RU2485301C1 - Oil production method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in oil production method involving preliminary performance of a set of hydrodynamic investigations and pumping to the formation of a microgel composition containing polyacrylamide, a cross-linking agent and water, at pumping of microgel composition there additionally added is oxyethylated alkylphenol or complex surface active substance - SAS; at that, microgel composition is obtained by adding to water suspension of polyacrylamide of 5-10% water solution of the cross-linking agent - aluminium salt and at the same time, oxyethylated alkylphenol or complex SAS at the following component ratio, wt %: polyacrylamide 0.03-0.5, cross-linking agent - aluminium salt 0.005-0.15, oxyethylated alkylphenol or complex SAS 0.05-0.3, and water is the rest; at that, prior to pumping of microgel composition, pumping of a gel-forming compound is performed, which is obtained by adding to water suspension of polyacrylamide of 3-10% water solution of the cross-linking agent - chrome salt, at the following component ratio, wt %: polyacrylamide 0.1-0.5, cross-linking agent - chrome salt 0.01-0.05, and water is the rest.

EFFECT: increasing oil extraction efficiency.

2 ex, 2 tbl

Description

The proposal relates to the oil industry, in particular, to methods for extracting oil from a heterogeneous oil reservoir by regulating the coverage of the reservoir by water flooding and redistributing filtration flows by reducing the permeability of highly permeable zones of the reservoir and can be used in the development of a heterogeneous oil permeability and oil saturation.

A known method for oil production from a heterogeneous oil reservoir based on the injection of a mixture of anionic polymer and polyvalent metal salt (patent RU No. 2215870, IPC E21B 43/22, publ. 10.11.2003).

The disadvantage of this method is the ratio of the crosslinking cation to the anionic link. When the ratio of the crosslinking cation to the anionic link in the mixture for injection into the oil reservoir is 0.01-1.07, there is a sharp decrease in the viscoelastic properties of polymer compositions as a result of separation of the polymer mass into a separate phase.

A known method of oil production, including the injection into the reservoir of polyacrylamide, aluminum salts and water (patent RU No. 2086757, IPC E21B 43/22, publ. 08/10/1997). Rims of solutions of polyacrylamide (PAA), fresh water and aluminum salt are sequentially pumped into the injection well. The method allows you to adjust the gelation time in the reservoir.

The disadvantage of this method is that in the reservoir does not completely mix the rims of PAA and aluminum salts. The contact of the rims occurs only at the interface between the rims of the PAA and the aluminum salt with each other. As a result, a solution of PAA and aluminum salt is formed only at the boundary between the rims and each other, therefore, there is no complete effective blockage of highly permeable zones of the formation and redistribution of filtration flows.

Also known composition for oil production containing polyacrylamide (PAA), nonionic surfactant and water (and.with. SU No. 1544958, IPC E21B 43/22, publ. 23.02.1990, bull. No. 7). The disadvantage of the composition is the injection of polyacrylamide in the form of a solution subjected to high shear stresses in the bottomhole formation zone, which increases the destruction of its molecules and worsens the oil-displacing properties of the injected composition. In addition, the use of a surfactant with a pour point above 0 ° C significantly complicates the injection process, and in winter it is impossible to pump such a composition without special equipment.

Also known is a method of developing an oil field (patent RU No. 2060373, IPC E21B 43/22, publ. 05/20/1996), including the injection into the reservoir of an aqueous solution of polyacrylamide and a surfactant, which is used as a biological surface active substance (BPAS) KSHAS. The disadvantage of this method is the low efficiency due to unsatisfactory oil displacing and laundering properties of an aqueous polymer solution and surfactant. Despite the high concentration of BPAS, it reduces the interfacial tension of water to only 30 mN / m.

The closest in technical essence to the proposed method is a method of oil production, including preliminary conducting a complex of hydrodynamic studies and injecting into the reservoir a composition containing, wt.%: Polyacrylamide 0.05-0.5, aluminum salt 0.0075-0.15 and water the rest. The specified composition is obtained in the form of a suspension of colloidal particles by continuous dosing of a 7-10% aqueous solution of aluminum salt in an aqueous suspension of polyacrylamide (patent RU No. 2292450, IPC E21B 43/22, publ. January 27, 2007).

