In hydraulic fracturing, the proppant-filled fracture length at the end of pumping strongly influences the fluid conductivity of natural oil and gas. Therefore, it is very important to regulate proppant bank height and suspended proppant concentration across the fracture to increase the recovery of shale hydrocarbon. From a control engineering viewpoint, hydraulic fracturing has been traditionally viewed as an open-loop problem. Well logs and mini-frac test results are interpreted prior to operation in order to obtain petrophysical and rock-mechanical properties of the formation. The operation is designed based on the properties and then is conducted accordingly. However, the open-loop operation may lead to poor performance, if there are large disturbances (e.g., pressure spike) and plant-model mismatch, and closed-loop operation of hydraulic fracturing is needed for the online adjustment of the flow rate and proppant concentration to achieve the specified control objectives.
To achieve this, we develop a model predictive control framework for the design of pumping schedules to regulate the spatial variation of proppant concentration across the fracture, which is directly related to the overall efficiency of the operation. Further research in this area involves considering multi-stage hydraulic fracturing to achieve uniform growth of simultaneously propagating multiple fractures, and the water management of hydraulic fracturing by integrating sustainability and economic considerations of the post-fracturing process into optimal pumping schedules.
P. Siddhamshetty, K. Wu, J. S. Kwon, “Optimization of simultaneously propagating multiple fractures in hydraulic fracturing to achieve uniform growth using data-based model reduction,” Chem. Eng. Res. & Des., 2018, 136, 675-686. DOI: 10.1016/j.cherd.2018.06.015
P. Siddhamshetty, S. Liu, P. P. Valko, J. S. Kwon, “Feedback control of proppant bank heights during hydraulic fracturing for enahnced productivity in shale formations,” AIChE J., 2017, 64,1638-1650 DOI: 10.1002/aic.16031
P. Siddhamshetty, S. Yang, J. S. Kwon, “Modeling of hydraulic fracturing and designing of online pumping schedules to achieve uniform proppant concentration in conventional reservoirs,” Comp. & Chem. Eng., 2017, 114, 306-317. DOI: 10.1016/j.compchemeng.2017.10.032