Abstract:
A High-Rate Multizone Gravel Pack System is provided that allows significantly higher gravel packing flow rates than were previously available. This system includes a fluid bypass which greatly enhances flow rate and decreases damage to the bypass due to erosion. The system is employed in a multi-stage arrangement which allows the gravel-packing of multiple production zones with a single trip into the well bore. A memory gauge sensing wash pipe pressure and temperature is incorporated to allow for data acquisition during the gravel packing process.

Description:
FIELD OF THE INVENTION 
     The field of the invention is circulating fluids and gavel packing formations in well bores. 
     BACKGROUND OF THE INVENTION 
     Gravel packing of a well is a recognized technique for preparing a formation for production and for improving a well&#39;s production characteristics. Gravel packing is generally carried out by pumping gravel-containing fluid down into the zone of the formation to be treated and filtering the returning fluid to insure that the gravel is deposited in the desired zone. The goal of gravel packing is to force gravel out of the well casing and into the producing formation. However, the gravel-containing fluid must be pumped through the interior of the down hole equipment string to prevent losses and contamination between the surface and the desired zone. At some point, it is necessary to use a bypass tool to switch the flow of gravel-containing fluid from the interior of the equipment string to the exterior of the string so that the fluid may be used to gravel pack the formation. The bypass tool must direct the downward-traveling fluid outward, and simultaneously direct the upward-traveling return fluid from the interior of the equipment string to the exterior for the return trip to the surface. 
     Current bypass tools restrict the maximum rate of flow to about fifteen barrels per minute. This restriction is caused by the fluid pathway used to exchange the positions of the fluid streams. The downward-flowing path requires a series of sharp tums which causes flow rate losses and subjects the tool to relatively high rates of erosion. This series of tums usually entails at least four right-angle tums to redirect the gravel bearing fluid from the tool&#39;s interior to its exterior. Because of this flow rate restriction, the pressure that can be used to gravel pack a formation is restricted. However, it is desirable in some cases to provide a gravel packing flow rate in excess of twenty barrels per minute or more to maintain higher gravel packing pressures. These higher pressures would allow gravel to be forced further into formation fractures, improving well production rates. 
     It is therefore desirable to have a bypass tool that allows higher flow rates, and accordingly higher treatment pressures, than present tools. This goal is accomplished by providing a tool which utilizes enlarged flow areas and direct exit ports to direct the flow of downward-traveling fluid from the interior to the exterior of the tool. In this way, the fluid is required to alter course only twice, rather than the usual four tums required by current bypass tools. Further, the amount of course alteration required by the slanted exit ports is substantially less than ninety degrees:, resulting in greatly lessened flow rate losses compared to current bypass tools. The lower velocities for a given flow rate have the additional advantage of lessening erosion of the bypass tool. 
     A retrievable memory gauge is also provided to read pressure and temperature data during gravel packing. This gauge is designed to collect data without being disturbed by the fluid flow passing through the ports above the gauge. 
     A High-Rate Multizone Gravel Pack System is provided that allows significantly higher gravel packing flow rates for a tool of a given size than were previously available. This system includes a fluid bypass which greatly enhances flow rate and decreases damage to the bypass due to erosion compared to current tools. The system can be employed in a multi-stage arrangement which allows the gavel-packing of multiple production zones with a single trip into the well bore. 
     It is a goal of this invention to provide a bypass tool that incurs lower fluid pressure losses compared to present bypass tools. 
     It is a further goal of this invention to provide a bypass tool that allows higher gravel packing flow rates at a formation than are allowed by present bypass tools. 
     It is another goal of this invention to provide a bypass tool that is less subject to erosion than present bypass tools. 
     It is another goal of this invention to provide a multi-zone gravel packing system that allows gravel packing at high flow rates in multiple production zones with a single trip of the apparatus into the well bore. 
     It is another goal of this invention to provide a retrievable memory gauge capable of sensing and recording pressure and temperature during gravel packing without being disturbed by the fluid flow through the bypass tool. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A-D is a partially cut away drawing of the High-Rate Multizone Gravel Pack System, showing the system in position to wash down a well bore. 
