RU2268355C1 - Multizone oil reservoir development method - Google Patents

Abstract

FIELD: oil industry, particularly enhanced recovery methods for obtaining hydrocarbons.

SUBSTANCE: method involves cyclically extracting oil from the reservoir zones through productive wells and injecting working agent into reservoir zones through injection wells. Discharge water and oil-field water of low mineralization having thickness of 1-1.005 kg/m³ is used as the working agent. Discharge water is cyclically injected in upper reservoir zones. Oil-field water of low mineralization is cyclically injected in lower reservoir zone for 7-9 months and discharge water is also cyclically injected in lower reservoir zone for 3-5 months.

EFFECT: increased output.

Description

The invention relates to the oil industry and may find application in the development of a multilayer oil reservoir.

A known method for the development of multilayer oil fields, including the allocation of production facilities, drilling production and injection wells at the selected production facilities, injection of a displacing agent into injection wells and oil extraction from production wells. First, determine the total increase in the initial amplitude oil production rate of the design wells. The selection of operational facilities is carried out in accordance with the criteria of rational integration (RF Patent No. 2142046, CL E 21 B 43/20, publ. 11/27/1999).

The known method allows you to select the main oil reserves, however, oil recovery remains low due to the formation in the reservoirs of washed channels through which the working agent passes, without affecting the bypassed zones, and the low displacing ability of the working agent.

Closest to the proposed invention in technical essence is a method of developing a multilayer oil reservoir, including assessing the average values of reservoir properties of the reservoirs, taking oil from the reservoirs through production wells, injecting water in a cyclic mode with a choice of the duration of the injection cycle and producing the reservoirs. The layers are divided into groups. Assessment of the average values of filtration-capacitive properties is carried out for each group. The first group includes formations with higher permeability. The second group includes less permeable formations. The duration of the water injection cycle is selected from the condition of ensuring the smallest difference in the averaged speeds of displacement of the displacement fronts along the layers of the productive section of the first and second groups (RF Patent No. 2132940, class E 21 B 43/20, publ. 10.07.1999 - prototype).

The known method allows you to select the main oil reserves and by pumping water in a cyclic mode, oil from stagnant zones. However, oil recovery remains low due to the low displacement ability of water (working agent).

The proposed invention solves the problem of increasing oil recovery deposits. The problem is solved in that in the method of developing a multilayer oil reservoir, including the selection of oil from the reservoirs through production wells, pumping the working agent into the reservoirs in a cyclic mode, according to the invention, wastewater and low-mineralized formation water are used as working agent in the upper reservoirs in in a cyclic mode, wastewater is pumped; in the lower reservoir, in a cyclic mode, is pumped for 7-9 months. formation water of low salinity and for 3-5 months. waste water.

The features of the invention are:

1. the selection of oil from the reservoir through production wells;

2. pumping the working agent into the reservoirs in a cyclic mode;

3. the use of wastewater as a working agent;

4. use of low-salinity produced water as a working agent;

5. injection into the upper layers in a cyclic mode of wastewater;

6. injection into the lower layer in a cyclic mode for 7-9 months. formation water of low salinity and for 3-5 months. waste water.

Signs 1, 2 are common with the prototype, signs 3-6 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

When developing an oil deposit, part of the reserves remains in the reservoirs. Existing methods allow you to select the main reserves from the deposit. However, oil recovery remains low.

The proposed method solves the problem of increasing oil recovery deposits.

The problem is solved as follows.

When developing a multilayer oil reservoir, oil is taken from the reservoirs through production wells and the working agent is injected into the reservoirs in a cyclic mode. As a working agent, wastewater generated after the separation of a water-oil emulsion extracted from a deposit and low-salinity produced water specially extracted from a water-saturated formation are used. Wastewater is pumped into the upper layers in a cyclic mode, and pumped into the lower layer in a cyclic mode for 7-9 months. formation water of low salinity and for 3-5 months. waste water. The cyclic injection mode of the working agent involves downloading for a certain time and stopping the download for a certain time as well. For example, injection within 10-20 days. and stopping the injection for 10-20 days. For each formation or even a section of the formation can apply its own mode.

As produced water of low salinity use produced water with a density of from 1 to 1.005 kg / m ³ . Produced water is produced through specially drilled water wells from formations located above the productive formations of the oil reservoir. Formation water is pumped through injection wells into productive formations of an oil reservoir immediately and without any preparation. In this case, the water is practically not cooled and not saturated with oxygen.

