RU2339803C2 - Method for equalizing of intake capacity profile in pressure wells and of limiting inflow in producing wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil industry, particularly to alteration of filter characteristics of non-uniform formations, to growth of oil withdrawal and to reduction of watering in producing wells with obtaining maximum effect at later stages of oil deposit development due to implementation of visco-elastic polymer compositions. According to the method of equalizing the intake capacity profile in pressure wells and limiting inflow into producing wells, including preparation and successive pumping into the formation of polymer gel-forming compositions, volume of pumping is preliminary determined, then 15% of porous volume of the first fringe of polymer composition is pumped, wt %: carboxymethyl cellulose - CMC - 0.3-5.0, cross-linker - chromium acetate - 0.05-0.5, water with mineralization - 0-290 g/l- the rest, where water with mineralization 50-290 g/l is used for preparation of cross-linker, then the second portion of the fringe is pumped in portions alternating with water pumping with surface active substance -SAS and the first fringe. The second fringe has the composition, wt %: polyacrylamide - PAA - 0.01-2.0, chromium acetate 0.05-0.5, water with mineralisation of 0-290 g/l - the rest. Then the well is stopped for process conditioning for 1-5 days. The invention is developed in dependent claims.

EFFECT: increased oil withdrawal of formation, reduced watering of producing wells, and expanded technological capabilities of method.

4 cl, 1 tbl

Description

The proposal relates to the oil industry, in particular, to change the filtration characteristics of heterogeneous reservoirs, increase oil recovery and reduce water cut in producing wells with maximum effect at the late stage of development of an oil reservoir based on viscoelastic polymer compositions.

Known methods for increasing the filtration resistance of highly permeable washed layers, aimed at increasing oil recovery, including the preparation and injection of various polymer gelling compositions.

The closest in technical essence and the problem to be solved is a method for aligning the injection profile in injection and limiting water inflows in producing wells, including preparing and sequentially injecting polymer gel-forming compounds into the reservoir (Usov S.V. et al., Aligning the injection profile in injection and limiting water inflows in producing wells with gelling agents, “Oil Industry”, No. 1, 1991, pp. 41-43). The technology is based on the plugging of formations under pressure by a filtered polymer gelling composition with subsequent consolidation by polymer compositions. The composition used for the treatments is an aqueous solution of polyacrylamide (PAA) with the addition of a crosslinker. All components of the composition are powdery and highly soluble in water. As water, low-saline or technical fresh water from the PPD system is used.

The disadvantage of this method is that when the temperature drops below 0 ° C, the crosslinker solution freezes, which prevents the preparation of the polymer composition. At a temperature of 0 ° C, the effectiveness of the crosslinker is reduced, and therefore, the effectiveness of the formation coverage by the impact is reduced. Also, when developing an oil reservoir at a late stage, it becomes necessary to frequently repeat the operations of the known method. Due to the depressive effect in the bottomhole zone, the gel is destroyed and the effect of isolation decreases. Similarly, when an aqueous solution of PAA is injected in the first rim, adsorption of PAA particles on the pore surface occurs, which leads to the formation of a system of insufficient strength. As a result, oil recovery is reduced.

The technical task of the proposal is to increase oil recovery and reduce water cut in producing wells by increasing the effectiveness of the reservoir coverage. As well as expanding the technological capabilities of the method.

The solution of this problem provides a method for aligning the injection profile in injection wells and limiting water inflow in producing wells, including the preparation and sequential injection of polymer gelling compositions into the formation.

New is that pre-determine the injection volume, inject the first rim of the polymer composition in the amount of 15% of the pore volume, the composition based on carboxymethyl cellulose (CMC) with a crosslinker in the following ratio of components, wt.%: CMC - 0.3 -5.0, chromium acetate - 0.05-0.5, water with a salinity of 0-290 g / l - the rest, and for the preparation of a crosslinker use water with a salinity of 50-290 g / l, then the second rim is pumped in portions, alternating with injection of water with a surfactant (PA ) and the first rim, as the second rim, use a composition based on polyacrylamide with a crosslinker in the following ratio of components, wt.%: PAA - 0.01-2.0, chromium acetate 0.05-0.5, water with a salinity of 0- 290 g / l - the rest, and then the well is stopped for technological shutter speed lasting from 1 to 5 days.

Also new is that the total concentration mass of the second rim is determined from the ratio of rims and injected water, respectively, 1: 0.5: 0.5.

Also new is that PAA for a dry product is 0.5-40% of the amount of CMC.

Also new is that for highly permeable formation intervals, starting at least from the second rim, an adjustable viscoelastic composition is injected, including polyacrylamide, a crosslinker, a filler, and water.

