CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation in part of U.S. application Ser. No. 15/080,251, filed Mar. 24, 2016, the disclosure of which is fully incorporated herein by reference.
FIELD OF THE INVENTION The present invention relates generally to perforation guns that are used in the oil and gas industry to explosively perforate well casing and underground hydrocarbon bearing formations, and more particularly to arranging shaped charges in rows in a cluster for explosively perforating a well casing and its surrounding underground hydrocarbon bearing formation.
PRIOR ART AND BACKGROUND OF THE INVENTION Prior Art Background During a well completion process, a gun string assembly is positioned in an isolated zone in the wellbore casing. The gun string assembly comprises a plurality of perforating guns coupled to each other either through tandems or subs. The perforating gun is then fired, creating holes through the casing and the cement and into the targeted rock. These perforating holes connect the rock holding the oil and gas and the well bore. “During the completion of an oil and/or gas well, it is common to perforate the hydrocarbon containing formation with explosive charges to allow inflow of hydrocarbons to the well bore. These charges are loaded in a perforation gun and are typically shaped charges that produce an explosive formed penetrating jet in a chosen direction” U.S. Pat. No. 7,441,601.
Hydrocarbon fracturing tunnels have certain preferred orientations where the effectiveness of extracting oil/gas is greatest i.e., when a perforation is aligned along the tunnels, oil/gas flows though the perforation tunnels without taking an alternate path that may become a restrictive path creating high tortuosity conditions.
It has been shown in studies that the fractures initiate close to the wellbore casing in an upward and downward direction. FIG. 1 (0100) generally illustrates a top view of a horizontal drilling pad (0104) within the metes and bounds of a lease or ownership. Multiple horizontal wells (0102) are generally drilled from a vertical well head (0101). Studies have shown that preferred fracturing planes (0103) are transversely perpendicular to the orientation of the horizontal wellbore casings. Multiple preferred fracturing planes that are parallel to each other may be targeted for maximum production efficiency. However, horizontal wellbores are often deviated as much as 100 ft in any direction over the length of 3 miles. Therefore, the orientation of the gun may not be horizontal and is often at an angle. The charges in the gun may or may not be optimally phased when perforating. Field results indicate that there is a single dominant perforation tunnel per stage. As there are multiple stages per well, multiple clusters per stage typically 3 to 15 and multiple perforating guns in each cluster typically 4-6, there is a need for an optimal phasing of the charges in each of the perforating guns per cluster so that the chances of perforating in the dominant channel is increased. A cross section of the horizontal wellbore casing (0207) drilled in a wellbore (0206) is further illustrated in FIG. 2 (0200). Due to the compression of rock (0205) from the surface, the hydrocarbon formation is pressed downwardly and the region proximal to the hydrocarbon formation has a discontinuity. The discontinuity creates a stress (0204) distribution around the wellbore. Studies from rock mechanics have indicated a high compression region (0201) about the sides and a low compression region (0203) around the upward and downward region. Therefore, there is a need to phase the charges to perforate in the low compression region (0202) so that fractures initiate in the low compression region for maximum fracture efficiency. There is a need to phase the charges so that the chances of placing a perforation tunnel in the effective regions of low compressive stress are improved. There is a need for the fracture to initiate at the top and bottom first that has the least principal stress so that there is enough flow rate to propagate the fracture. There is a need for a perforating gun that perforates such that the fracture permeates radially to the direction of the wellbore in an upward and downward direction.
By design, each perforation is expected to be involved in the fracture treatment. If all perforations are involved, and the perforations are shot with 0°, 60°, 90°, 120°, or 180° phasing, multiple fracture planes may be created, leading to substantial near wellbore friction and difficulty in placing the planned fracturing treatment. Field results indicate that there is a single dominant perforation tunnel per stage. Therefore, there is a need for minimal multiple fracture initiations that do not create ineffective fracture planes. Various prior art phasing in a perforating gun (0302) in a well casing (0301) is illustrated in FIG. 3. For example, FIG. 3 (0310) illustrates a 0° phasing where all the charges are phased to perforate in a downwardly direction. Similarly, FIG. 3 (0320) illustrates a 0°-180° phasing wherein charges are phased to perforate in an upward and downward direction. However, the chances of perforating in an upward and downward direction are low when the well casing is deviated and the perforating gun is not horizontal. There is an accuracy issue of positioning the guns (orienting) with respect to the up/down vector. Field results indicate that even with orientation of the guns, operational issues can cause perforations in a non-preferred region. The probability of perforating in the preferred upward and downward low compression region is very low for a 0° phasing or a 0°-180° phasing gun.
FIG. 4 further illustrates a perforating gun (0401) with a 0°-180° phasing wherein charges (0404) are phased to perforate in an upward and downward direction. As illustrated in FIG. 4 (0410) the charges (0404) are perfectly aligned to the preferred direction (0402) and the fracture treatment through the perforations may produce efficiently. However, since the wells are not perfectly horizontal and in most case deviated, the gun (0411) may be rotated as illustrated in FIG. 4 (0420) and the charges (0404) may be perforating into the high compression region or sideways and produce ineffective fracture treatment. Therefore, it is important to perforate to improve the probability of placing the perforations in the low compression region which are determined to be on the upward and downward directions.
FIG. 3 (0330) illustrates a 120° phasing wherein 3 charges are phased at 120° to perforate. The probability of perforating within 240° of the upward and downward low compression region is 100%. The chances are decreased to 50% for perforating within 120° and further decreased to 25% for perforating within 60° and further decreased to 12.5% for perforating within 30° of the upward and downward low compression region is 100%. Therefore, there is a need to improve the probability to at least 80% for perforating within 30° of the upward and downward low compression region.
FIG. 3 (0340) illustrates a 90° phasing wherein 4 charges are phased at 90° to perforate. The probability of perforating within 90° of the upward and downward low compression region is 100%. The chances are decreased to 50% for perforating within 90° and further decreased to 25% for perforating within 45°. Therefore, there is a need to place and phase the charges within in a cluster such that the chances of perforating in the preferred low compression region is at least 75%.
FIG. 3 (0350) illustrates a 60° phasing wherein 6 charges are phased at 60° to perforate into a hydrocarbon formation. Prior art perforating guns are generally loaded with 6 shots per foot (SPF) at 60 degree phasing. With the 60° phasing, the probability of perforating within 60° of the upward and downward low compression region is 100%. The probability of perforating within 30° of the upward and downward low compression region is 50%. Even with a double shot at the same phasing, the probability remains the same but requires 12 shots spanning 2 feet. Therefore, there is a need to improve the probability to at least 800% for perforating within 30° of the upward and downward low compression region (perforation angle).
