AU2020102179A4 - Release tube of carbon dioxide fracturing tube and carbon dioxide fracturing tube - Google Patents

Abstract

The utility model relates to the field of fracturing tubes, and discloses a release tube of a carbon dioxide fracturing tube and a carbon dioxide fracturing tube thereof. Several release holes communicated with an interior of the release tube are uniformly distributed along a circumferential direction of a tube wall of the release tube, a diameter of the release hole gradually decreases along the direction in which the carbon dioxide is emitted. There is at least one acute angle formed between an axis of the release hole and an axis of the release tube, for emitting carbon dioxide from a direction opposite to a flow direction of the carbon dioxide in the release tube. Therefore, when the carbon dioxide is emitted from the release hole, a component force pointing out of the borehole is generated, which causes the release tube to move into the borehole, so as to prevent the release tube from escaping out of the borehole. The release hole is set to a conical shape, which can increase the carbon dioxide emission rate, so as to ensure that the carbon dioxide emitted from the reverse release hole still has an excellent fracturing effect on rock strata, and improves the overall fracturing effect of the fracturing tube as well. 2/2 6 5 FIG. 3

Description

2/2

6 5

FIG. 3

RELEASE TUBE OF CARBON DIOXIDE FRACTURING TUBE AND CARBON DIOXIDE FRACTURING TUBE TECHNICAL FIELD The utility model relates to the field of fracturing tubes, in particular to a release tube of a carbon dioxide fracturing tube and carbon dioxide fracturing tubes. BACKGROUND Liquid carbon dioxide phase change fracturing technology is a blasting technology with advanced concepts, intrinsic safety, environmental protection, and significant blasting effect. Carbon dioxide blasting began in the 1950s and developed in the United States in the 1980s. It is mainly developed to avoid explosion accidents caused by flame due to explosive blasting and is specially developed for coal mining faces in high-gas mines. It can effectively improve the permeability of coal seams and strengthen gas drainage effect. At present, carbon dioxide fracturing tube is widely used in fracturing operation of rock strata and coal seams. For liquid carbon dioxide phase change fracturing technology, the fracturing tube containing liquid carbon dioxide is generally placed in a borehole. Then the liquid carbon dioxide expands rapidly by means of heating, emits from a release hole of a release tube (energy discharger) and impacts the coal seams, resulting in cracks in the coal seams. The release hole of the existing release tube is cylindrical, such as the utility model patent No. 201621154140.5 entitled "CARBON DIOXIDE CRACKER ENERGY DISCHARGE HEAD AND CRACKER". A hole diameter of the cylindrical release hole will directly affect the initial velocity of carbon dioxide emission, resulting in lower fracturing capacity of the fracturing tube. However, a reduced hole diameter of the release hole will cause greater local pressure loss. Therefore, how to improve the structure of the release hole to increase the initial velocity of carbon dioxide emission is of great significance. Besides, an axis of the existing cylindrical release hole is perpendicular to that of the release tube, which leads to the difficulty of carbon dioxide entering rock strata instantly and accumulating in the borehole during the fracturing operation of harder rock strata. As a result, carbon dioxide is emitted from the borehole with the fracturing tube, and the emission height of the fracturing tube can reach tens of meters, which, on the one hand, cause the fracturing operation cannot be carried out smoothly, on the other hand, it will cause the fracturing tube to fall to the ground and be damaged, and even cause safety accidents. SUMMARY The purpose of the utility model is to provide a release tube of a carbon dioxide fracturing tube and a carbon dioxide fracturing tube to solve the above problems in the prior art. By setting an acute angle between an axis of the release hole and an axis of the release tube, the release tube is prevented from escaping out of the borehole. The release hole is set to a conical shape, which can increase the initial rate of carbon dioxide emission, so as to ensure that the carbon dioxide emitted from the reverse release hole still has an excellent fracturing effect on rock strata, and improves the overall fracturing effect of the fracturing tube as well. In order to achieve above purpose, the utility model provides following solutions: the utility model provides a release tube of a carbon dioxide fracturing tube, and several release holes communicated with an interior of the release tube are uniformly distributed along a circumferential direction of a tube wall of the release tube. There is at least one acute angle formed between an axis of the release hole and an axis of the release tube, for emitting carbon dioxide from a direction opposite to a flow direction of the carbon dioxide in the release tube; and a diameter of the release hole gradually decreases along the direction in which the carbon dioxide is emitted. Preferably, there are four release holes, where angles formed by axes of two opposite release holes and an axis of the release tube are equal acute angles; axes of the other two release holes are perpendicular to the axis of the release tube. Preferably, angles formed by the axes of the four release holes and the axis of the release tube are equal acute angles. Preferably, the acute angle is 70-88°. Preferably, the acute angle is 80. Preferably, a relationship between a minimum diameter Al and maximum diameter A2 of a

