| dc.description.abstract | Although sand injectites have superior permeability and are promising targets for hydrocarbons and subsurface storage, they are relatively underexplored elements within the energy sector. There is a significant gap in understanding their origin, shape, and anisotropic properties. The uncertainty in sand injectite geometry can be mitigated through the application of sophisticated geophysical methods, which may offset the risks associated with exploring such formations.
This thesis delves into the detailed seismic analysis of sand injectites within Paleogene strata in the area around the Martin Linge field. Techniques such as spectral decomposition, amplitude versus offset (AVO), and extended elastic impedance (EEI) are used to analyse these bodies. The study area encompasses a km-scale mass transport complex situated between the Martin Linge and Oseberg fields, along the western and eastern margins of the Central Viking Graben in the northern North Sea.
The objective is to apply the techniques above for imaging sand injectites to determine their effectiveness and limitations. I also look at various challenges such as differences in sand injectite thickness and the presence of uncemented sands.
The thesis begins with spectral decomposition using various frequency bands to determine the tuning thickness of cemented and uncemented sand injectites. Next, AVO modelling is performed to create AVO class volumes defining the characteristics and fluid content of the sand injectites. Then, EEI is utilized to construct models of lithology and fluid volumes, integrating different chi angles to accentuate changes in lithology and fluids within the sand injectites and host claystone.
The results of the thesis demonstrate that while spectral decomposition marginally enhances the visualization of cemented sand features, it fails in detecting thinner sand injectites. Contradictions arise in AVO modelling as models based on well log data predict AVO Class II or III for studied injectites, but AVO analysis from seismic data leans towards a less certain Class I, although it still proficiently differentiates between shale and sandstone. Extended Elastic Impedance (EEI) analysis effectively discriminates between shale and sand, distinctly revealing uncemented top sands obscured in other seismic cubes. EEI at a -45° angle proves to be the most effective method, sharpening the definition of sand injectites' boundaries and facilitating precise geobody extraction.
This approach improves the mapping, reservoir characterization, and resource estimation of sand injectites, and the understanding of the analysed injection complex. The study highlights the advantages of employing the selected geophysical techniques and provides valuable insights for hydrocarbon exploration and production in the Martin Linge area and similar settings. | |
