Modeling Flowback Behavior or Flowback Equals "Slowback"

Abstract

Abstract Clear evidence is becoming available that shows that ultimate gas well performance is extremely sensitive to the early time well production management, during the time often referred to as the "flowback". Early time production management in shale gas wells is even more critical than in so-called traditional tight gas reservoirs. This production management problem is exacerbated by the plasticity of shale reservoirs, the need for extensive natural fracture swarms and the now common practice of multiple fracture stimulations of the long-reach laterals. This paper examines three data sets from actual wells that show the adverse impact of excessive early time flow rates, shut-ins during the early time production and the orientation of the laterals. Through numerical simulation and physical experiments, it becomes clear that the traditional performance metrics are at best misleading. Introduction Many aspects of the stimulation treatment(s), and particularly the early time production management practices impact the ultimate performance of gas wells producing from low permeability reservoirs, especially naturally fractured shale gas wells. Previous papers have demonstrated the adverse consequences of shut-ins during the initial well clean-up after a fracture stimulation (6, 7, 8). The effect of delaying production after the stimulation has been investigated (4, 11). A variety of methods to induce proppant immobilization have been discussed (3, 15, 20). Several diagnostic methods have been employed to attempt to quantify the impact of these early time production management strategies (1, 2, 4, 15, 17, 18, 19, 25, 26). The literature discusses the potential value or liabilities associated with stimulation fluid flowback rates ranging from a few tenths of a barrel per minute to 5 BWPM (1, 3, 15, 22, 23, 25). The literature has only begun to recognize the value of considering the physics governing flowbacks as the same basic physics governing waterflooding and coning mechanisms (6, 12, 13, 24). The fundamental used in this study have been reported previously (6, 7, 8). However, the conduct of several physical experiments and actual field data from shale gas reservoirs has added emphasis for the need to further examine commonly held beliefs and practices.