The disadvantage of this method is that microgel particles formed during the interaction of polyacrylamide and polyvalent metal salts are not able to effectively block highly permeable zones of the formation. Thus, for highly permeable zones of the formation, it is necessary to use large volumes of the injected composition to obtain a positive result, i.e. complete disconnection of highly permeable zones from further impact on the reservoir. This entails high costs for processing injection wells.

The technical task of the proposal is to increase the efficiency of oil production by increasing the coverage of the reservoir by displacement, increasing the oil recovery factor and saving used raw materials when exposed to cross-linked polymer systems on oil reservoirs that are heterogeneous in permeability and saturation.

The problem is solved by a method of oil production, including the preliminary conduct of a complex of hydrodynamic studies and injection into the reservoir of a microgel composition containing polyacrylamide, a crosslinker and water.

What is new is that when the microgel composition is injected, ethoxylated alkyl phenol or complex surfactants — surfactants — are additionally introduced, while the microgel composition is obtained by introducing a 5-10% aqueous crosslinker solution and simultaneously surfactant into the aqueous suspension of polyacrylamide in the following ratio of components, wt.%:

polyacrylamide 0.03-0.5 stapler - aluminum salts 0.005-0.15 Surfactant 0.05-0.3 water rest,

and before the injection of the microgel composition, the gel-forming composition is injected, which is obtained by introducing into the aqueous suspension of polyacrylamide a 3-10% aqueous solution of a crosslinker, in the following ratio, wt.%:

polyacrylamide 0.1-0.5 crosslinker - chromium salts 0.01-0.05 water rest.

The analysis of patent and scientific and technical literature allowed us to conclude that there are no technical solutions containing essential features of the proposed method that perform a similar task, therefore, the proposed method meets the criteria of "novelty" and "inventive step".

The following reagents are used to prepare the formulations:

- as polyacrylamide (PAA) use both low molecular weight and high molecular weight PAA with MM = 3-12 · 10 ⁶ and a degree of hydrolysis of 5-20%, for example, PAA brand DP9-8177, manufactured according to TU 2458-010-70896713-2006 , or its analogues ("Alcoflood 935", "Alcoflood 955", "Alcoflood 1175A", "Polydia PDA-1020" and others), approved for use in technological processes of oil production and transportation;

- aluminum salts are used as a crosslinker for the microgel composition: aluminum sulfate SKA (Al ₂ (SO ₄ ) ₃ · 18H ₂ O), aluminum chloride (AlCl ₃ · 6H ₂ O), potassium alum (AlK (SO ₄ ) ₂ · 12H ₂ O), aluminum ammonium alum (Al (NH ₄ ) (SO ₄ ) ₂ · 12H ₂ O), etc. For the implementation of the method, concentrated aqueous solutions of aluminum salts are used;

- chromium salts are used as a crosslinker for the gel-forming composition: chromium acetate - AH (CH ₃ COO) ₃ Cr), potassium chromium alum - HKK (KCr (SO ₄ ) ₂ · 12H ₂ O) and others. An aqueous solution of chromium acetate is produced according to TU 2499-001-50635131-00;

- as a surfactant, ethoxylated alkyl phenol based on propylene trimmers Neonol AF 9-12 or AF 9-9 (according to TU 2483-077-05766801-98) manufactured by OAO Nizhnekamskneftekhim, complex surfactants, etc. are used as surfactants. In winter (at temperatures below 0 ° C) it is possible to use complex surfactants with a low pour point, for example, Bixol grade B 40% (according to TU 2482-001-91222887-11, Atren SA (according to TU 2458-032-63121839-2011), Neominol (according to TU 2458-001-91222887-11) and others;

- for the preparation of microgel and gel-forming compositions use industrial water or water from the reservoir pressure maintenance system at the site of the production facility selected for the implementation of the proposed method with a density of 1.00 to 1.185 g / cm ³ and mineralization from 0.15 to 270 g / l.

The essence of the proposed method is as follows.

