classification of the reservoir and reservoir fluids

1. CLASSIFICATION OF
RESERVOIR AND
RESERVOIR FLUIDS
MUHAMMAD HAMZA
ROLL NO. PE-28

2. TABLE OF CONTETS
 INTRODUCTION
 OIL RESERVOIR
 BLACK OIL
 GAS RESERVOIR
 CONDENSATE(RETROGRADE GAS)
 WET GAS
 DRY GAS

3. OIL RESERVOIR:
If the reservoir temperature is less than critical
temperature of the reservoir fluid, the reservoir is
classified as an oil reservoir
GAS RESERVOIR:
If the reservoir temperature is greater than critical
temperature of the hydrocarbon fluid, the reservoir
is classified as an gas reservoir

4. BLACK OIL
 Black oils are made up of a variety of
components including large, heavy,
and non-volatile hydrocarbons
 When the reservoir pressure lies
anywhere along line 1 → 2, the oil is
said to be undersaturated
 If the pressure is at 2, the oil is at its
bubble point, and is said to be
saturated
 GOR between 200 and 700 scf/stb
 API gravity 15-40
 Stock tank oil color is usually
brown to dark green

5. CONDENSATE (RETROGRADE GAS)
 At point 1, the retrograde gas
exists completely in a gaseous
state.
 As the pressure decreases, the
condensate exhibits a dew point at
point 2.
 As the reservoir further depletes
and the pressure drops, liquid
condenses from the gas to form a
free liquid inside the reservoir.
 GOR between 8000-70,000
scf/STB.
 40 -60 API gravity

6. WET GAS
 Natural gas that contains significant
heavy hydrocarbons such as
propane, butane and other liquid
hydrocarbons is known as wet gas or
rich gas.
 The pressure path line does not
enter the phase envelope, meaning
no liquid is ever formed inside the
reservoir.
 No liquid is formed inside the
reservoir. However, separator
conditions lie within the phase
envelope, causing some liquid to be
formed at the surface.

7. DRY GAS
 Natural gas that occurs in the
absence of condensate or liquid
hydrocarbons, is called dry gas.
 It is primarily methane with some
intermediates
 The pressure path line does not
enter into the phase envelope in the
phase diagram, thus there is only
dry gas in the reservoir.
 the surface separator conditions also
fall outside the phase envelope
hence no liquid is formed at the
surface separator.