Currently, 1 to 12 perforation holes per stage are shot which will reconnect to the predominant fracturing plane during fracturing treatment. Most stages are completed with 6 shots per cluster and 6 shots per foot (“spf”) and at 60 degrees for obvious statistical reasons. Some of the perforation tunnels cause energy and pressure loss during fracturing treatment which reduces the intended pressure in the fracture tunnels. For example, if a 100 bpm (barrels per minute) fracture fluid is pumped into each fracture zone at 10000 PSI with an intention to fracture each perforation tunnel at 2-3 bpm, most of the energy is lost in ineffective fractures that have higher tortuosity reducing the injection rate per fracture to substantially less than 2-3 bpm. Consequently, the extent of fracture length is significantly reduced resulting in less oil and gas flow during production. Therefore, there is a need for a system to achieve the highest and optimal injection rate per perforation tunnel so that a maximum fracture length is realized. The more energy put through each perforation tunnel, the more fluid travels through the preferred fracturing plane, the further the fracture extends. Ideally, 1000 feet of fracture length from the wellbore is desired. Therefore, there is a need to get longer extension of fractures which have minimal tortuosity. For example, in order to achieve 2 bpm in each perforation tunnel, a total injection rate of 100 bpm at 1000 psi for 48 perforation tunnels requires 12 clusters each with 4 charges. Therefore, there is a need to shoot more zones with 4 perforating holes in each cluster that are oriented 2 up and 2 down. Active orientation systems commonly used such as 0 degrees or 180 degree orientations, have an accuracy of orientation that is estimated to be +−20 degrees with an external orientation and +− with an internal orientation. There is a need to improve the chances of proper placement without an active orientation system.
Perforation and fracturing are based on the premise that every perforation will be in communication with a hydraulic fracture and will be contributing fluid during the treatment at the pre-determined rate. Therefore, if any perforation does not participate, then the incremental rate per perforation of every other perforation is increased, resulting in higher perforation friction. Therefore, there is a need to angle and space charges to facilitate the fracturing process to achieve maximum production efficiency.
Prior art U.S. Pat. No. 7,303,017A discloses “a method includes arranging shaped charges in a perforating gun to produce perforation holes in a helical pattern that is defined in part by a phase angle; and choosing four adjacent perforation holes to be created that are adjacent nearest neighbors. The distances are determined between three of the four adjacent perforation holes to be created. A standard deviation is minimized between the three adjacent perforation holes. The phase angle is set based on the minimization.” However, U.S. Pat. No. 7,303,017A does not teach an optimal phasing of the charges in the bank so that charges perforate within desired perforation angles in a low compression region especially for a deviated well.
Deficiencies in the Prior Art The prior art as detailed above suffers from the following deficiencies:
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- Prior art perforation phasing systems do not provide for efficiently reducing tortuosity and energy loss in a perforation tunnel with minimum number of shots per foot.
- Prior art perforation phasing systems do not provide for longer extension of fractures which have minimal tortuosity with minimum number of shots per foot.
- Prior art perforation phasing systems do not provide for the highest and optimal injection rate per perforation tunnel so that a maximum fracture length is realized with minimum number of shots per foot in a cluster.
- Prior art perforation phasing systems do not provide for achieving a probability greater than 50% for perforating within +−15° of the upward and downward low compression region.
- Prior art perforation phasing systems do not provide for an optimal phasing of the charges in the perforating gun per cluster in order to achieve maximum perforation and fracturing efficiency.
- Prior art perforation phasing systems do not have an optimal statistical chance of perforation placement when less than or more than 6 shots are placed in a cluster.
While some of the prior art may teach some solutions to several of these problems, the core issue of reacting to unsafe gun pressure has not been addressed by prior art.
OBJECTIVES OF THE INVENTION Accordingly, the objectives of the present invention are (among others) to circumvent the deficiencies in the prior art and affect the following objectives:
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- Provide for efficiently reducing tortuosity and energy loss in a perforation tunnel with minimum number of shots per foot.
- Provide for longer extension of fractures which have minimal tortuosity with minimum number of shots per foot.
- Provide for the highest and optimal injection rate per perforation tunnel so that a maximum fracture length is realized with minimum number of shots per foot in a cluster.
- Provide for improving the probability to at least 50% for perforating within +−15° of the upward and downward low compression region.
- Provide for an optimal phasing of the charges in the perforating gun per cluster in order to achieve maximum perforation and fracturing efficiency.
- Provide for perforation phasing systems that have an optimal statistical chance of perforation placement when less than or more than 6 shots are placed in a cluster.
While these objectives should not be understood to limit the teachings of the present invention, in general these objectives are achieved in part or in whole by the disclosed invention that is discussed in the following sections. One skilled in the art will no doubt be able to select aspects of the present invention as disclosed to affect any combination of the objectives described above.
BRIEF SUMMARY OF THE INVENTION System Overview The present invention in various embodiments addresses one or more of the above objectives in the following manner. The present invention provides a system that includes an optimal phasing perforating phased gun system and method for accurate perforation in a deviated/horizontal. The system/method includes a gun string assembly (GSA) deployed in a wellbore with shaped charges in clusters. Within a cluster, the charges are separated into individual banks with a phase angle between the charges in each bank and an offset angle between banks. The number of charges per cluster, the phase angle and the offset angle are optimized such that there is a maximum probability of perforating into a low compression region in an upward and downward direction. The fracture treatment through the perforations in the low compression regions create minimal tortuosity paths for longer extension of fractures that enables efficient oil and gas flow rates during production.
Method Overview The present invention system may be utilized in the context of an overall optimal phasing perforating method, wherein the phased perforating gun as described previously is controlled by a method having the following steps:
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- (1) selecting a gun system for each cluster in a stage with the best statistical probability for the desired number of perforations in that cluster;
- (2) positioning a phased perforating gun system in a wellbore casing; and
- (3) perforating through the phased perforating gun system into a hydrocarbon formation such that at least one of the first plurality of charges and at least one of the second plurality of charges perforate within a upward perforation angle and a downward perforation angle; the upward perforation angle subtends in an upward direction about a center of the perforating gun and the downward perforation angle subtends in a downward direction about the center of the perforating gun.
Integration of this and other preferred exemplary embodiment methods in conjunction with a variety of preferred exemplary embodiment systems described herein in anticipation by the overall scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the advantages provided by the invention, reference should be made to the following detailed description together with the accompanying drawings wherein:
FIG. 1 is a top view of a horizontal drilling pad with multiple horizontal wells that are drilled from a vertical well head.
FIG. 2 is a cross section of the horizontal wellbore casing drilled in a wellbore in FIG. 1.
FIG. 3 illustrate various prior art phasing in a perforating gun in a well casing.
FIG. 4 illustrates a perforating gun with a 0°-180° phasing of the charges.
FIG. 5 shows an end view of a perforating gun illustrating an upward perforation angle and a downward perforation angle.
FIG. 6 generally illustrates a side perspective view of two charges phased in a perforating gun defining a phase angle and charge spacing.
FIG. 7A illustrates an exemplary 8-shot (charges) 2-bank, phased at 90° phase angle between charges in each bank, phased 45° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 7B illustrates an exemplary 8-shot (charges) 2-bank, phased at 90° phase angle between charges in each bank, phased 45° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 7C illustrates an exemplary 8-shot (charges) 2-bank non-converging, phased at 90° phase angle between charges in each bank, phased 45° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 7D illustrates an exemplary cross section view of 8-shot (charges) 2-bank, phased at 90° phase angle between charges in each bank, phased 45° offset angle between banks with a orienting reference point in a perforating gun according to a preferred embodiment of the present invention.
