RU2318997C1 - Method for oil reservoir development at later stage by water-gas hydrodynamic action during periodical gaseous phase dispersion change - Google Patents

Abstract

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

SUBSTANCE: method involves determining oil-saturated thickness distribution pattern; periodically operating highly-flooded well located in zones with decreased oil-saturated thickness; operating wells with increased oil-saturated thickness at accelerated fluid production regimes; injecting water-gas dispersed mixture through injection wells, wherein the water-gas dispersed mixture includes reservoir water and purified oil gas dispersed in water; periodically changing water-gas dispersed mixture dispersion. First of all water-gas dispersed mixture having bubble dimensions comparable with pore channel dimensions flushed with water is injected up to 2-6.1% reduction of water content in produced fluid. Then water-gas dispersed mixture with gas bubbles comparable with capillary and sub-capillary oil-containing pore channels is injected to provide 0.5-2.5% increase of water content in produced fluid. Said water-gas dispersed mixture dispersion alternation is maintained during total injection period.

EFFECT: increased oil recovery due to extended reservoir coverage with treatment and improved displacement efficiency.

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Description

The invention relates to the oil industry and can be used in the development of oil deposits at a late stage.

The problem of increasing the completeness of reserves development is an urgent task throughout the entire period of the oil industry. This problem is targeted - it is solved differently for different geological conditions of the developed facilities, depending on the capacitance and filtration properties of reservoirs, the structure of productive horizons, the structure of residual oil reserves and the state of development.

In relation to the late stage of development, due to the complexity of the process of displacing oil with water from the waterflood in conditions of high water cut of extracted products and the localization of undeveloped reserves in low-permeability reservoirs, with long-term operation of wells and, therefore, their technical condition is far from high-quality, the task of increasing the efficiency of reserves acquires special relevance.

A known method of developing an oil reservoir, including the injection of a working agent through injection wells and the selection of oil through production [B.C. Orlov. Design and analysis of oil field development under the regime of oil displacement by water. M .: Nedra, 1973, p.13]. The method does not allow oil production in the noted geological conditions with a high oil recovery coefficient.

A known method of developing an oil deposit, including one of the distinguishing features inherent in the proposed method, is a method of developing oil land, including pumping a working agent through injection wells in an unsteady mode and taking oil through production wells [M.L. Surguchov. Secondary and tertiary methods of increasing oil recovery. M .: Nedra, 1985, p.143-149]. This method allows you to extract more oil from the reservoir by changing the direction of the filtration flows, due to the unsteady nature of the water injection. However, it does not provide extraction of oil from all the numerous interlayers of the reservoir.

A method involving cyclic exposure of a reservoir by periodically injecting water and leveling the filtration properties of a productive section in injection wells [Method for developing an oil reservoir. RF patent No. 2087686. Leibin E.L., Boxerman A.A. and others], as well as the method [Method for the development of a multilayer oil reservoir. Patent R.F. No. 2132939. Boxerman A.A., Gumersky H.Kh., Jafarov I.S., Kashik A.S., Leibin E.L.] are very close in essence, but despite some similarities with the proposed solution, they lack technological techniques for managing work producing wells.

The development method has a certain similarity with the proposed technology [The method of developing a water-cut oil reservoir in a monolithic reservoir. RF patent №2060365. Leibin E.L., Sharifullin F.A. and etc.]. This method of developing a water-cut oil reservoir in a monolithic reservoir involves pumping a working agent through injection wells in an unsteady mode, establishing the nature of the distribution of oil-saturated thicknesses (formation thicknesses above the waterflood interval of the productive horizon), periodically operating highly water-borne wells located in areas of reduced values of oil-saturated thicknesses, and operation in forced modes of production wells located in areas with increased current oil enasyschennymi thicknesses. However, this method also does not provide oil recovery from all of the numerous interlayers of a different permeable formation having both a monolithic and a layered structure. Separate layers and accumulations of oil in the form of pillars appear to be undeveloped.

Closest to the invention in technical essence and the achieved result is a method of developing a water-flooded oil reservoir at a late stage by gas-hydrodynamic effects [A method of developing a water-flooded oil reservoir at a late stage by gas-hydrodynamic effects. RF patent No. 2236573 (prototype) Leibin E.L., Sharifullin F.A., Zanichkovsky F.M., Maksutov R.A.]. This method provides for the implementation of the same actions on production and injection wells as the previous method, but in addition to the previous method, to provide greater coverage and oil displacement from multiple sections of the reservoir with the presence of oil-containing interlayers and undeveloped oil pillars, it provides for the impact on the reservoir by injection of gas-water fine mixtures through injection wells. This method is adopted as a prototype.

