RU2299319C1 - Method for non-uniform oil bed development - Google Patents

Abstract

FIELD: oil production, particularly oil production from wells adapted to extract oil from bed having non-uniform permeability and comprising super conductors or cracks in bed section.

SUBSTANCE: method involves injecting aqueous solution of polymer and multivalent cation salt in oil bed with the use of gel particle dispersion. Gel particle dispersion in aqueous polymer solution is injected as the first plug. Then aqueous solution of polymer and multivalent cation salt is injected as the second plug. Forced fluid extraction may be additionally carried out.

EFFECT: increased oil recovery and decreased water content in oil well product, increased efficiency of deposit development.

2 cl, 2 ex, 6 dwg, 7 tbl

Description

The invention relates to the oil industry, in particular to the development of oil fields, and can be used to increase oil recovery and reduce water cut in the production of wells operating a permeable heterogeneous formation having super collectors or cracks in its section.

There are various compositions and technologies for treating the formation with viscoelastic compositions based on anionic polymers and salts of polyvalent metals / 1, 2 /; polymer dispersed systems containing, for example, polyacrylamide (PAA) and bentonite clay / 3 / or a biopolymer with starch / 4 /.

Their disadvantage is the low efficiency of reducing the permeability of cracks and super collectors.

A known method of processing a heterogeneous formation with a composition of a mixture of an aqueous solution of an anionic polymer and a salt of a polyvalent cation, additionally containing a dispersion of gel particles that swell 100-5000 times, but are not soluble in water / 5 - prototype /.

The disadvantage of this method is the low selectivity of the impact on a heterogeneous formation, having in its section super collectors or cracks, and the impossibility of forced fluid withdrawal from production wells after treatment of injection wells.

The low selectivity of the known method is due to the fact that all components of the composition are pumped into the reservoir at the same time; Thus, the dispersion of swollen gel particles in a cross-linked polyvalent cation anionic polymer, falling into the medium- and low-permeability intervals of the formation, leads to an almost complete attenuation of the filtration, which makes it impossible to pump large volumes of the composition (1500-3000 m ³ ) and excludes the possibility of effective application subsequent forced selection of the liquid due to compaction during the filtration of gel particles in a crosslinked polymer composition.

The problem and the expected technical result solved by the invention are to increase the efficiency of the method for developing a heterogeneous formation containing super collectors or cracks in its section, by increasing the selectivity of the impact with decreasing the permeability of super collectors and cracks while maintaining the permeability of the medium and low permeability intervals of the formation. Accordingly, it is possible to force fluid withdrawal from production wells after treatment of injection wells.

The problem is solved in that in a method for developing a heterogeneous oil reservoir, which involves injecting an aqueous polymer solution and a polyvalent cation salt into the formation using a dispersion of gel particles, the dispersion of gel particles in an aqueous polymer solution is pumped in the form of a first rim, and in the form of a second rim injected an aqueous polymer solution and salts of the polyvalent cation.

Additionally, it is possible to carry out forced fluid sampling.

The method is carried out by the following sequence of operations.

1. Injection of the rim of the dispersion of gel particles in an aqueous polymer solution.

2. Injection of the rim of the aqueous polymer solution and the salt of the polyvalent cation.

Additionally, it is possible to carry out forced fluid sampling.

The use as a first rim of a dispersion of gel particles not in water but in an aqueous solution of a linear polymer provides a synergistic effect of the rheological properties (effective viscosity and elastic modulus) of a dispersion of gel particles in an aqueous polymer solution relative to its constituents, an aqueous dispersion of gel particles and aqueous polymer solution. The use as the second rim of an aqueous polymer solution and a salt of a polyvalent cation allows to achieve the necessary rheological properties, not inferior to the prototype.

The effectiveness of the proposed method was determined using the following industrially produced reagents.

To prepare the dispersion of chemically obtained gel particles, we used an anionic water-absorbing acrylamide polymer, series AK-639, grade B-415, manufactured by Gel-Service LLC (Saratov), TU 6-02-00209912-592003, which is a powder white or close to white, quality indicators are shown in table 1.

