US2659209A - Underground liquid storage facility and the method of selecting and preparing the same - Google Patents

Description

Nov. 1 7, 1953 R. v. PHELPs 2,659,209 UNDERGROUND LIQUID STORAGE FACILITY AND THE METHOD OF SELECTING AND PREPARING THE SAME Filed March 25, 1951 Safz marly I saZe. aan q I 9 Sanaone.

l Zou-12s. Gmyzmy By l NOV. 17, 1953 R v PHELPS 2,659,209

UNDERGROUND LIQUID STORAGE FACILITY AND THE METHOD OF SELECTING AND PREPARING THE SAME Filed March 23, 1951 5 Sheets-Sheet 2 Nov. 17, 1953 v PHELPs 2,659,209

"R. UNDERGROUND LIQUID STORAGE FACILITY AND THE METHOD OF SELECTING AND PREPARING THE SAME Filed March 25, 1951 3 Sheets-Sheet 5 Ji' e z FJD/z 605, 5y

mm1/4A 77K Patentecl Nov. 17, 1953 UNITED `STATES Rex Victor Phelps, Tulsa, Okla., assignor to Warren Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Application March 23, 1951, Serial No. 217,211

13 Claims.

My invention consists in new`and useful im-V provements in underground liquid storage facili ties and the method of selecting and preparing the same, and although it may be used for any liquid products, it has been primarily designed for use in connection with such products as liquied petroleum gas and the like.

It has been generally customary ,in the past to store liquified petroleum gas in steel storage tanks and containers located above ground which has not only entailed considerable expense in construction and maintenance, but has been attended by fire hazard and danger to. personnel and property because of exposed equipment. Furthermore, the shortage of steel from time to time has created a deniteproblemboth in construction and maintenance of above ground ster-- age equipment.

Although some efforts have been made to the end of underground storage facilities, most of those with which I am familiar have not been practical because ofk the expense involved in lining underground caverns with metal or concrete Walls, and the cost of the type of equipment used.

It is therefore the object of the present invention to provide underground liquid storage facilities designed to take advantage of certain geological formations inherent in the earth which render unnecessary the lining of the storage cavern and make it possible to operate the same with a f minimum of installation and maintenance costs.

Another object ofthe invention, is to provide underground liquid storage `facilities wherein the only equipment exposed above ground is the con,- trol dome, thereby. not only minimizing fire haaards but insuring to a large extent against damopen'shaft drilled in a typical geological forma@ e tion suitable for use inV constructing my improved storage facility. i A r Figure-2 is a similar view on an 'enlarged scale, showingthe casingandfconduits installed in the shaft.' f i Figure 3 is a sectional view showing the above ground control dome.

Figure 4 is a sectional view taken online of Figure 3.

Figure 5 is a diagrammatic illustration of a vertical, longitudinal section of a typical shaft and storage cavern.

Figures 6 to 8, inclusive, are illustrations of various wall profiles which may be used for stor age caverns, and

Figure 9 isa diagrammatic illustration of.

method of providing a plurality of storage caverna L the storage of liquid petroleum gas and I have found that a safeminimum depth is one foot per pound'of pressure on the material to be stored. For example, for a pressure of 100 pounds (gauge) an excavation or storage cavity should` be located at least 100 feet below ground. This may be varied to some extent in cases where the roof formation is of `sufcientstrength to act as a conningmedium as well as an overburden, Such, Yfor example, as solid limestone or solid granite.

It is'also necessary that the storage cavity to bev excavated have a roof stratum consisting cf aformation which is impermeable, hard, and substantially free of fractures, and one having suflicient beam strength to support the necessary overburden. An example of a suitable formation for a roof structure would be massive limestone.

