Oil and Gas at Your Door? (2005 Edition) - Earthworks

STAGES OF OIL & GAS DEVELOPMENT
Next, tubing, which will carry the oil or gas to the surface, is threaded
into the casing. At the surface, a well head (sometimes referred to as a
Christmas tree) is installed, which has valves that control the flow of oil
or gas from the well. The valves connect the well to equipment that will
separate the oil, gas and water, and remove impurities. Finally, a pipeline
connection or storage tank is connected to the well to allow for transport
or storage of the product. In the case of natural gas, which cannot be
stored easily, a pipeline connection is necessary before the well can be
placed into production.
If there is not enough pressure in the reservoir to force the oil, gas or produced
water to flow naturally to the surface, pumping is necessary. 82
Pumping equipment is installed at the lower end of the tubing. There are
many different types of pumps that can be used: beam pumps; gas lift:
piston pumps; submersible pumps; jet pumps and pneumatic pumps.
The power to operate these pumps may be supplied by a gas or diesel
engine or an electrical motor.
FIGURE I-7. CHRISTMAS TREE
The wellhead of a gas well. The first step as natural
gas leaves the ground. Photo by OGAP.
A number of pits may be constructed at this stage. These may include a
skimming pit, which reclaims residual oil removed with produced water;
a sediment pit, which stores solids that have settled out in storage tanks;
or a percolation or evaporation pit, to dispose of produced water. 83
Stimulation
Often an oil- or gas-bearing formation may contain large quantities of oil
or gas, but have a poor flow rate due to low permeability, or from damage
or clogging of the formation during drilling. 84 This is particularly true
for tight sands, oil shales and coalbed methane, discussed later in this
chapter. Stimulation techniques may be used prior to production, or during
maintenance operations that take place after the well has been put
into production. In later years, when the flow of oil or gas from a well
begins to decline, stimulation techniques, as well as other enhancement
techniques, may be used to encourage oil or gas to flow to those wells.
Some of the more common stimulation techniques include: hydraulic
fracturing; acidizing; and cavitation, which will be described in the section
on coalbed methane.
FIGURE I-8. MUD RESERVE PIT
Torn liners can lead to groundwater contamination.
Hydraulic fracturing (also known as fracing, which rhymes with cracking)
is a technique used to create fractures that extend from the well
bore into rock or coal formations. These fractures allow the oil or gas to
travel more easily from the rock pores, where the oil or gas is trapped, to
the production well. 85 Typically, in order to create fractures a mixture of
water, proppants (sand or ceramic beads) and chemicals is pumped into
the rock or coal formation. Eventually, the formation will not be able to
absorb the fluid as quickly as it is being injected. At this point, the pressure
created causes the formation to crack or fracture. The fractures are
held open by the proppants, and the oil or gas is then able to flow
FIGURE I-9. WASTE PIT
Waste pits for fluids and sediments associated with
gas processing. These can contain water, sand,
hydrocarbons, glycol and other chemicals.
through the fractures to the well. 86 Some of the fracturing fluids are
pumped out of the well during the process of extracting oil, gas and any
produced water, but studies have shown that anywhere from 20-40% of
fracing fluids may remain underground. 87 I-17