Design Of Online Pumping Schedules In Naturally Fractured Shale Formations To Enhance Total Fracture Surface Area

Pre-existing natural fractures in shale formations often interact with hydraulic fractures, and generate complex fracture geometry by diverting fracture propagation. The currently available pumping schedule design techniques are primarily developed to achieve a desired fracture geometry without considering natural fractures. However, these techniques cannot be directly used as in naturally fractured shale formations, the primary goal has to be enhancing the drainage area available for oil recovery by increasing total fracture surface area (TFSA). Motivated by this consideration, in this work, we will design a new model predictive controller (MPC) to compute the fracturing fluid pumping schedule that maximizes TFSA for given fracturing resources. We have utilized Mangrove simulator as our virtual experiment, which is a recently developed model describing the interaction between natural and hydraulic fractures. Initially, we develop a reduced-order model (ROM) by using the simulation data from Mangrove. Then, the ROM is used to design a Kalman filter to estimate the ROM states by utilizing the available measurement. Next, we propose a MPC to maximize TFSA by manipulating the pumping schedule. A series of closed-loop simulation results demonstrate that the proposed pumping schedule is better in enhancing TFSA than existing ones which do not consider the complex interaction between natural and hydraulic fractures.