FIG. 8 illustrates an exemplary 12-shot (charges) 3-bank, phased at 120° phase angle between charges in each bank, phased 30° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 9A illustrates an exemplary 6-shot (charges) 2-bank, phased at 120° phase angle between charges in each bank, phased 60° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 9B illustrates an exemplary 6-shot (charges) 2-bank non-converging, phased at 120° phase angle between charges in each bank, phased 60° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 10A illustrates an exemplary 6-shot (charges) 3-bank, phased at 180° phase angle between charges in each bank, phased 90° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 10B illustrates an exemplary 6-shot (charges) 3-bank non-converging, phased at 180° phase angle between charges in each bank, phased 90° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 11A illustrates an exemplary 10-shot (charges) 2-bank, phased at 72° phase angle between charges in each bank, phased 36° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 11B illustrates an exemplary 10-shot (charges) 2-bank non-converging, phased at 72° phase angle between charges in each bank, phased 36° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 12A illustrates an exemplary 12-shot (charges) 2-bank, phased at 60° phase angle between charges in each bank, phased 30° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 12B illustrates an exemplary 12-shot (charges) 2-bank non-converging, phased at 60° phase angle between charges in each bank, phased 30° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 13A illustrates an exemplary 12-shot (charges) 3-bank, phased at 90° phase angle between charges in each bank, phased 30° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 13B illustrates an exemplary 12-shot (charges) 3-bank non-converging, phased at 90° phase angle between charges in each bank, phased 30° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 14A illustrates an exemplary 12-shot (charges) 4-bank, phased at 120° phase angle between charges in each bank, phased 15° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 14B illustrates an exemplary 12-shot (charges) 4-bank non-converging, phased at 120° phase angle between charges in each bank, phased 15° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 15A illustrates an exemplary 14-shot (charges) 2-bank, phased at 51.42° phase angle between charges in each bank, phased 25.5° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 15B illustrates an exemplary 14-shot (charges) 2-bank non-converging, phased at 51.42° phase angle between charges in each bank, phased 25.5° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 16A illustrates an exemplary 16-shot (charges) 4-bank, phased at 90° phase angle between charges in each bank, phased 11.25° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 16B illustrates an exemplary 16-shot (charges) 4-bank non-converging, phased at 90° phase angle between charges in each bank, phased 11.25° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention.
FIG. 17 illustrates a detailed flowchart of a preferred exemplary optimal phasing perforation method with shaped charges according to preferred exemplary invention embodiments.
FIG. 18 illustrates 4 charges arranged in 4 rows in a cluster and 8 charges arranged in 8 rows in another cluster according to preferred exemplary invention embodiments
FIG. 19 illustrates a 6-shot, 8-shot and a 12-shot cluster with charges arranged in rows according to preferred exemplary invention embodiments.
FIG. 20 illustrates a detailed flowchart of a preferred exemplary perforation method with shaped charges arranged in rows in a cluster according to preferred exemplary invention embodiments.
DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detailed preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiment illustrated.
The numerous innovative teachings of the present application will be described with particular reference to the presently preferred embodiment, wherein these innovative teachings are advantageously applied to the particular problems of optimal phasing perforating gun system and method. However, it should be understood that this embodiment is only one example of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others.
FIG. 5 (0500) generally illustrates an end view of a wellbore casing (0501). Hereinafter, an “upward perforation angle” (0504) is defined as the angle subtended in an upward direction (0511) about a center (0510) of the wellbore casing (0501). Similarly, a “downward perforation angle” (0514) is defined as the angle subtended in a downward direction (0512) about a center (0510) of the wellbore casing (0501). It has been reported that prior art perforating gun phasing achieve an accuracy within an upward perforation angle (0503) and a downward perforation angle (0513) which are +−75°. Most commonly used systems such as 6 SPF at 60° will place perforation in each 60 degree arc if the 6 shot bank is fully loaded. The chances of placing the perforation in the 60° arc further goes down if one shot is left out, i.e., 5 out of 6 shots loaded in a 60° gun. To achieve maximum fracturing efficiency, it is needed to perforate within a preferred upward perforation angle and preferred downward perforation are +−15° so that the perforation is achieved in an upward low compression region (0505) and a downward low compression region (0515). Furthermore, field results as indicated by a dominant perforation hole due to erosion during the fracture treatment have shown that a dominant tunnel exits on the low side (0515) 70% of the time, high side (0505) 20% of the time, and other sides 10% of time. The differences in the upward and downward production is due to smaller size of the perforation hole in the upward direction as compared to the size of the perforation hole in the downward direction. The size of the perforation holes are different due to the fact that the perforating gun is closer to the side wall of the casing in the downward direction. The perforating hole in the downward direction is sometimes twice as large as the perforating hole in the upward direction. Therefore, there is a further need to compensate for the disproportionate perforating hole sizes by orienting the charges to achieve a 50/50% production from both upward and downward low compression zones.
FIG. 6 (0600) generally illustrates a side perspective view of two charges (0602, 0603) phased in a perforating gun (0601). Hereinafter a “phase angle” between two charges may be defined as the angle between the perpendicular lines extending from the charges. For example, angle (0604) defines a phase angle between charge (0602) and charge (0603). In a 6-shot 6 SPF perforating gun, the phase angle is 60 degrees. Similarly, in a 4-shot perforating gun, the phase angle is 90 degrees. Hereinafter “Charge spacing” may be defined as the spacing between two consecutive charges in a perforating gun. For example, charge spacing (0605) may be defined as the spacing between consecutive charges (0602) and (0603).
Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun System (0700) An exemplary embodiment of the present invention may be generally illustrated in FIG. 7A, wherein a phased perforating gun assembly is deployed inside a wellbore casing along with 2 banks (0700, 0710), each of the banks comprise plural shaped charges. According to a preferred exemplary embodiment, the angular orientation of the wellbore casing is substantially horizontal. According to another preferred exemplary embodiment, the angular orientation of the wellbore casing is deviated. For example, horizontal wellbores are often deviated as much as 100 ft in any direction over the length of 3 miles. Therefore, the angular orientation of the gun may not be horizontal and is often at an angle with respect to a longitudinal axis of the casing. The charges in the gun may or may not be optimally phased when perforating.
The bank (0700) may comprise charges (0701, 0702, 0703, 0704) and the bank (0710) may comprise charges (0711, 0712, 0713, 0714). The plural shaped charges in the perforating gun together in bank (0700) and bank (0710) may herein be referred to as “cluster”. Even though four charges have been shown in each of the banks in FIG. 7A, the banks may comprise more than 2 four shaped charges according to a preferred exemplary embodiment.
