RU2528183C1 - Method of oil pool development - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: method includes extraction of the product through producers and injection of a working agent - water and polymer disperse system with modifying chemicals through injectors. According to the invention state of the deposit development is analysed against the current oil recovery factor and product water cut and when water cut of the product reaches 90% at the site in average and injectability of the injectors is equal to 250 m/day then together with polymer disperse system aqueous solutions of surfactants or their package are injected as modifying chemicals. When water cut of the product varies from 70% up to 95% at the site in average and injectability of the injectors is equal to 250-350 m/day then together with polymer disperse system aqueous solutions of salts of polyvalent metals are injected as modifying chemicals. When water cut of the product varies from 70% up to 99% at the site in average and injectability of the injectors is more than 350 m/day then together with polymer disperse system aqueous solutions of crosslinking agents are injected as modifying chemicals. At that aqueous solutions of chemicals are injected with density at least per 10% higher than density of the injected water in the form of separate banks, in the form of their mixture with components of polymer disperse system and buffer volume of water between components of polymer disperse system.EFFECT: increase in oil recover factor due to effective use of polymer disperse system.8 ex

Description

The invention relates to the oil industry and may find application in the development of heterogeneous flooded oil deposits.

A known method of influencing a reservoir with heterogeneous reservoirs, including sequential injection through injection wells of an aqueous solution of polyacrylamide and polymer dispersed system (PDS) containing caustic soda, with rims in the amount of 50-200 m ³ each to reduce the injectivity of the injection well by no more than 50% and selection of oil through production wells (RF Patent No. 2044872, publ. 09/27/1995).

The known method is often irreproducible, because with the injection of 50 m ³ PDS, a decrease in injectivity by more than 50% is possible. In addition, the creation of a movable PDS due to caustic soda promotes a rapid decrease in processing efficiency and leads to the need for frequent repeated downloads.

Closest to the proposed invention in technical essence is a method for developing an oil reservoir, according to which oil is taken through production wells and injected through the injection wells of the working agent and MPD. Before the second and subsequent injections of the VCP, the injectivity of the injection well is determined and compared with the injectivity of this injection well before the first injection of the VDS, with an increase in the injectivity of the well by 50-100%, the VCP is re-injected until the injectivity of the well is equal to 50-100% of the injectivity of the well after the first injection PDS. When re-uploading the PDS, a modified PDS is used (RF Patent No. 2164593, publ. 03/27/2001 - prototype).

The disadvantage of the prototype is the low reproducibility of the development results for the achieved oil recovery occurring due to the use of MPD without taking into account the properties of the reservoir and without selecting the qualitative and quantitative composition of the MPD for a particular reservoir. All this reduces the effectiveness of the application of MPD and oil recovery deposits.

The proposed invention solves the problem of increasing the effectiveness of the MPD and, thus, increasing oil recovery deposits.

The problem is solved in that in a method for developing an oil deposit, including product selection through production wells, injection of a working agent and polymer dispersed system with modifying chemicals through injection wells, according to the invention, the development status of the field is analyzed by the current oil recovery coefficient and water cut of the product and sections of injection wells are identified from reactive production wells and with water cut of the average area of up to 90% and the injection rate of injection wells zhin to 250 m ³ / day in conjunction with the polymer-disperse system as modifying chemicals pumped water solutions of surface-active substances (surfactants) or surfactant compositions, when water cut in the middle of portion of 70% to 95% and injectivity of injection wells 250 m ³ / day up to 350 m ³ / day, together with a polymer dispersed system, aqueous solutions of polyvalent metal salts are pumped as modifying chemicals, with an average water cut of the area from 70% to 99% and injectivity of injection wells its 350 m ³ / day, together with a polymer dispersed system, water solutions of crosslinking agents are pumped as modifying chemicals, and a modified PDS is used as a PDS; in the presence of bottom water of the treated reservoir, together with the polymer dispersed system, water solutions of chemicals with a density of at least 10% higher than the density of the injected water are pumped, while the modifying chemicals are pumped in the form of individual edges of the reagents before and / or after injection of the polymer dispersed system, and / or in a mixture with components, and / or with one component of the polymer dispersion system, and / or with a buffer volume of water.

