RU2643056C1 - Method for development of pools of superheavy oil or natural bitumen - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for developing heavy oil or natural bitumen pools includes drilling a horizontal production well near the bottom of formation, drilling above it in the same vertical plane parallel to production well of injection horizontal well at distance which provides creation of hydrodynamic connection between the wells for initiation of drainage process, injecting steam into the injection well and withdrawing liquid from the production well. The method also includes drilling an additional injection well above the horizontal injection well in parallel with it in a vertical plane at a minimum distance from the formation cap in consideration of technical possibility to keep the trajectory of the well without driving in the upper rocks, the moment of establishment of hydrodynamic connection between the upper injection and production wells is registered. After that, pumping of steam into the lower injection well is stopped and pumping of steam into the upper injection well is started until completion of production period of the displacement element.

EFFECT: reduced steam-oil ratio when developing heavy oil or natural bitumen pools, increased pool production rate, reduced amount of fresh purified water required for generation of steam.

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Description

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

There is a method of developing a reservoir of high-viscosity oil by the method of steam gravity impact on the formation, including drilling and arrangement of injection and production wells, controlled injection of steam into the injection well to warm the productive formation throughout its horizontal wellbore and raising the fluid from the producing well. At the same time, an injection well is drilled and equipped with a horizontal well of smaller diameter and length than that of the producing well, and there is at least one additional similar injection well to it. Moreover, the horizontal wells of injection wells are placed at a distance of not less than three meters above the horizontal well of the producing well. The modes of steam injection in each of the injection wells are changed based on the results of thermometry in the horizontal well of the producing well for uniform heating of the formation. RU 2444617 C1, publ. 03/10/2012.

The disadvantage of this method is that when it is used on deposits of heavy oil or natural bitumen that contain oil with low mobility in natural reservoir conditions, initiation of the drainage process requires injection and production wells to be kept at an extremely small distance of about 5 m from each other, because with a greater distance between the wells, it is impossible to establish a primary hydrodynamic connection. This leads to the impossibility of creating significant repression on the reservoir and achieving high injectivity of injection wells due to the risk of a direct breakthrough of injected steam into the production well. At a low injection well injectivity, the formation is heated and produced at a low rate, while a significant part of the heat injected into the formation goes into overlying rocks, which reduces the energy efficiency of development. In addition, the application of this method involves additional costs for drilling and equipping several shafts of injection wells.

A known method of developing deposits of highly viscous oil or bitumen, including the construction of pairs located on top of each other horizontal production and injection wells, as well as additional horizontal wells, pumping coolant through the upper injection wells with heating the reservoir and creating a steam chamber, product selection due to steam gravity drainage through producing wells and monitoring the state of the steam chamber. An additional well is built between the producing and injection wells. The solvent is pumped through an additional well at intervals into the zones of least heating. RU 2582256 C1, publ. 04/20/2016,

The disadvantages of this method include the fact that when it is used on heavy oil or natural bitumen deposits, it becomes necessary to drill injection and production wells at an extremely small distance of about 5 m from each other and the need to drill an additional well between them, which is extremely difficult from the point of view of technology drilling. In addition, this method involves feeding into the reservoir a solvent, which is a valuable hydrocarbon product, and its unavoidable technological losses.

A known method of developing a field of heavy oil or bitumen using double-well horizontal wells, including pumping coolant through a double-well horizontal injection well, heating the reservoir with the creation of a steam chamber and selecting products through a double-well horizontal production well. RU 2340768 C2, publ. 12/10/2008.

The disadvantage of this method, as well as other analogs given, is that when it is used on heavy oil or natural bitumen deposits, it becomes necessary to drill injection and production wells at an extremely small distance of about 5 m from each other. Another disadvantage of this method is the increase in penetration during drilling, metal consumption and cost of wells. In addition, this method involves additional costs for the arrangement of additional wellheads.