1 Al l cross section of the release hole is- < -. 4 A2 3

The utility model also provides a carbon dioxide fracturing tube, which includes above release tube. Compared with the prior art, the utility model achieves following technical effects: By setting an acute angle between an axis of the release hole and an axis of the release tube, for emitting carbon dioxide from a direction opposite to a flow direction of the carbon dioxide in the release tube, when the carbon dioxide is emitted from the release hole, a component force pointing out of the borehole is generated, which causes the release tube to move into the borehole. Thus, the release tube can be prevented from escaping out of the borehole, and the release hole is set to a conical shape, which can increase the rate of a carbon dioxide emission flow by reducing a diameter of a release hole outlet, so as to ensure that the carbon dioxide emitted from the reverse release hole still has an excellent fracturing effect on rock strata, and improves the overall fracturing effect of the fracturing tube as well. BRIEF DESCRIPTION OF DRAWINGS To describe the technical solutions in examples of the utility model or in the prior art more clearly, accompanying drawings to be used in the examples are briefly introduced below. Apparently, the accompanying drawings in following description show merely some examples of the utility model, and a person of ordinary skill in the art can still derive other drawings from these accompanying drawings without inventive efforts. FIG. 1 is a schematic diagram of a structure of a release hole whose axis forms an acute angle with an axis of the release tube; FIG. 2 is a schematic diagram of a structure of a release hole whose axis is perpendicular to an axis of the release tube; and FIG. 3 is a schematic diagram of the structure of a release tube being placed in the borehole; in the figures, 1. release tube; 2. release hole; 3. liquid storage tube; 4. borehole; 5. constant pressure shearing slice, and 6. hole sealer. DETAILED DESCRIPTION A clear and complete description of the technical solutions in the examples of the utility model will be given below, in combination with the accompanying drawings in the examples of the utility model. Apparently, the examples described below are a part, but not all, of the examples of the utility model. All other examples obtained by a person of ordinary skill in the art based on the examples of the utility model without inventive efforts fall within the scope of protection of the utility model. The purpose of the utility model is to provide a release tube of a carbon dioxide fracturing tube and a carbon dioxide fracturing tube thereof, to solve the problems existing in the prior art. By setting an acute angle between an axis of the release hole and an axis of the release tube, the release tube is prevented from escaping out of the borehole, and the release hole is set to a conical shape, which can increase the initial rate of carbon dioxide emission, so as to ensure that the carbon dioxide emitted from the reverse release hole still has an excellent fracturing effect on rock strata, and improves the overall fracturing effect of the fracturing tube as well. To make the above objective, characteristics and advantages of the utility model more understandable, the utility model will be further described below in detail in combination with the accompanying drawings and specific examples. The utility model provides following solutions: As shown in FIG. 1, the utility model provides a release tube 1 of a carbon dioxide fracturing tube, and several release holes 2 communicated with an interior of the release tube 1 are uniformly distributed along a circumferential direction of a tube wall of the release tube 1. There is at least one acute angle formed between an axis of the release hole 2 and an axis of the release tube 1, for emitting carbon dioxide from a direction opposite to a flow direction of the carbon dioxide in the release tube 1, and a diameter of the release hole 2 gradually decreases along the direction in which the carbon dioxide is emitted. When in use, the fracturing tube is placed into a borehole 4, and the borehole 4 is sealed by a hole sealer, as shown in FIG. 3. Then a liquid carbon dioxide in a liquid storage tube 3 is heated by a heating device in the fracturing tube. When a pressure in the liquid storage tube 3 increases to a certain extent, carbon dioxide destroys a constant pressure shearing slice 5 and enters the release tube 1, and then is emitted from the release hole 2 to fracture rock strata. In this example carbon dioxide is emitted in a direction opposite to the flow direction in the release tube 1 by setting an acute angle between an axis of the release hole 2 and an axis of the release tube 1, when the carbon dioxide is emitted from the release hole 2, a component force pointing out of the borehole 4 is generated, which causes the release tube 1 to move into the borehole 4. Thus, the release tube 1 can be prevented from escaping out of the borehole 4. However, a direction of the release hole 2 points to the surface of rock strata, and compared with the release hole 2 whose axis is perpendicular to an axis of the release tube 1, the carbon dioxide emitted from inclined release hole 2 reduces the fracturing effect on deep rock strata due to the existence of outward component force. In addition, the texture of hole wall rock strata and the surface layer of the rock strata of the borehole 4 is relatively loose, and when the velocity of carbon dioxide is insufficient and it is difficult to fracture dense deep rock strata, priority will be given to diffuse from the loose part of the rock strata, which will further reduce the fracturing effect on the deep rock strata. Therefore, in this example the release hole 2 is set to a conical shape, so that the initial rate of carbon dioxide emission is increased by reducing a diameter of an emission outlet of the release hole 2, so as to ensure that the carbon dioxide emitted from the reverse release hole 2 still has an excellent fracturing effect on the rock strata. Further, there are four release holes 2, wherein angles formed by axes of two opposite release holes 2 and an axis of the release tube 1 are equal acute angles; axes of the other two release holes 2 are perpendicular to the axis of the release tube 1, as shown in FIG. 2, so that axes of the release hole 2 are perpendicular to the axis of the release tube 1 to produce a relatively desirable fracturing effect, thus improving the overall fracturing effect on rock strata. It should be noted that the number of inclined release holes 2 can be adjusted according to the actual situation, in order to ensure a desirable anti-escaping effect, angles formed by the axes of the four release holes 2 and an axis of the release tube 1 can also be defined as equal acute angles. Since an excessively small acute angle will greatly compromise the fracturing effect, the acute angle a is 70-88° in this example, and preferably 80. In this range, the acute angle can be selected according to the density and hardness of rock strata. If compactness and hardness of rock strata are relatively low, and the carbon dioxide can penetrate rock strata immediately after it is emitted, without excessive accumulation in the borehole 4, then the release tube 1 with large acute-angled release hole 2 can be selected to ensure the fracturing effect of the fracturing tube on rock strata, and only cause the emitted carbon dioxide generate a small outward component force to prevent the fracturing tube from escaping. If compactness and hardness of rock strata are relatively high, then the release tube 1 with small acute-angled release hole 2 is selected to cause the emitted carbon dioxide generate a large outward component force, ensure that the fracturing tube will not escape, so as to avoid safety accidents. Further, a relationship between a minimum diameter Al and maximum diameter A2 of a

