RU2186959C1 - Emulsion for insulation formation water inflow in well - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention relates to compositions for limiting water inflow in oil wells to increase water flooding-stimulated formation oil recovery and to reduce permeability of formation sections in injectors with terrigenous and carbonate reservoirs. Appropriate emulsion contains, %: hydrocarbon fluid, 74-90; still bottoms from C17-C20-amine production, 3-5; and water additionally contains mineral aluminum salt, 2-4. As a result, increasing with time improvement of structural-mechanical properties of emulsion owing to reduced diffusion of emulsion composition at simultaneously increased stability thereof under formation temperature 30-45 C conditions and preserved stability of these properties under elevated temperature 95-110 C conditions when in contact with differently mineralized formation waters, and also owing to preserved inhibitory properties of emulsion and increased selective insulation properties thereof. EFFECT: enhanced efficiency of insulating water-permeable and fissured reservoirs of oil-production wells and injectors. 2 tbl, 2 ex

Description

 The invention relates to the oil industry, in particular to compositions for selectively restricting water inflows in oil wells, to increase oil recovery by water flooding and to reduce the permeability of formation intervals in injection wells with terrigenous and carbonate reservoirs.

 A known composition for isolating water inflow in oil wells, containing hydrocarbon liquid, nonionic surfactant (emulsion), calcium chloride, wood flour, nefras (see RF patent 2131 5/3, CL E 21 B 43/32 from 1997) .

 The disadvantage of this composition is that the composition, penetrating into the formation, causes the pores and cracks to become clogged with particles of wood flour, which eventually wash out and clog the bottom-hole formation zone (PZP). In addition, this composition does not provide the strength of the insulating screen in water-saturated formations with highly saline formation waters.

 A known composition for increasing oil recovery by water flooding, as well as for isolating water inflows to oil wells, containing aluminum chloride, urea, zeolite and water (RF patent 2143551, class E 21 B 43/22 from 1997).

A disadvantage of the known composition is that the formation in the formation of a voluminous gel-forming composition that insulates the formation is possible only at high temperatures (50-90 ^o C) and lasts for a long time.

 A hydrophobic emulsion is known for isolating water inflows in oil producing wells (G. A. Orlov, M.Sh. Kendis, V. I. Glushchenko. The use of inverse emulsions in oil production. - M .: Nauka, 1991), including hydrocarbon liquid, produced water or water a solution of calcium chloride or a solution of a strong acid and an emulsifier ES-2 is a product of the amidation of bottoms of synthetic fatty acids with dextramine.

 However, this emulsion is unstable in acidic and weakly mineralized media, namely in these media its viscosity and structural-mechanical properties are reduced.

Closest to the proposed solution for the purpose and technical essence is a hydrophobic emulsion for isolating the influx of formation water into the well (RF patent 2134345, class E 21 B 43/32 of 1997), containing in wt.%: Oil 32,0-56, 0; bottoms for the production of C ₁₇ -C ₂₀ amines or a polycondensation product for bottoms in the production of C ₁₇ -C ₂₀ amines and bottoms in the production of caprolactam 1.0-4.0 and potassium chloride type water with a density of 1060-1180 kg / m ³ - the rest .

 In such emulsions, the dense packing of amines in the interfacial layer with the formation of structured and extremely solvated dispersion medium adsorption films stabilizes the emulsions, giving them high structural and mechanical properties.

 However, in highly permeable porous and fractured reservoirs, a well-known emulsion initially thickens in water-washed channels of the formation after 4-6 months. (according to the results of experimental field trials) begins to erode under the pressure of the formation water due to the gradual weakening of its structural and mechanical properties, which makes the insulation of poor quality.

The present invention solves the problem of increasing the insulation efficiency of permeable and fractured reservoirs of oil producing and injection wells by improving the structural and mechanical properties of the proposed emulsion, increasing these properties over time by reducing the erosion of the emulsion composition while increasing its stability at low reservoir temperatures (30-45 ^o C) and maintaining the stability of these properties at elevated temperatures (95-110 ^o C) in contact with different mineralization and reservoir waters, as well as by maintaining the inhibitory properties of the emulsion and increasing its selective insulating properties.

