RU2296856C1 - Method for highly-viscous oil production - Google Patents

Abstract

FIELD: oil production, particularly flowing oil production with the use of heat and reagents for lifting and displacing of highly-viscous oil containing large amount of asphalt-tar-paraffin substances.

SUBSTANCE: method involves lowering flow string in casing pipe and lifting oil through annular space. Heat-insulated tube string provided with packer at end thereof, flow string with opened and sealed tube ends are serially lowered in the casing pipe. Heat-insulated tube string is lowered beneath level of paraffin crystallization initiation. Flow string with sealed tube ends are driven up to above level and flow string with opened tube ends are submersed so that space is created between flow strings with opened and sealed tube ends. Heat carrier is supplied in flow string with opened tube ends. Oil is lifted through annular space between heat-insulated and flow string with sealed tube ends. Chemical reagents and heat carrier used for bottomhole formation zone treatment is fed via above annular space. Heat carrier is supplied when well is packed. Space between casing pipe and heat-insulated tube string is filled with gas. Level of crystallization initiation is determined by measuring of temperature along well bore.

EFFECT: increased formation oil influx and oil lifting from well along with retailing oil quality, decreased waste heat and transportation losses.

3 cl, 2 dwg

Description

The proposal relates to the oil industry, in particular to the field of oil production using heat and reagents for lifting and displacing highly viscous oil containing a large amount of asphalt resin and paraffin.

A known method of thermal displacement of oil from a horizontal well (see patent RU No. 2067168, E 21 B 43/24, publ. 09/27/96), including the descent into the casing string of tubing with a packer, supplying coolant through it to the end part casing stringer for packer, product transportation along annular annulus.

The method allows for the production of highly viscous oil.

The disadvantage of this method is that when it is used, high energy costs are required, since energy losses occur during the transportation of products along the annular annulus, heat is taken from the products being raised by the casing string and the rock located behind it, and, in turn, the product cooled down as it is lifted takes heat away through tubing (tubing) from the coolant supplied through them. In addition, heat is lost after removal of the coolant from the well, which, when mixed with oil when rising, impairs its quality.

There is also a method of increasing oil recovery (see patent RU No. 2191895, E 21 B 43/24, publ. 04/25/02), including the descent into the casing string of the tubing, the descent into it of the second tubing string, the gas supply between the casing and the first string Tubing, and coolant along the second tubing string to the end of the casing string, product selection along the annular channel between the first and second tubing string.

The known method allows for the production of highly viscous oil by controlling the rate of flow of coolant into the reservoir and reduce heat loss to the rocks.

However, energy losses remain high, production efficiency is low, and the quality of oil lifted from the well is deteriorating.

The closest in technical essence and the achieved result to the proposed method is a method of producing highly viscous oil (see patent RU No. 2206728, E 21 B 43/24, publ. 06/20/2003), including the descent into the casing string of the tubing to the perforation interval , supplying coolant through it, raising the product along the annulus, and two tubing string are lowered into the casing, the first is lowered to the beginning, and the second through the first to the end of the perforation interval and the coolant is fed through it, and into the space between the casing and the first tubing string gas is supplied, products are lifted in the space between the tubing strings, after ensuring a given injectivity, the production is stopped, the coolant is pumped up to the calculated value, gas supply is continued, the space between the tubing strings is filled and maintained in this state, then the well is stopped for thermocapillary impregnation prior to the beginning of an intensive decrease in fluid mobility in the near-wellbore zone (PZ), the pressure in the well is depressurized, the product entering it is taken to reduce the flow rate, obtained In the natural mode of formation operation, the coolant injection and production selection cycle is repeated until a zone with moving fluid is created with the production well, after which the well is transferred to the injection well, and production is taken through the production well, production is selected by swabbing or supplying gas to the annular spaces.

The known method allows to reduce energy loss due to unproductive heating of rocks and energy consumption for the implementation of the method.

The disadvantage of this method is that in the production of highly viscous oil containing a large amount of asphalt-resin-paraffin substances, energy losses and energy costs remain high, and the efficiency of oil production is low, since the heat from the coolant supplied through the second tubing string is transferred through the product to be lifted and the gas supplied to heat the rocks behind the casing, and also carried out from the well to the surface with a coolant, raised together with the reservoir products, while the reuse of the raised heat the carrier is problematic because of the complexity and cost of separating it from well production and preparing for heating.

In addition, the quality of the products coming from the formation into the wellbore deteriorates when it is mixed with the coolant during the ascent at the wellhead due to increased water cut and the formation of a stable emulsion, the separation of which during oil preparation requires significant additional costs.

During cyclic coolant injection and selection of products from the well, the energy consumption for raising oil increases, which are associated with an increase in viscous friction due to a decrease in the temperature of oil being raised and an increase in its viscosity as it rises to the earth’s surface, which leads to complications in oil production and shutdowns of production wells and reducing the overhaul period of wells.

