Apparatus and method for abrasive jet perforating

A abrasive jet perforating tool comprises a generally cylindrically shaped tube with a side, an upper portion, and a lower portion; a plurality of holes tapped and threaded into the side of the tube; threaded abrasive jets mounted in at least some of the plurality of threaded holes; protective plates mounted on the side of the tube around the abrasive jets; gauge rings that slide onto an outer diameter of the upper portion and the lower portion of the tube; and a mechanical casing collar locator connected to the upper portion of the tube.

CROSS-REFERENCES TO RELATED APPLICATIONS

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FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

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SEQUENCE LISTING, TABLE, OR COMPUTER LISTING

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the field of treating wells to stimulate fluid production. More particularly, the invention relates to the field of abrasive jet perforating of wellbore casings.

2. Description of the Related Art

Abrasive jet perforating uses fluid slurry pumped under high pressure to perforate casing and cement around a wellbore and to extend a cavity into the surrounding reservoir to stimulate fluid production. Since sand is the most common abrasive used, this technique is also known as sand jet perforating (SJP). Sand laden fluids were first used to cut well casing in 1939. Abrasive jet perforating was eventually attempted on a commercial scale in the 1960s. While abrasive jet perforating was a technical success (over 5,000 wells were treated), it was not an economic success. The tool life in abrasive jet perforating was measured in only minutes and fluid pressures high enough to cut casing were difficult to maintain with pumps available at the time. A competing technology, explosive shape charge perforators, emerged at this time and offered less expensive perforating options.

Consequently, very little work was performed with abrasive jet perforating technology until the late 1990's. Then, more abrasive-resistant materials used in the construction of the perforating tools and jet orifices provided longer tool life, measured in hours or days instead of minutes. Also, advancements in pump materials and technology enabled pumps to handle the abrasive fluids under high pressures for longer periods of time. The combination of these advances made the abrasive jet perforating process more cost effective. Additionally, the recent use of coiled tubing to convey the abrasive jet perforating tool down a wellbore has led to reduced run time at greater depth. Further, abrasive jet perforating did not require explosives and thus avoids the accompanying danger involved in the storage, transport, and use of explosives. However, the basic design of abrasive jet perforating tools used today has not changed significantly from those used in the 1960's.

Abrasive jet perforating tools were initially designed and built in the 1960's. There were many variables involved in the design of these tools. Some tool designs varied the number of jet locations on the tool body, from as few as two jets to as many as 12 jets. The tool designs also varied the placement of those jets, such, for example, positioning two opposing jets spaced 180° apart on the same horizontal plane, three jets spaced 120° apart on the same horizontal plane, or three jets offset vertically by 30°. Other tool designs manipulated the jet by orienting it at an angle other than perpendicular to the casing or by allowing the jet to move toward the casing when fluid pressure was applied to the tool.

Occasionally, a tool employed a centralizer to keep the tool from touching the low side of the casing. Conventional tools typically have a uniform outer diameter, with the exception of the mounting locations for the jets. Mechanical casing collar locators generally consisted of a tool with a hollow shaft for fluid travel, and a “slip” (or “dog”) that resides in a pocket on the outside of the tool and is pressed against the casing by a spring located in between the pocket and the slip.

The following patents are representative of conventional abrasive jet perforating tools, along with apparatus and methods that may be employed with the tools.

U.S. Pat. No. 3,130,786 by Brown et al., “Perforating Apparatus”, discloses an abrasive jet perforating tool. The tool comprises a cylindrical conduit for abrasive fluid to be pumped through and jet nozzles laterally extending from the conduit to direct the abrasive fluid through the casing into the surrounding formation. Factors such as the pressure differential and the ratios of the diameter of the nozzle orifice to the length of the nozzles and to the size of the abrasives are kept within predetermined limits for optimum penetration.

