BY Muhammad Fahad Ansari 12IEEM14

2. ADDITIONAL OIL RECOVERY BY GASADDITIONAL OIL RECOVERY BY GAS
RECYCLINGRECYCLING
Syed Muhammad Raza QasimTaqvi (Group Leader) 07PG132
Syed Najaf Akhtar Zaidi (Assistant Group Leader) 07PG48
Muhammad Shoaib Khan 07PG135
Muhammad Fahad 07PG131
Ali Arsalan Pathan 07PG134
Junaid Ishtiaque 07PG52

3. Agenda & DistributionAgenda & Distribution
 INTRODUCTION
 Ali Arsalan Pathan
 OTHER MISCIBLE METHODS
 Muhammad Fahad
 CLASSIFICATION OF GAS RESERVOIRS & PRESSURE
MAIINTAINANCE IN CONDENSATE RESERVOIR
 Junaid Ishtiaque
 OVERVIEW OF CONDENSATE RESERVOIR & ITS PRODUCTION
HANDLING
 Muhammad Shoaib Khan
 THERMODYNAMICS OF GAS RECYCLING & WELL LOCATION
 Syed Najaf Akhtar Zaidi
 CASE STUDY
 S M Raza Qasim Taqvi

4. IntroductionIntroduction
By Ali Arsalan Pathan

5. IntroductionIntroduction
Worldwide reservoirs are depleting…..so
the need of today is to find more oil
deposits or other resources of energy….
◦ Cure the reservoirs…??
 Curing methods…
 IOR
 EOR
For the peculiar Gas Condensate
Reservoir….. Most suitable method is
“GAS RECYCLING”

6. Gas RecyclingGas Recycling
The re-injection of the produced gas back
into the reservoir is called GAS
RECYCLING
It can be carried out in initial as well as later
stages of the field
Gas recycling maintains the reservoir
pressure and allowing it to decline the
pressure slowly and gradually!!!
What is the basic purpose to choose this
method…?
 To debate…

7. Gas Recycling (Continue…)Gas Recycling (Continue…)
Gas Recycling in gas condensate Reservoir has been
recommended for several years as an optimum
production scenario of increasing condensate
recovery
As pressure reduces, liquid condenses from the gas
to form free liquid in the reservoir
Condensate liquid builds up near wellbore causing a
reduction in gas permeability and gas
productivity………required additional oil
recovery….by….GAS RECYCLING
The injection of Dry gas into gas condensate
reservoir helps in vaporizing the condensate and
increase its dew point
What is the future of this technique??

8. Other Miscible MethodsOther Miscible Methods
By Muhammad Fahad

9. Miscible MethodsMiscible Methods
The gas miscible methods are ……
MISCIBLE HYDROCARBON
DISPLACEMENT
CARBON DIOXIDE INJECTION
INERT GAS INJECTION

10. MISCIBLE HYDROCARBONMISCIBLE HYDROCARBON
DISPLACEMENTDISPLACEMENT
A Dissolving fluid will be introduced into the
reservoir to eliminate the forces causing oil
retention and helps in sweep efficiency.
In earlier days a solvent was injected followed
by liquid or gas but the result are not
effective.

11. MISCIBLE HYDROCARBONMISCIBLE HYDROCARBON
DISPLACEMENTDISPLACEMENT
 MISCIBLE SLUG PROCESS: A slug of liquid
hydrocarbon equivalent to 50% PV followed by natural gas,
or gas and water is injected.
 ENRICH GAS PROCESS: A slug of enriched natural gas
followed by lean gas is injected with the ration ranges
between 10-20% PV consist of ethane through hexane (C2-
C6).
 HIGH PRESSURE LEAN GAS PROCESS: A lean gas is
injected at a high pressure in order to cause retrograde
evaporation of the crude oil and formation of a miscible
phase, which contain C2-C6.

