Thermally insulated casing string

Abstract

The invention relates to downhole devices for delivering a high-temperature working fluid with a temperature of up to 700°С at a pressure of up to 60 MPa into a formation. A thermally insulated casing string contains sequentially connected sections of individual thermally insulated casing pipes, each of which comprises a thick-walled quartz pipe with upset ends. The outer surface of each of these pipes is wrapped in a first layer of a first heat-reflective material, which is a stainless steel foil. A second layer comprises a first thermally insulating coating, which is covered on top by means of a protective shell. A second heat-reflective material, which is a heat-resistant silver enamel, is applied to the inner surface of the first thermally insulating coating. Mounted to the outer surface of the protective shell is a second thermally insulating coating, which is mechanically fastened with stainless steel tape. The individual segments are connected into the thermally insulated casing string using a detachable flange connection. The areas of the joins between the individual segments of the thermally insulated casing string are covered by a sleeve. The cavity between the sleeve and the quartz pipe is filled with a thermally insulating coating which has an identical composition to the second thermally insulating coating. The result is an increase in the thermal insulation, strength and anti-corrosion properties of thermally insulated pipes.

Description

[0001] The invention can be used in the oil and gas industry and relates to downhole devices for delivering a high-temperature working agent (T up to 700°C) of high pressure (P up to 60 MPa) into a hydrocarbon-containing productive formation in the form of pseudo-ultra-supercritical fluids, pseudo-supercritical fluids or pure fluids in ultra-supercritical and supercritical forms (hereinafter, USC), as well as in geothermal energy for the selection of a coolant in the form of an ultra-supercritical or supercritical fluid from an artificially created underground heat exchange geothermal reservoir.

[0002] Oil companies have now begun developing oil-bearing shale formations, particularly the Bazhenov and Domanik Formations. The use of so-called thermochemical technologies, based on the injection of high-temperature, high-pressure, and high-recovery hydrocarbons into the reservoir, has been recognized as highly promising for their development.

[0003] A RAV with similar thermobaric characteristics is also required for the development of deep-seated hydrocarbon deposits, as well as for the continued profitable exploitation of traditional hydrocarbon deposits in the final stage of exploitation, including hard-to-recover hydrocarbon reserves (HRCR).

[0004] In turn, in geothermal energy, the direction known as "Enhanced Geothermal Systems" (EGS) continues to actively develop. The essence of this system is pumping cold water through an injection well into a pre-fractionated high-temperature granite formation located at a depth of up to 6000 meters and having a temperature of up to 500-700 °C, heating the cold water (fluid) as it passes through cracks in the high-temperature granite formation and withdrawing the heated high-temperature fluid to the daylight surface through a production well.

[0005] Naturally, the implementation of such technologies requires downhole devices that have high thermal insulation properties to reduce fluid heat loss during transportation, high strength properties to withstand high fluid pressure, high anti-corrosion properties necessary for operation in aggressive environments, and also ensure a reliable and hermetic connection when forming a pipe string for delivering RAVs to the productive formation from the daylight surface of the well.

[0006] There are potentially two alternative concepts for devices for transporting high-temperature, high-pressure RAW.

[0007] The subject of the first concept is the so-called vacuum insulated tubing (VIT), as well as tubing with a heat-insulating coating (TIP) without vacuumization.

[0008] Currently, such TLT or tubing with TIP, which optimally combine high thermobaric and anti-corrosion properties, as well as have reliable connecting elements for the formation of tubular columns, are absent both in the Russian Federation and abroad, which is one of the limiting factors for the use of modern thermochemical technologies, including the innovative Thermochemical Impact Technology (TTIC).

[0009] Naturally, numerous attempts have been made in the Russian Federation and abroad to develop designs for such TLTs or tubing with TIPs that meet such stringent requirements. However, this problem remains unresolved to date.