Of equal importance are the properties re quired for the walls of the excavation which should also be impermeable, reasonably dry, devoid of impurities or properties which might have a deleterious effect upon the liquid stored. A suitable formation for the cavern walls would be tight, sandy, shale to shaly 'sandstone and silty grey shale.Y This formation is dry, nonwaterbearing, tight, andvwill not effect the stored materials.v f'

It is desirable, although not necessary, that the cavern formation be followed immediately below by a hard formation suitable for a cavernr floor, such,U for example, as hard brittle limeformation which is located 100 feet below groundv is the hard, brittle limestonestratum I I It Will be noted, however, that immediately 'followingI the stratum Il is soft grey shale, sandstone, and soft flaky carbonaceous shale with a stratum of hard -brittle limestone interposed. With the exfception of the intermediate layer of the lime-- stone, these strata are waterbearing and the carbonaceous shale would have a deleterious elect upon the product to be stored because of its sulphur content.

Thus, it will be seen that the rst succeeding suitable roofV structure which is: sufficiently deep to provide the necessary overburden and is in turn. succeeded by a sufcient depth of desirable formation for cavity walls, is they stratum I2 of massive limestone. Following this stratum I2 is a relatively deep stratum composed of tight, sandy shale to Shaly limestone and silty grey shale, represented by the numeral I3, and this is followed bya hard brittlelimestone stratum t4 well adapted to serve yas a cavern oor. The stratum I3, being of sufficient` depth and possessing the necessary propertieais therefore-selected for the location of the cavern to be excavated.

The first step afterdrilling the open shaft i and locating Vthe position for the cavern, is to install a main casing IIS Ias will be seen from Figure 2. This casing is of sufficient diameter to serve first as a means of ingress and egress during the subsequent mining operation in ex cavating the cavern and, following this operation, is permitted to remainin. the shaft for connection to a. casingextension-lcA and to house the eduction'equipment as; will. hereinafter appear. Preferably the'casing i5 'and its extension ld are approxi-mately 3Eiinehes in inside diameter.

The. main casing [5 islewered vtotheproner depth in thev shaft id preferably about onefootbelowthe under-'face of thereof rock i2,.and is squeeze cemented from theA bottom of the.y roofl rockt tothe surface ofi ther ground. squeeze-cementing y is performed bythe usual oil held practice, thatv is, the shaft is filled with the proper quantity of cement and water isithen forced through the casing to squeeze the cement out of the bottom of the casing 'and back'up'around Vthe outside thereof, filling all' spaces and crevices' and tightly sealing the periphery of the casing inthe shaft, from'theV roof rock t2 to the ground surface, as shown at I5 inFigure 2. The cement is then allowed to set and :attain the Vrequired strength prior to testing the seal.

In order to test the seal so as to determine within a reasonable degree of accuracy, whether or not an excavation will be successful, a temporary cap isplaced on the top of the casing' I5 and` a hydrostatic test is conducted on the formation and cement seal. This testis conducted by the Iual methods and need not be described in detail. YIf the results of the test are satisfactory, the excavation of the cavern can be proceeded with. However, if there is any indication of leakage. around the cementvseal lr6, a. supplemental sealing structure, is-installed around the casing, adjacent the Vunder-side of the roof formation I2. This will be hereinafter referred to more in detail.

After the main casing I5 has been installed, sealed, and tested, the excavation of the cavern is proceeded with and any modern mining practices may be employed. At the commencement of` the mining operation, any excess cement or concrete at the bottom of the casing is drilled out and the shaft is continued in the stratum l 3 to the depth of the cavern to be excavated. A cavern I 'I ofthe desired size and shape is then cuthorizontally inY this stratum by the usual mining practices. This cavern I'I may take various Vshapes insofar as the profile of its Wall structure-.is concerned, depending upon the nature of the formation of the stratum I3 and giving due considera-tion to the most economical method of excavation. For example, if the substance of the cavern walls has no tendency to Slough or cave in, the Walls can be substantially vertical asshown in profile in; Figure 6. On the outher hand, in a stratum of denseshale or silty grey shale WhereV there is a likelihood of' sloughing, the cavern is excavated with sloping sides to avoid this fault'as shown in Figure 7. Figure 8 is simply another example of the profile of the walls of a cavern, in this instance being substantially cylindrical.

