| Title | Downhole Enthalpy Measurement in Geothermal Wells with Fiber Optics |
|---|---|
| Authors | Atalay, Nilufer; Horne, Roland N.; Sandler, Joel; Kewen Li |
| Year | 2008 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Void Fraction Measurements; Downhole Enthalpy; Fiber Optics; Dispersed-Phase Velocity; Water-Steam Flow |
| Abstract | Studies investigating ways to measure enthalpy downhole have been in progress at Stanford University for the last three years. So far, the void fraction and the dispersed-phase velocity, which are the two essential factors required for calculation of flowing enthalpy, have been determined by using resistivity and photosensors. Currently, research efforts have been oriented toward measuring downhole enthalpy by fiber optics. The normal reflection probe with the fiber tip surface cut at a right angle to the fiber axis was used to investigate the void fraction first in water-air flow and then in water-steam flow. A 4-inch tall plexiglass tube was used in these experiments. Comparison measurements for void fraction were made by using the fractional flow ratio detector (FFRD). Successful results were obtained for both the water-air flow and water-steam flow. After void fraction measurements, a new probe with two fibers of different lengths was designed for measurement of the dispersed phase velocity. The dispersed phase velocity values obtained from the fiber probe showed good agreement with values measured by using a video camera. After obtaining satisfactory results in the 4-inch tube, we tested our device in a 6.5-foot model wellbore and made comparison measurements for void fraction using a resistivity sensor. The results were in good agreement. It was observed that the correlation between resistivity sensor and fiber optic sensor increased with increasing airflow rates. |