RU2386801C1 - Method of high-viscosity oil pool development with usage of in-situ combustion - Google Patents

Abstract

FIELD: oil-and-gas production.

SUBSTANCE: method includes pumping of oxidising agent through injection wells, arrangement of in-situ combustion and withdrawal of products through producing wells. Into injection wells there is additionally injected in parallel to oxidising agent fuel. In the capacity of producing there are used wells with horizontal bore in suspended part of stratum, and in the capacity of injection wells - vertical, which are located at specific distance from end part of horizontal bore and from each other, excluding cracking of fuel or oxidising agents into other wells in the direction of continuation of horizontal bore. Fuel is pumped through vertical wells, close to horizontal bore, and oxidising agent-through remote. Bottom-hole pressure of fuel is implemented at pressure higher than pressure of opening of vertical cracks, and oxidising agent - higher than pressure of pumping fuel.

EFFECT: effectiveness increase of process displacement of high-viscosity oil by means of increasing of reservoir coverage of impact ensured sequential treatment of all stratum with holding of high permeability.

2 cl, 1 ex, 2 dwg, 1 tbl

Description

The invention relates to the oil industry and may find application in the development of a highly viscous oil field.

There is a method of developing an oil bitumen deposit (RF Patent No. 2287677, IPC E21B 43/24, publ. 2006.11.20), including wiring two horizontal shafts in the formation parallel to each other and injecting steam into the upper injection well and selecting products from the lower producing well.

The main disadvantage of this method is the low efficiency of the process, especially in thin formations due to large heat losses.

Closest to the proposed invention in technical essence is a method of developing deposits of highly viscous oil or bitumen (Application for invention of the Russian Federation No. 97107687/03, published. 1999.04.27 - prototype), including the injection of an oxidizer through an injection well, the creation of a straight-through combustion front, control over it the promotion and production of formation fluids through production wells. After the creation of the combustion front, the boundary of the influence of the high-temperature zone moving through the formation is determined, after which a production well that is not covered by heat is selected, through which the combustion gases are evacuated from the formation through the annulus, while the gas is evacuated until the formation temperature at the bottom of the production well increases by 10- 15 ° C.

The main disadvantage of this method is the low efficiency of the unregulated heating process. In addition, in the absence of a highly permeable formation and a weak hydrodynamic connection between wells, heating the formation is not possible. Oil recovery is reduced.

An object of the present invention is to enhance oil recovery, i.e. the efficiency of the process of displacing high-viscosity oil, including by increasing the coverage of the formation with an impact agent due to the consistent development of the entire formation while maintaining high permeability.

High-viscosity oils mean well production with a density of more than 0.870 kg / cm ³ , that is, they include heavy and bituminous oils (see GOST 51858-2002).

The problem is solved by the method of developing a highly viscous oil field using in-situ combustion, including the injection of an oxidizing agent through injection wells, the organization of in-situ combustion, and the selection of products through production wells.

What is new is that fuel is additionally injected into the injection wells parallel to the oxidizing agent, while the wells with a horizontal wellbore in the bottom of the formation are used as production wells, and vertical ones that are placed at a certain distance from the end of the horizontal well and from each other are used as production wells. friend, excluding the breakthrough of fuel or oxidizer into other wells, in the direction of extension of the horizontal wellbore, and the fuel is pumped through vertical wells, near ue to the horizontal well, and the oxidant - through remote, the bottomhole pressure fuel injection is performed at a pressure above the cracking pressure of the vertical and oxidizer - above the fuel injection pressure.

New is that the injection of fuel and oxidizing agent alternate with the injection of water in volumes that allow the maintenance of reservoir combustion.

Figure 1 shows a section in the horizontal plane of the reservoir: 1 - a horizontal well, 2 - a vertical well for injecting fuel, 3 - a vertical well for injecting air, 4 - a zone of advancement of a heated well medium, 5 - a heating zone, 6 - a combustion zone , 7 - productive layer.

Figure 2 shows a vertical section of the reservoir - 7.

The development of high-viscosity oil fields by in-situ combustion is accompanied by a low efficiency of the unregulated heating process, and with low permeability of the formation and weak hydrodynamic connection between the wells, heating of the formation becomes practically impossible. In this case, oil recovery is significantly reduced. The proposed method solves the problem of increasing the efficiency of the process of displacement of highly viscous oil, i.e. enhanced oil recovery by increasing the coverage of the formation with an impact agent due to the sequential development of the entire formation while maintaining high permeability.

The method is implemented as follows.

In a field with high-viscosity oil, production wells with a horizontal wellbore 1 are drilled along the grid. The horizontal section 1 is drilled in the bottom of the productive formation 7. In the end of each horizontal well 1, at a distance (not less than 5 m), a vertical injection well 2 is drilled for injection into the reservoir of fuel, for example, hydrocarbon gas, associated gas, heating oil, etc. At a certain distance, excluding a breakthrough (at least 5 m) from the drilled vertical injection well 2, another vertical injection well is drilled to inject the oxidizing agent 3 into the reservoir 7.

After heating with the steam-moving installation of the bottom-hole part of the formation 2, the required amount of fuel is injected, then the oxidizer is injected (oxygen, air), and the fuel is ignited into the end part of the horizontal well under the design pressure and a combustion zone 6 is created in the formation 7, and the oxidizer is injected at a pressure higher than the fuel injection pressure to create a uniform heating zone 5 towards the horizontal barrel 1, while simultaneously observing the injection of oxidizer and fuel at a pressure higher than the pressure openings of vertical cracks in the productive formation 7 to maintain high permeability of the formation.

