Insulating material for downhole heater and method of making

Abstract

The application discloses an underground heater insulating material with improved insulation performance by zirconium doping and a preparation method thereof. The insulating material is an insulating ceramic material prepared from mixed materials containing magnesium oxide, a doping material containing zirconium elements and a modifying agent, and is prepared through ball milling, drying and granulation, aging and forming and plastic sintering. Since the doping material containing zirconium elements and the magnesium oxide can form a solid solution, the lattice of the activated magnesium oxide crystal is improved, the compactness and strength of the material are improved, and the insulation performance is improved. The modifying agent reduces the vacancy defects of the MgO crystal grains, and the MgO-OH structure is not easy to be formed by moisture absorption, so that the volume resistivity is improved. Compared with the high-purity magnesium oxide ceramic material, the prepared insulating ceramic material has good high-temperature insulation performance, and can be used as an insulating material for a high-power underground heater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of downhole high-power heater and insulating material, in particular to a downhole heater insulating material with improved insulation performance by zirconium doping and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for oil and gas and the continuous consumption of conventional oil and gas resources, the effective development of unconventional oil and gas resources has important strategic significance for relieving the supply pressure of oil and gas resources and promoting the low-carbon transformation and green development of energy structure. Unconventional oil and gas mainly includes heavy oil, shale oil, shale gas, coalbed methane, etc. Downhole electric heater technology is applied to new fields such as downhole heating assistance of heavy oil and in-situ coal gasification, which has important significance for promoting the implementation of major projects such as downhole electric heating assistance of heavy oil thermal recovery, in-situ conversion of shale oil, and in-situ coal gasification.

[0003] Downhole high-power electric heating technology uses the heat generated by electric resistance heating to continuously heat the wellbore heat transfer medium (steam, water or oil reservoir). Downhole high-power electric heater is the core equipment of electric heating technology. The electric heater (mineral insulated heating cable) mainly uses single or multiple electric resistance heating alloy wires as the heat source, magnesium oxide as the heat-conducting insulator, and stainless steel or copper as the sheath, which is manufactured by special production process. When the heating core wire passes through the electric current, the electric energy is converted into heat energy to heat the oil reservoir.

[0004] Currently, electric heating technology mainly uses MI cable, and the insulating material in the MI cable is high-purity magnesium oxide. However, due to the influence of factors such as purity, chemical properties, particle shape, particle size distribution, crystal shape, and filling process, the thermal conductivity, thermal stability, insulation performance, and long-term service performance of the insulating material are limited. Therefore, it is of great practical significance to develop a preparation method of downhole high-power heater insulating material and to make it have good insulation, mechanical strength, thermal conductivity and stability. SUMMARY

[0005] In view of the above problems, the present application provides a downhole heater insulating material with improved insulation performance by zirconium doping and a preparation method thereof, which overcomes the above problems or at least partially solves the above problems.

[0006] In a first aspect, the present application provides a downhole heater insulating material with improved insulation performance by zirconium doping, which is an insulating ceramic material prepared from a mixed material containing magnesium oxide, zirconium-containing doping material and modification reagent, through ball milling, drying and granulation, aging and forming, and plastic sintering.

[0007] Optionally, the mass content of the zirconium-containing doping material in the mixed material is 0.5-2.8%, and the mass content of the modification reagent in the mixed material is 1-9%.

[0008] Optionally, the doping material containing zirconium element is a compound formed by zirconium and a nonmetal.

[0009] Optionally, the doping material containing zirconium element is an intermetallic compound formed by zirconium and a metalloid.

[0010] Optionally, the doping material containing zirconium element is a salt of zirconium.

[0011] Optionally, the doping material containing zirconium element is a zirconate.

[0012] Optionally, the modification reagent is at least one of sodium stearate, sodium dodecyl sulfate, sodium dodecyl sulfonate, CTAB and butyl titanate.

[0013] In a second aspect, the present application provides a preparation method of an insulating material of a downhole heater by doping zirconium to improve insulation performance, comprising:

[0014] The mixed material containing magnesium oxide, doping material containing zirconium element and modification reagent is subjected to wet ball milling to obtain a slurry raw material;

[0015] The slurry raw material is dried and sieved to obtain a powder material;

[0016] The binder is added to the powder material for granulation, and then the powder material is pressed into a ceramic green body;

[0017] The ceramic green body is crushed, reformed and aged to obtain a ceramic green sheet;

[0018] The ceramic green sheet is subjected to plastic arrangement sintering to obtain an insulating ceramic material.

