RU2247829C1 - Method for extraction of oil deposit - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes drilling of deposit according to row-wise non-even grid of wells with distance from force to extractive rows, greater than distance between extractive rows, pumping of displacing gent into force wells, extraction of product from product wells and transferring of displacing agent pumping front to extraction area. According to invention, transferring of displacing agent pumping front to extraction area is performed by drilling side horizontal shafts in all wells of force row and directed towards extractive row by beds ad zones with most remainder oil saturation level. Then among these wells are singled out, horizontal shafts of which pass along beds and areas with lesser oil saturation level. Pumping of displacing agent is restarted, and other wells are transferred to product category. These wells are operated with face pressures lower than saturation pressure until reaching 98% water saturation level. After that pumping of displacing agent is restarted along all other wells of force row. During that, rows of extractive wells are operated in normal mode.

EFFECT: higher efficiency.

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Description

The invention relates to the oil industry, in particular to methods for developing heterogeneous oil fields, and can be used to intensify the development of heterogeneous oil fields at various stages of development, with any grid of wells in the case when the designed development system does not provide maintenance of reservoir pressure at the design level.

A known method of developing a multilayer heterogeneous oil field [see RU patent No. 1606687 from 11.30.88 g, class E 21 B 43/20, publ. BI No. 42 of November 15, 1990], including the placement of wells in the main formation, the injection of water into the main and intermittent formations through injection wells and oil production through the production wells of the main and interrupted formations, followed by the transfer of production wells at the final stage for water injection to intermittent formations, while the transfer to injection of production wells at the final stage is carried out as they are flooded along the main formation in the presence of at least one intermittent formation in the section of these wells, and the transfer is producing x wells for pumping produced along the perimeter portion of the maximum number of exposed layers.

The advantage of this method is that the development efficiency is increased by increasing the coverage of the formation by flooding.

However, a significant part of the recoverable reserves remains not involved in development, since with a 3-row development system, the zones between the injection and production rows remain not involved in the development.

The closest in technical essence to the proposed one is a method of developing a heterogeneous oil field, including drilling it along a non-uniform grid with a distance from the injection to the production rows exceeding the distance between the production rows, injection of the displacing agent into the injection wells, selection of production from the production wells, shutting down production wells of the first rows when watering is below the maximum profitable and transfer of the front of injection of the displacing agent into the first rows of production wells [cm. book of A. Krylov "The state of theoretical work on designing the development of oil fields and tasks to improve these works. Sat. Experience in the development of oil fields." Gostoptekhizdat, 1957, p.116-139].

The approach of injection to the selection zone leads to an increase in current withdrawals (≈8%) and a reduction in development time (≈23%). The known method gives positive results with a very high degree of water cut in the first production rows (above 98%), which occurs at a late stage of development.

However, in practice, there is often a need to strengthen the impact system at an earlier stage of development due to the high rate of reservoir pressure drop, which affects the technical and economic performance of the development.

In addition, part of the recoverable reserves (3-5%) nevertheless remains not involved in the development due to the loss of oil reserves located in the zone between the injection and first production rows of wells due to incomplete flushing of the zone at the time of injection transfer.

The technical task of the proposed method for the development of heterogeneous oil fields is to increase the development efficiency due to the additional development of the zone between the injection and first production rows of wells and the intensification of oil production in the tightening rows due to the approach of the injection front to the selection zone without violating the existing flow kinematics and maintaining reservoir pressure at the design level .

The problem is solved by the described method, including drilling a field along a non-uniform row of wells with a distance from the injection to the production rows exceeding the distance between the production rows, pumping the displacing agent into the injection wells, selecting products from the producers and transferring the front of injection of the displacing agent to the selection zone.

What is new is that the front of injection of the displacing agent is transferred to the selection zone by drilling horizontal lateral shafts in all wells of the injection row and directed towards the producing row through the formations and zones with the highest residual oil saturation, then wells are separated from them, the horizontal shafts of which pass through reservoirs and zones with less oil saturation, and resume the injection of the displacing agent, and the remaining wells are transferred to the category of producing and exploit them at bottomhole pressure x below the saturation pressure until the maximum cost-effective water content, and then resuming download displacement agent for all injection wells series, wherein the series of production wells in normal mode is operated.

The mechanism of processes occurring in the reservoir when using the proposed method is as follows.

