Hydraulic Fracture Initiation and Propagation Model Provides Theoretical Ground for Hybrid-Type Fracturing Schedules in Unconventional Gas Reservoir in the Sultanate of Oman

Abstract

A recent series of tight gas discoveries in the Amin formation of the greater Fahud area represents some of the most exciting exploration success of this decade in the Sultanate of Oman. The structures have been evaluated as containing very significant amounts of gas locked in a challenging deep and hot environment requiring hydraulic fracture stimulation. Since their discoveries, the two primary challenges have been difficult breakdown of the formation and limited proppant placement during stimulation attempts. The early experience in the exploration and appraisal campaigns from 2009 to 2014 has led to fracture designs with conservative proppant amounts that could limit the full potential of the field. Several geomechanical studies have been commissioned in the past to guide completion strategies in well placement, perforation, and fracture stimulation design.The objectives of this study were to model hydraulic fracture initiation and breakdown in the three Amin zones (upper, middle, and lower) to provide some theoretical understanding of the impact of the different parameters on the observed field breakdown pressures. In agreement with field observations, the model showed that lowering the viscosity of the pad has a major impact in lowering the breakdown pressures. Consequently, current best practices include formation breakdown and hydraulic fracture propagation with low-viscosity fluids followed by proppant placement with high-viscosity fluids. When applied to tight gas formations in the Sultanate of Oman, the hybrid fracturing evolves from conventional designs for the purpose of successful fracture initiation, while still placing a successful job.

From Exploration to Production in 4 Years: Industry Collaboration Leading to Accelerated Learning Curve for Large Tight Gas Project in the Sultanate of Oman

“…They focused on different targets, such as horizontal well placement (Bate et al 2013), barrier identification within the productive zone (Bate et al 2015), hybrid fracturing schedules (Briner et al 2015b), and lowering the breakdown pressure while fracturing (Briner et al 2015b). With all these efforts, three horizontal wellbores were successfully drilled, and the success rate of fracture placement is approaching 100%.…”

“…Maximum gel loading was also reduced down to 3.6 to 5.4 kg/m 3 [30 to 45 lbm/gal], which helped with the post-fracture cleanup. A theoretical background for hybrid schedules application was established by Briner et al (2015b). All the treatments now employ the hybrid-type schedule (Fig.…”

Impact of Wellbore Orientation on Fracture Initiation Pressure in Maximum Tensile Stress Criterion Model for Tight Gas Field in the Sultanate of Oman

“…One of them used a model coupled with the fluid flow, described by Briner et al (2015b). Another project employed a maximum tensile stress criterion model; results of the project related to perforation orientation are highlighted by Briner et al (2015a).…”

Impact of Wellbore Completion Type on Fracture Initiation Pressure in Maximum Tensile Stress Criterion Model for Tight Gas Field in the Sultanate of Oman

“…They included two geomechanics projects: one based on a model fully coupled with the fluid flow, described by Briner et al (2015c), and the other one utilizing a maximum tensile stress (MTS) criterion model as highlighted by Briner et al (2015aBriner et al ( , 2015b. The current work was performed using the latter model.…”