Environmental Engineering Reference
In-Depth Information
Pipeline Construction
Construction of gathering and transmission pipelines is necessary before production can commence.
Oil from a small field can be trucked to storage facilities, but larger amounts of oil and natural gas
require pipelines. It is not practical to truck natural gas, so pipelines are necessary. Gathering lines
transport the oil and gas from the well site to collection facilities, while transmission lines move
it from storage to refineries. In the United States there are over 174,000 miles of oil pipelines and
over 1.5 million miles of natural gas pipelines (USDOT 2011, Table 1.1).
Field Operations
Production begins when the field and its transportation networks are developed for the initial dis-
covery wells. Many oil wells require an artificial lift to bring the oil to the surface. This primary
production accounts for about 25 percent of the oil in a reservoir. In fields where it is economically
feasible, “secondary” recovery methods are used. This involves pumping water or gas into the
reservoir to increase oil production by increasing the pressure in the reservoir. “Tertiary” recov-
ery methods can sometimes increase recovery rates if the viscosity of the oil is lowered so that it
flows more easily—either by heating the oil or by injecting chemicals into the reservoir (USDOI
1981b). Most gas wells produce by normal flow and do not require pumping.
Hydraulic fracturing (fracking), an increasingly used, controversial method of oil and gas
extraction, involves injecting pressurized water or other drilling fluids with sand and chemicals
into wells to fracture rock layers and release oil and gas so they may be extracted more easily
(Urbina 2011). The sand is to keep fractures open after they have been made. Elevated levels
of total dissolved solids and radioactivity have been found in shale drilling wastewater from
fracking. Total dissolved solids are a mixture of salt and other minerals from deep underground
during gas production. Drilling wastewater can be more than five times as salty as sea water,
and large amounts of these minerals can damage machinery at downstream power plants ( New
York Times 2011).
Hydraulic fracturing has resulted in significant increases of radioactive material, including
radium, and carcinogens, including benzene, in major rivers and watersheds ( New York Times
2011; Urbina 2011). Dilution of drilling wastes containing radium by discharge to rivers does not
eliminate the health risks posed by that waste. Such discharges constitute a potential increased
risk of cancer among people who often eat fish from waters where drilling waste is discharged
( New York Times 2011). Fracking entails the risk of spills of hazardous hydraulic fracturing fluids
(Litvak 2010; Mayer 2010). Fracking has seriously contaminated shallow groundwater supplies in
northeast Pennsylvania with flammable levels of methane (Lustgarten 2009). Methane concentra-
tions seventeen times above normal have been detected in samples taken from water wells near
shale gas drilling sites employing hydraulic fracturing (Lustgarten 2011; Osborn et al. 2011). It is
possible that natural gas drilling with hydraulic fracturing may have caused earthquakes in North
Texas (Keenan 2011; Casselman 2009). There is evidence that the frequency of local earthquakes
can be increased by injection of fluids in deep wells (Keenan 2011; Hsieh and Bredehoeft 1981)
even without fracking.
Various treating and separating facilities are located near wells to treat the oil before storage
and transportation. Similar units are used to separate condensate, moisture, and other undesir-
able products from natural gas. Depending on numerous factors, the life span of a field can vary
considerably; however, the estimated average life of a typical field is fifteen to twenty-five years.
Many fields go through several development phases. A field may be considered fully developed
 
Search WWH ::




Custom Search