Hydrocarbon Processing Flashcards
How Crude Oil and Natural Gas produced?
Production begins after the well is drilled. The mixture of oil, gas and water from the well is separated on the surface. The water is disposed of, and the oil and gas are treated, measured, and tested. Production operations include bringing the oil and gas to the surface, maintaining production, and purifying, measuring, and testing
4 Major Process
3‐Phase well fluid is received from Wells/Well Platforms and processed at large Process Platforms generally consisting of the following four Major Processing Modules:
* Separation (Oil, Gas and Produced water) & Oil dispatch
* Gas Compression & dehydration
* Produced Water Conditioning
* Sea water processing & injection system
Separation
- Oil , Gas and Water is separated from the Wellfluid.
- Well Fluid from various Wells/ Well Platforms / Subsea Manifold reaches the process complex via subsea pipelines and risers and is further processed in more than one train.
- Each Train will normally consist of a Production Manifold , Well fluid heater, Inlet Separator, Crude oil Manifold, Crude oil heater, Surge Tanks and MOL Pumps.
- Well Fluid is received in the Production Manifold . Demulsifier Chemical is dozed in Production manifold to promote breaking up of Water‐Oil emulsion
- Then it is heated in well fluid heater with Hot oil Flowing in Shell Side and well fluid in tube side. This heating enables better separation of oil and water in Inlet Separator.
- The Well Fluid from Well fluid heater reaches Inlet Separator.
Inlet Separator - 1st Stage Separation
- Inlet Separator is a vessel in which 3 phase separation of well fluid into Oil, Gas and Water occurs.
- Separation is by gravity mainly assisted by chemical and heat. Residence time in the vessel is an important criteria for better separation.
- Separated Gas is routed to Gas compression and dehydration Module.
- Compressed gas is sent to the Lift gas network for lifting the producers and excess gas is exported via pipelines to shore.
- Separated oil flows to the oil manifold.
- Separated water flows to Produced water conditioning unit.
- From oil manifold crude oil flows to crude oil heater in which crude oil is heated with hot oil. This enhances the separation of oil & water in Surge Tanks (second stage separation).
- Demulsifier chemical dozed in oil manifold further promotes the breaking of water‐Oil emulsion.
Surge Tank - 2nd Separation
- Surge tank is maintained at a lower pressure to stabilize crude i.e. to remove maximum of associated gas from the crude oil.
- Oil from surge tanks can be either pumped directly with MOL pumps or can be diverted to third stage separators (Surge tank‐3).
- Separated crude oil is pumped with CTP / MOL pumps to export trunk lines.
- Separated Gas is diverted to Gas compression module after boosting the pressure LP booster compressor.
- Separated Water is diverted to Produced water conditioning Unit.
Gas Compression
- Gas from Separators ,Surge Tanks and export gases if any from other process platforms are compressed to about 90‐100 kg/cm2
pressure as per the field gas lift requirement. - Normally Gas turbine driven Centrifugal compressors (PGC’s‐Process Gas Compressors) are used.
- Gases compressed in PGC’s is dehydrated to prevent formation of GAS HYDRATES. Gas hydrates are formed at low temperatures when moisture is present in Hydrocarbon gases. These gas hydrates are ice like substance which prevent the smooth flow or block the flow of gases in gas flow lines.
- Gas Hydrates can be formed in Adjustable Choke Valves ,PCV’s & GLV’s in GI Lines where throttling of gases give rise to low temperatures.(Joule Thomson effect).This can affect production phenomenally from Gas lift wells
Gas Dehydration
- Compressed Gas is dehydrated in a Glycol contactor with Tri
Ethylene Glycol(TEG)as an absorbent for moisture from
compressed gas. - Glycol contactor is bubble cap tray column with many bubble
cap trays. TEG flows counter current with compressed gas from
the top of the column. - TEG coming in contact with compressed gas in the bubble cap
trays selectively absorbs the moisture from the gas and
dehydrates it. - The dehydrated gas is sent to feed gas lift wells in priority basis
and remaining to export gas line. - The TEG rich in moisture is sent for re‐concentration , converted
to Lean glycol and recycled back to contactor for dehydration
Produced Water Conditioning
- The water produced along with Oil and Gas from the wells is to
be treated to within acceptable levels of quality in terms of oil
ppm before it is discharged in to the sea. - Produced Water Conditioning unit normally consists of Flash
Vessel ,CPI Separators, IGF (induced Gas floatation Unit) and
Sump caisson. - Flash Vessel
Receives water from Both Inlet Separators and Surge tanks .It
is maintained at 0.8 kg pressure. In flash Vessel most of the
dissolved gases in the produced water flashes out which is
routed to LP flare header. Associated Oil from the produced
water in the flash vessel is routed to closed drain header and
is collected in the sump caisson.
Flash Vessel
Receives water from Both Inlet Separators and Surge tanks .It
is maintained at 0.8 kg pressure. In flash Vessel most of the
dissolved gases in the produced water flashes out which is
routed to LP flare header. Associated Oil from the produced
water in the flash vessel is routed to closed drain header and
is collected in the sump caisson.
Produced Water Conditioning components:
- CPI separators
- IGF unit
- Sump Caisson
CPI separators
Water from the flash vessel flows to many CPI separators (corrugated
plate interceptor) in parallel. Oil from CPI Separator is collected in a
tank from which it is pumped to oil manifold. Gas goes to LP Flare
header
IGF unit
Water from CPI Separator Flows to IGF unit. IGF is a tank in which gas
bubbles are aerated with motor driven agitators. This bubbles float the
oil droplets to surface .This collected oil is pumped to CPI separators.
Sump Caisson
Water from IGF is routed to Sump Caisson which is a vessel with bottom
end open through which water continuously drains into the sea. Oil
floating in the surface of the sump caisson is collected in the blow
caisson and lifted up and flown into the skimmer with gas injection.
Water Injection
- Water Injection is done to maintain Reservoir pressure as well as
Water flooding. - To prevent damage to the Reservoir the quality of water injected
is strictly complied with. Also, the health of the pipelines carrying
the injection water to the wells and well platforms is taken care
of by dozing chemicals to prevent corrosion and generation
of H2S by SRB colonies.
Major components of Water Injection systems are:
– SEA WATER LIFT PUMPS
– COARSE FILTERS
– FINE FILTERS
– DEOXYGENATION TOWERS
– BOOSTERS PUMPS
– MAIN INJECTION PUMPS
– CHEMICAL DOSING SYSTEM
The wellhead performs three important functions :-
- Supports suspended casing and tubing string
- Contains and isolates the pressure of the tubular strings
- Provides interface with Blowout Preventer (BOP), X’mas tree
and tieback
wellhead is divided into sections :-
- A-section - Casing head (or Braden head)
- B-section - Casing spool (or intermediate head)
- C-section - Tubing head (or production head)
- X’mas tree (or production tree)
Casing Head
accepts the next string of
casing either a intermediate string or
production casing, depending on the needs of the well
Casing Spool
used to suspend either the production casing string or an
additional string of intermediate
casing, if required
Tubing Head
Suspends the production tubing and seals off the tubing casing annulus
X’mas tree
a system of gate valves that regulates the flow of the fluid from the well
X’mas tree functions
– Controls the flow of fluids from the wellbore
– Provides a means of shutting in the well
– Provides a means of entering the well for servicing and workover
Pretreatment Unit
to remove dirt particles and to allow for gas, liquid and water phase separation.
Acid Gas Removal Unit (AGRU)
to remove carbon dioxide and hydrogen sulfide from the gas stream.