12. CARBON DIOXIDE INJECTIONCARBON DIOXIDE INJECTION
 CO2 is forced into a reservoir which create a miscible front by a
gradual transfer of smaller, lighter hydrocarbon molecules from the
oil to the CO2.
 This miscible front is a essence a bank of enriched gas.
 Under favorable conditions this front will be soluble with the oil,
making it easier to move toward production wells
 Production comes from an oil bank that forms ahead of the
miscible front.
 As reservoir fluids are produced through production wells, the
CO2 reverts to a gaseous state and provides a "gas lift" similar to
original reservoir pressure
 This procedure may be repeated until oil production drops below a
profitable level.

13. CARBON DIOXIDE INJECTIONCARBON DIOXIDE INJECTION
ADVANTAGES
 Swells oil and reduces viscosity.
 Miscibility can be attained at relatively
low pressure in many reservoirs.
 Carbon dioxide is a non-hazardous,
non-explosive gas that causes no
environmental concern if large
quantities are lost to the atmosphere.
 May be available as a waste gas (gas-
processing plants or industrial plants)
or may be produced from reservoirs
containing CO2.
DIS-ADVANTAGES
 Injection of slugs of water is often necessary
to reduce fingering.
 Carbon dioxide with water forms highly
corrosive carbonic acid. Special metal alloys
and coatings for facilities are needed.
Corrosion mitigation can be a considerable
part of the cost of the process.
 The alternate injection of slugs of CO2 and
water requires a dual injection system,
adding to the cost and complexity of the
project.
 Large volumes of CO2 are needed. It may
take 5-10 MSCF of gas to produce one
barrel of stock tank oil.

14. INERT GAS INJECTIONINERT GAS INJECTION
 NITROGEN is injected into a reservoir forms a miscible
front by vaporizing some of the lighter components from the
oil.
 This gas, now enriched to some extent, continues to move
away from the injection wells, contacting new oil and
vaporizing more components, enriching itself further, this
action continues, the leading edge of this gas front becomes
so enriched that it goes into solution becomes miscible, with
the reservoir oil.
 Continued injection of nitrogen pushes the miscible front
through the reservoir moving a bank of displaced oil toward
production wells
 Water slugs are injected alternately with the nitrogen to
increase the sweep efficiency and oil recovery

15. INERT GAS INJECTIONINERT GAS INJECTION
ADVANTAGES
• Nitrogen can be manufactured
on site at less cost than other
alternatives
Nitrogen has an unlimited
source, and being completely
inert it is non-corrosive
DIS-ADVANTAGES
• Reservoir should have API gravity
higher than 35 degrees
• The oil should have a high formation-
volume
• The oil should be under saturated or
low in methane (C1).
• The reservoir should be at least 5,000
feet deep to withstand the high
injection pressure (in excess of 5,000
psi) necessary for the oil to attain
miscibility with nitrogen without
fracturing the producing formation

16. CLASSIFICATION OF GAS RESERVOIRS &CLASSIFICATION OF GAS RESERVOIRS &
PRESSURE MANTAINANCE IN CONDENSATEPRESSURE MANTAINANCE IN CONDENSATE
RESERVOIRRESERVOIR
By Junaid Ishtiaque

17. TYPES OF GAS RESERVOIRSTYPES OF GAS RESERVOIRS
 If the reservoir temperature is above the critical temperature of the
hydrocarbon system, the reservoir is classified as a natural gas
reservoir. On the basis of their phase diagrams and the reservoir
conditions, natural gases reservoir can be classified into four
categories:
Retrograde gas-condensate
Near-critical gas-condensate
Wet gas
Dry gas

