Can Geologic Factors be Predictive for Distinguishing between Productive and Non-productive Geothermal Wells?

摘要

Geologic data are examined in order to evaluate whether certain geologic characteristics occur in higher abundance or higher magnitude along geothermal production wells relative to nonproductive wells. A 3D geologic map, a 3D stress model, and fault-slip modeling are used to estimate fourteen different geologic factors that are hypothesized to control or be correlated with well productivity. The geologic factors are; heat, fault-damage zone thickness, distance from active faults, fault intersection/termination density, fault curvature, slip tendency of faults, dilation tendency of faults, dilation resulting from modeled fault slip, normal stress reduction resulting from modeled fault slip, Coulomb shear stress increase resulting from modeled fault slip, the summed thickness of'favorable' lithologies within a borehole, the summed thickness of fault damage zones in favorable lithologies within a borehole, the distance along the borehole to the nearest geologic contact, and the thickness of individual stratigraphic units. These geologic factors are quantified along fifty wells at Brady geothermal system, including twelve production wells and thirty-one non-productive wells. Results indicate that geologic factors such as stress changes associated with faulting, nearness to and thickness of fault zones, distance from geologic contacts, and heat occur in higher magnitude or higher abundance along production wells relative to non-productive wells. These geologic factors may play an important role, controlling the locations and distribution of fluid circulation in geothermal fields.