     FIG. 2A is a cut away side view of the external and internal bypass subassemblies showing flow paths in the circulating, or gravel packing, mode. 
     FIG. 2B is a cut away side view of an additional embodiment of the external and internal bypass subassemblies showing flow paths in the circulating, or gravel packing, mode. 
     FIG. 2C is a diagram of a prior art bypass tool, showing flow paths required to redirect flow from the interior to the exterior of the tool. 
     FIG. 3A-D is a partially cut away drawing of the High-Rate Multizone Gravel Pack System, showing the system in position to gravel pack a bottom zone. 
     FIG. 4A-D is a partially cut away drawing of the High-Rate Multizone Gravel Pack System, showing the system in position to reverse flow after gravel packing a bottom zone. 
     FIG. 5A-D is a partially cut away drawing of the High-Rate Multizone Gravel Pack System, showing the system in position to gravel pack an upper zone. 
     FIG. 6A-D is a partially cut away drawing of the High-Rate Multizone Gravel Pack System, showing the system in position to reverse flow after gravel packing an upper zone. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1A-D, one embodiment of the High-Rate Multizone Gravel Pack System is shown. The High-Rate Multizone Gravel Pack System comprises an outer equipment string 10 and an inner equipment string 110. The outer equipment string 10 comprises an upper packer 12, such as Baker Model `SC-9` (Product No. 488-20), circulation stages 14, such as Baker S-22B Anchor Latch Seal Assembly, and a sump packer 40, such as Baker Model `D` (Product No. 415-13). 
     The High-Rate Multizone Gravel Pack System may have multiple circulation stages 14 in the outer equipment string 10 as shown in FIG. 1A-D. Each circulation stage 14 comprises an external bypass subassembly 16, such as Baker Product No. 469-10, and pre-pack screens 30, such as Baker Product No. 486-19. Each circulation stage 14 except for the bottom-most circulation stage 15 also comprises an isolation package 31. The isolation package 31 comprises an upper seal bore 32, such as Baker Product No. 485-34, an isolation packer 34, such as Baker Product No.488-03, and a lower seal bore 36, such as Baker Product No. 485-34. Additionally, the upper-most circulation stage 13 comprises a knock out isolation valve 26, such as Baker Product No. 487-35. 
     The inner equipment string 110 comprises a setting tool 112, such as Baker Model `SC` (Product No. 445-21), an upper wash pipe 114, an indicating collet 116, such as Baker Model `A` (Product No. 445-34), an internal bypass subassembly 118, and a lower wash pipe 140. 
     Referring to FIG. 2A, the external bypass subassembly 16 and internal bypass subassembly 118 are shown in detail. The external bypass subassembly 16 comprises high-rate exit ports 18, retum channels 20, and a bypass extension 22. The internal bypass subassembly 118 comprises a first seal ring 120, an inner fluid pathway 121, first outlet ports 122, a memory gauge/landing assembly 124, a probe 125, a second seal ring 126, second outlet ports 130, a low bottom hole pressure check valve 132, a third seal ring 134, bypass 136, and lower seal rings 138. 
     This preferred embodiment provides a large improvement over the prior art in cross-sectional area of the inner fluid pathway and accordingly allows much lower flow velocities. For example, a prior art bypass tool with a four-inch outside diameter (&#34;OD&#34;) has an inner fluid pathway with a cross-sectional area of 1.77 square inches, or approximately 14% of the total cross-sectional area (12.56 square inches) of the inner bypass subassembly. The configuration of the present invention for a four-inch OD tool allows an inner fluid pathway with a cross-sectional area of 7.07 square inches, or approximately 56% of the cross-sectional area of the inner bypass subassembly. The following table shows comparisons of prior art tools of several OD sizes with the same-sized inner bypass subassemblies of the invention: 
     
         ______________________________________Tool   Tool     Prior art                    Prior art                             New  NewOD     XSA      XSA      %        XSA  %______________________________________4      12.56    1.77     14       7.07 564.75   17.72    2.75     16       7.07 406      28.27    4.01     14       18.65                                  66______________________________________ 
    
     In the above table, internal bypass subassembly OD&#39;s are stated in inches, XSA stands for &#34;cross-sectional area,&#34; cross-sectional areas are stated in square inches, the percentages are calculated by dividing the number in the corresponding &#34;XSA&#34; column by the corresponding number in the &#34;Tool XSA&#34; column, and the columns &#34;New XSA&#34; and &#34;New %&#34; represent values for bypass tools of the present invention. 
