Fractures are considered to be both problems and opportunities for exploration and production from petroleum reservoirs. The main aim of fracturing an oil medium is the stimulation of oil and gas production by inducing highly conductive channels leading to a well, from which hydrocarbons will flow. Many applications of hydraulic fracturing take place in soft sandstones using moderate to low viscosity fluids. Soft sandstones represent the host rock for a large portion of active aquifers and oil and gas reservoirs because their high porosity both enhances storage and facilitates extraction. The transitional nature of sandstones, in particular, presents some challenges to the safety of these operations and the understanding of the mechanical response of these materials under a variety of conditions is poor. The motivation of this research was to gain understanding of the fracture mechanics of soft media under low viscosity fluid injection. Synthetic rock specimens were generated via microbially induced carbonate precipitation (MICP), providing virtually limitless quantities and had customisable characteristics, allowing relevant structural parameters to be varied independently, and hence isolating their effects. The method was applied to produce realistic weak sandstone-like materials from a base sand through a bio-process that builds up calcium carbonate cementation around the particles. Once a single recipe was developed and the uniformity of the specimens and repeatability of process were assured, the mechanical and physical properties of the specimens were assessed with varying base materials (grain size, shape, width of particle size distribution) and levels of cementation. The artificial rocks sufficiently resembled soft sandstones to be used as a substitute in the subsequent laboratory investigation of the hydraulic fracturing experiments. Fracturing experiments were conducted with both cohesionless sands and bio-cemented samples at various confining conditions, flow rates, fluid viscosities, cementation levels and various base materials. The main aim was to get an insight into how each individual factor affects the fracture patterns and pressure response. For those experiments, two experimental setups were developed explicitly for this project that were able to apply actively or passively stresses to the medium which was repre- sented in three dimensions. The transitional behaviour of weakly cemented sandstones was clearly seen on both the fracture patterns and pressure responses obtained when conducting the hydraulic fracturing tests. The fractures transitioned from plane-like to string-like as the cementation level increased, while the deviation between the breakdown and propagation pressures was also more pronounced. Many observations in the literature concerning the fluid properties and rates were confirmed in this work, but also new information was added because of the ability to visualise the fracture initiation and propagation. The work conducted in this research bridges previous works on two-dimensional media, where visualisation of the fracture was possible, and three-dimensional media, where only post-test observations could be made.