In-situ automatic gas generation capsule dry ice as well as preparation method and application thereof

Abstract

The invention discloses capsule dry ice capable of automatically generating gas in situ. The capsule dry ice comprises a capsule and dry ice, wherein the capsule is composed of a plurality of parts and is internally provided with a cavity; wherein the dry ice is placed in the cavity. According to the in-situ gas self-generating capsule dry ice, the sublimation deflation time of the dry ice is prolonged, the liquid column density is reduced, the problem that liquid drainage is not smooth after a low-pressure gas well (or an oil well) is fractured or shaft accumulated liquid is rapidly drained out of a shaft accumulated liquid production well is solved, and the single-well yield is increased. In addition, the method does not need to intervene in any underground equipment, the dry ice is low in price and wide in source, and simple, economical and efficient oil and gas well liquid drainage is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of well discharge tube liquid accumulation, and in particular to an in-situ self-generating capsule dry ice, a preparation method and an application thereof. Background Art

[0002] For water-bearing reservoirs, after hydraulic fracturing is completed, a large amount of liquid in the wellbore cannot be discharged because the water production of some wells is large and higher than the critical liquid carrying rate of the gas well, resulting in a decrease in natural gas production. Discharging the accumulated liquid in the wellbore can effectively increase the production of a single well.

[0003] At present, the main auxiliary drainage artificial lifting methods include bubble rods, liquid nitrogen gas lift, velocity strings, and various pumps (jet pumps, submersible pumps) assisted gas lift. Bubble rods rely on the disturbance of the bottom hole airflow to form bubbles. Conventional gas lift requires gas source or continuous tubing operation, and the cost is relatively high. Using a small-sized velocity string is also a drainage option, but it is difficult to determine the size. Whether it is gas lift or pump-assisted auxiliary drainage methods, downhole equipment intervention is required, and there are occasional failures, which greatly increases operating costs and reduces operating efficiency.

[0004] In addition, dry ice is solid carbon dioxide, which can be obtained at a temperature of -78.5℃, with a sublimation point of 78.5℃, a solid-to-gas expansion ratio of 1:554, a density of 1.562gm / cm3, and a low price and wide supply. Dry ice can be dropped into the wellbore and sink by gravity. The dry ice sublimates and forms carbon dioxide gas in the wellbore, which helps to discharge the accumulated liquid. However, the sublimation speed of dry ice in the air and water is too fast, and it is completely released in a short time. On the one hand, the gas source cannot be continuously supplied, and on the other hand, the density of the accumulated liquid column cannot be effectively reduced, and thus the drainage effect cannot be guaranteed.

[0005] Therefore, how to prolong the dry ice sublimation and degassing time and reduce the density of the liquid column, so as to facilitate the rapid discharge of wellbore liquid during the post-fracturing drainage process of low-pressure gas wells (or oil wells) or the production process, and increase the single well production has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to provide an in situ self-generated capsule dry ice, a preparation method and an application thereof, wherein the capsule dry ice can prolong the sublimation and degassing time of dry ice and reduce the density of the liquid column, thereby facilitating the rapid discharge of wellbore accumulated liquid during the drainage process after fracturing of a low-pressure gas well (or oil well) or during the production process, and increasing the single well production.

[0007] To achieve the above object, the present invention provides an in-situ self-gasified capsule dry ice, the capsule dry ice comprising: a capsule composed of multiple parts with a hollow interior and dry ice;

[0008] Wherein, the dry ice is placed in the cavity.

[0009] Optionally, the capsule consists of two parts;

[0010] Correspondingly, a first cavity is formed by connecting the first part and the second part; the dry ice is placed in the first cavity.

[0011] Optionally, the capsule consists of three parts;

[0012] Correspondingly, a first cavity is formed by connecting the first part and the second part, and a second cavity is formed by connecting the second part and the third part; the dry ice is placed in the first cavity, and the foaming agent is placed in the second cavity.

[0013] Optionally, the upper surface of the first part is provided with holes for discharging carbon dioxide gas after the dry ice sublimates in the capsule.

[0014] Optionally, the capsule is a cylindrical capsule.

[0015] The present invention also provides a method for preparing in situ self-gas capsule dry ice, the method comprising:

[0016] Preparing a capsule composed of multiple parts and having a hollow interior;

[0017] Dry ice is placed in the cavity to obtain in situ self-gasified capsule dry ice.

[0018] Optionally, the method further includes:

[0019] preparing a capsule having a first cavity therein;

[0020] Placing dry ice in the first cavity to obtain in situ self-generating capsule dry ice;

[0021] The capsule is composed of two parts, and a first cavity is formed by connecting the first part and the second part.

[0022] Optionally, the method further includes:

[0023] preparing a capsule having a first cavity and a second cavity therein;

[0024] Placing dry ice and a foaming agent in the first cavity and the second cavity respectively to obtain in situ self-gassing capsule dry ice;

[0025] The capsule is composed of three parts, a first cavity is formed by connecting the first part and the second part, and a second cavity is formed by connecting the second part and the third part.

[0026] Optionally, the capsule is a cylindrical capsule.

