Method of preparing a well for delivery of a heat transfer agent to an oil-bearing formation

Abstract

The invention relates to the field of downhole hydrocarbon production and can be used for delivering a high-temperature heat transfer agent, produced above ground, to an oil-bearing reservoir, without heating up well production strings, by injecting a thermally insulating fluid (foam) into the well annulus. The thermally insulating foam is injected into the well annulus via a circulation valve installed in a production tubing arrangement above a packer. The thermal insulation of the string and of the production tubing riser can be regulated by adjusting the ratio of the components of the foam and the delivery rate. The method can be carried out using standard equipment that is widely used in the field. The claimed method of preparing a well for high-temperature treatment makes its technically possible to exert a high-temperature thermal effect (up to 450℃) on an oil-bearing reservoir in wells of up to 4000 metres in depth, without having a thermal effect on the well production string.

Description

[0001] MIC E21B 36 / 00 E21B 33 / 00 E21B 33 / 10

[0002] Method of preparing a well for supplying heat carrier to an oil-bearing formation

[0003] Field of technology

[0004] The invention relates to the field of downhole production of hydrocarbon raw materials and can be used to deliver a high-temperature coolant (with a temperature of up to 450°C) created on the earth's surface to an oil-bearing reservoir without thawing the production well casings by pumping a liquid heat insulator (foam) into the annular space of the well.

[0005] State of the art

[0006] Various methods for well thermal insulation exist in the prior art. A well-known example is the "Method for Thermal Insulation of an Injection Well" (patent RU 2120540). After the tubing string (TU) with a packer is installed in a cased well, a separator pipe is placed between it and the casing. Valves are installed at the wellhead to provide an inlet and outlet. Heat transfer fluid is then injected into the TU through annular channels formed by the separator pipe. A heat-insulating agent is also passed through these channels. Inert or associated gases, as well as drilling fluid, can be used as this agent.

[0007] A wellbore insulation method using silicate foam is known (patent US4024919A). Wellbore insulation is achieved by boiling a silicate-containing solution in direct contact with the wellbore, which results in the formation of a silicate coating on the surface of the wellbore. At the same time, a liquid largely devoid of silicate comes into contact with the wellbore, acting as a buffer for the lower portion of the wellbore, preventing it from coming into contact with the silicate solution. This liquid, which contains virtually no silicate, effectively prevents the formation of a silicate foam coating on the lower portion of the wellbore, thereby eliminating potential problems associated with such a coating.

[0008] The "Heat-Insulating Method" (patent RU2718765C1) is well-known. According to the invention, each section of heat-insulated pipe used in well construction is manufactured in a factory using the well-known "pipe-in-pipe" technology, with welded plates, poured and cured heat-insulating material, and a waterproofing coating along the ends of the outer pipe.

[0009] A wellbore thermal insulation method (patent US4296814A) is well known. The method is designed to reduce heat transfer between fluids flowing through a 3,000-foot-long wellbore and the surrounding formations. A gelling fluid is injected into the annular space between the wellbore and the tubing string located within. This fluid is activated by heating and exhibits thermal insulation properties when it thickens. Specific methods are used to thicken the fluid.

[0010] A "Method for Thermally Insulating a Wellbore" (Patent US4276936A) is known. According to the proposed method, a wellbore is thermally insulated by placing a flowable solid insulation material in the space between the casing and the wellbore. Vermiculite and perlite, for example, can be used as such a material. Furthermore, within the framework of this invention, the solid insulation material is introduced into the space between the casing and the wellbore without the use of a carrier fluid and is then removed by fluidization of the material.

[0011] A "Method for Thermal Treatment of the Bottomhole Zone of an Oil and Gas Well" (Patent RU 2168619) is known. According to this method, the wellbore annulus is filled with foam with a gas-to-liquid ratio of 2 to 100. A heat-transfer fluid is then pumped into the wellbore through a tubing string in a volume of 0.5 to 1 pore volume of the bottomhole zone of a highly permeable formation within a radius of up to 10 m, while foam is simultaneously injected into the annulus at a rate equal to or exceeding the foam breakdown rate in the annular space from the wellhead to the bottomhole. Heat-transfer and foam injection are stopped for 12 to 72 hours, and after the temperature in the highly permeable formation has equalized, a foam rim is injected into the formation at a pressure not exceeding the casing strength. Then, a heat-transfer fluid is pumped into the low-permeability formations while pumping foam into the annular space, after which the well is left undisturbed for 2-10 days before being put into operation.