[0010] The most successful development to date is the TLT developed by PAO TMK, which is suitable for transporting RAVs to the wellbore in the form of supercritical water, with temperatures up to 450°C and pressures up to 40 MPa. However, for the commercial development of oil-bearing shale formations, such as the Bazhenov Formation, using TLTs, RAVs in the form of supercritical water are required, with a wellhead temperature of at least 550°C and pressures up to 60 MPa.

[0011] The subject of the second concept is thermally insulated casing pipes (TIC).

[0012] A method for manufacturing insulated lift pipes (Russian Federation Patent No. 2585338, dated March 11, 2014, "Method for Manufacturing an Insulated Heat Pipe") is known. It can be used in oil wells operating in permafrost zones. This method simplifies the assembly process of the insulated lift pipe and enables its operation at sub-zero temperatures.A method for manufacturing a heat-insulated elevator pipe consisting of coaxially arranged inner and outer pipes and end liners, including installing the inner pipe and end liners in an outer pipe to form an inter-pipe space, connecting the inner and outer pipes by welding with the end liners in a protective gas environment, wherein the inner and outer pipes and end liners are made of steel, in the chemical composition of which the mass fraction of S <0.010%, the mass fraction of P <0.020%, and the connection of the inner and outer pipes with the end liners is carried out by welding after preheating the weld joint zone to a temperature of 100-400°C with the installation of a plug on the end of the outer pipe opposite to where the welding is carried out.

[0013] The disadvantages of the known method are the complex and expensive manufacturing process, and the design of the insulated lift pipe itself does not allow it to be used for transporting high-temperature, high-pressure RAW from the surface of the well to the bottomhole.

[0014] Also known is the "Method for Manufacturing a Thermally Insulated Casing String and a Casing String Made Using This Method" (RU Patent No. 2652776 dated June 29, 2017—the closest analogue to the claimed invention). The technical result is a reduction in the thermal conductivity of the structure. The method for manufacturing a thermally insulated casing string involves feeding thermal insulation material into the annular space between the inner and outer pipes coaxially installed in each section. The protruding joints of the inner pipes are secured with a collapsible connecting device. The outer pipes are covered with a shell, and the space between the inner pipes and the shell is filled with thermal insulation. Before assembling the pipes, through holes are made in the wall of the upper and lower parts of the outer pipe of each section for gas venting and are fitted with removable plugs for sealing.

[0015] The main drawback of the known method is the use of polyurethane foam (1ShU) as thermal insulation material, whose maximum operating temperature does not exceed 220°C. This is clearly insufficient to provide thermal insulation during the delivery of RAV, which has a temperature of up to 700°C, to the wellbore bottom.

[0016] The technical objective of the claimed invention is to create a thermally insulated casing (TIC) that has high thermal insulation properties to reduce heat loss of fluid during its transportation, high strength properties to withstand high fluid pressure, and high anti-corrosion properties necessary for operation in aggressive environments.

[0017] The technical problem has been solved as follows. In a thermally insulated casing (TIC) containing successively connected sections of individual thermally insulated casing pipes (TIP), what is new is that each of the TIPs includes a thick-walled quartz pipe with upset ends, the outer surface of which is wrapped in the first layer with the first heat-reflecting material - stainless steel foil, and then the first heat-insulating coating is placed in the second layer, covered on top with a protective casing, on the inner surface of which a second heat-reflecting material is applied - heat-resistant silver enamel, and on the outer surface of the protective casing a second heat-insulating coating is installed, mechanically secured with a stainless steel tape. At the same time, to connect individual segments of the TIP in the TIC a detachable flange connection is used, the joint zones of individual segments of the TIP are covered with a shell,and the cavity between the inner surface of the shell and the outer surface of the thick-walled quartz tube is filled with a heat-insulating coating identical in composition to the second heat-insulating coating.

[0018] The essence of the invention is explained by graphic materials, in which:

[0019] - Fig. 1 - longitudinal section of the heat-insulated casing column (HICC) 1 in assembly;

[0020] - in Fig. 2 - application of the first heat-insulating coating to pipe 3.