The technical problem to which the claimed technical solution is directed is to reduce energy losses in the production of highly viscous oil containing a large amount of asphalt-resin-paraffin substances, by reducing unproductive heating of rocks and heat transfer to the surface, as well as energy consumption for lifting oil from the well due to continuous circulation coolant, contributing to a decrease in its viscosity and a decrease in viscous friction, an increase in the efficiency of oil production and a decrease in additional materials total costs due to the reduction of complications and the increase in the overhaul period of production wells, the preservation of the quality of oil lifted from the reservoir by preventing the mixing of coolant with it.

The stated technical problem is solved by the described method of producing highly viscous oil containing a large amount of asphalt-resin-paraffin substances, including descent into the casing string of tubing strings arranged concentrically, supplying coolant and lifting oil through the annulus, while the casing string of thermally insulated pipes is sequentially lowered with packer at the end, tubing with closed and open ends of the pipes, and the column of insulated pipes is lowered below depths of onset of paraffin crystallization, tubing with a closed end to this depth, and tubing with an open end so as to form a gap between tubing with a closed end, while the coolant is fed into tubing with an open end , oil is lifted along the annulus of heat-insulated and tubing pipes with a closed end, chemicals and coolant when processing the bottom-hole zone of the formation are fed through the same annulus eplonositel fed at zapakerovannoy borehole space between the casing and the thermally insulated column is filled with gas, the depth of the beginning of crystallization of the wax is determined by measuring the temperature of the wellbore.

The tests showed that the descent into the casing string of insulated pipes with a packer at the end is lower than the depth of onset of crystallization of paraffin, into which the tubing string with the closed end is lowered to this depth, and into this casing the tubing string with the open end with a gap with the tubing string with closed end, organization of the coolant circulation in the well by feeding it along the tubing string with an open end and rising in space between the tubing strings, oil lifting in the space between the heat-insulated and tubing strings with the closed ntsom, filling the space between the casing and the gas-insulated pipes allows:

firstly, to reduce the heat loss of oil, including that heated from the coolant circulating in the well, when transporting it from the bottom to the mouth by reducing heat transfer to the rocks, since the thermal conductivity of a heat-insulated column made by evacuating its annulus is several orders of magnitude less, and the gas filling the space between the insulated and casing strings is an order of magnitude less than metal or liquid;

secondly, to reduce the heat loss associated with the heat transfer from the well by the coolant due to the use of heat removed during the circulation during reheating of the coolant, since it takes less energy to heat such a coolant than to prepare and heat a non-circulating coolant;

thirdly, to maintain the quality of the oil being lifted from the reservoir, to prevent the formation of a stable emulsion and to reduce the cost of oil preparation associated with its dehydration by preventing mixing of oil with the coolant during the ascent from the well, since the coolant and products rise to the mouth along isolated from each other annular channels;

fourthly, to reduce losses in the transportation of oil from the well by reducing the value of its viscous friction, since the lifted oil is heated by the coolant circulating in the well and has a lower viscosity;

fifthly, to reduce the complications during oil recovery associated with the reduction or overlapping of the flow cross-section by paraffin deposits, and to increase the overhaul period of production wells by heating the oil to be raised with the coolant circulating in the well.

In addition, the injection of chemicals during the processing of the well’s PZ through the space between the insulated and tubing strings with a closed end allows heating the injected reagent due to the coolant circulating in the well, since the reagent contacts it through the metal wall during transporting it from the wellhead to the bottom of the well.

The descent into the borehole on the string of insulated packer pipes and sealing the borehole when processing the PZ formation with a coolant helps protect the casing from high temperatures, thereby preventing its adhesion to annular cement due to temperature elongations and to reduce heat loss to the rocks behind it by preventing contact of the heat transfer medium with the casing string, since the cavity between the casing string and the casing string is insulated from the bottom by the packer.

Determining the depth of onset of paraffin crystallization by measuring the temperature along the wellbore prevents the onset of paraffin crystallization during oil lifting from the well by lowering the tubing strings and organizing coolant circulation to this depth with their help.

The set of distinctive features of the proposed method for the production of high-viscosity oil allows to reduce the energy loss of the coolant, to preserve the quality of the products being lifted from the reservoir, to reduce losses from transportation from the well and to ensure its rise at the wellhead and to increase production efficiency, to increase the well overhaul period by reducing complications in oil production.

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 "inventive step".

Figure 1 shows a diagram of an implementation of the proposed method for the production of highly viscous oil containing a large amount of asphalt-resin-paraffin substances.

In Fig.2 - the same, but when processing the bottom-hole zone of the reservoir with a coolant.

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

In the casing 1 (see Fig. 1), a string of thermally insulated pipes 2 with a packer 3, a tubing with a closed 4 and an open 5 pipe ends is successively lowered. Moreover, the column of thermally insulated pipes 2 with the packer 3 at the end is lowered below the crystallization depth of paraffin 6, tubing with a closed end 4 to this depth 6, and tubing with an open end 5 so that they form a gap 7 between the tubing with a closed end 4. The specific depth of descent columns of heat-insulated pipes into this well are determined by calculation taking into account the characteristics of this well (for example, the depth of the reservoir, flow rate, injectivity, etc.), the properties of the oil, the required temperature at the bottom when chemical agents or silt are injected into the reservoir coolant, the strength characteristics of thermally insulated pipes, etc. An annulus A is formed between the casing 1 and the column of thermally insulated pipes 2, an annulus B is formed between the column of thermally insulated pipes 2 and a tubing string 4 with a closed end 4, and annulus B is formed between the tubing strings 4 and 5.

