RockMech – CO 2 MBDCI Geology and CO 2 Sequestration in Kuwait Maurice B. Dusseault – U. of Waterloo Reza Oskui – KISR Roman Bilak – Terralog Technologies

RockMech – CO 2 MBDCI Kuwait  Oil  Energy  CO 2  Reservoirs  EOR  Technical issues…  Economics?

RockMech – CO 2 MBDCI Geological CO 2 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 CO 2 source?)  Availability of “pure” CO 2  Technical issues arising  Reservoir: fluids, flow, rates…  Geomechanics: stresses, pressures, seals…

RockMech – CO 2 MBDCI 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 – CO 2 MBDCI Some Sealing Issues for CO 2  Reservoir spill point, structure  Quality of stratigraphic seal against CO 2 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 – CO 2 MBDCI Structure and Unconformities…

RockMech – CO 2 MBDCI Spill Point Seal… U of Saskatchewan

RockMech – CO 2 MBDCI Complex Fault Structures  Stresses can change among fault blocks  Pressures as well (e.g.: compartments)  Fault mechanical, transport properties are different  Faults may affect CO 2 strategies  Essential inputs for sequestration Venezuela example

RockMech – CO 2 MBDCI Fault Structures… fold fault flat U of Saskatchewan

RockMech – CO 2 MBDCI Stratigraphic Traps U of Saskatchewan

RockMech – CO 2 MBDCI Geological Complexity…

RockMech – CO 2 MBDCI Capillary Isolation of Oil p+Δp p Capillary barriers and swept zones are created during high Δp displacement. These lead to severe difficulties in viscous oil development Oil zone, capillary barrier Zone swept by water capillary force barrier to water displacement

RockMech – CO 2 MBDCI Are Fractures Open or Closed? Source: N. Barton and A. Makurat

RockMech – CO 2 MBDCI Rough or Smooth Joints? Source: N. Barton and A. Makurat

RockMech – CO 2 MBDCI Different Joint Sets Source: N. Barton and A. Makurat

RockMech – CO 2 MBDCI Limestones and Sandstones  These are generalizations only: specific rocks must be measured character SandstoneLimestone porositygenerally 15%~30%generally 5%~15% permeability md md pore patternsall interparticle pores mainly interparticle, but other patterns also very important impact of fracturesnot importantvery important the relation between porosity and permeability high agreementgenerally no agreement

RockMech – CO 2 MBDCI Closure & Hysteresis Slate Dolomite Limestone Continued closure with cycles Hysteresis Normal Stress - MPa 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

RockMech – CO 2 MBDCI Deep Fractured Carbonates  Kuwaiti fractured carbonates reservoirs for CO 2 sequestration are of interest World distribution of carbonate rocks

RockMech – CO 2 MBDCI Depth range is also excellent…  To 10 km depth  Fractured carbonates  Sandstones  Huge storage volumes exist  EOR potential as well…

RockMech – CO 2 MBDCI High porosity clastics (sandstones) } Fractured carbonates } } Too deep and low porosity? } Too shallow?

RockMech – CO 2 MBDCI CO 2 in the Lower Fars?  Shallow reservoir – 100 – 250 m  CO 2 will be a gas, not a liquid  After thermal EOR, CO 2 can be used for inert gas injection, enhancing drainage, but…  Storage capacity is small

RockMech – CO 2 MBDCI Inert Gas Injection (Δρ process) dmdm oil gas water pp 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 – CO 2 MBDCI IGI, With Reservoir Structure oil bank, two-phase zone water-wet sand horizontal wells parallel to structure inert gas injection keep  p to a minimum gas rates are controlled to avoid gas (or water) coning three-phase zone if coning develops, drop pressures! best to monitor the process; mainly gas water, one phase  pp

RockMech – CO 2 MBDCI Zubair Sand  Top = m  Pressure = 15 MPa  Storage capacity is vast  Good porosity, good permeability

RockMech – CO 2 MBDCI

RockMech – CO 2 MBDCI Zubair Sandstone  Although it is a huge reservoir, it may not be a candidate everywhere for large-scale CO 2 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 – CO 2 MBDCI Sabiriyah Raudhatain N KUBER ISLAND UMM AL-MARADEM ISLAND QAROH ISLAND Bahrah Khashman Medina Abdali Dharif Wafra Umm Gudair Abduliyah Minagish AL-KHIRAN SE Ratqa Ratqa Greater Burgan FAILAKA ISLAND Saudi Arabia Iraq Kuwait Arabian Gulf

RockMech – CO 2 MBDCI How do We Rank Candidates?  Kuwait has many options for CO 2  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 – CO 2 MBDCI Limestones – Fabric - Scale

RockMech – CO 2 MBDCI Disqualifiers  A set of absolute disqualifiers is chosen  An open fault at the crest of the structure  Too shallow for SC-CO 2 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 CO 2 placement  Uncertain cases are downgraded

RockMech – CO 2 MBDCI Important Parameters - P i  Volume (porosity), thickness, dip…  Permeability  Depth and temperature  Presence of oil (EOR)  Proximity to CO 2 source  Stress conditions (reservoir, cap rock)  Reservoir condition  Penetrating wells and seal quality (t, k…)  And so on…

RockMech – CO 2 MBDCI Geomechanical Earth Model Young’s Modulus - MPa Faults Heterogeneity

RockMech – CO 2 MBDCI EXAMPLE ONLY! P i - Parameter Classification Z - Depth RangeClass Value Less than 800 m0 800 – 1200 m – 2000 m – 3000 m5 > 3000 m2

RockMech – CO 2 MBDCI Sandstones - Heterogeneity

RockMech – CO 2 MBDCI 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 CO 2 source – might be weighted as  5 = 0.2  Then, W is calculated = ∑  i ·P i

RockMech – CO 2 MBDCI 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 – CO 2 MBDCI Statistical 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 CO 2 use to be identified

RockMech – CO 2 MBDCI CO 2 Hydrates… T.H. Kwan, Geogia Tech What about phase changes?

RockMech – CO 2 MBDCI Final 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…