Referring to FIG. 7A, the perforating gun may include shaped charges that extend around a central axis of the gun in a helical, or spiral, pattern. Each shaped charge points radially outwardly toward a well casing, and adjacent shaped charge in the spiral pattern are radially separated by a phase angle of 90°. For example, shaped charge 0701 is radially separated to adjacent shaped charge 0702 by a phase angle of 90°. Similarly, shaped charge 0711 is radially separated to adjacent shaped charge 0712 by a phase angle of 90°. According to a preferred exemplary embodiment, the phase angle of the shaped charges in a bank may range from 1° to 359°. According to a more preferred exemplary embodiment, the phase angle of the shaped charges in a bank may range from 5° to 90°. According to a most preferred exemplary embodiment, the phase angle of the shaped charges in a bank may range from 15° to 30°. For example, phase angle of the shaped charge 0711 to adjacent shaped charge 0712 may range from 1° to 359°. According to yet another preferred exemplary embodiment, the phase angle of one bank may be equal to the phase angle of another bank in the cluster. According to yet another, preferred exemplary embodiment, the phase angle of one bank may be unequal to the phase angle of another bank in the cluster. According to another preferred exemplary embodiment, the shaped charges are equally spaced. For example, the charge spacing between consecutive shaped charges (0701), (0702) and (0703) may be equal. According to yet another preferred exemplary embodiment, the shaped charges are not equally spaced.
According to a preferred exemplary embodiment, the number of charges in each of the banks may range from 2 to 24. According to a more preferred exemplary embodiment, the number of charges in each of the banks may range from 2 to 8. According to a most preferred exemplary embodiment, the number of charges in each of the banks may range from 2 to 6. For example, the bank (0700) may comprise 2 to 24 charges and bank (0710) may comprise 2 to 24 charges. According to a preferred exemplary embodiment, the offset angle ranges from 1 to 90°. According to a more preferred exemplary embodiment, the offset angle of the shaped charges between the banks may range from 10° to 45°. According to a most preferred exemplary embodiment, the offset angle of the shaped charges between the banks may range from 15° to 30°. The offset angle may be the phase angle between charge 0701 and charge 0711. The offset angle between 0702 and 0712 would be same if the phase angles of charges in both the banks are the same. In the illustration shown in FIG. 7A, the offset angle is 45°. In this example, the offset angle between charges 0701 and 0711 is 45°. The offset angle may range from 1° to 90° depending on the required upward and downward perforation angles.
In the illustration presented in FIG. 7A with 4 charges per bank at a 90° phase angle between charges and a 45° offset angle (“offset phase angle”) between banks 0700 and 0710, the probability of perforating within a 45° upward perforation angle is 100%. Similarly, the probability of perforating within a 22.5° upward perforation angle is 50%. In contrast, for a prior art 8 charge system with a 90° phase angle between charges, the probability of perforating within a 45° upward perforation angle is 50% as compared to the exemplary 2 bank 8 charge system illustrated in FIG. 7A. An offset angle between each of the banks increases the probability of shaped charges perforating within a desired perforation angle so that fractures initiate in the low compression region for achieving maximum fracture efficiency. According to a preferred exemplary embodiment, a perforation angle within 30° with a probability greater than 75% is achieved.
The offset angle, also referred to as offset phase angle, between two banks may also be achieved by physically rotating one bank with respect to the other bank. As illustrated in FIG. 7D (0760), bank 0700 may be horizontally oriented with four charges at 90° phase angle and bank 0700 may be horizontally oriented with four charges at 90° phase angle. The reference orienting point (0761) may be the same. In this case the offset angle is zero. The bank 0710 may be physically rotated or twisted by the amount of the desired offset angle with a rotating means about a reference point (0761). The configuration of the banks 0700 and 0710 after rotating bank 0710 is generally illustrated in FIG. 7D (0770). When the perforating guns are deployed into a well casing, the guns may be connected to each other via a sub or a tandem (0790). The guns may be twisted or rotated about an orienting reference point (0761) with any widely available twisting means or mechanism such as ball bearings or threads or screws. The banks may be rotated about the reference orienting point (0761) to achieve a desired offset angle. Alternatively, the orienting reference point may be the same for all banks, but the desired offset angle may be achieved by phasing the charges in each of the banks as generally illustrated in FIG. 7A.
One of the banks within the cluster may be at the best orientation and therefore be the dominant bank within the cluster. The clusters will also be balanced as each cluster in a stage will have a statistical probability of having a bank with charges phased to perforate within an arc in the low compression zone. For example, referring to FIG. 7A, bank (0700) comprising charges (0701, 0702, 0703, 0704) may be the dominant bank while bank (0710) comprising charges (0711, 0712, 0713, 0714) may be the non-dominant bank. In this case, charge 0701 may be perforating upwards into the low compression zone within a 45° upward perforation angle with a probability of 100%. Similarly, charge 0703 may be perforating downwards into the low compression zone within a 45° downward perforation angle with a probability of 100%. Alternatively, bank (0710) may be the dominant bank and charges 0711 and 0714 may be the upward charges perforating into the low compression region and charges 0712 and 0713 may be the downward charges perforating into the low compression region. According to a preferred exemplary embodiment the downward perforation angle and the upward perforation angle may range from 1° to 45°. According to a preferred exemplary embodiment, within a stage, the phasing of the charges in the dominant bank in one cluster may be different than the phasing of the charges in the dominant bank in another cluster. Variations in placement of perforation tunnels with respect to low compression stress areas contributes to variation in “cluster perforation quality”. A variation in cluster perforation quality may imply some clusters in a stage will be treated unequally. For example, a bank similar to bank 0700 may be the dominant bank in one cluster and a bank similar to bank 0710 with a different phasing of charges may be the dominant bank in another cluster of the same stage. The advantages of having two different dominant banks with different phasings (phase angles) in two different clusters enables fracturing fluids to be distributed evenly without competing. In contrast, if the dominant banks with similar phasings in different clusters are treated, fracturing fluids may be dominated by the first dominant bank while starving the other dominant bank in the downstream cluster. According to another preferred exemplary embodiment, the phasing of the charges in the dominant bank in one cluster may be same as the phasing of the charges in the dominant bank in another cluster.
As illustrated in Table 1.0, the number of banks, and charges per bank may be selected to achieve a desired probability for a perforation angle within 30° or any other angle. The combination of charges per bank, number of banks, phase angle and offset angle may be chosen per cluster based on the diameter of the perforating gun, the length of the gun and the size of the gun. For example, a 2 foot gun may accommodate 12 charges or shots with 1 foot loaded and 1 foot for end connections, a 3-ft gun may accommodate 12 shots and a 4-ft gun may accommodate 18 shots. A conventional prior art perforating gun is generally loaded with 6 shots per foot (SPF) at a 60 degree phasing. With the 60° phasing, the probability of perforating within 60° arc which includes 60° of the upward and downward low compression region is 100%. The probability of perforating within 30° of the upward and downward low compression region is 50%. Even with a double shot at the same phasing, the probability remains the same but requires 12 shots spanning 2 feet. However, the probability substantially doubles with an exemplary configuration that may include a 2 bank, 6 charges per bank, 60° phasing, and 30° offset angle. The probability of perforating within 15° of the upward and downward low compression region is almost 100%. Therefore, the exemplary configurations illustrated in Table 1.0 provides for a more efficient perforations so that fractures initiate in the low compression region adjacent to the perforating gun for achieving maximum fracture efficiency. Prior art guns may be loaded at the normal shots per foot with charges loaded at 6 SPF at 60° phasing, 4 SPF at 90° phasing, 5 SPF at 72° phasing and 3 SPF 120° phasing. However, according to an exemplary embodiment, a 10 shot gun may be loaded at nearly 6 SPF density or a variable density. According to a preferred exemplary embodiment, the perforation angle may range from 0° to 30° and/or within +−15°. The upward perforation angle may be substantially the same as the downward perforation angle if the phase angle is the same for all the charges within a bank.
