New data about surface subsidence above gas reservoirs

Capillary effects and structural collapse cannot 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. Up to now the only explanation put forward for this was damage of the samples.