Abstract: A method of investigating an underground formation underneath the earth's surface, comprising obtaining a first data set representing change in a predetermined seismic parameter over a period of time for a plurality of points in the underground formation, which first data set is derived from a time-lapse seismic survey of the earth formation spanning the period of time; obtaining a second data set representing geodetic deformation over substantially the same period of time at a plurality of locations on the earth's surface, which second data set is derived from a geodetic survey spanning the period of time; jointly processing the first and second data sets to obtain a map of a parameter related to volume change in the underground formation; wherein a geomechanical model of the underground formation is postulated; also a method of producing hydrocarbons and a computer program.

Abstract: A method of detecting a lateral boundary of a compacting or expanding region in a subsurface formation, which method comprises determining non-vertical deformation of the earth' s surface above the subsurface formation over a period of time; identifying at least on contraction area and at least one adjacent dilatation area of the earth' s surface from the non-vertical deformation over the period of time; and using the contraction area and the adjacent dilatation area as an indication of a lateral boundary of the compacting or expanding region; and a method for producing hydrocarbons.

Abstract: A method of monitoring a subsurface formation underneath a sea bed, the method comprising determining non-vertical deformation of the sea floor over a period of time and inferring a parameter related to a volume change in the subsurface formation from the non-vertical deformation of the sea. Determining the non-vertical deformation of the sea floor comprises selecting a plurality of locations on the sea floor and determining a change in distance between at least one pair of the locations over the period of time.