SU1682539A1 - Method of oil recovery - Google Patents

Abstract

FIELD OF THE INVENTION The invention relates to the oil industry, in particular to methods for the extraction of water flooding. The purpose of the invention is to increase the efficiency of the process by increasing the coverage ratio of the deposit. A dispersion of solid particles in an aqueous solution of a non-ionic surfactant containing 0.005-1.0% of a water-soluble polymer by weight of the dispersion is injected into the formation. The dispersion of solid particles is a dispersion of water-insoluble salts, obtained by mixing water containing sediment-forming ions. Polyacrylamide or carboxymethyl cellulose is used as water-soluble polymers. The method allows an additional 150-300 tons of oil to be produced per ton of polymer. 1 hp ff, 2 tab.

Description

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The invention relates to the oil industry.

The aim of the invention is to increase the efficiency of the process by increasing the coverage rate of a flooding reservoir.

In order to carry out the process, a water-soluble polymer in an amount of 0.005-1.0% of the total mass of the dispersion is additionally introduced into the dispersion of solid particles in an aqueous solution of a surfactant.

Polyacrylamide (PAA) and carboxymethylcellulose (KM C) are used as a water-soluble polymer.

The dispersion of solid particles is a dispersion of water-insoluble salts, for example calcium carbonates or sulfates, barium, strontium, hydroxides or

oxides of magnesium, iron and others, which are obtained by mixing waters containing sediment-forming cations and anions.

In the proposed method, when a water-soluble polymer (PAA and KMC) containing a carboxyl anionic group is introduced into an aqueous surfactant solution and dispersion of solid particles, they are dispersed in the surfactant solution and polymer, which aggregate (the association of individual particles into flocs) and kinetically (the rate of separation of the dispersion into solid and liquid phases) is more stable than the dispersion of solid particles by a known method. Such dispersion stability is explained by the adsorption of individual floccules of particles containing surfactants on one polymer molecule due to the formation of a strong chemisorption bond between the surface of solid salt

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particles with a carboxyl group of the polymer and due to the ion-dipole interaction between the surfactant molecules and the polymer. The resulting polymer floccules of solid particles are larger in size than the floccules of solid particles formed by using only surfactants. This ensures a more efficient capture of the polymer-containing floccules by the porous medium of the oil reservoir and, consequently, a more efficient redistribution of the injected water flow into poorly drained oil-saturated streams. In contrast to the known methods of oil production, the proposed method significantly increases the coverage rate of a waterflood.

The dispersion and stability of the dispersion of solid particles in an aqueous solution of surfactants containing (the proposed method) and not containing (known) water-soluble polymer, and their effectiveness is determined by displacing oil from a heterogeneous reservoir model.

As a dispersion of solid particles, a calcium carbonate dispersion is used, which is obtained by mixing an aqueous 0.05% solution of calcium chloride with a 0.05% aqueous solution of sodium carbonate in a volume ratio of 1: 1, or a wastewater model containing,%: calcium chloride 0,195; magnesium chloride 0,013; sodium chloride 0.135; sodium bicarbonate 0.032, with a 0.025% aqueous solution of calcium carbonate in equal volumes.

Nonionic surfactant brands and neonol AF-10 or AF-12 products containing them, brands CHO-ZB or CHO-4D, are used as surfactants.

As the polymer used PAA mol. mass 107 with a degree of hydrolysis of 15% (P-1), PAA mol. mass 15.6 106 with a degree of hydrolysis of 25% (P-2) and CMC.

Dispersion of solid particles is obtained by mixing in equal volumes of aqueous solutions of surfactants containing a precipitating calcium cation (and magnesium in the waste water) and a polymer containing a precipitating forming anion-carbonate.

Prepared aqueous calcium carbonate dispersions (and magnesium carbonate in wastewater) contain (with magnesium carbonate water), wt%: CAS02.05-0.1; Surfactant 0,005-0,5; polymer is 0.001-1.0.

Example 1. Examine the dispersion and stability of the prepared dispersions over time. Stability is assessed by the change in optical density (D) of the prepared dispersions over time. Optical density is determined using a KFK-2 photoelectrocolorimeter at a wavelength of 590 nm and a cell length of 50.0 mm at room temperature.