To achieve the technical result, the known emulsion for isolating the influx of formation water in the well containing hydrocarbon fluid, bottoms in the production of C ₁₇ -C ₂₀ amines and water, additionally contains an inorganic aluminum salt in the following ratio of ingredients, wt.%:
Hydrocarbon Liquid - 74-90
Vat residues in the production of amines C ₁₇ -C ₂₀ - 3-5
Inorganic aluminum salt - 2-4
Water - Else
Amines form complex compounds with aluminum salts — micellar (associative) colloidal systems in which the additional association of molecules is probably due to the formation of coordination bonds of the Al ³⁺ ion with the nitrogen atom in the amino group.

 The tight packing of fatty amines on the interphase surface and the ability of amines to form bulk hydrophobic protective layers on the surface of globules of the dispersed phase, leading to thickening of the dispersion medium of the emulsion and the creation of a condensed adsorption layer, give high structural and mechanical properties and stability of the proposed emulsion. The formation of acid during the hydrolysis of aluminum salts and the subsequent reaction with amines with the formation of complex compounds extracted with the organic phase of the emulsion proceeds gradually, as a result of which the proposed emulsion gains structure over time, increasing the values of static shear stress with increasing stability.

The lower water content of the proposed emulsion and higher structural and mechanical characteristics ensure a decrease in the erosion of emulsions in the water-saturated channels of the formation and increase its stability at low formation temperatures (30-45 ^o С) and ensure the stability of the emulsion in conditions of elevated (95-110 ^o С ) temperatures.

 In the presence of acid-forming (in the process of hydrolysis) aluminum salts, the polarity and mutual solubility of the bottoms in the production of amines in the hydrocarbon and aqueous phases increases, which leads to a decrease in interfacial tension and an increase in the selective properties of the proposed emulsion composition.

To prepare the proposed emulsion in laboratory conditions, the following substances were used:
- oil fields of the Perm region;
- bottoms in the production of amines C ₁₇ -C ₂₀ grade B, produced by the Bereznikovsky OJSC "Azot" according to TU 2413-047-00480689-95 with the following characteristics:
the content of amines I in% - not less than 88.2;
the content of amines II in% - not more than 4.7;
hydrocarbon content in% - not more than 7.0;
- aluminum chloride 6-water, GOST 3759-75;
- aluminum sulfate 27% aqueous solution, manufactured by Halogen OJSC according to TU 2141-127-05807960-96;
- technical water.

To prepare the emulsion in laboratory conditions, bottoms are introduced into the oil in the production of C ₁₇ -C ₂₀ amines in the form of a 35% solution in kerosene and, after 5-10 minutes of mixing, the aluminum salt solution is gradually added dispersing the composition on a stirrer with a frequency of rpm 1500-2000 for 10-15 minutes.

Example 1. To 71 cm ^{3 of} oil from the Gozhanskoye field with ρ = 908 kg / m ³ and μ = 42 MPa • s add 14.5 cm ^{3 of a} 35% solution of bottoms in the production of amines C ₁₇ -C ₂₀ in kerosene (solution prepared in advance) and stirred for 10 min on a laboratory stirrer with a frequency of 1500-2000 rpm, then 14.5 cm ^{3 of a} 25% aqueous solution of aluminum chloride are added here during mixing. The composition is continued to mix for 10 minutes to obtain the proposed emulsion.

Example 2. To 73.5 cm ^{3 of} oil from the Karamorskoye field with ρ = 880 kg / m ³ and μ = 19 mPa • s add 14.5 cm ^{3 of a} 35% solution of bottoms in the production of amines C ₁₇ -C ₂₀ in kerosene and stirred for 10 min on a laboratory stirrer with a frequency of 1500-2000 rpm, then 12 cm ^{3 of a} 13.5% aqueous solution of aluminum sulfate are added thereto while stirring. The composition is continued to mix for 10 minutes to obtain the proposed emulsion.

