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Reservoir Engineering Course
The Main objective of this course is to give you (Petroleum Geology students) a very
basic knowledge about how petroleum reservoirs are treated from the engineering point
of view so that you can value your geological input and know how important it is for the
users (Reservoir Engineers) and helps you to start building your team working
capabilities as you will be an important discipline of that team in the very near future
...
By B
...
Craft and M
...
Hawkins,
Lousiana State University
...

In order to start we have to spend some good time getting familiar with the
Fundamentals of Reservoir Engineering
...
It is of prime importance to exert the required effort to be
familiar with that language
...
Traditionally, a glossary
appears at the end of a book and includes terms within that book which are newly
introduced, uncommon or specialized
...
glossary
...
slb
...


Oil Field Units of Measurements:
Any given quantity can be a variable, parameter, or constant depending on the particular
problem
...
(pressure, Temprature…etc)
Parameters —quantities which are fixed for a given physical system, but which may
change from problem to problem
...
(conversion factors

...

Page | 1

Our reference book is very helpful in this regard giving a very comprehensive list under
the title Nomenclature at the very beginning which will make it very easy to refer to in
order to understand the meaning of a specified Symbol and its (Oil Field or English)
units
...
A list
of Greek letters is given in the following table for your records:

A
B
G
D
E
Z
H
Q
I
K
L
M
N
X
O
P
R
S
T
U
F
C
Y
W

a
b
g
d
e
z
h
q
i
k
l
m
n
x
o
p
r
s
t
u
f
c
y
w

alpha
beta
gamma
delta
epsilon
zeta
eta
theta
iota
kappa
lambda
mu
nu
xi
omicron
pi
rho
sigma
tau
upsilon
phi
chi
psi
omega

a
b
g
d
e
z
h
q
i
k
l
m
n
x
o
p
r
s
t
u
f
c
y
w

On the other hand, we have to know that in petroleum Industry, two different unit
systems are used:



What is sometimes referred to as Oilfield (or English) units,
SI units
...
The SI system of units and its relationship with oilfield units is
discussed in detail in two articles from the Journal of Petroleum Technology
Page | 2

(Campbell and Campbell, 1985)
...

The following table lists some common quantities and their units in the two systems:
Quantity

Practical Oilfield Unit

Coherent SI Unit

Volume, liquid

STB,
psia

m³,

cubic meter measured at 15ºC, 1 amt = 101
...
65 psia

m³,

cubic mere measured at 15ºC, 1 atm

Production rate, liquid

STB/D, stock tank barrel per day

m³,

cubic metre per second

Production rate, gas

SCF/D,

standard cubic feet per day

m³,

cubic metre per second

Gas-oil ratio

SCF/B,

standard cubic feet per stock tank barrel

m³/ m³, dimensionless

Pressure

psi,

Temperature, absolute
Temperature, relative

ºR,
ºF,

Time

hr
...
,

Viscosity
Permeability

stock tank barrel measured at 60ºF, 14
...


centipoise

Pa-s, Pascal –second

md
...
158 987 3

=

cubic meters of crude oil

feet (ft)

x

30
...
894757E+03

=

Pascal

Page | 3

Hydrocarbon Reservoirs:
Conditions Favorable For Hydrocarbon Reservoir Formation
Petroleum deposits will be formed only in those areas where geological conditions
combine to form and trap them
...

 First, the reservoir rock must possess sufficient void space, called porosity, to
contain the oil and gas
...

 Third, sufficient quantity hydrocarbons must be accumulated into a trap of
impervious cap rock which prevents upward migration of the oil and gas from the
source beds, forming a petroleum reservoir
...
Traps are
described as structural traps (in deformed strata such as folds and faults) or stratigraphic
traps (in areas where rock types change, such as unconformities, pinch-outs and reefs)
...

A reservoir is that portion of a trap which contains oil and/or gas as a single
hydraulically connected system (see p-4 of chapter-1)

Page | 4

Aquifer

A body of rock whose fluid saturation, porosity and permeability permit production of
groundwater
...

Principal Classifications of petroleum reservoir forming Traps:

Page | 5

Reservoir Engineering may be defined as the application of scientific principles to the
drainage problems arising during the development and production of oil and gas
reservoirs
...

The working tools of the reservoir engineer are subsurface geology, applied mathematics,
and basic law of physics and chemistry governing the behavior of liquid and vapor phases
of crude oil, natural gas and water in reservoir rocks
...


