WO2015159304A2

WO2015159304A2 - A system and method for fracking of shale rock formation

Info

Publication number: WO2015159304A2
Application number: PCT/IN2015/000166
Authority: WO
Inventors: Jagadeesh Gopalan; Gundurao Sitharam Thallak; Bharathiramachar Akhilesh Katte; Polareddy Jagannatha Reddy Kalidevapura
Original assignee: Super-Wave Technology Private Limited
Priority date: 2014-04-15
Filing date: 2015-04-09
Publication date: 2015-10-22
Also published as: WO2015159304A3; US20170044885A1

Abstract

The various embodiments of the present invention provide a system for fracking a plurality of shale rocks in a shale reservoir. The system comprises a shock tube for generating a plurality of shock waves, a support system for holding the shock tube, a guide tube for directing the shock waves into the shale reservoir, a perforated cylinder for releasing the high pressured shock waves on to the shale rocks and a plurality of packer systems for aligning the guide tube and the perforated cylinder inside the shale reservoir. The Shockwaves creates a plurality of fractures on the shale rocks. The Shockwaves further cause widening of the existing factures on the shale rocks.

Description

A SYSTEM AND METHOD FOR FRACKING OF SHALE ROCK

FORMATION

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority of the provisional application with serial number 4633/CHE/2013 filed on October 15, 2013 post dated by six months to April 15, 2014 with title, "A SYSTEM AND METHOD FOR FRACKING OF SHALE ROCK USING SHOCK WA VE" and the contents of which is incorporated in entirety.

BACKGROUND Technical field

[0002] The present invention generally relates to a fracking technology and particularly relates to a field of fracking of Shale reservoir rocks. The present invention more particularly relates to a system and method for generating fractures in a shale reservoir by using a plurality of shock waves.

Description of the Related Art

[0003] The availability of petroleum and its products are getting depleted day by day. The oil source is mainly found in the reservoir rocks which are highly porous and permeable such as sandstone. Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen from which liquid hydrocarbons called shale oil is produced. Extracting oil from oil shale requires conversion of the solid hydrocarbons in the rock to liquid form, so that they can pumped or processed.

[0004] The key to extract these resources is through the process of fracking. Fracking has unlocked massive new supplies of oil and clean- burning natural gas from dense deposits of shale.

[0005] Hydraulic fracking is a popular technique used for shale oil extraction. Hydraulic fracking is a process in which large quantity of water is forced into a wellbore and pressurized between two packer systems (confined zone) to open-up the fractures. The injected water flows in the least resistance path through the fractures and thus opening of the fractures takes place in the weakest zone. Huge amounts of polluted water returns to the surface after the process is complete. This water is polluted with chemicals, salts and even mild radioactivity. The polluted water contaminates the groundwater aquifer and also surface water resources. Hydraulic fracking is also a highly tedious process which requires high skilled workmanship. If the shale gas wells are found inside the oceans, the requirement of large quantities of water is not an issue of concern. But many gas wells are found in the dry deserted areas. In that case the hydraulic fracking technique becomes impossible to carry out. This technique also involves chemical treatment process and is considered highly uneconomical.

[0006] Injection of C02 is another method having the same objective of inducing fractures. In this method, liquid C02 is injected into the shale formation, which has been isolated by inflatable packers. The introduction of the liquid C02 freezes the surrounding fluid inside the existing fractures. As the liquid C02 becomes gas, the fluid expands thereby extending the fractures. Carbon dioxide fracking poses many challenges besides the lack of infrastructure. Unlike water, gases are compressible. So it is more difficult for gases to reach the pressure needed to fracture the rock. Also, the carbon dioxide has to be separated from the natural gas before shipping the fuel to market, which adds to costs. And it is probably never economical to install carbon dioxide pipelines all the way to every fracking well. More number of trucks are needed to convey the carbon dioxide when compared with water fracking. This leads to increase in local noise, pollution, and road damage.

[0007] Hence there is need for an efficient system and method for fracking of oil shale rock which overcomes disadvantages of above fracking methods.

