US3527294A - Underwater exploration and completion system - Google Patents

Description

UNDERWATER EXPLORATION AND COMPLETION SYSTEM Filed 0G12. 24, 19GB Sept. 8, 1970 F. H. weiss ETAL 5 Sheets-Sheet l FIG- l R .J1 T HP H O a TS L Sm N EU M MWC. y HO E n D m Rw n E KVMI A @LA FR Sept 8, 1970 F. H. WEISS r-:TAL 3,527,294

UNDERWATER EXPLORATION AND COMPLETION SYSTEM l' INVENTORS FOLKER H. WEISS RAYMONDG. COURTRIGHTQJR.

Attorney 5 Sheets-Sheet 3 F. H. WEISS ETAL Sept. 8, 1970 UNDERWATER EXPLORATION ND COMPLETION SYSTEM Filed Oct. 24, 1968 Atorney Sept' 8, 1970 F. H. WEISS ETAL. 3,527,294

UNDERWATER EXPLORATION AND COMPLETION SYSTEM Filed Oct. 24, 1968 5 Sheets-Sheet 4g FIG-4 INVENTORS 4FOLKER H. WEISS RAYMOND O. COUR RIGHT; JR. l By Z/ W /Z' Attorney sept. s, 1970 F. H. wr-:lss ETAL 3,527,294

UNDERWATER EXPLORATION AND COMPLETION SYSTEM Filed Oct. 24. 1968 5 Sheets-Sheet 5 FIG-5 INVENTORS FOLKER H. WEI S S RAYMOND O. COURTRIG HT, JR.

United States Patent Office 3,527,294 Patented Sept. 8, 1970 3,527,294 UNDERWATER EXPLORATION AND COMPLETION SYSTEM Folker H. Weiss, Los Altos, and Raymond O. Courtright,

Jr., San Jose, Calif., assiguors to Lockheed Aircraft Corporation, Burbank, Calif.

Filed Oct. 24, 1968, Ser. No. 770,187 Int. Cl. E21b 7/12, 33/035 U.S. Cl. 166--5 5 Claims ABSTRACT F THE DISCLOSURE An atmospheric drill-through capsule arrangement is provided with a small number of blowout preventers and personnel in the capsule are utilized to interchange blowout preventer rams stored in the capsule as various diameter objects are passed into the Well during a wildcat drilling operation. A dual-capsule arrangement is also provided for performing completion and production operations in a single trip from the water surface to the underwater well.

BACKGROUND OF THE INVENTION The present invention relates to underwater equipment, such as oil well equipment for use in underwater locations, and pertains more particularly to a system for performing underwater drilling, completion and production operations.

For many years offshore wells have been drilled either from stationary platforms anchored to the ocean oor, movable barges temporarily positioned on the ocean door, or movable barges floating on the body of water in which drilling operations are being conducted. Regardless of the manner in 'which the wells are drilled, most wells have `been completed in a manner such that the outermost tubular member of the well extends upwardly from the ocean floor to the point above the surface of the body of water where a well assembly or Christmas tree is mounted for controlling the production of the well.

Wellheads extending above the surface of a body of water have the disadvantage that they constitute a hazard to navigation in the vicinity of the well. In addition, when such wellheads are positioned in salt water, such as found in the ocean, the structure extending above the water is subject to the corrosive action of salt water and air. Positioning the wellhead and/or casing head above the surface of the body of water has the advantage, however, that the dow-handling and controlling components of the wellhead may be readily secured thereto and adjusted by an operator working from a platform adjacent to the wellhead structure.

Recently methods and apparatus have been developed for drilling and completing underwater oil and gas wells in a manner such that the drilling and completion operations are carried out on the water floor. In practice, these wellhead assemblies are often positioned in depths of water greater than the depth at which a diver can safely and readily work.

These newer methods of performing underwater drilling and completion operations have presented a number of problems with respect to the use of such components as blowout preventers. For example, if a relatively small number of blowout preventers are positioned at the underwater wellhead then these preventers have to be recovered at the water surface each time a change in ram size is required due to a different diameter of drill pipe or casing, etc. This recovery operation is very time consuming and expensive since it requires pulling the entire marine riser conduit and blowout preventer stack and also capping of the well bore.

