Heat flow data and vertical groundwater movement, examples from southwestern Virginia

In the present study we show that estimates of vertical specific discharge are often obtainable from plots of conducted heat flow Q versus temperature T. Q‐T plots allow for variations in thermal conductivity across a zone of flow, whereas temperature gradient G versus T plots assume constant conductivity. It is demonstrated that the two different plots can provide quite different estimates of vertical specific discharge. By considering vertically convected heat flow across a zone, better estimates of regional (geologically representative) heat flow can be made. Agreement between corrected heat flow values, conducted heat flows calculated near fluid flow exit boundaries, and regional values suggests that the steady state flow model used is reasonably representative, although the fluid flow depth interval is typically difficult to estimate confidently. The effects of small continuous well bore flow can be removed if continuity in the temperature log results; otherwise, it is most difficult to estimate specific discharge as confirmed by unrepresentative corrected heat flow data.