The present invention relates to a well stimulation tool for oil and/or gas production. More specifically, the invention is a hydraulically-actuated propellant stimulation downhole tool for use in a hydrocarbon well.
In hydrocarbon wells, fracturing (or “fracing”) is a technique used by well operators to create and/or extend a fracture from the wellbore deeper into the surrounding formation, thus increasing the surface area for formation fluids to flow into the well. Fracing may be done by either injecting fluids at high pressure (hydraulic fracturing), injecting fluids laced with round granular material (proppant fracturing), or using explosives to generate a high pressure and high speed gas flow (TNT or PETN up to 1,900,000 psi) known as propellant stimulation.
Gas generating propellants have been utilized in lieu of hydraulic fracturing techniques as a more cost effective manner to create and propagate fractures in a subterranean formation. In accordance with conventional propellant stimulation techniques, a propellant is ignited to pressurize the perforated subterranean interval either simultaneous with or after the perforating step so as to propagate fractures therein. Typically, the propellant material is ignited due to shock, heat, and/or pressure generated from a detonated charge. Upon burning, the propellant material generates gases that clean perforations created in the formation by detonation of the shaped charge and which extend fluid communication between the formation and the wellbore.
In one embodiment there is provided a downhole tool comprising a detonation section for stimulating a hydrocarbon-producing formation. The detonation section comprises a first end, a second end, a propellant volume located proximate to the second end, and a wall. The wall has an inner surface, an outer surface, a rupture disc and an actuating assembly. The inner surface defining a central bore extending from the first end to the second end. The outer surface is exposed to a well annulus during operation of the downhole tool. The actuating assembly comprises a detonator chamber, a detonator assembly, a firing pin and a flow passage. The detonator chamber has a first end positioned adjacent to the propellant volume and a second end having an inlet. The detonator assembly is located within the detonator chamber proximate to the first end of the detonator chamber. The firing pin is located within the detonation chamber. The firing pin is retained proximate to the inlet until an actuating pressure is applied through the inlet. The flow passage is contained between the inner surface and the outer surface and is in fluid flow communication with the detonation chamber through the inlet. The rupture disc is positioned between the flow passage and the central bore such that it prevents fluid flow communication between the flow passage and the central bore until ruptured by the application of the actuating pressure in the central bore.
Additionally, in the above-described downhole tool, the flow passage can be contained between the inner surface and the outer surface so as to be entirely interior to the wall. The firing pin can be retained proximate to the inlet by a shear pin such that the shear pin holds the firing pin back from the detonator until the actuating pressure is applied through the inlet.
In a further embodiment of the above-described downhole tool, the wall can have a plurality of actuating assemblies spaced about the circumference of the wall. The flow path of each actuating assembly can be in fluid flow communication with a circumferential chamber, which is in fluid flow communication with the central bore when the rupture disc is ruptured such that fluid is distributed to each flow path through the circumferential chamber. Additionally, there can be no more than one rupture disc associated with the circumferential chamber and the plurality of actuating assemblies.
In another embodiment of the above described downhole tool, there can be a plurality of detonation sections arranged sequentially such that the central bore of each section aligns to form a continuous central bore running through the plurality of sections.
In still yet another embodiment, there is a downhole tool comprising a detonation section for stimulating a hydrocarbon-producing formation. The detonation section comprises a first end, a second end, a propellant volume and a wall. The propellant volume is located proximate to the second end. The wall has an inner surface and an outer surface. The inner surface defines a central bore extending from the first end to the second end. The outer surface is exposed to a well annulus during operation of the downhole tool. The wall is comprised of a first wall element connected to a second wall element so as to form a circumferential chamber running circumferentially through the wall. The first wall element having a plurality of actuating assemblies. Each actuating assembly comprises a detonator, a detonator assembly, a firing pin and a flow path. The detonator chamber having a first end positioned adjacent to the propellant volume and a second end having an inlet. The detonator assembly is located within the detonator chamber proximate to the first end of the detonator chamber. The firing pin is located within the detonation chamber. The firing pin is retained proximate to the inlet until an actuating pressure is applied through the inlet. The first flow passage is contained between the inner surface and the outer surface and extends from the circumferential chamber to the inlet of the detonation chamber. The first flow path is in fluid flow communication with the detonation chamber through the inlet and is in fluid flow communication with the circumferential chamber. The second wall element has a second flow passage extending from the circumferential chamber to the inner surface so as to provide fluid flow communication between the central bore and the circumferential chamber. The rupture disc is positioned in the second flow passage such that the rupture disk prevents fluid flow communication between the circumferential chamber and the central bore until ruptured by the application of the actuating pressure in the central bore.
In the above-described downhole tool, the rupture disc can be positioned adjacent to the inner surface. Also, the first flow passage and the second flow passage can be contained between the inner surface and the outer surface so as to be entirely interior to the wall. Additionally, there can be a plurality of detonation sections arranged sequentially such that the central bore of each section aligns to form a continuous central bore running through the plurality of sections.
In a further embodiment of the above-described downhole tool, the firing pin can be retained proximate to the inlet by a shear pin such that the shear pin holds the firing pin back from the detonator until the actuating pressure is applied through the inlet.
In still another embodiment, there is provided a method comprising:
Further, the detonation can be accomplished by an increase in pressure carried out under substantially static downhole tool conditions to rupture the rupture disc. The method can further comprise after step (a) and prior to step (b), introducing cement into the annular region to thus cement the casing in the wellbore. Also, step (b) can further comprise perforating the cement.
In the description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the invention. In the following description, the terms “upper,” “upward,” “lower,” “below,” “downhole” and the like as used herein shall mean in relation to the bottom or furthest extent of the surrounding wellbore even though the well or portions of it may be deviated or horizontal. The terms “inwardly” and “outwardly” are directions toward and away from, respectively, the geometric center of a referenced object. Where components of relatively well-known designs are employed, their structure and operation will not be described in detail.
Turning now to
Generally, detonation section 10 and wall 12 will be made up of one or more wall elements or sleeves. As illustrated, detonation section 10 has first wall element or first sleeve 26, and second wall element or second sleeve 28. First sleeve 26 and second sleeve 28 are configured such that when connected they form circumferential flow channel 30, which can better be seen with reference to
Rupture disc chamber 34, which can be better seen with reference to
Returning to
As can be seen with reference to
A flow passage 62 extends from inlet 54 to circumferential flow channel 30 and can be entirely interior to wall 12. Flow passage 62 places inlet 54 in fluid flow communication with circumferential flow channel 30 such, when rupture disc 38 is ruptured, inlet 54 is in fluid flow communication with central bore 18. Prior to the rupturing, rupture disc 38 prevents fluid flow communication with central bore 18.
The detonator assembly 56 includes a primer 80, primer case 82, shaped charge 84 and an isolation bulkhead 86. The primer 80 is spaced from the firing pin 58 within the primer case 82. The shaped charge 84 is positioned adjacent to the primer case 82 opposite from primer 80. The isolation bulkhead 86 is positioned adjacent the shaped charge 84 and proximate to the propellant volume 44. In this position, detonation of the shaped charge 84 will cause corresponding ignition of the propellant volume 44.
As can be best seen from
Also, as can best be seen from
With reference now to
After introducing of casing string 70 into wellbore 64, casing string 70 can be cemented in wellbore 64 as shown in
After cementing operations, if any, are completed, perforation and/or fracing can be performed as illustrated in
While various embodiments have been shown and described herein, modifications may be made by one skilled in the art without departing from the spirit and the teachings herein. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations, combinations, and modifications are possible. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims.
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