Shut-in based production optimization of shale-gas systems

• A novel cyclic operational scheme to enhance the utilization of late-life shale-gas systems.
• Reduced-order PDE-based well and reservoir proxy model.
• A nonlinear GDP formulation for optimization of shut-in times for multi-well systems.
• We report computational results on three different mixed integer models for the scheduling of well shut-ins.

This paper presents a novel operational scheme for enhanced utilization of late-life shale multi-well systems. These systems are characterized by a large number of geographically spread wells and pads, where a substantial number of the wells are producing at low erratic rates due to reservoir pressure depletion and well liquid loading. By applying a cyclic shut-in and production strategy, the scheme avoids well liquid loading and optimizes the production from a set of late-life wells at a shared production pad. The scheduling of well shut-ins is formulated as a generalized disjunctive program (GDP), using a novel shale-gas well and reservoir proxy model. The GDP formulation lends itself both to a complete MILP reformulation and reduced size MINLP reformulations; a computational study indicates in favor of the MILP formulation. We include numerical examples to demonstrate the potential benefit of applying the proposed cyclic scheme compared to a non-optimized approach.