SUMMARY OF THE INVENTION

When developing an inhomogeneous flooded oil reservoir, it becomes necessary to increase the degree of coverage of the reservoir by the action of a working agent pumped through injection wells. PDS, which are injected alternately with working agents, often have a weak effect and lead to a minimal decrease in the water cut of the extracted products and a slight increase in the oil recovery of the reservoir. There is a low reproducibility of the development results for the achieved oil recovery of the reservoir. This is a consequence of the use of MPD without taking into account the properties of the deposit and without selection of the qualitative and quantitative composition of the MPD as applied to a specific deposit. All this reduces the effectiveness of the application of MPD and oil recovery deposits. The proposed invention solves the problem of increasing the effectiveness of the MPD and, thus, increasing oil recovery deposits. The problem is solved as follows.

When developing an oil field, oil is taken through production wells, injection through the injection wells of the working agent and MPD. The development status of the field is analyzed by the current oil recovery and water cut coefficient, reservoir sections with different water cut and injectivity of injection wells are identified, with a water cut of the average area of 90% and injectivity of injection wells of up to 250 m ³ / day, together with a polymer dispersed system as modifying of chemical reagents inject aqueous solutions of surfactants or surfactant compositions, with an average water cut in the area of 70% to 95% and injectivity of injection wells about t 250 m ³ / day to 350 m ³ / day through injection wells together with a polymer dispersed system pump aqueous solutions of polyvalent metal salts, with an average water cut of the area from 70% to 99% and injectivity of injection wells over 350 m ³ / day together aqueous solutions of cross-linking agents are pumped with a polymer-dispersed system, and a modified PDS is used as a PDS, in the presence of bottom water of the treated reservoir, aqueous solutions of chemical substances are pumped together with a polymer-dispersed system agents with a density of at least 10% higher than the density of the injected water, while the modifying chemicals are pumped in the form of individual edges of the reagents before and / or after the polymer dispersed system is injected, and / or in a mixture with components, and / or with one component of the polymer dispersed system, and / or with a buffer volume of water.

The declared parameters of the deposits are selected based on the following considerations.

When the water cut of the product on average over the site is up to 90% and the injectivity of injection wells is up to 250 m ³ / day, water solutions of surfactants or surfactant compositions are pumped through injection wells together with polymer dispersed systems.

The need to use surfactants in conjunction with polymer disperse systems is due to the fact that in the process of developing fields using waterflooding, two types of residual oil reserves are formed.

Residual oil of the first type is formed in the form of trapped drops and in the form of film oil in water-washed zones of the reservoir and has a higher content of heavy components (resins, asphaltenes) than the original oil. It is possible to reduce the amount of film oil by the combined use of reagents - surfactants and PDS, which improve the wettability of the rock by displacing water. To displace capillary trapped oil, it is necessary to overcome the capillary forces that hold the oil, which is also achieved by the joint use of surfactants and compositions based on them and PDS. As surfactants can be applied as individual surfactants (neonols, cationic surfactants, petroleum sulfonates, etc.), and their compositions or compositions including them (micellar solutions, ULTRAFLO reagent, etc.).

The formation of residual oil of the second type is associated with uneven displacement of oil from an inhomogeneous reservoir, which leads to the formation of pillars of oil in poorly drained, stagnant zones, lenses and interlayers with poor filtration and capacitive properties. In its composition and properties, the residual oil of the second type differs little from the original oil of the field. In order to increase the degree of reservoir coverage by water flooding, flow diverting technologies are used, in particular polymer-dispersed systems, which allow more efficient use of the oil-displacing properties of injected water.

The most effective combination is flow diverting and oil displacing technologies, which allows both types of residual oil to be affected. PDS with a surfactant is used in the following options:

Option 1 - sequential injection of PDS and surfactant;

Option 2 - injection of one or (and) both components of the PDS in a mixture with a surfactant;

Option 3 - the introduction of surfactants in the buffer volume of water injected between the cycles of the MPD;

Option 4 - a combination of the above options.

