RU2361072C1 - Method of development of oil deposit - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil industry and can be implemented at development of oil deposit in cyclic mode. The invention facilitates increased oil yield of the deposit. The method consists in withdrawing of oil through producers, in pumping working agent via pressure wells, in determining intake capacity of pressure wells and in taking it into account at specifying modes of operation for pressure wells. Measurements of intake capacity and pressure of pumping are carried out at the pressure wells after constant mode of operation has been established. If idle time has lasted to 10 hours, measurements of intake capacity are taken not earlier, than in 3 hours. In case of prolonged idle time, like 10-15 days, measurements of intake capacity are started not earlier, than in 2 days. If intake capacity of pressure wells operating in continuous mode with capacity over 40 m³/day has risen, these wells are transferred to a short-term cyclic mode during 1-4 months till former intake capacity returns. Pressure wells with low intake capacity operating under continuous mode with level of capacity about 15-20 m³/day are transferred to a short-term cyclic mode of operation till rise of their intake capacity. Further, wells are returned to a constant mode of pumping.

EFFECT: growth of oil yield of deposit.

1 ex

Description

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

A known method of developing an oil reservoir, including pumping a working agent through injection wells and taking oil through production wells from the reservoirs (M.A. Zhdanov. Oilfield geology and oil and gas reserves calculation. M., Nedra, 1970, p.307-309) .

The known method does not allow the development of oil deposits with high oil recovery.

Closest to the proposed invention in technical essence is a method of developing an oil reservoir, including the selection of oil through production wells and pumping a working agent through injection wells in a cyclic mode. In this case, the arithmetic mean injection rate of injection wells is determined, wells with an injectivity of less than average are classified as low-injectivity, wells with an injectivity of more than average are classified as highly receptive. Group in pairs the territorially closest nearest highly-responsive and low-responsive injection wells. All injection wells communicate with each other hydrodynamically through a surface 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-responsive wells are stopped and started at the same time, and the injection cycle is assigned as follows: 10-20 days - injection, 10-20 days - stop (RF Patent No. 2303126, publ. 2007.07.20 - prototype).

The disadvantages of the method are low oil recovery deposits.

The invention solves the problem of increasing oil recovery deposits.

The problem is solved in that in a method for developing an oil reservoir, which includes taking oil through production wells, injecting a working agent through injection wells, determining injectivity of injection wells and taking it into account when assigning operating modes of injection wells, according to the invention, injectivity and injection pressure are measured at injection wells after the establishment of a constant mode of operation of the wells, i.e. after a short downtime of up to 4 hours, the determination of injectivity is carried out no earlier than 3 hours, after a long downtime of about 10-15 days, the determination of injectivity is carried out no earlier than 2 days, with an increase in the injectivity of injection wells with an injectivity of more than 40 m ³ / day, working in continuously perform their transfer to short to 1-4 months cyclic mode until the return to the previous pick-up and malopriemistye injectors operating in continuous mode with a pick-up order of 15-20 m ³ / day, PEREVI ny to intermittent cyclic operation to improve their pickup, after which the wells again in a constant pumping mode.

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. determination of injectivity of injection wells;

4. taking into account the injectivity in the appointment of operating modes of injection wells;

5. measuring injectivity and injection pressure in injection wells after establishing a constant mode of operation of the wells;

6. for wells after a long downtime of up to 4 hours, the determination of injectivity no earlier than 3 hours, after prolonged downtime of the order of 10-15 days, determination of injectivity no earlier than 2 days;

7. with an increase in the injectivity of injection wells with an injectivity of more than 40 m ³ / day, operating in a constant mode, their transfer to a short-term cyclic mode of up to 1-4 months until returning to the previous injectivity;

8. the transfer of low-pressure injection wells operating in a constant mode with a throttle response of about 15-20 m ³ / day, to a short-term cyclic mode of operation until their injectivity is increased;

9. re-transfer wells to a constant injection mode.

Signs 1-4 are common with the prototype, signs 5-9 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

During the development of an oil field, oil selection through production wells, pumping of a working agent through injection wells in a cyclic mode, determination of injectivity of injection wells and its accounting when assigning operating modes of injection wells. An inaccurate mode of operation of the injection well leads to an overrun of the working agent, breakthroughs of the working agent to the producing wells, flooding of the reservoir and burial of reserves in the reservoirs or to a decrease in reservoir pressure and to under-recovery of oil reserves. All this negatively affects the oil recovery of the reservoir. The proposed method solves the problem of increasing oil recovery deposits. The problem is solved as follows.

When developing an oil reservoir, oil is extracted through production wells, the working agent is injected through injection wells, and the injectivity of injection wells is determined. Measurements of injectivity and injection pressure are carried out on injection wells after establishing a constant mode of operation of the wells. The establishment of a constant mode for each well is individual and is determined by periodic measurements of injectivity after any shutdowns of the wells. However, in general, the following conclusion can be made. After a long downtime of up to 10 hours, the determination of injectivity is carried out no earlier than 3 hours, and after a long downtime of about 10-15 days, the determination of injectivity is carried out no earlier than 2 days (usually after 2-5 days). These figures (up to 10 hours and 10-15 days) are the most characteristic. As a rule, all injection wells have small shutdowns of the order of 2-10 hours, which is associated with the current operation of the cluster pump station (SPS), the presence of peak loads, redistribution of injections between wells, etc. In addition, injection wells can operate with long downtimes of the order of 10-15 days, which is associated with the cyclic operation of the wells, and the 10-15 day mode is a typical mode of cyclic water flooding.

