On InSAR Monitoring of the Ground Surface Movement Associated with the Shale Gas Exploration Activities in Poland
Chowaniec, Katarzyna1; Perski, Zbigniew1; Wojciechowski, Tomasz1; Nescieruk, Piotr1; Marinkovic, Petar2
1Polish-Geological Institute - National research Institute, Carpathian Branch, POLAND; 2PPO.labs, NETHERLANDS
The SAR interferometry has proven itself as an irreplaceable technique in monitoring and revealing ground deformation in many scientific and engineering applications, eg., tectonics, volcanoes, landslides, subsidence monitoring, etc. Despite many of the successful demonstrations, and obvious benefits of the technique that have been highlighted through different case studies, for its utilization in many of the operational and government regulated monitoring applications, eg, monitoring of gas field sites, different levels of the validation of the technique are still required.
Often, the InSAR community is of belief, that any further validation activities are not necessary, and that InSAR can be considered as a stand-alone and mature technique. However, while we openly agree with the InSAR community, we are also of belief that any validation requirements, bring yet another opportunity for strengthening the position of InSAR. Through further research, algorithmic development, and while openly re-evaluating and examining benefits and difficulties of the techniques, most of the validation studies strengthen the position of InSAR as a monitoring technique. Here we discuss and present the initial work, for one of such projects.
Hydraulic fracturing is the most common procedure of shale gas production intensifier, while arousing much controversy regarding environmental issues. According to the polish legislation (Act of 9 June 2011) the natural gas, including shale gas areas are treated as mining areas. For those areas, the law requires observations of any changes occurring on the surface and in the subsurface, as well as determining the value of the land surface subsidence due to mining activity.
Polish Geological Institute - National Research Institute (PGI-NRI) initiated the demonstration project (a pilot study) that aimed to monitor potential terrain surface deformation associated with hydraulic fracturing on selected shale gas investigation site in Poland. The synergy approach between, SAR interferometry and GNSS will be applied.
The monitoring infrastructure consists of geodetic (leveling, GNSS) benchmarks, and the radar corner reflectors (CR), that will be deployed prior to any fracturing operations. A series of SAR data from high resolution systems (TerraSAR-X or Cosmo SkyMed), as well as Sentinel-1 when available, will be acquired. It is expected that the terrestrial measurements in combination with CR-interferometry will reveal any potential deformations in the great detail, while the Persistent Scatterers Interferometry (PSI) based on natural scatterers will bring the information about the wider area. Moreover, the analysis will be preceded by exploration of data archives (ERS-1/2 and Envisat ASAR), that would determine whether any long-term, or previous terrain surface deformations occurred within the area of interest.
Considering that the project is in its very early stage and that there are many similar on-going or projects in their preparation, the aim of this contribution, is to share and disseminate experiences and knowledge aggregate while doing all the preparation and deployment work. The specifics about the decision making process on different issues will be discussed. For example,the number, dimension, deployment strategy of the reflectors; number of images and data processing strategy and algorithms; as well as legalese involved in regulating the test sites. Considering the number of ongoing validation projects, we believe that sharing experiences, even at this very early stage of the project, will be of community interest.
Furthermore, the toolbox for stack processing and interpretation of SAR and InSAR data, that is currently being developed as a joint effort by PGI-NRI and PPO.Labs, will be discussed and reviewed in context of this project.