Page | 6

Reservoir management:
Is an on-going, dynamic process of collecting, analyzing, validating, and integrating
reservoir description data and well/reservoir performance data into an optimal reservoir
development and depletion plan
...
In the example
below, contours are from seismic data
and correspond to the top of the cap rock
...

An isopacheous map shows the contours
of the inner surface of the cap rock with
equal thickness of pay
...

Early Mapping Is Generally Based On
Seismic Data Only, Then Well Logs For
Every Well Drilled Are Used To Update
And Develop Concurrent Maps
...


Review of Reservoir Rock Properties
Porosity, Ф
The percentage of pore volume (void space) or that volume within rock that can contain
fluids
...

Effective porosity is the interconnected pore volume in a rock that contributes to fluid
flow in a reservoir
...
Total porosity is the total void space in the
rock whether or not it contributes to fluid flow
...


Page | 8

Porosity must be determined by direct measurement on Core Samples in the laboratory
Or estimated from Open Hole Well Logs
Permeability, K
The ability, or measurement of a rock's ability, to transmit fluids, typically measured in
darcies or millidarcies (Oilfield units)
...


Formations that transmit fluids readily, such as sandstones, are described as permeable
and tend to have many large, well-connected pores
...

•

Absolute permeability is the measurement of the permeability conducted when a
single fluid, or phase, is present in the rock
...
The relative
saturations of the fluids as well as the nature of the reservoir affect the effective
permeability
...
If a
single fluid is present in a rock, its relative permeability is 1
...
Calculation of
relative permeability allows for comparison of the different abilities of fluids to
flow in the presence of each other, since the presence of more than one fluid
generally inhibits flow
...

Lateral permeability contrast can be particularly important in fractured
formations, where effective permeability in the direction of the fractures may
be many times greater than the matrix permeability
...
This can be detected
from well-test data
...
This is called vertical to horizontal permeability anisotropy
...

Page | 9

Subsurface Pressures
Pressure tends to increase with depth
...
The Normal value is taken as 0
...


Geostatic pressure (Overburden Pressure): is the pressure of the weight of
overburden, or overlying rock, on a formation; also called lithostatic pressure
...
* 1
...


Pore Pressure (Reservoir Pressure): is the pressure of fluids within the pores of a
reservoir, usually hydrostatic pressure, or the pressure exerted by a column of water from
the formation's depth to sea level
...
* 0
...

Pore Pressure (Reservoir Pressure): is directly measured by lowering a pressure gauge
into the wellbore and record its value at a specific depth
...


Page | 10

Subsurface Temperature, T
Since the earth is assumed to contain a molten core, it is logical to assume that
temperature should increase with depth
...

Ta , oF = Average Surface Temperature
...
usually taken as 1
...


Reservoir Fluids Behavior
Petroleum consists predominantly of paraffin series (Cn H2n+2) hydrocarbons together
with lesser quantities of cyclic hydrocarbons naphthalene (Cn H2n) and aromatics (Cn
H2n-6) mixed together in varying proportions
...
In general oils contain a higher fraction of heavy molecules,
while at the other end of the scale, methane and other light molecules predominate in
gases
...


Page | 11

Classification of oil
Crude oil chemistry is quite complex and a typical crude may contain several thousand
different compounds belonging to 18 different hydrocarbon series
...
g
...

Difficulty in classifying oils by the chemical composition of their constituents has led to
widespread use of simpler, less technical classifications
...
In the former, the paraffin predominate, and such oil, when cooled to low
temperatures, yields an appreciable amount of light-colored wax that is not readily
attacked by acids or dissolved by ether, chloroform, carbon disulfide
...
G),
which (is the relative density of petroleum liquid and the density of water)
...
If its API
gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and
sinks
...
For example, if
one petroleum liquid floats on another and is therefore less dense, it has a greater API
gravity
...
API gravity is gradated in degrees on a
hydrometer instrument
...

Crude Quality
Crude oil is a highly variant natural resource
...

One of the first indications of quality is color
...
Not all crude oil is black - higher quality
oils can be a golden or amber in color
...
6 to 0
...

Nitrogen, carbon dioxide, hydrogen sulfide, and helium when present in small amounts
are considered as impurities
...
N2 and CO2 do not contribute to the heat valve
of the gas and if present in large amounts, the gas may not burn
...