The following reagents are used to prepare the formulations:

- carboxymethyl cellulose (CMC), for example, according to TU 2231-002-50277563-2000. TU 2231-017-32957739-02, TU 2231-057-07508003-2002 (water-soluble, powdery);

- polyacrylamide (PAA), domestic according to TU 6-16-2531-81, TU 6-01-1049-81, TU 14-6-121-75, imported with a molecular weight of (3-15) -10 ⁶ , for example, DP9-8177, Alkoflood 935, Alkoflood 1175.

As a crosslinker use an aqueous solution of chromium acetate according to TU 6-0200209912-7000, a tanning agent of the brand "Aqueous solution of chromium acetate" TU 2499-001-50635131-00.

As water for the preparation of the crosslinker use water with a density of from 1.04 to 1.2 g / cm ³ with a salinity of 50-290 g / l.

Chalk, talc, wood flour, clay powder, cracker and others are used as filler in the amount of 1.0-10%.

As a surfactant, water-soluble surfactants are used, for example, NEONOL brand AF _9-10 , AF _9-12 with a concentration of 0.03-1.0%.

The essence of the proposal is as follows.

Based on the results of well surveys, the formation filtration properties are determined with the separation of interlayers with various degrees of absorption and the volume of injection of insulating compositions is determined. A crosslinker is preliminarily prepared by mixing chromium acetate with water with a density of 1.04 to 1.2 g / cm ³ , mineralization of 50-290 g / l, which eliminates the possibility of freezing of the crosslinker at a temperature below 0 ° C. Then carry out sequential injection into the reservoir of polymer gelling compositions, for example in the form of an aqueous solution or suspension. As the first rim, a composition based on carboxymethyl cellulose with a crosslinker is pumped into the formation in the following ratio of components, wt.%: CMC - 0.3-5.0; chromium acetate - 0.05-0.5; water with a salinity of 0-290 g / l - the rest, in the amount of 15% of the pore volume. Injection of the first rim allows isolating the highly permeable intervals of the formation, the limited volume of the rim will not allow penetration into the low permeability intervals. When the first rim moves along the formation, particles do not settle on the surface of the pores. Then the second rim is pumped in portions, alternating with the injection of water with a surfactant and the first rim. The concentration of surfactants depends on the salinity of the injected water. As the second rim, use a composition based on polyacrylamide with a crosslinker in the following ratio of components, wt.%: PAA - 0.01-2.0; chromium acetate 0.05-0.5; water - the rest with a mineralization of 0-290 g / l. The total mass of the concentration of the second rim is determined from the ratio of the rims and the injected water 1: 0.5: 0.5. PAA dry product is 0.5-40% of the number of CMC. For highly permeable formation intervals, starting at least from the second rim, an adjustable viscoelastic composition is injected, including polyacrylamide, a crosslinker, a filler, and water. The well is stopped for technological exposure lasting from 1 to 5 days.

Suspension or aqueous solutions of polymer compositions are prepared using jet pumps and an apparatus for preparing, dosing and pumping technological solutions into the well for this purpose.

The proposed method provides a uniform distribution of the injected compositions in the heterogeneous permeability zones of the formation, increases the strength of the formed insulating screen, which leads to a decrease in the permeability of the highly permeable zones of the formation and to increase the efficiency of the formation coverage. And, as a result, it leads to an increase in oil recovery, lowering the water cut of producing wells.

For experimental studies, a linear reservoir model was used, consisting of two identical columns (50 cm long, 6.4 cm ² cross-sectional area). By selecting the size of the quartz sand grains, the necessary channel permeability of the formation model was created.

The studies were carried out in the following sequence:

- after evacuation, the model was successively saturated with mineralized water and oil from the Romashkinskoye field, with a density of 0.810-0.890 g / cm ³ . The following parameters were determined: pore volume, initial water saturation, water permeability and oil saturation;

- carried out the displacement of oil by mineralized water, a density of 1.0-1.2 g / cm ³ with measurement at the output of the volumes of oil and water;

- a crosslinker was prepared by mixing chromium acetate with water with a density of 1.04 to 1.2 g / cm ³ , mineralization of 50-290 g / l, and then polymer-based compositions were prepared;

- the first rim of the polymer composition was pumped sequentially into the model in a volume of 15% of the pore volume, then the second rim in portions alternating with the injection of water with a surfactant and the first rim. The model was kept from 1 to 5 days for complete gelation, the formation of an insulating barrier. At high permeability of the formation model, starting from the second rim, an additional filler was added to the polymer composition of the first rim;

- after which the oil was replaced by mineralized water by pumping water with measuring the output of oil and water.

Thus, simulated the process of starting wells and oil production from the reservoir after the implementation of the proposed method.

As the oil displacing parameter, the oil displacement coefficient of a layered inhomogeneous porous medium was used after the primary displacement of oil by water and the final one after injection of polymer compositions.

The results of filtration studies are shown in the table.

The analysis of the research results was carried out on the example of the main filtration parameter - residual resistance factor (OFS), which characterizes the filtration resistance when filtering water of polymer compositions in comparison with the initial filtration resistance when filtering water before pumping compositions.

