Vacuum Tank for use in handling oil and gas well cuttings

Abstract: A vacuum tank apparatus (10) for use with oil and gas well drilling operations facilitates the removal of well cuttings generated by drilling. The tank apparatus (10) provides a frame (11) having a plurality of corners reinforced by structural corner columns (32). The columns (32) are connected at the base of the frame (11) to lower perimeter beams (31) as at the top of the frame (11) to upper perimeter beams (33). A shaped hopper (35) is supported by the frame (11) internally of the perimeter beams (31,32,33). The hopper (35) includes an interior (38) and a sidewall (12,13,14,15) comprised of a plurality of inclined wall sections. Each wall section includes an upper end portion that connects to the frame (11) at the perimeter beams (33) and a lower end portion that extends to the lower end portion of another inclined wall section. An outlet header (50) is provided at the bottom of the hopper (35) next to the lower end portions of the inclined wall sections. The outlet header (50) includes a discharge outlet (59) for discharging solid material from the hopper interior (38). The outlet header (50) also includes an inlet fitting (52) for injecting pressurised air into the outlet header (50) while emptying the tank. A top wall (16) of the hopper (35) has multiple hatches (17,18) that enable material to be added to the tank interior (38) during use, such as, for example by employing a pair of suction lines (75,76) that are connected to a single plate (72) covering one of the outlets (36,37) in the tank top (16) or a pair of suction lines that are mounted respectively to the pair of inlet openings. To be accompanied, when published, by Figure 1 of the drawings.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to oil and gas well drilling and more particularly to the handling of cuttings that are generated during oil and gas well drilling activity. Even more particularly, the present invention relates to an improved vacuum tank apparatus for use in handling cuttings that are generated during oil and gas well exploration. The tank has a specially configured hopper that communicates with an outlet header that enables air to be injected during the discharge of cuttings from the tank. 2. General Background of the Invention In the drilling of oil and gas wells, a drill bit is used to dig many thousands of feet into the earth's crust. Oil rigs typically employ a derrick that extends above the well drilling platform and which can support joint after joint of drill pipe connected end to end during the drilling operation. As the drill bit is pushed farther and farther into the earth, additional pipe joints are added to the ever lengthening "string" or "drill string". The drill pipe or drill string thus comprises a plurality of joints of pipe, each of which has an internal, longitudinally extending bore for carrying fluid drilling mud from the well drilling platform through the drill string and to a drill bit supported at the lower or distal end of the drill string. Drilling mud lubricates the drill bit and carries away well cuttings generated by the drill bit as it digs deeper. The cuttings are carried in a return flow stream of drilling mud through the well annulus and back to the well drilling platform at the earth's surface. When the drilling mud reaches the surface, it is contaminated with small pieces of shale and rock which are known in the industry as well cuttings or drill cuttings. Well cuttings have in the past been separated from the reusable drilling mud with commercially available separators that are know as "shale shakers". Other solids separators include mud cleaners and centrifuge. Some shale shakers are designed to filter coarse material from the drilling mud while other shale shakers are designed to remove finer particles from the well drilling mud. After separating well cuttings therefrom, the drilling mud is returned to a mud pit where it can be supplemented and/or treated prior to transmission back into the well bore via the drill string and to the drill bit to repeat the process. The disposal of the separated shale and cuttings is a complex environmental problem. Drill cuttings contain not only the mud product which would contaminate the surrounding environment, but also can contain oil that is particularly hazardous to the environment, especially when drilling in a marine environment. In the Gulf of Mexico for example, there are hundreds of drilling platforms that drill for oil and gas by drilling into the subsea floor. These drilling platforms can be in many hundreds of feet of water. In such a marine environment, the water is typically crystal clear and filled with marine life that cannot tolerate the disposal of drill cuttings waste such as that containing a combination of shale, drilling mud, oil, and the like. Therefore, there is a need for a simple, yet workable solution to the problem of disposing of oil and gas well