Chemical analysis of gases and volatile hydrocarbons, up to C5 or C6, is relatively easy
and inexpensive to perform by low-temperature fractional distillation, mass spectroscopy
or chromatography
...

Classification of natural gas by Specific Gravity, which is the ratio of the density of the
gas to the density of an equal volume of air at the same temperature, is invariably
available as it easily measured at the well site with a simple balance
...

Commonly, two or three different fluid phases* exist together in the reservoir
...

It is customary to represent the phase behavior of hydrocarbon reservoir fluids on the P-T
plane showing the limits over which the fluid exists as a single phase and the proportions
of oil and gas in equilibrium over the two phase P-T range
...
As an example of the behavior of a pure hydrocarbon substance as
temperature and pressure are varied, the PVT cell (shown at the following diagram) is
charged with ethane (C2 H6) at 60ºF and 1000 psia
...

* Component: Any pure chemical substance
...

If the cell volume is increased while holding the temperature constant at 60ºF throughout,
it will be found that the pressure falls rapidly until the first bubble of gas appears
...
Further increase of cylinder volume does not reduce the pressure
provided temperature is held at 60ºF, although heat must be added to the system to
maintain a constant temperature
...
This is called the dew point
...


A series of similar expansions can be performed at various constant temperatures from
which the three-dimensional chart of can be constructed
...
At pressures above the vapor pressure curve ethane exists
in the liquid phase and beneath it in the gaseous phase
...

As the critical point is approached the properties of the gas and liquid phases approach
each other, and they become identical at the critical point
...

Page | 14

Phase behavior of multi-component systems
Consider the phase behavior of a
50:50 mixture of two pure
hydrocarbon components on the
P-T plane shown
The vapor pressure and bubble
point lines do not coincide but
form an envelope enclosing a
broad range of temperatures and
pressure at which two phases (gas
and oil) exist in equilibrium
...


Fluid above the bubble point is in the liquid state and fluid state below the dew point line
is gas: in the space enveloped between the two lines, liquid and gas are in equilibrium
...

Each reservoir fluid has a unique
phase diagram
...

Fluid at reservoir temperature and
pressure at point A' exists as
under-saturated liquid
...
This is approximately the path that fluids
follow in moving horizontally through the reservoir to the well bore
...

The path from A to the pressure and temperature the separator is operated as is shown by
dashed line and indicates the fractions of gas and oil recovered at separator conditions
...


Page | 16

Reservoir Fluid Properties:
An exact knowledge of a reservoir fluids physical properties including compressibility is
needed to predict reservoir performance and interpret well test data and production logs
...


Well to be shut in (or slightly opened just before sampling)

Pressure during sampling should remain above the bubble point
...


flow rates must be stable

gas vented at stock tank must be included in the total GOR
B- Charts of correlated or "average" properties usually made on a basis of specific
gravity are used in absence of measured data
...
Gas volume factors are generally
accurate to within 1% for hydrocarbon gases with less than 5% impurities
...

C- In situ measurements with production tools:
The relative densities of oil/water/gas fluid columns can be measured in situ
using a Gradiomanometer in the shut in well
...

Where direct laboratory PVT measurements are not available, it may be
necessary to use charts to estimate fluid properties
...

The application at hand dictates which sources of data may be used
...

On the other hand, use of a gas volume factor based on specific gravity correlations is
probably better than needed to convert a down hole spinner flow meter volumetric rate to
surface conditions
...
7+gauge)
V = volume occupied by gas in cu ft
n = number of 1b-moles of gas (lbs of gas/molecular weight)
R = 10
...

The compressibility factor "Z",
which is a function of the gas
composition, pressure, and
temperature, is used to modify the
ideal-gas law
...


Page | 18

Conversion factors between surface and down hole volumes
The previous discussions provided the fundamentals needed to be understood in order to
perform one of the major functions of the reservoir engineer which is to convert reservoir
or down hole volumes to surface volumes at sales points
...
Before a discussion of volume factors, let us define the units commonly
used to measure hydrocarbon volumes
...
5˚C) and 14
...

Gas measurement
Gas is measured in standard cubic feet (SCF), at the same reference conditions 60˚F, 14
...

Gas oil ratio
Gas oil ratio, abbreviated GOR is the ratio of gas production to oil production – both
measured at standard conditions 60˚F, 14
...
Units are standard cubic feet/stock tank
barrel, SCF/STB
The basic surface/down hole volumetric relationships shown diagrammatically in the
following figures should be kept firmly in mind when dealing with fluid conversions
...