18. PRESSURE MAINTENANCE IN OIL RESERVOIRPRESSURE MAINTENANCE IN OIL RESERVOIR
BY GAS INJECTIONBY GAS INJECTION
INTRODUCTION AND BACKGROUNDINTRODUCTION AND BACKGROUND
INTRODUCTION
 Physical criteria for successful gas injection
operation are basically the same as for
type of fluid injection the same physical
and thermodynamics variable control the
displacement process
 Gas injection has been used-to maintain
reservoir pressure at some selected level
or to supplement natural reservoir energy
to a lesser degree by re-injection of a
portion of the produced gas
 Gas injection has also been employed
frequently to prevent migration of oil into
a gas cap in oil reservoir with natural
water drives, with down dip water
injection or both.
BACKGROUND
 Since 1978 and the passage of the Natural
Gas Policy Act, the increasing value of
sales gas resulted in a decline in the
number of new gas-injection projects.
However, some opportunities still exist in
remote areas where recovery
consideration are augmented by storage
aspect of such projects and by specialized
application in connection with gravity
drainage systems and attic oil recovery
projects.

19. TYPES OF GAS -INJECTIONTYPES OF GAS -INJECTION
OPERATIONOPERATION
 Gas-injection pressure maintenance operations are generally classified into two
distinct types depending on where in the reservoir, relative to oil zone, the gas is
introduced.
 TWO TYPES OF GAS –INJECTION OPERATIONS:
1. External gas injection: External gas injection operation frequently referred to as
crestal or gas cap injection use injection wells in structurally higher positions of
reservoir usually in primary or secondary gas cap
2. Dispersed Gas Injection: Dispersed gas injection operations frequently referred to
as internal or pattern injection normally used some geometric arrangement of
injection wells for the purpose of uniformly distributing the injection gas throughout
the oil productive portions of reservoir

20. OIL RECOVERY EFFICIENCIESOIL RECOVERY EFFICIENCIES
1.Unit Displacement Efficiency:
Unit displacement efficiency is the percentage of oil in place within a totally
swept reservoir- rock volume that is recovered as a result of the displacement
process
2. Conformance Efficiency:
Conformance efficiency is the percentage of the total rock or pore volume
within swept area that is contacted by displacing fluid.
3. Areal sweep efficiency:
Areal sweep efficiency is the percentage of total reservoir or pore volumes
that is
Within swept area, the area contacted by displacing fluid.
Each of the three efficiencies increases with continued displacement,
therefore,' each is a function of number of displacement volumes, injected .The
rate of increase in recovery efficiency in a -given portion of reservoir
diminishes as gas break through occurs. Therefore the maximum value of each
component efficiency and, consequently ultimate recovery efficiency is limited
by economics considerations.

21. CALCULATION OF GAS PRESSURE MAINTENANCECALCULATION OF GAS PRESSURE MAINTENANCE
PERFORMANCEPERFORMANCE
 Estimate of gas-injection performance are generally based on simultaneous solution
of one more forms of conventional material-balance equation and displacement
equation
 A complete engineering analysis of reservoir for purpose of evaluating gas-injection
operations will usually consist of four major phases:
 Assembly, preparation, and analysis of basic data';
 Analysis of past performance,
 Projection of future performance of current operations, and,
 Estimation of gas pressure maintenance performance,

22. Overview of Gas CondensateOverview of Gas Condensate
Reservoir & its ProductionReservoir & its Production
HandlingHandling
By Muhammad Shoaib Khan

23. Overview of Gas CondensateOverview of Gas Condensate
ReservoirReservoir
That contains fluids only as a gas phase under initial reservoirT &P.
• Condensate separate from gas in a process called retrograde
condensation.
• What happens to the particles of a gas when they condense?
• Why do we need gas recycling process ?
• Why methane is good for gas recycling?
• What is composition of gas condensate reservoir?

24. Continue Gas condensate reservoir…Continue Gas condensate reservoir…
 How does Gas condensate reservoir develop?
 By producing the reservoir by natural depletion. The produced fluids are
processed and the resulting dry gas and gasoline sold.
 By rejection of all or part of the dry gas produced back into the reservoir.
The attractiveness of this recycling technique depends on the particular
circumstances and on how the recycling is carried out.
 Pressure and Temperature Ranges of Gas-Condensate Reservoirs
are:
◦ Gas-condensate reservoirs may occur at pressures below 2,000 psi and
temperatures below 100°F
◦ Probably can occur at any higher fluid pressures and temperatures
within reach of the drill.
◦ Most known retrograde gas-condensate reservoirs are in the range of
3,000 to 8,000 psi and 200 to 400°F.

