RU2524738C1 - Polymer composition for in-bed water isolation - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: proposed composition comprises "givpan" acryl-containing polymer hydrolysed in alkali and sodium chloride. Note here that said composition comprises the additive, i.e. non-ionic surfactant with hydrophobic properties, that, water-repellant NG-1 composed of the mix of product of reaction of unsaturated fat acids with amines and their derivatives with solvents and functional additives. Composition features the following ratio of elements, in wt %: 3-10 wt % of givpan, 1-5 wt % of water-repellant NG-1, 0-10 wt % of sodium chloride and water-alkali solution.

EFFECT: higher penetrating and water-isolating capacity.

4 ex, 1 tbl

Description

The invention relates to the oil industry and can be used to isolate the zones of absorption or restriction of water inflow during well repair, to create a waterproof screen when disconnecting water-saturated and oil-saturated formations, as well as to align injectivity profiles of injection wells.

Sedimentary and gel-forming compositions for the selective isolation of formation water based on aqueous solutions of polymers of a number of acrylonitrile are known (RF Patent No. 2058479, publ. 04/20/1996), in which polyvalent metal ions (calcium, magnesium) are used as a precipitating agent (crosslinker) . As a source of calcium ions in the known compositions used highly saline formation water or a concentrated aqueous solution of calcium chloride.

The disadvantage of these polymer compositions is their low penetrating ability and low efficiency at elevated temperature of the reservoir, which is associated with a decrease in the volume of gel-like sediment under the influence of temperature. In addition, the disadvantage of the known compositions is the return of the formed sediment with the production of wells, which is associated with a weak chemical-physical interaction of the sediment with the rock of the reservoir.

Known gel-forming composition for isolating water inflow into a well, including a water-soluble polymer, salts of polyvalent metals, ammonium chloride and water (RF Patent No. 2169256, publ. 06/20/2001). Polyacrylamide is used as a water-soluble polymer, chromium acetate is used as a salt of polyvalent metals. The composition is used in a method for developing a waterlogged oil reservoir, which provides for the regulation of oil field development, isolating water inflow into the well, and creating insulating screens with improved technological parameters. An aqueous solution of polyacrylamide reacts with an aqueous solution of chromium acetate containing a stabilizer - ammonium chloride, which results in the formation of a continuous gel with a three-dimensional crosslinked structure, which improves the efficiency of isolation of water inflow into the well and regulates the injectivity profile of injection wells. The strength of the gel increases as a result of a decrease in the thermal degradation of the polymer and the formation of the gel in the entire volume. A disadvantage of the known composition is its low efficiency when water inflow into the well is used to isolate the injectivity profile of injection wells, since the gel formed is removed back from the well production, which is associated with insufficiently high strength and adhesive properties of the composition’s interaction with the formation rock.

Known gel-forming compositions based on alkali metal silicates (RF Patent No. 2065442, publ. 08.20.1996), aluminum salts (RF Patent No. 206185, publ. 01.01.1967, and RF Patent No. 206674, publ. 01.01.1968 g.), aluminosilicates (RF Patent No. 2089723, publ. 09/10/1997). The disadvantages of the known compositions is their low efficiency due to the complexity of controlling the rate of gelation, low structural stability, as well as the high cost of gel-forming components, which significantly limits the scope of the compositions.

Known sedimentary and gel-forming composition for isolating water inflow and leveling the injectivity profile of the formation (RF Patent No. 2064571, class E21B 33/138, publ. 07/27/1996), adopted as a prototype containing acrylic polymer (givpan), sodium silicate ( water glass), calcium chloride and water in the following ratio of components, wt.%: givpan - 1.0-5.0; sodium silicate - 0.33-3.0; calcium chloride - 2.0-5.0; water is the rest. However, the disadvantages of this composition are its low water-insulating ability in heterogeneous permeability formations, low adhesion of the formed sediment to the rocks of the formation. This is due to the fact that acrylic polymer (givpan) instantly coagulates in highly mineralized water, forming precipitation, and during insulation work, the composition, first of all, penetrates the highly permeable channels of the formation, leaving small pores and cracks with higher filtration resistance uninsulated. The precipitation formed clogs the narrowing of the channels when the composition is injected into the formation, but when the pressure of the sediment is equalized by gravitational forces, they can fall into a wider part of the channels, reducing the insulating effect.

The technical result of the invention is to increase the penetrating and insulating ability of a water-insulating polymer composition in conditions of water and oil-and-gas-saturated reservoir rocks that are heterogeneous in permeability.

