Publications

The effects of well damage and completion designs on geo-electrical responses in mature wellbore environments

Beskardes, G.D.; Weiss, Chester J.; Um, Evan; Wilt, Michael; MacLennan, Kris

Well integrity is one of the major concerns in long-term geologic storage sites due to its potential risk for well leakage and groundwater contamination. Evaluating changes in electrical responses due to energized steel-cased wells has the potential to quantify and predict possible wellbore failures, as any kind of breakage or corrosion along highly-conductive well casings will have an impact on the distribution of subsurface electrical potential. However, realistic wellbore-geoelectrical models that can fully capture fine scale details of well completion design and the state of well damage at the field scale require extensive computational e.ort, or can even be intractable to simulate. To overcome this computational burden while still keeping the model realistic, we use the hierarchical finite element method which represents electrical conductivity at each dimensional component (1-D edges, 2-D planes and 3-D cells) of a tetrahedra mesh. This allows well completion designs with real-life geometric scales and well systems with realistic, detailed, progressive corrosion and damage in our models. Here, we present a comparison of possible discretization approaches of a multi-casing completion design in the finite-element model. The e.ects of the surface casing length and the coupling between concentric well casings, as well as the e.ects of the degree and the location of well damage on the electrical responses are also examined. Finally, we analyze real surface electric field data to detect wellbore integrity failure associated with damage.