A complex of hydrodynamic studies is carried out at a site of a heterogeneous oil reservoir, represented by reservoirs of various permeabilities (from 0.2 to 1 μm ² ) and drilled at least by one injection and one production well: the injectivity profile of the injection well and the profile of the inflow of production wells are recorded. The injectivity of the injection well should be at least 100 m ³ / day and not more than 1000 m ³ / day at the maximum working wellhead injection pressure from the water conduit. Based on these studies, the presence of highly permeable washed zones in the reservoir, its extent in relation to the bottom of the well, and also its parameters: thickness, width and permeability are determined. Based on the studies, the volume of the gel-forming composition necessary for injection into the formation to completely disable highly permeable zones from further exposure to the formation is calculated. Based on the parameters of the heterogeneous oil reservoir, the volume of microgel composition required for injection into the reservoir is calculated.

The compositions are prepared and injected using standard facilities existing in oil production (for example, UDR-32M, KUDR, Baker-SAS, CA-320, etc.). A gelling composition is prepared as follows. Polyacrylamide in the form of a powder with a concentration of 0.1-0.5 wt.% Is metered into the water entering the water from the cluster pump station (SPS) with a salinity of 0.15 to 270 g / l through a jet pump (ejector). When polyacrylamide is mixed with water, a suspension forms, which is fed into an intermediate tank. In the same container, for example, using a metering pump, a 3-10% concentrated aqueous solution of a crosslinker with a final concentration in the injected composition of 0.01-0.05 wt.% Is metered. The resulting gelling composition is pumped into the well. After injection of the gelling composition, the microgel composition is injected. Polyacrylamide in the form of a powder with a concentration of 0.03-0.5 wt.% Is metered into the water entering the water from the cluster pump station (SPS) with a salinity of 0.15 to 270 g / l through a jet pump (ejector). When polyacrylamide is mixed with water, a suspension forms, which is fed into an intermediate tank. For example, a concentrated solution of aluminum salt (5-10 wt.%) With a concentration of 0.005-0.15 wt.% In the injected composition is dosed into the same container, for example, using a metering pump. At the same time, surfactants with a concentration of 0.05-0.3% wt. In the injected composition are dosed into a container with a PAA suspension. In the process of preparation and injection control the quality of the composition.

At the end of the injection, the gel-forming and microgel compositions are forced into the formation by water from a cluster pump station (SPS) with mineralization from 0.15 to 270 g / l and the injection well is turned on to pump water from the SPS. After the injection well reaches a stable injectivity, the injectivity profile is determined and the pressure recovery curve (HPC) is taken.

The viscosity of the microgel composition is significantly lower than the viscosity of the gelling composition.

When the gel-forming composition is injected, highly permeable washed zones of the formation are blocked, followed by redistribution of the microgel low-viscosity composition injected next into the less washed intervals of the formation, which increases the oil-displacing ability of the injected microgel composition by reducing the interfacial tension at the interface and changing the rock wettability; oil displacement from previously unaffected reservoir zones.

The result of the injection of compositions in the proposed method is to increase the coefficient of oil displacement, the alignment of the front of the displacement of the injected water, the connection to the development previously not involved by the influence of the formation zones, reducing the water content of the produced products.

A gel-forming composition is pumped into the highly permeable zones of the formation, which is superior in viscosity and strength to the composition of the prototype, which allows to reduce the volume and consumption of reagents for processing the well, then the microgel composition is pumped into the reservoirs with medium and low permeability, and the microgel composition has high hydrophobicity. In addition, the presence of surfactants in the microgel composition reduces interfacial tension at the interface and improves its oil-displacing properties. In addition, the microgel and gel-forming compositions after injection into the reservoirs create high filtration resistances, as a result of which high-permeability zones of the reservoir are blocked and the formation zones that were not previously used by the reservoir are connected to the development.

Moreover, the result of adding a surfactant to the microgel composition is an increase in the oil-displacing ability of the injected composition due to a change in the wettability of the rock, namely, an increase in the hydrophobization of the formation rock surface in order to connect stagnant and slightly drained formation zones to the development.

To assess the oil-displacing ability of the compositions, the interfacial tension indicator of aqueous solutions of surfactants at the oil-water interface in water of various salinity was used. The results are shown in table 1.

