In order to produce hydrocarbon fluids from subterranean formations, a borehole is drilled from the surface down into the desired formations. Subsequently, a casing is commonly provided in the borehole, thereby defining a hollow wellbore. In order for the hydrocarbon fluids to flow from the surrounding formations into the wellbore and up to the surface, it is necessary to perforate the casing. Perforating and fracturing a well is common practice in the oil and gas industry in an effort to stimulate the well and increase the production of hydrocarbons. This is typically done using a perforating gun, a downhole tool that detonates explosive charges at selected locations in order to form holes in the casing.
Perforation is an important completion stage technique used in cased-holes to establish downhole connectivity between the reservoir and the wellbore. Commonly, lateral holes (perforations) are shot through the casing and/or cement and/or formation surrounding the casing to allow hydrocarbon flow into the wellbore and, if necessary, to allow treatment fluids to flow from the wellbore into the formation.
During perforation, a tunnel is created from the casing or liner into the reservoir formation, through which oil or gas is produced. The most common methods employ jet perforating guns equipped with shaped explosive charges. As such, most of the commonly used perforators today are based on explosive content that requires special permits to use, cause environmental damage and may impose safety risks to nearby workers. However, other perforating methods include bullet perforating, abrasive jetting or high-pressure fluid jetting. The perforation and fracturing of a well can be rather time consuming and, thus, expensive to perform.
Conventional equipment, as described above, that is used to perforate and isolate a zone of interest of the well often do not allow multiple zones of the well to be stimulated at once. For example, a perforation gun is commonly employed to perforate the well casing and the rock formation such that the perforations in the formation may then be fractured. Perforation guns generally consist of a series of charges dispersed at various heights and angular orientations along a cylinder. After the perforation gun has been loaded with charges, it is run into the hole and positioned within a zone of interest. The charges are then set off causing multiple perforations through well casing and into the formation. However to perforate another zone of the well, the perforation gun must typically be removed from the well and loaded with new charges. This process limits the number of zones that can be perforated and then fractured in a single day.
Demolition agents have commonly been used in rock fracturing endeavors and their specific selection is directly dependent upon the target impacted material and the specific requisites of the project. Errors and problem arise in circumstances where incorrect or improper demolition agents are employed.
As a consequence of these issues, the operation at the well site may have to wait for the permission to be received. This can lead to delayed scheduling of critical/time-dependent oil and gas operations.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.
In one aspect, embodiments disclosed herein relate to methods for perforating a downhole formation that may include attaching a CO2 perforating device to a wireline, where the CO2 perforating device may include one or more CO2 filled perforating units. The process may further include disposing the CO2 perforating device at a depth within a wellbore and detonating the one or more CO2 filled perforating units to perforate one or more surfaces selected from the group consisting of the wellbore casing, cement, and the downhole formation.
In a further aspect, embodiments disclosed herein relate to methods for perforating a downhole formation that may include disposing a well tool in a wellbore, the well tool comprising one or more vessels filled with carbon dioxide liquid. The methods may also include rapidly heating the carbon dioxide liquid via an electrical charge to form high pressure carbon dioxide and then discharging the high pressure carbon dioxide via one or more directional outlets associated with each vessel to perforate the downhole formation.
In another aspect, embodiments disclosed herein relate to systems for perforating a downhole formation that may include a well tool disposed on a wireline. The systems may include a well tool that may further include one or more vessels filled with carbon dioxide liquid, one or more directional outlets associated with each vessel, an electrical charge generation device configured to rapidly heat the carbon dioxide liquid to form a high pressure carbon dioxide, a pressure relief device configured to discharge the high pressure carbon dioxide through the one or more directional outlets, and an actuation mechanism configured to activate the electrical charge generation device.
Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.
Embodiments in accordance with the present disclosure generally relate to methods and systems for perforating a downhole formation with a nonexplosive perforating device. Such methods and systems may provide a critical role in establishing initial hydraulic contact between the rock formation and the wellbore. The perforating device may include at least one nonexplosive perforating charge that can be remotely detonated to perforate the wellbore (cased or uncased) and allow the formation fluids to enter the wellbore.
As described above, perforation is an important completion stage technique used in cased-holes to establish downhole connectivity between the reservoir and the wellbore. Embodiments in accordance with the present disclosure generally relate to methods and systems for perforating a downhole formation. Such methods, according to one or more embodiments, may include attaching one or more CO2 filled perforating devices to a wireline and placing the devices in a wellbore where they may be detonated to perforate one or more of the wellbore casing, cement, and downhole formation.