When implementing technology according to option 1, as a result of injection of MPD, the degree of coverage of formations with water flooding increases, and subsequent injection of a surfactant improves oil washing. The results of laboratory studies and modeling of reservoir processes have shown that surfactants are most technologically and economically more profitable to use at earlier stages of field development when flooded reservoirs are not washed to the extreme degree. As such a criterion, the water cut of the product as a whole for the pilot sections of injection wells was taken no more than 80%. With a further increase in water cut of the product, the properties of the first type of residual oil (film and capillary retained oil) deteriorate (increase in viscosity, its amount decreases, etc.) and the cost of injecting surfactants does not pay off with additional oil.

When implementing the technology according to options 2 and 3, surfactants are introduced into one and (or) both components of the PDS - into a solution of PAA or clay slurry, as well as into the buffer volume of water, which not only improves the oil-displacing properties of the injected reagents, but also positively affects the properties of the components PDS. When surfactants are added to a clay slurry, the rheological and mechanical characteristics of the clay slurry are improved, the degree of its swelling increases, the ductility coefficient increases by 1.35-2.75 times, which increases the penetration depth into the formation. Due to the increase in the degree of clay powder swelling in the presence of surfactants, the injection of PDS with the introduction of surfactants into the clay suspension can be carried out in wells with lower injectivity.

When the water cut of the products on average over the site is from 70% to 95% and the injectivity of injection wells is from 250 m ³ / day to 350 m ³ / day, the combined use of PDS and surfactants becomes less effective. In this case, aqueous solutions of salts of bivalent and / or multivalent metals are pumped through injection wells together with polymer dispersed systems. The need to use aqueous solutions of multivalent metal salts together with PDS is caused by high watering of productive formations and the formation of productive intervals in the productive formations with low filtration resistance, which requires the creation of a waterproofing screen to reduce their hydraulic conductivity. As aqueous solutions of metal salts, water-soluble salts of calcium (calcium chloride), magnesium, aluminum, iron, copper (sulfate, chloride, etc.) and their compositions containing alumochloride-A, aqua-aurat, etc. are used.

The mechanism of action of aqueous solutions of salts of bivalent and multivalent metals is as follows. In the process of pumping into productive formations, the PDS-PAA components and aqueous suspensions of dispersed particles form polymer dispersed complexes that are 3-10 times or more larger than the sizes of the initial dispersed particles. Metal salts are pumped in the form of aqueous solutions in which their hydrolysis occurs. Under reservoir conditions, when diluted by injected and reservoir waters, ions of two and (or) multivalent metals are in different hydrated forms, which allows them to coordinate with the side functional groups of PAA macromolecules. As a result, PAA macromolecules are crosslinked and their viscoelastic properties increase.

With a water cut of an average of 70% to 99% over the site and an injection capacity of injection wells of more than 350 m ³ / day, the achieved cross-linking is not enough to increase oil recovery. In this case, aqueous solutions of crosslinking agents are pumped through injection wells together with polymer dispersed systems. At a late stage of field development, as a result of uneven advancement of the displacement front and breakthrough of injected water into production wells, washed out zones with low filtration resistance are formed in separate highly permeable formation intervals. With a high injectivity of injection wells of more than 350 m ³ / day and a water cut of produced products from 70% to 99%, the use of a water-insulating mass that is resistant to erosion, capable of creating high values of the resistance factor, and its volume should be sufficient to form a water-proof screen of sufficient length, so that the injected water could not quickly go around it. According to their characteristics, polymer dispersed systems that are pumped together with cross-linking reagents most fully meet. As crosslinking agents, chromium alum, potassium or sodium dichromate, AMH reagent, chromium acetate, trivalent metal salts, titanium chloride, etc., capable of irreversibly forming cross bonds in the polymer, are used. The mechanism of action of crosslinking agents is based on the crosslinking of polyacrylamide (PAA) macromolecules with a crosslinking agent (chromium acetate, chromium potassium alum, potassium dichromate, etc.) into the spatial structure, which can significantly improve the rheological properties of the composition and increase the thermal stability of PAA. When injected, the crosslinking agent is embedded in the particles of PAA and clay. Clay suspension particles injected or in the formation also interact with the free functional groups of PAA. The process of flocculation and crosslinking with the formation of a crosslinked polymer dispersed system in highly permeable zones of the formation, which leads to a redistribution of filtration flows, and subsequent injection of water helps to extract oil from low permeable zones of the formation. The injection of a crosslinking agent with a buffer volume of water modifies the surface of the porous medium, which contributes to a more complete interaction of the entire system.

