Integrated Workflow for Selecting Hydraulic Fracture Initiation Points in the Khazzan Giant Tight Gas Field, Sultanate of Oman

摘要

Core-calibrated petrophysical rock typing for gas rate deliverability profiling, coupled with field-calibrated mechanical stress models, represents a significant step forward in optimizing the value of hydraulic fracture stimulation in the Khazzan field unconventional tight gas reservoir. Our Mechanical Earth Model (MEM) is an important component of the integrated workflow currently being used for selecting intervals for successful hydraulic fracture initiation. When incorporated into an integrated subsurface performance prediction strategy, this technology enables optimization of well targeting, increased reserve recovery, and capital efficiency. The interaction of regional tectonics and local lithology controls the stress profiles of the layers in the Bank tight gas reservoir in the Khazzan field. Core measurements show a significant effect of rock fabric and diagenesis on effective gas permeability, elastic properties, and rock strength. The ability to incorporate lithology, rock fabric, and pore geometry in our dynamic to static calibrations provides new insights into our predictions of rock mechanical properties and reservoir quality, which are used to obtain calibrated "fracture initiation" profiles from core, log, and downhole stress measurement information. The MEM is calibrated using an integrated wellbore stability analysis and horizontal stresses are refined by honoring the observed borehole breakouts, formation breakdown and closure pressures. The models show that the adjacent layers in Khazzan field are under higher stress than the pay zones, which enhance fracture height containment and lateral fracture penetration. Previous studies have suggested that there are unequal horizontal stresses which are potentially due to tectonic effects. However, in some cases the magnitude of stress variation and reversal in stress-ordering across minor depths is problematic and confirms the pitfalls of oversimplified assumptions and models used in stress profiling in unconventional reservoirs. This work highlights the magnitude of stress variations within the formation and illustrates an integrated methodology to assist the decisions on selecting hydraulic fracture locations.