[0008] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

OBJECTIVES OF THE EMBODIMENTS

[0009] The primary object of the present embodiment is to provide a system and method to create fractures in a plurality of shale reservoir rocks and also to extend the dimensions of existing fractures by using a plurality of shock waves. [0010] Another object of the present embodiment is to provide a system for generating the Shockwaves on ground and directing the waves into a borewell.

[001 1] Yet another object of the present embodiment is to provide a system that produce the Shockwaves at the point of application inside the borewell, by using combustion of gases.

[0012] Yet another object of the present embodiment is to strike the high pressure Shockwaves onto the Shale rocks with a high velocity for creating a plurality of fractures along the weak zone of the shale formation.

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[0013] Yet another object of the present embodiment is to widen the existing fractures in the shale rock formation using the shock waves.

[0014] These and other objects and advantages of the present embodiment will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY

[0015] The various embodiments of the present invention provide a system for fracking a plurality of shale rocks in a shale reservoir. According to one embodiment of the present invention, the system comprises a shock tube for generating a plurality of shock waves, a support system for holding the shock tube, a guide tube for directing the shock waves into the shale reservoir, a perforated cylinder for releasing the high pressured shock waves on to the shale rocks and a plurality of packer systems for aligning of the guide tube and the perforated cylinder inside the shale reservoir. The Shockwaves creates a plurality of fractures on the shale rocks. The Shockwaves further cause widening of the existing factures on the shale rocks.

[0016] According to an embodiment of the present invention, the shock tube comprises of a driver section and a driven section separated by a metal diaphragm. The driven section is filled with a low pressure driven gas and the driver section of the shock tube is filled with a high pressure driver gas supplied by a high pressure gas cylinders.

[0017] According to an embodiment of the present invention, the guide tube and the shock tube are connected by an elbow bend. The shock wave travelling through the driven section of the shock tube is directed into the guide tube through the elbow bend.

[0018] According to an embodiment of the present invention, the diaphragm is ruptured using the high pressure gas to produce the shock waves. The shock waves produced propagate through the driven section.

[0019] According to an embodiment of the present invention, the diaphragm is busted to produce a series of shock waves. Each shock wave possess an increasing speed of sound, so that they compress into a shock propagating through the driven gas.

[0020] According to an embodiment of the present invention, the perforated cylinder is placed in a confined zone between the pluralities of packer systems to avoid a leakage of the Shockwaves. [0021] According to an embodiment of the present invention, the high pressure jets strike out horizontally into the shale rock formation through the perforations of the cylinder.

[0022] The various embodiments of the present invention provide a method for fracking a plurality of shale rocks in a shale reservoir. According to an embodiment of the present invention, the method comprises generating a plurality of Shockwaves in a Shockwave tube; guiding the generated Shockwaves into the shale reservoir through a guide tube; ejecting the high pressured Shockwaves through a perforated cylinder attached to the guide tube; and fracturing the shale rocks by exertion of the high pressure Shockwaves onto the shale rocks. The high pressure Shockwaves creates a plurality of fractures on the shale rocks. The Shockwaves further cause widening of the existing factures on the shale rocks.

[0023] According to an embodiment of the present invention, the method further comprises filling a driven section of the shock tube with a low pressure driven gas; and supplying a high pressure driver gas to a driver section of the shock tube. The driver gas exerts high pressure on a diaphragm for separating the driver section and the driven section. The diaphragm is ruptured to produce the Shockwaves.

[0024] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating the preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

[0026] FIG. 1 illustrates a side cross sectional view of a fracking system, according to an embodiment of the present invention.

[0027] FIG. 2 illustrates a perspective view of a hollow perforated cylinder in a fracking system, according to an embodiment of the present invention.

[0028] FIG. 3 illustrates a side sectional view of a shale rock formation indicating an effect of shock waves generated with a fracking system, according to an embodiment of the present invention.

[0029] FIG. 4 illustrates a flowchart explaining the steps involved in a method for fracking the shale rocks using the shock waves, according to an embodiment of the present invention.

[0030] Although the specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.

