Patent ID: 6813564
Filing Date: 2004-11-02
Classification: G01C,G01V

Abstract:
A method for monitoring possible subsidence of a seabed (14) of a survey area (8) caused by compaction of an underground hydrocarbon reservoir (1), comprising:conducting at least two measurement series (S1, . . . ,Si, . . . ,Sm) each comprising at least one time-indexed depth measurement (13a,13b, . . . ,13n), with a separation in time &Dgr;t between the at least two measurement series on the order of months or years; conducting each depth measurement (13a,13b, . . . ,13n) on a survey station (2a,2b, . . . ,2n) arranged on a benchmark (6a,6b, . . . ,6n) having fixed vertical and horizontal position relative to the local sea-bed (14a,14b, . . . ,14n); within each measurement series (Si), conducting at least one stationary time-indexed short-time local reference depth measurement series (19r) on at least one short-term local reference station (18r) on at least one benchmark (6), for correcting each depth measurement (13a,13b, . . . ,13n) for short-time depth variations; conducting the depth measurements (13,19r) relative to at least one depth measurement (13r) at a reference station (9) arranged on the seabed (14r) outside the survey area (8) at least once during each measurement series (Si), the reference station (9) essentially being unaffected by long-term effects taking place due to compaction in the reservoir (1) during the series of measurements (S1, . . . ,Si, . . . , Sm).