cuttings in an offshore marine environment and in other fragile environments where oil and gas well drilling occurs. Traditional methods of cuttings disposal have been dumping, bucket transport, cumbersome conveyor belts, screw conveyors, and washing techniques that require large amounts of water. Adding water creates additional problems of added volume and bulk, messiness, and transport problems. Installing conveyors requires major modification to the rig area and involves many installation hours and very high cost. Safeguard Disposal Systems, Inc. of Lafayette, Louisiana has manufactured, sold, and used publicly a cuttings disposal tank that includes hatch openings into which oil well cuttings can be placed. These prior art tanks also have attachments for enabling lift lines to be affixed to the tank so that it can be transported to and from offshore platforms and emptied when full. Further examples of these tanks are shown in one or more of the following United States Patents: 5,564,509; 5,402,857; Des. 337,809; and Des. 296,027. U.S. Patents 5,564,509 and 5,402,857 are incorporated herein by reference. WO 98/16717 discloses a vacuum tank apparatus comprising a shaped hopper, the hopper including an interior and a side wall comprised of a plurality of inclined wall sections, each wall section including an upper end portion and a lower end portion that extends to another lower end portion of another inclined wall section, an outlet header at the bottom of the hopper next to the lower end portions of the inclined wall sections and including a discharge outlet for discharging material from the hopper interior and a top wall of the hopper having a first hatch. GB 2 064 979 discloses a dust extraction system comprising hood collectors, a blower which produces an air flow which carries dust from the hoods through conduits to a common manifold. Dust is removed from the manifold by a conveyor which carries the dust to a central hopper. WO 95/18705 discloses a method of mixing drilling fluids at a drill site that includes the transportation of sealed silo assemblies that contain dry products in bulk to the well drilling site. The dry products are maintained within the silo assemblies in a dry and pressurised condition. BRIEF SUMMARY OF THE INVENTION An aspect of the invention provides a vacuum tank apparatus, comprising: a) a frame having a plurality of base perimeter beams, a plurality of upper perimeter beams, and a plurality of corners reinforced by structural corner columns connected structurally to said base perimeter beams and said upper perimeter beams; and b) a hopper supported by the frame internally of the perimeter beams, the hopper having an interior and at least a pair of inclined sidewalls having upper end portions connected to the frame at the upper perimeter beams and lower end portions that approach one another near the lower end of the frame; c) an outlet header at the bottom of the hopper next to the lower end portions of the inclined sidewalls and including a discharge outlet for discharging material from the hopper interior wherein the outlet header includes opposed open end portions and an inlet and an outlet, the inlet having a fitting for attaching a source of pressurized air thereto, the outlet having a fitting for attaching a suction line thereto; and d) a top wall of the hopper having a plurality of openings and a plurality of hatches for closing the openings. The present invention provides an improved vacuum tank apparatus that can be used to vacuum drill cuttings on an oil and gas well drilling rig through an open top hatch portion of the apparatus and then to discharge those cuttings through an outlet header using suction applied to the outlet header as well as compressed injected air that is transmitted to the outlet header. A shaped hopper is supported by the frame internally of the perimeter beams. The hopper includes and interior and sidewalls that are comprised of a plurality of inclined sidewall sections, each inclined wall section including an upper end portion that connects to the frame at the perimeter beams and a lower end portion that extends to another lower end portion of another inclined wall section. The two lower end portions of the inclined wall sections that are joined meet at an outlet header at the bottom of the hopper. This outlet header is mated to the lower end portions of the inclined wall sections and includes a discharge outlet for discharging material from the hopper interior via the outlet header. The top wall of the hopper has multiple hatches including a first hatch near a first perimeter beam and a second hatch next to another perimeter beam that is parallel to the first perimeter beam. The outlet header includes opposed open end portions that are fittings for directing fluid flow. One of the end portions is an air inlet for injecting air into the outlet header. The other end portion of the outlet header defines a fitting for connecting a suction