[0032] The various embodiments of the present invention provide a system for fracking a plurality of shale rocks in a shale reservoir. According to one embodiment of the present invention, the system comprises a shock tube for generating a plurality of shock waves, a support system for holding the shock tube, a guide tube for directing the shock waves into the shale reservoir, a perforated cylinder for releasing the high pressured shock waves on to the shale rocks and a plurality of packer systems for aligning of the guide tube and the perforated cylinder inside the shale reservoir. The Shockwaves creates a plurality of fractures on the shale rocks. The Shockwaves further cause widening of the existing factures on the shale rocks. [0033] According to an embodiment of the present invention, the shock tube comprises of a driver section and a driven section separated by a metal diaphragm. The driven section is filled with a low pressure driven gas and the driver section of the shock tube is filled with a high pressure driver gas supplied by a high pressure gas cylinders.

[0034] According to an embodiment of the present invention, the guide tube and the shock tube are connected by an elbow bend. The shock wave travelling through the driven section of the shock tube is directed into the guide tube through the elbow bend.

[0035] According to an embodiment of the present invention, the diaphragm is ruptured using the high pressure gas to produce the shock waves. The shock waves produced propagate through the driven section.

[0036] According to an embodiment of the present invention, the diaphragm is busted to produce a series of shock waves. Each shock wave possess an increasing speed of sound, so that they compress into a shock propagating through the driven gas.

[0037] According to an embodiment of the present invention, the perforated cylinder is placed in a confined zone between the pluralities of packer systems to avoid a leakage of the Shockwaves.

[0038] According to an embodiment of the present invention, the high pressure jets strike out horizontally into the shale rock formation through the perforations of the cylinder. [0039] The various embodiments of the present invention provide a method for fracking a plurality of shale rocks in a shale reservoir. According to an embodiment of the present invention, the method comprises generating a plurality of Shockwaves in a Shockwave tube; guiding the generated Shockwaves into the shale reservoir through a guide tube; ejecting the high pressured Shockwaves through a perforated cylinder attached to the guide tube; and fracturing the shale rocks by exertion of the high pressure Shockwaves onto the shale rocks. The high pressure Shockwaves creates a plurality of fractures on the shale rocks. The Shockwaves further cause widening of the existing factures on the shale rocks.

[0040] According to an embodiment of the present invention, the rhethod further comprises filling a driven section of the shock tube with a low pressure driven gas; and supplying a high pressure driver gas to a driver section of the shock tube. The driver gas exerts high pressure on a diaphragm for separating the driver section and the driven section. The diaphragm is ruptured to produce the Shockwaves.

[0041] The various embodiments of the present invention provide a system that produces a plurality of fractures and widens the existing fractures in shale rock formation using the shock waves. The system produces the high energy shock waves either on the ground using a shock tube and transmit it to the required location inside a borewell. In an alternate method, the system is configured to produce the shock waves in situ point of application in the borewell by performing combustion of gases supplied from a reservoir above ground.

[0042] FIG. 1 illustrates a complete cross sectional view of the fracking system, according to an embodiment of the present invention. The shale reservoir layer is present after a plurality of layers of soil formations 101 and rock formations 102. Depending upon the location of shale reservoir layer

103, a vertical borewell 104 is drilled into the earth. The borewell 104 is extended up to a several hundred to thousands meters deep vertically into a shale rock formation 103. With respect to FIG. 1, the fracking system comprises a shock tube 105 for generating shock waves, a support system 106 for holding the shock tube 105, an elbow bend 107 for directing shock waves generated in shock tube 105 into borewell 104, a guide tube 108 for directing the shock waves to bottom of borewell 104, the guide tube 108 is placed in the borewell 104 with the help of a casting wall 109, a perforated cylinder 1 10 for releasing the high pressured shock waves on to the shale rocks 103 and a packer system 1 11 for the proper alignment of the system inside the borewell

104. The shock tube 105 is placed horizontally on the ground and is anchored to the support system 106 to avoid jumping of the tube 105 due to a reflected pressure created by the propagating shock waves. The shock tube 105 comprises a driver section and a driven section separated by a metal diaphragm. The driven section is filled with a low pressure gas which is referred as a driven gas. The driver section of the shock tube comprises of a high pressure cylinders filled with high pressure, a driver gas. The shock waves are produced by rupturing the diaphragm using the high pressure driver gas. The bursting of diaphragm produces a series of pressure waves with each Shockwave increasing the speed of preceding shock wave so that the shock waves compress into a shock propagating through the driven gas.

