RU2307242C1 - High-viscosity oil production method - Google Patents

Abstract

FIELD: oil production, particularly to produce high-viscosity oil with the use of horizontal and vertical well system and thermal reservoir treatment.

SUBSTANCE: method involves installing perforated casing pipe in previously drilled horizontal well; cementing casing pipe up to horizontal section; drilling additional vertical well, which crosses end horizontal section of previously drilled one and communicating the wells; supplying heat carrier in horizontal well through flow string in beginning of horizontal section; producing well product from vertical well to provide predetermined intake capacity; continuing heat carrier supply in reservoir up to oil viscosity reduction in area located around horizontal well section bore; performing well shutdown to provide thermal capillary infiltration; extracting product from vertical well to calculated output decrease along with maintaining dynamic level below well crossing; repeating above supply-shutdown-extraction cycle to provide bottomhole zone drainage.

EFFECT: increased oil flow from reservoir in well due to decreased back pressure, decreased heat losses due to reduced heat carrier efflux from well during well product lifting.

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Description

The proposal relates to oil production using heat, mainly from reservoirs with heavy bitumen oil in combination with drilling a horizontal-vertical well system.

A known method of producing viscous oil during thermal exposure to the formation (see patent RU No. 2211318, ЕВВ 43/24, publ. 08/27/03), including drilling a continuous well with its entrance and exit to the surface, installing a casing string in it, cementing annular space, perforation of the casing string, installation of tubing strings in it, supplying coolant through them to dilute the oil around the wellbore, after which products are selected for the outlet section while continuing to pump the coolant along the inlet section of the well.

The known method allows the production of viscous oil from a horizontal well by lifting it from the well with a coolant.

However, the inflow of oil into the wellbore is insignificant due to backpressure on the formation, with significant heat loss due to the removal of the coolant from the well during production lifting.

The closest in technical essence and the achieved result to the proposed method is a method of increasing oil recovery (see patent RU No. 2191895, ЕВВ 43/24, publ. 27.10.02), including the descent into the casing of concentrically two tubing strings, supply through the inner coolant column to the end of the casing string, gas supply between the casing and tubing string to the beginning of the horizontal part of the barrel and product selection from this part between the tubing strings.

The known method allows the production of viscous oil from a horizontal well by raising it from the well with gas and to reduce heat loss associated with the removal of the coolant from the well with the product.

The disadvantage of this method is the low influx of products from the formation into the wellbore due to the large back pressure on the formation, and heat loss remains significant due to the removal of coolant from the well.

The technical problem to be solved by the claimed invention is directed is to increase the influx of oil from the formation into the well by reducing backpressure to the formation, reducing heat loss by reducing the removal of coolant from the well when raising the product.

The stated technical problem is solved by the described method of producing highly viscous oil, including installing a perforated casing string in a horizontal well drilled, cementing it to the horizontal part, supplying coolant to the terminal, and gas to the initial and selecting products from the initial perforated along the entire length of the horizontal casing string, additionally a vertical well is drilled, which is drilled in the terminal horizontal part and communicated with it, the coolant is fed into the horizontal the borehole along the tubing string to the beginning of the horizontal part, the products are taken from the vertical well to ensure a given injectivity, the coolant is fed into the reservoir until the oil is diluted around the horizontal part of the well, the well is stopped for exposure to thermocapillary impregnation, then the products are taken from the vertical well to calculated reduction in flow rate, while maintaining a dynamic level below the intersection of the wells, the supply - shutter cycle - the selection is repeated in the same way until wellbore zone drainage, after which the wells are transferred to injection or production wells.

The studies showed that drilling an additional vertical well, which crosses the drilled hole in the final horizontal part and communicates with it, supplying the coolant to the horizontal well through the tubing string to the beginning of the horizontal part, taking products from the vertical well to ensure the given injectivity allow warming the bottom hole zone, reduce the viscosity of oil in it and increase its mobility, and also begin to drain the bottom-hole zone due to the circulation of the coolant I along the horizontal part of the trunk and its entry into the bottomhole formation zone, as well as the selection of oil coming from the formation into the horizontal wellbore through the vertical.

Continue supplying the coolant to the formation until the oil is diluted around the horizontal part of the well, stopping the well for aging for thermocapillary impregnation, then taking products from a vertical well to a calculated decrease in flow rate, maintaining a dynamic level below the intersection of wells, repeating the supply - holding - selection cycle until deburring bottom-hole zones can increase the flow of oil from the reservoir into a horizontal well by increasing the mobility of oil in the reservoir around its horizontal part and create in the selection of products of maximum drawdown, and also can reduce heat loss by eliminating lifting and removal of the coolant output it at the same time from the well.

The set of distinctive features of the proposed method for the production of high-viscosity oil allows to increase the flow of oil into the well, reduce heat loss, increase the efficiency of production of high-viscosity oil with thermal effects on the reservoir.

From the patent and scientific literature we do not know the claimed combination of distinctive features. Therefore, the claimed method meets the criteria of the invention of "inventive step".

In Fig.1 shows a diagram of the implementation of the method to ensure throttle response, in Fig.2 - after the selection of products.

The system that implements the method includes a horizontal well 1 into which the casing 2 is lowered, a perforation 3, a first tubing string 4 located inside the casing, a second tubing string 5 lowered into the sump 6 of the vertical well 7 communicating with a horizontal well, swab 8, located in the second tubing string. After the casing is lowered into a horizontal well, the annular space is disconnected using a plug 9 and a cement stone 10 is installed.