U.S. Pat. No. 3,145,776 by Pittman, “Hydra-Jet Tool”, discloses protective plates for an abrasive jet perforating tool. The plates, made of abrasive resistant material, are designed to fit flatly to the body of the tool around the perforating jets. The plates are employed to protect the body of the tool from ejected abrasive material that rebounds. The protective plates disclosed in Pittman are not designed to protect the abrasive jets themselves.

U.S. Pat. No. 3,266,571 by St. John et al., “Casing Slotting” discloses an abrasive jet perforating tool designed to cut slots of controlled length. The slot lengths are controlled by abrasive resistant shields attached to the tool to block the flow from rotating abrasive jets.

U.S. Pat. No. 3,902,361 by Watson, “Collar Locator” discloses a mechanical casing collar locator that can be used with, among other tools, an abrasive jet perforating tool. A spring-loaded tagging element engages the annular shoulder formed between the spaced ends of adjacent casing joints joined together by the collars. A tubing weight indicator senses each time a collar is located.

U.S. Pat. No. 4,050,539 by Tagirov et al., “Apparatus for Treating Rock Surrounding a Wellbore”, discloses an abrasive jet tool for successively perforating and then fracturing reservoirs. The nozzles of the abrasive jets are designed to snugly fit against the casing to allow perforating at one pressure immediately followed by fracturing at a higher pressure.

U.S. Pat. No. 5,499,678 by Surjaatmadja et al., “Coplanar Angular Jetting Head for Well Perforating”, discloses a jetting head for use in an abrasive jet perforating tool. The jet openings in the jetting head are coplanar and positioned at an angle to the longitudinal axis of the tool. The angle is chosen so that the plane of the jet openings is perpendicular to the axis of least principal stress in the formation being fractured. The tool must be custom-made for each job, since the entire jet head is angled into the tool.

U.S. Pat. No. 6,832,654 B2 by Ravensbergen et al., “Bottom Hole Assembly”, discloses a bottom hole assembly (BHA) in the form of a straddle packer for positioning an abrasive jet perforating tool. The BHA includes a timing mechanism to keep dump ports open to flush underdisplaced fluids from the BHA, a release tool in case the BHA gets stuck in the wellbore, and a mechanical collar locator.

U.S. Pat. No. 7,159,660 B2 by Justus, “Hydrajet Perforating and Fracturing Tool” discloses an abrasive jet perforating and fracturing tool. The tool comprises both abrasive jet ports and fracturing ports having larger apertures than the jet ports. The fracturing ports are used to eject fracturing fluid into the formation at a faster rate than possible through the jet ports. The tool further comprises a rotating sleeve, turned by a power unit, with apertures that align or misalign with the jet ports and control ports to control flow through the ports.

A common concern for downhole tools in general, and abrasive jet perforating tools in particular, is the potential for getting the tool lodged or caught in the hole. As the abrasive jet perforating process begins, sand laden fluid is pumped through the tool at high pressure to cut through the casing and extend a cavity into the reservoir. As the fluid jet is cutting through the steel casing, all of the sand that passes through the orifice remains in the annulus of the casing. While some of this sand falls toward the bottom of the hole, some of the sand is pushed upward by the turbulent fluid action of the jet. If the fluid conditions (depending upon the viscosity of the fluid and the rate of fluid flow) are favorable, then the sand could return to the surface in the fluid flow, or, alternatively, the sand could travel a distance upward, lose velocity, and then fall back toward the bottom of the hole, settling wherever it can. Once the abrasive jet perforating tool has cut a hole in the casing, the sand particles enter the cavity that is being cut, but since the cavity is closed, most of the sand will return to the casing. The cuttings from the reservoir will also flow to the casing as the cavity is cut, creating more material in the annulus of the well. If the volume of the sand and formation cuttings deposited on the tool is too great, the tool could become trapped in the well by the material settling on the bottom hole assembly.