[0012] The "Process for Maintaining Thermal Conductivity of Insulation in a Permafrost Zone" (patent US3642065A) was selected as a prototype. The invention proposes the use of foam insulation created by blowing a gas with a lower thermal conductivity than air. The insulation is placed in an air-filled annular space located between intermediate concentric casing strings in the permafrost layer. This space is sealed below the insulation level. A liquid with a higher vapor pressure at permafrost temperatures and a lower evaporative thermal conductivity than air is injected into the annular space. Air is removed from the annular space, leaving it filled with liquid vapor, and the annular space is sealed in the upper position to create a hermetically sealed annular space filled with liquid vapor surrounding the insulation.

[0013] Despite the excellent thermal insulation properties of the above-mentioned method, its implementation requires significant technical modifications to the production casing design (running an additional concentric casing). Furthermore, pumping air and light liquid vapors (alcohols, ethers, and freon) is practically suitable for pumping wells up to 1,000 meters deep. An additional limitation is the explosive nature of alcohol, freon, and ether vapors when using a heat transfer fluid with a temperature of up to 450°C.

[0014] All of the above-mentioned analogs share the following limitation: pumping gases through the annular space of a well at depths greater than 1,000 m requires specialized compressor equipment and is not permitted by industry safety requirements. Furthermore, foam insulation applied (by various methods) to the tubing lift designed to deliver high-temperature coolant with temperatures up to 450°C will be destroyed due to thermal deformation of the tubing lift.

[0015] Disclosure of the essence of the invention

[0016] The present invention is aimed at preparing an existing well stock for performing heat treatment of the bottomhole zone of an oil and gas well reservoir using high-temperature heat carriers (water vapor, water in a supercritical state with a temperature of up to 450°C).

[0017] The technical result of the claimed solution consists of a method for preparing a well for transferring a high-temperature heat carrier (with a temperature of up to 450°C) created on the earth's surface into an oil-bearing reservoir, eliminating thermal deformation of production columns and tubing lift of existing wells, by pumping a liquid heat insulator (foam) into the annular space of the well.

[0018] The stated problem is solved and the technical result is achieved by the fact that the method of preparing a well for feeding a coolant into an oil-bearing formation includes installation in the production string of a lift made of tubing with temperature compensators, installation at the lower end of the tubing of a packer, characterized in that a circulation valve is installed in the tubing above the packer and the inter-tube space is filled with heat-insulating liquid foam, then a flexible tubing (CT) with a packer installed above the tubing packer and below the tubing circulation valve is placed inside the tubing, wherein the coolant is fed through the CT and at the same time reverse flushing of the well is performed by injecting heat-insulating liquid foam through a column valve into the inter-tube space and providing an outlet of the ascending flow of heat-insulating foam through the tubing circulation valve to the surface between the tubing and the CT, wherein the packers are made in heat-resistant design.Before supplying the coolant, the inter-tube space is pre-filled with heat-insulating liquid foam to form a primary heat-insulating layer along the entire length of the production string up to the circulation valve of the tubing. Implementation of the invention.

[0019] The main components of the arrangement of surface and downhole equipment are given in the table and shown in Fig. 1, 2, 3, where in one case, vacuum-sealed tubing (KT) or a "thermocase" is used to supply the coolant, and in the second case, conventional KT is used, and the supply of the high-temperature coolant is carried out through coiled tubing, or KT (thermocase) inside the KT lift.

[0020] No. Name of the equipment used

[0021] 1 Cementing unit CA-320 or similar

[0022] 2 Foaming liquid supply line

[0023] 3 Ejector

[0024] 4 Pressure gauge

[0025] 5 Pipe gate valves ZPShK 65-40-460 or similar

[0026] 6 Column valves ZPShK 65-40-460 or similar

[0027] 7 Choke chamber

[0028] 8 Foam discharge line

[0029] 9 Storage tank

[0030] 10 Thermally insulated tubing pipe (thermocase) TK114-73 -460V (or equivalent)

[0031] 11 Tubing pipe (min 73 mm)

[0032] 12 Temperature compensator KTR or similar

[0033] 13 Production casing

[0034] 14 Foam pipeline

[0035] 15 Ejector check valve will protect

[0036] 16 High pressure air line

[0037] 17 Compressor 18 Circulation valve

[0038] 19 Hydraulic heat-resistant packer PGT or similar

[0039] 20 Heat-resistant check valve

[0040] 21 Supercritical steam boiler

[0041] 22 Mobile high pressure steam pipeline

[0042] 23 Flexible tubing (CT), "thermocase" possible

[0043] 24 Coiled Tubing Unit

[0044] 25 Thermal insulating foam

[0045] Method G

[0046] When arranging an injection well, a tubing lift 10 (Fig. 1) (thermocase tubing) with a heat-resistant packer 19 is lowered into the production string 13 (Fig. 3). A circulation valve 18 and a tubular temperature compensator 12 are provided in the assembly above the “packer”. Before the high-temperature coolant is supplied, the well is backwashed by a cementing unit 1 along the foaming fluid supply line 2 into an ejector 3, where a compressor 17 supplies compressed air (or inert gas) via a high-pressure air line 16. Then, from the ejector 3, heat-insulating foam 25 (Fig. 3) is injected into the annular region via a foam pipeline 14. Through the column valve 6, foam 25 is directed downwards along the casing, and through the circulation valve 18, the upward flow of downhole process fluid is directed inside the tubing 10 to the surface. The foam is then directed through the pipe valve 5 along the foam discharge line 8 through the choke chamber 7 into the storage tank 9.