The size of the perforation holes are different due to the fact that the perforating gun is closer to the side wall of the casing in the downward direction. The perforating hole in the downward direction is sometimes twice as large as the perforating hole in the upward direction. According to a preferred exemplary embodiment, the configurations of Table 1.0, along with orienting the charges, compensate for the disproportionate perforating hole sizes to achieve a 50/50% production flow from both upward and downward low compression zones.
TABLE 1.0
Offset
No Of Phase Phase Perforation Perforation Perforation
Shots Charges Angle Angle Angle with Angle with Angle with
in Per No of in each Between 100% 50% 25%
Cluster bank Banks bank Banks probability probability probability
8 4 2 90 45 45 22.5 11.25
10 5 2 72 36 36 18 9
12 6 2 60 30 30 15 7.5
14 7 2 57.4 28.7 26 13 6.5
15 5 3 57.5 24 24 12 6
12 4 3 90 30 30 15 7.5
FIG. 7A (0720) generally illustrates phase angle (0721) vs charges (0722) for an unrolled gun. The charges in banks 0700 and 0710 are illustrated along with the phase angle and offset angle. For example, the phase angle (0730) between charge 0701 and charge 0702 is 90°. The offset angle (0740) between charge 0701 and charge 0711 is 45°.
According to a preferred exemplary embodiment, the charges in the first bank and the charges in the second bank may be further angled to place preferred initiation points on a transverse plane to the wellbore casing. The transverse plane may be perpendicular to the longitudinal axis of the wellbore casing. The initiation points may or may not intersect with each other, but charges may be oriented such that the initiation points intersect the preferred fracturing plane so that the fractures created from the initiation points create minimal tortuosity and longer extension of fractures. The initiation points in the preferred plane are particularly significant for wellbore completions to achieve maximum efficiency during oil and gas production. It has been known through several field studies and field data that the preferred plane is transverse about the horizontal direction of the wellbore casing. Initiation points are inherently present in perforation tunnels when shaped charges perforate. Not every point in the perforation tunnel is preferred. The preferred initiation points may lie at the end of the clear tunnel (tip) of the perforation tunnels and furthermore the preferred initiation points lie in a preferred fracturing plane. A fracturing fluid is then pumped at high pressures so that the fracture fluid extends the fractures to the maximum extent in the preferred perforating orientation. The extent of the fracture length extending radially outward from the wellbore casing may be 1000 feet according to a preferred exemplary embodiment. According to another preferred exemplary embodiment, the charges in at least two of the perforating banks are configured to place preferred initiation points on a single transverse plane to said wellbore casing. According to another preferred exemplary embodiment the charges in at least two of the perforating banks are configured to place preferred initiation points on a plurality of planes. Plurality of planes may be transverse to the wellbore casing. For example, the charges (0701, 0702, 0703, 0704) in bank (0700) may be oriented such that they intersect a first preferred fracturing plane while charges (0711, 0712, 0713, 0714) in bank (0710) may be oriented such that they intersect a second preferred fracturing plane that may be substantially parallel to the first preferred fracturing plane. Both the first preferred fracturing plane and the second preferred fracturing plane are transverse to the longitudinal axis of the wellbore casing.
Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun System FIG. 7B illustrates an exemplary 8-shot (charges) 2-bank, phased at 90° phase angle between charges in each bank, phased at a 45° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (0750), an end view (0751), and a perspective view (0752) of an exemplary phased gun system is generally illustrated in FIG. 7B. The system may comprise a first perforating bank (0700) and a second perforating bank (0710) similar to the banks illustrated in FIG. 7A. According to a preferred exemplary embodiment, at least one of the 4 charges in the first perforating bank and at least one of the 4 charges in the second perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (0700) and second perforating bank (0710) are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (0743, 0753) respectively.
Preferred Exemplary 8-Shot 2-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 7C, a cross section view (0790), an end view (0791), and a perspective view (0792) of an exemplary phased gun system is generally illustrated in FIG. 7B. The system may comprise 4 charges phased at a 90° phase angle in each of a first perforating bank and a second perforating bank. The first perforating bank and the second perforating bank are phased at an offset angle of 45°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 9-Shot 3-Bank Phased Perforating Gun System (0800) An exemplary embodiment of the present invention may be generally illustrated in FIG. 8, wherein a phased perforating gun is deployed inside a wellbore casing along with 3 banks (0800, 0810, 0820), each of the banks comprise plural shaped charges. According to a preferred exemplary embodiment, the orientation of the wellbore casing is substantially horizontal. According to another preferred exemplary embodiment, the orientation of the wellbore casing is deviated.
The bank (0800) may comprise charges (0801, 0802, 0803), the bank (0810) may comprise charges (0811, 0812, 0813) and the bank (0820) may comprise charges (0821, 0822, 0823). The plural shaped charges in the perforating gun together in the bank (0800), the bank (0810) and the bank (0820) may herein be referred to as “cluster”. Even though three charges have been shown in each of the banks in FIG. 8, the banks may comprise more than 2 shaped charges according to a preferred exemplary embodiment.
Referring to FIG. 8, the perforating gun may include shaped charges that extend around a central axis of the gun in a helical, or spiral, pattern. Each shaped charge points radially outwardly toward a well casing, and adjacent shaped charge in the spiral pattern are radially separated by a phase angle of 120°. For example, shaped charge 0821 is radially separated to adjacent shaped charge 0822 by a phase angle of 120°. Similarly, shaped charge 0811 is radially separated to adjacent shaped charge 0812 by a phase angle of 120°.
According to a preferred exemplary embodiment, the offset angle ranges from 1 to 90 degrees. According to a more preferred exemplary embodiment, the offset angle of the shaped charges between the banks may range from 10° to 60°. According to a most preferred exemplary embodiment, the offset angle of the shaped charges between the banks may range from 15° to 30°. The offset angle may be the phase angle between charge 0801 and charge 0811. The offset angle between 0802 and 0812 would be same if the phase angles of charges in both the banks are the same. In the illustration shown in FIG. 8, the offset angle is 30°. In this example, the offset angle between charges 0801 and 0811 is 30°. The offset angle may range from 1° to 45° depending on the required upward and downward perforation angles. According to a preferred exemplary embodiment, the offset angles between a set of banks may be equal to an offset angle between a different set of banks. According to a preferred exemplary embodiment, the offset angles between a set of banks may not be equal to an offset angle between a different set of banks. For example, the offset angle between bank 0800 and bank 0810 may be different from the offset angle between bank 0810 and bank 0820. The offset angle between bank 0800 and bank 0810 may be the same as the offset angle between bank 0810 and bank 0820.