As can be seen from the table, OFS according to the proposed method of development on inhomogeneous permeability of porous media increases 2.5 times in comparison with the prototype. The oil displacement coefficient increases by 1.4 times.

Thus, the proposed method for equalizing the injection profile in injection and limiting water inflow in producing wells allows to increase oil recovery and reduce water cut of producing wells by changing and leveling the filtration flows in heterogeneous formations by increasing the strength of the formed insulating screen, reducing the permeability of highly permeable formation zones and increasing the efficiency of formation coverage exposure. The proposal allows to expand the technological capabilities of the method.

Table The results of filtration studies of polymer compositions in bulk reservoir models No pp rim The injected composition, wt.% The density of water, g / cm ³ Pore volume, cm ³ The initial permeability to water, microns ² The injected volume of the composition, cm ³ The final permeability to water, μm ² The growth rate of oil displacement,% Residual Resistance Factor, R _ost CMC PAA chromium acetate water Surfactant filler one 2 3 four 5 6 7 8 9 10 eleven 12 13 fourteen fifteen one one 0.5 0.1 99,4 21 but 0.1 0.1 99.8 - 10.5 2 b 99.95 0.05 1.00 140 1.28 5.25 0.005 1.7 256 at 0.5 0.1 99,4 5.25 2 one 0.5 0.1 99,4 22.5 but 0.1 0.1 96.8 3.0 11.25 2 b 99.95 0.05 1.00 150 3.42 5.63 0.017 2,5 201 at 0.5 0.1 99,4 5.63 3 one 0.5 0.1 99,4 21 but 0.1 0.1 89.8 10.0 10.5 2 b 99.95 0.05 1.00 140 7.1 5.25 0.06 3.2 118 at 0.5 0.1 99,4 5.25 four one 1,0 0.2 98.8 eighteen but 0.3 0.2 99.5 - 9 2 b 99.97 0,03 1.00 120 1,0 4,5 0.004 1,2 250 at 1,0 0.2 98.8 4,5 5 one 3.0 0.3 96.7 21 but 0.5 0.3 99,2 - 10.5 2 b 99.92 0.08 1.00 140 1,2 5.25 0.005 2,5 240 at 3.0 0.3 96.7 5.25 6 one 5,0 0.5 94.5 21 but 1,0 0.5 98.5 - 10.5 2 b 99.9 0.1 1.00 140 1,1 5.25 0.004 5.5 275 at 5,0 0.5 94.5 5.25 7 one 0.3 0.05 99.65 22.5 but 0.006 0.05 99,944 - 11.25 2 b 99,2 0.8 1.00 150 0.63 5.63 0.003 2,4 210 at 0.3 0.05 99.65 5.63

Table continuation one 2 3 four 5 6 7 8 9 10 eleven 12 13 fourteen fifteen 8 one 0.3 0.05 99.65 22.5 but 0.006 0.05 99,944 - 11.25 2 6 99,2 0.8 1.06 150 0.63 5.63 0.004 2,3 158 at 0.3 0.05 99.65 5.63 9 one 0.3 0.05 99.65 1.18 150 0.63 22.5 0.0048 2,3 131 but 0.006 0.05 99,944 - 11.25 2 b 99.0 1,0 5.63 at 0.3 0.05 99.65 5.63 prototype one 0.5 0.3 99,2 1.00 140 6.8 42 0.09 1,1 75,5 2 0.2 0.2 99.6 1.00 140 1.3 42 0.015 1,5 86.7

Claims (4)

1. The method of alignment of the injectivity profile in injection wells and limiting water inflows in producing wells, including the preparation and sequential injection of polymer gelling compositions into the formation, characterized in that the injection volume is preliminarily determined, the first rim of the polymer composition is pumped in a volume of 15% of the pore volume, as the first rim use a composition based on carboxymethyl cellulose - CMC with a crosslinker in the following ratio of components, wt.%: CMC - 0.3-5.0, chromium acetate - 0.05-0.5, water with mi with a non-rationalization of 0-290 g / l - the rest, with water with a salinity of 50-290 g / l being used to prepare the crosslinker, then the second rim is pumped in portions alternating with the injection of water with a surfactant and the first rim, and the composition based on polyacrylamide is used as the second rim - PAA with a crosslinker in the following ratio of components, wt.%: PAA - 0.01-2.0, chromium acetate 0.05-0.5, water with a salinity of 0-290 g / l - the rest, and then stop the well at technological exposure lasting from 1 to 5 days. 2. The method according to claim 1, characterized in that the total concentration mass of the second rim is determined from the ratio of rims and injected water 1: 0.5: 0.5. 3. The method according to claim 1, characterized in that the PAA for the dry product is 0.5-40% of the number of CMC. 4. The method according to claim 1, characterized in that for highly permeable intervals of the formation, starting at least from the second rim, an adjustable viscoelastic composition is injected, including polyacrylamide, a crosslinker, a filler and water.