Page 21 - Petroleum Production Engineering, A Computer-Assisted Approach

Guo, Boyun / Computer Assited Petroleum Production Engg 0750682701_chap01 Final Proof page 9 4.1.2007 6:12pm Compositor Name: SJoearun

PETROLEUM PRODUCTION SYSTEM 1/9

Handwheel

Wellhead Choke
Packing

Gate

Port

Figure 1.11 A sketch of a surface valve.
two categories: single tube and double tube. Each type of
separator has specific advantages and limitations. Selec-
tion of separator type is based on several factors including
characteristics of production steam to be treated, floor Figure 1.12 A sketch of a wellhead choke.
space availability at the facility site, transportation, and
cost. such as those on offshore platforms where space is limited.
Horizontal separators (Fig. 1.13) are usually the first Because of the large vertical distance between the liquid
choice because of their low costs. Horizontal separators level and the gas outlet, the chance for liquid to re-vapor-
are almost widely used for high-GOR well streams, foam- ize into the gas phase is limited. However, because of the
ing well streams, or liquid-from-liquid separation. They
have much greater gas–liquid interface because of a natural upward flow of gas in a vertical separator against
large, long, baffled gas-separation section. Horizontal sep- the falling droplets of liquid, adequate separator diameter
arators are easier to skid-mount and service and require is required. Vertical separators are more costly to fabricate
less piping for field connections. Individual separators can and ship in skid-mounted assemblies.
be stacked easily into stage-separation assemblies to min- Spherical separators offer an inexpensive and compact
imize space requirements. In horizontal separators, gas means of separation arrangement. Because of their com-
pact configurations, these types of separators have a very
flows horizontally while liquid droplets fall toward the limited surge space and liquid-settling section. Also, the
liquid surface. The moisture gas flows in the baffle surface placement and action of the liquid-level control in this type
and forms a liquid film that is drained away to the liquid of separator is more critical.
section of the separator. The baffles need to be longer than Chapter 10 provides more details on separators and
the distance of liquid trajectory travel. The liquid-level dehydrators.
control placement is more critical in a horizontal separator
than in a vertical separator because of limited surge space.
Vertical separators are often used to treat low to inter-
mediate GOR well streams and streams with relatively 1.5 Pump
large slugs of liquid. They handle greater slugs of liquid After separation, oil is transported through pipelines to
without carryover to the gas outlet, and the action of the the sales points. Reciprocating piston pumps are used to
liquid-level control is not as critical. Vertical separators provide mechanical energy required for the transportation.
occupy less floor space, which is important for facility sites There are two types of piston strokes, the single-action

Figure 1.13 Conventional horizontal separator. (Courtesy Petroleum Extension Services.)