Dag Wessel-Berg

Vertical convection in an aquifer column under a gas cap of CO2

Abstract The basic equation for volume, heat and CO 2 flux in a porous medium which is subject to both a temperature field and molecular diffusion have been analysed with respect to the stability criteria for convectional vertical flow in a porous medium. This analysis reveals under what condition vertical convection may occur, which is important for the total storage capacity of CO 2 in aquifers.

Hydrodynamic activity and tilted oil-water contacts in the North Sea

The position of the oil-water contact (OWC) in a prospect or field is one of the most important factors in determining reserves. In the central North Sea, OWCs in the Cretaceous Chalk Group and in Paleocene sandstones can be naturally tilted by bed-parallel hydrodynamic activity as the Central Graben dewaters. Examples of fields with interpreted tilted OWCs are described, and set within their regional hydrodynamic context. In addition, laboratory experiments and computer simulations are used to examine the response of fluid contacts to aquifer heterogeneity in a hydrodynamic environment. These models can be used predictively, improving the understanding of tilted OWCs in fields, helping to explain dry wells and to improve planning and risk analysis for both exploration and development drilling.

On a Linear Stability Problem Related to Underground CO2 Storage

The analysis of gravitational instability of a diffusive boundary layer in porous media has been addressed in several papers over the years. In this paper we consider the linear stability problem for an infinite depth aquifer with anisotropic absolute permeability. We derive an explicit expression for the time evolution equations of the generalized Fourier coefficients corresponding to the linear stability problem. This allows us to study linear stability properties through the spectra of infinite symmetric matrices, showing excellent agreement with previously published results derived using the so-called quasi-static method.

Towards a methodology for top seal efficacy assessment for underground CO2 storage

Publisher Summary This chapter highlights that the quantitative assessment of leakage risk and leakage rates from planned underground CO 2 storage sites is a primary requirement for public acceptance, formal site approval, and credit for stored CO 2 quantities under CO 2 emission schedules. Leakage through the top seal can basically occur by three processes: diffusion through the pore system, capillary transport through the pore system of the seal, and multiphase migration through a fracture network; or by a combination of any of these. Diffusion results in very low leakage rates; maximum rates typically attained after several 100 000 years, being in the ppm range. Multiphase capillary migration is characterized by two main parameters: capillary breakthrough pressure and effective permeability to the non-wetting phase. The dependence of effective permeability to CO 2 on capillary pressure, which in turn is a function of CO 2 column height, is hysteretic in character with generally higher effective permeability during pressure decrease than during increase, at the same capillary pressure. Leakage is likely to stop at approximately 20 to 50% of the breakthrough pressure as suggested by the snap-off theory. Capillary breakthrough pressure and effective permeability is very difficult to measure for low-permeable rocks.

A large-scale infrastructure model for CO2 disposal and EOR—economic and capacity potential in the North Sea

Publisher Summary This chapter illustrates an injection scenario that includes most of the Norwegian oil reservoirs in the North Sea oil reservoir. In order to elucidate the possibility of combining CO 2 storage with EOR, a techno-economic model for a large scale scheme for CO 2 deposition in Norways North Sea oil provinces has been developed. A CO 2 -transportation module calculates the transportation costs for CO 2 from export terminals to the oil provinces. An EOR module predicts the increased oil recovery due to CO 2 injection in water-flooded reservoirs. In order to convert from a water-injection scheme to CO 2 injection large modifications of the oil production installations are needed. A possible solution for this has been sketched, and the costs for the necessary modifications and new installations for CO 2 injection have been estimated and are also included into the techno-economic model.