The technical result is achieved in that the polymer composition, including an alkali hydrolyzed acrylate polymer (for example, known as givpan) and sodium chloride, additionally contains a nonionic surfactant with hydrophobic properties - hydrophobizing agent NG-1, which is a mixture of the unsaturated reaction product fatty acids with amines and their derivatives with solvents and functional additives, in the following ratio of components, wt.%:

Hydrolyzed in alkali waste pan polyacrylonitrile fibers or fabrics (Givpan) 3-10 Nonionic Surfactant (water repellent NG-1) 1-5 Sodium chloride 0-10 Aqueous alkaline solution rest

Sodium chloride is added to improve the low-temperature properties of the polymer composition, if used in formations with low formation temperature, and as a density regulator.

An aqueous solution of sodium hydroxide (concentration of 3-12% by weight) is used as a water-alkaline solution.

As a polyacrylonitrile feedstock on the example of givpan (RF Patent No. 2169754, class C09K 7/02, publ. 06/27/2001), when producing an acryl-containing polymer hydrolyzed in alkali, the following can be used:

1. A copolymer of acrylonitrile with methacrylate.

2. Wastes of polyacrylonitrile fibers (“tows”).

3. PAN threads and their waste.

The effectiveness of the claimed polymer composition was evaluated in laboratory conditions by evaluating and comparing the filtration and water-insulating properties of the claimed composition and composition according to the prototype. The polymer compositions were evaluated based on the results of laboratory filtration experiments on their effect on the change in the permeability of water-saturated (waterlogged reservoir interval) samples of natural rocks (cores). The studies were carried out using the FDES-645 (Coretest Systems Corporation) formation damage assessment unit under conditions as close as possible to the thermobaric formation conditions of oil fields in Western Siberia.

For the preparation of the studied polymer compositions in laboratory conditions, the following components were used:

- hydrolyzed in alkali waste pan fiber or polyacrylonitrile tissue - givpan (prototype)

(hereinafter referred to as hydrolyzed acrylic polymer);

- nonionic surfactant with hydrophobic properties - hydrophobizer NG-1 (TU 2229-002-22650721-2002);

- table salt (NaCl);

- an aqueous solution of sodium hydroxide (3-12% of the mass.).

Each studied polymer composition was prepared by compounding the calculated amount of components using a laboratory stirrer until a homogeneous mass was obtained.

Example 1 (prototype).

The polymer composition obtained when used as components, wt.%:

Hydrolyzed Acrylic Polymer 8 Sodium chloride 10 Aqueous alkaline solution 82

Example 2

The polymer composition obtained when used as components, wt.%:

Hydrolyzed Acrylic Polymer 8 Sodium chloride 10 Nonionic Surfactant (water repellent NG-1) one Aqueous alkaline solution 81

Example 3

The polymer composition obtained when used as components, wt.%:

Hydrolyzed Acrylic Polymer 8 Sodium chloride 10 Nonionic Surfactant (water repellent NG-1) 5 Aqueous alkaline solution 77

Example 4

The polymer composition obtained when used as components, wt.%:

Hydrolyzed Acrylic Polymer 8 Nonionic Surfactant (water repellent NG-1) 5 Aqueous alkaline solution 87

The core permeability coefficient was calculated based on Darcy's formula:

,

,

where k is the core permeability coefficient, m ² ;

µ is the viscosity of the liquid, Pa · s;

L is the core length, m;

Q is the given flow rate of the fluid through the core, m ³ / s;

S is the cross-sectional area of the core sample, m ² ;

ΔР - pressure drop at the ends of the core sample at a given flow rate, Pa.

Filtration studies were carried out on the basis of the principle: fixed costs - changing pressure drops. The main controlled parameter during the experiments was the change in pressure drop, on the basis of which the change in the mobility of water or oil was determined as a result of pumping water-insulating compounds.

The direction of injection and filtration of working fluids in the core samples under study corresponded to the actual direction of formation fluids and injected water-insulating compositions in production wells. Direct filtration corresponded to the process of fluid inflow from the formation into the well and then to the “development” of the well, and reverse filtration simulated the process of “isolating” the flooded interval of the bottomhole zone of the well, which consists in pumping 5 pore volumes of the water-insulating composition through the core sample.

The technique of conducting filtration studies was as follows.

1. The prepared sample of natural core was saturated under vacuum with the prepared model of produced water. After saturation, the pore volume of the core was determined by weighing by the magnitude of the change in mass.

