PROJECT OVERVIEW:
Twenty-two optical Dissolved Oxygen (DO) sensors were installed in individual wells during a treatability pilot study. The chosen remedy involved the injection of compressed air at two permeable depths within the formation. The customer needed to monitor the delivery of oxygen in order to determine the remedy’s overall effectiveness. The sensors provided real-time DO data to the project team via the Internet to guide decisions, such as increasing air injection pressures or changing injection intervals.
TECHNICAL HIGHLIGHTS:
Individual data records of DO concentration were recorded from one- to 30-second intervals during a more than two-month study. Data collection intervals were established to obtain data sets that would document and reflect relatively quick and sharp increases in DO during the injection of compressed air into the formation. Access of real-time data via a secure web-user interface was critical for use in data trending, min-max assessment, averaging, and other data assessments. The project team monitored the operational status of and the last reading from each sensor, as well as the last one-hour and last one-day block averages Alerts levels notified select project team members for certain conditions. For example, when DO concentrations at a key well would elevate to certain criteria., the lead geologist would be notified of the increase (or decrease) in DO concentration. The sensors selected for this project were cost-effective, high-quality instruments that provided a simple and efficient 4-20 mA analog data output. The sensors were attached above grade to a self-healing mesh radio network for seamless data transmission across the site. All data was transmitted to the application servers via cellular connection and stored off site for immediate or future use. Due to the pressurized conditions within each well, the sensors remained located within the well riser so data could be obtained without disturbance of well head or subsurface pressures and conditions.
KEY OUTCOMES:
The customer assessed the effectiveness of the treatability study and made adjustments to the treatment system using real-time DO data that was available in an easy-to-use format. Air injection cycles, injection pressures, and the overall radius of influence of the injection process was gauged both during and after the treatability pilot study.