line thereto. A secondary air fitting for enhanced cleanout and material transfer can be provided at the discharge fitting. These two fittings enable material to be quickly discharged from the hopper even if it is very solid in nature such as granular cuttings that are the subject of oil and gas well drilling. These cuttings can be quickly discharged from the tank through the outlet header by injecting air into the outlet header at the first end portion of the outlet header and by suctioning the cuttings from the opposing end portion of the outlet header. The outlet header thus preferably comprises a longitudinally extended trough portion with an open top that communicates with the interior of the hopper. A pair of opposed end portions of the trough have fittings for attaching flow lines to the outlet header. The outlet header thus defines a closed structure with the lower end portion of the hopper and the fittings so that a vacuum can be held on the tank when the outlet header is not being used. The outlet header preferably provides valves at each end portion next to the two fittings so that the flow of air into the outlet header can be valved. Additionally, the discharge of solid material from the outlet header can also be valved. The apparatus of the present invention eliminates the dangerous and messy practices of lifting and/or tipping the tank frame on an oil rig in order to empty the tank contents. The inclined walls of the hopper remove any need to tip or lift the tank during emptying. The hopper is configured to completely empty of material using a vacuum and without tipping or lifting thus eliminating a crane or cranes. This also removes safety concerns involved with lifting or tipping such as spilling and pollution. Existing tanks must be lifted and tilted which requires dual block heavy lifting cranes since they can weigh over ten tons when loaded. This enables the apparatus of the present invention to be emptied at a location where there are no cranes. Several of such tanks can be transported from several oil rigs to a central processing location. This is valuable because drilling rigs are typically very crowded. Use of a lifting crane in such a crowded environment for dumping. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational view of the preferred embodiment of the apparatus of the present invention; Figure 2 is a sectional view taken along lines 2-2 of Figure 1; Figure 3 is a top view of the preferred embodiment of the apparatus of the present invention taken along lines 3-3 of Figure 1; Figure 4 is a sectional elevational view of the preferred embodiment of the apparatus of the present invention taken along lines 4-4 of Figure 1; Figure 5 is a fragmentary view of the preferred embodiment of the apparatus of the present invention illustrating the outlet header portion thereof, taken along lines 5-5 of Figure 1; Figure 6 is a sectional view taken along lines 6-6 of Figure 3; Figure 7 is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention showing the hatch and opening in an open position so that vacuum hoses can be attached; Figure 8 is a fragmentary elevational sectional view of the preferred embodiment of the apparatus of the present invention illustrating the compressed air inlet portion thereof; Figure 9 is a fragmentary sectional elevational view of the preferred embodiment of the apparatus of the present invention showing the discharge piping for removing material from the tank; and Figure 10 is a fragmentary sectional view showing an enlarged portion of the discharge piping for removing material from the tank. For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: DETAILED DESCRIPTION OF THE INVENTION Figures 1-4 show the preferred embodiment of the apparatus of the present invention designated generally by the numeral 10 in Figures 1-4. Vacuum tank apparatus 10 is supported by a structural frame 11. The frame 11 holds a hopper 35 that is comprised of a plurality of hopper walls 12,13,14,15. A vibrator motor 80 can be affixed to one or more of the walls 12-15 to enhance setting of material within hopper 35 interior 38. The hopper 35 also includes a top plate 16 that carries a large hatch 17 and a small hatch 18. Each of the hatches 17, 18 respectively covers large opening 36 and small opening 37 respectively. Large hatch 17 is preferably used to dump material from the interior 38 of hopper 35 if desired. Top plate 16 that seals the hopper 35 at its upper end portion so that a vacuum can be pulled on the interior 38 of hopper 35. An outlet fitting 19 carries rupture disk 20. The outlet fitting 19 can include a pair of spaced apart flanges 21, 22 as shown in Figure 7. Fitting 19 is mounted on tank outlet opening 23. An additional fitting is provided at elbow 24 that communicates with opening 26 in top plate 16. The elbow 24 carries a ball valve 25 that can be opened and closed. When hopper 35 is subjected to a vacuum, rupture disk 20 prevent tank rupture. Each