RU2394980C1 - Procedure for development of oil deposit - Google Patents

Abstract

FIELD: oil and gas production. ^ SUBSTANCE: extracted production is withdrawn through producers; working agent is pumped via pressure wells at operating pressure and consumption. Formation water purified to presence of solid suspended particles of not more 60 mg/l and oil emulsion not more 50 mg/l are used as working agent. When intake capacity drops, because vicinity of borehole of the pressure well has been mudded with solid suspended particles and oil emulsion, pressure of pumping is raised. Water without mudding substances is pumped into the pressure well at raised pressure facilitating well intake in volume sufficient for distribution of mudding substances in formation and sufficient for increase of intake capacity of the pressure well. At continuous pumping working agent is pumped with anew set working pressure and consumption. ^ EFFECT: increased recovery of oil deposit. ^ 1 ex

Description

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

A known method of processing the bottom-hole zone of the injection well, including organizing a bath of the working agent in a volume of 4-6 m ³ in the perforation interval with a technological exposure of up to 9 hours, selling the working agent with wastewater in the pulse drainage mode: increasing the pressure at the mouth to 11-13 MPa - depressurization with a number of pulses 30–50, pumping a 3–8% hydrochloric acid solution in a volume of 20–40 m ³ , holding technological excerpts for no more than 4 hours and pumping 20–40 m ^{3 of} wastewater (RF Patent No. 2258134, published 10.08.2005).

The use of wastewater for sale makes it almost useless to clean the bottom-hole zone, sealed with products introduced by wastewater as a working agent.

Closest to the proposed invention in technical essence is a method of developing an oil reservoir, in which the working agent is injected through an injection well, at least one, and oil is taken through a production well, at least one hydrodynamically connected to one or more injection wells. At the same time, in the injection well, the injectivity of the at least one reservoir in the reservoir is preliminarily determined depending on the injection pressure and with monitoring the coverage of the reservoir with the injected agent according to its power. Upon reaching the full coverage of the reservoir, characterized by effective pressure and effective throttle response, a further increase in the injection pressure is carried out. To do this, increase the flow rate of the injected agent to a critical pressure, characterized by a sharp increase in the injectivity of the reservoir. After that, the injection pressure is reduced below the critical value by 5-10% and a portion of the working agent is injected into the reservoir during the passage of the pressure wave from the injection well to the producing well. Then the injection of the working agent is stopped. The injection well is kept under pressure for a time until the pressure in it drops to the lower limit of the effective pressure. This completes the cycle of exposure to pressure on the reservoir. After this, the injection of the working agent is resumed with the rise of the injection pressure to the upper value of the effective pressure and the cycles of pressure application to the reservoir are repeated (RF patent No. 2185503, published. 2002.07.20 - prototype).

The known method does not allow to achieve high oil recovery due to the inability to maintain reservoir pressure due to the low injectivity of injection wells.

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

The problem is solved in that in the method of developing an oil reservoir, including the selection of produced products through production wells, pumping a working agent at a working pressure and flow rate through injection wells, and increasing the injection pressure, according to the invention, produced water purified using solid suspended solids is used as a working agent particles of not more than 60 mg / l and oil emulsion not more than 50 mg / l, injection pressure is increased with a loss of injectivity due to clogging of the borehole zone of the injection well solids with suspended solids and an oil emulsion, water is pumped into the injection well without collimating substances at elevated pressure, at which the well accepts in an amount sufficient to distribute the clogging substances in the formation and increase the injectivity of the injection well, and then, after continuous injection, they proceed to pump the working agent at the newly set operating pressure and flow rate.

SUMMARY OF THE INVENTION

The deterioration in the injectivity of injection wells due to the presence of suspensions and oil products in the injected water and their deposition in the near-wellbore zone is the main reason for the decrease in reservoir pressure in the reservoir area and the decrease in current oil recovery. Various technologies are used to clean the borehole zone, up to hydraulic fracturing. However, these technologies are expensive, have a number of limitations on applicability and are not always effective. The proposed method solves the problem of increasing oil recovery deposits due to the timely restoration of injectivity of injection wells. The problem is solved as follows.

During the development of an oil deposit, production is extracted through production wells and the working agent is injected at operating pressure and flow rate through injection wells. As a working agent, produced water is used, purified to the presence of suspended solids of not more than 60 mg / l and an oil emulsion of not more than 50 mg / l.

At present, waterflood deposits face the problem of utilization of produced produced water. In the vast majority of cases, this water is prepared for the reservoir pressure maintenance system, purified from mechanical impurities, from the remnants of the oil emulsion, possible other impurities such as sulfur, paraffins, etc. Absolutely pure water is not obtained due to the high cost of the process. According to the studies of the authors, it is advisable to bring the purification to the presence of solid suspended particles in the produced water, no more than 60 mg / l and oil emulsion no more than 50 mg / l. Due to a breakdown in the technological processes of wastewater treatment, one-time emissions may sometimes exceed these values by 2 or more times. Purified and prepared water is pumped as a working agent through injection wells.