According to the kinematics of the flows, the zone between the injection and the first producing rows of wells can be divided into two parts. The first is from the bottom of the injection to the end of the lateral horizontal shafts, where the discharge front changes its direction by 90 °. The second - approximately from the end of the lateral horizontal trunks to the first production rows. In this part, the kinematics of the flows is not disturbed and the contraction of the oil contraction contraction zone does not occur. The crowding out will occur from the less oil saturated to the more oil saturated zone, thereby eliminating oil displacement into the washed zone. Due to the approach of the injection front to the selection zone, the filtration rate increases, therefore, the coverage by displacement and the amount of oil recovery increase. In this case, the discharge pressure is set from the condition of a given compensation for the selection of liquid by injection of water, i.e. from the condition of maintaining reservoir pressure at the design level. Further intensification of the waterflooding system is carried out through the resumption of injection into wells transferred to the selection of products after reaching or maximum profitable water cut.

The proposed method is effective both at an early stage of development (with a relatively low degree of water cut) and at a later stage (with a degree of water cut of the first production rows above 98%).

Of the available sources of patent and scientific literature, the claimed combination of distinctive features is not known. Therefore, the proposed method meets the criteria of the invention "inventive step".

The method is carried out in the following sequence.

In an oil field represented by heterogeneous reservoirs drilled along a non-uniform line of wells with a distance from the injection to the production rows exceeding the distance between the production rows, if the designed development system does not provide reservoir pressure at the design level, in the injection wells at any development stages drill horizontal lateral shafts directed towards producing wells. Horizontal trunks are carried out in zones with the highest residual oil saturation for a length of 1/3 to 2/3 of the distance between the injection and the first production rows. The displacing agent is injected into the horizontal lateral wells of the injection row with the lowest residual oil saturation, the rest are transferred to the production category and operated at bottomhole pressures below the saturation pressure until the maximum profitable water cut is reached (98%). Then these wells are again transferred to the category of injection wells, and the injection of the displacing agent is resumed in them. Rows of production wells are operated as usual.

An example of a specific implementation.

An oil deposit in terrigenous sediments with an area of 9 km ² with balance reserves of 16,728 thousand tons was drilled along a three-row uneven grid of wells with a distance of 1,500 m from the injection to production rows and 500 m between the production rows and between wells. 20 wells were drilled. , including 12 mining and 8 injection. The density of the well network was 45 ha / well.

The initial reservoir pressure on the deposits is 19 MPa, a temperature of 40 ° C, and a gas saturation pressure of 8.75 MPa. The viscosity of oil under reservoir conditions is 3.34 mPa · s, water 1.94 mPa · s, oil density 862 kg / m ³ , gas factor 90.6 m ³ / t. The bottomhole pressure in production wells was maintained at the saturation pressure level and amounted to 8.8 MPa, in injection wells - 19.0 MPa.

With water cuts in the production of the first rows of producing wells above 98%, the injection wells were stopped and sidetracks were drilled in them in the direction of the production zones on both sides with a length of 1000 m. They resumed pumping the displacing agent into the wells of the injection row, and the rest were transferred to the category of production and operated with bottom-hole pressures P ₃ = 0.7 P _us until the water cut is higher than 98%, after which they are again transferred to the category of injection and the injection of displacing agent is resumed.

The expected oil production for the entire development period amounted to 7260 thousand tons with an oil recovery factor of 0.434 units (based on the prototype, respectively, 6708 thousand tons and 0.401 units).

The technical and economic efficiency of the proposed method for the development of a heterogeneous oil field consists of increasing oil recovery in the zone from the injection row to the first rows of production wells, as well as due to the possibility of applying it at any stage of development, with any grid of wells.

Claims (1)

A method for developing a heterogeneous oil field, including drilling a field along a non-uniform line of wells with a distance from the injection to the production rows exceeding the distance between the production rows, pumping the displacing agent into the injection wells, taking products from the producing wells and transferring the front of injection of the displacing agent to the selection zone, characterized in that the front of injection of the displacing agent is transferred to the selection zone by drilling horizontal sidetracks in all wells the veins of the injection row and directed towards the production row through the strata and zones with the highest residual oil saturation, then wells are distinguished from them, the horizontal trunks of which pass through the strata and zones with lower oil saturation and resume the injection of the displacing agent, and the remaining wells are transferred to the category of producing and exploiting at bottomhole pressures below saturation pressure until 98% water cut is reached, after which pumping of the displacing agent into all wells of the injection row is resumed , The series of production wells in normal mode is operated.