In Figure 5 I have illustrated a typical longitudinal cross section of a storage cavern which has been excavated horizontally from the bottom of shaft ID and wherein an uncut mass IB is permitted to remain immediately adjacent the lower portion of the shaft I0, with an upper drift I9 extending from the upper extremity of the cavern II to the shaft It. and a passage 25 extendingL horizontally from the lower portion of the cavern I'I to the bottom of the shaft III.

After the cavern I1 has` been excavated, an extension I5a is welded to Ythelower end of the casing I5, as shown at. ZI in Figure 2. This extension may belowered intoathe shaft in sections or inv collapsed form and then welded in tubular shape. In its nal .form the extension I5c; is provided with an entrance door or opening Zia. in its side wall, at the lower end of the extension, to afford access to the cavern from the casing. Also a vapor opening 22 is cut in the wall of the extension I Eagadjacent the upper drift I9, to admit vapo-r pressure into the space about the level of the liquid to stored inthe cavern IV'I, as will.' hereinafter appear.

An eductor tube 23 is then installed inthe casing I5 and extends from the bottom ofv the extension 15a, to the ground level where itis connectedthrough the wall of the casing to a liquid discharge conduit 24 having a control valve 25 interposedV therein. The top of the casing I5 is closed by a suitable control dome 26, welded to the.- upper end of; the casing I5. and having aremovably covered man hole 21 to permit entrance into the. casing. The bottom of the eductor tube 23 extends to theflower extremity of thefextension Ict and is preferably closed and sealed to a. steel plate 28 supported on a concrete base 29 which supports the bottom of ther extension 15a. One or more vertical slots 30 arev cut in the wall-of the tube 23, a prede termined distance `above its lower end so as to provide for the admission of stored vliquid intol the eductor tube, said slots being spaced upwardly from the bottom of the tube a sulicient distance to prevent the admission of water which may underlie the. stored liquid. Also extending vertically in the casing I5, is awater Siphon pipe 3|, the lower end of which terminates at the bottom of the extension in an angularly cut open end 32 so as to expose its inlet opening in a plane below the slot 3i) in the eductor tube 23. Thus, water can be withdrawn through tube 3! without including oil in the withdrawal. The

upper end of the water Siphon pipe 3I is connected through the wall of the casing I5 to a water drain conduit 33, as seen in Figure 4.

An air pressure conduit 34, leading from a suitable source of air or vapor pressure (not shown), is connected to the interior of the casing i5 through a sealed opening in its side wall as shown in Figures 3 and 4, whereby airor vapor under pressure may be introduced into the casing I5 during the discharge of liquid from the cavern il. This vapor line also serves the reverse funce tion of venting when the cavern is being charged with liquid to be stored.

In operation, the man hole cover 21 is first secured tightly in place and when it is desired to discharge liquiiied petroleum gas or otherliquid stored in the cavern I'I, air or vapor under suitable pressure, is introduced through conduit 34 into the casing I5. By means of the vapor opening 22 in the casing adjacent thev upper drift i9, the area above the liquid level in the cavity is subjected to the pressure required to force the liquid upwardly through the eductor tube 23 and into the discharge conduit 2li.

In storage facilities which are located at extreme depths, it may be advantageous to utilize a pump for withdrawing the liquid from the cavern. However, in most instances, I have found that the use of vapor pressure on the upper surface of the stored liquid is sufficient to effect a satisfactory discharge.