Table 1 Name of surfactant Interfacial tension, mN / m at the oil-water interface Mineralization of water, g / cm ³ Surfactant pour point, ° C 0.05% surfactant solution 0.1% surfactant solution 0.3% surfactant solution one 2 3 four 5 6 AF9-6 8.15 7.41 6.67 1.00 8-10 AF9-12 4.65 3.91 3.17 1.00 13-17 Atren 4.37 3.11 2.81 1.00 -twenty Bixol brand B 2.18 1.93 1,61 1.00 -twenty Neominol 6.39 4,57 4.2 1.00 -twenty AF9-6 15.1 13.85 13.06 1.09 8-10 AF9-12 5,6 4.3 3.56 1.09 13-17 Atren 3.37 2.97 2,617 1.09 -twenty Bixol brand B 1,57 0.782 0.431 1.09 -twenty Neominol 7.28 4.31 2.9 1.09 -twenty AF9-6 16.98 15.21 14.87 1.18 8-10 AF9-12 7.6 5,4 4.66 1.18 13-17 Atren 3.41 3.08 2.93 1.18 -twenty Bixol brand B 2.99 1,11 0.931 1.18 -twenty Neominol 8.98 6.65 3.11 1.18 -twenty

An analysis of the data shows that when using Atren and Bixol grade B surfactants, the lowest value of interfacial tension at the oil-water interface is achieved, which allows changing the wettability of the rock, namely, to achieve an increase in hydrophobization of the formation rock surface in order to connect stagnant and poorly drained formation zones. Also, the abovementioned surfactants have a pour point of up to minus 20 ° C, which allows them to be used in the winter period.

The oil-displacing and flow-rejecting potential of the compositions was studied on models of porous media after the initial displacement of oil by water and the final one after the injection of microgel and gel-forming compositions. At concentrations of PAA below 0.03 wt.% And a crosslinker for the microgel composition below 0.005 wt.%, The formation of a microgel composition does not occur. And at concentrations of PAA above 0.5 wt.% And a crosslinker for the microgel composition above 0.15 wt.% The use of the microgel composition is not economically viable. When surfactants are added to the microgel composition with a concentration below 0.05 wt.%, There is no decrease in interfacial tension at the oil-water interface, and the addition of surfactants to the microgel composition with a concentration above 0.3 wt.% Is not economically feasible. At concentrations of PAA below 0.1 wt.% And a crosslinker for the gelling composition below 0.01 wt.%, No gelling composition is formed. And at concentrations of PAA above 0.5 wt.% And a crosslinker for the gelling composition above 0.05 wt.% The use of a gelling composition is not economically viable. The injection volume of microgel and gel-forming compositions for the proposed method and prototype is 30% of the pore volume in the following ratio of components, wt.%:

microgel composition:

polyacrylamide 0.03-0.5 stapler - aluminum salts 0.005-0.15 Surfactant 0.05-0.3 water rest,

gelling composition:

polyacrylamide 0.1-0.5 crosslinker - chromium salts 0.01-0.05 water rest.

To assess the oil-displacing ability of the compositions used the coefficient of oil displacement from a layered inhomogeneous porous medium. The results of filtration studies are shown in table.2.

The analysis of the research results was carried out on the basis of the main filtration parameter - residual resistance factor (OFS), which shows how the permeability of the pore medium changed after filtering the proposed composition through it.

As can be seen from table 2, OFS for the proposed method of oil production increases in comparison with the prototype on average 10-15 times. The increase in the coefficient of oil displacement by the proposed method of oil production increases in comparison with the prototype on average 1.5-2 times.

An example of a specific implementation.

Example 1 (prototype). The test site with an injection well and four production wells is located within the Abdrakhmanovskaya area of the Romashkinskoye field, the production facility of which is represented by terrigenous reservoirs. Hydrodynamic studies are carried out, the results of the studies determine the injection volume of the compositions, the concentration of the component reagents, the initial injection rate of the injection well, which was 548 m ³ / day at 8.6 MPa.

