Page 420 - Compression Machinery for Oil and Gas

Midstream Chapter 9 399

Injection/Withdrawal Compressors
Storage compressors are used primarily to pump gas from a transmission pipe-
line into an underground gas storage field during the injection season. In addi-
tion to injecting gas into storage facilities during the summer season, the same
compressors are used to pump gas from the storage field to the pipeline during
the winter withdrawal period. Most storage field compressors are designed to
operate over a broad range of volumes and pressures. Because of widely varying
conditions storage conditions, these stations are generally very complex. Oper-
ation normally requires multiple stage compression, complicated piping
arrangements, and complex control equipment.
Storage compressor stations are usually more permanent, more efficient,
and definitely more costly than production stations of equivalent pumping
capacity. A typical storage station contains several reciprocating compressor
units ranging in size from 750 to 4500kW each. Maximum withdrawal pres-
sures are usually less than 7MPa, but injection pressures are often in the range
of 20–28MPa. Reciprocating compressors are usually best suited for this appli-
cation due to the flexibility in adapting to a wide range of operating conditions.
Occasionally turbine-driven centrifugal compressors are used in stored stations;
however, centrifugal compressors are not always as suitable for this type of ser-
vice as reciprocating compressors because of the broad range of operating con-
ditions imposed on the equipment.

Local and National Pipeline Regulations

There are numerous local and natural regulations in the United States that reg-
ulate the construction, power, safety, environmental impacts, and operation of
midstream pipelines and compressor stations.
The following are a few of the agencies that regulate natural gas pipelines:
l The Federal Energy Regulatory Commission (FERC) regulates things such
as natural gas transportation rates, pipeline capacity, pipeline siting, and nat-
ural gas quality requirements.
l The US DOT Pipeline and Hazardous Materials Safety Administration
(PHMSA) and their state and local agents provide regulation for the safe
transportation of natural gas through pipelines.
l The US Environmental Protection Agency (EPA), the Fish and Wildlife Ser-
vice and state environmental protection agencies provide regulations for the
protection of the environment and cultural resources during the construction
and operation of pipeline facilities.
l The US Occupational Safety and Health Administration (OSHA) provides
regulation for the safe working place for personnel.
l Various state regulations that mostly regulate intrastate, utility, and gas dis-
tribution lines. These regulations closely mimic the US DOT PHMSA rules,
and many states act as dual inspection and enforcement agents of the DOT
and PHMSA requirements.