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Collaborating Authors
Hitchen, Ken
Abstract The volume of CO2 that can be stored in the Captain Sandstone saline aquifer in the North Sea was investigated by building a geological model and performing numerical simulations. These simulations were also used to calculate the best position for the injection wells, and the migration and ultimate fate of the CO2. The overall migration of CO2 and the pressure response over the entire saline aquifer was studied by the calculated injection of 15 million tonnes CO2 per year. The injection rate was restricted to a maximum of 2.5 million tonnes CO2 per year for each of a possible 12 wells considered. An important objective was to predict how to avoid flow of the injected CO2 toward potential leakage points, such as the sandstone boundaries and faults. The migration of injected CO2 towards existing oil and gas fields was also a determining factor. The summary conclusions are: The Captain Sandstone saline aquifer has significant potential CO2 storage capacity. Even with all boundaries closed to flow, the probable storage capacity is calculated to be about 358 million tonnes, giving a storage efficiency of 0.6% of pore volume, with an expected operating life-span of 15-25 years. The possible storage capacity of the formation may be at least four times greater if the aquifer boundaries are open. This increase would be a result of displacement of salt water, and not CO2. The storage capacity if the sandstone is closed to flow may be increase from 358 to 1668 million tonnes of CO2 by significant additional investment in 15 to 20 water production wells. Injection of up to 2.5 million tonnes CO2 per year in one well has an impact on the pressure throughout the entire formation, and thus interference between different injection locations must be considered.
- North America > United States (1.00)
- Europe > United Kingdom > North Sea > Central North Sea > Moray Firth (1.00)
Summary Well-guided multi-wave-type decoupled imaging of conventional marine streamer data after Radon-type prestack signal enhancement has strong potential for delineating high-velocity layers and sub-volcanic targets. This is illustrated by the case study from NE Atlantic margin. Introduction The presence of thick basalt lava flows in the North Sea makes it difficult to image reflectors beneath the top-basalt boundary. Multi-wave-type decoupled imaging (Druzhinin, 2003, 2005) combined with the Radon-type signal enhancement (Spitzer et al., 2003; Druzhinin et al., 2004) has been demonstrated to be promising for delineating complex basalt lava flows and identifying weak sub-basalt reflections. To reduce model uncertainties typical for basalt-covered areas, we compare calibrated sonic logs and seismic data in terms of velocity values and key horizons (Christie et al., 2002; Morice et al., 2004). The aim of the present case study is to apply this integrated methodology to the marine streamer data set GWS94 (courtesy of Norsk Hydro) acquired with a single boat in North of Shetland (UK) (Figure 1). Following the recent geological analysis done by Jolley and Bell (2002), the objective is to consider evidence for the depositional environment of the strata of the Erlend Volcano revealed by seismic reflections. Seismic data were deconvolved and multiple reflections associated with the water bottom were removed prior to multi-wave-type processing. Some acquisition parameters are as follows: source/receiver spacing is 50 m, minimum offset is 95 m, maximum offset is 3045 m, record length is 3.5 s, and time sample rate is 4 ms. RMS velocities. Similarly, the linear, parabolic or generalized Radon transform may be used to increase the PP-wave signal-to-noise ratio and to identify non-PP events not interpretable on the PP sections, as illustrated in Figure 2. See Druzhinin et al. (2004) for more detail. Velocity Calibration Success in the Erlend Volcano study has required strict attention to the calibration between wells and 2D seismic. This calibration procedure guarantees that the check-shot survey will receive the same static treatment as the seismic survey. Firstly, we built an initial isotropic velocity model, using existing well control and time horizon maps consistent with the lithology column in Figure 3. Secondly, we estimated the Thomsen’s delta parameter (Figure 4) from the mismatches between effective P-wave velocities derived from surface seismic data after signal enhancement (Figure 2b) and compressional sonic logs after upscaling (Figure 3). Processing Results We run trial time migrations of moveout-corrected CDP gathers over a range of parameters to confirm that the final velocity model was optimal (Figure 5). Even though the application of PreSTM helped to improve the image of the base-basalt (BB) horizon (Figures 5 and 6a), the time section in Figure 6a has typical problems in basalt-covered areas: weak sub-basalt reflections and strong coherent noise (arrows indicate noise). To overcome these difficulties, we proceed as follows. Firstly, the focus is on the asymmetric wave mode PPSP to recover the detailed basalt structure between the TB and BB boundaries in Figure 6a. Here, PPSP means downgoing P wave and upgoing S wave with conversion to P wave at the sea floor.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.90)
Using Converted Shear-wave For Imaging Beneath Basalt In Deep Water Plays
Li, Xiang-Yang (Edinburgh Anisotropy Project, British Geological Survey) | MacBeth, Colin (Edinburgh Anisotropy Project, British Geological Survey) | Hitchen, Ken (Edinburgh Anisotropy Project, British Geological Survey) | Hanßen, Peter (Edinburgh Anisotropy Project, British Geological Survey)
ABSTRACT No preview is available for this paper.
- Geophysics > Seismic Surveying (0.40)
- Geophysics > Borehole Geophysics (0.40)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.40)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (0.40)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems (0.40)