The results of the study of dispersion and stability in the form of Omax and 0 (t) over time are given in Table 1. The more Omaks. the larger the particle size of the precipitate and the longer the optical density (D) is maintained, the higher the dispersion stability.

The dispersion and stability of solid particles in water is less than in a surfactant solution (experiments 1 and 10 compared with 2 and 9). However, the introduction into the dispersion of particles in solution

Surfactant polymer in an amount of 0.005-1.0% dramatically increases the dispersion and stability of the dispersion of solid particles in an aqueous solution of surfactants (experiments 4-6 compared with experiment 2, experiment 8 with experience 9 and experiments 11 and 13 s

experience 2). The minimum content of the polymer in the dispersion, ensuring its high dispersion and stability, is 0.005 wt.% (Experiments 2 and 3 compared with experiment 4), and the maximum 1.0 wt.%, Since this content of polymer reaches the maximum stability of dispersion in water (experiment 11).

Thus, the polymer content in

The stable dispersion of solid particles in an aqueous surfactant solution is 0.005-1.0 wt.%.

One polymer (without surfactants) does not provide maximum stability and dispersion of solid particles in water (experiment 6 compared to 7, 11 s 12).

Example 2. The efficiency of the proposed method and the known one is determined by filtering the dispersion of solid particles through homogeneous water and oil-saturated reservoir models represented by polymictic sandstone, 27 cm long, 1.1 cm in diameter, and permeability 5-5.5 µm2. A water saturated model is prepared by injection.

three pore volumes of water with a total salt content of 1.59% at constant pressure until they reach the established filtration mode and record the filtration time per unit volume of water (DM).

The oil-saturated model is prepared in the same way as the water saturated one, and then the oil is additionally pumped at a viscosity of 8.9 MPa s at 20 ° C until the residual water saturation is low. Experiments conducted

at 65 ° C.

About three pore volumes of the investigated calcium carbonate dispersion in an aqueous surfactant solution are pumped through the core to a steady filtration mode by a known method or aqueous solution.

The surfactant and polymer according to the proposed method, or an aqueous solution of the polymer of the same concentration as in the dispersion under investigation, according to a known method (without sediment) and record the filtering time per unit volume of the pumped liquid.

Determine the filtering resistance factor of each liquid in water (c) and oil-saturated (n) cores by the formula

pp, v, disp, p Mm1sM

where the surfactants, Gdisp and gp - respectively, the filtering time of the surfactant, dispersion and polymer. In relation

PC (VOXB.)

RPlAB,

.dis.

KpA.disp.p

is judged on the regulatory capacity (PC) or the change in the voxe coverage ratio. reservoir flooding during pumping of the tested compounds for one technology or another. The higher the number, the more effective the method.

The results of the experiments are given in table 2. Both the resistivity factor and the coverage ratio of the proposed method is more effective than the well-known polymer flooding method (experiments 1 and 2 compared with experiments 3-6, experiments 7 and 8 with experiments 9-12 and experiments 13 and 14 - with experiments 15-18).

Thus, the proposed method of oil extraction is more effective than the known methods due to more efficient redistribution of injected fluids from water to oil-saturated interlayers, and consequently, due to an increase in the coverage rate of the waterflood.

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The proposed method is used to enhance oil recovery by flooding it in two versions.

In the first variant, when an oil field is developed by pumping fresh water, and polymer, surfactants, concentrated aqueous solutions of salts (alkalis and acids), forming an insoluble precipitate between themselves or with formation water, are alternately dispensed into the reservoir, and the prepared dispersion is pumped into the formation.

In the second variant, when an oil field is developed by pumping wastewater containing suspended particles and oil from oil treatment plants or their mixture with fresh water, polymer and surfactants are metered into the water line with the calculation of obtaining 0.005-1.0% - their solution in the injected water.

Compared with the known method, the proposed oil displacement method allows an additional 150-300 tons of oil to be produced per ton of polymer.

Claims (2)

1. A method for extracting oil, which involves injecting a dispersion of solid particles in an aqueous solution of a surfactant into the reservoir, characterized in that, in order to increase the efficiency of the method by increasing the rate of coverage of the waterflood, the dispersion of solid particles in the surfactant solution additionally contains water-soluble polymer in the amount of 0.005-1.0% of the total mass of the dispersion. 2. A method according to claim 1, characterized in that polyacrylamide or carboxymethyl cellulose is used as a water-soluble polymer.