RU2754140C1 - Method for developing deposits of extra-heavy oil or natural bitumen - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to the oil industry, in particular to steam-thermal methods for the production of high-viscosity oil and natural bitumen. The method includes drilling a horizontal production well near the bottom of the formation, drilling a horizontal injection well above a horizontal production well parallel to it in a vertical plane at a minimum distance from the roof of the formation, pumping steam into the injection well and taking liquid from the production well. To create a hydrodynamic connection between the producing and injection wells, steam-cyclic well treatments are carried out. When steam is injected into the upper well, liquid is taken from the lower well, and when liquid is taken from the upper well, steam is injected into the lower well, the moment of establishing a hydrodynamic connection between the injection and production wells is fixed, and steam is continuously pumped into the upper injection well and products are taken from the lower production well until the end of the period of production of the displacement element.

EFFECT: oil production increases, the amount of produced water decreases, the steam-oil ratio decreases during the development of deposits, the rate of production of deposits increases.

4 cl, 3 dwg

Description

The invention relates to the oil industry and is aimed at increasing the technological efficiency of the development of deposits of heavy oil or natural bitumen by injecting water vapor into the deposit.

There is a known method for the development of heavy oil or natural bitumen deposits, including drilling a horizontal production well near the bottom of the formation, drilling above it in the same vertical plane parallel to the production well of an injection horizontal well at a distance that makes it possible to create a hydrodynamic connection between the wells to initiate the drainage process, steam injection into the injection well and withdrawal of fluid from the production well (RU 2643056 C1, publ. 30.01.2018). The method also drills an additional injection well above the horizontal injection well parallel to it in the vertical plane at a minimum distance from the formation top, taking into account the technical ability to maintain the well trajectory without drilling through the overlying rocks, fix the moment of establishing a hydrodynamic connection between the upper injection and production wells, and then stop steam injection into the lower injection well and start to pump steam into the upper injection well before the completion of the period of the expulsion element.

The disadvantage of this method is the drilling of an additional well, accompanied by a significant increase in capital and operating costs, significant time costs for creating a hydrodynamic connection between the lower production and injection wells by heating the formation. In addition, the lower pair of wells (production and injection) are located at an extremely small distance of about 5 m from each other, since with a greater distance between the wells, the period of establishing the primary hydrodynamic connection is significantly lengthened. FIG. 2 shows the dependence of the heating time by conductive heat transfer through the circulation of water vapor along the shafts of the production and lower injection wells, from which it can be seen that at a distance of 5 m it takes 6 months to establish a hydrodynamic connection, with a distance between wells of 10 m, the time of establishing a hydrodynamic connection is already 3.3 years , and at 20 m - 19.4 years. Therefore, in practice, in practice, the distance between the production and injection wells during steam-gravity drainage of the formation does not exceed 5-6 m, which leads to the impossibility of creating significant repression on the formation and achieving a high value of injection wells injectivity due to the risk of direct breakthrough of the injected steam into the lower production well. In this regard, the creation of a hydrodynamic connection between the upper injection and lower production wells takes a significant amount of time, which leads to an increase in the development time of a reservoir element.

There is a known method for the development of a deposit of high-viscosity oils and bitumen, including the construction of a production well with an opened horizontal section in the productive formation and an injection well with a profile parallel and similar to the profile of the production well, but located above it in the same productive formation, pumping a coolant into the injection well and withdrawing production from a production well, characterized in that a similar and parallel pair of horizontal wells are drilled at a distance of 180-200 m in the productive formation, and two lower production wells are evenly spaced between the horizontal production wells with horizontal sections parallel to the horizontal sections of the production wells, and between injection - one upper production well with a horizontal section parallel to the horizontal sections of injection wells, after which all wells are used for pumping a coolant in the form of superheated steam until a steam-gas chamber is created. ad by injection wells, after which the producing lower and upper wells are transferred to the selection of heated products. RU 2439305 C1, publ. 10.01.2012.

The main disadvantage of this method is the impossibility of creating a hydrodynamic connection between the wells by simultaneous injection into all wells, since with simultaneous injection without product withdrawal, the pressure in the reservoir rises rapidly, the repression to the reservoir decreases and the injectivity of the wells decreases to zero values. In addition, the disadvantage of this method is the drilling of additional wells, accompanied by a significant increase in capital and operating costs during their operation.

