Abstract:
An improved abrasive slurry delivery apparatus and associated method of using same that permits repeated and/or extended use of the apparatus in a subterranean wellbore, and reduces abrasive wear during fracturing operations while increasing pump rate and proppant mass delivery capabilities. In a preferred embodiment, an abrasive slurry delivery apparatus has a tubular crossover member with an internal flow passage and sidewall outlet openings formed with or without removable inserts formed from abrasive resistant materials. The internal flow passage is eccentrically offset to enlarge the effective flow cross-section, provide for tool passage clearance and to increase wall thickness for protection of a return flow passageway. The sidewall opening is positioned such that the opening is isolated from the secondary flow passageway.

Description:
BACKGROUND OF THE INVENTION 
     The present inventions relate generally to tools used in subterranean wells and, in a preferred embodiment thereof, more particularly provide a slurry delivery apparatus for use in formation fracturing operations. 
     Further, the present inventions relate to improvements in prior art slurry delivery tools and methods of the type shown and described in U.S. Pat. No. 5,636,691, entitled Abrasive Slurry Delivery Apparatus and Methods Of Using Same, which is incorporated by reference herein for all purposes. 
     As is explained in the above referenced patent, oftentimes, a potentially productive geological formation beneath the earth&#39;s surface contains a sufficient volume of valuable fluids, such as hydrocarbons, but also has a very low permeability. “Permeability” is a term used to describe that quality of a geological formation that enables fluids to move about in the formation. All potentially productive formations have pores, a quality described using the term “porosity,” within which the valuable fluids are contained. If the pores are not interconnected, the fluids cannot move about and, thus, cannot be brought to the earth&#39;s surface. 
     When such a formation having very low permeability, but a sufficient quantity of valuable fluids in its pores, is desired to be produced, it becomes necessary to artificially increase the formation&#39;s permeability. This is typically accomplished by “fracturing” the formation, a practice which is well known in the art, and for which purpose many methods have been conceived. Fracturing is achieved by applying sufficient pressure to the formation to cause the formation to crack or fracture, hence the name. The desired result being that the cracks interconnect the formation&#39;s pores and allow the valuable fluids to be brought out of the formation and to the surface. 
     A conventional method of fracturing a formation begins with drilling a subterranean well into the formation and cementing a protective tubular casing within the well. The casing is then perforated to provide fluid communication between the formation and the interior of the casing. A packer is set in the casing above the well treating equipment to isolate the formation from the rest of the wellbore. In some environments, it is preferable to use a packer of the type that is set using a ball-seat configuration. Dropping a ball through the well tubing to a seat in the tubing string located at the packer sets these packers. The ball acts as a temporary check valve-closing seat, permitting pressure within the tubing string to be increased at the packer to hydraulically set (install) the packer. After the packer is set, tubing pressure is increased further to a point where the ball seat fails and allows the ball to fall down the tubing string to reopen the tubing at the packer. Some fracturing equipment contains internal components made from corrosion resistant material such as carbide or ceramic which cannot tolerate impact with a ball being projected downhole when the seat fails. Some have no space for receiving and storing the ball. In those situations, the ball must be removed by reversing the flow in the well, to flow the ball from the well, rather than by failure of the seat. The process of reverse flow to remove the packer set ball is a time consuming and expensive process, which should be avoided. 
     In some applications, the tubing string installed with the packer includes perforating equipment located below the fracturing equipment. One type of perforating equipment uses explosive charges that are conventionally actuated by dropping a weighted bar through the tubing string. If the fracturing equipment contains fragile internal components, the weighted bar actuating system cannot be used. 
     After the packer is set, hydraulic pressure is applied to the formation via tubing extending from the packer to pumps on the surface. The pumps apply the hydraulic pressure by pumping fracturing fluid down the tubing, through the packer, into the wellbore below the packer, through the perforations, and finally, into the formation. The pressure is increased until the desired quality and quantity of cracks is achieved and maintained. Much research has gone into discerning the precise volume and rate of fracturing fluid and hydraulic pressure to apply to the formation to achieve the desired quality and quantity of cracks. 
