RockMech – CO2
MBDCI
Geology and COGeology and CO22 Sequestration Sequestration in Kuwaitin Kuwait
Maurice B. Dusseault – U. of Waterloo
Reza Oskui – KISR Roman Bilak – Terralog Technologies
RockMech – CO2
MBDCI
KuwaitKuwait
Oil Energy CO2
Reservoirs EOR Technical issues… Economics?
RockMech – CO2
MBDCI
Geological COGeological CO22 Sequestration Sequestration
Suitability of target reservoir Volume and storage capacity Permeability and continuity Quality of long-term geological seal Existing access (wells) or easy access Location (near CO2 source?)
Availability of “pure” CO2
Technical issues arising Reservoir: fluids, flow, rates… Geomechanics: stresses, pressures,
seals…
RockMech – CO2
MBDCI
Stratigraphy…Stratigraphy…
The sequence of strata and their physical properties constitute the base information
Then, the structural aspects are incorporated
Heterogeneity and other factors can be included
RockMech – CO2
MBDCI
Some Sealing Issues for COSome Sealing Issues for CO22
Reservoir spill point, structure Quality of stratigraphic seal against
CO2 diffusion and percolation Existence of potential breaches
Penetrating faults, not fully sealed Sinkhole structures from carbonate karst
features or salt dissolution Fracture pathways through cap rock
And, of course, the wellbores…
RockMech – CO2
MBDCI
Structure and Unconformities…Structure and Unconformities…
RockMech – CO2
MBDCI
Spill Point Seal…Spill Point Seal…
U of Saskatchewan
RockMech – CO2
MBDCI
Complex Fault StructuresComplex Fault Structures
Stresses can change among fault blocks
Pressures as well (e.g.: compartments)
Fault mechanical, transport properties are different
Faults may affect CO2 strategies
Essential inputs for sequestration
Venezuela example
RockMech – CO2
MBDCI
Fault Structures…Fault Structures…
fold
faul
t
flat
U of Saskatchewan
RockMech – CO2
MBDCI
Stratigraphic TrapsStratigraphic Traps
U of Saskatchewan
RockMech – CO2
MBDCI
Geological Complexity…Geological Complexity…
Wara
Mauddud3SU3SM
3SL
4S
Original oil -water contact
Wara
Mauddud3SU3SM
3SL
4S
Combined structural and stratigraphic traps in Kuwait
Original oil -water contact
RockMech – CO2
MBDCI
Capillary Isolation of OilCapillary Isolation of Oil
p+Δpp
Capillary barriers and swept zones are created during high Δp displacement. These lead to severe difficulties in viscous oil development
Oil zone, capillary barrierZone swept by water
r
2p ow
capillary force barrier to water displacement
RockMech – CO2
MBDCI
Are Fractures Open or Closed?Are Fractures Open or Closed?
Sou
rce:
N. B
arto
n an
d A
. Mak
urat
RockMech – CO2
MBDCI
Rough or Smooth Joints?Rough or Smooth Joints?
Sou
rce:
N. B
arto
n an
d A
. Mak
urat
RockMech – CO2
MBDCI
Different Joint SetsDifferent Joint Sets
Sou
rce:
N. B
arto
n an
d A
. Mak
urat
RockMech – CO2
MBDCI
Limestones and SandstonesLimestones and Sandstones
These are generalizations only: specific rocks must be measured
character Sandstone Limestone
porosity generally 15%~30% generally 5%~15%
permeability 50-5000 md 10-100 md
pore patterns all interparticle poresmainly interparticle, but other patterns also very important
impact of fractures not important very important
the relation between porosity and permeability
high agreement generally no agreement
RockMech – CO2
MBDCI
Closure & HysteresisClosure & Hysteresis
Slate
Dolomite
Limestone
Continued closure with cycles
Hysteresis
No
rma
l Str
ess
- M
Pa
Mechanical aperture - micrometers
-What is the behavior of a joint under normal loading?-Is the joint rough or smooth?-How is the permeability changed?
Bandis - 1990
RockMech – CO2
MBDCI
Deep Fractured CarbonatesDeep Fractured Carbonates
Kuwaiti fractured carbonates reservoirs for CO2 sequestration are of interest
World distribution of carbonate rocks
RockMech – CO2
MBDCI
Depth range is also excellent…Depth range is also excellent…
To 10 km depth Fractured
carbonates Sandstones Huge storage
volumes exist EOR potential as
well…
RockMech – CO2
MBDCI
High porosity clastics (sandstones)}Fractured carbonates}
} Too deep and low porosity?
} Too shallow?
RockMech – CO2
MBDCI
COCO22 in the Lower Fars? in the Lower Fars?