Volume of oil including dissolved gas at downhole conditions

βo =
Volume of oil at Stock Tank conditions
The units of βo is Bbl/STB

βo being dependent essentially on the amount of dissolved gas its value increases with
pressure up to the bubble point, where all of the available gas is dissolved and then
decreases at a rate determined by the liquid compressibility
...
70, Twf =200˚F, and Pwf = 2,000 psia
Using the following chart:
Select the group of temperature lines for γ = 0
...

Then the Gas volume at the reservoir conditions = 400 / 125 = 3
...


Page | 21

Gas Formation volume factor is not constant and changes with pressure and in general the
following graph represents that change

Bg

G as F orm ation V olum e F actor

P ressure
Page | 22

Page | 23

Fluid Viscosities:

µo)

Oil Viscosity, (

The viscosity of a crude oil decreases
with a temperature increases and with an
increase of dissolved base
Heavier oils are generally more viscous
than lighter oils of the same hydrocarbon
base
...
The centipoise is the unit
used throughout this course
...

If the pressure on the oil is above
bubble-point pressure its viscosity is
increased by the amount given by the
correlation curve
...
The Chart shows this
relationship
...
As a practical limit,
however, the viscosity of a water-in-oil
emulsion does not exceed 5 cp
...

The charts to the left; give viscosity as
a function of temperature and
pressure, for gases of five different gas
gravities
...


Page | 25

Calculations of hydrocarbon in place and hydrocarbon reserves
Periodic calculation (estimation) of the Reservoir Hydrocarbon (Oil and/or Gas) In Place and anticipated
Recoveries is one of the important tasks to be done
...

These calculations are to be done each time a map is updated as a result of new data from drilling more
wells or changes in the geological understanding of a reservoir
...

b) By Material balance equation
...
Later on when estimated after
some life time of the reservoir the terms Initial/Original are not used and
the values refer to the corresponding time
...
Recovery Factor is the percentage of hydrocarbon that
can be recovered from a certain reservoir
...

b) Correlations based on statistical studies of particular types of reservoir
mechanisms
...

Before getting into details we need first to learn the basis for calculating the reservoir Bulk Volume

(VB)
...

A net isopachous map shows lines connecting points of equal net formation thickness; and the individual
lines connecting points of equal thickness are called isopach lines
...

A subsurface contour map shows lines connecting points of equal elevations on the top of a marker bed
and therefore shows geologic structure is used in preparing the isopachous maps when there is an oilwater, gas-water, or gas-oil contact
...


The contact line is the zero isopach line
...


Page | 27

Two equations are commonly used to determine the approximate volume of the productive zone
from area readings
...


This equation is used to determine the volume between successive isopach lines, and the total volume is
the sum of these separate volumes
...
are the areas enclosed by

t

successive isopach lines in acres; avg is the average thickness above the top or maximum thickness
isopach line in feet; and h is the isopach interval
...
Because of its simpler form, however, the
trapezoidal formula is commonly used, but it introduces an error of 2% when the ratio of successive
areas is 0
...
Therefore, a commonly adopted rule in unitization programs is that

wherever the ratio of the areas of any two successive isopach lines is smaller than
0
...
Whenever the ratio of the areas of any two
successive isopach lines is found to be larger than 0
...


Page | 29

The following example shows the method of calculating the reservoir bulk volume VB for an idealized
reservoir from the isopachous map of 6 contour lines
...
83

5

Trap
...
8

5

Trap
...
76

5

Trap
...
67

5

Trap
...
48

5

Pyr
...


99 c
6713 ac-ft

a ΔV =

(231+154)=963 ac
...
ft

(74) = 99 ac
...

This provides an estimate of the hydrocarbons-in-place, from which ultimate
recovery can be estimated by using an appropriate recovery factor
...


Calculating the initial oil in place (N) at initial reservoir conditions:

Ф
Swi
Boi
Taking;

Initial oil in place, STB
bulk reservoir volume, Acre
...

average reservoir porosity, fraction
Initial average water saturation, fraction
Initial oil formation volume factor at reservoir pressure p, res
...
06

Ф=20

=

5
...
Ft/SCF

Swi=20

Bgi=
...
1 BSCF

Page | 33

Calculating the Initial Oil in Place (N) at initial reservoir conditions: 
Assuming that the previous example is an Oil Reservoir The equation to estimate the IOIP is as follows:  

 
 Initial oil in place, STB 
                  Reservoir Bulk Volume, acre
...
 