[0021] The heat exchanger 1 consists of sequentially connected individual sections of the heat exchanger 2, each of which has a thick-walled quartz tube with upset ends 3, with collapsible flanges 4 installed on the ends of the tube 3, the outer surface of which is wrapped with a first heat-reflecting material 5 - stainless steel foil, a first heat-insulating coating (composite) 6, made of a mixture of liquid glass obtained from dry powders for the manufacture of liquid glass and aluminosilicate microspheres, a protective casing 7, the inner surface of which is covered with a second heat-reflecting material - heat-resistant silver enamel (not shown in the figure), a second heat-insulating coating 8, made of foam glass having a density of 161 to 200 kg / m 3with closed cellularity, and the joint zones of individual segments of the heat-insulating tube 9 are covered by a shell 10, and the cavity between the inner surface of the shell 10 and the outer surface of the pipe 3 is filled with a heat-insulating coating, identical in composition to the second heat-insulating coating 6.

[0022] The use of a thick-walled pipe 3 made of quartz in the claimed invention is due to the fact that quartz products have:

[0023] • heat resistance - withstands heating up to 1200°C;• the ability to withstand temperature fluctuations in the range from 1000 to 1250°C;

[0024] • resistance to acids (except phosphoric and hydrofluoric);

[0025] • alkali resistance;

[0026] • corrosion resistance;

[0027] • have a low coefficient of thermal expansion; and

[0028] • high hardness (7 on the Mohs scale, for example, like one of the hardest heat-resistant alloys, Inconel).

[0029] The claimed invention can use thick-walled quartz glass pipes from companies such as: OOO TKK (Moscow), OOO NPF Kvartsevoe Steklo (St. Petersburg), OOO KS (Gus-Khrustalny) and other manufacturers.

[0030] In the claimed invention, to ensure the joining of individual sections of the TOT 2, a collapsible flange is used, known from the Russian Federation patent No. 2791791 of June 22, 2022, "A collapsible flange for pipes with thrust flanges at the ends."

[0031] The claimed invention utilizes a stainless steel mirror tape 5 with a thickness of 0.02 to 3 mm, manufactured, for example, by the Russian company "GK Stainless Steel Tape" (Moscow), as the first heat-reflective coating. The purpose of this heat-reflective coating is to reduce heat loss by providing a radiation barrier. The stainless steel mirror tape VA (mirror surface), like the aluminum tape, is capable of reflecting up to 95% of the radiation that would otherwise be absorbed by the first heat-insulating coating 6.

[0032] The claimed invention utilizes stainless steel tape (foil) instead of aluminum foil, as aluminum tape cannot be used for direct winding onto pipe 3 due to the high temperature of the coolant (up to 700°C). The temperature limit for aluminum foil does not exceed 550-600°C.

[0033] After applying the first heat-reflecting coating 5 to the pipe 3, we proceed to prepare the mixture for the first heat-insulating coating 6 by mixing aluminosilicate microspheres of the ANM-150 brand (diameter up to 150 µm) produced by the ForeSfera company (Yekaterinburg) with a dry concentrate for the preparation of liquid glass produced by the Ecoe company, Chelyabinsk.

[0034] The first thermal insulation coating is made of vacuum microspheres (or aluminosilicate microspheres, which are more readily available in Russia). Liquid glass (less than 50% of the mixture) is used as a binder, capable of withstanding high temperatures of up to 1200°C. The thermal conductivity of this insulation, the closest analogue of which is liquid thermal insulation, is approximately 0.06 W / (m*K).

[0035] Liquid glass is prepared from a dry concentrate (DC) for the rapid preparation of aqueous solutions of liquid glass (manufactured by the Ecoe company, Chelyabinsk), used as a binding material for various purposes, including coating metal welding electrodes, lining steel-smelting electric furnaces, pouring ladles, in the manufacture of casting molds and cores, etc.

[0036] The most significant qualities of such thermal insulation 6 are its ability to operate under high temperature conditions, water resistance, relatively high strength and durability of use.