     An alternative configuration of the present invention is shown in FIG. 2B. This configuration provides an external bypass subassembly 16, an internal bypass subassembly 118, inner fluid pathway 121, high rate exit ports 18, and retum channels 20. Because the return channels 20 are not located in the external bypass subassembly 16, the cross-sectional area of the inner fluid pathway 121 is not as large as in the preferred embodiment described above. However, this configuration would be useful when working with formations where there are large fluid losses into the formation, while still providing a large improvement in flow velocity over the prior art. Unless there are large fluid losses into the formation, this configuration would experience increased backpressure. 
     In contrast to the above described configurations, referring to FIG. 2C, a prior art bypass tool is shown. There, the upward-flowing fluid retum channels 214 are in the same portion of the tool as the downward-flowing fluid channels 210. This prior art design requires dividing the tool&#39;s cross-sectional area between downward- and upward-flowing channels. In the preferred embodiment of the present invention, positioning the return channels 20 in the external bypass subassembly 16 allows greater downward flow area in the internal bypass subassembly 118. Further, in the prior art design shown in FIG. 2C, the downward-flowing fluid pathway 210 requires a series of four right-angie turns 212 to redirect the liquid flow from the interior to the exterior of the tool. This reduced area pathway results in substantially higher pressure losses and greater tool erosion than does the design of the present invention. 
     Referring again to FIG. 1A-D, one embodiment of the High-Rate Multizone Gravel Pack System is shown in position to wash down a well bore 2. The well bore 2 comprises a casing 4 with perforations 6 into production zones 8. The sump packer 40 is set by conventional methods, either by electric line or mechanical setting tools. The outer equipment string 10 is disconnected from the sump packer 40, and the outer equipment string 10 and the inner equipment string 110 are lowered into position using the setting tool 112. The upper packer 12 and the isolation packers 34 on the circulation stages 14 are not set at this point, providing a fluid flow path in the annulus between the casing 4 and the outer equipment string 10. Fluid is pumped down the inner equipment string 110, passing through the upper wash pipe 114 and into the inner fluid pathway 121 of the internal bypass subassembly 118. The internal by-bass subassembly 118 is positioned so that the first seal ring 120 and the lower seal tings 138 form seals with the bypass extension 22. Fluid flows out of the inner fluid pathway 121 through the first outlet ports 122, through the annulus between the internal bypass subassembly 118 and the bypass extension 22, into the bypass 136, then through the lower wash pipe 140. The fluid exits the bottom of the lower wash pipe 140 and returns to the surface through the annulus between the casing 4 and the outer equipment string 10. The fluid is prevented from flowing upward in the annulus between the outer equipment string 10 and the inner equipment string 110 by the seal formed between the lower seal rings 138 of the internal bypass subassembly 118 and the bypass extension 22. 
     After the wash-down phase depicted in FIG. 1A-D is completed, the upper packer 12 and each isolation packer 34 are set. The upper packer 12 can be set by the hydraulic setting tool 112. This is usually accomplished by dropping a ball or by pressuring up against the well bore 2. Each isolation packer 34 is set by raising the inner equipment string 110 (using the setting tool 112) into position so that the first seal ring 120 of the internal bypass subassembly 118 forms a seal within the respective upper seal bore 32 in the isolation package 31, and the third seal ring 134 of the internal bypass subassembly 118 forms a seal within the respective lower seal bore 36 in the isolation package 31. Fluid pressure can then be used by pumping fluid through the upper wash pipe 114, the inner fluid pathway 121, and the first outlet ports 122 of the internal bypass subassembly 118 to inflate and set the isolation packer 34. 
