The Hot-Film Flow Log--A Formation Evaluation Tool Designed for Shallow In-Situ Oil Shale Experiments

Abstract

Abstract The Hot-Film Flow Log was developed for evaluating shallow in situ fracturing and retorting (combustion) experiments in Green River oil shale. Two logging probes are described which employ a temperature-compensated conical hot-film anemometer-type flow sensor. Wellbore fluid flow profiles and fluid entry or exit points can be recorded while continuously lowering or raising the probes in cased or uncased wellbores. Natural, hydraulic, and explosive fractures in oil shale have been evaluated by a combination of air injection, air production, and flow logging techniques. Fracture depths, types (horizontal or vertical), and flow characteristics within a single borehole or a system of boreholes can be interpreted from the logs. Gas flow profiles in in-situ retorting experiments can be determined before ignition, during formation combustion, and after combustion termination. Limitations and potential applications are discussed. Introduction The U.S. Bureau of Mines is presently conducting field experiments near Rock Springs, Wyo., to determine the feasibility of in situ or underground retorting of Green River Formation oil shale at depths of 75 to 450 feet. Most oil shale is an impermeable rock and does not contain oil; however, it contains a solid carbonaceous material known as kerogen which converts to a crude-oil like liquid when heated to 700 degrees to 900 degrees F. To be retorted in situ through a system of wells similar to those in an oil or gas reservoir, oil shale must first be fractured by some means to provide flow paths between wells for injected and produced fluids.