A regularity has been revealed, according to which for wells with an injection rate of more than 40 m ³ / day, operating in a constant mode, switching to a short-term up to 1-4 months cyclic mode reduces their injectivity, and for low-acceptivity wells operating in a constant mode with an injectivity of about 15 -20 m ³ / day, switching to a short-term cyclic mode of operation leads to an increase in their throttle response. The cyclic mode of operation includes, as a rule, 10–20 days injection and 10–20 days well shutdown. In accordance with this, it is recommended that when developing a deposit, the operating modes of injection wells be changed accordingly. After that, the wells are again transferred to a constant injection mode. This preserves the reservoir pressure, eliminates the overspending of the working agent, reduces the share of breakthroughs of the working agent to production wells, which positively affects the oil recovery of the reservoir.

Improved injectivity allows to increase the coverage of the reservoir by exposure, due to which to increase the oil recovery of the reservoir, reduce the injection pressure, which positively affects the cost of production.

By stopping the injection, we reduce the bottomhole pressure. With continued fluid withdrawal, the total fracture volume may decrease, some pores and cracks in the reservoir may close.

Absolutely established injection mode, especially in an heterogeneous reservoir, can not be. Injection wells during pumping from oil pump stations can behave completely illogically. At constant pressure, the flow rate can both increase and decrease. In some cases, with increasing pressure, the flow rate decreases. Different forces and factors act on the reservoir, so selection will never be exactly equal to the injection. When pressure changes, the total volume of cracks changes, the work of one injection well is affected by the work of neighboring injection wells, etc.

After a long shutdown of the pumping station and putting the wells into operation it will take considerable time to restore the hydrodynamic connection in the formation, which in low-permeability formations can be lost even after a relatively short shutdown of the pumping station.

Concrete example

An oil reservoir with the following characteristics is being developed: the depth of the reservoir is 1147.5 m, the depth of the oil-water contact is 1000 m, the reservoir pressure is 12.5 MPa, the reservoir temperature is 28 ° C, the porosity is 16%, the permeability is 0.171 μm ² , the oil saturation is 0.8, and the oil viscosity is reservoir conditions 1.8 MPa · s, oil density under surface conditions 0.916 g / cm ³ , saturation pressure 5 MPa, gas factor 3.557 m ³ / t, reservoir - pore. The permeability of the formations ranges from 0.176 to 0.083 μm ² . The balance reserves vary from 17,000 to 100,000 thousand tons in formations.

A working agent is injected - produced water through 180 injection wells, production (oil) is taken through 600 producing wells.

Half of the injection wells are in continuous operation, the other half are in cyclic mode; 15 days; injection; 15 days; shutdown.

For each injection well, the time to establish a constant mode of operation of the well after typical downtimes for a given well is determined. For this, after resuming the injection at regular intervals, for example, after 5 minutes with long downtimes and after 1 hour with long downtimes, the injectivity is measured. They fix the time when the throttle response becomes constant. This mode of operation of the well is considered constant.

Further, during the operation of each well, the injectivity is periodically measured. If there is an increase in the injectivity of the injection well with a working injectivity of more than 40 m ³ / day, operating in constant mode, by more than 20% of the constant mode, the well is switched to a cyclic mode 15 days injection - 15 days stop. They expect a decrease in injectivity to a constant level, after which the well is again transferred to a constant injection mode.

For low-pressure injection wells with an injection rate of 15-20 m ³ / day, operating in a constant injection mode, a cyclic mode of injection of the working agent is performed 15 days injection - 15 days stop until their injection rate improves to 25-30 m ³ / day, and then transfer again to a constant injection mode, which is stored for a long time at the well.

As a result, oil recovery increased by 1.2%.

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

Claims (1)

A method of developing an oil reservoir, including the selection of oil through production wells, pumping a working agent through injection wells, determining the injectivity of injection wells and taking it into account when assigning operating modes of injection wells, characterized in that injectivity and injection pressure are measured at injection wells after establishing a constant mode well operations, i.e. after a short shutdown of up to 10 hours, the determination of injectivity is carried out no earlier than 3 hours, after a long shutdown of about 10-15 days, the determination of injectivity is carried out no earlier than 2 days, with an increase in the injectivity of injection wells with an injectivity of more than 40 m ³ / day, operating in a constant mode, carry out their transfer to a short-term up to 1-4 months cyclic mode until they return to their previous injectivity, and low-injectivity injection wells operating in a constant mode with an injectivity of about 15-20 m ³ / day are transferred to short-term cyclic mode of operation to increase their injectivity, after which the wells are again transferred to a constant mode of injection.