A Computational Technique for Estimating the Fracture Surface Area Adjacent to a Newly Stimulated Well within an Engineered Geothermal System

Abstract

In the creation of an Engineered Geothermal System (EGS) a reservoir is hydraulically stimulated by injecting water into wellbores under high pressure. This enhances permeability in marginally conductive fractures that are optimally oriented and critically stressed for shear failure. The objective of the hydraulic stimulation process is therefore to create a high-surface-area heat exchanger within the reservoir. Currently, no methods exist for characterizing the newly created fracture surface area, which is critical for estimating the success of the hydraulic stimulation and the performance of the insipient reservoir. In this paper, we present a computational technique for calculating the near-wellbore fracture surface area by inverting data from a single-well injection/ backflow tracer test involving a thermally reactive tracer.