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Introduction to Petroleum Engineering

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The most important point in describing the flow of oil and gas is ... connate water expansion. reduction of porous volume. water influx. Production mechanisms ... – PowerPoint PPT presentation

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Title: Introduction to Petroleum Engineering


1
Introduction to Petroleum Engineering
  • Technishe Universiteit Eindhoven
  • from 3nd April to 5th May
  • College 4W100
  • room MA-1.50
  • Lectures tue/wen/thu 1330-1515

2
Week 15
3 - The oil and gas reservoirs structures and
origin This lecture will introduce few basic
elements of petroleum geology as formation of oil
gas accumulations and their structures.
5 - Petroleum engineering economics This lecture
will highlight the economics of petroleum
projects. Overviews of drilling, production and
exploration costs will be given.
6 - Properties and PVT behaviour of hydrocarbon
mixtures The most important point in describing
the flow of oil and gas is the volumetric
behaviour and the more complex aspect of
vapour-liquid equilibrium.
3
Week 17
7 - Driving mechanisms and production
forecasting One of the most important basic point
in correct understanding of the reservoir or well
production capability is the identification of
driving mechanisms.
8 - The production system surface facilities,
wells and reservoir This lectures aims to
introduce the structure of the oil gas upstream
industry with the peculiar objective to describe
the production system and its elements as well as
their complex interaction.
9 - The reservoir engineering and the connection
to the production engineering The high level of
complexity characterising the oil gas
reservoirs requires a specialised figure, the
reservoir engineer, that is called to manage the
reservoir in terms of flow and produced volumes
of oil gas.
4
The production system surface facilities, wells
and reservoir - Driving mechanisms and
production forecasting
5
Production system
Surface equipment
Well
Reservoir
6
Petroleum recovery
7
Recovery factor
  • The recovery factor is defined as
  • is formed by two components

Volumetric efficiency
Pore scale efficiency
8
Volumetric efficiency
  • The volumetric efficiency could be expressed as,
  • where
  • Ei is the vertical efficiency, it depends on
    vertical heterogeneities of the reservoir and
    from the mobility ratio
  • Ea is the areal efficiency, it depends on
    geometric distribution of wells and from the
    mobility ratio

9
Volumetric efficency
Ea
Chierici p. 139
Oil water
Oil water
water
Ei
10
Pore scale efficiency
  • The pore scale efficiency depends on the
    displacement process in the porous medium,
  • knowing fw dependencies, the Ed dipends mainly on
    the mobility ratio

11
Primary process
  • Different producing process could act in a
    reservoir
  • fluid expansion
  • gas expansion
  • liquid expansion
  • free gas expansion
  • gascap expansion
  • porous volume changes
  • connate water expansion
  • reduction of porous volume
  • water influx

12
Production mechanisms
  • The following production mechanisms could be
    identified
  • solution gas drive
  • gascap drive
  • natural water drive
  • compaction drive

13
Solution gas drive
Recovery 2-10
14
Gascap drive
Recovery 5-15
15
Water drive
Recovery 5-35
16
Comparison between production drives
17
Production forecasting
  • The production forecasting is a powerful tool in
    making decisions that must be linked to economics
  • to forecast the production from a reservoir two
    ways could be followed
  • material balance, an overall approach
  • flow simulation, a detailed description
  • more detailed simulations need more information
  • in early stages material balance is used, is easy
    and fast
  • when the needed information is available flow
    simulation is prefered to have also a confirm of
    acting phenomena

18
Material balance equation
  • The equation allows to evaluate the material
    balance after a reduction in pressure Dp in a
    reservoir with an initial volume of hydrocarbons
    N in SC
  • the material balance could be expressed as,

Oil production
Oil expansion
Solution gas expansion
Gascap expansion
Reduction of porous volume
19
Oil and dissolved gas expansion
  • The volume change due to liquid expansion is,
  • The dissolved gas expansion is,
  • Summing the two terms we obtain the expansion of
    the oil initially in place

20
Gascap expansion
  • The total volume of gascap in standard condition
    is
  • at the pressure p the volume in reservoir will be
  • the expansion will be

21
Change in pore volume
  • The reduction of pore volume for hydrocarbon is,
  • it can be expressed versus the pressure reduction
    ?p,