It is known that the oil recovery coefficient, even for good reservoirs, rarely exceeds 0.5-0.6. This means that 40-50% of the oil reserves remain in the reservoir in the form of accumulations that are not covered by the displacement process, and in the form of under-displaced oil from pores washed with water. The displacement coefficient usually also does not exceed 0.5-0.6-0.65.

An analysis of the nature of the distribution of under-recovered oil in the waterflood volume of the highly permeable AB4-5 formation at the Samotlor field showed various forms of localization of undeveloped reserves.

Therefore, in order to increase the production of reserves, a technological complex is needed that would ensure an increase in oil recovery both by increasing exposure to exposure and by increasing the displacement factor. A significant contribution to solving this problem in the development method under consideration is made by the injection of water-gas finely dispersed mixtures.

In case of long-term exposure to the reservoir through injection wells by various working agents, the formation is washed (produced) unevenly, and oil is pushed out from the pores with different completeness. More and less washed zones and areas of the formation are formed. Over time, these newly developed parts of the formation that were created at an earlier stage of development will become more and more prominent, as will the “more preferable” and “less preferable” filtering paths created. This situation reduces the impact of exposure even when exposed to the reservoir in effective ways, including by changing the direction of the filtration flows.

To increase the completeness of extraction of under-recovered oil reserves localized in the waterflood volume in the form of complex forms, it is necessary to minimize this difference and ensure uniform displacement of under-recovered oil, including during gas-hydrodynamic effects, both by increasing the degree of coverage of the displacement process and by increase the completeness of crowding out. This problem is solved by the present invention.

The technical result of the invention is the increase in oil recovery both by increasing the coverage of the exposure process, and by increasing the displacement coefficient.

The technical result is achieved by the fact that in the method of developing an oil reservoir at a late stage, including establishing the nature of the distribution of current oil saturated thicknesses or current oil saturation of the reservoir, the periodic operation of highly watered wells located in areas of low values of oil saturated thicknesses or oil saturation, the operation of wells located in zones increased values of oil-saturated thicknesses or oil saturation coefficient, in forced modes of fluid withdrawal, filling through injection wells of a water-gas dispersed mixture of VGDS, consisting of produced water and purified oil gas dispersed in it, characterized in that the injection of VGDS is carried out by periodically changing the degree of dispersion: first, the injection of VGDS with gas bubble sizes commensurate with the size of the pore channels, washed with water, until the water cut of the extracted products decreases by 2-6.1%, then - the injection of water-gas separation with the size of gas bubbles, comparable with the sizes of capillary and subcapillary oil content pore channels, until the water cut of the mined products after the indicated decrease rises by 0.5-2.5%, while maintaining the indicated periodic change in the degree of dispersion of the water-rich water supply throughout the entire period of its injection.

Thus, a less dispersed water-gas mixture is first injected with gas bubble sizes comparable with the pore sizes of water-washed pore channels (pore sizes in the formation, due to extreme lithological heterogeneity, vary over a wide range from 5 μm in fine-grained siltstones to 100-150 μm in medium coarse-grained sandstones), thereby preventing the flow of sweat (after the injection of a less dispersed mixture) into a more dispersed water-gas mixture, the main purpose of which is displacement of oil from oily capillary and subkapillyarnyh pore channels. A less dispersed water-gas mixture is again pumped to reduce the conductivity of other existing and washed filtration paths,

In fact, a new approach to gas-water treatment by periodically pumping differently dispersed water-gas mixtures is proposed.

The use of a dispersed water-gas mixture, in contrast to traditional water-gas treatment, has a number of technical and technological advantages. The technical advantages include the stability of a dispersed system - the possibility of bringing it to the formation without leaks in leaks in tubing and production tubing, especially in long-developed fields. Technological advantages are associated with changes in the rheological properties of the displacing and displacing agents. So the displacing agent increases the viscosity characteristic several times, and the displaced fluid reduces the viscosity. As a result, a more uniform displacement front is provided, gas breakthroughs are excluded, and greater coverage of the displacement process is ensured.

An example of a specific implementation of the method.

