Oman tight gas accumulation has been initially developed with fractured vertical wells targeting up to 10 different hydrocarbon units, as well as with dedicated highly deviated to horizontal wells targeting the most tighter zones. The intrinsic geomechanical, petrophysical and lithological heterogeneities of this tight units impact not only the fracture conductivity distribution but the drainage efficiency of the fractured zones, this is observed as mobility variations across this unit impact their contributions once all become commingle, with the areas of higher mobility dominating the total gas well production, this for all wells architectures.
This paper will discuss fundamental formation characterization requirements to assess in-situ stress dynamic variations during the life of the field; incorporating formation pressure points as integral part of the drilling program and in-situ stress measurements supported by comprehensive mini-fracture data evaluation. The use of radioactive tracers in combination with production logging were implemented to assess containment and fracture prediction, providing this an essential tool to determine fracture propagation behavior, deployment strategy and final conductivity distribution. It will be described the logging requirements as well as the lab characterization needed to determine key elastic properties to assess the hydraulic requirements for fracturing individual units or combination of them.
It will be discussed how variations on pore pressure and stress profiles, as the field developed, will impact perforation and fracture strategies for vertical, highly deviated and horizontal wells. It will be presented how increase of pressure confinement affects the in-situ elastic properties as depletion is experienced on specific gas units, inducing alterations on stress and net pressure profiles that impact fracture propagation and final conductivity distribution, this becomes of particular importance on highly deviated and horizontal wells where vertical connectivity with all hydrocarbon units is fundamental to maximize recovery.
Finally, it will discuss the methodology used for fracture deployment considering the differential depletion expected during the field development and its impact on completion integrity and fracture implementation strategies. We will share the identified best practice that will lead to optimum fracture development while maximize investment.