a surfactant - nonionic surfactant, and as a thickener - clay, in the following ratio of components, wt.%:
Clay - 3 - 4
Waste oil products based on petroleum oils - 20 - 30
Carboxymethyl cellulose - 0.8 - 1.2
Nonionic surfactant - 2.0 - 2.5
Water - Else9

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