The closest technical analogue of the proposed method is a method of developing a viscous hydrocarbon feedstock, which involves drilling two parallel horizontal wells in the reservoir, located in the same vertical plane at a short distance, and displacing oil with steam due to the gravity drainage mechanism. Moreover, the upper horizontal well is used for steam injection, and the lower well is used for pumping out a liquid containing oil. US 4344485 A, publ. 08/17/1982. - prototype.

A significant drawback of the closest analogue is that when it is used on deposits of heavy oil or natural bitumen, it is required to drill injection and production wells at an extremely small distance of about 5 m from each other, as the author of the patent (Butler RM Thermal recovery of oil and bitumen. - Prentice Hall, 1991, or PM Butler. "Horizontal wells for the production of oil, gas and bitumen." - M. - Izhevsk: Institute of Computer Research, Research Center "Regular and Chaotic Dynamics", 2010. - 536 p.), as well as other authors (Antoniadi D.G. "Handbook on thermal methods of oil production", Krasnodar: "Soviet Kuban", 2000; Zaripov A.T. on a productive reservoir ", dissertation for the degree of Doctor of Technical Sciences, Bugulma, 2015; Ibatullin T.R." Increasing the efficiency of steam technology gravitational action and optimization of its parameters based on the control of the component composition of the injected fluid ", dissertation for the degree of candidate of technical sciences, Moscow, 2010), while the value of the permissible repression and injectivity of the injection well decreases due to the risk of direct breakthrough of the injected steam into the production well ... This is especially evident in fractured reservoirs, where steam breakthrough through fractures increases the steam-oil ratio and makes it necessary to reduce the rate of steam injection, thereby reducing the rate of field development.

The technical result of the proposed invention is to increase the energy efficiency of the development of deposits of heavy oil or natural bitumen with steam, increase oil production, reduce the volume of produced water, decrease the steam-oil ratio, increase the rate of production of deposits of heavy oil or natural bitumen.

The claimed technical result is achieved by the fact that in a method for the development of deposits of heavy oil or natural bitumen, which involves drilling a horizontal production well, drilling a horizontal injection well above a horizontal production well parallel to it in the vertical plane, injecting steam into the injection well and withdrawing fluid from the production well, according to According to the invention, the injection well is placed near the top of the formation, the production well is at the bottom of the formation, and the hydrodynamic connection between the production and injection wells is created by means of cyclic steam treatment of wells (PCOS), and when carrying out cyclic steam treatments, injection and withdrawal into the upper well is performed in antiphase with the lower well, t .e. when injecting steam into the upper well, fluid is withdrawn from the lower well, and when fluid is withdrawn from the upper well, steam is injected into the lower well, the cyclic steam treatment of the wells is stopped after the establishment of a hydrodynamic connection between the injection and production wells and steam is continuously injected into the upper injection well and withdraw products from the lower production well before the end of the development period. When carrying out cyclic steam treatments, to accelerate the creation of a hydrodynamic connection between wells, hot water can be pumped into the upper well, and steam with a maximum degree of dryness can be pumped into the lower well. In addition, when carrying out cyclic steam treatments, the rate of injection of the coolant into the lower well may exceed the rate of injection of the coolant into the upper well, and inert or hydrocarbon gas can also be injected into the lower well together with steam.

It is essential that the injection well is located near the top of the formation, the production well is at the bottom of the formation, and the hydrodynamic connection between the wells is created by means of a DSP, and during DSP, injection and withdrawal into the upper well is performed in antiphase with the lower well, i.e. when injecting steam into the upper well, the liquid is withdrawn from the lower well, and when the liquid is withdrawn from the upper well, steam is injected into the lower well.

It is also significant that when conducting the DSP, the rate of injection of the coolant into the lower well exceeds the rate of injection of the coolant into the upper well.

It is also essential that when carrying out cyclic steam treatments, to accelerate the creation of a hydrodynamic connection between the wells, hot water is pumped into the upper well, and steam is pumped into the lower well with the maximum degree of dryness.