Table 1 Indicator According to TU Actually Mass fraction of nonvolatile substances,%, not less than 90 90.2 Mass fraction of residual acrylamide,%, no more 0.2 0.09 Equilibrium absorption in distilled water, g / g, not less than 600 690 Mass fraction of soluble part,%, no more fifteen 3.9

Also, for the preparation of a dispersion of chemically obtained gel particles, the product FS-305 was used according to the technical passport of OOO SNF S.A. (Moscow), which is a white powder with an absorption of distilled water 400 g / g.

To prepare the polymer solution, the FP-107 anionic polymer was used - a copolymer of acrylamide and sodium acrylate, manufactured by SNF Baltreagent LLC (Nikolskoye, Leningrad Region), which is a white powder, which, in accordance with the Technical Data Sheet, has an approximate Brookfield viscosity, cp:

at a concentration of 5.0 g / l - 1500;

at a concentration of 2.5 g / l - 600;

at a concentration of 1.0 g / l - 140.

Also, an anionic acrylamide polymer, series AK-642, grade AP-9405 manufactured by Gel-Service LLC (Saratov), TU 6-02-00209912-65-99, which is white or close to white powder, was used to prepare the polymer solution. white with a limit number of viscosity of the polymer in a 10% solution of NaCl at 25 ° C 4.4 dl / g

The salt of the AH polyvalent cation is chromium (III) acetate, technical, manufactured by Khimeko-Gang JSC (Moscow), TU 0254-031-17197708-96, quality indicators are shown in table 2.

table 2 Indicator According to TU aqueous solution TU powder Actually Appearance Dark viscous liquid Green crystals corresponds to Mass fraction of chromium (III),%, not less 11.35 20,0 11.54 Mass fraction of water-insoluble substances,%, no more 0.50 1.00 0,044

Bentonite clay (bentonite, to reproduce the analogue) produced by Almetyevsk Clay Powder Plant OJSC, Almetyevsk, Republic of Tatarstan, according to TU 39-0147001-105-93.

We used a reservoir water model with a salinity of 15 g / L and 20 g / L (20% CaCl ₂ and 80% NaCl) in distilled water.

The effectiveness of the proposed method in comparison with the prototype and analogues was determined using volumetric and slotted models of the reservoir.

Testing technique using the simplest three-dimensional model.

The simplest volumetric model of a heterogeneous reservoir (Fig. 1) consists of two core holders with porous media of various permeabilities, having a common input and separate selection of fluids.

In figure 1:

1 - Constant flow sensor (DPR).

2 - Capacity for oil and water.

3 - Crimp.

4 - Capacity for injected fluid.

5 - Piston tank.

6, 7 - Core Holders (CD).

8 - Filters.

9 - Mernik "water" (MB); oil meter (MN).

10 - Nitrogen.

11 - Assembled column.

12 - Power supply unit (PSU).

13 - Differential pressure gauge (DFM).

14 - An analog-to-digital converter (ADC).

15 - Computer.

The model of the granular supercollector was a porous medium obtained by proppant packing with a diameter of 0.540-0.994 (average 0.766) mm, and had a water permeability from 3743 mD to 3263 mD.

The low permeable porous medium was represented by the polymineral sandstone of the BS ₁₀ layer of the Mamontovskoye field with permeability from 310 to 336 mD.

The effectiveness of the method was determined by the degree of decrease in permeability of highly and low permeable porous media, after filtration through a volume model of 0.3 pore volumes of plugging compositions.

The results of the experiments to determine the effectiveness of plugging granular super collectors are presented in table 3. It can be seen that the inventive method significantly exceeds the prototype in maintaining the permeability of medium and low permeability intervals. The inventive method in this case quite effectively reduces the permeability of the granular supercollector; moreover, the permeability of the super collector becomes less than the permeability of the low permeable porous medium; and the permeability of the latter practically does not change: the reduction ratio is only 1.1-1.3 times (experiments 5-6 in table 3).

