RU2303126C1 - Oil field development method - Google Patents

Abstract

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

SUBSTANCE: method involves producing oil through producing wells and injecting working agent through injection wells in cyclic regime along with arithmetical mean injection well intake capacity determination; referring wells having intake capacity less than average intake capacity value to wells with low injectivity; referring wells having intake capacity greater than average intake capacity value to wells with high injectivity; pairing neighboring well with low injectivity and well with high injectivity; hydraulically communicating all injection wells through land-based water line system to provide working agent flow from well with low injectivity to well with high injectivity. As working agent is injected in cyclic regime paired wells with high injectivity and low injectivity are simultaneously shut-down and brought into operation. Injection cycle includes injection operation to be carried out for 10-20 days and well shutdown for 10-20 days.

EFFECT: provision of injection well cooperation after working agent injection termination and injection well bottom cleaning by outflow.

1 ex

Description

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

A known method of developing an oil field, including drilling a field with a grid of production and injection wells, introducing additional injection wells in the low-permeability zone of the formation, cyclic water injection through periodic operation of a cluster pump station. A feature of the method is that the injection cycle time by the cluster pump station is set based on the calculation in which the reservoir pressure in the highly permeable formation zone does not exceed the pressure in the low-permeability formation zone, while during the period of termination of the water injection, the cavities of the distributing pipelines are disconnected (RF Patent No. 2142556, class E21B 43/20, publ. 10.12.1999).

The method allows to increase the coverage of the low-permeability zone of the formation by water flooding. However, due to the separation of the cavities of the distribution pipelines, the method does not allow the interaction of injection wells when the injection is stopped, to redistribute the volumes of the injected working agent and to clean the bottom-hole zones of the injection wells due to the outflow.

Closest to the proposed invention in technical essence is a method of developing an oil reservoir, including the selection of oil through production wells to reduce reservoir pressure by 20-25% from the initial one, pumping the working agent through injection wells in a cyclic mode: 10-20 days injection, 10- 20 days stop (RF Patent No. 2061179, CL ЕВВ 43/20, publ. 05/27/1996 - prototype).

The known method by reducing reservoir pressure does not allow the interaction of injection wells when injection is stopped, because all injected working agent is absorbed by the formation, which makes it impossible to redistribute the volumes of injected working agent and to clean bottom-hole zones of injection wells due to spout.

The invention solves the problem of ensuring the interaction of injection wells after stopping the injection of the working agent and cleaning the bottom-hole zones of injection wells due to the spout.

The problem is solved in that in a method for developing an oil reservoir, including oil extraction through production wells and pumping a working agent through injection wells in a cyclic mode, according to the invention, injection wells are grouped by injectivity into highly-responsive and low-acceptivity and group in pairs the closest highly-responsive and low-responsive injection wells, injection wells communicate with each other hydrodynamically through a ground-based water conduit system with the possibility of fluid flow from low iemistoy vysokopriemistuyu wells in the well when the cyclic injection of working agent grouped pairwise and vysokopriemistuyu nizkopriemistuyu wells stops and starts simultaneously.

The features of the invention are:

1. the selection of oil through production wells;

2. pumping a working agent through injection wells in a cyclic mode;

3. grouping according to the injectivity of injection wells into highly sensitive and low sensitive;

4. grouping in pairs of the closest high-acceptivity and low-acceptivity injection wells;

5. communication between each of the injection wells hydrodynamically through a ground-based water conduit system with the possibility of fluid flow from a low-receiving well to a highly-receiving well;

6. stop and start simultaneously with cyclic injection of the working agent grouped in pairs of highly-responsive and low-acceptivity wells.

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

SUMMARY OF THE INVENTION

The working agents currently used in the reservoir pressure maintenance system, as a rule, are waste (associated) water produced with oil through production wells. Such working agents carry with them the remains of oil, resins, paraffins, mechanical particles and other products. When the working agent is pumped into the oil reservoir through the injection wells, accumulation of contaminants in the near-well zone of the injection well occurs, which clog the reservoir pores and reduce the well injectivity. To clean the bottom-hole zone of the injection well, the cheapest and one of the most effective is to pour the injected fluid from the well after the injection of the working agent has stopped. The proposed method solves the problem of cleaning bottom-hole zones of injection wells due to spout. In addition, the problem of ensuring the interaction of injection wells after stopping the injection of the working agent and the equalization of the volume of injection of the working agent in different parts of the reservoir is solved. The problem is solved as follows.