     With the upper packer 12 and isolation packers 34 set, the High-Rate Multizone Gravel Pack System can be used to gravel pack the production zones 8. Referring to Fig. 3A-D and FIG. 5A-D, the inner equipment string 110 is lowered to position in the desired circulation stage 14. The indicating collet 116 identifies the proper position by indicating its contact with the next-higher circulation stage&#39;s 14 isolation packer 34, or, in the case of the top-most circulation stage 13, with the upper packer 12. In this position, the internal bypass subassembly 118 is in the same position as is reflected in FIG. 2. In position for gavel packing, the first seal ring 120 of the internal bypass subassembly 118 forms a seal near the top of the external bypass subassembly 16, but below the uppermost openings of the return channels 20. The first outlet ports 122 are aligned with the high-rate exit ports 18. The second seal ting 126 forms a seal with the external bypass subassembly 16 below the high-rate exit ports 18. The second outlet ports 130 are positioned below the lowermost openings of the return channels 20. The third seal ting 134 and the bottom-most of the lower seal tings 138 form seals with the bypass extension 22. 
     Gravel packing is accomplished by pumping fluid containing the gravel packing material down through the upper wash pipe 114 and into the inner fluid pathway 121 of the internal bypass sub-assembly 118. The fluid exits the inner fluid pathway 121 through the first outlet ports 122 and flows through the high-rate exit ports 18 of the external bypass subassembly 16. The fluid then flows down through the annulus between the outer equipment string 10 and the casing 4 and is forced out of the casing 4 under pressure through the perforations 6 into the formation 8. Fluid is prevented from flowing further down hole by the isolation packer 34 if the gravel packing operation is being carried out at any circulation stage 14 except the bottom-most circulation stage 15, or by the sump packer 40 if the gravel packing is being carried out at the bottom-most circulation stage 15. Fluid is therefore forced to return through the pre-pack screens 30, which filter substantially all remaining gravel-packing material out of the fluid. The fluid flows up through the lower wash pipe 140 into the internal bypass subassembly 118. The fluid flows upwards through the low bottom hole pressure check valve 132, out the second outlet ports 130, and into and through the return channels 20 of the external bypass subassembly 16. After exiting the retum channels 20, the fluid continues to flow upward in the annulus between the inner equipment string 110 and the outer equipment string 10. 
     On completion of the gravel packing operation, the High-Rate Multizone Gravel Pack System can also be configured to reverse flow and remove any excess gravel packing material. Referring to FIG. 4A-D and FIG. 6A-D, two embodiments of the reverse flow position are shown. The inner equipment string 110 is raised so that the third seal ring 134 engages and seals the high-rate exit ports 18 of the circulation stage 14 which was most recently used for gravel packing operations. Fluid is pumped down hole in the annulus between the casing 4 and the inner equipment string 110. The upper packer 12 seals the annulus between the casing 4 and the outer equipment string 10, so that the fluid flows into the annulus between the inner equipment string 110 and the outer equipment string 10. The fluid is prevented from flowing beyond the third seal ring 134, and is forced into the inner equipment string 110 through the first outlet ports 122. The fluid then flows into and through the upper wash pipe 114 to retum to the surface. 
     The above steps can be repeated for each circulation stage 14 which is placed in the well bore 2 by repositioning the inner equipment string 110, so that each production zone 8 may be gravel packed with a single trip of the inner equipment string 110 into the well bore 2. When the last production zone 8 is gravel packed and the inner equipment string 110 is lifted out of the well bore 2, the knock-out isolation valve 26 in the upper-most circulation stage 14 closes, preventing the backwash of fluid from the inner equipment string 110 into the circulation stages 14. 
     At all times during these procedures, the memory gauge/landing assembly 124 records the formation pressure and temperature in the lower wash pipe 140 by means of probe 125. The probe 125 is place in a still location to sense formation pressure without interference from flowing liquid. This memory gauge/landing assembly 124 can be retrieved and re-inserted into the internal bypass subassembly 118 at any time during the procedures. When the memory gauge/landing assembly 124 is retrieved, the data stored therein can be downloaded to a computer system for analysis of downhole conditions. 
     Many modifications and variations may be made in the embodiments described herein and depicted in the accompanying drawings without departing from the concept of the present invention. Accordingly, it is understood that the embodiments described and illustrated herein are illustrative only and are not intended as a limitation upon the scope of this invention.