In order to avoid frequently pulling the blowout preventers to change the ram sizes therein it has been necessary to provide an extremely large number of blowout preventers which are stacked up one above the other at the wellhead. Such an arrangement has obvious economic drawbacks since many of the blowout preventers are idle during most of the drilling and completion operations. Also, if one of the blowout preventer rams should develop a leak the blowout preventer stack would still have to be recovered at the water surface in order to replace the ram that is leaking.

One of the objects of the present invention is to provide an atmospheric drill-through capsule with a relatively small number of blowout preventers whereby an operator stationed in the capsule may freely install various sizes of blowout preventer rams which are stored inside the capsule.

A further object of the invention is to provide a dual capsule system for performing underwater wall completion and production operations at an underwater wellhead whereby in a single trip to the underwater 'wellhead the well may be completed and placed on production and wherein no unnecessary components remain at the wellhead after it has been placed on production.

Other and further objects and advantages of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by Iway of illustration, show preferred embodiments of the present invention and the principles thereof and what are now considered to be the best modes contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and struetural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal view, partially in section, illustrating certain preliminary operations -which must be performed at an underwater well site prior to initiating a Wildcat drilling operation;

FIG. 2 is a longitudinal view, partially in section, illustrating an atmospheric drill-through capsule which has been lowered into position at an underwater wellhead for performing a Wildcat drilling operation;

FIG. 3 is a longitudinal view, partially in section, illustrating a wellhead cellar which has been lowered into engagement with an underwater wellhead; and

FIGS. 4 and 5 are longitudinal views, partially in section, illustrating the manner in which a dual capsule arrangement is utilized to complete the well and place the well on production, after which one of the capsules and all unnecessary components for producing the well are recovered at the water surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings there is illustrated an exemplary application of the invention in use in a body of water 21. In order to reach the condition depicted in FIG. 1 a template or support base 23 was previously lowered down by guide lines to the water floor 25. The support base 23 is a generally annular structure which is utilized to support various forms of equipment.

In FIG. 1 a rst drilling operation has previously been carried out to establish a rst drilled hole 27 which originally terminated near the bottom of a conductor pipe shown at 29. The purpose of the conductor pipe 29 is to prevent the side walls of the hole 27 from caving in.

It may be necessary to push the conductor pipe down simultaneously with the drilling operation because in some instances the sediments at the Water floor 25 are so unconsolidated that the walls of the hole Will not hold up.

In the operation shown in FIG. 1 the conductor pipe 29 has been lowered down through the central opening of the support base 23 by means of a guide frame shown generally at 31. The guide frame 31 was lowered into the position shown by means of guide lines 33 which extend from the support base 23 to the Water surface 21. A spherical ball element 35 is formed on the lower portion of the guide frame 31 and cooperates with an annular conical side Wall 37 on the support base 23 to insure that the conductor pipe 29 is installed in a vertical position.

After the conductor pipe 29 has been installed in the position shown in FIG. 1 cement 39 is pumped down through a drill string (not shown) out through the bottom of the conductor pipe and upwardly to lill up the annular space between the conductor pipe and the hole 27. The cementing operation serves to consolidate the Whole area around the conductor pipe 29.

After the conductor pipe has been installed and cemented in place a second drilling operation is performed to drill a second hole 41. When the hole 41 has been drilled to the desired depth, for example 700 feet, a guide frame 43 (shown in dashed outline) is utilized to lower surface casing 45 into the hole 41. After suicient surface casing 45 has been run into the hole 41 a pin is pulled from a hinge joint 47 on the guide frame 43 whereby the guide frame breaks away from the surface casing and may be pulled to the Water surface.

A wellhead housing 49 is then lowered on a running string 51 until a tapered shoulder 53 of the wellhead housing moves into rm seating engagement with a tapered Wall 55 formed near the top of the conductor pipe 29. The wellhead housing 49 is a relatively heavy, thick Walled piece of equipment and is used to support casing hangers and casing strings that go into the hole 41 after the surface casing 45 is run and the Well has been drilled to desired depth. The wellhead housing 49 is also utilized to support various other forms of equipment which Will be placed on top of the wellhead.

