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Collaborating Authors
Results
Summary Geoscience techniques that are well established for conventional oil and gas exploration and production are equally applicable to shale gas systems. A robust data set allowed lithostratigraphic classifications and reservoir characterizations to be carried out in the Horn River Basin of northeast British Columbia. When it was demonstrated that statistical relationships existed between the lithostratigraphic classifications and elastic rock properties it became possible to invert 3D seismic volumes for the elastic properties and map the lithostratigraphic units by directly applying the statistical relationships. These findings for lithostratigraphic classifications are also applicable to key shale gas reservoir properties such as porosity or total organic carbon. From these transformations it was straightforward to apply standard data-reduction and mapping processes to determine quantities needed for key project decisions such as pad design and land acquisition rankings.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.89)
- Geology > Geological Subdiscipline > Stratigraphy > Lithostratigraphy (0.87)
- North America > Canada > Saskatchewan > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Northwest Territories > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- North America > Canada > Manitoba > Western Canada Sedimentary Basin > Alberta Basin (0.99)
- (7 more...)
Planning for Success: The Tridacna 3D Seismic Survey, Scott Reef, Western Australia – 3D Ocean Bottom Cable Seismic Acquisition in a Sensitive And Remote Offshore Environment.
Weiss, Ralph (Woodside Energy Limited) | Fitzpatrick, Jeremy (Woodside Energy Limited) | Taylor, Mark (Woodside Energy Limited)
Summary In late 2011 Woodside Energy Ltd (Woodside), as operator of the proposed Browse LNG Development, acquired the Tridacna 3D Ocean Bottom Cable (OBC) seismic survey (Tridacna survey) over north Scott Reef. The remote offshore location, environmental sensitivity, tidally-emergent reef crests and a semi-diurnal macro-tidal setting imposed significant operational limitations at Scott Reef. The ocean bottom cable technique was selected as the most appropriate technological solution for 3D seismic acquisition in this setting. The survey design incorporated the technical requirements for the acquisition of good-quality seismic data necessary for reservoir imaging whilst cognisant of the operational realities associated with contractor and equipment availability, a shallow restricted marine survey location, complex environmental approval conditions and cost/timing considerations. The survey operations comprised a wide range of activities, operational restrictions and personnel not normally part of conven-tional offshore towed streamer seismic surveys, and required highly-detailed operational planning. The Tridacna survey was successful in acquiring subsurface data and was completed safely with minimal environmental impact.
- Oceania > Australia > Western Australia > Timor Sea > Browse Basin > Caswell Basin > Block WA-30-R > BCT Fields > Torosa Field (0.99)
- Oceania > Australia > Western Australia > Timor Sea > Browse Basin > Caswell Basin > Block WA-28/32-R > BCT Fields > Brecknock Field > Plover Formation (0.94)
- Oceania > Australia > Western Australia > Timor Sea > Browse Basin > Caswell Basin > Block WA-28/31 > BCT Fields > Calliance Field > Plover Formation (0.94)
Summary The region immediately south of West Timor, offshore Indonesia, has been largely underexplored, with only one well drilled onshore in the West Timor Block operated by eni, and no wells drilled offshore. The area is located along the Outer Banda Arc, a geologically complex, non-volcanic semi-circular belt where the Australian and Asian Plates obliquely collide. The main reservoir target is the clastic Plover formation. Imaging and resolution of the Top Jurassic horizon and the overlying accretionary section is the primary geophysical objective for prospect generation and poses a formidable challenge to marine seismic acquisition and processing. The seismic exploration history dates back to a legacy 2D survey in 1991. In 2009, a regional 2D survey using towed streamer dual-sensor broadband technology yielded significantly improved continuity of events beneath the accretionary section. Encouraged by these results, in 2010 eni acquired a pilot study of 2D lines and subsequently a 3D survey using the same broadband acquisition technology. Broadband marine seismic via dual-sensor streamer resulted in improved resolution of the overburden and greater penetration at the target level. These benefits are a direct consequence of eliminating the receiver ghost. Ghost-free data is rich in both low and high frequencies, has improved signal to noise ratio, and is easier to interpret. A second important contribution comes from utilizing a unique implementation of Beam Depth Migration to correctly image the complex overburden and underlying target structure. Unique aspects of this implementation include near-vertical steep dip imaging, residual multiple attenuation in the depth domain, and the ability to detect and correctly position weak signal. These features play an important role in imaging both the accretionary prism and the target structure. The combination of the broadband dual-sensor acquisition and the Beam migration imaging provided significant uplift in the understanding and interpretability of the seismic data promoting the development of a new exploration play in the region.
