A mechanism contributing to subsidence above gasreservoirs and its application to a case study

This paper aims to demonstrate that capillary effects and structural collapse can not be ruled out as significant factors in the development of subsidence occurring above gas fields. These phenomena provide sound explanations for continuing surface settlements when reservoir pore pressures stabilise and for additional settlements occurring even after the end of gas production. Conventional subsidence models fail to simulate this settlement behaviour. Capillary effects also explain the lower rock compressibilities observed in gas bearing strata as compared to the values obtained in the laboratory from fully saturated samples. Taking into account these aspects, the observed subsidence above a reservoir in the North Adriatic basin, Italy, is studied in detail.