An additional advantage of the proposed method is the preservation of the permeability of medium and low permeability intervals under conditions of forced fluid withdrawal (table 3 - increase the filtration rate). The use of the prototype method in the conditions of increasing the filtration rate leads to the complete blocking of medium and low permeability intervals (experiment 2 in table 3) due to the compaction of gel particles in a crosslinked polymer composition and end clogging of porous media.

Table 3 Determining the efficiency of plugging a granular super collector in a volumetric model Experience number Tampon composition,% wt. Permeability of porous media, MD, before exposure Permeability of porous media, MD, after exposure Permeability reduction rate Filtration rate, m / year 1 Prototype Gel particles AK-639 - 0.1 3350 12 279 300 Anionic polymer FP-107 - 0.25 AX Polyvalent Cation Salt - 0.025 326 0.11 2964 The rest is water 2 - Prototype followed by forcing - // - 3743 fifteen 246 300 319 0.02 15950 1285 3 Analogue / 1 / Anionic polymer FP-107 - 0.25 3448 622 5.5 300 AX Polyvalent Cation Salt - 0.025 The rest is water 310 119 2.6 4 - Analogue / 1 / followed by forcing - // - 3263 843 3.9 300 336 287 1,2 1285 5 The proposed method 1 rim: 3547 196 18.1 300 Gel particles AK-639 - 0.1 Anionic polymer FP-107 - 0.25 334 261 1.3 The rest is water 2 rims: Anionic polymer FP-107 - 0.25 AX Polyvalent Cation Salt - 0.025 The rest is water 6 - Proposal method followed by forcing - // - 3517
325 154
298 22.8
1,1 300
1285

Comparison with the analogue (experiments 3-4 in table 3) shows that the inventive method, having approximately equal performance with respect to maintaining the permeability of medium and low permeability intervals, significantly reduces the permeability of the granular super collector.

Testing technique using a crevice crack model.

When testing using the slit model, the latter was a calibrated rectangular slit cut from grouting cement with the dimensions:

Length - 15 cm

Width - 1.5 cm

Thickness - 0, 005 cm.

The slit model was made of two metal half rings filled with cement mortar; the thickness of the slit is set by metal foil. The crevice model was placed in a core holder with integrated crimping and connected to a filtration unit (Fig. 2).

In figure 2, the designations are similar to those in figure 1 and, in addition:

16 - metal half rings;

17 - cement;

18 - gap;

19 - foil.

To determine the effectiveness of plugging cracks through the model, water was first filtered, then one pore volume of the plugging composition, then water again, fixing the pressure drop across the water ΔРн (initial) and ΔРк (final). The residual resistance factor R was determined, with such a formulation of the experiment equal to the ratio of the pressure drops across the water:

Rost. = ΔРк / ΔРн.

The results of experiments to determine the effectiveness of plugging cracks are presented in table 4. It can be seen that the inventive method reduces the permeability of the cracks no less effectively than the prototype.

Table 4 Determination of the effectiveness of plugging cracks in the crevice model Experience number Tampon composition,% wt. Residual Resistance Factor 1 prototype Gel particles AK-639 - 0.1 7755 Anionic polymer FP-107 - 0.25 AX Polyvalent Cation Salt - 0.025 The rest is water 2 Analogue / 1 / Anionic polymer FP-107 - 0.2 14.3 AX Polyvalent Cation Salt - 0.02 The rest is water 3 Analogue / 3 / Anionic polymer FP-107 - 0.05 5.13 Bentonite - 0.5 The rest is water 4 Analogue / 4 / Biopolymer BP-92 - 10.0 15.3 Starch - 2.0 The rest is water 5 1 rim - a dispersion of gel particles in water 7239 polymer solution: Gel particles AK-639 - 0.1 Anionic polymer FP-107 - 0.25 The rest is water 2 rims: Anionic polymer FP-107 - 0.25 AX Polyvalent Cation Salt - 0.025 The rest is water 6 1 rim - the dispersion of gel particles in an aqueous polymer solution: 8329 Gel particles AK-639 - 0.5 Anionic polymer FP-107 - 0.25 The rest is water 2 rims: Anionic polymer FP-107 - 0.25 AX Polyvalent Cation Salt - 0.025 The rest is water

The results of the rheological testing of polymer systems based on FS-305 and FP-107 are shown in FIGS. 3-4 and in Tables 5-6, and on the basis of AK-639 and AK-642, in FIG. 5 and Table 7.

