Passive and active fiber optic distributed temperature sensing for downhole lithologic and porosity characterization at Terminal Island, Los Angeles County, California

The purpose of this study was to investigate if passive and active thermal monitoring with Fiber Optic Distributed Temperature Sensing (FODTS) leads to an improved interpretation of downhole lithology and porosity. A deep wastewater injection well located at Terminal Island, Los Angeles, California is equipped with a permanently installed FODTS system. Temperature data have been reinterpreted to assess the formation properties. Rock properties estimated from thermal response were compared with properties estimated from more traditional data including sidewall cores and a suite of standard geophysical logs. Variations in lithology could be detected through both passive and active thermal sensing. However, dynamic FODTS temperature sensing did not provide a more detailed interpretation of lithology and porosity than standard geothermal gradient derivative analysis.