new oil reservoirs along with the development of improved crude oil recovery
methods has led to optimal production of crude oil in a sustainable way.
Typically, the recovery of crude oil from these oil reserves proceeds as three
different processes: primary, secondary, and tertiary oil recovery. During the primary recovery process, the existence of natural geological pressure is sufficient to
produce oil from beneath the earth surface. This pressure leads to the recovery of
about 10–20% of original oil in place. However, with time this natural geological
pressure gradually decreases and therefore results in reducing percentage of oil been
recovered. The secondary oil recovery process is then implemented at this point to
re-pressurize the reservoir bottom-hole by water injection. Injection of water in the
injection well sweeps the oil along the flow path leading to recovery of crude oil
from the production well. About 40–50% of the residual oil in place is recovered
during this process (Gieg et al. 2011).
Secondary flooding process is also limited for a period of time. With continuous
injection of water, channels are formed along the flow path, termed as viscous
fingering, which further lowers the efficiency of the recovery process. Moreover,
much of the oil still remains in the reservoir, as the water to oil ratio increases in the
production fluid and thus leads to unprofitable production of oil. Recovery of the rest
percentage of crude oil involves implementation of different methods to recover
residual oil based on reservoir nature. These recovery processes are termed as
tertiary oil production or enhanced oil recovery (EOR) processes and are typically
adopted after secondary flooding. The EOR process is of different types, such as
chemical, thermal, miscible gas, and microbial based process. The chemical EOR
process (CEOR) involves injection of solvents, surfactant, and mostly polymers such
as xanthan gum and partially hydrolyzed polyacrylamide to improve the sweep
efficiency of the drive fluid. Thermal recovery process such as SAGD (steam
assisted gravity drainage) involves the injection of steam to lower oil viscosity and
especially applied during heavy oil recovery. Microbial enhanced oil recovery
(MEOR) is further implemented as a tertiary process which is recognized as a
greener and sustainable way of oil recovery process. In MEOR, microbial activity
is utilized for producing crude oil. Microbes are known to use oil organics for
production of biosurfactant, bioemulsifier, biopolymers, various acids and gases.
These microbial products aids in the oil recovery process by improving the efficiency of the drive fluid (Gbadamosi et al. 2019).
Additionally, two different types of oil fields are present throughout the world,
i.e., onshore and offshore oil fields. Onshore oil fields are those fields discovered on
the land, while offshore oil fields are found in the sea. Both these oil fields constitute
similar oil production systems that are composed of two types of facilities. The
downhole facilities include injection and production well components, while above
ground facilities comprise injection pipelines, production pipelines, and processing
terminal facilities. Water during the secondary oil recovery process passes from the
processing terminal to the injection well, and then is injected downhole which leads
to its recovery from the production well. The produced water then passes through the
three-phase separator and finally to the processing terminal where oil is separated.
This whole secondary process, therefore, requires large amounts of injection water.
114
G. Prajapat et al.
methods has led to optimal production of crude oil in a sustainable way.
Typically, the recovery of crude oil from these oil reserves proceeds as three
different processes: primary, secondary, and tertiary oil recovery. During the primary recovery process, the existence of natural geological pressure is sufficient to
produce oil from beneath the earth surface. This pressure leads to the recovery of
about 10–20% of original oil in place. However, with time this natural geological
pressure gradually decreases and therefore results in reducing percentage of oil been
recovered. The secondary oil recovery process is then implemented at this point to
re-pressurize the reservoir bottom-hole by water injection. Injection of water in the
injection well sweeps the oil along the flow path leading to recovery of crude oil
from the production well. About 40–50% of the residual oil in place is recovered
during this process (Gieg et al. 2011).
Secondary flooding process is also limited for a period of time. With continuous
injection of water, channels are formed along the flow path, termed as viscous
fingering, which further lowers the efficiency of the recovery process. Moreover,
much of the oil still remains in the reservoir, as the water to oil ratio increases in the
production fluid and thus leads to unprofitable production of oil. Recovery of the rest
percentage of crude oil involves implementation of different methods to recover
residual oil based on reservoir nature. These recovery processes are termed as
tertiary oil production or enhanced oil recovery (EOR) processes and are typically
adopted after secondary flooding. The EOR process is of different types, such as
chemical, thermal, miscible gas, and microbial based process. The chemical EOR
process (CEOR) involves injection of solvents, surfactant, and mostly polymers such
as xanthan gum and partially hydrolyzed polyacrylamide to improve the sweep
efficiency of the drive fluid. Thermal recovery process such as SAGD (steam
assisted gravity drainage) involves the injection of steam to lower oil viscosity and
especially applied during heavy oil recovery. Microbial enhanced oil recovery
(MEOR) is further implemented as a tertiary process which is recognized as a
greener and sustainable way of oil recovery process. In MEOR, microbial activity
is utilized for producing crude oil. Microbes are known to use oil organics for
production of biosurfactant, bioemulsifier, biopolymers, various acids and gases.
These microbial products aids in the oil recovery process by improving the efficiency of the drive fluid (Gbadamosi et al. 2019).
Additionally, two different types of oil fields are present throughout the world,
i.e., onshore and offshore oil fields. Onshore oil fields are those fields discovered on
the land, while offshore oil fields are found in the sea. Both these oil fields constitute
similar oil production systems that are composed of two types of facilities. The
downhole facilities include injection and production well components, while above
ground facilities comprise injection pipelines, production pipelines, and processing
terminal facilities. Water during the secondary oil recovery process passes from the
processing terminal to the injection well, and then is injected downhole which leads
to its recovery from the production well. The produced water then passes through the
three-phase separator and finally to the processing terminal where oil is separated.
This whole secondary process, therefore, requires large amounts of injection water.
114
G. Prajapat et al.