FIG. 2 illustrates an atmospheric, Wildcat drill-through capsule 60 which has been lowered down onto the top of wellhead housing 49 by means of a guide frame 62. The drill-through capsule 60 is securely and sealably fastened to the upper portion of the wellhead housing 49 by a remotely operated connector 63. The remotely operated connector 63 may comprise a plurality of hydraulically actuated locking dogs or any other suitable form of remotely operated latching means as are Well known in the art.

A similar remotely operated connector device 67 is positioned at the top of the drill-through capsule 60. The connector device 67 communicates a segmented marine riser pipe 69 With a bore 71 which extends longitudinally through the center of the capsule and communicates at its lower end With the wellhead casing 45.

The marine riser casing 69 extends all the way to the Water surface to provide conduit means between a drilling vessel (not shown) and the wellhead housing 49. Flexible joints are provided as at 75 on the marine riser casing 69 to minimize any bending moments which might be imparted to the marine riser due to Wandering movements of the drilling vessel at the Water surface.

A plurality of standard blowout preventers 77 are provided inside the capsule 60. The blowout preventers 77 are provided with typical ram elements 79. Additional dilferent size ram elements may be stored inside the capsule 60 as will be better understood from the preceding description. A shut-off valve 78 in bore 71 is closed in order to isolate the fluid column in the marine riser 69 during exchange of the ram elements 79 in the blowout preventers 77. Such a change of ram elements 4 may become necessary in the course of drilling an oil or gas Well. Means (not shown) are provided in the capsule 60 for operating the ram elements and the shutoff valve 78.

Typical choke and kill lines 81 lead from the blowout preventers to the Water surface. These conduits 81 are used to pump mud or Well fluids into the well during periods when the blowout preventers are closed and it is necessary to pump Well fluids into the hole to kill the Well.

An annular chamber 83 of the capsule 60 surrounds the blowout preventers 77 and is maintained at atmospheric pressure by means of an umbilical conduit -85 Which leads to the water surface. The umbilical conduit 85 also contains all necessary power and fluid lines for carrying out operations inside the capsule 60. Personnel may be transferred to and from the drill-through capsule 60 by means of la smaller transfer capsule 90.

As shown in FIG. 2 a Wildcat drilling opration is performed by lowering a drill string 92 down through the marine riser casing 69, the drill-through capsule 60, wellhead housing 49 and casing 45 into the hole. In order to perform the Wildcat drilling operation the blowout preventers 77 must be supplied with a series of rams 79 which are respectively capable of closing around the drill string 92 or closing off the entire bore 71 if nothing is in the bore. Normally, there are at least two different sizes of drill pipe used for drilling operations which means that there is another set of ram sizes required to close around the second size of drill pipe. In addition, there may be as many as three to four dierent diameter sizes of casings that would have to be run consecutively into the hole and it is therefore necessary to have further different sets of ram sizes in order to accomodate the various casing diameters.

It should be apparent that prior art underwater Wildcat drilling operations were hampered by a number of problems with respect to the blowout preventers. For example, if a relatively small number of blowout preventers Were positioned at the wellhead then these preventers had to be recovered at the Water surface every time a change in ram size was required due to a diiferent diameter of drill pipe or casing. This pulling of the blowout preventers is a very time consuming and expensive operation which requires pulling the entire marine riser and blowout preventer stack and also capping the Well bore to prevent contamination of the drilling fluids.

The only other prior art alternative to frequently pulling the blowout preventers to change the ram sizes therein is to provide an extremely large number of blowout preventers which are stacked up one above the other at the wellhead. Such an arrangement has obvious economic drawbacks since many of the blowout preventers are idle during most of the Wildcat drilling operation. Moreover, should one of the blowout preventer rams develop a leak the blowout preventer stack Would still have to be recovered at the Water surface in order to replace the ram that is leaking.

The atmospheric drill-through capsule 60` of the present invention eliminates the aforementioned problems with respect to providing proper size blowout preventers during a Wildcat drilling operation. The capsule 60 may be provided with a very small number of blowout preventers 77 and an operator stationed in the atmospheric chamber 83 of the capsule 60 may freely install various sizes of rams 79 which are stored inside the capsule 60. Thus, the Wildcat drill-through capsule of the present invention is an extremely valuable contribution to the art of underwater Wildcat drilling. By providing a relatively small number of blowout preventers inside the atmospheric chamber of the drill-through capsule an operator can quickly and easily change ram sizes thereby saving valuable time when compared with previous prior art underwart drilling operations.