But even such a small amount of suspended solids and oil emulsion in practice turns out to be significant clogging deposits in the near-well zone of the injection well. With low-productive reservoirs, even an insignificant amount of clogging substances over time creates a barrier in the near-wellbore zone on the path of the working agent, reduces or reduces permeability to zero. Injection through the injection well becomes impossible. The reservoir pressure in the area of the reservoir decreases, oil recovery decreases.

In the case of loss of injectivity due to the mudding of the near-wellbore zone of the injection well with solid suspended particles and an oil emulsion, water without clogging substances (fresh water or mineralized water with zero content of suspended solids and oil emulsion) is pumped into the injection well at an elevated pressure at which the well accepts in volume sufficient to distribute the clogging substances in the formation and increase the injectivity of the injection well.

Units are installed at the wellhead (for example, CA 320), and a high pressure line is assembled. Water is injected without clogging substances at a pressure of up to 40 MPa and a flow rate that the well can create, as a rule, from 4.6 to 66 l / s. The amount of water sufficient for the distribution of colmatizing substances in the reservoir is determined as follows. As a rule, colmatizing substances accumulate in the near-wellbore zone with a radius of up to 0.5 m. Since the concentration of substances in the near-wellbore zone with distance from the well decreases according to a quadratic law, then to reduce the concentration of clogging substances by 10 times, they must be distributed at a distance of about 1 from the well , 5 m. At the same time, the pore volume in the near-wellbore zone, purified from colmatizing substances, turns out to be almost equal to a tenth of the initially uncolumnated pore volume, which ensures sufficient for the development of well injectivity. With the most common reservoir interval width of 4 m and porosity of 20%, the volume of water to fill this zone is 3.14 · 1.5 ² · 4 · 0.2 = 5.6 m ³ or rounded 6 m ³ . To ensure a more complete cleaning, the minimum required volume of water without clogging substances is increased by 2–3 times and brought to a maximum of 18 m ³ .

The flow rate of water without clogging substances depends on the emerging injectivity of the well and injection pressure. They create a maximum injection pressure of about 38-40 MPa, while the flow rate can be from 4.6 to 66 l / s. After breaking through the so-called "cork", i.e. the appearance of greater injectivity during continuous injection, proceed to the injection of the working agent at the newly set working pressure and flow rate.

Concrete example

An oil reservoir with the following characteristics is being developed: depth 1730 m, reservoir pressure 15 MPa, reservoir temperature 33 ° C, porosity 21.2, permeability 300 μm ² , oil saturation 78.2%, oil density 802 kg / m ³ , oil viscosity 3, 8 MPa · s, the average thickness of the formation is 4 m. Oil is taken from the reservoir through 20 producing wells and the working agent is pumped - wastewater, through 5 injection wells. Due to the mudding of the near-wellbore zone of one of the injection wells, the injectivity decreased from 70 m ³ / day at wellhead pressure of 12 MPa to 0. An increase in pressure to 20 MPa did not cause the appearance of injectivity.

Determine the amount of water needed to clean the near-wellbore zone, which is equal to 18 m ³ . At the wellhead, 3 pumping units of the CA 320 type are installed, all flow lines of the units are connected to a high pressure line drawn from the units to the tubing string in the well. The tubing string is equipped with a packer located above the interval of the productive formation. At the same time include 3 pump units. Increase injection pressure. At a pressure of 22 MPa, a well injectivity appears with a water flow rate of about 10 l / s. Continue to pump water directly from 3 pump units. At the same time, the injection pressure is set at 38 MPa at a flow rate of 95-100 l / s. Inject 18 m ^{3 of} water. 2 pumping units are turned off and the steady-state injection mode is evaluated, which turns out to be 120 m ³ / day at a mouth pressure of 12 MPa. To the high pressure line connected to the tubing string, a water conduit with formation water purified to the presence of suspended particulate matter of not more than 60 mg / l and an oil emulsion of not more than 50 mg / l is connected. After the appearance of pressure from the water line in the high pressure line, the pump unit is turned off, ensuring that there is no decrease in pressure and the flow rate of the working agent is injected into the injection well. Further injection of the working agent lead from the water conduit.

As a result, it is possible to increase the injectivity of the injection well and increase the reservoir pressure at the development site. Due to such works, downtime of injection wells is reduced throughout the reservoir, reservoir pressure increases, due to which it is possible to increase the oil recovery of the reservoir by 0.2%.

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

Claims (1)

A method of developing an oil deposit, including the selection of produced products through production wells, pumping a working agent at operating pressure and flow rate through injection wells, and increasing the injection pressure, characterized in that formation water is used as a working agent, purified to the presence of suspended solids of not more than 60 mg / l and oil emulsions of not more than 50 mg / l, injection pressure is increased when the injection rate is lost due to the suspension of the borehole near the injection well being solid suspended particles and an oil emulsion, water is pumped into the injection well without collimating substances at an elevated pressure, at which the well receives, in an amount sufficient to distribute the clogging substances in the formation and increase the injectivity of the injection well, and then, with continuous injection, they proceed to pump the working agent to newly set working pressure and flow.