RU2256070C1 - Method for extraction of oil deposit with non-homogenous collector - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: method includes drilling vertical extraction and force wells, extraction of oil through product wells, forcing of working agent through force wells. Low-penetrable areas of deposit are detected. Side horizontal shafts are drilled into low-penetrable deposit zones in well by washing away rock under high fluid pressure 15-20 MPa with forming of thin and long channels, channels pass through cut aperture in casing column with use of flexible shaft and with consideration of condition for full opening of fractured crack in low-penetrable deposit zone. Forcing of working agent into low-penetrable zones is performed through side horizontal shafts with forcing of oil into highly penetrable zones.

EFFECT: higher oil yield.

1 ex

Description

The invention relates to the oil industry and may find application in the development of an oil field with heterogeneous reservoirs and hard-to-recover oil reserves.

A known method of developing an oil reservoir, including water injection and oil extraction through horizontal wells, with mutually perpendicular placement of horizontal wells (see V. Erokhin and others. Experience and problems in the construction of horizontal wells. // Oil industry, No. 9, 1997, p. 32-35).

The disadvantages of this development method are as follows: the mutually perpendicular placement of horizontal wells in the presence of a layered heterogeneity of the formation causes a decrease in production rates of at least a couple of wells in oil, as well as premature flooding of the produced products; These shortcomings predetermine a decrease in the final oil recovery coefficient.

Closest to the invention in technical essence is a method of developing oil deposits with low permeable heterogeneous reservoirs, including drilling production and injection wells, pumping water into the formation to displace oil to production wells and conducting hydraulic fracturing. According to the invention, production and injection wells are drilled with horizontal shafts parallel to each other in plan, with the intersection of all low-permeability formations from the roof to the bottom of the reservoir. In the arch of the structure, vertical wells are drilled along the identified or suspected trace of natural fracturing with the faces of these wells located on the extrapolation lines in relation to the horizontal wells of the injection wells. After that, in these wells, hydraulic fracturing is performed. Water is injected into vertical wells, in which hydraulic fracturing has been carried out, and into horizontal injection wells. Water is injected with chemicals that prevent the swelling of clay particles and interlayers, and reagents for leveling the injectivity profile, which are injected into the injected water after flooding the produced products by 50-80% (RF Patent No. 2208140, class E 21 V 43/20, publ. 07/10/2003 - prototype).

The known method provides improved efficiency when taking into account layered heterogeneity of the formations, reduced volumes of associated water, increased oil recovery by increasing the impact on poorly drained and hard to recover oil reserves in low permeability reservoirs.

The disadvantage of this method is the low oil recovery of low-permeability zones of the oil reservoir.

The invention solves the problem of increasing oil recovery deposits.

The problem is solved in that in a method for developing an oil reservoir with an inhomogeneous reservoir, including drilling production and injection wells with horizontal lateral shafts, pumping water through injection wells, taking oil through production wells and conducting hydraulic fracturing in injection wells, according to the invention, lateral horizontal the trunks are drilled into the low-permeability zone of the reservoir in injection wells by erosion of the rock under high fluid pressure with the formation of thin and long channels, and hydraulic fracturing is carried out in a low permeability zone through drilled horizontal lateral shafts.

The features of the invention are:

1. drilling production and injection wells with horizontal lateral shafts;

2. water injection through injection wells;

3. the selection of oil through production wells;

4. hydraulic fracturing in injection wells;

5. drilling horizontal lateral shafts into the low-permeability zone of the reservoir in injection wells by erosion of the rock under high fluid pressure with the formation of thin and long channels;

6. conducting hydraulic fracturing in the low-permeability zone through the drilled horizontal lateral shafts.

Signs 1-4 are common with the prototype, signs 5, 6 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

When developing a heterogeneous oil reservoir, part of the reservoir’s reserves remains unreached. The development covers mainly highly permeable zones. For these reasons, the oil recovery of a heterogeneous oil reservoir is 10–20 points lower than that of a conventional reservoir. The proposed invention solves the problem of increasing oil recovery of a heterogeneous reservoir due to a more complete coverage of formations by impact, involving previously undeveloped zones into development. The problem is solved by the following set of operations.