If the Wildcat drilling operation is successful an oil and/ or gas bearing formation is penetrated at which time a suitable packer is run down through the marine riser pipe 69 and is set in the casing 45 in the vicinity of the wellhead housing 49. The packer (not shown) is used to block olf the casing so that the drill-through capsule 60 may be recovered at the water surface and other apparatus for performing completion operations may be run down into engagement with the wellhead housing 49.

FIG. 3 illustrates a wellhead cellar 96 which has been lowered down into sealing engagement with the wellhead housing 49. The lowering operation for the wellhead cellar 96 is carried out by latching a running string 98 onto an internal upwardly protruding annular flange 100 which defines a central bore 102 for communicating the cellar 96 with the casing 45. A suitable hydraulically actuated latching mechanism 104 is affixed to the lower end of the running string 98 and may be actuated via a lluid conduit package 103 to lock onto the tlange 100.

The lower portion of the wellhead cellar 96 is provided with an external annular ilange 106 which is also provided with seals and a suitable hydraulically actuated latching means 108 (which may be actuated via conduit package 109) for securely locking the wellhead cellar onto the wellhead housing 49. A guide frame 110` is xedly secured to the external flange 106 of the cellar 96 to insure proper alignment of the cellar 96 with the wellhead housing 49.

During the lowering operation a hatch 112 of the cellar 96 is moved to an open position and an annular stabilizing element 114 is force tted into an opening at the top of the cellar and surrounds the drill string 98 t0 lend stability to the drill string during the loweringoperation. After the wellhead cellar 96 has been lowered down into engagement with the wellhead housing 49 and securely latched thereto by means of the latch means 108 the latch means 104 at the base of the drill string 98 is hydraulically actuated from the surface station to unlatch the drill string from the cellar flange 100. The drill string 98 is then moved upwardly toward the surface station. When the housing of the latch means 104 comes into contact with the stabilizing member 114 the stabilizer is jarred loose from its force t and moves upwardly with the drill string 98 to the water surface.

necting a marine riser pipe 122 to the upper portion 124 of the capsule such as by suitable latching mechanism shown at 126. Other means of lowering, such as a drill pipe running string or a hauldown cable system may also be applied, as can be appreciated by those skilled in the -art. The capsule 120 is provided with guide shoes 128 which tit about guidelines 130 that extend upwardly to the water surface from the permanent guide frame 31 located at the wellhead.

Referring to FIG. in conjunction with FIG. 4, it may be observed that during the lowering operation a valve 132 near the top of the drill-through capsule 120 is closed to shut oit one end of a bore 134 which extends longitudinally through the center of the capsule. In addition, a hatch 136 is closed during the lowering operation and an extension pipe 138 is not connected between a blockout preventer stack 140 and the wellhead cellar flange 100 as shown in FIG. 4, but rather is stored inside the drill-through capsule 120 (see FIG. 5). As in FIG. 2, the main chamber 142 of the drill-through capsule 120 is maintained at atmospheric pressure by means of an umbilical conduit 144 which also carries all necessary power and fluid lines to the capsule. In addition, choke and kill lines 145 lead from the blowout preventers to the water surface.

As the drill-through capsule 120 comes into contact with the wellhead cellar 96 a uidtight seal is established at 148. At this time the interior chamber 150 of the wellhead cellar as well as the chamber area shown at,152 are placed at atmospheric presure by a procedure which is described in detail in assignees copending application for Sealing System for Underwater Installation by Sydney S. Helmus, Ser. No. 760,807, filed Sept- 19, 1968, and now U.S. Pat. No. 3,485,056.

After the seal at 148 has been made the hatches 136 and 112 are opened by an operator who descends from the chamber 142 of the drill-through capsule 120. The operator then connects the extensible pipe section 138 to an annular flange 158 formed at the base of the blowout preventer stack 140.

