PETR3512Lectures3sl1-58

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Slide 1Dr Elena Pasternak

Reservoir characterisationPETR3512

Rock properties. Overview


Properties and characteristics of reservoirs & rocks

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PROPERTIES OF ROCKS» INTRODUCTION» MINERALOGY AND GRAIN SIZE» WHOLE ROCK

– Porosity and permeability– Acoustic Properties– Electrical Properties– Radioactive Properties– Magnetic Properties– Mechanical Properties– Characterisation of Matrix Composition

» POROSITY, GRAIN SURFACES & PORE THROATS– Pore Geometry– Wettability– Capillary Pressure– Isopore Throat Concepts


Mineralogy and grain size of reservoir and seal rocks

The most common minerals in reservoir rocks are quartz and calcite, while clays make up the major part of seals.

Trace minerals are often present as individual grains or as a cement.

Grain size is related to the properties of the minerals as well as the energy in the environment of deposition.

Grain size and sorting can vary considerably; however reservoir quality tends to reduce with reducing grain size. Accordingly, very fine grained rocks tend to have sealing properties.

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PROPERTIES OF ROCKS

Rock mainly composed of quartz with some feldspar (often altered) a few biotites and chlorites. Source : http://users.skynet.be/jm-derochette/sedimentary_rocks/

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PROPERTIES OF ROCKS

Quartz crystals surrounded by micas in a clay cement?Source: http://users.skynet.be/jm-derochette/sedimentary_rocks/


PROPERTIES OF ROCKS

Limestone containing skeletal material of small organisms.Source: http://www.glossary.oilfield.slb.com/

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PROPERTIES OF ROCKS

Shale. The fine grains are clays with organic material. The larger grains are quartz.Source: http://www.glossary.oilfield.slb.com/


Rock grain structure

Quartzite

Marble

(from B. Skinner, S.C. Porter, The dynamic Earth, 1995)

Conglomerate(from W.K. Hamblin, E.H. Christainsen, Earth’s dynamic systems, 1995)

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Sandstones

Brahmaputra River

Source:

5umA B

C D

http://webmineral.com/data/ http://webmineral.com/data/

Examples of clay minerals in sandstones.

(A) Kaolinite, (B) Smectite, (C) Chlorite, (D) Illite


More sandstones

Brahmaputra River

E F

USGS WebsiteUSGS Website

Examples of clay minerals in sandstones.(E) Kaolinite and Illite-smectite mixture (F) Glauconite (compacted grains).

Glauconite- Affects Log Readings Significantly– High Gamma-ray

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Brahmaputra River

Source: USGS website and Haddad et al. Liverpool University

•Zone A is characterised by zoning.•Zone B is a zone of “zero solutions”(i.e., no indexing, which

makes it likely that this area is SiO2 but not quartz). •Zone C is characterised by small, euhedral quartz crystal

outgrowths.•Zone D is porosity, filled with epoxy resin

The Effects of Burial on Reservoir Rocks: Quartz overgrowths

Quartz


Solid bodies and their behaviour under loading (examples)

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Folding and

kinking at micro level

(from L. Dengler, 1976. Microcracks in crystalline rocks. In: Electron microscopy in mineralogy, 1992)


Rock mass

folding

(from D. Powell, Interpretation of geological structures through maps, 1992)

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Solid bodies and their behaviour under loading (examples)

Solid Earth

Rock mass folding

Courtesy ACcESS

Courtesy Hans Mühlhaus


The microstructure of steel, showing large grains. This is a slice through one thread of a well-annealed nut. The nut came from a fireplace grate or andiron, so it was exposed to a lot of heat before being sliced in half and polished and prepared as a sample.

http://commons.wikimedia.org/wiki/Image:Microstructure_steel_annealed_nut.jpg

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The microstructure of unaffected A36 steel: (a-left) white-ferrite, dark-pearlite and (b-right) pearlite region. Pearlite forms in bands due to manganese segregation and prior hot working.

http://www.tms.org/pubs/journals/JOM/0112/Biederman/Biederman-0112.html


An EDX Analysis of eutectic region.

