RU2391378C1 - Backfill composition for selective restriction of water inflow in extraction wells - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to oil and gas industry and specifically to a backfill composition for selective restriction of water inflow in waterlogged oil and gas wells. The composition can also be used for cutting off bottom water, sealing behind casing leaks, shutting off flooded permeable seams, stopping water inflow with abnormally high formation pressure. The backfill composition for selective restriction of water inflow in extraction wells contains an inverted emulsion consisting of a dispersed hydrocarbon phase - oil or its processing products, an emulsion stabiliser - chemically modified silica - Polysil-DF and a dispersed phase. The dispersed phase is liquid sodium glass and the said composition also contains an oil-soluble surfactant in form of Sinol-EM, with the following ratio of components (pts. wt): oil or its processing products 25-40, liquid glass 60-75, Sinol-EM-3-5, Polysil-DF 0.4-0.7.

EFFECT: improved backfilling properties of the composition, reduced water content of the extracted product.

6 ex, 3 tbl

Description

The invention relates to the oil and gas industry, and in particular to process fluids for selectively restricting water inflows in flooded oil and gas wells. The composition can also find application for cutting off bottom water, isolating annular flows, shutting off waterlogged permeable layers, eliminating water phenomena with abnormally high reservoir pressures.

One of the main methods for extracting oil from reservoirs in the late stages of field development is to force it out by water being pumped into the reservoir through injection wells, which ultimately leads to a breakthrough of water directly into production wells. As a result, the production of water is irrigated, which leads to increased costs for oil recovery and lower oil recovery of productive formations.

To limit the water inflow of producing wells, injection of gel-forming and sediment-forming compositions, aqueous solutions of polymers, cement mortars and other compositions into the reservoir is used (Use of chemical reagents to intensify oil production / N.Kh. Ibrahimov et al. M .: Nedra, 1991. - 46 p. .), Most of these compositions relate to non-selective action materials, and their use leads to clogging of the entire reservoir. As a result, often after conducting insulating work, an irrigated part of the reservoir is opened.

When carrying out work to limit water inflows in producing wells, grouting materials of selective action give the greatest effect, which is ensured by their following physicochemical properties:

- solubility in oil and insolubility in water;

- a sufficiently high adjustable induction period of thickening at reservoir pressures and temperatures;

- adjustable mobility in a porous medium during the period of injection into the bottom-hole formation zone (PZP);

- a sufficiently high mechanical strength and a high shear gradient of the plugging material in a porous medium.

Materials of selective action include an aqueous solution of alkali metal silicates of the general formula R ₂ OmSiO _2? where R = Na, K or Li, m - so-called. siliceous module. Silicate compositions have found application for limiting water inflows of producing wells, especially in deposits with severe thermobaric conditions (A.I. Komissarov, K.Yu. Gaziev. The use of silicate compositions for limiting water inflows from deep-seated formations // Oil industry. - 1992. - No. 8 - p. 1345).

The duration of silicate compositions in reservoir conditions is almost unlimited, since they, unlike polymer systems, are not subject to thermal oxidative and biological degradation.

The disadvantages of silicate solutions include the fact that by their nature silicate solutions are alien to the produced oil, and if they are deeply filtered in the oil layer, then, as a rule, the permeability of the productive zone decreases sharply.

One of the most effective compositions for creating a screen from an aquifer is an invert emulsion solution (ESI), the external dispersion medium of which is oil. The advantages of such formulations over water-based formulations are manifested in the fact that they are in nature close to the produced oil. Once in the reservoir, the ESI does not block the oil-conducting channels, dissolving in the oil contained therein, and does not destroy the oil-bearing rocks, which is typical for water compositions.

When interacting with formation water, the composition forms a highly viscous, structured, inactive system. Penetrating through the aquiferous channels, the ESI hydrophobizes their surface, thereby increasing the filtration resistance for water and decreasing for oil. All these factors contribute to the formation of a water insulating screen in the bottomhole zone of the reservoir.

