Characteristics of surface deformation field of Changning shale gas block in southern Sichuan basin with InSAR data

In recent years, along with large-scale development of shale gas, the seismicity rate has increased dramatically, a series of microseismicity, felt earthquakes and even destructive earthquakes occurred in southern Sichuan basin, a relatively tectonic stable area. Some studies statistically infer whether these earthquakes were induced by industrial activities by using spatio-temporal correlations. This study, on the other hand, uses deformation measurements to analyze whether shale gas exploitation can produce detectable surface deformation, so as to analyze the relationship between deformation and shale gas exploitation, in an attempt to find an effective approach for shale gas exploitation monitoring. Long wavelength ALOS-2 satellite radar data has the potential for minimizing decorrelation effects of radar signals caused by vegetation, heavy water vapor and topographic relief in Sichuan basin. We used ALOS-2 InSAR data to measure surface deformation in Changning shale gas block in the past two or three years, found possible ground deformation caused by massive shale gas production and analyzed its basic characteristics. Meanwhile we also processed time-series of Sentinel-1 satellite radar data to measure the surface deformation during active periods of shale gas exploitation. Considering the errors and different observation geometries of the two datasets, the results from two databases are consistent in revealing the surface deformation. Furthermore, the meaured deformation field is in agreement with the spatial distribution of shale gas wells. Our observations show fast surface uplift during hydrofracture injection, also ground subsidence and horizontal motion in production period with fliud diffusion. We preliminarily reveal the non-steady deformation characteristics during shale gas production. Our study suggests that InSAR is an effective technique for shale gas production monitoring even in southern Sichuan basin where complex deformation occurs, and can provide insights supplementary for seismological observations.