The technology for stimulating the formation consists in injecting a predetermined volume of an aqueous PAA solution and clay slurry mixed with a crosslinker of a certain concentration into injection wells and selling it with a rim of water.

Case Studies

Example 1. Develop a heterogeneous multi-layer multi-element oil field. They carry out the selection of products through production wells, injection through the injection wells of the working agent. The state of development of the field is analyzed by the water content of the products and the injectivity of injection wells. A deposit section is identified with an average water cut of up to 90% over the section and with injection wells up to 250 m ³ / day. The reservoir has the following characteristics: reservoir thickness 10 m, oil-water contact depth 1800 m, reservoir pressure 10 MPa, reservoir temperature 35 ° C, porosity ranging from 5 to 30%, pore size 0.0002 ... 0.5 mm and more, permeability 250 μm ² , oil saturation 0.7, heterogeneity 0.5, oil viscosity at reservoir conditions 7.0 MPa · s, oil density 0.84 g / cm ³ , mineralization of produced water 260 g / l. The deposit is being developed by flooding. A working agent is pumped - produced water with a density of 1.10 g / cm ³ through 3 injection wells and products - a water-oil emulsion - are taken through 6 production wells.

The current oil recovery factor of the reservoir is 0.53.

Work is carried out on injection well No. 1. An aqueous surfactant solution is pumped through a injection well together with polymer dispersed systems in the form of a separate rim. Initially, the components of the MPDS-aqueous solution of PAA and clay suspension (4 cycles) are cyclically pumped, one cycle of the PDS includes the injection of reagents in the following sequence:

- 100 m ³ 0.1% aqueous solution of PAA brand Praestol-2540 (TU 2216-001-40910172-98);

- 6 m ³ buffer volume of water;

- 100 m ^{3 of a} 4% clay suspension of the PBMV grade (TU 39-0147001-105-93 with amendment No. 1-6);

- 6 m ³ buffer volume of water.

After pumping the entire volume of the PDS, an aqueous surfactant solution ULTRAFLO reagent is pumped in accordance with TU 2458-019-87869324-2011 with a concentration of 15% by weight and a volume of 20 m ³ . Water for the preparation of reagent solutions, buffer water, and water for transferring reagents into the formation are used from the PPD system.

As a result, the oil recovery coefficient of the deposit was 0.68. The application of the prototype method allowed to achieve a recovery factor of 0.56.

Example 2. Perform as example 1.

A deposit section is identified with an average water cut of up to 90% over the section and an injection well injection rate of up to 250 m ³ / day. Work is carried out on injection well No. 2. An aqueous surfactant solution mixed with clay suspension is pumped through an injection well together with polymer dispersed systems. MPDS is injected in the form of 3 cycles, each of which includes:

- 100 m ³ 0.1% aqueous solution of PAA brand DR-9-8177;

- 7 m ³ buffer volume of water;

- 100 m ³ 4% clay suspension with the addition of surfactants - 0.05% aqueous solution of neonol AF 9-12;

- 7 m ³ buffer volume of water.

The injected reagents are pressed into the reservoir with water of 30 m ³ volume. Water for the preparation of reagent solutions, buffer water, and water for transferring reagents into the formation are used from the PPD system.

As a result, the oil recovery coefficient of the deposit was 0.48. The application of the prototype method allowed to achieve a recovery factor of 0.36.

Example 3. Perform as example 1.

Allocate a plot of deposits with a water cut of the average area of up to 90% and injectivity of injection wells up to 250 m ³ / day. Work is carried out on injection well No. 3. An aqueous surfactant solution is pumped through an injection well together with polymer dispersed systems by adding PAA to the solution and, in addition, as a separate rim. MPDS is downloaded in the form of 5 cycles, each of which includes an injection

- 100 m ^{3 of a} 0.12% aqueous solution of PAA grade DKS-ORPF-40NT with the addition of 0.5% surfactant composition (composition — 5% petroleum sulfonate, 4.5% isopropyl alcohol, the rest is injected water);

- 7 m ³ buffer volume of water;

- 100 m ³ 2% clay suspension;

- 7 m ³ buffer volume of water.