As before indicated, if the concrete seal I il satisfactorily withstands the hydrostatic test 1n the initial operations of installing the facility, an additional sealing means is not necessary. However, in some instances a supplemental sealing of the casing is required. Such means is illustrated in Figure 2 of the drawings where f represents a at annular ring of suitable metal which is bolted into the roof structure I2 by means of expansion bolts 36 and surrounds the shaft opening radially beyond the concrete seal it. In installing the ring 35 the bottom surface of the limestone stratum i2 is ground to a polished sealing t with the adjacent surface of the ring 35 so that when the expansion bolts 38 are inserted, the ring 35 is maintained in sealing engagement with the under surface of the roof stratum I2. An annular bowl-shaped metallic head 3l surrounds the casing I5 immediately below the ring 35 and its upper edge is welded to the ring while its lower edge is welded to the casing extension Ilia. Thus, the pressure in the cavern has a self-sealing effect due to the structure of the head 31 which has a tendency to force the ring 35 into even tighter sealing engagement with the roof stratum I2 so as to prevent leakage through the roof stratum i 2 past the casing I5.

In practice, both the ring 35 and the head 31 may be lowered into the shaft in sections of a size to pass through the casing l5, and then welded together prior to installation. It is believed unnecessary to illustrate this particular phase of the operation as it will be clearly understood by those skilled in the art.

Facilities of this nature may be installed individually or a series of caverns may be arranged so as to utilize a common .unit of charg-V ing and discharging equipment. For example, invFigure 9 I have shown a series of caverns I'I which'radiate from a common shaft ID which is used both inthe excavation of the caverns and for the installation of charging and discharging equipment. Obviously, many different arrangements can be employed with equal effect, such, for example, as a series of caverns arranged in parallel rows communicating with a common shaft.

To facilitate the mining operation and to reduce costs, it may be desirable to sink an auxiliary shaft of small diameter such, for example, as 8 or 12 inches, to carry air, drilling tools, water, lights, or other utilities necessary for the operation. Normally this hole is plugged by cement after the excavation has been completed.

It will thus be seen that the use of my improved method and facility enables the underground storage of large quantities of liquilied petroleum gas or the like under most economical conditions and with a maximum degree of safety. Furthermore, the vapor loading and unloading system for withdrawing the liquid from the cavern is simple in construction and easyto install and operate. By the use of vapor pressure in discharging the liquid, I eliminate moisture from the product and the stored liquid can be with drawn at a greater rate per hour.

From the foregoing it is believed that my invention may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details disclosed, without departing from the spirit of the invention as set forth in the following claims.

I claim:

l. an underground storage facility for liquid under pressure, comprising a vertical shaft ex-A tending into the ground, a subterranean. cavern having an overburden of a depth of at least one foot per pound gauge pressure on the liquid to be stored formed in the ground, extending outwardly from and connecting into said shaft, said shaft leading from said cavern to grounr level, Va casing, closed at its upper end, lining said shaft and extending to the bottom of said cavern, an opening to the cavern, at the lower end of said casing, means sealing the casing in said shaft, an eductor tube in said easing and having an inlet opening in its lower end, substantially at the botn tom of said casing, a discharge conduit connected to the upper end of said eductor tube, and means for discharging liquid from said cavern through said eductor tube.

2. An underground storage facility claimed in claim l, including means for introducing a gaseous pressure 4medium through said casing to the area of said cavern above the liquid level therein, to displace liquid through said eductor tube.

3. An underground .storage facility as claimed in claim l, wherein said casing is of such transverse dimensions as to alford entrance and egress with respect to the cavern and its lower end is provided with a cut out portion adapted to serve as an entrance doorway to the cavern.

s. An underground storage facility as claimed in claim 3, including means for introducing a gaseous pressure medium through said casing to the area of said cavern above the liquid level therein, to displace said liquid through said eductor tube.

5. An underground storage facility as claimed infclaim, including a second ropening in said lin a vplane above the level of the liquid stored in the cavern, and means for hitroducing argaseous pressure'medmm through said casing and second opening, ico the area above the liquid level in said cavern, @to displacesaid liquid through said feduotor tube,

6.-An underground liquid :storage facility as claimed in claim l, wherein the inlet opening in said eductor -tu'be isspaced 'vertically from the bottom of the cavern to prevent the entrance of Water whichmay underliethe liquid stored in saidfcavern.

