Imbibition and Water Blockage In Unconventional Reservoirs: Well-Management Implications During Flowback and Early Production

TLDR

Field logistics in unconventional reservoirs often necessitate weeks to months of shut‑in after hydraulic‑fracture stimulation. A flow‑simulation model, calibrated with laboratory relative‑permeability and capillary‑pressure data that depend on stress, reproduces the observed water‑blocking behavior. Field experience shows that shut‑in periods improve early productivity and reduce water production, with multiphase‑flow mechanisms explaining the water‑blocking behavior and underscoring the need to limit water invasion to avoid significant blockage.

Abstract

Summary Driven by field logistics in an unconventional setting, a well may undergo weeks to months of shut-in after hydraulic-fracture stimulation. In unconventional reservoirs, field experiences indicate that such shut-in episodes may improve well productivity significantly while reducing water production. Multiphase-flow mechanisms were found to explain this behavior. Aided by laboratory relative permeability and capillary pressure data, and their dependency on stress in a shale-gas reservoir, the flow-simulation model was able to reproduce the suspected water-blocking behavior. Results demonstrate that a well-resting period improves early productivity and reduces water production. The results also indicate that minimizing water invasion in the formation is crucial to avoid significant water blockage.