RU2256069C1 - Method for extracting oil deposit - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: method includes drilling of vertical extracting and force wells, extraction of oil through product wells, forcing of working agent through force wells. Low-penetrable deposit areas are detected. Side horizontal shafts are drilled into low-penetrable deposit zones at decreased pressure in well by washing rock under high pressure of fluid with forming of thin and long channels. Washing of rock at end stage is performed using solution of hydrochloric acid. Working agent is forced into low-penetrable zones through side horizontal shafts with forcing of oil to highly penetrable zones. Horizontal shafts are driven under pressure in well for 5-10% lower than hydrostatic and through cut side port in casing column with use of flexible pipe. Washing fluid is fed under pressure 15÷20 MPa.

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 selective waterflooding of an oil field, including drilling production and injection wells according to a geometrically correct grid of their placement, identifying areas of reduced reservoir pressure and drilling there injection (injection) wells in order to maintain reservoir pressure (see Fazlyev R.T. M .: Nedra, 1979).

The disadvantages of the known technical solutions are the accelerated dynamics of irrigation of produced products, significant volumes of produced water, reduced value of the final oil recovery coefficient, significant capital and operating costs for developing the field.

Closest to the invention, the technical essence is a method of developing an oil field with heterogeneous reservoirs and hard-to-recover oil reserves, including drilling vertical wells along a rarefied grid to further investigate the heterogeneity of reservoir properties of the formation and extracting oil from drilled wells under an elastic filtration regime. According to the invention, according to the geological field analysis and well operation results, low-permeability zones with hard-to-recover oil reserves are identified. A water flooding system is formed by pumping water into low-permeability zones and displacing oil from there into highly permeable zones. For this, most injection well shafts for water injection are located in low-permeability zones by drilling horizontal injection wells during sidetracking of horizontal horizontal shafts, mainly from low-production vertical production wells. The ratio of the number of producing wells and the number of injection wells is less than one. Water injection compensates for the volumes of oil, gas and water produced. Maintain reservoir pressure at a given level (RF patent No. 2215128, class E 21 B 43/16, publ. 2003.10.27 - prototype).

The known method provides a reduction in the volume of associated water, an increase in the oil recovery coefficient by enhancing the effect on poorly drained and hard to recover oil reserves in low permeability reservoirs.

The disadvantage of this method is the relatively low injectivity of horizontal wellbores drilled into low-permeability zones of the carbonate reservoir, and therefore, the relatively low oil recovery of low-permeability zones of the oil reservoir with a carbonate reservoir.

The invention solves the problem of increasing oil recovery deposits.

The problem is solved in that in a method for developing an oil deposit with a carbonate reservoir, including drilling vertical production and injection wells, taking oil through production wells, injecting a working agent through injection wells, identifying low-permeability zones of the reservoir, drilling lateral horizontal shafts into low-permeability zones of the reservoir, injecting working agent in low-permeability zones through horizontal lateral shafts and oil displacement in high-permeability zones, according to the invention, lateral horizontal shafts The rocks are performed under reduced pressure in the well by erosion of the rock under high fluid pressure with the formation of thin and long channels into the low-permeability zone of the reservoir and erosion of the rock at the final stage with a hydrochloric acid solution.

The features of the invention are:

1. drilling of vertical production and injection wells;

2. the selection of oil through production wells;

3. pumping a working agent through injection wells;

4. identification of low-permeability zones of the reservoir;

5. drilling of lateral horizontal shafts into low-permeability zones of the reservoir;

6. pumping a working agent into low-permeability zones through horizontal lateral shafts and oil displacement into high-permeability zones;

7. the implementation of the horizontal lateral shafts under reduced pressure in the well;

8. the same erosion of the rock under high fluid pressure with the formation of thin and long channels into the low-permeability zone of the reservoir;

9. the same erosion of the rock at the final stage with a solution of hydrochloric acid.

Signs 1-6 are common with the prototype, signs 7-9 are the essential distinguishing features of the invention.

SUMMARY OF THE INVENTION

When developing an inhomogeneous oil reservoir with a carbonate 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 in a heterogeneous reservoir with a carbonate 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. Lateral horizontal shafts are performed under reduced pressure in the well.

Low pressure in the well is created in various ways. One of the most common is the air supply to the tubing string and its passage through the start-up sleeve into the annulus, where a gas-gas mixture is created with a density lower than the density of the well fluid.

Another possible method is the multiple swabbing of the tubing string with fluid withdrawal at the wellhead and the establishment of a lowered fluid column in the well. Based on the fact that the static fluid level is restored over time and gradually, at the time of operations in the well there will be a reduced pressure, accompanied by the influx of reservoir fluids through the formed lateral horizontal shafts.

To create a reduced pressure in the well, it is possible to connect the annulus of the well to the vacuum cavity of the jet pump operating at the wellhead. The use of other methods is not excluded. The optimum is to reduce the pressure in the well by 5-10% of hydrostatic.

Lateral horizontal shafts are performed under reduced pressure in the well by erosion of the rock under high pressure erosion fluid. Water or water mixed with a surfactant or a mixture of surfactants can be used as a flushing fluid.

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 pass 100 m with a diameter of several mm. The flow rate of erosion fluid is 1-2 l / s. At the final stage, in the last 2-5 minutes, the erosion fluid is changed to a 5-20% solution of hydrochloric acid and the rock is eroded with a simultaneous chemical effect on the carbonate rock. Due to this, the pore size in the walls of a thin lateral horizontal wellbore increases, erosion fluid is washed out of the pores, conditions are provided for increasing well productivity, reservoir coverage by impact, and therefore, for increasing oil recovery in the reservoir.

The effect of the erosion fluid occurs at reduced pressure in the well and, consequently, with the active flow of formation fluids through the resulting horizontal wellbore into the well. As a result of this, the walls of the horizontal trunk and the bottomhole zone do not become clogged with clogging substances, the resulting open (uncased) trunk is completely ready to receive the displacing working agent. The use of low-cost horizontal sidetrack drilling technology allows the entire process to be carried out at reduced pressure in the well. During the penetration of the lateral horizontal wellbore, the volume of pumped erosion fluid does not have time to fill the entire well and equalize the pressure in the well.

After the formation of the lateral horizontal trunk, the working agent is injected into the low-permeability zones through the horizontal lateral shafts and oil is displaced into the 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 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. Air is pumped into the pipe before it breaks into the start-up sleeve and the annulus of the well is filled. Well pressure is reduced from 16 to 13 MPa. 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. In the last 5 minutes, a 12% aqueous hydrochloric acid solution is pumped through a flexible pipe.

A working agent (produced water) is pumped through a lateral horizontal wellbore drilled in this way into the low-permeability zone of the reservoir and oil is displaced into highly-permeable zones.

As a result, the oil recovery of the deposit site increased by 1.6%.

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

Claims (1)

A method of developing an oil deposit, including drilling vertical production and injection wells, oil selection through production wells, pumping a working agent through injection wells, identifying low permeability zones of a reservoir, drilling horizontal lateral shafts into low permeability zones of a reservoir, pumping a working agent into low permeability zones through horizontal lateral shafts and oil displacement into high-permeability zones, characterized in that the lateral horizontal trunks perform in a low-permeability zone of the reservoir at manure in the well by 5-10% lower than hydrostatic pressure by erosion of the rock under a fluid pressure of 15-20 MPa with the formation of thin and long channels from the cut-out casing window, provided these channels are penetrated by a flexible pipe during the time when the volume of erosion fluid does not have time to fill the entire well and equalize the pressure in it, while the erosion of the rock at the final stage is carried out with a solution of hydrochloric acid.