One or more embodiments of the present disclosure relate to non-explosive techniques for perforating a downhole formation. By employing a non-explosive technique for perforating a downhole formation, certain time consuming steps regarding regulated measures relating to government approval for the transport and use of explosives may be bypassed. Specifically, this may reduce lead time for operations at the well site that may be delayed by such regulatory measures. Embodiments herein may also reduce associated risks that arise with the use of explosive devices.
Additionally, explosive based techniques of the prior art require secure storage and must be well maintained to delay material expiration. In contrast, the well tool of the present application requires no special storage, as it primarily only requires storing CO2 liquid, which has no expiration date. The use of a well tool, in accordance with one or more embodiments of the present disclosure, in a non-explosive perforation method requires no special transport, use, or import permissions from the government. This will aid in executing scheduled operations as planned. The methods and systems of the present disclosure also provide an environmentally friendly and safe-to-use option for on-site personnel.
For the purpose of the present disclosure, numerous components and conditions are customarily employed and well known to those of ordinary skill in the art of well production stimulation. Such accompanying components may not be shown or discussed herein.
One or more embodiments of the present disclosure relates to a well tool for perforating a formation. In one or more embodiments, the well tool may include one or more vessels filled with carbon dioxide liquid. The well tool may include a directional outlet, or discharge outlet associated with each vessel, as well as an electrical charge generation device, or electric charge source, configured to initiate heating of the carbon dioxide liquid to form a high pressure carbon dioxide gas or supercritical fluid. The well tool may further include a pressure relief device, such as a rupture disc, configured to discharge the high pressure carbon dioxide through the directional outlet. The well tool may also include an actuation mechanism configured to activate the electrical charge generation device. Further, embodiments herein may include a stabilization mechanism to position and stabilize the well tool in a wellbore.
The CO2 filled perforating devices according to embodiments herein may only require milliseconds to complete the perforation operation, once emplaced in the wellbore. In comparison, conventional non-explosive jetting-based perforation methods may take several minutes to complete the perforation operation. This provides an additional advantage over existing non-explosive perforation techniques.
As illustrated in
One or more embodiments of the present disclosure may include a well tool for perforating a formation, where the well tool may be a CO2 filled perforating device as described above and illustrated in
In one or more embodiments, the methods and systems herein may include disposing a well tool 10 on a wireline 30, as shown in
In other embodiments, multiple CO2 filled perforating devices may be connected via wireline, such that a section of wireline is provided between two or more CO2 filled perforating devices. This may allow for a single wireline operation to be used for perforating at multiple depths.
Unlike explosive perforators, CO2 filled perforating devices according to embodiments herein create the perforations through physical expansion due to a phase change induced by rapid electric charge heating, creating a “detonation.” This electric charge detonation may be controllably triggered to occur in every CO2 filled perforating device 20 unit simultaneously, or they may be triggered in a time series of detonations.
In some embodiments, where two or more CO2 filled perforating devices 20 are employed, such as depicted in
In one or more embodiments, the expanded CO2 will act as a sharp jet or stream of gas that is strong enough to create holes and penetrate one or more of the casing, cement, and formation in cased-hole completions. Such a device may also be used for open-hole completion. As shown in
In one or more embodiments, the perforating tool may include between 1 and 5 CO2 filled perforating devices, where each CO2 filled perforating device may include multiple discharge heads (ruptured discs).
In one or more embodiments, the CO2 filled perforating device may be configured alone, in parallel, or in series, and in configurations having more than one CO2 filled perforating devices, each CO2 filled perforating device 20 may be detonated simultaneously or individually. In one or more embodiments, the CO2 filled perforating device units may be controllably detonated independent of each other, when the modified perforation device includes more than one CO2 filled perforating unit. In one or more embodiments, the individual CO2 filled perforating devices may be detonated at selected times and depths. Upon detonation, perforations may be formed, as shown in
One or more embodiments of the present disclosure may be directed towards a method for perforating a downhole formation. Such a method may include disposing a well tool in a wellbore where the well tool may include one or more CO2 filled perforating devices as described above and shown in
According to one or more embodiments, the method may include one or more vessels filled with liquid CO2, where the CO2 may be discharged at specified depths. In embodiments where two or more vessels are attached on a wireline and disposed downhole in a formation, the two or more vessels may be discharged such that the perforation of two or more zones, of differing depth, may be accomplished simultaneously. The method may further include the removal of the one or more vessels after they have been discharged so that the spent liquid CO2 included within the vessels can be refilled at the surface and the vessels can be redeployed on a wireline.
