RU2153576C1 - Reverse emulsion for treating oil strata - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: emulsion contains 10.0-25.0% of liquid hydrocarbon, 0.3- 5.0% of special-type emulsifier, 0.2-4.0% of calcium chloride, and water. Such emulsion can be used when developing oil deposits on any watering phase in order to intensify operation of producing wells and to increase oil recovery of formation. EFFECT: increased heat resistance of emulsion and simultaneously preserved its oil-displacement property. 1 tbl, 2 ex

Description

 The invention relates to the extraction of oil from the reservoir and can be used in the development of oil fields at any stage of flooding, to intensify the work of producing wells and increase the current oil recovery.

Currently, in the development of oil fields, technologies using invert emulsion formulations are widely used. The closest analogue to the proposed invention in terms of technical nature and the achieved result is an invert emulsion for processing oil reservoirs containing liquid hydrocarbon 10.0-20.0 wt.%, Oil-soluble surfactant NEFTENOL H3 0.3-5.0 wt. %, calcium chloride 0.3-1.5 wt.% and water - the rest [RF Patent N 2110675, cl. E 21 B 43/22, 05/10/1998]. Although this composition has a sufficiently high oil-displacing ability with a relatively low consumption of chemicals, the resulting invert emulsions have not enough high thermal stability. This leads to a decrease in the effectiveness of the composition when applied to oil fields with a high temperature of the formation (70-80 ^o C) and a decrease in the duration of the positive effect of the treatment of the oil reservoir.

 The objective of the invention is to increase the thermal stability of the invert emulsion while maintaining its oil-displacing properties.

The problem is solved in that the invert emulsion for processing oil reservoirs containing liquid carbon, an oil-soluble surfactant, calcium chloride and water, contains an emulsifier SINOL-EM as an oil-soluble surfactant, a hydrocarbon solution of the reaction product of tall oil acids with triethanolamine and urea, alkyl chloride and hydroxyalkyl dimethylamine, in the following ratio, wt.%:
Liquid hydrocarbon - 10.0-25.0
SINOL-EM - 0.3-5.0
Calcium Chloride - 0.2-4.0
Water - Else
The essential features of the proposed technical solution are the following:
1. Invert emulsion;
2. Liquid hydrocarbon;
3. Oil soluble surfactant;
4. Calcium chloride;
5. Use as an oil-soluble surfactant emulsifier SINOL-EM;
6. The quantitative ratio of the components.

 Signs 1-4 are common with the prototype, signs 5-6 are significant distinguishing features.

The following can be used as a liquid hydrocarbon in an invert emulsion: hexane fraction, BFLH, straight-run or stable gasoline, gas condensate, diesel fuel and low-viscosity oils. In the laboratory experiments, a hexane fraction was used as a liquid hydrocarbon - a mixture of saturated hydrocarbons of a fraction of 32-110 ^o C. The hexane fraction is a by-product of petrochemical industries (TU 3810381-77) and is a transparent liquid, density at 20 ^o C - 690 ^o C - 730 kg / m ³ , viscosity at 20 ^o C - 0.57 cSt.

SINOL-EM is a complex emulsifier containing in its composition the product of the interaction of tall oil acids with triethanolamine and urea, a hydrocarbon solvent and additives - alkyl chloride and alkyldimethylamine oxide. SINOL-EM is an oily brown liquid. Density at 20 ^o C - 860-920 kg / m ³ ; pour point - below minus 40 ^o C. Produced by CJSC NPF BURSINTEZ according to TU 2413-048-48482528-98.

Technical calcium chloride - calcined, fused or liquid, is produced in accordance with GOST 450-77. The required amount of technical calcium chloride for the preparation of an invert emulsion is calculated based on the content of pure CaCl ₂ in it. For testing, we used liquid technical calcium chloride with a CaCl ₂ content of 38 wt.%.

Invert emulsions were prepared according to the following procedure. A calculated amount of a solution of an oil-soluble surfactant (emulsifier) in a liquid hydrocarbon was placed in a glass beaker with a capacity of 200 cm ³ . Separately, the aqueous phase was prepared — a solution of the calculated amount of technical calcium chloride in mineralized water (10 g / l NaCl and 2 g / l CaCl ₂ ). Then, a fan stirrer was placed in the glass and, with mechanical stirring, at a speed of 800-1000 rpm, the aqueous phase was introduced dropwise into the emulsifier hydrocarbon solution so that the time for the complete introduction of the aqueous phase was 15 ± 5 min. Upon completion of the introduction of the aqueous phase, the resulting finely divided emulsion of the type "water in oil" was kept under stirring for another 15 minutes until it was completely stabilized. After that, we started testing the obtained invert emulsion sample.