Ф                   Average reservoir porosity, fraction 
Swi                Initial average water saturation, fraction 
Boi                Initial oil formation volume factor at initial reservoir pressure p, res
...
  
 
 
Now let us assume that:                Ф=20%   Swi=20 %  and  Boi=1
...
 Bbl/STB 
 
Then The IOIP is:       

 
=     5
...
2 
Million Stock Tank Barrel of oil at its initial/Original conditions 
before starting any production
...
2* 0
...
3 MMSTB 
 
Therefore, we are expecting to recover only 1
...
  

 
Calculating the amount of Gas in place (G) at initial reservoir conditions: 
Assuming that the previous example is an Gas Reservoir The equation to estimate the IGIP is as follows:  

 
Initial Gas in place, SCF 
                   Reservoir Bulk volume, acre‐ft 
Ф                     Average reservoir porosity, fraction 
Swi                 Initial average water saturation, fraction 
Bgi                  Initial gas formation volume factor at initial reservoir pressure pi , Cu
...
 ft
...
0031 cu
...
1 BSCF 
 
This is simply means that our example reservoir contains 15
...
 
 
Now if we assume that the recovery factor is 40% then the 
initial Gas Reserves is: 
 
Initial Gas reserves = 15
...
40 = 6
...
04 Billion Standard 
Cubic Foot of Gas from our reservoir
...
1 Introduction
Recovery of hydrocarbons from an oil reservoir is commonly recognised to occur in several
recovery stages
...

Secondary recovery This is recovery aided or driven by the injection of water or gas from
the surface
...

Infill recovery Is carried out when recovery from the previous three phases have been
completed
...

This chapter discusses primary, secondary and EOR drive mechanisms and techniques
...
2 Primary Recovery Drive Mechanisms
During primary recovery the natural energy of the reservoir is used to transport hydrocarbons
towards and out of the production wells
...
Early in the history of a reservoir the drive mechanism will
not be known
...
The earliest possible determination of the drive mechanism is a primary
goal in the early life of the reservoir, as its knowledge can greatly improve the management
and recovery of reserves from the reservoir in its middle and later life
...
These are:
(i)
(ii)
(iii)
(iv)
(v)

Solution gas drive
Gas cap drive
Water drive
Gravity drainage
Combination or mixed drive

Table 3
...


Dr
...
1 Recovery ranges for each drive mechanism
Drive Mechanism
Solution gas drive

Energy Source

Recovery, % OOIP

Evolved solution gas and expansion

20-30

Evolved gas

18-25

Gas expansion

2-5

Gas cap drive

Gas cap expansion

20-40

Water drive

Aquifer expansion

20-60

Bottom

20-40

Edge

35-60

Gravity drainage

Gravity

50-70
A combination or mixed drive
occurs when any of the first
three drives operate together,
or when any of the first three
drives operate with the aid of
gravity drainage
...
1 and 3
...
Note
particularly that water drive
maintains
the
reservoir
pressure much higher than the
gas drives, and has a uniformly
low GOR
...
2
...

As
production occurs the reservoir
pressure drops, and the
exsolution and expansion of
the dissolved gases in the oil
and water provide most of the
reservoirs drive energy
...
Paul Glover

Page 20

Formation Evaluation MSc Course Notes

Reservoir Drives

expanding from the water phase
...
3
...

Saturated: Reservoir pressure ≤ bubble point of oil
...
In this regime reservoir drive energy is provided only by the bulk expansion of
the reservoir rock and liquids (water and oil)
...

When the gas comes out of
solution the oil (and water)
shrink slightly
...

Thus gas
expansion is the primary
reservoir
drive
for
reservoirs below the bubble
point
...
If the reservoir is
initially undersaturated, the
reservoir pressure can drop
by a great deal (several
hundred psi over a few
months), see Figures 3
...
2
...
In
this undersaturated phase, gas is only exsolved from the fluids in the well bore, and
consequently the GOR is low and constant
...
When this happens, the GOR rises dramatically (up to 10 times)
...
Paul Glover

Page 21

Formation Evaluation MSc Course Notes

Reservoir Drives

reservoir pressure, as production continues, can, however, lead to a decrease in GOR again
when reservoir pressures are such that the gas expands less in the borehole
...

