2 Facilities and processes
The oil and gas industry facilities and systems are broadly defined,
according to their use in the oil and gas industry production stream:
Exploration Includes prospecting, seismic and drilling activities that take
place before the development of a field is finally decided.
Upstream Typically refers to all facilities for production and stabilization
of oil and gas. The reservoir and drilling community often
uses upstream for the wellhead, well, completion and
reservoir only, and downstream of the wellhead as
production or processing. Exploration and
upstream/production together is referred to as E&P.
Midstream Broadly defined as gas treatment, LNG production and
regasification plants, and oil and gas pipeline systems.
Refining Where oil and condensates are processed into marketable
products with defined specifications such as gasoline, diesel
or feedstock for the petrochemical industry. Refinery offsites
such as tank storage and distribution terminals are included
in this segment, or may be part of a separate distributions
operation.
Petrochemical These products are chemical products where the main
feedstock is hydrocarbons. Examples are plastics, fertilizer
and a wide range of industrial chemicals.
2.
1 Exploration
In the past, surface features
such as tar seeps or gas
pockmarks provided initial
clues to the location of
shallow hydrocarbon
deposits. Today, a series of
surveys, starting with broad
geological mapping through
increasingly advanced
methods such as passive
seismic, reflective seismic,
magnetic and gravity surveys give data to sophisticated analysis tools that
identify potential hydrocarbon bearing rock as “prospects.” Chart: Norwegian
Petroleum Directorate (Barents Sea)
5
An offshore well typically costs $30 million, with most falling in the $10-$100
million range. Rig leases are typically $200,000 - $700,000 per day. The
average US onshore well costs about $4 million, as many have much lower
production capacity. Smaller companies exploring marginal onshore fields
may drill a shallow well for as little as $100,000.
This means that oil companies spend much time on analysis models of good
exploration data, and will only drill when models give a good indication of
source rock and probability of finding oil or gas. The first wells in a region are
called wildcats because little may be known about potential dangers, such as
the downhole pressures that will be encountered, and therefore require
particular care and attention to safety equipment.
If a find (strike, penetration) is made, additional reservoir characterization
such as production testing, appraisal wells, etc., are needed to determine the
size and production capacity of the reservoir in order to justify a development
decision.
2.2 Production
This illustration gives an overview of typical oil and gas production facilities:
Figure 1. Oil and gas production facilities
6
Although there is a wide range of sizes and layouts, most production
facilities have many of the same processing systems shown in this simplified
overview:
Figure 2. Oil and gas production overview
Production
Wellheads
Production
and Test
Manifolds
ø
Test Separator
Production Separators
1 stage
2 stage
Water treatment
Gas compressors
LP HP
Metering and
storage
Pig
Launcher
Gas
Meter
Oil
Meter
Gas
Pipeline
Oil Storage
Crude
pump
Pig
Launcher
Oil
Pipeline
Tanker
Loading
Injection
wells
Injection
manifold
Water injection
pump
Gas injection
compressor
Utility systems (selected)
Power Generation
Instrument Air
Potable Water
Firefighting
systems
HVAC
Export
Drilling
Mud and Cementing
7
Today, oil and gas is produced in almost every part of the world, from the
small 100 barrels-a-day private wells to the large bore 4,000 barrels-a-day
wells; in shallow 20 meter deep reservoirs to 3,000 meter deep wells in more
than 2,000 meters of water; in $100,000 onshore wells and $10 billion
offshore developments. Despite this range, many parts of the process are
quite similar in principle.
At the left side, we find the wellheads. They feed into production and test
manifolds. In distributed production, this is called the gathering system. The
remainder of the diagram is the actual process, often called the gas oil
separation plant (GOSP). While there are oil- or gas-only installations, more
often the well-stream will consist of a full range of hydrocarbons from gas
(methane, butane, propane, etc.), condensates (medium density
hydrocarbons) to crude oil. With this well flow, we also get a variety of
unwanted components, such as water, carbon dioxide, salts, sulfur and
sand. The purpose of the GOSP is to process the well flow into clean,
marketable products: oil, natural gas or condensates. Also included are a
number of utility systems, which are not part of the actual process but
provide energy, water, air or some other utility to the plant.
2.2.1 Onshore
Onshore production is economically
viable from a few dozen barrels of oil
a day and upward. Oil and gas is
produced from several million wells
worldwide. In particular, a gas
gathering network can become very
large, with production from thousands
of wells, several hundred
kilometers/miles apart, feeding
through a gathering network into a
processing plant. This picture shows a
well, equipped with a sucker rod pump
(donkey pump) often associated with
onshore oil production. However, as
we shall see later, there are many
other ways of extracting oil from a non
free-flowing well. For the smallest reservoirs, oil is simply collected in a
holding tank and picked up at regular intervals by tanker truck or railcar to be
processed at a refinery.
Onshore wells in oil-rich areas are also high capacity wells producing
thousands of barrels per day, connected to a 1,000,000 barrel or more per
8
day GOSP. Product is sent from the plant by pipeline or tankers. The
production may come from many different license owners, so metering of
individual well-streams into the gathering network are important tasks.
Unconventional plays target very
heavy crude and tar sands that
became economically extractable
with higher prices and new
technology. Heavy crude may
need heating and diluents to be
extracted. Tar sands have lost
their volatile compounds and are
strip-mined or can be extracted
with steam. It must be further
processed to separate bitumen
from the sand. Since about 2007,
drilling technology and fracturing
of the reservoir have allowed
shale gas and liquids to be
produced in increasing volumes.
This allows the US in particular to
reduce dependence on
hydrocarbon imports. Canada,
China, Argentina, Russia, Mexico
and Australia also rank among the
top unconventional plays. These
unconventional reserves may
contain more 2-3 times the
hydrocarbons found in conventional reservoirs. These pictures show the
Syncrude Mildred plant at Athabasca, Canada Photo: GDFL Jamitzky/Wikimedia
and the Marcellus Shale in Pennsylvania. Photo: GDFL Ruhrfisch /Wikimedia
2.2.2 Offshore
A whole range of different structures is used offshore, depending on size and
water depth. In the last few years, we have seen pure sea bottom
installations with multiphase piping to shore, and no offshore topside
structure at all. Replacing outlying wellhead towers, deviation drilling is used
to reach different parts of the reservoir from a few wellhead cluster locations.
Some of the common offshore structures are:
9
Shallow water complex, which
is characterized by several
independent platforms with
different parts of the process
and utilities linked with gangway
bridges. Individual platforms
include wellhead riser,
processing, accommodations
and power generation platforms.
(This picture shows the BP
Valhall complex.) Typically found
in water depths up to 100
meters.