     The fracturing fluid&#39;s composition is far from a simple matter itself. Modem fracturing fluids may include sophisticated manmade proppants suspended in gels. “Proppant” is the term used to describe material in the fracturing fluid which enters the formation cracks once formed and while the hydraulic pressure is still being applied (that is, while the cracks are still being held open by the hydraulic pressure), and acts to prop the cracks open. When the hydraulic pressure is removed, the proppant keeps the cracks from closing completely. Thus, the proppant helps to maintain the artificial permeability of the formation after the fracturing job is over. Fracturing fluid containing suspended proppant is also called “slurry.” 
     A proppant may be nothing more than very fine sand, or it may be a material specifically engineered for the job of holding formation cracks open. Whatever its composition, the proppant must be very hard and strong to withstand the forces trying to close the formation cracks. These qualities also make the proppant a very good abrasive. It is common for proppant to form holes in the protective casing, tubing, pumps, and any other equipment through which slurry is pumped. 
     Particularly susceptible to abrasion wear from pumped slurry is any piece of equipment in which the slurry must make a sudden or significant change in direction. The slurry, being governed by the laws of physics and fluid dynamics including the principles of inertia, tends to maintain its velocity and direction of flow, and resists any change thereof. An object in the flow path of the slurry, which tends to change the velocity or direction of the slurry&#39;s flow will soon be worn away as the proppant in the slurry incessantly impinges upon the object. 
     Of particular concern in this regard is the piece of equipment attached to the tubing extending below the packer, which takes the slurry as it is pumped down the tubing and redirects it radially outward so that it exits the tubing and enters the formation through the perforations. That piece of equipment is called a crossover. Assuming, for purposes of convenience, that the tubing extends vertically through the wellbore, and that the formation is generally horizontal, the crossover must change the direction of the slurry by ninety degrees. Because of this significant change of direction, few pieces of equipment (with the notable exception of the pumps) must withstand as much abrasive wear as the crossover. 
     In addition, the crossover is frequently called upon to do several other tasks while the slurry is being pumped through it. For example, the crossover typically contains longitudinal circulation ports through which fracturing fluids, that are not received into the formation after exiting the crossover, are transmitted back to the surface. Space limitations in the wellbore dictate that the circulation ports are not far removed from the flow path of the slurry through the crossover. If the crossover is worn away such that the slurry flow path achieves fluid communication with the circulation ports in the crossover, the fracturing job must cease. Once stopped, the fracturing job cannot be recommended or completed. Hence, it is very important that the crossover does not fail while the job is in process. If the fracturing job is not halted after the crossover fails, the slurry will enter the circulation ports in the crossover and travel back to the surface without delivering the proppant to the formation. 
     For the above reasons and others, the crossover has commonly been considered a disposable piece of equipment, usable for only one fracturing job, or worse, less than one fracturing job. Even when it survives a fracturing job, it is usually sufficiently worn that no further use may be made of it. This is unfortunate because the crossover is also typically one of the most expensive pieces of equipment used in a fracturing job due to its high machining and material costs. Further, customers are now demanding fracturing jobs with high flow rates, high pressures, higher volumes, and higher density proppant. All of this increase wear on the crossover increases the likelihood of crossover failure during the fracturing job. 
     Attempts have been made to provide a solution for these problems. One involves making the crossover out of extremely hard and abrasion wear-resistant materials. This has proven to reduce the rate of abrasion wear of the crossover. 
     It is, however, enormously expensive to make an entire crossover out of a sufficiently wear-resistant material. No economic advantage is actually achieved by this solution over the disposable crossover made of less wear-resistant, but much less expensive, materials. 