- Asia > Indonesia (0.72)
- North America > United States > Illinois > Madison County (0.45)
- Oceania > Australia > Western Australia > North West Shelf > Browse Basin > Block WA-315-P > Plover Formation (0.99)
- Oceania > Australia > Western Australia > North West Shelf > Browse Basin > Block WA-274-P > Plover Formation (0.99)
Summary In some areas, seismic data can exhibit the effects of strong azimuthal anisotropy (AA). One of the major causes of AA can be anomalous horizontal stress regimes, which can be modeled as horizontally transverse isotropy (HTI). The Stybarrow field, located offshore NW Australia in the Carnarvon sedimentary basin, is one such area, where strong horizontal stress conditions have been present throughout the basin’s tectonic history. We find evidence for AA in repeat 3D seismic data acquired at two separate azimuths over the Stybarrow field. AA is observed in amplitude versus offset (AVO) reflection amplitude difference maps and cross plots, and is consistent with dipole shear logs and borehole breakout data in the area. We model azimuthal AVO responses using Ruger’s HTI AVO equation, using the anisotropy parameters derived from dipole shear logs, and compare the results with AVO data from the two 3D seismic surveys. Certain fault blocks (but not all) exhibit the same AAVO trend in the seismic data as those modeled from log data, consistent with a stress-induced HTI anisotropic model interpretation.
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Exmouth Basin > WA-32-L > Stybarrow Field > Macedon Formation (0.99)
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Exmouth Basin > WA-255-P > Stybarrow Field > Macedon Formation (0.99)
SUMMARY The ability of the marine controlled source electromagnetic method to resolve anisotropy in the sediment conductivity is not very well understood. In this study, we address the resolvability of anisotropy using a Bayesian approach. Two markedly different methods, slice sampling and reversible jump Markov Chain Monte Carlo have been used for the Bayesian inversion of a synthetic model of a resistive oil reservoir trapped beneath the seabed. We use this to identify which components of data can provide the strongest constraints on anisotropy in the overburden, reservoir and underlying sediments.
- Oceania > Australia > Western Australia > North West Shelf > Carnarvon Basin > Exmouth Plateau > WA-1-R > Scarborough Field (0.99)
- Africa > South Africa > Western Cape Province > Indian Ocean > Bredasdorp Basin > Block 9 > EM Field (0.99)
- Reservoir Description and Dynamics > Reservoir Simulation > History matching (0.72)
- Reservoir Description and Dynamics > Reservoir Simulation > Evaluation of uncertainties (0.72)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.56)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (0.49)
- Information Technology > Artificial Intelligence > Machine Learning > Statistical Learning (0.55)
- Information Technology > Artificial Intelligence > Representation & Reasoning > Uncertainty > Bayesian Inference (0.34)
- Information Technology > Artificial Intelligence > Machine Learning > Learning Graphical Models > Directed Networks > Bayesian Learning (0.34)
Summary Uncertainties in marine controlled source electromagnetic (CSEM) data consist of two independent parts: measurement noise and position uncertainties. Measurement noise can be readily determined using stacking statistics in the Fourier domain. The uncertainties due to errors in position can be estimated using perturbation analysis given estimates of the uncertainties in transmitter-receiver geometries. However, the various geometric parameters are not independent (e.g. change in antenna dip affects antenna altitude, etc.) so how uncertainties derived from perturbation analysis can be combined to derive error-bars on CSEM data is not obvious. In this study, we use data from the 2009 survey of the Scarborough gas field to demonstrate that (a) a repeat tow may be used to quantify uncertainties from geometry, (b) perturbation analysis also yields a good estimate of data uncertainties as a function of range and frequency so long as the components are added arithmetically rather than in quadrature, and (c) lack of a complex error structure in inversion yields model results which are unrealistic and leads to "over-selling" of the capabilities of CSEM at any particular prospect.