of the hatches 17, 18 is mounted to the top plate 16 using hinges 27, 28 respectively. A closure 29, 30 can be respectively provided for each hatch 17, 18 in the form of a cammed rod such as the rods 39, 40 shown in Figure 3. Alternatively, ring nuts and bolts can be used to close hatches 17, 18. Frame 11 is comprised of a plurality of base beams 31, column beams 32 and upper perimeter beams 33 as shown in Figures 1-4. These respective beams 31, 33, and column 32 form a rectangular block-like enclosure that protects hopper 35 during transportation. The base perimeter beams 31 can additionally be provided with plate for decking if desired. Left and right sockets 41, 42 define receptacles for fork lift tines at each perimeter beam 31 so that the apparatus 10 of the present invention can be lifted and transported using a fork lift if desired. Each of the column beams 32 occupies a corner of the frame 11 as shown in Figure 1-4. Each column beam 32 provides a stacking pin 34 at its upper end portion as showing in Figures 1-4 and 7. A correspondingly shaped socket under each column 32 at a perimeter beam 31 receives a stacking pin 34 when one tank apparatus 10 is stacked upon another tank 10. Lifting eyes 79 and slings can be attached to tank apparatus 10 for enabling a crane to lift the apparatus 10 during transfer to and from the drilling rig. The frame 11 can also includes additional intermediate horizontal beams 43 and vertical beams 44 that define an interface in between selected ones of the base beams 31, column beams 32 and upper perimeter beams 33. The intermediate perimeter beams 43 are generally parallel to and below upper perimeter beams 33. Each intermediate beam 43 connects to and spans between two columns 32 as shown in Figures 1,2 and 4. Of the plurality of hopper walls 12, 13, 14, 15, at least two of these walls 12, 13 (and preferably all four walls 12-15) converge to form a connection with outlet header 50. Stiffners 77 can be welded to the walls 12, 13, 14, 15 for strengthening them. The walls 12, 13, 14, 15 each include inclined sections in between beams 31 and 43. The hopper 35 is thus shaped to enable complete emptying and discharge of drill cuttings and like material using a source of vacuum and without having to tip or lift the tank. The present invention eliminates the need for manual labor to shovel or scrape material to header 50. Each of the walls 12, 13, 14, 15 has a vertical section between beams 43 and 32. Outlet header 50 is shaped to facilitate discharge of material contained in hopper 35, shown in figures 1, 2, 4, 5, 8, 9, and 10. The outlet header includes a channel section 46 that is connected to the lower edge 47 of wall 12 of hopper 35 and to the lower edge 48 of wall 13 of hopper 35 as shown particularly in figures 4 and 5. The channel section provides a U - shaped trough in transverse cross section. The upper edges 49, 51 of channel section 49 are connected (e.g. welded) to the lower edges 47, 48 of sides 12, 13 of hopper 35. At wall 15 of hopper 35, an inlet fitting 52 is provided for injecting air under pressure. The fitting 52 can be a cylindrically shaped member having a central longitudinal bore with a central longitudinal axis that aligns with the central longitudinal axis 54 of channel section 49. Valve 55 can be positioned on the inlet 56 side of fitting 52 for closing the flow via fitting 52 to channel section 49. Upstream of valve 55 is a quick connect member that enables an air hose to quickly be connected to the assembly of fitting 52, valve 55 and quick connect member 57. In this fashion compressed pressurized air can be injected into header 50 for assisting in the movement of material that flows by gravity from hopper interior 38 to a discharge hose 81 and then to a second vessel 82. Such a second vessel 82 can be a cuttings collection and disposal tank such as shown and described in my prior U.S. Patent Nos. 5,564,509 and 5,402,857. This flow of pressurized air and material is indicated by arrows 58 in figures 1 and 8-10. The outlet or discharge side of outlet header is shown in figures 1, 2, and 9. An outlet fitting 59 is attached to the interface of wall 14 and channel member 49. The outlet fitting 59 can include a pair of pipe sections 60, 61 that form an angle of about 45 degrees as shown in figure 9. A cleanout plug 62 can be provided on fitting 59. In figure 9, a valve such 63 as a ball valve or butterfly valve can be provided for closing the flow of material from channel section 49 to the exterior of hopper 35 when the hopper is subjected to a vacuum. Valve 63 can be mounted between flanges 64, 65. A spool piece 66 with an open ended bore 70 can be fitted to flange 65 for transmitting material from hopper interior 38 via fitting 59 to a suction hose line 78. Fitting 71 on spool piece 66 can be used to couple an air line to the spool piece 66 as an additional means of moving material into discharge line 80 that is being removed from hopper 35 via