[0019] Optionally, after the ceramic green sheet is obtained, the method further comprises:

[0020] It is judged whether the particle size of the current ceramic green sheet meets the particle size requirement;

[0021] If not, the current ceramic green sheet is used as a raw material, and the step of obtaining the slurry raw material by wet ball milling is returned.

[0022] Optionally, the step of obtaining the slurry raw material by wet ball milling comprises:

[0023] The wet ball milling is performed by using agate balls and anhydrous ethanol as a medium to obtain the slurry raw material.

[0024] The above technical solutions provided by the present application have at least the following beneficial effects:

[0025] (1) The well heater insulating material with improved insulation performance by zirconium doping provided by the present application is an insulating ceramic material prepared from a mixed material containing magnesium oxide, a doping material containing zirconium element and a modifying agent, through ball milling, drying granulation, aging molding and plastic removal sintering.

[0026] (2) The preparation method of the well heater insulating material with improved insulation performance by zirconium doping provided by the present application is simple, easy to operate and suitable for industrial production.

[0027] The technical solutions of the present application will be further described in detail below through examples. BRIEF DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application and are used to explain the present application together with the embodiments of the present application, and do not constitute a limitation on the present application. In the drawings:

[0029] Figure 1 The preparation method flow chart of the well heater insulating material with improved insulation performance by zirconium doping in the present application. DETAILED DESCRIPTION

[0030] The exemplary embodiments of the present application will be described in detail below. Although exemplary embodiments are disclosed, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly and completely conveyed to those skilled in the art, and the scope of the present application can be fully conveyed to those skilled in the art.

[0031] In order to solve the problems in the prior art, the present application provides a well heater insulating material with improved insulation performance by zirconium doping and a preparation method thereof.

[0032] The present application provides a well heater insulating material with improved insulation performance by zirconium doping, which is a uniform insulating ceramic material with good high-temperature electrical resistance prepared from a mixed material containing magnesium oxide, a doping material containing zirconium element and a modifying agent, through ball milling, drying granulation, aging molding and plastic removal sintering.

[0033] Since the doping material containing zirconium element and magnesium oxide can form a solid solution, the lattice of the activated magnesium oxide crystal is improved, the density and strength of the material are improved, and the insulation performance is improved; the modification reagent reduces the vacancy defects of the MgO crystal grains, and the MgO-OH structure is not easy to be formed by moisture absorption, thereby improving the volume resistivity; the prepared insulating ceramic material has good high-temperature insulation performance, can be used as an insulating material of a downhole high-power heater, and can ensure that the insulating material is not broken down at a high temperature of 650 DEG C.

[0034] Optionally, the purity of the magnesium oxide is not less than 80%.

[0035] Optionally, the mass content of the doping material containing zirconium element in the mixed material is 0.5-2.8%, and the mass content of the modification reagent in the mixed material is 1-9%.

[0036] Optionally, the doping material containing zirconium element can be in the following forms:

[0037] (1) The doping material containing zirconium element is a compound formed by zirconium and a nonmetal

[0038] It can be zirconium oxide or zirconium oxychloride, and can also be zirconium iodide, zirconium chloride, zirconium fluoride, dichlorobis zirconocene, tetrakis (dimethyl ammonium) zirconium, etc.

[0039] (2) The doping material containing zirconium element is an intermetallic compound formed by zirconium and a metalloid

[0040] It can be zirconium carbide, zirconium nitride, and can also be zirconium sulfide, zirconium hydride, zirconium boride, etc.

[0041] (3) The doping material containing zirconium element is a salt of zirconium

[0042] For example, zirconium n-propyl alcohol, zirconium acetylacetone, and can also be zirconium silicate, etc.

[0043] (4) The doping material containing zirconium element is a zirconate

[0044] It can be ammonium fluorozirconate, barium zirconate, etc.

[0045] Optionally, the above modification reagent can be at least one of sodium stearate, sodium dodecyl sulfate, sodium dodecyl sulfonate, CTAB and butyl titanate.

[0046] The application provides a preparation method of an insulating material of a downhole heater with improved insulation performance by zirconium doping, as shown in Figure 1 The method comprises the following steps:

[0047] Step S11: The mixed material containing magnesium oxide, a doping material containing zirconium element and a modification reagent is subjected to wet ball milling to obtain a slurry raw material.

[0048] The specific materials of the magnesium oxide, the doping material containing the zirconium element and the modification reagent and the mass ratio thereof are described above.

[0049] The magnesium oxide raw material, the doping material containing the zirconium element and the modification reagent can be wet ball milled for 6-12 hours in a medium of agate ball and anhydrous ethanol to obtain a slurry raw material.