Eutectic formation (iron oxide-iron sulfide), etched 4% natal.


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Oxidation and intergranularmelting; unetched


Severely eroded I beam cross sections, nominal composition (%) of A36 steel plate is: (0.29C max, 0.80–1.2Mn, 0.04P, 0.05S, 0.15–0.3Si bal Fe)


Underlying structure

the microstructure of annealed brass as it is tensile tested.

http://www.matsci.ucdavis.edu/MatSciLT/materialsylvania/GalleryMatSci.htm

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Luders lines (bands) in steelhttp://www.matsci.ucdavis.edu/MatSciLT/materialsylvania/GalleryMatSci.htm

Luders bands forming during the initial phases of a tensile test.


Foam structures

Conventional open cell polymer foam. Scale mark: 2 mm.

http://silver.neep.wisc.edu/~lakes/sci87.html

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SWNT tested

Single-walled carbon nanotubes imaged using a scanning electron microscope.

http://www.matsci.ucdavis.edu/MatSciLT/materialsylvania/GalleryMatSci.htm


Why did we have ‘irrelevant’ microstructures here?

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Microstructure affects the quality of reservoir!!!


gzP

gzzP

ρ

ρ

=∂∂

=

=

Gradient Pressure

)(

Characteristics of reservoirs & rocks

pressure and temperature at depth» Pressure increases with depth

» Temperature increases with depth

PRESSURE (vertical):» the pressure on the fluid in the reservoir rock pores depends

on the overburden height and type:

2 extremes: If overburden is a column of water (totally supporting rock matrix)

Pressure gradient is 10MPa/km (hydrostatic pressure)overburden is a column of rock

Pressure gradient is 27MPa/km (geostatic pressure)

Overburden is a weight of what is ‘above’ you when you are underground

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Characteristics of reservoirs & rocksPressure increases with depth

10 MPa/km(hydrostatic limit)

27 MPa/km(geostatic limit)


Characteristics of reservoirs & rocksTemperature increases with depth

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pressure and temperature at depth» Pressure increases with depth

» Temperature increases with depth

TEMPERATURE:» Average temperature gradient is 30°C/km

» Ranges from 20 °C/km to 80 °C/km, depending on local heat fluxes, and thermal conductivities of rocks

What’s the source of the heat?


Characteristics of North West Shelf

Reservoir P ~ 35 MPa

Reservoir T ~ 110°C

Depth z ~ 3.5 km

⇒ Pressure gradient of 10MPa/km » ⇒hydrostatic regime

⇒Temperature gradient of ~ 25 °C/km» ⇒ normal hotness

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Temperature gradients examples!


Hot Dry Rock Reserves in the US

http://qvack.lanl.gov/HDR/barhdr.html

Clean geothermal energy

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ConceptWorld HDR energy resource is 30 times of fossil energy resourceAccessible: < 10 kmSite determination» Location» Depth/temperature

Reservoir development» Porous rock » Hydraulic fracture

http://qvack.lanl.gov/HOTDRYROCK.HTML


HDR in Australiahttp://www.petrol.unsw.edu.au/research/resource.html

Resource: 7,500 years of the current energy consumption in AustraliaOver 80 % of the resource is in the Eromanga Basin (in the north-eastern corner of South Australia and the south-western corner of Queensland

School of Petroleum EngineeringThe University of New South WalesSydney 2052 Australia

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HDR Process

Queensland

http://www.nrw.qld.gov.au/factsheets/pdf/mines/m7.pdf


Stresses are not hydrostatic!