An additional concern in openhole conditions (a well without a casing) is that large pieces of the formation might fall into the well bore as the abrasive jet cuts its path. With a cased reservoir, the perforation hole in the casing limits the particle size of the cutting that can be flushed back into the annulus. In openhole wells, the particle size is not limited and, depending on the strength of the reservoir, large pieces of rock could break loose and fall into the wellbore, lodging in between the tool string and the wall of the well.

Thus, a need exists for a sand jet perforating tool and method of use that provides improvements to the sand jet perforating tool design that allow for improved performance, more cost effective operation, and increased security of the intellectual property.

BRIEF SUMMARY OF THE INVENTION

The invention is an apparatus and a method for providing improved abrasive jet perforating in wells. In one embodiment, the invention is an abrasive jet perforating tool comprising a generally cylindrically shaped tube with a side, an upper portion, and a lower portion; a plurality of holes tapped and threaded into the side of the tube; threaded abrasive jets mounted in at least some of the plurality of threaded holes; protective plates mounted on the side of the tube around the abrasive jets; gauge rings that slide onto an outer diameter of the upper portion and the lower portion of the tube; and a mechanical casing collar locator connected to the upper portion of the tube.

In another embodiment, the invention is a method for performing abrasive jet perforating, comprising determining well parameters for a well; assembling an abrasive jet perforating tool according to the well parameters, wherein the abrasive jet perforating tool is the apparatus described above; and perforating the well with the assembled abrasive jet perforating tool.

While the invention will be described in connection with its preferred embodiments, it will be understood that the invention is not limited to these. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents that may be included within the scope of the invention, as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The invention is an apparatus and a method for providing improved abrasive jet perforating in wells. The invention includes improvements to existing designs that enhance performance of the tool, make it more cost effective to build and operate, and help protect it from unwanted duplication. Improvements include outer diameter designs to keep formation cuttings from causing the tool to become lodged in the hole, additional vertical jet locations to prevent sand and cuttings from depositing on the upper portions of the tool and improve circulation of cuttings to the surface. A mechanical casing collar locator is also incorporated into the tool allowing for precise depth measurement. Variable abrasive jet sizes and lengths, variations in protective plates around the abrasive jets, along with gauge rings allow one basic tool to be used in different casing sizes, and special jet head and protective plate configurations make the abrasive jets difficult to remove without the proper tools.

In one embodiment, the invention is an apparatus for performing abrasive jet perforating. That is, the invention is an abrasive jet perforating tool. In another embodiment, the invention is a method for performing abrasive jet perforating. That is, the invention includes a method for using the abrasive jet perforating tool of the invention.

FIG. 1shows a schematic side view of an abrasive jet perforating tool, such as may be used in the present invention, in a wellbore. A wellbore10is shown penetrating a reservoir11. The wellbore10is surrounded by a casing12, which in turn is surrounded by cement13, fixing the casing12to the reservoir11. Well tubing14extends vertically downward into the wellbore10. Suspended from the tubing14is an abrasive jet perforating tool15, which comprises gauge rings16to center the tool15in the wellbore10, abrasive jets17, and protective plates18. The abrasive jets17eject abrasive-carrying fluid slurry under high pressure to perforate the casing12, cement13, and reservoir11. The protective plates18protect the abrasive jets17from damage due to the rebound of abrasive material in the ejected fluid slurry. The purpose of the abrasive jets17is to provide a cavity19in the reservoir11that communicates through the cement13and casing12with the wellbore10. This cavity19provides improved fluid flow from the reservoir11to the wellbore10, preferably from a producing zone in the reservoir11. In an alternative situation called an openhole wellbore, there is no casing12or cement13, so the wellbore10directly contacts the reservoir11.

FIG. 2shows a schematic side view of a general embodiment of the tool of the invention. Depending on the specific application, the general embodiment may use one or more variations to this basic configuration.FIGS. 3-5show schematic side views of alternative embodiments of the tool of the invention shown inFIG. 2.