[0050] The slurry raw material is dried and sieved to obtain a powder material.

[0051] The slurry raw material is dried and sieved through a 40-100 mesh sieve to obtain a powder material under the sieve.

[0052] The binder is added to the powder material to granulate, and then the ceramic body is pressed.

[0053] The binder is added to the powder material to granulate, and then the ceramic body is pressed.

[0054] Further, the binder can be polyvinyl alcohol (PVA) with a mass fraction of 5-10 wt.%, or other binders.

[0055] The ceramic body is broken, reformed and aged to obtain a ceramic green sheet.

[0056] Optionally, after obtaining the ceramic green sheet, the following steps can be further included:

[0057] It is determined whether the particle size of the current ceramic green sheet meets the particle size requirement; if not, the current ceramic green sheet is used as a raw material, and the step of obtaining the slurry raw material by wet ball milling is returned.

[0058] In the process of using the current ceramic green sheet as a raw material to prepare a new ceramic green sheet, the previous preparation process can be kept unchanged, or a harder agate ball can be selected, and / or a smaller mesh sieve can be selected.

[0059] The ceramic green sheet is subjected to plastic sintering to obtain an insulating ceramic material.

[0060] The formed ceramic green sheet can be heated to 500-700℃ at a heating rate of 5℃ / min, and subjected to degassing treatment at the constant temperature for 30-120 min; then heated to 1000-2000℃ in a high-temperature muffle furnace, and subjected to high-temperature sintering at the constant temperature for 1-48 h to obtain the insulating ceramic material.

[0061] The preparation method of the insulating material of the downhole heater with improved insulation performance by zirconium doping is simple, easy to operate and suitable for industrial production.

[0062] Example 1

[0063] The 1000 g of magnesium oxide (purity 99.99%), 10 g of zirconium dioxide, 30 g of sodium dodecyl sulfate, and an appropriate amount of anhydrous ethanol were weighed and added to a star-shaped ball mill, and wet ball milling was performed for 9 h. The above raw materials were transferred to an oven and dried at 120 °C for 24 h, and sieved through a 40-mesh sieve. A ceramic green sheet was obtained by adding 5 wt.% of polyvinyl alcohol (PVA) as a binder to the powder, mixing the binder and the powder uniformly during the granulation process, and then pressing into a ceramic body. The ceramic body was broken, reshaped, and aged. The shaped ceramic green sheet was heated to 500 °C at a heating rate of 5 °C / min, and held for 30 min for degassing. Then, the ceramic green sheet was heated to 1400 °C in a high-temperature muffle furnace and held for 48 h for high-temperature sintering to obtain a ceramic sample.

[0064] Example 2

[0065] The 1000 g of magnesium oxide (purity 99.99%), 10 g of zirconium dioxide, 30 g of sodium dodecyl sulfate, and an appropriate amount of anhydrous ethanol were weighed and added to a star-shaped ball mill, and wet ball milling was performed for 9 h. The above raw materials were transferred to an oven and dried at 120 °C for 24 h, and sieved through a 40-mesh sieve. A ceramic green sheet was obtained by adding 5 wt.% of polyvinyl alcohol (PVA) as a binder to the powder, mixing the binder and the powder uniformly during the granulation process, and then pressing into a ceramic body. The ceramic body was broken, reshaped, and aged. The shaped ceramic green sheet was heated to 500 °C at a heating rate of 5 °C / min, and held for 30 min for degassing. Then, the ceramic green sheet was heated to 1400 °C in a high-temperature muffle furnace and held for 48 h for high-temperature sintering to obtain a ceramic sample.

[0066] Example 3

[0067] The 1000 g of magnesium oxide (purity 99.99%), 10 g of zirconium dioxide, 30 g of sodium dodecyl sulfate, and an appropriate amount of anhydrous ethanol were weighed and added to a star-shaped ball mill, and wet ball milling was performed for 9 h. The above raw materials were transferred to an oven and dried at 120 °C for 24 h, and sieved through a 40-mesh sieve. A ceramic green sheet was obtained by adding 5 wt.% of polyvinyl alcohol (PVA) as a binder to the powder, mixing the binder and the powder uniformly during the granulation process, and then pressing into a ceramic body. The ceramic body was broken, reshaped, and aged. The shaped ceramic green sheet was heated to 500 °C at a heating rate of 5 °C / min, and held for 30 min for degassing. Then, the ceramic green sheet was heated to 1400 °C in a high-temperature muffle furnace and held for 48 h for high-temperature sintering to obtain a ceramic sample.