The oil reservoir (self-development block) has the following characteristics:

- dimensions 4 × 4 km;

- layer thickness - 40 m;

- the permeability of the reservoir varies from tens of millions of Darcy to 2 Darcy;

- viscosity of reservoir oil - 1.2 s · Pz;

- pressure of oil saturation with gas - 13.0 MPa;

- initial reservoir pressure - 18.0 MPa.

The degree of dispersion should be such that the resulting gas bubbles have dimensions that do not impede their penetration into the pores of the reservoir.

The size of the bubbles - the degree of dispersion - depends on the speed of the jets of gas and water. This parameter is calculated and brought to the desired values during the bench test of the dispersant. For specific geological conditions of the AB4-5 formation, on the example of which experimental work is being carried out, at the first stage the size of the bubbles should be in the range of 10-40 microns.

Water was injected to create a finely dispersed water-gas system at bottomhole pressures up to 24 MPa. The pressure at the bottom of injection wells, at which technogenic fractures are formed, was 25.0-27.0 MPa according to hydrodynamic studies of the wells. Thus, the injection pressure was 1-3 MPa lower than the crack opening pressure.

Development of the site in the base case, i.e. according to the method adopted as a prototype, was carried out during the year. The main technological development indicators for the basic and proposed options are given in the table (table 1). For both compared options, the same duration of work (12 months) was adopted. In addition, the implementation period of the recommended option is divided into 3 stages. In each stage, two periods are distinguished: the first period of 1 month for the injection of a less dispersed water-gas mixture with sizes of gas bubbles of 10-40 μm and the second period of 3 months, during which the gas-gas effect was implemented by injection of a finely dispersed gas-gas mixture with the size of gas bubbles 5-10 microns. Each such second period ended after increasing the water cut of the extracted products by 1.0; 1.5; and 2.5% respectively for the first, second and third stages. After that, a less dispersed mixture was pumped. From the above technological indicators (table 1) it follows:

- For the same development time (1 year) in the basic version, water cut increased by 5.1% and reached 90.1%. When developing according to the recommended method, the water cut was stabilized at 82-85%.

- At the same time, the recommended option produced 102 tons of oil. more than the base (421.26 t.t. versus 319.5 t.t. or 32%).

Table 1 The results of the implementation of the proposed method in comparison with the indicators of the basic development method. Technological performance Basic version The proposed method VGMDS Stage 1 2 stage 3 stage VGMDS VGMDS VGMDS (D = 5-10 microns) VGMDS VGMDS (D = 5-10 microns) VGMDS D = μm 10-40 VGMDS (D = 5-10 microns) start of stage end of stage D = μm 10-40 Start the ending D = μm 10-40 Start the ending Start the ending Dates of work by stages 1.01 31.12 1.01-31.01 1,02 30.04 1.05-31.05 1.06 30.08 1.09-30.09 1.10 31.12 Fluid production, i.e. 2566.8 213.9 641.7 213.9 641.7 213.9 641.7 Oil production, i.e. 319.56 27.8 99.46 35.3 110.6 37,4 110.7 Contour value,% 85.0 90.1 90.1-84.0 84.0 85.0 85.0-82.0 82.0 83.5 83.5-81.5 81.5 84 Will continue. stage, months 12 one 3 one 3 one 3 Decrease in Rpl., MPa 1,5 1,0 1,2

Claims (1)

A method of developing an oil reservoir at a late stage, including establishing the nature of the distribution of current oil-saturated thicknesses or current oil saturation of the reservoir, the periodic operation of high-water wells located in areas of low values of oil-saturated thicknesses or oil saturation, the operation of wells located in areas of increased values of oil-saturated thicknesses or oil saturation coefficient , in forced modes of fluid withdrawal, injection through water-gas injection wells dispersed mixture (VGDS), consisting of produced water and purified oil gas dispersed in it, characterized in that the VGDS injection is carried out by periodically changing the degree of dispersion: first, the VGDS is injected with the size of gas bubbles comparable with the size of pore channels washed with water, until the water cut of the produced products decreases by 2-6.1%, then - the injection of water-gas separation with gas bubble sizes commensurate with the sizes of the capillary and subcapillary oil-containing pore channels, until the water cut nnosti produced after production of said reduction will increase by 0.5-2.5%, maintaining said periodic variation in the degree of dispersion VGDS throughout its injection.