Oil recovery from this type of reservoir is typically between 20% and 30% of original oil in
place (i
...
low)
...
There is
usually no production of water during oil recovery unless the reservoir pressure drops
sufficiently for the connate water to expand sufficiently to be mobile
...


3
...
2 Gas Cap Drive
A gas cap drive reservoir usually benefits to some extent from solution gas drive, but derives
its main source of reservoir energy from the expansion of the gas cap already existing above
the reservoir
...
The actual rate of
pressure decrease is related to
the size of the gas cap
...

As production
continues, the gas cap
expands pushing the gas-oil
contact (GOC) downwards
(Figure 3
...
Eventually the
GOC
will
reach
the
production wells and the
GOR will increase by large
amounts (Figures 3
...
2)
...

Dr
...

The recovery of gas cap reservoirs is better than for solution drive reservoirs (20% to 40%
OOIP)
...
e
...
Points of importance to bear in mind
when managing a gas cap reservoir are:
• Steeply dipping reservoir oil columns are best
...
This is to maximise the time before gas breaks through in the well
...

• Produced gas can be separated and immediately injected back into the gas cap to maintain
gas cap pressure
...
2
...
As production continues, and oil is extracted from the reservoir, the
aquifer expands into the reservoir displacing the oil
...
Two types of water drive are commonly recognised:
• Bottom water drive (Figure 3
...
5)
The pressure history of a water driven reservoir depends critically upon:
(i)
(ii)
(iii)

The size of the aquifer
...

The reservoir production rate
...

If the production rate is too high then the extracted oil may not be able to be replaced by water
in the same timescale, especially if the aquifer is small or low permeability
...
1)
...
2), as the
pressure decrease is small and constant, whereas if the pressure decrease is higher (weakly
water driven reservoir) the GOR increases due to gas exsolving from the oil and water in the
reservoir
...


Dr
...

When water
breakthrough does occur the
well can either be shut-down,
or assisted using gas lift
...

The recovery from water
driven reservoirs is usually
good (20-60% OOIP, Table
3
...

If the ratio of water to oil
viscosity is large, or the
production rate is high then
fingering can occur which
leaves oil behind in the
reservoir (Figure 3
...


Dr
...
2
...
This process can be used as a drive mechanism, but is relatively weak, and in
practice is only used in combination with other drive mechanisms
...
7 shows
production by gravity drainage
...

High vertical permeabilities
...
However, it is extremely efficient over long periods and
can give rise to extremely high recoveries (50-70% OOIP, Table 3
...
Consequently, it is
often used in addition to the other drive mechanisms
...
2
...
For example,
in the case shown in Figure 3
...
We have seen that the management of the reservoir for

Dr
...
g
...
If both
occur as in Figure 3
...
It is the job of the
reservoir manager to identify
the strengths of the drives as
early as possible in the life of
the reservoir to optimise the
reservoir performance
...
3 Secondary Recovery
Secondary recovery is the result of human intervention in the reservoir to improve recovery
when the natural drives have diminished to unreasonably low efficiencies
...
Paul Glover

Page 26

Formation Evaluation MSc Course Notes

Reservoir Drives

3
...
1 Waterflooding
This method involves the injection of water at the base of a reservoir to;
(i) Maintain the reservoir pressure, and
(ii) Displace oil (usually with gas and water) towards production wells
...
However, it should be noted that the successful outcome of a waterflood process
depends on designs based on accurate relative permeability data in both horizontal directions, on the
choice of a good injector/producer array, and with full account taken of the local crustal stress directions in
the reservoir
...
3
...
Again accurate relperms are needed in the design, as well as injector/producer
array geometry and crustal stresses
...
At first sight this may not seem a problem, as
recombination in the stock tank or afterwards may be carried out
...
Then the decision whether to gasflood is not
trivial (e
...
Prudhoe Bay, Alaska)
...
4 Tertiary Recovery (Enhanced Oil Recovery)
Primary and secondary recovery methods usually only extract about 35% of the original oil in place
...
Many enhanced oil recovery methods have been
designed to do this, and a few will be reviewed here
...
All are extremely expensive, are only used when economical, and are
implemented after extensive SCAL studies have isolated the reservoir rock characteristics that are causing
oil to remain unproduced by conventional methods
...
Paul Glover

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