![]() Additionally problematic, vibrator coupling deteriorates in areas with hard laterite at the surface. Laterite may form chunks and boulders in the subsurface which may act as scatterers. Laterites are typically rusty-red due to high iron oxide content (Wikipedia). Laterite is a soil and rock type which is rich in iron and aluminium, and is commonly formed in hot and wet tropical areas. Region 1 area is covered in red, iron-rich clay soils with areas of crystalline laterite at the surface (Figure 4). From Audry, Barbery, Boucquier, Bouteyre, Marius, and Vizier et. Regional soil map illustrating Region 1 with extensive near surface laterites and Region 2 with limited laterite and good surface conditions. This paper will focus on the tests and results in two areas: Region 1, which has near surface laterites and only fair-to-good data quality and Region 2, where mixed laterite / laterite free zones resulted in good-to-excellent data quality (Figure 3). Seismic acquisition tests acquired by Glencore between 20. Most of the acquisition tests were incorporated into the regular seismic acquisition production with little delay or additional cost, so that any potential improvements could be applied immediately. These tests include eight vibroseis parameter tests, four maximum offset/record length tests, three sweep effort tests, three 2D swaths (adding 50 km of high-resolution subsurface data), two noise tests, one receiver array test, one sweep force test and one 3D cross-spread test, which provided targeted 3D imaging. Eleven tests were acquired during the 2014-2015 seismic acquisition season for optimization of future seismic programs. Twelve of the tests were acquired during the 2013-2014 seismic acquisition season and were used to optimize acquisition parameters for data acquired during the 2014-2015 seismic acquisition season. In order to further improve imaging in areas with surface laterites/near surface scatters, twenty-three seismic acquisition tests were incorporated into the regular seismic acquisition (Fig 2). Glencore geoscientists observed that surface conditions influenced data quality with higher frequency data (70-80 Hz) obtained in areas with silt and sand versus lower frequency data (55-60 Hz) obtained in areas with surface laterites, as mapped on vintage soil maps. Data quality of previous operator data varied from area to area. Overall, the quality of data acquired between 20 is superior to previous acquisition programs with better frequency content, improved fault imaging and better reflection continuity at depth. Data quality throughout the area ranges from fair-to-good in the west to excellent in the east. Seismic data acquisition in Chad is conducted using a vibroseis source for logistical reasons. Glencore seismic acquisition programs in Chad – 2011 to 2015. This paper will provide an overview of the seismic acquisition tests with a specific focus on tests designed to improve imaging in areas with surface laterites/ near surface scatters, which impede imaging. Test results were used to improve operations in real time as data was being acquired, with the cooperation of seismic contractor BGP International (Chad). ![]() Seismic acquisition testing provided tremendous benefit by improving subsurface imaging, increasing operational efficiency and reducing costs. Over the past four years, Glencore has acquired four 3D seismic surveys covering 1200 km 2, 216 2D seismic lines covering 4500 km and twenty-three seismic acquisition tests in Chad (Figure 1). ![]()
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