As described above, well tools according to one or more embodiments of the present disclosure may include CO2 filled perforating devices. An example of such an embodiment is provided in
In one or more embodiments of the present disclosure, perforating methods may include filling the CO2 tube of the perforating device with liquid CO2 at the surface. Upon completion of the filling of the one or more units of the perforating device, the device may be attached to a wireline 30 and delivered downhole, as shown in
In accordance with one or more embodiments of the present disclosure, CO2 may be stored in liquid phase within the perforating device. In order for CO2 to remain in the liquid phase during downhole delivery, the temperature of the liquid CO2 may be maintained at a relatively low temperature, for example, less than 30° C., and at pressures above 1000 psia. Higher temperatures and pressures may also be tolerated during downhole delivery.
To help maintain the CO2 in a dense phase and avoid overpressure or early release due to downhole environmental conditions, in one or more embodiments, the CO2 perforated device may include an insulated tube 26 containing the liquid CO2. Insulation may be disposed, for example, around the liquid filled tube 26. In some embodiments, liquid filled tube 26 may be a vacuum insulated tubing (VIT) 29 (
A perforating unit as described above may be lowered into the wellbore 40 on a wireline tool 30 as shown in
As shown in
The angle of incidence may be measured between the well tool device, and a direction that is normal to an inner surface of the downhole casing at a point where the trajectory intersects the inner surface of the downhole casing. When the discharged gas jet stream contacts the surface at an angle of incidence that is outside the preferred angle of contact, the discharged gas stream may not penetrate and/or ricochet from, the surface.
If not controlled properly, the generated pressure of the CO2 expansion may impair the casing integrity as a whole instead of only creating the desired holes, and the generated CO2 gas jet stream may transmit elsewhere affecting other nearby components and/or tools in the wellbore such, as the wire-line or packers.
As such, in one or more embodiments, the well tool, or CO2 filled perforating device, may be positioned within the wellbore such that the discharge outlets would be proximal to the target surface to be perforated. To position the perforating device of the present disclosure, a stabilizer or stabilizing method may be incorporated. Examples of the stabilizer may include packer elements, extendable arms, sealing devices, and any other mechanisms suitable for stabilizing the perforating device within the wellbore. Such a mechanism may be used to mitigate issues related to impact occurrence, such as may result from the initial discharge of CO2 when detonated. For example, when one discharge port is provided, the stabilizing mechanism may prevent radial movement of the perforating device within the wellbore when detonated. Further, one skilled in the art may appreciate that burst discs, while rated to burst at a given pressure, may not all burst exactly at the same pressure (manufacturing tolerances, defects, etc.); when two or more discharge ports are provided, the stabilizers may prevent unwanted movement of the tool, for example, that may otherwise result from a prematurely bursting disc or a misalignment of ports. Stabilizing modifications may also be incorporated such that an operator does not risk damage to the wellbore or casing as the perforating tool is transported downhole to where it will be used. Accordingly, such stabilizing and/or expansion devices may be incorporated into CO2 filled perforating device/well tools.
Extendable arms may also be used to place the discharge heads 27 in proximity to the casing and/or wellbore. For example, as illustrated in
Stabilizers or packer elements may be initiated or engaged by a variety of means including common packing techniques associated with the packer elements, electrical signal, hydraulic signal, optical signal, and any other suitable signal that may be known in the art. Modified well tools in accordance with one or more embodiments of the present disclosure may include such stabilizer or packer elements to provide more precise and controllable means of positions the well tool within the wellbore, as defined by the casing of the well, or within a formation. In one or more embodiments, packer elements may be positioned within the wellbore adjacent to the CO2 filled perforating devices to stabilize the device within the wellbore. In one or more embodiments, the packer elements may be positioned proximally above and/or below the CO2 filled perforating devices to stabilize the device within the wellbore.
In yet other aspects, embodiments disclosed herein may include one or more sealing mechanisms. For example, a sealing mechanism, such as packer elements, may be provided above and/or below the discharge outlets, thereby focusing the increased CO2 pressure within a confined zone of the wellbore, allowing the expanding CO2 to perforate the wellbore while limiting pressure losses axially/vertically within the wellbore.
In some embodiments, the rupture disc may be in the form of a projectile, or may be placed proximal to a projectile, such that when the rupture disc bursts, the rupture disc may be propelled through the discharge port by the high pressure CO2 gas jet stream. Such embodiments may be particularly useful when perforation through casing or particularly hard formation is necessary.
As described above, embodiments detailed herein provide methods and systems for perforating a wellbore and/or formation that do not require the use of explosives and that are environmentally friendly. The safe, consistent, and reusable tool permits numerous advantages over conventional explosive perforating techniques, as noted throughout the description above.
Although the preceding description has been made herein with reference to particular means, materials and embodiments, it is not intended to be limited to the particulars disclosed herein; rather, it extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.
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