[0037] Aluminosilicate microspheres have the following properties:

[0038] 1. Correct spherical shape.

[0039] Cost-effectiveness. Spherical filler requires a minimal amount of binder to moisten the side surface; any other sealant shape will require more resin, binder, water, etc.

[0040] Quality. The regularly shaped spheres provide an efficient surface area-to-volume ratio and compact packing: the packing efficiency is 60-80% of the theoretical value. Therefore, aluminosilicate microspheres exhibit less shrinkage deformation than seals with a broken shape.

[0041] Convenience. The round shape of the filler gives the materials good flowability: they are easy to dispense (including gravity-flow), and convenient to apply to surfaces—by hand with a spatula, by spraying under pressure, by pumping, etc.

[0042] 2. Low density and high strength.

[0043] The density of aluminosilicate microspheres is several times lower than that of other mineral fillers (bulk density of aluminosilicate microspheres is 0.32-0.37 g / cm 3 , true density - 0.58-0.69 g / cm 3 ), therefore, it is more convenient to mix and more economical to transport. At the same time, the strength of the microsphere allows it to withstand hydrostatic pressures in excess of 100 atm. (The thickness of the microsphere walls ranges from 2 to 10 µm, the density of the wall material is 2.5 g / cm 3 ). The compressive strength of aluminosilicate microspheres is 150-280 kg / cm 2 , hardness on the Mohs scale is 5-6.

[0044] 3. Low reactivity.

[0045] Aluminosilicate microspheres do not affect the chemical composition or reactivity of most mixtures in which they are used as a filler. The main components of the microspheres' phase-mineral composition are aluminosilicate glass phase, mullite, and quartz. The main chemical components are silicon, aluminum, and iron. The gas phase inside the microspheres consists of nitrogen and carbon dioxide. The microspheres are pH-neutral and resistant to acids and alkalis.

[0046] 4. High melting point and low thermal conductivity.

[0047] Aluminosilicate microspheres retain their properties when heated to 980°C and melt at 1400-1500°C. Furthermore, aluminosilicate microspheres have low thermal conductivity, which imparts high thermal insulation properties to the materials and allows for the creation of fire-resistant coatings

[0001] .

[0048] After mixing, the mixture, consisting of aluminosilicate microspheres and dry powder for making liquid glass (proportions are determined experimentally), is mixed with water. Typically, 1 ton of dry powder yields 2 to 4 tons of liquid glass. The required density of the liquid glass is determined only by the amount of water added to the dry mixture. This thermal insulation grade 6 can be used at temperatures up to 1200°C.

[0049] This thermal insulation 6 is applied to the surface of the pipe 3 as follows (Fig.

[0050] 2).

[0051] A collapsible flange 4 is welded to a protective casing consisting of two shells made of stainless steel and connected by welding into a protective casing 7 in the form of a pipe, on the inner surface of which a second heat-reflecting coating (not shown in the figure) has been pre-applied (by any suitable method) - for example, enamel "Moskvichka KO-8101", and the pipe 3 itself, which is located coaxially inside the protective casing 7, is installed vertically so that the collapsible flange 4 welded to the protective casing 7 would be in the lower part of the pipe 3 and the protective casing 7. The thickness of the wall of the protective casing is from 3 to 5 millimeters. The vertically installed protective casing 7 is secured with supports 11, and the pipe 3 itself is put on the internal centralizer 12, which is installed on the vibrating table 13.Through the injection holes 14 of the protective casing 7, the inter-tube space between the pipe 3 and the protective casing 7 is successively filled from the bottom up with the first heat-insulating coating 6 in the form of a mixture of liquid glass with aluminosilicate microspheres. As the inter-tube space is filled with the heat-insulating coating 6, the injection holes 14, with the exception of the upper one, are closed with plugs (bolts, for example, are used as plugs). To compact the heat-insulating coating 6, the vibrating table 13 is turned on. After the compaction process is complete, the vibrating table is turned off and additional heat-insulating coating 6 is injected into the cavity between the pipe 3 and the protective casing 7 until this cavity is completely filled with the heat-insulating coating 6. After this operation is completed, the upper plug (not shown in the figure) is inserted into the upper injection hole 14.