Closest to the claimed invention (prototype) is the composition of an invert oil-water emulsion stabilized by hydrophobic chemically modified silica (SiO ₂ ). (Pat. RF № 2184836; Declared. 04.25.2000; Published. 07/10/2002.). The introduction of hydrophobic ultrafine silica with a particle size of 0.005-0.1 microns into the emulsion developed by the authors of the IER stabilizes the emulsion and prevents its destruction when it is forced into the reservoir.

The disadvantages of the known invention include a low pressure gradient, which withstands the IER in reservoir conditions. When creating a depression on the formation, the oil-water emulsion is gradually removed from the bottomhole formation zone, as a result of which the effectiveness of its tamping effect decreases. The insulating characteristics of such a water-oil emulsion can reduce the water cut of the produced products on average by only 10-15%, which, of course, is not enough.

These disadvantages are overcome in the present invention. A positive effect is achieved by the fact that for the selective limitation of water inflows in producing wells, a grouting composition has been developed for the selective limitation of water inflows in producing wells, including an invert emulsion consisting of a dispersed hydrocarbon phase - oil or products of its processing, an emulsion stabilizer - chemically modified silica - Polysil-DF and the dispersed phase, according to the invention, it contains sodium liquid glass as an dispersed phase and, in addition, oil-soluble glass surfactant - Sinol-EM in the following ratio of components (parts by weight):

oil or its refined products 25-40 liquid glass 60-75 Sinol-EM 3-5 Polisil-DF 0.4-0.7

The plugging effect of the oil silicate emulsion is as follows:

- when the emulsion is filtered through a water-saturated PZP interval, the dispersed / dispersion phase ratio increases and the composition forms a highly viscous structured inactive system, and the sodium silicate in the dispersed phase, in contact with polyvalent metal ions Ca ²⁺ , Mg ²⁺ , Fe ³⁺ , Al ³⁺ coagulates with the formation of an insoluble precipitate and thereby clogs the conductive channels in this zone;

- liquid glass does not coagulate when it enters the oil-saturated zone, since there is no source of polyvalent metal ions, the emulsion liquefies even more, its viscosity approaches the viscosity of the oil, and when the well starts to work, it is easily removed from the oil interval of the reservoir.

Polysil-DF, as in the prototype, performs the function of an emulsion stabilizer: located at the phase boundary, it “armor” the globules of the dispersed phase and thereby strengthens the emulsion, which increases the duration of the insulating effect of the developed composition. The DF policy is issued in accordance with TU 2311-002-04706-93.

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

As the dispersion phase, you can use oil or its refined products - diesel fuel, nefras, kerosene, a wide fraction of light hydrocarbons (BFLH), unstable gasoline and others.

A method for selectively restricting water inflows in producing wells using an oil-silicate emulsion involves injecting an invert oil-silicate emulsion into a PZP, pumping the emulsion into the formation, and holding for a response for 12-18 hours. During exposure due to thixotropy, the emulsion additionally increases its viscosity (according to laboratory data, 5-7 times).

Instead of salable liquid glass with a density of 1.41 g / cm ^3, you can use industrial salt dry salt, sodium metasilicate water - Na ₂ SiO ₃ · 5H ₂ O, soluble in warm water (50-60 ° C). In this case, to obtain marketable liquid glass with a density of 1.41 g / cm, it is necessary to take 90 g of salt per 100 ml of water.

The dispersion / dispersion phase ratio varies depending on the viscosity of the selected dispersion medium. So, if light oil is used as a dispersion medium, then this upper limit of this ratio varies from 2/1 to 2.5 / 1. If the oil is highly viscous, with a high content of asphaltenes and resins (ή> 200 cP), then the dispersion / dispersion phase ratio does not exceed 1.5 / 1. This ratio can be increased to 3/1 if various oil fractions are used as the dispersion phase - BFLH, nefras, diesel fuel, etc.

The sizes of discrete particles of chemically modified silicas are 2-4 orders of magnitude smaller than the average size of the pore channels, which allows invert emulsion under pressure to penetrate deep into the reservoir.

The concentration limits of the composition and its amount are selected depending on the type of complications in the well, permeability, formation porosity, fluid flow rate and water cut of the produced product. Before carrying out the work, the necessary volume of the emulsion is selected, comprising from 0.5 to 2.0 m ³ per 1 m of perforated thickness of the formation. Depending on the viscosity of the oil taken, the phase ratio, the amount of emulsifier and emulsion stabilizer are selected.

