Lec 1
Lec 1
Lec 1
Water flooding
Introduction
Introduction
Outline
Drive mechanism & oil recovery
What is water flooding
Why water flooding?
Objective of water flooding
Water flooding versus pressure maintenance
Sweep efficiency
Oil recovery due to water injection
Water flooding strategy example
Factors controlling Waterflood behaviour
Reservoir simulation case study
Principle reservoir engineering for Water flooding
Introduction
Drive mechanisms & oil recovery
Primary recovery:
Natural energy of reservoirs to displace hydrocarbons
Primary drive Mechanism include:
1- Gas cap drive (expansion of the gas phase) RF=20-40%
2- Solution gas drive (exsolution of solution gas) Rf=5-30% OIIP
3- Water drive (aquifer displacement) RF=35-75%
Introduction
Drive mechanisms & oil recovery
Secondary recovery:
Adding energy to the natural system
Water is injected to maintain pressure & displace oil
Also known as waterflood
Typical recoveries are 25-45% OOIP after primary recovery (average
32%).
Introduction
Drive mechanisms & oil recovery
Tertiary recovery:
All other methods used to increase the recovery factor
Such as: Miscible & immiscible gas injection, Polymer flooding, Steam
flooding, etc.
1- Water is available
2- Low cost relative to other injection fluids
3- Ease of injecting water into a formation
4- High efficiency with which water displaces oil
Introduction
Objective of water flooding
Areal sweep efficiency, EA: The fraction of the floodable pore volume area
swept by the injected water. It depends on permeability anisotropy and
inhomogeneity and mobility ratio.
Vertical sweep efficiency, Ev: The fraction of the floodable pore volume in
the vertical plane swept by the injected water. It is influenced by reservoirs
stratification
Np = N x EA x EV x ED
where
N = OIIP at the start of water injection, STB
EA = Areal sweep efficiency, fraction
Ev = Vertical sweep efficiency, fraction
ED = Displacement sweep efficiency, fraction
Introduction
Water flooding strategy: example
Injection water
At early time of WF, Time 1
Oil wells Produce 100 % oil only
Oil
Introduction
Water flood progression
Wettability
Relative permeability curve
Capillary pressure
Well pattern