[0068] Example 4

[0069] Example 1

[0070] Example 2

[0071] Example 3

[0072] Example 4

[0073] Example 5

[0074] Example 6

[0075] Take and add 1000 g of magnesium oxide (purity 99.99%) to the star-shaped ball mill, 10 g of ammonium fluorozirconate, 100 g of butyl titanate, and an appropriate amount of anhydrous ethanol, and wet ball mill for 9 h. Transfer the above raw materials to an oven and dry at 120°C for 24 h. Screen through a 40 mesh sieve. Add 5wt.% polyvinyl alcohol (PVA) as a binder to the powder for granulation. During the granulation process, mix the binder and the powder evenly. Then press into ceramic green bodies. Crush the ceramic green bodies, re-form, and age to obtain ceramic green sheets. Heat the formed ceramic green sheets to 500°C at a heating rate of 5°C / min, and keep the temperature for 30 min for degassing. Then heat to 1400°C in a high-temperature muffle furnace and keep the temperature for 48 h. High-temperature sintering of the ceramic green sheets to obtain ceramic samples.

[0076] Example 8

[0077] Take and add 1000 g of magnesium oxide (purity 99.99%) to the star-shaped ball mill, 10 g of ammonium fluorozirconate, 100 g of butyl titanate, and an appropriate amount of anhydrous ethanol, and wet ball mill for 9 h. Transfer the above raw materials to an oven and dry at 120°C for 24 h. Screen through a 40 mesh sieve. Add 5wt.% polyvinyl alcohol (PVA) as a binder to the powder for granulation. During the granulation process, mix the binder and the powder evenly. Then press into ceramic green bodies. Crush the ceramic green bodies, re-form, and age to obtain ceramic green sheets. Heat the formed ceramic green sheets to 500°C at a heating rate of 5°C / min, and keep the temperature for 30 min for degassing. Then heat to 1400°C in a high-temperature muffle furnace and keep the temperature for 48 h. High-temperature sintering of the ceramic green sheets to obtain ceramic samples.

[0078] Example 9

[0079] Take and add 1000 g of magnesium oxide (purity 99.99%) to the star-shaped ball mill, 10 g of ammonium fluorozirconate, 100 g of butyl titanate, and an appropriate amount of anhydrous ethanol, and wet ball mill for 9 h. Transfer the above raw materials to an oven and dry at 120°C for 24 h. Screen through a 40 mesh sieve. Add 5wt.% polyvinyl alcohol (PVA) as a binder to the powder for granulation. During the granulation process, mix the binder and the powder evenly. Then press into ceramic green bodies. Crush the ceramic green bodies, re-form, and age to obtain ceramic green sheets. Heat the formed ceramic green sheets to 500°C at a heating rate of 5°C / min, and keep the temperature for 30 min for degassing. Then heat to 1400°C in a high-temperature muffle furnace and keep the temperature for 48 h. High-temperature sintering of the ceramic green sheets to obtain ceramic samples.

[0080] Example 10

[0081] Take and add 1000 g magnesium oxide (purity 90.00%), 10 g zirconium dioxide, 30 g sodium dodecyl sulfate, an appropriate amount of absolute ethanol to the star-shaped ball mill, wet ball mill for 9 h, transfer the above raw materials to the oven, dry at 120°C for 24 h, pass through a 40 mesh sieve, add 5wt.% polyvinyl alcohol (PVA) as a binder to the powder for granulation, during the granulation process, the binder and the powder are mixed evenly, then press into ceramic blanks. Break the ceramic blanks, re-form, age to get ceramic green sheets. After forming, the ceramic green sheets are heated to 500°C at a heating rate of 5°C / min, and held for 30 min for degassing treatment; then heated to 1400°C in a high temperature muffle furnace and held for 48 h, the ceramic green sheets are high temperature sintered to get ceramic samples.

[0082] Example 11

[0083] Take and add 1000 g magnesium oxide (purity 95.00%), 10 g zirconium dioxide, 30 g sodium dodecyl sulfate, an appropriate amount of absolute ethanol to the star-shaped ball mill, wet ball mill for 9 h, transfer the above raw materials to the oven, dry at 120°C for 24 h, pass through a 40 mesh sieve, add 5wt.% polyvinyl alcohol (PVA) as a binder to the powder for granulation, during the granulation process, the binder and the powder are mixed evenly, then press into ceramic blanks. Break the ceramic blanks, re-form, age to get ceramic green sheets. After forming, the ceramic green sheets are heated to 500°C at a heating rate of 5°C / min, and held for 30 min for degassing treatment; then heated to 1400°C in a high temperature muffle furnace and held for 48 h, the ceramic green sheets are high temperature sintered to get ceramic samples.