It is also essential that to accelerate the creation of a hydrodynamic connection, together with steam, an inert or hydrocarbon gas is injected into the lower well.

Brief description of diagrams and drawings

FIG. 1. is a diagram showing the principle of the invention and well placement.

FIG. 2. - the dependence of the heating time by conductive heat transfer through the circulation of water vapor along the shafts of the production and lower injection wells.

FIG. 3. - dynamics of cumulative oil production over time for the prototype and the proposed method.

The proposed method for the development of high-viscosity oil deposits is illustrated using Fig. 1.

The method can be implemented as follows: in a heavy oil or natural bitumen deposit, two parallel horizontal wells are drilled, located one above the other: production 1, injection 2. A production well is drilled at a distance of 2 m above the bottom of the formation 3. An injection well is drilled at a distance of 2 m below the top of seam 4.

A hydrodynamic connection is created between the production and injection wells by means of cyclic steam treatment of the wells; moreover, during the DSP, injection and withdrawal into the upper well is performed in antiphase with the lower well, i.e. when injecting steam into the upper well, the liquid is withdrawn from the lower well, and when the liquid is withdrawn from the upper well, steam is injected into the lower well. In this case, the rate of injection of the coolant into the lower well exceeds the rate of injection of the coolant into the upper well. When carrying out cyclic steam treatments to create a hydrodynamic connection between the wells, hot water is pumped into the upper well, and steam is pumped into the lower well with the maximum degree of dryness. In order to accelerate the creation of a hydrodynamic connection between the wells during the PTOS, an inert or hydrocarbon gas is injected into the lower well together with steam.

Due to the high rates of steam injection during the DSP, the latter make it possible to quickly establish a hydrodynamic connection between wells. Also, the establishment of a hydrodynamic connection between the upper injection and lower production wells by means of the CSP is faster and in comparison with steam injection into an additional injection well located in the immediate vicinity of the production well (patent RU 2643056 C1, published on 01/30/2018), since the rate of steam injection into the latter case is limited due to the risk of direct breakthrough of the injected steam into the production well.

As a result of the DSPP, a displacement zone 5 appears in the reservoir volume, filled with steam, steam condensate and residual oil, which grows in volume over time, while its boundary 6 approaches the reservoir top, near which the upper injection well is located.

After the establishment of a hydrodynamic connection between the injection well and the production well, the CSP stops and steam injection into the injection well begins. This increases the mass flow rate of the injected steam.

Due to the greater removal of the injection well from the production well (in comparison with the prototype), the intensity of steam flow into the production well is reduced, which makes it possible to increase the injection rate and accelerate the production of oil from the formation.

At the same time, steam, due to its low density, does not tend to break through to the production well, but spreads along the top of the formation, ensuring uniform displacement of oil from the top to the bottom. As a result, the proportion of oil in the withdrawn fluid increases, the proportion of steam condensate decreases and, as a consequence, the oil production rate increases and the ratio of the amount of thermal energy removed from the reservoir to the amount of oil produced decreases.

The above is one of the main distinctive features of the proposed method, since when the two wells are vertically spaced practically over the entire thickness of the formation (which can reach 30 ... 50 and more meters), the possibility of the development of channel communication between the two wells under consideration through cracks or highly permeable formation differences is significantly leveled.

In support of the claimed technical result, a comparative calculation of technological indicators for the implementation of the closest analogue (prototype) in technical essence and the proposed method, performed using a specialized hydrodynamic simulator CMG STARS, is provided.

The geological and hydrodynamic model of the formation corresponds to the characteristic conditions of the bitumen deposit. The viscosity of oil in reservoir conditions is 10,000 mPa⋅s. The thickness of the formation is 36 m. The permeability of the formation is 1 Darcy. The calculated version of the closest analogue of the proposed method assumes the location of a production well with a length of 400 m at a distance of 2 m above the bottom of the formation and the location of an injection well with a length of 400 m in the same vertical plane at a distance of 5 m above the production well. In the prototype version, a hydrodynamic connection is established between the wells by heating the interwell space due to conductive heat transfer by circulating water vapor through the shafts of the production and injection wells for 6 months. Then they start to continuously inject steam into the injection well and produce products from the production well until the end of development, which is determined by the drop in oil production below 5 tons / day.