A composition is pumped into the injection well in a volume of 1000 m ³ , wt.%: PAA polyacrylamide - 0.1, SKA aluminum sulfate - 0.03, water - 99.87, this composition is obtained as a suspension of colloidal particles by continuous dosing of 10% concentrated aqueous solution of SKA in an aqueous suspension of PAA. The composition was injected within 6 days. The injectivity of the well after injection of the composition was 450 m ³ / day at 8.6 MPa.

After the injection, the technological effect in the producing wells lasted for 14 months. In two producing wells, oil production increased from 12.1 to 37.5%. In two producing wells, oil production decreased from 15.7 to 42.9%. Additional oil production amounted to 934 tons to this section during the technological effect.

Example 2 (the proposed method). The test site with an injection well and three production wells is located within the Abdrakhmanovskaya area of the Romashkinskoye field, the production facility of which is represented by terrigenous reservoirs. Hydrodynamic studies are carried out, the results of the studies determine the injection volume of the compositions, the concentration of the component reagents, the initial injectivity of the injection well, which was 580 m ³ / day at 8.4 MPa, determine the presence of highly permeable zones, their parameters.

A gel-forming composition is pumped into the injection well in a volume of 200 m ³ , wt.%: PAA polyacrylamide - 0.15, KKK chrome alum - 0.015, water - 99.835, the composition is obtained as a suspension of colloidal particles by continuous dosing of a concentrated KKK aqueous solution into an aqueous suspension PAA. Then the microgel composition is pumped in a volume of 400 m ³ , wt.%: PAA polyacrylamide - 0.1, SKA aluminum sulfate - 0.015, Atren SA surfactant - 0.05, water - 99.835, this composition is obtained as a suspension of colloidal particles continuous dosing of a concentrated aqueous solution of SKA and surfactant in an aqueous suspension of PAA. The total volume of injected compositions is 600 m ³ . The composition was pumped over 4 days.

In the process of injection, the pressure increased by 30.1%, the injectivity of the well after injection of the composition decreased by 51.2% (270 m ³ / day at 8.4 MPa) at equal pressure values, which is evidence of the disconnection of highly permeable washed zones of the formation and involvement in Active development of waterlogged intervals. After the compositions were pumped into the injection well, the oil production rate in the producing wells of the site increased from 32 to 54%, the water cut of the product decreased from 2.5 to 12.7%. Additional oil production amounted to 2314 tons to this area during the technological effect.

The technological advantage of the proposed method in comparison with the prototype is to reduce the injection volumes of the compositions into the well and to reduce the time required to carry out the injection process. In addition, the advantages of the proposed method are the complete blockage of highly permeable zones of the formation by a gel-forming composition and the redistribution of filtration flows due to the injection of microgel composition and reduction of the permeability of the most permeable zones of the formation, as well as the absence of adsorption of the composition in the formation.

Thus, the proposed method provides a uniform distribution of the injected compositions in the heterogeneous permeability zones of the formation, increasing the efficiency of oil production by adjusting the injectivity profile of the injection well by increasing the coverage of the formation by water flooding, involving in the development of the most low-permeable oil-saturated sections of the formation and increasing their oil recovery, increasing oil recovery coefficient blocking highly permeable zones with a gel-forming composition and, as a result, a decrease in days of well production.

Claims (1)

A method of oil production, including preliminary conducting a complex of hydrodynamic studies and injecting into the formation a microgel composition containing polyacrylamide, a crosslinker and water, characterized in that, when the microgel composition is injected, an additional ethoxylated alkyl phenol or a complex surfactant - surfactant is added, and the microgel composition is obtained by introducing into an aqueous suspension of polyacrylamide a 5-10% aqueous solution of a crosslinker - an aluminum salt and simultaneously hydroxyethylated alkyl phenol or ompleksnogo surfactants the following component ratio, wt.%:
polyacrylamide 0.03-0.5 stapler - aluminum salt 0.005-0.15 hydroxyethylated alkyl phenol or complex surfactant 0.05-0.3 water rest,
moreover, before the injection of the microgel composition, the gel-forming composition is injected, which is obtained by introducing into the aqueous suspension of polyacrylamide a 3-10% aqueous solution of a crosslinker — a chromium salt, in the following ratio of components, wt.%:
polyacrylamide 0.1-0.5 stapler - chromium salt 0.01-0.05 water rest