outlet header 50. The spool piece comprises larger diameter section 67, transition section 68 and smaller diameter section 69. When the tank apparatus 10 is to be used as a vacuum tank for collecting cuttings as part of a system for collecting oil and gas well drill cuttings, the outlet header 50 is closed by shutting valves 55 and 63. Drill cuttings can then be suctioned into the interior 38 of hopper 35 via one of the openings 36, 37 in top plate 16. This can be accomplished for example using a plate 72 attached to a selected opening 36 or 37 in the top plate of hopper 35 as shown in figure 7. Plate 72 has fittings 73, 74 for quick coupling and connecting respective inlet and outlet hoses 75, 76 to plate 72 when the hopper 35 is to be subjected to a vacuum. The inlet hose 75 is a suction hose for intake of drill cuttings. The discharge hose 76 connects to a vacuum source. Such a vacuum arrangement for vacuum of drill cuttings to a collection tank is shown and described in my prior U.S. patents 5,402,857 and 5,564,509 each of which is hereby incorporated herein by reference. In use of the tank apparatus 10, drill cuttings (not shown) are delivered to a cuttings receiving area (not shown) after having been separated from the well drilling fluid to enable the fluid to be recycled. An intake portion (not shown) of the inlet hose 75 is arranged at the receiving area to suction the drill cuttings and deliver them to the hopper 35 when a vacuum is created in the hopper 35, for example by connecting the outlet hose 76 to a vacuum source such as a blower with the air inlet valve 52 and cuttings outlet valve 59 closed. Liquids and solids may be prevented from entering the blower or similar power source by positioning a separating vessel in at least one of the vacuum lines, for example outlet hose 76. In this embodiment, the flow velocity in the suction line 75 is in the range 100 to 300 feet per second with a vacuum of between about 16 to 25 inches of mercury. These are examples of typical values of the flow and vacuum and it will be understood that these are subject to variation according to the requirements for optimum performance of the invention in a given application. The cuttings are discharged from the hopper 35 and transferred to vessel 82 via line 81 when the outlet valve 59 is opened. To assist transfer, the air inlet valve 52 may be opened to connect a source of pressurised air to the upstream end of the manifold 50. In this way, the cuttings are displaced towards the downstream end of the manifold 50 where the outlet valve 59 is connected. Alternatively, or additionally, discharge of cuttings from the hopper 35 may be assisted by suction in the line 81 by connecting an air line to the spool piece 66. As will now be appreciated, the present invention provides apparatus and method for use in handling cuttings generated during drilling operations that avoids or reduces the problems associated with the prior art. It will be understood, however, that the foregoing embodiments are presented by way of example only and that the scope of the invention is to be limited only by the following claims. The following table lists the parts numbers and parts descriptions as used herein and in the drawings attached hereto. PARTS LIST PART NUMBER DESCRIPTION 10 vacuum tank 11 frame 12 hopper wall 13 hopper wall 14 hopper wall 15 hopper wall 16 top plate 17 large hatch 18 small hatch 19 outlet fitting 20 rupture disk 21 flange 22 flange 23 outlet opening 24 elbow 25 ball valve 26 tank outlet opening 27 hatch hinge 28 hatch hinge 29 closure 30 closure 31 base beam 32 column beam 33 upper perimeter beam 34 stacking pin 35 hopper 36 opening 37 opening 38 interior 39 rod 40 rod 41 socket 42 socket 43 horizontal beams 44 vertical beams 45 vertical beams 46 channel section 47 lower edge 48 lower edge 49 upper edge 50 outlet header 51 upper edge 52 inlet fitting 53 central longitudinal axis 54 central longitudinal axis 55 valve 56 inlet side 57 quick connect member 58 arrow 59 outlet fitting 60 pipe section 61 pipe section 62 cleanout plug 63 valve 64 flange 65 flange 66 spool piece 67 larger diameter 68 transition section 69 smaller diameter section 70 bore 71 plug 72 plate 73 fitting 74 fitting 75 inlet hose 76 discharge hose 77 stiffners 78 suction hose 79 lifting eyes 80 vibrating motion 81 discharge 82 second vessel