A known method of developing heavy oil deposits, involving drilling a horizontal production well in an oil reservoir, drilling a horizontal injection well above it and injecting steam into it, drilling an additional horizontal injection well located at a distance from the first two more than 50 m in the plan for horizontal displacement of oil to production well, while the injection of steam into the first injection well can be stopped. RU 2510455 C2, publ. 03/27/2014.

The disadvantage of this method when using heavy oil and natural bitumen on deposits is the low efficiency of horizontal filtration, due to the inability to organize continuous injection of working agents into an additional well due to the lack of injectivity of an additional horizontal injection well due to its location, the need to displace fluid into the reservoir in the direction of the producing well until a hydraulic connection is established.

The closest in technical essence to the analogue of the proposed method is one of the variants of the method of developing viscous hydrocarbon feedstock, which involves drilling in deposits of two parallel horizontal wells located in the same vertical plane at a small distance, and the displacement of oil by steam due to the gravitational drainage mechanism. Moreover, the upper horizontal well is used to inject steam, and the lower well is used to pump liquid containing oil. US 4,344,485 A, publ. 08/17/1982.

A significant drawback of the closest analogue, as well as all the analogs cited, is that when it is used on heavy oil or natural bitumen deposits, injection and production wells are required at an extremely small distance of about 5 m from each other, while the allowable repression and injectivity are reduced injection well due to the risk of a direct breakthrough of the injected steam into the production well.

The technical task of the invention is the development of deposits of heavy oil or natural bitumen in the mode of gravitational drainage of steam with high energy efficiency.

The technical result of the invention is to reduce the steam-oil ratio in the development of deposits of heavy oil or natural bitumen, increase the rate of production of deposits, reduce the amount of purified fresh water needed to generate steam.

The claimed technical result is achieved by the fact that in the method of developing deposits of heavy oil or natural bitumen, which involves 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 a horizontal injection well at a distance that allows the creation of a hydrodynamic connection between the wells to initiate the drainage process, the injection of steam into the injection well and the selection of fluid from the producing well According to the invention, they drill an additional injection well above a horizontal injection well parallel to it in the same vertical plane at a minimum distance from the top of the formation, taking into account the technical ability to maintain the well’s path without penetrating overlying rocks, and fix the moment of establishing the hydrodynamic connection between the upper injection and producing wells, after which the injection of steam into the lower injection well is stopped and steam is injected into the upper discharge well until the end of the period of development of the displacement element.

What is new is that for gravity drainage of oil by water vapor, a system of three horizontal wells located in the same vertical plane is used, while the production well is located near the bottom of the formation, the lower injection well is located above the production well at a distance that allows establishing a hydrodynamic connection with the production well , the upper injection well is located near the top of the reservoir, taking into account the technical ability to withstand the trajectory of the well without pr stays overlying rocks.

It is also new that steam is injected into the lower injection well until a hydrodynamic connection is established between the upper injection well and the producing well, after which the lower injection well is closed and the steam is injected into the upper injection well.

The proposed method for developing highly viscous oil deposits is illustrated using FIG. one.

The method can be implemented as follows:

Three parallel horizontal wells, one above the other, are drilled in a heavy oil or natural bitumen deposit: production 1, lower injection 2, upper injection 3. The production well is drilled at a distance of 2 m above the bottom of the formation 4. The lower injection well is drilled at a distance of 5 m above producing well. The upper injection well is drilled at a distance of 2 m below the top of the formation 5.

A hydrodynamic connection is created between the producing and lower injection wells by heating the volume of oil-saturated rock located in the space between these wells due to the circulation of water vapor along the trunks of the producing and lower injection wells.

After establishing a hydrodynamic connection between the producing and lower injection wells, the process of gravitational oil displacement by steam is initiated so that steam does not break through into the producing well by injecting steam into the lower injection well and taking liquid from the producing well. Steam is pumped into the lower injection well with a limitation of mass flow so that steam does not break into the producing well.

As a result of the displacement of oil by steam injected through the lower injection well, a displacement zone 6 is formed in the reservoir volume, filled with steam, steam condensate and residual oil, which grows in volume over time, while its boundary 7 approaches the formation roof, near which the upper injection well.