 Compositions with different ingredients were prepared in a similar manner.

The resulting emulsion is thermostated at 20 ^o C (40 ^o C) and analyze its structural and rheological properties.

 The conditional viscosity, determined on a VZ-1 viscometer, characterizes the hydraulic resistance of the emulsion to the pumping process.

The effective viscosity, which characterizes the sum of the viscosity and strength resistance to the flow of the emulsion, was measured on a rotational viscometer at shear rates Dg = 1.5 s ^-1 and Dg = 656 s ^-1 .

 Static shear stress (SNA) was determined on the device SNA-2 after 1 and 10 minutes after mixing the emulsion, and also after 2 hours, days, 3 days, 10 days and a month. SNA characterizes the strength of the thixotropic structure of the emulsion at rest.

Thermostability was determined by keeping the emulsion in the thermostat at 20, 40, 95 and 100 and 110 ^o С (emulsions were kept at temperatures of 95, 100 and 110 ^o С for 16 hours) and visual observation of the absence of emulsion separation.

 The stability of the emulsion in various mineralized environments was determined by the resistance to mixing with formation water of various salinity.

 Data on the composition and structural-mechanical properties of the proposed and known emulsions are shown in table 1.

Data on changes in the structural and rheological properties of the proposed and known emulsions in time at a temperature of 40 ^o C are shown in table 2.

 The data shown in table 1 show that in all experiments the proposed emulsion (experiments 1-5, 8, 10, 11) has better structural and mechanical properties compared with the prototype (experiments 12, 13). Thus, the SNA of the proposed emulsions within 3 days increases by 1.3-12 (on average 6.7) times from 30-285 / 42-290 dPa after 1 and 10 min of rest to 247-450 dPa after 3 days. SNA of known composition after 1 and 10 min of rest is 28-75 / 46-140 dPa, respectively (table 1).

 In addition, the proposed emulsion is distinguished by a set of thixotropic structure in time, as well as a set of structure at reservoir temperatures (table 2), which reduces the erosion of the proposed emulsion in formations with high permeability and increases the duration of the insulation effect.

 Lower values of the initial conditional viscosity of the proposed invert emulsion in comparison with the prototype facilitate the process of its injection into the reservoir.

 The ratio of the concentration of aluminum salts in the proposed emulsion is 2-4 wt. % A decrease in salt concentration to 1% (composition 4, 7) impairs the structural and mechanical properties of the emulsion, and an increase in salt concentration in the composition of the emulsion to 5% (composition 6) is economically disadvantageous, since it does not improve its quality.

The range of concentrations of bottoms residues in the production of C ₁₇ -C ₂₀ amines was determined by the selection of concentrations aimed at obtaining optimally high structural and rheological properties and stability of emulsions, taking into account the cost of the chemical itself.

 The range of concentrations of hydrocarbon liquid (74-90 wt.%) And water (10-18 wt.% In the proposed emulsion was also determined based on the structural and rheological properties of the obtained hydrophobic emulsion composition and is aimed at increasing these properties over time and maintaining the stability of these properties in formation temperature conditions.

 Similarly to the prototype, the proposed emulsion does not lose its stability in the formation water of different salinity and pH values and, having high adhesion and adsorption, bears inhibitory properties to protect underground equipment.

 The inventive emulsion fully preserves the natural reservoir properties of the formation, since the acid formed during the hydrolysis of the aluminum salt is chemically bound: no traces of the reaction were found on the pieces of marble immersed in the emulsion.

 Due to the low volumetric water content of the claimed emulsion, it can be used in winter as a low-setting medium.

Claims (1)

An emulsion for isolating the influx of produced water in the well containing hydrocarbon fluid, bottoms in the production of C ₁₇ -C ₂₀ amines and water, characterized in that it additionally contains an inorganic aluminum salt in the following ratio of ingredients, wt.%:
Hydrocarbon Fluid - 74 - 90
Vat residues in the production of amines C ₁₇ -C ₂₀ - 3 - 5
Inorganic aluminum salt - 2 - 4
Water - Rest

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