Seismic mapping of the Utsira Formation. Petrophysical interpretations and fracture gradient estimates.

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1 Presentation March 4 th 2009 OG21 Innovation Seminar: TTA2 Exploration and reservoir Characterization Venue: StatoilHydro, Sandsli CO 2 Sequestration A geophysical and geological study related to CO 2 injection in the Utsira Formation.

2 Introduction Identification of alternative CO 2 injection points in the Utsira Formation Seismic mapping of the Utsira Formation. Petrophysical interpretations and fracture gradient estimates. Storage site characterisation Possible changes in reservoir properties caused by CO 2 injection. Loss of sealing capacity through leakage points. CO 2 injection projects in Australia ZeroGen full scale CO 2 injection project Otway Basin CO 2 injection monitoring

3 CO 2 Sequestration Injection and permanent storage of captured CO 2 into geological formations where major point sources of CO 2 are available. Sleipner Field: First industrial scale offshore injection site. The MPE has given Gassco, Gassnova, the Norwegian Petroleum Directorate and the Norwegian Water Resources and Energy Directorate the task of evaluating and recommending alternative solutions for capture, transport and storage of CO 2. 3D View: Top Hordaland/Top Utsira Top Utsira Fm Base Utsira Sands Top Hordaland Gp Illustration from:

4 Geophysical and Geological study related to CO 2 sequestration in the Utsira Formation Objectives of study: Evaluate the potential of injecting CO 2 in the Utsira Formation further east than at the current Sleipner Field injection site. Map the Utsira Formation within Quadrant 16 with special focus on blocks 16/10 and 16/11. Evaluate well logs and perform fracture gradient estimates to determine storage and sealing capacity.

5 Seismic database The seismic database consisted of two regional 2D surveys (UG97 and UGI98) and a 3D-survey (SNST). To fully cover the area of interest three additional 2D surveys were also interpreted: NA-85, PSL84 and ST /10 16/11

6 Seismic interpretation Utsira Formation A total of 6 seismic horizons was mapped over a regional defined area of about 6.48x10 9 m 2 covering the focus area (block 16/10 and 16/11) and parts of the surrounding blocks. The interpreted horizons: The main horizons: Top Utsira, Base Utsira Sand & Top Hordaland Additional horizons: Seabed, Upper Nordland group & Top Balder HORIZON NAME PEAK/TROUGH SEISMIC RESPONSE Top Utsira Trough Hard kick. The acoustic impedance in the lower layer is higher then for the upper layer. Top Utsira Base Utsira Sand Peak Soft kick. The acoustic impedance in the lower layer is lower then for the upper layer. Base Utsira sand Top Hordaland Trough Hard Kick. The acoustic impedance in the lower layer is higher then for the upper layer. Top Hordaland Gp

7 Seismic interpretation Utsira Formation W 3D survey SNST InLine 1116) E Top Utsira Base Utsira sand Top Hordaland Group Top Hordaland Pleistocene Top Utsira The horizon is reasonable easy to interpret for most of the area. Polygon: 16/10 & 16/11 Prograding Complex Base Utsira Sand The Base of the main Utsira Sand Unit is a downlap surface above Top Hordaland, often separating mounded reflections above from a more concordant and sometimes disturbed reflections below, with slumping and/or loading effects observed along this contact. Seismic section (UGI D survey SNST InLine 1116)

8 The correlation diagram shows a transition from the characteristic, blocky GR log profile of the Utsira sands in well 16/10-2, with increasing shale thickness towards the east as the sand system is pinching out. The top of the Utsira sand is marked by an increase in the GR log values.

9 Well data analysis Wireline data Evaluation results from representative wells show generally excellent storage capacity for the Utsira Formation sandstone. N/G from 0.6 to 1.0 Phie av = 29% (ranging from 23% to 31.3% in the wells studied) Fracture Gradients study LOT data compared with estimated Fracture Gradients suggest a reasonable correlation and sufficient sealing capability for the overlying claystones

10 Injection point suggestions 16/10 16/11 Based on seismic mapping of structural closure, combined with sufficient sand thickness, storage capacity of the Utsira sand and sealing quality of the overlying rocks two points of injection within the designated study area have been suggested, as indicated with a on the Top Utsira map. 16/10 16/11

11 Site Characterization a prerequisite to safe geological storage of CO 2 Documentation of the characteristics of any particular storage site will rely on the data that are available regarding the potential reservoir. Data essential for storage site characterization: Mineralogical information from core material for diagenetic studies. Identification of faults and fractures that could create leakage pathways. After start-up of CO 2 injection, perform formation pressure monitoring to map the rate and direction of flow.