Shallow reservoir – 100 – 250 m
CO2 will be a gas, not a liquid
After thermal EOR, CO2 can be used for inert gas injection, enhancing drainage, but…
Storage capacity is small
IRAQ
KUWAIT
Border
Lower Fars: Total Net Pay
Ratqa Field
0’
10’
20’
50’
30’
40’
Pilot 1
Pilot 2
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MBDCI
Inert Gas Injection (Inert Gas Injection (ΔρΔρ process) process)
dm
oil
gas
waterp
Generally, it is a top down displacement process,
gravitationally assisted and density stabilized
Note: in a water-wet reservoir,a continuous 3-D oil film exists,
providing that wg > og + wo
Gas is injected high in the reservoir to move the oil
interface downward
Recovery % can be high
RockMech – CO2
MBDCI
IGI, With Reservoir StructureIGI, With Reservoir Structure
oil bank, two-phase zonewater-wet sand
horizontal wellsparallel to structure
inert gas injection
keep p to a minimum
gas rates are controlled toavoid gas (or water) coning
three-phase zone
if coning develops,drop pressures!
best to monitorthe process;
mainly gas
water,one phase
p
RockMech – CO2
MBDCI
Zubair SandZubair Sand
Top = -1500 m Pressure = 15 MPa Storage capacity is
vast Good porosity,
good permeability
ShuaibaShuaiba
RockMech – CO2
MBDCI
RockMech – CO2
MBDCI
Zubair SandstoneZubair Sandstone
Although it is a huge reservoir, it may not be a candidate everywhere for large-scale CO2 sequestration. Why?
-There is no oil in the Zubair, but there is oil above (Burghan) and below (Ratawi)
-Apparently, the upper shaley sand & thin Shuaiba carbonate are fractured
-Hence, we would have to rely on seals at the top of the Burghan sandstone
RockMech – CO2
MBDCI
SabiriyahSabiriyah
RaudhatainRaudhatain
N
KUBER ISLAND
UMM AL-MARADEM ISLAND
QAROH ISLAND
Bahrah
Khashman
Medina
Abdali
Dharif
Wafra
Umm Gudair
Abduliyah
Minagish
AL-KHIRAN
SE Ratqa
Ratqa
GreaterBurgan
FAILAKA ISLAND
Saudi Arabia
Iraq
Kuwait
Arabian Gulf
RockMech – CO2
MBDCI
How do We Rank Candidates?How do We Rank Candidates?
Kuwait has many options for CO2
Geological data varies from highly quantitative to qualitative
Some scheme is needed to rank reservoirs as candidates
A methodology is presented here The variables and weighting factors
must be chosen appropriately…
RockMech – CO2
MBDCI
Limestones – Fabric - ScaleLimestones – Fabric - Scale
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MBDCI
DisqualifiersDisqualifiers
A set of absolute disqualifiers is chosen An open fault at the crest of the structure Too shallow for SC-CO2 placement No top seal (e.g. fractured cap rock) Other criteria as well…
If the candidate fails on any disqualifying factor…
It is rejected for CO2 placement Uncertain cases are downgraded
RockMech – CO2
MBDCI
Important Parameters - PImportant Parameters - Pii
Volume (porosity), thickness, dip… Permeability Depth and temperature Presence of oil (EOR) Proximity to CO2 source Stress conditions (reservoir, cap rock) Reservoir condition
Penetrating wells and seal quality (t, k…) And so on…
RockMech – CO2
MBDCI
Geomechanical Earth ModelGeomechanical Earth Model
Yo
ung
’s M
od
ulu
s -
MP
a
FaultsHeterogeneity
RockMech – CO2
MBDCI
EXAMPLE ONLY!
PPii - Parameter Classification - Parameter Classification
Z - Depth Range Class Value
Less than 800 m 0
800 – 1200 m 1
1200 – 2000 m 3
2000 – 3000 m 5
> 3000 m 2
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MBDCI
Sandstones - HeterogeneitySandstones - Heterogeneity
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MBDCI
Weighting Coefficients…Weighting Coefficients…
Each parameter is weighted according to its importance
For example, 2 will have a high weight (1.0) because its impact is great
D – distance from CO2 source – might be weighted as 5 = 0.2
Then, W is calculated = ∑ i·Pi ...DEORVkZW 654321
RockMech – CO2
MBDCI
Weighting Coefficient Choice…Weighting Coefficient Choice…
Choices for i will be different for different areas
One way to choose values is… Convene a small panel of experts
(geology, reservoir, geomechanics…) Let them choose a set of i values
Now, using the i values, we can look at the robustness of the classification (candidate ranking outcomes)…
RockMech – CO2
MBDCI
Statistical EvaluationStatistical Evaluation
Values of i are statistically varied (e.g. i = 0.5, varied from 0.3 to 0.7
Also, different parameter classes can be chosen (see depth example…)
Then, the robustness of the outcomes can be studied
This allows the best candidates for CO2 use to be identified
RockMech – CO2
MBDCI
COCO22 Hydrates… Hydrates…
T.H
. Kw
an
, Geo
gia
Tec
h
What about phase changes?
RockMech – CO2
MBDCI
Final CommentsFinal Comments
The geological model is fundamental to the choice of sequestration candidate
Many geological factors are difficult to quantify (e.g fracture intensity)
A scheme was presented to extract a semi-quantitative ranking of candidates
Of course, Kuwait is blessed with many excellent candidates…
Let the studies begin…
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