In the illustration shown in FIG. 8 with 3 charges per bank at a 120° phase angle between charges and a 30° offset angle between each of the banks 0800, 0810 and 0820, the probability of perforating within a 30° upward perforation angle is 100%. Similarly, the probability of perforating within a 15° upward perforation angle is 50%. In contrast, for a prior art 9 charge system with a 45° phase angle between charges, the probability of perforating within a 30° upward perforation angle is 75% as compared to the exemplary 3 bank 9 charge system illustrated in FIG. 8. An offset angle between each of the banks increases the probability of shaped charges perforating within a desired perforation angle so that fractures initiate in the low compression region for achieving maximum fracture efficiency.
FIG. 8 (0830) generally illustrates phase angle (0831) Vs location of charges (0832) for an unrolled gun. The charges in banks 0800, 0810 and 0820 are illustrated along with the phase angle and offset angle. For example, the phase angle (0850) between charge 0801 and charge 0802 is 120°. The offset angle (0860) between charge 0801 and charge 0811 is 30°.
As illustrated in FIG. 7A, the phase angle of the charges is 90° with two oppositely phased charges. For example, charges 0701 and 0702 are phased diametrically opposite to each other. As illustrated in FIG. 8, the phase angle of the charges is 120° with none of the charges diametrically opposite to each other. For example, charges 0701 and 0702 are phased diametrically opposite to each other 0801, 0802 and 0803 are phased with no two charges diametrically opposite to each other. It is more preferable to phase charges diametrically opposite to each other such as in FIG. 7A so that there is a better probability to perforate in the arc in a low compression zone upwards and downwards.
Preferred Exemplar 6-Shot 2-Bank Phased Perforating Gun System FIG. 9A generally illustrates an exemplary 6-shot (charges) 2-bank, phased at 120° phase angle between charges in each bank, phased 60° offset angle between banks in a perforating gun according to a preferred embodiment of the present invention. A cross section view (0900), an end view (0901), and a perspective view (0902) of an exemplary phased gun system is generally illustrated in FIG. 9A. The system (0900) may comprise a first perforating bank (0910) and a second perforating bank (0920). The first perforating bank (0910) comprising 3 charges phased at 120° phase angle to each other. Similarly the second perforating bank (0920) comprising 3 charges phased at 120° phase angle to each other. The first perforating bank (0910) and the second perforating bank (0920) are phased at an offset angle of 60°. According to a preferred exemplary embodiment, at least one of the 3 charges in the first perforating bank and at least the 3 charges in the second perforating bank are configured to perforate into a low compression region that is proximal to the well casing. The low compression region is similar to the upward low compression region (0505) and a downward low compression region (0515) described above in FIG. 5. According to a further preferred exemplary embodiment, the charges in the first perforating bank (0910) are oriented such that when the charges perforate, the charges intersect a preferred fracturing plane (0911). The preferred fracturing plane may be transverse to the orientation of the wellbore casing. Similarly, the charges in the second perforating bank (0920) are oriented such that when the charges perforate, the charges intersect a preferred fracturing plane (0911). The preferred fracturing plane (0911) and preferred fracturing plane (0921) may be parallel to each other as described above in FIG. 1 (0103). Multiple preferred fracturing planes that are parallel to each other may be targeted for maximum production efficiency.
Preferred Exemplary 6-Shot 2-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 9A, a cross section view (0930), an end view (0931), and a perspective view (0932) of an exemplary phased gun system is generally illustrated in FIG. 9B. The system (0930) may comprise a first perforating bank (0940) and a second perforating bank (0950). The first perforating bank (0940) comprising 3 charges phased at 120° phase angle to each other. Similarly the second perforating bank (0950) comprising 3 charges phased at 120° phase angle to each other. The first perforating bank (0940) and the second perforating bank (0950) are phased at an offset angle of 60°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun System FIG. 10A illustrates an exemplary 6-shot (charges) 3-bank, phased at 180° phase angle between charges in each bank, phased at a 90° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1000), an end view (1001), and a perspective view (1002) of an exemplary phased gun system is generally illustrated in FIG. 10A. The system (1000) may comprise a first perforating bank (1010), a second perforating bank (1020) and a third perforating bank (1030). According to a preferred exemplary embodiment, at least one of the 2 charges in the first perforating bank, at least one of the 2 charges in the second perforating bank and at least one of the 2 charges in the third perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (1010), second perforating bank and third perforating bank are each oriented such that when the charges perforate, the charges intersect a preferred fracturing planes (1011, 1021, 1031) respectively.
Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 10A, a cross section view (1040), an end view (1041), and a perspective view (1042) of an exemplary phased gun system is generally illustrated in FIG. 10B. The system may comprise 2 charges phased at a 180° phase angle in each of a first perforating bank (1050), a second perforating bank (1070) and a third perforating bank (1060). The first perforating bank (1050), the second perforating bank (1070) and the third perforating bank (1060) are phased at an offset angle of 90°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 10-Shot 2-Bank Phased Perforating Gun System FIG. 11A illustrates an exemplary 10-shot (charges) 2-bank, phased at 72° phase angle between charges in each bank, phased at a 36° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1100), an end view (1101), and a perspective view (1102) of an exemplary phased gun system is generally illustrated in FIG. 11A. The system (1100) may comprise a first perforating bank (1110) and a second perforating bank (1120). According to a preferred exemplary embodiment, at least one of the 5 charges in the first perforating bank and at least one of the 5 charges in the second perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (1110) and second perforating bank (1120) are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (1111, 1121) respectively.
Preferred Exemplary 10-Shot 2-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 11A, a cross section view (1150), an end view (1151), and a perspective view (1152) of an exemplary phased gun system is generally illustrated in FIG. 11B. The system may comprise 5 charges phased at a 72° phase angle in each of a first perforating bank (1130) and a second perforating bank (1140). The first perforating bank (1130) and the second perforating bank (1140) are phased at an offset angle of 36°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 12-Shot 2-Bank Phased Perforating Gun System FIG. 12A illustrates an exemplary 12-shot (charges) 2-bank, phased at 60° phase angle between charges in each bank, phased at a 30° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1200), an end view (1201), and a perspective view (1202) of an exemplary phased gun system is generally illustrated in FIG. 12A. The system (1200) may comprise a first perforating bank (1210) and a second perforating bank (1220). According to a preferred exemplary embodiment, at least one of the 6 charges in the first perforating bank and at least one of the 6 charges in the second perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (1210) and second perforating bank (1220) are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (1211, 1221) respectively.
