lec 1.pdf PETROLEUM PROPERTIES RESERVIOUR

Siv K. Ali
Petroleum Reservoir Engineering
Sivar.Kais@knu.edu.iq
Department of Petroleum Engineering - Knowledge University
Fundamental of Reservoir Engineering 2
Lecture-1: Introduction to Reservoir Engineering
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Outlines
•The nature of Petroleum
•Petroleum Reservoir
•Reservoir Rock Properties
•Integration Reservoir Engineering
•Activities of Reservoir Engineering
•Reserve Estimation
•Reservoir Rock Properties
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Siver K. Ali - Petroleum Engineering

The Nature ofpetroleum:
•All chemical compounds found in nature are classified as either
organic or inorganic. Organic compounds are those that contain
carbon. An important group within the organic family of
compounds is the hydrocarbons, which are compounds composed
of carbon and hydrogen only.
•Like coal, petroleum constitutes a prime source of hydrocarbons in
nature. It is a mixture of hundreds to thousands of compounds
and is found in many forms: in the gaseous state as natural gas, in
the liquid state as crude oil, or in the solid state as tar and
bitumen.
•Petroleum is mostly found trapped within sedimentary rocks at
various depths below the surface of the earth where it has
accumulated over millions of years.
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The Nature ofpetroleum:
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•A petroleum reservoir is a geological structure where petroleum
accumulates within a layer (formation) of sedimentary rock and
cannot move out of it.
•The obstacle to the movement of petroleum is caused by the
geometry of the layer or its properties, the properties of adjacent
layers, or a combination of factors.
•Petroleum migrates from where it is generated deep (source
rocks) under the surface into the trap. By doing so, petroleum
displaces water that originally fills the layer
The petroleumReservoir:
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The petroleumReservoir:
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The petroleumReservoir
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Reservoir Pressure
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•Because petroleum is lighter than water, it accumulates at the
top of the structure. However, layer above the trap is too
impervious to allow petroleum to continue its movement
upwards, which causes the petroleum to remain trapped in
the reservoir.
•Discovering a petroleum trap does not necessarily mean that
petroleum can be produced. This depends on two key factors:
a)The quantity of petroleum within the trap.
b)The rate at which it can be produced.
If these two parameters justify the cost of production then the
trap is considered a petroleum reservoir.
Petroleum Reservoir
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The reservoir engineer in modern oil and gas field
management is located at the heart of many of the activities
acting as a central co-ordinating role in relation to receiving
information processing it and passing it on to others.
Integration Reservoir Engineering
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Activities of ReservoirEngineering
categories:
i. The activities of reservoir engineering fall into
the following three general reservoir Estimation
(Geophysical, Log analysis, Laboratory)
ii.Development Planning
iii.Production Operations Optimisation
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Reserves are those quantities of petroleum which are anticipated
to be commercially recovered from known accumulations from a
given date forward.
•Reserve estimates involve some degree of uncertainty.
•The uncertainty depends chiefly on the amount of reliable geologic
and engineering data available at the time of the estimate and the
interpretation of these data.
•The relative degree of uncertainty
•may be conveyed by placing reserves into one of two principal
classifications:
Reserve Estimation
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Reserve Estimation
•Proved
•Unproved: less certain than
proved. Further subdivided to
express increasing uncertainty
•Probable
•Possible
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Probabilistic Representation ofReserves
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Reserve Estimation
•Proven reserves are those quantities of petroleum which,
by analysis of geological and engineering data, can be
estimated with reasonable certainty to be commercially
recoverable, from a given date forward, from known
reservoirs and under current economic conditions,
operating methods, and government regulations.
•Proved reserves can be categorized as developed or
undeveloped
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Reserve Estimation
Test 1
There are 950 MM stb ( million stock tank barrels) of oil initially in
place in a reservoir. It is estimated that 500 MM stb can be
produced. Already 100 MM stb have been produced. In the boxes
below, identify the correct answer.
