Enhanced Fiber Optic Distributed Acoustic Sensing for Reservoir Imaging

The recovery rate from oil reservoirs at present is of the order of 3540% before they are abandoned. Enhanced reservoir visualization is needed to improve this rate. Any increase in the oil recovery rate will have a considerable positive effect on the environment, as the remaining oil from marginal fields can be extracted with the existing infrastructure. Over the past years, sophisticated fiber optic based instrumentation for inwell monitoring has been made available to reservoir engineers (temperature, pressure, flow and seismic). These sensors are being used to map reservoirs, and understand how they develop over their productive lifespan. Considering reservoir visualization, seismic sensors are traditionally used. Enhanced visualization is accomplished by increasing the sensor count and their distribution throughout access points within the reservoir. This can be accomplished by adding more seismic sensors, however, the cost and complexity factor for increasing seismic sensor counts inwell is cost prohibitive limiting applications to only high value assets leaving the majority of reservoirs at current recovery percentages. What is needed is a substantially costeffective sensor suitable to complement seismic sensors while enhancing reservoir visualization. The proposed method involves a fiber optic sensing approach which utilizes Rayleigh scattering of coherent light to sense and localize fiber perturbations caused by external dynamic forces along a continuous length of fiber (up to 10s of kilometers). This technology is commonly known as Coherent Optical Reflectometry, and more recently as Distributed Acoustic Sensing (DAS). It has immense potential for applications related to dynamic sensing for reservoir imaging in that a very simple structure, a length of fiber is capable of defining a very large channelcount sensor array (1000s of channels) and can be easily deployed piggybacked to other sensor deployments or installations. Current DAS sensing technology needs to be enhanced in order to be effective for high resolution reservoir imaging. This includes spatial resolution to 1 meter and with high fidelity signal measurement capability. Such improvements relate to the development of higher performance DAS interrogation instrumentation and are the focus of this proposed SBIR work. Commercial Applications and Other Benefits Inwell high resolution 3D imaging and monitoring technology developed for reservoir enhanced visualization has direct economic application on enhanced oil recovery processes and other sensing applications (flow, pipeline protection) for the oil and gas industry. The enhanced DAS technology being developed also serves many other markets including: 1) civil structure distributed sensing (pipelines and bridges); 2) physical security (perimeters, boarders, critical assets) and 3) safety (mines, industrial facilities and structures).