Republic of Iraq
Ministry of higher education and scientific research
University of Kerbala
College of Engineering - Petroleum Dept.
Reservoir engineering
Name of exp. :- Porosity measurement
Supervision by : Dr.Tahseen Al Taei
Mrs. Hawraa zanky
Mr. Salam Khaled
Mrs.zahraa
By:- ♧Ahmed haider salam
Exp. Date : 2/Nov/2023
◇Raad Saad Abbas
Written in : 5/Nov/2023
♤Ali Mohammed abd-alhassan
The purpose of measuring porosity
is to assess the capacity of a rock or reservoir to store and transmit fluids, such as oil and
gas, which is essential in the oil and gas industry for estimating hydrocarbon reserves and
optimizing production strategies Using different methods, including helium
Introduction
An important geological and petrophysical parameter that is crucial to the
discovery and extraction of hydrocarbons, especially oil and natural gas, is reservoir
porosity. It describes the volume percentage of pores or void spaces found deep
under the surface of the Earth in a rock formation. These gaps may include fluids
like gas, oil, or water and might differ in size, shape, and connectedness.
●Because it directly affects a number of
important facets of the oil and gas sector,
porosity is a crucial attribute. It first
establishes a reservoir’s storage capacity.
Because they can hold more hydrocarbons,
rocks with high porosity are more
economically viable for production. On the
other hand, low porosity rocks might not
contain enough gas and oil to warrant
exploration and production.
●Second, porosity affects how
fluids flow through the reservoir.
Hydrocarbons
can
migrate
through the linked pores and
move from the reservoir rock to
the
producing
wells.
Comprehending the distribution
and connectivity of porosity is
essential for refining production
strategies and guaranteeing
effective resource recovery.
◇ Additionally,
porosity plays a
crucial role in the
characterization of
reservoirs, assisting
petroleum engineers
and geologists in
determining the
potential productivity
and quality of
subsurface
formations. It helps
determine the kind of
rock, its porosity
distribution, and
depositional
environment, all of
which have an impact
on choices about
drilling techniques
and well placement.
♡Types of Porosity:
Primary Porosity:
Innate porosity present
in the rock when it was
formed.
Secondary Porosity:
Porosity that develops
after the rock’s
formation due to
processes like
fracturing, dissolution,
or compaction.
♧ In conclusion, porosity is a basic feature of reservoirs that affects storage
capacity, flow velocity, and total productivity. It influences exploration, production,
and evaluations of economic viability. It is a fundamental component of decisionmaking in the oil and gas sector. Porosity must be understood and measured in
order to successfully extract hydrocarbons.
Theory
Porosity holds great significance in petroleum engineering for several reasons:
♤ Storage Capacity:
Porosity measures the void
space within a reservoir
rock. Higher porosity
generally means a greater
capacity to store
hydrocarbons. Accurate
porosity determination is
crucial for estimating the
volume of oil and gas that
can be recovered from a
reservoir.
♡ Reservoir Quality Assessment:
Porosity is a key parameter for
assessing reservoir quality. It helps in
categorizing reservoir rocks as porous
or non-porous and in evaluating the
effectiveness of reservoirs for
hydrocarbon production
◇ Hydrocarbon Reservoir
Evaluation: Porosity is a fundamental
factor in determining the potential of
a subsurface rock formation to hold
and produce oil and gas. It directly
affects the estimation of hydrocarbon
reserves within a reservoir.
♧ Enhanced Oil
Recovery (EOR):
Porosity information
guides the selection
of EOR techniques.
It’s crucial for
designing methods
like waterflooding,
steam injection, or
chemical injection to
improve recovery
efficiency.
Measurement of porosity
The most well-known and used equations is in core analysis :
Porosimeter : A device used to measure voids in a specific core using helium injection .
Device parts( Diagram )
Procedure:
Initial pressure setting To set 100 psi accurately
•Switch on the console
•Don’t connect the matrix cup
•Wait for half an hour to get transducer stability
•Reset the control valve on the console
•Connect the console to the helium facility
• Set at 120-150 psi at the facility
•Check that HV01 is open and HV02 is switched to “Exaust”
•Adjust the control valve until getting 100 psi sharp on the application display
•In case pressure is too high.
❖
❖
❖
❖
❖
Close HV01
Switch HV02 to expand for 1 second
Turn the control valve anticlockwise
Open HV01
Adjust the control valve to get 100 psi sharp
•Watch 2-3 minutes to check that the pressure is OK.
Discussion by Ahmed haider salam
Q/What factors affect porosity?
