Development of unconventional Wolfcamp resources is made possible using horizontal wells with multi-stage hydraulic fracture treatments. The Wolfcamp is productive in several zones separated by carbonate benches. Bed-bounded natural fracture systems play a significant role to well productivity. Several RTA techniques are available to quantify hydraulic fractures and matrix properties for well performance evaluation. However, these techniques have limitations in multi-phase flow system with rapid changes in fracture properties.
This paper presents the case study of two multi-stage, hydraulically-fractured, horizontal wells completed in Wolfcamp intervals with over two years of production history. Performances were analyzed using an integrated static Discrete Fracture Network (DFN) and dynamic reservoir simulation model. This allows detailed modelling of the rock properties variation along the well sections, dynamic changes in hydraulic fracture properties and effects on well performance under multi-phase flow condition.
The integrated history matched model indicates a significant loss of hydraulic fracture conductivity in the first six months of production. Early production of the wells were dominated by flushing of induced hydraulic fractures while the late time dominated by the stimulated rock volume (SRV). Depletion of the SRV combined with continuous fracture closure and unfavorable oil mobility as near wellbore saturation profiles were altered with continued drawdown below bubble point led to high GOR and severe reduction in oil productivity. The study also indicates that less aggressive and managed flow-back process may reduce possible fine migration. In addition, low productivity makes the wells candidates for refrac treatment and section down-spacing.
The information presented can be used to integrate static DFN and numerical reservoir simulation model, quantify the dynamics of hydraulic fractures in time and space, and identify well performance drivers and effect of multi-phase on well performance. The study provides a platform for managing well production, designing and optimizing stimulation jobs and flow-back process to reduce or mitigate rapid loss of hydraulic fracture conductivities in a long reach horizontal well draining a saturated unconventional reservoir.