Numerous technical publications were written in recent years on the effectiveness of reservoir simulation modeling in developing a tight gas resource. These papers question the applicability of existing numerical simulation methodologies to hydraulically fractured unconventional gas reservoirs. The rapidly changing dynamic flow behavior that occurs as fluids move from poor quality reservoir to a highly conductive fracture and then feed into an infinitely conductive wellbore creates complex solutions which are difficult to fully resolve with conventional reservoir simulation techniques. The lack of well to well dynamic interference during early stages of the production stacks the additional uncertainties around connected gas volume to the wellbore, thereby, increasing the chances of sub-optimal investment decision on well spacing, infill wells and number of fracs during the early stages of the field development.
This paper proposes a reservoir simulation strategy and the workflow for unconventional gas reservoirs. The strategy outlines the need to systematically move from simple to complex modeling solutions while creating a learning loop. It proposes an early modeling focus on single wells in small sector models to understand the impact of stimulation and well design related uncertainties. The paper also identifies a learning stage that allows a progression to the next stage of simulation i.e. sector models. The workflow identified in the paper also presents the disadvantages of how an untimely progression from sector to full field modelling can negatively impact final investment decisions and the field development strategy.
BP has successfully applied this framework in North America and this strategy has been outlined for reservoir simulation related work in the Sultanate of Oman to develop unconventional gas resources in Block 61.