In the upper injection well, temperature is measured to establish the moment at which the temperature rises enough to establish a hydrodynamic connection between the upper injection well and the producing well. The temperature sufficient to provide a hydrodynamic connection between the upper injection well and the producing well is estimated by calculating the distribution of heat and fluids in the formation using numerical hydrodynamic modeling.

After establishing a hydrodynamic connection between the upper injection well and the producing well, the injection of steam into the lower injection well is stopped and the injection of steam into the upper injection well begins. This increases the mass flow rate of the injected steam.

Due to the greater removal of the upper injection well from the producing well, the intensity of steam flow into the producing well is reduced, which allows to increase the injection rate and accelerate oil production from the reservoir. At the same time, steam, due to its low density, does not tend to break through to the producing well, but spreads along the top of the formation, ensuring uniform oil displacement 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 result, the oil production rate increases and the ratio of the amount of thermal energy transferred from the formation to the amount of oil produced decreases.

The allowable increase in the steam injection rate when switching from the lower injection well to the upper is estimated using numerical hydrodynamic modeling.

In support of the claimed technical result, a comparative calculation of technological indicators of the implementation of the closest in technical essence analogue and the proposed method is carried out using a specialized hydrodynamic simulator CMG STARS.

The geological and hydrodynamic model of the reservoir corresponds to the characteristic conditions of the heavy oil deposits of the Shentalinskaya group of uplifts. Oil viscosity in reservoir conditions is 27350 mPaПs. The thickness of the formation is 18 m. The permeability of the formation is 1 Darcy. The calculated version of the closest analogue of the proposed method involves the location of the production well 400 m long at a distance of 2 m above the bottom of the formation and the location of the injection well at a distance of 5 m above the production well. The calculated version of the proposed method assumes the presence of a producing well and a lower injection well, located identically to the producing and injection wells according to the closest analogue of the proposed method, and additional parallel to the lower wells of the upper injection well 400 m long, located in the same vertical plane 2 m below the formation roof .

Calculations show that the organization of steam injection into the upper injection well with selection from the production well to achieve the desired technical result without long-term mining of a pair of production and lower injection wells is not possible due to the high filtration resistances of the formation. To achieve the desired technical result, it is necessary to establish a hydrodynamic connection between the producing and upper injection wells by heating the formation between them during the injection of steam into the lower injection well and the selection of fluid from the producing well for 12 months.

In the embodiment of the proposed method, water vapor is pumped for 12 months only into the lower injection well, then only into the upper injection well. The moment of completion of development is determined by the drop in oil production below the level of 5 tons / day.

In FIG. 2 shows graphs of changes in oil production time. In FIG. 3 shows graphs of the change in time of the oil-vapor ratio (PNO). reflecting the energy efficiency of the development process.

The total steam-oil ratio during the implementation of the proposed method was 4.2 t / t, which is 20% less than the same indicator when implementing the closest analogue, which is 5.3 t / t. The period of development of the displacement element during the implementation of the proposed method was 12 years, which is 33% less than the same indicator when implementing the closest analogue, which is 18 years. Thus confirmed the claimed technical result.

The objects of application of the present invention can be deposits of heavy oil of the Orinoco belt, as well as all deposits of heavy oil and natural bitumen with formation filtration resistances that impede the use of common areal thermal methods of exposure.

Claims (1)

A method of developing deposits of heavy oil or natural bitumen, which involves 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 a horizontal injection well at a distance that provides the possibility of creating a hydrodynamic connection between the wells to initiate the drainage process, injecting steam into injection well and fluid withdrawal from the producing well, characterized in that additional pressure is drilled a well above a horizontal injection well parallel to it in a vertical plane at a minimum distance from the top of the formation, taking into account the technical ability to maintain the trajectory of the well without penetrating overlying rocks, the moment of establishing a hydrodynamic connection between the upper injection and producing wells is fixed, after which the steam injection to the lower injection is stopped well and steam begins to be pumped into the upper injection well until the end of the period of development of the displacement element.

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