Example 1. The aqueous phase prepared by dissolving 0.5 g of technical calcium chloride with a CaCl content _of 38 wt.% In 85.7 g of mineralized water was introduced dropwise with mechanical stirring into a solution of 0.29 g SINOL-EM in 9.66 g (13.6 cm ³ ) of the hexane fraction. The result was an invert emulsion of the following composition, wt.%:
Hexane fraction - 10.0
SINOL-EM - 0.3
Calcium Chloride - 0.2
Water - 89.5
The resulting emulsion at 20 ^o C had a density of 966 kg / m ³ and a dynamic viscosity of 15.5 MPa.s.

 Invert emulsions of a different composition were similarly prepared.

The thermal stability of the resulting emulsions was determined as follows. The finished emulsion in an amount of 15 cm ^{3 was} poured into a test tube with a capacity of 20 cm ³ , closed with a ground stopper and put to the test in thermostat at a temperature of 80 ^o C. The time of the emulsion stability was considered the time from the start of testing to the release of large drops of water from the emulsion.

The oil-displacing ability of the obtained invert emulsions was determined under the conditions of residual oil washing out on a linear model of a homogeneous reservoir, which is a 444 mm stainless steel column with an internal diameter of 30 mm filled with a disintegrated core of the BS11 Muravlenkovskoye deposit of 0.1-0.25 mm fraction. The model was saturated with water under vacuum, and the porosity and water permeability of the model were determined by weight. After that, oil was injected into the model under pressure until clean (without water) oil appeared at the outlet, and the initial oil saturation was determined. The experiments used natural oil from the Muravlenkovskoye field with a density of 860 kg / m ³ and a dynamic viscosity of 12 MPa. s at 20 ^o C. The initial displacement was carried out with water (three pore volumes) and the coefficient of oil displacement by water was determined. A reservoir water model was used with a total salinity of 12 g / L (2 g / L CaCl ₂ ; 10 g / L NaCl). Then, one pore volume of the tested invert emulsion and three pore volumes of water were filtered through the model, the growth and the total oil displacement coefficient were determined.

Example 2. Three pore volumes of water were pumped into a reservoir model with a water permeability of 3.5 μm ² and an initial oil saturation of 71.8%. Residual oil saturation after water flooding was 30.8%, oil displacement coefficient by water 0.57. A single pore volume of the rim of the invert emulsion was filtered through the model, containing, wt.%: Hexane fraction 10.0; SINOL-EM 1.5%; calcium chloride 1.0; water 87.5. The tip of the invert emulsion was promoted with three pore volumes of water. The residual oil saturation of the model after injection of the rim of the invert emulsion and its advancement with water is 12.9%, the total oil displacement coefficient is 0.82, and the increase in the displacement coefficient is 0.25.

 Invert emulsions of a different composition were similarly tested.

 The composition of invert emulsions, their oil-displacing ability and thermal stability are presented in the table.

 Compared with the prototype, the oil-displacing ability of the proposed emulsion does not decrease (an increase in the oil displacement coefficient of 0.22-0.34 versus 0.20-0.30), and the thermal stability of the resulting emulsion increases significantly (8-16 hours against 6-7 hours).

 When the content in the emulsion is less than 0.3 wt.% SINOL-EM emulsifier and calcium chloride less than 0.2 wt.% (Examples 16 and 18), unstable emulsions are obtained, therefore, this value can be taken as the minimum content of these reagents in the proposed composition.

 The increase in the content of oil-soluble surfactants above 5.0 wt.% And the concentration of calcium chloride above 4.0 wt.% (Examples 17 and 19) does not lead to a significant improvement in the oil-displacing properties of the emulsion and increase its thermal stability, therefore, use higher than proposed concentration these chemicals are impractical.

 Emulsions, where the concentration of liquid hydrocarbon is less than 10 wt.% (Examples 13 and 14), are characterized by a significantly lower increase in the coefficient of oil displacement and thermal stability. The increase in the liquid hydrocarbon content in the emulsion above 25 wt.% (Examples 20 and 21) also does not give a significant positive effect.

 The proposed invert emulsion is used as follows. The calculated amount of the pre-prepared emulsion or the amount at which a decrease in the injectivity of the well to a predetermined mark is pumped into the waterflood through the buffer valve of the injection well. After injection of the invert emulsion, water or an aqueous polymer solution is injected into the formation.

Claims (1)

An invert emulsion for treating oil reservoirs containing liquid hydrocarbon, an oil-soluble surfactant, calcium chloride and water, characterized in that it contains an emulsifier SINOL-EM as an oil-soluble surfactant, a hydrocarbon solution of the reaction product of tall oil acids with triethanolamine and carbamide, alkyl chloride and alkyldimethylamine oxide in the following ratio of components, wt.%:
Liquid hydrocarbon - 10.0 - 25.0
SINOL-EM - 0.3 - 5.0
Calcium Chloride - 0.2 - 4.0
Water - Else

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