Browsing by Author "Almalki, Saad A."

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Seismic imaging of reservoir, seal, and fluid conduits
(University of Manchester, 2024) Almalki, Saad A.; Huuse, Mads
Geo-energy industries demand highly accurate processing and interpretation of 2D and 3D reflection seismic data to improve pre-drill assessments of reservoir and fluid properties and seal integrity. Failure to correctly image the subsurface could arise from inaccurate acquisition or sub optimal processing, for example by employing overly smooth subsurface velocity fields. These issues could lead to significant mistakes in seismic interpretation and subsurface models. This research focusses on the issue of fluid flow ‘pipes’ that are widely interpreted in seismic profiles displaying vertical seismic anomalies such as push up, push down or disorder in the seismic events. The problem is that pipes might not be the only source of vertical stacking anomalies in seismic profiles but geological features near the seabed, such as channels, valleys, or gas hydrate plugs, could also be the source of such anomalies. Thus, the aim of this research is to characterize the difference between near surface bodies and real pipe seismic anomalies in seismic profiles by running models of pipes and geological features (channels) in near surface. Seismic angle stacks (near, mid and far) are used to exhibit seismic anomalies of real pipes and the geological features with different angles. Consequently, angle stack images exhibit a similar distortion pattern (fish tail) with far angle stacks and vertical stacking anomalies in near angle stacks with pipe-like structures and channels located near the seafloor. In parallel, the research delves into the imaging challenges associated with sandstone intrusion complexes, characterized by variable geometries and the influence of dip angles on seismic imaging. Using full-wave field seismic modelling, the study quantifies the reflection responses of these complexes, revealing that wing-like structures with dip angles between 10 and 50 degrees are detectable, whereas those above 50 degrees are not. Moreover, dikes change the characteristics of underlying top reservoir reflectors, increasing discontinuity and amplitude changes, especially as their thicknesses increase. In conclusion, this research has demonstrated that not all vertically stacking anomalies in seismic profiles represent pipes or fluid leakage pathways to upper layers; they may also arise from velocity anomalies (push-down or pull-up) induced by abnormal structures near the seabed, such as channels. This study has allowed guidelines to be established for the correct interpretation of fluid flow vs near surface derived vertical anomalies. Additionally, the study has effectively quantified the imaging limitations associated with wing-like sandstone intrusions and their associated crestal dike complexes through the use of full-wave field seismic forward modelling, highlighting the challenges in imaging and detecting such features, particularly when they exhibit complex geometrical properties.
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