[0043] According to an embodiment of the present invention, the shock wave produced in the shock tube 105 is guided to the bottom of borewell 104 using the guide tube 108. The diameter of guide tube 108 is identical to the shock tube 105 diameter. The guide tube 108 and the shock tube 105 are connected by the elbow bend 107 bent at an angle of 90°. The shock waves travelling through the driven section of the shock tube 105 are directed into the guide tube 108 through the elbow bend 107. In-order to maintain a proper alignment of the guide tube 108 inside the borewell 104, the packer system 1 11 is installed at a regular interval. A set of packer system 1 1 1 is also installed at the bottom of the guide tube 108 to ensure a confined zone around the shale gas source formation 103.

[0044] FIG. 2 illustrates a hollow perforated cylinder, according to an embodiment of the present invention. The guide tube is attached with a hollow cylinder 1 10 which has perforation 201 around its walls. A jet of pressurized shock waves strike out of the perforation 201 in the cylinder 1 10 into the rock formation, thereby creating the plurality of fractures on the shale rock formation. The shock waves further widens the existing fractures by exerting pressure on the factures. The diameter of perforated cylinder 1 10 is equal to the diameter of borewell. The perforated cylinder 110 is placed in the confined zone between the set of packer systems, to ensure that there is no leakage. The high pressure air behind the shock front propagates into the perforated cylinder 1 10. The high pressure jets strike out the shale rock formation horizontally through the perforations of cylinder 110.

[0045] FIG. 3 illustrates a diagram for explaining the effect of shock waves on the shale rock formation, according to an embodiment of the present invention. The shock wave 301 is generated by busting the diaphragm in the shock tube using high pressure gas. The shock waves 301 are generated back to back giving rise to a dynamic series of waves. With respect to FIG. 3, the generated shock waves 301 are guided to the bottom of borewell 104 through the guide tube 108. The high pressure jets 301 that emerge out of the perforation of cylinder 1 10 at the regular intervals, do not affect the walls of the borewell 104 but exerts the pressure on the shale rock formation 103. The pressure creates the plurality of fractures 302 in the rock formation 103. In case of the existing fractures 302, the high pressure Shockwaves penetrate through the fractures 302 creating a tensile failure, thus extending the length of the joints.

[0046] According to an embodiment of the present invention, the shock waves of required strength are produced locally at the point of application inside the borewell, by combustion or detonation of combustible gas mixture such as oxygen and hydrogen. The combustible oxygen and hydrogen gases are mixed in a required proportion on the ground level and the mixture is send into the borewell to burn the gases at a required location-using electrical or solar energy.

[0047] According to an embodiment of the present invention, the shock tube is typically manufactured from a plurality of high strength steel tubes for generating the shock waves. However, high strength polymer tubes are also used for deliver the combustible gases to the locations inside the borewell.

[0048] According to an embodiment of the present invention, the pressure levels in the driver section of the shock tube is up to 80 bars. The length of the shock tube is varied in multiples of 10 meters. The thickness of the diaphragm installed in the shock tube varies in the range of 1 mm to 5 mm. The strength of the shock wave produced is varied according to the thickness of the diaphragm used in the shock tube. The diaphragm material is replaced at a regular interval of time, based on the performance of the shock tube. According to an embodiment, the shock tube is mounted vertically inside the borewell to send the shock wave directly into the wellbore. The diameter of the shock tube is varied in multiples of 10 millimeter upto 100 millimeters. The depth of the point for discharge of shock pressure inside the borehole is varied from meters to kilometers. The gases used in the shock tube include, but not limited to, hydrogen, helium, nitrogen and the like. The gases are supplied from a commercial high pressure cylinder or from a compressor or the gases are manufactured on site. [0049] FIG. 4 is a flowchart illustrating steps involved in a method for fracking the shale rocks using the shock waves, according to an embodiment of the present invention. The method comprising of the steps: the shock wave is generated by busting the diaphragm in shock tube using high pressure gas (401). Shock waves are generated back to back giving rise to a dynamic series of waves. The generated shock waves are guided to the bottom of bore well through a guide tube (402). These high pressure jets that emerge out of the perforation of cylinder at regular intervals do not affect the walls of the wellbore but exerts pressure on the shale rocks (403). The pressure creates new fractures in the rock formation (404). When the fractures are already present, the high pressure jets penetrate through the fractures creating a tensile failure, thus extending the length of the joints (404).

