What is Evolution?

MISCIBLE DRIVE ENHANCED OIL
RECOVERY
Presented by:
Abdul Wahab Khuwaja---------------------------(Group Leader)
Sufi Shahzad Abbasi-----------------------------(A-Group Leader)
Waheed Malik--------------------------------------------------------(Member)
Aadil Raza----------------------------------------------------------------(Member)
Mehran University of Engineering & Technology SZAB
Khairpur Mir’s Campus
Department of Petroleum & Natural Gas Engineering
Supervised By: Engr. Asadullah Memon

Outline
Oil Recovery Mechanism
Introduction to Miscible Drive
Basic Methods of Miscible Drive
Improved Miscible Drive Methods

Oil Recovery Mechanism &
Introduction to Miscible Drive
Presented By:
Waheed Malik
K-11pg87

Enhanced Oil Recovery (EOR) Processes
 Enhanced oil recovery (EOR) processes include all methods that use external
sources of energy and/or materials to recover oil that cannot be produced,
economically by conventional means.
 The goal of any enhanced oil recovery process is to mobilize "remaining" oil.
 This is achieved by enhancing oil displacement and volumetric sweep
efficiencies.
 Oil displacement efficiency is improved by reducing oil viscosity (e.g., thermal
floods) or by reducing capillary forces or interfacial tension (e.g., miscible
floods).
 Volumetric sweep efficiency is improved by developing a more favorable
mobility ratio between the inject ant and the remaining oil -in -place (e.g.,
polymer floods, water alternating-gas processes).

Miscible Drive
Miscible Oil Displacement:
 It is the displacement of oil by fluid with which it mixes in all
proportions without the presence of an interface, all mixtures
remain as a single phase.
Miscible Agents:
1. Propane, LPG mixtures, and Alcohols.
2. Miscible CO2 drive.
3. Natural gas, and High pressure gas (N2).
4. Surfactant slug.

Miscible Drive
The practical interest of miscible displacement became apparent
when it was discovered that:
1. To attain miscibility it is sufficient to inject a slug of solvent of
limited volume displaced by a much cheaper follow up fluid.
(absolute miscibility)
2. Under certain conditions of pressure, temperature and phase
composition various fluids may become miscible with reservoir
oil. (thermodynamic miscibility)

Basic methods of miscible drive
Presented By:
Abdul Wahab Khuwaja
K-11pg57

Basic Methods of Miscible Drive
The main standard methods of miscible drive are:
1. High pressure gas injection.
2. Enriched gas injection.
3. LPG slug injection.
4. Alcohol slug injection.

High Pressure Gas Injection
Two types are commonly used in high pressure gas injection:
1. Natural (HC) gas injection.
2. Inert gas injection.

High Pressure Natural Gas Injection
A. Phase Conditions in The Reservoir:
The oil must be rich in intermediate components.

The experience of various operators indicates that a miscible bank
is created after the injected gas has traveled a dozen meters from the
injection well. The quantity of unrecoverable oil under these
condition will clearly be negligible.
High pressure gas injection is also known as “high pressure gas
drive” and “vaporizing gas drive”.

B. Miscibility Pressure:
On the ternary diagram drawn at reservoir T, miscibility can
only be achieved between gas and oil at a pressure equal or
greater than the “miscibility pressure”, at which the tangent at
the critical point passes through (O).

C. Application of High Pressure Natural Gas Injection:
a) High reservoir pressure (deep formation)
(3000-4500 psi)
b) Oil reach in intermediates (gravity ≥ 35 API)

High Pressure Inert Gas Injection
 Once miscibility has been achieved, most of the gas injected is only
needed to push forward the miscible front and fill up the porous
medium..
 It is possible to inject at first a limited volume of natural gas (around
5% of the pore volume) sufficient to ensure miscibility with the
reservoir oil, and then replace the injection of expensive natural gas
with that of a cheaper gas.
 A suitable gas, approximately 12% CO2 & 88% N2, may be obtained
by the combustion of relatively small volumes of separator gas.
CH4 + 2O2 + 8N2 → CO2 + 2H2O + 8N2

Basic methods of Miscible drive
Presented By:
Sufi Shahzad Abbasi
K-11pg41

Enriched Gas Injection
A. Description of The Process:
In this case the formation of a miscible bank is achieved by way of
the intermediate components in the natural gas.
The process is also known as “condensing gas drive”.

As the composition of the oil changes from O to ot the residual oil
behind the front swells due to the absorption of light and intermediate
components from the gas.
At a certain stage the oil saturation will have increased sufficiently
that the oil becomes mobile and a bank of oil of composition ot will
be formed.
At the end of this process there is no residual oil, in contrast to high
pressure gas drive in which the resulting heavy oil op is
unrecoverable.

B. Operating Conditions:
In case of enriched gas injection the operating parameters are
pressure, and the composition of the injected gas (can be made
richer by the addition of butane and propane or even LPG)

LPG Slug Injection
In this method, the miscible bank is formed at the outset by the
injection of LPG of composition L, followed by the injection of dry
gas G..
The LPG is fully miscible with the reservoir oil in place (O).

Alcohol Slug Injection
Most miscible displacement process, such as those we have
already discussed, suffer from the disadvantages:
1. High reservoir pressures are required.
2. The areal sweep efficiency is relatively poor because of the
large mobility contrasts between gas, solvent and oil.
3. Natural gas and LPG are not always available in sufficient
quantity in the oil field.

Alcohol Slug Injection
These constraints have led to the search for methods of miscible
displacement in which water is the driving fluid.
An obvious possibility is the use of alcohols as a slug between the oil
and the water, since they are miscible with both liquids.
Normal butyl alcohol is used in front of and methyl alcohol behind the
isopropyl alcohol, the total slug volume required is reduced to 10% pore
volume.
Even though this type of miscible displacement has not yet found
commercial application due to the high cost of various alcohols studied.

improved methods of Miscible drive
Presented By:
Aadil raza
K-11pg88

Improved Miscible Drive Methods
It has been shown that the injection of natural gas under conditions
leading to miscible displacement suffers from the following
disadvantages:
1. Poor vertical sweep efficiency in heterogeneous reservoir.
2. Poor areal sweep efficiency.
To improve matters:
1. Pre-injection of water.
2. Chasing the miscible slugs with water.

Pre-Injection of Water
 The injection of solvent in stratified reservoir normally results in
the most permeable layers receiving many times the solvent volume
required to achieve miscible displacement throughout the field,
before the least permeable layers have even received the minimum
volume required.
 During the pre-injection of water the most permeable zones take
more water than the least permeable zones, so the injectivity to
solvent in the most permeable zones suffers a greater reduction than
that in the zones of lower permeability, the result is a more even
distribution of the solvent subsequently injected.

Miscible Slugs Driven by Water
In miscible displacement by gas the gas-oil mobility ratio is often
very unfavorable and thus the sweep efficiency is poor.
The mobility ratio may be reduced by injecting water with the gas.

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