The abrasive jet perforating tool of the invention is designated generally by reference numeral20inFIGS. 2-5. InFIG. 2, the main body of the tool20comprises a conduit, preferably in the form of a generally cylindrically shaped tube21. Although the tool20is illustrated here with the preferred embodiment of a tube21as the body, this cylindrical shape is not necessarily a limitation of the invention. The body could have other appropriate shapes in other alternative embodiments. The tool20further comprises a side22, an upper portion23, and a lower portion24, threaded connection fittings (not shown) on the upper portion23and lower portion24of the tube21, and a plurality of holes25tapped and threaded into the side22of the tube21. The threaded holes25are oriented in a direction that is perpendicular, or near perpendicular, to the longitudinal axis26of the tube21. The threaded connection fittings on the upper portion23and lower portion24of the tube21are used to connect the tool20to other components of the well string. The tool20further comprises threaded abrasive jets27(nozzles) mounted in at least some of the threaded holes25on the side22of the tube21. The abrasive jets27further comprise jetting orifices28that extend throughout the length of the abrasive jets27.

In order to effectively perform sand jet perforating, a specific distance from the end of the jet orifice28to the casing (12inFIG. 1) is desired. That distance is a function of the jetting orifice28diameter. In order to achieve that desired distance with the above referenced tool design, tools with different outer diameters (OD) are needed for different sizes of casing. With numerous casing weights (differences in wall thickness) for each casing size, a tool with a different outer diameter might even be required in the same casing size. This means that to achieve the optimum distance from jetting orifice28to casing, several tools would be required in inventory to be able to meet a given customer's needs. Also, a non-standard size of casing or a damaged casing might require the manufacture of a specific tool for the job. The use of the abrasive jet perforating tool20of the invention is designed to avoid these problems associated with the perforating jets used in conventional tools.

In an alternative embodiment, the tool20can have abrasive jets27that extend radially out from the side22of the tube21toward the casing wall (12inFIG. 1). The tool20has protective plates29, also known as blast plates, also extending radially out from the side22of the tube21and surrounding the abrasive jets27to protect the abrasive jets27from damage. The abrasive-carrying fluid slurry ejected by the abrasive jets27can rebound back from impingement on the casing, cement, or reservoir (12,13, and11, respectively, inFIG. 1) and potentially damage the abrasive jets27. The protective plates29for the abrasive jets27are generally rectangular in cross section, as illustrated in bothFIGS. 2 and 3, but can also be round in cross section, as illustrated inFIGS. 4 and 5. In general, the cross-sectional shape of the abrasive jets27is not limited in the invention. In addition, the protective plates29can vary in radial extension length.

The tool20has gauge rings30(or their equivalent, as shown inFIG. 4) that slide onto the outer diameter of the upper portion23and the lower portion24of the tube21. The gauge rings30, also known as sizing rings or spacing rings, are designed to not interfere with the flow from the abrasive jets27, and are larger in outer diameter than the abrasive jets27mounted in the tube21. The gauge rings30center the tool20in the casing, protect the abrasive jets27from wearing against the casing, and will stop the tool20from advancing through the casing if the inner diameter of the casing does not permit the entire tool20to pass through. The gauge rings30may be very short longitudinally compared to the length of the tool20(such as, for example, 1″-2″), as shown inFIG. 2, or they may cover the entire tube21with cut out areas for the abrasive jets27and protective plate29locations, as shown inFIG. 4.

In an alternative embodiment, different materials could be used in the making of the various apparatus described. Specifically, the gauge rings30could be made from a steel alloy or from another material with good abrasive wear but lower structural strength (e.g., nylon) that could be pulled apart by some type of pulling unit if the gauge ring30were to become lodged in the well hole. Using abrasive jets27of different length in conjunction with protective plates29and gauge rings30allow one basic tool20to be used in wells of varying sizes. This will decrease costs by requiring fewer tools in inventory to service the customer.