[0050] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications. [0051] The present invention envisages a system and method to create fractures in a plurality of shale reservoir rocks and also to enlarge the dimensions of existing fractures by using a plurality of shock waves. The present invention facilitates utilizing gas instead of water for producing the fractures in the shale rocks. The use of gas protects the environment by avoiding a disposal of tainted/contaminated water in the water bodies. The present invention aims at reducing the cost of handling the fracturing process and the economics involved is expected to improve significance of the present invention. The present invention allows a complete free flow of gas from the exposed fracture. When water is used, mineral and salts react with water forming blockages around the fracture path impeding the path for the gas to reach the well. Since the present invention is a dry fracking process, the damage due to a blockage around the fracture path is eliminated, and the cleaning-up of well is expedited. The present invention further eliminates a requirement of high skilled workmanship for operating the fracking process.

[0052] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modifications.

[0053] Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications.

Claims

CLAIMS What is claimed is:

1. A system for fracking a plurality of shale rocks in a shale reservoir, the system comprises:

a shock tube for generating a plurality of shock waves;

a support system for holding the shock tube;

a guide tube for directing the shock waves into a shale reservoir;

a perforated cylinder for releasing high pressured shock waves on to the shale rocks; and

a plurality of packer systems for aligning the guide tube and the perforated cylinder inside the shale reservoir,

wherein the Shockwaves creates a plurality of fractures on the shale rocks, and wherein the Shockwaves further cause a widening of the existing factures on the shale rocks.

2. The system according to claim 1 , wherein the shock tube comprises a driver section and a driven section separated by a metal diaphragm.

3. The shock tube according to claim 2, wherein the driven section is filled with a low pressure driven gas, and wherein the driver section of the shock tube is filled with a high pressure driver gas supplied by a high pressure gas cylinders.

4. The system according to claim 1 , wherein the guide tube and the shock tube are connected by an elbow bend, and wherein the shock wave travelling through the driven section of the shock tube is directed into the guide tube through the elbow bend.

5. The system according to claim 1 , wherein the diaphragm is ruptured using the high pressure gas to produce the shock waves, and wherein the shock waves produced are propagated through the driven section.

6. The system according to claim 1 , wherein the diaphragm is busted to produce a series of shock waves, and wherein each shock wave possess a speed and wherein the speed of each shock wave is increased in multiples of a speed of sound, and wherein each shock wave is compressed to generate a shock that is propagated through the driven gas.

7. The system according to claim 1 , wherein the perforated cylinder is placed in a confined zone between the pluralities of packer systems to avoid a leakage of the Shockwaves.

8. The system according to claim 1 , wherein the high pressure jets strike out the shale rock formation horizontally through the perforations of the cylinder.

9. A method for fracking a plurality of shale rocks in a shale reservoir, and wherein the method comprises steps of:

generating a plurality of Shockwaves in a Shockwave tube;

guiding the generated Shockwaves into a shale reservoir through a guide tube;

ejecting high pressure Shockwaves through a perforated cylinder attached to the guide tube; and fracturing the shale rocks by exerting high pressure Shockwaves onto the shale rocks,

wherein the high pressure Shockwaves creates a plurality of fractures on the shale rocks, and wherein the Shockwaves further cause a widening of the existing factures on the shale rocks.

10. The method according to claim 9, further comprises steps of:

filling a driven section of the shock tube with a low pressure driven gas; and

supplying a high pressure driver gas to a driver section of the shock tube; wherein the driver gas exerts high pressure onto a diaphragm thereby separating the driver section and the driven section, and wherein the diaphragm is ruptured to produce the Shockwaves.