| Popis: |
Imaging of the base of salt and subsalt prospects with 3D seismic data is difficult and time consuming. The Mississippi Canyon Area was chosen to prove the value of integrating 3D full tensor gradient data with 3D seismic to enhance the geologic model for drilling and development. The full tensor gradient data was acquired by Bell Geospace using a gradiometer originally developed to navigate the U.S. Navy trident nuclear submarines. It has very high sensitivity and is able to capture meaningful high frequency data not found in normal gravimeter data. Because all nine gravity gradient tensors are measured, the data gives information on the size, shape, and edges of the salt. The gravity and gradient responses for an initial geologic model developed from 3D seismic data were subtracted from the Bell measured data. The results were used to reinterpret the seismic data and modify the geologic model until the differences were significantly reduced. The revised model reinterpreted the pay horizons as a broad anticline lying below the salt. The gradiometry data also refined the interpretation of the edge and base of salt, lowering the base as much as 1,250 feet in some areas. The final geologic model also had significant improvements in density, particularly in the shallow layers. This study proves that 3D gradiometry data provides an important independent constraint for successfully interpreting seismic data, particularly in areas of poorly imaged seismic reflectors. |