     Another proposed solution is to utilize surface treatment of less expensive alloy steels to achieve a wear-resistant crossover surface. Methods such as carburizing, nitriding, etc., which produce a high surface hardness, do indeed slow the abrasion wear rate of the crossover at less expense than using exotic materials. However, as soon as the hardened surface layer has been breached, the crossover begins to wear away rapidly. For this reason, surfacehardened crossovers are also not sufficiently durable for the newer high flow, high pressure fracturing jobs. The extra expense of surface-hardening a disposable crossover makes this solution uneconomical as well. 
     Other proposals involve placing replaceable protective sleeves or liners of wear or corrosive resistant materials in the crossover. These sleeves are placed in the areas subjected to abrasion such as the central tubing passageway. However, as previously pointed out, the better corrosive resistant materials are brittle and subject to impact damages from contact with packer setting balls and perforator activator bars. This potential for damage limits the use of these crossovers. Further protective sleeves take up space in the internal flow path, reducing the flow capacity and tool passage ability of the crossover. 
     Another area of concern concerning abrasion wear during fracturing jobs is the protective casing lining the wellbore. Since the crossover typically directs the slurry flow radially outward, the casing is directly in the altered slurry flow path. Unintended, misplaced holes in the casing are to be avoided, since it is the casing which provides the only conduit extending to the surface through which all other conduits and equipment must pass. 
     From the foregoing, it can be seen that it would be quite desirable to provide an improved slurry delivery apparatus, which does not have the economic disadvantages of the solutions, enumerated above, but which allows repeated use thereof. It would also be desirable to provide a slurry delivery apparatus that has a full bore internal passage to increase flow capacity and tool clearance. In addition, it would be desirable to locate replaceable wear resistant components out of the main passageway and out of potential tool damaging areas. Accordingly, it is an object of the present invention to provide such a slurry delivery apparatus and associated methods of using same. 
     SUMMARY OF THE INVENTION 
     In carrying out the principles of the present invention, in accordance with an embodiment thereof, an abrasive slurry delivery apparatus and method of using same are provided, which apparatus and method are specially adapted for utilization in formation fracturing operations in subterranean wellbores. 
     In broad terms, an abrasive slurry delivery apparatus and method is provided which includes a first tubular structure having a flow inlet communicating with an internal flow passage through which a pressurized, abrasive slurry material may be axially flowed in a downstream direction. The internal flow passage is positioned eccentrically within the tubular structure, to form a thickened axially extending wall section. An axially extending bypass flow passage formed in the thickened wall section, and an axial portion of the tubular structure having a side wall section, with an outlet opening therein through which an abrasive slurry material may be outwardly discharged from the internal flow passage. The outlet opening being circumscribed by a peripheral edge portion of the side wall section, and protective means for shielding the peripheral edge portion of the side wall section from abrasive slurry material being discharged outwardly through the outlet opening, with or without the protective means of abrasive resistant ported inserts removably or permanently mounted in the side wall flush with or recessed from the internal flow passage. It is preferable but not required that these outlet openings will be aligned such to promote maximum volume with equal distribution of flow throughout the length of the crossover with specific spacing, number and size of the ports. These outlet holes shall encompass the entire surface area (radially) with the possible exception of that area left for the bypass return ports. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings are incorporated into and form a part of the specification to illustrate several examples of the present inventions. These drawings, together with the description, serve to explain the principals of the inventions. The drawings are only for the purpose of illustrating preferred and alternative examples of how the inventions can be made and used, and are not to be construed as limiting the inventions to only the illustrated and described examples. The various advantages and features of the present inventions will be apparent from a consideration of the drawings in which: 
     FIG. 1 is a partially cross-sectional view of a portion of a tubing string containing a slurry delivery apparatus with a crossover tool embodying principles of the present invention; 
     FIG. 2 is an enlarged cross-sectional view of the crossover of the slurry delivery apparatus, taken along line  2 — 2  of FIG. 1 looking in the direction of the arrows; 
     FIG. 3 is an enlarged scale cross-sectional view of the crossover of the slurry delivery apparatus, taken along line  3 — 3  of FIG. 2 looking in the direction of the arrows; 
     FIG. 4A is an enlarged scale cross-sectional view of one embodiment of the insert mounted in the wall of the crossover of the slurry delivery apparatus; 
     FIG. 4B is an enlarged scale cross-sectional view similar to FIG. 4A of another embodiment of the insert mounted in the wall of the crossover of the slurry delivery apparatus; 
     FIG. 4C is an enlarged scale cross-sectional view similar to FIG. 4A of another embodiment of the insert mounted in the wall of the crossover of the slurry delivery apparatus; 
     FIG. 4D is an enlarged scale cross-sectional view similar to FIG. 4A of an embodiment of the port with no insert in the wall of the crossover of the slurry delivery apparatus; 
     FIG. 4E is an enlarged scale cross-sectional view similar to FIG.4A of another embodiment of the insert mounted in the wall of the crossover of the slurry device; and 
     FIG. 5 is a cross-sectional view of the slurry delivery apparatus of FIG. 1, further having a casing protective flow sub. 
