Repurposing of hydrocarbon wells for Enhanced Geothermal System (EGS) development

Abstract

The Groß Schönebeck research platform represents a case study for the reuse of the abandoned hydrocarbon well E GrSk 3/90. A detailed description of well selection criteria, subsurface conditions, and well modification procedures is presented as a workflow for the repurposing of hydrocarbon well as an injection well for an EGS development. The procedure is complemented by a sequence of hydraulic stimulations leading to the development of the site as an EGS doublet well system. In this study, numerical simulations were carried out using the CMG STARS software to validate the numerical model of the existing matrix-dominated EGS against the hydraulic tests carried out in the field between 2011 and 2013. A sensitivity analysis was performed and it shows that matrix permeability is the most influential parameter followed by fracture permeability. The calibrated model and the result of the sensitivity analysis were then used as the basis for a predictive model of a fracture-dominated EGS concept. The new concept is presented with the technical feasibility of repurposing Gt GrSk 4/05 (A2) well as an injection well, E GrSk 3/90 well as a seismic monitoring well, and a design layout for the new production wells. This concept, comprising 16 fractures with a parallel horizontal well configuration, exhibits a 16-fold increase in the Productivity Index (PI) and Injectivity Index (II) at a production rate of 60 m³ h⁻¹compared to the previous matrix-dominated EGS development concept. A production rate of 180 m³ h⁻¹is achievable with a maximum production life of 30 years with two production wells.