[0027] The present invention also provides an application of in-situ self-gasifying capsule dry ice in discharging wellbore fluid.

[0028] Technical effects and advantages of the present invention:

[0029] The present invention provides an in-situ self-generating capsule dry ice, which comprises: a capsule composed of multiple parts with a cavity inside and dry ice; wherein the dry ice is placed in the cavity.

[0030] The in-situ self-generating capsule dry ice prolongs the time of dry ice sublimation and degassing, reduces the density of the liquid column, solves the problem of poor drainage after fracturing of low-pressure gas wells (or oil wells) or rapid drainage of wellbore liquid in production wells, and increases the production of single wells. In addition, this method does not require any downhole equipment, the dry ice price is low and the supply is wide, realizing simple, economical and efficient drainage of oil and gas wells.

[0031] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the structural diagram of the capsule;

[0033] Figure 2 This is the structural diagram of the in situ self-generating capsule dry ice;

[0034] Figure 3 This is a diagram of unwrapped dry ice sublimating in water;

[0035] Figure 4 This is a diagram of capsule dry ice sublimating in water. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings provided by the present invention, and the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0038] In order to achieve gas lift drainage by relying on the sublimation of dry ice to generate a large amount of gas without the intervention of any downhole equipment, the present invention discloses an in-situ self-gassing capsule dry ice. In order to better understand the present invention, the concept of the present invention is first roughly described: the capsule used is a prefabricated cylindrical capsule, preferably a hard capsule with holes to wrap the dry ice, the capsule is preferably a three-section capsule, and two cavities are formed inside (the upper cavity of the capsule contains dry ice, and the lower cavity contains a foaming agent). There are small holes on the top of the capsule to prevent the dry ice from sublimating in the capsule and the gas pressure from being too high to burst the capsule. Put an appropriate amount of capsule dry ice into the well. Because it is wrapped in the capsule, it can slow down the rapid sublimation of the dry ice before it sinks to the bottom of the accumulated liquid, thereby prolonging the degassing time; the dry ice capsule is subjected to gravity (density 1.56g / cm 3 ) sinks to the bottom of the wellbore liquid. Due to the changes in temperature and pressure in the wellbore, the capsule gradually becomes hydrated, and the dry ice and the foaming agent react with water at the same time. The sublimation of dry ice intensifies, the foaming agent begins to dissolve, and a large amount of carbon dioxide gas is produced. The liquid in the wellbore is violently stirred, and the foaming agent produces a large amount of foam due to the stirring of the gas, which greatly reduces the density of the liquid in the wellbore, and the liquid is gradually lifted out.

[0039] The following is a detailed explanation of capsule dry ice: A self-generated capsule dry ice in situ, comprising: a capsule composed of multiple parts with a cavity inside and dry ice; wherein the dry ice is placed in the cavity.

[0040] Specifically, the capsule is composed of two parts; correspondingly, a first cavity is formed by connecting the first part and the second part; and the dry ice is placed in the first cavity.

[0041] Specifically, the capsule consists of three parts: Figure 1 As shown; correspondingly, a first cavity is formed by connecting the first part 3 and the second part 6, and a second cavity is formed by connecting the second part 6 and the third part 9; the dry ice 11 is placed in the first cavity, and the foaming agent 12 is placed in the second cavity, as shown Figure 2 shown.

[0042] Specifically, it can be understood as: the first part, the second part, and the third part are connected in sequence from top to bottom; and the upper surface 2 of the first part 3 is closed, and the lower surface 4 is open; the upper surface 5 of the second part 6 is open, and the lower surface 7 is closed; the upper surface 8 of the third part 9 is open, and the lower surface 10 is closed.

[0043] Of course, dry ice may also be placed in both the first cavity and the second cavity.

[0044] Specifically, the upper surface of the first part is provided with holes 1 for discharging carbon dioxide gas after the dry ice sublimates in the capsule.

[0045] Specifically, the capsule is a cylindrical capsule. Of course, it can also be other shapes as long as it can form a cavity for placing dry ice and foaming agent.

[0046] The present invention provides an in-situ self-generating capsule dry ice, which comprises: a capsule composed of multiple parts with a cavity inside and dry ice; wherein the dry ice is placed in the cavity.

[0047] The in-situ self-generating capsule dry ice prolongs the time of dry ice sublimation and degassing, reduces the density of the liquid column, solves the problem of poor drainage after fracturing of low-pressure gas wells (or oil wells) or rapid drainage of wellbore liquid in production wells, and increases the production of single wells. In addition, this method does not require any downhole equipment, the dry ice price is low and the supply is wide, realizing simple, economical and efficient drainage of oil and gas wells.

[0048] The present invention also provides a method for preparing in situ self-inflating capsule dry ice, the method comprising: preparing a capsule composed of multiple parts and having a cavity inside; placing dry ice in the cavity to obtain in situ self-inflating capsule dry ice.

[0049] Specifically, the method further includes: preparing a capsule having a first cavity therein; placing dry ice in the first cavity to obtain in situ self-generating capsule dry ice;

[0050] The capsule is composed of two parts, and a first cavity is formed by connecting the first part and the second part.

