Thermal Fracturing in High and Low Permeability Sandstone Reservoir in the North Sea

Thermally induced fractures, TIFs, occur in almost every water injection well. They are the result of the cooling of the reservoir rock as water reaches the sand face and near wellbore area. This cooling generates a contraction in the rock that results in a change in reservoir mechanical properties and the near wellbore stress conditions. The importance of understanding and engineering the process of TIFs is quite often underestimated, as TIFs are assumed to happen as under normal injection conditions. This paper presents the results of technical and field efforts carried out to overcome a variety of problems in water injection wells in two (2) particular types of reservoir: a high permeability (> 0.8 Darcy) and a very low permeability (< 0.03 Darcy); both sandstones located in the North Sea. Work was carried out in four(4) wells to utilize TIFs as a tool to maximize water injection and minimize well and reservoir integrity issues. This paper presents in detail the design process, its operational implementation and the results obtained for each reservoir. In both types of reservoirs, TIFs has allowed us to restore long term injectivity by overcoming a large number of constraints such as high levels of formation damage.