underground storage in rock caverns

8/4/2019 underground storage in rock caverns

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Underground Storage

InRock Caverns

November 9th2009

Rajan K Pillai


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Going UndergroundGoing Underground


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Types of Underground Storages

Salt Leached Caverns.

Aquifers or Depleted fields

Disused mines.

Underground Rock Caverns (Unlined & lined)


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Salt Dome

Salt Leached Caverns

Borehole

Water injection Brine

Several

hundredmeters Tens of

meters


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Aquifers

Impermeable stratum

Porous & Permeable

Geological formation

Hydrocarbon Storage


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Disused Mines

Water table


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The finished rock cavern for LPG at Visakhapatnam

Example of an Underground Unlined Rock Cavern


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Comparison of Depths of LPG andCrude Caverns

-30 m

-162 m

SALPG LPG Cavern ISPRL Crude CavernMean Sea Level


10/37Source : Geostock

Example of cavern using a rampfor Access

Inclined Ramp

Water

Curtain

Main Storage GalleriesOperation Shafts


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Access Ramp (AR)

Upper Connection (UC)

Intermediate connection

(IC)

Upper Shaft Connection (USC)

Access Shaft (AS)

Operation Shaft (OS)

Lower Shaft Connection(LSC)

Water Gallery Operation

Shaft Connection (WOC)

Water Gallery Access

Shaft Connection (WAC)

Water Curtain Gallery

(WCG

Sump which houses the

submersible pumps

Lower connection (LC)

Example of Cavern Using Vertical Shaftfor Access

Source : SALPG


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Equipment lowering throughShaft


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Systems required for

access & mucking in

case of Shafts


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Mean Sea Level(MSL)

Water Curtain

Boreholes Water curtain tunnels

Storage Caverns

Separation of differentproducts to be stored


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Design for light Products andCrudes (Flat Invert)

- Caverns for light products & crudes can be designed to

have flat inverts with water beds (water bed not required

for LPG)- These caverns have no heating systems.- Can be made for products which do not have major

sludge problems


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- Caverns are designed to have a slope for ensuring a proper

flow towards the sumps.- Heating system provided for heating and circulation of the

product stored.- The design permits storage of heavy oils and heavy crudes.

Design for Heavy Products and Crudes(Sloping Invert)


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Storage Caverns

Inertisation of caverns (products other than LPG)

Connecting the vapour spaces can reduce the requirement of inert

gas.


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Storage capacity

Cost/

m3o

fstorage

Caverns in less

favorable geological

conditions

Caverns in favorable

geological conditions

Lower Marginal Costs For larger volumes


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Large size- Need for benching

For large caverns there is a need to

excavate the caverns in steps. The topheading is completed first followed by

benching

Ten story

building

30 M

20 M

Top Heading

Benches


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Excavation method adopted forlarge caverns


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Need for Access to Various Levels inLarge Caverns


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Excavation Using Drill & Blast (For Hard Rock)

Two Boom Jumbo (Used for drilling in hard rock)

D illi & Bl ti M th d f E ti


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Drilling & Blasting Method of Excavation

Holes are charged

with explosives afterdrilling andcontrolled blastingcarried out

Jumbo used fordrilling holes inrock

D illi & Bl ti M th d f E ti


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Pull

Drilling & Blasting Method of Excavation


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Excavation using Road Headers(For Soft Rock)Road Headers (Used in case of soft to medium hard rock Limestone,

Chalk etc)

Example of Rock Cavern constructed using road headers for top heading &


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Example of Rock Cavern constructed using road headers for top heading &

blasting for benching followed by trimming by road headers. Cross section is

85 sq m

Source : Geostock


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Crude

Tankers

Crude

Cavern

Boiler

For

Horticulture

For Water Curtain

Inert Gas

Booster Station

Heat Exch.

Stage 1 Stage 2Carbon

Filter

ETP

Booster

Pumps

Flare

Submersibl

e Pumps

Typical Scheme for CrudeCaverns All aboveground facilities will

be as per standard Oil industry

practices. Layout shall be asper OISD guidelines


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Lined Rock Caverns

These types of storage facilities can be used for small or medium sized caverns.

The lining can be steel or plastics. In the depths are large the linings have to be

designed to counter the hydrostatic pressure or the can get

Steel or

plastic lining


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Over breaks and rock falls

Over breaks as shown can slow down progress to a

large extent. Also a major safety issue.


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Method of addressing poor rockconditions

To ensure there is good stability of the cavern, rock bolts need to be installed

and shortcrete applied. Poorer the rock strata, larger is the support

requirement.

Rock bolts

Shotcrete


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Example of Poor RockConditions

Large number of cracks and fissures in the rock could

lead to large over breaks .and excessive supports


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Example of a water bearingzone

Water bearing zones could result in large water ingress

if pre-grouting is not resorted to. The time taken up by

grouting could delay excavation.


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Pre-Grouting in excessive waterbearing zones

Pre-Grouting involves

drilling a number of

holes on the face and

pumping cement paste

under pressure into

them till sealing is

achieved.

High permeability and water bearing strata could

result in higher grouting and slow excavation

progress.


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Water Table Monitoring

Water table

Typical Excavation progress curves for


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Typical Excavation progress curves forUnderground caverns


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Advantages of going underground

Product is located at a depth and is fully isolated.

External Fires will not affect Storage

Maximum security. Safety hazards on account of sabotage, storms,

earthquakes and explosions are minimized.

Surface land requirement is low

Caverns by their very nature require very low maintenance.

Beyond certain capacities the capital cost per ton of storage is low.

Environment benefits. The rock debris generated can be used for

infrastructure development.


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underground storage in rock caverns

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