Novel methods for monitoring and mitigation of thermally induced fracturing in water injection wells

Abstract

Waterflooding is a common recovery method used to maintain reservoir pressure and improve reservoir oil sweep efficiency. However, injecting cold water into a reservoir alters the state of the in-situ formation stress and can result in the formation fracturing. In other words, it can result in the initiation and growth of Thermally Induced Fractures (TIFs) even when the original fracture propagation pressure is not exceeded. Consequently, TIFs can cause highly non-uniform distribution of the injected water flow in the wellbores, reduction in the sweep efficiency, and early water breakthrough in the nearby production wells. These reservoir management challenges caused by TIFs need to be addressed with the decisions informed by the appropriate monitoring and modelling of TIF development. This work describes methods to detect the onset and characterise TIFs followed by an example of evaluation of TIFs’ impact on the well and reservoir performance. Then, the performance and potential of Advanced Well Completions in horizontal wells in the presence of TIFs were investigated. The TIF characterisation problem was addressed by developing monitoring workflow that integrated and adapted several available analytical and semianalytical models previously developed for well performance analysis. The application of the workflow was illustrated and verified by reservoir geomechanical and fluid flow simulation. It was subsequently applied to real field data. Further, the effectiveness of an Advanced Well Completion to mitigate the negative effects of TIF was evaluated using a dynamic thermal reservoir model coupled with a TIF model, a geomechanical model and a detailed wellbore model. A history matched real field sector model was used for this study. The proposed methods proved to be efficient in detecting and monitoring TIFs as well as evaluating the metrics describing waterflood performance. These included flood efficiency, inter-well communication and pressure maintenance. Furthermore, the added value of advanced completions was quantified and shown to be effective in controlling TIF initiation and propagation as well as in improving the wellbore flow performance. TIFs surveillance and mitigation methods proposed in this thesis are novel and strongly contribute to the research aimed at improving waterflood performance in oil fields.