[0047] After the annular space is filled with foam 25, high-temperature (up to 450°C) coolant is injected. The coolant flows from the steam boiler 21 through the mobile steam line 22, through the check valve 20 and the gate valve 5, and through the insulated, vacuumized tubing 10 to the bottomhole zone. After the formation is thermally treated, this assembly is used for hydrocarbon production.

[0048] Method 2.

[0049] When arranging an injection well with tubing 11 (Fig. 2) and a heat-resistant packer 19, a circulation valve 18 and a tubular temperature compensator 12 are mounted in the assembly above the “packer”. Then, with the help of a coiled tubing unit 24, a coiled tubing 23 (or a “thermocase” coiled tubing) is lowered into the tubing and is also equipped with a high-temperature packer 19.

[0050] Before the coolant is pumped through coiled tubing 23, the well is reverse-flushed by injecting heat-insulating foam 25 into the annular region. Foam 25 is directed downward through column valve 6 and, through circulation valve 18, is directed upward through tubing 11 to the surface, where it is directed through pipe valve 5 along foam discharge line 8 and through choke chamber 7 into storage tank 9.

[0051] After the well has been pumped with insulating foam 25, high-temperature (up to 450°C) coolant is supplied through coiled tubing 23. After pumping is complete, before retrieving coiled tubing 23, tubing lift 11 is flushed with kill fluid, which allows the coiled tubing to be retrieved and production to commence.

[0052] Method 3.

[0053] If long-term thermal exposure is required, the assembly inside the well is assembled in the same way as for method 2.

[0054] Coiled tubing 23, lowered into tubing 11, is also equipped with a high-temperature packer 19. While high-temperature coolant is pumped through coiled tubing 23, the well is simultaneously reverse-flushed by injecting heat-insulating foam 25 into the annular region through valve 6. The upward flow of well fluid is directed through tubing 11 via the circulation system. After the coolant (with a temperature of up to 450°C) has been pumped through coiled tubing 23, before retrieving coiled tubing 23, the lift with tubing 11 is flushed with kill fluid. This allows for the retrieval of coiled tubing 23 and the commencement of hydrocarbon production.

[0055] The foam composition can be prepared, for example, using a pump unit (4AN-700) and a compressor (UKP-80). An aqueous surfactant solution is mixed with the supplied gas in the aerator, and the resulting foam is pumped into the well. The most commonly used surfactant is sulfonol at a concentration of 0.1% (1 ton of water + 1 kg of sulfonol).

[0056] Thus, in the technical solutions described above, the foam performs the function of thermal insulation of the production well casing, designed for injection of high-temperature (with a temperature of up to 450°C) coolant, and the following tasks are solved:

[0057] - To apply the proposed technical solution - a method for preparing a well for high-temperature (up to 450°C) treatment of an oil reservoir, standard equipment widely used in the industry was selected,

[0058] The use of technology for pumping liquid thermal insulators into a well creates the possibility of a multiple increase in the energy efficiency of the process of thermal treatment of oil-bearing reservoirs by reducing heat losses through the casing of injection wells, which under normal conditions reach 3-4% for every 100 m of well depth,

[0059] - the factor of thermal deformation and destruction of production columns and tubing lift is eliminated; - minimization of heat loss in the well creates the technical possibility of using high-temperature (with a temperature of up to 450°C) thermal impact on the oil-bearing reservoir in wells with a depth of up to 4000 meters.

Claims

Formula 1. A method for preparing a well for feeding a heat-transfer agent into an oil-bearing formation, which includes installing a tubing string with temperature compensators in the production string, installing a packer at the lower end of the tubing, characterized in that a circulation valve is installed in the tubing above the packer and the annular space is filled with heat-insulating liquid foam, then flexible tubing (CT) is placed inside the tubing with a packer installed above the tubing packer and below the CT circulation valve, wherein the heat-transfer agent is fed through the CT and simultaneously reverse flushing of the well is performed by injecting heat-insulating liquid foam through a column valve into the annular space and ensuring the exit of an upward flow of heat-insulating foam through the CT circulation valve to the surface between the tubing and the CT, wherein the packers are made in a heat-resistant design.

2. The method according to I.1, characterized in that before supplying the coolant, the inter-tube space is pre-filled with heat-insulating liquid foam to form a primary heat-insulating layer along the entire length of the production string up to the circulation valve of the tubing.

Images