Concrete example

An oil reservoir is developed with the following characteristics. The reservoir is multi-layer. Three productive strata are under development: the Tula stratum, the Bobrikov stratum and the Tournaisian stratum.

The Tula formation has the following characteristics: depth 1161-1171 m, pit terrigenous reservoir, average oil saturated thickness 2 m, porosity 19-23%, oil saturation 0.72, permeability 1.26-1.5 μm ² , initial formation temperature 25 ° C, initial reservoir pressure of 11.8 MPa, oil viscosity at reservoir conditions of 40.6 MPa · s, oil density at reservoir conditions of 868 kg / m ³ , gas saturation pressure of 3.2 MPa gas, oil gas content of 11.4 m ³ / t, the viscosity of the water in the reservoir 1.65 MPa · s, the density of the water in the reservoir 1160 kg / m ³

The Bobrikovsky formation has the following characteristics: depth 1173 m, terrigenous pore reservoir, average oil saturated thickness 2.7 m, porosity 23%, oil saturation 0.72, permeability 1.072 μm ² , initial reservoir temperature 25 ° C, initial reservoir pressure 12 MPa, oil viscosity in reservoir conditions 36.8 MPa · s, oil density in reservoir conditions 885 kg / m ³ , gas saturation pressure of 3.4 MPa gas, oil gas content of 13.9 m ³ / t, water viscosity in reservoir conditions of 1.65 MPa · s, the density of water in reservoir conditions 1160 kg / m ³ .

The Tournaisian reservoir has the following characteristics: depth 1181-1204 m, pore-fracture carbonate reservoir, average oil saturated thickness 9.0-11.5 m, porosity 10-12%, oil saturation 0.74-0.74, permeability 0.005-0.23 μm ² , initial reservoir temperature 25 ° С, initial reservoir pressure 12.1 MPa, oil viscosity at reservoir conditions 35 MPa · s, oil density at reservoir conditions 854 kg / m ³ , gas saturation pressure of gas 4.1 MPa, gas content of oil 27.5 m ³ / t, water viscosity at reservoir conditions 1.66 MPa · s, water density at reservoir conditions 1160 kg / m ³ .

All producing wells operate continuously. Injection wells operate periodically: 15 days. - injection of the working agent, 15 days. - stop.

Oil is taken from the Tula formation through production wells. Oil is taken from the Bobrikov reservoir through production wells. Oil is taken from the Tournaisian reservoir through production wells.

A working agent is pumped into the Tula reservoir through injection wells - wastewater in a cyclic mode for 15 days. - injection of the working agent, 15 days. - stop.

A working agent is pumped into the Bobrikovsky layer through injection wells - wastewater in a cyclic mode for 15 days. - injection of the working agent, 15 days. - stop.

To the Tournaisian reservoir through injection wells for 8 months. low-salinity formation water is injected in a cyclic mode for 15 days. - injection of the working agent, 15 days. - stop and for 4 months. sewage in a cyclic mode 15 days. - injection of the working agent, 15 days. - stop.

Wastewater has the following characteristics: density 1160 kg / m ³ , pH-6.2, oil content 14.67 mg / l, EHF 20.67 mg / l.

As the formation water of low salinity, use the formation water of the Sakmara stage, located at a depth of 300-500 m. The water composition is as follows, g / l: CL 0.8, SO ₄ 1.5, NSO ₃ 0.24, Ca * 0.13 , Mg * 0.23, Na + K 0.79, sum 3.68. The density of water is 1.003 kg / m ³ .

The average production rate of producing wells for oil is 4.13 tons / day, for liquids - 5.81 m ³ / day. The average injection rate of injection wells is 80 m ³ / day.

Oil recovery calculations of the reservoir show that as a result of the use of low-salinity wastewater and produced water, the modes of injection of wastewater and low-salinity produced water, it is possible to increase the oil recovery coefficient from the design 0.289 to 0.30.

The application of the proposed method will improve oil recovery of oil deposits.

Claims (1)

The method of developing a multilayer oil reservoir, including the selection of oil from the reservoirs through production wells and pumping the working agent into the reservoirs in a cyclic mode, characterized in that wastewater and low-salinity produced water with a density of 1-1.005 kg / m ³ are used as working agent, the upper layers in a cyclic mode pump sewage, the lower layer in a cyclic mode pump for 7–9 months low-salinity formation water and for 3-5 months waste water.