Figure 3 shows the dependences of the elastic modulus G 'on the moment of force f of both compositions FS-305 (10 g / l) and PAA linear structure of the brand FP-107 (2.5 g / l), and their initial components.

Figure 4 shows the effect of improving the effective viscosity (dispersion FS-305 in mineralized water due to the addition of FP-107.

The addition of linear polyacrylamide can approximately double increase the elastic modulus G 'and the effective viscosity η of the dispersion (Table 5-6). The increase in these parameters is non-additive, that is, G 'or η for the inventive mixture system is higher than the sum G' or the sum η of FP-107 solution and dispersion FS 305 separately, which indicates the structure formation due to the flocculating properties of polyacrylamide.

Table 5 Elastic properties (the study was carried out on a Carry-Med CSL ² rheometer manufactured by TA Instruments) Composition in water Mineralization, g / l Measurement temperature, ° С The elastic modulus G '(Pa) at a moment of force f 5 mN · m 1% FS-305 twenty twenty 0.56 0.25% FP-107 twenty twenty 0.08 1% FS-305 + 0.25% FP-107 twenty twenty 1.06 Table 6 Viscous properties (the study was carried out on a Carry-Med CSL ² rheometer manufactured by TA Instruments) Composition in water Mineralization, g / l Measurement temperature, ° С Effective viscosity ((Pa · s) at shear rate γ, s ^-1 0.3 1,6 14.5 1% FS-305 twenty twenty 0.51 0.09 0.01 0.25% FP-107 twenty twenty 0.11 0,07 0.04 1% FS-305 + 0.25% FP-107 twenty twenty 1,03 0.34 0.1

In comparative figure 5 presents the curves of the effective viscosity of both compositions AK-639 with PAA linear structure AK-642, and their initial components. As you can see, the increase in the effective viscosity of the composition in the entire measurement range is non-additive, that is, the value of its effective viscosity is higher than the sum of the effective viscosities of the initial solutions of AK-642 and the dispersion of AK-639.

Table 7 presents the indicators of the effective viscosity of the compositions based on AK-639 and AK-642.

Table 7 Values of effective viscosity (the study was carried out on a rheometer RheoStress-1 "Haake", Germany) Composition in water Mineralization, g / l Measurement temperature, ° С Effective viscosity ((Pa · s) at shear rate γ, s ^-1 0.35 1.91 15.71 0.5% AK-639 + 1.5% AK-642 fifteen twenty 0.19 0.17 0.13 1.5% AK-642 fifteen twenty 0.12 0.1 0.13 0.5% AK-639 fifteen twenty 0.002 0,0005 0,0002 1% AK-639 + 1.5% AK-642 fifteen twenty 0.39 0.35 0.26 1.5% AK-642 fifteen twenty 0.12 0.1 0.08 1% AK-639 fifteen twenty 0,03 0.02 0.009 0.5% AK-639 + 1.8% AK-642 fifteen twenty 0.40 0.37 0.27 1.8% AK-642 fifteen twenty 0.15 0.14 0.12 0.5% AK-639 fifteen twenty 0.002 0,0005 0,0002 1% AK-639 + 1.8% AK-642 fifteen twenty 1.3 1,1 0.67 1.8% AK-642 fifteen twenty 0.15 0.14 0.12 1% AK-639 fifteen twenty 0,03 0.017 0.009

Thus, for the aqueous dispersion of AK-639 gel particles in "carriers" - solutions of polymers of linear structure AK-642, a synergistic effect of improving the effective viscosity is shown in comparison with dispersion AK-639 and a solution of AK-642 in mineralized water (table 7) .