An/ :
Rock Type: Different types of rocks have inherent variations in porosity.
Sedimentary rocks, like sandstone and limestone, often have higher porosity
compared to igneous or metamorphic rocks. This is because sedimentary
rocks are formed from accumulated sediments, creating pore spaces
between grains.
Grain Size: The size and sorting of mineral grains within the rock significantly
impact porosity. Well-sorted and rounded grains tend to create more
interconnected pore spaces, leading to higher porosity. Smaller grain sizes
typically reduce porosity.
Sorting: Sorting refers to the uniformity of grain sizes within a rock. Wellsorted rocks have grains of similar size, leading to higher porosity, whereas
poorly sorted rocks have a wide range of grain sizes, resulting in lower
porosity.
Cementation: The presence of cementing materials, such as silica or calcite,
can reduce porosity by filling in pore spaces between mineral grains. Over
time, these cements can “glue” grains together, reducing the rock’s overall
porosity.
Compaction: As sediments are buried and subjected to increased overburden
pressure, compaction occurs, reducing porosity. The weight of overlying
sediments compresses pore spaces, decreasing the rock’s ability to store
fluids.
Fracturing: Natural fractures in rocks can enhance porosity by creating
additional void space. In some cases, these fractures can be significant
pathways for fluid flow within the rock.
Dissolution: in certain geological settings, dissolution of minerals can create
pore spaces. For example, the dissolution of limestone can result in the
formation of caves and increased porosity.
Primary vs. Secondary Porosity: Primary porosity is the innate porosity
present in the rock when it was formed, while secondary porosity develops
after rock formation due to processes like fracturing, dissolution, or the
leaching of minerals.
Depth and Pressure: porosity generally decreases with increasing depth due
to compaction and the weight of overlying sediments. However, deep burial
can also lead to the dissolution of minerals, creating secondary porosity.
Water Saturation: The presence of fluids within pore spaces can displace air
or gas, reducing the available void space and effective porosity.
Rock Fabric: The arrangement and orientation of mineral grains and cements
can affect the connectivity of pore spaces. Well-connected pore networks
result in higher effective porosity.Understanding these factors is critical in
reservoir characterization and petroleum engineering, as they influence the
potential for oil and gas accumulation, reservoir quality, and the design of
effective production strategies.
Q/what are the methods to measure porosity? What is the best way? And why?
AN/
Core Analysis: Involves taking core samples from wellbores and measuring porosity in a
laboratory. This method is highly accurate and considered a standard in reservoir
characterization.
Well Logs: Well logging tools, such as neutron, density, and sonic logs, provide porosity
measurements while drilling. They offer real-time data but may have limitations in complex
lithologies.
Seismic Data: Seismic surveys can help identify areas with variations in rock properties, which
indirectly relate to porosity. Seismic data do not directly measure porosity but can provide
valuable insights.
Wireline and LWD Tools: logging-while-drilling (LWD) and wireline logging tools can provide
real-time porosity measurements while drilling. They are advantageous for well planning and
geosteering.
Geophysical Methods; Techniques like nuclear magnetic resonance (NMR) and electrical
resistivity are used to estimate porosity based on how fluids interact with rocks at a
microscopic scale.
Laboratory Experiments: Techniques such as mercury intrusion porosimetry and gas
adsorption methods provide detailed information about pore size distribution and porosity.
They are highly accurate but time-consuming.
Computed Tomography (CT) Scanning: CT scanning can create 3D images of rock samples,
allowing for non-destructive measurement of porosity.
Well Testing: Pressure transient tests and well testing can provide indirect information about
porosity and permeability by analyzing pressure responses to production and injection.
The choice of ‘best’ method depends on the goals of the study:
Core analysis: is the most accurate but requires core samples, which may not always be
available.
Well logs: are useful for real-time data and are commonly used during drilling operations.
Laboratory experiments : provide high precision but may be time-consuming.
Geophysical methods: are advantageous for non-invasive measurements.
Well testing: can provide porosity information indirectly during production or injection tests.
There is no single "best" method; the most appropriate method depends on the specific needs
and constraints of the study. Often, a combination of methods is used to obtain a
comprehensive understanding of porosity in a reservoir.
Q/ Can porosity be zero??
An/ No, porosity cannot be zero in a natural rock or sediment, as there will always be some
level of void space or pore volume within the material.
References
Reservoir management -LinkedIn Blog by Chief.eng.Abbas Fadel
Oilserve Company.
Geological studies at Royal.H.U.j