7. An underground liquid storage facility as claimed fclaim J6, including a Water Siphon tube extending from -the bottom .of said cavern -to ground level and having Aan inlet opening at .its lower end disposed in aplane below the plane of the inlet opening to said eductor tube.

8. An underground storage facility for liquids under pressure, .comprising a subterranean cavern having a relatively deep overburden, said cavern being bounded at its 4upper extremity .by a Ageological roof rock formation which is hard, impermeable, and substantially free from `raotunes, and having a thickness vand beam strength to support lthe Weight of said overburden, the :cavern being formed in a selected .stratum which is impermea le, substantially dry, and free from properties which would :aiect the `quality and consistenc-y -of the liquid stored therein a shaft leading from said cavern to ground level, a Vcasing cio'sed at i-ts upper end, lining said shaft, and opening into sai-d cavern in la plane above the level of the liquid stored therein, means .sealing the casing in said shaft, an -eductor tube eftencln ing through said casingand .having an inlet opening at its lower end substantially at the bottom of saidcavern, a discharge conduit connected to the upper end .of said eductor tube, and means for discharging Pliquid from -said cavern through said `eductor tube.

9. In an underground storage facility as claimed in claim i8, a supplemental seal for said casing comprising av ilat annular ring in sealing engagement with the under surface of said roof rock formation around said shaft, means securing said ring to said roof rock formation, van annular, substantially `'bowl-.shaped head surrounding said casing beneath said ring and sealed vrespectively at its upper and lower extremities, to the under side of said ring Aand the periphery of .said casing.

l0. 1n underground storage facility as claimed in claim 8, a supplemental seal for said casing comprising a flat annular ring engaging the under surface of said roof rock formation around said shazft, with a ground and polished nt, means securing said ring to said roof rock formation, an annular, substantially bowl-shaped head surrounding said casing beneath said ring and sealed respectively at its upper and lower extremities, to the under :side of said ,ring and the periphery of said casing.

11. In combination with a subterranean cavern having a vertical :shaft extending therefrom and a casing lining said shaft, means sealing said casing with Yrespect to ysaid shaft comprising a at annular plate surrounding said casing and in sealing engagement with the roof of the cavern, means securing said plate in sealing engagement, and an annular, substantially bowl-shaped head surrounding said casing beneath said plate and sealed respectively at its upper and lower extremities, to the undersides of said plate and the periphery of said casing.

12. The method lof preparing an underground pressure :fluid storage `facility, comprising drilling a fcore 'to a geological formation having a hard rock stratum possessing suitable roof properties and a depth to provide a suicient overburden to retain pressure of the fluid to be stored, and immediately followed by a relatively deep second stratum which is dry, non-permeable by the iiuid to be stored, and devoid of impurities which will affect the huid to be stored, sinking a mining shaft along `the core bore, installing a casing in said shaft, sealing said casing with respect to the surrounding formation 'from the .bottom of the shaft to ground level, excavating an offset storage cavern in the second stratum from a point, adjocent the lower portion of said shaft, installing a liquid conducting discharge pipe through said casing from ground level 'to the bottom of the casing, and closing the top of Ysaid casing.

13. The method as claimed in cla-im l2, including sealing Vthe casing by introducing therein a quantity of cement in fluid state and then forcing Water under pressure, through said casing to squeeze said cement out through the lower end of the casing Iand up between the outer wall of the casing and the surrounding shaft,

REX VICTOR PEELPS.

References Cited in the le of this patent UNITED 'STATES PATENTS Number Name Date 2,433,896 Gay Jan. 6, 1948 2,459,227 'Kerr Jan. 18, 1949 OTHER REFERENCES Eng. News-Record, page '56, April 19, 1951.

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