    
    
     DETAILED DESCRIPTION 
     The present inventions will be described by referring to drawings of apparatus and methods showing various examples of how the inventions can be made and used. In these drawings, reference characters are used throughout the several views to indicate like or corresponding parts. In FIG. 1, there is an abrasive slurry delivery apparatus  10  which embodies principles of the present invention as illustrated. The top of the drawing is intended to be toward the surface and the bottom of the drawing page toward the well bottom. While wells commonly are laid out in a vertical direction, it is understood that inclined and horizontal configurations exist. When the descriptive terms “up and down” are used in reference to a drawing, they are intended to indicate location on the drawing page, and not necessarily orientation in the ground, as the present inventions have utility no matter how the well bore is orientated. 
     Apparatus  10 , as representatively illustrated in FIG. 1, is specially adapted for use within a tool string known to those skilled in the art as a service tool string (not shown), which is suspended from tubing extending to the earth&#39;s surface, the tubing being longitudinally disposed within protective casing in a subterranean wellbore. The service tool string is typically inserted through a packer (not shown) during a fracturing job. A pressurized, abrasive slurry is then pumped through the tubing and into the service tool string. Tubular upper connector  12  and lower connector  14  permit interconnection of the apparatus  10  into the service tool string. Accordingly, upper portion  16  of upper connector  12  is connected to the service tool string above the apparatus  10 , and lower portion  18  of lower connector  14  is connected to the remainder of the service tool string extending below the apparatus. Axial flow passage  20  extends longitudinally (i.e., axially) downward from the upper portion  16  of upper connector  12 , axially through the upper connector, and into a generally tubular crossover  22 . The axial flow passage  20  terminates at upper radially reduced portion  24  of tapered seat with ports and ball  26 . Seat  26  is either installed or is an integral part of lower portion  28  of crossover  22  . Sealing engagement between the seat  26  and the lower portion  28  of crossover  22  is provided by seal  30  disposed in circumferential groove  32  externally formed on the plug. 
     Radially displaced, longitudinally extending, circulation flow passage  34  extends downwardly from upper portion  16 , through the upper connector  12 , longitudinally through the crossover  22  in a manner that will be described more fully hereinbelow, through the lower connector  14 , and to lower portion  18 . When operatively installed in a wellbore  36 , the circulation flow passage  34  in the apparatus  10  is sealingly isolated from the wellbore external to the apparatus by seal  38  disposed in circumferential groove  40  internally formed on the upper connector  12 , and by seal  42  disposed in circumferential groove  44  internally formed on the lower connector  14 . The circulation flow passage  34  is sealingly isolated from coaxial flow passage  20  in the apparatus  10  by seal  30 , and by a pair of seals  46 , each disposed in one of a pair of circumferential grooves  48  externally formed on an upper portion  50  of the crossover  22  which extends coaxially into the upper connector  12 . 