FIG. 3shows a schematic side view of an alternative embodiment of the tool of the invention with a tapered lower portion. In this alternative embodiment, the tool20can further comprise smaller circulation jets31located in the upper portion23of the tube21. The circulation jets31are oriented in a direction that is near parallel with the longitudinal axis26of the tube21. The circulation jets31in the upper portion23of the tube21could vary in number and size, but also in the angle from parallel with the longitudinal axis26of the tube21. The circulation jets31would most likely not be exactly vertical (i.e., parallel with the longitudinal axis26of the tube21), due to concerns that the circulation jets31could damage the upper portion of the bottom hole assembly or the tubing string itself. Additional circulation jets (36inFIG. 5) could also be placed in a vertical downward facing direction on the lower portion24of the tube21to prevent sand from settling on portions of the tool20below these lower circulation jets. The addition of the vertical circulation jets31prevents sand from settling on the tool20, and helps avoid getting the tool20stuck in the wellbore.

In a further alternative embodiment illustrated inFIG. 3, the tool20may have an outer diameter32of the lower portion24of the tube21with a generally tapered or other non-uniform shape. The outer diameter32shape of the tool20for open hole may be a generally linear taper, the taper could curve as it reduces in size, or, as shown inFIG. 5, the taper in the tool20may contain small steps on which vertical circulation jets36could be placed facing downward. The tapered outer diameter32of the tool20in openhole conditions will allow the tool20to be more easily removed from the sand and cuttings that may settle below it, so that the tool20does not become lodged in the hole.

As illustrated in bothFIGS. 2 and 3, the tool20further comprises a mechanical casing collar locator33attached to the upper portion23of the tube21. The casing collar locator33is attached via the threaded connection fittings on the upper portion23of the tube21. The casing collar locator33comprises an adjustable bow spring centralizer that has “buttons”34attached at the outermost curvature of the bow springs35. The buttons34will attempt to seat in the space between two sections of casing where they are joined by a casing collar. The buttons34are tapered is such a way as to allow additional vertical force on the tool20to unseat the buttons34and allow the tool20to travel in the casing.

FIGS. 4 and 5show schematic side view of alternative embodiments of the tool of the invention shown inFIGS. 2 and 3, respectively.FIG. 4shows the tool with more bow springs and alternative gauge rings, whileFIG. 5shows the tool with more bow springs and an alternative taper shape. As illustrated in bothFIGS. 4 and 5, the mechanical casing collar locator33may contain several (for example, 3 or more) bow springs35with buttons34on them. One or more buttons34may be used and they could either be flat on top with angled sides or rounded. The mechanical casing collar locator33will provide valuable information about the depth of the tool20so that the tool20can be located precisely in the reservoir. This precision is very important in placing the perforations accurately in the productive hydrocarbon containing zones of the reservoir, which can be quite thin.

Locating a perforation with respect to depth in the well bore and the reservoir is of great importance, especially with very thin (for example, 2′-3′ thick) zones. Many conventional techniques use an electronic/magnetic casing collar locator to determine depth of the tool20. Encountered casing joints are recorded and compared to the log of the well to determine the exact placement of the tool20. While this logging method is accurate, it requires the use of electronics on board the tool20which both adds additional cost and could fail in the presence of high temperature or other adverse conditions. Another method for determining correct tool20placement depth is to set a bridge plug below the desired production zone. This generally requires a wireline logging truck to set the plug and verify depth and later requires the plug to be removed from the well bore. For tools run on jointed tubing, a gamma log could be run through the tubing and used to log the well and position the tool20. Again, this requires the use of additional equipment and services. Mechanical casing collar locators may also be used to determine depth by engaging a slip against the casing using a spring in a pocket on the locating tool. One problem with this method is the debris, sand, and cuttings that can accumulate inside the pocket, thus restricting the movement of the slip. The use of the casing collar locator33of the invention with the abrasive jet perforating tool20is designed to avoid all these problems associated with conventional casing collar locators.

