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Jones, Ian (ION) | Raffle, James (ION) | Earnshaw, Thomas (ION) | Fruehn, Juergen (ION) | Greenwood, Stuart (ION) | Singh, Jeet (ION) | Hagen, Claudia (ION) | Fuck, Rodrigo Rodrigo (ION) | Sassen, Doug (ION) | Luo, Zhijiang (ION) | Forsund, Svein (Centrica) | Ackers, Mark (Centrica) | Aamodt, Lars (Centrica)
The Ivory discovery lies within the Nyk High, located in the north-eastern part of the Vøring Basin, which has been tectonically active in several phases. The main challenge in mapping the extent of the Ivory discovery has been seismic imaging at the crest of structures bound by major faults (e.g. fault shadow effects), together with depth conversion uncertainty and a poor well to seismic tie. To address the uncertainties associated with these issues, a new Pre-Stack Depth Migration was run using a dataset re-processed with the latest demultiple and deghosting technology. From this final migrated volume, structural uncertainty was then estimated using a Bayesian statistical analysis of the tomographic resolution matrices in conjunction with prior uncertainty estimates.
Presentation Date: Tuesday, September 26, 2017
Start Time: 9:45 AM
Presentation Type: ORAL
Valler, Victoria (ION) | Payne, Nathan (ION) | Hallett, Thomas (ION) | Kobylarski, Marcin (ION) | Venkatraman, Girish (Engie E&P Norge) | Rappke, Jochen (Engie E&P Norge) | Fairclough, Dirk (Monarch Geophysical Services)
consuming area to be addressed during velocity model building. In addition to their impact on deeper structures and prospects, re-worked injectites are increasingly being considered for hydrocarbon potential themselves. In order to handle the challenges above we should consider ways of producing an accurate velocity model of these structures within a framework that is efficient and commercially timeviable. Here we present a holistic approach and case study to model-building in and around injectites that utilizes robust broadband data pre-processing, a semi-automated identification and modeling of injectite bodies and subsequent high-resolution tomographic updating. Our results show that this method enables us to produce a highly accurate and detailed model of a complex injectitefield and subsequent improvement on the deeper image within the timeframe of a conventional model building iteration.
Presentation Date: Wednesday, October 17, 2018
Start Time: 8:30:00 AM
Location: 208A (Anaheim Convention Center)
Presentation Type: Oral
Ramirez, Oscar (Spectrum Geo Inc.) | Chen, Genmeng (Spectrum Geo Inc.) | Saunders, Mike (Spectrum Geo Inc.) | Geiger, Laurie (Spectrum Geo Inc.) | Cvetkovic, Milos (Spectrum Geo Inc.) | Roberts, Mark (Spectrum Geo Inc.) | Clarke, Richard (Spectrum Geo Inc.)
Imaging sedimentary basins in the context of oil and gas exploration entails different but complementary objectives. Understanding the tectonic architecture of a basin requires acquisition and processing strategies that differ from those strategies that are required to understand play fairways and prospects. In this paper we demonstrate effective processing strategies that produce clear and consistent images of the Moho discontinuity and elements of the crystalline basement, with equally clear images of the sedimentary section showing amplitude anomalies consistent with the presence of hydrocarbons.
Presentation Date: Tuesday, October 16, 2018
Start Time: 1:50:00 PM
Location: 210C (Anaheim Convention Center)
Presentation Type: Oral
Abstract The availability of high quality seismic data is of critical importance in trying to unravel the complexities of subsurface geology. This paper illustrates how proper selection of seismic acquisition parameters and data processing techniques can successfully overcome geological difficulties and minimize uncertainties when exploring for hydrocarbons in the northern part of Block G11/48, Gulf of Thailand, without compromising safety and cost efficiency. Fluvial and fluvio-deltaic sediments of early to mid Miocene age in low relief faulted structural traps constitute the most common hydrocarbon habitat in the area of investigation. Amplitude support in identifying potential targets is also proven by nearby discoveries. To fully evaluate the exploration potential of this area, a 3D seismic acquisition campaign was successfully carried out using a high-end seismic vessel and without HSSE incidents. The Nong Nuch dataset was acquired using a 10 deep-flat towed 5.1 km streamer configuration with triple sources to increase cross-line resolution and reduce operational time. This long streamer length relative to the target depth provides necessary information to Full Waveform Inversion and Q-tomography in order to correct push-down effects in broadband anisotropic Pre-stack Depth migration. The dataset also helps to obtain high accuracy velocity model, de-multiple and quantitative interpretation. This acquisition and processing approach significantly improved the ability to image thin reservoirs and correct push-down effects and energy absorption due to gas clouds or unconsolidated sea floor channels. The large streamer spread and deep tow did not create any major problems throughout the acquisition. The implementation of broadband acquisition and leading edge processing techniques resulted in good signal to noise ratio as well as high vertical and horizontal resolution with minimal acquisition footprint. In addition, long offset data acquisition contributes to successful attenuation of short and long period multiples. Channel-like features and fault plane reflections are very clearly imaged in the dataset, helping to better understand of the depositional environment and structural setting of the area. Severe push-down and abnormal amplitude absorption effects were significantly corrected and compensated by building a high resolution, Full Waveform Inversion (FWI) derived velocity model as well as application of reflection tomography and Q-tomography techniques. Thus, definition of potential traps beneath gas clouds has significantly improved.
Historically complex salt bodies (e.g. Canopy, Salt Weld…) can introduced serious imaging issues for geophysicists with distorted seismic images both beneath salt body and in the vicinity of the salt flanks or welds (Ian F. Jones, et al., 2014). This is mainly related to absorption and scattering of the seismic ray path. The challenge is to produce a velocity model that is consistent with a geological concept, enabling the delineation of the salt bodies geometry and imaging beneath the salt bodies. In order to tackle this problem, a robust velocity model building strategy using four focus points was implemented: input dataset, velocity model building (VMB) workflow, imaging algorithm and intelligent stacking described in this case study. First, using re-processed and de-ghosted dataset to bring out the low frequency content in the data. Second, a robust velocity model building workflow which comprises of tomography update, Full Waveform Inversion (FWI), salt body interpretation and manual Vp update. Third, imaging using Reverse Time Migration (RTM) algorithm in order to handle the complex ray path and sharp velocity contrast between salt bodies and sediment layers. Finally, post-imaging processing using intelligent stacking in order to benefit from the multi-azimuth illumination coming from the wide-azimuth seismic acquisition (post-migration processing on full azimuth data was performed as well). This workflow has proven to be successful in producing a better focused high-resolution final image in areas affected by the salts which can be integrated into any other future salt-based imaging project. Note: This paperÂ wasÂ acceptedÂ into the Technical Program but was not presented at the 2020 SEG Annual Meeting.