Water for the preparation of reagent solutions and buffer water are used from the PPD system. After pumping the entire volume of MPDS, an aqueous solution of a surfactant composition is pumped (the composition is 5% petroleum sulfonate, 4.5% isopropyl alcohol, the rest is injected water) with a concentration of 2.5% by weight, volume 100 m ³ . The injected reagents are pressed into the reservoir with water of 30 m ³ volume.

As a result, the oil recovery factor of the deposit was 52%. The use of the prototype method allowed to achieve a recovery factor of 34%.

Example 4. Perform as example 1.

A deposit section is identified with an average water cut in the section from 70% to 95% and injection wells from 250 m ³ / day to 350 m ³ / day. Through injection well No. 4, together with polymeric disperse systems, aqueous solutions of polyvalent metal salts are pumped - the reagent Alumochloride-A grade A (TU 2151-002-42129794-2001). The technological process of pumping MPDS with aluminum chloride-A is carried out in the following sequence:

a) inject aluminum chloride-A in commodity form with a density of 1.21 g / cm ³ with a volume of 30 m ³ at the rate of 3 m ³ per 1 m of perforated formation thickness;

b) inject a buffer volume of water with a volume of 10 m ³ ;

c) cyclically (6 cycles), a 0.12% PAA aqueous solution of Praestol-2530 grade (TU 2216-001-40910172-98) with a volume of 50 m ³ and 50 m ^{3 of a} 6% suspension of PBM grade clay powder (TU 39-0147001-105 -93 with amendment No. 1-6) with a buffer volume of water between them of 6 m ³ ;

g) the reagents are pressed into the reservoir with water of 30 m ³ .

Water for the preparation of reagent solutions and buffer water are used from the PPD system.

As a result, the oil recovery factor of the deposit was 50%. The application of the prototype method allowed to achieve a recovery factor of 37%. Example 5. Perform as example 1.

A deposit section is identified with an average water cut in the section from 70% to 95% and injection wells from 250 m ³ / day to 350 m ³ / day. Through injection well No. 5, together with polymer dispersed systems, aqueous solutions of salts of multivalent metals — calcium chloride — are pumped. Water for the preparation of reagent solutions and buffer water are used from the PPD system. Reagents are injected cyclically in the form of 6 cycles, each of which is carried out in the following sequence:

a) inject an aqueous 15% solution of calcium chloride with a density of 1.13 g / cm ³ volume of 20 m ³ at the rate of 2 m ³ per 1 m of perforated thickness of the reservoir;

b) inject a buffer volume of water with a volume of 6 m ³ ;

C) inject an aqueous solution of 0.05% PAA brand Akkotrol-623 with a volume of 150 m ³ ;

g) pump a buffer volume of water 7 m ³ ;

d) pump 1% clay suspension with a volume of 150 m ³ ;

e) pump a buffer volume of water of 7 m ³ ;

As a result, the oil recovery factor of the deposit was 50%. The application of the prototype method allowed to achieve a recovery factor of 37%.

Example 6. Perform as example 1. Allocate the area of deposits with water cut on average in the area from 70% to 99% and the injection rate of injection wells more than 350 m ³ / day. Through injection well No. 6, 8 cycles of MPDS with crosslinking agents are pumped. As a cross-linking agent, AMG reagent is used - a gelling modifying agent according to TU 2146-003-42129797-2003, grade AMG-1. Water for the preparation of reagent solutions and buffer water are used from the PPD system. In the first three cycles of MPDS, reagents are pumped in the following sequence:

- 0.2% aqueous solution of PAA brand Praestol-2530 with a volume of 120 m ³ with the addition of 0.1% AMG-1;

- 8 m ³ buffer volume of water;

- 5% suspension of PBMA brand clay powder with a volume of 120 m ³ with the addition of 0.1% AMG-1;

- 8 m ³ buffer volume of water.

