Abstract

Variations of minimum horizontal stress (S_hmin) with depth and geological layering are observed frequently in unconventional hydrocarbon reservoirs through field stress measurements. In this study, we show that these variations can be predicted by laboratory creep experiments performed on rock samples from representative geological layers utilizing the concept of viscoelastic stress relaxation. We present a modified viscoelastic stress relaxation power law framework that can be applied for normal and strike-slip faulting environments and show its application to a case study in a prolific unconventional oil & gas formation located in the northeastern United States. We utilize viscoelastic power law parameters measured through laboratory creep experiments to compute a discrete 1-D S_hmin profile at depths corresponding to the rock samples. The computed S_hmin values are validated with field measurements conducted at the same depths and show that the laboratory measured creep parameters can be used to accurately predict field scale 1-D stress variations in unconventional reservoir formations. Finally, we show through offset stress measurements and microseismic data that the 1-D stress profile can be applicable over large spatial scales if there is continuity in the lithological layering.