At this juncture it should be noted that the top portion of the blowout preventer stack 140 is provided with a tubular shaped extension 160. The extension 160 is telescopically tted inside a tubular element 162 which protrudes downwardly from the top of the capsule 120. This telescopic joint which is denoted generally at 164 may be actuated by hydraulic or mechanical means (not shown) to longitudinally extend the blowout preventer stack 140 toward and away from the flange 100 formed near the base of the wellhead cellar 96. Thus, after the workmen in the drill-through completion capsule have connected the extension pipe 138 to the ange 158 at the base of the blowout preventers the telescopic joint l164 may be actuated to move a latchinug element 168 at the base of extension pipe 138 into locked engagement with the cellar flange After the extension 138 has been connected as shown in FIG. 4 the valve 132 at the top of the completion capsule 132 is opened and a drill string 170 is lowered down through the blowout preventer stack and on through the wellhead cellar 96 into the well itself to perform drilling and completion operations. The drillthrough completion capsule 120 has all of the advantages of the Wildcat drill-through capsule 60 referred to in FIG. 2. In other words a relatively small number of blowout preventers may be used since the blowout preventer rams 172 may be easily changed by an operator in the atmospheric environment of the chamber 1.42. During the completion operations production tubing is run into the well bore and is suspended in the wellhead housing on a hanger in the conventional manner. The extension 138 is removed after the shutoff valve 132 has been closed and production equipment is installed in the wellhead cellar 96.

Referring to FIG. 5 it will be observed that the operators have closed valve 132, disconnected extension conduit 138 and installed a standard production Christmas tree 175 inside the atmospheric chamber 150 of the Wellhead cellar 96. The Christmas tree components 4may have been stored in either the capsule 120 or the wellhead cellar 96 prior to installation. The Christmas tree 175 is provided with the usual master valves and wing connections for the delivery of petroleum products. These petroleum products may then be owed to a surface station or underwater gathering station by means of ow lines 177 which pass through a fluid tight guide mouth 179 formed in the wall of the cellar 96.

After the well has been placed on production as shown in FIG. 5 and while the completion capsule 120 is still in sealed engagement with the wellhead cellar 96 as shown in FIG. 4 the operators leave the wellhead cellar 96 and close the hatch 112. This maintains the interior chamber of the wellhead cellar 96 under atmospheric conditions and prevents sea water and marine life from fouling the Christmas tree which may from time to time require repair or other workover operations.

The operators then enter the atmospheric chamber 142 of the completion capsule 120 and securely close the hatch 136. It should also be observed that the valve 132 near the top portion of the completion capsule 120 has been previously moved to a closed position to further insure the atmospheric integrity of the chamber 142.

The personnel inside the completion capsule 120 may now be transported back to the water surface by means of a smaller transfer capsule 181. On the other hand, the smaller transfer capsule 181 may be utilized merely as a safety device should a dangerous condition develop in the atmospheric chamber 142 of the completion capsule 120. The completion capsule 120 may now be recovered at the water surface by retrieving a running tool 183 which has been attached to the upper portion of the capsule. Suitable buoys may be attached to the cable guide lines extending upwardly from underwater wellhead to relocate the wellhead should re-entry be required for purposes of repair or workover operations.

It should be apparent from the description relative to FIGS. 4 and 5 that applicants have provided a novel dual capsule arrangement (96 and 120) for achieving both the operations of completing an underwater well and placing the completed Iwell on production. The novel arrangement permits the performance of these operations in a single trip to the underwater well site and utilizes considerably less equipment than prior art systems since an atmospheric environment is provided for personnel at the underwater installation. In addition, after the completion and production operations have been completed the completion equipment, including blowout preventers, may be recovered thereby leaving only production components (Christmas tree and flowlines) at the underwater wellhead.

While we have illustrated and described preferred embodiments of our invention, it is to be understood that these are capable of variation and modification, and we therefore do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

What is claimed is:

1. An underwater Wildcat drilling system for drilling an exploratory well wherein a plurality of different size blowout preventer rams are required to accommodate various sizes of drill pipe and casing pipe, the improvement comprising:

(a) establishing an underwater wellhead housing on the water floor;

(b) lowering a drill-through capsule into aligned and sealed relation with said wellhead housing, said capsule having an atmospheric chamber for human personnel surrounding a walled bore extending longitudinally through said capsule, and said capsule bore having a plurality of blowout preventers associated therewith;

(c) storing a plurality of different size blowout preventer rams in said atmospheric chamber to accommodate varying diameter objects that may be passed through said bore;

(d) performing a Wildcat drilling operation from a surface vessel down through said bore of the drillthrough capsule; and

(e) utilizing human personnel in -said atmospheric chamber to interchange the blowout preventer rams stored in said chamber as different diameter drilling and casing components are passed through said capsule bore.

