3-month GPS subsidence analysis in North Sea, ELF/CEA-LDG interpretation

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:413537

Flouzat, M; Fourmaintraux, D; Maury, V; Halle, G

The authors process and analyze 3 months of continuous GPS offshore data provided by the operator from 10 single-frequency stations in the Ekofisk field in the north Sea for subsidence monitoring. This analysis is done using the Differential-GPS automatic software and method developed by the EAP/CEA-LDG. The mean subsidence rates obtained by the EAP/CEA method shows, over these three months, a maximum rate at the center of the subsidence of about 30 mm/month bowl in agreement with previous determinations. The accuracy of the results can be improved by smoothing techniques. However, the noise is still directly related to the distance between the monitored point and the reference points. For instance, the daily averages lead to an accuracy (root mean squares = r.m.s) of 1.1, 1.4 and 2.4 mm for the East, North and Vertical components of the movements for a 2 km baseline and 1.8, 3.7 and 3.8 mm for the East, North and Vertical components for a 24 km baseline. The choice of the best reference points in the network is discussed. Horizontal measurements are simultaneously detected and may be due either to platform tilt or to sea-bed horizontal movements. A further analysis (the 2-hours method) indicate that the noise in the results has a periodic daily structure. In addition, results from previous calibration experiments are used in the method to test the result quality, processed data interpretation.

• OSTI ID: 413537
• Report Number(s): CONF-960525--
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
DATA
DATA ANALYSIS
GEODETIC SURVEYS
GROUND SUBSIDENCE
NORTH SEA
OIL FIELDS
STRATA MOVEMENT