In an alternative embodiment, the buttons35on the mechanical casing collar locator33would be made from a material with excellent abrasion resistance and good impact resistance. This material includes, but is not limited to, carbide and tool steel.

To date, abrasive jet perforating technology has been offered only as a service provided by service companies for their customers. The service providers also provide equipment and personnel to complete the process. As the demand for this technology grows, these tools20will become rental items, much like downhole mud motors, drilling jars, or shock subs. With tool rental comes a decrease in the amount of control that the manufacturer has over the tool20since the tool20will likely be left with the customer without supervision. A new challenge of protecting intellectual property related to the unauthorized use or duplication of this property will present itself.

The jet end, or head of the abrasive jet27, is shaped is such a way as to prevent common hand tools (such as, for example, wrenches, sockets, pliers, and screwdrivers) from being able to remove the jets27from the tool unless a custom removal tool is used. For example, the jet head can be a square shape inside of a circle, a circle inside a circle with two holes, or other shapes that do not fit common hand tools, such as a triangle inside a circle. A specially shaped abrasive jet27and protective plate29will prevent the unwanted removal of the abrasive jets27and will thus help to protect the intellectual property in the tool20. This protection leads to cost savings for the service provider and, hence, for the customers.

Depending on the well parameters, some of the alternate features of the tool of the invention illustrated inFIGS. 3-5may not be used with in conjunction with the other features. These well parameters would include, but not be limited to, whether the wellbore is cased or uncased, type of completion, size and weight of the casing, depth, formation type, and special conditions. A variety of different jet quantities, orifice sizes, and placement locations can be used with the improvements listed for this tool.

FIGS. 6-8are schematic side views of additional alternative embodiments of the tool of the invention shown inFIG. 2.

FIG. 6shows another alternative embodiment of the tool of the invention for horizontal wells. In this alternative embodiment, pockets60are added around the outer diameter61of the gauge rings62to hold ball bearings63. The ball bearings63would then reduce friction at any contact between the tool and the casing, but especially in horizontal wells when the full weight of the tool will be lying on one side of the casing (and, in particular, on the gauge rings62). Maintaining string weight is a challenge in horizontal holes and any opportunity to reduce the drag of the string in the wellbore is very helpful.

FIG. 7shows another alternative embodiment of the tool of the invention for angled perforation. In this alternative embodiment, a jet inset70in the jet body71of the abrasive jet (27inFIGS. 2-5) is oriented at an angle72other than 90° with respect to the wellbore10and casing12. This angling provides an angled abrasive fluid flow73through the wellbore10and the casing12. The jet inserts are typically made of an abrasive-resistant metal, such as carbide. However, this is not a limitation of the invention. The jet inserts could also be constructed of other appropriate materials, such as ceramics. Conventionally, when jets are oriented at other angles, an angled hole is drilled in the tool for the entire jet to be at this angle, as exemplified in U.S. Pat. No. 5,499,678, discussed above. This alternative embodiment of the tool of the invention allows an angled hole to be perforated while still using a perpendicular abrasive jet. Hence, a unique cavity (19inFIG. 1) can be perforated by the tool of the invention without requiring the expensive and time-consuming manufacture of a custom-made specialty tool.

FIG. 8shows another alternative embodiment of the tool of the invention using an abrasive reservoir. In this alternative embodiment, an abrasive reservoir80is added in a chamber below the tool20. The abrasive reservoir80is attached to the tool20via the threaded connection fittings on the lower portion24of the tool20. It is extremely costly to pump abrasives in the high pressure fluid flow. The pumps that can withstand the abrasive and the high pressure are expensive to rent, purchase, or maintain. The abrasive reservoir80located below the tool would be open only to the internal cavity of the tool20, and would be filled with the appropriate abrasive and perhaps also with abrasive mixed with polymer gel. As the non-abrasive pressurized fluid flows through the tool20and out the abrasive jets27, turbulent, swirling flow is created that moves the sand from the abrasive reservoir80up into the inside of the tool20. The abrasive is then pushed through the abrasive jets27and perforates the casing. This embodiment would be useful for general perforating, but also for perforating followed by acid injection, because the abrasive reservoir80would only have to carry the amount of sand necessary to perforate the casing. In addition, the acid would assist in creating the cavity (19inFIG. 1).