     Annular antifriction seal rings  52  are disposed in longitudinally spaced apart external annular recesses  54  formed on upper portion  16  of upper connector  12 , between upper connector  12  and crossover  22 , and between crossover  22  and lower connector  14 . The antifriction seal rings  52  ease insertion and movement of the apparatus  10  within the packer and other equipment into which the apparatus  10  may be longitudinally disposed, as well as providing an effective seal there between. 
     Upper portion  50  of crossover  22  is threadedly attached to upper connector  12 , and lower portion  28  of the crossover is threadedly attached to lower connector  14 . 
     A plurality of cylindrical outlet openings or exit ports  56  provide fluid communication between the interior chamber  57  of crossover  22  which communicates with the axial flow passage  20  and the wellbore  36 . It is through these exit ports  56  that a slurry must pass in its transition from longitudinal flow in the axial flow passage  20  to radial flow into the wellbore  36 . Because of the substantial change of direction from longitudinal flow to radial flow of the slurry through the exit ports  56 , the exit ports are particularly susceptible to abrasion wear from proppant contained in the slurry. 
     In order to protect the exit ports  56  against abrasion wear, the ports  56  are preferably formed in inserts  58  or are hardened without inserts. These inserts are removably mounted in wall  60  of the crossover  22 . The inserts  58  are made of a suitably hard and tough abrasion resistant material, such as tungsten carbide, or are made of a material, such as alloy material, which has been hardened. If made of an alloy material, the inserts  58  are preferably through-hardened by a process such as case carburizing or nitriding. Other materials and hardening methods may be employed for the inserts  58  without deviating from the principles of the present invention. The inserts  58  are preferably made of tungsten carbide, ceramic or other abrasive resistant material. 
     The inserts  58  are secured into the wall  60  by press fit, threads, pins, snap rings or the like or a combination of fasteners. As will be described in detail herein, the interior ends  62  are contoured to conform to the interior surface of the chamber  57 . In other words, the interior facing surfaces on ends  62  form extensions of the interior surface chamber to form a smooth flow surface. The upper portion  64  of insert  58  extends axially upward past the exit ports  56  in the crossover  22 , thereby completely internally overlapping that portion of the crossover  22  in which the exit ports  56  are located. Transition surface  64  formed in crossover  22  provides a smooth transition between the passage  20  and chamber  57  maintaining a flush inside surface. 
     An upwardly opening interior hollow cylindrical volume within the crossover  22  above the upper portion  24  of the seat  26  forms sump area  66 . As the slurry flows longitudinally downward through the coaxial flow passage  20  into the crossover  22 , the slurry will enter the well  66  and quickly fill the sump area. Thereafter, the downwardly flowing slurry will directly impinge on the portion of the slurry, which has filled the sump  66 , effectively preventing the slurry from abrading any portion of the crossover  22  or seat with ball  26 , due to direct longitudinal impingement by the slurry. Alternatively, the crossover  22  could have a substantially solid and generally cylindrical sacrificial insert in place of the well  66 , as shown in FIGS. 4A and 4B of U.S. Pat. No. 5,636,691. 
     This has been described as a unique configuration of slurry delivery apparatus  10 , wherein the crossover  22  is protected from abrasion wear due to slurry flow by an abrasion resistant inserts  58 , the inserts acting to prolong the useful life. Sump area  66  effectively minimizes abrasion wear due to longitudinally directed flow of the slurry. 
     Turning now to FIG. 2, a cross-sectional view may be seen of the apparatus  10  representatively illustrated in FIG.  1 . The cross-section is taken through line  2 — 2  of FIG. 1 which extends laterally through the crossover  22 . In this view, the manner in which circulation flow passage  34  extends longitudinally through the crossover  22  may be seen. 
     In FIG. 2, three longitudinally extending and circumferentially spaced bypass circulation ports  90  are disposed in the wall  60  of the crossover  22 . In this embodiment bypass, ports  90  are positioned intermediate outer surface  92  of the crossover  22  and the interior surface  94  of interior chamber  57 . In the disclosed embodiment, three ports are shown, for example, only in that more or less could be utilized. The ports are illustrated as having equal cross sections, but it is possible that the ports may different diameters which would not sacrifice structural integrity. Ports  90  (secondary flow) are utilized in some processes, and it is essential the flow in ports  90  remain isolated from interior chamber  57  (primary flow). 