Preferred Exemplary 12-Shot 2-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 12A, a cross section view (1250), an end view (1251), and a perspective view (1252) of an exemplary phased gun system is generally illustrated in FIG. 12B. The system may comprise 6 charges phased at a 60° phase angle in each of a first perforating bank (1230) and a second perforating bank (1240). The first perforating bank (1230) and the second perforating bank (1240) are phased at an offset angle of 30°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 6-Shot 3-Bank Phased Perforating Gun System FIG. 13A illustrates an exemplary 12-shot (charges) 3-bank, phased at 90° phase angle between charges in each bank, phased at a 30° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1300), an end view (1301), and a perspective view (1302) of an exemplary phased gun system is generally illustrated in FIG. 13A. The system (1300) may comprise a first perforating bank (1310), a second perforating bank (1320) and a third perforating bank (1330). According to a preferred exemplary embodiment, at least one of the 4 charges in the first perforating bank, at least one of the 4 charges in the second perforating bank and at least one of the 4 charges in the third perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (1310), second perforating bank (1320) and third perforating bank (1330) are each oriented such that when the charges perforate, the charges intersect a preferred fracturing planes (1311, 1321, 1331) respectively.
Preferred Exemplary 12-Shot 3-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 13A, a cross section view (1340), an end view (1341), and a perspective view (1342) of an exemplary phased gun system is generally illustrated in FIG. 13B. The system may comprise 4 charges phased at a 90° phase angle in each of a first perforating bank (1340), a second perforating bank (1350) and a third perforating bank (1360). The first perforating bank (1340), the second perforating bank (1350) and the third perforating bank (1360) are phased at an offset angle of 30°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 12-Shot 4-Bank Phased Perforating Gun System FIG. 14A illustrates an exemplary 12-shot (charges) 4-bank, phased at 120° phase angle between charges in each bank, phased at a 15° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1400), an end view (1401), and a perspective view (1402) of an exemplary phased gun system is generally illustrated in FIG. 14A. The system (1400) may comprise a first perforating bank (1410), a second perforating bank (1420), a third perforating bank (1430) and a fourth perforating bank (1440). According to a preferred exemplary embodiment, at least one of the 3 charges in the first perforating bank, at least one of the 3 charges in the second perforating bank, at least one of the 3 charges in the third perforating bank and at least one of the 3 charges in the fourth perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank, second perforating bank, third perforating bank and fourth perforating bank are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (1411, 1421, 1431, 1441) respectively.
Preferred Exemplary 12-Shot 4-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 14A, a cross section view (1490), an end view (1491), and a perspective view (1492) of an exemplary phased gun system is generally illustrated in FIG. 14B. The system may comprise 3 charges phased at 120° phase angle in each of a first perforating bank (1450), a second perforating bank (1460), a third perforating bank (1470) and a fourth perforating bank (1480). The first perforating bank (1450), the second perforating bank (1460), the third perforating bank (1470) and the fourth perforating bank (1480) are phased at an offset angle of 15°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 14-Shot 2-Bank Phased Perforating Gun System FIG. 15A illustrates an exemplary 14-shot (charges) 2-bank, phased at 51.42° phase angle between charges in each bank, phased at a 25.5° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1500), an end view (1501), and a perspective view (1502) of an exemplary phased gun system is generally illustrated in FIG. 15A. The system (1500) may comprise a first perforating bank (1510) and a second perforating bank (1520). According to a preferred exemplary embodiment, at least one of the 7 charges in the first perforating bank and at least one of the 7 charges in the second perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank (1510) and second perforating bank (1520) are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (1511, 1521) respectively.
Preferred Exemplary 14-Shot 2-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 15A, a cross section view (1550), an end view (1551), and a perspective view (1552) of an exemplary phased gun system is generally illustrated in FIG. 15B. The system may comprise 7 charges phased at a 52.2° phase angle in each of a first perforating bank (1530) and a second perforating bank (1540). The first perforating bank (1530) and the second perforating bank (1540) are phased at an offset angle of 25.5°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary 16-Shot 4-Bank Phased Perforating Gun System FIG. 16A illustrates an exemplary 16-shot (charges) 4-bank, phased at 90° phase angle between charges in each bank, phased at a 11.25° offset angle between banks in a perforating gun system according to a preferred embodiment. A cross section view (1600), an end view (1601), and a perspective view (1602) of an exemplary phased gun system is generally illustrated in FIG. 16A. The system (1600) may comprise a first perforating bank (1610), a second perforating bank (1620), a third perforating bank (1630) and a fourth perforating bank (1640). According to a preferred exemplary embodiment, at least one of the 3 charges in the first perforating bank, at least one of the 3 charges in the second perforating bank, at least one of the 3 charges in the third perforating bank and at least one of the 3 charges in the fourth perforating bank are configured to perforate into a low compression region that is proximal to the well casing. According to a further preferred exemplary embodiment, the charges in the first perforating bank, second perforating bank, third perforating bank and fourth perforating bank are each oriented such that when the charges perforate, the charges intersect preferred fracturing planes (1611, 1621, 1631, 1641) respectively.
Preferred Exemplary 16-Shot 4-Bank Phased Perforating Gun Non-Converging System Similar to FIG. 16A, a cross section view (1690), an end view (1691), and a perspective view (1692) of an exemplary phased gun system is generally illustrated in FIG. 16B. The system may comprise 3 charges phased at 90° phase angle in each of a first perforating bank (1650), a second perforating bank (1660), a third perforating bank (1670) and a fourth perforating bank (1680). The first perforating bank (1650), the second perforating bank (1660), the third perforating bank (1670) and the fourth perforating bank (1680) are phased at an offset angle of 11.25°. The charges may be non-converging and may not be intersecting a preferred fracturing plane when perforating.
Preferred Exemplary Flowchart Embodiment of an Phasing Wellbore Perforation (1700) As generally seen in the flow chart of FIG. 17 (1700), a preferred exemplary optimal phasing perforation method shaped charges may be generally described in terms of the following steps:
-
- (1) selecting a gun system for each cluster in a stage with the best statistical probability for a desired number of perforations in that cluster (1701);
- (2) positioning a phased perforating gun in a wellbore casing (1702); and
- (3) perforating through the phased perforating gun into a hydrocarbon formation such that at least one of a first plurality of charges and at least one of a second plurality of charges perforate within an upward perforation angle and a downward perforation angle; the upward perforation angle subtends in an upward direction about a center of the perforating gun and the downward perforation angle subtends in a downward direction about the center of the perforating gun (1703).
