In an attempt to quantify post-stimulation flowback strategies, especially for high value wells with multi-stage stimulations, this study compares observed flowback production histories with multi-phase numerical simulation of flow in multiple fractures of various conductivities. A "fit for purpose?? finite difference simulator is able to treat the numerical problem of extremely high transmissibility contrast ratios in the fracture patterns with multi-phase flow in the fractures. After simulation of several systems, it became apparent that the greatest behavioral contrast was between gas and liquid-filled fracture systems, regardless of the fracture intensity. The results from this study offer insight into the effect of high versus low rate or drawdown flowbacks in the two systems. It suggests potential stimulation strategies for the maximization of long-term productivity, especially in multi-stage stimulation scenarios.
Many operators have begun to engage the belief that significant productivity value is being affected during the earliest portion of the well's productive life, the few hours to weeks of production immediately following cessation of stimulation activities, referred to here as the "flowback??. There are persistent stories about the "unpredictable?? behavior during these times. From extremely early time production performance analysis and analysis of the post-stimulation pressure fall-off analysis, it is clear that significant conductive fracture length is being achieved during the stimulations (Refs. 1, 2). However, especially production performance analysis also shows that the effective "performance?? length of the fracture rapidly deteriorates in many wells (Refs. 2, 3). There is clear evidence that shows initial and ultimate performance to be sensitive to flowback operating constraints (Ref. 4). There is also a persistent observation that in many wells the time from stimulation shut-down until first production has an important impact on early-time and ultimate performance (Ref. 5), sometimes adversely, sometimes beneficially.
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