RU2237804C1 - Method for extracting deposits of highly viscous oils and bitumens by slanted-horizontal wells - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes drilling wells according to certain mesh schematics, feeding displacing agent through force wells and extracting bed fluids through product wells. Drilling of wells is performed according to radial mesh. Force wells are placed along productive bed closer to upper limit of bed along most penetrable seams. Extracting wells are placed closer to lower limit of bed. At starting stage of extraction in all wells thermo-cyclic treatment of bed is performed with steam stimulation. Then, extraction of bed fluids is started through product wells with area effect on a bed through force wells.

EFFECT: higher productiveness of bed due to heat carrier treatment, lower areas of terrain used for wells drilling and later operation, better ecological factor of technological process.

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Description

The invention relates to the oil industry, in particular to the development of oil fields, namely, deposits of high viscosity oils and bitumen using heat in combination with inclined horizontal wells.

A known method of producing hydrocarbons from an underground reservoir using a network of horizontal parallel wells (see US patent No. 5273111, E 21 B 43/24, 43/30, 1995), of which some of the wells are drilled with shafts closer to the roof, and part - to the bottom of the reservoir. Moreover, the upper wells should be at least two with one lower well located between the two upper ones. In the upper (injection) wells, fluid is injected into the formation, which ensures the displacement of hydrocarbons into the lower production well. Hydrocarbons are extracted from one or several horizontal wells at a total speed exceeding the total rate of fluid injection into the upper horizontal wells.

The application of this method of hydrocarbon production provides a relatively uniform thickness production of the reservoir.

The disadvantage of this method is the need for a large number of wells for the implementation and allocation of significant land areas for the construction of wells on such a grid and their subsequent operation, leading to their environmental pollution.

There is also known a method of using horizontal wells (horizontal wells) located in radial directions to intensify fluid flow from a formation (see Russian patent No. 2130541, MKP6 E 21 B 43/25, E 21 C 41/24, 1999). To implement the method, the main wellbore is drilled with an increase in its diameter in the lower part and additional horizontal horizontal shafts of small diameter are drilled from 0.036 to 0.059 m in radial directions. Enhanced oil recovery is ensured by expanding the radius of action on the reservoir.

The method provides a relatively uniform development of the reservoir.

However, it relates to mine methods, has significant limitations on the lithological composition of the reservoir, and is expensive.

The closest in technical essence and the achieved result to the proposed method for the development of highly viscous oil (BH) and bitumen oil fields with inclined horizontal wells is a hydrocarbon production method with horizontal well placement on a triangular grid (see US Pat. No. 4,850,429, E 21 B 43/24). To implement the method, at least five horizontal wells are drilled so that the first, second and third wells are located on a triangular grid. The first well is drilled at the upper boundary of the interval, and the second and third are at the lower boundary on opposite sides relative to the first well. The third, fourth and fifth wells form a second triangle located next to the first. A fourth well is located near the upper boundary of the interval, so that the third well is between the second and fourth, and the fourth is between the third and fifth. A displacement fluid is injected into the formation and formation fluid is produced through the first and fourth wells. After a certain period of time, the first and fourth wells are closed and the displacing fluid is pumped into the second and fifth wells, producing formation fluid through the third well.

The method provides uniform reservoir development within the area covered by the wells.

However, at the same time, the coverage of the production zone by area is not large, since the relative position of the mouths of all five wells and their horizontal shafts are interconnected in a limited space by a triangular grid, for which the well bore 3 is interfaced. At the same time, wells are drilled from three clusters, including from the first bush - wells 2 and from the third bush - wells 3, 4.

The technical task of the invention is to increase the efficiency of the development of high-viscosity oil and natural bitumen deposits by providing the maximum possible coverage area for producing a productive formation with the least number of wells with a more environmentally friendly way of conducting work during the construction and operation of wells.

