RU2534873C2 - Method of oil pool development - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to the oil industry, in particular, to development methods of oil pools with reservoirs difficult to recover using thermal oil recovery methods. In the development method of an oil pool with reservoirs difficult to recover, which is implemented by the injection of an oxidiser and water fringes to injectors and by oil extraction from producers, before the oxidiser injection to the formation an aqueous solution of carbonic acid normal salt with a water-soluble acrylic polymer and an acid bath are injected to the formation. Besides, the injection of the aqueous solution of carbonic acid normal salt with the water-soluble acrylic polymer and the acid bath to the formation is made by turns, in cycles, in order to obtain the required volume of the fringe. When gas is broken to the producers, the highly permeable intervals of the formation are isolated.

EFFECT: improved efficiency of the method at the development of oil pools with normal and high viscosity due to the generation of the area with the required oil saturation, reduced fuel consumption for maintenance of the combustion process, more complete usage of the oxidiser and safer development of the pool with inhomogeneous and fractured reservoirs, increased coverage of the formation area with the combustion and displacement process.

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Description

The invention relates to the oil industry, in particular to methods for developing oil deposits with hard-to-recover oil reserves using thermal methods of influencing the reservoir.

There is a method of developing an oil reservoir, including the creation of an in-situ combustion zone in the reservoir by injection of oxidizing agent and water into the reservoir through injection wells, and the selection of oil through production wells (1.

In the known method, in order to make fuller use of the oxidizing agent, especially in fractured porous or stratified inhomogeneous formations, when the residual oil saturation may be insufficient for the formation of the fuel necessary during combustion, a coolant is pumped into the formation, followed by a decrease in pressure in the bottom-hole zone of the injection well formation.

The disadvantage of this method is the need to use energy from the outside (coolant from the surface). When a heat wave moves, oxygen can enter unheated sections of the formation. Isolation of highly permeable formation intervals is not provided to prevent oxygen breakthrough into production wells.

A known method of developing an oil reservoir with hard-to-recover oil reserves, including creating an in-situ combustion zone in the formation by injecting oxidizer and water into the formation through injection wells and extracting oil through production wells (2).

The known method is used in the development of deposits with oil of normal viscosity.

The disadvantage of this method is the low speed of advancement of the combustion front when developing deposits with high viscosity oils.

In addition, when developing deposits with heterogeneous and fractured formations during thermogas treatment, breakthrough of free oxygen in production wells is possible, which can lead to an explosion.

The aim of the invention is to increase the efficiency of the method in the development of deposits with oils of normal and high viscosity by creating the area of the necessary oil saturation, reducing fuel consumption for maintaining the combustion process, more complete use of the oxidizing agent and the safety of the process of developing deposits with heterogeneous and fractured formations, increasing the coverage of the formation zone the process of combustion and displacement.

The goal is achieved by the fact that in the method of developing an oil reservoir containing hard-to-recover oil reserves by injecting the fringes of the oxidizing agent and water into the injection wells and extracting the oil by means of producing wells, before the oxidizing agent is injected into the formation, an aqueous solution of a middle salt of carbonic acid with a water-soluble acrylic polymer and an acid solution.

In addition, the middle salt of carbonic acid with a water-soluble polymer of an acrylic series and an acid solution is injected into the formation alternately in cycles to obtain the required rim volume. In the event of a gas breakthrough into production wells, isolation of highly permeable intervals of the formation is performed.

The essence of the method is as follows.

When an aqueous solution of a medium carbonic acid salt and an acid solution is injected into the formation before the injection of the oxidizing agent (oxygen-containing gas), the formation of carbon dioxide occurs as a result of the exothermic reaction, and a pseudo-boiling gas-liquid rim (OPGS) is formed.

When carbon dioxide is dissolved in oil, the viscosity of the oil decreases, and the volume of oil increases (volumetric effect). The formation of the oil shaft in front of the combustion front is one of the most important aspects of maintaining the combustion process, because this shaft is a zone of high oil saturation. When moving OPGS, the oil shaft is constantly growing and increases the coverage of the formation zone by displacement.

In addition, the polymer added to the aqueous solution of a carbonic acid salt serves as a foaming agent, blocking highly permeable formation channels in the first stage. This increases the coverage of the formation by combustion.

The following reagents can be used in the method:

- an oxygen-containing gas, for example air, can be used as an oxidizing agent;

- as a medium salt of carbonic acid - any water-soluble salt of carbonic acid, but it is preferable to use the most available sodium carbonate;

- as an acidic solution, it is preferable to use an aqueous solution of hydrochloric acid;

- as a water-soluble polymer of the acrylic series, it is preferable to use polyacrylamide.

The method is as follows.

The choice of deposits is carried out from the condition that the reservoir temperature in it is at least 65 ° C, which contributes to a stable and spontaneous flow of the oil combustion process. On the developed reservoir using the system of producing and injection wells. Work begins with the injection into the reservoir through the injection well of an aqueous solution of a medium salt of carbonic acid and an aqueous solution of acid. If necessary, to prevent mixing of the reagents in the wellbore, a portion of fresh water is pumped between them. Working solutions are prepared immediately before injection. The necessary concentrations and volumes of injected reagents are determined on the basis of obtaining the required volume of a pseudo-boiling gas-liquid rim.

Then a rim of air and water are pumped. The ratio of the volumes of injected air and water is selected on the basis of maintaining the required combustion temperature of 300-400 ° C. The injection cycle of the water and air rims continues until the volume of air and water rims required by the technology is obtained.

Information sources

1. A.S. SU 1090060, ЕВВ 43/243, 1996

2. Patent RU 2109133, ЕВВ 43/243, 1998.

Claims (3)

1. A method of developing an oil deposit, including the creation of an in-situ combustion zone in the formation by injection of the fringes of the oxidizer and water into the formation through injection wells and the selection of oil by production wells, characterized in that an aqueous solution of medium salt of coal is pumped into the formation through injection wells acids with a water-soluble acrylic polymer and an acid solution. 2. The method according to claim 1, characterized in that the injection into the reservoir of a medium salt of carbonic acid with a water-soluble polymer of the acrylic series is carried out alternately by cycles. 3. The method according to claim 1 or 2, characterized in that the isolation of highly permeable intervals of the formation.