25. Continue Gas condensate reservoir…Continue Gas condensate reservoir…
•Formation GOR
• 5000 - 10000 scf/bbl
•What are the virtue exist in gas condensate reservoir for Pressure
maintenance?
• An active water drive
• water injection operations
• Injection of gas
• combination of all of these.
•What are the data Requirements for gas-condensate cycling study?
(1) Geologic data (2) Physical properties of the reservoir rock (3) Fluid
characteristics (4) Reservoir pressure history (volumetrically weighted) from
discovery to present (5) Condensate, gas, and water production data, from the
date of discovery (6) Proposed future production rates (7) Gas- and/or water-
injection data, past and future (8) Productivity, injectivity & Backpressure test
data on wells.

26. Handling of ProductionHandling of Production
 Main Equipment
 Separator , Compressor & fractionation equipment.
 Desulphurization:
 Reagents used:Sodium carbonate solution (regeneration by air
current).Sodium phenolate (regeneration by heating),Amines (regeneration by
heating).
 Dehydration:
 Various desiccants are used, both solids (silica gel, activated aluminum,
calcium sulphate, anhydrite, fluorite, etc.) and liquids (glycols). There is
practically no economic method for the removal of oxygen from gas.
 Filtration:
 Injection gas must be free from solid or liquid particles. Scrubbers and filters
are thus installed in the system so as to remove all particles larger than a few
microns.

27. Thermodynamics of GasThermodynamics of Gas
Recycling and well locationRecycling and well location
By Syed Najaf Akhtar Zaidi

28. THE THERMODYNAMICS OF GAS RECYCLINGTHE THERMODYNAMICS OF GAS RECYCLING
 Gas recycling may take place either:
 At a pressure higher than or equal to the dew-point pressure
pd.
 At a pressure lower than the dew-point.
 The idea of Thermodynamics of gas recycling is being given
by Standing in 1952.
 Re-injection of high pressure gas could be used to vaporize
crude oil and then be displaced by cycling as gas phase.
 This helps to maintain or restore the reservoir pressure in
order to increase the ultimate oil recovery.

29. WELL LOCATIONSWELL LOCATIONS
 Developed field: In which gas recycling starts after long period of natural
depletion
 Undeveloped field: By model study well arrangements are then selected.
pattern flooding
 Objective…….
To select a proper pattern that will provide the
Injection fluid with the maximum possible contact with the crude oil system.
Types:
◦ Direct line drive
◦ Stagerred line drive
◦ Five spot
◦ Seven spot / inverted seven spot( 1 injector + 6 producers)
◦ Nine spot

30. INJECTION ZONEINJECTION ZONE
 Gas injection into a gas-cap; when a gas-cap originally exist in a reservoir or
when it is formed by segregation during primary production.
 Gas injection into an oil zone; without presence of a gas-cap the injected gas
radially flows from the production wells.
 There are certain conditions under which water injection should not be considered:
(a) A very extensive gas-cap may form a preferential path for injected water
which will thus by-pass the oil zone. By comparison, gas injection into the gas cap
may result in additional oil recovery for the price of a few gas injection wells.
(b) A reservoir with a high initial water saturation may not be suitable for water
injection. There is a risk that no front will be formed and that oil and water will flow
in parallel, giving a low recovery efficiency.
If the reservoir has sufficiently high vertical permeability, gas-cap injection will
result in higher recovery than injection into the oil zone. The area at the gas-oil
contact is large, whereas in radial displacement the area of contact bet­ween gas and
oil is initially small.
 The capacity of each injection well can be estimated using an equation of the well-
known form: Q=C(P2
IW–P2
e)n