In the following five cycles of MPDS, reagents are pumped in the following sequence:

- 0.2% aqueous solution of PAA brand Praestol-2530 with a volume of 100 m ³ ;

- 8 m ³ buffer volume of water with the addition of 0.2% AMG-1;

- 5% suspension of PBMA grade clay powder with a volume of 100 m ³ with the addition of 0.15% AMG-1;

- 8 m ³ buffer volume of water.

As a result, the oil recovery factor of the deposit was 65%. The application of the prototype method allowed to achieve a recovery factor of 51%.

Example 7. Perform as example 1. Allocate a plot of deposits with water cut on average in the area from 70% to 99% and the injection rate of injection wells more than 350 m ³ / day. Aqueous solutions of crosslinking agents are pumped through injection well No. 7 together with MPDS. MPDS is injected in the form of 8 cycles of an aqueous solution of PAA, a clay suspension with the addition of chromium acetate with buffer water between the edges of the reagents. Water for the preparation of reagent solutions and buffer water are used from the PPD system. First, the reagents are pumped cyclically in the form of 7 cycles in the following sequence in one cycle:

- 7% clay suspension with a volume of 80 m ³ with the addition of 0.2% chromium acetate;

- 7 m ³ buffer volume of water;

- an aqueous solution of 0.15% PAA brand DKS-ORPF-40NT with a volume of 80 m ³ ;

- 7 m ³ buffer volume of water;

- 5 m ^{3 of a} 2% aqueous solution of chromium acetate;

- 7 m ³ buffer volume of water.

The injectivity of the well after injection of MPDS was 240 m ³ / day, i.e. less than 250 m ³ / day. Then inject an aqueous solution of a surfactant - ULTRAFLO reagent according to TU 2458-019-87869324-2011 with a concentration of 15 wt%, a volume of 30 m ³ , which is pressed into the reservoir with water in a volume of 30 m ³ . Water for the preparation of reagent solutions, buffer water, and water for transferring reagents into the formation are used from the PPD system.

As a result, the oil recovery factor of the deposit was 58%. The use of the prototype method allowed to achieve a recovery factor of 50%.

Example 8. Perform as example 1. Allocate the area of deposits with water cut on average in the area from 70% to 99% and injectivity of injection wells more than 350 m ³ / day. Aqueous solutions of crosslinking agents are pumped through injection well No. 7 together with polymer dispersed systems. The technology of the effect of MPDS on flooded oil reservoirs consists in the simultaneous dosing of the components of MPDS - an aqueous solution of PAA and clay slurry with the addition of a crosslinking agent. Water for the preparation of reagent solutions and buffer water are used from the PPD system. MPDS download includes parallel download:

- an aqueous solution of 0.05% PAA brand DKS-ORPF-40NT;

- 2% suspension of clay powder grade PBMB with the addition of 0.03% aqueous solution of AMG brand AMG-1.

As a result, the oil recovery coefficient of the deposit was 59%. The application of the prototype method allowed to achieve a recovery factor of 45%.

Application of the proposed method will improve the efficiency of the polymer dispersed system and, thus, increase the oil recovery of the reservoir.

Claims (1)

A method of developing an oil deposit, including selecting products through production wells, injecting a working agent — water and a polymer dispersed system with modifying chemicals — through the injection wells, characterized in that the state of development of the field is analyzed by the current oil recovery factor and water cut of the product and when the water cut is average per site up to 90% and injectivity of injection wells up to 250 m ³ / day in conjunction with a polymer dispersed system as modifying injection chemicals water solutions of surfactants — surfactants or surfactant compositions — are prepared, with an average water cut of the area from 70% to 95% and injectivity of injection wells from 250 m ³ / day to 350 m ³ / day, they are injected together with a polymer dispersed system as modifying agents chemical reagents aqueous solutions of salts of multivalent metals, with an average water cut of the area from 70% to 99% and injectivity of injection wells of more than 350 m ³ / day, they are pumped together with a polymer dispersed system as modifying chemicals aqueous solutions of crosslinking agents, while aqueous solutions of chemicals are pumped with a density of not less than 10% higher than the density of the injected water and in the form of their individual rims, in the form of their mixture with the components of the polymer dispersed system and with the buffer volume of water between the components of the polymer dispersed system.