Abstract This paper describes the results of an empirical one-dimensional model for toe thrust structures that enables both fluid pressure expectations and seal integrity to be evaluated. The growth of a deepwater thrust anticline is forward modelled with calibration made to a present-day structure. Two locations are used to describe the structural evolution: the crest of the anticline and the floor of the adjacent syncline. These locations are followed through structural growth and burial. Pore pressures in the evolving toe thrust are modelled by employing a centroid model for a pre-tectonic target reservoir interval, with shale pressures modelled using the concept of a variable fluid retention depth. A shale compaction model based on critical state soil mechanics is used to model top seal porosity and to aid the evaluation of the capillary top seal. Together with mechanical seal analysis this enables the controls on trapped hydrocarbon column heights to be assessed. Application of the model to two recently drilled toe thrusts is discussed, and results compared to model predictions. The model can be used to offer a generic seal integrity scheme for a toe thrust that may help focus attention on the key exploration risks.

Abstract Highly porous and soft calcarenites, often called ‘calcareous tuffs’, are commonly found throughout Southern Italy and are traditionally used as building materials. The petrophysical features of some of them were determined, focusing on the microstructure (fabric and porosimetric characteristics) and on the properties related to water absorption, drying and water vapour permeability; the compressive strength was also measured. The mineralogical composition was analysed and a variable presence of clay minerals was found for the different varieties. Diverse levels of damage under a salt crystallization test were related to the mineralogical, petrographic and porosimetric features, the latter being a source of the heterogeneity of the investigated stones. Results of laboratory tests and observations of decay in the field suggest protection against water penetration as the primary requirement for slowing down the decay of such highly porous and soft stones. Some water-repellent products were tested for effectiveness in reducing water absorption and for compatibility with the original stones’ properties. Their use in the presence of salts was taken into account, including the performances of the treated stones under the salt crystallization test. Treatment issues were found to be strongly influenced by the porosimetric characteristics of the studied materials.

Abstract Most buildings of architectural heritage in Paris and its surroundings are built with Lutetian limestone. Several historic buildings of the ‘Vexin Normand’ region show Lutetian limestone in the upper parts of their walls, while the lower parts are built with a chalk known as ‘Pierre de Vernon’. The ‘Pierre de Vernon’ appears up to the first metre, although in exceptional cases it can reach the middle height of a building. Commonly, chalks exhibit low durability due to their high porosity. However, ‘Pierre de Vernon’ is supposed to have greater durability than other chalks because of its historic use for basement construction. The objective of this research was to understand the use of the ‘Pierre de Vernon’ in the lower part of the constructions. A petrophysical characterization of Vernon chalk and Lutetian limestone was carried out, focusing mainly on the differences in porosity and water uptake. Salt crystallization tests were done to contrast their response to decay. Colour and roughness measurements and scanning electron microscope observations were performed. Results show that the different porous networks of these two limestones lead to a high contrast in their hydric properties and responses to decay, and the use of Vernon chalk in the lower sections of buildings has been found to be appropriate.

Abstract This study presents a new experimental chamber, which builds upon previous methods of testing salt weathering. This method is based on capillary rising in samples, as this corresponds to the actual imbibition process in building stone. This set-up allows control in setting both a specific thermal regime and cycling temperatures. Some of the significant additions of this experimental set-up are: continuous flow of the saline solution, as the samples will be fed with a constant concentration throughout the experiments; and continuous monitoring of environmental temperature, relative humidity and sample weights. Recorded results in this research belong to limestone samples from Mokattam, Cairo. Results are also considered as a proof to the practical advantages of the experimental chamber in salt-weathering studies and its environmental controls.

Abstract This study gives an example of the steps that a repair work must include to be successful. It deals with a specific building, repair material (lime mortar) and application (render), but also with the study of the repair mortar in the laboratory and on site. Firstly, the original materials of the wall were characterized to ensure compatibility with the new repair mortars. Secondly, the suitability of different mortar mixes, made with lime and calcareous aggregate, was assessed by characterizing their properties after 15 months. At the same time, the repair mortars were applied in testing panels, and their behaviour under environmental conditions was studied and compared with that of the laboratory mortars. Mortar properties (shrinkage, adhesion, mineralogy, microstructure and texture) developed differently according to the curing conditions. The carbonation degree was higher in mortars cured on site (especially those with higher aggregate content), although in both cases it depended on mortar porosity. Testing the type of application on site was helpful to define the best performance of the designed mixes and to choose the most suitable one among them, which was found to be the 1:6 binder-to-sand ratio mortar applied in both layers of the render.

Abstract Naturally fractured reservoirs (NFR), such as the large carbonate reservoirs in the Middle East, contain a major part of the world’s remaining conventional oil reserves, but recovering these is especially challenging as the fractures only constitute fluid conduits while the oil is trapped in a low-permeability rock matrix. Recovery factors are therefore difficult to estimate, permeability anisotropy is high, size and shape of drainage areas are difficult to constrain, early water breakthrough is likely to be associated with a high and irreversible water cut, and secondary recovery behaviour is unusual. Outcrop-analogue model-based discrete fracture and matrix (DFM) simulations have emerged recently, helping us to disentangle and rationalize this erratic production behaviour. They allow us to understand the emergent flow behaviour and resulting saturation patterns in NFRs. Thus, classical simulation approaches, such as dual-continua conceptualizations, can be critically evaluated and improved where they fail to capture the flow behaviour of interest. This paper discusses recent advances in DFM simulation of single- and multi-phase flow processes in geologically realistic outcrop-analogue models, and solved with finite-element (FE) and finite-volume (FV) methods. It also reviews key results from recent DFM simulation studies, in particular how new measures such as the fracture–matrix flux ratio and velocity spectra can provide new means to analyse flow behaviour in heterogeneous domains or how results from outcrop-based simulations can be used to test the suitability of conventional upscaling approaches for NFR and guide the development of new ones. We close by enlisting outstanding challenges in outcrop-based flow simulations such as the need to capture the fracture–matrix transfer processes due to capillary, gravity and viscous forces accurately, which often implies detailed grid refinement at the fracture–matrix interface and small time-steps to resolve the physical processes adequately. Thus, we explore how outcrop-based flow simulation could be applied more routinely in NFR reservoir characterization and simulation workflows.