A comparison of the rheological properties of the water-polymer system of the prototype method and the second rim of the proposed method is clearly illustrated in Fig.6, which shows the dependence on the shear rate of the effective viscosity of the water-polymer systems:

- polymer AK-642, crosslinked with chromium acetate AX (second rim according to the present method);

- a mixture of chromium acetate crosslinked AH polymer AK-642 with gel particles AK-639 (prototype).

It can be seen that the effective viscosity curves of the two indicated water-polymer systems practically coincide, i.e. the prototype method for effective viscosity is equivalent to the use of the second rim according to the claimed method.

Thus, the results of comparative filtration and rheological tests allow us to draw the following conclusions.

1. The inventive method significantly exceeds the prototype in the selectivity of the impact on a permeable heterogeneous reservoir containing interlayers of super collectors or cracks; while the effectiveness of reducing the permeability of super collectors and cracks in the present method and in the prototype is almost the same, and the permeability of medium- and low-permeability intervals in the present method is significantly higher than the prototype.

2. The rheological properties of the first rim according to the claimed method provide reliable insulation of cracks and super collectors due to the detected synergistic effect.

3. The rheological properties of the second rim of the claimed method are not inferior to the prototype method.

4. Due to the sequential injection of the first and second rims, it is possible to significantly - by an order of magnitude - increase the injection volumes of the polymer system and at the same time accelerate the production of liquid from production wells, which significantly increases the technological effect.

The effectiveness of the proposed method is confirmed in the field.

Example 1. In four injection wells of the AC ₄ formation _of field “A” selected on the map of current selections, 200 m ^{3 of the} rims of the dispersion of gel particles in an aqueous polymer solution (PAA) were pumped; as a second rim, an aqueous polymer solution (PAA) was pumped with a stapler in the amount of 6000 m ³ in each well.

A total of 26 injection wells injected 26291 m ³ PAA working solution with a concentration in the solution of 0.1% wt. Consumption of commercial reagents amounted to 38.099 tons of PAA Sedipur brand and 1.8 tons of superabsorbent FS-305 for the preparation of a dispersion of gel particles.

The dynamics of the performance indicators of the wells in the area was analyzed before and after the impact of the claimed technology.

The analysis showed that after exposure, water cut decreased from 94 to 89%, oil production increased. Calculation of the technological effect by the integrated displacement characteristic (Kambarov; vn = 4.1072E + 6-1.0878E + 13 / Vzh) showed that 23.2 thousand tons of oil was additionally produced. The duration of the effect was 19 months.

Example 2. The integrated impact of the present method is carried out on the site of the reservoir BS ₆ field "B". In 13 injection wells, 100 m ^{3 of the} first rim — the dispersion of gel particles in a PAA solution, was pumped, then 2,400 m ^{3 of the} second rim — a PAA solution with a crosslinker, were pumped. Sedipur brand polyacrylamide was used, chromium acetate was used as a crosslinker. To prepare the dispersion of gel particles, FS-305, a water-soluble polymer with a high swelling coefficient, with a concentration of 0.2-0.5 wt%, was used. At the same time, measures were taken at 20 production wells to force fluid withdrawal. As a result of the complex impact, water cut was stabilized, 133.3 thousand tons of oil were additionally extracted. The duration of the effect was 32 months.

Information sources

1. A.S. USSR No. 985255, E 21 B 33/138, publ. 30.12.1982.

2. Patent No. 2039225, Е 21 В 43/22, Е 21 В 33/138, publ. 09/07/1995.

3. A.S. USSR No. 1710708, Е 21 В 43/22, Е 21 В 33/138, publ. 07.02.1992.

4. RF patent No. 2223396, E 21 B 43/22, publ. 02.10.2004.

5. RF patent No. 2167281, E 21 B 43/22, publ. 05.20.2001.

Claims (2)

1. A method of developing a heterogeneous oil reservoir, comprising injecting into the reservoir an aqueous polymer solution and a salt of a polyvalent cation using a dispersion of gel particles, characterized in that the dispersion of gel particles in an aqueous polymer solution is pumped in the form of a first rim, and pumped in the form of a second rim an aqueous solution of the polymer and salts of the polyvalent cation. 2. The method according to claim 1, characterized in that it additionally carry out forced selection of the liquid.

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