Estimation of positioning repeatability noise in 4D streamer acquisition
Jean‐Marc Mougenot, Daniel Vaxelaire, Pierre Spindler · 2006
During the 4D surveys acquired by Total on the Girassol field, strong and unpredictable currents prevented any attempt to repeat source and streamer positions. The present study was performed to estimate the 4D noise generated by these non-repeated source and streamer positions. Two different approaches were used: - a 3D fold decimation test performed on the Girassol first monitor data in an area having strong fold redundancy - repeatability test lines acquired during the last Girassol monitor survey. Both methods indicate that a 10% average amplitude variation within the reservoir window can be regarded as an upper limit of the 4D noise generated by this non-repeatability of positioning. This 4D noise level is acceptable considering the strong 4D signal measured on Girassol. Repeating source and streamer positions would decrease this 4D noise level but is not achievable in the local current conditions. A modeling approach was also performed to see whether the impact of this non-repeatability of positions could be predicted from navigation data.