Engineering properties of chalk with regards to cliff slope stability: Mechanical properties of chalk and the impact of weathering on the UCS and tensile strength

Coastal chalk cliff instability is a major issue in the UK’s southern region. In order to further the understanding into what drives and influences chalk cliff collapse, a series of laboratory tests have been done on samples taken from West Melbury Marly Chalk, Seaford Chalk, Newhaven Chalk and Lewes Nodular Chalk. Tests have been done to find...

Geomechanical Characterization of the Buntsandstein including a Fracture Model

With an increased demand for renewable energy sources, geothermal developments have moved into the spotlight, including sedimentary structures. In the western part of the Netherlands, cretaceous sandstone bodies are already in use for the geothermal energy production. However, these reservoirs are generally producing water at temperatures less...

Physical Characterization of the Lower Carboniferous Limestone as a potential Geothermal Reservoir

To develop high enthalpy geothermal systems in the Netherlands, reservoirs with a depth greater than 4000 m need to be targeted. The Lower Carboniferous limestone is proposed as the main target due to its depth and wide occurrence. To investigate the potential of this formation, the physical rock properties are studied in a variety of laboratory...

Effects of Thermal Shock on the Creation of Microfractures and Mechanical Properties of Various Volcanic Rock Types, including Samples from the Indonesian Geothermal Field (Tangkuban Perahu)

This thesis aims at investigating the effect of a thermal shock of a couple of hundred degrees on the creation of the thermal microfractures and in what way the mechanical properties of volcanic rocks change. In the geothermal field, thermal microfractures can contribute to increase the permeability and produce more steam to the surface. We...

Hydraulic fracturing under waterflooding conditions in unconsolidated sands: Exploring fracture creation capabilities using low viscosity injection fluids

Rapid injectivity decline is frequently observed during injection in unconsolidated sand reservoirs. Field data suggests that hydraulic fracture processes are directly or indirectly related to this injectivity decline. Conventional fracture theories do not apply to unconsolidated sand since this material has little to no cohesion and tensile...

The Fracturing Behavior in Layered Rocks: Modeling and Analyses of Fractured Samples

Hydrocarbon or geothermal reservoir often consists of several rock layers from different lithology. The various lithologies have their own number of mechanical properties and the layering effect introduced the term of mechanical contrast, which represents the ratio of rock strength between adjacent layers. Mechanical contrast and confining...

The influence of mechanical contrast on industrial and natural hydraulic fracturing

The heterogeneity of layered systems leads to variation in rock or soil mechanical properties, influencing the resistance to failure. A formation breaks by fracture propagation when the effective stress surpasses the formation strength. The propagation of a fracture through a mechanical interface depends on whether the formation strength of the...

Heat Exchange in Tensile Fractures: an Experimental and Numerical Approach

Geothermal energy is a relatively sustainable energy source of which the essence is to extract heat from hot subsurface rocks. Circulating fluids serve as the transport agent of heat. The contact area between the fluids and the rocks is where the relevant heat transfer occurs, i.e., where the water is heated up. In some geothermal reservoirs,...

Influence of Mechanical Contrast and Confining Pressure on Fracture Behaviour in Layered Rocks

A rock fracture is a mechanical break or discontinuity that separates a rock body into two or more parts. The continuity or cohesion of the rock body is lost across a fracture. Fractures are formed in response to stress on a rock. A rock breaks and forms a fracture when the applied stress reaches the rock strength. Vertical fractures improve...

Experimental analysis of passive acoustic emission, in particular the Kaiser Effect, under dynamic stress conditions: Exploring the implications for in-situ failure monitoring in underground mines

Irreversible damage induced by stress in brittle rock is accompanied by the formation of micro-cracks. The strain energy released during the fracturing process is released in the form of acoustic emission. This thesis applied the non-intrusive method of acoustic emission monitoring to assess the deformation process of brittle rock during...