Referring to FIG. 18, a perforating gun may include shaped charges that extend around a central axis of the gun in a helical, or spiral, pattern. Each shaped charge points radially outwardly toward a well casing, and adjacent shaped charge in the spiral pattern are radially separated by a phase angle. FIG. 18 (1810) generally illustrates an unwrapped perforating gun with charges (1811, 1812, 1813, 1814) in a cluster that are arranged in rows (1811, 1822, 1823, 1824). Each charge occupies a row according to a preferred exemplary embodiment. For example each of the charges (1811, 1812, 1813, 1814) occupy the rows (1811, 1822, 1823, 1824) respectively. A 4-shot shot gun may comprise one cluster with 4 charges. It is noteworthy that no two charges occupy the same row as in conventional perforating gun designs. Therefore a 4-charge cluster in a perforating gun may occupy 4 rows. Similarly, a 8-charge cluster may occupy 8 rows as generally illustrated in FIG. 18 (1820). FIG. 19 (1910) generally illustrates a front view of 6-shot gun comprising 6-charges per cluster. Similarly, FIG. 19 (1920) generally illustrates a front view of 8-shot gun comprising 8-charges per cluster. FIG. 19 (1930) generally illustrates a front view of 12-shot gun comprising 12-charges per cluster. The more the number of charges in a cluster arranged in non-overlapping individual rows the more the efficiency of perforation in an upward and downward perforation angle. For example, the 6-shot (1910) has an uncertainty of 50%, the 8-shot (1920) has an uncertainty of 33%, and the 12-shot (1930) has an uncertainty of 0%. The uncertainty may be a measure of the effectiveness of the perforation in an upward and downward direction. To achieve maximum fracturing efficiency, it is needed to perforate within a preferred upward perforation angle and preferred downward perforation which are +−15° so that the perforation is achieved in an upward low compression region (0505) and a downward low compression region (0515). According to a preferred exemplary embodiment, when perforating through the perforating gun system into a hydrocarbon formation, at least one of the plurality of charges in the cluster perforate within an upward perforation angle and at least one of the plurality of charges in the cluster perforate within an a downward perforation angle; the upward perforation angle subtends in an upward direction about a center of the wellbore and the downward perforation angle subtends in a downward direction about the center of the wellbore. According to a preferred exemplary embodiment, the phase angle of the shaped charges in a cluster may range from 1° to 359°. According to a more preferred exemplary embodiment, the phase angle of the shaped charges in a cluster may range from 5° to 90°. According to a most preferred exemplary embodiment, the phase angle of the shaped charges in a cluster may range from 15° to 30°. According to another preferred exemplary embodiment, the shaped charges are equally spaced. For example, the charge spacing between consecutive shaped charges (1811), (1812), (1813) and (1814) may be equal. According to yet another preferred exemplary embodiment, the shaped charges are not equally spaced.
According to a preferred exemplary embodiment, the number of charges in each of the clusters may range from 2 to 24. According to a more preferred exemplary embodiment, the number of charges in each of the clusters may range from 2 to 8. According to a most preferred exemplary embodiment, the number of charges in each of the clusters may range from 2 to 6. For example, the cluster (1810) may comprise 4 charges and cluster (1820) may comprise 8 charges.
The number of charges in each of the clusters may be balanced as each cluster in a stage will have a statistical probability of having a cluster with charges phased to perforate within an arc in the low compression zone. According to a preferred exemplary embodiment the downward perforation angle and the upward perforation angle may range from 1° to 45°. According to a preferred exemplary embodiment, within a stage, the phasing of the charges in one cluster may be different than the phasing of the charges in another cluster. Variations in placement of perforation tunnels with respect to low compression stress areas contributes to variation in “cluster perforation quality”. A variation in cluster perforation quality may imply some clusters in a stage will be treated unequally.
Preferred Exemplary Flowchart Embodiment of an Phasing Wellbore Perforation (2000) As generally seen in the flow chart of FIG. 20 (2000), a preferred exemplary perforation method may be generally described in terms of the following steps:
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- (1) selecting the total number of said plurality of charges for the cluster for each of the plurality of perforating guns in a stage with the best statistical probability for a desired number of perforations in said cluster (2001);
- (2) positioning a perforating gun system in a wellbore casing (2002); and
- (3) perforating through the perforating gun system into a hydrocarbon formation such that at least one of said plurality of charges perforate within an upward perforation angle and at least one of the plurality of charges perforate within an a downward perforation angle; the upward perforation angle subtends in an upward direction about a center of the wellbore and the downward perforation angle subtends in a downward direction about the center of the wellbore (2003).
Method Summary The present invention method anticipates a wide variety of variations in the basic theme of implementation, but can be generalized as a for use in a wellbore casing operating in conjunction with a perforating gun system comprising a plurality of perforating guns; each of the plurality of perforating guns configured with a plurality of charges; the plurality of charges arranged in a plurality of rows in a cluster; and a total number of the plurality of charges is equal to a total number of the plurality of rows;
wherein the method comprises the steps of:
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- (1) selecting the total number of the plurality of charges for the cluster for each of the plurality of perforating guns in a stage with the best statistical probability for a desired number of perforations in the cluster;
- (2) positioning the perforating gun system in the wellbore casing; and
- (3) perforating through the perforating gun system into a hydrocarbon formation such that at least one of the plurality of charges perforate within an upward perforation angle and at least one of the plurality of charges perforate within a downward perforation angle; the upward perforation angle subtends in an upward direction about a center of the wellbore and the downward perforation angle subtends in a downward direction about the center of the wellbore.
This general method summary may be augmented by the various elements described herein to produce a wide variety of invention embodiments consistent with this overall design description.
System/Method Variations The present invention anticipates a wide variety of variations in the basic theme of oil and gas extraction. The examples presented previously do not represent the entire scope of possible usages. They are meant to cite a few of the almost limitless possibilities.
This basic system and method may be augmented with a variety of ancillary embodiments, including but not limited to:
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- An embodiment wherein the wellbore casing is substantially horizontal.
- An embodiment wherein the wellbore casing is deviated.
- An embodiment wherein the plurality of rows are equally spaced.
- An embodiment wherein the plurality of rows are unequally spaced.
- An embodiment wherein a phase angle of the plurality of charges ranges from 1 to 359 degrees.
- An embodiment wherein the upward perforation angle ranges from 0 to 45 degrees.
- An embodiment wherein the downward perforation angle ranges from 0 to 45 degrees.
- An embodiment wherein the plurality of charges are further angled to place preferred initiation points on a transverse plane to the wellbore casing.
- An embodiment wherein at least two of the plurality of charges in each of the plurality of perforating guns are configured to place preferred initiation points on a single transverse plane to the wellbore casing.
- An embodiment wherein at least two of the plurality of charges in each of the plurality of perforating guns are configured to place preferred initiation points on a plurality of planes; the plurality of planes transverse to the wellbore casing.
One skilled in the art will recognize that other embodiments are possible based on combinations of elements taught within the above invention description.
CONCLUSION An optimal perforating gun method for accurate perforation in a deviated/horizontal wellbore has been disclosed. The method includes a gun string assembly (GSA) deployed in a wellbore with shaped charges arranged in rows in a cluster and a total number of the shaped charges is equal to a total number of the rows. A total number of charges for each cluster in a stage is selected with the best statistical probability for a desired number of perforations in the cluster. The number of charges and the number of rows per each cluster in a stage is optimized such that there is a maximum probability of perforating into a low compression region in an upward and downward direction.
CLAIMS Although a preferred embodiment of the present invention has been illustrated in the accompanying drawings and described in the foregoing detailed description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.
