The ability to achieve and sustain injectivity has a fundamental and significant bearing on the success or failure of a water injection project. Restricted and/or impaired injectivity can result from a number of factors ranging from poor reservoir quality to process-induced formation damage issues among others. For the case of poor reservoir quality, a solution may lie in adapting wellbore configurations to maximize reservoir contact. However, applying these solutions demands an extensive prior evaluation of risk-weighted benefits of available technology options, including implications under varying degrees of uncertainty.
This paper compares multilateral and hydraulically fractured well technologies as means to enhance injectivity in low permeability reservoirs. A conceptual approach – from a simplified homogenous model to a more detailed heterogeneous model - is employed. A reference high angle injector well type is selected, and an injectivity improvement factor calculated for different multilateral and fractured well options. Several sensitivities were also performed to assess the exposure of selected wellbore configurations to subsurface uncertainties. The evaluations were also extended to naturally fractured syste m sensitivities.
We find that as reservoir quality deteriorates, the benefit in injectivity improvement becomes even more accentuated with carefully selected wellbore configurations. Additionally, the need for proper considerations for well placement is highlighted. Finally, the work underlines some broad guidelines supporting discussions on meeting of water injection and reservoir management objectives in similar reservoirs.