oil field processing oil field processing

oil field processing.pdf

1. introduction to
Oil field treatment

2. What are the objectives from oil field
processing
Safe and environmentally acceptable handling of the crude is
assured by treating the produced crude in the GOSPs and
related crude processing facilities.
In the upstream oil industry, a gas–oil separation plant
(GOSP) is temporary or permanent facilities that separate
wellhead fluids into constituent vapor (gas) and liquid (oil
and produced water) components.
GOSPs were first used to relieve the excess pressure due to
associated gas in the produced crude.
As the water content of the produced crude increased,
facilities for control or elimination of water were added. Later, as
the effects of corrosion due to salts in the crude were
recognized, modern desalting equipment was included in the
GOSP design. With the construction of the Master Gas System,
gas compression and recovery facilities have been added,
saving gas that was previously flare

3. The sour, wet crude must be treated to make it safe and environmentally
acceptable for storage, processing, and export. The concerns, due to
various contaminants, are shown in the following table.
Contaminant Safety Environmental Corrosion
Water X
Salt X
Gas X X
H2S X X X
Specifications of crude for export include:•
➢Water content –0.3 vol %, maximum
➢ Salt content – 10 pounds (as NaCl) per 1000 barrels
➢Vapor pressure –11 psig TVP (4-5 psi RVP)
➢H2S –70 ppm

4. Gas is evolved from the produced crude when the pressure is
reduced to the crude bubble point, the temperature and pressure at
which part of a liquid begins to convert to a gas.
For example, if a liquid is held at constant pressure, but its
temperature is increased, a point is reached at which bubbles of
gas begin to form in the liquid.
This is the bubble point. Similarly, if a liquid is held at constant
temperature but the pressure is reduced, the point at which gas
begins to form is the bubble point.

5. Process Flow
A modern GOSP includes the process equipment required for :
❑pressure reduction,
❑gas removal and recovery,
❑water and salt removal,
❑ water cleanup and disposal,
The GOSP has evolved as engineers sought to control additional
crude quality concerns close to the point of production (water, salt,
recovery of gas). The design also reflects the quality, in terms of
pressure, water and salt content of the crude, and accessibility to gas
gathering systems. Thus, it is not practical to establish one
GOSP design as a standard for all production fields in the Eastern
Province.

6. A typical GOSP flow diagram is shown
in Figure 2.
A typical GOSP flow diagram is shown in Figure 2.

7. The dominant features of all GOSPs are the long,
cylindrical oil-gas separators used for stepwise
pressure reduction.
A modern oil-gas separator or trap, as shown in
Figure 3, contains elements designed to ensure
smooth flow and elimination of oil mist
carryover into the gas stream
.

9. The horizontal separator has the maximum liquid surface area for
releasing gas from a large volume of crude oïl.
Key components of a modern trap, as shown in Figure 3, include:
A. Impact baffle – reduces the velocity of the incoming crude
B. Defoaming element – breaks up foam produced by gas
escaping from the liquid crude
C. Mist extractor – collects fine droplets of crude oil mist that is
carried from the oil by the gas so that the gas leaving the trap
will be as “dry” as possible
D. Wave breaker – keeps the liquid surface as smooth as
possible for gas release and for control of the liquid level in the
vessel

10. Modern desalting operations use wash water and
emulsion-breaking chemical injection to remove salts
carried by the formation water produced with the crude
oil.
A modern two-stage desalting operation is depicted in
the flow diagram shown in Figure 4. Details of a
desalter/dehydrator are shown in Figure 5

14. GOSP process diagram

15. After stabilization, the crude oil should meet all
specifications for shipment.
• RVP 4 psia, maximum (11 TVP, maximum)
• H2S 70 ppm, maximum
• Salt 10 pounds per 1000 barrels, maximum
• Water 0.3 vol %, maximum
Figure 8 shows the overall crude processing including
spheroids and stabilizers.
The stabilized crude is ready for export or refining. The
gas collected from the spheroids and stabilizers is
compressed, cooled to condense materials heavier than
ethane, and then distilled to separate methane and
ethane from heavier materials, which are sent for further
fractionation

16. GLOSSARY
associated gas: Gas released from the crude oil when the
pressure on the crude is lowered below the crude bubble point.
Associated gas comes from he crude as opposed to gas produced
from a gas well.
bubble point : The temperature and pressure at which part
of a liquid (crude oil) begins to be converted to a vapor (released
gas).
desalting : The process of using chemicals, heat, wash water,
and an electromagnetic field to remove salts from the crude oil.
emulsion : A mixture in which one liquid (water) is uniformly
and homogeneously distributed in another liquid (crude oil).
.

17. flow diagram : A graphical representation of a process or system
showing major flows, equipment, and control schemes for that system.
Small flow and instrumentation details are not included.
gas recovery : The processes and systems used to recover gas
released from the crude for a useful purpose rather than flaring the gas.
GOSP Gas-oil Separation Plant.
material balance : The concept, applied to a process or system, of
accounting for all input materials in the output streams ( “what goes in
must come out”).
pressure reduction : The process of systematically lowering the
pressure held on produced crude to allow gas to be released and make
the crude safe for Handling atlow pressure