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Reserve Estimation
Solution:
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Reserve Estimation
•Test 2
Before starting production it was estimated that there was a 90%
chance of producing at least 100 MM stb, 50% chance of producing
500 MM stb and 10% chance of producing 700MM stb. That is we
are sure we can produce at least 100MM stb, and we will probably
produce as much as 500 MM stb, and we will possibly produce as
much as 700 MM stb.
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•Proved :
•Probable :
•Possible :
•Proved :
•Proved & Possible
•Proved & Probable &
Possible :
100 MM stb
500 - 100 = 400 MM stb
700 - 500 = 200 MM stb
100 MM stb
500 MM stb
700 MM stb
Solution
Reserve Estimation
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•Unproved reserves are based on geologic and/or engineering data
similar to that used in estimates of proved reserves; but technical,
contractual, economic, or regulatory uncertainties preclude such
reserves being classified as proved.
•Probable Reserves: are those unproved reserves which analysis of
geological and engineering data suggests are more likely than not to
be recoverable. In this context, when probabilistic methods are used,
there should be at least a 50% probability that the quantities actually
recovered will equal or exceed the sum of estimated proved plus
probable reserves.
Reserve Estimation
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Reserve Estimation
•Possible Reserves are those unproved reserves which analysis of
geological and engineering data suggests are less likely to be
recoverable than probable reserves.
•Undeveloped Reserves: Undeveloped reserves are expected to be
recovered:
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Reserve Estimation
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Reservoir RockProperties
The specifications of a reservoir rock are such that there must be a
large enough capacity to store economically viable amounts of
hydrocarbon and the hydrocarbon flow at economical rates when
penetrated by a well. The factors which may affect the capacity and the
flow properties are
•Porosity
•Permeability
•capillary pressure
•Compressibility
•fluid saturation.
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•Porosity of rock is the ratio of pore volume to bulk volume and is
usually expressed as percentage
•Saturation of a phase is the fraction of the pore volume occupied by
the phase
•Permeability is a measure of ‘ ease of flow’ or the capacity of
formation to transmit fluids
•Capillary pressure is a combination effect of surface and IFT of the
rock and fluid, pore size and geometry & wettability of the system.
•Wettability is the tendency of a fluid to spread or adhere to a solid
surface in presence of another immiscible fluid ‘
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•In the case of a reservoir rock, these are not standard characteristics
determined before formation of the rock, but are closely linked to the
geological processes that brought the sediments together and deposited
them in the sequences and under the chemical and physical changes
inherent in the system.
•In order to extract the fluids, the rock must be permeable which requires
that there be sufficiently large, interconnecting pores.
•Although a permeable rock must also be porous, a porous rock is not
necessarily permeable.
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•The pore spaces (or interstices) in reservoir rock provide the container for
the accumulation of oil and gas and these give the rock its characteristic
ability to absorb and hold fluids.
•Most commercial reservoirs of oil and gas occur in sandstone, limestone
or dolomite rocks, however, some reservoirs occur in fractured shale.
•For the reservoir engineer, porosity, permeability, capillary pressure,
relative permeability are the most important rock properties as a
measure of the space available for accumulation of hydrocarbon fluids.
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Reservoir Rock PropertiesMeasurements
•Core measurements
• Well log
• Density log
• Sonic log
• Neuron log
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•Rock properties are determined by performing laboratory analyses on
cores from the reservoir to be evaluated.
•The cores are removed from the reservoir environment, with
subsequent changes in the core bulk volume, pore volume, reservoir
fluid saturations, and, sometimes, formation wettability.
•There are basically two main categories of core analysis tests that are
performed on core samples regarding physical properties of reservoir
rocks. These are:
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Routine core analysis tests
•Porosity
•Permeability
•Saturation
Special tests
•Overburden pressure
•Capillary pressure
•Relative permeability
•Wettability
•Surface and interfacial tension
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Cores
•Used to correlate
indirect measurements,
such as wireline/LWD
logs
•Used to test compatibility of injection
fluids
•Used to predict borehole stability
•Used to estimate
probability of formation
failure and sand
production
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