To facilitate the injection and increase the phase permeability, a small amount of oil (2-3 m ³ ) or its lighter fraction is pumped before the emulsion. As a squeezing liquid, oil or produced water is used.

Examples of specific implementation.

Example 1 (parts by weight).

40.0 degassed, highly viscous oil (carbon, ή = 227 mPa.s) are placed in a flask equipped with a stirrer with a rotational speed of at least 1000 rpm and 3.0 with Sinol-EM emulsifier are added with stirring (600 rpm) and 0.4 Polysil-DF. After 5 minutes of stirring, the stirrer is turned on for the maximum number of revolutions and 60.0 liquid glass (Na ₂ O / mSiO ₂ ) with a density of 1.41 g / cm ³ (siliceous module 2.52) is gradually added in small portions over a period of 15-20 minutes. . Stirring is continued for another 15-20 minutes. At the end of the dispersion, the resulting emulsion is held for at least 6 hours to degass and stabilize aggregative processes. The properties of the emulsion obtained, measured on a Fann-35 viscometer, are shown in table 1.

Table 1. Properties of invert oil silicate emulsion. No. Characteristics Indicators at 20 ° C at 75 ° C one Density, g / cm ³ 1.13 1,115 2 Water loss, cm ^3/30 min 4.9 7.8 3 Effective viscosity, MPa · s 80.3 46.0 four Plastic viscosity, MPa · s 64.5 33.9 5 Dynamic shear stress, dPa 173.5 80.6 6 Static shear stress, 01, dPa 33.5 14,4 7 Static Shear Stress, 010 dPa 38.3 19.2 8 Electrical stability, V 288 231

As can be seen from the data in the table, the emulsion obtained both at room temperature and at 75 ° C has high structural and rheological properties. Noteworthy is the low fluid loss emulsion solution, not to exceed the temperature range 20-75 ° C. 10 cm ^3/30 min. This indicates the sedimentation stability of the emulsion, which allows us to expect that when it is injected into the reservoir under pressure, phase separation will not occur.

The resulting oil silicate emulsion has high thermal stability. So when the emulsion was heated at a temperature of 75 ° C for 3 days, the emulsion did not delaminate and maintained its stability.

Example 2

By the procedure of Example 1, an invert emulsion was prepared in which the light oil with ή = 2.2 MPa · s served as the dispersion phase. This made it possible to increase the content of the dispersed phase in the emulsion to the liquid glass / oil ratio as 2.5 / 1, respectively.

The formulation of the emulsion composition (parts by weight):

oil (ή = 2.2 MPa · s.) 29th water glass, ρ = 1.41 g / cm ³ (module 2.52) 71 Surfactant Sinol-EM 4.0 Polisil-DF 0.6

Since the selected light oil contained a low percentage of resinous compounds and was extremely mobile, in order to maintain high structural and rheological characteristics, the concentration of surfactants and stabilizer emulsion Polysil-DF was increased compared to example 1.

After the preparation of the emulsion, viscosity, thermal and sedimentation stability were determined. At a temperature of 20 ° C, the plastic viscosity of the emulsion, measured on a Fann-35 viscometer, was 56.3 mPa · s. When the emulsion was heated at a temperature of 75 ° C for 3 days, the emulsion, as in Example 1, did not delaminate and retained its stability.

Examples 3-5

Hydrocarbons were taken as the dispersion phase: diesel fuel, a wide fraction of hydrocarbons (NGL), and nefras. The characteristics of the obtained hydrocarbon-silicate emulsions are shown in table 2.

Table 2. Properties of hydrocarbon-silicate emulsions Example No. The dispersion phase, parts by weight The correlation phases w.s * / hydrocarbon Concentration, parts by weight Water loss, cm ^3/30 min Plastic viscosity, MPa · s Sinol-EM Psilisil-DF 3 Diz. fuel 2,5 / 1 4.0 0.5 5.3 43,4 four ShFLU 3/1 5,0 0.7 6.1 56.9 5 Nefras 3/1 4,5 0.7 6.0 62.0 * railway station - liquid glass

The above results show that, regardless of the nature of the oil refined products taken, stable hydrocarbon-silicate emulsions are formed as the dispersion phase, the viscosity of which is determined by the selected hydrocarbon / liquid glass phase ratio. Water loss of emulsions varies slightly and does not exceed 10 cm ^3/30 min.