     It is to be noted that the wall  60  adjacent to the interior chamber  57  has a non-uniform thickness. As seen in FIG. 2, in the twelve o&#39;clock location, the wall has its maximum thickness, and at the six o&#39;clock location, the wall has its minimum thickness. This change in thickness is created by the fact that the interior chamber  57  is eccentrically offset from, and is larger, than the flow passage  20  in the upper portion  22 . The offset creates a thicker wall portion around the ports  90  adding to the structural integrity and resistance to erosion failure by connecting the bypass port  90  to the chamber  57 . Offsetting the chamber  57  achieves an additional advantage in that it increases the cross sectional area in comparison to U.S. Pat. No. 5,636,691, which in turn lowers flow velocities in the crossover to reduce flow erosion. 
     FIG. 2 illustrates another advantage in preventing abrasion wear of the crossover  22 . It can be clearly seen that if exit ports  56  are allowed to wear appreciably circumferentially outward, the exit ports  56  are axially spaced from the circulation ports  90 . Any abrasive wear occurring around ports  56  would not engage ports  90  because of their radial spacing there from. 
     Turning now to FIG. 3, a cross-sectional view of the crossover  22 , taken laterally along line  3 — 3  of FIG. 2 may be seen. For illustrative clarity, only the crossover  22  is shown in FIG. 3, and details of the offset between chamber  57  and flow passage  20  is shown. Note that the offset is eccentric to the flow chamber but not larger in inside diameter. FIG. 3 further illustrates the manner in which the circulation ports  90  are formed in the crossover  22 . 
     FIGS. 4A-4C illustrate various embodiments of the insert  58 . In FIG. 4A, the insert is identified as  58   a.  Insert  58   a  (and the other inserts illustrated and described herein) is constructed from hard abrasive material such as carbide, ceramic or the like. Insert  58   a  has a cylindrical exterior surface  59   a,  which mates with a cylindrical bore in wall  60 . Radial shoulders  61   a  are formed in the wall of bore and on the exterior surface  59   a  adjacent the inner end  62   a  to locate the insert  58   a  in the bore. A snap or other type of retaining ring  63   a  can be mounted in wall  60  to removably retain insert  58   a  in the bore. It should be noted that the port  56   a  formed in insert  58   a  is inclined with respect to the surface  58  and bore. The interior and exterior ends of insert  58   a  are concentric with the interior surface  94  and exterior surface  92  of wall  60 . 
     In FIG. 4B, insert  58   b  is removably mounted in the bore in wall  60  by threaded engagement between interior threads in the bore and exterior threads on the insert  58   b.  As in the FIG. 4A embodiment, the port  56   b  is inclined in the insert  58   b.  The ends of this insert  58   b  are likewise concave and convex shaped to be concentric with the respective surfaces of wall  60 . The interior end  62   b  of the insert is formed concentric with the interior surface  94  of wall  60 . 
     In FIG. 4C, insert  58   c  has a cylindrical exterior surface, but is mounted in an inclined bore in wall  60 . Port  56   c  in insert  58   c  is coaxial with the center of the exterior surface. The interior end  62   c  is formed concentric with the interior surface  94  of wall  60 . The exterior end of insert  58   c  is likewise concentric with the exterior surface  92  of wall  60 . Insert  58   c  is illustrated as being mounted in the bore in wall  60  by press fit, but it is to be understood that any of the illustrated inserts could be mounted by any of the means illustrated herein, or by other mechanical means. 
     In FIG. 4D the bore in the wall  60  is shown as in FIGS. 4A-4C to form the port  56   d  the surface  57  of the bore is hardened in a manner known in the arts. 
