Geology and CO 2 Sequestration in Kuwait

1. Geology and CO2 Sequestration in Kuwait Maurice B. Dusseault – U. of Waterloo Reza Oskui – KISR Roman Bilak – Terralog Technologies

2. Kuwait • Oil • Energy • CO2 • Reservoirs • EOR • Technical issues… • Economics?

3. Geological CO2 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…

4. 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

5. Some Sealing Issues for CO2 • 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…

6. Structure and Unconformities…

7. Spill Point Seal… U of Saskatchewan

8. Complex 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

9. Fault Structures… U of Saskatchewan fold flat fault

10. Stratigraphic Traps U of Saskatchewan

11. Geological Complexity… Wara Wara 3SU 3SU Mauddud Mauddud 3SM 3SM 3SL 3SL 4S 4S Original oil Original oil - - water contact water contact Combined structural and stratigraphic traps in Kuwait

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

13. Are Fractures Open or Closed? Source: N. Barton and A. Makurat

14. Rough or Smooth Joints? Source: N. Barton and A. Makurat

15. Different Joint Sets Source: N. Barton and A. Makurat

16. Limestones and Sandstones • These are generalizations only: specific rocks must be measured Sandstone Limestone character porosity generally 15%~30% generally 5%~15% permeability 50-5000 md 10-100 md mainly interparticle, but other pore patterns all interparticle pores patterns also very important impact of fractures not important very important the relation between porosity high agreement generally no agreement and permeability

17. Closure & Hysteresis Continued closure with cycles Normal Stress - MPa Hysteresis Mechanical aperture - micrometers -What is the behavior of a joint under normal loading? -Is the joint rough or smooth? -How is the permeability changed? Slate Dolomite Limestone Bandis - 1990

18. Deep Fractured Carbonates • Kuwaiti fractured carbonates reservoirs for CO2 sequestration are of interest World distribution of carbonate rocks

19. Depth range is also excellent… • To 10 km depth • Fractured carbonates • Sandstones • Huge storage volumes exist • EOR potential as well…

20. } Too shallow? } High porosity clastics (sandstones) } Fractured carbonates } Too deep and low porosity?

21. CO2 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

22. Inert Gas Injection (Δρ process) Gas is injected high in the reservoir to move the oil interface downward dm Generally, it is a top down displacement process, gravitationally assisted and density stabilized gas water Dp Note: in a water-wet reservoir, a continuous 3-D oil film exists, providing that gwg > gog + gwo oil Recovery % can be high

23. IGI, With Reservoir Structure inert gas injection gas rates are controlled to avoid gas (or water) coning mainly gas three-phase zone horizontal wells parallel to structure oil bank, two-phase zone water-wet sand Dr water, one phase keep p to a minimum Dp best to monitor the process; if coning develops, drop pressures!

24. Zubair Sand • Top = -1500 m • Pressure = 15 MPa • Storage capacity is vast • Good porosity, good permeability

26. Zubair 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

27. Ratqa Abdali Iraq SE Ratqa Arabian Gulf Bahrah Kuwait Medina FAILAKA ISLAND Khashman Dharif Abduliyah KUBER ISLAND Minagish Greater Burgan QAROH ISLAND Umm Gudair Saudi Arabia UMM AL-MARADEM ISLAND AL-KHIRAN Wafra N Raudhatain Sabiriyah

28. 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…

29. Limestones – Fabric - Scale

30. Disqualifiers • 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

31. Important Parameters - Pi • 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…

32. Geomechanical Earth Model Young’s Modulus - MPa Heterogeneity Faults

33. Pi - Parameter Classification EXAMPLE ONLY!

34. Sandstones - Heterogeneity

35. Weighting Coefficients… • Each parameter is weighted according to its importance • For example, 2will 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

36. Weighting Coefficient Choice… • Choices for iwill 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 ivalues • Now, using the ivalues, we can look at the robustness of the classification (candidate ranking outcomes)…

37. Statistical Evaluation • Values of iare 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

38. CO2 Hydrates… T.H. Kwan, Geogia Tech What about phase changes?

39. 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…