The calculated version of the proposed method assumes the presence of a production well located identically to the production well according to the version of the closest analogue (prototype) of the proposed method at a distance of 2 m above the bottom of the formation 400 m long, and an injection well 400 m long located in the same vertical plane 2 m below the top of the reservoir.

Calculations show that the organization of steam injection into the upper injection well with withdrawal from the lower production well in order to achieve the required technical result without performing the DSP in both wells is not possible due to the high filtration resistance of the formation. To achieve the required technical result, it is required to conduct cyclic steam treatments of wells with steam injection in both wells in antiphase (i.e., when steam is injected into the upper well, fluid is withdrawn from the lower well, and when fluid is withdrawn from the upper well, steam is injected into the lower well) within 6 months.

In the event that the rate of steam injection into the lower well exceeds the rate of steam injection into the upper well by a factor of 2 during the QSP, the duration of establishing a hydrodynamic connection between the wells is reduced to 5 months.

In the event that hot water is pumped into the upper well during the QSP, and steam is pumped into the lower well with a dryness degree of 0.95 unit fraction. at a rate 2 times higher than in the upper well, the duration of establishing a hydrodynamic connection between the wells is reduced to 3.7 months.

In the event that hot water is pumped into the upper well during the QSP, and steam is pumped into the lower well with a dryness degree of 0.95 unit fraction. together with methane and the rate of injection of the steam-gas mixture is 2 times higher than in the upper well, the duration of establishing a hydrodynamic connection between the wells is reduced to 3.0 months.

After the establishment of a hydrodynamic connection between the wells, the CSPs are stopped and they begin to continuously pump steam into the upper injection well, and withdraw the product from the lower production well.

FIG. 3 shows the dynamics of cumulative oil production over time for the prototype and the proposed method.

The total cumulative production of the proposed method amounted to 290.9 thousand tons, which is 7.1% more than the same indicator of the closest analogue (271.1 thousand tons). The accumulated volume of produced water in the proposed method amounted to 788.8 thousand tons, which is 6.7% less than the same indicator for the sale of the closest analogue, which amounted to 845.1 thousand tons. The steam-oil ratio in the implementation of the proposed method was 2.7 t / t, which is 12.7% less than in the implementation of the closest analogue, which amounted to 3.1 t / t. The period of development of the displacement element during the implementation of the proposed method was 85.2 months, which is 13.4% less than the same indicator for the implementation of the closest analogue, which was 98.4 months. Thus, the claimed technical result is confirmed.

Note that the reservoir considered in the example was practically homogeneous (did not contain vertical fractures or highly permeable zones). In the presence of such zones in a real reservoir, the results of the proposed method will even more significantly exceed the performance of the prototype method.

The objects of application of the proposed invention can be all deposits of heavy oil and natural bitumen with filtration resistances of the formation, which prevent the use of widespread areal thermal treatment methods.

Claims (4)

1. A method of developing heavy oil or natural bitumen deposits, providing for drilling a horizontal production well, drilling a horizontal injection well above a horizontal production well parallel to it in a vertical plane, injecting steam into an injection well and withdrawing fluid from a production well, characterized in that the production well is located near the bottom of the formation, the injection well near the top of the formation, create a hydrodynamic connection between the production and injection wells by means of cyclic steam treatment of wells; when injecting steam into the upper well, fluid is withdrawn from the lower well, and when fluid is withdrawn from the upper well, steam is injected into the lower well, the cyclic steam treatment of the wells is stopped after the establishment of a hydrodynamic connection between the injection and production wells and steam is continuously injected into the upper injection well and withdraw products from the lower production well before the end of the displacement element production period. 2. The method according to claim 1, characterized in that when carrying out cyclic steam treatments to create a hydrodynamic connection between the wells, hot water is pumped into the upper well, and steam is pumped into the lower well with a maximum degree of dryness. 3. The method according to claim 2, characterized in that when carrying out cyclic steam treatments, the rate of injection of the coolant into the lower well exceeds the rate of injection of the coolant into the upper well. 4. The method according to claim. 2, characterized in that when carrying out cyclic steam treatments together with steam, an inert or hydrocarbon gas is pumped into the lower well.

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