Example 6

To carry out work to limit water inflow, the treatment of the bottom-hole zone of a producing well with an oil-silicate emulsion is performed in the following sequence:

- installation of the packer over the injection zone of the emulsion, piping of the wellhead with the pump unit;

- injection into the reservoir of a buffer volume of oil (2 m ³ ) to increase the phase permeability of water-saturated layers;

- preparation of the hydrocarbon phase (with a surfactant and with an emulsion stabilizer Polysil-DF) in the CA-320 unit;

- preparation of an invert emulsion in the CA-320 unit using a dispersant with a hydrocarbon / liquid glass ratio of 1 / 1.5 to 1/3 (depending on the initial viscosity of the hydrocarbon);

- injection of the emulsion and its pushing into the formation (in a volume depending on the state of the well: water cut, perforation interval, injectivity, etc.);

- well shutdown for response within 12-18 hours;

- raising the packer, launching the well into operation.

It should be noted that to enable the planned volume of the insulating composition to be injected into the formation before the emulsion, it is advisable to inject into the formation a buffer liquid, which is an aqueous solution of sodium carbonate. Sodium carbonate, forming insoluble compounds with calcium and magnesium ions, removes them from formation water, as a result of which the oil-silicate emulsion injected behind it is additionally protected from premature coagulation.

The tamping ability of the oil silicate emulsion was compared with the prototype by performing filtration tests on a reservoir model on a BS-805 installation. Two bulk models were prepared from ground core of the Sredne-Khulymskoye field with a length of 50 cm and with a permeability of 169.0 and 184.4 mD. Two invert emulsions with the same phase ratio, the same concentration of surfactant and Polysil-DF were also prepared. Their difference was only in the fact that in the prototype mineralized CaCl ₂ water was used as the dispersed phase, and in the second case, salable liquid glass.

Filtration tests were carried out according to standard methods. 0.5 pore volume of the emulsion was pumped into each model. The results are shown in table 3.

Table 3. The change in the permeability of the reservoir model after treatment with invert emulsion systems Example No. The composition of the emulsion, parts by weight Plastic viscosity, MPa · s Water permeability, MD before processing after processing 7 Diz. fuel
Water, ρ == 1.07 g / cm ³
Sinol-EM
Polisil-DF 33.3
66.6
4.0
0.5 28.7 169.0 8.5 8 Diz. fuel
Zh.s. *., Ρ = 1.4 g / cm ³
Sinol-EM
Polisil-DF 33.3
66.6
4.0
0.5 33.8 184.4 2,8 * siliceous liquid glass module 3.5

From the above data it can be seen that the replacement of a dispersed phase in water invert emulsion - water with liquid glass leads to an increase in the plugging effect. So, the treatment of a water-saturated reservoir model with a water-oil emulsion in the volume of 0.5 V _pop . leads to a decrease in permeability by 95.0%, and when pumping oil-silicate emulsion, the permeability of the model decreases by 98.5%.

After measuring the permeability, changing the input to output, the backpressure gradient that the emulsion withstands was determined. The breakthrough of water filtration in bulk models of the reservoir of experiments 7 and 8 was 13.7 and 24.3 MPa / m, respectively.

The data presented show that the use of liquid glass as the dispersion phase instead of water leads to the formation of emulsion systems with enhanced tamponing properties.

Claims (1)

The grouting composition for selectively restricting water inflows in producing wells, including an invert emulsion consisting of a dispersed hydrocarbon phase - oil or products of its processing, an emulsion stabilizer - chemically modified silica - Polysil-DF and a dispersed phase, characterized in that it contains as a dispersed phase sodium liquid glass and optionally an oil-soluble surfactant - Sinol-EM in the following ratio of components, parts by weight:
Oil or refined products 25-40 Liquid glass 60-75 Sinol-EM 3-5 Polisil-DF 0.4-0.7