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Geomechanics and some Geomechanics and some ““ Other UsesOther Uses””for Sedimentary Basinsfor Sedimentary Basins

Maurice Dusseault

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Some Other Uses for BasinsSome Other Uses for Basins

� Carbon sequestration �CO2 injection for EOR or for sequestration

�Direct injection of petroleum refinery coke

� Injection of organics (animal and human biosolids)

� Waste disposal�Waste water and slurried solids injection

�Diluted radioactive wastes and shale injection

� Geothermal energy and thermal energy storage

� Salt caverns and reservoirs for storage

Only a CO2 example will be presented

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KuwaitKuwait

� Oil

� Energy

� CO2

� Reservoirs

� EOR

� Technical issues…

� Economics?

� Is Kuwait a good area for CO2sequestration as a national policy?

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Geological COGeological CO22 SequestrationSequestration

� 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…

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COCO22 BehaviorBehavior

We must understand the behavior of CO2 and the site conditions!

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COCO22 BehaviorBehavior……

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Pure COPure CO22 BehaviorBehavior

� Gaseous state storage…�Low density, low viscosity, under low p, T

� Liquid state storage…�High density, low µ, high p, low T <35ºC

�Not compatible with real reservoirs

� Supercritical state, > 35ºC, > 7.2 MPa� (> 95ºF, > 1035 psi, approximately)

�Higher ρ (0.25 – 0.88, very low µ)

�Miscible with water and oil

� Hydrate formation – low T, high p, +H2O

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Depth and CODepth and CO22 State State -- IIII ……

� Most reservoirs to Z = 3 km: hydrostatic pressures ~10 kPa/m

� Pure CO2 is SC below ~750 m, if T > 35ºC

� In general, CO2 is a supercritical fluid at Z > 800 m (~2620’)

� Otherwise, it is a gas or a liquid, depending on p & T

0

1000

2000

20 40 60 0

Depth below ground - m

T - ºC

TSC

pSC

liquid

gas

gas

liquid

SC-CO2

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Depth and CODepth and CO22 State State -- II……

� T increases w. depth ~20-25ºC/km

� In most areas, T > 35ºC below ~800 m

� Only in cold conditions, will pure CO2 be in a liquid state, mostly SC

� In the presence of water and high p, a CO2-H2O clathrate (hydrate) forms

0

1000

2000

20 40 60 0

Depth below ground - m

T - ºC

TSC ~35°C

Typical range of T with depth

7.2 MPa

Practical conditions

for CO2placement

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Sealing Issues for COSealing Issues for CO22

� Reservoir spill point, structure,

� Quality of stratigraphic seal against SC-CO2

diffusion and percolation

� Can we count on capillary seals for SC-CO2?

� 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…

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Structure and UnconformitiesStructure and Unconformities……

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Spill Point SealSpill Point Seal……

U of Saskatchewan

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Fault StructuresFault Structures……

fold

faul

t

flat

U of Saskatchewan

Are faults seals or pathwaysfor SC-CO2? The answer may be different than for gas or H2O-capillary barrier impairment?

-miscibility with water, oil-SC-CO2 very low density

-very low viscosity for SC-CO2

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Stratigraphic TrapsStratigraphic Traps

U of Saskatchewan

How good are shale seals to super-critical CO2 for 1000 -10,000 years?

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Geological ComplexityGeological Complexity……

Wara

Mauddud3SU3SM

3SL

4SOriginal oil -water contact

Wara

Mauddud3SU3SM

3SL

4S

Combined structural and stratigraphic traps in Kuwait

Original oil -water contact

Are these overlying sealing rocks fractured or not?

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Are Fractures Open or Closed?Are Fractures Open or Closed?

Sou

rce:

N. B

arto

n an

d A

. Mak

urat

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Deep Fractured CarbonatesDeep Fractured Carbonates

� Kuwaiti fractured carbonates reservoirs for CO2

sequestration are of interest to our industry…

World distribution of carbonate rocks

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Depth range is also excellentDepth range is also excellent……

� To 10 km depth

� Fractured carbonates

� Sandstones

� Huge storage volumes exist

� EOR potential as well…

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High porosity clastics (sandstones)}Fractured

carbonates}} Too deep and

low porosity?

} Too shallow?

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Zubair SandZubair Sand

� Top = -1500 m

� Pressure = 15 MPa

� Storage capacity is vast

� Good porosity, good permeability

� This reservoir has a large capacity for disposal of carbon dioxide and should be carefully studied.

ShuaibaShuaiba

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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

But, is it fully sealed?

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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…

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Geomechanical Earth ModelGeomechanical Earth Model

You

ng’s

Mod

ulus

-M

Pa

FaultsHeterogeneity

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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 anydisqualifying factor…

� It is rejected for CO2 placement

� Uncertain cases are downgraded

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Important Parameters Important Parameters -- PPii

� 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…

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EXAMPLE ONLY!

PPii -- Parameter ClassificationParameter 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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Sandstones Sandstones -- HeterogeneityHeterogeneity

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Weighting CoefficientsWeighting Coefficients……

� Each parameter is weighted according to its importance (a team of experts may decide this)

� For example, α2 will have a high weight (1.0) because its impact is great

� D – distance from CO2 source – might be weighted as α5 = 0.2

� Then, W is calculated = ∑ αi·Pi

...DEORVkZW 654321 α+α+α+α+α+α=

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Weighting Coefficient ChoiceWeighting Coefficient Choice……

� Choices for αi 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 αi values y concensus

� Now, using the αi values, we can look at the robustness of the classification (candidate ranking outcomes)…

� Also capturing the expert knowledge!

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Statistical EvaluationStatistical Evaluation

� Values of αi are statistically varied (e.g. αi =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

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Other Uses for Sedimentary BasinsOther Uses for Sedimentary Basins

� CO2 placement for sequestration

� Deep liquid disposal through injection wells into suitable saline aquifers�Strata “clean” the water over transit distance…

� Solids disposal as well (Duri, Indonesia)

� Energy storage (natural gas, compressed gas?)

� Salt caverns & reservoirs for liquids, gas…

� Geothermal energy (low grade, high grade)

� Other ideas??