12 Understanding diagenetic effects caused by CO 2 injection is critical To secure long-term and safe sequestration of CO 2 we must understand: The distribution of rock properties, facies variations, seal and reservoir quality at microscopic scales. Fluid behaviour in geologic formations CO 2 in supercritical state + Brine + minerals of the host reservoir Fedolomite Siderite Kaolinite Pyrite Quartz

13 Possible diagenetic effects of injected CO 2 : Dissolution of carbonate cements owing to high PCO 2. Dissolution rates of dolomite approach that of calcite at very high PCO 2 However, re-precipitation of calcite may occur upon: (a) decrease in PCO 2, e.g. due to gas leakage through fractures (b) thermodynamic re-equilibration Dissolution of feldspars, particularly plagioclase: anorthite + CO 2 + 2H 2 O kaolinite + calcite Reaction with Fe-rich silicates (e.g., chlorite, berthierine and biotite) to form siderite and ankerite Moderate volumes are sequestered by dissolution (as HCO 3 ) in formation waters Absorption by coal, displacing methane. Hence: mineral precipitation and plugging of pore throats will pose a significant risk to the injectivity of CO 2 for purposes of sequestration.

14 Seismic section through wells 16/8-2 & 16/11-1 fault identification NNW 16/8-2 SSE Large regional fault are cutting through and displacing Top Hordaland and Base Utsira Fm No Utsira Fm are observed in this well cf. Lithostratigraphy related to well 16/11-1 factpages at Top Utsira Fm Base Utsira Sand Top Hordaland

15 Dissolution of carbonate cementation. Carbonate cementation can occur above HC accumulations as a result of HC leakage. (1) linear anomalies caused by leakage along a fault; (2) circular anomalies caused by point leakage, often at the intersection of two faults. Dissolution of these cemented pathways can create a serious risk to the CO 2 sequestration process.

16 World potential for CO 2 storage Major CO 2 injection projects

17 Geosequestration - Current Projects in Australia ZeroGen IGCC-CCS Project Full scale CO 2 injection project Central Queensland AGR Role: Prime Field Contractor 2005 to present Otway Basin Pilot Project Monitoring of CO 2 injection Victoria AGR Role: Field Monitoring Contractor 2006 to present

18 CO 2 sequestration projects are basically identical to regular petroleum projects Subsurface Management Well Management Facility Management Reservoir evaluation and characterisation Seismic services Appraisal Design and Economics Full Field Development modeling Well and completion design Well testing, specifically CO 2 injection Well integrity programs Technical & Managerial Support Decommissioning and abandonment Advanced drilling techniques Carbon Dioxide facilities Material selection Measuring, Monitoring and Verification Maintenance & compliance services

19 AGR role: Engineering, Procurement, Construction Management and Operations Completed 2 well pilot with water injection test Permeability test Completion optimisation test 6 stratigraphic wells Upcoming concept design 2 well pilot with CO 2 injection Drill Truck CO 2 Surface facilities EPCM Field operations Future Demonstration is for 20 wells Project intends to progress to full-scale commercial operation

20 - Otway Basin Pilot Project AGR Role: Monitor CO 2 injection into a depleted reservoir Completed Stage 1 CRC No. 1 well drilled Naylor monitoring equipment Pipeline installation Plant installation (gas process skid, compressor and air cooler) Electrical work completed Pre-commissioning of plant & pipeline Successful re-perforation of the injection well (CRC-1) Commenced CO 2 injection Operations ongoing Future Stage 2 Drill additional well 2009 Huff-n-Puff testing for residual trapping Operations to end late 2010

21 - Otway Basin Pilot Project The project is one of 19 sequestration projects endorsed by the Carbon Sequestration Leadership Forum (CSLF) Source:

22 Summary: The potential of injecting CO 2 into the Utsira Formation at alternate injection points compared to the current Sleipner Field position has been demonstrated and documented in this study. In order to safely inject and permanently sequester CO 2 the link between the macroscopic structural mapping and the microscopic detail of the reservoir properties need to be studied. The oil industry has the knowledge and the technology to contribute in a constructive manner towards solving the challenges that the various CO 2 injection projects represent.