Geosteering in Complex Fields, Bloc 17 (Angola)
Nigel Williams and Antoine Massala
Total E & P Angola, Luanda, Angola
Following Girassol/Jasmim field experience, geosteering in Angola’s Block 17, Dalia and Rosa fields, has enabled Total EP Angola to drill long, complex, single and multi-reservoir, horizontal and sub-horizontal wells, with great success.
The initial planning of high offset geosteered wells, in the project stage, enabled TEPA to minimise the number of sub-sea manifolds and the number of wells, necessary, in order to bring the two fields into development, and to maximise the number and length of reservoir penetrations.
Real-time geosteering of such complex wells inside a single dynamic flow unit, even though still a challenge, is currently achieved with a high success ratio, also in thin (less than 10m-thick) sandbodies.
Successful geosteering of these wells has further enabled optimisation of the well pattern. As new information has become available during field development, it appears sometimes possible to substitute 2 wells by a more complex geosteered well, with multi-reservoir targets.
The tools enabling successful geosteering of wells in Block17 are the excellent seismic image quality, coupled with the availability of ‘At Bit’ logging whilst drilling technology. In addition, Total’s ‘Sismage’ seismic software enables sharing of data between the rig-site and Luanda, thus allowing the tie-in of the well in the seismic image, in real-time.
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