22
Change in pore volume
  • The final expression is,
  • this balance term is usually neglected due to the
    low compressibility of water and rocks,
  • Co 15x10-6 psi-1
  • Cw 3x10-6 psi-1
  • Co500x10-6 psi-1

23
Reservoir Production
  • The volume of produced oil in reservoir is equal
    to the sum of the produced oil at SC, Np, and the
    associated gas
  • The production into the reservoir can be written
    as,
  • where Rp is the production Gas-Oil Ratio

24
General balance equation
Oil expansion
Solution gas expansion
Oil production
Reduction of porous volume
Gascap expansion
Water influx
25
Istantaneous GOR equation
  • As istantaneous Gas-Oil Ratio is defined,
  • the gas production can be the results of free gas
    as well as of solution gas production. The two
    components can be written as,

26
Istantaneous GOR equation
  • From those definitions the following expression
    for GOR can be obtained,
  • The gas and oil flowrate can be expressed by
    Darcy equation in radial flow form

27
Istantaneous GOR equation
  • Substituing the following equation for the
    istantaneous GOR is obtained,

28
(No Transcript)
29
Saturation equation
Gas cap expansion
Water influx
Gas cap expansion
Water influx
30
How to use volumetric balance equations ?
Material balance eq.
Solution gas reservoir
Saturation eq.
Istantaneous GOR eq.
31
Tarner Method (1944)
Produced Gas - from material balance eq.
Produced Gas - from istantaneous GOR eq.
Attention!
32
Tarner Method
Choose a value for recovery factor
Calculate the produced gas from material balance
eq.
New value of recovery factor
Gp(MB) Gp(GOR)
Calculate the istantaneous GOR
Calculate the produced gas from istantaneous GOR
eq.
yes
End
33
Solution from Tarner method
34
Depletion drive reservoir
Fonte Cole, Reservoir Engineering Manual, 1969
  • Depth 6500 ft
  • Initial Pressure 2925 psia
  • Bubble Pressure 2100 psia
  • Reservoir Temperature 175 F
  • Swi 15
  • STOIIP 100,000,000 STB

35
Oil Properties
36
Summary of calculation results
37
Recovery Factor, Reservoir Pressure and GOR
38
Reservoir Performance time
  • To link reservoir performance with the time a
    well defined production policy is needed,
  • The link could be realized via the Productivity
    Index (PI o J) defined as,
  • the Productivity Index can be related to
    reservoir characteristics by means of Darcy
    equation

39
Production policy
  • maximum daily flowrate 15,000 STB/d
  • producing wells 60
  • single well productivity index 0.75 Bbl/d/psi
  • minimum bottomhole pressure 1500 psia
  • reservoir productivity index
  • 60 x 0.75 45 Bbl/d/psi

40
Production flowrate procedure
Calculate maximum possible flowrate from PI
Reduce BHP
qmax gt qall.
BHP lt Pres
yes
Flowrate equal to qall.
yes
Flowrate equal to qmax
Next step
41
Pressure production vs. time
42
Secondary processes and pressure maintenance
  • It consists in giving energy to the reservoir
    injecting non miscible fluids
  • this process is also known as reservoir pressure
    maintenance
  • objective is attain a better recovery increasing
    the volumetic displacement efficiency
  • those processes are commonly known as

43
Petroleum recovery II
44
Factors influencing the secondary recovery
  • Mobility ratio
  • inclination of reservoir
  • heterogeneities in the reservoir
  • geometry continuity of reservoir
  • production flowrates
  • position configuration of wells

45
Reservoir pressure vs. recovery factor
46
Production pressure vs. time
47
EOR and Improved recovery processes
  • Objective of improved revoery is to increase the
    recovery factor over natural limits
  • the processes act improving the volumetric
    displacement efficency as well as the pore scale
    displacement efficiency
  • they are classified on the basis of their
    chemical physical interaction mechanisms among
    injected fluids, hydrocarbons and reservoir rocks

48
Petroleum recovery III
49
Vapour injection
Archer p. 205
50
Huffpuff - alternate vapour injection
Archer p. 205
51
In-situ combustion
Archer p.206
52
Miscible gas displacement
53
Polimers displacement
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