In another embodiment, the invention is a method for performing abrasive jet perforating, using the abrasive jet perforating tool of the invention, described above.FIG. 9is a flowchart illustrating an embodiment of the method of the invention for performing abrasive jet perforating.

At block90, parameters are determined for a well to be perforated. These well parameters include, but are not limited to, the type and thickness of casing, the type and thickness of cement, the type of reservoir rock to be encountered in the zones to be perforated, and the depth of the zones to be perforated.

At block91, the appropriate components of an abrasive jet perforating tool are assembled according to the well parameters determined in block90. The abrasive jet perforating tool is the tool of the present invention, as described above with reference toFIGS. 2-5. The assembly of the tool can take place onsite or off-site, wherever is convenient. If the tool is assembled offsite, then the tool is shipped to the well site, where the tool assembly can be easily changed if the well parameters have changed or turn out to be different than originally expected.

At block92, the well is perforated with the abrasive jet perforating tool assembled in block91.

FIG. 10is a flowchart illustrating an alternative embodiment of the method of the invention for performing abrasive jet perforating.

At block100, an abrasive jet perforating tool is deployed in a well. The abrasive jet perforating tool is the tool of the present invention, as described above with reference toFIGS. 2-5.

At block101, the abrasive jet perforating tool from block100is positioned at a desired location in the well using a casing collar locator.

At block102, the abrasive jet perforating tool is centered in the well at the desired location positioned in block101using gauge rings.

At block103, the well is perforated using an abrasive fluid pumped at high pressure through the abrasive jet perforating tool and ejected through the abrasive jets.

At block104, the process in blocks101to103is repeated as desired to perforate at the next desired location.

The improved apparatus could also be used to clean out open holes that have been recently drilled and need to be irrigated. In this alternative embodiment, the tool is run within a drill string as a clean-up tool after the initial drilling of the well. A ball is then pumped to close the circulation sub, diverting fluid through the jets. The tool string is then rotated by the drilling rig as the assembly is lowered to clean out and irrigate the open hole. This clean-up version of the tool could be much larger than the tubing conveyed devices described above for perforation, but would carry the same jets. This larger size is not a limitation of the invention, though, since this clean-up version of the tool could be a similarly-sized tool as described above for perforating.

Another alternative embodiment of the invention is the use of the tool for cleaning cased holes having scale built up in casing. The scale-removal tools would be a similar size to the clean-up tools described above for open holes and would be intended to wash scale from casing inner diameter in a similar rotating and lowering method as described above.

The sand jet perforating method and apparatus described in this disclosure has numerous advantages. The addition of vertical jets prevents sand from settling on the tool, and helps avoid getting the tool stuck in the hole. The tapered outer diameter of the tool in openhole conditions will allow the tool to be removed from the sand and cuttings that may settle below it. Using jets of different length in conjunction with protective plates and sizing rings allow one universal tool to be used in wells of varying sizes. This will decrease costs by requiring fewer tools in inventory to provide service for the customers. The mechanical casing collar locator will provide valuable information about the depth of the tool so that the tool can be located precisely in the reservoir. A specially shaped jet and protective plate will prevent the unwanted removal of the jets and will help to protect intellectual property.

It should be understood that the preceding is merely a detailed description of specific embodiments of this invention and that numerous changes, modifications, and alternatives to the disclosed embodiments can be made in accordance with the disclosure here without departing from the scope of the invention. The preceding description, therefore, is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined only by the appended claims and their equivalents.