PETE 301

RESERVOIR ENGINEERING

Ibrahim Kocabas Petroleum Engineering Department

King Fahd University of Petroleum & Minerals

Reservoir Engineering

Learning Objectives of Lecture 1:

n Define/describe a reservoir n Define Reservoir Engineering n Describe/list role/functions of Res. Eng. n State objectives of Res. Eng. n Pet. Res. Hyrdrocarbon (HC) fluids n Classification based on phase diagram n Types/forms reservoir energies

Reservoir Engineering

Branches of Petroleum Engineering: Drilling engineering Production engineering Reservoir engineering.

Definition of a Reservoir

A reservoir is that portion of a trap which contains oil and/or gas as a single hydraulically connected system.

-it is a rock layer -porous so that stores oil -permeable so that allows flow of oil -has a mechanism to prevent escape of

oil(trapping mechanism)

How many reservoirs?

What are the trapping mechanisms?

DEFINITIONs OF RESERVOIR ENGINEERING Craft “The application of scientific

principles to the drainage problems arising during the development and production of oil and gas reservoirs“.

DEFINITIONs OF RESERVOIR ENGINEERING Colhoun “The phase of engineering

which deals with the transfer of fluids to, from or through the reservoirs“.

Functions OF RESERVOIR ENGINEERING

To continuously monitor the reservoir and collect relevant data and interpret it to be able to

1. Determine (present conditions)) 2. Estimate ( future conditions) and 3. Control the movement of fluids through the

reservoir so that

Objectives of reservoir engineering

we can a) enhance ( increase recovery factor)

and b) accelerate ( increase production

rate) the oil recovery

Petroleum reservoir HC fluids

n Oil Reservoirs - Produce mainly oil and gas and in some cases also water

- Heavy oil - Conventional oil

- Black oil - Volatile oil

n Gas Reservoirs - Produce mainly gas and in some cases also water

- Dry gas - Wet gas

n Gas Condensate Reservoirs - Produce gas which contains hydrocarbon liquid

- Gas condensate

PHASE DIAGRAM OF RESERVOIR FLUIDS

Phase Diagram of Black Oil

Phase Diagram of Dry Gas

Phase Diagram of Wet Gas

Phase Diagram of Gas Condensate

CLASIFICATION OF OIL RESERVOIRS

n Under Saturated Oil Reservoirs - Reservoir pressure is initially above

the bubble point pressure n Saturated Oil Reservoirs - Reservoirs pressure is initially below

the bubble point pressure

STAGES OF OIL RECOVERY

Recovery (production): is the displacement of oil and gas

towards the production wells and to the surface, and divided into: – Primary recovery – Secondary recovery – Enhanced oil recovery

STAGES OF OIL RECOVERY

Primary Recovery Production is accomplished through

the use of natural energy of the reservoir.

What is(are) form(s) of natural reservoir energy?

Types of reservoir energy

1. - Energy of compression of water and rock within the reservoir

2. - Energy of compression of oil within the reservoir

3. - Energy of compression of gas within the reservoir

4. - Energy of compression of water that are in adjacent or underlying aquifers

Types of reservoir energy

5. The gravitational energy that causes oil and gas to segregate within the reservoir

6. The surface energy manifesting itself in capillary pores

Types of reservoir energy

Note: n First four are potential energies

stored in compressed constituents.

n Equivalent to the potential energy stored in a spring.

n When converted to pressure-volume work, we can produce fluids.

Types of reservoir energy

Note: As mechanisms of energy release

are provided by drilling and operation of wells the reservoir pressure declines, fluid expands, flow is induced and hence fluids are produced.

Reservoirs classified based on dominant natural energy

Can we classify reservoirs based on dominant producing energy type?

- no consensus on the definitions and classifications.

Producing mechanisms based on dominant reservoir energy being released

Expansion drive Water drive Compaction drive

Imbibition drive Oil drive Gas drive partial full

Solution Gas drive Gas cap drive Gas drive

Segregating Nonsegregating

From Lake and Walsh

Producing mechanisms based on dominant reservoir energy being released

Common special

Depletion drive

Gas cap drive

imbibition compaction

Solution Gas drive

Full Partial

Segregating Nonsegregating

Water drive Combination drive

Formation drive I.Edge

II.Bottom I.Edge

II.Bottom

gravity