Through the shutoff member 8 along the tubing string with an open end 5, a coolant, for example, using steam or hot water, is fed into the well to the bottom of the tubing string with a closed end 4, and then lifted along the annulus B at the mouth, where pass through the shut-off element 9 and heated, for example, by a mobile or stationary steam generator and again fed through the shut-off organ 8 into the well and thus organize the circulation of the coolant in the well to the depth of onset of paraffin crystallization 6. Fountain method m oil at annulus B is raised to the mouth and through the shut-off valve 10 is fed to the collection system. In this case, starting from the depth of onset of crystallization of paraffin 6, the oil to be lifted is heated from the coolant circulating in the well through the tubing string wall with the closed end 4, thereby crystallizing paraffin is prevented, and the viscosity of the oil and, accordingly, the viscosity friction during lifting are reduced. In addition, due to this, the transportation of heated oil from the wellhead to the place of its collection is also facilitated.

With a decrease in the filtration characteristics of the PZ formation due to asphalt-resin-paraffin deposits in it, which is judged by a decrease in the flow rate of the well at a constant reservoir pressure, the PZ formation is treated with solvents of these deposits. To do this, through the shut-off element 10 (see Fig. 2), the solvent is fed into the annulus B, while for better response in the formation PZ, it is heated by the coolant circulating in the well in a similar manner described when heating the oil lifted from the well.

To reduce the viscosity characteristics of oil in reservoir conditions and to improve its inflow into the well, the formation PZ is treated with a coolant, such as steam or hot water. To do this, the well is sealed with a packer 3, thereby protecting the casing 1 from contact with the coolant pumped into the formation, through the shut-off element 10, the coolant is fed into the annulus B and its flow through the shut-off element 8 to the tubing string with open end 5 is stopped.

If it is necessary to further reduce unproductive heat transfer to the rocks, for example, at large depths of the well, passing through permafrost zones, etc., the annulus A is filled with gas (for example, nitrogen, carbon dioxide, etc.) through the shut-off element 11 or gas entering the well from the formation.

The depth of onset of paraffin crystallization is determined when the well is operating and there is no coolant circulation in it. To do this, a depth thermometer is lowered into the tubing string with an open end 5 through a shut-off element 12 and the temperature is measured along the wellbore. The known temperature at which crystallization of paraffin begins, determines the depth at which crystallization in a given well begins.

Sequential descent into the casing string of insulated pipes with a packer at the end, tubing with a closed and open ends of pipes, and the descent of a string of insulated pipes below the depth of crystallization of paraffin, tubing with a closed end to this depth, and tubing with an open end so that they form a gap between the tubing with a closed end, while the coolant is supplied to the tubing with an open end, the oil rises along the annulus to the area of insulated and tubing pipes with a closed end, the supply of chemicals and coolant, while treating the bottom-hole zone of the formation, along the same annular space, and the flow of coolant with a sealed well, filling the space between the casing and heat-insulated column gas, determining the depth of onset of paraffin crystallization by measuring temperatures along the wellbore provide inflow from the reservoir and rise from the well of highly viscous oil, while maintaining the quality of raised from the reservoir and the oil in the heat transfer decreases unproductive rocks through the casing, and the heat loss from the well-cooled, reduced costs for the transportation of oil from the bottom to the mouth and before the collection space and its preparation, reduced complications and increases the turnaround time of production wells.

Thus, the application of the proposed method for the production of high-viscosity oil containing asphalt-resin-paraffin substances, allows to increase the efficiency of oil production by increasing the influx of oil from the reservoir and to ensure the rise of oil from the well while maintaining its quality, reducing unproductive heat losses and transportation losses.

Claims (3)

1. A method of producing highly viscous oil, including descent into a casing string of tubing strings arranged concentrically, supplying a coolant and lifting oil through the annulus, characterized in that a string of heat-insulated pipes with a packer at the end of the tubing is successively lowered into the casing string with the closed and open ends of the pipes, and the column of thermally insulated pipes is lowered below the depth of onset of paraffin crystallization, tubing with a closed end to this depth, and the pump open-ended dredging pipes so that they form a gap between closed-end tubing, the coolant is fed into the open-ended tubing, oil is lifted through the annular space of the heat-insulated and closed-ended tubing, chemicals and the coolant when processing the bottom-hole zone of the formation is fed along the same annular space, and the coolant is supplied with a sealed well. 2. The method according to claim 1, characterized in that the space between the casing and insulated columns is filled with gas. 3. The method according to claim 1 or 2, characterized in that the interval for the onset of crystallization of paraffin is determined by measuring the temperature along the wellbore.

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