Freshwater, which is indispensable to oil operations and renewable energies alike, is a vital resource under growing pressure. Management to ensure its sustainability represents an ever more crucial challenge: ORCAD (Online and Realtime Characterization of Aquifer Dynamic), the fruit of Total’s dynamic of innovation, fully meets this challenge. A new-generation monitoring system, ORCAD provides the key to minimizing the environmental impact of E&P’s industrial sites on underlying underground water.
A 3D View of Groundwater Dynamics
Subsoil water does not flow in long, calm rivers. The lack of underground geological uniformity makes its movement more complex. Flows, the speed of which varies according to their immediate environment, follow routes that offer the least resistance. This dynamic eludes the classic approach to monitoring: sampling and the laboratory analysis of water samples taken periodically in fact only deliver a static 2D map of concentrations of potential contaminants.
ORCAD, a breakthrough system for monitoring this water continuously in situ and in real time, is a game-changer: for the first time, it gives access to a 3D view of the movement of underground water flows. Whilst revealing the twists and turns in the path taken by a flow, ORCAD also computes spatial and temporal variability of its speed. Two vital sets of information for predicting the route and flow, i.e. the propagation, of contamination from its source to a potential receiver (supply well, the water table, river, agricultural area, inshore marine environment etc.), and thus to effectively guide the strategy that will enable its effects to be minimized.
ORCAD was developed by Total’s SESD (Safety, Environment and Sustainable Development) and CCUS (Carbon Capture, Utilization and Storage) teams, which began work on the project in 2017 at the Total research center laboratories at Lacq, in France (PERL). It was then trialed in the ADYCHATS (Aquifer DYnamic CHAracterization Tools System) pilot deployed in 2018 on PERL’s experimental six-hectare platform at the Lacq plant. The convincing results enabled the practical application of this innovative approach to a real-life case that involved monitoring and characterizing an existing contaminant plume using an industrial demonstrator produced in 2020 with RETIA, a Total affiliate specializing in the rehabilitation of industrial sites.
High-Performance, Low-Cost Monitoring
ORCAD owes its performance to the integration of innovative technology designed to enable high-resolution measurements at the lowest possible cost.
Measuring the flow speed of water (direction and amplitude) directly in situ is the key element in the technological leap made by ORCAD. It is achieved using point velocity probes (PVPs) developed with the University of Kansas in the USA. Manufactured using 3D printing, these probes are as accurate as they are economical. They are connected with one another by PVC tubes, then lowered to the required depth(s) in a cased wellbore. When the tubing is withdrawn, the surrounding earth collapses in on the probes, which then come into direct contact with the water table. ORCAD also has three other genuinely revolutionary features:
- measurements that are not altered by the filter effect present in the piezometer used in classic monitoring;
- 3D flow measurements through lateral and vertical sensors fitted to the probes, indicating the direction of a flow to within a few degrees;
- unrivalled precision, measuring the amplitude of the rate of flow to within one unit, whereas current monitoring only enables flow speed to be estimated, and even then, with a far greater order of uncertainty.
The physical and chemical characterization of water in CADYLACQ used a temporary intermediate solution: a portable gas phase chromatography kit, deployed on the surface. In addition, on-site sample analyses delivering results in 30 minutes (as compared with a few days for a laboratory analysis). In the future, monitoring the physical and chemical parameters and the concentration of potential contaminants in water will, like measuring flow rate, be undertaken directly, continuously and in situ, by a set of very economical passive microsensors, which are currently being patented and are already being tested in ADYCHATS.
Digital technology currently under development will in the future process and display (in 3D) the data acquired in situ and transmitted wirelessly to a remote monitoring center to assist with real-time decision-making if an anomaly is detected.
Improved Protection of Freshwater
Designed to enable even more effective monitoring of the dynamics and quality of underground water than is required by current legislation, ORCAD demonstrates the proactivity of the Group’s environmental R&D, who, through their dedication, imagination and expertise, provide tangible proof of Total’s ambition to become the major in responsible energy.
Industrial sites are only the first area in which ORCAD can be applied, as it has the potential to meet the overall challenge represented by the protection of freshwater resources. The system will be also able to be adapted to monitor geological storage of CO2 using fiber optics instead of microsensors in order to detect any leaks of CO2 into a water table.
Many other activity sectors, both industrial and agricultural, will in the future be able to make ORCAD an effective ally in their quest to protect freshwater resources.
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Total's Research Center (PERL) in Lacq