2. A saturated core sample was placed in the core holder of the FDES-645 filtration unit, where pressures were created that were as close as possible to the formation ones. The temperature was set within 20 ° C.

3. Filtration was performed through a core sample of the formation water model. In this case, the initial phase permeability of the core in formation water was measured in a constant flow rate mode (0.5 cm ³ / min) until the pressure gradient stabilized at standard temperature and reservoir pressure. The direction of filtration is “direct”.

4. In the constant flow mode (0.5 cm ³ / min), the studied water-insulating composition was pumped. The injection volume of the composition, measured by the weight at the outlet of the core, was 5 pore core volumes (or the maximum possible at high injection pressures). The direction of filtration is “reverse”.

5. After the completion of the process of pumping the water-insulating composition into the core sample, the temperature in it increased to the average reservoir (80 ° C) and the system was kept at rest. The exposure time of the system under thermobaric conditions was 24 hours.

6. After the core sample was kept at rest, its final phase permeability through produced water was measured at a constant flow rate (0.5 cm ³ / min) until the pressure gradient stabilized. The direction of filtration is “direct”.

Processing the results of filtration studies was as follows.

1. The pressure and mobility gradients of the produced water were determined before and after the injection of the water-insulating composition, based on which the phase permeability coefficients for the produced water (or oil) were calculated before and after the injection of the composition into the core.

2. The pressure gradient of the injection of the water-insulating composition was fixed after pumping through the core of the pore volume.

3. The calculation of the residual resistance factor of the core sample after processing it with the studied waterproofing composition was performed:

,

,

where R _OST - residual resistance factor, units;

gradP ₁ - pressure gradient of water core injection into the sample before the process of “isolation”, Pa / m;

gradP ₂ is the pressure gradient of water injection into the core sample after the “isolation” process, Pa / m.

The results of laboratory tests are summarized in table.

From table 1 it is seen that the inventive polymer composition (examples 2, 3 and 4) has advantages over the prototype (example 1) for filtration and water-insulating properties:

- the inventive composition has an increased penetrating into the porous environment of the rock ability - provides a decrease in the pressure gradient of injection into the core sample compared to the prototype (up to 2 times);

- the inventive composition has a high waterproofing ability;

- provides an increase in the residual resistance factor compared to the prototype (1.05 ... 1.12 times).

Thus, the inventive polymer composition is very promising. The presence in it of a nonionic surfactant with hydrophobic properties (hydrophobizer NG-1) gives the polymer composition during its gelation in formation water increased plasticity, which provides deeper penetration into the water supply channels of reservoir rocks and, as a result, their more reliable clogging, as well as increased water repellent ability with respect to the surface of reservoir rocks, providing higher adhesion of the composition to the rock and, as a result, formation in a porous Rede breeds are more durable waterproofing screen.

The use of the invention in the oil industry will improve the efficiency of water inflow control by partially blocking the water-washed intervals of the formation and connecting stagnant and weakly drained productive zones of the formation to the filtering process. The use of the claimed composition can increase the coverage of the formation by water flooding due to the inclusion of previously inactive intervals of productive formations. This ensures the involvement of oil reserves in poorly drained and stagnant zones of productive formations.

Table 1 Polymer composition for in-situ waterproofing Options Polymer Compounds According to the prototype
(example 1) The inventive composition
(example 2) The inventive composition
(example 3) The inventive composition
(example 4) The permeability of the core sample in water prior to injection of the composition, μm ² 0.0082 0.0061 0.0049 0.0076 The permeability of the core sample in water after injection of the composition, μm ² 0.0021 0.0015 0.0011 0.0017 Pressure gradient of the composition injection into the core sample (after pumping 1 pore volume), MPa / m 286 260 141 138 Residual Resistance Factor 3.9 4.1 4.4 4,5

Claims (1)

The polymer composition for in-situ waterproofing during the exploitation of oil fields, including for limiting water inflows in production wells and alignment of injection profiles in injection wells, including alkaline hydrolyzed wastes of pan fiber or polyacrylonitrile fabrics - givpan and sodium chloride, characterized in that it contains as an additive, a nonionic surfactant with hydrophobic properties is a hydrophobizer NG-1, which is a mixture of the unsaturated reaction product fatty acids with amines and their derivatives with solvents and functional additives in the following ratio of components, wt.%:
Hydrolyzed in alkali waste pan fiber or tissue polyacrylonitrile - Givpan 3-10 Nonionic surfactant - water repellent NG-1 1-5 Sodium chloride 0-10 Aqueous alkaline solution rest