The air contains nitrogen, which is not chemically involved in the combustion reactions, but is present in the combustion zone. Since the air contains 21 vol.% Oxygen and 79 vol.% Nitrogen, during combustion of air, 79: 21 = 3.76 volumes of nitrogen fall on one volume of oxygen.

For example, the equation of the combustion reaction of natural gas (methane) in air can be written as follows:

CH ₄ + 2O ₂ + 2 · 3.76N ₂ = CO ₂ + H ₂ O + 2 · 3.76N ₂ .

The combustion process is organized according to this equation so that in the combustion zone 1 m ^{3 of} combustible gas accounts for 9.5 m ^{3 of} air, which contains the required 2 m ^{3 of} oxygen. A combustible mixture (or part thereof) is provided with a heat pulse of sufficient power to start a combustion reaction. As a result of complete combustion of 1 m ^{3 of} methane, 36,000 kJ of heat are released and more than 10.5 m ³ of combustion products (a mixture of carbon dioxide, water vapor and nitrogen) are formed. The ignition temperature of methane in air is from 545 to 850 ° C. Since formation water is contained in the formation, during the combustion process the water turns into steam, forming a steam chamber in the heating zone. Combustion products created steam moves through the reservoir, heating the borehole medium, forming a zone of heating the borehole medium. As you progress through the reservoir, various zones are formed: a heated wellbore environment, heating and combustion. Since the heated well medium and nitrogen have a specific gravity less than the well production, a heating zone 5 is formed in the roofing part of the formation 7. Due to gravitational forces, the production of the well flows into the bottom of the formation 7 and is taken to the surface in a horizontal well 1.

The created localized combustion zone 6 allows heat to be generated in the reservoir, which allows for displacement both in the section and in the area; the sequence of development of the reservoir 7 occurs from top to bottom and through the reservoir 7 by supplying fuel and an oxidizing agent to the corresponding wells 2 and 3 in the end part of the trunk, followed by selection from the horizontal trunk 1.

Injection into the vertical wells 2 nearest to horizontal well 1 of fuel 2, and in remote 3 oxidizer injections, it is possible to alternate with water injection in volumes that allow maintaining controlled formation combustion and increasing the steam chamber for greater reservoir coverage.

This helps to reduce the cost of development without reducing oil recovery for a long time due to the opening of cracks and a greater coverage of heating the formation.

Concrete example

They are developing a site in the Ashalchinskoye field of the Republic of Tatarstan. In the Ashalchinskoye field with highly viscous oil at a depth of 90 m, heterogeneous formations are 8-15 m thick with a temperature of 8 ° C, a pressure of 0.5 MPa, a water saturation of 0.34 units, a porosity of 30%, and a permeability of 0.365 μm ² , saturated with oil having a density of 956 kg / m ³ and a viscosity of 10206 MPa · s. Drill a horizontal well. Drilling a horizontal section with a length of 75 m is carried out in the plantar of the reservoir (Fig.1-2). At a distance of 10 m and 20 m from the end of the horizontal section of the producing well 1, vertical injection wells 2 and 3 are placed, respectively, which excludes the breakthrough of injected fuel and oxidizer in a vertical projection of the horizontal wellbore direction.

To warm the formation, steam is injected with a temperature of 320 ° C into well 2. Then methane is pumped into the well to create a bottomhole pressure of 1.2 MPa. Air is pumped through well 3 to create a bottomhole pressure of 1.6 MPa to ignite the fuel. Air and methane are injected at a pressure above the opening pressure of vertical cracks.

Methane is injected at a rate of 10 thousand m ³ per day, and air - 95 thousand m ³ per day.

Oil recovery amounted to 65% (which is higher than similar methods). After water injection through injection wells, oil recovery continues.

Due to the consistent development of the entire interval, the reservoir coverage is increased by the impact and all sections of the reservoir are uniformly produced around the well and, as a result, oil recovery is significantly increased. Comparison of the effectiveness of the proposed method are shown in table 1.

Table 1 Comparison of the technical and economic effectiveness of the proposed method Indicators Prototype The proposed method Balance reserves, thousand tons 9 9 The average oil flow rate, t / day one thirty The coefficient of coverage of the reservoir impact, unit 0.10 0.90 The coverage coefficient of the formation by water flooding, d.ed. 0.60 0.90 The displacement factor, unit 0.50 0.80 Oil recovery ratio, unit 0,03 0.65 Recoverable oil reserves, thousand tons 0.3 5.8 Additional oil production, thousand tons - 162.5 The value of additional oil production, million rubles - 94 Costs, million rubles - 50,0 Profit, million rubles - 44

From table 1 it follows that the application of the proposed method leads to additional oil production, i.e. to increase oil recovery.

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

Claims (2)

1. A method of developing a highly viscous oil field using in-situ combustion, including injecting an oxidizing agent through injection wells, organizing in-situ combustion and selecting products through production wells, characterized in that fuel is additionally injected into the injection wells in parallel with the oxidizing agent, while wells using horizontal trunk in the bottom of the formation, and as injection wells - vertical, which are placed on a certain distances from the end of the horizontal well and from each other, which excludes the breakthrough of fuel or oxidizer into other wells, in the direction of extension of the horizontal well, whereby the fuel is pumped through vertical wells closest to the horizontal well, and the oxidizer through remote, while the bottomhole fuel injection pressure produced at a pressure above the opening pressure of vertical cracks, and the oxidizing agent is higher than the fuel injection pressure. 2. The method according to claim 1, characterized in that the injection of fuel and oxidizing agent alternate with the injection of water in volumes that allow the maintenance of reservoir combustion.

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