2, A system for performing well completion operations at an underwater well which has lbeen successfully drilled in accordance with the improved system of claim 1 comprising:

(a) recovering said wildcat drill-through capsule at the Water surface;

(b) lowering a wellhead cellar into sealed fluid-tight relation with said wellhead housing, said cellar having walls defining a main chamber provided with a first opening at its lower end for communicating With an opening in said wellhead housing leading to the drilled Well, and a second opening near the top of said cellar chamber to provide a passageway for personnel and equipment;

(c) lowering a drill-through capsule into aligned and sealed relation with said wellhead cellar, said capsule having an atmospheric chamber for human personnel and a bore formed in said capsule having a plurality of blowout preventers associated therewith;

(d) a closeable hatch opening at the lower end of said capsule for passing personnel and equipment between the drill-through capsule and said cellar;

(e) establishing atmospheric conditions in said wellhead cellar chamber;

(f) opening said drill-through capsule hatch to communicate the atmospheric capsule chamber with the atmospheric cellar chamber;

(g) establishing a fluidtight conduit connection between the drill-through capsule bore and the first opening of said wellhead cellar;

(h) performing well completion operations through the bore of said drill-through capsule and utilizing personnel in said capsule to change blowout preventer rams as different diameter components are passed through capsule bore to complete the well.

3. A system for performing 4well production operations at an underwater well which has been successfully drilled and completed in accordance with the improved system of claim 2 comprising:

(a) removing the fluidtight conduit connection between the drill-through capsule bore and the first opening of said wellhead cellar;

(b) installing a production Christmas tree at the rst opening of said wellhead cellar and placing the well on production; l

(c) closing off the second opening of the cellar to preserve atmospheric conditions inside the cellar;

(d) closing the hatch opening at the lower end of said drill-through capsule; and

(e) recovering the drill-through capsule at the water surface.

4. A system for performing well completion operations at an underwater wellhead situated on the water floor comprising:

(a) lowering a wellhead cellar into sealed fluidtight relation with a wellhead housing, said cellar havmg walls defining a main chamber provided with a first opening at its lower end for communicating -with an opening in said wellhead housing leading to the drilled well, and a second opening near the top of said cellar chamber to provide a passageway for personnel and equipment;

(b) lowering a drill-through capsule into aligned and sealed relation with said wellhead cellar, said capsule having an atmospheric chamber for human personnel and a bore formed in said capsule having a plurality of blowout preventers associated therewith;

(c) a closeable hatch opening at the lower end of said capsule for passing personnel and equipment between the drill-through capsule and -said cellar;

(d) establishing atmospheric conditions in said wellhead cellar chamber;

(e) opening said drill-through capsule hatch to communicate the atmospheric capsule chamber with the atmospheric cellar chamber;

(f) establishing a fiuidtight conduit connection between the drill-through capsule bore and the first opening of said wellhead cellar;

(g) performing well completion operations through the bore of said drill-through capsule and utilizing personnel in said capsule to change blowout preventer rams as different diameter components are passed through capsule bore to complete the well.

5. A system for performing production operations at an underwater wellhead which has been successfully com- 9 10 pleted in accordance with the system of claim 4 com- References Cited Pfinf: th .df ht d .tconnectbn between UNITED STATES PATENTS a removmg e u1 1g con u1 1 the dri1l-through capsule bore and the first opening 2783970 3/1957 Gluesple 166-'5 of Said Weuhead Cellar; 3,032,106 5/1962 FfJChE et al 166e. (b) installing a production Christmas tree at the first 5 lggm lgs/i9 O Neill etlal' T- 1661-6-65 opening of said wellhead cellar and placing the 3 17 9 Watt et a' Well on production; 3,353,364 1l/l967 Blandlng et al 166-.5 X (c) closing olf the second opening of the cellar to pre- 3391734 7/1968 Townsend 166""'5 serve atmospheric conditions inside the cellar; 10 MARVIN A. CHAMPION, Primary Examiner (d) closing the hatch opening at the lower end of said R. E' FAVREAU Assistant Examiner dull-through capsule; and

(e) recovering the drill-through capsule at the Water U.S. Cl. X.R.

surface. 175--7

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