Hydrostatic(a) if overburden is a column of water (vertical

pressure)(b) if they are the same in all directions (rock

mass is similar to a liquid)

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Borehole breakouts 1

Dog earingDyskin (2007)



Maximum principal

stress

Breakout

depth

angle

Dyskin (2007)

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Borehole breakouts

A. Dyskin

http://www.hydrofrac.com/hfb_home.html

3 m diameter drift at 420 m level in the Underground Research Laboratory (URL), Canada

8/7/2008 41

Slide 42Dr Elena PasternakA. Dyskin

Shapes of borehole breakouts

http://www.itascacg.com/petro_borehole.html

8/7/2008 42

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http://earthquakes.ou.edu/RaSim6_Hiroshi_Poster.pdf

8/7/2008 43


Underground Research

Laboratoryhttp://inisjp.tokai.jaeri.go.jp/ACT95E/4/4-10.HTM

Whiteshell Laboratories, Eastern Manitoba, CanadaNuclear Fuel Waste Management Program, 1990-1993

8/7/2008 44

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URL Experiment

8/7/2008 45


Observed Fractures

(After Read and Martin, 1996)8/7/2008 46

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Original (Virgin) Stress StateGravitational stressTectonic stressResidual stress

Factors influencing the stress state•Surface topography•Erosion•Non-Homogeneity•Discontinuities

•influence the stress state•serve as indicators of the existing stress state

•Time•Presence of other mines and excavations

Dyskin (2007)


Gravitational Stress

Heim’s hypothesis

σv

σh=K σv

h

Terzaghi: Rock mass is modelled as an isotropic elastic body with lateral constrain (ν is Poisson’s ratio)

K K=−

≤ ≤νν1

0 1,

p ~ γhHydrostatic hypothesis(γ is the average rock unit weight)

σv , σh

Weight of overburden

Shear stresses are neglected

σv ~ γh

Dyskin (2007)

γ=ρg – self-weight

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Australia Stress Map

http://www.asprg.adelaide.edu.au/asm/maps.html

Dyskin (2007)


Dependence of depth

Brown and Windsor (1990)

Dyskin (2007)

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Dependence of depth - 2

Brown and Windsor (1990)

Dyskin (2007)


Injection Induced Earthquakes(after Hsieh and Bredehoeft et al., 1981)

8/7/2008 52

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Petroleum Induced SeismicitySegall (1989)

8/7/2008 53


Gazli Gas Field, UzbekistanShallow gas reservoir (≈2 km)No prior seismic historyThe strongest reported earthquake correlated to gas production (M = 7+)No noticeable subsidencePressure decline from 7 MPa in 1956 to 1.5 MPa in 1985Deep locations of induced earthquakes (≈ 10−15 km)

Simpson and Leith(1985)8/7/2008 54

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Intact rock(no through-going fractures)

Rocks and Rock Masses

Direct measuring of fundamental propertiesIndex testing as a comparative measure of rock quality

Discontinuities(fractures)

Rock Mass

DislocationsMicrocracks (microfissures)Cracks (fissures)JointsBedding planesFaults

Important Factors•Rock structure•In situ stress•Fluid flow in the rock mass


Rock PropertiesSpecific gravity γrock/ γwater = 2.1 - 7.6Porosity (0.1% - 40%)Permeability (low)Thermal properties (low thermal conductivity)FrictionStrength» Uniaxial (unconfined) compressive strength» Tensile strength» Parameters of strength (fracture) criteria for triaxal

compression» Point load index

Deformability» Static moduli» Dynamic moduli

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types of rock» traps made up of porous rock (containing

hydrocarbon fluid) and sealed by non porous/impermeable shales.

» Porous rock:Sandstones (90% of reservoirs)Carbonates

» porosity & permeability are the key rock characteristics

» others are mechanical strength, degree of consolidation, distribution of particle & pore sizes, etc


Mechanical properties of rocksKnowledge of the mechanical properties of rocks is important in formation evaluation, drilling, development planning and production.

These properties include the inelastic properties such as fracture pressure gradient and formation strength as well as the elastic properties such as Young’s modulus, shear modulus, Poisson’s ratio and bulk pore compressibility.

Estimation of these properties requires lithology, porosity, bulk density, together with compressional and shear wave slowness as log data input.

These properties are useful in borehole stability analysis, sandproduction prediction, hydraulic fracture design and optimization, compaction/subsidence studies drill bit selection, casing point selection and casing design and other applications

PETR3512Lectures3sl1-58

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