Characterisation of geological storage on the UKCS from interpretation of seismic reflection data

Abstract

This thesis investigates the impact of interpretation uncertainty on subsurface storage sites for the purposes of storing either hydrogen or carbon dioxide. 3D seismic and well data were used alongside complementary modelling methods to quantify uncertainties and sensitivities. The work investigates three themes, the interpretation of the complex internal structure of evaporites; the impact of geological uncertainties on salt cavern developments, and the variation in seismic response expected under different fluid saturations. The internal structure of the Zechstein Supergroup shows high levels of deformation and geometries that increase in complexity basin-ward. The internal deformation was interpreted and characterised, identifying six unique deformation styles which were parametrised and mapped spatially. This has implications for storage site suitability. Geological uncertainties were quantified for salt cavern developments, using a stochastic workflow that was developed to model potential cavern emplacement locations and hydrogen capacity. The potential hydrogen storage capacity in salt caverns in the UK sector of the Southern North Sea (80+ PWh) is far greater than any potential storage demand (100 TWh). Total energy storage demand could be met with as few as 73 caverns in an area 28 km2. The variation in the seismic response of siliciclastic reservoirs on the United Kingdom’s continental shelf was investigated after fluid substitution of non-hydrocarbon fluids to further understand seismic monitoring approaches. The results show that typical monitoring approaches, such as 4D amplitude comparisons, may not be suitable due to the limited change in elastic properties of the reservoir rocks once substituted with the pore filling fluid. This thesis quantifies and constrains the uncertainty of the subsurface for storage of non hydrocarbon fluids within the UKCS for both porous media and salt caverns.