A Comparative Study on Wellbore Pressure Transmission of Water and Carbon Dioxide during Fracturing
By: Caiyun Xiao, Hongjian Ni, Bo Zhao, Ning Li (August 2020)
This study delves into hydraulic fracturing, a crucial method for unlocking unconventional oil and gas resources. With growing interest in CO2's potential as a substitute for water in this process—owing to its advantages in unconventional reservoir development and CO2 utilization—the research focuses on the role fluid properties play in affecting wellbore pressure transmission, especially during CO2 fracturing. The authors introduce a wellbore pressure transmission model grounded on fluid compressibility, integrating it with a wellbore flow model for compressible fluids. This combined approach provides insights into the borehole pressurization rates during both water-based and CO2 fracturing. Validated with field data, the findings highlight that as the pumping rate goes up, so does the borehole pressurization rate for both fracturing methods. However, water-based fracturing has a borehole pressurization rate that's 10 to 20 times higher than CO2 fracturing at identical pumping rates. Additionally, while the pressurization rate for water-based fracturing rises linearly with the pump rate, an overly high pump rate could diminish the pressurization rate in CO2 fracturing. These insights offer valuable guidance for refining actual hydraulic fracturing operations.