Abstract

A basic goal for geologists and reservoir engineers is to understand the flow potential of a reservoir. Though several factors influence the well's productivity after completion, such as reservoir pressure, effective net pay, reservoir heterogeneities and effective propped fracture lengths, in-situ reservoir permeability dictates the relative magnitude of the production response. As such, in-situ permeability is a key variable for development opportunities. A method is presented here for determining in-situ permeability through pressure falloff analysis of fracture treatment diagnostic pump-in tests. A direct correlation is then made between the pump-in derived permeability value and the subsequent production response.

The discussion reviews the classical methods for determining in-situ reservoir permeability by highlighting the advantages and limitations of these procedures. The paper then introduces the theoretical premise for an alternative method and demonstrates the evaluation technique by presenting case studies in the Lewis, Almond, Frontier and Red Fork formations. The case studies show the relationship between the leakoff coefficient value, the pump-in derived reservoir permeability and the post-treatment production response. By relating these variables, a relative indicator of rock quality and flow capacity for a given reservoir can be determined during and immediately following the hydraulic fracture treatment. Given a statistically valid data set, the development of a permeability indicator provides the ability to predict production responses based on the pressure falloff observed while treating the well. Application of this technique may eventually lead to a reservoir / production tool that provides "real-time" go / no-go decision capabilities for geologists and reservoir engineers in completing multiple intervals in a well.