[0084] According to the sample size requirements of the performance to be tested, the ceramic sheets are machined, for the samples for electrical performance testing, the surface of the machined ceramic sheets is coated with silver electrodes, and the electrodes are fired at 800°C for 30 min, and then the corresponding electrical performance test is carried out.

[0085] The electrical performance test results of the ceramic samples prepared in the above 11 examples and the 4 comparative examples at the corresponding temperature are shown in Table 1:

[0086] Table 1 Raw material composition of examples 1-11 and electrical performance test results of examples 1-11 and comparative examples

[0087]

[0088] It can be seen that the volume resistivity of the ceramic sample prepared in Example 1-11 is higher than 160MΩ·cm even at high temperature of 650℃, and the ceramic sample prepared in the present embodiment has high insulation performance and can meet the working condition requirement of not being broken down at high temperature. The high-purity magnesium oxide ceramic material has a high risk of being broken down at high temperature.

[0089] It can also be found from the comparison of Examples 1 and 9-11 that the higher the purity of magnesium oxide in the mixed material, the better the insulation of the prepared insulating ceramic material.

[0090] Further, it is found in more examples that the insulating ceramic material meeting the requirement of insulation performance can be obtained by using at least two of sodium stearate, sodium dodecyl sulfate, sodium dodecyl sulfonate, CTAB and butyl titanate as the modifying agent in the preparation process, screening the formed ceramic green sheet with a 40-100 mesh sieve, performing degassing treatment on the ceramic green sheet at a constant temperature of 500-700℃ for 30-120min, and heating the ceramic green sheet to 1000-2000℃ in a high-temperature muffle furnace and keeping the temperature for 1-48h.

[0091] It should be further noted that the raw materials used for preparing the insulating ceramic material in the present embodiment and the materials involved in the comparative examples are all commercially available general products.

[0092] The above description includes examples of one or more embodiments. Of course, those skilled in the art should recognize that the various embodiments can be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations falling within the scope of the appended claims. In addition, the term "comprising" used in the specification or claims is intended to have the same scope as the term "including" as explained in the interpretation of the term "including" as a transitional phrase in a claim. In addition, any one of the terms "or" used in the specification or claims is intended to mean "non-exclusive or".

[0093] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the concept and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. An insulating material for downhole heaters with improved insulation properties through zirconium doping, characterized in that, The insulating material is an insulating ceramic material made from a mixture of magnesium oxide, zirconium-containing dopants and modifying agents, which is ball-milled, dried and granulated, aged and sintered. The modifying agent is at least one of sodium stearate, sodium dodecyl sulfate, sodium dodecyl sulfonate, CTAB, and tetrabutyl titanate; The mass content of the zirconium-containing dopant in the mixed material is 0.5-2.8%, and the mass content of the modifying reagent in the mixed material is 1-9%.

2. The downhole heater insulation material with improved insulation performance through zirconium doping as described in claim 1, characterized in that, The zirconium-containing doped material is a compound formed by zirconium and a nonmetal.

3. The downhole heater insulation material with improved insulation performance through zirconium doping as described in claim 1, characterized in that, The zirconium-containing doped material is an intermetallic compound formed by zirconium and a metalloid.

4. The downhole heater insulation material with improved insulation properties through zirconium doping as described in claim 1, characterized in that, The zirconium-containing doping material is a zirconium salt.

5. The downhole heater insulation material with improved insulation performance through zirconium doping as described in claim 1, characterized in that, The zirconium-containing doped material is a zirconate.

6. A method for preparing an insulating material for a downhole heater with improved insulation properties through zirconium doping as described in any one of claims 1 to 5, characterized in that, include: A mixture of magnesium oxide, zirconium-containing dopants, and modifying agents is wet-milled to obtain a slurry raw material. The slurry raw material is dried and then sieved to obtain powder material; The binder is added to the powder material for granulation, and then pressed into a ceramic blank; The ceramic blank is crushed, reshaped, and aged to obtain ceramic green sheets; Insulating ceramic materials are obtained by sintering raw ceramic sheets with plasticity.

7. The preparation method according to claim 6, characterized in that, After obtaining the ceramic green sheet, the process further includes: Determine whether the particle size of the current ceramic green chips meets the particle size requirements; If not, use the current ceramic raw material as raw material and return to the step of obtaining slurry raw material through wet ball milling.

8. The preparation method according to claim 6, characterized in that, The slurry raw material obtained by wet ball milling includes: A slurry raw material was obtained by wet ball milling using agate balls and anhydrous ethanol as the medium.

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