[0052] Before the heat-insulating coating 6 hardens, a second collapsible flange 4 is welded to the upper part (upper end) of the protective casing 7. In this case, the heat-insulating coating 6, which is in a liquid state, fits tightly and is well secured to the inner surface of the collapsible flange 4.

[0053] Thermal insulation coating 6 hardens after 5-6 hours. After hardening, the thermal insulation coating gains significant strength, and then the process of forming the second thermal insulation coating 8 begins.

[0054] The heat-insulating coating 8 is formed on the outer surface of the protective casing 7 by fastening to it shells made of closed-cell foam glass using the heat-insulating coating 6 in liquid form (as a “glue” for sealing joints and heat-insulating the joints of the shells between themselves, as well as for gluing these shells made of foam glass to the outer surface of the protective casing 7) with their subsequent mechanical fastening with reinforced tape 15 (AISI 4300.5x20).

[0055] In the claimed invention, products of the company "TIM" (St. Petersburg) [2] 000 "NEFTEZOL", Moscow [3] OOO "Navites", Moscow, manufactured in Vladimir [4] etc. can be used as shells made of closed-cell foam glass.

[0056] Foam glass consists of sealed, non-communicating glass bubbles, completely impermeable to vapor and water. It is a durable, fire-resistant, and environmentally friendly material. All of its physical properties remain unchanged, even in high humidity conditions, for over 100 years, even when reused. There is no other material with similar properties. It is a unique thermal insulation material, free from all the drawbacks of traditional insulation materials.

[0057] Due to its high mechanical strength, vapor and water resistance, the thermal insulation coating 8 made of foam glass does not require a special external protective casing.

[0058] After its installation on the outer surface of the protective casing 7 and after the heat-insulating coating 6 has hardened, TOT 2 is ready for use.

[0059] During the construction of a well, individual segments of the TOT 2 are assembled into a TOK 1 using prefabricated flange connections, while the joint zones 9 of individual segments of the TOT 2 are covered by a shell 10, which is secured to the heat-insulating surface 8 of both TOT 2 using, for example, liquid glass or heat-resistant glue "KS" (manufactured in Russia) with its subsequent mechanical fastening with reinforced tape 15 (AISI 4300.5x20).

[0060] The insulated casing is manufactured and ready for use.

Claims

Invention formula 1. A heat-insulated casing string comprising sequentially connected sections of individual heat-insulated casing pipes, characterized in that each of the heat-insulated casing pipes includes a thick-walled quartz pipe with upset ends, the outer surface of which is wrapped in a first layer with a first heat-reflecting material - stainless steel foil, and then a first heat-insulating coating is placed in a second layer, closed on top with a protective casing, on the inner surface of which a second heat-reflecting material is applied - heat-resistant silver enamel, and on the outer surface of the protective casing a second heat-insulating coating is installed, mechanically secured with a stainless tape, while for connecting individual segments of the heat-insulated casing pipe into a heat-insulated casing string a detachable flange connection is used, the joint zones of individual segments of the heat-insulated casing pipe are covered with a shell,and the cavity between the inner surface of the shell and the outer surface of the thick-walled quartz tube is filled with a heat-insulating coating identical in composition to the second heat-insulating coating.

2. A thermally insulated casing string according to paragraph 1, characterized in that each of the thermally insulated casing pipes contains a first thermally insulating coating, compositely consisting of aluminosilicate microspheres and, as a binder, hardened liquid glass prepared from a dry concentrate of liquid glass.

3. A thermally insulated casing string according to paragraph 1, characterized in that each of the thermally insulated casing pipes contains a second thermally insulating coating in the form of closed-cell foam glass shells, secured to the protective casing using glue, followed by their mechanical fastening.

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