This goal is achieved by the described method of developing high-viscosity oil and natural bitumen deposits by inclined horizontal wells, including drilling wells on a specific grid, injecting a displacing agent through injection wells and selecting reservoir fluids through production wells.

What is new is that the wells are drilled along a radial grid, so that the injection wells are located in the productive formation closer to the upper boundary of the formation along the most permeable layers, and production wells are located closer to the lower boundary of the formation, and at the initial stage of development, all wells are thermocycled reservoir with steam stimulation with the subsequent transition to the selection of reservoir fluids through production wells with areal exposure to the reservoir through injection wells.

From the available sources of patent and scientific and technical literature, we do not know the claimed combination of distinctive features. Therefore, the proposed method meets the criterion of "inventive step".

Figure 1 presents a vertical section of the field and deviated horizontal wells;

figure 2 is a horizontal section of the field and deviated horizontal wells.

The method is carried out in the following sequence (combined with an example of a specific implementation).

In the natural bitumen deposit, represented by heterogeneous formations 8-10 m thick with a temperature of 7.5-8.5 ° C, a pressure of 0.45-0.55 MPa, a porosity of 27-35%, and a permeability of 0.5-0.7 microns ² , with a viscosity of 3000 mPa · s, inclined horizontal wells No. 1-6 are drilled from one well in radial directions, of which conventionally horizontal shafts with a length of about 100 m of injection wells 1, 3, 5 are located closer to the upper boundary of the productive formation at the most permeable seams ⁽² permeability 0.9-1.2 microns) and production wells 2, 4, 6 - toward the lower end etc. reductive formation (see. the attached Figs.). Casing strings with a diameter of 168.3 mm are lowered into the wells and cemented along the entire length, sections of all conventionally horizontal wellbores are perforated in the interval of the reservoir. Inside the casing strings, tubing has been installed, equipped with centralizers, through which 150–200 tons of coolant is pumped into all wells to provide steam stimulation of the formation (overheated steam) per cycle under pressure up to 2.5 MPa, which is higher the in-situ pressure of the reservoir, but below the fracture pressure, and in the annular space, air is simultaneously pumped in the amount of 500-600 m ³ / t of steam to prevent overheating of the wellhead and to maintain the pressure and temperature of the reservoir. After the steam is injected into the formation, exposure (stop) is carried out for 2-3 days to realize the temperature of the steam for heating the formation, followed by the selection of the heated volume of oil. To ensure steam stimulation of the reservoir, at least three of the above cycles are carried out.

After steam stimulation of the reservoir in wells No. 1-6, further injection of the coolant was continued only into injection wells No. 1, 3, 5, and from the producing wells 2, 4, 6, they began the constant selection of bitumen oil.

Field trials have shown that for three cycles of steam injection, the formation is preheated, which allows subsequent steam injection into injection wells (wells 1, 3, 5) and the selection of fluid from production wells (wells 2, 4, 6). Subsequent injection of steam ensures uniform heating of the formation in thickness within the limits determined by the radially-located horizontal sections of all inclined-horizontal wells.

The advantages of the proposed method compared to the prototype are:

- at least a three-fold increase in the coverage area of the reservoir by treatment with the coolant due to the radial arrangement of horizontal sections of wellbores with the location of the mouths of all wells on one well;

- a three-fold decrease in land allotment for well construction and their subsequent operation, which provides a more environmentally friendly way to develop a field.

Claims (1)

A method for developing highly viscous oil and bitumen deposits with inclined horizontal wells, including drilling wells on a specific grid, injecting a displacing agent through injection wells and selecting formation fluids through production wells, characterized in that the wells are drilled along a radial grid, so that the injection wells are arranged along the productive formation is closer to the upper boundary of the formation along the most permeable layers, and the producing ones are closer to the lower boundary of the formation, and at the initial stage Development in all wells conducts thermal cyclic treatment of the formation with steam stimulation, followed by the transition to the selection of formation fluids through production wells with areal exposure to the formation through injection wells.

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