In unconventional reservoirs, the application of many rate-transient-analysis (RTA) techniques relies heavily on the identification and analysis of the linear flow regime, which is characterized by a ½-slope on a log-log plot of Δp vs. t. Through our analysis of more than 2,500 wells with downhole gauges in the Wolfcamp Shale of the Permian Basin. We observed power-law behavior, but with slopes much different from ½-slope last for years.
This talk presents pressure-transient-analysis (PTA) examples of pressure interference tests and pressure buildups (PBU), and RTA examples. The characteristics observed from PTA and RTA examples demonstrate the representative flow regimes derived from the fractional diffusion in fractured rocks produced through horizontal wells with multiple, hydraulic fractures. Using the model, we develop a workflow for RTA by honoring the first flow regime dominated by the fracture and the second flow regime dominated by the matrix.
This talk also compares EURs derived from decline-curve analysis (DCA) and RTA and illustrates an EUR estimate using DCA with knowledge of the matrix dominated flow regime from RTA. We also compare EURs from oil, water and two-phase of oil and water.
Weichun Chu retired from Pioneer Natural Resources (PXD) in 2019 as an Engineering Technical Specialist. He has 40 years of reservoir engineering experience in both conventional and unconventional reservoirs with primary focus on pressure analysis. Before returning to PXD, he was with OMV in Vienna, Austria and PXD in London, UK. In 2000, he also retired from Marathon Oil Company as a Technical Consultant in Littleton, Colorado. He has designed and analyzed all types of well tests for oil, gas and water reservoirs around the world including formation testing. Weichun holds a BS degree in Chemistry from New Mexico Tech and a PhD degree in Petroleum Engineering from the University of Tulsa and is a member of SPE.