     In FIG. 4E, insert  58   a  is disposed in the wall  60  in the manner of the embodiment shown and described in FIG.  4 C. In this embodiment, however, the insert  58   e  is mounted in the bore  60  with a retention bushing  61  threaded on its inner  63  and outer  65  surfaces. Corresponding threads are provided on the inner surface of the bore and the outer surface of the insert. 
     FIG. 5 is a sectional view of a crossover tool  22  of the present invention similar to FIG. 1 positioned in and outer flow sub  140  in a subterranean well casing  102 . FIG. 5 shows the apparatus  10  having a coaxially disposed outer tubular flow sub  140  completely exteriorly overlapping the crossover  22 . An annular flow area  142  is thereby formed radially between the outer surface  92  of the crossover  22  and inner diameter  144  of the flow sub  140 . Outer surface  146  of the flow sub  140  is exposed to the wellbore  36  contained in casing  102 . An upper portion  148  of the flow sub  140  extends longitudinally upward, and is suspended from the packer (not shown). A lower portion  150  of the flow sub  140  is threadedly secured to a lower connector  152  from which further equipment may be attached and suspended. 
     Extending radially through the flow sub  140  and providing fluid communication from the annular flow area  142  to the wellbore  36  are circumferentially spaced slurry ports  154  (only two of which are visible in FIG.  5 ). Slurry ports  154  are inclined with respect to the centerline  130  in order to induce a longitudinally downward component to the radially directed slurry flow as it exits the slurry ports  154 . 
     The inclination of the slurry ports  154  acts to reduce direct impingement of the radially directed slurry flow on any equipment external to the flow sub  140 . In particular, the inclination of the slurry ports  154  reduces abrasion wear of the casing  102 . It is to be understood that a range of inclination angles and number of slurry ports  154  may be utilized without departing from the principles of the present invention. It is also understood that the slurry ports may be used in conjunction with a closing sleeve assembly instead of a flow sub. Slurry ports  154  are longitudinally downwardly displaced relative to the exit ports  56  in the crossover  22  such that the slurry cannot flow directly radially outward from the exit ports  56  and through the slurry ports  154 . The slurry must flow, after exiting exit ports  56 , at least partially longitudinally downward through annular flow area  142  before it may flow radially outward through slurry ports  154 . Thus, the slurry is made to impinge upon the inner wall  144  of the flow sub  140  after the slurry exits the exit ports  56 . 
     An annular sump area  156  is longitudinally downwardly disposed relative to the slurry ports  154 . Annular sump area  156  performs a function similar to that performed by sump area  66  within crossover  22 . Soon after the slurry flow commences, annular sump area  156  will fill with the slurry material and provide a fluid “cushion” for the longitudinally downward flow of the slurry in the annular flow area  142 . Flow sub  140  is preferably made of an abrasion resistant material. Since the slurry flow impinges upon the inner diameter  144  of the flow sub  140  before exiting the slurry ports  154 , the inner diameter  144  is particularly susceptible to abrasion wear therefrom. For this reason, the flow sub  140  is preferably made of an alloy material and surfaced hardened at least on the inner diameter  144  by a nitriding or carburizing treatment. It is to be understood that other materials and surface treatments may be utilized without departing from the principles of the present invention. 
     The embodiments shown and described above are only exemplary. Many details are often found in the art such as: packer assemblies, packer seals, packer actuators, explosives, charges and carriers therefore. Therefore, many such details are neither shown nor described. It is not claimed that all of the detail parts, elements, or steps described and shown, were invented herein. Even though numerous characteristics and advantages of the present inventions have been set forth in the foregoing description, together with details of the structure and function of the inventions, the disclosure is illustrative only, and changes may be made in the detail, especially in matters of shape, size, and arrangement of the parts within the principles of the inventions to the full extent indicated by the broad general meaning of the terms used the attached claims. 
     The restrictive description and drawings of the specific examples above do not point out what an infringement of this patent would be, but are to provide at least one explanation of how to make and use the inventions. The limits of the inventions and the bounds of the patent protection are measured by, and defined in the following claims: