Optimizing the 3D Seismic Acquisition in Colombian Foothills Using the Ray Tracing Theory. Study Case: Recetor Block

Vega, Juan C.¹
 Piedrahita, Carlos C.²

From a 3D geological model with complex structural geology on the ECOPETROL database, it was proposed to apply a synthetic seismic acquisition based on ray theory, in order to optimize the seismic illumination and have a better quality in the seismic image.

Initially, we used illumination maps for displaying the seismic parameters of acquisition as Fold and incidence angle. It was possible to see some problems in actual acquisition. Therefore, new acquisition parameters were proposed. The original design was modified to optimize the low quality in the seismic image. The designs were constructed using seismic acquisition software, and then exported to seismic modeling software, this new design is a wide azimuth survey. We started from a 3D complex structural geology Recetor. Furthermore, the model has faults as strike slip faults, inverse faults and regional faults that are affecting the geology of the zone. So, the principal problem is the low quality in the seismic image due to the complex structural geology, weather and rough in the topography.

With the seismic parameters data used in the field in the year 2002, we simulated the acquisition over our model using the seismic modeling software applying the WF construction method. Afterwards, with the information generated, we constructed a set of illumination maps. These maps are more useful because they display graphically the areas with the major problems in illumination. Furthermore, in the South of the area there are not rays or illumination and this area is the most crucial in the exploration of new prospects, because this is an anticline structure with imbrications, and this area have active wells today.

After we have the best direction of the patch and offset, we find that is necessary to add more lines of shots and receivers in order to improve the quality in the seismic image. The principal differences between the original survey and this new arrangement are in the acquisition direction of the survey and template. The first design had an azimuth of 115 N with maximum offset of 5000 m (inline). In the our final design, the acquisition direction is 35 N and we add 5 shots lines to the South of the model and survey with máximum offset crossline of 5000 m and inline offset 3000 m and template of 32 receivers lines per shot.