Claims: A vacuum tank apparatus (10), comprising: a) a frame (11) having a plurality of base perimeter beams (31), a plurality of upper perimeter beams (33), and a plurality of corners reinforced by structural corner columns (32) connected structurally to said base perimeter beams (31) and said upper perimeter beams (33); and b) a hopper (35) supported by the frame (11) internally of the perimeter beams (31,33), the hopper (35) having an interior (38) and at least a pair of inclined sidewalls (12,13) having upper end portions connected to the frame (11) at the upper perimeter beams (33) and lower end portions (47,48) that approach one another near the lower end of the frame (11); c) an outlet header (50) at the bottom of the hopper (35) next to the lower end portions (47,48) of the inclined sidewalls (12,13) and including a discharge outlet for discharging material from the hopper interior (38) wherein the outlet header (50) includes opposed open end portions and an inlet and an outlet, the inlet having a fitting (52) for attaching a source of pressurized air thereto, the outlet having a fitting (59) for attaching a suction line thereto. d) a top wall of the hopper having a plurality of openings and a plurality of hatches for closing the openings. The tank apparatus of claim 1 wherein the lower end portions (47,48) of the inclined sidewalls (12,13) are joined to respective side portions (49,51) of the outlet header (50). The tank apparatus of any preceding claim wherein the outlet header (50) has an open top that communicates with the hopper interior (38). The tank apparatus of claim 1, wherein the outlet header (50) comprises: a) a longitudinally extended trough portion (46) with an open top having a generally U-shaped transverse cross section; b) a pair of opposed end portions of the trough (46) having the fittings (52,59) for attaching flow lines to the outlet header (50); and c) a closed structure being defined by the fittings (52,59), connected hoses, trough (46), and the lower end portions (47,48) of the inclined sidewalls (12,13). The tank apparatus of claim 1 wherein the hopper (35) is a closed structure capable of holding a vacuum. The tank apparatus of any preceding claim, wherein the frame (11) includes a plurality of stacking pins (34) on the upper perimeter beams (33) and a plurality of sockets at the base perimeter beams (31) for enabling one of said tanks (10) to be stacked upon another of said tanks (10) by fitting the stacking pins (34) of one tank (10) to the sockets of another tank (10). The tank apparatus of any preceding claim, further comprising a source of pressurized air for injecting air into the inlet (52) of the outlet header (50). The tank apparatus of any preceding claim, further comprising a vacuum source for pulling a vacuum on the hopper (35) at the outlet (59) of the outlet header (50). A method of removing drill cuttings from an oil and gas well platform that uses a drill bit supported with a drill string and a well drilling fluid during a digging of a well bore, comprising the steps of: a) separating drill cuttings from the well drilling fluid on the drilling platform so that the drilling fluids can be recycled into the well bore during drilling operations; b) transmitting the separated drill cuttings to a cuttings receiving area; c) suctioning the separated drill cuttings with a first vacuum line having an intake end portion that can be positioned at the cuttings receiving area; d) transmitting the drill cuttings via the suction line to a vessel (10) comprising the vacuum tank apparatus according to claim 1 that has a solid material outlet valve (63) that can disallow flow of solid material from the vessel (10) when a vacuum is present in the vessel interior (38); and e) forming a vacuum within the vessel interior (38) with a vacuum source that is in fluid communication with the vessel interior (38) via a second vacuum line; and f) separating liquids and solids from at least one of the vacuum lines before said liquids and solids can enter the vacuum source; and g) emptying the vessel (10) of drill cuttings by discharging the cuttings through the solid material outlet valve (63) via the outlet header (50) from the vessel interior (38), wherein the vessel (10) has an air inlet valve (55) for connecting a source of pressurized air to the outlet header (50) inlet to assist the discharge of solid material from the vessel (10). The method of claim 9, wherein the drill cuttings are discharged to a second vessel from the outlet header (50). The method of claim 9 or claim 10 wherein the flow velocity in the first vacuum line is about 30.5 to 91.5 m/s (100-300 feet per second). The method of any one of claims 9 to 11, further comprising the step of injecting air into the outlet header (50). The method of any one of claims 9 to 12, wherein the vacuum formed within the tank (10) in step "e" is between about 54 to 85 Pa (16-25 inches of mercury). The method of any one of claims 9 to 13 wherein both fittings(52, 59) of the outlet header (50) are valved. The method of any one of claims 9 to 14 further comprising valves (55,63) on both of the outlet header (50) fittings (52, 59) for closing the outlet header (50) when the tank is closed. The method of any one of claims 9 to 15 further comprising the step of positioning a separator vessel in between the vacuum source and the first vessel (10) in the second vacuum line.

Inventors: DIETZEN GARY H, DIETZEN, GARY H.
Applicants: MI LLC, M-I L.L.C.
Application year: 1999
Main classification: E21B21
IPC codes: B63B25, E21B41, E21B21, B63B35