When developing an oil deposit, oil is taken through production wells and the working agent is injected through injection wells in a cyclic mode. Injection wells are grouped by injectivity into highly responsive and low responsive. For this, the arithmetic mean injection rate of injection wells is determined. Wells with injectivity less than average are classified as low-acceptivity. Wells with a higher injection rate are considered highly responsive. In addition, injection wells group in pairs the geographically located closest highly-responsive and low-acceptivity injection wells. All injection wells communicate with each other hydrodynamically through a ground-based water conduit system with the possibility of fluid flow from a low-receiving well to a highly-receiving well. During the cyclic injection of the working agent, grouped in pairs highly-responsive and low-responsive wells are stopped and started simultaneously.

The duration of the injection and shutdown cycle is determined based on the properties of the formation. In most cases, a regimen of 10–20 days is an injection; a stop of 10–20 days is optimal.

When wells are stopped in the reservoir in the area of a low-well well, there is an increased reservoir pressure. Compared with this, in the area of a highly responsive well there is a reduced reservoir pressure. After stopping the wells, due to the difference in reservoir pressure, the fluid is intensively spilled from the bottom-hole zone of the low-pressure injection well to the water conduit and to the bottom-hole zone of the high-pressure injection well. There is a redistribution of fluid in the formation without loss, equalization of the volume of injection of the working agent in different parts of the reservoir.

Bottom-hole zones of low-receiving wells paired with highly-receiving wells are less polluted. The overhaul period for cleaning the bottom-hole zone of such wells is 3-4 times longer than conventional wells under the same conditions. At the same time, highly-responsive wells, due to the larger pore size and greater permeability, absorb incoming pollution. At the same time, the periods of the overhaul periods of highly-responsive wells practically do not change.

Concrete example

An oil reservoir with the following characteristics is being developed: depth 1100-1300 m, reservoir pressure 11-14 MPa, reservoir temperature 40 ° C, average reservoir thickness 3.4 m, porosity 11-18%, permeability (40-100) × 10 ^{- 3} μm ² , oil saturation 55-87%, oil viscosity 18.7 MPa · s, oil density 855.4 kg / m ³ , formation water density 1165 kg / m ³ , formation water viscosity 1.72 MPa · s, coefficient oil recovery of 0.440.

The deposit has been developed for 20 years. Oil is taken through 200 production wells. A working agent is pumped - wastewater of the same reservoir, through 60 injection wells.

The arithmetic mean injection rate of injection wells in the reservoir is 80 m ³ / day. Injection wells with an injection rate of less than 80 m ³ / day are classified as low-acceptivity. Injection wells with an injection rate of more than 80 m ³ / day are classified as highly responsive. Injection wells group in pairs the territorially closest nearest highly-responsive and low-acceptivity injection wells. So, a highly-responsive injection well No. 409 with an injection rate of 132 m ³ / day and an adjacent injection well No. 389 with an injection capacity of 63 m ³ / day are combined in a pair. All injection wells communicate hydrodynamically with each other through a surface system of water conduits. Provide the possibility of fluid flow from a low-well well to a highly-responsive well. This is achieved by the absence of check valves on the mouths of injection wells. During cyclic injection of the working agent, 15 days of injection, 15 days of shutdown, grouped in pairs highly-responsive and low-responsive wells are stopped and started simultaneously. During the first 2 days after stopping, an intensive outflow of fluid from the bottomhole zone of injection well No. 389 into the water conduit and into well No. 409 is observed. The bottom-hole zone of well No. 389 is cleaned up, the fluid is redistributed in the formation without loss, and the level of injection of the working agent is equalized to different parts of the reservoir. The overhaul period of well 389 was 2 years instead of 0.9 years before the application of this technology, while the overhaul period of well No. 409 remained unchanged at 1.2 years.

The application of the proposed method will ensure the interaction of injection wells after stopping the injection of the working agent and cleaning the bottom-hole zones of injection wells due to spout.

Claims (1)

A method for developing an oil reservoir, including oil extraction through production wells and pumping a working agent through injection wells in a cyclic mode, the arithmetic mean injection rate of injection wells being determined, wells with injectivity less than average are classified as low-acceptivity, wells with injectivity more than average are classified as highly sensitive, grouped in pairs geographically located closest high-receiving and low-receiving injection wells, all injection wells communicate between hydrodynamically through a ground-based water conduit system with the possibility of overflow of a working agent from a low-receiving well to a highly-receiving well, during cyclic injection of the working agent, grouped in pairs highly-responsive and low-receiving wells are stopped and started simultaneously, and the injection cycle is assigned as follows: 10-20 days - injection, 10- 20 days - stop.