31. Case StudyCase Study
By S M Raza Qasim Taqvi

32. Case studyCase study
Recommended field
 Kunnar oilfield and LPG plant
Interesting point….initial feed up
Started date of project 1998
Started date of Gas recycling 2000
NO: of production well 6
No: of Gas injection well 1 (1-A)
Injection pressure 1650-1750
Ni 31.6 MM BBLS
Gi 124 BCF

33. Flow Rate before and afterFlow Rate before and after

34. WHFB Before & After InjectionWHFB Before & After Injection

35. Table of Flow Rate ShowingTable of Flow Rate Showing
Decline In 2 YearDecline In 2 Year

36. Declining of Flow Rate in 2 YearsDeclining of Flow Rate in 2 Years
0.96 1.2
6.12
0.432
2
0
0
9
2
0
1
1
2
0
0
9

37. Comparison of Decline Rate in 2Comparison of Decline Rate in 2
YearsYears

38. ConclusionConclusion
 IOR from gas injection has in the long run proved more
economical than expected
 Considering the huge amount of gas currently being flared, gas re-
injection is a fast and valuable alternative to avoid flaring and
thereby reduce CO2 emission and safe the environment
 Gas Recycling is a well know method of storing gas instead of
flaring
 The initial decline in a pressure and flow rate will be easily
maintained
 The recovery of condensate may be increased to a greater level by
utilizing the gas, that comes out of the same well
 Many fields of OGDCL specially chanda, bobi, can use that
techniques to optimize their oil production. Such like; bobi field is
also using Gas re-injection. Gas Condensates fields are the most
suited field for this operation

39. ReferencesReferences
 The development study on gas recycling injection in Yaha Gas Condensate
Field, Tarim Basin, China
 Effect of Gas Recycling on the Enhancement of Condensate Recovery,
Case Study: Hassi R’Mel South Field, Algeria
 Energy Information Administration:”U.S. Crude Oil, Natural Gas, and
Natural Liquids Reserves 2002 Annual Report:. December 2003
 Moritis, G.:”EOR Continues to Unlock the Oil Resources”, Oil & Gas
journal ,pp.45-52 April12,2004.
 Simulation of Experimental Gas-Recycling Experiments in Fractured
Gas/Condensate Reservoirs
 Kenyen.D and behei.: Third SPE comparative Project: Gas cycling of
retrograde condensate reservoir, SPE Paper 12278, Journal of petroleum
technology p 981-997, Aug, 1987.a
 Trans AIME Ballard,J.R. and Smith, L.R.” Reserves Engineering Design of a
Law Pressure Rich Gas Miscible Slug Flood:Jour Pet .Teach

40. References (Continue...)References (Continue...)
 Gao, J., Zheng,D. and Guo, T.: “ Solubility of Methane, Nitrogen, Co2 and a Natural gas
mixture in Aqueous Sodium Bicarbonate Solutions under High Pressure Elevated
Temperature”, J.Chem.Eng.Data, Vol.42, p 69-73, 1997.
 Fundamental of Enhanced Oil Recovery by Jacques Hagoort
 Applied Reservoir Engineering by B.C Craft and M.F.Hawkins
 Petroleum Engineering Hand Book-II by Howard B.Bradly
 Stalkup, F.I.: “ Miscible Displacement”, SPE Monograph Series, New York, p.129.
 Oil Reservoir Engineering Hand Book by G.Georege Segeler
 Mechanics of Secondary Oil Recovery by Charles Robert Smith
 Fundamental of Reservoir Engineering by L.P.Dake
 Enhanced Oil Recovery by Marcel Latil
 Reservoir Engineering HandBook By Tarek Ahmed
 WEBSITES:
 http://www.tutorvista.com/chemistry/realgases
 http://www.springerlink.com/index/h75555775817076.pdf
 http://www.rigzone.com/training/insight.asp?insight_id=345&c_id=4
 http://www.naturalgas.org.com
 http://www.pet.hw.ac.uk/research/rfi/index.htm