When developing an oil reservoir, vertical production and injection wells are drilled and a reservoir is developed by taking oil through production wells and injecting a working agent through injection wells. In the course of development, low-permeability zones of the deposit that are not affected by exposure are identified. From existing injection wells, from production wells with a minimum flow rate or waterlogged production wells, lateral horizontal shafts are drilled into low-permeability zones of the reservoir.

To form a lateral horizontal wellbore in an existing well in the casing string at the depth of the reservoir, a side window is cut out and a future horizontal well is planned. A thin flexible pipe with a nozzle device at the end is inserted into the cut window. Under high pressure of the order of 15-20 MPa, erosion fluid is supplied through a flexible pipe and at the same time it is advanced into the formation along the resulting thin horizontal lateral trunk. Thus, in 20-30 minutes, it is possible to walk 100 m with a diameter of several millimeters. The flow rate of erosion fluid is 1-2 l / s.

After the formation of the lateral horizontal wellbore, the fracturing fluid with propant is injected selectively into the formed lateral horizontal wellbore under pressure of the fracturing. After that, the working agent is injected into low-permeability zones through horizontal lateral shafts and oil is displaced into highly permeable zones.

Concrete example

An oil reservoir of the Romashkinskoye field is being developed with the following characteristics: porosity - 18.4%, average permeability - 0.646 μm ² , oil saturation - 61.1%, absolute mark of water-oil contact - 1530 m, average oil-saturated thickness - 4 m, initial reservoir pressure - 16 MPa, reservoir temperature - 29 ° С, reservoir oil parameters: density - 930 kg / m ³ , viscosity - 46 MPa · s, saturation pressure - 1.8 MPa, gas content - 15.2 m ³ / t, sulfur content - 3 , 64%. After drilling on the site of the deposit, oil is taken through 24 producing wells and pumping a working agent through 7 injection wells. The distance between the wells is 400-500 m.

In the reservoir, a low-permeability zone of the reservoir with a permeability of the order of 0.3 μm ^{2 is} detected. Stop the nearest injection well. A cement bridge is installed in the well below the interval of the reservoir. A pipe with a starting sleeve at a depth of 500 m and with a bend at the end is lowered into the well in the interval of the reservoir. A flexible shaft with a ball mill is passed into the pipe. At the depth of the reservoir by means of a rotating flexible shaft and a ball mill, a hole is cut out in the casing of the well and the beginning of the horizontal well is formed by driving the latter several meters. The flexible shaft and ball mill are removed from the pipe. A flexible pipe with a nozzle apparatus at the end is lowered into the pipe and the nozzle apparatus is introduced into the horizontal barrel being formed. The erosion fluid, which is a 0.2% aqueous sulfonol solution, is pumped into the flexible tube. The leaching fluid is pumped under a pressure of 20 MPa with a flow rate of 1 l / s. A flexible pipe is gradually fed into the drilled hole, while the erosion fluid erodes the formation rock. As a result, in 20 minutes a horizontal lateral trunk is formed with a diameter of about 50 mm and a length of 100 m in the direction of the low-permeability zone.

A column of tubing with a packer placed above this interval is lowered into the horizontal borehole interval. Through the drilled horizontal lateral well into the low-permeability zone of the reservoir, fracturing fluid with propant is pumped under a fracturing pressure of 30 MPa. In this case, the fracture crack is almost completely opened in the low-permeability region, due to which the permeability of this zone increases.

Next, a working agent (produced water) is pumped into a drilled horizontal lateral shaft and oil is displaced into highly permeable zones.

As a result, the oil recovery of the deposit site increased by 1.5%.

The application of the proposed method will increase the recovery of deposits.

Claims (1)

A method for developing an oil reservoir with an inhomogeneous reservoir, including drilling production and injection wells with horizontal lateral shafts, pumping water through injection wells, taking oil through production wells and conducting hydraulic fracturing in injection wells, characterized in that the horizontal lateral shafts are drilled into a low permeability zone deposits from injection wells through a cut out side window by erosion of rock through a flexible pipe under a pressure of 15-20 MPa to form a tone and their long channels, and the hydraulic fracturing in the low permeability zone is carried out through the formed channels.