October General Meeting: Fractional Dimension Rate Transient Analysis

Fractional Dimension Rate Transient Analysis (FD-RTA): A Key to
Unconventional Wells and Complex Fracture Networks
Jorge A Acuña
J Acuna Consulting, LLC.

Abstract:
Unconventional wells show features that make them very difficult to characterize. One of them is the “transitional” flow regime that lasts months to years and is different from known flow regimes such as linear or boundary dominated flow. Fractional Dimension RTA (FD-RTA) is based on work on fractals and fractional dimension systems from the late 80’s and early 90’s. These principles were significantly expanded with innovative elements, rigorous solutions, modeling techniques, and adapted to the geometry of unconventional wells. The result is FD-RTA, a new technique to analyze and understand fracture networks ranging from complex ones with rock fragments of many different sizes to simple ones with equally spaced fractures. This lecture explains the evolution of these ideas and the power of the fractional dimension approach to explain “transitional” flow regimes as the result of fracture complexity. In this new approach, known flow regimes such as radial or linear flow are only special cases of a single general transient solution. The approach can be easily converted to a numerical model and explains several previously unexplained features, such as rapidly increasing gas-oil-ratio, apparent fracture closure with time, etc. The power of FD-RTA is demonstrated by applying it to parent-child well interference. I would like the members to take away the idea that basic methods for pressure and rate transient analysis can explain previously unexplained features of unconventional well behavior but only when the correct model for fracture geometry is considered.

Biography:
Dr. Jorge Acuna graduated from USC in 1993, where he worked on transient behavior of fractal networks of fractures. He joined Chevron (then Unocal) in 1996. He became a leading expert in geothermal modeling and reservoir engineering. He started work in unconventional pressure and rate transient analysis in 2012 and developed Fractional Dimension RTA between 2016 and 2020. The method was published and implemented in commercial software. He retired from Chevron in 2022 to start his own consulting firm J. Acuna Consulting. He has authored more than 30 papers, regularly reviews SPE papers and has participated as session chair in SPE conferences.

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