[0051] Specifically, the method further includes: preparing a capsule having a first cavity and a second cavity therein; placing dry ice and a foaming agent in the first cavity and the second cavity respectively to obtain in situ self-gasifying capsule dry ice;

[0052] The capsule is composed of three parts, a first cavity is formed by connecting the first part and the second part, and a second cavity is formed by connecting the second part and the third part.

[0053] The present invention also protects an application of in-situ self-gasifying capsule dry ice in draining wellbore fluid, and the specific application method includes:

[0054] 1. Put the dry ice capsule into the wellbore.

[0055] 2. Under the action of gravity, the capsule dry ice falls into the accumulated liquid. Since the density of the capsule dry ice is greater than the density of the accumulated liquid, it will sink to the bottom of the accumulated liquid.

[0056] 3. Under the formation temperature and pressure conditions, the capsule gradually hydrates, and the dry ice and the foaming agent react with water at the same time. The sublimation of dry ice intensifies, and the foaming agent begins to dissolve and produce a large amount of carbon dioxide gas. The accumulated liquid in the wellbore is violently stirred, and the foaming agent produces a large amount of foam due to the stirring of the gas, which greatly reduces the density of the accumulated liquid in the wellbore, and the accumulated liquid is gradually lifted out.

[0057] In order to better explain the feasibility of this scheme, an experimental test was also conducted on the in situ self-gas capsule dry ice, as follows:

[0058] Figure 3 This is a picture of unwrapped dry ice (mass 50g) sublimating in water. The observation time of the pictures from left to right is: before adding dry ice, 5 seconds after adding dry ice, and 10 seconds after adding dry ice;

[0059] Figure 4 These are pictures of capsule dry ice (mass of dry ice is 50 g) sublimating in water. The observation times of the pictures from left to right are: before adding capsule dry ice, 60 seconds after adding capsule dry ice, and 300 seconds after adding capsule dry ice.

[0060] Depend on Figure 3 and Figure 4 It can be seen that when the mass of dry ice is the same, when capsule dry ice and dry ice are put into water at the same time, capsule dry ice can significantly slow down the sublimation of dry ice.

[0061] In order to verify the foaming performance, the present invention adopts the pouring method to measure the foaming performance of the dry ice and foaming agent mixed samples at different ratios of dry ice and foaming agent.

[0062] Prepare samples according to the mass fractions of dry ice and foaming agent of 10:0.1, 10:0.5, 10:1, and 10:2. Use 4 250mL measuring cylinders to prepare 100mL of 60℃ water each. Add dry ice and foaming agent samples to the water respectively, and allow them to foam naturally. After the foaming stops, record the foam height. The results are as follows:

[0063] Dry ice and foaming agent mass ratio No foaming agent 10:0.1 10:0.5 10:1 10:2 Foam height (mm) 0 42 59 102 185

[0064] It can be seen from this that the optimal range of the mass ratio of dry ice to foaming agent is 10:1 to 10:2.

[0065] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A self-generating dry ice capsule, characterized in that: The capsule dry ice comprises: a capsule composed of multiple parts with a hollow interior and dry ice; Wherein, the dry ice is placed in the cavity.

2. The dry ice capsule according to claim 1, characterized in that: The capsule consists of two parts; Correspondingly, a first cavity is formed by connecting the first part and the second part; the dry ice is placed in the first cavity.

3. The dry ice capsule according to claim 1, characterized in that: The capsule is composed of three parts; Correspondingly, a first cavity is formed by connecting the first part and the second part, and a second cavity is formed by connecting the second part and the third part; the dry ice is placed in the first cavity, and the foaming agent is placed in the second cavity.

4. The dry ice capsule according to claim 2 or 3, characterized in that: The upper surface of the first part is provided with holes for discharging carbon dioxide gas after the dry ice sublimates in the capsule.

5. The dry ice capsule according to claim 1, characterized in that: The capsule is a cylindrical capsule.

6. A method for preparing in situ autogenerated capsule dry ice, characterized in that: The method comprises: Preparing a capsule composed of multiple parts and having a hollow interior; Dry ice is placed in the cavity to obtain in situ self-gasified capsule dry ice.

7. The method according to claim 6, characterized in that The method further comprises: preparing a capsule having a first cavity therein; Placing dry ice in the first cavity to obtain in situ self-generating capsule dry ice; The capsule is composed of two parts, and a first cavity is formed by connecting the first part and the second part.

8. The method according to claim 6, characterized in that The method further comprises: preparing a capsule having a first cavity and a second cavity therein; Placing dry ice and a foaming agent in the first cavity and the second cavity respectively to obtain in situ self-gassing capsule dry ice; The capsule is composed of three parts, a first cavity is formed by connecting the first part and the second part, and a second cavity is formed by connecting the second part and the third part.

9. The method according to claim 6, characterized in that The capsule is a cylindrical capsule.

10. Use of the in-situ self-gas capsule dry ice according to any one of claims 1 to 5 in draining fluid from a wellbore.

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