Reservoir Dive

Mechanisms

Group # 2

Group Members

Umar Khalid 2013-PET-06

M.Usman Manzoor 2013-PET-05

Ahsan Ali 2013-PET-08

Abdi Aziz Rashid 2013-PET-53

AbdulRahman 2013-PET-07

Discussion Outline

Definition of Reservoir Drive Mechanism

Types of Reservoir Drive Mechanisms

Primary Recovery

Drive Mechanisms in Primary Recovery

Secondary Recovery & its Drive Mechanisms

Tertiary Recovery(EOR) & its Mechanisms

Infill Recovery

References

Overview

Queries

Reservoir Drive MechanismRecovery of hydrocarbons from

Petroleum/oil reservoir.

It supplies energy that moves the

hydrocarbons located in a reservoir

toward the wellbore as fluid is removed

near the wellbore.

Types of Reservoir Drive Mechanism

Recovery of hydrocarbons from an oil reservoir is commonly recognized to occur in several recovery stages .We use different mechanisms in these stages.These are :

Primary recovery

Secondary recovery

Tertiary recovery (Enhanced Oil Recovery, EOR)

Infill recovery

Primary Recovery

Natural energy of the reservoir works as Drive

Expansion of original reservoir fluids

Natural energy is determined by Production data (Reservoir

Pressure and Fluid production Ratios)

Use of the pressure already in the reservoir

Drive Mechanisms in Primary Recovery

Solution Gas Drive

Gas Cap Drive

Water Drive

Gravity drainage

Combination or Mixed Drive

Solution Gas Drive Mechanism

Reservoir rock surrounded by impermeable barrier.

At the start of Production, expansion of dissolved gases occur.

Change in fluid volume results in production of Reservoir fluids.

A solution gas drive reservoir is initially either considered to be

1. Under saturated

2. Saturated

Solution Gas Drive Mechanism

Oil Recovery from Solution Gas Drive Reservoirs

Initial reservoir

pressure

bubble point pressure

0 5 10 15

reservoir

pressure

(psig)

Dissolved gas

reservoirs typically

recover between 5

and 25% OIIP and

60 to 80% GIIP.

Oil recovery ,% of OOIP

Gas Cap Drive

Expansion of already present Gas Cap above the reservoir .

Decrease in pressure during the production, expansion of Gas cap occur.

As production continues, the gas cap expands pushing the gas-oil contact (GOC) downwards.

Better than Solution gas drive .

The recovery of gas cap reservoirs is better than for solution drive reservoirs (20% to 40% OOIP).

Gas cap Drive

Water Drive Mechanism

Reservoir bounded by aquifers.

During Pressure Depletion, the compressed water expands and

overflow towards reservoir.

Invading water drive the oil towards producing wells.

Water influx acts to mitigate the Pressure Decline.

The recovery from water driven reservoirs is usually good (20-60%

OOIP)

Oil recovery from water drive reservoirs typically ranges from 35

to 75% of the original oil in place

Water Drive Mechanism

Gravity Drainage

Density Differences segregate oil, water and gas .

Relatively weak mechanism

Can be used as drive mechanism in combination with other drive mechanism

The best conditions for gravity drainage are:

1. Thick oil zones.

2. High vertical permeabilities

Rate of production generated by gravity mechanism is vey low(50-70% OOIP).

The rate of oil gravity drainage in the reservoir is usually low compared to field

production rates.

Gravity Drainage

Combination or Mixed Drive

In practice, reservoir usually incorporates at least two main drive

mechanisms.

The management of the reservoir for different drive mechanisms

can be diametrically opposed.

For example Gas cap & Aquifer are sometime present together.

Strength of drives must be identified as early as possible in the life

of reservoir to optimize the reservoirs performance.

Combination or Mixed Drive

Secondary Recovery

Results from human intervention in the reservoir to improve

recovery after the low efficiencies of Natural /Primary Drive

mechanisms.

Two techniques are commonly used :

(i) Water flooding

(ii) Gas flooding

Water Flooding Mechanism

Injection of water in the base of reservoir .

Water flooding maintain the reservoir pressure.

Displace oil (usually with gas and water) towards production wells.

The successful outcome depends on

1. Designs based on accurate relative permeability data in both

horizontal directions,

2. The choice of a good injector/producer array

Water Flooding Mechanism

Gas Flooding Mechanism

Same as Water Flooding.

Injection of a gas.

e.g CO2, N2 or flue gases are generally used.

Categorized into two types :

1. Immiscible gas injection.

2. Miscible or high-pressure gas injection.

Gas Flooding Mechanism

Immiscible gas injection

Inefficient fluid for additional oil recovery.

The gas is non-wetting to reservoir rocks

The gas will move through the larger spaces of the reservoir rock

Thus the initial gas may be displacing gas not oil.

Miscible gas injection The gas is wetting the reservoir rock.

The gas moves through smaller pores.

The injection of non aqueous hydrocarbons solvent.

The displacement of oil occurs.

An important factor is that the mass transfer between displaced and the displacing factor/ phase.

Leads to the formation of oil bank, to move.

Gas Flooding Mechanism

Tertiary Recovery (EOR)

Extraction by Primary and Secondary recovery methods is about

35% of the original oil in place.

Many methods are used:

(i) Thermal

(ii) Chemical

(iii) Miscible gas

Thermal EOR

Use of heat to improve oil recovery by reducing the viscosity of heavy oils and

vaporising lighter oils and hence improving their mobility.

This technique includes :

1. Steam injection

2. injection of a hot gas that combusts with the oil in place.

3. Microwave heating downhole

4. Hot water injection.

thermal EOR is probably the most efficient EOR approach.

Thermal EOR

Chemical EOR

Use of Chemicals added to water in the injected fluid of a Waterflood to improve oil recovery.

This can be done in many ways, examples are listed below:

1. Increasing water viscosity (polymer floods)

2. Decreasing the relative permeability to water (cross-linked polymer floods)

3. Increasing the relative permeability to oil (micellar and alkaline floods).

4. Decreasing the interfacial tension between the oil and water phases(micellar and alkaline floods)

Chemical EOR

Miscible Gas

Uses a fluid that is miscible with the oil

A fluid has a zero interfacial tension with the oil.

In practice a gas is used since gases have high mobilities and can easily

enter all the pores in the rock providing the gas is miscible in the oil.

Three types of gas are commonly used:

1. Carbon di oxide

2. Nitrogen

3. Hydrocarbon gases

All of these are relatively cheap to obtain..

Miscible Gas

Infill Recovery

At the end of the reservoir life.

To improve the production rate.

To carry out infill drilling,

Directly accessing oil that may have been left unproduced.

By using all the previous natural and artificial drive mechanisms.

Infill drilling can involve very significant drilling costs

Additional production may not be great.

References

• http://homepages.see.leeds.ac.uk/~earpwjg/PG_EN/CD%20Contents/Formation%20Evaluation%20English/Chapter%203.PDF

• https://www.metu.edu.tr/~kok/pete110/PETE110_CHAPTER5.pdf

• http://wiki.aapg.org/Drive_mechanisms_and_recovery

• Petroleum Reservoir Engineering ----Basic Concepts

• general view of oil recovery

• https://www.google.com.pk/slideshare

Any Question ??????