Fracture Propagation Prediction in an Openhole Horizontal Injector Well: An Applied Geomechanic Study

Abstract

Abstract Understanding and predicting fracture propagation behaviour in a geotectonically complex, layered reservoir presents major challenges. In particular, an accurate prediction of vertical fracture extension in horizontal injection wells is fundamental to the overall waterflood injection performance assessment. Water injection in an open hole horizontal well in a low permeability formation may generate one or multiple fracture planes depending principally on the orientation of the well with respect to the in situ stress field, as well as the combined effects of high injection rates, low injectivity and stress reduction due to thermal effects. Conventional fracture generation prediction in horizontal sections considers predetermined areas where the fractures will propagate. In an open hole environment, the number of fractures that will be generated over time is often too complex to allow accurate prediction. A novel methodology, based on a fracture energy dissipation approach, has been developed to overcome the problems associated with conventional models in horizontal open hole sections. This strategy integrates the field geomechanical model with a commercial transient fracture simulation model. The simulation model was used to predict the vertical extension of the fractures by studying the energy dissipation that takes place under specific injection conditions. A relationship has been found between the initiation area, injection flow rate and the non-dimensional vertical propagation factor that can be used to predict (and ultimately control) vertical fracture growth even in heterogeneous sand-shale sequences. The introduction of selective initiation areas along the horizontal well section will radically improve the control of fracture vertical extension. Using this methodology, it is possible to design and evaluate completion strategies, which optimise fracture energy dissipation and fracture containment performance in open hole horizontal injection wells in low permeability formations.