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

In addition to the horizontal well 1, a vertical well 7 is drilled, which crosses a horizontal well in the terminal horizontal part of the trunk and forms its sump 6. In this case, wells 1 and 7 communicate with each other. Through the first tubing string 4, a coolant, for example steam, is used, is fed to the beginning of the horizontal part of the casing 2 with perforation 3 along the entire length of the horizontal part located in the reservoir, from where it moves to the end part along the casing 2, as well as passing through perforation 3, along the annular space between the casing and the horizontal bore. In this case, local heating of the reservoir around the horizontal bore occurs and due to thermal expansion, lower surface tension and viscosity, gravity, “hot” oil enters the bore and through the perforation into the casing and together with the coolant moves to the end of the casing 2, and then enters a vertical well 7 and rises to the surface along the tubing string 5.

With an increase in the radius of heating of the reservoir around the horizontal wellbore, its throttle response also increases, which can be judged by the pressure drop of the supplied coolant, at a constant rate of its supply or by an increase in the rate of supply at a constant pressure of injection. Upon reaching the desired injectivity, the selection of products from the vertical well 7 is stopped.

Through the first column of tubing 4, the coolant continues to be fed into the formation until a viscous oil is liquefied around the horizontal wellbore 1. At low reservoir pressure, gas is used in combination with the coolant to increase the elastic reservoir energy, for example, using air which when it oxidizes oil, it additionally increases the temperature and reduces its viscosity. The flow rate of the coolant, the injection pressure, as well as the amount of coolant pumped into the reservoir are determined by calculation or experimentally, taking into account the depth of the reservoir, its characteristics, the properties of saturating fluids, the proximity of aquifers, the distance between wells and other factors and are set separately in each case .

After the coolant is injected, the well is stopped for exposure to thermocapillary impregnation, at which temperature and fluid flows in the reservoir are redistributed due to temperature and pressure gradients arising between the layers with different permeability, which increases the coverage of the reservoir by exposure both in thickness and in area . As the temperature gradient decreases, heat transfer rates and oil viscosity decrease in the zones of the reservoir that are subject to temperature influence, and, accordingly, the rate of fluid flow redistribution. Since the dependence of oil viscosity (respectively, its mobility) on temperature is non-linear and is characterized by a slow change in viscosity in the range of high temperatures and its intensive change in the range of lower temperatures, therefore, as the temperature decreases in the reservoir, the mobility of the fluid saturating it decreases sharply. The thermocapillary impregnation time is determined for a particular field taking into account the indicated dependence, as well as taking into account the characteristics of the formation and the parameters of the coolant pumped into it.

After exposure to a swab 8 or a downhole pump (not shown in FIG. 2), from a sump 6 of a vertical well 7, products that enter there from the horizontal part of the well 1 are selected and raised to the surface along the tubing string 5. The dynamic level in the vertical well 7 is supported below its intersection with the horizontal part of the well 1, which ensures maximum depression on the formation and an increase in oil flow from it to the horizontal part of the wellbore 1. This is especially important at low reservoirs s pressures typical, usually for bituminous deposits lying at shallow depths. As the selection of products coming from the heated bottom-hole zone of the productive formation to the horizontal part of the wellbore 1, its temperature decreases due to the arrival of colder and, therefore, less mobile oil from the remote zones of the formation, which leads to a decrease in flow rate. The selection of products from the well 7 is carried out until the estimated reduction in flow rate, which is determined taking into account economic and technological considerations, while the bottom-hole zone of the reservoir is drained.

The cycle of pumping the coolant into the reservoir, extracts for thermocapillary impregnation and selection of products from it are repeated, which leads to an increase in the radius of heating of the reservoir, increase around the horizontal part of the well 1 zone with a reduced viscosity of oil in it and the zone of drainage of viscous oil. The cycles of coolant injection, holding and product selection are repeated until the bottom hole formation is de-drained, after which the wells are transferred to injection or production wells.

According to the proposed method, drilling an additional vertical well, which crosses the drilled in the terminal horizontal part and communicates with it, supplying the coolant to the horizontal well through the tubing string to the beginning of the horizontal part, selecting products from the vertical well to ensure the given injectivity, continuing supplying the coolant to formation before liquefying oil around the horizontal part of the barrel, shutting the well for exposure for thermocapillary impregnation, then selecting products from a vertical well to a calculated decrease in flow rate, maintaining a dynamic level below the intersection of the wells, repeating the supply - shutter cycle - selecting in the same way until the bottom hole is de-energized, provide injectivity of the coolant layer, heating its bottom zone and increasing inflow from it into the well, reducing heat loss and increasing high-viscosity oil production efficiency with thermal effect on the reservoir.

Claims (1)

A method of producing highly viscous oil, including installing a perforated casing in a horizontal well drilled, cementing it to the horizontal part, supplying coolant to the end, and gas to the initial and selecting products with initial perforated along the entire length of the horizontal part of the casing, characterized in that a vertical well is drilled, which is drilled in the terminal horizontal part and communicated with it, the coolant is supplied to the horizontal well through the pump-compressor string weed pipes to the beginning of the horizontal part, the products are taken from a vertical well, to ensure a given injectivity, the flow of coolant into the formation is continued until the oil liquefies around the horizontal part of the well, the well is stopped for aging, then the products are taken from a vertical well to an estimated reduction in flow rate, while maintaining the dynamic level is below the intersection of the wells, the feed-shutter-selection cycle is repeated in the same way until the bottom hole is razedreniya, after which the wells are transferred to oppressive or extractive.

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