1 Al l cross section of the release hole 2 is - < -; those skilled in the art should know that A1 4 A2 3

should not be too small, it needs to ensure that carbon dioxide should be completely released

within a specified time, and ensure that the instantaneous impact force should be large enough,

while A2 should not be too large, which would mean that the internal space of the release tube 1

is significantly increased, resulting in a large pressure loss of the carbon dioxide entering the

release tube 1, thereby reducing the emission speed of carbon dioxide and affecting the fracturing

effect.

The utility model also provides a carbon dioxide fracturing tube, which includes the above release tube 1. Adaptable changes according to actual needs are within the protection scope of the utility model. It should be noted that it is obvious to those skilled in the art that the utility model is not limited to details of above exemplary examples, and the utility model can be implemented in other specific forms without departing from the spirit or basic features of the utility model. The examples should be regarded as exemplary and non-limiting in every respect, and the scope of the utility model is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of equivalent elements of the claims should be included in the utility model. The reference numeral in the claims should not be considered as limiting the involved claims.

Claims (5)

1. What is claimed is: 1. A release tube of a carbon dioxide fracturing tube, wherein several release holes communicated with an interior of the release tube are uniformly distributed along a circumferential direction of a tube wall of the release tube, there is at least one acute angle formed between an axis of the release hole and an axis of the release tube, for emitting carbon dioxide from a direction opposite to a flow direction of the carbon dioxide in the release tube; and a diameter of the release hole gradually decreases along the direction in which the carbon dioxide is emitted. 2. The release tube of a carbon dioxide fracturing tube according to claim 1, wherein there are four release holes, angles formed by axes of two opposite release holes and an axis of the release tube are equal acute angles; axes of the other two release holes are perpendicular to the axis of the release tube. 3. The release tube of a carbon dioxide fracturing tube of claim 1 or claim 2, wherein the acute angle is 70-88°. 4. The release tube of a carbon dioxide fracturing tube according to claim 1, wherein a
2. relationship between a minimum diameter Al and maximum diameter A2 of a cross section of the
3. 1 All1 release hole is - - A - .
4. 4 A2 3
5. 5. A carbon dioxide fracturing tube, comprising the release tube according to any one of claims 1-4.